I

I

OCStudy

MMS 95-0049

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Monitoring Assessment of Long-Term

II Changes in Biological Communities in

II the Santa Maria Basin: Phase III

i Final Report

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i U.S. Department of the Interior

M Minerals Management Service

I PacificOCSRegion

I
I OCS STUDY

MMS 95-0049

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I MONITORING CHANGES IN ASSESSMENT BIOLOGICAL COMMUNITIES OF LONG-TERM

IN THE SANTA MARIA BASIN:

i PHASEIII

i FINAL REPORT

i November 1995

I Submittedby

I ScienceApplications 10260 CampusInternational Point DriveCorporation

San Diego, California 92121

andI MEC Analytical Systems, Inc. 2433 Impala Drive

Carlsbad, California 92009

i

This study was funded by the

i U.S. Department of the Interior, Minerals Management Service/

National Biological Service,

under Contract No. 14-35-0001-30584

m

i SAIC and MEC. 1995. Monitoring Assessment of Long-Term Changes in Biological Communities in the Santa Maria Basin: Phase III, Final Report. Report submitted to the U.S.

Department of the Interior, Minerals Management Service/National Biological Service, under

I Contract No. 14-35-0001-30584.

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I PROJECTORGANIZATION

i PROGRAMANAGER

Dr. Andrew Lissner

I_ Applications Corporation

Science International

I 10260 Campus Point Drive

i San Diego, California 92121

CONTRACTING OFFICER'S TECHNICAL REPRESENTATIVE

I Mr. Lyman Thorsteinson

U.S. Department of the Interior

National Biological Service

Western Office

Regional

909 First Avenue, Suite 800

Seattle, Washington 99804

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PRINCIPAL AUTHORS

i Dr. Andrew Lissner--SAIC: Benthic Ecology, Integration, Technical Editor

Mr. Charles Phillips--SAIC: Marine Chemistry

Dr. Evans Waddell--SAIC: Physical Oceanography

I Dr.Dr.Peter Arthur Hamilton--SAIC: Bamett--MEC:-Larval PhysicalExperiments Oceanography

Dr. Douglas Diener--MEC: Benthic Ecology

I Dr. FrankDr.Bohlen--University PeterRaimondi--UCSB: of Connecticut: LarvalExperiments Physical Processes

CONTRIBUTING AUTHORS

I Mr.John Evans---SAIC:MarineChemistry,Methods

Mr. Danny Heilprin--SAIC: Marine Ecology, Methods

t Dr.Dr. Thomas Paul Berger--SAIC: Krause--MEC: Physical Larval Experiments Oceanography

Mr. John Ljubenkov--MEC: Benthic Ecology

i Ms. Suzanne Benech--Benech Biol. and Assoc.: Benthic Ecology, Integration

QUALITY REVIEW BOARD MEMBERS

I Dr. James Brooks---Texas A&M University Dr. Donald Boesch--University of Maryland

Dr. Roger Green--University of Western Ontario

I Dr. Judith Dr. Clinton McDowell Winant--Scripps Capuzzo---Woods Institution Hle Oceanographic of OceanographyInstitute

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i DISCLAIMER

This Management report has Service been/National reviewedBiological by the Service, U.S. Department and approvedof for thepublication. Interior (DOI), The opinions, Minerals

findings, conclusions, or recommendations expressed in this report are those of the authors, and

I dodoesnotnotnecessarily constitute reflect endorsement the viewsor recommendation of the DOI. Mention for use. of trade Thisnames report orhascommercial not been edited productsfor

conformity with DOI editorial standards.

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| CONTENTS

I page

I Table of Contents i

List of Tables v

t List of Figures vi Abbreviations, Acronyms, and Conversions viii

I EXECITIVE SUMMARY ES-1

1.0 INTRODUCTION ES-1

I

2.0 METHODS ES-2

I 2.1 PHYSICAL OCEANOGRAPHY ES-2

i 2.2 SEDIMENT PHYSICAL AND CHEMICAL PROPERTIES ES-5

2.3 PARTICLE FLUXES AND SEDIMENT RESUSPENSION ES-6

I 2.4 HARD-BOTTOMCOMMUNITIES ES-6

I 2.5 LARVAL SETTLING EXPERIMENTS ES-7

2.6 LABORATORY TOXICITY TESTS ES-7

! 3.0 RESULTSANDCONCLUSIONS ES-8

I 3.1 PHYSICAL PROCESSES ES-8

.. 3.2 CHEMICALPROCESSES ES-11

I 3.3 BIOLOGICAL PROCESSES ES- 11

3.3.1 BiologicalCommunity ES-11

i 3.3.2 In Situ Larval ES-13 Experiments

3.3.3 LaboratoryToxicityTests ES-13

/ 4.0 OVERALL CONCLUSIONS ES-13 I

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chapter 1 I

INTRODUCTION 1.1 OVERVIEW 1-1 1-1 i

1.2 PURPOSE AND GOALS 1-2 I

1.3 TECHNICAL ITEMS AND HYPOTHESES 1-5 I

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1.4 DESCRIPTIONOF STUDYAREA 1-10

chapter 2 I

MATERIALS AND METHODS 2-1 I

2.1 OVERVIEW OF FIELD SURVEYS 2-1

2.2 PHYSICAL PROCESSES 2-21 i

2.2.1 Current Measurements 2-22

2.2.1.1 Field Survey 2-22 ill

2.2.1.2 Laboratory/Data Analyses 2-27 m

2.2.2 Wave/Tide/Wind Measurements 2-29

2.2.2.1 Field Survey 2-29 i

2.2.2.2 Laboratory/Data Analyses 2-30 W

2.2.3 Satellite Imagery 2-33

2.2.3.1 Field Survey 2-33

2.2.3.2 Laboratory/Data Analyses 2-33 e

2.2.4 Physical Measurements Arrays 2-37 ill

2.2.4.1 Field Survey 2-37 i

2.2.4.2 Laboratory/Data Analyses 2-40 I

2.2.5 Sediment Measurement Rods 2-40

2.2.5.1 Field Survey 2-40 i

2.2.6 Particle Transport Modeling 2-41

40

PROCESSES 2-43 i

2.3 CHEMICAL

2.3.1 Field Surveys 2-43

lgW

2.3.1.1 Surface Sediments 2-43 ;d

2.3.1.2 Surface and Subsurface Sediments 2-44 |

2.3.1.3 Suspended Particles 2-44

2.3.1.4 Platform Samples 2-45 m

2.3.1.5 Quality Assurance/Quality Control 2-45 I

2.3.2 Laboratory Analyses 2-45

2.3.2.1 Hydrocarbons 2-46 i

2.3.2.2 TraceMetals 2-47 I

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I 2.3.2.3 TotalOrganicCarbon 2-47

2.3.2.4 InorganicCarbon 2-48

I 2.3.2.5 2.3.2.6 Grain Mineralogy /Particle Size Distribution 2-48 2-48

2.3.2.7 TotalDryWeight(Flux) 2-48

I 2.3.3 DataAnalyses 2-49

2.4 BIOLOGICALPROCESSES 2-50

i 2.4.1 Hard-BottomCommunityAssessment 2-50

2.4.1.1 FieldSurvey 2-50

2.4.1.2 LaboratoryAnalyses 2-52

I 2.4.2 LarvalExperiments 2-54

2.4.2.1 InSituExperiments 2-54

i 2.4.2.2 Toxicity Tests 2-57 2.4.3 Reconnaissance of Anchor Scar/Drill Cuttings Effects 2-63

2.4.3.1 FieldSurvey 2-63

i 2.4.3.2 Laboratory/Data Analyses 2-63

t chapter3

INTEGRATION 3-1

I 3.1 OVERVIEW 3-1

3.2 CONCLUSIONS AND INTEGRATION 3-3

I 3.2.1 3.2.2 Phase PhaseIIIIIOResults verviewandIntegration 3-3 3-6

I chapter4

I RECOMMEND 4.1 ATIONSPHYSICAL PROCESSES 4-1 4-1

4.2 CHEMICALPROCESSES 4-3

4.3 BIOLOGICALPROCESSES 4-4

t BiologicalCommunityStudy

4.3.1 4-4

4.3.2 InSituLarvalExperiments 4-4

i 4.3.3 ToxicityTests 4-6 4.3.4 ROVReconnaissance 4-6

I REFERENCES REF-1

m ..,

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APPENDICES I

A PHYSICAL OCEANOGRAPHY A-I i

(Currents, Waves, Tides, Wind, Satellite Imagery, Physical W

Measurements Arrays, and Particle Transport Modeling) ! B CHEMICAL MANUSCRIPT B-1 '

(PlatformDischarges, Sediment and SuspendedParticles

Chemistry, and Particle Fluxes) l

C IN SITU LARVAL EXPERIMENTS AND LABORATORY C-1 /

TOXICITY TESTS MANUSCRIPTS i

D - BIOLOGICAL COMMUNITY MANUSCRIPT D-1 I

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| TABLES

t page

I Table ES-1. Summary of DOI Phase III Objectives and Methods. ES-2

i Table ES-2. Summary of DOI Phase IIT Results and Conclusions. ES-9

Table 1.1-1. Summary of Drilling Activities in the General Phase IT

i (Steinhauer and Imamura 1990) and Phase III Study Region. 1-4

i Table 2.2-1. Current Meter Mooring Deployment Information, DOI Phase III. 2-23

i Table 3.2-1. Among Comparison Studyof Sites, Predrilling DOIPhase and During-Dril 111. ling Period Impacts 3-7

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FIGURES

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Figure ES-1. General Location of DOI Phase I, Phase II, and Phase III !

Studiesin the Pt. Conceptionto Pt. ArguelloRegion. ES-4

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Figure 1.1-1. General Location of DOI Phase I, Phase II, and Phase III

Studiesin the Pt. Conceptionto Pt. ArguelloRegion. 1-3 i

't

Figure 1.3-1. Hierarchical, Conceptual Model of a Marine Ecosystem

Consisting of Physical, Biological, and Chemical Subsystems: R

DOIPhaseIII. 1-6

Figure 1.3-2. Interrelationshipof Study Components: DOI Phase III. 1-9 i

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Figure 1.4-1. Summary of Discharge Volumes from the Santa Ynez, San

Antonio, and Santa Maria Rivers During Phase Ill (water years I

1987-1990) and Phase III (water years 1991-1994). 1-11

Figure 2.1-1a. Summary of DOI Phase III Survey Activities and Sampling: i

PhysicalProcesses. 2-2 J

Figure 2.l-lb. Summary of DOI Phase III Survey Activities and Sampling: i

PhysicalandChemicalProcesses. 2-4 II

Figure 2.1-1c. Summary of DOI Phase III Survey Activities and Sampling: I

Chemical Processes. 2-6 m

Figure 2.1-1d. Summary of DOI Phase III Survey Activities and Sampling: I

BiologicalProcesses-ROVSurveys. 2-8

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Figure 2.1-1e. Summary of DOI Phase III Survey Activities and Sampling: i

BiologicalProcesses-LarvalExperiments. 2-10

Figure 2.1-2. Interrelationship of Methods and Data Types Collected for i

DOIPhaseIII. 2-12

Figure 2.1-3. Approximate Location of Biological Community Study Sites I

(PH-E through PH-W), Primary Current Meter Mooring (P),

Variable-Location Current Meter Moorings (S1-$6), and il

Platforms,DOIPhaseIII. 2-13 |

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t Figure 2.1-4. Approximate Location of Sediment Trap and Van Veen

Sample Collection Sites Relative to Hard-Bottom Features

I (PH-E through PH-W), Primary Current Meter Mooring (P), Variable-Location Current Meter Moorings (S1-$6), and

I Platforms, DOI Phase III. 2-14

Figure 2.1-5. Approximate Location of Larval (Filming) Mooring, Larval

i (Igloo) Meter Mooring Array, Physical Measurements Arrays, Primary Current (P), and Variable-Location Current Meter

Moorings ($1-$6), DOI Phase III. 2-15

I Figure 2.1-6. Approximate Location of Radial Arrays of Box Core Sampling

Stations for Platforms Hidalgo, Harvest and Hermosa, DOI

i PhaseIII. 2-16

Figure 2.2-1. Schematic of Moorings Deployed as Part of the DOI Phase III

I Program. 2-25

Figure 2.2-2. Example of the Effects of Depth on Wind-Wave Attenuation

i at the Bottom (138 m). 2-31

Figure 2.2-3. Representative Composite Satellite Thermal Image of the

PhaseIIIStudyArea. 2-35

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ABBREVIATIONS, ACRONYMS, AND CONVERSIONS

I

The following is a list of abbreviations and acronyms used in the report. A table of metric .i

equivalents is included to allow conversions from metric to U.S. units.

t

AdvancedVeryHighResolutionRadiometer AVHRR n

aluminum A1 g

analysisof covariance ANCOVA

analysis of variance ANOVA I

arsenic As 'N

barium Ba

beryllium Be i

cadmium Cd

centimeter cm Iim

chlorite and smectite C/S

chromium Cr

chrysene C

circa ca. i

coefficient- ofVariation CV

cold vaporatomicabsorptionspectrophotometer CVAAS al

copper Cu I

cubicentimeter cm3

cyclesperday cpd i

DataManagement System DMS |

degrees Celsius (Centigrade) °C

Department of the Interior DOI IN

dibenzothiophenes D J

dry weight dry wt

empiricalorthogonal function EOF m

EnvironmentalProtectionAgency EPA m

feet ft

flameatomicabsorptionspectrophotometer FAAS I

flame ionizationdetector-gaschromatography FID-GC

fluorenes F

gallonsperday gpd n

gas chromatography/mass spectrometry-selected ion monitoring GC/MS-SIM

GeneralOceanics GO

globalpositioningsatellite GPS n

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gram g

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| ABBREVIATIONS, ACRONYMS, AND CONVERSIONS

(cont'd.)

I grams per cubic centimeter g/cc

grams per square meter per day g/m2/day

I graphite greaterthan furnace atomic absorption spectrophotometer >GFAAS

greaterthanorequalto >

I higher HourLown-alkanes Pas HALKLP

illite and smectite I/S

I inch instrumentalneutronactivationanalysis inINAA

iron Fe

I kilometer kilogram kgkm

laboratorycontrolsample LCS

i lead Pb lessthan <

lessthanorequalto <

I liter L lower n-alkanes LALK

mean _

I MEC Analytical Systems, Inc. MEC

mercury Hg

meter m

I methylene DCM chloride

micro #

micr micrograms ogram #g /gram #g/g

micrograms/kilogram /_g/kg

i micr micrometer ograms/liter /#mzg/L

milligram mg

i milligrams milligrams//gram kilogram mg mg//gkg

milligrams/liter mg/L

I miillimeter lliliter mLm

milliongallonsperday MGD

I Minerals Management Service MMS nanogram ng

| ix

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ABBREVIATIONS, ACRONYMS, AND CONVERSIONS |

(cont'd.) 1

nanograms/gram ng/g t

naphthalene N

NationalBiological Service NBS I

NationalDataBuoyCenter NDBC Ii

National Oceanic and Atmospheric Administration NOAA

NationalWeatherService NWS a

nickel Ni I

opticalbackscattersensor OBS

Outer Continental Shelf OCS i

phenanthrenes+anthracenes p B

physicalmeasurementsarray PMA

phytane Ph i

polycyclicaromatichydrocarbon PAH

pound Ib

pounds per day lb/day t

practicalsalinityunits psu

JIB

principalcomponentanalysis PCA

pristane Pr i

relativepercentdifference RPD

remotelyoperatedvehicle ROV

quality assurance/quality control QA/QC i

Ryan-Einot-Gabriel-Welch Quotient REt3WQ

SanDiegoStateUniversity SDSU i

Science Applications International Corporation SAIC |

ScrippsInstitutionofOceanography SIO

sea surface temperature SST i

second see |

secondssquared see2

sedimentmeasurement rod SMR i

sediment trap ST g

silver Ag

SmartAcousticCurrentMeter SACM ,i

species sp |

species(morethanone) spp

squarecentimeter cm2 _1[

squarekilometer km2 i

squaremeter m2

standard std i

StandardOperatingProcedure SOP

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ABBREVIATIONS, ACRONYMS, AND CONVERSIONS

(cont'd.)

I Statistic Analysis System SAS

suspendedmaterialconcentration SMC

I temperature Texas A&M University/Geochemical and Environmental Research Group TTAMU/GERG

totalhydrocarbons THC

I total n-alkanes organic carbon TALK OC

University_ of California Santa Barbara UCSB

i University unresolvedofcomplex Connecticut mixture UCONN UCM

vanadium V

_ weight Western wt InstrumentCorporation WIC

wet weight wet wt

I X-ray diffraction XRD zinc Zn

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ABBREVIATIONS, ACRONYMS, AND CONVERSIONS

(cont'd.) 1

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Metric System With U.S. Equivalents

Metric Unit U.S. Equivalent I

Length

millimeter (mm) 0.04 inches I

centimeter (cm) 0.39inches

meter (m) 39.37 inches/3.28 feet I

kilometer (kra) 0.62 miles

Area I

square centimeter (cm2) O.155 square inches

square meter (m 2) 1.196 square yards i

squarekilometer(km2) 0.3861squaremiles

Weight I

milligram (mg) 0.015 grains I

gram(g) 0.035ounces

kilogram (kg) 2.2046 pounds I metric ton (MT) 1.1 tons

Speed i

centimeter/second 0.0194 knots

Volume I

cubic centimeter (cm 3) 0.0611cubic inches I cubicmeter(m3) 1.31cubicyards

Capacity, Cubic I

milliliter (ml) 0.06 cubic inches

liter (1) 61.02 cubic inches I

kiloliter(kl) 1.31cubicyards

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xii I
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I

II EXECUTIVESUMMARY

I

I 1.0 INTRODUCTION

I The Department of the Interior (DOI), Minerals Management Biological Service/National Service

has been performing long-term studies in the Santa Maria Basin, offshore southern California,

i since and development 1983 to determine activities. potential The impacts present tostudy, the benthic entitled environment "Monitoring fromAssessment oil and gas of Long-Term production

Changes in Biological Communities in the Santa Maria Basin: Phase III", was conducted by

i Science Contract Applications No. 14-35-0001-30584. International Other Corporation key team(SAIC; members San Diego, includedCA)MECfromAnalytical 1991-1995,Systems, under

Inc., University of California Santa Barbara, University of Connecticut, and consultants Ms.

I Suzanne Quality Review Benech,Board Dr. Joseph membersConnell, were Dr. Drs. Paul DonaldDayton, Boesch, Dr. Mick Keough, and Dr. Jerrold Zar. James Brooks, Roger Green, Judith

McDowell Capuzzo, and Clinton Winant.

The initial; Phase I, program focused on defining baseline environmental conditions and

providing recommendations of long-term study sites for hard-bottom communities in the southern

I Santa Maria Basin (SAIC 1986). Phase II (Steinhauer and Imamura 1990; Hyland et al. 1994) initiated monitoring of physical, chemical, and biological processes at nine selected study areas

in the vicinity of Platforms Hidalgo, Harvest, and Hermosa during predrilling, during-drilling, and

I post-drilling periods. The Phase III study extended long-term monitoring at these sites, but focused additionally on physical and chemical processes that can affect natural and dischargerelated changes in the biological communities.

t Specific objectives of the Phase IT[ program were to:

I • better understanding of the environmental fate and effects of chronic, Develop a

low-level discharges of drilling wastes and their potential for long-term and/or

i cumulative impacts to hard-bottom communities; and

• Improve knowledge of the processes controlling changes in the communities.

I Specific tasks to fulfill these objectives included continuation of Phase II studies on ocean

currents, waves, and tides; sediment grain size and chemical contaminants; particle fluxes; and

I photographic (Table ES-1). documentation New tasks for Phase of thel]-Idistribution focused onandin situabundance larval settling of hard-bottom experiments;communities laboratory

I ES-1

I
+ I

+_,_ +,+ _. .,_o

= +--"''+ _:__ |

0 o,-., +_ "_ _ =. " 0 >' _

I

..+_ ++++ - .m+

-' +_++!m I

+++ -+ + I

• ., _ = _+= m + _E o : +-, m-,-+-," _ _:+ .::,,. _ .

_ +.-++_ ': _-- _ _: _ _ _ _ -= _ _ .- ,,-,

°+° +-°-+-+-+'" + ++ I

• + _ • +,.c:,m ,+.,+• + ;=:_ £ _ m.='_. •

,_....,

..,+,_,.= 0 .'_ + '_

+==+.+ +, ++_,=._ ++=+.m_-.+o+

_C_ ," ,_-_ u..a m -- _°: ,.._. _ += -:.== .+ + I

:-' <.++o= o: o_,_

_p='_ o" +=--_ _ _ _+ _ _-' mI-" m_' _ 0 'I-':

_ _ _, ".-- _ ," _ ._ __ _ ...._ ..+,.-. _, ,,.,.o_ = - _ _ +:=_-_'_'_

--++, o.= ++ •

I

= +_ ++ !I .+

_ _P.. +.,+, .- " 8+ .. .- + _ +=

- _-.=_ _ _ "m=°- _ m

° +_+++++

l

:m_ ==__ _ ++_ ++ _ _--' _ m

C_ _ _ _

• _ _._-++ • .-+_ _o _ -_- I

O ._ m)

.. om -+.+m _+ m _ o.=+m

+ o+++ +m ++-,+++++II

o+++ +_+_. +++ " +-

_, ._+.++ ?- yo+ oo o

I

:_ = ._= n

o .l m

ES-2 I
I toxicity tests; near-bottom current measurements; assessment of the distance over which regional

currents are similar; sediment resuspension; and additional measurements of particle fluxes at

I high- and low-relief heights (Table ES-1). The overall Phase III study design included assessments of (1) post-Phase II drilling impacts, and (2) drilling and post-drilling impacts during

Phase III.

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2.0 METHODS

I

I The field Phase surveysIIIfocused programonwas nineconducted hard-bottomfromsitesOctober near Platform 1991 through Hidalgo,November with additional 1995. sediment Thirteen

collections and larval settling experiments performed near Platforms Harvest and Hermosa

i (Figure ES-1). Survey depths ranged from approximately 90--215 m.

Six general tasks were conducted for the program, ranging from physical oceanography and

i characterizations documentation of changes of chemical in biological contaminants communities, in sediments larval settlement and suspended patterns, andsediments laboratoryto

toxicity tests (Table ES-1).

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2.1 PHYSICAL OCEANOGRAPHY

I

Physical oceanographic studies included current meter measurements at the same (primary)

I mooting location near Platform Hidalgo that was used during Phase II, as well as at a secondary, variable-location mooring that was moved quarterly to biannually within a few to several

kilometers from the platform. The primary mooring used three Smart Acoustic Current Meters

I (SACM) at of 14, 53, and 125 and back-up General Oceanic (GO) Mk2 meters at 1

depths m,

m below the main instruments. The mooring also had a Sea Data wave/tide recorder attached

to a secondary anchor. The secondary mooring normally was outfitted with GO meters

(representing onlyextrameters were available) (2-3) depth

the that that varied in number and

depending on the mooring location. The moorings, including the bottom anchor weights, were

i recovered for periodic servicing and data recovery using an acoustic release system.

Supporting satellite data for the current meter deployment periods were obtained from the

i NOAA- Weekly 11composite Polar Orbiting Satellite Advanced Very High Resolution Radiometer (AVHRR). images subsequently were prepared from these data.

I Specially (igloo-shaped) designedsteelPhysical frame, Measurements into which anArrays $4 current (PMA),meter, initiallytwoconsisting optical backscatter of a hemispherical sensors

(OBS), and sediment traps were secured, were used to document near-bottom currents, sediment

I resuspension Concerns aboutevents, interference and particle from thefluxes, framerespectively, with current formeasurements the first twosubsequently years of theresulted program.in

I ES-3

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I

I I

"i i :i Ii ; i i i -"i i _!iii _:I I I II''" _ r I I _ _ • ° __)

.............. iiii,,'" I • -(_ •

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tii..... : ''-- / , I

.......... :::;y ,,, ,•I <Zo •,, == -@

,--,

:::::::::. • | •

........... " ': /' II Ill:l:.:.:,:," I ! I II =

II

• | / I •

. . . .g

g . ,, . | ,.., -

/I l/ I sl "_ "1 _ _l)

• I • I / • "¢_

_' # • I • #

I.- _.... _/ _ _ I/ •, _, I_ ?: ==

I , , , I , = _ :=

_ """ ; : / ' " - _ I

•, .; ',_ . : / • ,,' _ ._

I _ I • • I

I_ m O. • n • / " "_

I ,,, _ _v _, z .,! - _ -_ _ l

. , _ .+= ,, _ -_ ./ _X\_ o _ _- .._ _, | : -.-..-,,_ a_. _ ,, _ :_

i

/ _ _ _ _-mE/ ,, c _.

l ..'" :I" / 4l_ ,' _,"

. , _u_ ,_ _., ; [] !1

/ .-'" _'_ i, _--'" : _ -- I-- ./" .k k'_, / __ .--" ._

I ., 8-_ = . __. "_ ,. = I

I ,/ \_ _ "' "_:- : ," "_ I ,'\ _d _ ,'_ _, ," I / I _ ,, _: ,, m

l-- / _1_ ." n , i

/ .. ÷11 ,, , |

/ .--" _w / ,,"

_-. ..,...._ ,,." ,,." _-

l- '"........ " ' _ _ |

",, ,,, .._ _ ._

,. / ,.- ..- ._

", "-. , .--. ,' ._ = _ -- _

,, "--'1_'-, ", ., , • _ _ =

,-, , %.'_..._ ", "- ." + * . "_ .- III _ .

, .. . _ ,_.., _....._ _ _=_I •, ,, ... # _,_ "... ,, _ z,, ._ -, = "_ ..9= o_

- ,,,...-" _ ",, ==_ _ -_=

! ',-.... - "INII ___

- ; / i,=,,-, _ _ >,_

/ """ _') 0

I

ES-4 I

II
!

t a redesign of the PMA to an in-line configuration for the third year. One PMA each was located

at approximately 200 m depth at a nearfield and a farfield location relative to Platform Hidalgo.

I Particle fluxes and sediment resuspension are discussed additionally in Section 2.3.

I 2.2 SEDIMENT PHYSICAL AND CHEMICAL PROPERTIES

I Surface sediments were sampled for physical (grain size and mineralogy) and chemical (total

organic carbon, trace metals, and hydrocarbons) analyses using a 0.1 m2 Van Veen grab. The

samples monitoredwere for biological collected community from nine changes stations (Figure adjacentES-1). to theSurface hard-bottom and subsurface features(10--12 that were cm)

sediment samples also were collected using a 0.015 m2 box corer at a radial array of stations near

I Platforms produced water Hidalgo, wereHarvest, obtainedandfromHermosa. the platformRepresentative operators for samples comparisons of drillingwithmuds, the sediment cuttings, and

particle flux and modeling data (Section 2.3). A sample of a petroleum product (diluent) from

I the comparison Guadalupewithoilsediment field alsoandwasparticle obtainedsamples from thefromCalifornia the PhaseDepartment III study area. of Fish and Game for

I Grain size analyses were performed by first separating gravel and sand particles from the samples using decreasing sieve sizes, followed by pipette analysis to determine the silt-clay fractions.

Data were expressed as percentages of gravel, sand, silt, and clay. Mineralogy analyses were

I conducted by smearing < 4 micron size particles on microscopic slides, followed sequentially by air drying, glycolation, heat treatment, and X-ray diffraction analysis. Total organic carbon

content was determined using an infrared spectroscopy method.

I Trace metal chemical analyses (except barium) consisted of a strong acid (nitric and hydrofluoric)

digestion, followed by flame atomic absorption spectrophotometry (AAS) for aluminum and

I chromium; graphite furnace AAS for arsenic, silver, cadmium, copper, lead, nickel, and zinc; and cold vapor AAS for mercury. Barium (Ba) concentrations were measured by irradiation with a

Triga Reactor and instrumental neutron activation analysis.

I Hydrocarbon analyses involved Soxhlet extraction of the samples followed by chromatographic

separation using silica gel. Final extracts for saturated n-alkanes and selected isoprenoids and

I polycyclic aromatic hydrocarbons (PAHs) were then concentrated and analyzed by flame

ionization detector-gas chromatography (FID-GC) and gas chromatography/mass spectroscopyi selected ion monitoring (GC/MS-SIM), respectively. Analyses of selected samples for saturated biomarkers (terpanes and steranes) also were performed using GC/MS-SIM.

i Statistical and temporal analyses trendsincluded and relationships linear regression, betweent-tests, the physical and analysis and ofchemical variancevariables. to evaluateFurther, spatial

patterns of excess Ba (as an important surrogate of drilling mud discharges) in sediments was

I calculated concentrations, from and the platform then interpolating radial arraythedata resultsby subtracting over the nearfield the background region offromthe platforms. the measured

I ES-5

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2.3 PARTICLE FLUXES AND SEDIMENT RESUSPENSION

I

Suspended particles were collected from sediment traps, each of which had four, 1 m high III

collection tubes, located near each of the nine Van Veen sediment sample and hard-bottom sites. I!

The traps were bottom-oriented and recovered using an ROV. Samples from the traps were

analyzed for trace metals, hydrocarbons, total organic carbon, and grain size using the same

methods as noted in Section 2.2. Statistical analyses of these data also were performed using II

methods similar to those described for sediment samples. Additionally, principal component

analysis was used to compare selected hydrocarbon components (PAHs, sterane, and terpane m

biomarkers) from diluent and crude oil samples with concentrations in sediment trap samples. I!

A particle ti'acking model was used to predict the thickness of drilling material discharges on the am

bottom and the size of the area over which it is distributed. The Phase III model separately im

tracked three size classes of particles (coarse sand, coarse silt, and clay-silt) using current data

from multiple mooring locations, as compared to modeling using only one size class and a single i

mooring during Phase II. Data for compositions of the three size classes were based on analyses I

of drilling mud samples from the platforms. Based on the available current meter data, the

accuracy of the dispersion and deposition estimates decreases with distances from the moorings

of 10-20 and 5-10 kilometers in the along- and cross-isobath directions, respectively.

2.4 HARD-BOTTOM COMMUNITIES I

I

A remotely operated vehicle (ROV) was used to collect photographic and video data of the

biological communities inhabiting high- and low-relief features at the nine hard-bottom sites, m

Photoquadrats representing a 1 m2 surface area were taken randomly using a 70-mm or 35-mm I

camera that was oriented using dual lasers on the ROV to standardize the offset distance from

the feature (and thereby the surface area). In high-relief areas the camera was oriented in a i

forward-looking direction, while a downward-looking angle was used for low relief. The study I

planned for the collection of 60 photoquadrats in each relief category at each site. However,

after the photoquadrats were reviewed to exclude poor quality (e.g., low water clarity) slides a Im

total of 476, 815, and 744 photographs were used for analysis from surveys in 1991, 1992, and II

1994, respectively. The color video camera, used to document broader-scale community features

than typically are possible using photoquadrat data alone, was angled at approximately 45 degrees i

from the bottom. I

Laboratory analysis of the photoquadrats was done by projecting color slides at life size (1 m2)

onto a 50 dot, point contact grid. The species or substrate type that was contacted by each dot I

was then recorded on coding sheets to provide percent cover estimates. Counts of all taxa in

each slide also were recorded, regardless of whether they were contacted by a dot. Video i

analysis included species presence-absence determinations along non-overlapping band transects.

ES-6 i

!
I The transects represented approximately 20 one-minute video segments of the different relief

categories within each study site.

I Statistical analysis included multivariate cluster analysis to distinguish community types,

correlation of abundance with physical and chemical variables to evaluate potential cause and

I effect relationships, linear regression to evaluate trends in abundance over time, and analysis of covariance to determine changes in abundance with distance from Platform Hidalgo. Power

analyses also were performed to determine the statistical ability to detect significant decreases

I in coverfor dominanttaxa.

percent

I 2.5 LARVAL SETTLING EXPERIMENTS

Two types of in situ larval settling experiments, focusing on manipulated red abalone (Haliotis

rufescens) and natural colonizers, were performed at one nearfield and one farfield site adjacent

I toeacheachexperiment, of the threeplexiglass platformssettling duringplates predrilling were exposed and during in /thepost-drilling field at eachtimesiteperiods. to allow Prior naturalto

microbial films to become established. Reciprocal transplants of the filmed plates between the

I sites filmedwereplates then were performed attachedto determine to speciallythe potential designed effect hemispherical on settlement. steel For framesthe experiments, (igloos) and

deployed to the sea bottom (approximately 200 m depth). Plates were attached to the igloos at

I both acoustichigh-release and /low-relief pop-up buoy heights. system. Recovery The of redtheabalone igloos studies normallywere was conducted accomplishedby using injectingan

precompetent (ready to settle) larvae into holding chambers attached to the igloos. After three

I days settleddeployment on the bottom the red abalone experiments were recovered and the number of larvae was determined. For the natural settlement experiment, larvae that settled naturally

on the plates were identified and quantified over exposure periods extending from 3 to 1,000

I days.

Statistical analysis of the red abalone data was performed using a fixed effect analysis of variance

I procedure to determine potential drilling-related impacts. Analysis of variance also was used for the natural settlement studies to address waterborne and relief height effects relative to the

i drillingperiod.

I 2.6 LABORATORYTOXICITY TESTS

I Toxicity stearnsii) tests adultson were red abalone conducted(gametes, using azygotes, series ofanddrilling larvae)mudanddilutions brown cupfromcoral0.002(Paracyathus to 20,000

mg/L. Final experiments focused on concentrations greater than 200 mg/L because preliminary

I laboratory red abalone experiments tests assessedindicated fertilizationno toxicity success; effects zygote atdevelopment; concentrationsandlesssurvivorship, than 200 mgsettlement, /L. The

I ES-7

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and viability of larvae. The settlement experiments included evaluations of the potential m

interference of drilling mud with a natural inducer of settlement, specifically, coralline algae

crusts that are known to induce red abalone larvae to settle. For the brown cup coral experiments •

the endpoints were survivorship and tissue loss of adults. w

analyses used toxicity data expressed as percent fertilization, survivorship, etc. I

Statistical

compared to a control. Types of tests included regression an_dysis and, for the cup corals,

analysisofcovariance. R

3.0 RESULTSANDCONCLUSIONS IF

Results and conclusions from the Phase III monitoring program are summarized in Table ES-2 Ill

and detailed in Sections 3.1-3.3. II

3.1 PHYSICALPROCESSES i

I The study area is located in a dynamic physical oceanographic regime that is subject to strong

waves and currents associated with various cross-over regions of the California Current System

and exposure to Pacific storms. Because of this, the water column is well mixed to •

approximately 100 m bottom depths and can result in resuspension of sediments that are

w

transported along and across the shelf. Sediment transport events below these depths also can

be substantial; however, they do not appear to be caused by surface winds and waves, and likely g

are due to cross-shelf movement of material from shallower regions. Rainfall runoff from land

is one likely source. The significantly greater rainfall and river discharge volumes, as well as m

presumed sediment transport, during Phase III as compared to drought conditions during Phase II

II may have contributed to some of the differences in the biological communities (e.g., decreasing

trends in abundance for some species; see Section 3.3) noted between phases, i

Current measurements from the primary and secondary moorings indicated that flows were

predominantly upcoast during summer and winter and downcoast during spring; however, there •

was substantial variability in the timing and intensity of these patterns among phases and years. II

Eddies and meanders contributed to this variability and likely influenced the small scale (from

a few to several kilometers) of similarity in currents between the primary and secondary am

locations. II

Large spatial and temporal variability was also reflected in the timing and size of near-bottom

sediment transport events, although as noted above transport in deeper locations was not related II

to local wind and wave events. Near-bottom concentrations of suspended particles typically were

low (e.g., 1-5 mg/L) but aperiodic events were associated with suspended particle concentrations i

up to several orders of magnitude higher. Consistent with these general trends, data from IW

ES-8 i

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_-_ <,_E_ ,_ _,, _._+-. ,. ,,_-_c:_"__= _ _ _ I_ m <" •

t

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ES-IO I
!

I sediment traps indicated that particle fluxes were higher at shallow compared to deep stations.

Further, the sediment traps at different relief heights on the PMAs indicated that fluxes were

I approximately 25-65% higher at low- compared to high-relief heights. These types of differences also may be reflected in some of the differences noted in the biological communities (Section

3.3).

I Results from the particle tracking model were reflective of the dynamic current regime in the

study area, as well as the relatively shallow discharge depth (35 m, equating to at least 100 m

I bottom) relatively small discharge volumes. These calculations predicted only very

above the and

thin layers of accumulation on the bottom (average of 1.5-7.5 microns), representing a very large

footprint area for fine-grained materials (approximately 100-550 square kilometers). Thus, it

I appears unlikely based on these conclusions that particulate contaminants from the platform

discharges (also see Section 3.2) would cause significant impacts to hard-bottom communities.

!

3.2 CHEMICAL PROCESSES

!

Analysis of sediment and sediment trap (suspended particle) data indicated that the only residual

I Phase II drilling effects, prior to the onset of Phase III discharges, were slightly elevated Ba

concentrations in bottom sediments, primarily near the platforms. No increases above

background concentrations were evident for other metals or petroleum hydrocarbons, although

I non-drilling related increases in low molecular weight PAHs were noted at a few stations during the October 1991 survey. These latter increases-were potentially attributable to a land-based spill

of a petroleum product (diluent) from a site located approximately 50 km north, in addition to

I natural seep and anthropogenic combustion products.

The only Phase 111drilling period effects were slight increases in Ba in suspended particles at

I three sites near Platform Hidalgo. ResidualBa from Phase II the three discharges near platforms

also were evident at concentrations up to an order of magnitude above background. This general

lack of effects for other contaminants is consistent with their low concentrations in the

I discharges,the solubilityof lowermolecular PAHs, natural of weight large variability background

hydrocarbon concentrations, low discharge volumes (only 10% of the Phase U discharges), and

i apparently high dispersion of this material by dynamic oceanographic conditions (Section 3.1).

i 3.3 BIOLOGICALPROCESSES

I 3.3.1 Biological Community

I The combined data from Phases II and III indicated a diverse hard-bottom epifaunal community having at least 286 taxa dominated by cnidarians (cup corals, colonial corals, sea fans, anemones,

I ES-11

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and hydroids), echinoderms (particularly feather stars, seastars, and brittlestars), and sponges, i

Primary and secondary determinants of community composition are water depth and substrate

relief height, respectively. Taxa characteristic of shallow depth sites (105-119 m) included

several species of cup coral and seastars, while deeper sites (160-212 m) were typified by other I

corals and seastars in addition to various sponges, anemones, and basketstars. Species that

occurred broadly over the full depth range included brittlestars, large anemones (Metridium), i

feather stars, and tunicates (sea squirts). High-relief (> 1 m) taxa were characterized by filter w

and particle feeders such as sponges, basketstars, and some corals; low-relief (0-1 m) organisms am

included ophiuroids, and some anemones, cup corals, and seastars. It is theorized that many of i

these patterns are influenced by relative tolerances for particles fluxes and sediment movement

(shallow and low-relief habitats are subjected to higher loading), although direct evidence for i

these relationships are not presently available. l

The rank order of dominance of most hard-bottom taxa was relatively stable over time as am

compared to periods of Phase II and Phase III drilling discharges and distance from Platform l

Hidalgo. However, analysis (linear regression) of temporal trends for common taxa indicated that

35% exhibited decreasing abundance (percent cover), although there was no consistent, platform- I

related pattern for any one taxon. Other statistical analyses (analysis of covariance and Chi- |

square contingency analysis) to test for changes in abundance with distance relative to the

platform indicated that the combined positive and negative trends may be due to chance alone. III

Therefore, there did not appear to be any statistically significant, large-scale impacts from the II

discharges. These conclusions are undoubtedly influenced by apparently large natural variability

in the hard-bottom communities and the low statistical power to ,rletect changes using present, i

random photoquadrat techniques. The statistical power to detect significant (_ = 0.05) decreases g

in mean percent cover for 15 dominant taxa was 50% or gre,ater for only 14 out of 57

combinations of the taxa and three habitats (deep high- and low-relief and shallow low-relief). •

Increases in the number of photoquadrats per habitat and site,, would improve the power Ill

somewhat, but it is recommended that future studies also incorporate sampling at fixed in

additiontorandomlyselectedstations. I

These conclusions are consistent with the lack of any apparent large-scale physical/chemical

impacts from the particulate components of the discharges (Sections 3.1 and 3.2). However, the i

trends in decreasing abundance noted for some taxa may represent more subtle, long-term effects. w

The platform-related mechanism(s) for such effects, if they occurred, are presently unknown but

are not obviously related to particulate discharges or, based on substantial initial dilution and R

mixing of aqueous discharges, with produced water. Nonetheless, the monitoring studies to date

i

have not focused directly on dissolved contaminants associated with the discharges, although a

other field studies (e.g., Krause 1995) have concluded that impacts to larvae can result from i

exposure to produced water.

I

!

ES-12 I

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I 3.3.2 In Situ Larval Experiments

I Results from the in situ experiments indicated that natural microbial filming of the larval settling

plates was important to achieve optimal settlement, regardless of the type of experiment.

I Manipulated red abalone larvae were associated with significant decreases in settlement at nearfield stations during Phase III drilling periods. However, natural settlement was not

significantly affected by the discharges. Common taxa from the natural settling experiments

I included a bivalve, two bryozoans, two hydroids, a colonial protozoan, and a tube worm.

Preferences by some taxa were evident for high- versus low-relief settling heights; these results

provide a important example of early settlement patterns that may produce later community

I differences. Very low natural settlement (only 9 of approximately 50 taxa occurred on even 5%

of all plates) undoubtedly limited the ability of these experiments to detect potential impacts.

i This abaloneemph_isizes studies, intheassessing importanceimpacts of controlled to larval field communities. experiments, such as represented by the red

I 3.3.3 Laboratory Toxicity Experiments

I Laboratory experiments on two hard-bottom species indicated that the fertilization mechanism

and early development stages of red abalone were not affected by exposures to used drilling

I muds. In contrast, the ability of larvae to respond to a natural inducer of settlement (coralline algae crusts) was significantly reduced. Further, adult brown cup corals also were significantly

impacted due to progressive tissue loss and mortality following exposure to the drilling muds.

I These types of effects may suggest a mechanism for impacts to hard-bottom communities through reductions in recruitment of some larvae and direct impacts to some adults. However, as noted

above the specific cause of the effects is still unknown, suggesting that additional studies may

I be appropriate for example, effects from dissolved chemical contaminants. on,

I 4.0 OVERALLCONCLUSIONS

I Conclusions from the Phase II and l]I studies did not indicate severe, large-scale impacts to the

hard-bottom communities from platform drilling discharges, although possible effects to larvae

i could in particularnfluenceprovided some long-term deep-watertrends data infromabundance a uiqueandsetspecies ofn situcomposition. experiments.TheHowever, larval studies any

effects that may have occurred to larvae or adults appeared to be subtle and limited to nearfield

I (within significantapproximately decreases inonethekilometer) abundanceregions of dominant of the platform. hard-bottomLowtaxastatistical was influenced power tobydetect the

combination of high natural variability and the reliance on random photoquadrat field methods.

I Use The of both fixed location and random sampling should improve the ability to detect change. drilling-related mechanisms that may cause impacts to larvae and adults are not obviously

I ES-13

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caused by the particulate fractions of the discharges. However, based on other field and I

laboratory studies, effects from dissolved fractions may be important to address.

! The long-term studies represented by the combined Phase I - Phase III programs provide a

growing but as yet incomplete picture of the full life-cycle and potential effects from oil and gas

production and development activities in the Santa Maria Basin. Presentation of the majority of I

the Phase III results and conclusions in the form of manuscripts for publication represents the

literature.high interest of DOI in making these continuing studies broaclly available in the primary I

!

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ES-14 I

I
m_

II._L
I

I chapter 1

I INTRODUCTION

I

I 1.1 OVERVIEW

I This report presents the background, results, and conclusions of the U.S. Department of the

Interior (DOI), National Biological Service (NBS)/Minerals Management Service (MMS) program

I on "Monitoring Assessment of Long-Term in Communities in the Changes Biological Santa Maria

Basin: Phase III." The program was conducted by Science Applications International Corporation

(SAIC) between 1991 and 1995 under Contract No. 14-35-0001-30584. Primary subcontractor

I support was provided by Analytical Systems, Inc. (MEC), the University of Califomia

MEC

Santa Barbara (UCSB), the University of Connecticut (UCONN), Texas A&M

i University International, /Geochemical and WesternandInstrument Environmental Corporation Research (WIC).GroupAdditional (TAMU/consultant GERG), Oceaneering support was

provided by Ms. Suzanne Benech (Benech Biological and Associates), Dr. Joe Connell (UCSB),

I Dr. Melbourne), Paul Dayton Dr. Jon [Scripps WitmanInstitution (Northeastern of Oceanography University),(SIO)], and Dr. Dr.Jerrold Mick Keough Zar (Northern (University Illinoisof

University). The Quality Review Board was comprised of Dr. James Brooks (TAMU), Dr.

I DJudith onald McDowell Boesch (University Cappuzzoof(Woods Maryland), HoleDr.Oceanographic Roger Green (University Institute), and of Western Dr. Clinton Ontario) Winant , Dr.

(SIO).

I The principal results and conclusions are presented as a series of manuscripts. Each manuscript

is included in an appendix (Appendices B-D) to this report in a format that is consistent with the

I peer-reviewed journal to which it will be submitted for publication. As such, each appendix is self-contained, providing detailed methods, results, conclusions, and references by study task.

In contrast, the first four chapters of the report address the general Phase III program as follows:

I overview, including technical items, hypotheses, and study area description (Chapter 1); synopsis of methods (Chapter 2); integration of study results as presented in the appendices (Chapter 3);

and recommendations (Chapter 4). Appendix A, addressing the physical oceanographic and

I modeling tasks is the only section that is not planned for publication due to the overall descriptive nature of this study segment.

I The Phase III extends the period of research and monitoring initiated in the Santa Maria program

Basin, California, during the MMS Phase I (SAIC 1986) and Phase II (Steinhauer and Imamura

1990) programs. The Phase I program included baseline studies and recommendations of

I long-term study sites for hard-bottom communities in the Pt. Conception to Pt. Arguello region

I 1-1

I,\

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!

n

(Figure 1.1-1) (SAIC 1986). Phase I sites included hard-bottom features in the vicinity of m

Platforms Harvest, Hermosa, and Hidalgo (Figure 1.1-1). The Phase II program initiated

monitoring studies at nine hard-bottom sites near Platform Hidalgo (Figure 1.1-1), focusing on

potential impacts to epifaunal communities from platform discharges of drilling muds (Steinhauer g

and Imamura 1990). The Phase II study included predrilling, during-drilling, and postdrilling iiim

periods, with the last drilling activity from Platform Hidalgo occurring in January 1989 HI

(Table 1.1-1). Drilling from Platform Irene occurred from 1986 through October 1989; however,

its location over 10 km to the north of the study area suggested that these discharges had am

minimal, if any, additional effects near Platform Hidalgo (Steinhauer and Imamura 1990). Other

components of the Phase II program included soft-bottom studies (infauna and sediment

chemistry) focusing on the region of the then-planned Platform Juliius. This platform was to be m

located off Pt. Sal, approximately 40 km north of Pt. Arguello. However, installation was II

delayed indefinitely, precluding meaningful studies in this specific area by MMS for the Phase III

program. N

The Phase III field program, initiated in October 1991 and concluding in January 1995,

represented the continuation of monitoring in the Phase II study region near Platforms Harvest, •

Hermosa, and Hidalgo (Figure 1.1-1). However, based on the extensive Phase II monitoring data |

at the hard-bottom sites near Platform Hidalgo, this platform was the continued focus of Phase

III studies. The overall Phase III study design included assessments of continued (since Phase I

II) "post"-drillingand"during"-drillingimpacts. I1

Drilling discharges during Phase III occurred only from Platforms Hermosa and Hidalgo and

were substantially lower (e.g., factor of two to one order of magnitude) than during Phase II g

(Table 1.1-1). Other differences included much higher rainfall and runoff (and presumably,

natural sediment transport) during Phase 111(Section 1.4), and potential effects near the beginning

of Phase III from a spill of hydrocarbon-based diluent that was discharged from a site U

approximately50kmtothenorth(AppendixB). n

u

1.2 PURPOSEANDGOALS I

The overall purpose of the Phase I, II, and III monitoring programs was to conduct long-term •

studies on the cumulative effects of offshore drilling and production activities on the marine II

environment. Knowledge of the physical, chemical, and biological processes in the study region

is necessary to distinguish background changes and inherent variability from oil- and gas-related

impacts. II

Impacts to hard-bottom communities, particularly epifauna, are of interest because of the greater

sensitivity of many of these species tp increased particulate loads and the generally uncommon

U

occurrence of hard-bottom compared to soft-bottom habitats in the study region (SAIC 1986;

Lissner et al. 1991). Impacts to epifauna can include smothering fi,om sediment movement and

accumulation, and fouling of filter-feeding structures (Lissner et al. 1991). Other potential

1-2 I

!
I

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I 1-3

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Table 1.1-1. Summary of Drilling Activities in the General Phase II (Steinhauer and I

Imamura 1990) and Phase HI Study Region. I

I

Drilling Mud Barite Cuttings I

Platform Period " Discharged Discharged Discharged

(m 3) (kg) (m 3) ..,

I

Harvest I

Phase II 11/86-05/88 16,340 1,844,136 DI

Phase HI ND ND ND ND

I

Hermosa

Phase II 01/87-09/88 16,373 1,470,95:5 3,114 1

Phase m 09/93-11/93 822 84,321 136 m

Hidalgo !

Phase II 11/87-01/89 7,963 1,805,000 2,294

Phase HI 11/93-05/94 3,850 770,000 739 I

I

Irene I

Phase II 04186-10189 12,967 612,455 4,585

Phase IH ND ND ND ND .--

1

!

DI=Data incomplete; ND=No discharge I

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1-4 |

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I impacts, such as toxicity to larvae and adults and larval-settling effects (Boesch and Rabalais

1987), are not well documented for hard-bottom organisms and are the subject of some Phase III

I studies described in this chapter and in Appendix C.

The Phase I monitoring program included an extensive reconnaissance (predrilling) study of softI bottom and hard-bottom communities of the Santa Maria Basin and westem Santa Barbara Channel, and associated physical/chemical parameters. This study provided an important basis

of site selection for the Phase II program. The Phase II monitoring program resulted in extensive

I data on physical, chemical, and biological conditions during predrilling, during-drilling, and

postdrilling periods. However, impacts to the hard-bottom communities were not demonstrated

conclusively, and only preliminary linkages to physical and chemical processes were suggested

I (Steinhauer Imamura 1990). studies focused additionally on natural and and The Phase III

anthropogenic (drilling-related) factors and processes that may influence spatial and temporal

i variability in hard-bottom communities near Platform Hidalgo.

Overall Phase III goals were twofold:

I (1) To increase understanding of the environmental fate and effects of chronic,

low-level inputs of drilling wastes and their potential for sublethal, long-term,

I and/or cumulative impacts to hard-bottom communities; and

(2) To improve knowledge of the fundamental processes controlling natural variability

I inchanges the communities. associated withThisnatural, knowledge variability is critical compared becauseto itthosedistinguishes associated biotic with

drilling discharges.

I To maintain comparability and continuity with the Phase II program, many of the Phase III study

methods were consistent with the previous program. Study methods in common included those

I used to measure ocean currents; particle fluxes and sediment resuspension, as measured by sediment traps; sediment chemistry; and monitoring of hard-bottom epifauna. However, as noted

in Chapter 2, modifications were made to some methods to better address specific questions

I without affecting data comparability between the phases. Several new studies also were added to the Phase III program---optical backscattering probes and current meters located in the benthic

boundary layer, and extensive larval settling experiments (including natural settlers and

I laboratory-reared red abalone)--to evaluate physical and biological processes that influence the hard-bottom communities.

! 1.3 TECHNICAL ITEMS AND HYPOTHESES

!

The Phase III program included six technical items, specified by DOI to monitor spatial and

I temporal trends in the study region. A hierarchically designed, conceptual model was generated to express how these technical tasks are organized and interrelated (Figure 1.3-1). At the highest

I 1-5

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Marine Ecosystem

!

Physical

(cu_entsand I

Biological Chemica I

!

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I

I I i

Transpoff Discharges

i

1. OceanOJ_enls0tem 2) Structure "1.BottomSedmentSamples

2.SatelliteImagery(Item2) (Items3and4)

3. Wave/iide I LarvaI 2. SedimentTrap Scrnples I

Measuremenls _ltem2) Settlement (Item 3)

3.Integrate_ithphysiccd

B.Natural/Dischczge-Related: processes I

1. SedimentTraps(Item 3) |

2. Oplical Bacl_catter Probes 0tern 5) A Natural Variabililyof Hard-Bottom Biota:

1.70ram Photoquadrals (_tem 1) Hi

2. Colorvideo(ttem 1) |

3./Y_chor scar/c_illcutlings survey(Item 4)

4. Integrate _ilh physical and chemical processes

B._ Settlement. I

1. In-situManipulations (Item 5)

2. Integrate_th physicaland chemical processes Iw

Figure 1.3-1. Hierarchical, Conceptual Model of a Marine Ecosystem Consisting of I

Physical, Biological, and Chemical Subsystems: DOI Phase Ill.

I

Black arrows represent the degree of influence of one subsystem on another. Insets I

provide detail of each subsystem with the primary variables of interest "boxed" in each

subsystem. Below the individual subsystems are analytical details of how the variables IBm

measured by different technical items. I

were

1-6 I
!

I level is the marine ecosystem, which is subdivided into three process-oriented subsystems:

physical, chemical, and biological. These three subsystems represent the basic study elements

I of the Phase HI design. Ecosystems often are conceptualized as hierarchical systems of biological processes that are strongly affected by physical and chemical forces (O'Neill et al.

1986). This is depicted in Figure 1.3-1 where the physical and chemical subsystems have a

I substantial influence on the biological subsystem but there is relatively little assumed influence of the biota on the other subsystems. The scale of effects to biota, which can range from small

patches of centimeters to meters in area to regional or landscape scales of tens to hundreds of

I kilometers, are also important to evaluate (Fahrig and Freemark 1995). Note also that square

physical processes can strongly affect the chemical subsystem (Figurel.3-1). Each of these

subsystems can be isolated from the conceptual model to study its structure, and to identify and

I quantify componentsare important. which

i Within of interest. the physical Of particular subsystem, concernparticle is distinguishing transport, asbetween influenced particleby transport currents, isproperties a primaryassociated variable

with drilling activities and those associated with natural background events. As depicted in

i Figure affect the1.3-1, biotica primary and chemical goal ofsubsystems the physical in themeasurements study area. tasks Three was technical to determine tasks (Items how 2, they3,

and 4) focused on physical processes. Item 2 involved obtaining data on local physical

I oceanographic These data provided conditions criticalviainformation current meters, on water satellite mass imagery, movementsandandwave transport /tide measurements. potential, and

were used to interpret sediment-related results obtained under Item 3, including data on bottom

I sediments Hidalgo, Harvest, and suspended and Hermosa, material.andItema remotely 4 involvedoperated additional vehiclesediment (ROV)sampling reconnaissance near Platforms survey

of anchor scar and drill-cutting impacts to biological communities. Item 4 also included

I computer modeling to estimate the deposition patterns of material discharged from the platforms.

A primary variable in the chemical subsystem is platform discharges (Figure 1.3-1). However,

I other sources such as the diluent spill noted above also may be important. Item 3 (also see physical subsystem) involved collection of data on platform discharges, bottom sediments, and

suspended material. Item 4 was designed to characterize short- and long-term sediment fluxes

I and chemical concentrations in the benthic boundary layer. By integrating this information with the data collected on physical oceanographic conditions (Item 2), suspended particle contaminant

fluxes can be calculated, as well as contaminant accumulation in bottom sediments. This

I combination of physical and chemical data is essential to address the potential effects of contaminated sediments and suspended material on the biological subsystem.

I Two primary variables of interest in the biological subsystem are epifaunal community structure

and larval-settlement dynamics (Figure 1.3-1). Item 1, using 70-mm and 35-mm photoquadrat

and color video surveys from an ROV, provided detailed information on the variability of

I hard-bottom epifauna in the study area. Combining the community structure data with the

synoptically collected physical and chemical data allowed assessment of (1) relationships between

i community structure and environmental factors; and (2) hypothesis generation regarding these relationships. Item 5 employed in situ manipulative experiments to investigate the effects of

I 1-7

!
!

drilling muds on larval settlement. A series of these unique experiments was used to monitor I

larval settlement, growth, and survivorship; the results are integrated with physical and chemical

data (currents and particle concentrations). Finally, Item 6 addressed toxicity of drilling muds n

to selected species (red abalone and the cup coral Paracyanthus stearnsii) in the laboratory. J

A schematic summary of the Phase III study elements is presented in Figure 1.3-2. I

Each of the technical items (1-6) outlined above has associated general hypotheses. These m,

hypotheses are listed below based on their relationship to the physical, chemical, and biological I

subsystems summarized in Figure 1.3-1, as opposed to being listed in numerical order, although

it is recognized that some hypotheses are applicable across the artificially constructed subsystem •

boundaries. |

I. PhysicalndChemicalHypotheses I

Item 2 Ho 1: There is no difference between physical oceanographic conditions measured during

PhaseIII comparedto PhaseII andotherregionalstudies, n

w

Item 2 Ho2: There is no difference between currents measured by a primary mooring at a fixed

site and currents measured by a secondary mooring positioned at variable locations relative to n

the primary mooring. l

Item 3 Hol: There is no difference between concentrations of barium and other chemical II

contaminants measured during Phase III, including pre-, during-, and postdrilling periods,

compared to Phase II background conditions.

Item 4 Hol: There is no difference between boundary-layer currents and particle fluxes, I

including pre-, during-, and postdrilling periods, at nearfield and farfield locations relative to

Platform Hidalgo or between particle fluxes measured at high- versus low-relief heights during n

Phase III. I

Item 4 H02: There is no difference based on particle transport modeling in the dispersion of n

drilling muds relative to Platforms Hermosa and Hidalgo during Phase 111.

Biological Hypotheses I

II.

Item 1 Ho_: There is no difference between biological communities, observed during Phase II and n

Phase III, including pre-, during-, and postdrilling periods, at nearfield and farfield sites relative

to Platform Hidalgo, or at high- versus low-relief heights and at shallow versus deep bottom

depths. I

Item 5 HOl: There is no difference between larval settlement and recruitment, including pre-,

during-, and postdrilling periods, at nearfield and farfield sites relative to Platforms Hidalgo, •

Harvest, and Hermosa, and at high- versus low-relief heights during Phase llI. II

1-8 |

!
I 1-9
!

|

Item 6 Ho_: There is no difference in laboratory toxicity test results between organisms exposed m

to various concentrations of drilling muds compared to controls. I

1.4 DESCRIPTIONOFSTUDYAREA .,,.

B

The study area consists of a portion of the continental shelf, extending from shore to n

approximately 110 m depth, and the continental slope off southern California, between Pt.

Conception and Pt. Arguello (Figure 1.1-1). The coastal axis and bathymetric contours in the

region are oriented approximately southeast-to-northwest. Bottom study depths range from n

approximately 90 to 215 m.

U

The oceanographic conditions of the region are dominated by the California Current System, an n

eastern boundary current of the North Pacific Gyre (summarized in Steinhauer and Imamura i

1990). The California Current is predominantly southward-flowing, extending from the surface roll

to approximately 200 m, and moving from along the seaward edge of the continental shelf to as •

much as 1,000 km from shore (Blumberg et al. 1984; Chelton et _d. 1982).

i

Mean current flow in the Pt. Conception to Pt. Arguello region is generally parallel to the n

coastline and the bathymetric contours (Chelton et al. 1982). However, despite the long-term,

generalized patterns exhibited by the California Current System, the local current structure can m

be quite variable, consisting of numerous transient features including eddies, swirls, filaments, i

and jets (M0oers and Robinson 1984). These patterfis also are influenced strongly by interannual

variations associated with drought conditions, such as those that persisted in California from •

approximately 1985 through at least early 1991, and E1 Nifio events that occurred in 1992 U

through 1994 (United States Geological Survey 1988-1993, 1994 in press). E1 Nifio events, in

particular, can cause a reduction in seasonal (usually March to June) upwelling of nutrient-rich •

water that normally causes a significant increase in primary production in the study region II

(Dugdale and Wilkerson 1989; Chelton et al. 1982).

i

The United States Geological Survey (USGS) data, referenced above, include flow volumes from i

several rivers and creeks that discharge into the DOI study region. These data are available for

the Phase II and most of the Phase III study period, and allow direct comparisons of the i

relatively low and high discharge volumes, respectively, associated with these two phases (Figure II

1.4-1). River flow data indicate an approximate twofold to tenfold increase in volumes during

Phase III, corresponding to water years (October of one year through September of the following i

year) 1991 through 1994 and up to December (1994) of water year 1995, compared to Phase II,

which corresponded to water years 1987 through 1990.

Data on sediment loads associated with these river discharge volumes are not available for the •

same time period. However, Drake et al. (1971) estimated conservative sediment loads associated

with single, strong rainstorms in the general region of approximately 3 x 10 6 metric tons per n

storm. Further, analyses of local geologic landforms suggest that up to 30% of the sediment bed

IIF

1-10 B

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I 1-11
!

load can comprise sands, which typically settle out in the nearshore region (Taylor 1978). This I

means that approximately 70% of the "original" (Drake et al. 1971) bed load, primarily i

comprising a mixture of clays and silts, may be transported further offshore into the general DOI i

study region. If it is assumed (based on continental shelf/margin dynamics) that approximately

i

50% of this remaining sediment is then transported out of the study region (i.e., is unavailable i

for local deposition), the final volume of sediment subject to depos]ition near the study sites may i

comprise approximately one-third of the original bed load volume, or about 1 x 106 metric tons.

Using this bed load value for a typical heavy storm year (e.g., wate,r year 1992), and an average i

of 10 storms per year, up to 10 x 10 6 metric tons of sediment may be deposited on the

continental shelf area (- 200 km2) including the study sites. Assuming the sediment is •

predominantly quartz minerals (Drake et al. 1971), a specific den,;ity of 2.65 g/cm 3 (Cornelius i

et al. 1985) can be used to convert the yearly sediment load to a volume of approximately

3.8x 1012cm3. i

i

Therefore, using the following relationship: depth of sediment coverage (deposition) = sediment

discharge volume (3.8 x 1012 cm3)/area of study region (200 km2), a uniform layer of sediment II

deposited over the study sites would be approximately 2 cm thick.

This thickness is only a rough order-of-magnitude estimate and does not account for local II

differences, including currents and low- to high-relief, hard-bottom features (Denny 1988), which •

may cause uneven (thicker or thinner) sediment deposition. The "100-year" storm events that

characterized the California region during the winter of 1994-199.5 (not shown in Figure 1.4-1

since data for water year 1995, extending from October 1994 - end September 1995, are not yet

available) undoubtedly were associated with even higher sediment discharges and deposition on

the continental shelf. Nonetheless, large differences in rainfall and associated sediment loads H

from runoff likely result in significant differences in sediment deposition over the study region. i

This in turn may affect the quality and quantity of benthic habitats, including hard-bottom

features characterized by organisms that may be sensitive to burial and increased sediment loads i

(e.g., Lissner et al. 1991).

i

As noted above, the distribution of nearshore and offshore sediments is influenced strongly by I

discharges of silts, clays, and sandy materials from rivers and streams, primarily to the north of

Pt. Arguello, and littoral transport of sands from the north and south of the study area (SAIC •

1986). Sediment types in the study area range from approximately 35-85% fines and 15-65% i

sand, with no predominant trends with depth or distance offshore (Steinhauer and Imamura 1990).

Hard-bottom features, ranging in vertical relief from a few centimeters to over ten meters, are •

scattered throughout the study region (Figure 1.1-1) but are relatively uncommon (SAIC 1986). II

Some riverine discharges, representing natural sources of the minerals barite and chromite i

(barium sulfate and oxides of bivalent chromium, respectively), contribute to the sedimentary l

loads of these materials to the study area (SAIC 1986). However, in addition to natural sources,

barium, in particular, is a major component of drilling-mud discharges, and chromium was used am

historically as an additive by the oil and gas industry.

1-12 i

!
!

I Other natural chemical sources in the study region include hydrocarbon seeps (e.g., Reed and

Kaplan 1977; Simoneit and Kaplan 1980). Evidence of submarine oil seeps in the Santa Maria

I Basin includes macroscopic tar particles observed in bottom sediment samples from Phase II (Steinhauer and Imamura 1990) and observations of bacterial mats (Beggiatoa spp.) associated

with seeps and gas bubbles at some hard-bottom sites (BBA/ROS 1986; Lissner et al., pers. obs.,

I October1992).

The primary sources of anthropogenic inputs to the study region are associated with historical

I oil- and activities from Platforms Harvest, Hermosa, and and gas-drilling Hidalgo (Steinhauer

Imamura 1990). Historical discharges associated with production operations from these platforms

are summarized in Table 1.1-1. Further, releases of several million gallons of a hydrocarbonI based diluent occurred over a period of years from an oil and gas production facility in

Guadalupe, CA, (approximately 50 km north of Pt. Arguello), representing contaminants from

i land-based include atmospheric sources that deposition, flowed into tankerthe/shipping coastal environment. discharges andOther spills anthropogenic (e.g., PAC BARsources ONESS), can

and wastewater discharges from platforms and vessels. The coastal area in this region is

i relatively undeveloped, contributing to the generally undisturbed nature of the environment.

Biological communities of the study region are very diverse, particularly in intertidal to shallow

I biogeographic subtidal areas,provinces: in association the Oregonian with theirto theoccurrence north of Pt. in Caonception transitionandzonethe Californian between twoto

the south (Newman 1979). Biological organisms at study area depths (approximately 100-200

I m) of thealsoCalifornia are abundant shelfandanddiverse. slope (BBAHowever, /ROS the 1986;-S communities AIC and MEC are very1989; similar Lissner to other et al.regions 1991).

I Hard-bottom epifauna, the biotic focus of the Phase III program, are influenced strongly in their distribution and abundance by depth and substrate relief (SAIC 1986; SAIC and MEC 1989;

Steinhauer and Imamura 1990; Hardin et al. 1994). Sediment movement, potentially resulting

I in burial or exposure of some organisms, can have significant effects on the local distribution and abundance of populations (Lissner et al. 1991). These effects are most pronounced in areas of

low relief (e.g., < 0.5 m), although many of the characteristic species appear to be adapted to

I these sediment dynamics (Lissner et al. 1991).

Common species in the hard-bottom areas, as summarized by SAIC (1986) and Steinhauer and

I Imamura (1990), include the anemones Stomphia didemon and Amphianthus californicus, and the corals DesmophyUum dianthus (formerly crista-galli) and Lophelia pertusa (formerly californica)

in areas of high relief. Common species in areas of low relief include the corals Caryophyllia

I spp. and Paracyathus stearnsii, serratissima, ophiuroid the crinoid Florometra and the

Ophiacantha diplasia. Other common species found in a variety of relief types include the

I anemone Metridium giganteum (formerly senile), numerous species of rockfish (Sebastes spp.), the asteroids Stylasteriasforreri and Mediaster aequalis, and numerous "mat-like" organisms such

as hydroids, ectoprocts, zoanthids, and komokoiacean protozoans.

!

I 1-13

!
IIIIIIII

Thispageintentionallyleftblank.IIIIIIIII

1-14II
,l 1
i chapter 2

II MATERIALSANDMETHODS

i

I This surveys--including chapter providesdescriptions an overviewofofvessels, the Phasenavigation, III materialsandandsampling methods.activities--which An overview of were fild

conducted from October 1991 through January 1995, is presented in Section 2.1. General

I laboratory are describedand indataSections analysis2.2, methods 2.3, andfor 2.4, studiesrespectively, of physical,withchemical, detailedandmethods biological presented processesin

Appendices A through D.

!

2.1 OVERVIEW OF FIELD SURVEYS

!

I Field periods:surveys October-November corresponding to1991thirteen (Cruiseseparate No. 1),cruises April were 1992 conduc (CruisetedNo.in2),theApril-May following 1992 time

(Cruise No. 3), July 1992 (Cruise No. 4), September 1992 (Cruise No. 5), October 1992 (Cruise

i No. 9), December 6), January1.993 1993(Cruise (CruiseNo. No.10), 7),January August 1993 1994_(Cruise (Cruise No. No. 8), 11),SepJulytember 1994 1993 (Cruise(Cruise No. No. 12),

and January 1995 (Cruise No. 13). Summaries of the methods and types of samples collected

I on2.1-3thethrough cruises 2.1-6. are presented in Figures 2.1-1 and 2.1-2. Station locations are shown in Figures

I, location Studies oused f physical duringprocesses Phase II,included as well current as at a second, meter measurements variable-locationat themooring same primary within mooring a few to

several kilometers of the primary site. Wave/tide gauge measurements also were made at the

I primary mooring. Satellite images were collected of the general study region. Wind data were collected from the National Oceanographic and Atmospheric Administration (NOAA)

meteorological buoys located in the general study region. Sediment flux and resuspension was

I monitored with bottom-located sediment traps (STs) in addition to STs and optical backscattering probes mounted on specially designed physical measurements arrays (PMAs). These arrays,

including a near-bottom current meter, provided physical effects data for comparison with results

I from in situ larval experiments (see below). Finally, specially designed sediment measurement

rods (SMRs) were deployed to assess evidence of any large-scale sediment movement or

accumulation. (The current meter and ST data were used for subsequent particle transport

I modeling tasks.)

Studies of chemical processes included analyses of trace metals and hydrocarbons from ST

I samples and bottom sediments collected with Van Veen grab samplers and box corers. Grain

I 2-1

I


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I
I size and mineralogy analyses were performed on some of the sediment samples. Compilation of

platform discharge records was performed with data provided by the Environmental Protection

I Agency (EPA) and MMS.

Studies of biological processes involved the use of a remotely operated vehicle (ROV) to collect

I 70-mm or 35-mm photographic quadrats (Figure 2.1-1d) and color video data to assess hard- bottom communities in the vicinity of Platform Hidalgo. An ROV reconnaissance survey also

was conducted near Platform Hidalgo to assess community effects from platform anchoring and

I disposal cuttings. Finally, settling experiments (natural manipulated

of drill in situ larval and

using red abalone larvae) were conducted at one nearfield and one farfield site each associated

with Platforms Harvest, Hermosa, and Hidalgo, and laboratory toxicity tests were performed using

I drilling muds and species characteristic of the study area.

i bottom-located The overall studySTs, design Van focused Veen grabon the collections PlatformofHidalgo surface region. sediments, Assessments and SMRsandwerestudies conducted using

in the immediate vicinity of nine hard-bottom sites (Figure 2.1-4). Current meter moorings were

i sited experiment in the sites samewere general located rgionnear(Figure two of2.1the-3).nineAdditionally, hard-bottom thesites,PMrepresenting As and two one of thenarfield larval

and one farfield location. The remainder of the study sites were located near Platforms Harvest

and core Hermosa. stations arranged These sites in a included radial arraythe around other four all three locations platforms for the(Figures larval experiments 2.1-5 and 2.1-6). and box

I As of Platform describedHidalgo above,,there with was someaties hightodegree conditions of spatial and biological integrationeffects of dataassociated collected with in thePlatforms vicinity

Harvest and Hermosa.

I The field studies were performed using five different survey vessels: the U.S. Navy-owned M.V.

INDEPENDENCE (Pt. Hueneme, CA) for Cruise Nos. 1, 3, 6, 8 and 13; the M.V. GLORITA

i provided by GEO 3 (Santa Barbara, CA) for Cruise Nos. 2 and 4; the M.V. RAMBO from Aries Marine (Lafayette, LA) for Cruise No. 11; and the R.V. CAVALIER for Cruise Nos. 5 and 7 and

the M.V. WM. A. McGAW for Cruise Nos. 9, 10 and 12, as provided by SAIC (Goleta, CA).

t The INDEPENDENCE is a 200 ft x 40 ft vessel with a large (40 x 77 ft) rear deck space, deck winches, and an extendable reach crane that assisted in handling of equipment for the ROV and

larval experiment tasks (Section 2.4). The vessel also is equipped with bow thrusters and a

I dynamicpositioningsystem are maintaining position during rough sea

that critical for vessel and

weather conditions that are typical of the study region. The RAMBO is a 185 ft x 45 ft cablelaying vessel that was substituted due to scheduling constraints for the INDEPENDENCE on one

I cruise, mobilizationof andwinches outfitthevesselfor major Separate a crane was required to

handling the ROV and larval experiments. The GLORITA, the CAVALIER, and the McGAW

i are 147 ftx 27 ft, 110 ft x 26 ft, and 106 ft x 26 ft vessels, respectively, with appropriate crane and winch capacities for conducting smaller-scale study tasks, such as deployments and recoveries

of current meters and larval filming plate moorings.

!

I 2-17

!
!

!

Survey navigation on the INDEPENDENCE and the RAMBO utilized trisponder-based systems

(2 3 m accuracy) for all sample collections and deployments, including larval experiment igloos, m

STs, SMRs, and Van Veen and box corer sample collections. The trisponder system was linked B

to an O.R.E. Trackpoint system (+ 3 m accuracy) for all tasks that required the ROV, including

biological community surveys, the anchor scar/drill cuttings reconnaissance survey, and ST lm

recoveries. Navigation on the GLORITA, CAVALIER, and McGAW was accomplished using I!

a global positioning satellite (GPS) system (+ ~ 50 m) calibrated against LORAN measurements.

Brief summaries of accomplishments for each cruise in the Phase III program are provided below. B

Cruise No. 1 (October 31 through November 10, 1991): I

Physical Processes--Twelve STs from the Phase II program were recovered and one ST was

redeployed near each of the nine hard-bottom sites from Phase II; SMRs were deployed at each _l

of the nine ST stations; reconnaissance surveys were conducted with the ROV near Platform m

Hidalgo to assess impacts from drill cuttings, anchor scars, or debris; samples of surface

sediments were collected with a Van Veen grab sampler near the nine ST stations; and samples i

of surface and subsurface sediments were acquired with a box corer at fifteen stations surrounding m

Platform Hidalgo and nine stations each surrounding Platforms Harvest and Hermosa. II

Chemical Processes--Surface sediment and ST samples were collected for trace metal and U

petroleum hydrocarbon analyses from the twelve ST, nine Van Veen grab, and fifteen + nine + l/

nineboxcorerstationsdescribedforPhysicalProcesses. I

Biological Processes--ROV monitoring studies (70-mm photoquadrats and color video) of Ilil

biological communities were conducted at the nine hard-bottom sites established during Phase II. I

Cruise No. 2 (April 2-4, 1992):

m

Physical Processes--Two current meters were deployed to assess the scale of coherency of

currents. One of the locations was at a site used historically near Platform Hidalgo during Phase i

II; the second location was several kilometers upcoast. g

Biological Processes--"Warm season" larval experiments were initiated by deploying settling ill

plates to monitor the growth of natural microbial films (i.e.:, plate conditioning). The n

deployments were at one near-platform and one reference site each, associated with Platforms

Harvest, Hermosa, and Hidalgo (six sites total). The plates were collected during Cruise No. 3. i

m

Cruise No. 3 (April 16-22 and May 13-15, 1992, corresponding to Legs 1 and 2,

respectively): I

Physical Processes--Three of nine STs were recovered and redeployed during Leg 1 and three

additional STs were deployed during Leg 2. Adverse weather conditions prevented recovery and i

redeployment of the six remaining STs. One PMA each was deployed at one near-platform II

2-18 I

!
I (nearfield) and one reference site (farfield) associated with Platform Hidalgo. Each PMA was

outfitted with a current meter; water temperature, conductivity, and pressure sensors; optical

I backscatter probes; and STs.

Chemical Processes--ST samples were collected for trace metal and petroleum hydrocarbon

I analyses from the three ST stations described for Physical Processes.

Biological Processes--All settling plate moorings that had been deployed at the six sites for larval

I experiments during Cruise No. 2 were recovered. Larval experiment arrays (igloos) were

deployed at the same six sites during Leg 1 of Cruise No. 3. Weather delayed recovery of the

i igloos settling until experiments. Leg 2, at The whichsixthtimeigloofivecould of thenotsixbewere recovered recovered due toanddifficulties redeployedassociated for long-termwith

the acoustic release; it was recovered during Cruise No. 6.

Cruise No. 4 (July 7-10, 1992):

I Physical variable-location Processes--Tw mooring o curre was ntmoved metertomaoosecond rings were location recovthat eredw, aserviced, s nearer toandshore redeployed. than the The sit

occupied during Cruise No. 2.

I Cruise No. 5 (September 24-27, 1992):

I Physical and Processes--The current meter mooring from the historical site was recovered, serviced, redeployed.

I Biological Processes--"Cold season" larval experiments were initiated by deploying settling plates for filming at the same six sites described for Cruise No. 2. The plates were collected during

Cruise No. 6.

i Cruise No. 6 (October 15-24, 1992):

l Physical Processes--Twelve STs were recovered (three from Leg 1 of Cruise No. 3, three from Cruise No. 3, and the six remaining STs that were not recovered during Cruise No. 3); the STs

were redeployed at each of the nine historical stations; the two PMAs were recovered, serviced,

I and at the stations described for Cruise No. the second redeployed 3; current meter mooring was

deployed; and sediment samples were collected with a Van Veen grab sampler near the nine ST

stations.

!

Chemical Processes--Surface sediment and ST samples were collected for trace metal and

petroleum hydrocarbon analyses from the twelve ST and nine Van Veen stations described for

I PhysicalProcesses.

I Biological No. 5 wereProcesses--The recovered; The larval six larval settlingexperiment plate moorings igloos atdeployed the sitesatdescribed the six sitesfor during Cruise Cruise No. 3

I 2-19

I
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were recovered and redeployed; and ROV monitoring studies (70-mm photoquadrats and color m

video) of the biological communities were conducted at the nine hard-bottom sites surveyed

duringCruiseNo.1. N

Cruise No. 7 (January 19-21, 1993): ll

II

Physical Processes---CMs were recovered from two stations, one primary mooring near Hidalgo

and the second located approximately 1.5 nautical miles inshore and northeast. All data were m

collected from both CMs, and redeployed. I

CruiseNo.8(August2-7,1993): ]1

e

Physical Processes--PMAs and CMs were recovered and redeployed at two stations, with the

secondary CM moved to a new location. Nine STs were recovered from their respective stations, iI

All STs were redeployed, with two being relocated from Hidalgo to Hermosa in anticipation of II

upcoming discharge events.

ill

Chemical Processes--ST samples were collected from nine stations for chemical analyses. "Tufty I

Scrubbers", representing settling substrates, were placed for Scripps Institution of Oceanography

(SIO) on STs at five of the nine ST locations and the two relocated stations. 1

Biological Processes--Six larval igloo arrays were recovered, the settling plates were

photographed, and the igloos redeployed. _l

U

Cruise No. 9 (September 17-18, 1993):

Biological Processes--This part of the survey was cancelled prior to deployment of settling plate l

conditioning moorings due to the rapidly progressing drilling schedule at Hermosa. II

Cruise No. 10 (December 18-21, 1993): _1

Physical Processes--Two CMs were recovered and redeployed and all data were collected, except I

for the General Oceanic (GO) current meter at the bottom of CM No. 1, which was damaged by llr

an unknown cause. I_

II

Biological ProcessesmA total of 12 settling plate conditioning moorings were deployed (as

described in Cruise No. 3) to initiate larval experiments for the platform drilling period. II

!!1

Cruise No. 11 (January 5-18, 1994):

Physical Processes--PMA instrumentation was redeployed on "in-line" moorings (i.e., without m

igloos) due to potential interference of the $4 current meters by the igloo frame. A total of nine

STs (eight STs which were recovered plus one reserve) were redeployed at the recovery stations; Ill

the ST at PH-I could not be recovered. |

2-20 N

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I Chemical Processes--Sediments from eight STs were collected for chemical analyses. A single

VV grab also was taken at the two Hermosa stations.

I Biological Processes--All six larval experiment igloos were recovered, settling plates

photographed and injected with red abalone larvae, and redeployed for a 3-day settling

I experiment. The igloos recovered and Plankton

were subsequently settling plates analyzed.

recorders were deployed at two stations. ROV biological surveys (35-mm photoquadrats and

i color video) were completed at their nine respective stations.

Cruise No. 12 (July 20-23, 1994):

I Physical Processes--Two CMs were recovered and all data were retrieved; CM No. 1 was

redeployed; CM No. 2 was not redeployed (by plan). PMA No. 2 was recovered at Farfield No.

I 1 location, while PMA No. 1 could not be recovered, presumably due to failure of the acoustic release.

I Biological Farfield No.Processes--Neither 1 of the PR igloos could be recovered from Hidalgo Nearfield or locations due to failure of the acoustic release batteries.

I Cruise No. 13 (January 6-15, 1995):

Physical Processes--The final PMA was recovered (see Cruise No. 12) at Hidalgo Nearfield and

I all data were retrieved from the $4 current meter, sediment trap tubes, and optical backscattering sensors. Four passive acoustic reflectors (to mark permanent photoquadrat stations) were

deployed at high- and low-relief sites at PH-R and PH-I. All STs were recovered, seven from

I hard-bottom locations and two from relocated positions at ST-LA3 and ST-LA6.

Chemical ProcessesDSTs were recovered and sampled for PAHs, PHCs, selected biomarkers, Ba,

i A1, and TOC. Box core samples were taken at 15 stations. All VV surface sediment samples

were collected and analyzed for PAHs, selected biomarkers, Ba, and AI.

I Biological Processes--Two PR igloos were recovered from Hidalgo Nearfield and Farfield

locations. ROV monitoring studies (35-mm photoquadrats and color video) were conducted at

their nine respective stations. !

l 2.2 PHYSICAL PROCESSES

I Physical processes tasks included current measurements (Section 2.2.1), wave/tide/wind measurements (Section 2.2.2), satellite imagery (Section 2.2.3), physical measurements arrays

(Section 2.2.4), sediment measurement rods (Section 2.2.5), and particle transport modeling

I (Section 2.2.6). Parameters such as sediment grain size and mineralogy that are closely integrated

I 2-21

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integrated with evaluations of chemistry data from ST, Van Veen t,n'ab, and box corer collections

areaddressedunderchemicalprocesses(Section2.3). I

2.2.1 CurrentMeasurements I

2.2.1.1 Field Survey i

Current measurements were made at a primary, fixed-location mooring near Platform Hidalgo I

and at a secondary mooring that varied in position by a few to several kilometers from the

platform (Table 2.2-1 and Figure 2.1-1a). Design of the moorings was similar to Phase II 11

(Steinhauer and Imamura 1990). The primary mooring was placed at the same location as during w

Phase II and was intended to maintain continuity with these earlier measurements. The purpose

of the secondary mooring was to assess the scale over which cun-ents were coherent (similar) li

compared to the data from the fixed mooring.

Current meters used included Neil Brown Smart Acoustic Current Meters (SACMs) as primary I

instruments and General Oceanics MklI (GO) current meters as backups. The primary mooring

consisted of Current/temperature sensors placed at water column depths of 15, 54, and 126-m m

(Figure 2.2-1). The original design for Phase II utilized telemetry to transmit data to shore from II

the primary mooring. However, the design was altered for Phase III such that backup current

meters were placed at each of the three depth levels and data telemetry was eliminated. The

secondary mooring had a similar configuration to the primary mooring except that the current l

meters generally did not have backup instruments (Figure 2.2-1). Use of backup instruments

proved to be a very successful method for maintaining continuous current measurements at the Jl

primary mooring site over 2.5 years. Consequently, data return was much greater than during l'

Phase II.

i

Both mooring designs included a subsurface float (for line tension and vertical stability) that was B

linked to a surface float. The surface float was the primary mean,,; of mooring deployment and

recovery. An "anchor last" approach was used during deployment and recovery of the current JR

meters. For this procedure, the survey vessel approached the mooring site by steaming slowly

into the current along the target isobath. During deployment, the upper portion of the mooring

was placed in the water and allowed to move away from the vessel due to the current and the i

ship's forward movement. Once at the site, the anchor was lowered to the bottom using an Re

onboard winch and A-frame. When the anchor was on the bottom, an in-line acoustic release

was activated and the winch wire was separated from the anchor. A similar procedure was used il

to deploy the separate (but linked) wave/tide gauge (Section 2.2.2) and the secondary mooring. I

During recovery, a line in a canister, which was attached above and below the acoustic release,

was used to retrieve the anchor. When the release was activated, the main (taut) mooring i

separated from the anchor and was brought onboard the vessel by sequentially retrieving all

2-22 i

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I Table 2.2-1. Current Meter Mooring Deployment Information, DOI Phase III.

!

Station Latitude Longitude Deployment Bottom

i (N) (W) Period Depth (m)

H P1 34°30.1 ' 120°43.1 ' Aprilto 1992 133

January 1995

l

S1 34o32.8 ' 120o46.0 ' April 1992 130

to

i July1992

I $2 34°31.4' 120044.2' October1992 91

and to

I $3 January1993

$4 34030.3' 120042.2' January 1993 109

|

August

to

1993

I $5 34028.3' 120°40.1' August1993 130

to

a December 1993

I $6 34029.4' 120043.9' December to 1993 280

July 1994

I

P = primary mooring location

t S = secondarymooring locations

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Secondary Mooring Primary Mooring

,'.t

I

1 () (_)Subsurface Float

14m 14m SACM

1 _ _ _n__ _o_,, 1

53m SACM

1 __

I 125m SACM

125m _

126 m

I GOMkll

i _I Rope Cannistert _ Acoustic Benthos Connecting Release ,_[__ Sea 635-11 Data

............... __.'.%_ ._,",,-!.. :%_

I Figure 2.2-1. Schematic of Moorings Deployed as Part of the DOI Phase Ill Program.

Throughout the field activities, the primary mooring remained in the same location as

I occupiedduring Phase II. The secondary mooring was moved every three to six months to provide observations for evaluating coherence scales of horizontal currents.

SACM meter; Sea = Smart Data Acoustic 635-11 isCurrent the waveMeter, /tide gauge. GO MkII = General Oceanics;Mark II current

I 2-25
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I elements from the top down. Once the mooring was recovered, the rope link was used to recover

the anchor. The ground line then was used to recover the wave/tide gauge. This approach

I resulted in all anchors being retrieved.

I 2.2.1.2 Laboratory/Data Analyses

I During mooring rotation cruises (Figure 2.1-1a), current meter instruments were cleaned, data

were retrieved, and performance of the instruments was evaluated. Data from the SACMs were

i the storedsurvey in digital vesselformandinscanned internal tomemidentify ory. These any performance data were downloaded problems, tousually a computer basedonboard on the

amount and consistency of tape advance compared to the expected advance.

I Each current meter record represents time series of perpendicular (orthogonal) components for

current velocity and temperature values at user-specified intervals. During data processing, each

I velocity component and temperature record was linked temporally.

The following data processing steps were used:

t • Translation of current and temperature data from internal instrttment formats to

calibrated (ASCII formatted) engineering units; and

I •- Data cleanup, using an interactive computer routine, as appropriate, to remove

outlier values and interpolate data gaps to the basic sampling interval.

I If the sampling interval was less than or equal to one hour, one- or two-point outliers or data

gaps were replaced with interpolated data. For such short records, straightforward linear

interpolation of each component was used. For between one and approximately six hours,

gaps

a bicubic spline under tension was used to provide interpolated values. The frequency and

magnitude of the expected current variability was evaluated prior to any interpolation over gaps

I largerthan six hours.

Following translation and cleanup, all time series data were entered into an SAIC Physical

I Oceanographic Management System (DMS) for further processing. The DMS standardizes Data

data formats, allows incorporation of consistent data processing routines, and provides a method

of linking any given time series to earlier or later data records. Data recorded as speed and

I direction then were converted to component vectors for preliminary data analysis.

i Preliminary data analysis included the following:

• 3- and 40-Hour Low Pass (HLP) filtering;

I • Auto spectra(of velocitycomponents);

I 2-27

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• Coherenceandphase(of velocitycomponents);and m

• Statistical analyses. II

For sampling intervals less than 60 minutes, the first step was to apply a 3-HLP filter (with a

Lanczos taper) to the data and decimate the filtered data to hourly increments (e.g., At = 60 m

minutes). The 3-HLP filter suppresses only the very highest frequency variability (e.g., one- to J

two-hour periods) within the time series. The decimation ensures comparison of current/

temperature estimates at comparable time periods. Within a given :_tudyperiod, time series were m

truncated to a common start time (t = 0), typically representing that time when the last instrument I

began providing useful data. This procedure provided a common period for subsequent detailed

analyses(i.e.,spectrandstatistics). I

II

For time series with initial sampling intervals greater than or equal to 60 minutes, the initial step

involved applying a 40-HLP filter (with a Lanczos taper) to the data and decimating the filtered II

data to six-hour increments. The 40-HLP filter suppresses the: amplitude of variability at l

frequencies greater than or equal to the diurnal frequency.

Ill

Auto spectra were used as a method for partitioning the variability of each current component I

by frequency. This partitioning identified the frequencies at which the more important (largeramplitude) current fluctuations occur and provided a preliminary step toward resolving and Ill

characterizing circulation processes in the study area. This information, when available from El

different depths and different moorings, provided insight into the regional and depth-dependent

structureofthesepatterns, m

Coherence analyses provided an estimate of the correlation between two time series (in this case

between the primary and secondary moorings) at each frequency. Similarly, phase data provided n

an estimate of the relative lag at each frequency between the coherent (correlated) components g

of the two signals. This analysis helped resolve the following items: i

• Relationships between velocity components for a given instrument (u versus v); and

• Horizontal and vertical coherence between comparable velocity components, which I

helped to define time-averaged spatial scales of the circulation patterns.

w

Standard statistical analyses of each time series included calculation of the mean, variance, N

skewness, principal axes, maximum and minimum values, and the ratio of 40-HLP to 3-HLP

variance. Additional data products included 3-HLP component and temperature data plots, and II

vector "stick" plots of 40-HLP data. Velocity variance was directly proportional to kinetic energy I

at the measurement site. Therefore, this ratio indicated the relative importance of energy at

frequencies above and below the diurnal period. A value of 1 meeaas no high-frequency energy t

and a value of zero means no sub-diurnal current variability. The statistical routine also II

computed the principal axes of the currents (i.e., relative to true north), thereby minimizing the

variance of the cross-axis current component. To help interpret these processes, the principal n

axes were compared to the general orientation of the isobaths to eva_Luatethe importance of cross2-28 I

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I isobath (onshore) flow. Many of these statistical quantities are displayed graphically in the form

of 40-HLP variance (or standard deviation) ellipses and mean vectors. A variance ellipse

I summarizes the standard deviations of the 40-HLP currents in the orthogonal directions of the principal axes (see Appendix A).

I To help resolve fluctuations for higher-frequency currents, tidal analysis was applied to the

current time series. These results provided an estimate of the amplitude and phase of all primary

and interactive tidal constituents. Those constituents that contributed significantly to the observed

i velocity presented graphically as hodographs (Appendix A).

field then could be tidal

!

2.2.2 Wave/Tide/Wind Measurements

I

I 2.2.2.1 Field Survey

I Wave and tide measurements were made using a bottom-located incorporated as part of gauge

the primary current meter mooring (Figure 2.2-1). The deployment period and methods for

deployment and recovery were described earlier for the primary mooring (Section 2.2.1). Wind

I data were obtained from NDBC Nos. 46023, 4601 and PTGC1. Buoy 1,

The Sea Data 635-11 Wave and Tide Gauge used for the study was a self-contained, digitally

I recording a quartz pressure sensor with a 0-400 psia instnlment. It included ParosScientific

(pounds per square inch atmospheric) range to measure bottom pressure and a thermistor to

i measure by a ground waterlinetemperature. to the primary The instrument mooring anchor housing(Figure was attached 2.2-1). directly This placement to an anchor helpedconnected ensure

that measured variations in pressure resulted from changes in the height of the overlying water

I column rather than changes in the depth of the sensor.

The instrument allowed for separate, user-selected schemes for tide and wave measurements.

I Wave second data for 1,024 collected seconds as a(approximately burst of high-frequency 17 minutes)pressure and recorded measurements once everyweresixtaken hours.oneTime per

series data for tidal water level and temperature resulted from pressure and temperature

I measurements processed as described averaged below. over 3.75 minutes, producing 16 estimates per hour. These data were

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2.2.2.2 Laboratory/Data Analyses "

I

Processing of wave and tide gauge data was accomplished by first downloading the tape followed

by creation of a hexadecimal data file. File creation was performed by Sea Data during the initial in

stages of Phase III, and then by Woods Hole Instruments, Ltd. (after the owner of Sea Data

instruments dropped support for the line).

The resulting data files represented mean pressure and burst,; of high-frequency pressure I

measurements. Mean pressure provided information on tides and other processes producing

fluctuations in water level with periods greater than approximately 10 to 12 minutes. The burst II

duration of approximately 17 minutes also allowed for calculations of statistics for wind-wave II

frequency fluctuations. Mean tidal pressure was filtered using a 3-HLP filter and then decimated

at hourly intervals. During processing, the wave data for each burst were evaluated and a in

variance of pressure was computed. The variance was used as an indicator of significant wave II

height for those waves that produced pressure effects (i.e., wave-induced velocities) at the bottom.

Significant wave height was defined as the average height of the highest one-third of the waves. I

Pressure due to surface (wind-induced) waves was not evaluated. This type of pressure is

attenuated with depth as a function of wave length or, equivalently, wave period. This pressure II_

attenuation factor operates as a low-pass filter such that, for a given water depth, the higher- II

frequency waves are attenuated more severely than low-frequency waves. As a consequence, the

high-frequency pressure observations made by the Sea Data gauge do not reflect the complete I

surface wave field. Rather, they reflect an amplitude attenuated (low-pass filtered) wave field. .J

An example of the pressure attenuation factor for the depth of the Sea Data gauge is shown in

Figure 2.2-2. These data indicate that there was a significant reduction in the sensed pressure II

created by surface waves, even for relatively long-period waves (10 seconds). The pressure

attenuation factor is independent of wave height and is only dependent on wave period and water

depth. As a consequence, the variance-based estimate of pressure fluctuations was only used as •

an indicator of events that might produce appreciable wave-induced bottom currents.

Data for wind speed (meters per second) and direction as well as sea-surface temperature (SST) I

(°C) were measured by NDBC buoys as a time series at one-hour intervals. Initial processing

consisted of checking the data for gaps. Relatively short gaps were, filled by interpolation, while Ill

longer gaps were excluded from the database. The wind data were converted to component forms II

such as north and east vectors, which were rotated to provide components aligned along and

across the local isobaths. The data were processed through a 40-HLP filter to remove noise and /

decimated to six hour intervals in the same manner as the current meter data. |

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2-30 I

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0.50

I ._0 0.45 lWaterDepth = 138m I

.f--.

0 0.40

I LLE_ 0.35 ..................................... IPress KPisthuereatt resenuponsatie°nduefatcto°wr avf°esr the dynamic I"

E

(I)0.25 ......

c_

I _ 0.20

o.15 .......... (I)

c).. I 0.10

CL

0.O.5 ! 0.00

I 4 5 6 7 8 Wave 9 I0 Period II 12(see) 13 14 15 16 17 18

I

Figure 2.2-2. Example of the Effects of Depth on Wind-Wave Attenuation at the Bottom

I (138 m).

For even an 18.5-second wave, the effects of depth have reduced the pressure to little

t more than 30% of that measured near the surface. For approximately 10 second waves, no dynamic pressure was sensed at the bottom; that is, the dynamic pressure was

completely attenuated at the bottom (138 m).

I

I 2-31

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2-32I!
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I Standard statistical techniques applied to the wind and temperature data included calculation of

means and variances of the filtered and decimated wind records and the SST records. Statistics

I showing frequency of occurrence and duration of different wind speed and direction classes were calculated for monthly intervals and displayed in tabular form and as wind roses. Spectral

techniques were used to determine the principal time scales (most energetic frequency bands) in

I the wind records at each station. Coherence and phase among components at different stations

and between stations and the current meter records also were computed.

I

2.2.3 Satellite Imagery

I

I 2.2.3.1 Field Survey

I SST data were collected by the Advanced Very High Resolution Radiometers (AVHRRs) onboard NOAA's polar-orbiting satellites. These sensors measure visible and infrared radiation in four

or five separate bandwidths at a spatial resolution of approximately 1.1 km (pixel size). These

I data were converted from radiance to and corrected for atmospheric effects. Each temperature

polar-orbiting satellite passes over a portion of the west coast, including the study area, twice a

day. This is generally one daytime and night pass. SST images can be obstructed by cloud cover

I and which shields the surface and absorbs sea-surface radiation in the fog, underlying water

thermal band. Typically, cloud tops appear as c0nsolidated cold/cool areas which are often easily

detectable by their shape and location in the images. I

i 2.2.3.2 Laboratory/Data Analyses

i Raw by SAICdigital to create imagesdaily wereorreceived twice daily fromimages a subcontractor of a 512 km(Ocean x 512Imaging, km area Inc.) centered and then approximately processed

on Pt. Conception (Figure 2.2-3). For the study, 1,812 images were acquired for the period

I November screening images 1, 1991to reject throughthoseApril with 30, extensive 1994. cloud The cover. data processing Adjustmentsprocedure were thenfirstmadeinvolved to the

navigation parameters to place the image precisely over known geographic locations. An overlay

i was developed that masked the land areas and showed selected bathymetry and other features of interest including the moorings. To minimize the amount of the sea-surface imagery that was

cloud-covered, "warmest pixel" compositing was used. This method involved selecting the

i warmest pixel at each location from among the images. These warmest pixels were then used to create a composite image. The goal was to create one composite per week that showed the

study area as essentially cloud free.

I

i 2-33

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I

I

I

I

I

l

I

l

I

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l

I

I

i Figure 2.2-3. Representative Area. Composite Satellite Thermal Image of the Phase TITStudy

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2-36i!
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I The study region often was characterized by a convergence of cooler water from the north and

warmer water from the south, which resulted in comparatively strong horizontal thermal

I gradients. To distinguish these differences most easily, one-degree Celsius intervals were assigned separate colors. For the images used in this report (e.g., Figure 2.2-3), the warmest to

coolest temperatures were presented sequentially as red, orange, yellow, and green to blue. Cold

I cloud tops were designated as white so they could be easily identified. Specific temperatures are

not shown because patterns rather than actual SSTs are used to indicate regional circulation

i patterns.

For the images presented, scaled vectors that represented current data collected at the upper

i current were meters (approximately 15 m below the surface) at the primary and secondary moorings overlaid on the SST image. These vectors represent daily-averaged currents that

corresponded to the time period of the composite image. This method provided at least two sets

i ocirculation f in situ/current observations patternsthatforwere those used dates.with the temperature patterns to aid in describing

i Into this identify report,circulati imagery on was patterns used typical in the analyses of eddiesprimarily (circular,in aswirling qualitativemotimanner, ons) andforupwelling example,

(patches of cold water along the coast). Evaluations were made routinely of SSTs measured at

I the features NDBCidentified buoys compared in the imagery to satellite could -determined be properly related temperatures. to featuresSuchobserved checksinensured the current that

meter records.

I

2.2.4 Physical Measurements Arrays

I

I 2.2.4.1 Field Survey

I Measurements of near-bottom suspended material and currents in the vicinity of Platform Hidalgo

were conducted using two specially designed PMAs, each of different design (Appendix A).

I One array was located at a nearfield site approximately 800 m to the southwest of Platform

Hidalgo, near Station PH-N, in 195 m of water (Figure 2.1-5). The second array was placed at

I amfarfield of watersite(Figure approximately 2.1-5). Both 5 km arrays to the were northwest placedof intheclose platform, proximity near Stati to mixed-relief on PH-W,,inhard- 215

bottom features as determined from earlier ROV surveys (Section 2.4.1). The farfield array was

I cmodeling onsidered to be beyond the influence of drilling-associated discharges, based on Phase II (Coats 1994), and was intended to represent a control for the nearfield site. The

general northwest-southeast trend of the depth contours to the east of Pt. Conception (Figure 2.1-

I 5) is interrupted in the vicinity of the farfield station by a canyon-like formation with a major

axis oriented along a northeast-southwest line. This feature, in combination with rocky outcrops

I 2-37

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I

in the area, complicates the bathymetry, and presumably the current structure, in the vicinity of R

the farfield station.

I The first PMA design was utilized from April 1992 to August 1993. These PMAs were

approximately 2 m high and nearly hemispherical in form, with a network of eight cylindrical

legs extending upward from the base to a horizontal platform (.Appendix A). This platform II

provided support for a spherical segment of syntactic foam flotation held in place by an acoustic

release (Datasonics ATR-397). A cylindrical line canister containing 300 m of 9.5 mm Kevlar

line

was positioned below the float and adjacent to the acoustic release. This line, with one end I

anchored to the upper platform and the other attached to the float, served as the primary recovery

lineforthearray. II

J

Array subsystems as described below were mounted on specially designed, stainless steel

(Type 304) frames (Appendix A). The profile, strength, and weight of these frames was intended II

to minimize the potential for interference with (or disturbance by) bottom fishing activities. The II

frames were octagonal in form with a maximum width of approxi[mately 4 m. Contoured lead

weights were bolted in place around the perimeter of the base, providing a stable, low-profile •

mass to anchor the array and provide a footing with minimal fronted area and presumed potential U

for flow disturbance.

d_

However, following analysis of $4 current meter records from Deployments 1 and 2 (Figure 2.1- I

l a), including comparisons with nearby (primary) mooring data, it was determined that the

stainless steel frames were adversely affecting the velocity data by producing a clear bias in both II

speed and direction. Since the factors responsible for the apparent anomalies could not be simply J

defined, the decision was made to replace the stainless frames with a taut-wire (in-line)

configuration consisting of a fioatation array supported by a stainless mounting bracket bolted to

and extending upward from the $4 current meter. The lower attachment point on the current W

meter was shackled to a short length of dacron braided line, which in turn was attached to an

acoustic release (Datasonics ATR-397) and a recovery line canister mounted on a lead dead- I

weight anchor. In this configuration, the optical sensors were positioned approximately 3 m

III

above the sediment-water interface at a single point on the vertical attached to the stainless

bracket holding the floatation (Appendix A). Sediment traps were located at two points on the I

vertical: one set mounted immediately adjacent to the optical sensors (3 m above the bottom

w

(mab)) and a second attached to the recovery line canister on the anchor (<0.5 mab). Data I

reviews indicated that, although the modified configuration did not provide the physical protection I

afforded by the original stainless frames, it did serve to eliminate the velocity bias apparent in

the data obtained during Deployments 1 and 2. This in-line design was utilized for the II

Deployment3 period (January1994-January1995;Figure 2.1-1a).

Regardless of the design (hemispherical or in-line), each array contained a single electromagnetic I

current meter (InterOcean $4) with integral sensors for water temperature, conductivity, and II

pressure. The current meter and associated sensors were positioned to sample conditions

approximately 1 m above the sediment-water interface. This position corresponded to an •

intermediate substrate relief height relative to the low relief (< 0.5 m) and high-relief (- 1.0 m+) II

2-38 I

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I heights studied for other components of the Phase III program (discussed in this section and

Section 2.4.1). The current meter also provided power for and received data output from two

I optical backscattering probes (Downing & Associates OBS-3) designed to monitor suspended material concentrations. These probes were located approximately 1.0 and 1.5 m above the

bottom for the 1992-1993 deployments and 3 m above the bottom for the 1994-1995 studies (see

I above).

During Deployment 1, each current meter system was programmed to "burst-sample" all sensors

I at a rate two hertz a periodof approximatelysixtyseconds. For four times each hour of for

Deployments 2 and 3, the burst sampling rate was reduced to two times per hour. Following

burst-averaging, all data were recorded internally on a solid-state memory system having a one

I megabytecapacity.

i InTwoaddition of the traps to thewere electronic positionedsystems, immediately each instrument adjacent array to the contained sediment-water four "mechanical" interface and STs. two

were placed at a higher elevation, approximately 1.5 m and 4.5 m above the bottom for the 1992-

I (6.6 1993cmandinternal 1994-1995 diameter) deployments, with anrespectively. approximate All lengthtrapsofwere 45 cm. constructed Alusterofofclear10 acrylic mm diameter tubing

plastic tubes were used to form a honeycomb (baffle) structure in the upper 10 cm of each trap.

I Chemical additives to inhibit biological activity in the traps were not used.

Prior to deployment of the PMAs, the electronic subsystems were calibrated in the laboratory to

I ensure accuracy and proper functioning. The current meter and associated sensors for water temperature, conductivity, and pressure were calibrated by the manufacturer. The optical sensors

were laboratory-calibrated at the University of Connecticut using various concentrations of

I sediments suspended by mechanical agitation in a saltwater bath. Characteristics of the calibrating sediments, with particular emphasis on grain size, were similar to those expected at

the study sites. The laboratory data indicated that the response of the sensors was reasonably

I linear over a concentration range of 0-80 mg/liter (SAIC and MEC 1993). These maxima generally exceeded concentrations observed along exposed continental shelf areas.

I The PMAs were deployed by careful lowering while attached to the winch cable on the survey

vessel. Following placement of the array on the bottom the cable was released acoustically.

Recovery normally was planned using activation of the acoustic release and subsequent surfacing

I to However,duringsomesurveysthe acousticrelease

of the float attached the Kevlar line.

system did not function properly, thus requiring the use of an ROV equipped with a lifting-line

attachment.

!

After recovery of the PMAs, the internally recorded data were downloaded onboard the survey

i vessel initially using screened a portable to evaluate computer. sensor performance Calibration data and anythenneedwereforapplied sensor and replacement. each recordTypical was

problems included partial malfunction of several of the optical sensors, with some portion of

i signal removeddegradation from an array, associated visuallywithexamined biofouling. (notingAdditionally, stratification, each inclination of the ofmechanical the sediment-water STs was

I 2-39

I
!

interface, color, and presence or absence of biota) and then emptied into precleaned glass jars. I

The jars were refrigerated and returned to the University of Connecticut laboratory for analysis

ofthe dry weightof materialandthe combustiblefraction. I

2.2.4.2 Laboratory/Data Analyses I

II

Manufacturer's software (InterOcean, Inc.) was used to convert current speed and direction, i

pressure, salinity, and temperature data from the $4 current mete]" systems to engineering units.

Data for optical backscattering were output as voltages, which _ten were converted to units of i

milligrams/liter using a regression equation derived from calibration data (SAIC and MEC 1993). |

All data then were plotted and visually inspected for outlier value:s, which were eliminated from

the database. After this first-order quality control procedure, time series data files and plots of II

instantaneous burst-average values were generated. These instan_aeous values were essential for II

evaluation of local sediment resuspension and/or deposition and, in combination with the low-pass

filtered current meter data, complemented efforts to resolve larger-scale routes and fates of i

sediment transport. II

Spectral analysis of selected time series data used a standard Fast-Fourier Transform algorithm III

(Matlab Mathematical Software). The data were binned and transformed such that each frequency m

estimate represents an ensemble average having particular degrees of freedom and associated

confidence limits. The 95% confidence interval for the spectral estimate also was calculated, i

The resulting frequency spectrum was plotted with-the accompanying 95% confidence intervals. II

Sediment flux values (g/m2/day) for the STs were based on dry weight determinations of the i

material recovered in each trap. The ST samples also were combusted at 550 ° C for one hour i

and reweighed to determine organic content (i.e., weight loss on combustion). D

2.2.5 SedimentMeasurementRods l

2.2.5.1 FieldSurvey I

!1

Assessments of changes in bottom sediment levels, potentially associated with sediment transport i

events, were planned as an incidental activity associated with ROV recoveries of the STs

(Section 2.3). For this purpose, SMRs were deployed in October/qqovember 1991 at each of the I

nine ST sites (Figure 2.1-4). Each SMR consisted of an approximately 0.75 m2 steel base (for i

stability) with a spring connection to an upright, 1 m tall rod. The spring system was intended

to minimize interferences associated with bottom trawling activities. Each rod was coded with i

separate identifying marks and the length of the rod was marked in centimeters to indicate the

2-40 i

I
!

I height of any sediment accumulation. Location and documentation of changes in sediment levels

was to be accomplished using the video system on the ROV. Deployment of each SMR was

I performed by lowering it to the bottom while attached to the survey vessel's winch cable. Release of the SMR from the cable was accomplished using a pelican-hook system.

I Following deployment of the SMRs in October/November of the units have been 1991, none

observed again during normal survey operations using the ROV. The reason for the

disappearance of the units is unknown but may be related to the low "reflective" profile of the

I SMRs. Thus, no SMR data are available for this report.

I 2.2.6 Particle Transport Modeling

I A simple particle tracking model, detailed in Appendix A, was utilized for the Phase III study.

The model is similar to the model of Fry and Butman (1991) which was used to estimate the

I footprint that would result from the dumping of municipal sludge at the deepwater 106-Mile Site,

offshore of New Jersey. The Fry and Butman (1991) model is also the basis of the drilling mud

deposition model used in Phase II (Coats 1994), although Coats used only one particle size class

I instead of the three classes used for Phase III, and Phase III used instead of multiple single

current meter mooring data (discussed below).

I Tracking a surrogate particle class, in this case coarse sand, coarse silt, and clay-silt, of each size

is a good representation of the dispersal of a cloud 6f material as long as all scales of motion are

i sampled. This will be the case if sufficient numbers of particles are released over the drilling periods. The number of particles released per hour is proportional to the daily discharge of

drilling muds. Thus, the discharge rate of particles is time variable with a daily time step. The

i basis on dispersion of the surrogate by particle assumption is the theories of Batchelor (1952) and Taylor (1954) random movements. The main result, applicable to particle settling models, is

that cloud dispersion from an ensemble mean position is given by single particle statistics (Fischer

i etal. 1979).

The Phase III model advects particles of the three size classes horizontally according to estimates

I of local current velocity at each time step. The vertical distance traveled is given by the sinking velocity. The particle's position is computed according to equations presented in Appendix A.

I This equation is repeated for all active particles in the water column. To estimate velocity components, (u and v), all available current meter records were used from nearby moorings. For

the September 1993 to June 1994 drilling periods, records were used from the Primary (P) (near

I Hidalgo), $5 (near Hermosa), $6 (offshore from P; Figure 2.1-1a), and the SIO Santa Barbara Channel mooring SMIN. Where records are missing or short, the continuous sections of the 3-

HLP records (Appendix A) were merged together using flag values. Thus, each meter position

I has an associated velocity (u, v) time series covering the year-long deployment period, with flag values denoting data gaps.

I 2-41

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|

At each time step, the valid velocity records at each position for all the moorings are identified, m

An objective method (Appendix A) is used to find the nearest velocity position to the particle. II

The procedure weights the nearest mooring more strongly than velocity values at similar depths II

to z but on moorings further away. In this manner, data gaps on a particular mooring are

w

minimizedby employingdata at similar depths from other positions, n

n

Linear interpolation between velocity positions on the selected mooring is used to find u and v

at depth z, where appropriate. In this manner, the model attempts to account for the vertical and Ii

horizontal spatial variability of the current field seen by a particle as it moves away from the |

disposal site. Some scales of motion, such as tidal variability, will only be partially captured

because of the limited vertical and horizontal distribution of the cub.rentmeasurements. Data gaps •

also cause a deterioration in the quality of the local interpolated velocities. However, over many II

realizations of particle tracks, the stochastic behavior of disper,;ing particles should be well

captured on average. The larger scale variability of the flow should also be captured, in its II

essentials, by using an array of moored instruments rather than just a single mooring, as is more II

usual in particle tracking models.

Because the model estimates the current field at any one time frora a limited number of current I

meters, the accuracy of the estimation deteriorates at distances from the moorings of more than

10-20 km and 5-10 km in the along-isobath and cross-isobath directions, respectively. Thus, the •

cumulative deposition footprints calculated by the model should be regarded as indicative of the II

general patterns of deposition that result from platform discharge.,; during Phase III.

n

The random dispersion velocities are used to account for dispersion caused by small scale

turbulence and motions not well resolved by the moored array. The velocity components are

randomly selected from the range [-p,p] at each time step (Appendix A). The random velocity I

fluctuations are related to a horizontal dispersion coefficient (D). For offshore ocean

environments, a dispersion coefficient of 1 m2/s is typical (Ledwell and Watson 1991). The imam

results are not sensitive to values of D less than 10 m2/s. I

The time step is chosen from the time for a particle to fall 50 m or the velocity time series Ill

interval of 1 hour, whichever is less. Before each execution of the primary model formula, the II

position of the particle is checked to see if it has intersected the bottom of one of the outer

boundaries of the grid. If the particle has intersected the bottom, it is flagged and its position m

recorded. If it has exited the grid, it is flagged as "lost". At the end of the particle tracking m

period, the positions on the bottom where the surrogate particles have settled are accumulated

ontoa regulargridintermsof particlespergridcell.

The model is run for all valid size classes, and the results are reported as concentrations per

square meter per kilogram dumped of each size class. I

m

The percent loss is calculated for each size class and then weighted to produce the percent of the

total solid material dumped that is not deposited and which escapes through the boundary of the I

|

2-42 U

I
!

I grid. This total percent loss is entirely accounted for by coarse silts and clay-silt (classes 5 and

6).

l

2.3 CHEMICAL PROCESSES !

I Chemical processes tasks included field surveys (Section 2.3.1) for collections of (1) surface sediment samples using a Van Veen grab, (2) surface and subsurface sediment samples using a

box corer, and (3) suspended particle samples using STs. Representative platform discharge

I samples, including drilling muds, cuttings, and produced waters, as well as formation oils, and a petroleum product (diluent) from the Guadalupe oil fields, also were collected. Laboratory

analyses (Section 2.3.2) included analyses of samples for trace metals and hydrocarbon

I parameters, as well as measurements of sediment grain size (particle size), total organic carbon (TOC) concentrations, and mineralogy. Data analyses (Section 2.3.3) were used to evaluate

spatial and temporal trends relative to the platforms and between phases, respectively. !

2.3.1 Field Surveys !

i 2.3.1.1 Surface Sediments

I Surface sediments were collected at nine sites near the hard-bottom study locations associated

with Platform Hidalgo (Figures 2.1-1 c and 2.1-4). Three separate samples were collected at each

I station with a 0.1 m2, Kynar-coated Van Veen grab. The 0-2 cm layer of sediments in each sample was removed from the sampler with a Kynar-coated scoop. The three samples were

subsequently combined in the analytical laboratory into a single composite for each station. Prior

I tomethanol. sampling, the sampler was cleaned by sequential rinses with filtered seawater, hexane, and

I The composite samples of surficial sediments (i.e., from the three grab samples at

a given station)

were analyzed for trace metals, hydrocarbons, TOC, inorganic carbon, grain size, and mineralogy.

Samples for trace metal and hydrocarbon analyses were placed in precleaned glass jars and stored

I analysis. Samples analysis TOC,inorganiccarbon,grain

at approximately .20 ° C until for of

size, and mineralogy were placed in Ziploc bags and stored at 4° C. These latter samples were

not frozen to avoid chemical and physical changes caused by freezing that could compromise

I analytical results for these parameters.

!

I 2-43

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!

|

2.3.1.2 Surface and Subsurface Sediments "

!

A 0.015 m2 box corer was used to collect surface and subsurface sediment samples from the

radial array of stations near Platforms Hidalgo, Hermosa, and Harvest (Figures 2.1-1 c and 2.1-6).

After retrieval of the samples onboard the survey vessel, the box portion of the corer was U

removed and placed on top of an extrusion stand. The sediment then was pushed through the box

portion of the sampler. The surface layer (0-2 cm) was collected with a Kynar-coated scoop and m

placed in a precleaned glass jar. The subsurface layer (10-12 cm) then was pushed through the |

box, collected with the scoop, and placed in a glass jar. All samples were stored at

approximately 4° C or -20° C until analysis, as appropriate for the different sample types as noted •

above for surface sediments. I

2.3.1.3 Suspended Particles I

l

Samples of suspended particles were collected in STs from nine stations associated with Platform [I

Hidalgo (Figure 2.1-4). STs that had been deployed in October 1990 during Phase II first were

collected during Phase III in October 1991. The ST arrays for Phase III then were deployed for

periods of either six or twelve months (Figure 2.1-1 b). The variation in collection schedules for

some STs was due to unfavorable weather conditions that forced delays in some recoveries.

Sediment trap arrays consisted of a 1 m diameter cement base with spring supports of stainless

steel for four individual traps. Each trap was constructed of butyrate tubing having Hexcel

baffles with 1 cm cell spaces in the mouth of the tube to reduce turbulence. The diameter of

each trap is 6.6 cm, and the height:diameter ratio of the baffle cells was approximately 7:1.

Replicate traps were seven diameters apart and the openings were 1 m above the sea bed.

Sodium azide was added to each trap as a preservative. I

For retrieval, ST arrays were located using the ship's precision navigation system and the ROV

color

sonar system. A snap-hook with a line was attached using the manipulator arm on the ROV I

to a lift ring in the center of the array. The line then was used to hoist the trap array to the

survey vessel, n

upon recovery of each array, individual traps were removed and the particles were transferred

to prelabeled sample jars. The sampling tubes were thoroughly cle,aned with freshwater and the II

azide preservative was replenished prior to redeployment. Occasionally, the baffles of several I

ST tubes were completely or partially blocked by attached anemones (Metridium giganteum).

In these cases, an estimate was made of the percent coverage of the tube by the anemones. I

Sediments from these tubes were not used for measurements of sample mass. l

Samples for measurements of trace metal and hydrocarbons were stored onboard the survey vessel n

at approximately -200 C. Samples for TOC and particle size measurements were stored at II

2-44 U

!
!

I approximately 4° C. Samples were analyzed for total dry weight (for particle flux calculations);

trace metal, hydrocarbon, and total organic and inorganic carbon concentrations; and grain size

I distributions.

I 2.3.1.4 Platform Samples

I Representative samples platform discharge (drilling muds, cuttings, produced of materials and

waters) and formation oils from Platforms Hidalgo and Hermosa were collected by the operators

and placed in precleaned glass jars provided by SAIC. (No samples were collected from Platform

I Harvest because no drilling occurred from this platform during Phase III). Samples from multiple

wells at each of the two platforms subsequently were composited by well depth into surface, midi

the depth, Guadalupe near bottomoil field (mudsalsoonly), was and obtained bottomfromsamples. CaliforniaA sample Department of the ofpetroleum Fish andproduct Game. from

I 2.3.1.5 Quality Assurance/Quality Control

I Collections of field samples were performed according to Standard Operating Procedures (SOPs)

developed for this program. The SOPs included protocols for cleaning sampling equipment prior

I to deployment, collecting samples using noncontaminating methods, sample labeling, completing chain-of-custody forms for sample shipments, and-collecting field blanks and equipment rinse

samples to evaluate possible contamination during collection and shipping procedures. QA/QC

I samples for the field collections consisted of field blanks (i.e., empty sample containers that were taken on a field survey and returned to the analytical laboratory), field equipment rinses (i.e.,

distilled, deionized water rinses for cleaned sampling equipment in the field), and duplicate field

I samples. The frequency of collection of each of these three QA/QC sample types was approximately 5% of the total number of field samples.

I 2.3.2 Laboratory Analyses

!

Analyses for trace metals and hydrocarbons were performed by Texas A&M University/

I TGeochemistry OC, and and Environmental Research Group (TAMU/GERG). Analyses for grain size, inorganic carbon were performed by MEC. Mineralogy analyses were performed by

the Clay Minerals Analysis Laboratory at San Diego State University (SDSU).

I Triplicate samples collected using the Van Veen grabs were composited in the analytical

laboratory prior to removal of aliquots for individual chemical analyses. Samples from STs and

I box cores were aliquoted directly from original containers.

I 2-45

!
!

|

2.3.2.1 Hydrocarbons II

Sediments and suspended particles, drilling muds and cuttings, formation oils, and the Guadalupe U

diluent were prepared for hydrocarbon analysis according to TAMU/GERG SOP No. 8902 mm

(Extraction of Sediments for Hydrocarbon Analysis). Briefly, samples were Soxhlet-extracted I_

in methylene chloride (DCM). Extracts were combined and dried by passing through anhydrous

u

sodium sulfate, concentrated, and then solvent-exchanged from DCM into hexane. Final extract m

volumes were reduced and extracts were subjected to liquid-.column chromatography for I

separation into saturated and aromatic fractions.

Chromatographic separation into saturated and aromatic fractions were performed using silica gel. N

Saturated hydrocarbons were initially eluted with hexane; aromatic hydrocarbons were

subsequently eluted with a mixture of DCM and acetone (1:1, v:v). Final extracts for saturated m

and aromatic hydrocarbons were concentrated and analyzed by flame ionization detector-gas II

chromatography (FID-GC) and gas chromatography/mass spectroscopy-selected ion monitoring

mode (GC/MS-SIM), respectively. Saturated biomarkers (steranes and terpanes were analyzed

in selected suspended and surficial sediment samples, drilling muds and cuttings, and formation I

oils. Analyses for triterpanes and steranes were performed by GC/MS-SIM (m/z 191 and 217)

according to TAMU/GERG SOP No. 9221 (Quantitative Analyses of Steranes and Triterpanes

in Sediment Extracts and Oils by GC/MS).

Prior to analyses for saturated or aromatic hydrocarbons, linear calibration curves were developed •

with standard solutions of appropriate target analytes at five concentration levels. Surrogate II

spikes were performed in the laboratory for all field samples and quality control samples.

Laboratory spikes and analyses, consisting of matrix spikes and matrix spike duplicates, were

performed for every 20 samples or with every sample set, wtfichever was more frequent. J

Duplicate analyses by FID-GC or GC/MS-SIM were performed with a frequency of one for every

20 samplesor sampleset,whicheverwasmorefrequent. I

Analyses of saturated hydrocarbons were performed according to TAMU/GERG SOP No. 8904

[Quantitative Determination of Aliphatic Hydrocarbons and UCM (Unresolved Complex I

Mixture)]. Samples were analyzed for n-alkanes, pristane, phytane, total resolved hydrocarbons,

w

and UCM. Procedural (method) blanks were analyzed at a freque_acy of one for every batch of im

1 0 samples. FID-GC analyses for saturated hydrocarbons were performed on a Hewlett Packard

5890 Gas Chromatograph with splitless injection mode and a 30 rn long x 0.32 mm I.D. DB-5

fused silica capillary column. Output from the GC was processed using an automated HP-LAS In

3357 data acquisition software package. |

Analyses for polynuclear aromatic hydrocarbons (PAHs) were performed by GC/MS-SIM a

according to TAMU/GERG SOP No. STO-3 [Quantitative Determination of Polynuclear l

Aromatic Hydrocarbons by Gas Chromatography/Mass Spectrometry (GC/MS)-Selected Ion

Monitoring (SIM) Mode]. Selected target analytes were identified and quantified using primary •

II

2-46 U

I
!

I quantitation ions and accompanying secondary confirmation ions. Final confn'mation of target

analytes was based on specific retention-time data for selected compounds.

I Detection limits for individual n-alkanes, isoprenoids, and PAHs were estimated to be three times

the standard deviation about mean values from replicate analyses of low-level matrix spike

I samples. One quantitation ion and two confirmation ions monitored for per compound were

PAH compounds in specific retention-time windows to establish baselines. Generally, detection

limits for saturated and PAH compounds were estimated as 12.5 ng/g dry weight and 5 ng/g dry

I weight, respectively, samples. for sediment

I 2.3.2.2 Trace Metals

I Samples of sediments, suspended particles, and drilling muds and cuttings were acid digested for

subsequent analysis of trace metals (except barium) according to TAMU/GERG SOP No. STO-8

i digested (Digestionin ofconcentrated Sediment fornitricTrace(HNO3) Metal andAnalysis). hydrofluoric Samples (HF)were acidsinitially at 130°freeze-dried C. Following and

digestion, the samples were diluted to final volume with boric acid (HaBO3). Samples for barium

I (Ba) flux ofanalyses 1 x 10_3n were/cm2 dried, /secplaced with thein heat-sealed TAMU Trigapolyvials, Reactor.and then irradiated at a thermal neutron

I Digested samples were analyzed by (1) flame atomic absorption spectrophotometry (FAAS) for aluminum (AI) and chromium (Cr); (2) graphite fm-nace atomic absorption spectrophotometry

(GFAAS) for arsenic (As) silver (Ag), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb),

I nickel (Ni), and zinc (Zn); (3) cold vapor atomic absorption spectrophotometry (CVAAS) for mercury (Hg); and (4) instrumental neutron activation analysis (INAA) for Ba. The methods are

described in TAMU/GERG SOPs STO-9 (Analyses of Trace Metals by Flame Atomic

I Absorption), STO-10 (Analysis of Trace Metals by Graphite Furnace Atomic Absorption), STO-11 (Analysis of Mercury by Cold-Vapor Atomic Absorption), and STO-16 [Quantitative

Determination of Selected Trace Elements by Instrumental Neutron Activation Analysis (INAA)].

I Analyses of procedural blanks, duplicates and matrix spikes, and certified reference materials

were performed at the same frequencies as noted for hydrocarbon analyses.

I 2.3.2.3 Total Organic Carbon

I

Analyses for TOC were performed on suspended particles and surface sediments, and drilling

i mud CarbonandSample cuttingsProcessing). samples asSamples describedinitially in MECwereSOP-III.C.3, treated with Revision phosphoricNo. acid,1 (Total distilledOrganic water,

and potassium persulfate, and then purged with oxygen to remove residual inorganic carbon.

i carbon Samplesdioxide then were by sealed oxidationin individual at elevatedglass temperature ampules and and the pressure. organic The carbonconcentration was converted of theto

I 2-47

!
!

! resultant carbon dioxide was determined by infrared spectroscopy. QA/QC analyses were

performed in conjunction with field samples and consisted of duplicate analyses, surrogate spikes,

and external reference standards that were analyzed with every sample set at a frequency of 10%. I

2.3.2.4 Inorganic Carbon I

iota

Total inorganic carbon in sediment sampleswas measuredin accordancewith MEC SOP-III.C.9 IB

(Total Inorganic Carbon Processing Procedures). Inorganic carbon was converted to carbon U

dioxide by addition of phosphoric acid, followed by sample combustion. The concentration of

the resultant carbon dioxide was determined by infrared spectroscopy. QA/QC analyses consisted •

of a minimum of 10% duplicates. Additional instrument carbon dioxide standards were checked l

before and after each batch of readings.

!

2.3.2.5 Grain/Particle Size Distribution

!

Grain size analyses were performed on all samples collected in STs and Van Veen grabs, as well

as drilling muds and cuttings samples. Percentages of gravel, sandt,silt, and clay fractions were II

determined according to MEC SOP-III.C.2, Revision No. 2 (Gra:in Size). Samples first were I

treated with a deflocculant to break up aggregated sediment particles. Gravel and sand particles

then were separated using decreasing sieve sizes. The separated particles were dried and weighed i

for percentage determinations. A pipette analysis was performed to determine the silt-clay g

fraction. Triplicate analyses and analysis of reference standards were performed routinely with

eachsamplebatchofoneto sevensamples.

2.3.2.6 Mineralogy I

m

The < 4-micron size fraction of bottom sediments from Van Veen grab samples was analyzed for •

mineralogical properties according to procedures in Berry and Nocita (1977). Aliquots of the

m

samples first were dispersed in deionized water. The < 4-micron size particles then were smeared In

on microscope slides and subjected to air drying, glycolation, and heat treatment. Final X-ray I

diffraction analysis was performed using a Diano X-ray diffraction (XRD) instrument.

!

2.3.2.7 Total Dry Weight (Flux)

!

Measurements for total dry weights were performed on solid mate:rials from each of the STs to

determine particle flux. Fluxes were calculated with the following; equation: m

I

2-48 l

I
!

I Flux = (g/mE*day)

I where:

Flux = grams dry weight per mE per day,

I = dry weight of particulatematterin a tube, g

m2 = surface area of tube (0.0034 m2), and

i day = deployment period (ca. 6 and/or 12 months in units of days).

I 2.3.3 Data Analyses

I Approaches to analyzing the chemical data emphasized (1) consistency with the Phase II program to permit direct comparison between different phases of the monitoring program, (2) integration

with time series data compiled during Phase II, and (3) applications of hydrocarbon composition

I information to "fingerprint" or identify sources of hydrocarbons in samples. For example, composition information was used for evaluating the relative contributions of petrogenic,

pyrogenic, and biogenic hydrocarbons. This procedure facilitated distinctions between oils

I derived from natural in the study area and other anthropogenic sources.

seeps

Statistical analyses, including linear regression, t-tests, and analysis of variance (ANOVA), were

I evaluate and trends and between different and used to spatial temporal relationships physical

chemical variables. Additionally, patterns of excess Ba in sediments near each of the three

platforms were evaluated using the procedure developed by Boothe and Presley (1985). Total

I excess Ba was calculated from measurements in surface and subsurface sediments at the radial

array of stations around a platform. Excess Ba was calculated by subtracting the background Ba

i concentration from the measured concentration. The background concentration was interpolated over the nearfield region of the platform from subsurface sediment concentrations at sites 500 m

and 1,000 m from the platform. This approach was used to account for the depth-related gradient

i inby sediment multiplyingBa the concentrations. area describedTheby volume a linear ofdecrease sedimentwithcontaining depth to "excess a presumed Ba" was background calculatedin

Ba concentrations by an unit surface area. The linear decrease with depth represents a reasonable

I approximation Unit volumes were of sediment multipliedBa byprofiles the sediment reporteddensity by Crecelius (assumed(1990) to befrom2.6 the g/cmPhase 3) andIItheprogram. excess

Ba concentration. Excess Ba (in kg) was summed for all unit areas within 500 m of Platforms

I Hidalgo, Hermosa, and Harvest.

Principal component analysis (PCA) was performed using hydrocarbon (PAHs, sterane, and

I terpane biomarkers) data from selected suspended sediment samples from Stations PH-N, PH-R, and PH-K, formation oil from Platforms Hidalgo and Hermosa, a seep oil collected near Platform

Hondo, and petroleum product (diluent) collected at the Guadalupe oil field. The PCA was

I performed using the program SIRIUS (Pattern Recognition Systems A/A, Bergen, Norway). The data were scaled prior to analysis to avoid biases caused by parameters with large variances.

I 2-49

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2.4 BIOLOGICALPROCESSES _t

Biological processes tasks are described in the following sections for the hard-bottom community •

assessment (Section 2.4.1); larval experiments, including in situ and laboratory toxicity tests

(Section 2.4.2); and reconnaissance of anchor scar/drill cuttings effects (Section 2.4.3).

!

2.4.1 Hard-Bottom Community Assessment

!

2.4.1.1 FieldSurvey I

The study sites for the hard-bottom community assessment consisted of nine rocky reef areas in B

the vicinity of Platform Hildago (Figure 2.1-3). These sites were chosen in Phase II to

encompass (1) various distances from Platform Hildago (approximately 0.5-6.5 km), (2) a range •

of water depths (shallow depths of 105-119 m and deep depths of 160-212 m), and (3) different

relief heights (low relief of approximately 0-0.5 m and high relief of greater than 1.0 m).

m

Epifaunal surveys in both phases were limited to low-relief habitat,,; at Stations PH-F, PH-U, and I

PH-N, while surveys in Phase III noted areas of substantial high :relief at Stations PH-I, PH-J,

and PH-E that were not found in Phase II. Another difference between Phases II and III was the •

reported presence of extensive areas of high relief but no low-relief areas at Station PH-K during

Phase II, whereas opposite trends were noted in the Phase III surveys. III

Phase II sampling was conducted in October 1986, July and November 1987, October 1988, May

and October 1989, and October 1990. Phase III sampling occurred in November 1991, October

1992, and January 1994. Surveys at all sites also were conducted in January 1995; however, •

analysis of these data was beyond the present financial scope and therefore is not addressed in

this report. I

Survey methods for Phase III generally followed those of Phase II using an ROV equipped with

color and black and white video cameras, a 70-mm still camera and strobe, two split-beam lasers m--

for

focus, and a Mesotech color side-scan sonar (Hardin 1988; Hardin et al. 1991). One I

difference was the use ofa 35-mm still camera system during the January 1994 and 1995 cruises.

This change was made due to the increasing scarcity of 70-mm cameras for lease, considerable II

time and expense for film processing, and judgment by the project biological observers (who have |

extensively used both 35-mm and 70-mm systems and data) that there were no important

differences in data quality for this study area when 35-mm was used. The ROVs used for the 1

2-50 I

!
!

I 1991, 1992, 1994 and 1995 surveys were RECON-IV, PHANTOM, and Benthos SEAROVER

respectively.

I Photoquadrats: A 70-mm or 35-mm Photosea still camera system and Osprey color video camera

were used for collecting photoquadrat and broader-view community data, respectively. The still

I had internaldatachamberthat with thetime and station

camera an was synchronized number,

allowing for cross-referencing with navigational data (time and navigational position of the ROV)

and the video record. Laser images determined the proper distance from the camera to the

I bottom so that the photographed area represented 1

m 2"

I The sites field includedsurveypresurvey, methodssurvey, used toandcollect postsurvey photographic testing andand video data collection data at theactivities. nine hard-bottom Prior to

an ROV launch, the still camera was test fired, the video color image was checked, and the ROV

i was the bottom. visually inspected. Once the ROVThe ROV was onwasthethenbottom, deployed an from the navigation the surveyandvessel all other and maneuvered systems wereto

verified as functional, the color video and observer commentary were initiated. Biological

I ooperation. bservers provided The observers video recorded commentary, photographic directed information the ROV operati (e.g., otime n, andof photographs controlled theandcamera relief

height) and summarized the species, habitats, and any notable events (e.g., unusual organisms or

I substrate features) on survey log sheets.

Photographic surveys followed procedures established during Phase II for low- and high-relief

I stations. The two different relief methods were combined in mixed habitat areas and did not affect data comparability. At low-relief stations, the ROV was directed on a random heading,

with the camera directed downward, photographing hard-bottom features approximately once

I every sixty seconds. When a soft-bottom area was encountered, the ROV was directed along another random heading and the process was repeated. At high-relief stations the procedure was

similar, but with the camera directed forward. When a high-relief feature was encountered, the

I ROV was maneuvered around, up, and down a rock feature, taking non-overlapping photographs. After the feature was photographed, the ROV travelled along another random heading until the

next feature was located. In mixed habitat, the relief height determined the photographic method

I thatwas used.

Attempts were made to obtain at least 60 photographs (70-mm or 35-mm slides) for each relief

I category However, some difficultiesorthe lackof appropriate at each site. because of technical

substrate at a few study sites, fewer photographs were obtained in some areas. A total of 476,

I 815, and 744 photographs were analyzed for 1991, 1992, and 1994 respectively.

!

!

I 2-51

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2.4.1.2 Laboratory Analyses ==

Still Photographs: Still photographs from the surveys were analyzed using a point-contact method I

m

that initially included twelve random grid patterns. Each grid pattern contained fifty randomly n

placed dots. A different

pattern was selected for each slide by random draw from a pool of I

numbers. Each slide was projected, at life size (1 m2), onto a screen containing one of the

random dot patterns. This random grid pattern method was used for the 1991 and 1992 data; n

however, based on consultation among project scientists, the QRB, and DOI, an evenly spaced,

50-dot grid pattern was used for the 1994 analyses. This change was based on common usage

of evenly-spaced grids by several other studies (P. Dayton, pers. comm.) and the greater []

efficiency achieved during analyses as compared to use of the random grids. Irrespective of the U

grid pattern, the species or substrate type under each point, as well as the counts of individual

or solitary species, were recorded onto computer keypunch sheets. In addition, counts of all taxa

that occurred in the slide, regardless of whether they fell under a contact point, also were II

recorded. A default percent cover of 0.5% was assigned to species, counted within each slide but

for which percent cover estimates were not appropriate (e.g., for crinoids). This default percent n

also was used for discrete organisms that were counted but did not fall under a contact point. |

However, one of the inherent problems in the Phase II databases was that these default

percentages were recorded as 1.0%. Because of this, default percentages could not be

distinguished from percentages that fell under a contact point and had an actual value of 1.0%.

Another difficulty with the Phase II database was that the sum of the percent cover for all

organisms in a slide often exceeded 100% by as much as 20-40%. This overestimate also limited •

comparisons of some Phase II and Phase III data. Similar to methods used in Phase II, the

percent cover was adjusted for dots that fell on shadows or soft sediments; counts of individual

organisms were normalized to the visible hard substrate in each photograph. I

Another difficulty in comparing data between Phases II and III involved taxa that only could be

identified by a descriptive name (e.g., yellow encrusting sponge). To maintain taxonomic n

consistency and comparability of data between phases, a list of all taxa recorded from Phase II

was used to establish data sheets for the analysis of Phase III photographs. However, many taxa iml

observed in Phase III were not listed for the Phase II study and, therefore, these new taxa were •

added to the master list. All taxonomic differences could not be resolved based on available w

information. However, the results indicated that the data sets were comparable for most of the t

common taxa. When differences were noted, temporal plots of these taxa combined all species I

for a particular group at a more general taxonomic level. This allowed greater consistency

between Phase II and III comparisons. Some differences also existed in the level to which II

taxonomists identified various species groups between Phases II and III. For example, ophiuroids |

and polychaetes were identified to a lower level (e.g., Genus or Species) during Phase III than

duringPhaseII.

Statistical analysis of the community data used multivariate classification analysis of the 50 most

dominant taxa for low- and high-relief habitats to delineate the major trends in biological []

communities, and the 20 most dominant taxa for characterizing the ]habitats. The analysis utilized []

2-52 I

!
!

I the mean percent cover for each taxon averaged for the Phase III surveys. Data were square-root

transformed and normalized to the standard deviation before calculation of Bray-Curtis distance

I (Bray and Curtis 1957). This step was done to keep the most abundant taxa from dominating the analysis. Cluster analysis using the Bray-Curtis dissimilarity coefficient and group-average

sorting strategy were used to group the data (Smith 1976). Both normal (stations) and inverse

I (species) analyses were conducted and plotted as dendrograms. A table of coincidence two-way

was produced to aid interpretation of the cluster results and to provide insights on physical

features that were associated with community trends. The analyses were run using SAS Version

I (SAS1990).

6

i Additionally, to evaluate potential relationships among biological parameters and physical/

chemical measurements, correlation coefficients (Pearson product moment) and linear regressions

were calculated for dominant taxa and sediment trap physical/chemical data collected near each

i hard-bottom percent cover site of dominant (Section taxa 2.3).to evaluate Analysis differences of covariance relative(ANCOV to distance A) also fromwasPlatform performed Hidalgoon

(Appendix D). Finally, power analyses (Green 1989), based on mean percent cover of dominant

i taxa, drillingwereperiods used (Appendix to estimate D). the power to detect decreases in abundance between pre- and postI Video Thirty Transect 1-minute Data: segmentsVideo (banddataquadrats) collectedof oneachrocktaperelief were were reviewed analyzed for each for site. all nineThesestations. band

quadrats were selected using non-overlapping navigational reference points that traced the location

I of the ROV coverage. This coverage was located on the video tapes by using the intemal time code that was synchronized with navigational records and continuously recorded on tape. In

order to obtain reasonably comparable bottom coverage among band quadrats, a standardized time

I increment of one minute of visually acceptable video was used. Time was counted only when the ROV was in motion and visibility was good. Visibility was considered unacceptable if the

ROV was too far off the bottom, or if excessive suspended sediments and/or organisms (e.g.,

I swarms of mysids) prevented identification of benthic taxa and substrate.

Within each band quadrat, all recognizable substrate features and organisms were listed as either

I present or absent. Substrate type was separated into four general categories: (1) soft-bottom, (2) extremely low-relief (< 0.15 m), (3) low-relief (< 1 m), and (4) high-relief (> 1 m). Other

descriptive substrate categories listed as present or absent were shell debris, tar, and oil or gas

I Individualorganisms identifiedto the lowest and either seeps. are possible taxon given

taxonomic or descriptive names that were as consistent as possible with Phase II designations.

These data were entered on coded data sheets for direct computer entry. !

Statistical analysis of the video data included assessments of communities and species by substrate

i type fish cand ommunity cluster utilized analysis allasfish described data, while for themacr 70-mm oinvertebrate photographic data were data. uCluster sed onlyanalysis when a oftaxthe on

occurred in more than twenty 1-minute segments for the entire survey.

!

I 2-53

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I

!

2.4.2 LarvalExperiments

I

Larval experiments consisted of in situ tests of settling and laboratory toxicity tests.

!

2.4.2.1 In Situ Experiments

!

In situ manipulations of larval settlement were conducted at sites near to and far from drilling

platforms. Two types of experiments, one using laboratory-cultured red abalone larvae and one II

using natural settlement, were performed. The red abalone experiments provided a basis for

u

determining factors which affected the settlement of a controlled population. Because natural

settling rates are relatively low (Mullineaux 1988), manipulations were performed in which II

known numbers of larvae were exposed to a series of treatments in the field to determine how

settlement was affected by: (1) waterborne factors (e.g. suspended solids, food, dissolved I

chemicals); (2) surface films on settlement plates (e.g. bacteria and.particulates incorporated into

the surface film); and (3) reef height. The specific design of these experiments allowed for the

determination of causation related to drilling operations. The natural settlement experiments were I

conducted over a variety of exposure durations from 3 to 1,000 days to evaluate settlement and I

recruitment over time, and included both pre- and during/post-drilling periods.

Three nearfield oil platforms and three farfield reference sites were utilized for the study. I

Nearfield sites were located near hard-bottom reefs adjacent to Platforms Hidalgo, Harvest, and

Hermosa (Figure 2.1-5), at approximately 200 m depth. The farfield sites also were near hard- •

bottom reefs, upcoast (1 site) and downcoast (2 sites) of the platforms along the same depth I

contour. The farfield sites were selected to be beyond the major iinfluence of Phase III drilling

activities based on dispersion and deposition information from previous studies (Phase II, Coats III

1994). In addition, experiments were conducted at two heights (0.25 and 0.75 m) above the II

ocean bottom corresponding to low and high relief reefs in the region (Hardin et. al. 1994).

II

Red Abalone Settlement

Red abalone larvae (Haliotis rufescens) were used for this settlement experiment. This species II

and life history stage has a number of desirable characteristics for use in in situ bioassays R

(Appendix C; Raimondi and Schmitt 1992), and preliminary studies showed that red abalone

larvae could survive and grow for exposures up to 23 days in the field at depths up to 200 m 11

(Raimondi and Barnett, unpublished data). Surviving individuals showed signs of healthy Ill

metamorphosis to the juvenile stage, active feeding on bacterial films on the plates, and normal

growth. These observations demonstrate that red abalone larvae can settle, survive, and grow !

under conditions typical of the natural field conditions in the study area.

I

Manipulated in situ settlement experiments using red abalone larvae were conducted in October I

1992 and January 1994 from the survey vessels M/V RAMBO and M/V INDEPENDENCE,

2-54 I

I
!

I respectively. Generally, each experiment consisted of a filming period and subsequent exposure

period, as described below.

I Settlement plates were placed into canisters and deployed approximately three weeks prior to the

start of the scheduled experimental period (Appendix C). The filming canisters were covered

I with 100 Nitex mesh to preclude natural settlement of larvae during the filming _tm process.

Filming canisters were placed at each of the six experimental sites at each of two heights, 0.25

and 0.75 m above the bottom.

!

Following the filming period, the plates were retrieved from the filming canisters and sorted to

I distribute plates from each filming site to each incubation (exposure) site (a reciprocal transplant design). Plates were secured into individual chambers attached to deployable larval arrays

referred to as igloos (Appendix C). Igloos were three-dimensional structures that carried plates

i onheldfour oneseparate settling plate faces and to accou was ncovered t for potentially with 100 confounding gm Nitex mesh. effects Plateofchambers currents. were Each"injected" chamber

with 500 (+ 50) competent red abalone larvae prior to deployment of the igloos for a planned

I three-day incubation incubation to prevent period. spontaneous Platesnatural remainedsettlement covered ofwithother Nitexinvertebrates mesh for, thepredation, duration and of theto

contain the red abalone larvae within the chambers. Four replicates were conducted of each

I combination original of filming site, incubation site, and relief height. Plates that were returned to their filming site were replicated by an additional four plates. In addition to the plates from

each filming site, sterile plates (no surface filming) also were transplanted to each site (4

I replicatesper site).

Completed trays were stored in cool seawater in the dark until just before igloo deployment.

I When all trays were completed (abalone larvae having been injected into all chambers), covers were placed over the trays to keep them bathed in cool seawater prior to deployment, and covered

trays were attached to the igloos. Igloos were then lowered from the ship to a depth of 8-10 m.

I Divers were deployed to remove tray covers and expose the chambers to in situ conditions.

After the three-day incubation period, the igloos were retrieved and brought onboard the survey

I vessel. Settled abalone larvae are resistant to desiccation and were attached firmly to plates; therefore, the igloos were brought directly from the bottom to the ship's deck without any

attachment of covers on the trays. However, once onboard, covers were immediately placed on

I each and the were moved back to the cool seawaterbaths in darkened until the tray trays a room

settlers could be counted. The number of settled red abalone larvae were counted microscopically

within two hours of igloo retrieval. Experiments carried out in October 1992, and January 1994

I yielded one data set each for the "pre-" and "during-drilling" periods.

i Data log e (x+l) were transformed analyzed usingdatafixed to meet effectassumptions analysis ofofvariance homoscedacity. proceduresFor(SASthis Institute design, if1988) drillingon

had an effect on settlement it would have been evident as an Experiment x Incubation or

I Experiment removed fromx Film the analysis). Type interaction Other effects (after Platform on settlement Harvest, associated where with no drilling patformoccurred, activities,is

I 2-55

!
!

besides drilling, should be evident as either effects of surface film:_(after the "no film" treatment I

is removed from the analysis) or of incubation location.

Natural Settlement Experiments ]]

For the natural settlement experiments, pre-settlement bacterial filming steps (using larval B

canisters) and deployment and recovery methods (utilizing three-dimensional igloos for

attachment of the settling plates), were conducted as described above for the red abalone

experiments and as detailed in Appendix C. Natural settlement experiments were conducted from i

April 1992 through January 1995. Exposure durations varied from short (3-21 days), to medium

(180-365 days), to long (460-1,000 days) time intervals. To belxer separate drilling effects, a •

series of medium length (300-365 days) experiments were also performed in both the pre-and |

during/post-drilling periods. Following retrieval of the igloos for each experiment, some settling

plates were photographed and redeployed to the bottom and others were returned to the laboratory •

for analysis. II

In April and October 1992, plates removed from the arrays for analysis were preserved in •

formalin and returned to the laboratory for identification and emtmeration of settled larvae. In

August 1993 and January 1994, all plates were photographed with 35-mm slide film, long-term

plates were returned to the arrays, and a subset of the plates was preserved and returned to the i

laboratory for analysis. In addition, in January 1994 a new set of filmed plates was deployed at

each site to determine effects from the during/post-drilling period. In January 1995 all plates

were retrieved, removed, photographed, and preserved in formalin for laboratory analysis. I

To address whether settling plate surface conditions (texture) might affect the settlement of

larvae, an additional experiment was conducted between August 1993 and January 1994. Three

plate surface conditions were tested: (1) smooth plates identical to those used throughout the i

study; (2) grooved plates; and (3) roughened plates (Appendix C).

!

In the laboratory, settling plates and slides were examined under a dissecting microscope. The

entire surface of the plate was examined and all organisms identified to the lowest possible taxon.

Organisms occurring as individuals were counted. Coverage estimates were made for colonial i

organisms which could not be enumerated. Additionally, photographs collected of the same

m

plates over time were used to estimate the growth and survivorship rates for selected taxa.

Fecundity was estimated by observing plates with high (>50%) coverage of hydroids on plates i

recovered following 365 days exposure during the during/post-drilling period. The proportion

of reproductive polyps in each colony was calculated for each plate. To determine if data from i

photographs of plates were comparable to data collected from direct observation of the plates, an i

evaluation was made using data collected from a subset of plates that were photographed prior

tolaboratoryanalysis. •

i

All data were coded in the NODC taxonomic coding system, double-entry keypunched, and

subjected to a minimum 10% QA/QC check on all data fields. Data were stored as SAS •

databases and all statistical analyses were performed in SAS (SAS Institute 1988). All species i

2-56 !

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I occurring were summed for the total number of organisms settled. All organisms except colonial

organisms (i.e., hydroids, protozoa, etc.) and eggs were summed for the total number of

I multicellular organisms settled. ANOVA was performed on data from each set of incubations

to examine waterborne and relief height effects. Only taxa that occurred on at least five percent

of the plates were analyzed individually.

!

2.4.2.2 Toxicity Tests

!

I Drilling Laboratorymudstoxicity used tests were conducted using drilling muds collected from Platform Hidalgo. in these experiments were water based muds, and samples were collected

from active drilling platforms before discharge to the ocean. A sample of drilling mud was

i collected at the University by platformof California, personnel Santa and shipped Barbara in(UCSB). PVC containers At the laboratory on ice to theit was bioassay storedlaboratory in a cold

(4° C) room until used in experiments. All experiments were conducted within 14 days of

I collection of drilling muds.

Concentrations of drilling muds used in experiments were set from 0.002 mg/L to 20,000 mg/L

I plus controls, except as noted (Appendix C). In the field, concentrations of drilling muds greater than 200 mg/L would be expected only very close to the point of discharge (Coats 1994).

Preliminary experiments on fertilization and development indicated no effects for concentrations

I between 0.002 and 200 mg/L. Therefore, concentrations above 200 mg/L were included to determine if drilling muds had any effect-on-the targeted performance parameters (i.e.

fertilization, development, and survivorship). The period of exposure to drilling muds was

I generally 52 hours except for assays of fertilization and development, which were shorter because of the shorter duration of these stages.

I Collection and Laboratory Handling of Test Organisms

Stocks of adult red abalone are maintained in a flow-through seawater system at UCSB. Methods

I for spawning, fertilization and larval culturing are described in Morse et al. (1977, 1979b, 1980). Stock animals were collected originally from a subtidal reef near Santa Barbara, CA and have

been maintained as spawning animals for ongoing studies over several years. In order to mimic

I meters, some experiments were conducted, as feasible, at 9° C in the conditions that exist at 200

dark. However, because the results of preliminary experiments indicated that development times

for cultures were unstable at 9° C, parallel experiments were also performed at 15° C, the typical

I rearing temperature for red abalone. To help prevent bacterial infection in the laboratory,

antibiotics (2 mg/1 Rifampicin) were added to laboratory vessels holding larvae; antibiotics do not

i replicate interfere with container normalappeared settlement to beof severely red abaloaffected ne larvaeby(Mbacterial orse et al.infection 1979b).that If individuals replicate wasin any not

used. Typically 2-3 replicates per treatment (concentration) have been used for survivorship and

I variability settlement isassays generally with lowred among abalone replicates. larvae (Morse Experiments et al. 1979a; describedRalmondi in this and studySchmitt used between 1992);

I 2-57

I
!

3 and 10 replicates per treatment (concentration); the number was in large part dictated by i

logistical constraints of the experiment. Due to limited holding times for the drilling muds, as

noted above, most of the experiments were carried out concurrently, i

Individual adult brown cup corals were collected from subtidal rocky reefs near Santa Barbara, i

CA, at depths between 10 and 20 meters and maintained in the UCSB laboratory. Until use, !1

corals were kept at 9° C in the dark in a flow-through seawater system. The corals were not fed

i

duringtheexperiments. II

Specific Methodology of Experiments: Red Abalone

Gametes- (fertilization). I

i

This experiment tested the relationship between the concentration of drilling muds and the

fertilization success of abalone, expressed as a percentage of eggs showing evidence of I

fertilization. At least 2 male and 2 female adult red abalone were spawned using the method of 1

Morse et al. (1977). Sperm were collected via pipette from spawned abalone. Sperm

concentration was determined by first diluting a sample of concent_:ated sperm 1:10,000 in sterile •

sea water, then counting 10 /_I samples of the diluted sperm solution on a hemocytometer.

Freshly spawned eggs were allowed to settle in 50 mL conical tubes. To determine settled egg

density, a 20/zl sample of settled eggs was mixed in 1 mL of sterile sea water, and 20/zl samples l

of the suspended eggs were counted on depression slides.

Concentrations of drilling muds tested were: 200, 20, 2, 0.2, 0.02, and 0.002 mg/L. Clean, sterile iI

sea water was used for control conditions. Subsamples (10 mL) of each drilling fluid dilution

were pipetted into individual wells of Falcon six-well tissue culture plates. Ten replicates of each

concentration and ten replicates of control conditions were included in this experiment. Ii

Approximately 500 settled eggs were pipetted into each well of the Falcon tissue culture plates,

and freshly diluted sperm at a ratio of approximately 800 sperm per egg were added to each well. l

Fertilization was allowed to proceed at 15° C for 5 hours on a shaker apparatus. At the end of i

5 hours, fertilization was stopped by the addition of approximately 1 mL of 10% formalin. i

Maximum resolution of fertilization success was achieved by sampling 5 hours after gametes had •

been mixed. Tests for fertilization were only conducted at 15° C because that was the

i

temperature at which the fertilization protocol was established. Due to logistical constraints, it m

was not feasible to complete the fertilization tests at 9° C. Fertilization success was measured i

by observing the presence of polar bodies or cell division under a microscope (Hunt and

Anderson 1989). At least 100 eggs were counted per well for each replicate, i

i

Zygotes- (development)

Experiments on zygotes tested the relationship between drilling mud concentration and early II

larval development. Freshly spawned red abalone eggs were fertilized at 15° C. Fertilized eggs l

were examined under the microscope to ensure the presence of between 10 to 50 sperm per egg.

Drilling muds were diluted, using sterile sea water, to the following concentrations: 2000, 200, •

20, 2, 0.2, 0.02, and 0.002 mg/L (plus control; 0 mg/L). Approximately 500 fertilized eggs were

2-58 i

I
!

I added per well of Falcon six-well culture dishes, into which 10 mL of each drilling mud dilution

were pipetted. Ten replicates were done per concentration, and sixteen replicate controls in sterile

I water were performed. Development was allowed to proceed at 15° C on a shaker

sea apparatus

for 52 hours.

I At the end of 52 hours, approximately 1 mL of 10% formalin was to

added each well. At least

100 individuals were scored for normalcy of development. Larvae were defined as "normal",

based on characteristic calcified, striated, snail-shaped shells with smooth borders identifed in

I Hunt and Anderson (1989). "Abnormal" shells showed deviations such as indentations in the

shell margins or mis-shapened shells (Hunt and Anderson 1989).

I Larvae - (survivorship, settlement, viability)

Survivorship was measured as the proportion of organisms alive at the end of the test.

I the Settlement proportionwas ofmeasured individuals as thethatprosurvived portion oandf survivors the proportion that settled. settled.Viability It is anisestimate the product of theof

proportion of individuals that successfully made the transition from the planktonic to the benthic

I stage.

Precompetent larvae: This experiment tested the relationship between exposure of precompetent

I larvae to varying concentrations of drilling muds and subsequent survival to competency, settlement (as competent larvae) or viability. Approximately 500 precompetent abalone larvae

were placed in 800 mL of drilling mud solution, and maintained at 9° or 15° C for 52 hours. The

precompetent stage was defined as under 7 days post fertilization for individuals reared at 15° C and under 10-12 days for individuals reared at 9°-C; the length of the precompetent period is

more variable at lower temperatures. Drilling mud was diluted to the following concentrations:

I 20,000, 2,000, 200, 20, 2, and 0.2 mg/L (plus control; 0 mg/L) for the 9° C experiment and 200, 20, 2, 0.2, 0.02, and 0.002 mg/L (plus control) for the 15° C experiment. Different

concentrations were used for the 9° C experiment for two reasons. First, the results of the 15°

I C experiment (done first) indicated that the lowest concentrations tested (0.002 and 0.02 mg/L) had no effect on larval performance. Second, because only limited numbers of larvae were

available for testing, all treatment conditions could not be made. Consequently, it was decided

I to forego two higher (2,000 20,000 mg/L) drilling the lower concentrations and include the and

mud treatments to better bracket the expected effects.

I After 52 hours of exposure to the various drilling mud dilutions, larvae were transferred to 800

mL fresh, sterile sea water containing 2 mg/L Rifampicin and were maintained at either 9° or 15°

i were C (in cltransferred osed systems). into Upon 20 mLreaching disposable competency, beakers approximately and challenged75with of theGABA exposedplusindividuals 2 mg/L

Rifampicin for 24 hours. There were 3 and 9 replicates per concentration for the 9° and 15° C

i were experiments, scored respectively. as settled (attached Temperatures to thewere beaker) maintained , not settled as in the(lyingprecompetent on their side), phase. orLarvae dead

(movement could not be detected).

!

I 2-59

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!

Competent larvae: These experiments tested the relationship between exposure of competent

N

larvae to varying concentrations of drilling muds, and their survival, settlement, or viability.

These tests were done to examine the effects of longer term exposure to drilling muds, including H

the ability to settle and survive during the period of exposure. They were included to evaluate

m

how larvae drifting into, and remaining in, an area of impact might be affected by exposure to

drilling muds. m

Settlement ability of abalone larvae exposed to drilling muds at 9° and 15° C during the •

competent stage: 28h exposure to drilling muds n

Competent abalone larvae, reared at 9° or 15° C were exposed 1:odilutions of drilling fluids, []

ranging from 20,000 mg/L down to 0.002 mg/L (plus control), for 28h at 9° or 15° C. II

Approximately 400 individuals were exposed in 800 mL volumes of the dilutions, replicated two

times per dilution for the 9° C experiment and three times per dilution for the 15° C experiment. []

After 28h, approximately 50 larvae per replicate were transferred to 20 mL disposable beakers U

containing 10 mL fresh sterile sea water. They were then challenged with 2 mg/L GABA plus

2 mg/L Rifampicin. For the 9° C experiments, three replicates per exposure group were set up []

for a total of six replicates per dilution. Only one replicate per exposure group (three replicates II

total) was used for experiments at 15° C. Larvae were scored as settled (attached to the beaker),

not settled (lying on their side), or dead (movement could not be detected), n

Settlement ability of abalone larvae exposed to drilling muds at 9° and 15° C during the

competent stage." 52h exposure to drilling muds and settlement challenge in the presence of II

drilling muds

Competent abalone larvae, reared at 9° or 15° C in a closed system (see above), were exposed to n

dilutions of drilling fluids, ranging from 20,000 mg/L down to 0.002 mg/L (plus control), for 52h II

at 9° or 15° C. Approximately 400 individuals were exposed in 800 mL volumes of the dilutions,

replicated two times per dilution for the 9° C experiment and three times per dilution for the 150 n

c experiment. For the 9° C experiment, before the last 24h of exposure, as many larvae as were

available per replicate were split among three 20 mL disposable beakers along with 10 mL of the m

drilling fluid dilution. Larvae were challenged to settle by the addition of 2 mg/L GABA plus H

2 mg/L Rifampicin. A total of six GABA challenge replicates per dilution were performed. For

the 150 C experiment, before the last 24h of exposure, 50-150 lmvae from each replicate were II

put into 20 mL disposable beakers along with 10 mL of the drilling fluid dilution. Larvae were n

challenged to settle by the addition of 2 mg/L GABA plus 2 mg/L Rifampicin. A total of three

GABA challenge replicates per dilution were run. Larvae were scored as defined for the 28h []

exposure. |

Interference with settlement inducers Hi

This experiment was designed to test whether settlement of larval red abalone was affected by

alteration of settlement surfaces due to deposition of drilling muds. As such, this experiment II

differed fundamentally from the other tests using larval red abalone. The other experiments l

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!

I tested whether drilling muds had direct physiological effects that translated into loss of larval

performance: fertilization, development, and the ability to settle. In contrast, this experiment

I tested indirect effects on the performance of individuals (ability to settle) through interference

with a necessary step in the settlement process (contact with an inducer). With this treatment the

reaction of competent abalone larvae to fouled surfaces was examined. The focus was to

I mightreactto potentially occurringinthezoneofimpact

determine how larvae inductive surfaces

for drilling muds. This treatment was intended to mimic short-term exposure of these inductive

surfaces.

I

Coralline crusts (known to induce red abalone larvae to settle; Strathman 1987) were placed in

i solutions 20,000, 200, of drilling 2, and 0.02 mudsmgfor 28 hours at 90 C in the dark at the following concentrations: /L (plus control: 0 mg/L). After 28 hours, crusts were transferred

to small containers (8 crusts per concentration) containing a new solution of drilling muds that

i was to reduce identical the possibility in concentration of contamination to that usedwhen in thetheinitial abalone 28 hrlarvae period.wereNewadded. solutions Approximately were used

500 competent abalone larvae were added to each container. After 24 hours the crusts were

I percent sampledofmicroscopically the crust surfaceto that determine was clear the ofdensity drillingof muds. settlers The on coraUine latter parameter crusts aswaswellsampled as the

to separate interference with settlement due to effects on the inductive quality of the surface (e.g.,

i the chemical surfaceeffects with mud. on the inducers) from interference with settlement due to physical covering of

I This experiment alone was not sufficient to distinguish interference with inducers from physiological effects of larvae. To evaluate this distinction, it must be determined that exposure

to drilling muds during the competency phase does not affect larval settling ability. This was

I tested in the previously described experiment on competent larvae using GABA as an inducer. In this experiment, the GABA induced settlement was repeated and, additionally, coralline crusts

were used to induce settlement. Coralline crusts and GABA were both used to determine if

i larvae exposed to natural and artificial inducers responded differently.

For this test, larvae were placed into solutions of the same concentrations as noted above (five

I replicates each), but without coralline crusts for 28 hours. After 28 larvae removed hours, were

from the drilling mud solutions and put into containers of clean seawater. The larvae from each

of the replicates were split into two containers: one containing clean coralline crusts, the other

I containing 2 mg/L GABA solution. Settlement was scored as noted above after 24 hours in these containers.

I Specific Methodology of Experiments: Brown Cup Coral

i realistic This expeconcentrations riment was designed of drillingto muds. test whether The effect adultcould Paracyathus result fromare either affectedof two by exposure sources: t1)o

toxicity from a chemical or biological component of the drilling muds, or 2) toxicity from the

I fine feedingparticulate or respiration) matter inof drilling a filter feeder muds that suchmight as Paracyathus interfere .withSurvivorship physiologicalandprocesses tissue loss(e.g. in

I 2-61

!
!

! adult cup corals were examined as endpoints. For corals such as Paracyathus, tissue loss has a

direct bearing on reproduction because gonads are located in external tissue in the septa, i

Individual Paracyathus, 11 per concentration, were randomly selected from a population of adults

and placed in solutions of drilling muds with the following concentrations: 20,000, 200, 2, and i

0.02

mg/L (plus control; 0 mg/L). Experiments were maintained in a cold room at 90 C. Every i

two days for 10 days individuals were examined microscopically _br survivorship and tissue loss

(sub-lethal effects). Individuals were scored as either exhibiting or not exhibiting tissue loss. •

An additional variable, relative viability, was calculated as the product of survivorship and the |

proportion of individuals showing tissue loss. Relative viability should be a good predictor of

the likelihood of continued survival and reproduction under exposure to drilling muds. New •

solutions were made of the experimental concentrations of drilling muds every two days (all l

concentrations were made using drilling muds that were less than 14 days post-collection).

Following examination, individuals were replaced into the appropriate fresh experimental •

concentrations of drilling muds. Since adult Paracyathus are sessile, the period that they could U

be affected by drilling muds is longer than for a larvae. Consequently, this experiment was

carried out over a longer period of time. This time frame was within the average period for i

discharge of drilling muds during drilling activity at the Santa Maria Basin platforms, which

usually lasts for several weeks or months (Steinhauer et al. 1992; Raimondi et al. in preparation)

foreachwelldrilled, i

i

Data Analysis

Results from the experiments are expressed as percent fertilization, survivorship, etc. compared i

to a control. All values were standardized to -the-mean for the control set of replicates (the 0

B

mg/L treatment), including each of the control replicates. This approach allows direct

comparisons of results from different experiments with differing units or measured parameters. I

Regression analyses were used for all experiments testing for physiological effects of drilling i

muds on gametes, zygotes, or larval red abalone. All statistical analyses were performed using •

SAS software (SAS Institute 1988). Separate analyses were done using the concentration and the

m

log of the concentration of drilling muds as the independent variable. This was done because i

dose

response curves have been shown to follow both linear and log-linear trajectories, and there i

was no objective reason to predict which, if any, was the probable model for biological response

todrillingmuds. an

Experiments testing for interference with inducers of settlement used both multiple and simple

regression models. Analysis ofcovariance models were used to evaluate results from experiments •

designed to test for the effects of drilling muds on adult brown cup corals. Finally, even though l

higher exposure concentrations were used, in some experiments, only concentrations < 200 mg/L

were included in the statistical analyses. Since concentrations above this level were not •

representative of conditions in the field. The higher concentrations, however, were included in !1

figures to demonstrate whether very high levels of drilling muds _fffected the test organisms.

!

2-62 i

I
I

I 2.4.3 Reconnaissance of Anchor Scar/Drill Cuttings Effects

!

I 2.4.3.1 Field Survey

I The Hildago reconnaissance on Novembersurvey 2 andusing3, 1991. the ROVTheRECON survey IVfocused was conducted on conditions in thewithin vicinityapproximately of Platform

500 m of the platform. The ROV was equipped with a color video camera, 70-mm photographic

camera with strobe, and a Mesotech color side-scan sonar for locating bottom features. Weak flashes with the 70-mm strobe and subsequent camera problems prevented use of the photographic

data. However, extensive video data was collected during five ROV transects (Transects 1-5)

I representing almost six hours of bottom time in the vicinity of Platform Hildago.

I 2.4.3.2 Laboratory/Data Analyses

I A qualitative review of the video tapes and navigation postsurvey plots of the ROV transects was

used to make a spatial assessment of substrate modification and any evidence of community

impacts related to the platform-associated debris field. Additional notes and observations were

made on debris and lost equipment (e.g., ladders, tires, and cables), mooring chain, and pipelines.

I

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2-64I!
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I

I chapter 3

II INTEGRATION

I

i 3.1 OVERVIEW

I The primary focus of the DOI Phase II and HI studies was to conduct long-term monitoring of

the effects and related processes of oil and gas platform discharges on deep-water, hard-bottom

I biological communities. As summarized in Chapter 1, and further detailed in the Appendices, DOI's objectives for the Phase HI program included the following:

I • Extend Phase I and Phase II studies the fate and effects of residual

on platform

discharges; and

I process-oriented studies on potential long-term, chronic impacts from the

Conduct

discharges to hard-bottom communities, as distinguished from natural variability.

I Potential or actual impacts to biological communities from chemical contaminants can be

considered on relatively small scales corresponding to habitat patches (e.g., tens to hundreds of

i square to hundreds meters)of orsquare at landscape kilometers) scales(reviewed representingin Fahrig the aggregation and Freemark of multiple 1995). patches The appropriate (e.g., tens

scale of study is best determined by evaluating the type, size, and frequency of disturbance

i (Lissner and the demographic et al. 1991); andthe dispersal structure characteristics (e.g., patchiness) of theofspecies the habitat /populations (Fahrig (Fahrig and Freemark and Freemark 1995);

1995). These considerations appear to be equally appropriate for evaluations of both terrestrial

I and aquatic ecosystems.

For the DOI study area, the relatively sparse hard-substrate habitat in the general region of

I Platf on scales orms ofHidalgo, centimeters Harvest, to kilometers, and Hermoseparated sa is comprised by a relatively of discontinu homogenous ous patches soft ofbottomexposedof muds rock

and fine sands (BBA/ROS 1986; Steinhauer and Imamura 1990; SAIC and MEC 1993). These

I conditions produce a corresponding patchiness in the distribution of sessile and attached marine organisms and, presumably, their abundances as well, as influenced by the size and location of

a habitat patch relative to other patches (Lissner et al. 1991; Freemark 1995).

I Potential effects to hard-substrate communities from drilling mud discharges should be evaluated

in terms of localized and regional (i.e., landscape scale) influences. The severity of any impacts

I will be greatest when the effects from local patches to scales. The propagate landscape

m 3-1

1
!

|

probability that "toxic events" will propagate in such a manner was ranked, from lowest to u

highest, by Fahrig and Freemark (1995) based on the type of event and populations, including:

(1) Single,localeventin a continuouspopulation; •

(2) Single, local event in a patchy population; I

(3) Multiple, local events in a continuous population; /

i

(4) Single, large-scale event in a continuous population;

(5) Multiple,localeventsin a patchypopulation;and i

(6) Single, large-scale event in a patchy population. HIll

To this list might be added the following:

(7) Multiple, large-scale events in a patchy population (the significance of which would i

depend, among others, on the frequency of the events).

/

Using this theoretical background, the likelihood of impacts to deepwater hard-substrate i

communities from discharges of drilling muds can be placed in.to a comparative ecological

framework. For example, discharges in the Phase 11I study area appear to correspond most i

closely to item (7) above, representing multiple,.point source event,; of which the majority of the R

material is deposited over many tens of square kilometers (see Appendix A) onto patchy hard

substrate habitat. The critical focus for this study then relates to 1:heassessment of changes in i

the biological communities or test organisms, represented in the study design as discharge-period III

changes to populations of multiple species, and documentation of the occurrence of toxic levels

ofanycomponentsfromthedischarges, i

A generalized ecosystem model of the DOI study region, including physical, chemical, and i

biological subsystems, is described in Chapter 1 (Figure 1.3-1). This model provided a i

conceptual framework upon which the Phase 111study design, summarized in Chapter 2 and

Appendices A through D, was structured. This design represented a field and laboratory analysis In

program with collections and measurements that primarily were conducted synoptically (Figure |

2.1-1) within a discrete study region (Figures 2.1-3 through 2.1-61). This temporal and spatial

focus allowed direct comparisons and integration among many task elements comprising the in

model subsystems. For example, data were collected from both low- and high-relief heights, at II

nearfield and farfield locations relative to Platform Hidalgo, for particle flux measurements

(Appendices A and B), biological community analyses (Appendix D), and larval filming and In

settlement experiments (Appendix C). Further, data for community analyses and for chemical II

dose/particle flux evaluations were collected near the same nine hard-bottom sites (Appendix B).

In situ and laboratory toxicity tests addressed potential acute and chronic effects from platform •

discharges to larval and adult invertebrates (Appendix C). Measurements of water column and I!

3-2 i

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!

I bottom boundary layer currents, as well as concentrations of suspended particulate matter in nearbottom waters, provided information for evaluating transport and dispersion of platform

I discharges (Appendix A). Finally, modeling of drilling mud discharges was performed to extend the spatial scales for predicting depositional fluxes and exposure dose (Appendix A). This study

design allowed the specific objectives of the Phase llI program to be addressed and provided

I continuity with the long-term monitoring objectives represented by Phase I and Phase II

programs.

!

3.2 CONCLUSIONS AND INTEGRATION

!

Key questions that were addressed by the Phase llI program include the following:

I • Is there a difference in the physical oceanographic conditions between phases and

between locations during the same phase?

I • Is there a difference in the concentrations of barium (Ba) and other chemical

contaminants from drilling activities between phases and drilling periods?

I • Is there a difference in particle fluxes at platform nearfield compared to farfield sites,

at high- (> 1.0 m) versus low-relief (0-1.0 m) heights, or at shallow versus deep

bottom depths,duringdrillingversus

non-drilling periods?

• Is there a difference in biological communities between phases and drilling periods,

I high-versus heights,or at versusdeepbottomdepths?

at low-relief shallow

i • Iscompared there atodifference farfield sites, in orlarval at high- settlement versus low-relief and recruitment heights, atduring platform drillingnearfield versus

non-drilling periods?

I • Is there a toxicity response by larval and adult invertebrates from laboratory

exposures to drilling muds?

!

3.2.1 Phase II Overview

!

This section contains a synopsis of the Phase II results and conclusions as a framework for

I Questionsregardingdifferencesbetweenphasesinclude integration with the Phase III results.

specific changes in predrilling, drilling, and postdrilling conditions.

!

I 3-3

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|

The Phase II studies were conducted from October 1986 through October 1990. The focus of •

these studies was to assess potential long-term changes in physical, chemical, and biological

characteristics in the vicinity of oil and gas platforms and to determine whether observed changes n

were caused by drilling-related activities or by natural processes (Steinhauer and Imamura 1990; W

Brewer et al. 1991; Coats 1994; Hardin et al. 1994; Steinhauer et al. 1994). Phase II studies

focused on hard-bottom communities in the vicinity of Platform Hidalgo. Initial studies of n

soft-bottom communities were discontinued because of delays irt drilling at a proposed site

u

(Platform Julius). However, these background surveys provided useful information on physical, ill

chemical, and

biological processes within the general vicinity of the :rite (Steinhauer and Imamura H

1990).

Production drilling at Platforms Hidalgo, Hermosa, and Harvest occurred during January 1987 I

to January 1989. Drilling operations resulted in total discharges of 11,225,500 kg of drilling

muds and 5,400 kg of cuttings (Steinhauer and Imamura 1990; Tab]ie 1.1-1). Muds and cuttings I

samples collected from the platforms contained elevated concentrations of several inorganic and l

organic constituents. Specifically, average concentrations of Ba, zinc, lead, and polycyclic

aromatic hydrocarbons (PAHs) were up to 150, 18, 130, and 350 times higher, respectively, than

corresponding concentrations in bottom sediments (Steinhauer eta]. 1994). |

During periods of active drilling, collections and analyses of bottom sediments and suspended •

particles indicated increases in Ba concentrations up to 40% an cl 300% above background, !1

respectively (Steinhauer et al. 1994). These increases were attributed to episodic discharges of

drilling muds and cuttings from the platforms through subsurface shunts with subsequent settling i

to the bottom. Based on estimates of the amounts of excess Ba (i.e., relative to background U

concentrations) in suspended particles, the contributions of particulate wastes to the total particle

fluxes in the vicinity of the platforms were calculated as approximately 2% (Hyland et al. 1994;

Coats 1994). Computer simulations of these discharges were performed to estimate depositional

fluxes of waste particulates at distances of 1-10 km from Platform Hidalgo (Coats 1994).

Results from these simulations were in reasonable agreement with flux measurements from n

sediment traps, and suggested that much of the initial deposition of drilling muds was not derived W

from Platform Hidalgo. Instead, relatively greater contributions to the particulate fluxes were

from Platforms Harvest and Hermosa discharges, which were dispersed and eventually overlapped i

with depositional patterns from Platform Hidalgo discharges (Coat.,; 1994). n

With the exception of Ba, no significant changes in concentrations of other chemical constituents, H

or in grain size or mineralogical properties of the bottom sediments or suspended particles were

g

associated with the platform discharges (Steinhauer and Imamura 1990). Barium was the most i

sensitive indicator of

drilling mud and cuttings discharges because it is highly enriched (relative i

to background concentrations) in the source material, it is essentially insoluble in seawater, and

it is not expected to be altered by natural, chemical, or biological processes (Steinhauer et al. •

1994). Despite the fact that concentrations of some classes of hydrocarbons (e.g., lower l

molecular weight PAHs) were elevated in muds and cuttings, concentrations and component

ratios of these hydrocarbons in bottom sediments and suspended particles did not indicate B

significant contributions from particulate wastes. Although increases in total petroleum n

3-4 |

!
!

I hydrocarbons occurred during the drilling period, the general absence of lower molecular weight

PAHs suggested that these increases could be attributed to natural, petrogenic sources (Steinhauer

I et hydrocarbons al. 1994). either Any were contributions masked byfromtheplatform dominant discharges backgroundto signal concentrations of hydrocarbons of petroleum from

natural sources (e.g., local oil seeps) or reduced due to selective solubilization and/or microbial

I degradation of these less refractory compounds.

Overall, increased Ba concentrations were the only chemical or physical characteristics of bottom

I sediments and suspended particles that were affected significantly by platform discharges (Steinhauer et al. 1994). Barium, in the chemical form associated with drilling muds (barite), is

considered to be essentially nontoxic to marine organisms, including embryos and larvae (NRC

i 1983). Nevertheless, excess Ba concentrations (i.e., levels above background) in suspended

particles were used during the Phase II studies as a surrogate measure of the relative exposure

or dose to hard-bottom organisms of the particulate fractions from platform discharges.

I subsequentlywere used as a for analysisof variancein the Estimated dose levels factor

hard-bottom community data (Steinhauer and Imamura 1990).

I Comparisons between predischarge and postdischarge surveys in the abundances of 22 taxa

associated with high- and low-relief hard-bottom sites indicated significant differences (p < 0.05)

i for Caryophy four Utaxa: sabellid polychaetes, the tunicate Halocynthia hilgendorfi, the cup coral ia spp., and galatheid crabs. These differences were restricted to deeper reefs

(160-212 m) near Platform Hidalgo, whereas no significant differences were apparent at

i shallower differences reefs likely(105-119 were not m) related(Hyland to a toxic et al.response 1994)., because The Phasethe IIonlystudyconstituent concludedthatthat appeared these

to be elevated compared to background concentrations was Ba. Instead, it concluded that these

I differences particulate wastes. probablyThewere effecta was response presumed to increased to be relatedparticle to disruption fluxes represented of feeding, byrespiration, settling

and/or postlarval survivorship due to burial (Hyland et al. 1994). However, the possibility that

I differences drilling mudswere(e.g., duenaphthalenes to an acute response and phenanthrenes) to toxic, butcould transient, not bepetroleum evaluatedconstituents from theseofdata the

(Steinhauer and Imamura 1990).

I Independent of the source of impact, any effects appeared to be localized near the platform and,

based on combined Phase II and Phase III data, were not expected to extend in a significant

I manner from these "patches" to a larger landscape scale (e.g., Freemark 1995). Source populations outside of an effect zone would be expected to contribute to recolonization in the

absence of additional disturbance (Lissner et al. 1991).

I Subsequent to the end of the drilling period, concentrations of Ba in suspended particles

decreased over time. By the end of the Phase II study, concentrations of Ba in suspended

I collectedfromsediment had reached concentrations.In particles, as traps, background contrast,

Ba concentrations in bottom sediments still were considered slightly elevated due the presence

of residual barite particles (Steinhauer and Imamura 1990; Hyland et al. 1994). !

m 3-5

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!

3.2.2 Phase III Results and Integration I

I

The Phase III field studies, conducted from October 1991 to January 1995, corresponded to two

main drilling-related periods: (1) post-Phase II drilling/pre-Phase [tl drilling (generally October I

1991 through August 1993) and (2) Phase III drilling and post drilling (September 1993 through II

January 1995). A summary of impacts by study element for the two periods is presented in

Table 3.2-1. The first period represented approximately a four and one-half year interval since I

the last Phase II discharges in January 1989 (Table 1.1-1), and was anticipated to be []

characterized by progressive decreases in any discharge-related changes noted from the Phase II

studies. This hypothesis was based on expected dispersion and mixing of sediment contaminants II

by local transport processes, as well as natural colonization and recovery by biological organisms, m

in the absence of new discharges (e.g., Lissner et al. 1991). Further, severe or large-scale _m

impacts to the biological communities would not be predicted during the second (drilling) period II

since the discharges were only 10% of those during Phase II. I

Physical Oceanography/Sediment Transport I

The physical oceanographic conditions of the study area are subject to strong waves and currents I

associated with confluence regions of the California Current System, as well as exposure to l

numerous Pacific storm systems that impinge on this relatively open area of the coast. These

conditions produce strong mixing of the upper water column and, potentially, resuspension of []

sediments in relatively shallow shelf regions, extending from shore to approximately 100-m |

bottom depths (SAIC and MEC 1993; Appendix-A). Results from the Phase m studies

emphasized the dynamic nature of these currents and transport mechanisms, also as noted during II

Phase II (Steinhauer and Imamura 1990; Appendix A). These conditions likely serve as an 1

effective dispersal mechanism for the eggs and larvae of invertebrates and fish, thereby resulting

in large (landscape) areas over which potential colonizers may be distributed. Further, the study II

area is in a region of active upwelling (Dugdale and Wilkerson 1989) as well as near a transition 1

zone of two biogeographic provinces (Newman 1979), all of which should serve to enhance the

diversity and abundance of source populations for colonization/recolonization, i

II

Detailed current measurements indicated that flows were generally upcoast during summer/winter

and downcoast in spring, although the duration and characteristic.,; of these seasonal patterns _l

varied among the phases and study years. Features such as eddies and meanders also produce II

much local variability. This was reflected in the relatively small scale of coherence between

currents measured at a long-term mooring near Platform Hidalgo compared to a variable-location _l

mooring that was positioned from a few to several kilometers away (Appendix A). III

The near-bottom sediment transport regime also exhibited large spatial and temporal variability. 1

Substantial differences between the phases in rainfall and associated runoff from land (Figure 1.4- n

1) may have resulted in much greater sedimentation and transport during Phase I]I. Increased 1

sedimentation including, in extreme cases, burial of hard substrate and biota or reduced feeding II

efficiency (by clogging) of filter feeding organisms, has been theorized to potentially reduce the

l

3-6 I

I
I

I _ i _ .__ _'_ -_^_,. I _ ] _

i _.=.

I _ _ _

I °

i _ _ __

o. "_ _._

I _ _'__ _ __

I

I _ _ _ __ .. _ <_

,°°°°°°

I

_

-

____ __ _'_ ___o __ _ _-_ _ z____

I _ _ _ • ._z._ ..._

I

3-7

I
!

abundance of many species (Lissner et al. 1991). This may be particularly evident in low-relief I

habitats that are more susceptible to burial by sediment encroachment. II

Results from wave and tide gauge measurements during Phases II and ]I1 indicated that surface- i

generated waves usually did not cause resuspension at deeper bottom depths (e.g., >138 m,

representing the primary mooring depth). This conclusion was substantiated further during Phase i

III by current and sediment resuspension data from near-bottom (200 m depth) physical

m

measurements arrays. These results indicated very limited resuspension of bottom materials i

associated with

meterological events and surface waves (Appendix A). Near-bottom i

concentrations of suspended particles typically were low, averagi_Lg 1-5 mg/1, and correlations

between suspended particle concentrations and current speeds were poor. However, aperiodic i

increases in near-bottom particle concentrations were up to several orders of magnitude above |

background conditions. Several suspended sediment movement events were noted at both

nearfield and farfield sites relative to the platform, although it appears most likely that these i

events were caused by resuspension in shallower, inshore areas, and runoff from storm events, l

followed by movement offshore through the study region. Large-scale events such as increased

storm activity and rainfall runoff during Phase nI, compared to drought conditions that prevailed •

during Phase ]I, would be expected to have a significant effect on coastal and shelf transport |

processes (Section 1.4). There was no evidence of drilling-period re,lated increases in suspended

sediments; however, this conclusion undoubtedly is influenced by the,somewhat limited discharge i

volumes during Phase III. II

The potential for greater transport and resuspension at shallower depths is consistent with particle •

flux data from sediment traps located at both shallow_(105-119 m) a:addeep (160-212 m) bottom

depths (Appendix B). These traps represent particle collections from approximately 1 m off the

bottom, corresponding to a distance that is intermediate between the low- and high-relief heights i

associated characteristically with natural differences in biological communities. Particle fluxes i

during both phases were higher at shallow compared to deep stations. For example, a significant

negative correlation between depth and particle fluxes was observed during Phase II (Steinhauer i

and Imamura 1990). The physical measurements arrays, which were located at a single depth i

(approximately 200 m), supported individual traps positioned at both low- and high-relief heights,

consistent with the distinctions for the biological communities. Fluxes were approximately 25 i

to 65% higher at low- compared to high-relief levels, reflecting the greater amounts of

u

resuspended sediments in water layers closer to the bottom (Appendix B). These results likely U

indicate a higher potential for biological impacts in low-relief areas due to sediment cover and i

burial, although common species (e.g., several cup coral species artd seastars) in these habitats

i

should be adapted to relatively high particle/sediment fluxes (Lissner et al. 1991). i

Chemical Contaminants

Pre-Phase III drilling (period one) results indicated that concentrations of chemical contaminants, i

other than slightly elevated Ba in bottom sediments from residual (P]aase II) platform discharges,

remained at or near background levels in surficial and suspended particle (i.e., sediment trap) •

l

3-8 i

!
!

I samples (Appendix B). Changes in concentrations of other drilling-related contaminants,

including petroleum hydrocarbons and other metals, were not evident.

I The only other contaminant-related trend in the period one data was unusual increases in low

molecular weight PAHs in surficial and suspended sediments that occurred sporadically at

I selected stations during October 1991 (Appendix B). These increases possibly were caused, in part, by discharges of a non-drilling related petroleum product ("diluent") from a land-based spill

source during 1990 and 1991. Chemical "fingerprinting" analyses and the correspondence of spill

I timing with contaminant results suggest, based on weight-of-evidence, that the diluent was present in these samples. Other petroleum hydrocarbons also were present that appeared to be

related to natural seeps and anthropogenic combustion products (Appendix B).

I During the drilling period (period two) for Phase III, slight increases in Ba were evident, but only

for suspended particles (from sediment traps) at three stations near Platform Hidalgo. Residual

I from Phase II in sediments within 500 of the

excess Ba, primarily discharges, was present m

three platforms at concentrations up to an order of magnitude higher than background. These

elevated levels likely are associated with drill cuttings deposited near the platforms (see Phase

I III modeling results in Appendix A; Coats 1994). No significant increases in other metals or

hydrocarbons were observed during Phase IlL This likely is due to the minimal enrichment of

i most naturalmetals variability in the indischarges, backgroundsolubility hydrocarbon of lowerconcentrations, molecular weight relatively PAHslowin drilling dischargemuds, volumes large

(only 10% compared to Phase II), and high dispersion related to dynamic local and regional

i currents dischargedandmaterial relativelyaredeep confirmed water depths. by resultsThese fromlatter the particle assumptions trackingof high modeldispersion performedof the for

Phase III (Appendix A). Sediment deposition depths and bottom footprint size are influenced by

I differences layers (average in discharge bottom volumes accumulation and current of 1.5-7.5 velocitymicrons) and direction. of deposited However, material onlyareverylikely, thin

corresponding to a very large footprint for fine-grained particles (approximately 100-550 square

I kilometers, dispersed beyond depending the study on theregion. particleBasedsize), on the andchemistry substantialandfineparticle material tracking(40-80%) model that resultsis

alone, deposition of particulate contaminants from platform discharges would not be expected to

I cause significant impacts to hard-bottom communities in the study region.

This type of depositional pattern and the irregular frequency of platform discharge events is

I consistent with an impact model of multiple, large-scale events in a patchy population (Section 3.1). Substantially greater discharge volumes occurring at more frequent intervals should produce

correspondingly greater effects, although the highest Phase II discharges only represented 2% of

I the total particle fluxes in the vicinity of the platforms (Coats 1994).

Biological Community

I The hard-substrate epifauna of the Santa Mafia Basin are diverse (286 taxa from Phases II and

III combined) and abundant (Appendix D). Dominant phyla are cnidafians, echinoderms, and

I sponges. Primary secondary in the biological communities are associated with and differences

I 3-9

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differences between shallow and deep hard-bottom sites and high- versus low-relief features, •

respectively (Appendix D). Combined Phase II and Phase III results indicated that deeper sites

(160-212 m) have more taxa (mean = 20.7) and higher percent cover (mean = - 40%) than i

shallow sites (105-119 m; mean taxa = 15.6; mean % cover = - 29%), and more taxa favored I

high relief (mean = 22) than low relief (mean = - 17) (Appendix D). Taxa characteristic of

shallow sites include several cup corals (Balanophyllia, CaryophyUia, and Paracyathus) and i

seastars (Mediaster, Stylasterias, and Rathbunaster), while deep siLtesare typified by other cup

i

corals (Desmophyllum), colonial corals (Lophelia), and seastars (Hippasteria and Poraniopsis), II

in addition

to various anemones, sponges, and basketstars (Gorgonocephalus). In contrast,

numerous taxa such as ophiuroids, large anemones (Metridium), crinoids (Florometra), and

tunicates (Halocynthia and Pyura) are ubiquitous, generally occuIring over the range of study II

depths. Most of the shallow water taxa preferred low-relief, although this may be influenced by l

the scarcity of shallow high-relief study sites (Appendix D).

Some of the community patterns may be associated with differences in particle fluxes and i

i

sediment movement between depths and relief heights, although direct evidence for this

relationship is not available. Nonetheless, review of the ecology and natural history of key taxa •

associated with these communities indicates that many of the high-relief species, such as m

anthozoans and sponges, are filter or particle feeders that are likely to be sensitive to high

concentrations of suspended particles (Lissner et al. 1991). Obserwttions from submersibles and •

remotely operated vehicles (ROVs) have documented numerous examples of hard-bottom

organisms, such as cup corals, that were partially to fully buried iz,ysediments, or examples of

attached filter feeders, including sponges, that appeared to be heavily fouled by sediment particles •

(BBA/ROS 1986; SAIC 1986; SAIC and MEC 1-989;Lissner et al., personal observations during

Phase III surveys). Natural sediment and particle transport, as well as discharges of drilling

muds, can contribute to the fluxes to which these organisms are exposed. Impacts potentially can i

result from physical effects such as burial or clogging of filter-feeding structures, or from toxic i

effects (see larval and toxicity experiments below). Taxa, including ubiquitous species, that are

common in shallow and/or low-relief habitats are assumed to be reasonably adapted to high B

particle fluxes and sediment resuspension. Fluxes in these habitats can be twice as high as in

HI

deep and/or high-relief habitats (Appendix B). Ubiquitous taxa are mainly represented by i

comparatively large, mobile forms that would be expected to have broad habitat tolerances, i

particularly as related to an ability to relocate to more favorable areas or to potentially extend

i

above turbid, near-bottom waters (Lissner et al. 1991). However, it is notable that several small a

(e.g., 1 cm tall), sessile cup coral taxa also prefer shallow, low-relief habitats. The success of i

these cup corals may be related to greater reproductive output and/or growth rates compared to

the larger taxa, although definitive studies are presently lacking. Other relatively motile species, •

such as sea stars, brittle stars, feather stars, and crustaceans, or "tall" (e.g., 1 m high) species, I

such as the anemone Metridium, should be able to emigrate from or avoid areas of high particle

fluxes, thereby minimizing exposure and potential impacts (Lissner et al. 1991). i

Based on combined Phase II and Phase III data, the rank order of dominance of most hardbottom taxa was relatively stable over time as related to drilling discharge periods and distance •

from Platform Hidalgo (Appendix D). Linear regression analyse,s of changes in abundance

3-10 i

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!

I (percent cover) for 24 dominant taxa indicated significant negative trends for 35% of the 72

possible combinations of taxa and depth/relief height, although there was no consistent, platformI related pattern for any one taxon. ANCOVA tests of abundance changes for 20 taxa with distance from the platform identified 18 positive and 17 negative effects. However, Chi-square

contingency analysis of the significance of the multiple positive, negative, and inconclusive

I results from ANCOVA analyses indicated that the results may be expected based on chance alone (Appendix D, Table 9). The negative effects were observed for a wide variety of taxa, most of

which are filter or suspension feeders. Only two of these taxa (Caryophyllia and Halocynthia)

I alsoassociatedwiththe effects PhaseII et

were sanle potential drilling-related during (nyland

al. 1994; Appendix D). Overall conclusions were that the combined trends for the various taxa

were not statistically significant. !

Photographic characterizations of the hard-bottom community provide little evidence of

i

limited significant, particle broad-scale dischargeseffects and from physical drilling /chemical discharges effects.(Appendix However,D).someThisof istheconsistent difficultieswithin

distinguishing platform effects are related to the apparently high variability and patchiness of the

i hard-bottom to detect change habitat basedandonassociated the randomcommunities, photoquadratas well study asdesign the relatively (AppendixlowD).statistical power

I A(based ky onresidual ANCOVA) questionforfromse thetaxabiological have long-term community ecological resultsignificance. is whether the As discussed negative trends in the

section on chemical contaminants, there were no persistent toxic components from the particulate

I Further, fractions of the platform discharges that would be expected to cause these negative effects. the small amount of additional particulates from the discharges, particularly as compared

to Phase II, should be inconsequential relative to the overall particle and sediment transport

I budget of the study region (Appendix B). A natural variable that may influence these results is the substantially greater sediment loading to the shelf ecosystem that likely occurred from storm

runoff during Phase III as compared to Phase II (Chapter 1). The occurrence of negative effects

I at shallow low-relief sites, and to a variety of taxa and feeding types, may be indicative (in part) of broad-scale, natural sediment transport events. Such effects might be expected based on (1)

greater sediment fluxes in these habitats (compared to deep, high-relief), and (2) natural

I differences between the nearfield sites (PH-E, -I, and -J) and the farfield (reference) site, PH-U. PH-U is located in relatively close proximity to a canyon system (Figure 2.1-3) and could be

associated with different oceanographic and sediment flux regimes (as noted in Appendix A for

I deep nearfield and farfield sites studied with the physical measurements arrays). Differences in these regimes could result in some of the apparent statistical differences in species trends

observed from this study. !

Alternately, assuming (as noted above) that effects associated with the particulate fractions of

platform discharges are inconsequential, the only other potential platform-related source of

I contaminants is dissolved chemical components such as those present in produced water (see

larval and toxicity experiments discussion below). Dissolved petroleum hydrocarbons have been

I shown 1993). to be a toxic agent in oil-field produced waters (Cherr et al. 1993; Higashi and Crosby

I 3-11

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l

Larval Experiments and Toxicity Tests •

The in situ larval settling experiments provided a focused study design for evaluating drilling n

discharge-related effects to (1) red abalone as an indicator species during manipulated studies,

and (2) natural (unmanipulated) colonizers. The larval settlement experiments tested location

(platform versus reference), waterborne (particulate and dissolved fractions combined), and i

substrate relief height (high versus low) differences, and were the first studies to integrate w

potential impacts to the larval community into the Santa Maria Basin monitoring program. This 1

was of particular importance since factors that affect larval recruitment can have longer-term i

effects at the population and community level (Mullineaux 1988; R_timondi 1990). Results from

I

both experiments indicated that natural filming of settling plates by bacteria was necessary to 1

optimize settlement by the larvae (Appendices C-1 and C-2). However, relief height was not a i

significant factor, independent of the general filming site location. Results from the red abalone

experiments concluded that settlement at near-platform and reference sites was lower during •

drilling than predrilling periods. Settlement was significantly lower near the platforms than at 1

the reference site, thereby suggesting drilling-related impacts (Appendix C-l).

1

In contrast, natural settlement experiments that tested growth, survivorship, and fecundity did not i

imply significant drilling-related effects (Appendix C-2). This was the case for both newly

settled organisms and those that were established (previously settled) on the plates as part of i

longer-term (e.g., 300 days or more) studies. Approximately 50 different taxa were identified

from the natural settlement experiments, although only nine, including one bivalve (Delectopectin

sp.), two bryozoans, two hydroids (e.g., Triticella sp.), Komokoiacea, total organisms, total i

multicellular organisms, and serpulid worms, occurred on even 5% of all plates (Appendix C-2).

Overall results indicated very high spatial and temporal variability in settlement. The patchy

distribution may reflect low larval abundance and/or food availability, as also influenced by i

physical oceanographic factors. This limited settlement restricted the ability of natural settlement

experiments to detect drilling-related effects and supports the use of manipulated in situ

experiments to assess larval impacts, as performed using the red abalone larvae (Appendix C-1). i

Nevertheless, some significant differences between natural settlement at high- versus low-relief

heights was observed for four taxa, but height preference also varied by taxon (i.e., some 1

preferred low- and some high-relief). The reasons for these differences cannot be determined •

based on the present data; however, the results provide a distinct example of early settlement i

patterns that potentially could produce later community differences. Qualitative observations of

the larval experimental structures (igloos) in the field indicated that the lower-relief heights often •

were characterized by higher amounts of sediments in the experimental trays holding the settling

plates. Assuming that this represented actual differences in suspended material loads, consistent

with the results from the physical measurements arrays (Appendix A), these differences could 1

represent larval selection for substrates having less sediment cover.

Laboratory toxicity tests indicated that the fertilization mechanism arid early developmental stages i

of red abalone larvae were unaffected by exposure to drilling muds (Appendix C-3). In fact,

some experiments suggested that survivorship may be enhanced at higher concentrations. In •

contrast, significant negative effects were found for the ability of the larvae to respond to a I

3-12 i

I
!

I natural settlement inducer. This is consistent with the general finding of drilling-period impacts

to in situ manipulated red abalone larvae. Negative effects also were evident for adult brown cup

I corals, which had significantly increased mortality due to progressive tissue loss following exposure to drilling muds (Appendix C-3). These effects were observed even under the lowest

concentrations tested (0.02 mg/L), and may provide evidence of a mechanism for direct impacts

I to at least this member of the hard-bottom community.

Marine larvae can be highly selective in their search for a suitable settlement site (Keough and

I Downes 1982; Rodriguez et al. 1993). This often involves biochemical process complex

mechanisms (Morse 1990) that can be disrupted by waterborne contaminants and suspended

particulates which interfere with physiological receptors of the larvae. Post-settlement processes

I including metamorphosis from larval to juvenile forms also may be affected. Even slight effects

to larval settlement can result in reductions in recruitment, thereby leading to broader, populationi or community-level changes (Keough and Black 1995; Nisbet et al. 1995). Such effects may partly explain Phase II results which indicated significant decreases in the mean abundance of

four taxa following a drilling period. However, the time lag between any significant reductions

I intaxarecruitment (e.g., long-lived, and corresponding slow-growingdecreases spongesin adult compared populations to manywould mat-forming vary substantially species such amongas

hydroids) and be very difficult to predict due to limited life history information on most of the

I species. understood, Atrepresenting present thean processes active arealinking of ongoing larvalresearch and adult (Raimondi benthicanddynamics Schmitt are 1992), poorly and

the specific mechanism, presumably chemical, in the Santa Maria Basin study region is presently

I unknown. ~

The timing of abundance decreases for some hard-bottom epifauna and the reduced settlement

I noted from the in situ red abalone experiments appears to coincide with periods of active drilling and platform discharges. However, analyses of bottom sediments and suspended particles did

not indicate significantly elevated concentrations of metal or hydrocarbon contaminants, other

I than Ba. This suggests that any alterations in biological communities were attributable to conditions or exposures to sources other than particle-sorbed contaminants. Other possible

explanations include: (1) exposures of epifaunal organisms to dissolved lower molecular weight

I hydrocarbons that partitioned from settling/deposited muds and cuttings to bottom waters; or (2)

exposures of organisms to dissolved components of the produced water plume.

I Recent studies (e.g., Krause 1995) have demonstrated toxic effects to invertebrate at high gametes

dilutions (low concentrations; 10--0.0001%) of produced waters. The toxic component(s)

responsible for these effects have not been identified. However, produced waters, including those

I analyzedfor the known to contain elevated concentrationsof present study, are the more toxic

lower molecular weight PAHs (e.g., naphthalenes), as well as dissolved Ba. Low concentrations

of dissolved Ba (e.g., 100 _tg/L) have recently been shown to inhibit developmental stages of

I some invertebrate species (Cherr, pers. comm., 1995). Since 1992-1993, several million liters

per day of produced waters have been discharged from Platforms Harvest, Hermosa, and Hidalgo.

i Theoretically, greater the likelihood the higher thatthethedensity plume ofwould the produced sink and expose waters compared benthic communities to ambient toseawater, potentiallythe

i 3-13

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|

toxic concentrations of soluble contaminants. However, the density of the produced water •

discharged from Platform Hermosa is less than one (Chevron 19!)4); consequently, the plume

initially would be buoyant. Further, initial dilutions of the produced water plume of 970:1 are n

expected to occur within approximately 30 m of the platform (Chevron 1994). This dilution rate I

alone would reduce the concentrations of PAHs and Ba in the receiving waters by approximately n

three orders of magnitude. Therefore, it is apparent that the prociuced water plume would be •

highly diluted, and concentrations of dissolved components would be greatly reduced, prior to

w

potential exposures to epifaunal communities. Some pelagic larvae likely would be subjected to n

less diluted

components, particularly near the discharge; however, the percentage exposed out of i

the total available larvae in the region should be very low. Nonetheless, it appears unlikely based

on considerations of plume density and initial dilution that dissolved components of produced •

water discharges represent a significant impact source to the hard-bottom communities of the |

Santa Maria Basin.

Synopsis i

Decreasing trends in abundance (percent cover) were observed for many common taxa from •

Phase II to Phase III, but there were no consistent, platform-related patterns for any one taxon. l

ANCOVA tests of changes in abundance relative to distance from Platform Hidalgo, based on

combined Phase II and Phase NI data for 20 taxa, indicated a nearly even number of positive and i

negative effects (Appendix D, Table 8). Chi-square contingency analyses of the combined

negative, positive, and inconsistent results for the various taxa suggest that these differences may

be attributable to random chance alone (Appendix D, Table 9). A conclusion of no significant •

drilling-related impacts would be consistent with results from the physical/chemical studies,

which indicated no changes in particle-associated contaminants or sediment fluxes due to

platform discharges (Appendices A and B). Further, it is unlikely based on general i

characteristics of the produced water discharges (buoyant relative to seawater and highly diluted)

that dissolved components would cause these types of community effects, although dissolved

fractions have not been studied directly by the Phase I-Phase m studies. Additionally, since the i

produced water discharges were not initiated until 1992, only the Phase l/I changes could be i

relatable to these exposures. Nonetheless, potential effects that may be represented by the n

ANCOVA results seem to be relatively subtle and do not suggest severe, broad-scale impacts, i

Natural factors that may influence the community results could include large-scale events such IB

as E1 Nifio, and a return to normal rainfall patterns (after extended drought conditions during

Phase II) that may be associated with increased particulate loads from runoff, as well as i

resuspension and transport of nearshore sediments from storms. However, no direct studies have

u

been conducted on the potential effects of these types of particulate loads on hard-bottom m

epifaunaofthestudyregion.

The chemistry and community studies are somewhat in contrast to :results from the in situ larval •

settling experiments and laboratory toxicity tests (Appendix C) which suggested some effects |

from drilling discharges. The in situ larval experiments provided a more sensitive measure of

impacts from drilling activities than was possible using community data alone (Appendices C •

and D). Differential settlement of larvae or greater sensitivity to low concentrations of l

3-14 I

I
!

I waterborne contaminants could result in chronic, long-term impacts to some species, with

corresponding community effects. However, species-specific variability and incomplete

I knowledge on life history and growth rates for most taxa limit predictions of time lags between impacts to larvae and subsequent changes in adult populations. Nonetheless, independent of the

chemical or physiological mechanisms, long-term, large-scale (i.e., landscape) impacts to hardI bottom epifaunal communities from the combined Phase II and Phase III drilling discharges were

not evident based on the present data.

I

I

I

I

I

I

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I

I

I

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I

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I 3-15

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3-16ii
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I chapter 4

| RECOMMENDATIONS

I

i Rec tasksommendations are presented forin mSections odificati4.1 ons through and additi 4.3, onsrespectively. to the physical, chemical, and biological study

4.1 PHYSICALPROCESSES

I

The primary objective of the physical oceanographic component of the Phase III program has

been to provide a description of the current regime to which biological, chemical, and sediment

I monitoring could be related, and to provide data on current fields for input into a numerical

particle tracking model that aids in predicting drilling mud transport and deposition. The present

i study has been successful in providing continuous times series of current velocity and temperature data at three depths for over two and one-half years. This is in addition to the

several years of similar data collected at the same (primary) mooring location during Phase II.

i Such resolvinglong-term, trends and continuous interannualrecords variability. are relatively This israre particularly in oceanography relevant inandthecancomplex be important transitionin

zone that is representative of the study area. Consequently, it would be very beneficial if at least

I the recommendations primary mooringonwasdeployment redeployed ofto maintain additional andmoorings continue these shoulddatabe records. coordinated Any other with

measurements available to DOI from other major studies, such as the SIO/MMS Santa Barbara

I Channel coherence andscaleSantaof currents Maria Basin in thefield vicinity experiments. of Pt. Arguello Because(Appendix of the locally A), it would short, cross-isobath be important

to conduct additional studies of this variability, particularly offshore of the primary mooring. In

I a regional context, an improved understanding of this often abrupt transition between current patterns may have application to other regions in the Southern California Bight (e.g., Santa

Monica Bay). The design of further current monitoring studies should consider more modem

I instrumentation (such as bottom-mounted ADCPs) that could provide better resolution of the current field. Regular drifter deployments from the platforms could also be useful for resolving

Lagrangian scales of the dispersion of drilling muds.

I The oceanographic regimes that influence seasonal and other low frequency currents in the

vicinity of Pt. Arguello and Pt. Conception often have an expression in the sea surface

I temperature field. As shown during the present project, satellite thermal images are one of the

few data sources that provide a synoptic, regional view of this key oceanographic variable.

i Consequently, SST imagery in conjunction with subsurface observations of currents and

I 4-1

I
n

temperature would help provide regional-scale, three-dimensional descriptions of the •

oceanographic regimes that govern local transport patterns.

m

Near-bottom clouds of suspended material measured during this study do not appear to be caused B

by conditions that are local to these measurements. Consequently, to understand the potential

for biological impacts from suspended material, including ambient material, it is important to i

conduct studies, such as through the use of PMAs, of remote resuspension events and subsequent n

offshore transport of the material towards the hard-bottom study t;ites. Based on the recurring

long period and potentially high local wave field, wave-induced resuspension in shallower water

and advection to these deeper sites is a likely candidate for this p_rocess.

m

specificrecommendations are: I

Thus,

(1) Continue and extend monitoring of the physical oceanographic regime, []

including sediment and bottom boundary layer processes. |

(2) Maintain and continue the primary mooring in its present location. Different i

configurations may provide greater vertical resolution of currents using |

similar effort. However, the three depths (approximately 14, 53, and 125

m) monitored during Phases II and III should be maintained at a minimum, i

U

(3) Deploy a small scale array of current meter moorings to investigate crossisobath scales of variability. A possible design would be two secondary []

moorings, one at the site of $4 and another on the 500-m isobath seaward []

of $4. This could be linked to the coastal currents by a mooring on

approximately the 50 m isobath, just seaward of the three-mile limit. I

i

(4) Regular deployments (e.g., 1 or 2 per week) from a platform of satellitetracked drifters should be evaluated as a method for estimating dispersion

and providing a Lagrangian perspective of variability of the current field.

(5) Design and deploy near-bottom instrument arrays, such as PMAs, containing i

instruments to measure local instantaneous velocities, temperature, and i

suspended particle loads. The PMAs should be placed at several (2-3)

inshore locations in 25-50 m water depths. At least one of these could be R

placed on a shoreward extension of the small mooring array described in (3)

i

above. In this context, the wave-tide gauge used at the primary mooring i

would provide more useful wave data if deployed in shallower water, i

(6) Continue satellite imagery collection for use in conjunction with moored and

bottom-mountedinstrumentation, n

Collection of optical data from PMAs that are of sufficiently high accuracy to permit calculation []

of concentrations of near-bottom suspended materials would require: maintenance of sensor units |

4-2 n

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!

I on approximately three-month servicing cycles. Despite the use of aggressive antifoulants, data

quality degrades rapidly beyond this period due to intensive biological growth on the sensor

I windows. Therefore, ship scheduling and array recovery procedures should be modified to permit maintenance on a quarterly schedule. This may require some redesign of array recovery systems

to provide a reliable backup and to facilitate recovery in the absence of support by an ROV.

I Alternatively, if longer-term deployments must be maintained, alternative sensing techniques

including acoustics and/or revised optical systems should be evaluated.

! 4.2 CHEMICAL PROCESSES

I

Continued analyses of surface sediments and suspended particles, as well as platform discharges,

I formation oils, and seep oils, for hydrocarbons and selected metals are recommended to evaluate potential effects of future drilling activities. The present list of hydrocarbon analytes is very

useful for distinguishing and quantifying contributions from petrogenic, pyrogenic, and biogenic

I sources. Additionally, it is recommended that measurements for stable petroleum biomarkers (e.g., triterpanes and steranes) be incorporated into the measurement program on a routine basis.

Measurements for these compounds will enhance the ability to detect signals from petrogenic

I sources, even when more traditional chemical indicators for oil [e.g., n-alkanes and polycyclic aromatic hydrocarbons (PAHs)] have been reduced to nondetectable levels.

I Limited useful information is gained from laboratory analyses for mineralogy, carbonate, or metals other than barium and aluminum. Other metals are not particularly enriched in drilling

muds or cuttings, and are at or near background concentrations in sediments and suspended

I particles. Therefore, present operational discharges platforms not appear to

from do affect these

analytes, and the ability to detect potential changes related to drilling operations is low.

Therefore, some reduction in the list of analytes is possible, although this may be less important than maintaining the consistency of the long-term monitoring record.

I Because during periods resultsofofactive the indischarge situ larvalmaysettling be associated experiments with suggest some adverse that proximity effects (Appendix to platforms C),

additional measurements of the dissolved and particulate fractions of produced water plumes

could and phenanthrenes) be informative. inInreceiving particular,waters analyses nearofthelower basemolecular of platforms weightcould PAHsbe(e.g., usednaphthalenes to evaluate

exposures and potential toxicity of organisms to hydrocarbons which are present in the dissolved

I phase elevatedofconcentrations produced waters of these (Cherr relatively et al. toxic 1993;compounds Higashi andcouldCrosby provide1993). better The correlations presencewithof

observed effects to larval organisms than measurements of suspended or surficial sediments.

!

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4.3 BIOLOGICALPROCESSES i

i

4.3.1 Biological Community Study I

m

Substantial high-relief habitat was identified and surveyed at Stations PH-I, PH-J, and PH-E that il

was not reported from Phase II. This high-relief habitat occurs at shallow-depth stations and w

provides an important basis for comparison of high-relief habitat between shallow and deep

stations. Cluster analysis of dominant taxa from the Phase II and Phase III data indicated that

high-relief habitats were distinct for the shallow and deep depths and from associated low-relief

habitats. This additional information provides for a more balanced study design as well as ill

additional insights on epifaunal community structure and organization. Therefore, it is |

recommended that these additional high-relief habitats continue to be monitored in all future

surveys, i

Some of the key limitations in distinguishing effects to epifaunal communities from drilling

discharges as compared to natural changes is the apparently high ,;patial variability of the hard- I

bottom communities. Therefore, an important element of future studies should be to perform il

additional monitoring at permanent stations representing low- ancl high-relief reefs, located at

shallow and deep depths and at nearfield, midfield, and farfield distances from a platform(s). []

Close-up photography including measurement scales in the photographs could be used to augment I..

studies at permanent stations, particularly as related to temporal trends in the size structure of

populations (e.g., cup corals). These studies would be in addition to randomly-collected •

photoquadrat and color video data as performed during Phases II and III, and should be initiated []

during a non-drilling period to allow sufficient time to document natural temporal and spatial

variability. !

Finally, from a methodological standpoint, either 35-mm or 70-mm photographic techniques

appear to be appropriate for documenting the types of communities in the study region. []

However, based on the greater ease and cost effectiveness provided by 35-mm photography, this Hi

is recommended as a better long-term approach (Section 2.4). "/

i

4.3.2 InSituLarvalExperiments ..|

The settlement following experiments. recommendations are based on the natural and! manipulated (red abalone) I

• The present in situ experiments demonstrated conclusively that biogenic surface films i have a statistically significant effect (increases) on :_ettlement. Therefore, it is

4-4 I

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I important to ensure adequate filming by retaining transplantation of settlement plates

in the experimental design. Additionally, this procedure will help determine how

I perturbations such as drilling discharges may affect film development, how settlement is affected by films from disturbed areas, and aid in the design of further laboratory

experiments.

I • Given that natural settlement rates are very low and probably variable (this may be

typical for deep-sea environments), it is important to retain manipulated settlement

i experimentsto questions impactsto settlement. Suchexperimentshave

address about

at least three benefits, as noted below:

(1) Encounter rate is standardized between locations, thereby removing a potentially

confounding source of variation.

I (2) Settlement numbers can be relatively high over short periods (e.g., 3 days). This

allows settlement questions to be addressed that are not complicated by postt settlementmortality.

(3) Short-term settlement experiments allow empirical questions to be addressed

I concerning versus surfaceparticular film effects. mechanisms of toxicity, for example, waterborne effects

I • Natural sufficientlarval settlement experiments to develop shouldforbemeaningful maintained statistical in situ for analysis. at least 180 days to enable

I ° Experiments still need to be conducted with plankton recorders to estimate the supply of meroplankton. This would allow better estimates of larval encounter rates and

improve understanding of settlement mechanisms from the natural experiments.

I These exposuredatatimes. also would aid in verifying recommendations for 180-day minimum

I ° The existence of location-related (nearfield and farfield) effects to larvae should be verified further by continued experiments using selected taxa for which waterborne

effects were demonstrated.

i ° In situ experiments have many advantages over laboratory studies because the latter

usually cannot simulate the appropriate range of naturally fluctuating variables,

I thereby introducinglaboratory-related

bias.

• Based on the lack of evidence of significant chemical contamination from field

I measurements of sediments and particle flux, future in situ larval experiments should

be coordinated with studies of dissolved- as well as particulate-phase chemical

I contaminants. This recommendation is consistent with studies on toxicity from

I 4-5

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|

dissolved petroleum fractions, particularly in produced waters (Cherr et al. 1993; n

Higashi and Crosby 1993).

I • The filming and larval array (igloo) study methods and equipment represented an

excellent approach for performing deep-water in situ experiments. However, the

design of smaller-scale equipment may be desirable due to requirements for a large n

survey vessel (e.g., 180-200 ft) to deploy and recover the igloos. U

/

4.3.3 ToxicityTests

i

The larval red abalone and adult brown cup coral laboratory experiments demonstrated some

toxic responses from exposure to drilling muds, although the mechanisms are presently unknown.

Therefore, future studies of this nature should focus on identifying the chemicals (or physical n

mechanisms) involved in these responses. In particular, since field measurements focusing on

particulates have not indicated any significant chemical contamination, studies of dissolved-phase

contaminants may be important (Section 4.3.2). w

4.3.4 ROVReconnaissance

I

ROV reconnaissance efforts to evaluate near-platform community impacts from drill cuttings and

anchor scars were limited by the extensive occurrence of shell debris (from the platform) which

obscured most features. Therefore, it is recommended that future surveys of this type be i

eliminated, or significantly limited, for platforms that have been :in place for a period of years

and which likely are associatedwith significantshell-debrismounds. I

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i REFERENCES

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of particles. Proceedings of the Cambridge Philosophical Society 48:345-362.

I BBA/ROS. 1986. Biological Survey of "Proteus" Lease OCS P-0512 Offshore Point

Conception, California. Report to Texaco USA.

I Berry, R.W. and B. Nocita. 1977. Clay mineralogy of recent marine sediments found on the

Southern California Outer Continental Shelf. Short Contributions to Califomia Geology,

I California Division of Mines and Geology, Special Report 129:101-106.

i Blumberg, Oceanographic A.F., L.H. Kantha, Circulation H.J. Herring, Model. andFinal G.L.Report Melbor. 1984. California Shelf Physical (Volumes 1 and 2) to the U.S.

Department of the Interior, Minerals Management Service. Dynalysis of Princeton,

i Princeton, New Jersey.

Boesch, D.F. and N.N. Rabalais. 1987. The Long-Term Effects of Offshore Oil and Gas

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I Boesch, D.F. and G.A. Robilliard. 1987. Physical alteration of marine and coastal habitats

resulting from offshore oil and gas development activities. Pages 1-53, In: D.F. Boesch

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I Boothe, P.N. and B.J. Presley. 1985. Distribution and Behavior of Drilling Fluids and Cuttings Around Gulf of Mexico Drilling Sites. Final Report to the American Petroleum Institute,

Washington, D.C.

I Bray, J.R. and J.T. Curtis. 1957. An ordination of the upland forest communities of southern

Wisconsin. Ecological Monographs 27:325-349.

i Brewer, G.D., J.L. Hyland, and D.D.Hardin. 1991. Effects of oil drilling on deepwater reefs

offshore California. American Fisheries Society Symposium 11:26-38.

I Chelton, D.B., P.A. Bernal, and J.A. McGowan. 1982. Large-scale interannual physical and

biological interactions in the California Current. Journal of Marine Research 40:1095-

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i Cherr, G., petroleum R. Higashi, and produced J. Shenker, waterandcomponents T. Fan. 1993. Assessment of chronic toxicity of to marine organisms. Final Report for the

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Southern California Education Initiative. University of California, Davis and Minerals i

Management Service. Contract No. 30761. i

Chevron. 1994. Discharge Monitoring Report - Platform Hermosa. Unpublished report

submitted to EPA, Region IX for NPDES Permit No. CA0110516.

Coats, D.A. 1994. Deposition of drilling particulates offshore Point Conception, California.

MarineEnvironmental Research37:95-127. Ii

J

Cornelius, N.I., N.I. Kline, and S.H. Cornelius, Jr. 1985. Manual of Mineralogy, 20th Edition.

JohnWileyandSons,NewYork,NewYork. i

In

Crecelius, E. 1990. Chemical analysis of trace metals in sediments, pore waters, and animal

tissues. In: M. Steinhauer and E. Imamura, editors. California OCS Phase II Monitoring i

Program, Year Three Annual Report. Report to the U.S Department of the Interior, I!

Minerals Management Service, Pacific OCS Region, under Contract No. 14-12-0001-

30262. i

Denny, M.W. 1988. Biology and Mechanics of the Wave-Swept Environment. Princeton

UniversityPress,Princeton,NewJersey. I

Drake, D.E., P. Fleischer, and R.L. Kolpack. 1971. Transport and deposition of flood sediment,

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Dugdale, R.C. and F.P. Wilkerson. 1989. New production in the upwelling center at Point 'U

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Fischer, H.B., E.J. List, R.C.Y. Koh, J. Imberger, and N.H. Brooks. 1979. Mixing In Inland and

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Hardin, D.D., J. Toal, T. Parr, P. Wilde, and K. Dorsey. 1991. Spatial variation in hard-bottom

I epifauna in the Santa Maria Basin, California: The importance of physical factors.

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I OCS Camarillo, California. Region,

Hardin, D.D., J. Toal, T. Parr, P. Wilde, and K. Dorsey. 1994. Spatial variation in bottom

I epifauna in the Santa Maria Basin, California: The importance of physical factors.

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Hardin, D.D. 1988. Hard-bottom epifaunal assemblages. Chapter 2.11, In: Summary Report

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Higashi, R. and D. Crosby. 1993. Environmental degradation and identification of toxic

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I Hunt, J.W. and B.S. Anderson. 1989. Sublethal effects of zinc and municipal effluents on larvae

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Ledwell, J.R. and A.J. Watson. 1991. The Santa Monica Basin tracer experiment: A study of

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Lissner, A.L., G.L. Taghon, D.R. Diener, S.C. Schroeter, and J.D. Dixon. 1991. Recolonization

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Mullineaux, L.S. 1988. The role of settlement in structuring a hard-substratum community in i

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Newman, W.A. 1979. California transition zone: Significance of short-range endemics. Pages H

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I Raimondi, P.T. and R.J. Schmitt. 1992. Effects of produced water on settlement of larvae:

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DataGuide,CaliforniaWaterYears1987-1994. i

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i APPENDIXA

I (Currents, Waves, PHYSTides, ICAL WOCEA inds, NOSatellite GRAPHYImagery, Physical

Measurements Arrays, and Particle Transport Modeling)

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I TABLE OF CONTENTS

I SECTION PAGE

TABLE OF CONTENTS ............................................... i

I LI LISTST OF OF TABLE FIGURES S ................................................... iii .................................................. iv

I 1.0 INTRODUCTION ............................................. 1-1 1.1 OVERVIEW............................................ 1-1

1.2 REPORT ORGANIZATION ................................. 1-2

I 2.0 DATA ACQUISITION AND PROCESSING 2-1 2.1 DATA ACQUISITION .................................... 2-1

2.1.1 Introduction ....................................... 2-1

2.1.2 Taut-Wire and Instrumentation Mooring Arrays 2-4

2.1.2.1 Benthos 865-A Acoustic Release ................. 2-4

2.1.2.2 E G & G Smart Acoustic Current Meter (SACM) ..... 2-6

I 2.1.2.3 General Oceanics Mk2 Niskin Winged Current Meter .. 2-6

2.1.2.4 Sea Data 635-11 Wave and Tide Recorder .......... 2-6

i 2.1.3 Physical Measurements Arrays (PMAs) and Instrumentation ..... 2-7 2.1.4 Instrument Calibrations .............................. 2-18

2.1.5 Field Procedures ................................... 2-18

i 2.1.5.1 2.1.5.2 Introduct Taut-WireionMoorings ..............................

......................... 2-18

2.1.6 Time Lines and Data Return .......................... 2-20

I 2.1.6.1 2.1.6.2 Moorings Physical Measurements ................................ Arrays ................. 2-20 2-20

2.1.7 SatelliteImagery ................................... 2-25

I 2.2 DATA 2.2.1 Introduction PROCESSING...................................... .................................... 22-27 -27

2.2.2 Data Processing - Time Series ......................... 2-27

I 2.2.3 Satellite Imagery ................................... 2-28 2.2.4 Particle Transport Modeling Techniques .................. 2-31

3.0 RESULTS .................................................. 3-1

I 3.1 3.2 INCIRCULATION TRODUCTIONPATTERNS ........................................ ................................ 3-1 3-1

3.2.1 Background ....................................... 3-1

I 3.2.2 Seasonal Characteristics ............................... 3-2 3.2.3 Statistics, Spectra, and Coherence ........................ 3-8

3.2.3.1 Spring 1992 ............................... 3-8

I 3.2.3.2 Summer-Winter 1992 3-16

3.2.3.3 Spring 1993 .............................. 3-16

3.2.3.4 Summer-Winter 1993 ........................ 3-23

I 3.2.3.5 1994 3-30

Spring

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SECTION PAGE I

3.2.3.6 Total Statistics ........................... 3-35

3.2.4 Tides ......................................... 3-35 I

3.3 NEAR-BOTTOM CURRENTS AND SEDIMENT DYNAMICS ...... 3-42 !m

3.3.1 Introduction..................................... 3-42

3.3.2 Near-Bottom Hydrographic Characteristics ................ 3-42 U

3.3.2.1 Deployment 1 (18 April 1992 - 17 October 1992) ... 3-42

w

3.3.2.2 Deployment 2 (18 October 1992 - 7 August 1993) ... 3-50 I

3.3.2.3 Deployment 3 (9 January 1994 -. 7 January 1995) ... 3-59 II

3.3.3 Near-Bottom Suspended Material Field .................. 3-71

3.3.3.1 Deployment 1 (18 April 1992 - 17 October 1992) ... 3-71 it

3.3.3.2 Deployment 2 (18 October 1992 - 7 August 1993) ... 3-81 I

3.3.3.3 Deployment 3 (9 January 1994 -7 January 1995) ... 3-92

3.3.4 Discussion ...................................... 3-99 II

3.4 TRANSPORT OF DRILLING MUDS ........................ 3-100 II

3.4.1 Introduction..................................... 3-100

3.4.2 ModelInputs .................................... 3-101 I

3.4.3 Results ........................................ 3-101 |.

4.0 SUMMARY AND RECOMMENDATIONS .......................... 4-1

4.1 INTRODUCTION ...................................... 4-1 m

4.2 REGIONAL CIRCULATION PATTERNS ...................... 4-2 II

4.3 NEAR BOTTOM CONDITIONS ............................ 4-3

4.4 PARTICLE TRANSPORT MODELING ....................... 4-3 _l

4.5 RECOMMENDATIONS.................................. 4-4 J

5.0 REFERENCES .................. ........................... 5-1

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I LIST OF TABLES

I TABLE PAGE

Table 2.1-1. Current meter mooring cruises and dates ........................ 2-1

I Table 2.1-2. Deployment information for the Primary mooring (P) ............... 2-3

I Table 2.1-3. Deployment information for the Secondary mooring (S) 2-3

Table 2.1-4. Deployment sites and water depths for the Physical Measurements

I Arrays (PMAs) 2-4

Table 2.1-5. Specifications for the InterOcean $4 current meter ................. 2-8 !

Table 2.1-6. Specifications for the Optical Backscatter Sensor (OBS) ............ 2-10

I Table 2.1-7. Specifications for the Datasonics Model ATR-397 Acoustic

Release .............................................. 2-13

I Table 2.1-8. Data return summary for each instrument type deployed on the

Primary (P) and Secondary (S) Santa Maria program mooring

i arrays (April 1992 - July 1994) .............................. 2-21

Table 3.2-1. Tidal height analysis of the pressure gauge record at the Primary

I mooring October1,(P7)1993and ........................................ SBC (I6) locations, October 1, 1992 through 3-38

I Table 3.4-1. Phase III platform discharges of drilling muds .................. 3-105

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LISTOFFIGURES l

FIGURES PAGE N

Figure 2.1-1. Map of study area showing the location of moorings, buoys and

CMAN stations from which data were used ..................... 2-2 n

Figure 2.1-2. Schematic drawing of the Primary and Secondary moorings as

originallyplanned ....................................... 2-5 I

Figure 2.1-3. Schematic drawing of the PMA as originally proposed and

fabricated

............................................. 2-9 1

Figure 2.1-4. Schematic drawing of the PMA after the foam float at the top n

of the array was removed following Deployment 1 ............... 2-11 1

Figure 2.1-5. Schematic of the PMA in plan view ......................... 2-12 _l

Ill

Figure 2.1-6. Schematic of the mooring used in place of the PMA during

Deployment3 ......................................... 2-15 I

Figure 2.1-7. December 1993 calibration data for four optical backscattering

units which relates measured and recorded voltages to I

suspended load (mass per volume) .......................... 2-16 U

Figure 2.1-8. April 1992 calibration data for four optical backscattering units

which relates measured and recorded voltages to suspended g

load (mass per volume) .................................. 2-17

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Figure 2.1-9. Comparison of concurrent and adjacent current measurements I

made with the GO and SACM current meters .................. 2-19

I

Figure 2.1-10. Time line of observations used to determine the circulation J

patterns and for particle transport estimates during the modeling

phase .............................................. 2-22 I

Figure 2.1-11. Map showing bathymetry and the location of the ]PMAs at the

Nearfield (adjacent to Platform Hidalgo) and Farfield (several

miles northwest of Platform Hidalgo) sites ..................... 2-23

Figure 2.1-12. Time line showing the duration of the three deploymentsof the n

PMAs at the Nearfield and Farfield sites ...................... 2-24

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I FIGURES PAGE

Figure 2.1-13. Stick plots of currents measured by $4 current meters; one was

I imooring n the PMA frame and the other was on a short, tautline

............................................. 2-26

I Figure 2.2-1. Example of a tidal hodograph with notation which indicates how it graphically presents a fairly complete description of a

tidal constituent ....................................... 2-29

I Figure 3.2-1a. 7-DLP currents and winds, and 40-HLP temperatures (midi depth solid) and pressures for the primary mooring P .............. 3-3

Figure 3.2-1b. 7-DLP currents and winds, and 40-HLP temperatures (midi depth solid) and pressures for the primary mooring P .............. 3-4

Figure 3.2-2a. 7-DLP currents and winds, and 40-HLP temperatures (midi depth O solid) and pressures (dashed MO-6) for moorings I and in the Santa Barbara Channel ............................. 3-6

i Figure 3.2-2b. 7-DLP depth solid) currents and and pressures winds,(dashed and 40-HLP MO-6) temperatures for moorings (mid- I and

O in the Santa Barbara Channel ............................. 3-7

I Figure 3.2-3. Spring 1992 40-HLP means and variances (P only). Inset:

Kinetic Energy spectra in variance preserving form for P ........... 3-9

I Figure 3.2-4. 40-HLP currents and near-surface temperatures (dashed - 1 m

level at I and 15 m level at S1, solid - 14 m level at P) for

I moorings I, P, and S1 ................................... 3-10

Figure 3.2-5a. Composite NOAA-11 AVHRR image for 26 April - 2 May

I 1992 ............................................... 3-11

Figure 3.2-5b. Composite NOAA-11 AVHRR image for 7-13 June 1992 .......... 3-13 Ii

Figure 3.2-6. Coherence squared and phase differences for the indicated

i wind, P, I, and S1 records for Spring 1992 .................... 3-15

Figure 3.2-7. Summer-Winter 1992 40-HLP means and variances (P only).

Inset: Kinetic Energy spectra in variance preserving form for

I P ................................................. 3-17

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FIGURES PAGE I

Figure 3.2-8. 40-HLP currents and near-surface temperatures (clashed - 1 m

level at I and O, solid - 14 m level at P) for moorings I, O, n

andP .............................................. 3-18 J

Figure 3.2-9. Composite satellite images for 8-14 November 1992 .............. 3-19 I

Figure 3.2-10. Coherence squared and phase differences for the indicated

wind, P, and I records for Summer-Winter 1992 ................. 3-21 U

Figure 3.2-11. Spring 1993 40-HLP means and variances (P only). Inset:

Kinetic Energy spectra in variance preserving form for P .......... 3-22 I

Figure 3.2-12. 40-HLP currents and near-surface temperatures (cLashed- 1 m Ii

level at I and O, solid - 14 m level at P) for m,3orings I, O, |

andP ............................................... 3-24

Figure 3.2-13. Composite NOAA-11 AVHRR image for 2-8 May 1993 ........... 3-25 I

Figure 3.2-14. Summer-Winter 1993 40-HLP means and variances (P only). II

Inset: Kinetic Energy spectra in variance preserving form for II

P .................................................. 3-27

Figure 3.2-15. 40-HLP currents and near-surface temperatures (dashed - 1 m U

level at I and O, solid - 14 m level at P) for moorings I, O,

and P .............................................. 3-28 I

Figure 3.2-16. Coherence squared and phase differences for the indicated

wind, P, I, and O records for Summer-Winter 1993 .............. 3-29 m

Figure 3.2-17. Spring 1994 40-HLP means and variances (P only). Inset:

Kinetic Energy spectra in variance preserving for.rnfor P .......... 3-31 !

Figure 3.2-18. 40-HLP currents, temperatures (solid - 53 m level at P and 128

m level at $6) and pressure for moorings P and $6 ............... 3-32 I

Figure 3.2-19. 40-HLP currents and near-surface temperatures (dashed - 1 m am

level at I and O, solid - 14 m level at P) for moorings I, O, il

and P .............................................. 3-33

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Figure 3.2-20. Coherence squared and phase differences for the indicated

I wind, P, S6, I, and O records for Spring 1994 .................. 3-34

Figure 3.2-21. 1992-1994 40-HLP means and variances (P only). Inset:

I Kinetic Energy spectra in variance preserving form for P 3-36

Figure 3.2-22. Coherence squared and phase differences for the indicated

I alongshore current (V) and wind records from P and pressure,

I for 1992-1994 ....................................... 3-37

I Figure ellipses for the semi-diurnal lunar tide (M2) for the 3.2-23. Tidal

indicated instrument locations ............................. 3-39

I Figure 3.2-24. Tidal ellipses for the luni-solar diurnal tide (KI) for the

indicated instrument locations ............................. 3-40

I Figure 3.2-25. M 2 and K1 tidal ellipses for moorings O, I, $5, and $3 ............ 3-41

i Figure 3.3-1. Time 1: (a)series near-bottom observationscurrent from Nearfield speed, (b)station near-bottom for Deployment current

direction, (c) hydrostatic pressure, (d) water temperature, and

I (e) salinity (practical salinity scale) .......................... 3-43

Figure 3.3-2. Time series observations from Farfield station for Deployment

I direction, 1" (a) near-bottom current speed, (b) near-bottom current (c) hydrostatic pressure, (d) water temperature, and

(e) salinity (practicalsalinity scale) .......................... 3-44

I Figure 3.3-3. Spectral analysis of near-bottom hydrostatic pressure for

Deployment1 ......................................... 3-45

I Figure 3.3-4. Meteorological observations from CMAN station PTGC1 and

concurrent near-bottom hydrostatic pressure from Nearfield

I station for Deployment 1 3-47

Figure 3.3-5. Meteorological observations from CMAN station PTGC1 and

I concurrent near-bottom from Farfield hydrostatic pressure

station for Deployment1 ................................. 3-48

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FIGURES PAGE I

Figure 3.3-6. Average daily streamflow for the Santa Ynez River for

Deployment 1 (USGS Gage Station 11123500 Santa Ynez, m

California)........................................... 3-51 Ul

Figure 3.3-7. Time series observations from Nearfield station for Deployment m

2: (a) near-bottom current speed, (b) near-bottom current

w

direction, (c) hydrostatic pressure, (d) water temperature, and m

(e) salinity (practicalsalinity scale)........................... 3-52 m

Figure 3.3-8. Time series observations from Farfield station for Deployment m

2: (a) near-bottom current speed, (b) near-bottom current |

direction, (c) hydrostatic pressure, (d) water temperature, and

(e)salinity(practicalsalinityscale).......................... 3-53 l[

Imp

Figure 3.3-9. Spectral analysis of near-bottom hydrostatic pressure for

Deployment2 ......................................... 3-55 I

w

Figure 3.3-10. Meteorological observations from CMAN station PTGC1 and

concurrent near-bottom hydrostatic pressure from Nearfield m

stationfor Deployment 2 .................................. 3-57 l

Figure 3.3-11. Meteorological observations from CMAN station PTGC1 and IN

concurrent near-bottom hydrostatic pressure from Farfield e

stationfor Deployment2 ................................. 3-58

Figure 3.3-12. Average daily streamflow for the Santa Ynez River for 11

Deployment 2 (USGS Gage Station 11123500 Santa Ynez,

California)........................................... 3-60 I

Figure 3.3-13. Time series observations from Nearfield station for Deployment mint

3: (a) near-bottom current speed, (b) near-bottomcurrent m

direction, (c) hydrostatic pressure, (d) water temperature, and m

(e) salinity (practical salinity scale) .......................... 3-61

m

Figure 3.3-14. Time series observations from Farfield station for Deployment

3: (a) near-bottom current speed, (b) near-bottom current _t

direction, (c) hydrostaticpressure, (d) water temperature, and m

(e) salinity (practical salinity scale) .......................... 3-62

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Figure 3.3-15. Spectral analysis of near-bottom hydrostatic pressure for

I Deployment 3 ......................................... 3-63

Figure 3.3-16. Spectral analysis of near-bottom current speed for Deployment

I 3 3-65

Figure 3.3-17. Meteorological observations from CMAN station PTGC1 and

t concurrent near-bottom velocity from Nearfield station for Deployment3 ......................................... 3-68

I Figure 3.3-18. Meteorological observations from CMAN station PTGC1 and

concurrent near-bottom velocity from Farfield station for

i Deployment 3 ......................................... 3-69

Figure 3.3-19. Average daily streamflow for the Santa Ynez River for

i Deployment California) 3 (USGS Gage Station 11123500 Santa Ynez, ........................................... 3-70

i Figure 3.3-20. Near station-bottom for Deployment suspended material 1 ................................. concentrations from Nearfield 3-72

I Figure 3.3-21. Near-bottom stationfor Deployment suspended 1m................................. aterial concentrations from Farfield 3-73

I Figure 3.3-22. Spectral analysis of near-bottom suspended material concentrations from Nearfield station for Deployment 1 ........... 3-75

I Figure 3.3-23. Spectral analysis of near-bottom suspended material concentrations from Farfield station for Deployment 1 ............ 3-77

I Figure 3.3-24. Time series observations of near-bottom suspended material concentrations from Nearfield station for Weeks 1-2 of

Deployment1 ......................................... 3-79

I Figure 3.3-25. Time series observations of near-bottom suspended material

concentrations from Farfield station for Weeks 1-2 of

I Deployment 1 3-80

Figure 3.3-26. Meteorological observations from CMAN station PTGC1 and

I concurrent surface wave conditions for Deployment 1 ............. 3-82

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LISTOFFIGURES m

FIGURES PAGE I

Figure 3.3-27. Near-bottom suspended material concentrations from Nearfield

stationfor Deployment2 .................................. 3-83 I

Figure 3.3-28. Near-bottom suspended material concentrations from Farfield

stationfor Deployment2 ................................. 3-84 U

Figure 3.3-29. Spectral analysis of near-bottom suspended material

concentrations from Nearfield station for Deployraent 2 ........... 3-85 1

Figure 3.3-30. Spectral analysis of near-bottom suspended material Im

concentrations from Faffield station for Deployment 2 ............ 3-87 Ii

Figure 3.3-31. Time series observations of near-bottom suspended material

concentrations from Nearfield station for We,eks 1-2 of |

Deployment2 ......................................... 3-89

Figure 3.3-32. Time series observations of near-bottom suspended material n

concentrations from Farfield station for Weeks 1-2 of

Deployment2 ......................................... 3-90 nm

Figure 3.3-33. Meteorological observations from CMAN station PTGC1 and

concurrent surface wave conditions for Deployment 2 ............. 3-91 n

Figure 3.3-34. Platform Hidalgo discharge and concurrent average daily

streamflow from the Santa Ynez River for January - May, m

1994 ............................................... 3-93 n

Figure 3.3-35. Time series observations of near-bottom suspended material n

concentrations from Nearfield and Farfield :_tations for w

Deployment3 ......................................... 3-94

m

Figure 3.3-36. Spectral analysis of near-bottom suspended material m

concentrations from Nearfield and Farfield stations for mm

Deployment3 ......................................... 3-95 I

Figure 3.3-37. Time series observations of near-bottom suspended material m

concentrations from Nearfield and Farfield stations for Weeks m

1-2 of Deployment3 .................................... 3-97

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I LIST OF FIGURES

I FIGURES PAGE

Figure 3.3-38. Meteorological observations from CMAN station PTGC1 for

I Deployment 3 ......................................... 3-98

Figure 3.4-1. Mid-depth 40-HLP currents and Hermosa and Hidalgo drilling

I mud discharges for the drilling periods ...................... 3-102

Figure 3.4-2. Class 1 particle concentrations from Hermosa discharges .......... 3-103

I Figure 3.4-3. Class 5 particle concentrations from Hermosa discharges .......... 3-104

Figure 3.4-4. Deposition in lam from Hermosa discharges ................... 3-106

i Figure 3.4-5. Class 1 particle concentrations from Hidalgo discharges .......... 3-107

Figure 3.4-6. Class 5 particle concentrations from Hidalgo discharges .......... 3-108

I Figure 3.4-7. Deposition in _tmfrom Hidalgo discharges ................... 3-109

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I 1.0 INTRODUCTION

I 1.1 OVERVIEW

!

This appendix presents the objectives, results, conclusions, and recommendations for the DOI

I Phase III physical oceanographic tasks, including currents, waves, tides, wind, satellite imagery, physical measurements arrays, and particle transport modeling.

As summarized in Chapter 1, the physical oceanographic measurements and studies have been

I used to provide:

• Improved discharged understanding from oil and gasof circulation platforms during patternsdrilling, affectingand the transport of material

I • An observational data base for use by a particle transport model that estimates the diffusion and deposition of material released from platforms in the Phase III study

region.

I The plan to measure currents at three levels on a single taut-wire mooring, as originally proposed,

was adjusted, in response to a recommendation by the Quality Review Board, to incorporate a

I second instrumented mooring. This second mooring was deployed and relocated approximately every three months to a different along shore or cross-shelf location. A comparison of data from

these moorings (primary and secondary) provided a quantitative estimate (the spatial coherence

I scale) of how far from the primary mooring it could be assumed that currents remained similar to, and hence represented by, those measured at the primary mooring. The result from this

comparison determined whether velocity data from the primary mooring alone could be used for

I all sediment modeling. transport

Data on water column currents were supplemented by near bottom current measurements, optical

I backscattering sensors (OBS), traps, objective program was

and sediment The of this element

to document the potential for local resuspension of muds and cuttings as well as the total

sediment depositional load. !

To support the overall task objectives, field observations were supplemented by satellite thermal

i imagery, coastal/buoy winds and air and water temperatures, and coastal water levels. All of these latter data were obtained directly from NOAA, either through the National Weather Service

(NWS) or the National Data Buoy Center (NDBC).

I As a supplement to the present study, current measurements made by Scripps Institution of

Oceanography (SIO), under separate contract with the Minerals Management Service, were used

I to provide a broader, more regional basis for understanding circulation patterns at the primary

I 1-1

I
I

mooring site. Dr. C. Winant is thanked for making data available from two SIO moorings at the !

western end of the Santa Barbara Channel.

A numerical model was used to quantify deposition of drilling muds and cuttings discharged from I

local platforms. With the model, using concurrent histories of discharge from the rig and the

measured current profiles, muds and cuttings were dispersed and eventually either deposited on I

the local bottom or transported out of the study area. The model allows for any combination of

size classes (settling velocities), uses actual bathymetry on a closely spaced grid, and time

dependent current profiles. Model results include the pattern and amount of deposition by size I

class and accumulated depth. This information is available for individual or

composite sizeclasses. I

1.2 REPORTORGANIZATION !

The physical oceanographic report is organized into five chapters: I

• Chapter 1: Introduction provides a brief overview of objectives, methods, and

activities associated with circulation patterns in the water column and near the bottom. I

• Chapter 2: Data Acquisition and Processing describes the methodology used in

these modeling. activities, including instrumentation, field procedures, data processing, and I

• Chapter 3: Results presents information developed irt support of the overall task I

objectives as presented in the Introduction. This involves a discussion of the general

circulation patterns, near-bottom currents and material transport, and modeling results.

• Chapter 4: Summary and Recommendations provides a summary presentation of I

conclusions and recommendations as related to the project objectives.

• Chapter5: References I

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1-2 I

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I 2.0 DATA ACQUISITION AND PROCESSING

I 2.1 DATA ACQUISITION

I

2.1.1 Introduction

I

Two taut-wire moorings were deployed in the study area and rotated at three- to seven-month

i intervals (Table 2.1-1).

I Table 2.1-1. Current meter mooring cruises and dates.

Vessel Dates

I M/V GLORITA 04/02/92 - 04/04/92

i MM//VV GLORITA CAVALIER 0709//0724//9292 -- 0709//1027//9292

I M/V CAVALIER 01/19/93 - 01/22/93 M/V INDEPENDENCE 08/02/93 - 08/06/93

I M/V WM. A. MCGAW 12/18/93 - 12/21/93

M/V WM. A. MCGAW 07/20/94 - 07/22/94

I

The primary mooring was maintained at the same location in approximately 130 m water

I depth for a 28-month interval beginning in April 1992 and ending in July 1994. The secondary mooring was maintained over this same interval but was moved to along shore or

shallower/deeper sites with each rotation. Figure 2.1-1 shows the mooring locations. Tables

I 2.1-2 and 2.1-3 provide specific deployment information including the deployment intervals, locations, water depths, and instrument depths.

I Physical Measurements Arrays (PMAs) were deployed at two locations (Nearfield and Farfield sites) for three deployments over the course of the field program (Table 2.1.4).

I

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I 2-1

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I

121=00' W 120=45' W 120° 30' W 120=15' W 120° 00' W I

35° 00' N 200_"m '_: I _ 35° 00' N

1Ohm 50m( BE

I

No.46011

NDBCBuoy _.

"'_ _" I

V I

34° 45' N -- ) '; :' 34° 4S' N

, /

oo "_ ,3

.... / ) CMAN

"_ / _ _ Station

,-, s.x_ .,,, ',.% • _. _.. _ .._

l

34°30'N _ • _. --_ '.

"x _,_ _" ..,, _. 34" 30' N

Ill

\,._ ;, _ : _._. 1= San Mi_uel Inshore ....... 100 nl

" * _./._ IkNDBC Buoy _,._"

,: .,,_,,<_ v No. 43054 ._

340 15' N :'_" _ NDBC Buoy ,_-.

-- No. 43023 V"_ _ Santa Barbara-- 340 15' N

': '\ " I

:'- A'"_ Channel

_ ¢ ¢_" O = San MmguelOffshore _

, y_"_-..L..,, ""_._ _"_"_'_-_,'_'_00 In-.

• ' LongTermMoorings :" k "_-* . _"'_. N. <... _'._':-.'_.. .,;7.00I1_"

NDBCBuoys&CMANStations _:) _. _; ._ "_ %\ _) "%'"""'_"_2_"_.100m I I

SecondaryMoorings -_ _ ". _. -- I

3 "_ "_, "" =;_'_% ,_..... "_Ot_ .I

,-, "'. \ ", <<<__ .... -" ""..... /_ _-:I

.... "..... l I

¢ .... . ); _ _, .

...,,.._ooom _ \--", "_. "", i!.

34° 00' N ----" I ", - _.,'_-. _-........ I 340 00' N

121000' W 120° 45' w 120° 30' w 120=15' w 120° 00' w

BB

• Moorings I and 0 were maintained by ScrippsInstitute of Oceanographywith I

fundingfromthe MMS. SIO made these data available tothe PhaseHIProgram.

Figure 2.1-1. Map of study area showing the location of moorings, buoys and CMAN stations I

from which data were used. Moorings I and O are part of an MMS-funded

program being conductedby ScrippsInstitutionof Oceanography. I

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2-2 I

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Table 2.1-2.Deployment information for the Primary mooring (P).

I Dates Location Water Depth Instrument Depths

(m) (m)

I 04/04/92 - 07/08/92 34 ° 30.145q_1 120" 43.077%V 130 14", 53", 125", 130

07/10/92 - 09/26/92 34* 30.441q',1 120" 43.357'W 132 14", 54, 126, 130

I 09/27/92 - 01/20/93 34 ° 30.180_ 120" 43.630'W 129 14", 53", 125", 130

01/22/93 - 08/03/93 34" 30.120_N 120 ° 43.070'W 130 14", 53", 125", 130

I 08/05/93 - 12/19/93 34 ° 30.120qq 120" 43.070'W 130 14", 53", 125", 130

12/21/93 - 07/21/94 34 ° 30.441qq 120" 43.409'W 130 14", 53, 125", 130

I 07/22/94 - 01/14/95"* 34 ° 30.150_ 120" 43.080_V 130 14", 54, 125", 130

i * Also backup instrument one meter deeper. • * Recovered by Scripps Institution of Oceanography; data not discussed in this report.

I Table 2.1-3.Deployment information for the Secondary mooring (S).

I Dates Location Water Depth Instrument Depths (m) (m)

I 04/04/92- 07/08/92 34* 32.873_ 120" 46.032'W 130 15, 54, 126 07/10/92 - 08/14/92" 34* 31.324qq 1i0 ° 41.264'W 91 14, 87

I 10/16/92 - 01/20/93 34* 31.371_ 120" 41.336'W 91 14, 54 01/21/93 - 08/04/93 34* 30.3002q 120" 42.170"q_r 112 15, 54

I 08/06/93 - 12/20/93 34* 28.560qq 120" 40.162'W 130 15, 54

12/21/93 - 07/21/94 34* 29.390'N 120" 43.880_V 256 28, 128

I * Recovered early by fishing vessel.

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I 2-3

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Table 2.1-4. Deployment sites and water depths for the Physical Measurements Arrays (PMAs). m

Station Latitude Longitude Water Depth m

Nearfield 34°29.23 I'N 120°42.364'W 195m

Farfield 34°31.448'N 120°45.496'W 215m m

|

2.1.2 Taut-Wire Mooring Arrays and Instrumentation w

I

The primary mooring, when fully instrumented, included three Smart Acoustic Current Meters

(SACMs), three Mk2 Niskin winged current meters (as backups to the SACMs) and one m

wave/tide recorder (Figure 2.1-2). As shown, the wave/tide recorder was attached to a secondary Ii

anchor and set off from the primary mooring at the end of 160 m of 1/2 inch Yalex rope. The

secondary mooring was initially outfitted with one SACM and three Mk2 current meters. This •

was subsequently adjusted to just two Mk2 current meters to move one SACM to the primary II

mooring as a replacement. The number of Mk2s was reduced as an accommodation to the three

month changes in the water depth at which this mooring was deployed. Both moorings were •

equipped with an acoustic release and appropriate flotation to implement mooring recovery. They |

were also equipped with rope canisters to implement anchor recovery during each rotation.

m

Mooring hardware elements included 5/16" Nilspin wire, 3/8" chain, a 37" diameter subsurface m

float, some vinyl floats (to support the chain), and a 30" diameter surface float with a flasher.

l

2.1.2.1 Benthos 865-A Acoustic Release

I

The 865-A release was used on both the primary and secondary moorings. It has a load capacity

of 10,000 lbs and a depth rating of 12,000m. Release is implemented by acoustically activating m

a motor driven actuator which, in turn, retracts a locking pin holding the release hook closed. m

This uncouples the release from the anchor and the mooring rises to the surface with its flotation

elements, m

The instrument is powered by a battery pack composed of 12 alkaline D-size batteries (to provide m

two strings at a nominal nine volts and 16 amp-hour (AH) capacity). The projected operating m

life is 12 months and 250,000 transponds. However, batteries were generally replaced at fourw

to seven-month intervals due to the close proximity of an operational drilling rig and the I

instrument's inabilityto "sleep" (notrespond to environmentalnoise), m

I

2-4 m

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I Schematic Drawings of Primary and Secondary Moorings

(NottoScale)

Example of

I SecondaryMoodng Primary_JMooRashe ringr

I _ SubsurfaceFloat

I 14m 14m

SACM

I 15 m _ GO Mkll

1 5 m

k_

' l

53 m SACM

iI

125 m

SACM

126m _ SeaD_

I GO Mkll 635-11

Benthos

AcousticRelease

I Rope Ground Conecting Line

I

I

Figure 2.1-2. Schematic drawing of the Primary and Secondary moorings as originally planned.

I As S was moved to different locations and two instruments were lost, the secondary mooring was changed to include only a near surface and near bottom

current meter.

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I 2-5
I

2.1.2.2 E G & G Smart Acoustic Current Meter (SACM) I

This instrument measures currents by monitoring the phase shift of an acoustic signal. The I

measurement range is 0 to 360 cm/s with a stated accuracy of + 10 cm sl or + 3%, whichever

is greater. Directional accuracy is stated as + 2.0°. The temperature range is -2 to 35°C with •

a stated accuracy of + 0.05 ° C. w

were deployed at up to three levels on the primary mooring. The instruments were set I

SACMs

to collect data every thirty minutes with either an "on" time of 5 minutes and an "off" time of

25 minutes, or an "on" time of 11 minutes and an "off" time of 19 minutes. This latter setting •

was not planned but was a default setup that could not be overridden on one of the instruments. l

Each instrument was configured with 64 Kbytes of memory and was powered by a lithium

battery pack. The battery packs were generally replaced at 9- to 12-month intervals. I

2.1.2.3 General Oceanics Mk2 Niskin Winged Current Meter I

This instrument measures currents by determining the tilt of a winged cylinder attached by a •

swivel assembly to a wire mounting support called a standoff (see Figure 2.1-2). Three different

wing sizes are available: low speed (0 to 70 cm sX), standard (0 to 225 cm s_), and high speed

(0 to 300 cm sa). Only the low speed and standard wings were used during this program. Speed B

accuracy is stated as + 1 cm s_ and directional accuracy as + 2°. The temperature range is -5 II

to 45° C with a stated accuracy of + 0.25 ° C.

Mk2 current meters were deployed at up to three levels on the primary and secondary moorings.

The instruments were set to collect vector averaged data at 30-minute intervals using a twosecond burst interval and 32 samples per burst, for a total averaging time of 64 seconds. Data n

were recorded on Phillips-style data cassettes with a capacity of 20,000 samples. Each unit was

powered by a 7.8 volt (14 AH) lithium battery pack composed of two D-size lithium batteries.

The batterypackswerereplacedat 9- to 12-monthintervals, n

2.1.2.4 Sea Data 635-11 Wave and Tide Recorder n

am

This instrument is equipped with a 400 psia (272m) Paroscientific DIGIQUARTZ pressure sensor

with a stated accuracy of + 2.72 cm _ 0.01% of full scale). The temperature range is -4.5 to

34.5 ° C with a stated accuracy of + 0.07 ° C.

- !

The 635-11 wave and tide recorder was deployed on the bottom (in approximately 130m water

depth) adjacent to the primary mooring. The instrument was equipped to record 30,800 data •

records on a 300 foot cassette tape. It was programmed to measure tides at 3.75 or 7.5 minute •

2-6 |

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I intervals (384 or 192 tide samples/day) and waves at six hour intervals (four wave bursts/day)

with 512 or 1024 wave samples/burst. Wave sample bursts were programmed at one scan every

I two seconds or one scan each second, respectively. The recorder was powered by a 20 AH SDB- 4 alkaline battery pack, good for six months or two full cassettes. This power pack was replaced

during each servicing.

!

2.1.3 Physical Measurements Arrays (PMAs) and Instrumentation !

I During current meter Deployments (InterOcean1 and$4)2,witheachintegral of thewater bottomtemperature, arrays contained conductivity, a single and pressure electromagnetic sensors

(Table 2.1-5) supported within a stainless steel frame (Figure 2.1-3). All instruments were

i positioned The currento meter sample provided conditionspower appoximately for and one received mter the abovedatatheoutput sediment-water from twointerface. optical

backscattering probes (Downing & Associates OBS-3 - Table 2.1-6). The OBS are designed to

I monitor the bottom. suspended During material Deployment concentrations 1 each meter andwas for this programmed study wereto located burst-sample 1 m andall 1.5 sensors m above four

times each hour at a rate of two hertz for a period of sixty seconds. Following burst-averaging,

I all Deployments data are internally 2 and 3,recorded programming on solid-state was modified memorytohaving providea capacity two burstofsamples one megabyte. per hour. DuringAll

other sampling characteristics remained unchanged.

I During Deployments 1 and 2, the array subsystems were mounted on a stainless steel (Type 304)

frame. For Deployment 2, the floatation subsystem on the array was modified slightly due to the

I loss of the integral hemispherical floats. This was caused by corrosion of the attachment brackets during Deployment 1 (Figures 2.1-3 and 2.1-4). The main body of the frame remained identical

to that used in Deployment 1.

I The profile, strength, and weight of these frames were intended to minimize the potential for

disturbance by bottom fishing activities. In plan view, the frames were octagonal in form with

I a maximum width of approximately four meters (Figure 2.1-5). Contoured lead weights were bolted in place around the perimeter of the base providing a stable, low-profile mass to anchor

the array and to provide a footing having minimal frontal area and potential for flow disturbance.

I Inelevation, the 2 in and informwith array was approximately m height nearly hemispherical

a network of eight cylindrical legs extending upward from the base to a horizontal platform. As

originally deployed, this platform provided support for a spherical segment of syntactic foam

I flotation held in place by a transponding acoustic release (Datasonics ATR-397; Table 2.1-7).

Following loss of the foam, floatation was provided by two glass spheres, 40 cm in diameter,

i housed in molded plastic retainers ("hard-hats") and held in place by the acoustic release. In both configurations, a cylindrical line canister containing 300 m of 9.5 mm Kevlar line was mounted

on the frame, below and adjacent to the acoustic release. This line, with one end attached to the

i upper platform and the other to the float, served as the primary recovery line for the array.

I 2-7

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® _ _ -_

go ..c:o

c m o.o

_o-_ E _ _.:- __ _ .__ | ,.: ® ,_ -- ..

.-_o__o. _-_ o_o_._°_.° I

_' _ " I

_,_ o,,__o'_"0_,_ "-

... !

r_° !

= g

° _ _ _ |

0 _ _ m

.o "_,_ g _ "_ _ "_o ._ "_

o |

©

f2_

_'_- :_ _ I

?_-8 I
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Table 2.1-6. Specificationsfor the Optical Backscatter Sensor (OBS). m

I

DYNAMIC RANGE

Turbidity...................... 0.02- 2000FTU •

i

Mud (maximum) a ................. 0.1 - 5000 mg/l g

Sand (maximum): ................. 2 - 100,000 rag/1

FREQUENCY RESPONSE ........... 10Hz I

AMBIENT LIGHT REJECTION ....... Optical filtering and synchronous detection I

TEMPERATURE COMPENSATION .... Solid state temperature Ixansducer

NONLINEARITY3 I

Turbidity(formazin,0-2000FTU) ...... 2.0%

Mud (0-4000rag/l)................ 2.0% i

Sand (0-60,000 mg/l) ............... 3.5% I

DRIFT

Time' ........................ -3.5% per decade I

Temperature .................... 0.05% /*(2 I

SUPPLY VOLYAGE COMPLIANCE .... 250 uV/V

SETTLING TIMES I

Power-up...................... < ls

25"C Step Change in Water Temperature . . 15s

m

OUTPUT SPAN5 (maximum) ......... 0 - 5V f.s. B

OUTPUT IMPEDANCE ............ < 300 Ohms

RMS NOISE AT 0 FTU ............. < 50 uV !

POWER REQUIREMENTS _ .......... +6 - 15V/12mAuf

OUTPUT FILTER ................ 20 Hz(-3dB)

I

PHYSICAL DIMENSIONS (Inches/pounds) I

Sensor ........................ 2 x 0.7

HousingLength .................. 4.5 it

HousingDiameter " 1.2 I

Weight(air)..................... 0.4 J

Weight(submerged)................ 0.16

i

WORKING DEPTH ............... 2000 meters I

Amazon River Mud, D_o = 10urn.

z Beach Sand, D_o = 200urn. •

3 Maximum deviation of response from a least-squares straight line, II

expressed as a percentage of the calibration range.

"The output will not drift more than -3.5%, continuous operation, or more ml

than -3.5% x (duty cycle), burst operation, in the first 2000 hours. •

5 Output span depends on adjustable gain settings. I

9-12V/32mA for units with 4-20mA current loop.

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I Table 2.1-7. Specifications for the Datasonics Model ATR-397 Acoustic Release.

!

MODEL ATR-397 RELEASABLE ACOUSTIC TRANSPONDER

I GENERAL SPECIFICATIONS

i Interrogate Frequency: 26KHz for the Model 397/30

Reply Frequency: Model 397/30 kHz

I 28KHz 29KHz

30KHz

31KHz

I 32KHz (user-selectable)

!

I Command Frequency: Model 397/30 kHz 24KHz "A"

25KHZ "B"

I 27kqqz "C"

(user-selectable)

Release Command: Pulse-time coded FSK (27 codes - user-selectable)

I Pulse Width: Model 7 milliseconds 397/30

Turn-around Time: 20 milliseconds (stability 0.i milliseconds)

I : Transmit-inhibit (LOCKOUT): Model 397/30

1 second

I Source Level: 188 Db ref 1 @ 1 meter

upa

i BeOperating am PatternLife: : Horizontal @ 188 Db -- - 1 omnidirectional yr / i00,000/Vertical replies - cardioid

I Battery Packs: Transceiver Release /Battery Receiver A397-3955 B397-3589

AA Alkaline Solid Pack Receiver 6v blue,

Transmitter 12v red

I Operating Depth: 0 - !000 meters Groundgreen

Maximum Release Load: 1500 pounds

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n

Following analysis of $4 current meter records from Deployments 1 and 2, including comparisons •

with nearby (primary) mooring data, it was determined that the,,stainless steel frames were

adversely affecting the velocity data by producing a clear bias in both speed and direction. Since n

the factors responsible for the apparent anomalies could not be simply defined, the decision was

made to replace the stainless frames with a taut-wire configuration consisting of a floatation array

supported by a stainless mounting bracket bolted to and extending upward from the $4 current n

meter. The lower attachment point on the current meter was shack]ed to a short length of dacron i

braided line, which in turn was attached to an acoustic release (Datasonics ATR-397) and a

line cannister mounted on a lead dead-weight anchor. In this configuration, the optical i

recovery

sensors were positioned approximately 3 m above the sediment-water interface at a single point

i

on the vertical attached to the stainless bracket holding the floatat]on (Figure 2.1-6). Sediment i

traps were located at two points on the vertical: one set mounted immediately adjacent to the i

optical sensors (3 m above the bottom (mab)) and a second attached to the recovery line cannister

on the anchor (<0.5 mab). Data reviews indicated that, although tile modified configuration did •

not provide the physical protection afforded by the original stainless frames, it did serve to m

eliminate the velocity bias apparent in the data obtained during Deployments 1 and 2.

Prior to Deployments 1 and 3, all of the electronic subsystems were, calibrated to insure accuracy U

and proper functioning. The electromagnetic current meter and associated water temperature,

conductivity, and pressure sensors were calibrated by the manufacturer just prior to delivery and •

retumed for recalibration prior to Deployment 3. The optical sensors were laboratory calibrated |

at the University of Connecticut using various concentrations of sediments suspended by

mechanical agitation in a salt water bath. The sediments usecl in these calibrations were II

laboratory archival samples selected to provide grain size characteristics similar to those expected n

at the study sites. The laboratory data indicate that the response of the sensors is reasonably

linear over a concentration range of 0-80 mg/1 (Figures 2.1-7 and 2.1-8). This maximum n

generally exceeds that observed on exposed continental shelves. m

In addition to the electronic systems, each instrument array contained four mechanical sediment n

traps. Two of the traps were positioned immediately adjacent to the sediment-water interface,

and two were placed at a higher elevation. During Deployments 1 and 2, the upper traps were

located approximately 1.5 m above the bottom. During Deployment 3, the modified mooring n

configuration resulted in the placement of the upper traps at a point approximately 4.5 m above

the bottom. All traps were constructed of clear acrylic tubing 6.6 cm i.d. and approximately 45

cm in length. An assemblage of 10 mm diameter plastic tubing was used to form a honeycomb

structure in the upper 10 cm of each trap. Chemical additives to inhibit biological activity were

i

not used in the PMA sediment traps. Despite the extended duration of several of the I

deployments, there was little indication of bio-fouling sufficient to affect trap efficiency. U

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I Sediment

Traps

I Hardhatencasedglassspheres

i i oyancy=100lbs

2 optical backscatter units

I _ _ $4 EMCM

!

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| _E

I Acoustic Sediment

I Release _ Trap

I _ Line Canister

I ~600Ibmooring

i Figure 2.1-6. Schematic Deployment of3.the mooring used in place of the PMA during

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II

2.1.4InstrumentCalibrations •

!

All of the instruments used on the primary and secondary moorings were provided by the MMS

from an existing instrument pool. Five SACMs and two waveltide recorders were provided

directly from the Phase II contractor's storage facility and eight Mk2 current meters were I

provided directly from MMS storage in Herndon, Virginia. One each of the SACMs and

i

wave/tide recorders was inoperable and unrepairable and was subsequently used for parts to

maintain the remaininginstruments, i

All eight of the Mk2s had been recaiibrated by the manufacturer in February or March 1990 at i

which time the clock batteries had also been replaced. Each of the four operational SACMs was |

tested under zero current conditions and in a towed configuration in a test tank to evaluate

general operation. The wave/tide recorder was also tank tested for general operation and •

reasonableness of data. l

A number of direct comparisons between the SACM and Mk2 current meters were possible due •

to the close proximity of the instruments (one meter apart) on the primary mooring. These l

comparisons indicated good correlation of both temperature and current velocity. An example

isprovidedinFigure2.1-9. •

n

2.1.5FieldProcedures i

2.1.5.1 Introduction i

Prior to deployment, each instrument underwent an operational check and physical inspection, i

Repairs and anode replacements were made and the instruments 'were cleaned and refurbished

with new batteries and cassette tapes, as applicable. Anti-fouling paint was applied to the Mk2

currentmeterspriortotheinitialdeployment, i

2.1.5.2 Taut-WireMoorings i

Both of the taut-wire moorings were deployed and recovered in the same manner. Deployment i

was initiated by trailing the surface buoy behind the vessel while steaming slowly towards the

deployment site. All subsequent in-line elements were trailed behind the vessel leaving on board n

only the main anchor and a coiled length of 1/2 inch Yalex rope (in a barrel) attached to a II

smaller secondary anchor, all of which were positioned on the ste;rn. A length of 3/8 inch line

was then tied to the secondary anchor and secured to the vessel. When the station was reached, n

the main anchor was deployed while the vessel continued to steam slowly past the site. The

2-18 I

!
I

Comparison of GO and SACM Velocity Measurements

i 40 (Mid-depth, Primary Mooring; &t=30min.; No filtering or decimation)

30 [ ........................... -............................ ,: !............................ !............................ :............................. {............................ _...........................

i i" I-- Go(u)I i i i _ _, ,_•

I -301 3/17/93 \ 3/18_/93 3/19i/93 3/20i/93 3/21i/93 3/22/93 i 3/23i/93 3/24/93

Date

I 401 l l I I I I '

o

3o ....................... i.............................. _..................... i............................ i ............................ i......................... i...................... n

_o ............ ' ..........i.................... ..-!......................... _.............. .--.......................... _.........

10 -- :-- ' ............. _ ........................Q

g

-10 ............................ _............................... i .......................... _................... ,_ ........ _ ............................. _ ............................. 4............................

i i |-- ! i i

I 8 iii:ii i-:::sLL;iiiiiiiiill iiiii!, , , ,

>- T......... I _ ............................... !........................... i........................... i........................... i......................

i -3ol 3 i _ _ i t .

/17/93 3/18_93 311 1193 3_20/93 3/21193 3122/93 3/23/93 3/24/93

Date

40- t II _ .30[ ....................... Lo_ .................................................................................. .......................... _ ........................ _ ....................... l

I ._. 20 [ : o' i _ o. i , ............. _..... ?................ }............................. b................. : .......

o2

if}

I .,o:.i.2.SACMSpeedI

-20 _ ....... GO Speed I......................................................................................................................................................

O Diff(GO-SACM)I

-30[ t

I 3/17/93 3/18193 3/19/93 3/20/93 3/21/93 3/22/93 3/23/93 3/24/93

Date

I Figure 2. 1-9. Comparison of concurrent and adjacent current measurements made with the GO

and SACM current meters. The only changes to these original data were

I elimination of a few obvious outliers, i.e., single point spikes.

I 2-19
I

m

Yalex rapidly uncoiled and put tension on the secondary anchor. This tension was allowed to •

build briefly before the 3/8 inch line was cut and the secondary anchor was pulled overboard and

deployed, m

Mooring recoveries were implemented by activating the acoustic release or by grapnelling during

infrequent events of release failure. On several occasions, duldng the longer deployments, m

grapnelling was required as the release batteries had died due to the noisy environment (an active

m

drilling rig) and the instrument's inability to ignore and not respond to such noise. !

Following release activation, during normal recovery, the mooring elements were brought onboard, beginning with the surface buoy. Once the release was on-board, a length of 1/2 inch m

Yalex (from the rope canister), extending up from the main anchor, was recovered along with m

the main anchor, and then more 1/2 inch Yalex and the secondaEy anchor. If grapnelling was

required, the length of line between the two anchors was the target for the effort and the mooring •

was recovered bottom first including both anchors. |

2.1.6TimeLinesandDataReturn I

|

2.1.6.1Moorings •

The data return from the taut-wire mooring instrumentation was quite good (96.2% for all m

measurement levels) as most of the data losses were attributable to the backup current meters

installed on the primary mooring. Here, two Mk2 current meters were lost during grapnel m

recoveries of the mooring, a third unit experienced a clock battery failure, and a fourth unit had m

a tape advance problem. One SACM collected only a short record (for unknown reasons) during

its initial deployment and the wave/tide recorder had a defective battery connector which caused m

it to collect no data during its second deployment. Some additional SACM data were lost during m

the sixth deployment due to instrument memory limitations. The ,data return is summarized by m

instrument type and mooring in Table 2.1-8, and time lines of available data for each instrument m

level are presented in Figure 2.1-10.

m

m

2.1.6.2 Physical Measurements Arrays m

!

Field observations of the near-bottom suspended material field associated with the PMAs in the

vicinity of Platform Hidalgo began on April 18, 1992 with the deployment of two instrument •

arrays, designated "Nearfield" and "Farfield," respectively (Figure 2.1-11). Each array was l

I

2-20 m

!
i Table 2.1-8. Data retum summary for each instrument type deployed on the Primary (P) and

Secondary (S) Santa Maria program mooring arrays (April 1992 - July 1994).

!

Percent Data Return

Instrument Type Mooring

I (No.Deploym of Instrument (No. of Measurement Comments ents) Levels) Instruments Levels

i EG&GSACM(16) Instrumentfailureduring first deployment and

P(3) 91.4% memorylimitations

during sixth deployment.

i GeneralOceanics 96.4%* Oneclockbatteryfailure,

MK2(17) P(3) 73.6% onetapeadvancefailure,

I [Backup] and two instrument losses during _apnel efforts.

GeneralOceanics S1(3) 85.0% NodatabetweenAugust

MK2(13) $2(2) 14,1992andOctober16,

$3(2) 100.0%** 100.0%** 1992as instrumentsnot

$4(2) inwater.

I $5(21 $6(2)

SeaData635-11(6) Badbatteryconnector

I P(1) 84.4% 84.4% duringsecond deployment.

I TOTAL: (52) All 86.9% 96.2% Entire Program.

* Obtained by combining SACM and MK2 data records to fill data gaps as instruments were deployed at same

i depth (one meter apart).

** During the second deployment period, the mooring was recovered early by a fishing vessel.

!

bottom mounted, self-contained, and free-standing. Both arrays were placed in close proximity

I to mixed relief hard-bottom features. Farfield was considered to be beyond the influence of drilling associated discharges and was intended to represent a control for the measurements

obtained at Nearfield. The in-water intervals for Deployments 1, 2, and 3 are shown in Figure

I 2.1-12.

On July 8, 1992 the M/V GLORITA attempted to recover the PMAs by acoustic command. The

i was unsuccessful due to the lack of response by the acoustic releases and, as discovered

attempt

on the recovery, the loss of the spherical floatation elements. On October 17, 1992 the PMAs

deployed in April were recovered using an ROV to place a lifting line. Following recovery,

i instruments were serviced, data downloaded, configuration were

the floatation and release

I 2-21

I
I

Santa Maria Basin, Phase III- "l'ime Line []

- * , _,_i_,;,_ . i

4_23(o,oy) r---- -" "- - --- -; - - - : - -'- - _- : - -'- - - - ---1_ ..... ij_i_!- -, _i!iiiiii_iiiiii_ii!iiiiiiii_ iii__ii_iili!ii_:iiilli : 'iiii_ilili j

,==,,o_o,) r ............... ;.................... i_iiiia_-;;_i;_i_i_ ii i_i___,_...... -_ l

- ................... r ....... tF .......... _ i_ i_ - - - _ _!_ _ _ _ _ _ _i;_ _ _I::_i_:,i_ ..... 14 •

Currents (Scripps) ................

$M-MI-1 lm r r ,-_::_; - - •:!:i;!:_:i:_]:!_:i_:i!_:i:_:!:_:;:_;;_i_!;!:i;$_;

SM-M,-3 25m " F ....................................... ii_l_i_... _ _<'_!_i_i_'i_ii_!_i_li_i_!i_ ;

SM-MI-4 45m I- ....................................... !_i_ _ - - _ _ _;_i;:_ _i_ _ii_iii_? _i::_ _ _i_ ...... _"

I

SM-MI-5 6_m I P ....... I P .... ................... _(_::i::;_l- - - _i:i_il ;_::i_i_i_;::i_i_::!_i:_i!i_i_::i:_

I

I

- , i;!_iii::i ::iiiiiill i_ ::_::iii::_i_iiiii_iiiiiii -

SM-MI-6 l_m P ....................................... _;:_ - - _:i_ _ _i_i_ _i_i_i_ ......

I

L i !:_g:::: ;]] -- S_-M_ Sm . - -- -,- - -I k............ _ - --_:i_ --1 I

SM-M_3 25m I F - - q F ....... I F ............ _ii_i!_i- - -i_ii_i

=M-=_,m ,_ _ _............ _,",i_',i'---i_i!i',ii -

SM-M_5 65m P - - _ P .......... !i! _i:#: ii_ i :::_iil!i!i!i_:ii_iiiii_!l_i _!:_:!_iiiii!iii_:i:.iii_ii::iiii_:iii_i - []

i ::::::::::::::::::::::i_i :: :::.::i::iiiiii ii_il]il_]:#:]::::_::[]i i]_:::i::::: i::::i_]i_::ii _

I

SM-MO-6 100m k _ -I I- _!:_i ii _i :_i>ii!i!i

Primary Mooring

SM-P-1 14m l

SM-P-3 53m

SM-P-5 125m

SM-P-7 130m (Pressure) i_

!

Secondary Mooring , iiiiiiii:.ii i::]ililili i ::i_iiii::i i:: :_i::::;i:ii:ii_. ::i::i_i:,_i:,:i

, :_i:::ii ::ii iii _ !;i :::4#:iiIi:. !i iiiii_ ::::i:.:. :::;:ii: :: =

SM-SI-2 15m r ...... _ _i_ ::::::::::::::::::::::::::::: ;iil iii_: :i_ii ::i::[i

SM-S1-3 54m '_- - - - - - _ , iEil ;iii::i!i_lii iil i ii_-_i ;:.ii;iiiii_ii _ ii

SM-SI_ 126m , ::i::_i;!i iili!!iiiii_iiiii !_!: ; i !i _ - •

P------_ , _i :; iiiiii_::iiii_iiiiiE|_ iii !i []

' ' ' ' ::i_ii_! i i; i_;_ iii::;i::!_ii :'iii::i_i i_i_ i_ -- i

i

8M-$3-2 I 14m I-..... ,- d _li:l_?::ii;

SM-$3-3 ._,m I- ..... ,- -I i[i _i !_i_iiiiii i!iili!iiiiiiiiiii::i_iiii::i_iiii{! _iii

' . , i:::_ii:: ::::::::::::::::::::::::::::: ii:::::::::: ii::ii::iiiii!iiii ::::::::::::::: iiiiiii::i::i i_::i_:::iii::i -

SM-_-2 15m ' _ .............. I :: il:i::ii::::::i ::_iiiii_ii:iiiiiii]iiii::_iiii_iiiiiiiiii!il;!i_;i :

, - ........ • iiiiiiiiiii i_]_i_i£_:_ii_iiiiii_i::iii_;_!_ii_,!!i_i_ii_iii_i1:ii_Ii_ii

sM-s_-__m : .__=__ i

SM-$5-2 54m , -_--_- _iii_i_ - - "_ii_ii_ i: iii i ii i_ [iii_;;_!!;;;:.i!;i ;;

: '_i_ !i _ - [] SM-S6-1 28m ::::ii:ii ::::::i::ii_:: _i!_[_!_ _i_ _ - -I

SM-S6-2 128m : i _: _ _ i i _ _'_i_i_ _ _ _;_ _ - - - -I l

_ii i_iil _iii_iii!iiiiiiiii iii][i _iiiiii ]iiii_!_]i

I I I i _f _ I _ _ | _i!_:_:]t [ _ |:_;_q I I

_Solid Line = Current Yelodty A M J a A S O N O J F M A M a J A S O N D J F M A M J J A II

Dashed Line = Temp¢raturt 1992 1993 1994 I

Figure 2.1-10. Time line of observations used to determine the circulation patterns and for I

particle transport estimates during the modeling phase. Gray patterns

indicateplatformdischargeperiods. I

2-22 I

I

° "IO ' l

o _., N

° I

N °

_ _o I

I

_ _-_ _ i

,

o )-- ) °_

m

2-24
!

I modified, and the arrays prepared for redeployment. Deployment 2 began on October 18, 1992

with the bottom mounted arrays placed at the same locations used during Deployment 1 (Table

I 2.1-4).

Deployment 2 ended on August 7, 1993. Following recovery and data downloading, the

instruments were returned to the laboratory for servicing and recalibration. The current meters

were recalibrated by the manufacturer. The optical sensors were calibrated at the University of

Connecticut laboratory using procedures identical to those used prior to Deployment 1. !

Deployment 3 began on January 9, 1994. Prior to array placement, a short field test was

i conducted to examine the possibility that anomalies observed in the near-bottom velocity data obtained during Deployments 1 and 2 were caused by the stainless mounting frame. A single

$4 meter was taut-wire moored in close proximity to the Nearfield array for a period of

i approximately twenty-four hours. Subsequent analysis of these data (Figure 2.1-13) indicated a

bias in the velocity record from the array mounted instrument. As a result, the stainless steel

arrays used in Deployments 1 and 2 were replaced by simple in-line taut-wire moorings. These

moorings were placed by the M/V RAMBO at the same locations occupied during Deployments 1 and2.

command. On July 21,The1994Farfield recoveryarrayof was the taut-wire successfullybottomrecovered, arrays but weretheattempted acoustic using release acoustic on the

Nearfield array failed to respond. As a result, the Nearfield mooring remained on station until

I January Nearfield7,array 1995actually when it ended was recovered in September using1994 an ROVdue toto battery place /adata recovery storageline.limitations. Data from the

I 2.1.7 Satellite Imagery

I Infrared imagery of the earth's surface is available from the NOAA Polar Orbiting satellites'

advanced very high resolution radiometer (AVHRR), which measures visible and infrared

I radiation in four or five bandwidths. Each satellite has a slightly different suite of instruments; however, the even numbered satellites (NOAA-6, -8, and -10) generally measure radiation in four

bandwidths (channels) while the odd numbered satellites (NOAA-7, -9, and -11) and NOAA-12

I in five bandwidths. Data transmission is five channels. The fifth data

measure always

transmission channel repeats the fourth bandwidth of radiometer data from a four channel

radiometer. Technical details and data formats are given in the NOAA Polar Orbiter Data Users

i Guide (Kidwell 1991). A review of the uses of satellite data, including a discussion of errors,

can be found in Abbott and Chelton (1991).

i Spatial resolution of the AVHRR is nominally 1.1 km at nadir and temperature resolution is

about 0.10K in the study region. High resolution data are broadcast continuously in the High

I Resolution transmission Picture to NASATransmission ground stations (HRPT)as mode Lcal orArealimited Coverage time periods (LAC) data.re stored Data for are later also

I 2-25

!
I

I

I

Hidalgo Deployment Jan 94 : Single In-line Mooring

i

1/7 1/8 1/9

, i

I

I

Hidalgo Deployment Jan 94" Frame I

1/7 1/8 I

!

!

Figure 2.1-13. Stick plots of currents measured by $4 cuJrrent meters; one was in the

PMA frame and the other was on a short, taufline mooring. Although only i

about 100 m apart, there was an evident difference in the measured

currents. This provided strong evidence of current velocity data bias

resulting from some aspect of the PMA frame prior to Deployment 3. I

With these data it became apparent that the tautline mooring would have

to be used if usable data were to be obtained.

|

2-26 "1
I

I averaged and stored in the satellite in a lower resolution Global Area Coverage (GAC) mode.

The GAC data provide global coverage at a maximum resolution of four kilometers.

Ii

One thousand eight hundred twelve images, consisting of separate channel 4 (10.3-11.3 _tm) and

5 (11.5-12.5 grn) data from the NOAA-11 satellite, were acquired during the period November

1, 1991 through April 30, 1994. These data were screened to reject scenes with a significant

amount of cloud cover. During the first four months (120 days) of 1994, for example, there were

about twenty relatively cloud free views of the central California coast. Eighty-five morning pass

I and 101 afternoon weekly composites, each from two or three pass prepared images, provided

a relatively cloud free view of the study area beginning April 1, 1992 when current meter data

were available from most of the moorings. There were five weeks (four in 1993 and one in

I 1994) when no usable composites could be prepared. During six weeks in 1992 and 10 weeks

in 1993 no morning pass composites were possible while two additional weeks in 1992 permitted

I no afternoon pass composites.

2.2 DATAPROCESSING

i 2.2.1 Introduction

I Primary data types included time series of environmental variables and sea surface temperature images obtained from satellite borne sensors. A brief discussion of processing steps is given

below.

I Time series observations include current and wind velocity, bottom pressure, temperature, and

optical backscattering. For each of these data types, a sequence of observations was made at

i intervals half hour Some of the instruments recorded regular (e.g., during a deployment).

instantaneous values while others internally processed instantaneous observations and recorded

values that were averages over a user determined sampling interval. I

Satellite imagery was obtained from Ocean Imaging of San Diego and processed at SAIC,

i Raleigh, NC.

i 2.2.2 Data Processing - Time Series

i All oceanographic and meteorological data were processed using tested and verified procedures and algorithms. A key step in all processing was thorough quality control procedures which

assure that all data have been thoroughly examined and evaluated by several oceanographers prior

I to being included in the program data base. After the QA steps, all data were entered into a

physical oceanographic data management and analysis system for further processing. This data

I 2-27

I
I

m

base system, interactively linked analysis, and graphics routines form the basis for all subsequent U

ocean data analysis and presentation. ii

Because currents often tend to flow in the direction of the general trend of the bottom contours n

(along isobaths), the current velocity data used in these analyse,s were rotated so that the v- I

component of velocity was directed along isobath and the u-component of velocity was directed i

across or normal to the isobaths. The magnitude of this rotation !isindicated on the appropriate

m

figures in the following form: "R330" which indicates that the coordinate frame was rotated 3300 m

clockwise from north so that the positive v-component is directed along isobath in this direction. !

Basic processing of time series data, such as components of current velocity or temperature, ai

involved all or some of the following methods: three hour and forty hour low pass filtering, I!

spectral analysis, and coherence and phase analysis. Three hour low 12ass(HLP) filters suppress

fairly rapid fluctuations with periods of three hours or less. Given the time scale of processes m

of interest in the present study, 3-HLP time series were sampled at one-hour intervals and used !1

as the primary data record. This resampling of 3-HLP data assured that comparisons between

time series were always done at comparable times. Forty-HLP filtering suppresses fluctuations i

with periods less than approximately 40 hours. Hence, semi-diurnal and diurnal tidal oscillations I

would be eliminated from the time series. Spectral analysis divides the variance of a time series

according to the frequency at which the variance occurs. Thus, spectral analysis helps resolve II

the relative contribution that different periodic fluctuations contribute to the measurement record. n

Coherence and phase analysis identifies how well fluctuations at a given period in one time series

are correlated with fluctuations at that same period in another time series. If this correlation is

statistically significant, then phase information quantifies what time lag may exist at a specific U

periodic fluctuation between two records.

n

A comprehensive statistical analysis was also conducted. It identified for each time series U

maximum and minimum values, the mean, the 3- and 40-HLP variance, and the principal axis.

The latter is a quantitative method of determining a preferred orientation or direction for vector HI

data. In addition, as discussed in subsequent sections, several special analytical methods (e.g., IB

tidal analyses) were used to help isolate and resolve the circulation patterns and processes. l

Tidal analysis was applied to the current velocity time series to help resolve fluctuations of n

higher frequency current fluctuations. These results provide an estimate of the amplitude and

phase of all primary and interactive tidal constituents. Those constituents that contribute i

significantly to the observed velocity field can then be presented graphically as tidal hodographs

i

(Figure 2.2-1). '!n

2.2.3SatelliteImagery i

Two bandwidths (channels 4 and 5) of the five channel radiometer are generally used in il

determining sea surface temperature (SST). A third bandwidth (channel 3 (3.55-3.93 lam)) of

2-28 i

I
I

1

!

1 Tidal Ellipse

l Or Tidal Hodograph

Ellipsedescribes the

path taken by the end of

I the tidal current vector with its origin at the center as it Lm Minor

changes over a tidal cycle. X 5IT,_ Minimum TidaAIXis

Current

I __ A

Tidal current vector _ \ 3+\ / I

I at 0000GMT __I_-- _

-5 -4 -3 -_ -1 _,i/ _ 3 4 5

,,

Arrow head points in the

Ill MajorAxis _ .._.j, \ _

direction the tidal

current vector rotates.

MaximumTidalCurrent

-4-

!

-5 _

i s

Background gives the geographic direction and scale of the vectors (in cm/sec}.

l

1

I

Figure 2.2-1. Example of a tidal hodograph with notation which indicates how it graphically

presents a fairly complete description of a tidal constituent.

1

2-29
n

infrared data is also available but the instrument tends to be noisy and of limited usefulness []

(Barton 1995, Kidwell 1991). The satellite scan data were converted from radiance (counts on

10-bit scale) to temperature (8-bit scale) using an inverse of Planck's Law (Kidwell 1991). I

The temperature data may be corrected for water vapor in the atmosphere (but not for clouds)

if two radiometer channels are available, remapped to a user .selected map projection, and 11

displayed as color enhanced images. A single channel image provides valuable information about n

spatial patterns at the sea surface which can aid in understanding regional processes. The use

of two channels of data to determine SST results in a more accurate temperature estimate I

(McClain et al. 1983; Abbott and Chelton 1991; Barton 1995).

images acquired were separated into channel 4 and channel 5 images and converted I

The 1812

from byte data to temperature. Navigation parameters were applied to the images to allow

application of geographic data such as bathymetry, coastlines, and vectors to the images. The m

amount of cloud cover in each scene was noted for later use in choosing scenes to be composited |

as a means of cloud removal.

The image compositing routine involved a pixel by pixel comp_trison of two images with the I

warmer pixel being chosen for retention. This takes advantage of the relationship that clouds are

generally cooler than the sea surface at the study area latitude, and they exibit movement. A Ill

secondary effect of the compositing process is to smear the edges of moving features such as l

eddies. Images were selected such that a composite included either all morning (descending) or

all aftemoon (ascending) passes and the time span between images was constant. Thus, two II

composite images of the study area (32°28.1'N to 37°31.8'N, 117°54.4'W to 124°04.8'W) were il

prepared from the channel 4 (10.3-11.3 lam) data during each week of the study. Daily average

current and wind vectors, centered on the date and time of the co_a'esponding composite, were i

overlaid on the composite images of the April 1, 1992 through April 30, 1994 period. After n

compositing was complete, remaining clouds were 'zeroed' by discarding values less than a value

determined through visual inspection. Cloud values were generally less than 9.5-11.0 ° C. The i

composites were photographed for use in evaluating processes for the data report. II

For certain cases where accurate SST was needed, a two channel correction was made to specific i

images using the NOAA crossed product (CPSST) algorithm (Walton 1988) for mid-latitude i

summer (equation 1) or winter (equation 2) conditions. The algorithm has the form (Barton

1995): 1

SSTsummer = T4+ 1.632"(T4- Ts)+ 0.53 (1) i

l

SSTwint_r = T4 + 1.179"(T 4 - Ts) + 0.44 (2)

After the correction was applied the images were composited in the same sequence as the original i

channel 4 composite.

i

2-30 I

!
!

I 2.2.4 Particle Transport Modeling Techniques

I

Drilling muds are discharged from the platforms in irregular amounts on a daily basis while wells

are being drilled. A description of this process is given in Coats (1994). Muds primarily consist

I of clay and silt sized particles with a small fraction of heavy sand sized particles. Discharge is

from a pipe about 34 m (100 feet) below the surface. Since a primary interest is in the farfield

i dispersion of mud particles, as they slowly sink to the sea floor, the nearfield dynamics of the discharge are not considered as in Coats (1994). The focus is on dispersion caused by horizontal

advection in the current field, and horizontal diffusion by oceanic turbulence. A major

i assumption tracked (as the is that material the material descendscanthrough be splittheintowater particle column) size byclasses surrogate that canparticles. be independently

i Tracking cloud of material a surrogate as long particle as allofscales each ofsizemotion class areis asampled. good representation This will be ofthethecasedispersal if sufficient of a

numbers of particles are released over the drilling periods. The number of particles released per

I hour of particles is proportioned is time variable to the with daily adischarge daily timeofstep. drillingThe muds basis inof barrels. the surrogate Thus,particle the discharge assumptionrate

is the theories of Batchelor (1952) and Taylor (1954) on dispersion by random movements. The

I main mean result, applicable to particle settling models, is that cloud dispersion from an ensemble position is given by single particle statistics (Fischer et al. 1979).

I The simple particle tracking model, described below, is similar to the model of Fry and Butman (1991) which was used to estimate the footprint that would result from the dumping of municipal

sludge at the deepwater 106-Mile Site, offshore of New Jersey. The Fry and Butman (1991)

i model is also the basis of the drilling mud disposition model used in Phase II (Coats 1994).

The model advects particles horizontally according to estimates of local current velocity at each

I time The vertical distance traveled is given by the sinking velocity. The particle's position step.

is computed according to:

I (x', y', z') ---(x + (u + ud)At,y + (v + vd)At,Z+ w_St) ()

1

I where x', y', z" is the particle's new position at time t + At;

x, y, z is the particle's position at time t;

i u, v(x,y,z,t) are estimates of the local east and north velocity components; us,vd are random diffusion velocity components;

wk is the sinking velocity for a particle of class k;

i and At is the time step.

This equation is repeated for all active particles in the water column. To estimate u and v, all

I available June 1994current drillingmeter periods, records records werewere usedused fromfromnearbythemoorings. Primary (P)For(near the September Hidalgo), $51993(nearto

I 2-31

I
!

Hermosa), $6, and the SIO Santa Barbara Channel mooring SMI2';I. Where records are missing Ii

or short, the continuous sections of the 3-HLP records (Figure 2.1-10) are merged together using

flag values. Thus, each meter position has an associated (u,v) time series covering the year-long I

deployment period, with flag values denoting data gaps. i,

At each time step, the valid velocity records at each position for all the moorings are identified. 1

An objective method is used to find the nearest velocity position to the particle at (x,y,z). The

roll

procedure weights the nearest mooring more strongly than velocity values at similar depths to /

z but on moorings further away. In this manner, data gaps on a particular mooring are I

minimized by employing data at similar depths from other positions. The weights, W O, are

calculated from: I

Rj = max (rj, train,)

Rmi n = min(Rj, j=l, n),where n is the number of moorings /

mzij _- max (IAzijl,AZrain), II

and wij = Rj_./(R_i° AZm,_), (2)

where rj is the horizontal distance between mooring j and the particle at (x,y); 'l

rmin is a minimum radius (1000 m);

Azij is the vertical distance between meter i on mooring j and the particle II

at depth z; il

and AZmi n is a minimum depth difference (50m).

Iit

The (i,j) record selected has the minimum W_jof all valid positions. I

Linear interpolation between velocity positions on the selected mooring is used to find u and v ,i

at depth z, where appropriate. In this manner, the model attempts to account for the vertical and llg

horizontal spatial variability of the current field seen by a particle as it moves away from the

disposal site. Some scales of motion, such as tidal variability, will only be partially captured

because of the limited vertical and horizontal distribution of the current measurements. Data gaps IN

also cause a deterioration in the quality of the local interpolated velocities. However, over many mira

realizations of particle tracks, the stochastic behavior of dispersing particles should be well l

captured on average. The larger scale variability of the poleward flow should also be captured, i

in its essentials, by using an array of moored instruments rather than just a single mooring, as aa

is more usual in particle tracking models. I

The random dispersion velocities are used to account for dispe:rsion caused by small scale n/

turbulence and motions not well resolved by the moored array. The velocity components are |

randomly selected from the range [-p,p] at each time step. The value of p can be related (MaierReimerand Sundermann1982)to a dispersioncoefficient,D, by lid

II

!

2-32 'l

!
I 1 2

I D= gp At _ (3)

I A dispersion coefficient of 1 mZ/s is appropriate for offshore ocean environments. The results are not sensitive to values of D less than 10 m2/s.

i The time is chosen from the time for a particle to fall 50 m or the velocity time series step, At,

interval of 1 hour, whichever is less. Before each execution of formula (1), the position of the

particle is checked to see if it has intersected the bottom or one of the outer boundaries of the

I grid. If the particle has intersected the bottom, flagged position it is and its recorded. If it has

exited the grid, it is flagged as "lost". At the end of the particle tracking period, the positions

on the bottom where the surrogate particles have settled are accumulated onto a regular grid in

I terms of particles per grid cell.

I The squaremodel meteris per runkgfordumped all validofsize eachclasses, size class. and the If thisresults is denoted are reported as ck, then as concentrations the depositionperis

given as

Ii akVt_ckQ

1-n_ (4)

!

where dk is the deposition depth of size class k;

I VQk isis the the fractional total volumevolumetric of material concentration dumped over of size the time class period k

and nk is a functionof the voids ratio, rk

I

I where r_ (5) nk- l+r

i Total deposition, d, is then given by the sum over the size classes

I d = Ed k

(6)

The percent loss is calculated for each size class and then weighted by Vkto produce the percent

I of the total solid material dumped that is not deposited and which escapes through the boundary

of the grid. This total percent loss is entirely accounted for by coarse silts and fine silts (classes

i 5 and 6).

I 2-33

!
!IIiIII

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2-34'1!
I 3.0 RESULTS

I 3.1 INTRODUCTION

!

Physical oceanographic field measurements were made to support both an improved

i understanding from oil and gasof local platforms oceanographic in the studyconditions area. Section and transport 3.2 presents modeling a discussion of drillingofdischarges measured

current velocity and temperature profiles in conjunction with satellite sea surface temperature

I imagery. hence material Thesetransport data describe in the vicinity the sequence of th platforms. of circulationSection patterns 3.3 presents which control a discussion currentsof near and

bottom currents at two PMA locations with a goal of understanding the processes and pattems

I byconsideration which sediment of temperature, is transported, salinity,deposited, and suspended and resuspended. sediment loadThis in close effortproximity incorporateso thea

bottom. Finally, Section 3.4 describes the transport and deposition of material released from

I field local drilling observations platforms of local as estimated currents. by a numerical sediment transport model in combination with

Each relevantof these to the sections overall program provides goal an improved of characterizing understanding the differential of processes impact or conditions of drilling which muds and are

cuttings on high and low relief hard bottom sites in the Phase III study region.

!

3.2 CIRCULATION PATTERNS

!

i 3.2.1 Background

i The warmer primary watercurrent meter mooring was located in a transition region between poleward flowing exiting the Santa Barbara Channel, as associated with the Southern California

Counter Current (Hickey 1991), and the cooler, fresher water of the southward flowing coastal

I California spring (BrinkCurrent and Muench (Hickey 1986). 1979).TheIn addition, outflow fromPt. Arguello the Santa isBarbara often anChannel upwellingis often centerconfined in the

to the northern side with an associated cyclonic eddy between Pt. Conception and San Miguel

I Island of the that channel entrains (Brinkcooler and California Muench 1986). CurrentNorth waterofintoPt. the Arguello, southernlimited half ofcurrent the western measurements entrance

indicate poleward flow near the coast in opposition to the equatorward winds which occur over

I most and Sanof theFrancisco year. Chelton Bay although et al. (1988) the majority reportedofpoleward their current flow inmeters springwerebetween deployed Purisima at 70mPointor

deeper. They also reported that for spring 1984, the alongshore currents off Pt. Conception were

I poorly correlated with currents north of Purisima Point, and surface drifters deployed north of Purisima Point tended to move rapidly northward. Drifters deployed off Pt. Arguello moved both

I 3-1

I
I

I

north and south, often in complex eddy-like paths. In the study area, winds are equatorward n

throughout the year except between December and March when w!inter storm activity can disrupt

this normal pattern. The prevailing wind direction is approximately parallel to the coast between I

Pt. Arguello and Pt. Conception. all

The two-and-a-half year continuous time series of current velocit3' and temperature at the Phase I

III primary mooring (P) allows investigation of seasonal signals and interannual variability of

IIR

these variables. Similar long time series are available from instruments on two moorings on the m

100m isobath in the western entrance to the Santa Barbara Channe]L.These arrays were deployed |

and maintained by SIO under separate contract to MMS. In this report these SIO moorings are

referred to as SMIN (San Miguel Inner) and SMOF (San Miguel Outer) which will be shortened n

to I and O (for Inner and Outer). Time lines showing data availability are given earlier in Figure II

2.1-10. Access to the data taken by SIO provides information on the coupling of the flows off

Pt. Arguello with those in the western end of the Santa Barbara Channel. I

3.2.2Seasonal Characteristics n

Based on the time series of low frequency currents at the primary mooring, a spring and a 1_

summer-winter regime can be identified each year between April 1992 and July 1994. These I

regimes are reasonably distinct in characteristics and are based on conditions off Pt. Arguello.

Different seasonal characteristics apply elsewhere as will be sihown for the Santa Barbara

Channel. The 7-day low pass (7-DLP) currents and 40-HLP temperatures and subsurface n

pressure are given in Figure 3.2-1 for the complete Phase III recorcts at the primary mooring (P).

Spring seasons were characterized by strongly sheared equatorward flows. The equatorward

events had the largest flows at the surface and weaker and sometiraes northward flows at depth.

The events were interrupted by several days of weak poleward currents which correspond with n

temporary weakening of equatorward winds. Many of the southward events had a strong offshore

component at the surface. Examination of SST satellite images shows colder upwelled coastal m

water from north of Pt. Arguello being directed past the mooring. Water temperatures generally ]l

cooled during the spring with minimums being reached in May or June. The spring regimes in

1992 and 1994 were quite vigorous. In 1993, the spring regime was much less well-defined and lb

appears to have been shorter, not being established until late March (as compared to the end of |

January for 1994) and abruptly transitioning to the summer-winter regime in mid-June (in

contrastwithlateJulyfor1992).

Q

The summer-winter regime was characterized by an abrupt transition from the preceding spring

and appears not to be influenced by local winds. This was particularly noteworthy in July 1992 Im

where strong equatorward winds persisted through the transition. Currents were poleward, often II

with maximum flows at mid-depth, and sometimes exceeding 50 cm/s. Bottom currents were

northward and stronger than in spring (Figure 3.2-1). Water temperatures warmed until January. !11

The source of this warm water was the Santa Barbara Channel and the Southern California Bight. II

3-2 I

!
i

I

I ,s10 -,--__ Spring 1992 Spring 1993

_= _ , ,_/_J__ _c'

I _. .,o"-_-f r#,/,,_z,_'ffp,_ rF/' r" y # -15 -'=

20 -- 14m 53m 125m

o

i - Upcoast _ .

o. 4,

& on-- ,,m

,,,'_ 6o-- /',r "" "'""'-"_r '_ .,_t_,=_ , ,, . I _11/_.,_'\\_ '1_\ _"'_1_'''_"JIIl_l_,..,_........ r,.. r_/_.,,.,,,,

o. l o- 4o 17.5m

7

_- -20 "

I -4o--

l_m

, , u l I I I I I I I I .I ...I. ... -O.10- - ....

t 9 29 9 2g 19 8 28 18 27Ep T 16 26 1S 25; 14 23MAR 1S 4 24 14 3

_._ ...,. .,, J.., _u., ,Jo,,r. o&' .or °_c ,,, ,_ _..,.,_ ..,

1993

JUUANDAY 4OUS_ 9/lS92 7-Day Low Pass Currents -- Primary Mooring at Point Arguello

I

Figure 3.2-1a. 7-DLP currents and winds, and 40-HLP temperatures (mid-depth

I solid) and pressures for the primary mooring P.

I 3-3

I
,

® ': i!ii:_ii i!iiii!i!iiiS_e_i_e:_:.._i i!i i iiiii_i Spring 1994

........ :°_ 7"P'TYfJ'V"FJ /r 'Fe'lY"" r v¢li/f¥fflNp

15

2o--__ 125m i

is - 14m 53.m 123m ^.,,_ II

;- ls'-z I ,,','l//';t,_.;, ,..",,,._-"" " .,-,...--..-._

m" _ 14 -- . / _ '#' _" _' .%JT_ .'_, _,I _ _ '%t ,v ,_j_,_._,

1__ ,,,, _,,r,,/¢-, ;_,r n:i _:_'-,._e,,,.... w .,_ _.<"x.._..,,r_,.,=-_..,,',.,_ ,_._ I

"_ _,e'z '_'_.....r '_'}l .',/ ,. '_" I h,...,d I, ._l]IJ[.',_l, ,k_1 r"_',,4111_'."__. "-_//_/ - i4m IF' -'r

....... ¢11i_,.,_\'_rIl. I.......... I I i. -_.... i\\ll, . *1_ .... S3m I

I

60 I

40I

125m

_. .2o I

-40 " Upcoast

,, - ;!i_i iiii!!iiiiiil:_i:ii iii:i_iii!iiii#ili iiiiiiilliii_iiii!!ii iiiliiiiiii iiilii_lii i!:ii iiiii ::iiiiiiiii : ii_i! !!i!_ ilJii ,,_ _,

z_o.oo- -, _,.,_. ,.. _ • . ,_

-0.10---- t I .... I I I I I I I I I .... i .... i . , i I i .... i,I ,,1 .... l I .... i,l.,,i .... I •

10 30 20 9 29 19 8 28 17 7 27 16 6 26 IE 4 24 16 5 25 15 4 24 14 3

MAY JUNE JULY AUGUST SEPT OCT NOV DEC JAN FEB MARCH APRIL MAY JUNE JULY I

1994

JULIANDAY100IS 4/10/1993

7-Day Low Pass Currents at Point Arguello Primary Mooring

I

Figure 3.2-1b. 7-DLP currents and winds, and 40-HLP temperatures (mid-depth I

solid) and pressures for the primary mooring P. [

3-4 I

I
I Top-to-bottom temperature differences of 6° to 8° C occurred in late fall before the onset of

winter storms which mixed and deepened the surface layer. Mixing of the surface layer occurred

i pressure in Januarysystems for thewhich summer-winter moved over 1992theperiod west incoast. response Winterto a

storms regularwere sequence not asofprevaleiat winter lowin

1993-1994, resulting in the upper water column remaining stratified until February. The

I transition back to the spring regime was less well defined than the spring-to-summer change. The poleward flow regime had noticeable clockwise rotations of current vectors indicating that

the poleward current flowing past Pt. Arguello had embedded eddies or meanders (Figure 3.2-1).

I The short-lived, weak equatorward reversals were associated with decreases in surface and middepth temperatures indicating that the front between the poleward flow and the colder offshore

i equatorward flow was fairly close to the mooring.

The low frequency velocity and temperature data for the Santa Barbara Channel moorings (I and

O) are given in Figure 3.2-2 for the two-and-a-half year period. The same seasonal divisions as

I seen in records from P are evident. However, there is a much less clear cut demarcation between

the different seasons, although it does correspond somewhat with data taken further north. Flows

i

reversals. at I, on theFlownorthern at O side was ofgenerally the channel, in the were opposite almost direction continuously and nottoasthestrong east with with evidence only a fewof

considerable eddying at the surface instrument. The oppositely directed flows at P and O could

be considered as part of the cyclonic eddy in the western entrance to the channel (Brink and

I Muench1986).

I The westward summer-winter flows at I having periodsa had cyclonic the greatest rotary component. similarity with Clearly, data these from westward mooring P, events withandstrong the

poleward events at P correspond. The differences are that the maximum currents at I tended to

I occur I is more at thesheltered surface though from thethereopposing was littlewinds, shear between which would the 5 mtendandto45retard m levels. poleward Presumably, surface

currents at P. The spring periods did have some changes in character, though the timing was

I different. marked February to May in 1993 and 1994 had periods of weaker westward flows (at I) with anticyclonic rotations of the current vectors. In April 1993, flow at the 5 m level at O

was northward towards I. The cause of this event is unknown. The reversals to eastward

I directed currents that occurred at I were associated with both strong equatorward events at P and weak reversals to the west at O (e.g., - June 8, 1992, - December 7, 1992, and - October 13, 1993).

I Although there was less of a seasonal current signal in the channel, temperature records showed great similarities with those at P. There was cooling in spring with a minimum at depth in May

or June, then warming until December. A deep mixed layer developed in winter with the onset

I of the winter storms. Differences are that there was weaker and stronger stratification in the lower and upper column (50 to 100 m and 0 to 50 m, respectively) than at P. Surface

temperatures were also generally warmer at I than P in most periods and warmer at O than P in

I the summer-winter periods.

!

I 3-5

!
m

,5 Spring 1992 _ _::_!_Summe_i_!_ih_i_j_2_i _ ] Spnng 1993

-10

-15

201 !' _ "'_ '_

18 -h I _,_ _ _." "l / _4"ta,, _i &.,_". _.'_-'_

•-. _5 _ ,_ . _I r'_0 1,_,. _ ,I_ _' "-_.__

'_ .,,--,-__":.: ___V,.7-".'-:,,,'_.,,_/A".... _-."_",,,,._, " .

20

". 45m --...-_n L,..__'_,_

12 _ lOOm _, ',,'-_, .

8

° -°r I

@.1@

- I:

-o.10 , .... ,t. I I I

...i...i .... i ---i .... i .... i --.i .... i .... i--- i .... i .... i .... i .... i .... i .... i,.... i .... i .... i

9 29 20 9 29 19 8 28 18 7 27 15 6 26 1S 5 25 14 3 23 15 4 24 "14 3

MARCH APRIL MAY JUNE JULY AUGUST SEPT OCT NOV DEC JAN FEB MARCH APRIL MAY

1993

JUUAN DAY 401S 2/9/1992

7-Day Low Pass Currents - Santa Barbara Channel Entrance

I

I

Figure 3.2-2a. 7-DLP currents and winds, and 40-HLP temperatures (mid-depth

solid) and pressures (dashed MO-6) for :moorings I and O in the t

Santa Barbara Channel. I

3-6 I

I
I 15"=

lO- _z__::::i_:_: Spring 1994

<o s_ ................................................................................................................................................... PTGC1

| ._° ,-:-;io4;_f_ ef"_/V'Wj e_',, r'-r'er_yr,r_,',mf//_fff_W_e

i 20-- J lm 45m 100m

f,,_t,,,,,,','__'_ • --

",'2 _4- , _. _.r _

:- ,,':,,'r_,""_''"'_,[,V,,:,lv'; :_ __,.,A'._"_._"r''_.U"_V "_"-""_ "__'".,,,, _'-:'rv_" ..,_.,.,,_ ''J_'"J_,',j ,";,'.,".._)_,_"

. :"_ '_ _j

8

2o-- lm .,_ _ 45m

lO-_

! ,

' i

° -2o-

=E

-40-- I "Cre)horn

0 5m

I= _=E 40 - I_._........ ,, ._. ._,, ,_._...__..,,--.____ r_

2o-- 0 45m

0.10- _ L I 100m _,_o_o- _._- '-., _ •

-0.03- '

I .0.10- "J' I I I I I I I I I [.... I

10 30 20 9 29 19 8 28 17 7 27 16 6 26 1S 4 24 16 5 25 15 4 24 14 3

MAY JUNE JULY AUGUST SEPT OCT NOV DEC JAN FEB MARCH APRIL MAY JUNE JULY

1994

JULIANDAY100IS 4/10/1993

7-Day Low Pass Currents -- Santa Barbara Channel Entrance

!

I

Figure 3.2-2b. 7-DLP currents and winds, and 40-HLP temperatures (mid-depth

I solid) Santa Barbara and pressures Channel.(dashed MO-6) for moorings I and O in the

I 3-7

I
I

I

3.2.3 Statistics, Spectra, and Coherence m

3.2.3.1Spring1992 !

I

The means and variances for the available records in spring 1992 are shown in Figure 3.2-3. The

kinetic energy spectra for the primary mooring are given as an inset and show that most of the III

kinetic energy was at periods longer than 10 days and decreased markedly with increasing depth. |

This is reflected in the standard deviation ellipses which show a ]arge anticlockwise rotation of

the principal axes with depth. The rotation is consistent with upwelling and downwelling. Thus, all

a southward relative fluctuation at the surface had an offshore component; at mid-depths, the l

major principal axis was parallel to the isobaths; and at the bottom there was an onshore

component. Surface and bottom onshore-offshore fluctuations reversed for northward i

fluctuations. In contrast, the mean currents at P and S 1 all had offshore components. The S1 |

record is quite similar to P except for larger southward means. Thus, it appears that the

southward mean flow at P and S1 was being deflected offshore by the outflow from the channel, i

At I, the surface mean flow was deflected southwestward, but the mid-depth was parallel to the II

isobath and opposed the weak 50m southward mean currents at P and S 1. This convergence may

account for the relatively large (- 5 cm/s) offshore directed means at the bottom instruments at R

P and S1. I

Figure 3.2-4 shows the 40-HLP current vectors at I, P, and S 1 along with the surface temperature

records. It is clear that strong westward events at I caused a reduction in the southward flows i

at P and S 1. Conversely, strong southward events (e.g., June 6-15, 1992) could move cold water i

into the channel and reverse the flow there. These two situations _treillustrated by the composite

satellite images for the weeks of April 26 and June 7, respectively (Figure 3.2-5). The former

shows Santa Barbara Channel water moving out into a band of cold water that extended down

the central California coast and south of the Channel Islands. The June 7-13 image shows the i

cold water extending across the entrance and along the south side of the channel. II!

The coherence squared and phase differences for the records shown in Figure 3.2-4 are given in I

Figure 3.2-6. It can be seen that the near surface longshore current was well correlated with the

w

mid-depth current, but the mid-depth current had little correlation with bottom currents. I

Longshore wind fluctuations were also not coherent with the surface current fluctuations at P1. n

This is in contrast to current measurements made north of Purisima Point in the spring of 1984

(Chelton et. al. 1988), where fluctuations of longshore wind were related to near coast current HI

fluctuations despite the northward mean current opposing the mean equatorward winds. II

Coherence squared between the surface longshore current fluctuations at I, P, and S 1 are quite

high for periods longer than 5 days. Currents at the 5 m and 45 rn levels at I were more highly HI

correlated than the 45 m and 53 m levels at P and S1. The signal at I occured prior to that of l

P, and P before that of S 1, for coherent frequencies. This indicates the possible presence of

northward propagating shelf waves, as discussed by Chelton et. al. (1988) and Hickey (1992). m

l

3-8 |

I
I 04/09/92 to 07/23/92

121° 00' W 120° 45' W 120° 30' W 120° 15' W 120° 00' W

35°00'N _ ; I j 35°00'N

I 200 m ._

_< 100m 50 m KINETIC ENERGY SPECTRA

¢

,.. ._ "

,' i _. //I

o _ 1

o. •

34° 45' N -- <_ 34° 45' N

_'_ 14 _"

' i ",

I / w v s I I_I'TTll ,,

_'_.+j..,; 10-2 10-1 1 • CYCLES/DAY

1. SM-P-I, R318 14m SOLID

I 2. SM-P-5, R318 53m DASHED

v,_ 3. SM-P-5, R318 125m SOLID

Date: 92/04/10 Time Sedes Length: 86 DAYS

Degreesof Freedom: 22 Bandwidth: 012865498 CPD

34° 30'N _ 34°30'N

\___,. " ..... -_" :_..... ".......... IOOm.2oo

/J

,_,:_ Z/j/-'500 m....

¢_•_

_/', : _. 340 15' N

34° 15' N -- _ _-_ --

I ..F...... <-.,_. ....

,.._, ..,,_ ._. ",_

.• < . ,

' '" ' " ' "" "'--"2_,,,,;_............ % _oo'"

I _", ",",, ", _, -.'-/ .... ;c"

34oooN I - - ,".......... 34o00'N

121° 00' W 120° 45' W 120° 30' W 120° 15' W 120_ ,0' W

I 40-HLP Means and Variances, Spring 1992

I Figure 3.2-3. Spring Energy 1992 spectra40-inHLPvariance meanspreserving and varianformces (Pforonly)• P. Inset: Kinetic

I 3-9

I
I

"_l° / ", Spring1992 " ,. I

8 I

Is: I

a

q so -"',s, _. . • - ....... ..,_ _......................... A_ll...... /ll_ s4m

N -2o

-4O

-6O

" I

14m

, % _ • ,, , _. _\1/_

=a

2.1 soq ,/_/[[/_,///f'"_'T"I/r ..... -. ,_,._ -,,,_ ,,.._.,,_..... [I--h .,V,_,,,..__.,,_,ll,/._l//.........."_,_IV ,11_........ "\\1tl _llb'-' "" IIII

..... _ _ J_',_,_I_N\'_.

. 0 t _ I- --_ =r -_ ",, ....... - ---,/[ " _-- ....... _ - -- -- .r-. --r--

_ Upcoast

20 4s_

_ _ "._--I ,.""_llH.h,J_._/k,,Ik -........."' =''"" u_/_l,,,,....... l,, ,/,,.'"AI I

I , , , , .... , .... , I , , , , .... , .... , ,I, , , , .... , .... _ ,I , , ,

30 9 19 29 9 19 29 8 18 28 8 /11

APRIL MAY JUNE JULY | JUL_NOAYSO_S_r_19_ 40-HourLowPassCurrents_ Pt.ArguelloandSantaBarbaraChannelEntrance

!

I

i

Figure 3.2-4. 40-HLP currents and near-surface temperatures (dashed - 1 m level at I

and 15 m level at S1, solid - 14 m level at P) fi_rmoorings I, P, and S1. I

3-10 !

I
!

I

I

I

!

!

!

I

g

I

I

i

!

I

Figure 3.2-5a. Composite N@_-! 1 AVH_ image for 26 April - 2 May 1992.

I Daily averaged 40-HLP current and wind vectors for the center of the period are overlayed on the image. Vector and temperature

scales are shown in the land area. Note difference in wind and

I current corrected. scales. Temperature has not been atmospherically

I 3-11

I
!III

IIIii

This page intentionally left blank.IiI!IlII!

3-12I!
I

I

I

I

I

l

I

I

i

I

I

I

I

i

I

I

Figure 3.2-5b. Composite NOAA-11 AVHRR image for 7-13 June 1992.

i Annotated as in Figure 3.2-5a.

I 3-13

!
IlIIIIII

This page intentionally left blank.I!!

II!i!!!

3-14I!
I

P

ZZZZZZ_

OQOOOOZ.

I "

33N3S3H03 _ 3S_Hd T _ _ _=° ._

I -

- ZZZZZZ_

• _-_ ZZZZZZ_

I i1_1 m

33N3W3H03 _ 3SVHd T

°_

I 3-15

I
I

|

3.2.3.2 Summer-Winter 1992 m

Statistics for the summer-winter 1992 poleward flow season are shown in Figure 3.2-7. Mean I

currents were poleward off Pt. Arguello, and the westward means, at I strengthened. At P, the

mid-depth mean current exceeded that of the surface, and the current variances were virtually the

same. The bottom standard deviation ellipse is larger than its spring counterpart, and the mean

m

current at 125 m had a northward component as well as the offshore component seen previously.

Currents at the $3 mooring (deployed October 1992 - January 1993) in 90 m water depth, |

inshore of P, also experienced strong northward means. The 54 ra levels had a strong onshore

component, perhaps being indicative of persistent upwelling off Pt. Arguello during the fall and II

early winter. Instruments on mooring O recorded eastward directed flows with a larger mean at II

depth. These were oppositely directed to and weaker than the means at I. Spectra show the

dominant energy was at 20 days but with subsidiary higher frequency peaks at 7 and 4--5 days Im

(Figure 3.2-7). |

The 40-HLP time series of currents and surface temperatures are shown in Figure 3.2-8. Surface I

temperatures at I were 4-6 ° C warmer than at P for most of the sumrner except when short-lived |

current reversals occurred. By November, temperatures at P had warmed to those at I and O.

This pattern, in conjunction with the persistent poleward directed currents, indicates that warm IN

water from the channel was being advected northward past Pt. Arguello. The frequent rotary I

motions of the current vectors are evidence of eddies and meanders in this current field. The

SST image for the week of November 8, 1992 (JD 313) clearly shows (Figure 3.2-9) that warm m

water from the channel moved north around Pt. Arguello while a tongue of cooler water moved I

eastward along the north shore of San Miguel Island. Note the eviLdenceof a cyclonic eddy off

Pt. Arguello. It appears that when westward currents at I reversed (e.g., - December 5), the m

surface currents at O also reversed, indicating that intrusions of northern waters may not have W

moved far into the channel but rather exited on the southern side.

m

The coherences between alongshore velocity components on mooring P (Figure 3.2-10) are quite U

different from those in spring. During summer-winter 1992, upper level currents were highly

coherent, and even the bottom currents showed moderate to high coherence squared with those

at the 53 m level. Between I and P, coherences were now poor with some barely significant m

peaks between 5- and 10-day periods. Alongshore winds were slightly more coherent with m

currents at 14 m at P than in the spring, but again it was confined to about 5-day period motions.

The implications are that the northward flows at P were more decoupled from the flows out of

thechannelthaninthespring, i

3.2.3.3 Spring 1993 IB

n

As discussed above, the spring regime during February to June 1993 was quite short and not well •

developed. The statistics (Figure 3.2-11) show similarities with the spring of 1992. Mean II

3-16 I

!
I

07/23/92 to 02/24/93

I 121°00'W 120°45'W 120°30'W 120°15'W 120°00'W

.5ooo.. 200=m. :,_ I := 35ooo,.

i 100 m 50'm KINETICENERGYSPECTRA iliiii

:"¢ _" i i_::::iii:: ',iiiiiiiiiii

,.. ; ij_jiiil _

i

? k 10 0 i!::iiiii_

_/ :iiiii!ii

_ _ E Xso34045'N _" "" ;" "_ I/_ :.i:iii'34° i_liil 45'N

I "- CYCLES/DAY :ii!ii::

1. SM-P-1 R318 14m Solid _,_i i_ii

2. SM-P-3 R318 53m Dashed .:i:::_iiii

3. SM-P-5 R318 125m Solid :i

Date: 92/08/0£ Time Series Length: 206 Days :_:_:_.

I Degreesof Freedom: 22 Bandwidth: 0,(_52798 CPD _i!;iii 34" 30' N _ 34° 30' N

I ,,-_.500m_...../ # /'"

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I _m _..._ ,_"

e _

34° 15' N _ ,',,,..._;'"w" ,""_" -- 34° 15' N

.... _1 I % .,. .. -.._¢ ,.... ..... "_._'" "---100 m,

,_ '%, "-.,__ "_ __ .... J~,._.- ..,:

I _ _-_'_" L "'_'4 "-_-;..... _ ]

34° 00' N .... I "" "" r'" _ "" --J'_ I 34° 00' N

121°00'W 120°45'W 120°30'W 120°15'W 120° 00'W

i 40-HLP Means and Variances, Summer-Winter 1992

i Figure 3.2-7. Summer-Winter Kinetic Energy spectra 1992 4in0-HLP variancemeans preserving and variances form for (PP. only). Inset:

I 3-17

I
!

2° " I

--so I.... i , , I I .... I '1 ' I . , , , , I, _ .... _ , I , i , j , , . I I .... I , I, , , _ .... I I |

28 18 7 27 16 6 2B 15 5 2S 14 3

JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER JANUARY

1993 I

JULIAN DAY 180 IS 6/28/1992

40-Hour Low Pass Currents/Temperature at Point Arguello (Primary) and Santa Barbara Channel Entrance

I

Figure 3.2-8. 40-HLP currents and near-surface temperatures (dashed - 1 m level at I

and O, solid - 14 m level at P) for mooringsI, O, and P. I

3-18 I

!
!

i

!

!

D

!

I

i

I

I

I

I

I

I

I

Figure 3.2-9. Composite satellite images for 8-14 November 1992. Daily averaged 40-

HLP current vectors for the center of the period are overlayed on the

i image.

i 3-19

!
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02/24/93 to 06/10/93 •

II 121° 00' W 120° 45' W 120° 30' W 120° 15' W 120° 00' W

3s°oo'. _ _ I : 3s°oo'.

200m • f "(

i. 100 m I

= 50 m KINETIC ENiERGYSPECTRA

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,. - ?

_i i i i J),l , J i ::l:l

% 10"1 I_, _ CYCLESK)AY

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2. SM-P-3 R31B 53m Dashed

3. SM-P-5R31_L 125rn Solid

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Oegrees of Freedom: 22 Bandwidth: 0.10377360CPD II

34° 30' N -- "_ 34° 30' N

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I 34°00'N ""-'" \ -'. ]"C'_,.. ""........ l( 34° 00' N

121° 00' W 120° 45' W 120° 30' W 120° 15' W 120° 00' W

40-HLP Means and Variances, Spring 1993 I

Figure 3.2-11. Spring 199340-HLP means and variances (P only). Inset: Kinetic I

Energy spectra in variance preserving form for P.

3-22 !

I
I currents were not as large and offshore flow took place at mid-depth rather than the bottom at

P. Mooring I had a southward component of the near surface mean, probably caused by the

I southward at 45m but surface northwardflownearer at Pt.theArguello surface. asThis before. was caused Currentsbyata mooring remarkableO had episode eastward in Aprilmeans and

May (Figure 3.2-12) where flows were northward or westward at 5 m but eastward at 45 m. An

I SST image from this period is shown in Figure 3.2-13 (May 2-8, 1993). A surface patch of cold water which seemed to cause a cyclonic rotation of the surface currents was just west of San

Miguel Island. The 50 m currents were more as expected, being eastward at O and northward

I at P. The show a peak at about seven days (Figure 3.2-11) and generally the fluctuations spectra

had shorter periods and were more variable in direction than during the comparable period in

1992.

!

The secondary moorings $2, $3, and $4 were deployed inshore of P between June 1992 and July

1993. $2 and S3 were 3.5 km and $4 was 1.5 km from P, and, as might be expected, the records

I at equivalent depths were essentially the same as at P (not shown).

I 3.2.3.4 Summer-Winter 1993

I The summer and winter of 1993 were much closer to their 1992 counterparts than to the

respective springs. The main difference was somewhat lower energy levels, although the spectral

I peaks mid-depthat 20,and7,theandsurface 5 daysatareP andsimilar I,espectively. (Figure 3.2-14). CurrentsMeanat Icurrents were somewhat were at more a maximum sustainedat

than measured previously (Figure 3.2-15). Beginning in June, surface temperatures increased

I most both Irapidly and O atwere I andflowing slowestwestward at P. It is(e.g., notedOctober that there 11-19, were1993). some events in the channel where

I Coherence squared and phase differences for the summer 1993 alongshore velocities and wind are given in Figure 3.2-16. Currents at the three levels at P were again moderately coherent at

periods longer than 5 days. The wind velocity was moderately coherent with the alongshore

I surface current velocity at about 5- to 7-day periods. This response is a little stronger than the 5-day coherence the previous summer. As before, the flows at I (45 m) were poorly correlated

with those at P (53 m); however, there was moderate coherence with O (45 m) between 20- and

I 5-day periods. Phase differences were 120° to 180° which indicates that fluctuations at O and I were opposed. Surface and mid-depth, along-channel velocity components at O were highly

correlated as they were for I in Figure 3.2-6. Thus, again, there appears to have been a

I disconnect between the channel and Pt. Arguello flows in summer although there was clearly a

strong relation between inflows and outflows on the south (O) and north (I) sides of the channel,

i respectively.

I

I 3-23

I
1

I

Spring 1993

20-- I - lm , .'_%-_x I

18__ I-lm k t ', " t_. -i_.ll 't ;,-r, i.

_210--- -_L._ ___,., , _ I _,_,4' ,_. _! I _ P - 14m I

P - 14m I

40

2 _o-- P - 125m

" _-" I

-60

i 20-- O 45m

_-I o _l,.l tl -.I ,_i ,... l

" " I

.60 , , I , _ .... I .... , , , 1, , _ .... I .... _ , . I . _ .... I .... _ . , ,I , _ ....

20 9 1 21 10 30 20 9 29 19 8 28 I

FEBRUARY MARCH APRIL MAY JURE JULY AUGUST

1993

JUIJAHDAY 20IS 1/20t1993 40-Hour Low Pass Currents -- Point Arguello and Santa Barbtira Channel Entrance

I

Figure 3.2-12. 40-HLP currents and near-surface temperatures (dashed - 1 m level I

at I and O, solid - 14 m level at P) for moorings I, O, and P.

3-24 I

!
I 121 06/10/93 to 01/21/94 ° 00'W 120° 45'W 120°30'W 120° 15'W 120°00'W

I 200m _

100 m 50"m KINETIC ENERGY SPECTRA

I ' i' ' /!A iiilii

"-,::" _. eo _iilii ....

34° 45' N

\

I "L%... , ,_. o10-2 .............. 10"1 ,,i:,ii_,ii ii]i:=!iil

"" : _. CYCLES/DAY !ilii!i

2. SM-P-3R318 53m Dashed

I 3.SM-P-5R318125mSolid !i!!I

Date:93/07101 TimeSeriesLength:206Days

DegreesofFreedom: 22 Bandwidth: 0.05352798 CPD

34° 30' N _ 34° 30' N

i 14m ". .,.,,.,._._-'" m._.._....

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121° 00' W 120° 45' W 120° 30' W 120° 15' W 120° 00' W

I 40-HLP Means and Variances, Summer-Winter 1993

I Figure 3.2-14. Summer-Winter 1993 40-HLP means and variances (P only). Inset: Kinetic Energy spectra in variance preserving form for P.

I 3-27

I
I

,o_ o-lm Summer - Winter 1993 I

-_/v_,y_,_ _ _ _v10--

. |

'_ 3¢ _ _ "_ "-'0 " '

o

d ,2o-

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- I

. , I . i .... I .... i., .I. _ .... ,I ...... I . .... _ .I. , , _ ,,, I,. .... _.I... ,

.so

20 9 29 19 8 28 17 '_ _' 16 6 25 15

JUNE JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER JANUARY

1994

JULIANDAY140IS 5/20/1993 aIim

40-Hour Low Pass Currents --Point Arguello and Santa Barabara Channel Entrance l

BE

Figure 3.2-15. 40-HLP currents and near-surface temperatures (dashed - 1 m level I at I and O, solid - 14 m level at P) for raoorings I, O, and P.

3-28 I

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I 3-29

I
I

I

3.2.3.5 Spring 1994 ==

I The spring 1994 season had strong similarities to spring 1992. The means, variances, and spectra

are shown in Figure 3.2-17. The mean flow was convergent between I and P with strongest i

southward currents at the surface. The secondary mooring, $6 in 250 m water depth and only i

2 km further offshore than P, had upper layer (28 m) currents that were much more parallel to

I

local isobaths than at P. This implies further convergences between Pt. Arguello and Pt. am

Conception. Examination shows that the time series of current vectors (Figure 3.2-18) have some i

similarities between the 14 m and 28 m levels on P and $6, respectively, particularly for the large

southward event in April. However, even during this event, occa,;ional large offshore flows at i

P occurred which were not seen in the southward flows at $6. Also noteworthy is the general I

tendency of the 28 m flows at $6 to have been southward more often.

In the first part of January, before the start of the spring 1994 season at P, flows were southward I

at $6 and northward at P. This is a good indication that flow characteristics changed rapidly with

distance offshore of Pt. Arguello, and that the transition between southward flowing and •

northward flowing water can occur over a very short distance. This result also implies that the II

determination of the length of the seasons based on current characteristics (as done for P) may

be dependent on the location of the mooring. This is noted in the ,discussions of the currents at I

moorings I and O. A distinct spring regime was noted at I and to a lesser extent at O in 1994 i

(Figure 3.2-19). It began around January 21, as at P, and was characterized by weaker and more

variable flow than in the summer. However, it only lasted until mid-May when strong westward II

flows became established at I, with P still having weak variable currents. W

This variability is reflected in the spectra (Figure 3.2-17) which show most of the energy at i

periods of less than 10 days. The coherence squared and phase dit_Ferences between the various W

alongshore current components are given in Figure 3.2-20. The upper level records at P and $6

are not significantly coherent except at long periods (>20 days). However, the 125 m level il

records are highly coherent at all frequencies. This is a further indication that the surface layer HI

flOWS changed characteristics between P and $6. Longshore winds were moderately coherent

with P1 at periods between 2.5 and 7 days which is similar to the previous springs. The i

relationship of the Pt. Arguello alongshore currents to those in the channel also had similarities.

P and I were moderately coherent at periods shorter than 10 days. Moorings I and $6, and I and am

O were not significantly coherent except at isolated frequencies (Figare 3.2-20). Mooring O also i

was not coherent with $6 except for an isolated peak at 5-day periods (not shown). Thus, again

it was evident that there was a relationship between the reduction c,f southward flows at P with II

outflows from the channel at I during the spring regime. Surface flow at $6, only a little further II

offshore, was not part of this regime.

!

I

3-30 I

!
I 01/21/94 to 07/04/94

121° 00' W 120° 45' W 120° 30' W 120° 15' W 120° 00' W

35° 00' N z ,¢, j <c 35° 00' N

I 200m ; <_

100_m 50m KINETICENERGY SPECTRA

80"

1

• 5 ><

34° 45' N -- ? g / _ 34°45'N

I ,, ,> ,p

_ _ _ 20" 2,j..s

\ "+ , ,,**. i i , ° ,,,

I _ _ °'_2 ' 1_1 "_, _ CYCLES/DAY

_, • • _ 1. SM-P-1,R318 14m Solid

"_J 2. SM-P-3R318 53m Dashed

3. SM-P-5R318 125m Solid

X Date : 94/01/21 Time Sedan Length : 106Days

53m -'_ Degreesof Freedom: 22 Bandwidth: 0.10377360 CPD

34° 30' N -- 5: II_ 34° 30' N

I "-._ .. _.,.._...--."...... ",50NI.... .... '...

_. ..... "/J" .......... 100

E "'.,...'""'500 m.

_ .% /

34° 15' N -- f-,_N O"; __ 34o15' N

.o # r-- %.¢,,_

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34°00'N '+----" I "% "'_'"T "_''_'..... ''- "_....._',, I I34°00'N

121° 00' W 120° 45' W 120° 30' W _120 ° 15' W 120=00' W

I 40-HLP Means and Variances, Spring 1994

i Figure 3.2-17. Spring Energy 1994 40-HLP means and variances (P only). Inset: Kinetic spectra in variance preserving form for P.

I 3-3t

I
i__ 96.29. Spring 1994 i

,,_.....,......... _, S..m _ ,,1 ......._.\_-

8 _ '"_ I

6

18 P-14m II

1$ _ I_ P-53m P-128m I

g ,,_ W_ ....%" "'-"%-..... ,,. ...., ._:,

6_

" I

-60 ----_

I

I

°-- [

L O_hore

o. _ "-" wW1 d'_ _L_A^ d "_ _"J--

.010 J I [ I I

i .... i .... i .... i .... i • , • l .... l .... i .... i .... i .... i ....

Is 2E 4 24 16 S 2S IS 4 24 14 3

JANUARY FI"BRUARY MARCH APRIL MAY JUNE JULY

1994

JUL_NDAY3_0tS_Z_9_3 40-Hour Low Pass Currents/Temp./Press. from Point Arguello Primary and Secondary Moorings

I

I

Figure 3.2-18. 40-HLP currents, temperatures (solid - 53 m level at P and 128 m I

level at $6) and pressure for moorings P and $6.

3-32 I

I
I

I

,.2 Spring 1994

I1-lm

I

s Pl - 14m

ilit ii i,/g" P "_m

• _-.,,.,_,f_re,

I - "t2_

r .... " S0 ] atll_ I - 4_m

I

I | _ _ ._. o..

____ _ _ ...... _ __-

! i ;o._. o..

I

•6o ,I, .,.., .... f .... . ,I , , ' I , , . I _ .... , ,I , , , , . .,.,_1., ,,,-, ,,, , I, . , I'"'. ." . ,I

25 15 4 24 16 5 25 15 4 24 14 3

JANUARY FEBRUARY MARCH APRIL MAy JUNE JULY

1994

I JULIANDAY360IS1_Y2_/199_40-Hour Low Pass Currents andTemperature at Point Arguello and Santa Barbara Channel Entrance

I Figure 3.2-19. 40-HLP currents and near-surface temperatures (dashed - 1 m level at I and O, solid - 14 m level at P) for moorings I, O, and P.

I 3-33

I
I

I

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3-34 i

I
I 3.2.3.6 Total Statistics

I Statistics for the two year interval from July 1992 to July 1994 and incorporating two spring and

two summer-winter regimes, are dominated by the summer-winter results because of the vigor

I of the poleward flows and the longer length of this season as compared to spring (Figure 3.2-21). The spectra clearly show a dominant peak at 20 days that has also been identified in the Southern

California Bight (Hickey 1992) and a band of energetic frequencies between 4 and 10 days.

I Results of coherence analysis for the various periods and moorings indicate that currents

measured on moorings onshore of P ($2, $3, and $4) were highly coherent with records at the

I The offshore $6, showed coherence for the level but

same depths. one mooring, no upper high

coherence for the lower level. This, however, may only apply in spring and the results may be

different for summer and winter. On the same isobath, P and S1 (7 km to the northwest) and

I $5 (5 km to the southeast) were also highly coherent in both seasons (S 1 in spring, $5 in winter).

However, at 28 km from P, I showed moderate coherence in spring at periods shorter than 7 to

i 10 days and poor coherence for the summer-winter regime.

Coherence squared and phase differences for the longest common records from P and I, including

i pressure at all frequencies from P7 and with 16phase are shown differences in Figure not significantly 3.2-22. The different pressure records from zero. wereLongshore highly coherent winds

were moderately coherent with pressure and surface longshore currents at P. Apart from a very

i lownoteworthy. frequencyCurrents coherence, at Ipeak (45 coherences m) were much wereless similar coherent with thewith20-,the7-,pressure and 5-dayrecord periods except beingat

very low frequencies (>60-day period). However, P and I currents did show moderate coherence

I consistent at periods longer with thethanpoleward 20 dayspropagation and 7 days ofwithcontinental I leading shelf P at waves. all coherent This frequencies. result indicatesThisthatis

there were complex connections between Pt. Arguello and the outflow from the channel, but these

I were restricted to specific frequency bands.

I 3.2.4 Tides

I Tidal analysis of the record from the primary and Inner SBC moorings indicated pressure gauge

mixed diurnal and semi-diurnal features that are characteristic of the west coast. The amplitudes

and phases of the principal constituents are summarized in Table 3.2-1. These data indicate that

I the and constituents had similar and that there little difference M2 K1/O 1 very amplitudes is in

amplitudes and phases between moorings I and P. The constituents at I lead slightly over P

i which Tidal analyses is consistent of with northwards propagation of the tidal waves along the continental margin. the M2 and K1 currents are presented in the form of hodographs (ellipses) in

Figures 3.2-23 and 3.2-24, respectively. The ellipses trace out the end of the tidal current vector

!

I 3-35

I
I

I

07/23/92 tO07/04/94 I

m

121° 00' W 120° 45' W 120° 30' W t20 ° 15' W 120° 00' W

_i:+i_i_i 350 00' N

3soOO'N : "_ I _ ._-_.

2o0 m 10[) m < _Jiiiii!_iii I

S0m .............

_ _ _ S0

KINETIC ENERGY SPECTRA _iii_i_ii+ I

_ ; \ ++++ ++++ |

_°4_'.- +_ / ) i _+++34° 45' N

1 _ iiiiiii_ I

........ [:[]!]]]

10-2 10"1 ::]_]_::_!:

CYCLESADAY ]ii!+::![ii!::i::i]

1. SM-P-1,R31_ 14m Solid !i_!!_!!i:_

2. SM-P-3,R318 53m Dashed il

3. SM-P-5,Ft31_ 125m SoSd

Dat_ : 92/_PJ02 Time Series Length : 644 Days l

Degrees of Freedom: 30 Bandwidth: 0.09331003 CPD '_+_'_:

r_:_ 34° 30' N

34° 30' N --

- I

100 nz .

J +,.-soom.... .,

34° 15' N _ +._,_ ¢.'_ -- 34 ° 15' N

(_"_++,,(._ " "".o._.,_._.. I

c .... _-_ 0 "_. "\_

l

I

34° 00' N "''" I \ "+". p'--'"+_: _ ......... } 34° 00' N

121° 00' W 120° 45' W 120° 30' W 12(t° 15' W 120° 00' W l

40-tILP Means and Variances, 1992 - 1994 i

Figure 3.2-21. 1992-1994 40-HLP means and variances (P only). Inset: Kinetic I

Energy spectra in variance preserving fo:rm for P.

3-36 1

I
I

i z ZZ=_

zwzz_m "_

g ..... _

I 33N3W3H03 i .... "

zzz=_

m

!

| =-

mm_m_

<-_ _ _

I _ .... _

| "=

I 30N3_3HO0 3SVHd ....

I 3-37

I
n

Table 3.2-1. Tidal height analysis of the pressure gauge record at the Primary mooring (P7) •

and SBC (I6) locations, October 1, 1992 through October 1, 1993.

!

Constituent Period Amplitude Greenwich Phase

(hours) (cm) i

P7 16 P7 16

M2 12.421 46.0 48.0 158° 159° n

N2 12.658 10.7 11.2 1310 134o

n

S2 12.000 15.6 16.6 153° 154o U

K_ 23.934 34.8 34.9 :211° 212°

P1 24.066 11.0 11.0 :207° 209° i

O1 25.819 21.8 22.1 196° 197° i

II

I

through the specified tidal

period. The M2 ellipses at P had amplitudes of approximately 3 cm/s, i

were rectilinear, and were directed at slight angles to the isobaths. The tidal currents were inphase through the depth range and with the tidal heights. Thus, the M2 tide at the primary m

mooring had the characteristics of a pure barotropic progressive wave. In contrast, at the B

secondary mooring, during the first deployment, the amplitudes were larger at the surface and

bottom, and there was a 90 ° phase shift between the amplified (-7 crn/s) bottom M2tidal currents •

and mid-depth. The inclination of the major axes of the ellipses was also directed across the |

isobaths, particularly at the bottom. This implied that active internal tide generation had occurred

at the secondary mooring but not at the primary mooring. A steeper bottom slope at the ann

secondary mooring may have accounted for this pattern. II

The K_ ellipses (Figure 3.2-24) were not as consistent as those for M2, but the currents were •

generally weaker (-2 cm/s) and decayed with depth. The major axes tended to be more aligned |

with the isobaths, and phase differences between currents and elevations suggest a mixed standing

and progressive wave. Internal tides were not generated at diurnal frequencies because internal II

waves were not supported at periods longer than the inertial period. The Mz and K1 current

ellipses were calculated for the upper and mid-depth instruments for the $5, $3, O, and I

moorings (Figure 3.2-25). The secondary moorings have similar characteristics to the primary n

with no indication of any amplification or substantial phase differences with depth. At I, in the U

SBC, the tidal flows are larger than at P and more parallel to the isobaths. The Mz flows have

little depth variation between the near-surface and mid-depth. Maximum flood and ebb currents n

precede slightly those at P, also indicating the northward propagation of a progressive M 2 tidal n

wave. Tidal flows at O on the south side of the channel entrance are also vigorous, particularly .,

U

3-38 I

i
III _

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I 02 H2 12 _2 $51H_ $32 H2

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SSI K1 S32 KI

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m 3-41

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for the K1. There is a noticeable reduction of the M2 amplitudes at the near-surface compared m

to mid-depth. The reason for this is unclear.

!

3.3 NEAR-BOTTOM CURRENTS AND SEDIMENT DYNAMICS I

3.3.1 Introduction I

Evaluation of the influence of drilling mud discharges on the marine biological system in the •

Santa Maria Basin requires an understanding of the ambient sediment transport field including i

both average background characteristics and the effects of aperiodic storm events. Previous

investigations have detailed regional surficial sedimentology and selected aspects of the n

suspended material field in the area (Steinhauer and Imamura 1.990) but provided relatively

limited time series data and essentially no field observations detailing storm response. In an

effort to obtain these data, a field experimental program that placed primary emphasis on the n

characteristics of the near-bottom suspended material field in the vicinity of Platform Hidalgo

was initiated in April 1992.

!

3.3.2 Near-Bottom Hydrographic Charateristics

3.3.2.1 Deployment 1 (18 April 1992- 17 October 1992) I

As noted in Section 2.1.6, there was an apparent bias in the velocity records for Deployments 1 i

and 2. Therefore, analysis of the near-bottom hydrographic characteristics for these deployments I

focuses on the tidal regime and the density field. The velocity data from these deployments are

appropriate to provide qualitative evaluations of short-term perturbations, including the passage •

of high energy storm events or anomalously high river discharge. I

The near-bottom pressure observations during Deployment 1 show periodicity in sea level at both n

the Nearfield and Farfield stations (Figures 3.3-1 and 3.3-2). Spectral analysis of these data

indicates dominant periods of approximately 12 and 24 hours coincident with the principal semidiurnal lunar (M2) and diurnal luni-solar (KI) components of the astronomical tide (Figure 3.3-3). II

Tidal ranges in the area display a monthly cycle with values varying from more than 2 m during II

spring tides to less than 1m during neap tides. In addition to these higher frequency components,

the time series show longer term variability most probably associated with regional i

meteorological forcing and/or some large scale, Farfield effects. Reviews of the meteorological

data from CMAN Station PTGC1 located near Pt. Conception indicate that the winds during

Deployment 1were predominantly from the north with average hourly maxima of approximately n

15 m/s (Figures 3.3-4 and 3.3-5). The system is evidently energetic with relatively few extended u

3-42 I

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Pressure Spectra - Deployment #1 - 4/19 to 10/18 1992

I , ....... J ........ i ....... I ........

10 2 .

10"_ '_

.................. !

10 .4 _ ) ) _ T ) i _ I _ _ _ _ _ ) _ _ I _ _ _ _ ) _ ) r I _ ) _ _ _ ) ) _

I -2 *!

10 10 10° 1¢ 102

I 2

10 ........ t ..... I ..... t .......

_°°o

I _ !.:.!!!!.:.!:!:.!!!!!!!!!!!!.:. I

"_ -2 ............. •............... ¢,...

............. i_ i

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K1 M2

=4 i I I I I I I I [ I I I I I ) I I I I r I ) ) I f I I t I I I I I [

10

I 10"2 10"1 100 1¢ 10 frequency (cpd)

! dashed lines delimit the 95% confidence interval

record length = 181 days

I degrees of freedom = 32 bandwidth = 0.09375 cpd

I Figure 3.3-3. Spectral analysis of near-bottom hydrostatic pressure for Deployment 1.

I 3-45
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I periods of near calm conditions (i.e., winds less than 5 m/s). Against this persistent high energy

background, short term perturbations in the wind field, such as those observed on or about May

I 6, 1992 and August 25, 1992, produce finite but small amplitude variations in tidal range and slight readjustments in phasing. Simple cause and effect relationships associated with these

perturbations are difficult to establish due to the unconfined nature of the system and the

I. resulting potential for influence from both local and Farfield factors.

Examination of the qualitative character of the current meter record indicates that high energy

wind events alter both flow speed and direction patterns. The event of May 6, 1992, for may

example, apparently resulted in a marked reduction in near-bottom speeds and a shift in dominant

flow direction at the Nearfield station (Figures 3.3-1 and 3.3-4). Variations in the flow pattern

I are also evident aroundJune 28 and August9, 1992although speed

the correlation with wind

conditions is less evident. The data suggest that local wind events may cause an adjustment in

i near-bottom circulation patterns in the vicinity of the Nearfield station.

Reviews of the Farfield flow data provide only a limited indication of wind associated

perturbations. around June 28Inandcommon Augustwith9, the 1992.Nearfield However, station, variations in flow patterns are evident the character of this pattern shift differs

substantially from that observed at Nearfield. At this latter station, the flow variations consisted

I of primarily aeduction of a reduction in speed inandflowa shift variability in dominant with a direction. minimal change The Farfield in direction. variations I addition consistedto

these differences, the current meter record from Farfield displays no pattern shift on or about

i May regime,6, 1992. as compared The cause(s) to thatforobserved the apparent at Nearfield differences is unknown. in the response It mayof the be Farfield the resultflowof

differences in water depth or instrument artifacts associated with the frame induced bias.

I In common with pressure and velocity, near-bottom water temperatures and salinities varied over

a variety of temporal scales (Figures 3.3-1 and 3.3-2). Records from both stations display diurnal

I variations in temperature and salinity of approximately 0.50 C and 0.25 psu, respectively. These variations appear to be dominated by a combination of tidal factors and short-term variations in

air temperature. The presence of these latter variations is consistent with the relatively high

I energy wave field in the area and suggests that the local water column was reasonably well mixed over the vertical, at least in certain seasons. Beyond these high frequency fluctuations,

water temperatures and salinities at both stations displayed a variety of lower frequency

i variations and some slight spatial variability. Water temperatures at the Farfield station were slightly less, and salinities slightly more, than those observed at Nearfield. These differences

appear to be primarily the result of the slight difference in water depths at the two stations with

I a possible secondary influence associated with the complex bathymetry in the vicinity of the Farfield station.

I Consistent with local seasonal characteristics, average water temperatures at

both stations

increased progressively over the period of deployment from approximately 8.5-9.0 ° C in April

i tooccasions, 10-11 ° Cwith in October a particularly (Figuresevident 3.3-1 and 3.3-2). This upward trend was interrupted on several reversal occurring about June 7, 1992. Temperatures

I 3-49

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decreased progressively over a 2-3 week period before resuming their upward trend. A second •

perturbation, characterized by a significant short-term increase in water temperature, occurred on

September 27, 1992. Salinities at both stations displayed a slow but persistent decrease of

approximately 1 psu over the deployment period, apparently in re,,;ponse to regional streamflow Ii

characteristics (Figure 3.3-6). Variations in near-bottom salinity showed limited correlation with

concurrent temperature variations, and both were weakly correlated with local wind conditions, i

'i

3.3.2.2 Deployment 2 (18 October 1992 - 7 August 1993) I

/

The

pressure records obtained at the Nearfield and Farfield stations during Deployment 2 differed

from those of Deployment 1 only in average depth values indicating a slight difference in station

location and depth (shallower) during Deployment 2 (Figures 3.3-7 and 3.3-8). The pressure field []

continued to have high frequency periodicity dominated by the diurnal and semi-diurnal II

components of the astronomical tide (Figure 3.3-9). Tidal range was identical to that observed

during the initial deployment, varying from slightly more than 2 m during spring tides to i

approximately 1 m on the neap tides. Again, the response of the pressure field to meteorological il

forcing is finite but limited with the passage of major wind events such as that of January 12-13,

1993 and/or February 9-10, 1993 producing only slight reductic_ns in range with no evident •

variation in phase. The observed tidal response to these wind systems is subtle and appears to l

be easily obscured by the variety of factors affecting the hydrodynamics of this portion of the

shelf, i,

The near bottom flow patterns observed during Deployment 2 were qualitatively similar to those

of Deployment 1 with differences primarily associated with the directional characteristics, i

Qualitatively, the directional patterns are simply reversed with F.arfield during Deployment 2

displaying characteristics similar to Nearfield in Deployment 1 and vice-versa. Although the

cause(s) of this pattern reversal cannot be easily defined, the fact that the current meters used at •

each station were the same in each deployment suggests that it is the result of frame-induced

interference with the magnetic compass in the current meter.

i

With the above limitations in mind, wind conditions during Deployment 2 (Figures 3.3-10 and

3.3-11) were essentially identical to those during Deployment 1, with only a slight increase in

peak wind speeds and the percentage of southerlies in the winter months. Despite these i

similarities, the number of perturbations in the bottom flow record coincident with high energy

wind events was substantially less than observed during Deploym_nt 1. This lack of response i

may be an instrument artifact associated with frame interference or alternatively the result of i

alterations in the regional wind field relative to conditions observed during Deployment 1. As

i

discussed above, high energy wind events occurring in this first deployment were predominantly JR

northerlies. Periods of southerly winds tended to be low energy and relatively quiescent (Figures

3.3-4 and 3.3-5). During the second deployment, the high energy wind events were more

commonly southerlies (140 ° T) (Figures 3.3-10 and 3.3-11). This shift significantly alters fetch []

il

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Pressure Spectra - Deployment #2 - 10/19/92 to 7/26/93

I 102 ........ _ ....... m ..... i , ....

10 o

E

10-2 ....... __ _"

v" " ':..-'7'\:'_" :-"___ I

-4 L I I I I 11 11 I I 1 I I I I II t t t I t t I II I I I , , i ,

i 10 -2 -I o ] 2

10 10 10 10 10

I 102 _ i i

r i i i i i i i i i _ i , _ J J r t f i J i i i i i i

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t_

10.2 -.,.._...._ _._,._i _...,.S4g_,___h_..._e,_

...... ,...,,..:...... w:.,,i_ ,_:_d_.._,.

K1 M2

-4 I i i l I I I I I t I I I I i I I I t i I i t I I II r i i I I i _ t

j 10 -2 -_ o _ 2

10 10 10 10 10

frequency (cpd)

I dashed lines delimit the 95% confidence interval

recordlength= 273days(NF), 186days(FF)

I degrees bandwidthof =freedom 0.04687=cpd 24(NF), (NF &16FF) (FF)

I Figure 3.3-9. Spectral analysis of near-bottom hydrostatic pressure for Deployment 2.

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I conditions affecting both the surface wave field conditions and the character of the wind driven

currents, thereby reducing the potential influence of the wind field on near bottom currents.

i Near-bottom water temperatures during Deployment 2 decreased slightly but progressively during

the late fall and winter months to a minimum in March. They then began to increase through

, the spring and early summer, similar in rate and magnitude to that observed during Deployment 1 (Figures 3.3-7 and 3.3-8). Short term perturbations of this long term trend often resulted in

temperature variations of 1-2 ° C which are similar in magnitude to the long-term increase.

I Several of these short-term perturbations are coincident with high energy wind events, particularly during the fall-winter period. These data suggest, at least for some period of the year, that shortterm, energetic wind events can and do affect the density structure of the entire water column

I study area.

within the

On the average, near bottom salinities during Deployment 2 were lower than those observed

I during Deployment 1 (Figures 3.3-7 and 3.3-8). For the interval from 19, to

October 1992

approximately January 11, 1993, values at both Nearfield and Farfield displayed only a slight

i long-term trend with high frequency variations about the mean of approximately 0.15 psu. After January 1993, average values at both stations began a progressive decline to minima in late

February at Farfield and late April at Nearfield. This latter decline is approximately coincident

with in timing the gaged and amplitude increase inofdischarge long-termfromchange the Santa and Ynez the seeming River (Figure lack of3.3-12). sensitivityThe differences in Farfield

salinity to local streamflow conditions suggest that these stations are located in different

I possibility hydrodynamicmustregimes be recognized or are affected in evaluations by differing of the components relative utilityof ofthetheregional Farfieldsystem. station This as a

reference in the scaling of the Nearfield response.

!

3.3.2.3 Deployment 3 (9 January 1994 - 7 January 1995)

1

The modifications in the bottom array configuration for Deployment 3 served to remove the bias

i apparent in the Deployment 1 and 2 current meter data and provided a reliable current velocity time series that was consistent with data obtained from the nearby long-term moorings. During

Deployment 3, near-bottom flows at both the Nearfield and Farfield stations displayed regular

I reversals in response to local tidal conditions (Figures 3.3-13 and 3.3-14). Spectral analysis of the near bottom pressure and current records continued to indicate the dominance of the M2 and

K_ components of the astronomical tide (Figures 3.3-15 and 3.3-16). Currents in the vicinity of

I Nearfield were slightly more energetic than those at Farfield with an average speed over the observation period of approximately 14 cm/s and maxima in excess of 50 crn/s. Average speed

at Farfield was approximately 11 cm/s while maxima seldom exceeded 40 cm/s. Long-term net

I drift at Nearfield was westerly with an average approximately value of 8 cm/s. This drift

displayed moderate seasonality with a maximum of 9.3 cm/s observed during spring and a

I minimum of 7.1 cm/s during summer. The residual circulation at Farfield was southerly at an

I 3-59

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o0 0_1 ,

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0

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Pressure Spectra - Deployment #3 - 1/11 to 9_25 1994

l 102 I J J

i r J J i i i i r J 1 r i i J i i i i i i i i i i t , , i w D

NEARFIELD

I 10o

lO"4 i i _ i i i i , I , _ i , , , , , I L _ , , t , , , I , _ i i , , , ,

A_

i -2 -I 0 i

lO lO 10 10 lO2

I 10 2 ........ I .... ; .... t ....

I f

._ 10°

t_

._0 ............... ...

I ".... i

10"2 ...., ......,',,-'_''",..._, Z. _ :_ fi ._.

i -2 -1 I

l0 l0 10° 10 10z

frequency (epd)

i drecord ashed lines delimit the 95% confidence interval len_h = 256 days (NF), 190 days (FF)

degrees of freedom = 24 (NF), 18 (FF)

bandwidth = 0.04687 cpd (NF & FF) I

Figure 3.3-15. Spectral analysis of near-bottom hydrostatic pressure for

i Deployment 3.

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Velocity Spectra - Deployment #3 - 1/11 to 9_25 1994 !

I0 ......... , ....... i ........ i .........

•._ 103 ............ .. "...

"e__ __ ._..... _... -4\ _!i_). :_ _

- ,.,._....3V:'."__,__...'_._ _r:_ &

•* ...........,U! \;' ":',N/ _.._:.." " .. ,_,

I 8 ]¢ ' ' _,_:_:W_J,.

(-q

o_ 10 l

I NEARFIELD ' '_[_

]0 ( , , , ) , , , , I , , , , _ , , , I , , , , , , , , I , _ , _ , ) , )

I -2 0 1

10 104 10 10 10:

I IU 4 '1 .... I ........ ] .......

, i , , o

'---.,...,,"!

FARFIELD K] M2

•10 0 t i i i i I i [ I I } i i } 1 i I I I i i ) t i I i I i i i [ i f i t

104 104 10° 10 _ 10_ frequency (cpd)

!

dashed lines delimit the 95% confidence interval

record length = 181 days

degreesoffreedom= 32 bandwidth = 0.09375 cpd

i Figure 3.3-16. Spectral analysis of near-bottom current speed for Deployment 3.

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I average speed of approximately 4.5 cm/s. For this interval, maxima were observed during the

winter months.

I In addition to the regular tidal and low frequency long-term average conditions, both the

Nearfield and Farfield current meter records displayed several high frequency perturbations,

I although none were temporally coincident. Perturbations in the Nearfield record were observed around the 18th of January 1994 and again near the 12th of April, 10th of May and 1st of July

(Figure 3.3-13). In each event both speed and direction changed relative to pre- and post-event

i conditions. None of these appear in the Farfield record. The Farfield perturbations differed in timing and apparent character with the events being longer-lived and more nearly periodic. The

cause for these differences cannot be specified beyond those already discussed for water depth

I and regime. hydrodynamic

Review of the meteorological data for the deployment period provide little indication that

I alterations in near-bottom flow characteristics at either were directly

station associated with the

surface wind field (Figures 3.3-17 and 3.3-18). Winds during Deployment 3 were similar in

character to those observed during Deployments 1 and 2 with directions dominated by northerlies

I and maxima approaching 20 rn/s. Quiescent periods tended to be dominated by southerly winds.

However, in contrast to the earlier deployments, maxima during Deployment 3 were less

I pronounced with lower peak values. Given these characteristics, the absence of clear correlation between bottom flows and surface winds in this deployment is not surprising. Under these

conditions, the observed variations in near-bottom flow appear to be the result of the regional

i flow field, with station to station differences mediated by local bathymetry and siting.

Water temperatures at the Nearfield station during Deployment 3 were essentially identical to

I those minimumobserved in April during and then Deployment increasing2 (Figure slowly to3.3-13) a maximum with values near thedecreasing end of theinitially record.to Ina

contrast, temperatures at Farfield during Deployment 3 were lower than those observed during

I Deployment were similar 2towithNearfield significant withhigh a minimum frequencyinvariability April followed (Figureby3.3-14). a slow The increase long-term throughtrends the

spring and summer.

I Near-bottom salinities at both stations were initially higher than those observed during the

previous deployments (Figures 3.3-13 and 3.3-14), with values of approximately 34 psu. Farfield

t values remained relatively consistent throughout the period of record ending in mid-July 1994 when the instrument array was recovered. Nearfield displayed similar characteristics but during

the extended period of deployment, with data ending in late September, began to indicate a

I progressive decrease in salinity with values approaching 32.5 psu. The cause for this progressive decrease is generally unknown. Reviews of the local streamflow conditions, as indicated by the

discharge from the Santa Ynez River, show a maximum in February followed by an extremely

I drysummer(Figure3.3-19). again, appears studyarea

Once it that near-bottom conditions in the

are more commonly controlled by larger scale regional factors than smaller scale local conditions.

i These characteristics complicate establishing cause and effect relationships.

I 3-67

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I 3.3.3 Near-Bottom Suspended Material Field

I 3.3.3.1 Deployment 1 (18 April 1992 - 17 October 1992)

I Data output from the optical sensors (OBS) indicates progressive but expected degradation of the

sensor performance during each deployment period. This is most probably associated with bioI of the vertical surface of the instrument windows. At both Nearfield and Farfield, fouling output

from the OBS began to degrade significantly within four to six weeks following deployment

(Figures 3.3-20 and 3.3-21). Significant fouling of the upper sensors at Nearfield occurred within

four to six weeks of deployment. The lower instruments operational approximately remained for

ten weeks (Figure 3.3-20). The situation at Farfield was reversed with the lower sensors showing

i the weekshigher fouling rate with significant signal degradation within approximately four to five after deployment (Figure 3.3-21). The upper sensors remained operational for nearly ten

weeks. Following the onset of significant fouling, the data provided by the optical sensors are

i invalid.

OBS data indicate that Deployment 1 near-bottom concentrations of suspended material at both

I the 10 mgNearfield /1 (Figures and Farfield 3.3-20 andstations 3.3-21). wereWater generally samples low with obtained average on April values18,ranging 1992, between just following 1 and

the deployment of the arrays, show initial concentrations ranging between 0.85 and 1.35 mg/1.

I Both Nearfield OBS exceeding records display that observed significantat high Farfield. frequency Overall, variability the timing with the of these standardhighdeviation frequencyat

perturbations is rather haphazard with spectral analysis of each of the suspended material records

I providing no evidence of tidal harmonic signatures (Figures 3.3-22 and 3.3-23). None of the records display visual correlation between suspended material concentrations and instantaneous

speed. Examination of the suspended material distributions and speeds during the first week of

I the deployment, when bias due to biofouling was minimal, shows variations proceeding over a variety of time scales consistent with the spectral analysis (Figures 3.3-24 and 3.3-25). This

response appears representative of a turbulent debris flow in which velocities serve primarily to

I transport and disperse suspended materials introduced from a variety of sources. In such a

system, erosion from the local sediment-water interface is a rare event and near-bottom transport

is dominated by recycling of the materials moving as a suspension in the turbulent flow. The

I immediate sediment-water interface in such a system tends to be dominated by relatively high

water content materials that can be easily displaced by mechanical agitation. Views of the

bottom in the vicinity of the Nearfield and Farfield stations provided by the ROV systems, during

I PMA recovery operations, a throughout study area.

indicate dominance of such material the

i Despite the relatively unconsolidated nature of the sediment-water interface in the study area, the array observations provide little indication of significant aperiodic resuspension associated with

the passage of meteorological events. Analysis of the pressure records indicates that several

t systems a significant passedincrease by theinstudy surfaceareawind duringwavetheenergy. deployment Four period events which were observed were sufficient on Aprilto 22, produce May

I 3-71

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NEARFIELD - DEPLOYMENT #1

150 "r T r T r i

aN

F I

1O0 TOP

_o_ I

i '

0 -_ I

150 I J , i i I

100 BOTTOM i

0o,-,___L,,.. ,,,__:.!. _, , !

4/19 5/03 5/17 5/31 6/1_. 6/28 7/12 I

i

!

Figure 3.3-20. Near-bottom suspended material concentrations from Nearfield

stationforDeployment1. I

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i FARFIELD - DEPLOYMENT # 1

15o t , ' ' '

I

1O0 TOP

I so / _ ,a.

I

0

I 150 _ _ _ t _ ]

I

| 1®

50

I

0 I I I I I

4/1' 5/03 5117 5/31 6/14 6/28 7/12

I

I

I

Figure 3.3-21. Near-bottom suspended material concentrations from Farfield

station for Deployment 1.

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NEARFIELD - Deployment #1 - April 19 to May 31 1992 ! 10

,

......... 1"--.-4 ' ....... I ........ I .......

...... ""q\ :......._"". ."/N".

"_ 102 \ y',---,,"___-__", _,.." / \-. ;_...:_ ._

•,..... ",_,-_ _ _!._: '_ _...__ i "

",.-" ",,!.,"" I -:.g i

, W/'il

I _ '- F_':

• li

10 "2 , , , , , , ,,I , , , , _ , ,_I ; , , , , , ,,1 , , _ , , , _

I -2 -i l

10 10 10° 10 102

]0 ........ I ..... I ....... F .......

lO_ _;_

...... _ ., , ,.: ," :,",,,..j. :_:., ....

G)

:_ ':''_:_""_::I_"i:"__i_i :

c_o 10 0 BOTTOM ' _ t i !'ii!" :_'ili"_.i_i[_'_l#i

lO r , i , , _ , rl + i I 1 , * t I [ t I I I I t I I l I I I I I r I

I 10.2 101 10° lOt lOfrequency (cpd)

I

Figure 3.3-22. Spectral analysis of near-bottom suspended material concentrations

from Nearfield station for Deployment 1. Dashed lines delimit the

95%confidenceinterval.

I 3-75

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FARFIELD - Deployment #1 - April 19 to Jul 12 1992

I .......... ,..........., ....... i ........ i ........

104

........ "\ ......."........... -.i ',.

_10 , "....... , ,:- , ,_ ,_ ',.. ........ ",.:t..' _ ' i • _ !>'_.._, ,

_'_ 10° TOP "_ illi;_l

i 1 : I! i_

10 "_ I I I I I I I i [ I I I i ' I I I [ I ' I I I I ' ' I f I I i I t I I

!

102 10l 10° 101 10

• . •............. - .....• ,.,_..;_:,!-_.,_.',....... ;,,._

10° l_o'rTo.',,i " '_,_ ':_!:''i__ : !:_"_._!1'=_,

i

lO2 , , , , , , ,,I , , , , , , ,,I , , , , , , ,,I , , , , , , ,,

I -2 -1 0 I 2

10 10 10 10 10

frequency (cpd)

I

Figure 3.3-23. Spectral analysis of near-bottom suspended material concentrations

I from Farfield station for Deployment 1. Dashed lines delimit the 95% confidence interval.

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t NEARFIELD - DEPLOYMENT # 1

i 80 TOP

i _ 60

40

i 2o

I 0 i I i I I

i 20 , , , , , , , , , , , ,

i 15 BOTTOM

0 i , i i

4/19 4/20 4/21 4_22 4123 4_24 4125 4/26 4_27 4_28 4129 4/30 5/01 5102 5103

!

I

I

Figure 3.3-24. Time series observations of near-bottom suspended material

I concentrations 1. from Nearfield station for Weeks 1-2 of Deployment

I 3-79

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FARFIELD - DEPLOYMENT #]i i

_,o I

0 I I I I I I I I I I I

50 i I I I I I I _ _ i _ I I

40 BOTTOM I

30

20:

]0 _ I

0 I I I I I I I I I I I I I

4/19 4/20 4/21 4/22 4/23 4/24 4/25 4/26 4/27 4/28 4/29 4/30 5/01 5/02 5/03 i

!

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Figure 3.3-25. Time series observations of near-bottom suspended material

concentrations from Farfield station for Weeks 1-2 of Deployment i 1.

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I 2, May 10, and May 22, 1992 (Figure 3.3-26). The optical data provide no indication that the

April 22nd, May 10th or May 22nd events measurably perturbed near-bottom suspended material

concentrations second event appears at eitheronlythe inNearfield the near-bottom or Farfieldsensor stations. at theA Farfield perturbationstationcoincident (Figure with 3.3-23). the

There is some indication of a delayed response, particularly associated with the April 22nd event,

I which may be the result of advection of materials from distant, and most probably inshore, sites rather than local resuspension.

I 3.3.3.2 Deployment 2 (18 October 1992 - 7 August 1993)

I

During Deployment 2 near-bottom suspended material concentrations at the Nearfield station

remained low and essentially identical to those observed during Deployment 1. Both the upper

I and lower sensors indicate concentrations in the vicinity of 2 mg/1 at the beginning of the record

(Figure 3.3-27). Values slowly increased as bio-fouling accumulated on the sensor windows.

i Fouling was particularly intense on the upper sensor resulting in a period of operation of approximately one month. The fouling rate was significantly lower on the bottom sensor

resulting in nearly three months of useful record (Figure 3.3-27).

I Suspended material concentrations at Farfield were higher than those observed during

Deployment 1 with the upper level instrument indicating values ranging from 10 to 25 mg/1 and

I the waslower maximum sensoratvalues the lower betweensensor 5 andresulting 15 mg/1in(Figure aseful3.3-28). record Atlength this station of approximately the fouling rate on

month. The upper level record remained useful for slightly more than two months before

I abruptly spectral signatures fouling. Once coincident again,withneither the Nearfield nor the Farfield record displayed evident the dominant tidal frequencies or any other primary feature

of the local hydrographic system (Figures 3.3-29 and 3.3-30). The absence of simple periodicity

I is visually evident in the suspended material time series with blowups of the first two weeks of the record from each station over a variety of time scales (Figures 3.3-31 and 3.3-32). The

patterns appear representative of a turbulent flow with suspended material concentrations varying

I in a relatively random manner.

Beyond the persistent high frequency variability, review of the time series records from both the

I Nearfield and Farfield stations indicates several short-term perturbations during which suspended material concentrations more than doubled resulting in maximum concentrations approaching 50

mg/1 (Figures 3.3-27 and 3.3-28). The lack of coincidence between these perturbations and

I concurrent winds and associated surface wave conditions (Figure 3.3-33) suggests that the perturbations are not caused by local resuspension and are more likely the result of advection of

materials resuspended in shallower waters and moving past the monitoring sites. In addition, the

I absence of in the observed in the Nearfield record relative that evident in similarity response to

the Farfield data provides another indication of the differences in the hydrodynamic regimes

i affecting each site. The near independence of the records from each station suggests that the spatial correlation scales in this segment of the study area are less than 5 km.

I 3-81

I
II

II

1

II

II

DEPLOYMENT #1

20t I J I t I I n

l

_ o

I

,_ 400s , t i , , I i

II 5/ , i , i J

0 I I i f f

I

&

I f 1 I I t

4/19 5/03 5/17 5/31 6/14 6/28 7/12 i

I

i

!

Figure 3.3-26. Meteorological observations from CM:d',I station PTGC1 and

concurrent surface wave conditions for Deployment 1. i

3-82 I

i
!

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!

I NEARFIELD - DEPLOYMENT #2

150 1 r r T T

I

100

I TOP

| _o

i o_1_

I 150 "r 1 T

I 100

BOTTOM

50

0 _

10119 11/02 11/16 11/30 12114 12/28 1/I 1

t

I

I

Figure 3.3-27. Near-bottom suspended material concentrations from Nearfield

I station for Deployment 2.

I 3-83

I
!

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FARFIELD - DEPLOYMENT #2 I

150 I I J I

I

100

•o_ I

_o |

o_-- I

150 I I I J I I

,

o "_'_ S_'YZi_Z':--:J , , ,

10/19 11/02 11/16 11/30 12/14 12/28 1/11

I

!

!

Figure 3.3-28. Near-bottom suspended material concentrations from Farfield

stationforDeployment 2. t

|

3-84 i

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I

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i

NEARFIELD -Deployment #2 - 10/19/92 to 1/11/93 I

]0 ........ I ....... , ....... , .....

'_"_"_"".. t%

_ 1o2 "_'"-,...../2".,:_i,, ,_ _,

_r_10° TOP

!

I -2 -1 0 1

10 10 10 10 102

I 4

10 ....... , ....... _ .... , ........

102 "-'---_' •........

e>

r)* '3{_ II

a

m 10° BOTTOM

I I{ i

10 .2 , i i , i , i r [ , i i i , i i , I i , , i i i 1 , I i i i I I , , ,

I -2 -1 1 2

10 10 10° 10 10

frequency (cpd)

I

Figure 3.3-29. Spectral analysis of near-bottom suspended material concentrations

I from 95% Nearfield confidence station interval.for Deployment 2. Dashed lines delimit the

I 3-85

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This page intentionally left blank.I!!I!!!!!

3-86I!
I

I

FAR.FIELD - Deployment #2 - 10/19/92 to 1/11/93

I 10 4 ...... I ...... I ........ i ........

"_102 ...... ................. ...

l O° TOP ' { ' ":'"_'q_'_', ' _!'.:"i' ",';i_!

I

10-2 , , , _ , , , ,I , , , , , , , rl , , , , , , , ,I , L , f f , , ,

I -2 -1 0 1 2

10 10 10 10 10

I 4

! iiiiii ...........

_lO2 __ ....

r"_,,.) ' ' : ", ",:'"-r-'./''.:'.J'::/'.Y_L.,_.-_'_,._.._i_

|0° BOTTOM i

10 2 , , , , , , ,,t , , , , , , ,,I , , , , , , ,,I , , , , , , ,

I -2 -1 I 2

10 10 10° 10 10

frequency (cpd)

I

Figure 3.3-30. Spectral analysis of near-bottom suspended material concentrations

from Farfield station for Deployment 2. Dashed lines delimit the

I 95%confidenceinterval.

I 3-87

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II

II

II

li

II

Thispageintentionallyleftblank.I!!I!!I!!

3-88 II

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I NEARFIELD - DEPLOYMENT #2

I I I I I I I t I I I I I

!

6

I _4

I 0 I I I I I I I I I I I I I

i 8 I I I I I I I I I I I I I

I 6 BOTTOM

2

I 0 I I I I I I I l I I I I I

10/19 10/21 10/23 10/25 10/27 10/29 10/31 11/02

I

!

!

Figure 3.3-31. Time series observations of near-bottom suspended material

I concentrat 2. ions from Nearfield station for Weeks 1-2 of Deployment

I 3-89

!
I

I

I

FARFIELD - Deployment #2 - 10/19/92 to 1/11/93

15o i t , , , i

,oo 50 TOP , ,,l_tit I

,, / Ii

,_..._'_._ ,_,,r_i_ ,Ah_I

o , _ , 1 i, :_.-._._._._.--..._,'

I

tB 150 ! t

1oo " _ ' l

BOTTOM

0 i I i

10/19 11102 11/16 11/30 12/14 12/28 1/11 •

|

I

Figure 3.3-32. Time series observations of near-bottom suspended material

2.c°ncentrati°ns from Farfield station for Weeks 1-2 of Deployment i

3-90 I

!
I

!

I

I

I DEPLOYMENT#2

201 , J l , , I

I _o

!

I -'-- 400

[--,

200

| "-_ _ 0

I I0 _ , , ,

E

_-_ 5 -

i "_- 0 I I i I

i

201 , , , z ,

I

_I0 _-

0 I I I I I

I 10/19 11102 11/16 11/30 12/14 12/28 ]/i "

I

I

Figure 3.3-33. Meteorological observations from CMAN station PTGC1 and

I concurrentsurfacewaveconditionsfor Deployment2.

I 3-91

I
I

I

3.3.3.3 Deployment 3 (9 January 1994- 7 January 1995)

u

Platform Hidalgo was operational during much of this deployment, aperiodically discharging I

spent drilling muds and cuttings into the water column (Figure 3.:t-34). Platforms Harvest and []

Hermosa were not operational during this period. Suspended material concentrations at both

w

Nearfield and Farfield were low with average values remaining below 10 mg/1 for the period of nl

observation (Figure 3.3-35). The response observed at each of the stations was similar to that R

observed at the upper sensors during the previous deployments. Again the records fail to provide

any indication of dominant spectral signatures with energies disl_ributed over three orders of •

magnitude (Figure 3.3-36). Review of the initial weeks of the suspended material record II

indicates that distributions at both stations were best characterized as a low mean value with

small, near-random variations (i.e., aperiodically perturbed by large amplitude, relatively short I

duration events; Figure 3.3-37). II

The optical data from each station again display progressive degradation apparently due to bio- i

fouling. These effects were most pronounced at Nearfield, thereby limiting the useful period of II

record to approximately two months (Figure 3.3-35). The Farfield record remained relatively

uncontaminated fornearlysixmonths. I

In contrast to the relatively unperturbed nature of the record obtained during Deployment 2, time

series suspended material concentrations during Deployment 3 di.,;played a number of marked i

perturbations with the largest amplitude, longest duration event appearing in the Nearfield record i

over the period February 10 to February 28, 1994 (Figure 3.3-35). Peak concentrations during

this event approached 100 mg/1. Although similar concentrations were observed during previous I

deployment periods none of the earlier events displayed the persJistence of the February 1994 W;

perturbation. No coincident event appeared in the Farfield record although an evident

perturbation, albeit smaller in amplitude, began on March ]l, 1994 and continued for i

approximately one week (Figure 3.3-35). Several additional perturbations appear in the Farfield

i

record, one just after the beginning of the deployment and several later in April. i

B

Review of the meteorological data for the deployment period (Figalre 3.3-38) fails to provide a

clear indication of a correlation between instantaneous wind stress and near-bottom suspended Ill

material concentrations. Several wind events occurred during Deployment 3 but none were R

coincident with the observed perturbations in suspended load. Several wind events precede

observed periods of increased concentration, again suggesting that the materials passing the •

monitoring site could be sediments suspended by the local wave field in shallower waters and II

subsequently transported offshore. An alternative view is that the observed perturbations are due

to material discharges from the operating platform. However, reviews of the platform data Im

indicate that during the period of the maximum concentration pertalrbation, around the 22nd of

February, there was no-discharge of muds or cuttings (Figure 3.3-34). This no-discharge period

extendedfrom approximatelythe 10th of Februaryto the 1st of M_ch. •

g

3-92 I

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I

I

I

I

I DEPLOYMENT #3

,, 0:.o.. o ,___, _ , ool0_ . O_._4t_ _

I

1500, I I I I I _ I _ I

I .,o5000 _nrdol_n_ o. _ _ _n-_._

1_ j _

I

I I I I I I I I

i -F=500

o

I/I 1 1125 2_08 2/22 3/08 3_22 4_05 4/19 5_03 5/17 5/31

I

I

Figure3.3-34. Platform Hidalgo discharge and concurrent average daily

I streamflow from the Santa Ynez River for January - May, 1994.

I 3-93

I
FARFIELD . DEPLOYMENT #3

200 _ _ i , I I l , a I , l _ --7- j _ i

]50 r

_zoo

I ! - | I _._L I

I

2c_ NEARFIELD. DEPLOYMENT #3

t I I t I -- I

15¢

I

o I [ [ A ! I

i/1 I/25 2/08 2/22 3/08 3/22 4105 4/19 5/03 5/17 5/3 ]

I

Figure 3.3-35. Time series observations of near-bottom suspended material I

3?ncentrations from Nearfield and Farfield stations for Deployment I

3-94 I

!
I

I

I

i FARFIELD - Deployment #3 - Jan 11 to March 28 1994

6

It) ........ L ........ f ...... _ .......

I o

. 10_ . ...., .......... _-,.,._. ._ ,_ _

__ _

10° i ","' _ '"

!

10.2 , , , , , , , ,1 , , , , , , , ,I , , , , , , , ,I , , , , , , ,

I -2 -I 0 1

10 10 10 10 10_

I NEARFIELD - Deployment #3

4

l0 ........ i ...... i .......

_:_ .... ?.-: "..... _..,_.., ,." ..

I -_ "\ ..',

_ 10°

I

"2 i I I I I , , I I , I I I I ] I I I I I I I I I I I

I 1010 10° 10_ 102 frequency (cpd)

I

Figure 3.3-36. Spectral analysis of near-bottom suspended material concentrations

I from lines delimit Nearfieldthe and95%Farfield confidencestations interval. for Deployment 3. Dashed

I 3-95

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3-96I!
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I

I FARFIELD- DEPLOYMENT #3

80 I , , I , , ; l , i i , , t

' t' 60

I ++o -

I 2o _ _ -

I 0 _ '

I NEARFIELD - DEPLOYMENT #3 I00 _ _ , , , J a , _ + , , ,

I +o I

60

40

| 20 a

0

1/1 1/12 1/13 1/14 1/15 1/16 1/17 1/18 1/19 1/20 1/21 1/22 1/23 1/24 1/25

I

I

I

Figure 3.3-37. Time series observations of near-bottom suspended material

concentrations from Nearfield and Farfield stations for Weeks 1-2

U of Deployment3.

m 3_97

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DEPLOYMENT #3 I

20 I I t J I I i J I I I I I I t I I I I i

15

! '

!

!

, !

I

!

0

1/25 2_08 2/22 3_08 3/22 4105 4119 5_03 5117 5/31 i

I

I

Figure 3.3-38. Meteorological observations from CMAN station PTGC1 for

Deployment 3. i

3-98 I

I
I In addition to Farfield resuspension and transport or platform discharge, the suspended material

perturbation at Nearfield could be the result of high discharge from local freshwater streams.

I Using the Santa Ynez River as an indicator of local streamflow conditions, late February, 1994 was a period of increased streamflow with a maximum around the 22nd (Figure 3.3-34).

However, despite this coincidence the limited response of the salinity field to local streamflow

I conditions, discussed above, makes it less likely that this is the only source. Rather, the perturbation may be the result of several factors acting in combination. For this event, the

combined effects of nearshore, wave dominated resuspension and river discharge, with the

I resulting suspended load transported offshore the monitoring station, to be the past appear

dominant factors. In such a system the perturbation observed at Farfield would be produced by

the same range of factors, with the delay representing the result of the variant trajectories

I field. Onefactorthat involvedin the observed is affecting the flow was not perturbation

platform-associated discharges of drilling muds and cuttings.

!

3.3.4 Discussion

!

Data from the bottom mounted arrays provide an indication of significant spatial and temporal

I variability This variability, in thenoted near-bottom in previoussediment investigations transport addressing regime in local the region drillingnear mudPlatform dischargeHidalgo. effects

(Steinhauer and Imamura 1990), complicates data analyses and requires the use of relatively long

I and comprehensive data sets for process-oriented studies. This complexity makes it difficult to establish cause and effect relationships. The system is clearly perturbed by a variety of factors,

acting singly and collectively, that serve to alter both the supply of suspended materials and their

I transport rates and pathways. These interactions yield a material field characterized by low, long- term average concentrations which are aperiodically perturbed by the passage of high

concentration ':clouds" of sediment laden waters. Suspended material concentrations in these

I clouds can exceed the long-term average values by two orders of magnitude over periods of more than seven days. These characteristics determine the sediment exposure affecting the local

biological communities. The infuence of platform-associated discharges must be scaled against

I the characteristic variability of the natural that affect the regional suspended material processes

field.

I The evidentin the materialdataandthe absenceof correlationswith variability suspended simple

surface wind and/or wind wave conditions provides clear indication that both the Nearfield and

Farfield stations are, under most conditions, beyond the area of direct surface wave influence.

I This appears consistent with previous observations on the California shelf which indicate that

waves become a significant factor affecting sediment transport inshore of the 145m isobath

i (Cacchione, by advection etofal.sediments 1987). Materials that are moving resuspended past these by waves stationsacting appear in shallower to be primarily inshoresupplied areas,

particulates introduced via river discharge and atmospheric deposition, intruding oceanic waters,

i and with water this system columnareproductivity. small, thus establishing The scales ofsome variability, constraintsbothonspatial samplingand temporal, protocols ifassociated accurate

I 3-99

!
II

identification of the relative contribution of each of these sources is to be determined. For n

example, the array data indicate that the dynamics of the region :in the vicinity of the Farfield

station are substantially different than those affecting Nearfield. These differences, appearing in •

both the near-bottom flow and the suspended material field, suggest that 5 km may be an II

approximate maximum for the spatial scales of variability in thJLsarea. Further, the lack of

correlation between events at Nearfield and Farfield may affect the utility of the latter station as

a control since local biota would be exposed to a different range of conditions than those U

experienced at Nearfield. These differences need to be factored into the evaluations of the

potential effects of drill platform discharges on the adjoining biological community, n

m

3.4 TRANSPORT OF DRILLING MUDS U

3.4.1Introduction I

II

Platforms Hermosa and Hidalgo began drilling operations in September and November 1993, •

respectively. Hermosa discharged 820 m 3 of drilling muds over a 30-day period and Hidalgo,

3850 m 3 over a six-month period. Drilling muds are primarily composed of fine silt and clay m

particles with only a small fraction of large particle sizes. As described in Section 3.2, the

currents are quite dynamic off Pt. Arguello with a tendency to flow poleward during the summer

and winter and equatorwards in spring. Drilling muds are discharged about 34 m below the •

surface, equating to about 100 to 150 m above the sea-bed. Strong currents, slow particle sinking g

speeds, and a highly variable discharge rate means that drilling muds are likely to be dispersed

over a wide area. The exception will be the heavy fraction of material (sand-sized particles) that n

will be deposited close to the platform.

In Phase II, three platforms, Hermosa, Harvest, and Hidalgo, discharged a combined total of I

41,380 m3 of drilling muds over a two-year period (February 1987 to January 1989). These

m

deposition and sediment fluxes were modeled using a plume and particle tracking model with a m

single sinking rate (Coats 1994). The large volume discharge means that there was a substantial n

flux of the principal tracer of drilling muds, barium, to the sea floor, and reasonable agreement

was achieved between modeled and measured barium fluxes over three deployments of sediment im

trap arrays (Coats 1994). An independent modeling approach for determining the region of the

sea floor that receives settling drilling muds has been used for the Phase III discharges. The

present model is similar to that used by Coats (1994) in that a simple particle tracking algorithm II

is used. However, differences are that more than one size class of particles is considered, more U

than one current meter mooring is used to estimate the horizontal advection of the particles, and

higher resolution bathymetry is used. The model is described in Hamilton and Ota (1993) as •

used to investigate the deposition of dredged material from propo,;ed deep water disposal sites II

off San Francisco.

U

3-100 I

!
I 3.4.2 Model Inputs

I The particle deposition model (Section 2.2.4) requires detailed bathymetry, current velocity time

series data, and discharge data in the form of drilling mud composition, and discharge rate. The

I bathymetry is constructed from the NOAA/NOS 15 second gridded depth data for the 1° x 1°

latitude x longitude square surrounding Pt. Arguello. The grid is not complete but is very dense

in coastal regions with depths less than 200 m. These data were interpolated to a 250 m UTM

I which is the basic of the model. The can artificial hills and grid grid interpolation produce some

holes, but these are restricted to deep water areas where the original data are sparse.

I Current records are from the P, $5, $6, and I moorings (Figure 2.1-1). $5 was just north of

Platform Hermosa during its September 1993 discharge period, and P was adjacent to Platform

i Hidalgo. offshore or$6toandthe Isoutheast, provide some respectively. Farfield data The for mid-depth, the more40-HLP slowly sinking currents particles from thesethatmoorings disperse

during the discharge period are shown in Figure 3.4-1. The Hermosa discharges took place

i during spring the regime poleward with weak flowingfluctuating summer-winter currentsregime. at P andThestrong Hidalgosouthward dischargesflows wereatmostly $6. These in the

records are discussed in more detail in Section 3.2.

I The daily volume discharge (bbls) of drilling muds from Platforms Hermosa and Hidalgo are also

shown in Figure 3.4-1. It can be seen that discharges are highly variable (e.g., 0-1300 bbls) with

I estimated 100-200 bbls as thebeing average typical. of a number The composition of differentofsamples Hermosataken and from Hidalgodifferent muds well (Tabledepths 3.4-1)during was

the drilling periods. Size classes represented are 1, 5, and 6, with silts and clays predominating.

I The Hidalgo total number of particles used for each size class are 5,160 and 16,390 for the Hermosa and discharges, respectively. Table 3.4-1 also gives the voids ratio for the particle size

classes (Section 2.2.4) and the time required to sink 100 m. For example, at 30 cm/s, a common

I velocity in Figure 3.4-1, class 6 particles will travel a horizontal distance of 60 km in the time taken to descend 100 m. Thus, many class 6 particles are lost out of the grid, particularly during

the poleward flowing summer-winter regime.

!

3.4.3 Results !

i Deposition pattems were calculated for the Hermosa and Hidalgo drilling periods in 1993 and 1994. Hermosa only drilled for 30 days and the relative concentrations in lag/m2/kg of particle

size class dumped are given for size class 1 (large heavy particles) and class 5 (coarse silts) in

i Figures platform 3.4-2 and cover and 3.4-3, an area respectively. of only 2.75Askmexpected, 2. In contrast, the heavythe particles silt-sized arematerial clusteredis widely around and the

thinly dispersed by the strong poleward currents in September 1993, and none of the material is

I deposited onshore ofnear the the platform. drilling This platform. probablyNoteis caused that someby the material southward is deposited flows atto $5theafter southabout and

I 3-101

!
I

I

I

I

1500 _ I

1250 "-_

SO0-

250- I

0 ...... A ....

t_pcoa_

Ln,ho_ 28m I

-_ _/_/_

-25-

•50-= I

-7s I , , , i , , ,1, i .... i ,I, , , n , , ,I, a .... n I n , , II _ I a I i n I u I

28 17 7 27 16 6 26 15 4 24 16 5 25 15 4

SEPT OCTOBER NOVEMBER DECEMBER JANUARY FEB MARCH APRIL MAY

1994 I

JUIJ_N DAY IS

40-Hour Low Pass Currents and Platform Discharge

I

I

I

Figure 3.4-1. Mid-depth 40-HLP currents and Hermosa and Hidalgo drilling mud

discharges for the drilling periods, i

3-102 I

!
I

I SANTA HARIA RUN 11

-120.7 93/ 9/14 - 93111/29 -120.6

34.5 , 34.5

"-., "'_00" "'-.. .... ,,

.... . , "°" , -,

., ,. "'-. . ._ ........ . '_

4o0. ', ,, .... ,.

I . _ ",, "'... .... 00o "

• . "-% ,.._ ..-"

i .% ". .... :

• .... -.. _

,, "" % • . °, ,.-"

I . -.. , , :

"- ]

Area _overed . _.75 sqkm ¢00. ',

Me&n &".M&ximum . 363_ &3056.2 Ug/sqm/kg "-..... "" ".. -. ....

34.4 34.4

I -120.7 Class . 1D;spersion Coeff . 1.00 m2/s -120.6

Percent Loss . 0.00

I

Figure 3.4-2. Class 1 particle concentrations from Hermosa discharges. Contour levels

I are with1,a2,circle 5, 10,and20,diamond, 50, 100, respectively, 200, etc. Moorings 500 m and in width. platforms are marked

I 3-103

I
i

I

SANTA MARIA RUN 15

-120.9 g3/ g/14 - g3/11/20 -121_.5 _I

I

34.7 :, ! , _) 34.7 I

"%e. -,.

-. • !:'-,

"'..; ',.. _ "',:: ",

, ,, .....;

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\ : :,. '.......... :, I •.. _...._--,...,..,,-'

: ',, .:,.--.,,...,# .,

ii:::::-:.:;:-::{:;- ;; i -.:,..:'--.:-., ..... !

'. :'.."_:.:i::" ' i ° :-'-_'::">':'-:.:"" ",. _ _

;,.:::: . :. ............ I

",.. "...o.-'q)" ",. "'. ".... ".......-:!_ :.(_. _ "'..

: _ "..... ", '.tic"! ." "--'"'.. ".... ". .....:'".."". -.. "..... <,> _.".. '.

"' ". " ""_e.".; "".'"...... """. ".... "'"' ""'. "'' "'"". '..... "':'" _ ..... _'--_"> "

• ",...-. _..;." : ',, ,. ..°, ", ,., .. :, -,. -..._. "..,, .... , _dO)f

". '"'. "--":",_.",'.:'',. ", "": .."."."....... '....._" '"JV_- :", '"":. 7, i

--,.....,...., , .,,'.::..":....-._ ::!:,,... ::'-..,. , :: -..,..,..,..-...-.... _.,.,.._.:....> .... ......

I

\ ",.".[ ....... _',_,. ',, .,,. ,..... ...,',. .,. .; ....• . ,: ,,,';

Ar'ea

-..

"t"over'_

;

d l:[

,.,,

"_''1_'°

........

76""'_k_ .""

: ';

!

-..

".

.

"'",

• -;,

""

.

"".....

.......

",

...

}

,

....

..

;_"_"

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..-_:,

'_" .....

'-;,

'"': "'" I

34.4 _ean ). Maxl"_u_A,i: 6.4 &'.". 7},.5 Ug/_.Rm./,kg : ;, ' '" "'""': " :'°""'": "'"" "" "" 34.4

-12(_.c/ Class , 5 Dispersion Coeff . 1 .(_ m2/s -129.5 •

Perc_t Loss , 29.99

I

I

Figure 3.4-3. Class 5 particle concentrations from Hermosa discharges. Contour levels

with are 1,a2,circle 5, 10,and20,diamond, 50, 100, 200, etc. Moorings and platforms are marked I respectively, 500 m in width.

3-104 I

I
I October 10. Thirty percent of class 5 material is advected out of the system and over 80% of

class 6 (not shown). Deposition is calculated for the volume fractions in Table 3.4-1 and are

I shown in Figure 3.4-4. Nearly 50% of the material does not settle in the region of the map and the patterns of deposition resemble a combination of class 1 and class 5 (Figures 3.4-2 and 3.4-

3). The results imply that between 1 and 60 microns of material is deposited by the short period

I of Hermosa drilling operations. This is far too small a volume to detect using chemical tracers (barium).

I Table 3.4-1. Phase III platform discharges of drilling muds.

I Fractional Volumes

I Sinking Time Sinkto Hermosa Hidalgo

Class Particle Velocity Voids lOOm (%) (%)

I Type (m/s) Ratio (hours)

1 CoarseSand 0.086 0.67 0.32 1.55 0.77

I 5 Coarse Silt 0.0014 0.67 20

9.91 12.28

6 Clay-Silt 0.0005 4.00 56 7.27 17.87

I Fluid ........ 81.27 69.08

I Discharged Volume ........ 820 3850

(m3)

I

Platform Hidalgo drilled for nearly six months beginning in November 1994. The relative

I concentrations of class 1 and 5 materials are shown in Figures 3.4-5 and 3.4-6, respectively. Again, the heavy material is clustered around the platform and covers an even smaller area (1.2

km z) than for Hermosa because of a less vigorous current regime and more shallow water depths

I (130 m versus 180 m) at the Platform Hidalgo site. The class 5 material is about equally

dispersed northwest and southeast of the platform. This is a consequence of the more variable

current regime in the spring, which also means that less of class 6, the silt-clays, is lost (-40%;

I not shown) to the system than Hermosa. However, region deposition a

for the of with thickness

greater than one micron is extensive, over 566 km 2, because of the strong dispersion of the

i particles (Figure 3.4-7). The average deposition thickness is only five times that of Hermosa (7.3 gm versus 1.5 gm) and thus is still minuscule. Such low sediment fluxes are unlikely to be

detected directly by the sediment traps. This is consistent with the lack of elevated barium or

gradients of barium concentrations in the sediment trap records near the platforms for the drilling

I periods (Appendix B).

I 3-105

|
I

-120.9 9SANTA 3/ 9/14fIAR[-A 9"_RUN/11/20 1 -13_.4 I

34.8 34.8

I

•,.. _!,. " ......%,,. ; i I

: : i ..',.:.':.:", ::: • .'

:'. "'-. "', :';',::':;:'"" "" " "'_.'(°_ " - 1 "".

•: '- ":"*"_ : _-'__%_-_-_ ...."...... _ I

---, .::, -..,.. :......,,....,._=o.-.,_,./; ,, ..........

_._,-':°i,-,--- o.,,.-!.'..,.-::::.: -.,,i;.... _,.:.-",-_--,:: _.., |

,..''_.........: .... :...'.. "" : . ..,. ',,,,

•! _ ".... ". ',:6B_._':""-"", "*'". "ee'"';'".,'"'.""'.....;_ _ :"', _ }L:._ \

• ", "'--"''-_':";':"'," '"-- "" '"" :"""-:_i_, -_ ':- - '_" _ I

_.t_ _'_o:_:"..i_,_-._h°_=_U..°_' -,. '"- :; ': ", '. "- "'".....," i _;___--"'_""".."]:i; '"". I

Ar_ Co;=r_'.e",':...-- , _7..;.2_ $q_ . ',. ... .... ... "......, -. ..... ,_::_ e..,.. ...:.... ....... .,....

34.4 ,_e=r_ & f4"_x,_,_._ , ":L._ & _e.7 Um_ " :" "'" """'* "; "'"'": " "'*" "'"'" !" "..... """" 34.4

- 12t}, 9 Hermosa MUdSpercentDispersiCono¢fLfo47. ss:04:1.00 m2/s - 121]. 4 i

I

Figure 3.4-4. Deposition in _aa from Hermosa discharges. Contour levels are 1, 2, 5,

10, 20, 50, 100, 200, etc. Moorings and platforms are marked with a I circle and diamond, respectively, 500 m in width.

3-106 I

I
I

I

SANTA MARIA RUN 21

I -120.8 93/11/21 - g4/ 6/30 -12{}.6 34.6

34.6 ,,-_ ..... ,,

i

| '

%'-. \

; "%

"".._ %_j ,

;;:: ::;"

% i . "%-%%

", "'""-"'-'" ,.-200, "'" ..... -

• / /

"-: .-',,"i.",i,. ' .."-0 -.... i ".,.....-;: """

•.....,----.;._... "-..._"'-...."-... -'",:.....". .......

I '-..Y"" , .-"...... 'i "",--.-,. "..)--.."......... %",0 _:..,"'",... :,',: --,..-'",,.

., _.] :; .-'.. "'..... . ....._0_..,..",.....-,......""'-,.,""-... "..., """

B

I ,..,.. "'. _, "--.... ',. --.. ......... "_'_'_, "-...

,.,',,,, ' ""-. ". '-._... ".. ', '-..Q0_'. ' "-'°,, • .

.: ," , ". , _..-, _. . _'C-""

_q'-.. "'. _. "% .

l • ' ""-""""4 '. ', , " :

.. _ _ '.,. "'. : . "°

'_rea Csverdd 1.1g _qkm _, "'"' , ""

Plean & Hax_,mum , 842.1 &9445.4 Ug/_qm/kg " " ""....---..

34.4 34.4

I -120.8 Class , 1 D;spers_sn Cseff 1 .00 m2/s -12e.6

Percent Lsss , 0.00

I

Figure 3.4-5. Class 1 particle concentrations from Hidalgo discharges. Contour levels

I with are 1,a2,circle 5, 10and, 20,diamond, 50, 100, respectively, 200, etc. Moorings 500 m and in width. platforms are marked

I 3-107

I
I

I

SANTA MARIA RUN 25

-120.9 93/11/21 - 94/ 61318 -120.5 •

I

' i

; _.,.". _,.,: "..

• .

. "", : II

• ,' ,' i I

: ....: ,.:,"!.i "'..,.

%,

• !

o..

",,,'_.., C3° , "-,.

i?-,- ', °" " I

i",_'_ _ "'-. ..'.,...-, ,. ".. "

", i'_--,. "'.,...."-'_ :" ',,._',...'. "'"" ',

:' "" " " '" ' I

• "., , _ ,- -_, -,. ", -., ".., '.-,.

• ', ',, .V'"(':"."- ""-. ' ",. "' . ....

"'.. ",. ',2:::;'/ ".._ ", "'.. : ;...': ..."",,..

"'" """ • *....." "-"'_ "", ", _f " "_ : " ",-'" I , "...'_". _ "' >. _., _0_'" ":':; "

•,.o "., .. i(':' /......'...._"",, ".,_3. <<_ ".. L_....._..L.;:.":..... : .-., I

_'e•, "• ." ,": .,! ....... ..... ,,..., .: .., ;. "'",, "",: _,... _ -__E,,, /'.,"':: ,_ee,__.... ......",.'" ,---.

•. . .,:.. ; '...; .. . .. • .. *_ "-..

• : _.... .,,, _. ,. , ,. _ _-_'--. .-,

• " " _ ': : " ; " _ _ " ".... e -....--',,'"_4_,._-';_,..0 ..... '.

, - -.._ "..: _ : _ ,-..; ... • ,, . _ •., ,_.- -. ... .---..

• ".: : ; ,_ '. , , . ;. _ , • o ._ . _ -- ,., "_

• co ,........ . , .. .... :._^_ , _-_---., :., ....

'.,., -. ",,,.',,,:"-.,..-,',.......,",., • :. '....... - '............. ..

• _ ; '. • .. z ", : ', _ '. _ '.-''. - "..

: "'_" " "'" : : " ' .... ' ',"" "'""" "_ I

I :_,.: ,, : ", ,, ,•. '. ._, ,, _ - ._,

Ar-_a=.....,_'. "--"21_._2"_d_';,':.', ." "". ' "...........

Mean _. Ma*_,','_":: 'W_"&'-.'-_T'._. U_Vsqo/k_' ........ ". " "'" """-;"

34.3 ' " "'"" 34.3

-120. c) Class , 5 Dispet'sien Coeff , 1 .00 m2/s -120.5 • Percent Loss . 16.18 I

I

Figure 3.4-6. Class 5 particle concentrations from Hidalgo discharges. Contour levels

are with 1, a2,circle 5, l 0,and20, diamond, 50, 100, respectively, 200, etc. Moorings500 m and in width. platforms are marked I

3-108 I

!
!

I

I SANTA MARIA RUN 2

-!20.9 93/11/21 - 94/ 6/31_ -129.3

34.8 34.8

1 t

t

_ , o' J

"'; "X ;:,

i ,.., ", ,.:, ,

I "

I 'Z........... -,.:

: ....,,. _..._,".....--.J ", ', ":?,,!-!-:: ,' i

I ! ',.:,':;;! _,,.',. ,..-, •

", -_ _"" "" " ""e --'- "" 0

.Q... ,----. ..... .,

'..: , :.--.. ; ',,._.:: :- _ ",..... "........ ,..:,

; ',, ;-,, ., ; ,.,. _ ",. ;, ,, ._. : .:',. .

, ,, , , . .. ,, , ,. , ....... .

; " :::_,_ ,-, : ...., ... - " ", -,: ': e_....... "-'.-.......... :--

: _,'.,, : _:..4 "-, :' ".. ', '.......... ',

I i "i : '!';.":.i i..'-*,_,?-'-,.' ',,...-,,,., - ..-_ .."-"_oo. .....

.-,;,,"., (_ ',, ,,, ...- , . --, :--.,.,, ',, :- ,.... ,,: .: ,, --, ...... ,---

:,._ :: ,:, ...,-,..: ..-_. --: -_: "::_...... .,;: . :"',::','..,..-:. --,.. .

i ..., , : ., ,,. _ "-..-. ..C _ . : . ,,.._:... :":, - .... .--

',, -, .:.-: ! ..... . .. "-.,:.-.-_ ,..:----_...... ';._,._..,..'-'--'._--. _ ,-....

Total L'o_. , ",, 3.85 Th'ousand _',_ ":_" :.._,, ," ...:;,,... ":'.'"'-' : . "-:t_\'_-_._...

Area Cove.t'e_1"-.,",. 565;88 sc_k_--'" :. "..',"--',"---", .;_'" ;';-*.'-"'".-,'" ,*"'---."-':-:'-'.', '; .........

Mean & Maximum , 7.3 & 455.6 Um

34.2 34.2

Muds Coeff 1.00 m2/s -12Z,3

Hd|go OTsperslon I

Percent Loss , 28.74

I

Figure 3.4-7. Deposition in lam from Hidalgo discharges. Contour levels are 1, 2, 5, 10,

20, and 50, diamond, 100, 200, respectively, etc. Moorings 500 mand in width. platforms are marked with a circle

3-109

I
IIIIIIIII

This page intentionally left blank.

I!I!IIII

3-110II
I 4.0 SUMMARY AND RECOMMENDATIONS

!

4.1 INTRODUCTION

!

Current velocity, temperature, and bottom pressure were measured for approximately two and a

I half and years a variable on moposition orings placed (th secondary at one fixedmooring) position alongshore (the primaryandmoocross-shore ring near Plat fromformthe Hidalg primaryo)

mooring. Resulting data have been used in conjunction with satellite SST imagery to describe

I elements deposition ofofthedrilling circulation mudspatterns and cuttings which discharged might be expected to affect transport and subsequent from local oil and gas platforms. These

current velocities were supplemented with current/temperature observations made by SIO at the

wes available tern endto ofsupport the Sansynthesis ta Barbaraof Channel. oceanographicTakenprocesses as a group, and nearly numerical continuous particle datransport ta were

modeling.

I Additionally, for three extended deployments over a three-year measurement effort, near bottom

observations of current velocity, salinity, temperature, and suspended and deposited sediment load

I were made at two sites. One site was close to Platform Hidalgo (Nearfield) and one (Farfield) was placed sufficiently far north that it was expected to be outside the sphere of direct deposition

of muds and cuttings. Due to instrument problems, bottom current data measured during the first

I two deployments are of less use than during the third deployment.

A numerical particle tracking model was used to simulate transport, deposition, and accumulation

I of muds and cuttings discharged from Platforms Hermosa and This Hidalgo. methodology

allowed estimation of the magnitude and areal distribution of material from these releases.

I study area an oceanographic transition zone between warmer poleward flowing water

The is in

associated with the Southern California Countercurrent (coming to the area through the adjacent

i Santa California Barbara Current. Channel) The and cooler, often slightly fresher water of the southward flowing Coastal broader transition zone between these two controlling patterns can move

up- and downcoast as well as on- and offshore so that the study area is under the influence of

i differe vicinitynt ofregimes Point Arguello having variable and the magnitudes. Santa BarbaraBecause Channel,ofspecific the complex patternsnaturein measured of currentscurrents in the

can vary over comparatively short distances. This is shown in the differing currents that occurred

I at between the primary the primary and secmooring ondary mooring and thosewhenmoorings the latternearer was the offshentrance ore of theto primary the Channel. mooring, and

I Winds betweeninPt. theArguello study areaandwere Pt. Conc usuallyeption. directedDuring downcoast winter, andmigrating approximately storms canparallel bringtosignificant the coast

wind, rain, and wave events to the area. Increased rainfall and associated larger than usual

I discharges from local streams may contribute to the variations in sediment load measured by some of the near bottom sensors. Given the considerable water depth near Platform Hidalgo, it

I 4-1

!
is unlikely that direct wave action was a cause of locally measured turbidity events. It is more I

likely that wave events caused material to be resuspended i!n shallower water and then

transportedtothesedeepersites. II

4.2 REGIONALCIRCULATIONPATTERNS I

Data indicate that local tides are mixed with semidiurnal and diurnal components. Semi-diurnal •

(ME) tidal currents at the primary mooring had amplitudes of approximately 3 cm s"1,were

relatively invariant with depth, and were rectilinear with a slight cross isobath orientation. In •

contrast, the semidiumal tidal currents at the secondary mooring locations showed depth II

variations in current magnitude with greater currents speeds (_7 cm s1) at some of the secondary

mooring sites. The diurnal (K_) tidal currents at the primary mooring were generally weaker, •

more aligned with local isobaths and more depth variable than the M 2 tides. At the secondary |

mooring, K] tides varied depending on location and water depth. Tidal currents are a regular and

periodic contributor to local currents, but are relatively weak compared to the potentially vigorous II

background and low frequency currents.

Mean currents over the entire measurement interval were dominated by a seasonally more II

vigorous and longer lasting summer/winter season and associated poleward directed transport of

warmer water from the south. Low frequency currents were different in the summer/winter

season and spring season: flow was generally upcoast (poleward) in summer/winter and

equatorward in spring. The duration and characteristics of these seasonal patterns varied between I

years.

The spring season was characterized by equatorward currents in if.reupper portions of the water

column. With increasing depth, mean currents varied in direction and decreased in magnitude.

Strongest downcoast currents were near the surface with a wea_ker and sometimes reversing •

current nearer the bottom. These equatorward events were interrupted at times by weak poleward

D

currents that were often associated with relaxation of the normally downcoast directed winds. i

In

spring, water temperatures decreased as the equatorward flow moved cooler water into the area I

from north of Point Arguello.

A rather abrupt transition can occur from the equatorward flows of spring to the poleward flows I

of summer/winter. This transition did not appear to be linked directly to local winds. Poleward

currents were often at a maximum at mid-depth (e.g., Figures 3.2-]14 and 3.2-21), which may be •

associated with some slowing of surface currents by the downcoast winds. This general flow II

pattern brought warmer water to the Point Arguello area from the south through the Santa

Barbara Channel. The resulting water column was stratified until the onset of winter storms and •

associated vertical mixing. Because of variations in the path, timing, and local intensity of these |

winter storms, the timing of the creation of the mixed surface layer varied significantly from year

to year. It is possible that embedded in the generally poleward directed currents were eddies and

meanders that produced clockwise rotation seen in the current vectors. The transition from

4-2 I

I
!

I summer/winter to the following spring season was generally more gradual than the fairly abrupt

transition into this season.

I

, 4.3 NEAR-BOTTOMCONDITIONS

i The usable temperature and current velocity data are generally consistent with an extension to

near the bottom of some patterns described in the discussion of regional oceanographic

conditions. As might be expected the amplitude of the temperature response of the bottom water

I was less than seen higher in the water column im

Data from the bottom mounted arrays showed that the near bottom sediment transport regime has

I significant variability in time and space. It was common that correspondence did not occur in the time varying suspended material concentration between the Nearfield and Farfield sites even

though they were relatively close to one another. It may be significant that the water depth at

Nearfield was about 140 m and approximately 200 m at Farfield.

Substantial sediment concentration events were recorded at both sites; however, it was generally

I not possible to identify a local forcing mechanism that might produce the observed clouds of suspended material. This fairly consistent lack of correspondence in timing between aperiodic

wind/wave events and increased concentrations strongly suggests that locally observed suspended

E material resulted from non-local processes. One possible scenario is that material passing the

sensors originated in shallower water, possibly being resuspended due to wave action, and was

then transported by regional circulation patterns to the measurement site. During Deployment

I 3, some of the observed suspended material have resulted in from substantially larger may part

local stream discharge caused by increased rainfall amounts. Although probably of remote origin,

near bottom clouds of material increased the local suspended material concentrations several

I orders of the undisturbed concentration. The influence magnitude over average, or background

of the relatively limited discharge from Platform Hidalgo during this program should be scaled

against this characteristic and naturally occurring variability in the regional suspended material

i field. Time series from the OBS provided no indication of material that could be identified as

being discharged from Platform Hidalgo.

I

4.4 PARTICLE TRANSPORT MODELING

I

Phase III drilling at Platforms Hermosa and Hidalgo resulted in discharges of relatively small

i quantities of muds and cuttings. This material was discharged 34 m below the water surface, subsequently transported by regional circulation patterns and, for some size classes, deposited in

the general study area. A numerical particle tracking model was used to simulate and quantify

i this expected sequence of transport and deposition.

I 4-3

!
!

|

To establish a frame-of-reference for the following discussion, it is helpful to scale the magnitude

of the discharge being modeled in the present study. During a prior program (CAMP II), m:

approximately 42,380 m3of drilling muds were discharged over a two-year measurement interval I

which was 10 times larger than the volume of muds and cuttings released during the present

study. I'

The present model allows the volume by size class (and hence settling velocity) to be

incorporated in the model input and subsequent particle tracking. Modeled transport of material I

used all available current profile data such that the closest available current data (i.e. primary, P

secondary, or supplemental, SIO, mooring data) controlled movement of a settling particle. In

this scheme, the controlling time-dependent current profile used to transport a particle shifted i

depending on the location of the particle relative to a mooring. Bottom deposition was II,

accumulated by size class over real bathymetry.

m

The differential distribution between material released at Platform Hermosa and Platform Hidalgo

reflects the currents occurring during the different discharge intervals. During the summer/winter

season when Platform Hermosa was releasing muds and cuttings, currents were larger with 11

consequently wider dispersion and an associated larger sediment footprint. These conditions also m

allowed a larger percentage (as compared to Platform Hidalgo) of material to be advected out

of the study area prior to being deposited on the bottom. Because of the amount of material

leaving the area and the larger sediment footprint in combination with relatively small platform B

discharge, the depth of deposition of material from Platform Hermosa was between 1 and 60

microns - a very thin layer - with an average depth of 1.5 microns. I

More material was released from Platform Hidalgo and the smaller more variable currents during IE

the spring season resulted in less dispersion. However, these conditions combined to produce an i

average bottom accumulation of only about five times that at Platform Hermosa, or about 7.5

i

microns. Thevolume of material from either platform was insuffic,ient to produce an identifiable rig

volume or chemical (barium) signal in the sediment traps placed in the depositional footprint |

during the discharge periods.

!

4.5 RECOMMENDATIONS

I

The primary purpose of the physical oceanographic component of Phase III was to provide a J

description of the current regime to which biological, chemical, and sediment monitoring could I[

be related, and to provide current fields for input into a numerical particle tracking model for II

predicting drilling discharges transport and deposition. The present project has been successful

in making continuous times series of current velocity and temperature at three depths for over 'il

two and a half years. Such long-term, continuous records are relatively rare in oceanography []

and, if sufficiently long, can be used to resolve trends and periodic interannual variability. This

is particularly relevant but fairly complex in a transition zone such as the present study area. For I]

these and several other reasons, it would be beneficial if at lea_t the primary mooring was

4-4 I

!
I redeployed to maintain and continue these data records. Any other recommendations on

deployment of additional moorings should be coordinated with measurements available to NBS

I from other major studies, such as the SIO/MMS Santa Barbara Channel and Santa Maria Basin field experiments. Because of the locally short cross isobath coherence scale of currents in the

vicinity of Pt. Arguello seen in data from this study, it would be appropriate and productive to

i investigate and better understand this variability, particularly offshore of the primary mooring.

In a regional context, an improved understanding of this often abrupt transition between current

regimes may have application to other regions in the Southern California Bight, such as the Santa

I MonicaBasin.

i The vicinityoceanographic of Pt. Arguello regimesandthatPt.influence Conception the seas often onal have and other an expression low frequency in thecurrents sea surface in the

temperature field. As shown during the present project, satellite thermal images are one of the

I, fewConsequently, data sourcesSSTthat imagery provide ainsynoptic, conjunctionregional withviewsubsurface of key observations oceanographicofvariable, currents SST. and

temperature can help provide regional scale, three-dimensional descriptions of the oceanographic

I regimes governing local transport patterns.

Because of potential impacts on local hard-bottom communities, partitioning sediment deposition

I between sediments sources is a concern such asin local the present oil andseries gas activities of ecological and from studies.ambient Ambient or background deposition issuspended assumed

to come from either resuspended sediments or from suspended material discharged primarily from

rivers and creeks. Observations to date indicate that suspended sediment events in the vicinity of the hard bottom study sites generally were not from natural, local sources. Rather, these

sediments likely were either resuspended at remote onshore locations and then transported

I towards mouth the measurement sites, or they were transported by the regional circulation from the of a local river or creek.

i To understand better the local sediment budget, it is to know where resuspension necessary

occurs and what causes it. Based on our present knowledge of local conditions, it is

i recommended that future studies measure near bottom currents and suspended sediments concentrations at a cross shelf sequence of stations. This design, in combination with regional

wave observations made by NDBC, should provide information concerning the linkage between

i resuspension events at various depths and both waves and near bottom currents.

Resolving transport of locally discharged suspended sediments requires detailed information on

i the three-dimensional structure of current and sediment concentration fields. Transport patterns can be obtained from either hydrodynamic models or observations. Given the complex and

dynamic nature of circulation in this region, a numerical model(s) should be used to reproduce

i current suspendedpatterns. sedimentThisconcentrations type of modelwould may not needbetopresently be measured available. over atConsequently, least a boundary current gridandat

a resolution determined from time and spatial scales seen in existing and recommended current

I measurements. In conjunction with the material presented in this report, the above scenarios

m 4-5

!
!

|

provide a brief framework for specific recommendations to enhance the understanding of regional U

and local circulation patterns:

I (1) Maintain and continue the primary mooring in its present configuration and

location. I

(2) Deploy a small scale array of current meter moorings (in addition to the primary

mooring) to investigate the cross isobath scales of variability. A possible design n

would be two secondary moorings: one at the $6 mooring site and another on the l

500 m isobath seaward of $6. This could be linked to the coastal currents by

another mooring placed on approximately the 50 m isobath, just seaward of the i

three-mile limit. II

(3) Design and deploy near bottom instrument arrays, such as PMAs, containing III

instruments to measure local instantaneous velocities due to waves and background |

currents, temperature, and suspended load. The arrays should be placed at several

(2-3) inshore locations in 25-50 m of water depth with an objective of better ll_

understanding the role of remote sediment resuspension on deeper hard bottom II

sites. At least one of these could be placed on a shoreward extension of the small

mooringarraydescribedin(2). I

U

(4) Quantify the potential contribution of naturally occurring sources of sediment

which can provide background sediment deposition, i,

(5) Develop information sufficient to characterize modifications to the regional/local

circulation patterns and sediment transport due to the presence of bathymetric

features such as canyons, n

(6) As part of continued modeling of sediment transport, incorporate a sediment N

resuspension module based on contemporary formulations of the combined effects

u

of currents and waves, i

|

(7) Continue collection of satellite thermal imagery te, be used in conjunction with

data from moored and bottom mounted instrumentation. These data provide a

valuable

synoptic view of surface temperature patterns which are closely linked U

to circulation.

i

The above recommendations provide a realistic basis for substantial improvement in !

understanding circulation patterns and processes, and the movement and deposition of suspended

sediments in the study area. This, in turn, provides a expanded basis for resolving and in

partitioning the impacts on local hard bottom communities of sediments originating from ambient II

sources or local oil and gas activities.

I

4-6 |

!
I

t 5.0 REFERENCES

!

Abbott, M. and D. Chelton. 1991. Advances in remote sensing of the ocean. Review of

Geophysics Supplement, U.S. National Report to the IUGG 1987-1990, 571-589. !

Batchelor, G.K. 1952. Diffusion in a field of homogeneous turbulence. II. The relative motion

of particles. Proceedings of the Cambridge Philosophical Society 48:345-362.

Barton, I.J. 1995. Satellite-derived sea surface temperatures: Current status. Journal of

i Geophysical Research 100:8777-8790.

Brink, K.H. and R.D. Muench. 1986. Circulation in the Point Conception-Santa Barbara region.

I Journal of Geophysical Research 91(C 1):877-895.

Cacchione, D.A., W.D. Grant, D.E. Drake, and S.M. Glenn. 1987. Storm dominated bottom

i boundary dynamics on the northern California continental shelf: Measurements and predictions. Journal of Geophysical Research 92(C2): 1817-1827.

I Chelton,California D.B., A. Bratkovich, during R.L. Bernstein, and P.M. Kosro. 1988. Poleward flow off central the spring and summer of 1981 and 1984. Journal of Geophysical

Research 93(C9): 10604-10620.

Coats, D.A. 1994. Deposition of drilling particulates off Point Conception, California. Marine

Environmental Research 37(2):95-127.

I Fischer, H.B., E.J. List, R.C.Y. Koh, J. Imberger, and N.H. Brooks. 1979. Mixing in Inland and

Coastal Waters. Academic Press, New York, New York. 483 pp.

I Fry, V.A. and B. Butman. 1991. Estimates of the seafloor area impacted by sewage sludge

dumped at the 106-Mile Site in the Mid-Atlantic Bight. Marine Environmental Research

i 31: 41-160.

Hamilton, P. and A. Ota. 1993. Assessing effects for disposal sites off San Francisco. Pages

I 14-28, In: M.L. Spaulding, K. Bedford, A. Blumberg, R. Cheng, and C. Swanson (eds.).

Estuarine and Coastal Modeling III, Proceedings of the 3rd International Conference,

I sponsored of Civil Engineers, by the Waterway, Oak Brook,Port, Illinois, CoastalSeptember and Ocean8-10,Division 1993. ofASCE, the American New York,Society New

York. 682 pp.

I, Hickey, B.M. 1979. The California Current System - Hypotheses and facts. Progress in

Oceanography 8:191-279.

|

I 5-1

!
!

Hickey, B.M. 1991. Variability in two deep coastal basins (Santa Monica and San Pedro) off 1

Southem Califomia. Joumal of Geophysical Research 96:16689-16708.

Kidwell, K.D. (ed.). 1991. NOAA Polar Orbiter Data Users Guide. U.S. Department of '_

Commerce, National Oceanic and Atmospheric Administration, Washington, D.C. 281

PP" i

Lynn, R.J. and J.J. Simpson. 1987. The California Current System: The seasonal variability of m

its physical characteristics. Journal of Geophysical Research 92:12947-12966. I

Maier-Reimer, E. and J. Sundermann. 1982. On tracer methods in computational li

hydrodynamics. Pages 198-217, In: M.B. Abbott, and J.A. Cunge (eds.). Engineering |

Applications of Computational Hydraulics, Volume 1. Pitman, Boston, Massachussetts.

McClain, E.P., W.G. Pichel, C.C. Walton, Z. Ahmed, and J. Sutton. 1983. Multichannel I

i

improvements to satellite derived global sea surface temperatures. Proceedings of the

XXIVCOSPAR,Advancesin SpaceResearch2:43-47. i

il

Sleath, J.F.A. 1984. Sea Bed Mechanics. John Wiley & Sons, New York, New York. 335 pp.

i

Steinhauer, M. and E. Imamura (eds.). 1990. Sedimentology. Chapter 4, In: California OCS 'I

Phase II Monitoring Program. Year Three Annual Report. Volume 1. Report No. MMS

90-0055 prepared for the U.S. Department of the Interior, Minerals Management Service,

Pacific OCS Region, Los Angeles, CA. l

Taylor, G.I. 1954. The dispersion of matter in turbulent flow through a pipe. Proceedings of _ll

theRoyalSocietyofLondon,SeriesA 223:446-468. In

Walton, C.C. 1988. Nonlinear multichannel algorithms for estimating sea surface temperature I

with AVHRR satellite data. Journal of Applied Meteorology 27:115-124. up

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, APPENDIXB

i (Platform CHEMICA Discharges, L Sediment MANUSCRIPT and Suspended

l Particles Chemistry, and Particle Fluxes)

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!liIi1!tI
I TEMPORAL TRENDS IN SEDIMENT CONTAMINANT

CONCENTRATIONS ASSOCIATED WITH DRILLING-RELATED

i DISCHARGES IN THE SANTA MARIA BASIN, CA

I Charles Phillips, John Evans, Wilson Hom, and John Clayton*

Science Applications International Corporation

10260CampusPointDrive San Diego, California

*presentaddress: Ogden Environmental and Energy Services

5510 Morehouse Drive

I San Diego, Califomia

I ABSTRACT

i Nine year (1986-1995) records of metal and hydrocarbon concentrations in surficial, subsurface,

and suspended sediments near offshore oil and gas development and production platforms in the

i Santa Maria Basin, California, were analyzed to evaluate the long-term effects of discharges, drilling muds, cuttings, and produced water. Changes in metal and hydrocarbon concentrations

in surficial and suspended sediments were minimal during and after periods of active drilling

i despite period elevated from 1986-1989 levels in thersulted muds and in significant cuttings. Drilling changesduring in bariumn initial(Ba)(Phase concentrations II) monitoringin

suspended particles and surficial sediments, whereas the relatively shorter, 1993-1994 (Phase 1II)

i drilling No effectsoperations resulted in only minor increases in Ba concentrations in suspended particles. from platform discharges or drilling operations on hydrocarbon concentrations were

apparent, although significant increases in PAIt concentrations in surficial and suspended

i sediments were observed during November 1991, possibly due to a petroleum product spill approximately 50 km upcoast from the study area. Depositional fluxes of particles were not

affected by discharges of drilling muds and cuttings. Residual excess Ba was present in

i sediments within 500 m of the platforms at concentrations up to an order of magnitude above background concentrations. These elevated levels probably are associated with cuttings particles

deposited near the base of the platforms. !

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INTRODUCTION !

The Department of the Interior (DOI), Minerals Management Service/National Biological Service 1

sponsored a multiphase program to evaluate the long-term effects of development/production

drilling and platform discharges on deep water (100-200 m), hard-bottom, epifaunal communities /

in the Santa Maria Basin region off central California. The conceptual design of the program l

is described by Brewer et al. (1), Hyland et al. (2,3), and SAIC and MEC (4). An integral part

of this study was measurements of metals and hydrocarbons in platform waste sources and in

bottom sediment and suspended particles in near-bottom layers. The purpose of these 1!

measurements was to determine whether drilling wastes altered the geochemical environment and

represented a significant source of contaminants and toxicity to epifaunal organisms, i.

11w

Phase I of this monitoring program (5) included baseline studies and recommendations of

long-term study sites for hard-bottom communities in the Pt. Conception to Pt. Arguello region _-

(Figure 1). The Phase II program initiated monitoring studies at nine hard-bottom sites near II

Platform Hidalgo, focusing on potential impacts to epifaunal communities from platform

discharges of drilling muds (6). The Phase II study included predrilling, during-drilling, and i

postdrilling periods, with the last drilling activity occurring in January 1989 (Table 1). Drilling U

from Platform Irene occurred from 1986 through October 1989; however, its location over 10 km

to the north of the study area suggested that these discharges had minimal, if any, additional •

effects near Platform Hidalgo (6). The Phase III field program, initiated in October 1991, n

represented the continuation of monitoring near Platforms Harvest, Hermosa, and Hidalgo (Figure

1). The Phase III studies focused additionally on natural and anthropogenic (drilling-related) .•_

factors and processes that may influence spatial and temporal variability in hard-bottom

communities nearPlatformHidalgo.

IIi

Overall Phase HI goals were twofold:

(1) To increase understanding of the environmental fate and effects of chronic, 1

r,

low-level inputs of drilling wastes and their potential for sublethal, long-term,

and/or cumulative impacts to hard-bottom communities; and i

,Hi

(2) To improve knowledge of the fundamental processes controlling natural variability

in the communities. This knowledge is critical because it distinguishes biotic lh

changes associated with natural variability from changes associated with drilling |

discharges.

The Phase 1II study design included assessments of continued (since Phase U) "post"-drilling and n

"during"-drilling impacts. Phase 111provided an opportunity to evaluate further the persistence

of chemical residues (i.e., Ba) from discharges during Phase II, as well as the effects from a

discharge phase of substantially shorter duration and lower mass emissions. II

The Phases II and III drilling operations are summarized in Table 1. Phase III drilling occurred

at two platforms (Hermosa and Hidalgo) over an eight-month period, resulted in drilling/redriUing II

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of 5 wells, and generated a total of 4700 m3 of muds and 875 m3 of cuttings. The drilling

l operations were sequential; therefore, concurrent discharges from the two platforms did not occur during Phase III. Produced water discharges (0.8-1.6 x 10 6 L/day) also were initiated during

Phase III. In contrast, Phase II drilling occurred over a period of 26 months, generated 39 wells,

I and watersresulted were indischarged dischargesduring of 40,700 Phasem3II. of drilling Concurrent muds discharges and 5400 mfrom3 of cuttings; two or more no produced of the

platforms occurred during a significant portion of the Phase II drilling period. This potentially

results in important differences between the two drilling phases in the magnitude of drilling waste

depositionalfluxes.

i relation The purpose t drilling of thisoperations paper is and to describe natural processes, temporal changes primarilyinduring contaminant Phase III. concentrations Results fromin

measurements of metals and hydrocarbons, and modeling of drilling mud discharges during Phase

i IIresidual are described effects fromby Hyland the Phase et al.II(3), drilling Steinhauer and effects et al.from (7), andthe Coats Phase (8). III drilling This paper operations. focuses on

i Study Area

The physical, chemical, and biological characteristics of the study area are described by SAIC

i (5) shoreandto Hyland approximately et al. (2). 110The m depth, generalandregion the continental consists ofslope the continental off southernshelf, California, extendingbetween from

Pt. Conception and Pt. Arguello (Figure 1). The coastal axis and bathymetric contours in the

region approximately are oriented 90 to approximately 215 m. southeast-to-northwest. Bottom study depths range from

i Oceanographic and geochemical characteristics of the study area are influenced strongly by interannual variations associated with drought conditions, such as those that persisted in

California from approximately 1985 through at least early 1991, and E1 Nifio events that occurred

l in 1992 1994. River flow data (9) indicate an approximate four- to tenfold increase in

through

volumes during Phase III, corresponding to water years 1991 through 1994 and up to December

i (1994) of water year 1995 compared to Phase II, corresponding to water years 1987 through 1990. (A water year is defined as extending from October of one year through September of the

following year.)

i The distribution of nearshore and offshore sediments is influenced strongly by discharges of silts,

clays, and sandy materials from rivers and streams, primarily to the north of Pt. Arguello, and

i littoral transport of sands from north and south of the study area (5). Sediment types in the study area range from approximately 35-85% fines and 15-65% sand (6).

tl Natural chemical sources in the study region include hydrocarbon seeps (10, 11). Evidence of

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submarine oil seeps in the Santa Maria Basin includes macroscopic tar particles observed in

bottom sediment samples from Phase II (6) and observations of bacterial mats (Beggiatoa spp.)

i associated sources canwithinclude seeps and atmospheric gas bubblesdeposition, at some hard-bottom tanker/shippingsitesdischarges, (12). Otherandanthropogenic wastewater

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discharges from platforms and vessels. Further, releases to the ocean of several million liters of

a petroleum product (diluent) occurred over a period of several years from the Guadalupe oil

field, north of Pt. Sal and approximately 50 km from the study site. Otherwise, anthropogenic

influences to the coastal area in this region are relatively minor.

!

METHODS AND MATERIALS

This section summarizes methods used for collections and analyses of sediment and suspended I

particle samples for chemical analyses during Phase HI. Detailed descriptions of methods are

provided in SAIC and MEC (4). Sample collection and analytical procedures were in most cases

identical to those employed for Phase II (6, 7) to ensure data comparability between phases. U

Surface sediments were collected at nine sites near the hard-bottom study locations associated _

with Platform Hidalgo (Figure 1). Three separate samples were collected at each station with

a 0.1 m2, Kynar-coated Van Veen grab. The 0--2 cm layer of sediments in each sample was ..

removed from the sampler with a Kynar-coated scoop. The three samples were subsequently /

combined into a single composite for each station. Composite samples of surficial sediments 11

were analyzed for trace metals, hydrocarbons, total organic carbon (TOC), and grain size.

Samples for trace metal and hydrocarbon analyses were placed in precleaned glass jars and stored i_ j

at approximately -20°C until analysis. Samples for analysis of TOC and grain size were placed n

in Ziploc bags and stored at 4°C.

During October/November 1991 and January 1995, a 0.015 m2 box corer was used to collect l..,

surface and subsurface sediment samples from a radial array of stations at distances of 50, 125, ¢,,

250, 500, and 1000 m from Platforms Hidalgo, Hermosa, and Harvest. The surface layer (0-2 I1 cm) was collected and placed in a precleaned glass jar. The subsurface layer (10-12 cm) then

was extruded through the box, collected with the scoop, and placed in a precleaned jar. All ,it

samples were stored at approximately -20°C until analysis. |

Suspended particles were collected in sediment traps from nine stations associated with Platform til

Hidalgo. Sediment trap arrays consisted of a 40-inch diameter cement base with spring supports IN

of stainless steel for four individual traps. Each trap was constructed of butyrate tubing having

Hexcel baffles with 1 cm cell spaces in the mouth of the tube to reduce turbulence. The diameter ilb

of each trap was 6.6 cm, and the height:diameter ratio of the baffle was approximately 7:1. |

Replicate traps were seven diameters apart and the openings were 1 m above the sea bed.

Sodiumazidewasaddedto eachtrapas a preservative. _/

w

Samples from the sediment traps were frozen at approximately -20°C onboard the survey vessel,

except that samples for TOC and particle size measurements were stored at approximately 4°C. _,

Suspended sediments were analyzed for total dry weight (for particle flux calculations); trace |

metal, hydrocarbon, and TOC concentrations; and grain size distributions.

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I Field blanks and equipment rinses were collected at an overall frequency of approximately 5%

of the total number of field samples. In all cases, field QA samples were free from

i contamination.

Drilling mud and cuttings samples were collected by the operators, based on established sampling

instructions, at Platforms Hidalgo and Hermosa. Samples from multiple wells at each of the two platforms subsequently were composited by well depth into surface, mid-depth, near-bottom

(muds only), and bottom samples. Produced water and formation oil samples also were collected

I from Platforms and Hermosa. Muds and for metals, Hidalgo cuttings were analyzed

hydrocarbons, TOC, and grain size; produced waters were analyzed for metals and hydrocarbons;

i and Guadalupe formationoil field oils were also was analyzed analyzed for hydrocarbons for hydrocarbons only.(alkanes, A sample aromatics, of the anddiluent saturated from

biomarkers).

Sediment and suspended particle samples for hydrocarbon analyses were Soxhlet-extracted in

methylene chloride (DCM). Extracts were combined and dried by passing through anhydrous

sodium volumes sulfate, were concentrated, and then solvent-exchanged from DCM into hexane. Final extract reduced and extracts were subjected to liquid-column chromatography for

separation using silica gel into saturated and aromatic fractions. Saturated hydrocarbons were

I initially DCM andelutedacetone with (1:1, hexane; v:v).aromatic Final hydrocarbons extracts for saturated were subsequently and aromatic elutedhydrocarbons with a mixturewereof

concentrated and analyzed by flame ionization detector-gas chromatography (FID-GC) and gas

I chromatography Polycyclic aromatic /mass hydrocarbons spectroscopy-selected (PAHs) ionweremonitoring identifiedmodeand(GCquantified /MS-SIM),using respectively. primary

quantitation ions and accompanying secondary confirmation ions. Final confirmation of target

I analytes suspendedwassediment based onsamples specificalsoretention-time were analyzeddataforforsuites selectedof triterpane compounds.andSelected sterane compounds surface and

(rn/z 191 and 217, respectively) using GC/MS-SIM.

i Laboratory control and matrix spike samples and standard reference materials were analyzed with

every 20 samples or with every sample set, whichever was more frequent. Duplicate analyses

i by FID-GC or GC/MS-SIM were performed with a frequency of one for 20 samples or

every

sample set, whichever was more frequent. Compound quantitation limits for most target saturated

and aromatic analytes were approximately 1-5 ppb and were comparable to or lower than those

I achieved during the Phase U

program.

Samples of sediments and suspended particles for metals analyses were initially freeze-dried and

digested HNO3 at Followingdigestion,the sampleswerediluted

in concentrated and HF 1 30°C.

to final volume with H3BO3. Sediment, suspended particl e, and drilling muds and cuttings

i samples for Ba analyses were dried, placed in heat-sealed polyvials, and irradiated (thermal neutron flux of lxl013 n/cm2/sec) with a Triga Reactor. Digested samples were analyzed by

FAAS (A1 and Cr), GFAAS (As, Ag, Cd, Cu, Pb, Ni, and Zn); CVAAS (Hg), and INAA (Ba).

i Analyses were performed of procedural at the same blanks, frequencies duplicatesas and for hydrocarbon matrix spikes,analyses. and certified reference materials

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TOC analyses were performed using a combustion method and infrared spectroscopy. QA/QC I

analyses were performed in conjunction with field samples and consisted of duplicate analyses,

surrogate spikes, and external reference standards that were analyzed with every sample set at \l]

a frequency of 10%. W

Monthly platform discharge data were obtained from Discharge Monitoring Reports submitted i

by the operators to the U.S. Environmental Protection Agency (EPA), Region IX. Additional

daily discharge reports and drilling mud inventories were obtained from the operators.

i

Statistical analyses, including linear regression, t-tests, and analysis of _,ariance (ANOVA), were

used to evaluate spatial and temporal trends and relationships between different physical and i

chemical variables. Principal component analysis (PCA) was performed on PAH and biomarker I

data for selected formation and seep oils, the Guadalupe diluent, and suspended particle samples

to evaluate potential hydrocarbon sources to the suspended materials. Excess Ba in sediments ill

near each of the three platforms was calculated from measurements in surface and subsurface I

sediments at the radial array of stations using the procedure developed by Boothe and Presley

(13). The excess Ba was calculated by subtracting the background Ba concentration from the II

measured concentration. The background concentration was interpolated over the nearfield region II

of the platform from subsurface sediment concentrations at sites 500 m and 1,000 m from the

platform. This approach was used to account for the depth-related gradient in sediment Ba '/

concentrations. The volume of sediment containing "excess Ba" was calculated by multiplying i

the area described by a linear decrease with depth to a presumed background in Ba

concentrations by a unit surface area. Based on the Phase HI data, the linear decrease with depth II

represents a reasonable approximation of sediment Ba profiles reported by Crecelius (14) from _

the Phase II program. Unit volumes were multiplied by the sediment density (assumed to be

2.6 g/cm 3) and the excess Ba concentration. Excess Ba (in kg) was summed for all unit areas

within 500 m of Platform Hidalgo. In two cases, highly elevated Ba concentrations were not

included because they were considered unrepresentative of spatial trends and artificially skewed

thecalculation, i

RESULTS i

Chemical Compositions and Mass Emissions of the Platform Wastes /b

I

The drilling mud formulations used during the Phase HI drilling activities contained

approximately 40% by weight of barite, 24% bentonite, and <10% each of potassium chloride m

and carbonate; other additives comprised approximately 25% of the total dry weight. These I

formulations were similar to those used during Phase II drilling operations. Metal and

hydrocarbon concentrations in muds and cuttings, composited over specific well depth ranges for II_

Platform Hidalgo are listed Tables 2 and 3, along with the corresponding concentrations for I

samples analyzed during Phase II. Contaminant levels typically increased with well depth.

Specific metal and total hydrocarbon concentrations (THC: sum of resolved and unresolved II

components) in the Phase HI muds and cuttings generally were comparable to those in platform

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waste materials discharged during Phase II (3, 7). Differences in concentrations of some

constituents between drilling phases of up to an order of magnitude occurred for various well

I depths (e.g, Ba and THC in muds from the bottom well depths), presumably due to differences in downhole conditions and changes in the specific drilling mud formulations. Hydrocarbon

compositions, particularly the patterns and relative concentrations of alkanes and parent and

i PAHs, of muds and cuttings resembled those of the formation oil, indicating that alkylated

hydrocarbons in waste material probably were primarily from the formation instead of mud

additives (Figure 2).

I Barium was the only metal in muds and cuttings that was consistently elevated relative to crustal

i abundances (Table 5). Barium concentrations in muds were up to two orders of magnitude higher than background concentrations in surficial sediments; concentrations of other metals generally

were within 2-3 times the background sediment concentrations. Elevated Pb and Zn

t concentrations occurred in selected cuttings samples, probably due to contamination from mud additives.

l Concentrations typically were below of individual 1 mg/L, metals with thein exception produced ofwaters Ba which from ranged PlatformsfromHermosa 5.2-16 mg and/L.Hidalgo Total

hydrocarbon concentrations ranged from 2.2-33 mg/L. Other than the more soluble naphthalenes,

I PAHs concentrations in the produced ranged waters from 0.3-0.4 generallymg/were L. at or below the detection limits; total PAH (EPAH)

Mass cuttingsemissions dischargesof atindividual Platform Hidalgo metal andranged hydrocarbon from 0.3-120,000 componentskg (Table from Phase 4). Produced III mudswater and

discharges from Platform Hidalgo represented additional emissions of 5720 kg Ba/yr, 779 kg

l THC/yr, and 112 kg PAH/yr. Deck drainage, cooling waters, and sanitary wastes also were discharged at the platforms, although the mass emissions associated with these waste sources are

expected to be relatively small. Phase III mass emissions were typically lower, but within an

i order Platforms of magnitude, Harvest andofHermosa, those fromdischarges Phase II.of muds Assuming and cuttings proportional duringmass the Phase emissions II andfromIII

drilling operations combined represented contaminant emissions ranging from approximately 3.6

i kg (Hg) up to 1.8xl06kg (Ba), as well as 30,000 kg THC and 830 kg PAH. With the exceptions of Ba and Zn, mass emissions associated with platform discharges were up to several orders of

magnitude lower than mass inputs associated with natural riverine flow and oil seeps (Table 4;

I ref6).

Sediment Fluxes

I

During Phase III, particle fluxes (mass dry weight per unit area and time) in sediment traps at

the nine monitoring stations ranged from 18-91 g dw/m2/day (Figure 3). Shallower sites

l typically exhibited relatively greater fluxes, as well as smaller median grain size and higher

percentages of fines (<62 um diameter particles), than deeper stations. Depth-related trends are

i expected at the shallower due to thecompared generally tofiner deeper grainsites. size andParticle predictedfluxeshigher measured rate of sediment by sediment resuspension traps on

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physical measurements arrays deployed at nearfield and farfield sites (15) were similar to those i

collected at the monitoring sites. Specifically, fluxes in the upper traps (1.5 m above the bottom)

at the nearfield and farfield sites ranged from 18-25 g/m2/day and 23-33 g/m2/day, respectively, \/

during the three deployment periods. Bottom traps(1.0 m above the bottom) at the nearfield and W

farfield sites collected 30--38 g/m2/day and 3A.44 g/m2/day, respectively. For comparison, the

range in particle fluxes measured during Phase II, 1986-1990, (120-90 g/m2/day; ref 6) was !

consistent with those measured during Phase III. mr

at individual monitoring stations were reasonably constant over time with a few I

Fluxes

exceptions, presumably related to natural sediment resuspension and transport events. Temporal

and spatial variability appeared to be unrelated to drilling operations. The highest fluxes at the i/

110-120 m stations occurred between October 1989 and May 1!;190,coinciding with a post- |

drilling phase and relatively low river flow. Relatively higher fluxes occurred at Stations PH-K

and PH-N during August 1993-January 1994, overlapping with drilling operations at Platform II!

Hidalgo (from November 1993 to May 1994). However, due to the short period of overlap, and J

limited emissions, this relationship to drilling is probably coincidental. Similarly, SAIC and

MEC (15) observed that trends in concentrations of suspended particles in near-bottom waters I

during Phase HI were unrelated temporally with periods of drilling operations. II

Metals in Surficial and Suspended Sediments Imr

With the exception of Ba, surficial and suspended sediment metal concentrations generally

reflected average crustal abundances and, therefore, were equivalent to the respective background II

concentrations (Table 5) as reported from other studies in the Santa Maria Basin (5,7), western I!

Santa Barbara Channel (5,16-18), and Southern California Bight (119-21). Over the nine-year

monitoring period, changes in Ba concentrations in suspended particles were the most prominent II

geochemical effect attributable to the drilling discharges (Figure 4). However, during Phase III,

trends in Ba concentrations in suspended and surficial sediments at the nine monitoring stations

were relatively constant. For example, during the post-Phase II drilling period (October m

1989-August 1993), Ba concentrations in suspended sediment samples ranged from 582-815 III

ppm, consistent with expected background levels (e.g, refs 5, 7). Barium concentrations in

sediment trap samples ranged from 404-913 ppm during surveys coinciding with the subsequent i

(Phase III) drilling period (September 1993-May 1994). Barium concentrations in suspended 411

particles collected during January 1994-January 1995 at near-platform Stations PH-I, -K, and -N

were relatively higher (867-913 ppm) than those at the other monitoring stations (653-757 ppm). |

However, differences between surveys that coincided with Phase III drilling for five pooled

nearfield stations (PH-I, -J, -K, -N, and -R) were not statistically significant (ANOVA, p>0.05). I

These results indicate minimal effects from drilling mud fluxes during Phase III. R

Using the approach of Hyland et al. (3), drilling mud dep0sitional fluxes over the nine-year _.

monitoring program were calculated from the excess Ba concentrations in sediment trap materials |

(Table 6). The Phase II depositional fluxes from Hyland et al. (3) were recomputed based on

the lowest Ba concentration measured during the combined Phase II/Phase III periods. Mean and /

maximum depositional fluxes for moderate and high flux (i.e., near-platform) stations during the II

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I Phase HI drilling period were substantially lower than those estimated for the Phase II drilling

period. Phase III drilling depositional fluxes at the high flux stations were only a factor of two

times greater than post-drilling fluxes, and depositional fluxes at the low and moderate flux (i.e., up to several kilometers from the platform) stations during the Phase III drilling period were

essentially unaffected by the platform discharges.

i During October 1991 through January 1995, sediment Ba concentrations at the five nearfield

stations ranged from 724-1090 ppm. The highest concentrations, averaged over the three Phase

III occurredat StationsPH-I and PH-J (950-990 ppm). Comparedto premonitoring surveys,

drilling levels defined by Steinhauer et al. (7) and SAIC (5) (i.e., approximately 700-800 ppm),

i mean concentrations were consistently higher at most stations during drilling and post-drilling surveys (Figure 4). However, differences between surveys for the Phase III period were not

statistically significant (one-way ANOVA on ranks; p>0.05).

I Some statistically significant differences between siarveys were apparent for concentrations of

other metals such as Pb (ANOVA; p<0.05). However, based on the results of multiple

i comparison drilling periods. tests Despite (SNK orelevated Dunns concentrations method) thereofwere Pb andno Znsignificant in selectedtemporal cuttingsrelationships samples, thereto

was no corresponding evidence of altered concentrations for these metals in surficial or

I suspended cuttings to sediments. background Based sediment o similarities concentrations between(Table concentrations 5), little orofnoother dtectable metals ineffects mudsfromand

platform discharges would be expected (7).

I Measurements of Ba concentrations in surface and subsurface sediments at near-platform

locations were performed to evaluate residual inventories and residence times of excess Ba.

I During from 770-1700 Novemberppm1991, andBafromin surface 570-1170and ppm, subsurface respectively. sedimentsThenearhighest PlatformBa Hidalgo concentrations ranged

occurred within 50 m of the platform. The magnitude of the Ba concentrations, as well as the

i Ba/A1 ratios, indicated the presence of residual Ba within 1 km of the platform. Elevated Ba/A1 values (approximately 200-300 x 104) were apparent in surface sediments at distances up to 125

m from the platform in alongshore and offshore directions. In contrast, Ba/A1 values from

I subsurface sediments were consistently <200 x 10 4 and essentially equal to the baseline ("pollution-free") Ba/A1 range of 125-175 x 10 4 defined by Finney and Huh (20, 21) for San

Pedro and Santa Monica Basins.

In January 1995, Ba in surface and subsurface sediments near Platform Hidalgo ranged from

853-9699 ppm and from 667-964 ppm, respectively. With the exception of two surface sediment

I from the 125 m radius of stations, Ba/A1 values in all other core samples were <200 x

samples

104 .

Concentrations of Ba >1600 ppm also occurred during October January

1991 and 1995 in surface

and subsurface sediments within 125 m of Platforms HermoSa and Harvest. Several of the

i samples with the highest Ba concentrations, including a subsurface sediment sample with 30,510

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ppm Ba collected 125 m from Platform Harvest, likely contained cuttings particles coated with I

drilling muds. II

Differences between the 1991 and 1995 samples in Ba concentrations in surface and subsurface

sediments within 1000 m of the three platforms are shown in Figure 5. Negative differences,

indicating decreases in mean Ba concentrations between 1991 and 1995 occurred at most |

platform, depth, and distance combinations except in surface sediments >._250m from Platform

Hidalgo. The greatest change in surface Ba concentrations occurred at sites within 50 m of the IL

platforms. Also, the relative change in Ba concentrations at the 50 m sites near Platforms |

Hidalgo and Hermosa, where drilling occurred, was comparable to that of Platform Harvest where

no Phase IB drilling occurred. /

It

Hydrocarbons in Surficial and Suspended Sediments

Sediment and suspended particle hydrocarbons measured during Phase 1II reflected a complex I

mixture of petrogenic, biogenic, and pyrogenic (i.e., combustion-derived) sources. These various

input sources were characterized by a large chromatographic hump, corresponding to an II

unresolved complex mixture (UCM) of weathered branched and cyclic hydrocarbons, dominant II

terrestrial plant wax n-alkanes (nC27, C29, C31), the diagenetic PAH perylene, and other 4- and

5-ring PAHs from combustion and runoff sources. Similar features have been described in

sediments and suspended particles from the Santa Maria Basin (5, 7, 22, 23), western Santa m

Barbara Channel (5, 11, 24-26), and Southern California Bight (27, 28). Characteristics and

concentrations of hydrocarbons in bottom and suspended sediments during the Phase III period

generally were comparable to those described by Steinhauer et al. (7) for the Phase II period. q

There were no trends in key hydrocarbon parameters obviously related to periods of active ,/

drilling (Figure 6). During Phase III, mean concentrations of THC in suspended and surficial

sediments at the nine nearfield stations ranged from 32-207 ppm and from 36-250 ppm,

respectively. Corresponding concentrations measured during Phase 1I were 48-524 ppm and

24--217 ppm, respectively. The highest THC concentrations in suspended sediments occurred II

during May 1988-May 1989, during Phase II drilling at Platforms Hermosa and Hidalgo. This ml

after Ba concentrations had started to decline from maximum levels in May-October 1987. was

ANOVA of THC normalized to organic carbon in surficial and suspended sediments from the

five nearfield stations indicated significant differences between surveys. However, multiple ill

comparison tests did not reveal any significant temporal patterns related to the Phase II or Phase l

I11 drilling periods. Further, as noted by Steinhauer et al. (7), there was no evidence from

compositional features of the hydrocarbon samples that increases of THC in suspended sediments II

during Phase II drilling were related to platform discharges. 1!

Based on results of ANOVA, sediment EPAH concentrations during the November 1991 survey I1_

were significantly higher (p<0.05) than those during all other surveys. The mean EPAH !

concentration in bottom sediments was 3.0 ppm, with a maximum concentration of 7.0 ppm.

Mean EPAH concentrations in bottom sediments decreased to presumed background levels (i.e., II

0.1 ppm) by October 1992. The mean EPAH concentration in suspended sediments collected in II

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I November 1991 was 0.7 ppm, and the highest concentration was 1.1 ppm. Concentrations of

ZPAH in suspended particles also declined during subsequent surveys but remained at or above

I, 0.2 ppm through January 1995 (Figure 6). By comparison, between May 1988 and October 1990, and throughout the period of Phase II drilling, mean ZPAH concentrations in surficial and

suspended sediments from the nine sites were <_0.1 ppm. Prior to the start of drilling (during the

I May 1987 survey), higher EPAH concentrations occurred in sediment traps at nearfield Station PH-I and farfield Station PH-U (0.9 ppm and 1.1 ppm, respectively). Relatively higher ZPAH

concentrations (up to 1.5 ppm) also occurred in surficial sediments at several sites during the

l October 1986 survey--also prior to initiation of drilling. Statistically significant differences

between surveys inZPAH concentrations in suspended sediments also were evident (ANOVA,

i p<0.05), although patterns related to drilling periods or other events could not be discerned from multiple comparison tests. In contrast, concentrations of the higher molecular weight PAHs (i.e.,

4- and 5-ring compounds) and perylene in suspended and surficial sediments remained relatively

constant emissions over of PAHs the nine-year and naturalmonitoring period (Figure 5), suggesting that combustion/runoff (diagenetic) sources remained uniform.

i Temporal exemplifiedtrends by patterns in the lower at Stations molecularPH-Nweight andPAHs PH-R and chrysenes during Phase III are further (Figure 7). Alkylated naphthalenes and

fluorenes were primary components of the ZPAH during November 1991. However, the

I abundances ratios of PAHs of these observed PAHsin declined the November substantially 1991 samples during subsequent were appreciably surveys.different Abundances from those and

reported for Phase II (7).

During the Phase III November 1991 survey, several of the surficial and suspended sediment

samples exhibited features characteristic of a fresh (i.e., unweathered) hydrocarbon product.

Specifically, elevated concentrations (up to several hundred ng/g per compound) of naphthalenes, fluorenes, and phenanthrenes, especially the C 1 through C4- alkylated homologues, occurred

sporadically in both surficial and suspended sediments. Because no drilling occurred during this

i time, the presence of fresh petroleum was attributed to sources other than platform discharges. Further, the presence of the triterpane 17o_,2213,28,30-bisnorhopane, which is a unique biomarker

for Monterey formation crude oils (25), suggested a locally sourced oil. During Phase II,

I Steinhauer et al. (7) noted sporadic evidence for petroleum hydrocarbons in suspended sediments, and attributed these occurrences to the presence of seep oils and/or tar balls. However, elevated

naphthalenes and enriched n-alkanes within the C13 to C23 range in the November 1991 samples

I were inconsistentwith expectedcharacteristicsof oil 1, 26, 29). levels

seep (1 Notably higher

of tricyclic terpanes and short-chain (Cz0 and C21) steranes also were present in suspended

sediments from selected stations. These patterns are suggestive of a petroleum product, such as

I a fuel, a Monterey withthe compositionof the

diesel from formation oil and consistent

Guadalupe diluent (30).

Results from PCA of selected source and suspended sediment samples indicated contributions

from multiple hydrocarbon sources, including Guadalupe diluent, seep oils, and combustion

t materials, (designatedtonlsuspended and rl, respectively, particles collected in Figureat Stations 8). Bivariate PH-N plots and PH-R of PCAduring axesNovember 1 and 2, which 1991

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explained 58% and 14% of the variance, respectively, show distinct differences between samples I

n l and rl relative to samples collected at Stations PH-N and PH-R during subsequent surveys

and to all suspended sediment samples collected at Station PH-IC Differences along PCA axis _l_

1 are related primarily to enrichment in 4- and 5-ring PAHs (positive values) and enrichment in

alkylated naphthalenes, alkylated dibenzothiophenes, and lower molecular weight tricyclic

terpanes and steranes (negative values). The Guadalupe diluent contained elevated concentrations II

of alkylated naphthalenes and lower molecular weight terpanes and steranes. Samples n 1 and rl

also exhibited greater similarities to the diluent, and separation from the seep and formation oils, /

in bivariate plots of PCA axes 2 and 4. Groupings of samples nl and rl along with the diluent I!

corresponded to enrichment with alkylated fluorenes and Cz9-C21 terpanes. Thus, the separation

of samples n 1 and rl from other suspended sediment samples reflected differences in the relative

contributions of lower and higher molecular weight PAHs from petroleum and combustion 11

sources, respectively (e.g., ref 31). Although the suspended sediments exhibited contributions

from multiple hydrocarbon sources, the PCA results clearly demonstrate similarities between I_

samplesnl andrl andthediluent. m

DISCUSSION I

EffectsonGeochemicalCharacteristics 1

mW

Discharges of muds, cuttings, and produced waters from the Phase III drilling and production

operations had minimal effects on contaminant concentrations in bottom and suspended _l

sediments. During 1991-1995, no residual effects from the Phase II drilling or from the limited g

Phase III drilling were evident in the metal concentrations. The exception was slightly elevated

Ba concentrations in sediments, presumably from previous Phase II discharges of cuttings, in the ,/

immediate vicinity of the platforms. Further, no residual effects from drilling or discharge

operations on sediment and suspended particle hydrocarbon concentrations were evident during

Phase III. Hydrocarbon concentrations in suspended and surficial sediments reflected changes II

in natural background sources (natural seeps and biogenic materials) and, during October

1990-November 1991, the possible effects of a petroleum product (diluent) spill approximately lira

50 km from the study site (30). I

During the Phase II drilling period, platform discharges resulted in increased Ba concentrations h,

of 10--40% in surface sediments and 200-300% in suspended particles (7). Elevated Ba |

concentrations in suspended sediments persisted throughout the drilling period, and then

decreased within a period of 1-1.5 years to background concentrations. In contrast, Ba II

concentrations in surface sediments did not return to pre-drilling levels, but remained l

approximately 10% higher than background. The Phase 1I drilling operations did not significantly

alter concentrations of other metals or hydrocarbon constituents in surficial sediments or U_

suspended particles (3, 7). |

The absence of altered metal and hydrocarbon concentrations--other than Ba--is attributable to II

several factors. Concentrations of metals in the drilling muds and cuttings, except for enriched II

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I Ba and occasionally elevated Zn and Pb in contaminated cuttings, generally were comparable to

background concentrations for bottom sediments. Consequently, platform wastes were not

l expected to substantially alter the concentrations of metals other than Ba (7). Hydrocarbons in the study area are characterized by a large and temporally variable background signal. The

petroleum hydrocarbons most highly enriched in the platform wastes, particularly the lower

I molecular weight PAHs (e.g., unsubstituted and alkylated naphthalenes), are relatively soluble and, therefore, are expected to be released readily from the particulate to the dissolved phases

of discharged drilling mud (32). Although concentrations of these hydrocarbons were present in

muds and cuttings at concentrations to several orders of above up magnitude background

sediment concentrations, the absence of corresponding increases in concentrations in suspended

i and surficial sediments was attributed to losses from selective solubilization and/or microbial degradation of these less refractory compounds. Consequently, the ratios of hydrocarbons to Ba

in dispersed muds and cuttings were expected to change with time, and depositional fluxes of

i PAHs would not be proportional to those of Ba. Finally, since the mass emissions of contaminants from the Phase III drilling operations were substantially lower than those during

Phase II, and the three platforms did not discharge wastes concurrently, significant alterations in

l the geochemical conditions--other than increases in Ba concentrations--were not expected.

Because average Ba concentrations in waste materials were up to 150 times higher than

I background to natural orlevels, cuttingsandparticles Ba is relatively likely would insoluble, be evident subsequent from deposition measurementsof barite of theor BaBa signature adsorbed

in bottom or suspended sediments (33). In contrast, the saturated and PAH compounds

I traditionally might be affected used byas diagnostic platform discharges, of relativelywerenon-weathered rarely observedpetrogenic in surfacehydrocarbons, sediments or and suspended which

particles during or after drilling. Any contributions from platform discharges to concentrations

I of petroleum hydrocarbons either were masked by the dominant background signal of hydrocarbons from natural sources (e.g, local oil seeps) or reduced due to solubilization and/or

weathering.

i Drilling Mud Inventories

I Modeling of drilling mud discharges, based on the actual discharge rates and particle sizes of muds used during Phase III, predicted that approximately 50% of the total mass of muds

discharged would be advected out of the study area and, therefore, would not contribute

substantially to the drilling mud deposition flux (15). These estimates be reasonable appear to

given the generally high water content and predominant fine grain sizes of the drilling muds and

the vigorous currents off Point Arguello that disperse and transport suspended particles (15). Of

I the total mass of drilling muds predicted by the model to be within the deposited study area, only

the coarse fraction would be deposited near the platforms. Silt and clay-sized particles were

, predicted Platform Hidalgo to be widely woulddispersed. be deposited Coatsnear (8) also the base assumed of thethatplatform. 20% of theFurther, muds discharged based on actual from

Phase III discharges at Platforms Hermosa and Hidalgo, and corresponding current patterns, mean

i depositional relatively largethicknesses areas of ocean of drilling bottom.mudEstimated were predicted maximumto depositional range from thicknesses 1.5-7.3 microns of 59over and

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456 microns were associated with discharges at Platforms Hermosa and Hidalgo, respectively. I

The mean drilling mud deposition thickness would result in upper ]limit increases in sediment Ba

concentrations of approximately 1%, based on assumed drilling mud and sediment densities of _11

4.5 g/cm 3 and 2.6 g/cm 3, drilling mud and background sediment Ba concentrations of 50,000 ppm

J

and 800 ppm, respectively, and a sediment mixed layer of 10 cm thickness (ref. 14). Increases

in Ba concentrations up to 1.5 times above background (i.e., 1200 ppm) would be associated with _i

the predicted maximum depositional thicknesses. Based on measured Ba concentrations in w

drilling muds, suspended sediments, and surface sediments, Hyland et al. (3) estimated that /

discharged drilling muds comprised 2.0% of the suspended particle flux and 0.32% of the surface I

sediments at Station PH-J during Phase II. Relative to the Phase III estimates, the higher Phase

II contributions probably were due to concurrent discharges from multiple platforms. Boothe and

Presley (13) noted that effects from multiple well discharges on the mass of excess Ba in near- 1

platform sediments were directly additive; whereas, CSA (34) concluded from studies in the Gulf

of Mexico that discharges from multiple wells affected the thickness of deposited particles but III

not the magnitude of Ba enrichment in surficial sediments. I

The calculated total excess Ba in sediments within 500 m of Platform Hidalgo in November 1991 II

and in January 1995 was 52,200 kg and 53,100 kg, respectively (Table 7). The total mass of Ba I

discharged during the Phase II and Phase III drilling operations at Platform Hidalgo was 520,000

kg. Thus, the calculated excess Ba in sediments within 500 m of the platform during October I_

1991 and January 1995 represents 13% and 10% of the original discharges associated with Phase !

II and with Phases II and III combined, respectively. These values probably overestimate the

residual Ba because contributions of Ba associated with drilling mud particles advected from I

Platforms Harvest and Hermosa are significant (7). Boothe and Presley (13, 35) reported I

inventories of excess Ba within 500 m of platforms in the Gulf of Mexico ranging from 1.5-12%

of the total Ba used in drilling operations. They concluded that depth-related differences in the

magnitude of sediment resuspension and transport were the primary variables controlling the II

magnitude of excess Ba contained in bottom sediments; a relatively greater mass of excess Ba

was retained in the vicinity of deeper than shallower platforms. The length of time since drilling Ill

operations ended had little effect, over the duration of the study, on the magnitude of the excess

I

sediment Ba.

II

Differences between the November 1991 and January 1995 excess Ba inventories near Platform

Hidalgo were negligible, suggesting that the net loss in Ba due to sediment mixing or _,

resuspension and transport was essentially equal to the Ba accumulation associated with Phase |

III discharges. The total excess Ba, and percentages of the total Ba mass emissions, in sediments

near Platform Hermosa were comparable to those at Platform Hidalgo (Table 7). The absolute t

change between 1991 and 1995 in excess Ba (-15%; Table 7) was appreciably greater than that I

at Platform Hidalgo, reflecting the relatively lower Ba emissions during Phase El. Because no

Phase ]I1 drilling occurred at Platform Harvest, the difference between the 1991 and 1995 excess j_

Ba inventories was relatively higher (-25%), and represented an apparent loss of 20,000 kg of |

Ba from sediments within 500 m of the platform.

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I The residual Ba near Platform Hidalgo likely was associated with the heavier cuttings particles

and coarser grained particles in the muds that were deposited near the base of the platform. In

I fact, of thethetotal residual Ba mass Ba inemissions near-platformassociated sediments withduring cuttingsJanuary discharges 1995 (53,100 (i.e., 60,000 kg) waskg;within Table15%4).

This difference is probably within the error range of the estimate. Similarly, Boothe and Presley

I (13) concluded that much of the Ba within 500 m of platforms in the Gulf of Mexico probably

was associated with cuttings, instead of muds, because discharged drilling muds were likely to

be transported distances >500 m (in water depths greater than 40-50 m) before the particulate

I fractionsettled. Similarpredictions madefor of from

were dispersion cuttings discharged

platforms in 15-72 m of water off Nova Scotia (37).

i The slightly elevated (by approximately 10%) Ba concentrations in surficial sediments at the nine

monitoring stations suggest that some residual excess Ba also was present outside of the 500 m

i radius area canof ntheot platforms. be extrapolated The t

from otal excess the present Ba (orstation drillingarray. mud residue) remaining within the study

Data GEOPROBE collectedmeasurements during Phaseat III a sitefromapproximately the physical50 measurements km upcoast (38),arrayindicate (15),that as well currentsas

with sufficient energy to resuspend and transport bottom sediments are uncommon at the depths

of the platforms. Therefore, decreases in the present residual excess sediment Ba presumably 210 will be related more to mixing and dilution by newly deposited sediments. Based on Pb

measurements, Crecelius (14) estimated conservative sedimentation rates for the region of 0.2-0.3

I cmapproximately /yr. At these5-10%rates,perpredicted 10 years. decreases Similarly,inrecent excessstudies Ba concentrations in the Gulf ofwould Mexicobe (ref. small-- 36)

concluded that little change in Ba enrichment is expected in deeper water (_>_50-70m)

I depositional environments after periods of 5-10 years following cessation of discharges. Additional monitoring will be required to determine whether these predictions also pertain to the

Santa Maria Basin region.

!

CONCLUSIONS

i Only minor alterations of the geochemical environment were attributable to Phase III platform

drilling operations off Point Arguello. The Ba signal in suspended particles--which was the most

I sensitive chemical signature of platform waste discharges during Phase II--was minimal during Phase III. The absence of significant changes in the chemical compositions of suspended and

surficial sediments likely was due to several factors including minimal enrichment of most metals

I wastematerials,solubility weight drillingmuds,large

in of lower molecular PAHs contained in

natural variability in background hydrocarbon concentrations, relatively low discharge volumes,

I high dispersion of drilling muds, and the absence of simultaneous discharges from multiple platforms associated with Phase III drilling. Based on these observations, deposition of

particulate contaminants from platform discharges should have negligible impacts to the deepi water, epifaunal communities in the Point Arguello region. Other, short-term increases noted for lower molecular weight PAHs during November 1991 appeared to be related to a spill of

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petroleum product tens of kilometers from the study site and not due to drilling or platform !

discharges.

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ACKNOWLEDG EM ENTS

i This program was funded by the U.S. Department of the Interior, Minerals Management

Service/National Biological Service under Contract No. 14-35-0001-30584 to Science

i Applications of the operators Intemational of the vessels Corporation. M/V INDEPENDENCE The authors wish toandacknowledge M/V RAMBO; the support T. McDonald and help

(TAMU/GERG) for coordinating the chemical analyses; R. Requejo (PRA) for performing the

I PCA; for assistance D. Heilprinin providing (SAIC) forcopies assistance of platform with theDischarge graphics;Monitoring Eugene Bromley Reports;(EPA, DanRegion KnowlsonIX)

(MMS) for assistance in obtaining platform waste samples and daily platform discharge logs; and

I R. diluent. RickerComments (CDFG/OSPR) providedfor byproviding A. Lissner, a sample, J. Brooks, and funding D. Boesch, for and analyses, S. Benech of theonGuadalupe an earlier

version of this manuscript were very beneficial.

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1

LITERATURE CITED i

(1) Brewer, G.; F. Piltz; Hyland, J. Proceedings, 1989 Oceans Conference. MTS _ll

Washington, D.C., 1989. W

(2) Hyland, J., D. Hardin, E. Crecelius, D. Drake, P. Montagna, M. Steinhauer. Oil and I

Chem. Poll. 1990, 6, 195-240.

(3) Hyland, J.; Hardin, D.; Steinhauer, M.; Coats, D.; Green, R.; Neff, J. Mar. Environ. Res. t

1994, 37, 195-229.

(4) SAIC and MEC (Science Applications International Corporation and MEC Analytical 1

Systems, Inc.). Monitoring Assessment of Long-Term Changes in Biological

Communities in the Santa Maria Basin: Phase III. Final "Year One Report to the U.S. i_

Department of the Interior, Minerals Management Service, Pacific OCS Region, |

Camarillo, California, under Contract No. 14-35-0001-30584. 1993.

(5) SAIC. Assessment of Long-Term Changes in Biological Communities of the Santa Maria I

i

Basin and Western Santa Barbara Channel-Phase I. Final Report (Volumes MMS 86-

9911 and MMS-9912) to the U.S. Department of the Interior, Minerals Management t

Service, Pacific OCS Region, Los Angeles, California, under Contract No. 14-12-0001-

30032. 1986.

(6) Steinhauer, M.; Imamura, E. (eds.). California OCS Phase II Monitoring Program, Year 1

Three Annual Report. Report to the U.S. Department of the Interior, Minerals

Management Service, Pacific OCS Region, under Contract No. 14-12-0001-31262. 1990. I

(7) Steinhauer, M.; Crecelius, E.; Steinhauer, W. Mar. Environ. Res. 1994, 37, 129-163.

(8) Coats, D. Mar. Environ. Res. 1994, 37, 95-127. t

(9) USGS (United States Geological Survey). Water Resources Data Guide, California Water i

Years 1988-1994. 1988-1993, 1994. Q

(10) Allen, A.; Schlueter, R.; Mikolaj, P. Science. 1970, 170, 974-977. J

(11) Reed, W.; Kaplan, I. J. Geochem. Explor. 1977, 7, 255--293. I

i

(12) Lissner, A. et al., pers. obs., October 1992.

(13) Boothe, P. and B.J. Presley. Distribution and Fate of Drilling Fluids and Cuttings Around I

Gulf of Mexico Sites. Final Report to the American Petroleum Institute, Washington,

D.C.,1985. i

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(14) Crecelius, E. Chemical analysis of trace metals in sediments, pore waters, and animal

tissues. In: California OCS Phase II Monitoring Program, Year Three Annual Report.

t Steinhauer, Minerals Management M. and E. Imamura (eds.) Report to the U.S. Department of the Interior, Service, Pacific OCS Region, under Contract No. 14-12-0001-

31262. 1990.

I (15) SAIC and MEC. Monitoring Assessment of Long-Term Changes in Biological

Communities in the Santa Maria Basin: Phase III. Final Report to the U.S. Department

i of the Interior, Minerals Service, Pacific OCS Management Region, Camarillo, California,

under Contract No. 14-35-0001-30584. 1995.

I (16) Bruland, K.; Bertine, K.; Koide, M.; Goldberg, E. Environ. Sci. Technol. 1974, 8, 425--432.

1 (17) Ng, A.; Patterson, C. Geochim. Cosmochim. Acta. 1982, 46, 2307-2321.

z.-

i (18) Chow, Sediments. T. andSouthern J. Earl.California Trace Metal BaselineDistribution Study, Benthic in Southern Year 2California Final Report, OCSVolume Benthic2

(SAI-77-917-LJ). Report to the U.S. Department of the Interior, Bureau of Land

Management.1979.

(19) Katz, A.; Kaplan, I. Mar. Chem. 1982, 10, 261-299.

I (20) Finney, B.; Huh, C. Environ. Sci. Technol. 1989, 23, 294-303.

(21) Finney, B.; Huh, C. Mar. Poll. Bull. 1989, 20, 181-187.

(22) Curiale, J.; Cameron, D.; Davis, D. Geochim. Cosmochim. Acta. 1985, 49, 271-288.

I (23) Kennicutt, M.; Brooks, J. Appl. Geochem. 1988, 3, 573-582.

I (24) Crisp, P.; Brenner, S.; Venkatesan, I.; Ruth, E.; Kaplan, I. Geochim. Cosmochim. Acta.

1979, 43, 1791-1801.

(25) Simoneit, B.; Kaplan, I. Mar. Environ. Res. 1980, 3, 113-128.

(26) Stuermer, D.; Spies, R.; Davis, P.; Ny, D.; Morris, L.; Neal, S. Mar. Chem. 1982, 11,

I 413-426.

i (27) Venkatesan, I.; Brenner, S.; Ruth, E.; Bonilla, J.; Kaplan, I. Geochim. Cosmochim. Acta.

1980, 44, 789-802.

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(28) Eganhouse, R.; Venkatesan, I. Chemical oceanography and geochemistry. In: Ecology 1

of the Southern California Bight: A Synthesis and Interpretation. Daily, M.; Reish, D.;

Anderson,J. (eds.), Univ. CaliforniaPress. Berkeley,CA. 1994. I

(29) Kennicutt, M.; Brooks, J.; Denoux, G. Mar. Chem. 1988, 24, 35-59.

II

(30) Phillips. C.; Clayton, J.; Evans, J.; Hom, W. in prep. '_

(31) Brooks, J.; Kennicutt, M.; Wade, T.; Hart, A.; Denoux, G.; McDonald, T. Environ. Sci. t v

Technol. 1990, 24, 1079-1085.

(32) Boehm, P.; Brown, J.; Requejo, R. The fate and partitioning of hydrocarbon additives I

to drilling muds as determined in laboratory studies. In: .Drilling Wastes. Engelhardt,

F.; Ray, J.; Gillam, A. (eds.), Proceedings of the 1988 International Conference on

Drilling Waste. Elsevier Applied Sciences. NY. 1989. ,|

(33) Trocine, R.; Trefrey, J. Environ. Sci. Technol. 1983, 17, 507-512. I

II

(34) Continental Shelf Associates, Inc. (CSA). Environmental Monitoring Program for

Exploratory Well No. 3, Lease OCS-G 3316, Block A-384, High Island Area, South t

Extension near the West Flower Garden Bank. Draft Report to Union Oil Company. II

Tequesta, Florida. 2 Vols. 1983.

/

(35) Boothe, P.; Presley, B.J. Trends in sediment trace metal concentrations around six I

petroleum drilling platforms in the northwest Gulf of Mexico. In: Drilling Wastes.

Engelhardt, F.; Ray, J.; Gillam, A. (eds.). Elsevier Applied Sciences. NY. 1989. I

(36) Kennicutt, M. (ed.) Gulf of Mexico Offshore Operations Monitoring Experiment. Phase

I: Sublethal Responses to Contaminant Exposure. Final Report to the U.S. Department J,

of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New n

Orleans, Louisiana, under Contract 14-35-001-30582. 199'5.

II

(37) de Margerie, S. Modeling drill cuttings discharges. In: Drilling Wastes, Engelhardt, F.; _

Ray, J.; Gillam, A. (eds.). Elsevier Applied Sciences. NY. 1989.

I

(38) Drake, D., Cacchione, D. Cont. ShelfRes. 1992, 12, 1331-1352.

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I LIST OF TABLES

I Table 1. Summary of Drilling Activities: Phase II(a)and Phase III(b)-

Table 2. Metal and Hydrocarbon Concentrations (ppm dry weight) in Drilling Muds

I Collected at Platform Hidalgo, Phases H (a) and ]_I.

Table 3. Metal and Hydrocarbon Concentrations (ppm dry weight) in Drill Cuttings

t at Hidalgo, and 11I.

Collected Platform Phases iI (a)

i Table 4. Total Contaminant Mass Emissions From Drilling Operations at Platform Hidalgo During Phases II and 1II and From Natural Sources.

i Table Surficial5. and Suspended Mean MetalSediments and Hydrocarbon During Phase Concentrations III. Concentrations in DrillingareMuds ppm anddry Cuttings weight. and

i Table Concentrations 6. Drilling in Sediment Mud Traps. Depositional Phase IIFluxes Data From (mg/m2Hyland /dy) Computed et al. (Ref. From 3) WereExcess Recomputed Barium

Based On the Lowest Phase II/III Barium Mean Concentration.

Table 7. Total Excess Barium in Sediments Within 500 m of Platforms Hidalgo, Hermosa,

and Harvest.

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LISTOFFIGURES I

Figure 1. General Location of Sampling Stations and Oil Platforms in Pt. Arguello Region of

the Santa Maria Basin, California.

Figure 2. Ratios of Alkylated to Parent PAHs in Drilling Muds, Cuttings, Produced Water, and I

FormtionOilsfromPlatformHermosa.

Figure 3. Particle Fluxes (g/m2/day) at Nine Hard Bottom Sites During Phases II and III. t

Figure 4. Ba Concentrations (ppm) in Suspended and Surficial Sediments During Phases II and II

III. 11

Figure 5. Mean Percent Difference in Ba Concentrations in Surface and Subsurface Sediments

From Platforms Hidalgo, Hermosa, and Harvest Between 1991 and 1995. Percent differences are I!

calculated as (conc1991 - conc1995/conc1991 ) x 100. Note discontinuous scale for the subsurface

sediment plot. I

Figure 6. Concentrations of (A) THC; (B) EPAHs; (C) Total 4.- and 5-Ring PAHs; and (D)

Perylene in Suspended Sediments Near Platform Hidalgo During Phases II and III. THC

concentrations are ppm; all other concentrations are ppb. It

Figure 7. Concentrations (ppb) of Parent PAHs and Alkylated Homologues in Suspended

Sediments at (A) Station PH-N and (B) Station PH-R. U

Figure 8. Bivariate Plots of PCA Axes for PAH and Saturated Biomarker Data for Source Oils el

and Suspended Sediment Samples. n, r, and k represent Stations PH-N, PH-R, and PH-K,

respectively; 1-5 correspond to the Nov. 1991, Apr. 1992, Aug. 1993, Jan. 1994, and Jan. 1995

surveys, respectively. Hidalgo and Hermosa correspond to the platforms from which the

formation oils were obtained, seep oil is from the vicinity of Platform Hondo, and diluent is the n

petroleumproductfromtheGuadalupeOilField. I

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I Table 1. Summary of Drilling Activities: Phase II(a)and Phase III(b).

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Platform Discharges

Platform Study Phase DPeriod rilling Duration No. of (months) Wells Produced

Muds Cuttings Water

I (m3) (m3) (L/dxl0 6)

Harvest Phase II 11/86 - 05/88 18 19 16,340 n/a 0

t Phase III n/a n/a 0 0 0 0.80 (c)

Hermosa Phase II 01/87 - 09/88 20 13 16,373 3,114 0

Phase III 09/93 - 11/93 2 1 822 136 1.6_d)

I Hidalgo Phase II 11/87 - 01/89 14 7 7,963 2,294 0

Phase m 11/93 - 05/94 6 4 3,850 739 0.95(d)

1

(a) Phase II data from Steinhauer and Imamura (Ref. 6). (b) Phase III data from NPDES Discharge Monitoring Reports and MMS (pers. com.).

(c) Starting 7/94.

I (d) Starting 9/93.

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Table 2. Metal and Hydrocarbon Concentrations (ppm dry weight) in Drilling Muds 1

Collected at Platform Hidalgo, Phases II<a)and III.

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Surface Mid-Well Near-Bottom Bottom I Trace

Metals Phase Phase Phase Phase Phase Phase Phase Phase

II III II III II III II III IL

Silver 0.19 0.20 0.36 0.46 0.31 0.30 0.23 0.52

Aluminum n/a 64,000 n/a 56,800 n/a 24,800 n/a 20,600 /

Cadmium 0.84 0.91 1.24 0.97 1.40 0.99 1.33 1.81 t

Copper 26 18.9 38.1 25.2 28.0 17.3 27.0 33.8

Nickel II 49 35.6 51 47.7 40 33.4 22 37.6

Lead 20 21.4 3.2 31.6 2.3 12.3 51 25.5 II

Arsenic 8.95 8.98 4.41 8.38 5.28 8.03 6.74 15.7 _.

Barium 24,742 17,700 49,083 30,000 178,900 148,000 178,405 19,900

Chromium 82 76 126 88 96 83 37 118 |

Zinc 126 114 138 117 182 142 714 296 m

Mercury 0.085 0.067 0.102 0.067 0.154 0.222 0.182 0.061 J

Vanadium 78 84 99 78 69 62 38 82 i

Iron rda 29,800 rda 27,700 rda 19,500 rda 17,600 J'

THC 159 427 137 770 268 421 988 3,227

Naphthalene 0.27 2.4 5.4 11 28 6.7 39 10 m

Fluorene <DL 0.22 0.38 0.26 2.0 0.69 4.I 1.1 m

Phenanthrene 0.34 0.37 0.94 0.45 5.3 1.4 4.5 3.4 I

Dibenzothiophene 0.03 0.33 0.71 0.40 2.9 1.1 3.9 2.2 j])

ZPAH 0.87 2.4 8.0 13 39 10 51 16 n

(a) PhaseII data from Steinhauerand Imamura(Ref. 6). "1

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B-24 I

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I Table 3. Metal and Hydrocarbon Concentrations (ppm dry weight) in Drill Cuttings

Collected at Platform Hidalgo, Phases II (a) and III.

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I Surface Mid-Well Bottom Trace

Metals Phase Phase Phase Phase Phase Phase

II III II HI II III

t Silver 0.20 0.48 0.86 0.42 0.66 0.60

i Aluminum Cadmium 1.37 n/a 53,800 1.21 2.56 n/a 36,50 2.570 2.95 n/a 14.90 0,400

i Copper Nickel 4353 47.7 29 6083 44.2 130 4164 47.9 50

Lead 5,559 139 25 903 193 28.3

I Arsenic 9.5 8.2 9.4 12 11 9.8

i Barium Chromium 2,547 106 2,040 103 3,355 209 42,400 112 9,697 140 811 96

Zinc 2,871 128 179 1,670 988 193

I Mercury 0.089 0.054 0.122 0.111 0.092 0.032

Vanadium 71 87.0 122 92.0 122 121

Iron n/a 25,300 n/a 30,000 n/a 14,300

THC 600 539 95 2,001 526 1,343

I Naphthalene 1.2 1.5 8.9 20 96 11

Fluorene <DL 0.03 0.35 0.40 8.2 1.9

I Phenanthrene 0.79 0.63 0.64 4.7 9.3 3.9

Dibenzothiophene <DL 0.30 0.40 3.3 8.1 3.7

I _PAH 2.3 2.9 12 29 121 26

I (a) Phase II data from Steinhauer and Imamura (Ref. 6).

I

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II

Table 4, Total Contaminant Mass Emissions From Drilling Operations at Platform Hidalgo R

During Phases II and III and From Natural Sources.

!

Mud Discharge Cutting Discharge Produced Water Riverine and I

Mud/Cutting (kg) (kg) (kg/y) Petroleum Seep m

Constituent Input (b)

Phase II(a) Phase HI Phase II(a) Phase Ill (kg/y) I

wm

Silver 1.0 0.7 3.6 1.0 <0.35 88

Arsenic 22 17 6.0 19 <83 6,700 I

Cadmium 4.2 2.0 13.7 5.6 <0.35 460

Copper 104 41 290 130 <3.5 12,000 I

Chromium 300 154 910 200 3.5 99,200

Mercury 0.4 0.2 0.6 0.1 29 56 I

Nickel 140 66 400 90 <6.9 33,600

Lead 66 39 11,000 684 < 10 12,000 i

IIIIIII1

Vanadium 250 130 630 190 <3.5 45,600

Zinc 1,000 280 8,000 1,300 13 57,600 _1

Barium 370,000 91,000 31,000 29,000 5,720 670,000

THC 1,300 2,030 2,900 2,500 779 2,230,000 i_

ZPAH 86 17 230 36 112 18,500

!

(a) Source: Steinhauer et al. (Ref. 7).

(b) Source:Steinhauer andImamura(Ref.6). I

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I Table 7. Total Excess Barium in Sediments Within 500 m of Platforms Hidalgo,

Hermosa, and Harvest.

t

I Total Excess Ba (kg) % Total Ba Emissions

Nov. 1991 Jan. 1995 % Change Nov. 1991 Jan. 1995 <a)

t Hidalgo 52,200 53,100 +1.7% 13 10

Hermosa 57,500 49,000 -15% 17 14

I Harvest 74,900 54,200 -25%

I (a) Total of Phase II and Phase III Ba emissions.

m Cannot be determined due to incomplete Phase II data.

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i APPENDIX C

I IN SITU LARVAL TOXICITYEXPERIMENTS TESTS MANUSCRIPTS AND LABORATORY

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i APPENDIX C-1

I IN SITU RED ABALONE SETTLEMENT EXPERIMENT MANUSCRIPT

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I EFFECTS OF OFFSHORE OIL AND GAS DEVELOPMENT ON MARINE

LARVAL SETTLEMENT: IN SITU MANIPULATED FIELD EXPERIMENTS

I

Peter. T. Raimondi 1,Arthur M. Barnett 2, and Paul R. Krause 2

I 1Marine Science Institute, University of California, Santa Barbara 93106

I MEC Analytical SystemsInc., Carlsbad,

2 CA 92008

i [To be submitted to: Journal of Marine Biology and Ecology or Marine Environmental Research]

i ABSTRACT

A series of in situ, manipulated field experiments were conducted to determine the effects of oil

I and (Haliotis gas drilling rufescensmud ). The and produced study areawater focuseddischarges on a seriesonofthethree settling oil platforms ability ofandlarval threeredreference abalone

sites between Pt. Arguello and Pt. Conception in the southern Santa Maria Basin, California.

I Study groups depths of settlingwereplates approximately 200 m. The experiments involved reciprocal transplants of that first were "filmed" with bacteria at each site, and then transplanted

to all other sites at each of two heights ("high" and "low") from the bottom. Unfilmed plates

I were used to test the effects of the filming treatments. Plates were placed into specially designed chambers, covered with mesh, and placed onto recoverable larval arrays for deployment

to the sea bottom. Approximately 500 laboratory-reared red abalone larvae, competent for

I settlement, were placed into separate chambers (each containing a settling plate) prior to deployment. One experimental array containing replicate larval chambers was deployed on the

sea floor for 3 days at each of the six locations. Upon recovery, settled abalone larvae were

I counted to test location-related (platform vs. reference sites), waterborne, and height effects on settlement. Experiments were carried out over a three year period that incorporated pre-drilling

and drilling phases. Discharges during drilling occurred sequentially from two of the three

I platforms, with somewhat overlapping particle dispersion patterns between the platform sites. Results showed: (1) red abalone are suitable for deep ocean in situ bioassay work; (2) the

presence of a bacterial film significantly affected the number of abalone larvae that settled onto

I and settlement lowerat alllocationsin the settlement plates; (3) was period during drilling; at

drilling platforms relative to reference sites was depressed significantly further.

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I (C-1)1

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INTRODUCTION I

Offshore oil and gas drilling activities along the California Outer Continental Shelf (OCS) have I

prompted concern for ecological effects associated with such activity (Piltz 1986; Brewer et al.

w

1991). One area that has been extensively studied and which has been the site of several I

exploratory and development/production platforms is the Santa Maria Basin offshore of Pt.

Conception in southern California (SAIC 1986; Steinhauer et al. 1992; Steinhauer and Imamura

1990; Hyland et al. 1994; Steinhauer et al. 1994). The oil fields in this area are among the a

largest discovered in OCS waters and contain 50 of the 102 active lease tracts in the Pacific OCS m

region (Steinhauer et al. 1992). Previous and potential drilling activity represent substantial

discharges of drilling wastesto the marine environmentof this region, n

Oil and gas drilling discharges (e.g., muds, cuttings, fluids, and produced waters) to the marine

environment may have far reaching effects at several ecological levels; however, much of the II

recent research in the California OCS region has focused on effects to adult populations (Brewer g

et al. 1991; Hardin et al. 1994; Hyland et al. 1994). Few studies have addressed other factors

such as changes in larval settlement, recruitment of new individuals, or how such changes might II

influence population dynamics. Larval settlement and recruitment can be affected by interactions g

with both biotic and abiotic factors (Crisp 1974; Crisp 1984; Rodriguez et al. 1993). Factors

affecting larval recruitment may have long lasting effects at the population level leading to n

community wide effects (Connell 1985; Mullineaux 1988; Raimondi 1990). Thus, studies U

addressing these factors can provide early evidence of potential effects at higher ecological levels.

n

Until recently, the use of bioassays to detect impacts to marine systems has been largely

restricted to the laboratory. This was chiefly due to the logistical constraints of working with

live animals in field situations and because the bioassays often took so long to perform that it II

was infeasible to maintain them in the field. However, relatively new approaches to assess

w

biological impacts have been developed to overcome these problems (Raimondi and Schmitt _t

1992; Krause 1995; Raimondi and Reed 1995). These methods utilize early life history stages n

instead of adults. Early life stages are small, manipulatable, and respond rapidly to perturbations.

u

Moreover, early life stages are generally more susceptible to disturbances, making them ideal test m

systems for bioassay experiments (Neff et al. 1976; NRC 1983; Krause et al. 1992; Raimondi and I

Schmitt 1992).

The purpose of the present study was to examine the extent to which oil and gas drilling activity I

might affect larval settlement. This study was performed in conjunction with several concurrent

investigations as part of the Department of the Interior, Minerals Management Service III

(MMS)/National Biological Service (NBS) Phase III Long-Term Monitoring Program of the Santa |

Maria Basin. The Phase III program was designed to assess cumulative effects of offshore

drilling and production activities on the marine environment of the study region (SAIC and MEC I

1993). II

For this study, in situ assays of larval settlement were conducted at sites near and far from II

drilling platforms. The experiments provided a basis for determining factors that affected the U

(C-I) 2 I

I
I settlement of a controlled population, in this case red abalone larvae. Because natural settling

rates are relatively low (Mullineaux 1988), manipulations were performed in which known

I numbers of larvae were exposed to a series of treatments in the field to determine how settlement was affected by: (1) waterborne factors (e.g., suspended solids, food, and dissolved chemicals);

(2) surface films on settlement plates (e.g., bacteria and particulates incorporated into the surface

I film); and (3) reef height (relief height from the bottom). The specific design of these experiments allowed for the determination of causation related to drilling operations.

I METHODS

I Study Site

i The Conception study was conducted along a portion of the southern California continental shelf between Pt. (34 ° 28' N 120° 28' W) and Pt. Arguello (34 ° 35' N 1200 38' W), at water depths of

160 - 210 m (Figure 1). Three nearfield oil platforms and three farfield reference sites were

I utilized Hidalgo, forHarvest, the study. and Nearfield Hermosa (Figure sites were1). located The farfield near hard-bottom sites were alsoreefsnearadjacent hard-bottom to Platforms reefs,

upcoast (1 site) and downcoast (2 sites) of the platforms along the same depth contour. The

I farfield on dispersion sites were andselected dpositionto beinformation beyond the major from Phase influenceII studies of Phase(Coats III drilling 1994).activities, In addition, based

experiments were conducted at two heights (0.35 and 1.25 m) above the ocean bottom

I corresponding to low and high relief reefs in the region (Hardin et al. 1994).

Current patterns in the region that may affect dispersion of drilling discharges and larvae are

I influenced of the studybysitetheisCalifornia characterizedCurrent. by along-shelf Current meter surfacedataflows showthat thatgenerally the physical run parallel oceanography to the

shoreline (Chelton et al. 1982; SAIC and MEC 1993). The general coastal orientation of the

I region is southeast to northwest. Hyland et al. (1990) found that there is a high-frequency tidal influence that produces across-shelf currents. These currents can be particularly strong near the

bottom. Influences of along-shelf and across-shelf currents cause patterns of circulation at the

I study site that are complex and often consist of eddies, swirls, filaments, meanders, and narrow jets (Mooers and Robinson 1984; SAIC and MEC 1993).

I Natural and anthropogenic factors can affect the abundance and type of organisms present in a

community. Natural factors include oil seeps and variability in physical substrates that can

interfere with larval settlement. Natural oil seeps have not been characterized to a great degree

I in the but known to be the southern California coast study area, are present along (Wilkinson

1972). Previous studies in the area have observed microscopic tar particles in the bottom

sediments (Steinhauer et al. 1994), even though hydrocarbon concentrations in sediments are

I generally low (Steinhauer and Steinhauer 1990). The general topography of the area includes

extensive soft-bottom areas of mud and, much less commonly, hard-bottom areas of rocky

i outcrops of varying relief height (Lissner et al. 1991; SAIC and MEC 1993). The Phase II study classified the hard-bottom substrates of the area into two distinct height groups: low relief

I (c-1) 3

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(0.2-0.5 m) and high relief (>1 m) (Hardin et al. 1994). These., areas were distinguished by m

differences in the abundances and types of organisms, including meroplanktonic larvae, m

throughout the area (SAIC and MEC 1993; Hardin et al. 1994; Diener and Lissner, in _i

preparation). w

Study Organism i

Red abalone larvae (Haliotis rufescens) were used for the study. This species and life history ii

stage has a number of desirable characteristics for use in in situ bioassays (Raimondi and Schmitt I

1992). The species has a broad depth range from the intertidal to more than 180 m, and its larval

life history is well documented (Morris et al. 1980). Further, it is easy to culture and use in in n

situ bioassays and is sensitive to a suite of potential anthropogenic disturbances, both physical II

and chemical in nature (Morse et al. 1980; Raimondi and Schmitt 1992). Its life history also is

similar to a number of other marine species, potentially making :it a good indicator organism.

Finally, larval red abalone have been used in a large number of laboratory and some field II

bioassay programs, so results can be compared to other studies (e.g., Hunt and Anderson 1989;

Raimondi andSchmitt1992). 1ram'

Preliminary studies indicated that red abalone larvae could survive .and grow on settlement plates

in exposures up to 23 days in the field at depths of up to 200 m (Raimondi and Barnett, _l

unpublished data). Surviving individuals showed signs of healthy metamorphosis to the juvenile

stage, active feeding on microbial films on the plates, and normal growth. These observations

demonstrate that red abalone larvae can settle, survive, and grow under conditions typical of the i

natural field conditions in the study area. J

In situ Experiments i

In situ settlement experiments using red abalone larvae were conducted in October 1992 and

January 1994 from the survey vessels M/V RAMBO and M/V INDEPENDENCE, respectively, i

Each experiment consisted of a filming period and subsequent exposure period, as described

i

below.

l

Plexiglass settlement plates (10 x 10 cm) were placed into filming canisters and deployed

approximately three weeks prior to the start of the scheduled experimental period (Figure 2). The m

canisters were covered with 100 lam Nitex mesh to preclude natural settlement of larvae during I

the filming process. Canisters were placed at each of the six experimental sites and at each of

two heights (0.35 and 1.25 m) above the bottom. This general protocol to assess affects of i

microbial filming on settlement has been used successfully by Todd and Keough (1994) and |

Keough and Raimondi (1995).

Following the filming period, the plates were retrieved from the canisters and sorted to distribute i

plates from each filming site to each incubation (exposure) site, thereby representing a reciprocal

transplant design. Plates were secured into individual chambers, and then attached to deployable Jl

larval arrays referred to as igloos (Figure 2). Igloos were three dimensional structures that

(C-l)4 I

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I carried plates on four separate faces to account for the potentially confounding effects of currents.

Each chamber held one settling plate and was covered with 100 lam Nitex mesh. Plate chambers

I were "injected" with 500 (_t_50)competent (biologically capable of settling) red abalone larvae prior to a three day deployment of the igloos. Plates remained covered with Nitex mesh for the

duration of the incubation to prevent spontaneous natural settlement of other invertebrates,

I predation, and to contain the red abalone larvae within the chambers. Four replicates were conducted of each combination of filming site, incubation site, and relief height. Plates that were

returned to their original filming site were replicated by an additional four plates. In addition

I to the plates from each filming site, sterile plates (no surface filming) also were transplanted to

each site (4 replicates per site).

I Sorting plates was an laboratory cool, plates were

of done in onboard in dark conditions, and

continuously immersed in seawater. Completed trays (see Figure 2) were maintained in cool

i seawater in the dark until just before igloo deployment. When all trays were completed (abalone larvae injected into all chambers), covers were placed over the trays to keep them bathed in cool

seawater prior to deployment, and covered trays were attached to the igloos. Igloos were then

I lowered to exposeusing the chambers the ship's tocrane in situto conditions. a depth of 8-10 Following m and removal scuba divers of theremoved covers thethe igloos tray covers were

lowered slowly to the sea floor.

I After the three-day incubation period, the igloos were retrieved. Settled abalone larvae are

resistant to desiccation and were attached firmly to the settling plates, permitting the igloos to

I beon brought the trays.directly However, fomonce the bottom onboard,tocovers the ship's were deck immediately without underwater placed on eachattachment tray and ofthecovers tray

were moved back to the cool seawater baths in the darkened shipboard laboratory until the

I settlers microscopically could bewithincounted. two hoursTheof igloo numberretrieval. of settled Experiments red abalone carried larvae out in were Octobercounted 1992,

and January 1994 yielded one data set each for the "pre-" and "during-drilling" periods.

I Experimental Design and Analysis

I The experiment as described above was performed twice. The first experiment was performed in October 1992, during a period when no drilling was occurring or had occurred at any of the

three platforms since 1989 (Steinhauer and Imamura 1990). This was defined as the pre-drilling

I period. The second experiment was conducted in January 1994 at which time drilling was occurring at Platform Hidalgo, had just been completed at Platform Hermosa, and had not

occurred at Platform Harvest. This was defined as the drilling period.

!

In summary, the overall experimental design consisted of the following:

I (1) Two experimental periods: pre-drilling and drilling;

(2) Two levels of plate surface filming: near platforms and far from platforms (at

i reference sites);

I (c-1) 5

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(3) Two levels of incubation location (locations to which plates were transplanted and u

at which settlement occurred): near platforms and far from platforms (reference

sites); and I

(4) Two levels of relief height (plate height): low (0.35 m) and high (1.25 m).

The basic statistical design is a Before-After-Impact-Reference factorial ANOVA design (Green I

1979; Stewart-Oaten et al. 1986) with three replicates of the platform sites and three replicates

of the reference sites. With true "field" replication such as this, the question of whether impacts II

were attributable to some aspect of drilling discharges could be addressed; without true replicates, II

the effect of a platform would be confounded with location-to-location variability. If activities

associated with the operations at the platform sites were contributing to changes in settlement •

then this should be seen as differences (deltas) in settlement between the before and after periods. II

This statistical design has been advocated by several authors as the most powerful technique to

demonstrate environmental impacts using field studies (Green 1979; Hurlburt 1984; StewartOaten et al. 1986; Underwood 1994). II

Settling plate replication within this factorial design was achieved as follows: 1

(1) At all incubation sites there were plates that were :filmed at all filming sites;

(2) The mean number of settlers for all plates filmed at a site and transplanted to an II

incubation site was considered one replicate. (As ,an example, at Reference Site

1 four of the plates filmed at one relief height were transplanted to Reference Site

2 forincubationat thesamereliefheight);and

(3) The mean number of settlers from those four plates was considered to be a single J

replicate. In this way "psuedoreplication" was avoided (Hurlburt 1984). ! Data were analyzed using fixed effect analysis of variance procedures (SAS Institute 1988) on

log_ (x+l) transformed data to meet assumptions of homoscedacity. Specific analyses are

described below. I

RESULTS I

Assessment of variability in settlement

J

Variability in settlement during the before-drilling period was assessed by comparing settlement

of red abalone larvae at the three reference sites (Table 1). Sites near the platforms were I

excluded from this analysis to avoid any confounding effects related to the platforms. In U

addition, the set of unfilmed plates was included in the analysis to determine the effect of no

filming on larval settlement. Thus the three-way factorial ANOVA (filming site x incubation x II

plate height) had four treatments for the filming factor (three reference sites and one no-film |

treatment). With only three reference stations, and two sets of film conditions, the degrees of

freedom were insufficient to test all of the interaction terms in the three-way factorial design. II

Consequently, interactions involving relief height were treated as part of the overall error term. II

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I The ANOVA was followed by a Ryan-Einot-Gabriel-Welch multiple comparison test (REGWQ;

SAS Institute 1988) to separate filming and incubation site means (Day and Quinn 1989).

I Results indicated there were no effects of relief height or the interaction between filming and

incubation location on settlement (Table 1). However, both filming location and incubation

I location affected settlement of red abalone. For the film location effect, plates with no microbial films had lower settlement than that found on plates from any of the reference sites. No

differences in settlement were evident for films from different reference sites. The significant

I effect of incubation location was largely driven by Reference Site 3, which exhibited lower

settlement than the other two sites. These results indicated: (1) filming increased settlement;

(2) there was no strong evidence of differences in filming among locations that was sufficient

I to cause settlement; (3) was significant among-site variability differences in and there in

settlement.

I Effect of drilling activity on settlement

I Drilling period drilling activitiesoccurred did notonly occuratasPlatforms anticipatedHidalgo at the and threeHermosa platforms;(Table during2).theTherefore experimental the

"impact" site near Platform Harvest was dropped from the analysis.

I The location of Reference Site 1, located >5 km northwest of Platform Hidalgo (Figure 1)

received only low flux of drilling muds during the major drilling operations of Phase II (Hyland

i et receive al. 1994) no fluxand,during based theon limited extrapolation drillingfromf Phase deposition III. However, maps of Coats a second(1994), modelwasapplied expectedto theto

actual amount and size of particles discharges in Phase III, indicated that low sediment fluxes

I and 1995). deposition Since thewaspresent probable experiments in the areawere of Reference expected toSitebe 1sensitive (see Appendix to low levels A in SAIC of depositional and MEC

and waterborne effects, Reference Site 1 was excluded a priori from the analysis.

I The result of these changes was an ANOVA model with two sites near platforms (impact sites,

where drilling occurred during or just before the second half of the experiment) and two far from

I drilling activity (reference sites). A three-way factorial ANOVA was implemented with treatments of: (1) filming location (the "no film" level was excluded from this analysis), (2)

incubation location, and (3) plate height. Each datum was the difference (delta) between the

I means of settling plate replicates in the pre-drilling and drilling periods. Using deltas resulted in removal from the analysis of potentially confounding effects of geographic location. The null

hypothesis is that there is no difference in the deltas from platform or reference sites. The

I alternative hypothesis is that if there is a negative effect of drilling on settlement (either due to

filming or waterborne effects), then the observed deltas from impact locations will be greater (in

absolute terms) than those from reference locations. For example, there would be evidence for

I a negative effect if the predrilling-drilling delta was -35 (in mean number of settled larvae) for

reference locations and -120 for impact locations.

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I The results of the analysis on red abalone settlement are clearly interpretable because there were

no significant interactions (Table 3). Settlement was similar at high and low plate heights (Table I

3A). However, the effects of both incubation and filming location were significant (Table 3A). i

Settlement on plates filmed and incubated close to drilling platforms had greater deltas than those

filmed or incubated at reference sites (Table 3B). These results indicate that abalone settlement

was generally reduced (for undetermined reasons) in the post-drilling period, but that the I

reduction in larval settlement was even greater on settling plates filmed or incubated at sites close

todrillingplatforms. I

DISCUSSION I

Data presented in this study indicate that drilling activities in the Santa Maria Basin had a

significant negative effect on the settlement of red abalone larvae (Table 3). Moreover, two Im

separate, independent factors (filming and settling) were apparently related to these reductions. i

Microbial films that developed on settling plates located near platforms where drilling was

occurring (Hidalgo) or where drilling had recently occurred (Harvest) induced less settlement than I

films developed far from drilling sites, regardless of whether settlement occurred near drilling g

platforms or at reference sites. Furthermore, settlement on plates located near platform sites was

less than settlement far from platforms, regardless of where microbial films were developed, i

An alternative explanation (i.e., that some other geographic-specific factor caused these effects)

for these results is unlikely. If a platform-related characteristic other than drilling discharges m

induced a negative effect on settlement, the reductions would have been reflected in the pre- g

drilling as well as the drilling stage. Utilization of deltas (differences in settlement between predrilling and drilling periods) eliminated this type of effect. Reductions in settlement near i

platforms would have occurred in both periods such that the delta should have been no greater

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than that of reference stations.

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The same logic applies to all potential influences other than those that were manifested only near

drilling platforms in the during/after drilling period. Clearly, the most likely candidate that meets m

thesecriteriaisplatformdrillingactivity. I

Competent red abalone larvae typically settle on surfaces covered with crustose coralline algae II

or bacterial films (Morse et al. 1979a, b). Once settled, metamorphosis of the adult form II

typically is completed within 24 hours (Morse et al. 1980). This larval settlement process is

complex and may be associated with several mechanisms that account for the effects observed m

in the present study. Results showed that bacterial films greatly influenced the settlement of |

abalone larvae. When plates were filmed with bacteria prior to deployment, settlement was

approximately twice as high as that observed when a film was not present (Table 1). This m

demonstrates the importance of filming to the larval settlement and recruitment process. II

Marine larvae are known to be selective in their preference of a suitable habitat for settlement i

(Doyle 1975; Keough and Downes 1982; Rodriguez et al. 1993). This process often involves m

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I complex biochemical mechanisms (Morse et al. 1979a, 1979b; Morse 1990) that initiate the

settlement process. Waterborne factors, including dissolved chemicals and suspended particulates,

I may interfere with physiological receptors of larvae that serve to identify suitable settlement sites or initiate the settlement process. In a similar manner, post-settlement processes (both physical

and biochemical) that initiate metamorphosis from a free swimming larva to settled juvenile may

I be interrupted by waterbome factors. Newly settled abalone also feed on the microbial films present on the settlement surface (Raimondi, pers. obs.). Material incorporated into, or present

on this matrix such as food particles, sediment particles, or adsorbed chemicals, may have a

I direct impact on the post-settlement survival of larvae.

Dissolved chemicals from effluents of drilling and production activities such as produced waters

I were thoughtto dilute rapidly below (Montalvo Brady 1979;

harmful levels and Rose and Ward

1981; Middleditch 1984; Neff 1987). However, recent research has challenged this idea and

i demonstrated that dissolved chemicals may be responsible for toxicity of benthic invertebrate larvae observed in the water column (Krause et al. 1992; Raimondi and Schmitt 1992; Krause

1995) In similar work, Cherr et al. (1993) and Higashi and Crosby (1993) showed that dissolved

I petroleum of marine organisms. products inThe produced presentwaters study were did not of primary attempt toimportance determine inwhether inducingwaterborne chronic toxicity factors

responsible for the observed effects on abalone settlement were derived from dissolved or

I particulate constituents,fractions, suggestingbut thethatresults they observed may playareanconsistent importantwithroletheasprevious a mechanism studies for on dissolved inducing

effects.

I Effects observed in this study focused on larval settlement, potentially one of the most

ecologically important steps in the population dynamics of marine systems (Keough and Black

I settled 1995). populations Slight effectsof onorganisms larval settlement and lead torateswider canspread result population in significantlevelreductions changes in(Murdoch recruits toet

al. 1989; Nisbet et al. 1995). This may be especially true in areas of low natural settlement such

I asLarval in the Santa Maria Basin (Barnett et al. 1995; see Appendix C-2 in SAIC and MEC 1995). settlement results from the present study may correspond to observed effects in previous

MMS sponsored studies of adult benthic invertebrates from the Santa Maria Basin. Hyland et

I al. (1994) found that 4 of 22 hard-bottom taxa showed significant decreases in mean abundance following drilling activities over a four year period. Nonetheless, processes linking larval and

benthic dynamics are poorly understood and the ecological significance of decreased settlement

I rates remains an area of active research (Nisbet et al. 1995; Raimondi and Schmitt 1992).

Similar results to the present study were noted from a companion laboratory study (Raimondi et

I al., in preparation; see Appendix C-3 in SAIC and MEC 1995). These results indicated that

expected field concentrations of drilling muds had negative effects on settlement of red abalone

larvae and caused decreases in survivorship and increased tissue loss in a cup coral, Paracyathus

I stearnsii.

i Further, similar experiments to the present study tested the effect of drilling activities on natural settlers in the Santa Maria Basin (Barnett et al. 1995; see Appendix C-2 in SAIC and MEC

I (C-1)9

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1995). Because natural settlement rates in that experiment were low, it was not possible to assess I

as accurately the effects of drilling on settlement (as defined by Keough and Downes 1982) or

on microbial inducers of settlement (microbial films). Bamett et al. (1995) investigated n

recruitment for durations greater than 300 days in the pre-drilling and drilling periods. These

results suggested some drilling-related effects, even though the tests had low statistical power.

However, in contrast to the present in situ study and the laboratory red abalone and cup coral n

studies, most of these effects were positive (enhanced recruitment). The basis for the difference w

between the studies is unresolved. Several hypotheses may be plausible to explain these roll

differences: (1)species specific responses to drilling; (2) results of the natural settlement •

experiment are confounded by other (presently unknown) events that occurred during the long

(>300 day) experimental periods; or (3) differences in effects at settlement and recruitment

stages. I

The design of the particular experiments used in this study showed the advantage of large-scale II

field experiments in detecting subtle effects in the field. In situ experiments can provide valuable II

information on the complex mechanisms associated with large-scale perturbations to ecosystems.

These studies have the advantage of testing for responses in the field rather than in more artificial •

systems such as in the laboratory (Krause 1994). Laboratory testing often requires multiple |

systems to control naturally fluctuating variables such as temperature or salinity. Further,

laboratory experiments that attempt to allow natural variance of abiotic variables are prohibitively II

expensive and generally impractical to perform. In situ studies allow the experimental

manipulation a variable(s) of interest while still exposing the variable to natural fluctuations. The

results are often very powerful aids in evaluating important phenomena such as environmental m

impacts.

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I ACKNOWLEDGMENTS

I We wish to thank the Department of the Interior (DOI), Minerals Management Service/National Biological Service, G. Brewer, F. Piltz, G. Reetz, and L. Thorsteinson for their support of this

extended application of bioassay. The efforts of D. Diener, M. Gunnels, D. Reed, and D.

I Canestro in the field, S. Watts in data analysis, and A. Lissner in editing are greatly appreciated.

This work was supported as part of DOI Contract No. 14-35-0001-30584 to Science Applications

International Corporation. I

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LITERATURE CITED I

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w

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I Green, R. 1979. Sampling Design and Statistical Methods for Environmental Biologists. J.

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Santa Maria Basin. Oil and Chem. Pollut. 6:195-240.

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I Todd, C.D. and M.J. Keough. 1994. Larval settlement in hard substratum epifaunal

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I Gas Pub. No. TR-08, 1 lp.

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LISTOFTABLES I

Table 1: (A) Analysis of variance on numbers (loge (x + 1) tran,;formed) of abalone settlers in I

the pre-drilling period using reference site data (Sites 1, 2, and 3). Datum is the mean across

similar treatment combinations at a settlement site. Log data are normally distributed. (B) Mean

settlement of red abalone on plates at reference sites (untransformed data). Dashed lines indicate I

sites that are not significantly different as determined by REGWQ.

Table 2: Summary of drilling schedules and discharges from each platform during the I

experimental periods.

Table 3: (A) Analysis of variance of deltas (loge (x + 1) transformed) using Reference Sites I

2, 3, and Platforms Hidalgo and Hermosa. Datum is the mean across similar treatment

combinations tl = pre-drillingat aabundance settlementandsite.t2 =Logdrilling deltasabundance). (log_ t2 - log_(B)tl)Mean are normally deltas fordistributed settlement (where of red I

abalone (untransformed data).

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I LIST OF FIGURES

I Figure 1. Study area and station locations.

Figure 2. Diagram of filming canisters and larval settlement arrays (igloos) showing the

I rrangement of settling plates in both units (each igloo has four sides). Upper, unmeshed levels of canisters were not used for present experiments. Settling plate scale is 10 cm on a side.

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Table 1: (A) Analysis of variance on numbers (log_ (x + 1) transformed) of abalone settlers in i

the pre-drilling period using reference site data (Sites 1, 2, and 3). Datum is the mean across III

similar treatment combinations at a settlement site. Log data are normally distributed. (B) Mean •

settlement of red abalone on plates at reference sites (untransformed data). Dashed lines indicate

m

sites that are not significantly different as determined by REGWQ. ,.

|

Source SS df MS F p

FilmingSite 4.293 3 1.431 8.713 0.003* •

IncubationSite 5.601 2 2.801 17.050 0.000" m

FilmingSitexIncubationSite 0.455 6 0.076 0.461 0.823 •

Plate Height 0.166 1 0.16{; 1.008 0.337 |

Error 1.807 11 0.164

*=statistical significance atp=0.05 i

(B) I

Filming Site Ref 1 Ref 2 Ref 3 Unfilmed I

I

Mean 104.4 170.7 !10.6 71.0

SE 14.4 23.5 13.1 9.1 B

n 12 12 12 12

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Incubation Site Ref 1 Ref 2 Ref 3

Mean 142,3 149.0 61.6 I

w

SE 12.9 21.3 9.1

n 14 14 14 •

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i Table 2: Summary of drilling schedules and discharges from each platform during the

experimental periods.

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Platform Discharges

I Drilling Total Total Produced Water

Drilling Duration No. of Muds (m3) Cuttings (MGD)

I Platform Period (mo.) Wells (m3)

Harvest no drilling no drilling 0 0 0 0

Hermosa 9/93 - 11/93 2 1 822 136 0.592

I Hidalgo 11/93 - 5/94 6 4 3850 739 1.72

i MGD = millions of gallons per day

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Table 3: (A) Analysis of variance of deltas (log_ (x + 1) transformed) using Reference Sites •

2, 3, and Platforms Hidalgo and Hermosa. Datum is the mean across similar treatment

combinations at a settlement site. Log deltas (log e t2 - log e tl) a_renormally distributed (where ,_

tl = pre-drilling abundance and t2 = drilling abundance). (B) Mean deltas for settlement of red B

abalone (untransformed data). !

Source SS df MS F p

FilmingSite 6.792 I 6.792 4.74 0.040* []

IncubationSite 14.230 1 14.230 9.93 0.004* _'

PlateHeight 0.046 1 0.046 0.03 0.860 []

FilmingSitex IncubationSite 2.454 1 2.454 1.71 0.203 I

FilmingSitex PlateHeight 0.002 1 0.002 0.00 0.969

m

IncubationSitex PlateHeight 0.003 1 0.003 0.00 0.963 I

FilmingSite x IncubationSite x Plate Height 0.123 1 0.123 0.09 0.772

34.389 24 1.433 I

Error

*=statisticalsignificanceatp=0.05 -m

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Filming Site Incubation Site

Reference Platforms Reference Platforms I

Mean -71.8 -142.2 -54.8 -159.2

SEN28.2 34.8 26.4 33.4 i'

16 16 16 16

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I Figure I
Figure 2 I

Canisters Filming '_i ,

toPlates IglooTransferred I "

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TrainWheel LarvalRimingCanisterDetail ,,

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I APPENDIXC-2

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IN SITU LARVAL SETTLEMENT EXPERIMENT MANUSCRIPT

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IIIII!I!II
I EFFECTS OF OFFSHORE OIL AND GAS DEVELOPMENT ON LARVAL

i SETTLEMENT: FIELD EXPERIMENTS ON THE OUTER • CONTINENTAL SHELF OFF POINT ARGUELLO, CALIFORNIA

I Arthur M. Barnett1, Paul R. Krause1 and Peter T. Raimondi 2

I 1MEC Analytical Systems, Inc. Carlsbad, CA 92008

2 University of California, Marine Science Institute, Santa Barbara, CA 93106

i [To be submitted to: Journal of Experimental Marine Biology and Ecology

or Marine Environmental Research]

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ABSTRACT

i A series of field surveys and experiments were conducted to assess variability in recruitment of

sessile marine invertebrates and potential impacts of offshore drilling activities to these

, organisms. of approximately These 200 studies m. were Sampling performed sites onwerethenear California to, andOuter far fromContinental (referenceShelfsites), at depths three

drilling/production platforms in the southern Santa Maria Basin between Pt. Arguello and Pt.

I plexiglass Conception.settlingRecruitment plates. Results was assessed showed that overtheaoverall varietysettlement of temporal rate scales was veryonlow10, compared x 10 cm

to rates typical in shallower water, with little Settlement occurring in the fin'st 6 months of

i exposure. Settlement was higher during exposure periods between one and two years. Over 50 taxa were observed on the settling plates throughout the experimental period. There was

considerable spatial variability in recruitment across sites and relief heights (0.35 and 1.25 m off

I the bottom). Growth, survivorship and fecundity were determined for some taxa on the plates. The potential effect of drilling at sites close to oil platforms was also assessed. Sets of plates

were exposed for 300 days before drilling, and for 360 days during and just after drilling. Thus,

the incorporated both "before" and "during/after" drilling periods. Some experimental design

plates also were left in the field for the entire experimental period of up to 1000 days.

Throughout the incubation periods, the settling plates were retrieved at specific intervals to

t determine the amount and type organisms colonizing plates. Upon some plates

of the retrieval,

were photographed and returned to the bottom, while others were returned to the laboratory for

'- analysis. This allowed the effects of drilling to be tested on both existing benthic communities

I (thoseorganismsestablishedon the plates) new (thoseorganisms and settlement and recruitment

newly settling onto the plates) in the study area. Nine taxa (or groups of taxa) were present in

i sufficient numbers to facilitate statistical tests of drilling effects on new settlement and recruitment, while five taxa (or groups) were identified for effects on established organisms.

Recruitment patterns of six taxa showed a response to drilling either as new recruits or

I established negative effect. organisms. In addition, Five of nothedifference responses suggested was founda inpositive growth,effect, survivorship while oneorsuggested fecunditya

between organisms recruiting to either reference or drilling sites throughout the study. Thus, an

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overall conclusion is that esentially no effects to natural larva2 settlement were evident from

drillingactivitiesduringthestudyperiod. /

INTRODUCTION I

Offshore oil and gas development may affect marine communities in several ways (for review

see Capuzzo 1987). In particular, anthropogenic impacts that affect larval settlement may also 1

influence the dynamics of populations and communities (Nisbet et al. 1995; Raimondi and It

Reed 1995). This may be especially true for sessile macrobenthic organisms inhabiting deepwater environments (Gage et al. 1980; Gage 1991). However, the extent to which waste plumes l_

influence benthic population dynamics through impacts to larvae has not been fully determined, _n

even for shallow water communities (Keough and Black 1995).

ii/

A variety of other factors can affect larval settlement and recruitment. These include the I

suitability of surfaces for settlement and post-settlement survivorship. Larvae are active samplers Jk

of benthic surfaces while searching for suitable settlement locations (Keough and Downs 1982; ,

Rodriguez et al. 1993). Larvae respond to specific settlement cues including physical-chemical f

settlement inducers from microbial films (Morse et al 1984; Bonar et al. 1990; Todd and Keough

1994; Keough and Raimondi 1995), the presence of a food source (Morse and Morse 1984; t

Rowley 1989), or the occurrence of conspecific organisms (Highsmith 1982; Jensen and Morse mr

1984; Raimondi 1988). Wastes discharged into the marine environment can interfere with these

settlement cues and disrupt larval settlement and recruitment processes (Raimondi and Schmitt ,N

1992;Raimondi andReed1995). _n

Much of our understanding of settlement processes for benthic invertebrates comes from shallow /

water studies (<30 m depth), since working in deeper water usually requires special equipment u

(e.g., remotely operated vehicles, submarines, and large support ships), and larval settlement rates u

in deeper water are low compared to those in shallower water (MuUineaux and Butman 1990; iI

Mullineaux et al. 1991; Kim et al. 1994; Mullineaux et al. 1995). However, the relative paucity

of larvae at depth may increase the importance of settlement dynamics to adult community /

structure. I

This study was designed to address natural variability in larval settlement and recruitment on hard j

surfaces in the southern Santa Maria Basin, CA, and to examine the effects of drilling activity '!

on these processes. Field experiments were conducted to evaluate the variability of settlement

and recruitment over time, space, and relief heights, and to assess the potential drilling effects i

on settlement,recruitment,survivorship,growth,and fecundity. II

The study was performed in conjunction with the U.S. Department of the Interior (DOI), Minerals i_-

Management Service/National Biological Survey Phase III Study' Program. This program was II

designed to conduct long-term studies on the cumulative effects of offshore drilling and

production activities on the marine environments of the southern Santa Maria Basin (SAIC and I

MEC 1993). The DOI Phase III program follows earlier Phase. I (SAIC 1986) and Phase II Ii

(Steinhauer and Imamura 1990) programs. The Phase I program gathered baseline information

on hard-bottom communities prior to the onset of drilling activities, while the Phase II program n

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included monitoring studies to address impacts to epifaunal communities from drilling operations

Ir (Steinhauer and Imamura 1990; Hyland et al. 1994).

i ETHODS

Study Area

i The study was conducted along a portion of the southern Santa Maria Basin on the California

Outer Continental Shelf (Fig. 1) between Pt. Conception (34° 28' N; 120° 28' W) and Pt. Arguello

reference (34° 35' N;sites120were ° 38'located W). Three at depthsnearfield betweendrilling 160 and /production 210 m. Nearfield platform sites sites with and three adjacentfarfield har

strata were selected within 300 m of Platforms Hidalgo, Harvest, and Hermosa (Fig. 1). The

t reference based on dispersion sites were andoutside deposition of theestimates major influence from previous of the studies expected(Coats Phase1994). III drilling One reference activity,

site was located north, and two others south of the platforms. Experiments were conducted at

0.35 m and 1.25 m above the bottom, which represented "low" and "high" relief heights, respectively, in the study region (Hardin et al. 1994; Hyland et al. 1994).

I The general coastal axis in this area is southeast to northwest. Current patterns in the region are generally influenced by the California Current (Brink et al. 1984), and the study site is

characterized by along-shelf surface flows that run parallel to the shoreline (Chelton et al. 1982).

I Previous studies in the area (Hyland et al. 1990; SAIC and MEC 1993) show a high-frequency tidal influence resulting in across-shelf currents that are particularly strong along the bottom.

Because of these two predominant current regimes, patterns of circulation at the study site are

I complex, often resulting in eddies, swirls, filaments, meanders, and narrow jets (Mooers and Robinson 1984).

I The general topography of the area includes both soft-bottom areas of mud and hard-bottom areas of rocky outcrops with varying relief height. Hardin et al. (1994) classified the hard substrates

into two relief height groups, rocky areas of low relief (0.2-0.5 m) and higher relief reefs (>1.0

I These differencesin abundancesof organismsthroughoutthe area

m). were distinguished by

(Hardin et al. 1994; Diener and Lissner, in preparation). Natural oil seeps are not well

characterized in the study area, but are known to be present along the southern California coast

I (Wilkinson 1972), and some seep areas have been noted vicinity in the of the Phase III hardbottom areas (Lissner et al., personal observation). Microscopic tar particles have been observed

in bottom sediments from the area (Steinhauer et al. 1994), although the hydrocarbon content is

generally low (Steinhauer and Steinhauer 1990). Other potential sources of contaminants include

a several million gallon spill between 1990 and 1991 of an oil distillate into the sea

i approximately 50 km north of the study area (C. Phillips, pers. comm.).

Study Design

I Field experiments were conducted through the deployment of settling plates for varying lengths

of time before drilling and during/after drilling at the study platforms and reference areas. This

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two-way experimental design (Green 1979), with replication, allowed determination of effects on !11

naturalsettlementandrecruitmentdueto drillingactivity. .,

Im

The original design utilized three platform and three reference sites, with the expectation that

drilling would occur simultaneously at the three platform sites to facilitate a true "before vs. I

after" controlled study. However, this study design had to be abandoned when it became

apparent that drilling operations at the three sites would not be sinmltaneous. Drilling occurred

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at Platform Hermosa between September 1993, and October 1993, at Platform Hidalgo between /

October 1993 and May 1994, and did not occur at Platform Harvest. This differential drilling i

pattern provided a unique opportunity to study the natural pattern of effects over three distinctly

different drilling regimes: active, recent, and none. Thus, all comparisons were made using each il

platform site individuallyand compared to the collective reference group.

The field exposure schedule for the experiments is summarized in Figure 2. Natural settlement i

experiments were conducted between April 1992 and January 1995. Exposure durations were |

very short (3-21 days) to test for filming related effects, medium (300-360 days) to assess effects

of drilling on settlement, and long (480-1000 days) to test for effects on the established settled j

community. Recruitment to plates was compared at two distinct time intervals. The medium i

durations correspond to effects on recruitment of new individuals; that were not present at the

beginning of the time interval, and the long durations correspond to effects on organisms that ]l_j

comprised the settling plate community at the beginning of the time interval. II

Specific Methodology '11

Surface Filming: plexiglass settling plates (10 x 10 cm) were used for the experiments. The

surface of the plates was not roughened, although surface smoothness was altered by the _

development of a natural bacterial film prior to transplantation to larval settlement arrays in the i

field. Settling plates were filmed at two relief heights (0.35 and 1.25 m) above the sea floor

using retrievable canisters (Fig. 3). For each canister, the settling plates (180 per canister) were

attached to stainless steel rods and mounted in PVC cylinders. The lower portion of each canister III

was covered with 100 _tm Nitex TM mesh to prevent natural settlement and predation during a 2-3 .

week filming period. Other plates were left uncovered to allow both filming and short-term i

settlement of invertebrate larvae. l

filming moorings with two canisters each (one for each relief height) were deployed at the I

Two

six study sites (three platform and three reference). Two moorings were used to ensure the

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likelihood that at least one would survive over the filming phase of the experiments. In almost ill

every case both moorings were recovered, but only one was used, based on the availability of

enough plates, for subsequent experiments. Upon retrieval the plates were kept cool, dark, and

wet in a shipboard laboratory with a filtered running seawater system. The plates were then ,I1_

sorted by incubation site, and mounted onto deployable larval arrays, hereafter referred to as 11

"igloos"becauseof theirdistinctivehemisphericalshape(Fig. 3).

.4

Deployment and In Situ Incubations: Each combination of filming site, incubation site, and relief i

height was replicated by four plates on each igloo. Plates were secured to the igloos in trays

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containing ten PVC cylinders, each holding one plate (Fig. 3). Trays were arranged on all four

i sides of the igloos to avoid problems associated with the orientation of deployment in the field.

On board the ship, the tray assembly was covered with a black lucite cover, designed to (1) retain

I water inside the tray, and (2) keep plates in dark conditions. Trays were stored in cold-water tanks to maintain ambient conditions. Plates were kept wet throughout manipulation on deck and

deployment. Hoses were connected to the igloos to direct seawater into the trays. This allowed

i the surveytraysvessel, and plates and toprevented be continuously degradationsubmerged of microbial in cold films seawater anduntil settleddeployment organisms.from For the

deployment, igloos were lifted off the deck with a crane and lowered into the ocean to a depth

i of approximately 10 m. SCUBA divers then decoupled the seawater hoses and removed the tray • covers, and checked the integrity of the trays and plates before the igloos were deployed to the

sea floor.

I Retrieval: After the designated duration on the bottom, termed the "incubation time", the igloos

were retrieved for plate processing. On site, an acoustic release system was used to release a

I surface buoy. The arrays were then lifted aboard ship and secured. The on-board filtered seawater system was re-attached to the settling trays to keep the plates cool and wet during

processing as described above. In April and October 1992, short-term plates were preserved in

formalin and returned to the laboratory for identification and enumeration of settled larvae. In

August 1993 and January 1994, all plates were photographed using 35-mm slide film. Long-term

plates were returned to the arrays, but a subset of the plates (medium-term exposures) were

I andreturnedto the In 1994, offilmedmedium-term preserved laboratory. January a new set

plates was deployed at each site to determine effects in the "during/after" drilling period. In

January 1995 all plates were recovered, photographed, and preserved in formalin for laboratory

t, analysis.

i Deployment of Plankton Recorders: In addition to the in situ igloos, automated plankton recorders were deployed at high and low relief heights on their own igloos at one platform

(Hidalgo) and one reference (northern) site. The concept of this igloo design followed the Hardy

i plankton a 12 x 18recorder cm opening (Hardyand1936; throughLonghurst 60 m mesh et al. at1966), a ratewith of 56.7 waterL/min. drawnTheby battery system pump was setintoto

operate for 30 min every 16 hrs for 180 days. This would result in 270 1.73 ms samples, with

i mesh sampling was periods drawn beyond staggeredthe through filtering the areadayand and simultaneously night. Uponmerged completion with a ofsecond each mesh sample, whichthe

covered the sample. Finally, the combination was drawn onto a reel in a storage chamber

containing container fromfrmalin. a concentrated To counteract sourceanyvessel dilution, overadditional the 180 day formalin deployment was pumped period.into the storage

I Unfortunately, samples from being mechanical capturedproblems per deployment with theperiod. mesh uptake These data systemwereprevented not furthermore analyzed. than 14

j Plate Surface Effects: Initial results indicated that either there was very low natural settlement or very high post-settlement mortality, because there were few recruits on experimental plates.

One possibility was that the relatively smooth surface on the plates inhibited settlement or

i increased post-settlement mortality (Raimondi 1988). An additional experiment was conducted

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between August 1993 and January 1994 to determine if plate surface conditions (texture) might

affect the settlement of larvae. Four replicate plates of three types (smooth, grooved, and

roughened) were exposed at both high (1.25 m) and low (0.35 m) relief at each site throughout |

a 160 day exposure period. The response variable was mean recruitment to each type of plate.

Smooth plates were consistent with those described above, grooved plates were made by cutting II

a series of grooves (1 mm deep, 0.5 cm apart) into the surface of the plates, and roughened plates ',II

were scuffed with sandpaper.

Laboratory Analyses: Settling plates and photographic slides of plates were examined under a I

dissecting microscope. The entire surface of the plate was examined and all organisms identified

to the lowest possible taxon. Solitary organisms were counted, _tad percent cover was estimated i

for colonial organisms which could not be counted directly. A statistical (regression) comparison _

was done to determine if data from photographs were comparable to data collected from direct

observation. This analysis was done on three taxa representing both colonial and solitary _

organisms.

Additionally, photographs were taken of the same plates over time and used to estimate the

growth and survivorship for selected taxa that could be tracked photographically. Morphometric gJ

measurements were made using an optical micrometer at a magnification of 12X. Colonial

organismsweremeasuredby determiningthe areaof the colony. 1n

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Data Analysis

I

All data were coded in the NODC taxonomic coding system, double-entry keypunched and '_

subjected to a minimum 10% QA/QC check on all data fields. Data were stored in SAS

databases and statistical analyses were performed in SAS (SAS Institute 1988). In general, i

analysis of variance (ANOVA) was performed on data from each set of incubation times to w/

examine platform proximity and relief height effects. Treatment means were compared following /'L

the ANOVA using the Ryan-Einot-Gabriel-Welch multiple comparison test (REGWQ; SAS

Institute 1988). The REGWQ test is effective for making pairwise comparisons of main effects

following ANOVA (Day and Quinn 1989) and is applicable when replicates are unequal (SAS _-

Institute 1988). This separation technique allowed better understanding of the direction and I

magnitude of changes between the periods (before vs. during/after drilling) at each of the sites.

Film effects were not observed in any initial analyses and were thus dropped as a factor in the I

ANOVA model in subsequent analyses. Only taxa that occurred on at least five percent of the

plates were analyzed individually. In addition, taxonomic groups (e.g., total non-colonial

organisms) that occurred on at least five percent of plates were _dsoanalyzed.

NaturalVariabilityinRecruitment: i_

III

To address spatial and temporal variability in recruitment, data from the three reference sites "-

were analyzed to avoid any platform-related effects. Data from long-term plates were tested with

a 3-factor ANOVA with site (Reference Sites 1, 2 and 3), incubation time (3, 42, 180, 480, 640, l

or 1000 days), and relief height as factors. The significance of the relief height term was

evaluated to determine effects of plate height above the bottom on settlement over the entire 1000 i

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I day exposure period. If no relief height effect was observed the reference site data were pooled

for further comparisons. If there was a significant relief height effect the data were analyzed

i separately by height (high or low). The data were then re-analyzed with a 2-factor ANOVA using site and drilling period as the factors, followed by a REGWQ test (Day and Quinn 1989)

to separate the incubation site means. For each taxon (or taxonomic group), if the data from a

I, reference site different from the other reference sites, it treated single was statistically was as an

outlier and dropped from the reference site pool. If all three sites were statistically different

from one another, these sites were pooled, and the results of the subsequent analyses were

I interpreted with caution, because of the increased variability indicated between sites. Thus, if

a given reference site was acting independently of the other two it was dropped, but if all three

/ sites acted independent of one another then they were kept in the analysis. l

Drillin_ Related Effects:

I' Detection of drilling related effects on recruitment

Data from long term settling plates deployed for either 480 days (before drilling) or 1000 days

I (du Because ringafter thesedrilling) plates were wereincubated used to test for long effects periods on thetheyestablished contained settling higher numbers community of organisms (Fig. 2).

than those with shorter duration exposure plates. Medium term exposure plates (300 days before

i drilling recruited andorganisms. 360 daysBecause during/these after incubation drilling) were periodsusedwereto relatively test for drilling short theyeffects often oncontained newly

small numbers of settlers.

I To test for drilling effects on the established benthic community, mean abundance data from

plates exposed for 480 days in the before-drilling period were compared to data from the same

I plates at the end of the 1000 day incubation. This was tested by a 2-factor ANOVA using incubation period (480 or 1000 days) and incubation location (pooled reference sites, Hidalgo,

Harvest, Hermosa) as factors, and by observing the interaction term. A significant interaction

between period and location would indicate that the abundances of organisms present on the plates changed differently at the sites between periods (before drilling vs. during/after drilling).

Those taxa that showed significant interactions in the 2-factor ANOVA were then tested using

I a 1-factor ANOVA with settlement at each site for each of the time periods as the only factor. Following this analysis each of the means were separated using the REGWQ test.

I onnew were usinga approachas

Effects recruitment tested similar noted above. Recruitment

data from settling plates incubated for 300 days in the period before drilling, and settlement onto

i new plates incubated for 360 days in the period during/after drilling, were used in the analyses.

Physical parameters

i To address physical factors that may influence recruitment variability within the Santa Maria Basin system, recruitment data from the northern reference site (Reference Site 1) and from

Platform Hidalgo were used in a stepwise multiple regression model. This technique was used

i inTheanregression exploratorymodel manner used toseveral determine physicalthe oceanographic major source ofvariables. variationData (Sokal for theandvariables Rohf 1981). were

collected from physical measurements arrays (SAIC and MEC 1995, Appendix A) deployed at

i the same time periods and near the recruitment igloos at the respective sites (Fig. 1). Variables

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available for testing were temperature, salinity, current velocity, total suspended solids, surficial

particulate loading (measured as optical fouling), and drilling. Temperatures, salinities, and /

current velocities averaged over each incubation time were nearly constant (9 + 0.5 ° C, 32.5 + I

0.1 ppt, 25 + 1 cm see-l), and thus were excluded from the regzression since they offered little

predictive power. Consequently, variables tested in the stepwise multiple regression model IN

included: total suspended solids (average, maximum, and time weighted by exposure period); I

optical fouling rate (the time in months to foul optical backscatter instruments); and drilling

(presence or absence). Measures of these variables were available under six of the eight possible i_

conditions (2 sites x 2 periods x 2 relief heights; measures from lower relief height in the |

during/after drilling condition were missing). Therefore, the results from this analysis are

consideredpreliminary, i'

Performance measures

Fecundity was estimated for "dense" hydroid colonies by observing plates with high (>50%) 'l._

coverage following a 360 day during/after drilling exposure period. The proportion of N

reproductive zooids in each colony were determined for 10 plates from the reference sites, and

14 plates from the platform sites. Data for each group were tested with a Student's t-test (Sokal ]l

andRohlf1981). _

RESULTS i

More than 50 taxa were observed in the study (Appendix C-2A), although only seven were 1_

present on at least 5% of all plates (Table 1). In general, only these taxa and certain group totals J

(e.g., total colonial and total non-colonial organisms) were used in the data analysis for the

recruitment experiments. Other organisms could be analyzed when individual performance '!

measures were tracked. I

Photographic methods comparisons: Data from photographs of settling plates corresponded well i

with direct plate observations for both colonial and solitary organisms. Regressions comparing

the slope and intercept of photographic or plate data found no significant difference from a 1:1 md

relationship for three taxa with sufficient pairs to be tested. Mat forming protozoa N

(Komokoiacea) showed the strongest relationship (F1.21=508.6;p<0.0001; xa--0.962). The slope

of the regression was not significantly different from 1 (F1.20=0.53;p=0.48), and the intercept was III

not different from zero (F1.20=0.69; p=0.41). The colonial hydroid, Oplorhiza gracilis, showed n

similar results with a strong relationship between the percent: cover determined from both

photographs and plates (F_.7=52.3; p<0.0004; rZ=0.897). Both slope (F_,6=1.68; p--0.24) and liil

intercept (F1,6=1.02; p=0.35) values were not significantly different from a 1:1 relationship. II

Counts of the solitary mollusc, Delectopecten sp., exhibited a :slightly weaker yet significant

relationship (F_.13--40.6;p<0.001; r2=0.772). As with the other species tested, the relationship i

observed was not different from 1:1 (F_._2=2.85; p=0.12) with a zero intercept (F_.I_=I.00; |

p=0.34). These results indicate that data recovered from the photographs were of similar quality

to those data recovered from direct observations of the settling plates, and could be substituted ,/I

where necessary. i

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Natural Recruitment Processes

I Plate surface effects: Five taxa were found on the plates used for the surface-effects experiment.

Settlement on smooth, rough, and grooved surfaces was tested by a two-factor ANOVA using

i plate each plate surfacewere and tested relief height. separately. EachTaxa taxon,ortotal taxonomic multicellular groupsorganisms, did not appear and total to favor organisms a singleon

plate type. Overall, there was no significant difference between the mean numbers of total

organ someisms effectsor oftotaleither multicellular plate surface organisms or height settlingwereondetected any type of plate (Table 2). However, for individual taxa: Oplorhiza

graciIis showed a preference for smooth plates, and Delectopecten sp. exhibited the highest

i settlement on grooved or rough plates.

Natural Variability in Recruitment: Natural variability in recruitment was determined based on

i data from reference site results. Recruitment rates were very low throughout the early experimental periods and no appreciable settlement occurred on plates with incubation times up

to 180 days. After this time appreciable increases occurred. This temporal variability was most

I notable the firstin300the total days, nufollowed mber of non-colon by large ialincreases organism(Fig. s for4).whichBecause low recruitment there was was virtually found noin

recruitment in the early period, differences that occurred in plate filming prior to conducting

I cross-transplants be assessed. were not measurable. Therefore, filming effects on natural settlement could not

I Recruitment on plates at the three reference sites showed that there was considerable spatial variability at the reference sites. This was characterized by differences in the recruitment at the

two relief heights (Table 3) and differences between reference sites (Table 4). Comparisons of

I settlement at the three reference sites showed significant relief height differences in settlement for four of the nine taxa or groups (Table 3). The remaining five taxa showed no relief height

difference; plates from both heights were combined in subsequent analyses of these taxa.

I Large-scale spatial variability was considered in a preliminary assessment of whether a reference

site was an outlier and therefore should be dropped from reference vs. platform site comparisons.

i An example of a high degree of variability at by a single the reference sites introduced site

outlier is exemplified by the response of serpulid worms (Table 4; Fig. 4). Serpulids settled in

high numbers at the southern reference site (Reference Site 2), but fairly evenly at the other

I reference sites and at the platform sites (not shown or tested). Consequently, Reference Site 2

was not used in subsequent comparisons for serpulid worms.

i Total colonial organisms exhibited extreme variability between reference sites (Fig. 4), with over

two orders of magnitude greater variability found between sites than within a site (Table 4).

i Subsequent analysis by REGWQ showed that all three reference sites were statistically different from one another. However, because no site was identified as an outlier, all three were pooled

for subsequent comparisons.

l Oplorhiza gracilis, Cyclostomata, and total colonial organisms showed no differences in

settlement between relief heights. Delectopecten sp., Komokoiacea, colonial hydroid colonies,

I and total non-colonial organisms showed significant differences between relief heights; thus,

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analyses of these taxa or groups were done separately for eaclh relief height. Variability in

settlement between sites was high for organisms on lower plates; all of the taxa showed i

differential settlement for at least one reference site (Table 4). 13,electopecten sp. and total non- |

colonial organisms had significantly higher settlement on plates at the southern reference site

(Reference Site 2), while dense hydroid colonies showed higher settlement at the middle I

reference site (Reference Site 3). Komokoiacea mats on the lower plates were much more tl

variable between than within sites (MSB=1126 v. MSE=87; Table 4); this was influenced by very

low settlement at Reference Site 1. Similarly, Komokoiacea mats on the upper plates had Nil

significantly lower recruitment at the northern reference site. These outlier reference sites were m

dropped from subsequent analyses.

Total non-colonial organisms on upper plates had a high degree of variability (between site ,!

MSB=7699; within site MSE=141) (Table 4). All reference stations were significantly different

from one another and none was considered an outlier. D"

mm

Performance Measures (Growth, Survivorship, and Fecundity): Organisms on plates exposed less

than 400 days were considered new recruits (e.g., Fig. 4). Growth data for these organisms were [_

obtained by dividing the organism size at the end of the period by the total number of months g

the plate was in the field. This yields a proportional growth rate measured as an increase factor

per month (i.e., x times larger per month). For example, a growth rate of 0.75 means that the rn

organism increased three-quarters of its original size each month. This assumes that the xl_

organisms settled at the beginning of the period and represents a measure of minimum growth

rate. '1

Five taxa of newly recruited organisms were evaluated for growth of colonies or individuals. i

Because the growth of new recruits was measured by observation of individual organisms or _

colonies over time, new taxa were included that otherwise were not tested in this study;

however, these represented species of the larger groups included throughout this study. These m

new taxa were the bryozoans Cabera ellisi and Microporella sp., the sponges (Porifera) as a •

group, and the solitary serpulid polychaete, Haplopomatus biformus. Average growth for newly _/

recruited colonial organisms at the reference sites was variable,, ranging between 0.792 for m

Porifera to 5.00 for the Cyclostomata (Table 5). The polychaete H. biformus showed an increase il

of 0.914, almost doubling in size each month. Although the sample sizes were small, these

growth estimates represent the first measure for these taxa in deep waters. _m

Established organisms were defined as those that had recruited to the settling plates by 480 days

of exposure in the field. Only colonial forms were available for growth measurements of il

established organisms. Since a record existed (photographs) of the organism size at the beginning J

of each period a more accurate growth record could be established. Therefore, growth data for

established organisms were obtained by dividing the difference between the colony size from one _lm

time period to another by the total number of months between periods. This yielded a I

proportional growth rate per month that could be compared across taxa. "_

if

Colonies on settling plates were evaluated for five taxa that we:re represented by the colonial U

organisms used throughout this study (Table 5). Average growth was generally similar for all

taxa and ranged from 0.278 for dense hydroid colonies to 0.874 for colonies of Komokoiacea. I

(C-2) 10

!
!

As with the growth for newly recruited organisms, measurements for established colonies were

i limited and most sample sizes were small.

Survivorship for newly recruited organisms was high with most organisms showing 100%

survival over the entire 5 month tracking period (August 1993 to January 1994). Only the

l polychaete H. biformus showed decreased survival with surviving

42% of 12 individuals

throughout the tracking period (Table 5). Survivorship of established colonies, tracked over 17

i months The hydroid (AugustOplorhiza 1993, January gracilis1994, showed and January 1995), was lower than that for new colonies. low but even survivorship over time with 25-33%

survival over the 17 month period. Survivorship of the Komokoiacea was higher initially with

j 87% after 5 months declining to approximately 50% up to 17 months.

Only one species exhibited measurable reproductive activity in this study. Fecundity of dense

i hydroids, average ofas11.53% measured (SE=0.960, by the n=14). density Fecundity of reproductive was measured zooids inin the January colony, 1995wasfollowing low witha 360an

day incubation period on plates, and may represent a seasonal (winter) low. No other

l measurements seasonality of reproductive from this study zooid ordensity data infromdeep-water other studies hydroids. were available to compare the

Detection of Drilling-Related Effects

Drilling at the study area platforms was not synchronous and did not occur at Platform Harvest.

t Drilling at Platform Hermosa was conducted between September and November 1993 and resulted in the discharge of approximately 800 m 3 of drilling muds, 130 m3 of drill cuttings, and

an average of 0.59 million gallons per day (MGD) of produced waters. Drilling operations at

Pmlatform Hidalgo occurred between November 1993 and May 1994, and discharged over 3800 3 of muds, 730 m3 of cuttings, and 1.72 MGD of produced water.

I Two distinct biological responses of the biota (positive or negative) at the study sites could be indicative of drilling-related effects, whether persistent or short-term. These outcomes would be

i reflected in the response pattern found at the platform sites in relation to the response at the reference sites. Patterns can be discerned by observing the difference, commonly referred to as

the "delta (A)" (Green 1979; Stewart-Oaten et al. 1986; Underwood 1994), between time periods

(before vs. during/after drilling) at each site. Since drilling activity was different at the three

I platforms throughout study (active drilling at Hidalgo, previous drilling

the Platform at Platform

Hermosa, and no drilling at Platform Harvest), the degree of effect might be expected to follow

i a similar pattern. Four specific scenarios that describe potential positive and negative outcomes • are outlined below. Since no drilling occurred at Platform Harvest, all scenarios would be

independent of changes occurring there.

Scenario 1A (persistent negative effect of drilling):

I A Reference > A Hidalgo and A Hermosa

This pattern would be observed when the temporal change (A) at the reference site is greater than

i that observed at both Platforms Hidalgo and Hermosa. It would indicate that relative to the

(C-2) 11

!
II

reference sites, organisms at platforms that underwent drilling exhibited decreased performance ml

regardless of the history of the drilling, and that even when drilling ceased (Hermosa) c.

performance at that platform continued to be diminished compared to the reference sites. I

Scenario 1B (short-term negative effect of drilling): II

AReference=AHermosa g

AReference>AHidalgo

U

This result would occur when the temporal change at Platform Hermosa was similar to that at

the reference sites, and the changes at both the reference sites and Hermosa were greater than

those at Hidalgo. This would indicate that organisms at sites with ongoing drilling activity _l

(Hidalgo) performed relatively poorly, while sites with recent drilling (Hermosa) responded

similarly to the reference sites. Therefore the negative effect of drilling is transitory in nature, i

W

Scenario 2A (persistent positive effect of drilling):

lib

AReference<AHidalgoandAHermosa 'U'

This scenario is similar to the first, with the exception of the direction of response. Responses -_

that are greater at both Platforms Hidalgo and Hermosa than at reference sites would indicate a !I

net enhancement of performance regardless of the temporal scale of drilling.

/

Scenario 2B (short-term positive effect of drilling): '_'

AReference<AHidalgo ,n

A Reference = A Hermosa

This last scenario shows that a positive effect of drilling (enhancement of performance) is I

detected only when drilling is underway (Hidalgo); it is not observed after drilling ceases

_m

(Hermosa). Like Scenario 1B it would show the transitory nature of the effect. _1

l

Effects were identified through a two-step process. First a 2-factor ANOVA using drilling period

(Before and During/After drilling) and site (Reference, Hidalgo, Harvest, and Hermosa) was

performed on each taxon or taxonomic group. A significant iLnteraction term suggested a

potential drilling discharge effect. The pattern of the temporal changes (deltas) at the different

sites were then compared, to a delta range corresponding to a 50% change at the reference sites i

(A Reference + 50%). This level was used as a conservative indicator for the detection of I

environmental impacts in a recent field study of invertebrate populations near a nuclear

generating station (Schroeter et al. 1993). Several authors have advocated using a conservative

indication level when determining environmental impacts to increase the confidence of any 11

impacts concluded from such studies (Osenberg et al. 1993; Schroeter et al. 1993; Underwood "_

1994). Deltas from platform sites outside this conservative range were considered representative am

of real drilling related effects. Any response pattern that did not fit within one of the above !!

scenarios was considered inconclusive or indicated that there was no detected effect of drilling

activities, i

(C-2) 12

!
!

Effects on new recruitment: As above, organisms on plates exposed less than 400 days were

i considered new recruits. Seven taxa and two groups of taxa showed significant interactions between experimental site and period (Table 6). These organisms represented both solitary and

colonial forms.

Comparisons of delta patterns revealed drilling-related effects on four taxa/groups. Three taxa

showed patterns consistent with positive effects and one with a negative effect (Table 7). The

l colonial greater increase hydroid inOplorhiza cover occurring gracilis and at bothdenseplatform hydroidsites matsthanbothat showed the reference similar(2Apatterns persistent with

positive effect). Oplorhiza gracilis displayed increases at the platforms that were over two times

i that reference. of the reference, Total non-colonial while denseorganisms hydroidsshowed increaseda short-term by up to twopositive orderseffect of magnitude with the over delta theat

Platform Hidalgo over two times that of the reference, while the delta at Hermosa was within

i 50% of the referencesite.

Komokoiacea showed the only negative effect of drilling observed in this study and this was a

i short-term decreased (over effect4 (Table times lower) 7). Coverage comparedoftothese a netmat-forming increase at theprotozoans reference atsite. PlatformHowever, Hidalgo the

delta at Platform Hermosa was within the range of the reference. Thus, Komokoiacea

I performance drilling had ceased was worse for awhen perioddrilling of time.was active, but no change was evident at the site where

I Effects on established organisms: Established organisms (defined as those organisms that had recruited to the settling plates by 480 days) were censused in the before drilling period after they

had become established on the plates. The objective was to evaluate how drilling activities may

I have affected these established recruits over time in the during/after drilling period. They were recensused after the plates had been incubated for 1000 days.

I Only two taxa (Cyclostomata and dense hydroids) and two (non-colonial organisms and groups

colonial organisms) showed significant interactions between experimental site and drilling period,

indicating a change in the relationship of the established community between the periods (Table

I showed interactionsforboth andlowrelief while 6). Dense hydroids significant high heights

total non-colonial organisms showed a significant term for low relief plates only. All of the

i organisms that showed interactions between 480 and 1000 days exposure were colonial forms. All other taxa (or groups of taxa) showed no effect.

i Response patterns based on analysis of the difference (deltas) between the recruitment at 1000 days and 480 days revealed effects only to Cyclostomata and total non-colonial organisms (Table

7). Both taxa/groups showed patterns consistent with enhancement of recruitment in response

t to drillingactivity.

Total non-colonial organisms recruiting to lower plates showed a pattern consistent with a

i persistent greater thanpositive that at effect the reference (2A) withsite.deltas In fact, at bothtotalPlatforms non-colonial Hidalgo organisms and Hermosa decreasedbeing(negative much

delta) at the reference site, while both platform sites experienced as much as 28-30 times the

I originally censused recruitment between the 480 and 1000 day incubation times (Table 7).

(C-2) 13

I
!

Cyclostomata showed a large increase in coverage at Platform Hidalgo relative to the reference,

but no change at Platform Hermosa. The pattern in Cyclostomata was consistent with a short- i

term positive effect (2B). II

Relation to Oceanographic Variables: Stepwise multiple regression on recruitment of organisms i

at the northern reference site (Site 1) and Platform Hidalgo revealed several physical J

oceanographic variables that may be responsible for the recruitment patterns at the two sites. For

example, four of the eight taxa tested (Cyclostomata, Oplorhiza gracilis, Triticella sp., and total

colonial organisms) showed that the presence of drilling explained most of the variation (Table S

8). For two taxa (Serpulidae and total non-colonial organisms) incubation time (either 300 days

or 360 days) explained most of the variation observed. The total suspended material, weighted

for the incubation time (300 or 360 days), was the factor most associated with recruitment of t1"

Delectopecten sp. Recruitment of Komokoiacea was explained best by the length of time it took

to foul optical instruments on the physical measurements arrays. This suggests that biofilming

of hard substrate led to a more suitable recruitment site for Komokoiacea. The relationship may U

also have resulted from differential recruitment of Komokoiac:ea to the optical instruments

themselves, leading to fouling of the optics. However, this was never tested directly and no

samples of the matter on the optical instruments were collected (SAIC and MEC 1995). g

Effects on Performance Measures (Growth, Survivorship, and ]Fecundity): Average monthly a

growth of newly recruited organisms at the platform sites was generally similar to that observed

from the reference sites. Growth at platform sites ranged from 1.01 times (an approximate

doubling per month) for the polychaete Haplopomatus biformus _Lo4.25 times for Cyclostomata ._

(Table 5). Statistical comparisons of platform and reference growth rates for Haplopomatus II

biformus, Cyclostomata, and Porifera showed no significant difference. While sample sizes were i

larger than those for the reference sites, due to higher recruitment at the platform sites, sample ]_

sizes were still small. v

Growth for established colonial organisms (Table 5) was also :similar between reference and R

platform groups. It ranged from 0.04 times for Cyclostomata to 2.89 times for dense hydroid

colonies at platform sites. No statistical difference was detected between sites for any i

taxon/group. l

Survivorship varied for both new recruits and established colonies. For 70% of the taxa, greater t

than 80% of the organisms survived for as least 5 months (Table 5). Survivorship ranged from l

33-66% for the others. Survival of new Porifera colonies dropped off from 100% at 5 months

to only 20% by 17 months. Established colonies of the hydroid Oplorhiza gracilis was generally _i

low but relatively even (10-25%) over the entire 17 month tracking period. Survivorship at tl

platform sites was either higher (e.g., Komokoiacea for 12 months) or not significantly different

(e.g., Oplorhiza gracilis) than the survivorship observed at reference sites for the same

taxon/group. |

Mean fecundity of dense hydroid colonies at reference sites was 11.53% (SE=0.960, n=14) _1_

while that at platform sites was 9.41% (SE=1.375, n=10). The,re was no difference between !1

!

(C-2) 14

!
!

reference sites and platform sites (t-test; t22=1.31; p=0.20), although the sample size tested was

i very small and yielded rather low power (0.54) to detect differences.

i DISCUSSION

Recruitment of Hard Bottom Organisms in the Santa Maria Basin

t Numerous experimental studies have shown that plate surface roughness can influence the microhydrodynamics around a settlement surface, thereby influencing the degree of recruitment

I did (Mullineaux not influence and Butman the density1990). of recruits, Mullineaux it did(1988) influence demonstrated the numberthatofwhile taxa surface recruitingroughness to each

type of surface. In the present study, plate surface roughness was found to be a factor that

I influenced of recruitment recruitment influencein four amongof thetaxasevenor taxonomic cases testedgroups. (Table 2);Members however, oftherethe was sameno general pattern

taxonomic group (e.g., colonial organisms) demonstrated strikingly different recruitment patterns.

I When surfaceallconditions non-colonial wasorganisms observed. were Although pooled,roughness no significant was difference found to bein recruitment a factor, its toeffect different was

constant for each taxon because a single plate type (smooth) was used throughout the study.

I Recruitment estimates or organisms that preferentially settle onto grooved or roughened surfaces (e.g., Delectopecten sp.) might be lower in this study.

i Recruitment to settling plates exhibited a high degree of spatial and temporal variability _ throughout the study. This was especially evident based on recruitment results from the reference

sites since they were not confounded by effects from drilling activities. Spatial variability was

I evident on both vertical and horizontal scales. For example, taxa settled differentially onto plates • at varying heights from the sea floor (Table 3) and at different reference sites (Table 4), often

by factors of 2 and 10, respectively. However, no obvious spatial pattern in settlement was

I discerned for taxa for taxonomic Some solitary taxa preferentially settled onto specific or groups.

high or low plates, while others settled in relatively equal numbers between plate heights. This

was true for the colonial organisms as well and demonstrates the high degree of variability

I observed throughout experiments.

these

i The observations from this study are similar to several literature reports of natural recruitment in the deep sea. Mullineaux (1988) showed that early recruitment of deep sea larvae (primarily

Formanifera) onto hard surfaces was strongly influenced by elevation of the surface above the

i sea floor. Her study was performed at a much greater depth (1300 m) than the present study

(about 200 m), although the recruitment levels were similar. In a similar study, Keough and

Downes (1982) showed that spatial variation in recruitment of marine larvae to different surfaces

(rocks some species, with refuges possiblyvs. flat to avoid rocks)predation. could be explained by the active selection of microhabitats by

I Astudy. high degree Not onlyofdidtemporal it tkevariation a long time in recruitment (> 180 days)to settling for substantial plates was recruitment also observed to occur, in this but

recruitment was different among the reference sites. No reference site showed consistently low

I (or high) recruitment across all taxa. For example, Reference Site 2 in the south had relatively

(C-2) 15

1
!

higher recruitment for solitary (non-colonial) organisms, while ,colonial organisms at the same

site showed an intermediate degree of recruitment compared to the other reference sites (Table II

4). The patchy nature of this recruitment possibly may reflect local oceanographic conditions. ,11

Several researchers have linked recruitment of benthic invertebrates in the deep sea to local,

small-scale, turbulent hydrodynamic events such as eddies or jets (Eckman 1983; Mullienaux i

1988; Grassle and Morse-Porteous 1987; Mullineaux 1995). C_ceanographic measurements in e

the area showed a predominant yearly summer/winter cycle in the general current patterns (SAIC

and MEC 1995), although small-scale eddy conditions near the bottom were not measured or /I

observed due to the scale of sampling during the present study. g

A long period of exposure was required before substantial numbers of recruits were observed on I

the settling plates in this experiment. In general, greater than _L80days was necessary before _J

plates had consistently observable recruits (Fig. 4). The most probable reasons suggested by -.

Mullineaux (1988) are very low larval and/or food availability at these depths. This was II

addressed using automated plankton recorders, but due to mechanical problems those data were |

unavailable to corroborate this hypothesis.

It

Several studies of recruitment in the deep sea have observed similar periods to achieve I'

sustainable recruitment. Kukert and Smith (1992) found that experimental plots on the Santa

Catalina Basin (>1200 m depth) required more than 23 months before colonizing organisms /

displayed enhanced species diversity. In a study of macrofanual colonization of disturbed I!

sediments in the deep sea, Grassle and Morse-Porteous (1987) found that over a five-year period

organisms colonizing azoic trays never reached the density of the natural community. These I

studies indicate that natural colonization rates in the deep sea may be very long and not q

inconsistent with those observed in the Santa Maria Basin.

II

Very few estimates of survival, growth, or fecundity exist for deep-sea benthic organisms, and

the estimates presented here are the first for organisms of the Santa Maria Basin. In general, /

survival of colonial organisms recruiting to plates was high for both initial recruits, and _i

established colonies over the study period (Table 5). Both colonial and solitary new recruits

it

survived well for the early period following recruitment (< 5 mo), but significant losses occurred i

after that. No

comparativesurvivorshipinformationis available. R

It has been reported that many encrusting organisms, such a'_ hydroids (Braverman 1963; _lm

Jormalaien et al., 1994), sponges (Johnson 1979), and polychaetes (Qian and Chia, 1994) can I!

grow to become reproductive within the first five months of settlement, although these studies

focused on shallow water species only. Survival for up to five months in the deep sea may not

be long enough for many recruiting organisms to become fully reproductive. Estimates of t

fecundity for hydroids at the Santa Maria Basin study site showed that only 11% of the zooids

were reproductive after one year in the field. For comparison, Jormalaien et al. (1994) I_

demonstrated that a colonial hydroid at peak reproductive output: had an estimated 80% of the l

zooids that were reproductive.

a

It is likely that lower temperature or food limitation, or both, may be responsible for delayed I

reproductive output in benthic organisms at depth; however, growth estimates obtained for

organisms in this study were comparable to those reported in the literature for similar organisms J

(C-2) 16

!
!

in shallower water. As an example, Quian and Chia (1994) showed growth rates of a capitellid

polychaete in temperate waters to be approximately equal (1-2 times increase per month) to those

observed here. Similarly, hydroids from temperate fouling approximately

communities doubled

in size over a yearly growing period (Schmidt and Warner 1991). One notable exception is the

Porifera. month whereas NewlyBergquist recruited sponges (as a group) in this study increased in size by 0.792 times per (1978) reported a growth rate of approximately 6 times per month for

Haliconia sp., a ubiquitous sponge.

Drilling-Related Effects

I Because experimental drilling designat had the study site was variable and recruitment was very low, the present low power to detect effects. However, the overall pattern of recruitment

at the platform compared to the reference sites suggests some possible effects of drilling. If

I activities recruitmentassociated (or performance) with operations of organisms at the drilling then itsites shouldwerebecontributing evident whento changes observingin the the

differences (deltas) in the response variables between the before and during/after periods. This

I technique environmental has been impacts advocated in fieldbystudies severalwhere authorsreplication as the most in space powerful is likely technique to be tolimited demonstrate (Green

1979; Hurlburt 1984; Stewart-Oaten et al. 1986; Underwood 1994). Because the pattern analysis

i utilized in this study relied only on statistically significant interactions between site (reference vs. drilling) and period (before vs. during/after) (Table 5), and was restricted to patterns relative

to a delta of 50% change at the reference sites (Table 6), there is confidence that the patterns are

i truly indicative of the effects of drilling at the study site.

The responses observed for established organisms showed that when the pattern was indicative

I of an effect, it was primarily positive (Table 6B). Enhancement of recruitment was observed for both the Cyclostomata (bryozoan) and the group of all non-colonial organisms. All other

organisms (3 of 5) showed a pattern that was not consistent with an effect (either positive or

I negative). Similarly, when effects were noted for newly recruited organisms, the patterns were

generally positive (Table 6A). The notable exception was for the mat-forming protozoans of the

Komokoiacea, which showed the only negative effect associated with drilling activities.

I However, that effect considered short-term since it was observed only at

even negative was

Platform Hidalgo where drilling was on-going, and not at Platform Hermosa where drilling had

occurred recently, but was not active. The most logical conclusion is that effects from the

i activities at Platform Hidalgo (e.g., drilling, effluent discharges, or unknown activities) partly

restricted new recruitment of Komokoiacea, but once they were established at Platform Hidalgo,

no further effects were observed.

Based on step-wise multiple regression analysis on the relationship between recruitment and

i oceanographic important factor /drilling in the observed variables patterns. (Table 8),While drilling this analysis activitieswaswerelimited, furtherdrilling implicated activityaswas an

suggested as the primary source of recruitment variability in 50% of the species tested.

I Measures of the performance (growth, survivorship, and fecundity) of recruited organisms were

similar between platform sites as a group and reference sites as a group. The lack of a

I significant difference between these two groups suggest no significant effect of drilling activity

(C-2) 17

I
|

on these parameters in the field. The major limitation of these a:aalyses was that the study was -_

limited to small sample sizes and, therefore, low statistical power to detect differences. The low dim

sample size was a consequence of low and patchy recruitment throughout the study. This is

always a risk when conducting a natural experiment in the field. Laboratory studies in which ,v

important variables such as toxicant dose, larval availability, or the ability to accurately track i

individual performance are highly controlled and may lead to betl:er estimates of drilling effects; |

however, this would be at the expense of a higher degree of reality as represented by the present

type of natural experiment (Raimondi et al., in preparation; see Appendix C-3 in SAIC and MEC _tm

1995). U

Conclusions and Recommendations for Future Research '_l

This study suggests that natural recruitment of hard-bottom organLismsin the Santa Maria Basin

is extremely variable in both time and space. Patchy distribution may reflect low larval it

abundance and/or food availability, as also influenced by physical oceanographic factors. The l

high degree of natural variability in recruitment made it extremely difficult to detect drillingrelated effects (observed in 6 of 22 tests in 4 of 11 taxa/groups), regardless of the direction I

(positive or negative). However, the results suggest that when drilling activities were associated S

with changes in recruitment, they generally acted to enhance settlement.

The study was restricted in its ability to detect drilling effects due to low or variable rates of !

natural recruitment. Given the large number of taxa observed (>50; Appendix C-2A), relatively

few (11) were able to be tested, either because of low settlement at most sites or high recruitment

of a taxon at only oneor two sites withno recruitmentat others.

Larger, less variable sample sizes of settlement and recruitment were possible based on the design

of an additional study using in situ settlement conducted at the Santa Maria Basin study sites Ur

(Raimondi et al., in preparation; see Appendix C-1 in SAIC and M[EC 1995). In this study larval

availability was controlled by manipulating the density of larvae (red abalone, Haliotis rufescens). I

Trading off a level of natural realism for increased control may prove to be a more powerful rig

technique in addressing environmental impacts than using natural experiments. I

W_

ACKNOWLEDGEMENTS !

We wish to thank the Department of the Interior (DOI), Minerals Management Service/National

Biological Service, G. Brewer, F. Piltz, G. Reetz, and L. Thorsteinson for their support of this /

natural recruitment study. The efforts of D. Diener in the field, J. Ljubenkov in the laboratory, I

and A. Lissner in editing are greatly appreciated. This work was supported as part of DOI

Contract No. 14-35-0001-30584 to Science Applications International Corporation.

n

!

!

(C-2) 18

!
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I collection of multiple serial plankton samples. Deep Sea Res. 13:213-222.

Mooers, C.N. and A.R. Robinson. 1984. Turbulent jets and eddies in the California Current and

i inferred cross-shore transports. Science. 223:51-53.

Morse, A.N.C., C.A. Floyd, and D.E. Morse. 1984. Molecules from cyanobacteria and red algae

that induce larval settlement and metamorphosis in the mollusc Haliotis rufescens. Mar.

Biol. 81:293-298.

I Morse, induced A.N.C. byandmolecules D.E. Morse. uniquely1984.available Recruitment at the surfaces and metamorphosis of crostose redof Haliotis algae. J.larvae Mar.

Biol. Ecol. 75:191-215.

I Mullineaux, L.S. 1988. The role of settlement in structuring a hard-substratum community in

the deep sea. J. Exp. Mar. BioL Ecol. 120:247-261.

I Mullineaux, L.S. 1995. Implications of mesoscale flows for dispersal of deep-sea larvae. In:

Young, C.M. and K.J. Eckelbarger (eds.). Reproduction, larval biology, and recruitment

I of the deep-sea benthos. Columbia University Press. NY, pp. 201-222.

Mullineaux, L.S. and C.A. Butman. 1990. Recruitment of encrusting benthic invertebrates in

I boundary-layer flows: A deep-water experiment on Cross Seamount. Limnol. Oceanogr.

35(2):409-423.

i Mullineaux, L.S., P.H. Wiebe, and E.T. Baker. Hydrothermal vent plumes: 1991. Larval

highways in the deep sea? Oceanus. 1991:64-68.

Mullineaux, L.S., P.H. Wiebe, and E.T. Baker. 1995. Larvae

of benthic invertebrates in

hydrothermal vent plumes over Juan de Fuca Ridge. Mar. Biol. 122:585-596.

Nisbet, R.M., W.W. Murdoch, and A. Stewart-Oaten. 1995. Consequences for adult fish stocks

of human induced mortality on immatures. In: Schmitt, R.J. and C.W. Osenberg (eds).

I The in press design . of ecological impact assessment studies: Conceptual issues and application.

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Osenberg, C.W., R.J. Schmitt, S.J. Holbrook, K.E. Abu-Saba, and A.R. Flegal. 1994. Detection _W

of environmental impacts: Natural variability, effect size, and power analysis. Ecol.

Appl. 4(1): 16-30. 'i

Qian, P-Y and F-S Chia. 1994. In situ measurement of recruitment, mortality, growth, and

fecundity of CapiteUa sp. (Annelida: Polychaeta). Mar. Ecol. Prog. Ser. 111:53-62. !

Raimondi, P.T. 1988. Rock type affects settlement, recruitment, and zonation of the barnacle

Chthamalus anisopoma Pilsbury. J. Exp. Mar. Biol. Ecoi'. 123:253-267. B

Raimondi, P.T., A. Barnett, and P. Krause. The effects of drilling muds on marine invertebrate i

larvae and adults, in preparation.

l

Raimondi, P.T., A. Barnett, and P. Krause. Effects of offshore oil and gas development on /

marine larval settlement: In situ manipulated field experiraents, in preparation. II

Raimondi, P.T. and D.C. Reed. 1995. Determining the spatial extent of ecological impacts i

caused by local anthropogenic disturbances in coastal marine habitats. In: Schmitt, R.J. ti

and C.W. Osenberg (eds). The design of ecological impact assessment studies:

Conceptual issues and application, in press. I

Raimondi, P.T. and R.J. Schmitt. 1992. Effects of produced water on settlement of larvae: Field

tests using red abalone. In: J.P. Ray and F.R. Englehardt (eds). Produced water: i

Technological/Environmental issues. Plenum, New York, NY, pp. 415-430. W

Rodriguez, S.R., F.P. Ojeda, and N.C. Inestrosa. 1993. Settlement of benthic marine

invertebrates. Mar. Ecol. Prog. Ser. 97:193-207. 'Q

Rowley, R.J. 1989. Settlement and recruitment of sea urchins (Strongylocentrotus spp.) in a sea- \'_

urchin barren ground and a kelp bed: Are populations regulated by settlement or postsettlement processes? Mar. Biol. 100:485-494.

!

SAIC (Science Applications International Corporation). 1986. Assessment of long-term changes

in biological communities of the Santa Maria Basin and western Santa Barbara Channel:

Phase I, Vol. II Synthesis of Findings. Report to the U.S. Department of the Interior, il

Minerals Management Service, Pacific OCS Region, Los Angeles, CA, under Contract

No.14-12-0001-30032. j

SAIC and MEC (MEC Analytical Systems, Inc.). 1993. Monitoring and Assessment of LongTerm Changes in Biological Communities in the Santa Maria Basin: Phase III, Year One i,

Report. Report to the U.S. Department of the Interior, Minerals Management Service, |

Pacific OCS Region, Camarillo, CA, under Contract No. 14-35-0001-30584.

i

SAIC and MEC. 1995. Monitoring Assessment of Long-Term Changes in Biological i

Communities in the Santa Maria Basin: Phase III, Final Report. Report to the U.S.

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I Department of the Interior, Minerals Management Service/National Biological Service,

under Contract No. 14-35-0001-30584.

I SAS Institute. 1988. SAS/STAT User's Guide, Release 6.03 Edition. Cary, NC.

t Schmidt, G.H. and G.F. Warner. 1991. The settlement and growth of Sertularia cupressina (Hydrozoa, Sertulariidae) in Langstone Harbour, Hampshire, UK. Hydrobiologia.

i 216/217:215-219.

Schroeter, S.C., J.D. Dixon, J. Kastendiek, R.O. Smith, and J.R. Bence. 1993. Detecting the

ecological effects of environmental impacts: A case study of kelp forest invertebrates.

I Ecol. Appl. 3(2):331-350.

i Sokal, R.R. and F.J. Rohlf. 1981. Biometry, 2nd Edition. W.H. Freeman and Co., San Francisco, CA.

I Steinhauer, water,M. and and animal W. Steinhauer. tissue. California 1990. Chemical OCS analysis Phase II ofMonitoring hydrocarbonsProgram: in sediments, Year-Three pore

Annual Report. Vol. I. Report to the U.S. Department of the Interior, Minerals

" Management 0001-30262. Service, Pacific OCS Region, Los Angeles, CA, under Contract No. 14-12-

I Steinhauer, concentrations M., E. Crecelius, of hydrocarbons and W. Steinhauer. and trace 1994. metals Temporal in the vicinity and spatial of anchanges offshorein oil- the

production platform. Mar. Env. Res. 37:129-163.

Steinhauer, M. and E. Imamura (eds). 1990. California OCS Phase II Monitoring Program:

Year-Three Annual Report. Report to the U.S. Department of the Interior, Minerals

I, Management 0001-30262. Service, Pacific OCS Region, Los Angeles, CA, under Contract No. 14-12-

I Stewart-Oaten, A., W.M. Murdoch, and K.R. Parker. 1986. Environmental impact assessment: "pseudoreplication" in time? Ecology. 67:929-940.

I Todd, C.D. and M.J. 1994. Larval settlement in hard substratum Keough. epifaunal

assemblages: a manipulative field study of the effects of substratum filming and the

presence of incumbents. J. Exp. Mar. Biol. Ecol. 181"159-187.

Underwood, A.J. 1994. On beyond BACI: Sampling designs that might reliably detect

environmental disturbances. Ecol. Applications. 4(1):3-15.

Wilkinson, E.D. 1972. California offshore oil and gas seeps. California Division of Oil and

i GasPub.No.TR-08,1lp.

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,

LISTOFTABLES t

list of organisms observed on at least fiw', percent of all settling plates. I

Table 1: Taxonomic

These taxa or groups were used in settlement/recruitment analyses at reference stations. Taxa

wereidentifiedtothelowestpracticallevel. I

J

Table 2: Mean numbers of solitary organisms, percent cover of _vlonial ,'^" organisms per plate

and results of ANOVA for plate surface experiment. ANOVA probabilities of rejection of I-Io:

no difference in settlement; ns = p > 0.05. Rankings of settlement surface type were determined l

through REGWQ analyses following the ANOVA.

Table 3: Results of 3-factor ANOVA (site, relief height, and deployment period) for effects of I

relief height (RH) on settlement of taxa observed on five percent or more of plates at reference

sites only. Reference data for taxa that did not show significant differences were pooled for t

subsequent comparisons. I

Table 4: Results from 2-factor ANOVA (reference site by deplLoyment period) indicating the II

degree of variability in recruitment on settling plates at reference (Ref) sites. Significant results g

from REGWQ test were determined at a significance level of p=0.05. If single reference sites

were determined to be outliers, relative to the other two reference sites and the platform sites,

they were dropped from further analyses. Retained reference sites were pooled in before and l

during/after groups.

m

Table 5. Growth and survivorship of new recruits (tracked as individuals or colonies) and "I

established colonial organisms (tracked as percent cover of colony on entire plate). Growth is

expressed as proportional increase per month and survivorship as percent surviving over a given II

time period. Plates were observed in August 1993, January 1994, and January 1995. Data were

combined for plate height and plates were grouped as either reference or platform sites. Where

applicable, growth data for groups are tested against each other with either a Student's t-test or _I

Mann-Whitney Rank Sum Test. Both statistical tests are evaluated at a level of (t = 0.05. When m

tested, no significant differences in growth rates were found between reference and platform sites g

foranytaxa. 1

Table 6: Results of 2-factor ANOVA on (A) established organisms and (B) new recruits

showing results of testing the interaction of settlement location (Reference, Hidalgo, Harvest, and 11

Hermosa) and incubation period (480 days [before drilling] vs. 101_ days [during/after drilling])

for effects. Reference locations used in the individual analyses correspond to those determined !1

to be most relevant (see Table 4). Plate heights were combined when no difference due to plate I height (high vs. low) was determined (Table 3).

Table 7: Ranking of observed responses of (A) established organisms and (B) new recruits 1

following drilling activities. Responses are ranked based on comparison of the delta values for

Platform Hidalgo and Hermosa relative to a 50% change from the delta observed from the II

reference. Response scenarios correspond to one of the four patterns outlined in the text. II

I

(C-2) 24

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Table 8: Stepwise multiple regression analysis of selected physical oceanographic variables and

settlement at the northern reference site (#1) and at Platform Hidalgo. Physical oceanographic

I variables are from SAIC and MEC (1995). All variables shown in the multiple regression model

are statistically significant at the o_=0.15 level. No other variables met the o_=0.15 significance

i level for inclusion in the model.

APPENDIX C-2A. Complete taxonomic list of organisms observed on all settling plates

I throughout this study. Taxa were identified to the lowest practical level.

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(C-2) 25

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LISTOFFIGURES i

Figure 1: Study region showing platform and reference locations, i

Figure 2: Natural settlement plate deployment and retrieval schedule. Arrows in upper level I

signify retrieval, observation, and redeployment of plates.

Figure 3: Larval array "igloos" with relative configurations of trays, chambers, and settling i

plates.

Figure organisms4: demonstrating Three common littlepatterns settlementof/recruitment settlement byand180recruitment: days; (2) serpulid (1) total wormnon-colonial data from 1

Reference Site 2 representing outliers compared to other reference and platform sites (the latter

are not shown); and (3) total colonial organism data indicating wide variability between sites, i

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(C-2) 26

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I Table 1: Taxonomic list of organisms observed on at least five percent of all settling plates.

These taxa or groups were used in settlement/recruitment analyses at reference stations. Taxa

I were identified to the lowest practical level.

Taxon Faunal Type

Cyclostomata Bryozoa

Delectopecten sp. Mollusca (Bivalvia)

DenseHydroids Coelenterata

i Komokoiacea Oplorhiza gracilis Protozoa Coelenterata (Hydroid)

Serpulidae Polychaeta

Triticella Bryozoa (colonial)

sp.

i Toaxtalonomic non-colonial Groupsorganisms

Total colonialorganisms

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Table 2: Mean numbers of solitary organisms, percent cover of colonial organisms per plate _i

and results of ANOVA for plate surface experiment. ANOVA probabilities of rejection of Ho:

no difference in settlement; ns = p > 0.05. Rankings of settlement surface type were determined II

through REGWQ analyses following the ANOVA.

1

Lower Plates (0.35 m from bottom) Upper Plates (1.25 m from bottom) i

Surface Surface I!

Taxon Grooved Rough Smooth Grooved Rough Smooth

Cyclostomata o1 oo o1 oo o0 l

V

Delectopecten sp. 1.0 0.5 0.3 1.9 13 0.0

Komokoiacea 1.0 1.0 0.9 1.0 0.9 1.0 _.

|

Oplorhiza gracilis 0.0 0.1 0.8 0.3 0.3 0.8

Triticella sp. 0.8 0.1 0.1 0.1 0.3 0.4

Total non-colonial 2.4 0.9 1.6 2.4 1.8 1.3 I

organisms

Totalorganisms 3.4 1.9 2.5 3.4 2.6 2.3 i

Ill

Plate Relief Surface x I

Taxon Surface Height Height Description of Difference

Cyclostomata p<0.01 <0.01 ns Grooved > Smooth, Rough il

Delectopecten sp. p<0.01 ns ns Grooved, Rough > Smooth _,

Komokoiacea ns ns ns

Oplorhiza gracilis p<0.01 ns ns Smooth > Grooved, Rough t

Triticella sp. ns ns p<0.01 Lower: Grooved > Smooth, Rough II

Upper: Rough, Smooth > Grooved

/

Total non-colonial ns ns ns I

organisms

Totalorganisms ns ns ns g

II

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(C-2)28 i

I
I

t Table 3: Results of 3-factor ANOVA (site, relief height, and deployment period) for effects of

relief height (RH) on settlement of taxa observed on five percent or more of plates at reference

I sites only. Reference data for taxa that did not show significant differences were pooled for subsequent comparisons.

!

Lower Upper

Tax Cyclostomata a Plates 0.07 Plates 0.07 1,70 df M0.015 S(RIt) 0.33 F 0.5701 p

Delectopecten sp. 3.3 5.3 1,222 1681 4.62 0.0337*

Dense Hydroids 4.4 12.3 1,70 1768 7.88 0.0065*

Komokoiacea mat 9.4 18.6 1,70 168 10.66 0.0017*

I Oplorhiza gracilis 2.3 5.0 1,70 132 10.2 0.3155 Serpulidae 0.9 0.8 1,122 0.09 0.07 0.7970

Triticella sp. 11.3 4.6 1,70 355 1.62 0.2069 !

Total non-colonialorganisms 6.0 10.8 1,274 1958 21.16 0.0001*

Totalcolonialorganisms 39.0 34.8 1,158 636 1.26 0.2628

df = de_ees of freedom (factor, error)

I MSE = mean squareerror F = F-ratio [MS(RH)/MSE]

p = probability of accepting null hypothesis

I * = statistical significance at p=0.05

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I (C-2)29

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0 o

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I (C-2)31
II

Table 6: Results of 2-factor ANOVA on (A) established organisms and (B) new recruits g

showing results of testing the interaction of settlement location (Reference, Hidalgo, Harvest, and

Hermosa) and incubation period (480 days [before drilling] vs. 1000 days [during/after drilling]) i

for effects. Reference locations used in the individual analyses correspond to those determined

to be most relevant (see Table 4). Plate heights were combined when no difference due to plate

height (highvs. low) was determined(Table3). I

A. Newly Recruited Organisms

Taxa Height df MSE F p

Cyclostomata Combined 3,704 0.24 8.78 0.0001" inn

I1 Delectopecten sp. Low 3,290 2.11 4.58 0.0054*

Delectopecten sp. High 3,348 9.26 1.77 0.1520 "-

DenseHydroid Low 3,296 456 5.79 0.0007* m

DenseHydroid High 3,355 225 1.49 0.2182 n

Komokoiacea Low 3,348 126 4.37 0.0049*

Komokoiacea High 3,289 195 2.42 0.0667

Oplorhiza gracilis Combined 3,704 285 8.13 0.0000" It

Serpulidae Combined 3,587 0.19 4.27 0.0054*

Triticella sp. Combined 3,587 113 2.91 0.0339* I

Total non-colonialorganisms Low 3,595 701 1.85 0.0001"

Totalnon-colonialorganisms High 3,711 903 2.48 0.0590* .I

Total colonial organisms Combined 31,423 14243 19.19 0.0001" II

B. Established Organisms 1

Cyclostomata Combined 3,129 3.19 9.90 0.0001" _i

II Delectopecten sp. Low 3,49 7.15 1.63 0.1938

Delectopecten sp. High 3,61 27.9 6.31 0.9730

DenseHydroid Low 3,56 3914 25.58 0.0001" i

DenseHydroid High II 3,68 3181 10.80 0.0001"

Komokoiacea Low 3,57 355 1.68 0.1822

Komokoiacea High 3,58 806 2.02 0.1230 _:

Oplorhiza gracilis Combined 3,129 150 0.99 0.3972 _.

Serpulidae Combined 3,107 0.34 1.42 0.2399

Triticella sp. Combined 3,106 28.3 1.54 0.2087 I

W

Total non-colonialorganisms Low 3,113 1576 8.58 0.0001*

Totalnon-colonialorganisms Upper 3,137 365 0.81 0.4904 t

Total colonial organisms Combined 3,273 17850 19.86 0.0001" B

* = statistical significance at p = 0.05 I

(C-2) 32 i

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1 _° _"_ _ _ _":___ Lu

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(C-2)33
II

Table 8: Stepwise multiple regression analysis of selected physical oceanographic variables and n

settlement at the northern reference site (#1) and at Platform Hidalgo. Physical oceanographic

variables are from SAIC (1995). All variables shown in the multiple regression model are

statistically significant at the c_=0.15 level. No other variables met the or=0.15 significance level _qg

forinclusionithemodel. I

Taxon Variable Partial r z Model rz F P

Cyclostomata

Drilling 0.939 0.9'39 62.1 0.0014*

TSSm_ 0.047 0.986 10.21 0.0495* I

Delectopecten sp.

TS S,,_d 0.466 0.4.66 3.49 0.1352

Komokoiacea I

Sedrate 0.766 0.7'66 13.07 0.0225*

Oplorhiza gracilis II

Drilling 0.838 0.838 20.64 0.0105" ,_

TS S,vg 0.110 0.948 6.31 0.0868

Serpulidae I

Incubation 0.958 0.9'58 91.45 0.0007*

Sedrate 0.032 0.9'90 9.689 0.0528

Triticella sp. I

Drilling 0.996 0.9'96 1062 0.0001"

Total non-colonial

organisms I

Incubation 0.7912 0.7!)12 15.16 0.0176*

Totalcolonial i

organisms

Drilling 0.714 0.714 10.01 0.0341"

Variables: I

Drilling - no drilling or drilling

TSS- Totalsuspendedsolids(average,maximum,and timeweighted) J

Sedrate - Sedimentation rate (time in months to foul optical instruments) U

Incubation - Incubation Period (before or during/after drilling)

Temperature Current Velocity (average and maximum) 1

Relief Height (High or Low).

* = statistical significance at ff_=O.05. II

(C-2)34 I

!
I APPENDIX C-2A. Complete taxonomic list of organisms observed on all settling plates

throughout this study. Taxa were identified to the lowest practical level.

I Taxon Faunal Type

Eggs UnidentifiedEggs

I Egg Arenaceous capsule Foraminifera Protozoan

Folliculinidae

I Foraminifera Komokoiacea (colonial)

Stalked ciliate

I Stalked Poriferaciliate sp. A Poriferan

Star Sponge

I Anemone, Bougainvillidae unid.(colonial) frag. Cnidarian

Campanulariidae (colonial)

I Campanulinidae Clava sp. (colonial) (colonial)

Clavidae

I Coral Corymorpha sp. A

Dense hydroid (colonial)

I Eudendrium Halecium sp. sp.

Hydrozoa (colonial)

Oplorhiza gracilis (colonial)

Oplorhizapolynema (colonial)

Pandea sp.

i Plumularia mobilis Star hydroid

Flatworm Flatworm

Notoplana sp.

I Stylochus Nemerteasp. Nemertean

Glycera sp. Polychaete

I Hirudinea Polychaeta

Serpulidae

Spirorbid Trochophore larvae

Worm tube

I Calliostoma platinum Gastropod Dendronotus sp.

Gastropoda

i Haliotis Mang sp. elia sp.

I (c-2)35

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Taxon FaunalType i

Mitrella sp.

Mollusceggcapsule Gastropod,continued I

Nudibranchia J

Onchidoris bilameUata

Onchidoris Bivalviahystricina Bivalve 'I

Delectopecten sp.

Mytilus Pectinidaesp. i

Acarina Arachnid

Pycnogonida Amphipodtube Pycn_ogonid Crustacean 1

Arcoscalpellum californicum

Cumacea Gammaridea I

Harpacticoida

Alcyonidium sp. (colonial) Bryozoan (colonial) III

Bryozoa (colonial) 11

Caberea ellisi (colonial)

Caulibugula californica (colonial) a

Caulibugula sp. n

Crisia sp. (colonial)

Cyclostomata (colonial)

Ectoprocta (colonial) I

Membranipora villosa (colonial)

Microporella columbiana (colonial)

Microporella sp. (colonial) i

Porella columbiana (colonial)

Scrupocellaria sp. (colonial)

Triticella sp. (colonial) i

Vesiculariidae W

Loxosomatidae(colonial) Entoproct

Florometra Asteroidserratissima Echinoderm I

Ophiuroidea

Aplousobranchi Boltenia echinata Urochordate I

Botryllus sp. (colonial)

Chelyosoma productum sp. I '

Didenmum sp.

Tunicate Trididemnum strangulatum I

Organism,unid. Unidentifiable

Unid.spherical colonies im

Whips (colonial) tl

(C-2)36 I

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Figure 3

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Canisters

I toIgloo

TrainWheel LarvalRimingCanisterDetail

I

I

I Igloo

I

i

t Settlement Chambers

I

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I j-PVC Cap

*-Nytex Screen

I

Settling Plate I

PVCChamber -- PVCChamber I

I
Figure B

!

J,-.--Reference 11 Total number noncolonials settled - Lover Rates

I-- Reference21 A

so I" Re_ence31 !

0 1O0 200 300 400 500 600 700 800 900 1000

Lenglhof Deployment(Days)

61 i--Reference11 Serpulidae Upper Plates B 1 t

I I-- ReferenceZl I

0 100 200 300 400 500 600 700 800 900 1000 l

Ler_h of Der_oyment_I:x:_)

130 _ I

-- Reference 1 Total nLrnber colonials settled - Upper Rates g

120 I-- Referenoe2

110 t

4

""' Reference 3

IO0

9O

_70 _.._ _

_40

20

10 -_

0 _ , 9"-- , _I

II 0 100 200 300 400 500 600 700 800 900 1000

Length of Deployment (Days)

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i APPENDIX C-3

I LABORATORY TOXICITY TESTS MANUSCRIPT

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This page intentionally left blank.1!!!!!!i!!!
I

I THEEFFECTSOFDRILLINGMUDS

i ON MARINEINVERTEBRATELARVAEAND ADULTS

Peter T. Raimondi a, Arthur Barnett z, and Paul R. Krause z

I

1University of California, Marine Science Institute, Santa Barbara, CA 93106

i 2MEC Analytical Systems, Inc. Carlsbad, CA 92008

[To be submitted to: Environmental Toxicology and Chemistry]

l

ABSTRACT

I A series of laboratory experiments were conducted to determine the effects of drilling muds on

marine invertebrate larvae and adults. Experiments were conducted with the gametes and larvae

I of abalone the redexperiments abalone (Haliotis testedrufescens effects) and of exposure adult brownto cupdrilling corals muds (Paracyathus on fertilization, stearnsii). early Red

development, survivorship, and settlement. Larval viability, calculated from survivorship and

t settlement, and the degree to which drilling muds might interfere with settlement inducers (those chemicals that promote larval settlement) also were assessed. Experiments on adult brown cup

corals tested effects of exposure to suspended and settled drilling muds on adult survivorship,

I viability, and tissue loss. Drilling muds used in all experiments were collected from an active drilling platform in the southern Santa Maria Basin, offshore southern California. Laboratory

exposure conditions (duration and temperature) were comparable to field conditions in the Santa

Maria Basin. Concentrations of suspended drilling muds used in experiments included those expected to occur in the field as determined by a plume model. Exposures to drilling muds did

not show an effect on abalone fertilization or early development. However, exposures of

I precompetent and competent larvae (planktonic larval stages that are not and are physiologically able to settle, respectively), indicated effects on their ability to survive or settle. Several

exposures resulted in weak, but significant positive effects of drilling muds on both survivorship

I (in larvae) and settlement (in larvae). In settlement of red precompetent competent contrast,

abalone larvae on natural coralline algal crusts decreased with increasing concentrations of

drilling muds. This suggests that drilling muds affect either the abalone's ability to detect

I settlement inducers, or the inducer itself. Exposure of brown cup corals to concentrations

natural

of drilling muds adversely impacted their survivorship and viability. These effects were likely

caused by increased tissue mortality of the coral polyps. Results of these studies suggest that

I exposure to drilling muds at environmentally realistic concentrations, in a controlled laboratory

setting, can result in impacts to marine invertebrates at both the larval and adult levels.

I

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INTRODUCTION I

Offshore oil and gas development activities can result in the discharge of large amounts of l

drilling wastes to the marine environment. During drilling activities, drilling fluids (muds) are

used to facilitate the operation of the drilling machinery and transport the drill cuttings to the I

surface of the well. Typical drilling muds used in southern Ca].ifornia are water-based fluids |

(Steinhauer et al. 1992) that represent mixtures of clays and/or synthetic weighting agents that

are diluted with either fresh or salt water (EHA 1990). The major weighting agent used in i

typical water-based drilling fluids is barium sulfate (BaS04), resulting in a fine grained mud with g

a characteristically high density (4.5 g/mL). Barium sulfate is added to drilling muds in amounts

that range from 1% to up to 85%, although the exact make-up of ,:lrilling muds is specific to the n

drilling operation and type of substrate through which the drilling will occur (EHA 1990). lll[

Current and projected offshore drilling in the southern California area has prompted interest in 111

the ecological effects of the discharge of these drilling wastes to the marine environment II

(Steinhauer et al. 1992). This is especially true for areas where 1abedischarge of drilling muds

may influence organisms associated with hard bottom structures such as rocky outcrops and reefs, I]

which are commonly found in the Santa Maria Basin, California {Hyland et al. 1990; Brewer et tl

al. 1991; Lissner et al. 1991; Hyland et al. 1994). This study was designed to examine the effects

of environmentally realistic concentrations of drilling muds on several aspects of the life history I

of hard-bottom organisms native to deep offshore regions where drilling has occurred. Organisms I1

chosen for these experiments were larvae of the red abalone (Haliotis rufescens) and adult brown

cup coral (Paracyathus stearnsii). I

The study was performed in conjunction with additional studies as part of the U.S. Department

of the Interior, Minerals Management Service (MMS)/National Biological Survey (NBS) Phase n

iIi Study Program. The Phase III program was designed to conduct long-term studies on the 'mr

cumulative effects of offshore drilling and production activities on the marine environment of the /

southern Santa Maria Basin, CA (SAIC and MEC 1993). R

Study Organisms I

Larvae of the red abalone (Haliotis rufescens Swainson)

Red abalone is a long-lived (up to 15 years), dioecious (separate sexes), commercially important m

species that lives on rocky reefs between the intertidal zone to depths exceeding 180 m on the I

west coast of the United States (Morris et al. 1980). Spawning abalone can be found year round,

but the height of the spawning occurs in the spring and summer months (Morris et al. 1980). I

This species is common in the Santa Barbara Channel, a region of considerable offshore oil I!

production, and adults can be found on submerged pipelines that link offshore platforms with

onshore processing facilities (S. Anderson, University of California, Santa Barbara, personal I

observations). Abalone have free-swimming lecithotrophic larvae that enter the water column II

and subsequently settle and metamorphose into the adult body form. At 15° C the planktonic

phase can be divided into an initial period of 5 - 7 days when the larva is developmentally I

incapable of settling (= precompetent stage), followed by a 2 - 5 week period when it is t!

(C-3) 2 I

I
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I competent to settle in response to an inducer (Morse et al. 1979a; Morse 1990). Because of the

short pre-competent period and behavioral mechanisms, such as active swimming and response

I to diel cycles (Prince et al. 1987, 1988), the distances that abalone larvae disperse from the point of origin are likely to be relatively short. The average dispersal distance for red abalone larvae

may be about 1-10 km (M. Tegner, Scripps Institution of Oceanography, personal

I communication).

Larvae were chosen to study the effects of drilling muds because these early developmental

i tobe sensitiveto hydrocarbonsandothercontaminantsthan stages are thought more petroleum

older life stages (for review see Capuzzo 1987; Neff 1987). Specifically, normal development

of "wild" larvae that encounter waste plumes can be greatly altered. For example, Weis et al.

I foundthat naturalstocksof fishlarvae treated (1989) and Kings ford (1995) encountering

municipal wastewaters had higher incidences of deformations than did laboratory reared or

i natural stocks of fishes from uncontaminated areas. There is also evidence that brief exposure of early life stages to low concentrations of petroleum wastes (produced water) can result in a

developmental response at later larval stage (Krause et al. 1992; Raimondi and Schmitt 1992).

i Furthermore, life history wheneffects biochemical of toxicants pathways may bearemost initiated pronounced or repressed. at transition For many phaseslarvae, in ananorganism's important

transition phase involves settlement and metamorphosis in the adult habitat.

I Competent red abalone larvae typically settle on surfaces covered with crustose coralline algae

or bacterial films (Strathmann 1987). In addition to natural settlement inducers, they can also

I be(GAinduced BA) (Morse tttleet al. and1979a, metmorphose 1979b, 1980). by an Morse analog etof al. the(1979a) natural found inducer,thaty-aminobutyric 10-6 molar GABAacid

resulted in 98% settlement in 18 hours. Once settled, metamorphosis to the adult body form

I typically of is completed within 24 hr (Morse et al. 1980). This potent inducer allows measurement the effect of different exposure regimes on settlement. Competent larvae settle in the presence

of GABA. This technique has been used to assess interference of settlement of red abalone by

I pesticides and other contaminants (Morse et al. 1979b) and by produced water (a by-product of oil production; Raimondi and Schmitt 1992).

I Brown cup coral (Paracyathus stearnsii Verrill) The brown cup coral is a fairly large (polyps sometimes > 4 cm diameter), solitary coral that

lives on rocky reefs from 7 to at least 900 meters deep (Fadlallah and Pearse 1982). It is a

I dioecious, obligately sexual species with gonads on all septa. Fertilization is external and zygotic development culminates in a planula larva about 160 gm long (Fadlallah and Pearse 1982). It

is not known if brown cup coral larvae, like those of many other coral species (Morse et al.

I 1994) use specific inducers to cue settlement. In culture, individuals persist without settling for

up to 4 weeks before perishing, an indication that external induction of settlement may be

required. Populations of brown cup corals are common organisms found on hard surfaces of both

I platforms and local rocky reefs throughout the Santa Maria Basin (SAIC 1986; Brewer et al.

1991; Lissner et al. 1991; Hardin et al. 1994).

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METHODS i

Collection and handling of drilling muds I

The study was conducted using drilling muds collected from Platform Hidalgo. This .11

drilling/production platform is one of a series of three platforms (Hidalgo, Hermosa, and Harvest) i

operating along a portion of the southern California continental shelf between Pt. Conception (34° i

28' N; 120° 28' W) and Pt. Arguello (34° 35' N; 120° 38" W). Drilling muds used in these w

experiments were water-based muds, and samples were collected from active drilling platforms a

before discharge to the ocean. Drilling mud samples were collected by platform personnel and |

shipped in PVC containers on ice to the bioassay laboratory at the University of Califomia, Santa

Barbara (UCSB). At the laboratory they were stored in a co]ld (4° C) room until used in i

experiments. All experiments were conducted within 14 days of collection of the drilling muds. II

StudyDesign I

Determination of exposure periods and close

In order to utilize realistic drilling mud concentrations in the laboratory, a series of assumptions il

and calculations were made based on existing data on current patterns and the concentrations of g

drilling particulates recorded from previous studies (SAIC and MEC 1993; Coats 1994). First,

it was assumed that competent larvae drift into the study area at an average near-bottom current i

speed of 7 cm sec_ (SAIC and MEC 1993; E. Waddell, SAIC, personal communication). l

Second, based on Coats (1994), it is assumed that the drilling mud footprint from the three

production platforms (Hidalgo, Hermosa, and Harvest) is an ellipsoid about 13 km in major axis

(longshore), based on concentrations of 200 mg m-2 day _ particulate flux due to the initial g

deposition of daily discharges of drilling muds. Using these assumptions it would take a larva

about 26 hours to reach the center from the edge of the footprint and approximately 51.6 hours i

to travel along the axis of the ellipsoid. gl

Most competent larvae can settle within 2-3 days (Morse et al. 1979a, b). While larvae are

planktonic (about 7-8 days for red abalone at 150 C) in the footprint area they would be exposed I

to a solution that contains about 10 mg/L total suspended solids (SAIC and MEC 1993) of which

about 2% or 0.2 mg/L is drilling mud (Coats 1994). When they settle onto a hard surface, the I

sedentary stage will be exposed to drilling mud fluxes of between 200 and 500 mg m"2day _

(Coats 1994). Therefore, concentrations of drilling muds used in experiments were set from I

0.002 mg/L to 200 mg/L plus controls, except as noted. In the field, concentrations greater than

200 mg/L would be expected only very close to the platform discharge (Coats 1994).

Collection and laboratory handling of test organisms I

Stocks of adult red abalone are maintained in a flow-through seawater system at UCSB. Methods

for spawning, fertilization and larval culturing are described in Morse et al. (1977, 1979b, 1980). t

Stock animals were collected originally from a subtidal reef neat' Santa Barbara, CA and have II

been maintained as spawning animals for ongoing studies over several years. In order to mimic

conditions that exist at 200 m, some experiments were conducted, as feasible, at 9° C in the dark. m

However, because the results of preliminary experiments indicated that development times for l

(C-3) 4 i

i
I cultures were unstable at 9 degrees, parallel experiments were also performed at 15° C, the

typical rearing temperature for red abalone. To help prevent bacterial infection in the laboratory,

I antibiotics (2 mg/1 Rifampicin) were added to laboratory vessels holding larvae; antibiotics do

not interfere with normal settlement of red abalone larvae (Morse et al. 1979b). If individuals

in any replicate container appeared to be severely affected by bacterial infection that replicate

I was not used. Typically 2-3 replicates per treatment (concentration) have been used for survivorship and settlement assays with red abalone larvae (Morse et al. 1979a; Raimondi and

Schmitt 1992), and variability is generally low among replicates. Experiments described in this

I usedbetween3 and10 thenumber in study replicates per treatment (concentration); was large

part dictated by logistical constraints of the experiment. Due to limited holding times for the

i drilling muds, as noted above, most of the experiments were carried out concurrently.

Individual adult brown cup corals were collected by scuba divers from subtidal rocky reefs near

i Santa Until use, Barbara, coralsCA, wereat kept depthsat 90between C 10 and 20 m and maintained in the UCSB laboratory. in the dark in a flow-through seawater system. The corals

were not fed during the experiments.

I Specific Methodology of Experiments

I PHYSIOLOGICAL EFFECTS OF DRILLING MUDS ON RED ABALONE

Gametes - (fertilization)

I This fertilization experiment successtestedof theabalone, relationship expressedbetween as a thepercentage concentration of eggsof drilling showingmuds evidence and theof

fertilization (Figures 1 and 2). At least 2 male and 2 female adult red abalone were spawned

I using the method of Morse et al., (1977). Sperm were collected via pipette from spawned abalone. Sperm concentration was determined by first diluting a sample of concentrated sperm

1:10,000 in sterile sea water, then counting 10 laL samples of the diluted sperm solution on a

I hemocytometer. Freshly spawned eggs were allowed to settle in 50 mL conical tubes. To determine settled egg density, a 20 gL sample of settled eggs was mixed in 1 mL of sterile sea

water, and 20 gL samples of the suspended eggs were counted on depression slides.

I Concentrations of drilling muds tested were: 200, 20, 2, 0.2. 0.02, and 0.002 mg/L. Clean, sterile

sea water (0 mg/L) was used for control conditions. Subsamples (10 mL) of each drilling fluid

I dilution were pipetted into individual wells of Falcon six-well tissue culture Ten plates.

replicates of each concentration and ten replicates of control conditions were included in this

experiment. !

Approximately 500 settled eggs were pipetted into each well of the Falcon tissue culture plates,

i Fertilization and freshly diluted was sperm at a ratio of approximately 800 sperm per egg were added to each well. allowed to proceed at 15° C for 5 hours on a shaker apparatus. At the end of

5 hours, fertilization was stopped by the addition of approximately 1 mL of 10% formalin.

i Maximum been mixed.resolution Tests offorfertilization fertilizationsuccess were was onlyachieved conductedby sampling at 15° C5 hours becauseafterthat gametes was had the

I (c-3) 5

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temperature at which the fertilization protocol was established. Due to logistical constraints, it

was not feasible to complete the fertilization tests at 9° C. Fertilization success was measured i

by observing the presence of polar bodies or cell division under a microscope (Hunt and II

Anderson 1989). At least 100 eggs were counted per well for each replicate.

Zygotes - (development) g

i

Experiments on zygotes tested the relationship between drilling mud concentration and early

larval development (Figures 1 and 2). Freshly spawned red abalone eggs were fertilized at 15° a

C. Fertilized eggs were examined under the microscope to ensttre the presence of between 10 |

to 50 sperm per egg. Drilling muds were diluted, using sterile sea water, to the following

concentrations: 200, 20, 2, 0.2, 0.02, and 0.002 mg/L (plus control; 0 mg/L). Approximately 500 i

fertilized eggs were added per well of Falcon six-well culture dishes, into which 10 mL of each I

drilling mud dilution was pipetted. Ten replicates were conducted per concentration, and sixteen

replicate controls in sterile sea water were performed. Development was allowed to proceed at

15° C on a shaker apparatus for 52 hours. i

At the end of 52 hours, approximately 1 mL of 10% formalin was added to each well. At least

100 individuals were scored for normalcy of development. Larvae were defined as "normal", lit

based on characteristic calcified, striated, snail-shaped shells with smooth borders, as identified

in Hunt and Anderson (1989). "Abnormal" shells showed deviations such as indentations in the

shell margins or mis-shapened shells (Hunt and Anderson 1989). m

Larvae - (survivorship, settlement, and viability) i

Survivorship was measured as the proportion of organisms alive at the end of the test. W

Settlement was measured as the proportion of survivors that settled. Viability is the product of i

the proportion of individuals that survived and the proportion that settled. It is an estimate of •

the proportion of individuals that successfully made the transition from the planktonic to the w

benthicstage. I

Precompetent larvae

This experiment tested the relationship between exposure of precompetent larvae to varying a

concentrations of drilling muds and subsequent survival to competency, settlement (as competent g

larvae), or viability (Figures 1 and 2). Approximately 500 precompetent abalone larvae were

placed in 800 mL of drilling mud solution, and maintained at 9" or 15° C for 52 hours. The I

precompetent stage was defined as those larvae under 7 days pest fertilization for individuals I!

reared at 15° C and under 10-12 days for individuals reared at 9°; the length of the precompetent

period is more variable at lower temperatures. Drilling mud was diluted to the following i

concentrations: 200, 20, 2, and 0.2 mg/L (plus control; 0 mg/L) for the 9° C experiment, and I!

200, 20, 2, 0.2, 0.02, and 0.002 mg/L (plus control) for the 15° C experiment. Different

concentrations were used for the 9° C experiment for two reason,;. First, the results of the 15° II1

C experiment (done first) indicated that the lowest concentrations tested (0.002 and 0.02 mg/L) II

had no effect on larval performance. Second, because only a limited numbers of larvae were

available for testing, all treatment conditions could not be performed. Consequently, it was i

decided to forego the lower concentrations in the subsequent 9° C experiments. II

(C-3)6 O

I
I After 52 hours of exposure to the various drilling mud dilutions, larvae were transferred to 800

mL fresh, sterile sea water containing 2 mg/L Rifampicin and were maintained at either 90 or 15°

I C (in closed systems). Upon reaching competency, approximately 75 of the exposed individuals were transferred into 20 mL disposable beakers and challenged with GABA plus 2 mg/L

Rifampicin for 24 hours. There were 3 and 9 replicates per concentration for the 9° and 15° C

I experiments, respectively. Temperatures were maintained as described for the precompetent phase. Larvae were scored as settled (attached to the beaker), not settled (lying on their side),

or dead (movement could not be detected). !

Competent larvae

These experiments tested the relationship between exposure of competent larvae to varying

I concentrations of drilling muds, and their survival, settlement, or viability (Figures 2).

1 and

These tests were done to examine the effects of longer term exposure to drilling muds, including

i the ability to settle and survive during the period of exposure. They were included to evaluate how larvae drifting into, and remaining in, an area of impact might be affected by exposure to

drilling muds.

I Settlement ability of abalone larvae exposed to drilling muds at 9° and 15° C during the

competent stage: 28h exposure to drilling muds

I Competent abalone larvae, reared at 9° or 15° C were exposed to dilutions of drilling fluids,

ranging from 200 mg/L down to 0.002 mg/L (plus control), for 28h at 9° or 15° C.

I Approximately times per dilution400forindividuals the 9° C experiment were exposedandinthree 800 times mL volumes per dilution of thefordilutions, the 150replicated C experiment. two

After 28h, approximately 50 larvae per replicate were transferred to 20 mL disposable beakers

I containing 2 mg/L Rifampicin. 10 mL freshForsterile the 9°seaC experiments, water. They three were replicates then challenged per exposure with 2 mg group/L GABA were setplus up

for a total of six replicates per dilution. Only one replicate per exposure group (three replicates

I total) was used for experiments at 15° C. Larvae were scored as described for the precompetent larvae experiments.

I Settlement ability of abalone larvae exposed to drilling muds at 9° and 15° C during the competent stage: 52h exposure to drilling muds and settlement challenge in the presence of

drilling muds

I Competent abalone larvae, reared at 9° or 15° C in a closed system (see above), were exposed

to dilutions of drilling fluids ranging from 200 mg/L down to 0.002 mg/L (plus control) for 52h

I at 9° 15° C. 400 individuals were exposed in 800mL volumes of the dilutions,

or Approximately

replicated two times per dilution for the 9° C experiment and three times per dilution for the 15°

C experiment. For the 9° C experiment, before the last 24h of exposure, as many larvae as were

I available per replicate were split among three 20 mL disposable beakers along with 10 mL of

the drilling fluid dilution. Larvae were challenged to settle by the addition of 2 mg/L GABA

i plus For 2 mg/L Rifampicin. A total of six GABA challenge replicates per dilution were performed. the 15° C experiment, before the last 24h of exposure, 50-150 larvae from each replicate

I (C-3)7

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I

were put into 20 mL disposable beakers along with 10 mL of the drilling fluid dilution. Larvae II

were challenged to settle by the addition of 2 mg/L GABA plus 2 mg/L Rifampicin. A total of

three GABA challenge replicates per dilution were run. Larvae were scored as defined for the

precompetent larvae and 28h exposures.

II

Interference with settlement inducers I

This experiment was designed to test whether settlement of larvaL1red abalone was affected by

w

alteration of settlement surfaces due to deposition of drilling muds. As such, this experiment l

differed fundamentally from the other tests using larval red ab_done. The other experiments I

tested whether drilling muds had direct physiological effects that translated into loss of larval

performance: fertilization, development, and the ability to settle. In contrast, this experiment I!1

tested indirect effects on the performance of individuals (ability to settle) through interference I

with a necessary step in the settlement process (contact with an inducer). With this treatment

the reaction of competent abalone larvae to fouled surfaces was examined. The focus was to IB

determine how larvae might react to potentially inductive surfaces occurring in a zone of drilling I

mud particles. This treatment was intended to mimic short-terra exposure of these inductive

surfaces. I

Coralline crusts (known to induce red abalone larvae to settle; Strathmann 1987) were placed in

solutions of drilling muds for 28 hours at 9° C in the dark at the following concentrations (see

Figure 1): 200, 2, and 0.02 mg/L (plus control; 0 mg/L). After 28 hours, crusts were transferred II

to small containers (8 crusts per concentration) containing a new solution of drilling muds that

was identical in concentration to that used in the initial 28 hr period. New solutions were used II

to reduce the possibility of contamination when the abalone larvae were added. Approximately I

500 competent abalone larvae were added to each container. After 24 hr the crusts were sampled

microscopically to determine the density of settlers on coralline crusts as well as the percent of

the crust surface that was clear of drilling muds. The latter parameter was sampled to separate J

interference with settlement due to effects on the inductive quality of the surface (e.g., chemical

effects on the inducers) from interference with settlement due to physical covering of the surface I

with mud.

However, this experiment alone was not sufficient to distinguish interference with inducers from I

physiological effects of larvae. To evaluate this distinction, it was necessary to determine w

whether exposure to drilling muds during the competency phase affected larval settling ability. mt

This was tested in the previously described experiment on competent larvae using GABA as an I!

inducer. In this experiment, the GABA induced settlement wits repeated and, additionally,

coralline crusts were used to induce settlement. Coralline crusts and GABA were both used to /s

determine if larvae exposed to natural and artificial inducers responded differently. I

For this test, larvae were placed into solutions of the same concentrations as noted above (five am

replicates each), but without coralline crusts for 28 hours. After 28 hours, larvae were removed I

from the drilling mud solutions and put into containers of clean seawater. The larvae from each

of the replicates were split into two containers: one containing clean coralline crusts, the other Is

I

(c-3) 8 I

!
I containing 2 mg/L GABA solution. Settlement was scored as noted above after 24 hours in these

containers. !

PHYSIOLOGICAL EFFECTS OF DRILLING MUDS ON THE BROWN CUP CORAL:

I ADULTMORTALITYANDTISSUELOSS

i This realisticexperiment concentrations was designed of drilling to test whether muds (seeadultearlier Paracyathus discussion are affected of rationale by exposure for theto

concentrations). The effect could result from either of two sources: 1) toxicity from a chemical

I or drilling biological muds component that might ofinterfere the drilling with physiological muds, or 2) toxicity processesfrom(e.g., the feeding fine particulate or respiration) matter ofin

a filter feeder such as Paracyathus. Survivorship and tissue loss in adult cup corals were

I reproduction examined as because endpoints.gonads For arecorals locatedsuchinasexternal Paracyathus tissue, intissue the septa. loss has a direct bearing on

I Individual and placed Paraeyathus in solutions, of11drilling per concentration, muds with thewerefollowing randomlyconcentrations: selected from 200, a population 2, and 0.02of adults mg/L

(plus control; 0 mg/L). Experiments were maintained in a cold room at 9° C. Every two days

I for 10 days individuals were examined microscopically for survivorship and tissue loss (sub-lethal effects). Individuals were scored as either exhibiting or not exhibiting tissue loss. An additional

variable, relative viability, was calculated as the product of survivorship and the proportion of

I individuals showing tissue loss. Relative viability should be a good predictor of the likelihood of continued survival and reproduction under exposure to drilling muds. New solutions were

made of the experimental concentrations of drilling muds every two days (all concentrations were

I made using drilling muds that were less than 14 days post-collection). Following examination, individuals were replaced into the appropriate flesh experimental concentrations of drilling muds.

Since adult Paracyathus are sessile, the period that they could be affected by drilling muds is

I longer than for a larvae. Consequently, this experiment was carried out over a longer period of time. This time flame was within the average period for discharge of drilling muds during

drilling activity at the Santa Maria Basin platforms, which usually lasts for several weeks or

I months (Steinhauer et al. 1992;Raimondi et al. in for each well drilled. preparation)

Data Analysis

I Results from the experiments are expressed as percent fertilization, survivorship, etc., compared

to a control. All values were standardized to the mean for the control set of replicates (the 0

i comparisons mg/L treatment), of including each of the control replicates. This approach allows direct results from different experiments with differing units or measured parameters.

i muds Regression on gametes, analyses zygotes, were usedor for larval all experiments red abalone testing (Figure for1).physiological All statistical effects analyses of drilling were

performed using SAS software (SAS Institute 1988). Separate analyses were done using the

i concentration was done because and thedoselogresponse of the concentration curves have ofbeendrilling shownmudsto asfollowthe independent both linear variable. and log-linear This

I (C-3)9

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trajectories, and there was no objective reason to predict which, if any, was the probable model

for biological response to drilling muds. II

II

Experiments testing for interference with inducers of settlement (F:igure 1) used both multiple and

simple regression models. Analysis of covariance models were used to evaluate results from all

experiments designed to test for the effects of drilling muds on adult brown cup corals (Figure II

1).

!

RESULTS

PHYSIOLOGICAL EFFECTS OF DRILLING MUDS ON RED ABALONE I

i

Fertilization and development 41

The results of the fertilization and development assays are presented in Table 1 and Figure 3. II

There was no significant relationship between concentration of drilling muds and fertilization in

red abalone. Similarly, there was no significant relationship bew, een concentration of drilling

muds and development of red abalone zygotes. Fertilization and development was similar across It

all drilling mud concentrations, including the controls.

Precompetent larvae I

It was not possible to calculate settlement and survivorship compared to controls for the 9° C

experiments due to bacterial contamination of the drilling mud control (0 mg/L). Relative II

measures were considered important because they allowed direct comparisons among different II

experiments. Therefore, for the experiments where controls were contaminated, survivorship and

settlement were calculated relative to the mean of the 0.2 and 2 mg/L treatments. The mean of

the two lowest concentrations was used because preliminmy experiments showed that Ilp

concentrations < 2 mg/L are not significantly different from the control for either settlement or

survivorship. Experiments at 15° C were standardized to the control mean as explained in the n

methods. Survivorship and viability were not assessed in the 15° C experiment because m

experimental chambers were lost after settlement was evaluated. I

The only performance parameter showing a significant relationship with concentration of drilling

muds in precompetent larvae was survivorship in experiments done at 9° C (Table 1; Figure 4). a

However, the relationship is positive indicating that survival increased as a function of increasing |

concentrations of drilling muds.

Competent larvae I

Results from experiments involving competent larvae are presented in Figures 5-7 for

survivorship, settlement, and viability, respectively. This grouping was done to facilitate II

comparisons among measures of performance. The only parameter that was significantly |

correlated with concentration of drilling mud was settlement, for which 3 of the 4 experiments

showed a significant effect. However, in two of these experiments (28 and 52 hr exposure to II

drilling muds at 9° C) the relationship was positive (for log-tran,,;formed concentrations only), II

(C-3) ]0 I

I
!

while in the other (28 hr exposure to drilling muds at 15° C) the relationship was negative (for

non-transformed concentrations only; P=0.023) (Table 1). Therefore, even these results were

I somewhatequivocal.

i Interference Settlement ofwith inducers of settlement red abalone larvae on coralline crusts decreased with increasing concentrations of

drilling muds (Figures 8a and 8b), although the effect was not attributable to physical masking

i of regression the crustanalysis, surfacewhich by muds. indicatedThisthatconclusion only the concentration was based onofthedrilling resultsmuds of theandmultiple not the

percentage of free space was significantly correlated with settlement (Table 2a), although this

I relationship on larvae duewasto their weakexposure (r2--0.493). to drilling Additionally, muds were thereresponsible was no evidence for thethat pattern physiological shown in effects Figure

8a. Settlement of individuals that were exposed to drilling muds and then removed and put in

I containers muds (Figures with either 8c andcoralline 8d; Tablecrusts2b).or GABA Moreover, did not results vary fromwith initial experiments concentration describedof drilling earlier

demonstrated that larval settlement was unaffected by even continuous exposure to high

I concentrations muds negativelyof affected drilling muds. the quality The most of thereasonable inducer. explanation for these results is that drilling

I PHYSIOLOGICAL EFFECTS OF DRILLING MUDS ON THE BROWN CUP CORAL:

ADULT MORTALITY AND TISSUE LOSS

I Results of the analysis of covariance (ANCOVA) for all parameters measured (survivorship,

proportion of individuals showing tissue loss, and relative viability) indicated that there was a

I significant interaction between concentration of drilling muds and exposure time (days; Table 3). This indicates that slopes of the response curves were not homogeneous (Figure 9), and is

important because it shows that the response did not vary over time in a similar manner between

I dose conditions (drilling mud concentrations). Survivorship decreased, of individuals proportion

showing tissue loss increased, and relative viability decreased over time with increasing

concentration of drilling muds, although the response was slightly different at each concentration. !

DISCUSSION

!

Exposure of abalone larvae to drilling muds revealed that there was no statistically significant

i effect on the fertilization mechanism, or the early developmental stages of abalone larvae (Figure 3). Experiments on precompetent larvae showed that drilling mud exposure may have enhanced

the survivorship of abalone larvae. This relationship was driven primarily by the results of the

i treatment treatments with (Figure2004).mgHowever, /L drillingthismuds resultwhich may showed be an artifact much ofgreater the waysurvivorship the data were thantreated other

when the controls were lost. It is not possible to know from the data presented whether the

relative increase in survivorship observed at high concentrations is real or a result of the data

I manipulation without proper controls.

I (c-3)11

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Similar positive relationships were found at 9° C for settlement of' competent larvae (Table 1 and

Figure 6). However, the relationship is probably of little ecological significance. The increase

observed, while statistically significant, shows that settlement increased only by approximately I

2-3% over the range of concentrations tested. In comparison, the similar treatment with

competent larvae at 15° C showed a negative relationship. These results suggest that there may m

be some enhancement of survivorship and/or settlement in abalone larvae with drilling muds, at II

least for the range of experimental concentrations, but the specific mechanism remains unknown.

In contrast, significant strong, negative effects were found on the ability of larvae to respond to I

a natural settlement inducer (Figure 8). This type of effect may be very important in influencing

population dynamics for some marine organisms (Keough and Black 1995). Effects such as these II

on larval settlement could result in significant reductions in recruits to settled populations, and II

lead to more widespread population level changes throughout abe, nthic community (Murdoch et

al. 1989; Nisbet et al. 1995). However, because the ecological processes that link larval Ill

dynamics and benthic populations are still poorly understood, 1:he significance of changes in II

settlement rates remains largely unknown (Raimondi and Schmitt 1992; Nisbet et al. 1995).

i

Somewhat in contrast to most of the red abalone results, experiments on adult cup corals showed I

that under environmentally realistic exposure conditions there was increased mortality due to

progressive tissue loss (Figure 9). Unlike the larval effects noted above, this would have a direct II

impact on adult coral populations in the vicinity of drilling mud discharges. Experiments showed I!

that even under the lowest drilling mud concentration tested (0.02 rag/L) relative viability of adult

corals dropped to only 60% after eight days of exposure, and at a high concentration of 200 mg/L II

all adults died after only 6 days of exposure (Figure 9).

Throughout this study controls were maintained that consisted of only clean seawater. An

additional control for sediment load or particle size in the absence of the other fractions of U I

drilling muds may have been appropriate as well. This was not done because of the difficulty

in maintaining a drilling mud substitute that contained only the particulate load expected from I

the drilling mud samples. It is possible that the effects observed in this study are not caused by u

the dissolved fraction of the muds but rather by the particulate material carded by the muds. A I

thorough search of the literature yielded no studies that have addressed this hypothesis directly.

Future studies need to distinguish the differences between this particulate load and direct toxicity

qlW

from dissolved fractions to better address the mechanisms of effect that were noted here and I

elsewhere. Dissolved petroleum fractions have been shown to be the primary toxic agent in I

several studies of oil-field effluents, particularly produced waters (Neff et al. 1992; Cherr et al.

1993; Higashi and Crosby 1993). Field and laboratory studies of produced water toxicity have

shown impairment in fertilization and development of marine invertebrates and plants (Krause

et al. 1992; Raimondi and Schmitt 1992; Reed 1993; Krause 1995). The results of these studies

further raise questions of the mechanism(s) of toxicity observed in the present study and I

emphasize the need to separate effects from dissolved and particulate fractions. II

The majority of recent laboratory studies on drilling muds have addressed lethal effects on adult II

organisms (Neff 1983; Neff et al. 1989; Daan et al. 1994; Payne et al. 1989; Parrish et al. 1989), II

(C-3)12 I

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while fewer studies have addressed sublethal effects on more sensitive larval forms (Crawford

i and Gates 1981; Carls and Rice 1984; Conklin and Rao 1984). Laboratory bioassays have shown that, in general, drilling fluids can cause acute toxicity in high concentrations (1,000 - 10,000

mg/L), and chronic toxicity at lower concentrations (10-100 mg/L) to a variety of organisms

i (Neff sensitive1983). larvalResults stages ofandtheadults present in toxicity study showtesting. the importance Data presentedof addressing here suggest effects that ondrilling both

muds used in the Santa Maria Basin may elicit indirect effects (on settlement inducers; Figure

i 8), and direct effects (on sessile adults; Figure 9).

As noted above, while these results suggest that drilling muds interfere with the settlement

I inducer of a toxicological mechanism, response it was nottopossible the drilling to determine mud or whether a physicalthe interaction observed effect with was drilling the result mud

particulates. Barium sulfate has been shown to cause toxic effects in fertilization and early

I developmental 1982). Barium stages has alsoof been sea urchin larvae at concentrations as low as 23 mg/L (Schatten et al. implicated in developmental effects associated with the discharge

of produced water from production platforms (Krause et al. 1992). Somewhat in contrast, in a

I field study near Santa Barbara, CA, Jenkins et al. (1989) concluded that barium from deposited drilling muds is probably not soluble enough to contribute to toxicity. However, Jenkins et al.

(1989) did not address physical processes that may result in mortality or reduced physiological

I performance, in the drilling ormuds produce contributed toxicological to theeffects overalltoobserved sensitive larvae. effects reported It remainsherepossible for boththat abalone barium

larvae and adult cup corals. Future work should focus on separating the physical and

I toxicological nature of effects observed here, as well as helping to understand the possible toxicological impacts of chronic low level barium exposure in marine systems.

I This investigation has shown that drilling muds may contribute to impacts on important larval

processes, and have direct effects on sessile adult organisms typical of hard-bottom communities

of the Santa Maria Basin. Drilling muds that are discharged from drillingkproduction platforms

I may hinder larval recruitment by interference with natural settlement inducers of marine organisms. Furthermore, drilling muds may directly cause mortality to sessile organisms that are

not able to escape the exposure through mobility. The use of environmentally realistic test

I emphasizes studyareof themagnitudelikelyto occur

concentrations that effects found in this

in the field.

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ACKNOWLEDGMENTS I

We wish to thank the Department of the Interior (DOI), Minerals Management Service/National I

Biological Service, G. Brewer, F. Piltz, G. Reetz, and L. Thorsteinson for their support of this

extended editing areapplication greatly appreciated. of bioassay.ThisThework effortswasofsupported E. Derry asin the part laboratory, of DOI Contract and A.No. Lissner 14-35-in I

0001-30584 to Science Applications International Corporation.

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I LITERATURE CITED

I Brewer, G.D., J.L. Hyland, and D.D. Hardin. 1991. Effects of oil drilling on deepwater reefs offshore California. Am. Fish. Soc. Symp. 11:26-38.

I Capuzzo, J.M. 1987. Biological effects of hydrocarbons: Assessments from petroleum

experimental results. In: Boesch. D.F. and N.N. Rabalais (eds). Long-term environmental

effects of offshore oil and gas development. Elsevier Applied Science, New York. pp.

I 343-410.

i Carls, M.G. larvalandshrimp S.C. andRice.crabs. 1984.MarToxic . Env.contributions Res. 12:45-62. of specific drilling mud components to

i Cherr, petroleum G., R. Higashi, and produced J. Shenker, waterandcomponents T. Fan. to1993. marineAssessment organisms. ofFinal chronicReport toxicity for theof

Southern California Education Initiative. University of California, Davis and Minerals

I Management Service. Contract No. 30761.

Conklin, P.J. and K.R. Rao. 1984. Comparative toxicity of offshore and oil-added drilling muds

I toToxicol larvae. 13:685-690. of the grass shrimp (Palaemonetes intermedius). Arch. Environ. Contam.

I Coats, D.A. Mar. Env1994. . Res.Deposition 37:95-127of drilling particulates offshore Point Conception, California.

I EHA (Espy, Houston and Associates, Inc.). 1990. A review of drilling mud research. Prepared for Mobil Oil Exploration and Producing Southeast, Inc. New Orleans, LA. Document

No. 890601.

I Fadlallah, Y.H. and J.S. Pearse. 1982. Sexual reproduction in solitary corals: Synchronous

gametogenesis and broadcast spawning in Paracyathus stearnsii. Mar. Biol. 71:233-239.

I Hardin, D.D., J. Toal, T. Parr, P. Wilde, and K. Dorsey. 1994. Spatial variation in hard-bottom

epifauna in the Santa Maria Basin, California: The importance of physical factors. Mar.

I Env. Res. 37:165-193.

Higashi, R. and D. Crosby. 1993. Environmental degradation and identification of toxic

I compounds of petroleum and associated materials. Final Report for the Southern

California Education Initiative. University of California, Davis and Minerals Management

i Service. Contract No. 30761.

Hunt, J.W. and B.S. Anderson. 1989. Sublethal effects of zinc and municipal effluents on larvae

I of the red abalone Haliotis rufescens. Mar. Biol. 101:545-552.

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Jenkins, K.D., S.H. Howe, B.M. Sanders, and C. Norwood. 1989. Sediment deposition, u

biological accumulation and subcellular distribution of barium following the drilling of am

an exploratory well. In: F.R. Engelhardt, J.P. Ray, and A.H. Gilliam (eds.). Drilling i

Wastes. Elsevier Applied Science. New York. pp. 587-608. w

Kings ford, M.J. 1995. Influence of pollutants and oceanography on abundance and deformities i

of wild fish larvae. In: R.J. Schmitt and C.W. Osenberg (e,ds.). The design of ecological

IlW

impact assessment studies: Conceptual issues and applications, in press. I

II

Krause, P.R. 1995. Spatial and temporal variability in receiving water toxicity near an oil

effluent discharge site. Arch. Env. Cont. Toxicol. In press. I

wt

Krause, P.R., C.W. Osenberg, and R.J. Schmitt. 1992. Effects of produced water on early life

stages of a sea urchin: Stage specific responses and delayed expression. In: J.P. Ray II

and F.R. Englehardt (eds.). Produced water: Technological/Environmental issues. II

Plenum, New York, NY. pp. 431-444.

me

Lissner, A.L., G.L. Taghon, D.R. Diener, S.C. Schroeter, and J.D. Dixon. 1991. Recolonization I

of deep-water hard-substrate communities: Potential impacts from oil and gas

development. Ecol. Appl. 1(3):258-267. I

Morris, R.H, D.P. Abbott, and E.C. Haderlie. 1980. Intertidal invertebrates of California.

StanfordUniversityPress.Stanford,CA. I

Morse, D.E. 1990. Recent progress in larval settlement and metamorphosis: Closing the gap

between molecular biology and ecology. Bull. Mar. Sci. 46:465-483. I

Morse, D.E., H. Duncan, N. Hooker, and A. Morse. 1977. Hydrogen peroxide induces spawning

in molluscs, with activation of prostoglandin endoperoxide ,_ynthetase. Science 196:298- II

300. g

Morse, D.E., H. Duncan, N. Hooker, A. Baloun, and G. Young. 1980. GABA induces i

behavioral and developmental metamorphosis in planktonic molluscan larvae. Fed. Proc.

39:3237-3241. i

Morse, D.E., N. Hooker, H. Duncan, and L Jensen. 1979a. _,-aminobutyric acid, a

neurotransmitter, induces planktonic abalone to settle and begin metamorphosis. Science I

204:407-410. II

Morse, D.E., N. Hooker, L. Jensen, and H. Duncan. 1979b. Induction of larval abalone settling I

and metamorphosis by y-aminobutyric acid and its congeners from crustose red algae: II. l

Applications to cultivation, seed production and bioassays: Principal causes of mortality

and interference. Proc. World Maricult. Soc. 10:91-91. i

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I Morse, D.E., A. Morse, N. Hooker, and P.T. Raimondi. 1994. Morphogen-based chemical

flypaper for Agaricia humilis larvae. Biol. Bull. 186:172-181.

I Neff, J. 1983. The biological effects of drilling discharges. In: Drilling Discharges in the

Marine Environment. National Academy Press, Washington D.C. pp. 75-128.

I Neff, J.M. 1987. Biological effects of drilling fluids, drill cuttings and produced waters. In:

Boesch. D.F. and N.N. Rabalais (eds.). Long-term environmental effects of offshore oil

I and gas development. Elsevier Applied Science, New York. pp. 469-538.

I Neff, J.M., waterT.C. Sauer, Jr., and M. Maciolek. 1992. Composition, fate and effects of produced discharges to nearshore marine waters. In: J.P. Ray and F.R. Englehardt (eds).

Produced water: Technological/Environmental issues. Plenum, New York, NY. pp. 371-

i 385.

Prince, J.D., T.L. Sellers, W.B. Ford, and S.R. Talbot. 1987. Experimental evidence for limited

I dispersal Ecol of haliotid larvae (genus Haliotis: Mollusca: Gastropoda). J. Exp. Mar. Bio.

. 106:243-263.

I Prince, between J.D., T.L.theSellers, localizedW.B.abundance Ford, andofS.R. breeding Talbot.stock1988. and Confirmation recruitment forofHalio a relationship tis rubra

Leach (Motlusca: Gastropoda). J. Exp. Mar. Biol. Ecol. 122:91-104.

I Raimondi, P.T. and R. J. Schmitt. 1992. Effects of produced water on settlement of larvae:

Field tests using red abalone. In: J.P. Ray and F.R. Englehardt (eds). Produced water:

I Technological/Environmental issues. Plenum, New York, NY. pp. 415-430.

Reed, D. 1993. Potential biogenic habitat alteration by OCS activities: Adverse effects to early

I life stages of giant kelp from chronic disturbances. Final Report for the Southern California Education Initiative. University of California, Davis and Minerals Management

Service. Contract No. 30761.

I SAIC (Science Applications International Corporation). 1986. Assessment of Long-Term

Changes in Biological Communities in the Santa Maria Basin and Western Santa Barbara

I Channel.Final theU.S. of the Minerals Report to Department Interior, Management

Service, Pacific OCS Region, Los Angeles, CA, under Contract No. 14-12-0001-30032.

I SAIC and MEC (MEC Analytical Systems, Inc.). 1993. Monitoring and Assessment of LongTerm Changes in Biological Communities in the Santa Mafia Basin: Phase III, Year One

i Pacific Report. OCSReport Region, to U.S. Camafillo, Deptartment CA, under of theContract Interior.No.Minerals 14-35-0001-30584. Management Service,

I SAS Institute. 1988. SAS/STAT User's Guide, Release 6.03 Edition. Cary, NC.

I (C-3)17

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Schatten, G., C. Simerly, and H. Schatten. 1982. Effects of barium sulfate on sea urchin I

fertilization and early development. In: Duedall, I.W., D.R. Kester, P.K. Park, and B.H.

Ketchum (eds.). Energy wastes in the ocean. John Wiley and Sons, New York. pp. 233- I 239.

Strathmann, M.F. 1987. Reproduction and development of marine invertebrates of the northern I

Pacific coast: Data and methods for the study of eggs, embryos, and larvae. University

ofWashingtonPress. Seattle,WA. pp220-267. I

Steinhauer, W.G., E. Imamura, J.R. Barminski, and J.M. Neff. 199'2. California study compares

natural/drilling discharge contaminants offshore. Oil and Gas J. May 4:74-93. I

Weis, P., S.J. Weis, and A. Greenburg. 1989. Treated municipal wastewaters: Effects on

development and growth of fishes. Mar. Env. Res. 28:52'7-532. I

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I LIST OFTABLES

I Table 1: Summary of regression analyses for experiments testing for physiological on

effects

red abalone larvae due to exposure to varying concentrations of drilling muds. P-values using

concentration and log(concentration) as the independent variable are given. If the relationship

I between the dependent variable and concentration or log(concentration) was significant (P<0.05)

the direction of the slope is shown (+ or -). Non-significant results are denoted by "ns" See

i Figures 3-7.

Table 2A: Results of multiple regression analysis for experiments testing for effects on inductive

i quality drilling ofmuds) surfaces was byuseddrilling as themuds. independent Results variable. did not differ Asteriskqualitatively (*) indicates if loga (concentration significant resultof

(P<0.05). ANOVA results are depicted for the regression line of concentration of drilling mud.

I red B: Summary abalone larvae of regression due to exposure analyses toforvarying control concentrations experiments testing of drilling for physiological muds. P-values effectsusingon

concentration and log (concentration) as the independent variable are given. If the relationship

I between direction the of thedependent slope is shown variable(+ and or -).concentration Non-significantor logresults(concentration) are denoted bywas"ns". significant See Figure the

8.

I Table 3: Results for analysis of covariance for effects of drilling muds (categorical variable)

over time (day = covariate) on several measures of performance for the brown cup coral,

I Paracyathus stearnsii. For all performance parameters (survival, individuals exhibiting tissue loss, and viability) there was a significant (P<0.05) interaction term in the analysis. This

indicates that the slopes were not homogeneous. Significant terms are denoted by asterisks (*).

I See Figure 9.

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I (C-3)19

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LISTOFFIGURES u

representation of experimental design for laboratory bioassays. I

Figure 1: Schematic

Figure 2: Timeline of important physiological events for red abalone larvae and timing of m

experimental treatments. |

Figure 3: Fertilization (A) and development (B) of red abalone as a function of concentration III

of drilling muds. Data are mean ( + SE). Means are normalized to the control mean (see text). II

See Table 1 for statistics.

Figure 4: Effects of drilling mud exposure on precompetent red abalone larvae. Data are mean i

( + SE). See Table 1 for statistics. (A) Survivorship at 9° C of larvae exposed to drilling muds

for 52 hours as precompetent larvae followed by 24 hours as competent larvae in clean seawater I

with GABA. (B) Settlement (proportion of survivors that settled) at 9° C of larvae exposed to II

drilling muds for 52 hours as precompetent larvae followed by 24 hours as competent larvae in

clean seawater with GABA. (C) Viability (product of survivorship and settlement) at 9° C of i

larvae exposed to drilling muds for 52 hours as precompetent l_a'vae followed by 24 hours as II

competent larvae in clean seawater with GABA. (D) Settlement at 15° C of larvae exposed to

drilling muds for 52 hours as precompetent larvae followed by 24 hours as competent larvae in II

clean seawater with GABA. Note: data were standardized to mean of the 0.2 and 2.0 mg/L

treatments in the 9° C experiment (controls were lost due to bacter_ial infection) and to the control

mean in the 15° C experiment (see results). Survivorship and viability were not assessed in the II

15° C experiment. ND indicated that no data were available for these treatments. See Table 1

II

for statistics.

i

Figure $: Survivorship of red abalone exposed as competent laJwae to varying concentrations I

of drilling muds. Data are mean ( + SE). Data were normalized to the control mean (see text).

See Table 1 for statistics. (A) Survivorship at 9° C of larvae exposed to drilling muds for 28 I

hours followed by exposure of 24 hours in clean seawater with GABA. (B) Survivorship at 9°

I

C of larvae exposed to drilling muds for 28 hours followed by an additional exposure of 24 hours

in drilling muds with GABA. (C) Survivorship at 15° C of larvae exposed to drilling muds for •

28 hours followed by exposure of 24 hours in clean seawater with GABA. (D) Survivorship at

w

15° C of larvae exposed to drilling muds for 28 hours followed by an additional exposure of 24

hours in drilling muds with GABA. •

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Figure 6: Settlement (proportion of survivors that settled) of red abalone exposed as competent

larvae to varying concentrations of drilling muds. Data are mean ( + SE). Data were

I normalized to the control mean (see text). See Table 1 for statistics. (A) Settlement at 90C of

larvae exposed to drilling muds for 28 hours followed by exposure of 24 hours in clean seawater

i with GABA. (B) Settlement at 9° C of larvae exposed to drilling muds for 28 hours followed by an additional exposure of 24 hours in drilling muds with GABA. (C) Settlement at 15° C of

larvae exposed to drilling muds for 28 hours followed by exposure of 24 hours in clean seawater

i with GABA. (D) Settlement at 15° C of larvae exposed to drilling muds for 28 hours followed by an additional exposure of 24 hours in drilling muds with GABA.

I Figu varying re 7:concentrations Viability (survivorship of drilling muds. x settlement) Data areofmean red abalone ( + SE).exposed Data were as competent normalizedlarvae to theto

control mean (see text). See Table 1 for statistics. (A) Viability at 90 C of larvae exposed to

I drilling Viabilitymuds at 9 for ° C28of hours larvaefollowed exposed bytoexposure drilling ofmuds 24 hours for 28inhours clean seawater followed with by anGAadditional BA. ('B)

exposure of 24 hours in drilling muds with GABA. (C) Viability at 15° C of larvae exposed to

I drilling Viabilitymuds at 15for° C28ofhours larvaefollowed exposedbytoexposure drilling ofmuds 24 hours for 28in hours clean seawater followed with by anGABA. additional (D)

exposure of 24 hours in drilling muds with GABA.

I Figure 8: Interference with settlement inducer for red abalone as a function of concentration of

drilling muds. Data (mean + SE) were normalized to the control mean for Figures 8a, 8c, and

I 8d (see Results). See Table 2 for statistics. (A) Settlement, while exposed to drilling muds, on coralline crusts as a function of concentration of drilling muds. (B) Percent free space (mean +

SE) on coralline crusts (area not covered by mud) as a function of concentration of drilling muds

I (these data are from the same experiment as in 8a). (C) Settlement, on coralline crusts, following exposure to varying concentrations of drilling muds. (D) Settlement, in the presence of GABA,

following exposure to varying concentrations of drilling muds.

I Figure 9: Survivorship (A), proportion of live individuals showing tissue loss (B), and relative

viability (survivorship x proportion of live individuals showing tissue loss) (C) of brown cup

I corals as a function of concentration of drilling muds and period. See Table 3 for exposure

statistics.

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! Table 1: Summary of regression analyses for experiments testing for physiological effects on

red abalone larvae due to exposure to varying concentrations of drilling muds. P-values using

concentration and log(concentration) as the independent variable are given. If the relationship I

between the dependent variable and concentration or log(concentration) was significant (P<0.05) w

the direction of the slope is shown (+ or -). Non-significant resalts are denoted by "ns" See

Figures3-7. I

!

P-Value

Experiment Dependent Variable df Concentration Concentration Log Slope I

Fertilization Fertilization 1,69 0.397 0.069 ns,ns i1

Development Development 1,74 0.909 0.325 ns,ns I

Precompetent Larvae-9 ° C Survivorship 1,10 0.001 0.002 +,+

Settlement 1,10 0.497 0.641 ns,ns 1

Viability 1,10 0.880 0.994 ns,ns

PrecompetentLarvae-15° C Settlement 1,61 0.186 0.191 ns,ns II

CompetentLarvae-9° C Survivorship 1,40 0.613 0.602 ns,ns

28 hr drilling mud Settlement 1,40 0.259 0.043 ns,+ m

24 hr GABA/Clean SW Viability 1,40 0.398 0.080 ns,ns I

CompetentLarvae-9° C Survivorship 1,39 0.848 0.918 ns,ns

28 hr drilling mud Settlement 1,39 0.362 0.048 ns,+ I

24 hr GABA/drilling mud Viability 1,39 0.248 0.069 ns,ns

Competent Laiwae - 15° C Survivorship 1,19 0.387 0.130 ns,ns III

28 hr drilling mud Settlement 1,19 0.023 0.057 -,ns

24 hr GABA/Clean SW Viability 1,19 0.093 0.249 ns,ns

CompetentLarvae-15° C Survivorship 1,19 0.137 0.861 ns,ns I

28 hr drillingmud Settlement 1,19 0.703 0.086 ns,ns

24 hr GABA/drilling mud Viability 1,19 0.884 0.122 ns,ns

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(C-3) 22 I

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I Table 2A: Results of multiple regression analysis for experiments testing for effects on inductive

quality of surfaces by drilling muds. Results did not differ qualitatively if log (concentration of

I drilling muds) was used as the independent variable. Asterisk (*) indicates a significant result (P<0.05). ANOVA results are depicted for the regression line of concentration of drilling mud.

I Variable Coefficient P

Intercept -0.551 0.833

I Concentration of Muds -0.002 0.016"

Drilling

Percentfreespace 0.014 0.605

I

Analysis of Variance

I Source S_SS df F P

Regression 2.055 2 16.062 0.001 *

i Residual 1.855 29

Adjusted squared multiple R: 0.493

I

I effects Table 2B: on redSummary abalone oflarvae regression due to analyses exposure forto control varying experiments concentrationstesting of drilling for physiological muds. Pvalues using concentration and log (concentration) as the independent variable are given. If the

I relationship between the dependent variable and concentration or log (concentration) was significant the direction of the slope is shown (+ or -). Non-significant results are denoted by

"ns". See Figure 8.

I

P-Value

I Dependent Log

Experiment Variable df Concentration Concentration Slope

I 2284 hr hourdrislling Coralmuds line Settlement 1,18 0.586 0.454 ns

crusts/clean SW

I 28 hr muds Settlement 0.386 0.333 drilling 1,18 ns

24 hours

i GABA/clean SW

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Table 3: Results for analysis of covariance for effects of drilling muds (categorical variable) I

over time (day = covariate) on several measures of performance for the brown cup coral,

Paracyathus stearnsii. For all performance parameters (survival; individuals exhibiting tissue B

loss, and viability) there was a significant (P<0.05) interaction term in the analysis. This

indicates that the slopes were not homogeneous. Significant terms; are denoted by asterisks (*).

SeeFigure9. I

Analysis of covariance - Survival I

Source df SS F P I

Concentration of drilling muds 3 0.0002 0.10 0.960

Day 1 0.062 107.59 <0.001 * •

Interaction 3 0.116 66.37 <0.001 * 1

Residual 16 0.009

I

Analysis of covariance - Individuals Exhibiting Tissue Loss I

Source df S__SS F P

Concentration Day of drilling muds 3 0.010 0.24 0.867 I 1 1.353 95.67 <0.001 *

Interaction 3 0.607 14.30 <0.001 *

Residual 16 0.226 I

|

Analysis of covariance - Viabilit_ i

df SS E P i

Source

Concentration of drilling muds 3 0.024 0.62 0.614

Ill

Day 1 0.804 62.16 <0.001 * i

Interaction 3 0.341 8.79 O.001 * I!lid

Residual 16 0.207

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(C-3) 24 i

I
I Figure 1

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I Figure 3

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I Concentrotionof DrillingMud (rag/L)

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Figure 41

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5.0[A] 1

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Concentretion of Drilling Muds (rag/L) I

I
I Figure 5

I

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Figure 6 I

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I Figure 7

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Figure 8 I

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I Figure 9

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i APPENDIX D

I BIOLOGICAL COMMUNITY MANUSCRIPT

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I LONG-TERM VARIABILITY OF HARD-BOTTOM

EPIFAUNAL COMMUNITIES: EFFECTS FROM OFFSHORE OIL

, AND GAS PRODUCTION AND DEVELOPMENT

I Douglas R. Diener1 and Andrew L. Lissner2

MEC Analytical Systems, Inc., Carlsbad, CA

I Science Applications Corporation, Diego,

2

International San CA

i [To be submitted to: Marine Environmental Research (Alternate, Deep-Sea Research)]

i ABSTRACT

Epifaunal communities occurring on nine deep-water reefs in the Santa Maria Basin, California

t were and spatial photographed vriabilityoverandantoeight determine year period the effects (October of platform 1986 to January discharges1994) fromto offshore assess temporal oil and

gas production and development activities. The nine reefs varied in depth (105-212 m) and

i distance from platform from Platform discharges. HidalgoThe (0.5 composition to 6.4 km),of thus theserepresenting communitiespotentially was strongly different ifluenced exposuresby

water depth and relief height. Over 200 taxa, dominated by cnidarian and echinoderm suspension

i feeders, taxa withwere loweridentified percentages from ofthecover reefs.compared Hard-bottomto thereefs mostnearest distantPlatform reefs. However, Hidalgo hadtemporal fewer

plots and linear regression of abundance (percent cover) for 24 dominant taxa provided little

I evidence for changes in community parameters associated with drilling periods. Thirty-five percent of the regressions showed significant (predominately negative) temporal trends for percent

cover. However, an analysis of covariance (ANCOVA), which tested for changes with distance

i from the platform, found no consistent pattern of response for any one taxon. Further, Chi-square contingency analyses of the cumulative ANCOVA results indicated approximately equal numbers

of positive and negative effects, thereby suggesting the trends could have been due to chance

I alone and not platform effects. Subtle or gradual long-term effects are consistent with drilling discharge impacts to some larvae and adults as indicated by companion results from in situ

experiments and laboratory bioassays, respectively. Such impacts, particularly sublethal effects,

I may require years to as changes percent cover, especially using

be manifested and detected in

current, random photographic techniques alone. Long-term natural effects such as Et Nifio cycles

and changes in biomass of macrozooplankton also may complicate these evaluations. I

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INTRODUCTION I

The United States Department of the Interior (DOI), Minerals Management Service/National I

Biological Service has been conducting multiyear environmental :studies to assess the impacts of

oil and gas development and production activities on the biological resources of the Pacific Outer m

Continental Shelf(OCS) (SAIC and MEC 1995). Biological resources at risk include soft-bottom I

infaunal communities, hard-bottom epifaunal reef communities, and associated fish and

macroinvertebrates (Piltz 1986). This study focused on hard-bottom epifaunal reef communities, 41

which are important because of their relative scarcity and generally unknown tolerance to II

platform discharges.

Recommendations for long-term studies of the Pacific OCS were first presented in MMS (1982), I

with site selection and reconnaissance studies (Phase I) conducted from 1983 to 1985 (SAIC

1986; Piltz 1986). Phase II and Phase III monitoring studies were performed from October 1986 [l_

to October 1990 (Brewer et al. 1991; Hardin et al. 1994; Hyland et al. 1994), and from October U

1991 through January 1995 (SAIC and MEC 1993, 1995), respectively. The study sites, located

in the Santa Maria Basin, off Point Arguello, California, were chosen because a mixture of soft- I_

and hard-bottom habitats occur in the area. The sites are relatively isolated, with no major W

anthropogenic input sources (e.g., wastewater outfalls), and no oil or gas platform discharges

prior to 1985. Development of the Point Arguello field included the installation of three ]1_

production platforms, Harvest, Hermosa, and Hidalgo (Table 1). Phase II drilling operations (39

wells) began in November 1986 and continued until January 1989, and Phase III drilling

operations (5 wells) occurred from September 1993 to May 1994 (Table 1). The Phase II drilling _1_

period discharged 46,084 cubic meters of drilling muds and cuttings, while substantially less IIIJ

material (5,547 cubic meters of muds and cuttings) was discharged during Phase III (Table 1).

Because of the use of barite in drilling muds, barium concentrations provide a unique sediment

and flux marker for assessing the spatial distribution, concentration, and persistence of the

discharges onto nearby hard-bottom reef communities. Other metals and hydrocarbons are not i

present in high enough concentrations to be useful tracers (Hyland et al. 1994). |

Three main types of impacts may result from oil and gas development and production activities:

(1) physical alteration of the habitat; (2) discharge of potentially toxic materials; and (3) changes I

in flux and sedimentation rates that may affect biological processes (e.g., feeding and respiration)

(Lissner et al. 1991). Physical alteration of the habitat has been documented for anchoring il

operations related to exploratory drilling operations (Texas A&M 1976, 1981; Ecomar 1978; II

Environmental Science and Engineering, Inc. 1987; Dustin et al. 1991; MEC 1995) and pipeline

installations (Centaur Associates, Inc. 1984; MMS 1987; Marine,, Research Specialists 1992). /I

Impacts from anchoring can include crushing and changes in the size of hard substrate, disruption |

and breakage of organisms and substrate, overall changes in the amount of hard substrate, and

the creation of large furrows (Lissner et al. 1991; MEC 1995). These impacts differ from those li

caused by natural disturbances, although some fishing activities, such as trawling and dredging, II

may cause disturbances to soft-bottom (van der Veer et al. 1985; Butman et al. 1988; Van Dolah

et al. 1991) and hard-bottom communities (Van Dolah et al. 1987; pers. obs.). Alteration of /I

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I benthic habitats also can occur from the accumulation of drill cuttings and muds beneath the

platform (Boesch and Robilliard 1987; SAIC and MEC 1993).

I In contrast, impacts from sedimentation can occur naturally (e.g., from resuspension, slumping,

and advective transport) or from anthropogenic inputs (e.g., discharge of drilling muds and

I cuttings, and dredge material disposal). In addition to direct effects of sedimentation (e.g., burial,

smothering, and decreases in suspension feeding efficiency), which may be similar for both

natural and anthropogenic inputs (Cimberg et al. 1981), there can be additional concerns

I associatedwithchronic from mudsand hard-bottom toxicity drilling hydrocarbons. However,

epifauna in the study area likely have some tolerance for sedimentation effects and exposure to

I hydrocarbons as these are natural features of the study area (e.g., natural oil seeps). Adequate knowledge of natural disturbances and the role they play in structuring communities is critical

to distinguishing these natural impacts from man-induced disturbances (Lissner et al. 1991).

t Hard-bottom reef communities and habitats are relatively rare in occurrence and spatial

distribution along the Pacific OCS and, until recently, little was known about their natural history

i and Site ecology specific, (SAIC primarily1986; qualitative SAIC andsurveys MECwere 1989;associated Lissner etwithal. oil 1991; andSAIC gas exploration 1994; MECactivities 1995).

that occurred from the late 1970s through the mid-1980s. These studies resulted in the

I delineation preferences (Chambers of some hard-bottom , Consultants habitats and Planners and generated 1982; Damespreliminary & Moore 1982, data on1983; species Engineering habitat

Science 1984; Hooks McCloskey 1982; Nekton 1981; Nekton and Kinnetic Laboratories 1983;

I SAIC, communities, 1986). particularly However, most the ofenvironmental these early effvariables orts provided that affected few insights them.intoSubstantially the ecology ofmore the

focused studies were initiated by DOI with the performance of long-term, monitoring studies of

i hard-bottom, epifaunal communities of the Santa Maria Basin (SAIC 1986; Steinhauer and Imamura 1990; Hardin et al. 1994; Hyland et al. 1994).

I The Phase II program specifically targeted nine hard-bottom reef areas before, during, and after the production drilling phase of platform development (Steinhauer and Imamura 1990). General

goals of the studies were to establish a quantitative baseline and expand the knowledge of the

I factors that regulate the spatial and temporal variability of these communities. Specific objectives included: (1) determine species composition and abundances of hard-bottom communities in the

study area; (2) describe and determine the causes of temporal variation of these communities; and

i determinethe between variation in the communitiesand levels of (3) relationship temporal

contaminants associated with oil and gas development (Steinhauer and Imamura 1990).

I analysis communitiesfrom high- and low-reliefhabitatsat both

Phase II studies included of

shallow and deep locations within the vicinity of Platform Hidalgo (Figure 1 and Table 2).

i Results indicated that the distribution and abundance of hard-bottom epifauna were strongly related to water depth, vertical relief, and current orientation (Brewer et al. 1991; Hardin et al.

1994; Hyland et al. 1994). Similar results have been observed from other surveys in the study

i area and MEC and studies 1989;ofLissner similar etcommunities al. 1991; MEC off central 1995).andFour northernout California of 22 common (SAICtaxa 1986;showed SAIC

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significant (p<0.05) reductions in abundance during the drilling period (Hyland et al. 1994). I

These impacts were restricted to the deeper reefs (160-212 m) _ad were noted for three sessile m

suspension feeders (sabellid polychaetes, the cup coral Caryophyllia sp., and the tunicate ,_

Halocynthia hilgendorfi igaboja) and mobile, detrital-feeding gedatheid crabs. There were no

,u,

apparent effects to these or other species occurring on shallower reefs (105-119 m). Estimated m

concentrations of chemical contaminants from the drilling discharges were thought to be below |

toxic levels. Therefore, the observed biological changes were hypothesized to be influenced by

physical effects associated with increased particle loading during the drilling phase (Parr et al. II

1991; Hyland et al. 1994). These effects could be caused by disruption of suspension feeding, IB

respiration, and/or decreased post-larval survivorship due to burial. However, no direct effects

wereevidentfromthePhaseIIdata. uR

The objectives of the present study (Phase III) were to continue monitoring epifauna at the nine

hard-bottom subtidal reefs surveyed for Phase II and evaluate community responses during post- "_.

Phase II drilling and Phase III drilling periods. Since the Phase III drilling period was much less

than forecasted, analytical efforts focused on community responses in the post-drilling period that

couldberelatedtoplatformeffects. I

MATERIALS AND METHODS I

The study area consisted of nine, hard-bottom reefs in the vicinity of Platform Hidalgo (Figure

1). Sites were selected as part of initial Phase 1I studies to encompass various distances from the

platform from nearfield to farfield (0.5-6.4 km), range of water depths from shallow (105-119

m), to deep (160-212 m), and low (0-1.0 m) and high (> 1.0 m) relief heights. Table 2 lists the Bill

key factors for each site and illustrates the similarities and differences between Phase II and Phase

III surveys.

w

Sampling for Phase III was conducted in November 1991, October 1992, and January 1994.

Sampling methods generally followed those of Phase II studies, and included a Remotely

Operated Vehicle (ROV) equipped with a color video camera, a 70 or 35 mm still camera and im

strobe, two split-beam lasers for optimizing focus and standardizing the area of photoquadrats to I

1 m 2, and a color sidescan sonar (SAIC and MEC 1995; Hardin et al. 1994). Survey navigation

utilized a satellite differential Global Positioning System (GPS) interfaced with an acoustic m

navigational system on the ROV, thus providing positioning accuracy for the ROV of less than |

3 meters. Photographs were taken with the camera angle pointed[ downwards in suitable, lowrelief habitat. In high-relief habitat, the camera angle was oriented :ina more forward (horizontal) !1

direction. Photographs were taken randomly at approximately 130second intervals or more, il

depending on substrate occurrence, thereby preventing any overlap of photographic data. Color

video data, with the camera angled at approximately 45° from the bottom, were collected 111

incidentally to the photoquadrats to document larger-scale comm_mity characteristics. II

In addition to the photographic information, monitoring included documentation of sediment /I

contaminants (Hyland et al. 1994; Phillips et al., in preparation; ,;ee Appendix B in SAIC and It

D-4 I

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I MEC 1995), sediment and contaminant deposition and flux (sediment traps) (Coats 1994; Hyland

et al. 1994; SAIC and MEC 1995; Phillips et al., in preparation), ocean currents (Steinhauer and

I Imamura 1990; Coats 1994; SAIC and MEC 1995), drilling mud toxicity (Raimondi et al., in preparation; see Appendix C-3 in SAIC and MEC 1995), and in situ bioassays and settling

experiments (Raimondi et al. and Barnett et al., in preparation; see Appendices C-1 and C-2,

I respectively, in SAIC and MEC 1995). These studies provided data for estimating the exposure potential of the nine reefs to platform discharges.

I analyzedby a randompoint-contactmethodusing gridpatternsthat Epifaunal photographs were

contained 50 points. Each photograph was projected at life size (1:1) onto a grid pattem, and the

i species or substrate type under each point, as well as counts of individual or solitary species, were recorded. In addition, counts of all taxa that occurred in the photograph, regardless of whether

they fell under a contact point, were recorded. Because many taxa have not been previously

t described or were not identifiable to species, a descriptor name (e.g., "white encruster") was given in these cases. For data calculations, these latter taxa were assigned a default percent cover of

0.5 % as described for Phase II methods (Hardin et al. 1994). Percent cover estimates also were

i adjusted normalizedfor todotsthethat visible fell ohard n shadows substrateor soft in each sediments, photograph. and counts To produce of individual a continuous organismsbaseline were

and maintain consistency between studies, the Phase II epifaunal databases were acquired from

DOI successful, to demonstrate although some reproducibility taxonomic of issuesthe remain Phase unresolved. II results. This However, intensive the results effort indicate was largely that

for the common taxa, the Phase II and Phase III results can be analyzed as a continuous database

I (SAIC and MEC 1995).

Multivariate classification analysis using the 50 most numerically dominant taxa was used to

I delineate the major features of the study area. The analysis utilized the mean percent cover for each taxon for the eight-year (i.e., combined Phase II and Phase III) study period. The data were

square-root transformed and normalized to the standard deviation before calculation of Brayi Curtis distances (Bray and Curtis 1957) to keep the most abundant taxa from dominating the analysis. The Bray-Curtis dissimilarity coefficient and flexible sorting strategy (B= -0.25) was

used to cluster the data (Smith 1976, Tetra Tech 1985). Both normal (sites) and inverse (species)

I analyses were conducted and plotted as dendrograms. A two-way coincidence table with dendograms was produced to aid in interpretation of the cluster results and to provide insights

on the defining, physical features of the communities. The analysis was run using SAS Version

i (SAS1990).

6

To evaluate potential relationships among biological parameters and physical measurements,

I correlation coefficients calculated for dominant taxa and (Pearson product moment) were physical

and chemical measurements from sediment flux traps near each hard-bottom site. Sediment

i parameters consistently measured and/or detected included 11 metals; Ag, As, Ba, Cd, Cr, Cu, Hg, Ni, Pb, Va, and Zn; percent clay; percent fines (silt + clay sediment fraction); median size

of flux particles; flux rate (mg/m2/day); and total organic carbon.

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Potential long-term (e.g., sublethal) effects were evaluated by plotting, visual analysis, and linear m

regression of temporal trends in percent cover for 24 dominant taxa. The regressions were

performed for 3 habitats (deep high- and low-relief and shallow low-relief; see below) by taxon, ,_

representing 72 combinations of temporal patterns.

To test for differences in abundance trends as a function of distance from Platform Hidalgo, an I

analysis of covariance (ANCOVA) was performed on percent cow,_rof dominant taxa by survey.

m

The covariate in the analysis was distance from Platform Hidalgo (nearfield, midfield, and Ill

farfield) for the hard-bottom sites. This required three sets of analysis for each of the 20 ]B

dominant taxa at deep high-relief, deep low-relief, and shallow low-relief sites. Too few data

were available for shallow high-relief sites for them to be tested. The null hypothesis for the i

ANCOVA was that changes in percent cover for dominant taxa by habitat type were independent |

of distance from Platform Hidalgo. Significant differences between sites nearest Platform

Hidalgo (nearfield) compared to sites farthest away (farfield) would reject the null hypothesis and tl

suggest a possible platform effect. Effects were indicated when the rate of change in percent W

cover for the nearfield site was significantly different from the, farfield site. Effects were

interpreted to be positive when the nearfield site had increasing percent cover or less rapid iI

decreases compared to decreases at farfield site. Positive effects were also indicated if the I

percent cover at the nearfield site increased significantly faster than the increase at the farfield

site. Platform effects were interpreted as negative when percent cover at the nearfield site

decreased faster than decreases at the farfield site. Negative effects were also indicated when

percent cover at the nearfield decreased or increased more slowly than increases at the farfield

site. When there were no significant differences between the nearfield and farfield sites, the ,_

results were interpreted as being inconsistent with a platform gradient effect and were assigned I

a 0 value. When the survey x distance interaction was nonsign]ificant no further testing was

appropriate. I

Determination of the statistical power to detect changes in mean vaJ[uesis important for assessing

the significance of the study results. Power analysis was based on Taylor's Power Law for

comparison between two sample means of a given variable (Green 1989). An appropriate III

comparison might be between two sites at a given time or between two sampling periods. m

Comparisons between sites for the pre-drilling phase were conducted in Phase II (Hyland et al. n

1994). For Phase III, comparisons of pre-drilling with post-dril]ing abundances provided an

w

estimate of statistical power for the dominant taxa by comparing the mean percent cover for the ilt

first two surveys of Phase II (October 1986 and May 1987, considered a baseline or pre-drilling If

phase) and the mean of six post-drilling surveys (Phase II = May and October 1989, and October

1990, and Phase l]I = November 1991, October 1992, and January 1994). The analysis focused !11

on the occurrence of significant decreases in percent cover for the post-drilling surveys since this U

would be representative of a negative platform effect. For those taxa having significant

decreasing temporal trends in the post-drilling surveys, the data were detrended. This did not i

affect mean values but generally reduced the variance estimate for the post-drilling period. The II

results are presented in two forms: (1) the actual power (1-13,o[=0.05) in percent, and (2) as the

size decrease in the mean that would be detectable with a power of 80% (13=0.2). i

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I RESULTS

Biology of Hard-Bottom Reefs

A total of 4,438 photographs from eight surveys were analyzed for Phase II, and 2,032

I photographs over three surveys were analyzed for Phase III. From these photographs, 216 and 220 taxa (including qualitative descriptions, e.g., "sponge, tan encrusting") were identified from

Phase II and Phase III, respectively. The combined phases yielded 286 separate taxa. This

I diversity most encrusting taxa (e.g., sponges, tunicates,

estimate of is conservative because small

and ectoprocts) cannot be identified to species from the photographs. To overcome difficulties

i in identifying organisms from photographs, and to achieve consistency between the Phase II and III surveys, some taxa were consolidated into gross taxonomic groups (e.g., galatheid crabs).

i Classification community structure. analysis showed This that water depth was the most significant determinant of finding is consistent with other studies of hard-bottom (e.g.,

Vinogradova 1962; Rowe and Menzies 1969) and soft-bottom communities (Thompson et al.

I more 1993;similar Diener toet al. the 1995) other (Figure two deep2).sites For [PH-R example,(212Sites m) PH-K and PH-W(160 m) (195andm)]PH-Nthan (166 to anym)ofwere the

five shallow sites. However, there also is an indication that distance from Platform Hidalgo was

evidence an important for adeterminant gradient in reef of community communitiesorganization. relative to Platform The arrangement Hidalgo (Figures of site clusters 1 and 2).provides Thus,

Sites PH-E, PH-I, and PH-J can be considered shallow nearfield sites, Site PH-F shallow

I midfield, midfield, and Site Site PH-UPH-Wshallowdeep farfield, farfield (Figure Stes PH-K 2). Thisandclassification PH-N deep isnearfield, consistent SitewithPH-Restimated deep

exposures from drilling mud (high, medium, and low dosage) of the same sites from the Phase

I II drilling period (Table 2; Coats 1994; Hyland et al. 1994).

The depth preference (occurrence) of the 50 most dominant taxa was evident from the two-way

I table (Figure 2) and a rank of the taxa by mean percent cover (Table 3). Based on Figure 2, taxa with a preference for the shallow site depths are represented by the first 10 taxa (Rathbunaster

californicus - a seastar - to Paracyathus stearnsii - a cup coral); taxa preferring the deeper sites

I encompass the next 11 taxa (Lophelia pertusa - a colonial coral - to Swiftia kofoidi - a small gorgonian); taxa found at all depths are considered ubiquitous, as represented by the next 14 taxa

i (Pyura haustor - a tunicate - to "sponge-tan encrusting"); and the remaining 14 taxa (Laqueus californianus - a brachiopod - to "sponge-shelf") generally had highest coverage at the two

deepest sites (PH-R and PH-W). Within these species clusters additional patterns are related to

depth and distance from Platform Hidalgo. For example, some shallow site taxa (e.g., the

I seastars R. californicus and Mediaster aequalis) have higher mean percent cover at nearfield sites,

while other taxa (e.g., Octopus sp., the seastar Stylasteriasforreri, and the cup coral P. stearnsii)

have adultshigher of thiscoverage species have at farfield been sites. shown This to begradient sensitiveintocuplaboratory coral distribution exposures isofintriguing drilling muds since

from Platform Hidalgo (Raimondi et al., in preparation; see Appendix C-3 in SAIC and MEC

i a1995). platformTaxagradient associated (Figureprimarily 2). Forwith example, the deeper the sixsitesaxaalso frmshowed L. pertusa sometotrends "anemone consistent -white wdisc ith

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with purple tentacles" and the eleven taxa from "ascidian-blue grey encrusting" to "sponge-shelf" I

prefer the two deepest, farfield sites, PH-R (212 m) and PH-W (195 m). In contrast, the three

taxa from L. californianus to "anemone-tan zoanthid" showed the opposite pattern with a _

preference for the two deep nearfield sites, PH-K (160 m) and PH-N (166 m). I

A second cluster analysis included relief height for the nine hard-bottom sites (Figure 3). These J_

results also indicate the important influence of relief height on community composition,

u

especially at the shallow sites. Variation in relief height of as little as one meter can have a lira

profound influence on community composition. The site dendrogram for the shallow sites shows

that both relief height and distance from Platform Hidalgo affect community composition, with

u

relief height being the more important factor. Shallow nearfleld sites PH-E, PH-I, and PH-J i

tended to be more similar to each other than to the other sites farther from Platform Hidalgo. tl

However, the two-way table indicates that these distinctions are subtle since most shallow reef

taxa had their highest percent cover in the low-relief habitat, _d no taxa showed a strong 111

preferenceforshallow,high-reliefhabitat. l

Most of the 50 dominant taxa showed a preference for a particular water depth and/or relief II

height (Figure 3 and Table 4). In addition to the 10 taxa discussed above (Figure 2), inclusion II

of relief height adds three more taxa, Phidolopora pacifica and Cellaria sp. (ectoprocts or

bryozoans), and the cup coral Caryophyllia spp., that prefer shallow reefs. Most of the shallow twater taxa preferred low relief, although this may be a partial artifact of sampling since the Ii

shallow reef sites had little high relief. Three ahermatypic cup corals (BalanophyUia elegans,

P. stearnsii, and CaryophyUia spp.) clearly preferred shallow reefs with low-relief habitats

(Tables 3 and 4). BalanophyUia and Paracyathus were rare at the deeper reefs, while _

Caryophyllia spp. was fairly common at the deeper depths and high-relief habitat. This habitat

preference is somewhat surprising since sediment fluxes were alraost twice as high at shallow ,J

(30-80 g/m2/day) compared to deep sites (24-40 g/m2/day) and fluxe,s for high relief (18 g/m2/day) Xll

were a little more than half that for low-relief habitat (30 g/m2/day) (Parr et al. 1991, SAIC and

MEC 1993; Phillips et al., in preparation; see Appendix B in SAIC and MEC 1995). This I

suggests that these cup corals may be naturally adapted to high amounts of sediment resuspension g

and suspended particle flux.

I

The ubiquitous taxa were dominated by echinoderms, including total ophiuroids, the ophiuroids

Ophionereis sp. and Ophiacantha diplasia, and the crinoid F. serratissirna (Figure 3). Of the kit

seven taxa in this cluster, only one is sessile (gorgonian) suggesting that large, relatively mobile |

taxa may have broader habitat tolerances than attached taxa. Seven taxa showed a preference for

high-relief habitat, with six of these characterized by patterns that were independent of water in

depth. Desmophyllum dianthus (formerly known as D. crista-gall'i), an ahermatypic cup coral, N

was found most commonly at deep high relief sites. Other taxa preferring high-relief habitat

included the colonial ahermatypic coral (Lophelia pertusa; formerly known as L. californica), an Ill

anemone (Metridium giganteum; formerly called M. senile), white encrusting organisms, sponge- Ii

tan encrusting, and a seastar (Peridontaster crassus). The remainin_,_23 taxa preferred the deeper

sites with eight of these taxa primarily occurring at the deepest sites (PH-R and PH-W). Thirteen n

of these taxa are exclusively hard-bottom epifauna, including two tunicates (Pyura haustor and il

D-8 |

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I "blue-gray ascidian"), total Polychaeta, a brachiopod (Laqueus), basket star (Gorgonocephalus

eucnemis), three sponge taxa, five anthozoans, including four anemones (Amphianthus

i californicus, anemone "tan zoanthid", anemone "white disc purple tentacles", and Stomphia didemon), and a small gorgonian (Swiftia kofoidi).

I Overall from Figure 3 indicate that shallow, low-relief nearfield sites (PH-E, PH-I, PH-J) patterns

were more similar to each other than to the midfield (PH-F) or farfield sites (PH-U). For the

i deep sites, midfield and farfield sites PH-R and PH-W were most similar to each other based on relief height (high relief). Nearfield sites PH-K (high relief) and PH-N (low relief) showed

strong similarities independent of relief height. Site PH-K (low relief) was different from other

I deep, K low-relief sites. This relationship also is influenced by the lack of low-relief data from PH- during Phase II, and the observation that most of the deep-water taxa at this site have lower

abundances than for other comparable sites (Figure 3).

t The mean number (listed in parentheses) of taxa per photograph was higher for deep (20.7)

compared to shallow (15.6) sites, and was also higher for high-relief (22.0) compared to lowrelief and abundant (16.8) habitats biota than (Tableshallow, 5). Thus, low-relief deep, high-relief habitats. habitats Similar are trendscharacterized were observed by more for percent diverse

cover of the 20 most dominant organisms by depth and relief height categories (Tables 3 and 4).

I The range in mean number of taxa (16.0 to 16.3) per photograph for shallow sites was almost identical for far-, mid-, and nearfield sites (Table 5). Deep, nearfield sites had somewhat fewer

taxa (18.4) compared to midfield (20.8) and farfield (23.0) sites. This gradient for deeper sites

I was evident for both low- and high-relief habitats.

Mean percent cover for all taxa at the shallow low-relief sites was intermediate at the farfield site

I (29.4%), lowest at the midfield site (26.1%), and highest at the nearfield sites (30.7%) (Table 6). For the deep sites, total percent cover was lowest for the nearfield sites (37.9%), intermediate for

the midfield site (43.7%), and highest at the farfield site (45.1%). These differences were not

i statistically significant; however, the results indicate that the deep reefs nearest to Platform Hidalgo have a lower density of taxa with less percent cover than observed for reefs farther

away. These gradients and possible effects from Platform Hidalgo are discussed below.

I The 20 most abundant taxa are listed by depth category (shallow versus deep) and by relief

height (low versus high) in Tables 3 and 4, respectively. Different taxa dominate all four

i categories, including ophiuroids, total white encrusters, F. serratissima, O. diplasia,

total

galatheid crabs, M. giganteum, sponge-tan encrusting, H. hilgendorfi, P. haustor, and gorgonianred or pink. The dominant phyla are cnidarians (44%), echinoderms (16%), and Porifera (12%)

i with the remaining five phyla combined accounting for 28% (Urochordata-8%, Arthropoda-8%,

Brachiopoda-4%, Ectoprocta-4%, and annelid polychaetes-4%). Table 7 lists the overall rankings

of the dominant taxa by habitat type.

Correlations of percent cover of dominant taxa with sediment flux trap parameters were examined

i to13help of thedefine 16 parameters possible mechanisms measured, the for observed most important tends. ofSignificant which included correlations percentwere clayfound (43% forf

I D-9

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I

II

the dominant taxa correlated with this parameter), cadmium (38%),, size of flux particles (33.3%), W

copper (28.6%), flux rate and total organic carbon (23.8%), and percent fines, mercury, and

nickel concentration (19% each). No significant correlations were found for silver, lead, and

vanadium. The remaining parameters (arsenic, barium, chromium, and zinc) were correlated less Im

than 14% of the time with dominant taxa. Generally, correlations were negative with percent

clay, percent fines, and flux rate, but usually were positive with the other parameters. These

results suggest that fine particles and high sediment fluxes may be detrimental for filter and

suspension feeding organisms. This would be consistent with reduced feeding efficiency and/or /

clogging of filtering structures for these biota. The generally positive correlations with metals IN

suggest that toxicity (as often associated with metal contaminants)is not a significant factor for

thedominant taxa. !1

J

Trends in Dominant Biota

The relative dominance (rank order) of the most common epifauna has remained generally I

consistent over the eight year study period. Temporal plots and linear regression of mean percent

cover by phylum and dominant taxa were used to illustrate the range of changes observed during II

the study and aid in visualizing the relationships to drilling periods (Figures 4-11). Further, I!

ANCOVA results were applied to statistically evaluate survey x distance (from the platform)

trends. I

Cnidaria

m

Cnidarians (anemones, corals, and gorgonians) were the most conspicuous biota observed during '1

both phases, exhibiting a preference for deep (11.8%) versus shallow (8.0%) sites and high-relief

(15.8%) versus low-relief habitat (6.8%). Decreasing temporal trends in percent cover were _

observed for deep, high- (p=0.07, I"2=0.26) and low-relief habitats (t)=0.06, I-2=0.28). In contrast, W

no significant trends were evident for shallow low-relief habitats (Figure 4). To determine if the ,-,it

decreases coincided with the Phase II drilling period, the tempo:ral plots were evaluated for

nearfield and farfield, deep sites (Figure 5). ANCOVA result,; for all cnidaria combined 111

indicated positive (enhancement) effects for deep high- and low-relief habitats, based on roll

increasing percent cover for nearfield sites and decreasing trends for the farfield site. The

opposite pattern was indicated for the shallow low-relief habitat suggesting a negative platform w

effect, i

Of the 21 dominant taxa (based on percent cover), ten were cnidarians including five cup corals,

four anemones, and a gorgonian (Table 7). All the cup cor_ds showed specific habitat roll

preferences, with B. elegans, Caryophyllia, and P. stearnsii preferrinl; shallow low-relief habitats, II

and D. dianthus and L. pertusa preferring deep high-relief habital:s. No significant temporal

trends or correlations were found between B. elegans and the 16 sediment flux parameters.

ANCOVA results indicated that for deep high-relief habitats, percent cover at the nearfield site IN

(PH-K) decreased significantly faster than at farfield (PH-W) and midfield (PH-R), suggesting

a negative platform effect (Table 8). In contrast, a positive effect was indicated for shallow low- II

relief habitat where percent cover at the farfield site (PH-U) decreased significantly faster than ii

D-IO '!

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I at nearfield sites (PH-J, PH-I, and PH-E). For deep low-relief habitats there was no significant

survey x distance interaction. Caryophyllia spp. had significant decreasing temporal trends for

I habitats, deep high-relief Caryophyllia (r2=0.42) had and significant deep low-relief correlationshabitats with (r2=0.73) (Figure 6). For low-relief four sediment flux measurements (Cu

r2=0.37, Ni 1"2=0.43, % clay r2= -0.34, flux rate 1"2=0.40). ANCOVA results for Caryophyllia

I showed a negative platform effect for deep high- and low-relief habitats (i.e., percent cover for nearfield sites decreased significantly faster than the farfield site and there was no significant

i survey x distance interaction for shallow low-relief habitat) (Table 8 and Figure 6). Caryophyllia generally was not found on low-relief habitats near Platform Hidalgo. P. stearnsii exhibited a

significant decreasing temporal trend for all habitats (deep high-relief r2=0.63, deep low-relief

r2=0.75, and shallow low-relief r2=0.46) and was significantly correlated with two sediment flux

I parameters (Ni r2=0.37 and % clay r2= -0.32). ANCOVA results indicated no significant

difference between near- and farfield sites for deep high-relief habitat, possible negative platform

effect low-relief for deep habitat.low-relief habitats, and no significant survey x distance interaction for shallow

t DNo. dianthus significantwastemporal significantly trends correlated were notedwith for the fourtwofluxdeepparameters high-relief(Ascorals. r2= -0.50, Percent Cr r2=cover-0.55, for

Zn r2= -0.51, and flux rate r2= -0.53), while L. pertusa correlated only with As (r2= -0.46). For

i Dpertusa . dianthus, there was a positive platform effect for deep high-relief habitats (Table 8). For L. , a negative platform effect was indicated for shallow low-relief habitats. In summary,

for the five cup corals, ANCOVA results showed two positive effects, one with no significant

I difference distance interactions between near- (Tableand8).faffield, In the preferred five negative habitateffects, of theseandspecies, seven non-significant based on percentsurvey cover,x

there were two positive and three non-significant survey x distance interactions. In contrast, in

I less preferred habitats there was one non-significant difference between near- and farfield, five negative effects, and four non-significant survey x distance interactions. These results suggest

that proximity to the platform may be beneficial for a species in its preferred habitat but

I detrimental in less preferred habitats.

For anemones, decreasing temporal trends at deep low-relief habitats were observed for two of

the four species, Amphianthus californicus (1"2=0.25)and Stomphia didemon (r2=0.41). These

anemones prefer high-relief habitat and, except for Metridium, prefer deeper habitat. Metridium

giganteum, the tallest (e.g., to 1 m) West Coast anemone, was the second most dominant species

I over depths heights. M. giganteum preferred shallow (2.11%) versus deep (1.39%),

all and relief

and high (2.36%) versus low (1.23%) sites. The preference for high-relief habitat was more

evident for shallow sites (high, 5.48%; low, 1.29%) than for deep sites (high, 1.68%; low,

1.16%). Nearfield sites had higher percent cover (2.74%) than midfield (0.62%) or farfield

(0.72%). The percent cover variance estimates for this species was high (Tables 3 and 4),

i probably reflecting its patchy distribution and ability (at least by a congener) to detach and drift to new areas (Wahl 1985). M. giganteum was not significantly correlated with sediment flux

parameters. ANCOVA results indicated no significant difference between near- and farfield sites

i for 8). deep A. californicus high-relief was habitats significantly (Figure 7)correlated and a negative with three effectsediment for shallowflux low-relief parameters habitats (Zn r2=(Table -0.48,

I D-11

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% fines r2= -0.50, and TOC r2=0.75). ANCOVA analysis showed positive platform effects for I

deep high- (Figure 7) and low-relief habitats. Anemone "tan zoanthid" was not significantly a_

correlated with sediment flux parameters. ANCOVA analysis indicated positive platform effects

for deep high-relief and shallow low-relief habitats. S. didemon was significantly correlated with

five sediment flux parameters (Cd 1"2=0.56, % clay 1"2=-0.80, flux rate r2= -0.52, median flux size

rZ=0.60, and TOC r2=0.75). ANCOVA found no significant difference between near- and farfield

sites for deep high- and low-relief habitats. In summary, based on ANCOVA, four positive

platform effects, three results indicating no difference between near- and farfield sites, three non- /

significant survey x distance interactions, and only one negative effect were observed for the four II

anemone taxa (Table 8). These results suggest that these anemones may generally benefit from

closerproximityotheplatform. II.

The small unidentified pink gorgonian, possibly a species of Lophogorgia, also showed positive

platform effects for deep high- and low-relief habitat. In summary, for the ten cnidaria,

ANCOVA results indicated eight positive and seven negative effects. In preferred habitats there II

were five positive and no negative effects, while in less preferred habitats there were three

positiveandsevennegativeeffects. N

-/

Echinodermata

/

Echinoderms were the second most abundant taxonomic group, representing the dominant biota I

at some sites. Many seastars were easily identifiable from photographs, while speciating the

ophiuroids was more difficult. To ensure that taxonomic limitations did not influence the

analysis, the ophiuroids were combined into an "all ophiuroids" group; this was the dominant

taxon for all habitats (Table 7). Ophiuroids had a significant de,creasing temporal trend for

percent cover only at shallow low-relief habitats (r2=0.55). Signifilcant correlations were found _,

between percent cover of ophiuroids and six sediment flux parameters (Cd r2=0.47, Cu r2=0.44, mlr

Hg 12=0.40, % clay 1"2= -0.45, % fines r2= -0.48, and median flux size r2=0.47). ANCOVA

analysis indicated a positive platform effect for deep high-relief habitats and a negative effect for

shallow low-relief habitats (Table 8). w

The dominant echinoderm species (based on percent cover) was the crinoid, Florometra n

serratissima. This species was almost equally abundant at the two depth categories (shallow,

ww

2.48%; deep, 2.59%), but preferred low relief (low, 2.85%; high, 1.73%), and showed an

increasing temporal trend for deep high-relief habitat (r2=0.42) (Figure 8). For shallow low-relief m

sites percent cover was highest in the nearfield (3.92%), intermediate at midfield (1.15%), and

lowest at farfield (0.50%) locations. For deep sites, no consistent .gradient was evident. High- II

relief habitat had the highest percent cover (3.19%) at nearfield site,s and lowest values (0.61%) I!

at midfield. For low-relief habitat, the highest percent cover (4.75%) was at midfield and the

lowest (2.24%) was at nearfield sites. There were no significant co:rrelations with sediment flux

parameters. ANCOVA results showed a negative platform effect for deep high-relief habitat I

(Figure 8 and Table 8).

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I Porifera

I Sponges are another important component of the hard-bottom epifaunal community but, similar to many of the smaller taxa, are difficult to identify from photographs. Percent cover for all

sponges combined was highest for deep high-relief habitats. A significant decreasing temporal

I trend was observed only for deep low-relief habitats (r_=0.23). Sponges had significant correlations with seven flux parameters (Cd r2=0.56, Cu 1"2=0.50,Hg r2=0.31, % clay 1_= -0.48,

flux rate r2= -0.38, median flux size r2=0.42, and TOC r2=0.63). ANCOVA analysis indicated

i effectsfor all threehabitat For "total white encrusters"(a conglomerate positive platform types.

grouping of all small, encrusting organisms including sponges, tunicates, and ectoprocts that were

white in color), there was a preference for deep high-relief habitat but only the shallow low-relief

I habitat had a significant decreasing temporal percent cover

trend for (:=0.55). Total white

encrusters were significantly correlated with seven sediment flux parameters (Cd r2=0.67, Cu

I 1"2=0.62,Hg r2=0.35, Ni r2=0.40, % clay r2= -0.47, median flux size r2=0.46, and TOC r2=0.56). ANCOVA analysis showed a positive effect for all three habitats; Figure 9 depicts the trends for

deep high-relief habitats. "Tan encrusting sponge" showed a significant decreasing temporal trend

i, for withtheeight shallowsediment low-relief flux parameters habitat (r2=0.42) (Ag r2=and-0.54, significant Bar 2= (predominantly -0.58, Cd r2= -0.63, negative) Cur 2=correlations -0.73, Ni

r2= -0.55, Zn r2= -0.53, % clay r2=0.63, and median flux size r2=0.68). ANCOVA analysis

I indicated high-relief a habitats. negative platform "Shelf' sponges effect forhadshallow a significant low-relief decreasing habitat and temporal a positive trendeffect only for for deep deep

low-relief habitats (r2=0.49) and two significant correlations with flux parameters (% clay r2= -

0.34 deep and high-amedian n shallow flux size low-r2=0.38). relief habitats. ANCOVA In summary, analysis for identified the threea positive taxa thereplatform were sixeffect positive for

and one negative effect suggesting that sponges may benefit from close proximity to the platform.

I Brachiopoda

I The brachiopod, L. californianus, was relatively common in all habitats in the study area and is easily identified from photographs, thus representing a good species for assessing temporal trends

and patterns relative to Platform Hidalgo. This species had significant decreasing temporal trends

I inlow-relief percent r2=0.68) cover for(Figure all habitats 9) but(deep was significantly high-relief r2=0.45, correlateddeepwithlow-relief only threer2=0.92, flux parameters and shallow(Ba

r2=0.54, Cd r2=0.59, and % fines r2= -0.69). ANCOVA showed a negative platform effect for

I deep and shallow low-relief habitats (Table 8).

Urochordata

I Tunicate species are common on hard substrate but most are difficult to identify from

i photographs. Tunicates had a slight preference for deep high-relief habitat and ANCOVA results indicated a positive effect for deep high-relief and a negative effect for deep low-relief habitat

(Table 8). The solitary tunicate Pyura sp. had significant negative temporal trends for all three

habitats (1"2=0.40-0.45). ANCOVA results indicated a positive effect for deep high-relief habitat

I and negative effects for deep and shallow low-relief habitats. Halocynthia, a large colonial

I D-13

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tunicate had one significant negative temporal trend for deep low-relief habitat (1-2=0.40). !

ANCOVA results indicated negative effects for deep high- and low-relief habitats (Table 8). am

Tunicates, unlike the sponges, had more negative than positive e,ffects. 'I

Four Taxa Characterized by Phase II Drilling Period Effects ,i

II

The Phase II study identified four dominant taxa, Caryophyllia, galatheid crabs, the tunicate H.

hilgendorfi, and sabellid polychaetes, that displayed significant, negative responses to drilling mud ._

discharges (Hyland et al. 1994). Except for Caryophyllia, which also had a significant survey |

x dose interaction for deep high-relief habitats, these effects were: restricted to deep water, lowrelief sites. No other potential negative effects on reef epifauna related to drilling phases were I

suggested from the Phase II studies. Temporal plots of these utxa by distance from Platform II

Hidalgo (as related to drilling mud dose; Table 2) are presented to evaluate the potential

relationship to Phase II and Phase III drilling phases (Figures 6, 10, and 11; note that "Sabellidae"

are included in the "Polychaeta" data in Figure 11). The cup coral Caryophyllia spp., had the gl

lowest percent cover at deep nearfield (0.51%), was intermediate a_tmidfield (0.64%), and highest

at farfield sites (0.80%) for Phase II and III. As noted above, and consistent with the Phase II l_

findings, the ANCOVA analysis indicated a negative effect near Platform Hidalgo for deep high- g

and low-relief habitats (Figure 6, Table 8). However, a concurrent decrease in percent cover did

not occur at shallow nearfield sites. This suggests that the Phase II results for Caryophyllia spp. i

(Hyland et al. 1994) may have been due to either (1) natural variability or (2) variability in the !

sampling methods. However, the ANCOVA analysis may indicate potential long-term negative

platformeffects, i

At the deep, low-relief nearfield sites, galatheid crabs (Figure 10) and the ttmicate H. hilgendorfi m

showed decreases in percent cover during the Phase II drilling perJiod. These decreases were not B

evident for shallow sites or deep, high-relief sites. Galatheid crab,,;were more abundant (percent

cover) at deep (1.42%) as compared to shallow sites (0.52%). For deep sites, percent cover was

lowest at nearfield sites (0.99%), highest at midfield (1.86%), and intermediate at farfield n

(1.44%). Percent cover decreased at the deep low-relief nearfield site, while it increased at the

deep high-relief nearfield site. Since galatheid crabs are mobile, it is feasible that some I

movement occurred from low-relief to high-relief habitat, perhaps in response to drilling muds n

discharges during Phase II. This may be reasonable since galatheid crabs were associated with

significant negative correlations with sediment fluxes (r2= -0.58). However, the lack of a I_

negative response at the high-relief sites suggests that if vertical migration occurred in response n

to drilling effects, the impact on this taxon appears to have been of minor significance. The rapid

return to higher percentage cover following the drilling period suggests that any effects were of l

short duration. Galatheid crabs showed a significant decreasing temporal trend only for deep I

low-relief habitats (Figure 10) and had significant correlations with two sediment flux parameters

(flux rate and TOC I2=0.64). ANCOVA analysis found no significant difference between nearand farfield sites for deep high- and low-relief habitats (Table 8). This suggests that the Phase U

II findings of potential negative effects were either of short duratio:a and/or resulted from natural

or method variability and not drilling effects.

g

D-14 I

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I H. hilgendorfi had a slightly higher occurrence at deep (0.58%) compared to shallow sites

(0.43%) and a slightly higher occurrence in low- compared to high-relief habitat. Percent cover

was at midfield highest at the deep nearfield sites for both relief heights (low, 0.80%; high, 1.09%), lowest (low, 0.39%; high, 0.16%), and intermediate at farfield sites (low, 0.64%; high,

0.37%). Figure 10 shows the decrease in percent cover at the deep low-relief farfield and

I nearfield sites. However, the decrease at the nearfield sites appears to be influenced more by high values observed in May and October 1987 than to drilling activities, since the mean percent

cover has been comparable or higher since the Phase H drilling period than for the initial survey.

I Overall, this had significant decreasing temporal trends for deep high- (r2=0.31) and low- species

relief habitats (r2=0.40) and significant correlations with three flux parameters (Ba 1"2=0.57,Cd

r2=0.56, and % fines 1-2=-0.58. ANCOVA results indicated negative effects for changes in

I withdistancefromthe for andlow-reliefhabitats, percent cover platform deep high- thereby

supporting the Phase II results for this species.

i The Phase II analysis indicated that Sabellidae was a common taxon that showed a drillingrelated effect Hyland et al. (1994). However, this taxon was poorly represented in Phase HI

i photodocumentation, identified. This suggests although some other problems polychaete in consistently families identifying (e.g., Serpulidae polychaetes and Terebellidae) to family during were

the photographic analyses. To overcome this taxonomic difference, the present study combined

I all commonly polychaeteat deep data into (3.91%) a common comparedgroup, to shallow "Polychaeta". sites (0.96%) As defined, and percent Polychaeta coveroccurred at deep most sites

was lowest for the nearfield sites (2.02%), intermediate at midfield (3.95%), and highest at

I farfield sites but(5.92%). was consistent A distance for bothgradient high- from and low-relief Platform Hidalgo at the deepwassites. not evident This suggests for the shallow that the

deep reefs nearest the platform had substantially fewer Polychaetes (Figure 11). The temporal

I plots of Polychaetes for deep nearfield and farfield sites showed no obvious effects of drilling- related impacts (Figure 11), although there was a significant decreasing temporal trend for deep

high- (r2=0.52) and low-relief habitats (r2=0.70) (Figure 11). The most significant trend for this

I group has been the dramatic, unexplained decline in percent cover at the deep mid- and farfield site following the Phase H drilling period. Comparable trends were not observed for the nearfield

sites. Polychaetes were significantly correlated with five flux parameters (Cd 1"2=0.70,Cu

r2=0.72, Ni r2=0.69, % clay r2= -0.80, and median flux size r2=0.67). Even though percent cover decreased at nearfield sites, the ANCOVA analysis showed a positive platform effect for deep

high- and low-relief habitats, mainly due to the rapid decrease in percent cover at mid- and

I farfield sites (Table 8, Figure 11).

In summary, the temporal patterns for the four potentially sensitive taxa identified in Phase II and

I the results of the ANCOVA analysis in the study provide support for significant drilling- present

related changes in percent cover for Caryophyllia at deep high- and low-relief habitats and for

- Halocynthia at deep low-relief habitat. ANCOVA indicated a positive effect for Polychaeta and

I no significant effect for galatheids on deep low-relief habitat, although a negative did occur

effect

for galatheids in shallow low-relief. ANCOVA results for these four taxa found two positive

i platform effects, three no significant effects, five negative effects, and two non-significant survey x distance interactions. These results support in part the findings of the Phase II analysis;

I D-15

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however, these potential effects may be influenced by natural variation or may have persisted for N

only a short time.

ANCOVA Results For Additional Dominant Taxa !

Percent cover for individual hard-bottom taxa potentially could inc:rease, decrease, and/or change I

little (if at all) over time with respect to the proximity to Platform i[-Iidalgo. The ANCOVA tests

lip

for the 20 dominant taxa produced 18 positive effects, 17 negative effects, and 11 that were not a

significant (Table 9). There also were 14 tests with non-s:ignificant survey x distance |

interactions. The distribution of the observed results was tested for significance using Chi-square

contingency analysis (Zar 1974). Results from this analysis indicated that the combined lit

ANCOVA conclusions were not significant, suggesting that the observed pattern of potential I

effects may have been due to chance alone. Therefore, while positive and negative changes in

percent cover were found to be significant for proximity to Platform Hidalgo, the cumulative d_

distribution of these results appears unrelated to platform effects. ,|

PowerTest I

The power (l-p) to detect significant decreases (_=0.05) in mean percent cover at a site for

dominant taxa in the post-drilling phase (6 surveys) compared to the mean percent cover for the

pre-drilling period (2 surveys) is presented in Table 10. The power test was structured to detect i

decreases in mean percent cover in the post-drilling phase that would be consistent with negative

impacts. The 15 taxa tested for three habitats at two sites produced 90 possible combinations.

Of these 90, not enough data were available or they showed an increase in percent cover in 33 i

tests for the post-drilling surveys. Fifty-seven responses indicated a decrease in percent cover

for the post-drilling surveys. However, only five of these 57 had greater than 80% power and i

14 responses (8 out of 29 nearfield and 6 out of 28 farfield) had a power of 50% or greater. By

I

habitat type, 5of 16 responses had a power of 50% or greater for deep high-relief habitats, 6 out

of 20 for deep low-relief habitats, and 3 out of 21 for shallow low-relief habitats. This suggests I _

that there would be low power to detect significant differences in percent cover in these habitats u

using the present, random photoquadrat study design.

Discussion 1

Hard-substrate epifauna of the Santa Maria Basin are diverse and abundant with most taxa having 'l

preferences for particular depth ranges and substrate relief heights. Other important factors that

W

help structure these communities include orientation to bottom current flows (Hardin et al. 1994) I

and substrate size and type (MEC 1995). In the present study, the deeper sites had more taxa and

higher percent cover than the shallow sites, and more taxa favored high- compared to low-relief

habitats. The extensive list of Santa Maria Basin biota is supplemented with many new species

that have been described from the DOI Phase I through Phase III surveys. The Taxonomic Atlas II

of the Santa Maria Basin, a 14 volume series sponsored by MMS, describes many new species

and provides additional natural history information (Blake and Lissner 1993).

I

D-16 I

I
I Oil and gas production platforms have the potential to impact hard-bottom epifauna by physical

disturbances related to platform installation and discharges of drilling muds and cuttings, which

I can are not buryexcessive, epifauna share and hard-bottom similarities with habitats. naturalTheprocesses physical ofeffects resuspension of these and discharges, sediment when transport they

(Lissner et al. 1991). The exception concerns the discharge of potentially toxic substances (e.g.,

I drilling muds, oil spill products, and produced water) which typically do not have natural counterparts. However, reef epifauna in the study area are likely to have some tolerance to crude

oil exposure, as there are numerous natural oil seeps in the area.

I Toxicity associated with drilling muds has decreased substantially over time due to stricter

environmental controls and reductions in the use of toxic additives (e.g., chromium). However,

I mud fromPlatform exhibited in testswithadultbrown drilling samples Hidalgo toxicity bioassay

cup coral, Paracyathus stearnsii (Raimondi et al., in preparation; see Appendix C-3 in SAIC and

i MEC 1995). Furthermore, in situ bioassays using larvae of the red abalone, Haliotis rufescens,

during the Phase ffI drilling period found lower settlement rates near the platform (Raimondi et

al., in preparation; see Appendix C-1 in SAIC and MEC 1995). In contrast, natural settlement

i experiments al., indicated a general enhancement of settlement during drilling activities (Barnett et in preparation; see Appendix C-2 in SAIC and MEC 1995). Particle tracking models

performed during Phase II and Phase ffl (Coats 1994; SAIC and MEC 1995) and sediment trap

I data muds(Parr are widely et a. 1991; dispersed Phillipsandetconcentrations al., in preparation) at nearfield indicatereefs, that thewhilefinelow, particulates could reach of drilling levels

determined from the bioassays to reduce growth and viability in the brown cup coral P. stearnsii

I (18-25 that platform ppm drilling discharges mud).mayThus, affect results someof the epifaunal in situ organisms bioassays andby laboratory causing sublethal bioassayseffects suggest on

settlement, growth, and viability. Consequently, impacts from drilling discharges may not be

I immediately discernable.apparent and could require a longer time period before community changes are

I Phase II ANOVA testing (based on time-dose interaction) of effects related to drilling discharges identified four possible taxa that were consistent with negative responses to the discharge (Hyland

et al. 1994). Since only 11% of the volume of drilling muds and cuttings was discharged in

Phase _I compared to Phase II (Table 1), the finding of new effects was unlikely. However, as a result of classification analysis and ANCOVA testing (based on survey-distance from platform

interaction), the Phase II and 11I data showed a decreasing trend for many taxa over the nine

I with some different trends near as compared to farther from the platform. This years, away

suggests some distance effects that might be related to drilling periods or to the expression of

more subtle platform-related impacts over a longer time period. !

The Phase II drilling period results suggested negative effects to Caryophyllia at deep high- and

i low-relief habitats, and to galatheid crabs, Halocynthia, and polychaetes at deep low-relief habitats near Platform Hidalgo. However, the Phase III ANCOVA tests, considered as postdrilling analyses for the Phase II drilling period, only supported negative effects in the same

i habitats low-relief.as Phase ANCOVA II for analysis Caryophyllia suggested at deeppositive high- platform and low-relief effectsandforforpolychaetes Halocynthia(including at deep

I D-17

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!

Sabellids) and no significant effect for galatheid crabs for deep low-relief habitat. Temporal plots N

suggested that decreases in percent cover during the Phase II drilling period were of limited

duration. Thus, the combined Phase II and III trends for galatheids and polychaetes appeared to i

be due to short-term responses of the biota, natural variability, or variability inherent in the llp

sampling methods. Furthermore, based on ANCOVA tests of survey x distance (from platform)

effects and subsequent Chi-square contingency analysis for 20 dLominanttaxa, the cumulative

positive and negative results could have been due to chance alone. While some taxa appear to

benefit from proximity to Platform Hidalgo (e.g., cup corals in preferred habitats, anemones, and m

sponges) others may be negatively effected (e.g., cup corals in non-preferred habitats and l

tunicates). Additional studies would be necessary to conclusiw;ly demonstrate that platform

effects have contributed to changes in percent cover for the dominant taxa. Clearly, the drilling i

operations to date have not produced large-scale catastrophic irapacts to the majority of the Q

dominant taxa. Small-scale changes for a few taxa are not separable from natural variability and

the variability associated with the sampling methods. However, these trends may reflect longer- ,i

term effects from platform activities. n

The cup coral P. stearnsii has been shown to be sensitive to Platform Hidalgo drilling muds in /

laboratory conditions (Raimondi et al., in preparation; see Appendix C-3 in SAIC and MEC

1995). Close examination of the data for P. stearnsii indicates that this species occurred most

commonly (2.11%) at shallow compared to deep sites (0.27%), with a preference for low-relief _

(1.16%) as compared to high-relief habitats (0.37%). More importantly, for shallow, low-relief II

habitats percent cover was lowest (1.71%) at nearfield sites, intermediate (2.88%) at midfield,

and highest (3.24%) at farfield. This gradient in percent cover with distance from Platform I

Hidalgo is consistent with possible exposure to drilling muds, but was not supported by the 41

ANCOVA which found no significant survey x distance interactions. Because of the naturally

low overall abundances for the deeper sites, ANCOVA results for deep low-relief habitat was n

more likely related to chance or to natural or methodological variability. qlV

Independent of the ANCOVA results and the evaluations of trends in the temporal plots, all of "1

which are based on data collected using commonly applied methods (photoquadrats taken u

randomly by an ROV), the power analyses suggest that only major changes in the community d

are likely to be detected. This limitation is strongly influenced by the lack of fixed sampling

locations that could document, for example, complete loss of habitat, such as burial of a low- Im

relief community by sediment encroachment (natural or anthropogenic). As an example, based

on present methods that randomly sample exposed hard-substrate, a reef that was buried between

surveys would not be resampled since it then would not represent target, hard substrate. A

combination of fixed and random methods may be more appropriate for further studies, m

Furthermore, sublethal effects to slow growing, large organisms (e.g., sponges) may take long II

time periods (years) for changes in percent cover to be manifested and detected. The Phase II

study showed that the power to detect changes between two reefs f0r any survey or two surveys

at a hard-bottom site was high (primarily due to pseudoreplicates of 60 photographs for each II

habitat) (Hyland et al. 1994). In contrast, the Phase III power tests (pre- and post-drilling surveys

at one site) generally indicated poor statistical power to detect differences in mean percent cover. I

II

D-18 I

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I Thus, the sampling methods used for the Phase II and III studies represented poor power to detect

long-term sublethal effects.

t_ Results from the linear regression of temporal trends in percent cover for 24 dominant taxa x 3

habitats found two increasing trends, 25 negative trends, and 45 nonsignificant patterns. Thus,

although most of the dominant taxa showed no significant temporal trends, 35% were characterized by a significant decrease in percent cover over the study region. It cannot be

determined from the present data whether these broad-scale changes are due to natural variability

I or to long-term anthropogenic effects, including drilling discharges, since there are no comparable data from other regions. As noted above, drilling-related impacts may be less likely since the

primary source of potential contaminants, produced water discharges, has only been occurring

I since 1992-1993 (during Phase 111). Other, large scale natural changes could be influenced by

E1 Nifio cycles or the apparently large decreases in the biomass of macrozooplankton in the

southern California and Point Conception areas since 1951 (Roemmich and McGowan 1995).

I These decreases could reduce the availability of larvae as well as the food supply for epifauna

on hard-bottom habitats. The plankton decreases appear to be related to increases in oceanic

i temperatures, which also can directly affect the distribution of biota.

In summary, long-term data from photographic surveys of large epifauna on hard-bottom reefs

I changes suggests tothatnearby oil andcommunities. gas drillingApproximately operations andequal platform numbersdischarges of positivehaveandnotnegative caused effects major

were indicated for dominant taxa, and there was no consistent pattern of response for a single

I taxon concluded over that the three the cumulative habitats (deep distribution high- andoflow-relief responses andcouldshallow have low-relief). been due toStatistical chance alone. tests

The Phase HI results support the negative associations of two taxa (Caryophyllia and

I Halocynthia) in the same habitats identified in Phase II as affected by drilling discharges, but could not support the Phase II findings for the other two taxa (galatheid crabs and polychaetes).

Subtle and/or long-term gradual changes in percent cover likely are not detectable due to

i relatively high natural variability, as well as the variability associated with present field methods. It is recommended that future studies incorporate fixed quadrats in addition to "random walk"

photographic surveys to reduce the variance estimates associated with the small-scale

heterogeneity of reef habitats and to better assess sublethal effects to selected organisms over time. Additional in situ bioassays and laboratory experiments also are needed to demonstrate

cause and effect relationships.

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ACKNOWLEDGMENTS I

We wish to thank the Department of the Interior (DOI), Minerals Management Service/National t

Biological Service, G. Brewer, F. Piltz, G. Reetz, and L. Thorste,inson for their support of this

long-term community study. The efforts of L. Craft, S. Benech, M. Gunnels, D. Hart, D.

Heilprin, and J. Ljubenkov in the field and laboratory, S. Watts and M. White in data analysis, t

M. Patzius and D. Millis for word processing and editing, and P. Dayton for technical comments

are greatly appreciated. This work was supported as part of DOI Contract No. 14-35-0001-30584 !

to Science Applications International Corporation.

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D-20 I

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Coats, D.A. 1994. Deposition of drilling particulates offshore Point Conception, California.

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Dames and Moore. 1983. Site-specific marine biological survey, Chevron Platform Hermosa

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LISTOFTABLES I

Table 1. Summary of oil and gas drilling activities in the Point Arguello region for Phase i

II and Phase III. Ri

Table 2. Site description and classification for hard-bottom epifauna for Phase II and Phase 1_

III studies (1986-1994).

Twenty most abundant hard-bottom taxa at deep- (n=3,348) and shallow-water i

Table 3.

(n=3,122) stations in the vicinity of Platform Hidalgo for Phase II and Phase ]II studies

(1986-1994). i

Table 4. Twenty most abundant hard-bottom taxa at low- (n=4,649) and high-relief

(n=1,821) stations in the vicinity of Platform Hidalgo for Phase II and Phase m studies I

(1986--1994). II

Table 5. Mean number of taxa per photograph (& 1 standard deviation) by depth, relief /

height, and gradient classification for Phase II and Phase llI studies (1986-1994). Q

Table 6. Mean percent cover for all taxa per photograph (+_1 standard deviation) by depth, I

relief height, and gradient classification for Phase II and Phase III studies (1986-1994). II

Table 7. Overall mean ranking of dominant taxa by relief height and depth categories. RIra'

Table 8. Results of ANCOVA for taxonomic groupings and dominant taxa.

am

Table 9. Contingency table based on results of the ANCOVA analysis (see Table 8). I

Table 10. Powertestfordominantaxaby habitattype. J

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LISTOF FIGURES

I Figure 1. General location of DOI Phase I, Phase II, and Phase I_ studies in the Pt. Conception to Pt. Arguello Region.

I Figure 2. Results of cluster analysis, two-way table with site and species dendrograms based

on mean percent cover for the 50 most abundant taxa by water depth for the nine study sites

from Phase II and Phase HI studies (1986--1994).

I Figure 3. Results of cluster analysis, two-way table with site and species dendrograms based

on mean percent cover for the 50 most abundant taxa by water depth and relief height for the

I Phase II and Phase ]I1 studies nine study sites from (1986-1994).

i Figure (lower) 4.sitesTemporal by reliefplot height. of mean Shallowpercent= 105-119 cover of meters; all cnidarians Deep for = 160-212 deep (upper) m. Shaded and shallow areas

indicate drilling periods for Platform Hidalgo.

I Figure 5. Temporal plot of mean percent cover of all cnidarians for deep farfield site PH-W

(upper) and deep nearfield sites PH-K and PH-N (lower) by relief height. Shaded areas indicate

I drilling periods for Platform Hidalgo.

Figure 6. Temporal plot of mean percent cover of the cup coral Caryophyllia spp. for deep

I high- Midfield(upper) = PH-R; and low-relief and Farfield (lower)= PH-W. sites withShaded distanceareasfromindicate Platformdrilling Hidalgo. periods Nearfield for Platform = PH-K;

Hidalgo.

I Figure 7. Temporal plot of mean percent cover of the anemones Metridium giganteum (upper)

and Amphianthus californicus (lower) for deep high-relief sites with distance from Platform

I Hidalgo. Nearfield = PH-K; Midfield = PH-R; and Farfield = PH-W. Shaded areas indicate drilling periods for Platform Hidalgo.

Figure 8. Temporal plot of mean percent cover of the crinoid Florometra serratissima for deep high- and low-relief habitats (upper) and for deep high-relief sites with distance from Platfrom

Hidalgo (lower). Nearfield = PH-K; Midfield = PH-R; and Farfield = PH-W. Shaded areas

I indicate drilling periods for Platform Hidalgo.

Figure 9. Temporal plot of mean percent cover of all white encrusting biota for deep high-relief

siteswithdistancefromPlatform andof the californianus Hidalgo (upper) brachiopod Laqueus

for all habitats (lower). Nearfield = PH-K; Midfield = PH-R; and Farfield = PH-W. Shaded areas

i indicate drilling periods for Platform Hidalgo.

I

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Figure 10. Temporal plot of mean percent cover of galatheid crabs for all habitats (upper) and I

of the tunicate Halocynthia hilgendorfi igaboja for deep low-relief sites (lower) with distance

from Platform Hidalgo. Nearfield = PH-K and PH-N; Midfield = PH-R; and Farfleld = PH-W. i

Shaded areas indicate drilling periods for Platform Hidalgo.

Figure 11. Temporal plot of mean percent cover of all Polychacta for all habitats (upper) and I

for deep low-relief sites (lower) with distance from Platform Hil,:lalgo. Nearfield = PH-K and

PlatformPH-N; MidfieldHidalgo. = PH-R; and Farfield = PH-W. Shaded areas indicate drilling periods for I

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I Table 1. Summary of oil and gas drilling activities in the Point Arguello region for Phase

II and Phase III.

!

Platform Discharges

I Date DOI Platform Study Drilling Duration No. of Produced

Platform Installed Phase Period (months) Wells Muds Cuttings Water

I (m 3) (m 3) (MGD)

Harvest 6/12/85 Phase II 11/86 - 05/88 18 19 16,340 n/a n/a

i Phase III n/a n/a 0 0 0 0

Hermosa 10/5/85 Phase II 01/87 - 09/88 20 13 16,373 3,114 n/a

Phase HI 09/93 - 11/93 2 1 822 136 0.592

I Hidalgo 7/2/86 Phase II 11/87 - 01/89 14 7 7,963 2,294 n/a

Phase HI 11/93 - 05/94 6 4 3,850 739 1.720

I MGD = million gallons per day.

n/a = not available

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i

° I

_ _ [HI

•.= _ _ = al

__'_ o. ° "-_ I

_.. .,= o

._ _ |

•__-_° 1

_, _ _ _ _ o _E_ •

•- -- -= -= _ _ -- _ .-_

O

--- _ _'_

._ _,, o o o o o =., _ _=,. =.. --

I

•,,.o_ ._---. ._, ,_. _]

_,.. _ o'., _ _ o', _ ,,_ ,_'_ _ _ __.,._

I:}..,

I

o_ _.o -.__=_

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°z !

_ _. _. _ _. _ _. _. _. o_ o,, o z I

II

D-30 I

I
I Table 3. Twenty most abundant hard-bottom taxa at deep- (n=3,348) and shallow-water

(n=3,122) stations in the vicinity of Platform Hidalgo for Phase II and Phase

I m studies (1986--1994).

Mean % Standard

I Rank Taxa Taxa Group Cover

Deviation

Deep-Water Stations

I 1 Total Ophiuroidea Echinodermata 5.36 6.11

2 TotalPolychaeta Polychaeta 3.91 4.64

I 3 Total white encrusters Porifera, 3.06 2.71

Urochordata,

i 4 Florometra serratissima Ectoprocta Echinodermata 2.59 6.82

5 Amphianthus californicus Anthozoa 2.58 4.06 60phiacantha diplasia Echinodermata 1.48 2.80

7 Galatheidae Cmstacea 1.42 1.67

I 8: Metridium giganteum Anthozoa 1.39 4.76

9 Desmophyllum dianthus Anthozoa 1.18 2.74

j 10 Sponge, tan encrusting Porifera 1.13 1.95

11 Stomphia didemon Anthozoa 0.96 2.72

I 12 Pyura haustor Urochordata 0.95 1.53

13 Anemone,tan zoanthid Anthozoa 0.90 2.01

I 14 Laqueus californianus Brachiopoda 0.84 1.56

15 Anemone,white and purple Anthozoa 0.77 1.34

t 16 Lophelia pertusa Anthozoa 0.77 4.22

17 Sponge,shelf Porifera 0.75 2.68

I 18 Gorgonian, red or pink Anthozoa 0.75 1.25

19 CaryophyUia spp. Anthozoa 0.63 0.82

I 20 Halocynthia hilgendorfi Urochordata 0.58 1.09

t TOTAL 32.0

!

I D-31

!
|

Continued. I

!

Mean % Standard I

Rank Taxa TaxaGroup Cover Deviation m

Shallow-Water Stations

lit

1 Total Ophiuroidea Echinodermata 5.95 7.31 I

2 Florometra serratissima Echinodermata 2.48 7.38

3 Paracyathus ....stearnsii Anthozoa 2.11 2.48 i

4 Metridium giganteum Anthozoa 2.11 2.48 i

5 Total white encrusters Porifera, 1.59 1.88 W

Urochordata,

!Ectoprocta

"" I 6 Caryophyllia spp. Anthozoa 1.52 1.58

70phiacantha diplasia Echinodermata 1.46 3.14 /

8 TotalPolychaeta Polychaeta 0.96 1.61 U

9 Sponge, tan encrusting Porifera 0.85 1.59 11

10 CeUaria sp. Ectoprocta 0.75 1.07 J

11 Gorgonian,red or pink )Anthozoa 0.64 0.89 iN

12 Pyura haustor !Urochordata 0.63 1.04

13 Balanophyllia elegans Anthozoa 0.62 1.01 Im

14 Galatheidae Crustacea 0.52 0.77

15 Halocynthia hilgendorfi iUrochordata 0.43 0.86 ill

16 Ophionereis sp. Echinodermata 0.27 0.53 t

17 Sponge,shelf Porifera 0.22 1.30 It

18 Anemone, tan zoanthid Anthozoa 0.22 0.60 U

19 Laqueus californianus Brachiopoda 0.20 0.46

20 Paguridae Crustacea 0.17 0.45 l

TOTAL 23.7 i

I

D-32 I

I
|

t Table 4. Twenty most abundant hard-bottom taxa at low- (n--4,649) and high-relief

(n=1,821) stations in the vicinity of Platform Hidalgo for Phase II and Phase

I III studies (1986-1994).

I I Rank Taxa Group Mean % Standard

Taxa Cover Deviation

I Itigh-Relief

I 1 Total Ophiuroidea Echinodermata 4.39 4.89

2 Totalwhiteencrusters Porifera, 4.15 3.04

I Urochordata, Ectoprocta

i 34 Amph Totalianthus Polychaeta californicus Anthozo Polychaeta a 3.74 2.92 4.97

56 Metridium Desmophyllumgiganteum dianthus Anthozoa Anthozoa 2.36 2.03 6.89 3.47

7!Florometra serratissima Echinodermata 1.73 6.15

I 8!Sponge,tanencrusting Porifera 1.70 2.82

9]Galatheidae Cmstacea 1.70 1.81

I 10 Lophelia pertusa Anthozoa 1.49 5.79

11 Ophiacantha diplasia Echinodermata 1.16 2.43

I 12 Sponge,shelf Porifera 1.10 3.11

13 Stomphia didemon Anthozoa 1.07 2.70

I 14 Anemone, tan zoanthid Anthozoa 0.98 2.43

15 Pyura haustor Urochordata 0.85 1.39

I 16 Anemone, white and purple Anthozoa 0.80 1.49

17 Gorgonian,red or pink Anthozoa 0.78 1.37

I 18!Laqueus californianus Brachiopoda 0.73 1.42

191 Caryophyllia spp. Anthozoa 0.70 0.87

I 20 Paguridae Crustacea 0.48 0.67

TOTAL 34.9

!

I D-33

!
!

Continued. t

!

Mean % Standard II

Rank Taxa Taxa Group Cover Deviation |

Low-Relief

m/

1 TotalOphiuroidea Echinodermata 6.50 7.22 I

2 Florometra serratissima Echinodermata 2.85 7.41

3 TotalPolychaeta Polychaeta 2.33 3.93 I

4 Totalwhiteencruster Porifera, 1.65 1.73

Ectoprocta Urochordata, _1

50phiacantha diplasia Echinodermata 1.59 3.15 m

6 Paracyathus stearnsii Anthozoa 1.46 2.23 I

7 Metridium giganteum Anthozoa 1.23 5.09 I

8 Caryophyllia spp. Anthozoa 1.20 1.43 II

9 Pyura haustor Urochordata 0.77 1.30 II

10 Sponge, tan encrusting Porifera 0.71 1.03 g[

11 Galatheidae Crustacea 0.71 1.05 I

12 Gorgonian,redorpink Anthozoa 0.66 0.96 J

13 Halocynthia hilgendorfi Urochordata 0.53 1.02 Im

14 Laqueus californianus Brachiopoda 0.45 1.10 n

15 Anemone,tan zoanthid Anthozoa 0.41 0.96 III

16 Balanophyllia elegans Anthozoa 0.41 0.88 I

171 Amphianthus californicus Anthozoa 0.40 1.17

18 Paguridae Crustacea 0.34 0.66 I

19 Ophionereis sp. Echinodermata 0.31 0.60 IN

20 Stomphia didemon Anthozoa 0.30 1.66 I

TOTAL 24.8 !

!

D-34 I

!
|

Table 5. Mean number of taxa per photograph _ 1 standard deviation) by depth, relief

height, and gradient classification for Phase II and Phase III studies

(1986-1994).

i Low Relief High Relief Total ShallowStation 16.2+ 6.48 10.3+ 2.77 15.6+ 6.46

I Deep Station 17.6 + 8.19 24.5 + 7.84 20.7 + 8.74

Total 16.8+7.24 22.0+ 9.05

!

Farfield Midfield Nearfield

I Shallow Low Relief 16.3 + 6.51 16.0 + 6.42 16.3 + 6.49

ShallowHighRelief NA NA 10.3+ 2.77

I Total 16.3+ 6.51 16.0+ 6.42 15.3+6.44

I Deep Low Relief 19.3 + 8.63 18.1 + 7.22 15.8 + 8.21

DeepHighRelief 26.9+ 8.89 23.8+ 6.89 22.5+ 6.78

Total 23.0+ 9.54 20.8+ 7.63 18.4+8.35

!

!

!

I

i

i

l

I D-35

!
!

Table 6. Mean percent cover for all taxa per photograph _ 1 standard deviation) by I

depth, relief height, and gradient classification for Phase II and Phase III

studies (1986-1994). I

Low Relief High Relief Total I

'Shallow Station 29.5 + 16.0 22.1 + 15.1 28.7 + 16.1

DeepStation 34.7+ 18.3 51.5+ 18.7 42.1+ 20.3 !

Total 31.5+ 17.2 46.2+21.4

I

Farfield Midfield Nearfield

Shallow Low Relief 29.4 + 15.1 26.1 + 14.4 30.7 + 16.8 I

ShallowHighRelief NA NA 22.1+ 15.1

Total 29.4+ 15.1 26.1+ 14.4 29.2+ 16.8 I

Deep Low Relief 38.4 + 19.6 34.1 + 17.7 32.1 + 17.2 I

DeepHighRelief 52.3+ 20.3 54.:5+ 18.9 47.1+ 15.5

Total 45.1 + 21.1 43.'7 + 21.0 37.9 + 18.1 I

|

I

!

!

I

!

!

D-36 I

I
I Table 7. Overall mean ranking of dominant taxa by relief height and depth categories.

* = rank greater than 20; note that "missing" numbers in the sequences from

I 1-20 by category correspond to taxa other than those listed.

i Taxa Group All Rank Deep by Mean Percent Cover Shallow High Low

Habitats Water Water Relief Relief

I TotalOphiuroidea Echinodermata 1 1 1 1 1

Totalwhiteencrusters Porifera 2 3 5 2 4

I Urochordata Ectoprocta

i Florometera TotalPolychaeta serratissima Echinodermata Polychaeta 3 4 2 7 2 4 2 8 4 3

i Metridium giganteum Anthozoa 5 8 4 5 7 Ophiacantha diplasia Echinodermata 6 6 7 11 5

I Sponge, Galatheidae tan encrusting Porifera Crustacea 7 10 9 8 10 8 7 14 9 11

t Amphianthus californicus Anthozoa 9 5 * 3 17 Pyura hauster Urochordata 10 12 12 15 9

I Paracyathus stearnsii Anthozoa 11 * 3 * 6

CaryophyUia spp. Anthozoa 12 19 6 19 8

I Desmophyllum dianthus Anthozoa 13 9 * 6 *

Gorgonian,redorpink Anthozoa 15 18 11 17 12

I Anemone, tan zoanthid Anthozoa 15 13 18 14 15

Laqueus californicus Brachiopoda 16 14 19 18 14

I Stomphia didemon Anthozoa 17 11 * 13 20

Sponge,shelf Porifera 18 17 17 12 *

I Lophelia pertusa Anthozoa 19 16 * 10 *

Halocynthia hilgendorfi Urochordata 20 20 15 * 13

Balanophyllia elegans Anthozoa * * 13 * 16

|

I D-37

!
!

Table 8. Results of ANCOVA for taxonomic groupings and dominant taxa. Nearfield !

(near), midfield (mid), and farfield (far) represent distances from Platform i

Hidalgo (see Table 2). Distances connected by lines are not significantly

different from the farfield site used as the reference (p < 0.05). Distances are

w'

ordered from left to right with reefs having the,, greatest rate of change (plus m

or minus) on the left. Arrows indicate temporal trends (increasing or i

decreasing percent cover). Effects are rated as + for enhancement of percent

cover for taxa near the platform, m for decreasing percent cover, 0 for no II

significant difference between farfield reference: and nearfield sites, and ns to |

indicate that the survey x distance interaction term was nonsignificant and no

furthertestingcouldbe done. I

Parameter and Habitat Distance from Platform Hidalgo Effects I

and Percent Cover Trend

All Ophiuroidea (brittlestars) I

Deep high relief near 1" far ,1, mid ,], + g

Deeplowrelief ns l

Shallow low relief mid $ near ,1, far t B

Total white encrusters (sponges,

tunicates, bryozoans) I

Deep high relief far ,1, mid 1" near "_" +

Deep low relief far ,1, near _, mid T + g

Shallowlowrelief mid1" near1" far1" +

B

Florometra serratissima (crinoid) I

Deep I! highrelief far 1" near 1" mid 1"

Deep low relief mid $ far 1" near 1' 0 i

Shallow low relief mid ,J, far 1" near $ 0 II

All Polychaeta (worms)

Deep high relief far ,], mid ,[, near ,1, + B

Deep low relief far $ mid ,1, near ,1, + m,

Shallowlowrelief ns 1

Metridium giganteum (anemone)

Deep high relief near 1" far 1" mid ,1, 0 I

Deeplowrelief ns

Shallow low relief far 1" mid ,1, near,l, i

gg

D-38 i

I
!

I Table8. Continued.

I ParameterandHabitat DistancefromPlatformHidalgo Effects

and Percent Cover Trend

I Sponge, tan encrusting

Deephighrelief mid1" near1" far1" +

I Deep low relief far .1, near .], mid ,1, 0

Shallowlow relief near ,1, mid $ far,],

I Galatheidae(crabs)

Deep high relief near $ far ,l, mid 1" 0

I Deep low relief mid ,J, near ,1, far $ 0

Shallow low relief far 1" mid $ near ,1,

t Amphianthus californicus (anemone)

Deephighrelief far$ mid$ near1" +

I Deep low relief far ,J, mid ,l, near $ +

Shallowlowrelief ns

I Pyura haustor (tunicate) Deep high relief far $ mid $ near ,1, +

I Deep Shallowlowlowrelief relief near near $,1, far mid $,1, mid far $,1,

I Paracyathus stearnsii (cup coral) Deep high relief near ,1, far ,1. mid .1, 0

I Deeplowrelief near$ mid.1, far$

Shallowlowrelief ns

I Caryophyllia spp. (cup coral)

Deephighrelief near,1, far,1, mid $

I Deep low relief near $ mid $ far ,1,

Shallowlowrelief ns

!

|

I D-39

!
!

Table 8. Continued. I

!

Parameter and Habitat Distance from Platform Hidalgo Effects

and Percent Cover Trend

Desmophyllum dianthus (cup coral) I

Deep high relief far ,], near 1" mid $ + I

Deeplowrelief ns

Shallowlowrelief ns I

Gorgonian, red or pink

Deep high relief far $ mid $ near _, + I

Deep low relief far $ near $ mid ,1. +

Shallow low relief near ,l. far $ mid $ 0 1

Anemone, tan zoanthid

Deep high relief far .I, mid $ near 1' + I

Deep low relief near ,1. mid ,1. far ,].

Shallow low relief far $ near ,1, mid ,1, + I

Laqueus californicus (brachiopod)

Deephighrelief ns I

Deep low relief near ,1. far $ mid $

Shallow low relief near $ far ,1. mid $ I

Stomphia didemon (anemone)

Deep high relief mid $ far $ near _, 0 I

Deep low relief mid $ far $ near ,1, 0

Shallowlowrelief ns I

Sponge, shelf

Deep high relief far $ mid ,1. near $ + I

Deeplowrelief ns

Shallowlowrelief far$ near$ mid1" + I

!

D-40 I

!
!

I Table 8. Continued.

Parameter and Habitat Distance from Platform Hidalgo Effects

and Percent Cover Trend

I Lophelia pertusa (cup coral)

i Deep Deephigh relief ns lowrelief ns

Shallow low relief far 1" mid 1" near ,1,

I Halocynthia hilgendorfi (tunicate)

I Deep high relief near ,], far ,1, mid ,1,

Deep low relief near $ far ,[, mid $

I Shallow low relief mid ,J, far ,J, near ,], 0

Balanophyllia elegans (cup coral)

I Deephighrelief near$ mid$ far$

Deeplowrelief ns

I Shallow low relief mid ,1, far $ near ,J, +

!

!

!

!

I

!

!

I D-41

I
!

Table 9. Contingency table based on results of the ANCOVA analysis (see Table 8). !

Numbers represent a summation of potential platform effects for dominant taxa

by habitat type (e.g., 10 taxa at deep, high-relief reefs showed increases or less •

rapid decreases in percent cover compared to the farfield site, indicating a

possible enhancement effect near Platform Hidalgo). Numbers in parentheses m

are the frequency expected if Ho is true. Ho: ctianges in percent cover of g

dominant taxa by habitat type is independent of proximity to Platform Hidalgo.

Honotrejected,;(24df=4.07,p > 0.25. I

Habitat

Platfo Effects rm Deep Deep I Shallow Total

High Relief Low Relief Low Relief

+ 10 (7) 4 (5) 4 (5) 18 I

0 4(4) 4(3) 3(3) 11 /

4(5) 6(5) 7(5) 17

Total 18 14 14 46 I

|

!

!

!

!

!

!

e

D-42 1

!
!

i Table 10. Power mean percent test forcover dominant for thetaxasix bypost-drilling habitat type. surveysPower compared is basedto the on amean decrease percentin

cover of the two predrilling surveys. Percent cover was arcsin transformed and

significant are the power temporal (1-trends B, ¢x=0.05) for the inpost-drilling percent probability survey were(e.g., detrended. 0.64=64%Numbers for

Amphianthus) of detecting a significant decrease in mean percent cover for in the

I post-drilling observed decrease phase.in mean Numbers percent in parentheses cover that would represent be needed the percentage to be detectable of the

with a power of 80% ([3=0.2). For example, 0.19 for Metridium would indicate

I that the observed decrease in percent cover was only 19% of the change needed to detect a significant decrease with 80% power.

I Deep Reefs Deep Reefs Shallow Reefs

Taxa High Relief Low Relief Low Relief

I Farfield Nearfield Farfield I Nearfieid Farfield Nearfield

Cnidaria

I Amphianthus Anemone, californicus 1.00 (2.4) 0.64 (.80) 0.11 (.16) tan zoanthid 0.26(.40) 0.09(.12) 0.07(.08) 0.05(.06)

i Metridium Stomphia didemon giganteum 0.13 (.20) 0.07 (.06) 0.16 0.10 (.(. 19) 13)

Cnidaria (cupcorals)

I Balanophyllia elegans 0.09 (0.08) 0.12 (.21)

CaryophyUia spp. 0.12 (.18) 0.98 (1.50) !0.24 (.38) 0.44 (.60) 0.08 (.09)

I Desmophyllum dianthus 0.77 (.96) 0.09 (.14) 0.05 (.07) 0.08 (.10)

Lophelia pertusa 0.51 (.67) 0.10 (.14) 0.10 (.15)

I Paracyathus stearnsii 0.16 (.26) 0.15 (.24) 10.16 (.28) 0.51 (.67) 0.52 (.68)

Cnidaria gorgonian

I Gorgonian, red or pink 0.34 (.50) 0.82 (1.04) 0.08 (.10) 0.16 (.26) 0.07 (.08)

Brachiopoda

I Laqueus californianus 0.06 (.04) 0.23 (.36) 1.00 (1.47) 0.09 (.15) 0.70 (.88) Crustacea (crabs)

I Echinodermata Galatheidae 0.12 (.19) 0.72 (.89) 0.06 (.05)

Florometra serratissima 10.17(.28) 0.37 (.52)

I Urochordata

Halocynthia hilgendorfi 0.07 (.05) 0.09 (.10) 0.25 (.40) 0.42 (.58) 0.10 (.10) 0.12 (.17)

Pyura haustor 0.74 (.92) 0.06 (.02) 0.29 (.43) 0.95 (1.30) 0.12 (.18) 0.52 (.69)

I D-43

I
Figure 4

-.,i1 ,

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I STATIONS Figure 2

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SPECIES

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Sponge,shelf(Pac_gk_ae)

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Legend:0.0= O.O<X<0.5=• 0.5<X<1.0=• 1.0<X<1.5=• 1.5<X<2.0=• 2.0<X= •

I
STATIONS Figure 31 DistanceBetweenClusters

3- -3 I

i

2- -2

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°

" I

SPECIES - I

Distance Between Clusters 0 - - 0

Shallow , Deep

4 3 2 1 0 =" I ._"

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I I I.l.. I ] I I ]

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•!.!.!-!* • IB

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|
I Figure 4

I

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20

| 16

I ,2 = /

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_ 6

" I /

I 4 -

2 Jim

| oIRelief _High o e eLow .t t .

CNIDARIANS:ShallowSites

I ,_ _ -_, PHASE 2------ --"- _ _'- _-" " PHASE 3---- m,

I

18

16 N

// /

I _p. 1210 °

2

0

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I

I

I

I
Figure 1

!

CNIDARIANS: Deep,Far Sites I

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/ ,

27

24

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_9

. I

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I

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24 |

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o 15

g.12

6 |

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I

I

I

I
I Figure6

Caryophylliaspp.: HighRelief,DeepSites.

• --- --- --- P.ASE2_ ---- -- _ m - PHAS3--e--

I i °' " _

| o'o _

I °°"/ d / °°'*/ °°*/" °°_*/ °°_/" °°_/" °°'*/ °°'*

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.o 0.6_ /@

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!

l " IDistance _ Faffield Midfield z, ,_ z.Nearfield I

gl i

I

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I
Figure 71

Metridiumgiganteum:HighRelief,DeepSites I

PHASE 2 _ "--- m mm _ ",, PHASE 3 m-- ---.. ,

7

° I

g.3 I

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0 " _ D D -_Midfield, i _- iNearfield f I

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!

I IDistance _ Farfield _ [] o Midfield '_'--_'_ ? I

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I

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I
I Figure8

I

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i

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o

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!

!
Figure

!

Whiteencrusters: High Relief,DeepSites. I

i i-- PHASE 2 m I .i i i-,.. PHASE 3 -'-- _'- ,

II I I

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o |

i

Laqueus californianus

I I / PHASE 2 1 1 / I / I PHASE 3 1 / I

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I Figure10

I

Galatheidae, unid.

,i .2.7 2.4ot---

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I a. 1.21

m

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i!! / IIIII

As theNation's principal conservationi

agency, the Department of the Interior has

responsibility for most of our nationally ==

owned public landsand natural resources.•

This includes fostering sound use of our

land and water resources; protecting our

fish, wildlife, and biological diversity;

preservingthe environmentaland cultural•

values of our national parksand historical

places; and providing for the enjoyment of life through outdoor recreation. The

•

Departmentassesses our energy and

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mineral resources and works to ensure that

their development is in the best interests of

I

all our peoplebyencouragingstewardship•

and citizen participation in their care. The

w

Departmentalsohasamajor responsibility

for American Indian reservation =R

communitiesand forpeoplewho liveinI

island territories underU.S. administration. !I