Long-Term Monitoring at the

East and West Flower Garden Banks

Lnhui

U.S. Deøartment of the Interior

Minerals VIanagement Service Gulf of Mexico OCS Region

OCS Study

MMS 96-0046
Long-Term Monitoring at the

East and West Flower Garden Banks

Prepared by

Continental Shelf Associates, Inc.

Prepared under MMS Contract

14-35-0001-30662

by

Continental Shelf Associates, Inc.

759 Parkway Street

Jupiter, Florida 33477

Published by

U.S. Department of the Interior Minerals Management Service Gulf of Mexico OCS Region

OCS Study

MMS 96-0046

New Orleans

January 1997
DISCLAIMER

This report has been reviewed by the Minerals Management Service and approved for

publication. Approval does not signify that the contents necessarily reflect the views and

policies of the Service, nor does mention of trade names or commercial products

constitute endorsement or recommendation for use.

REPORT AVAILABILITY

Extra copies of this report may be obtained from the Public Information Unit (Mail

Stop 5034) at the following address:

U.S. Department of the Interior

Minerals Management Service

Gulf of Mexico OCS Region

Public Information Unit (MS 5034)

1201 Elmwood Park Boulevard

New Orleans, Louisiana 70123-2394

Telephone Number 1-800-200-GULF or

(504) 736-2519

CITATION

Suggested citation:

U.S. Department of the Interior, Minerals Management Service. 1996. Long-term

monitoring at the East and West Flower Garden Banks. Prepared by Continental

Shelf Associates, Inc. OCS Study MMS 96-0046. U.S. Department of the Interior,

Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA.

77 pp. + app.

III
ABSTRACT

This study was designed to be a continuation of the long-term monitoring study

conducted from 1989-1991. Study sites and selected permanent stations established at

the East and West Flower Garden Banks during the previous study were used, when

possible, during the present study in an effort to maintain a database consisting of

comparable data sets between banks and between years.

Coral cover, relative dominance, diversity, evenness, and accretionary and

encrusting growth rates were estimated from data collected in 1992 (prior to field efforts

for this study), and during field efforts conducted in 1994 and 1995. Significant

differences were found in the population levels of certain coral species for the 1992,

1994, and 1995 data sets, both between banks and between years. Comparisons with

similar data collected during 1989-1991 suggest no significant long-term trends or

degradation of habitat, but rather suggest spatial variability in the distributions of

individual coral species within the two study sites.

Permanent stations established during the 1989-1 991 study for the

measurement of accretionary and encrusting coral growth of Montastrea annularis and

Diploria strigosa were found during the 1994 field effort to be unsuitable for further use.

This was primarily due to natural changes in the measured coral tissue borders which

would not permit accurate measurement of subsequent accretionary or encrusting growth

estimates. Estimates of accretionary growth rates of M. annularis from 1994-1 995 for

permanent stations and coral core samples, which were also collected and analyzed,

agree well with the range of values collected during the 1989-1991 monitoring study.

Problems were discovered in the lateral growth photographic data collected at

permanent stations in 1992. In addition to the aforementioned tissue border changes,

many permanent station photographs taken during this period were unsuitable for analysis

due to incorrect camera angle. Statistical comparisons between lateral growth data

collected during 1992 and those collected during the 1994-1 995 period were not

performed as a result of the relative low number of suitable 1992 photographs. However,

estimates of encrusting growth rates of D. strigosa between 1991-1 992 and 1994-1 995

suggest favorable conditions of growth at the two study sites. Relative tissue growth

(advance) and retreat rates during these two periods were comparable.

Encrusting growth rates of M. annularis were estimated only from data

collected during 1992. Net growth rates were negative at the East Flower Garden Bank

study site and positive at the West Flower Garden Bank study site. Retreat to advance

ratios for this species indicate net tissue loss at both study sites during this period. Due

to aforementioned problems in data collected in 1992, these data may also be an artifact

of sample error and not realistic estimates. From these data, it is apparent that the

period of time over which permanent stations for the measurement of accretionary and

enOrusting growth of corals may be reliably used is finite.

Coral bleaching was observed in repetitive quadrat photographs taken in 1992,

1994, and to a much greater extent during 1995. The extent of bleaching within the study

sites was even more pronounced in November 1995. Bleaching during these periods

v
coincided with periods of elevated bottom temperatures (above 30°C) which are not

uncommon during late summer. Colonies that exhibited bleaching usually sustained only

minor tissue loss.

Accidents resulting in the release of oil in the vicinity of the Flower Garden

Banks remains a realistic threat. Impacts to the reefs resulting from offshore oil and gas

exploration and development have not been detected. Regulations at the Flower Garden

Banks associated with their National Marine Sanctuary status will decrease or alleviate

potential threats from commercial fishing, spearfishing, vessel anchoring, and the

unregulated collections of reef resources.

vi
TABLE OF CONTENTS

Paqe

ABSTRACT v

LIST OF FIGURES xi

LIST OF TABLES xv

ACKNOWLEDGEMENTS xvii

EXECUTIVE SUMMARY xix

vii

1.0 INTRODUCTION 1 1.1 OVERVIEW OF THE FLOWER GARDEN BANKS 1 1.1.1 Habitat Description and Zonation 1 1 .1 .1 .1 Diploria-Montastrea-Porites Zone 7

1 .1 .1.2 Stephanocoenia-Millepora Zone 7

1.1.1.3 Leafy Algae Zone and the Madracis Zone 8

1.1.1.4 Algal-Sponge Zone 8

1.1.1.5 Antipatharian Zone 9

1.1.1.6 SoftBottomZone 9

1.1.2 Human Activities 9

1.1.3 Historical Research 10

1.2 STUDY OBJECTIVES 12

2.0 METHODS 13

2.1 FIELD LOGISTICS 13

2.2 STUDY SITES 13

2.3 RANDOM TRANSECTS 16

2.4 ACCRETIONARY GROWTH 17

2.4.1 Permanent Growth Stations 18

2.4.2 Sclerochronology 19

2.5 ENCRUSTING GROWTH 20

2.6 REPETITIVE QUADRATS 22

2.7 VIDEO TRANSECTS 25

2.8 ANCILLARY MEASUREMENTS 25

2.8.1 Recording Thermometers 25

2.8.2 Water Profiles 25

2.8.3 Light Recorders 25

2.9 SEDIMENT COLLECTIONS 27

3.0 RESULTS 29

3.1 RANDOM TRANSECTS 29

3.1.1 Coral Cover and Relative Dominance 29

3.1.2 Species Diversity and Evenness 32
TABLE OF CONTENTS

(Continued)

Paqe

3.2 ACCRETIONARY GROWTH 32

3.2.1 Permanent Growth Stations 32

3.2.2 Scterochronology 36

3.3 ENCRUSTING GROWTH 36

3.3.1 Net Growth Rates 39

3.3.2 Advance and Retreat Rates 39

3.3.3 Retreat to Advance Ratios 41

3.4 REPETITIVE QUADRATS 41

3.4.1 1992 Survey 41

3.4.2 1994 Survey 41

3.4.3 1995 Survey 41

3.4.4 1992 to 1995 Period 48

3.5 VIDEO TRANSECTS 48

3.5.1 East Flower Garden Study Site 51

3.5.1.1 Transect 1 - Northwest to Northeast Site Boundary Line . 51

3.5.1.2 Transect 2- Northeast to Southeast Site Boundary Line . 51

3.5.2 West Flower Garden Bank Study Site 52

3.5.2.1 Transect I - Southeast to Southwest Site Boundary Line 52

3.5.2.2 Transect 2 - Southwest to Northwest Site Boundary Line 52

3.6 ANCILLARY MEASUREMENTS 53

3.6.1 Water Profiles 53

3.6.2 Recording Thermometers 53

3.6.3 Recording Light Meters 55

4.0 DISCUSSION 61

4.1 CORAL COMMUNITY STRUCTURE - STATUS AND TRENDS 61

4.2 CORAL GROWTH - STATUS AND TRENDS 61

4.3 CORAL BLEACHING 63

4.4 DISEASES IN REEF BIOTA 65

4.5 PRESENT ENVIRONMENTAL THREATS 65

4.5.1 Oil Spills 65

4.5.2 Oil Spill Dispersants 66

4.5.3 Operational Wastes 67

4.5.3.1 Produced Waters 68

4.5.3.2 Drilling Fluids and Cuttings 68

4.5.4 Recreational Diving 68

4.6 WATER QUALITY PLAN 69

5.0 CONCLUSIONS 71

6.0 LITERATURE CITED 73

viii
TABLE OF CONTENTS

(Continued)

ix

Paqe

APPENDICES 79

APPENDIX A STRATIFIED RANDOM TRANSECT DATA A-i

APPENDIX B ACCRETIONARY GROWTH DATA B-i

APPENDIX C REPETITIVE QLJADRAT DATA C-i

APPENDIX D ANCILLARY DATA D-1
LIST OF FIGURES

Fiqure Description Paqe

1 Location of the East and West Flower Garden Banks relative to

other topographic features in the northwestern Gulf of Mexico 2

2 Topography and biotic zonation of the East Flower Garden Bank

(From: Bright et al., 1985) 3

3 Topography and biotic zonation of the West Flower Garden Bank

(From: Bright et al., 1985) 4

4 Schematic depiction of the biotic zones and conspicuous biota of

the East Flower Garden Bank (From: Bright and Rezak, 1976) 6

5 Location of MMS regulatory zones and National Marine Sanctuary

boundaries around the East and West Flower Garden Banks 11

6 Map of the 100 m x 100 m study site at the East Flower Garden

Bank, showing graduating boundary lines, relative positions of

permanent stations, and conspicuous features 14

7 Map of the 100 m x 100 m study site at the West Flower Garden

Bank, showing graduating boundary lines, relative positions of

permanent stations, and conspicuous features 15

8 Diver using camera and stainless steel rectangular frame to

photograph 10 m (33 ft) random transects 16

9 Example of a 10 m (33 ft) random transect photograph from the

East Flower Garden Bank 18

10 Permanent station for determination of accretionary growth in the

coral Montastrea anna/arts ( M. faveolata) 19

11 Diver using pneumatic drill and 2.5 cm (1 in.) coring bit to collect

core sample from the coral Montastrea annularis ( M. faveolata)

for determination of accretionary growth 20

12 Permanent station for determination of encrusting growth in the

coral Diploria strigosa 22

13 Permanent 8 m2 quadrat station marker 23

14 Diver using camera and aluminum T-frame to photograph 8 m2

repetitive quadrats 24

xi
LIST OF FIGURES

(Continued)

Fiqure Description Paqe

15 Example of a 8 m2 repetitive quadrat photograph from the East

Flower Garden Bank 24.

16 Layout of equipment used to record incident light at underwater

sites on the East and West Flower Garden Banks study sites 26

17 Recording underwater light meter in position at the East Flower

Garden Bank study site 27

18 Comparison of percent cover of corals, reef rock, conspicuous biota,

and sand between the East and West Flower Garden Banks study

sites during the 1992 to 1995 period 30

19 Comparison of relative dominance of corals between the East and

West Flower Garden Banks study sites during the 1992 to 1995

period 33

20 Comparison of accretionary growth rates of Montastrea annu/aris

during 1994-1 995 from permanent growth stations and collected

coral cores 37

21 Accretionary growth rates of Montastrea annularis measured from

cores collected at the East and West Flower Garden Banks 38

22 Retreat to advance ratios (total coral tissue lost divided by total

tissue gained) of Montastrea annularis from 1991-1 992 and Dip/aria

strigosa from 1991-1 992 and 1994-1 995 at the East and West

Flower Garden Banks study sites 42

23 Coral bleaching observed in 8 m2 quadrats, 1992, 1994, and 1995 49

24 Numbers of colonies in permanent 8 m2 quadrat stations with

disease during the 1992, 1994, and 1995 field efforts 50

25 Seafloor temperature data on the Flower Garden Banks, September

1993 to August 1995 54

26 Total daily irradiance on the East and West Flower Garden Banks

from August to November 1995 (Period 1) 56

27 Total daily irradiance on the East Flower Garden Bank from

November 1995 to February 1996 57

xli
LIST OF FIGURES

(Continued)

Fiqure Description Paqe

28 Percent of surface light transmission to the East and West Flower

Garden Banks from August - November 1995 58

29 Percent of surface light transmission to the East Flower Garden

Bank from November 1995 to February 1996 59

30 Coral bleaching in Montastrea annular/s observed during the 1995

monitoring survey at the Flower Garden Banks 64
LIST OF TABLES

Table Description Paqe

1 Summary of the results of the statistical analysis of percent coral

cover from random transect data 31

2 Summary of the results of the statistical analysis of relative

dominance of coral taxa from random transect data 34

3 Summary of the results of the statistical analyses of coral species

diversity (H') and species evenness (E) based on colony counts and

percent cover 35

4 Accretionary growth of Moritastrea arinu/aris from 1994-1995,

measured from growth spikes installed at the East and West Flower

Garden Banks study sites 36

5 Net growth rates of Diploria strigosa 40

6 Net growth rates of Montastrea annular/s 40

7 Mean advance and retreat rates of Diploria strigosa 40

8 Mean advance and retreat rates of Montastrea annu/aris 40

9 Percent coral cover at East Flower Garden Bank repetitive 8 m2

stations during 1992, 1994, and 1995 43

10 Percent coral cover at West Flower Garden Bank repetitive 8 m

stations during 1992, 1994, and 1995 45

11 Observations of growth, retreat, coral bleaching, and disease at

permanent B m2 quadrat stations photographed during the 1992 field

effort at the East and West Flower Garden Banks 47

12 Observations of growth, retreat, coral bleaching, and disease at

permanent 8 m2 quadrat stations photographed during the 1994 field

effort at the East and West Flower Garden Banks 47

13 Observations of growth, retreat, coral bleaching, and disease at

permanent 8 m2 quadrat stations photographed during the 1995 field

effort at the East and West Flower Garden Banks 48

14 Minimum and maximum temperatures recorded on the East and

West Flower Garden Banks during 1993 - 1995 53

15 A comparison of accretionary growth rates of Montastrea annular/s

estimated from sectioned core samples collected during recent

studies of the East and West Flower Garden Banks 62

xv
ACKNOWLEDGEMENTS

Continental Shelf Associates, Inc. recognizes the support of Contract

No. 14-35-0001-30662 with joint sponsorship of the project by MMS and the NOAA

National Marine Sanctuary Program.

Several non-CSA divers participated on field data collection efforts. These

included the following:

Glen Armand

Jan Culbertson

Les Dauterive

Ken Deslarzes

David French

Stephen Gittings

Coley Groth

Judith Ovard

Douglas Peter

Gary Rinn

Their efforts are herein acknowledged and greatly appreciated. Thanks also to the crew

of the RN FLING for logistic support during field efforts and assistance in the periodic

cleaning of underwater light meter sensors during subsequent sport diving trips. Mobil

personnel on the High Island 389A platform were supportive in the deployment and

maintenance of the terrestrial light meter and datalogger. Mr. Harold Hudson is

acknowledged for his expertise in the processing and analysis of accretionary growth

rates from collected coral cores.

xvH
EXECUTIVE SUMMARY

INTRODUCTION

The Flower Garden Banks are located on the outer continental shelf of the Gulf

of Mexico, approximately 204 km (110 nmi) southeast of Galveston, Texas. They are

topographic prominences of bedrock that have been uplifted by the upward intrusion of

underlying salt deposits, or diapirs. The bedrock has been capped with a layer of hard

bottom, formed from the skeletons of corals and other calcareous organisms, and

biogenic calcareous sands and gravels.

The Flower Garden Banks are unique in many respects. Thriving coral reefs

comprising 18 species of hermatypic (reef-building) scleractinian corals occur on the

banks in a geographic area that is considered to be near their northern physiological

limits. Reef-building activity at the Flower Garden Banks is due to favorable conditions of

substrate, water depth, temperature, salinity, and water clarity. The Flower Garden Banks

are the northernmost thriving tropical coral reefs on the North American continental shelf.

Because of their latitude and relative isolation, the biological communities on the Flower

Garden Banks are less diverse than typical western Atlantic and southern Gulf of Mexico

coral reefs. Nevertheless, abundance and growth rates of corals at the Flower Garden

Banks compare favorably with those in more tropical regions at similar depths.

Potential environmental threats to the Flower Garden Banks from development

of petroleum hydrocarbon resources and other human activities on and in proximity to the

banks, and the sensitive nature of their coral reef communities, prompted the U.S.

Department of the Interior, Minerals Management Service (USD01, MMS) to conduct a

long-term monitoring program on the banks which addresses concerns regarding both

chronic and acute impacts. These studies were initiated in the mid-1970s. MMS required

monitoring and studies have also been conducted by oil companies since the late 1970s

in conjunction with the development of petroleum hydrocarbon resources in regulated

lease areas in the vicinity of the banks.

The Flower Garden Banks were designated as a National Marine Sanctuary in

January 1992. Regulations and restrictions associated with Sanctuary status have greatly

increased the level of protection afforded to the banks. However, increased levels of

public awareness of the banks has also brought about a marked increase in the

recreational use of the area.

The primary objectives of the present long-term monitoring study at the Flower

Garden Bank were:

to provide relevant and timely environmental data to agencies that

develop policies concerning oil and gas exploration and development in

the vicinity of biologically sensitive habitats;

to document acute and long-term changes in reef-building and other

associated communities within the high-diversity Diploria-MontastreaPorites Zone at the Flower Garden Banks that may be attributed to

xix
xx

impacts of oil and gas exploration and development or other human

activities (e.g., recreational diving);

to document natural variation in reef-building and associated

communities within this biotic zone on the banks; and

to duplicate methodologies and, whenever possible, to utilize study

stations developed during the previous long-term monitoring study in an

effort to maintain a continuous database of information on the banks.

Contract requirements for this study specified field data collections and analyses to be

completed in 1994 and 1995, and the analysis of photographic data which had been

collected in 1992 at both East and West Flower Garden Bank study sites by Texas A&M

University. The 1992 data set was collected between the 1989-1 991 and present contract

periods, and was representative of conditions on the Flower Garden Banks from 1991-

1992.

METHODS

The scope of the present monitoring contract specified analyses of field data

collected during 1992 (which had not been analyzed) and the collection of field data and

associated analyses during 1994 and 1995. Field sampling efforts were conducted during

11-16 September 1994 and 20-25 August 1995.

Field efforts in 1994 and 1995 were conducted within a previously established

100 m by 100 m study site on each bank. These sites were marked with permanent

mooring lines and attached surface floats. Their corners were demarcated using

subsurface marker floats attached to small stainless steel eyebolts cemented into areas of

reef rock. During each field effort, the sites were clearly defined by extending color

coded, graduated polypropylene lines between the corner marker eyebolts, forming an

enclosed square. On the West Flower Garden Bank, additional site boundary lines were

extended between halfway marks on each line, forming four smaller squares, or blocks

within the site. These lines were invaluable for relocation of permanent stations and diver

navigation within the sites.

During each field effort, fourteen, 10 m (33 ft) stratified random transects were

photographed within each site. Population levels of corals and other associated reef biota

were determined planimetrically by their areal coverage and abundance in transect

photographs. Each transect photograph was analyzed separately. Corals were identified

to species level within the photographs. The sum of areas for each coral species, and all

sponges, leafy algae, and reef rock in each set of transect photographs were converted to

values of relative percent cover. The areas and numerical densities of each coral species

were then used to calculate relative dominance (specific percent coral cover relative to

total percent coral cover), species diversity (H') (the natural log variant of the Shannon

Weaver Diversity Index), and species evenness (J) (species diversity divided by the

maximum possible diversity, i.e., the natural log of the total number of species present).

The dominant coral species on the Flower Garden Banks, Montastrea annularis, has

recently been subdivided into three separate species, M. annularis, M. faveolata, and

M. franksi (Holland, 1991). Data analyses in this report have combined these species as

M. annularis.
Two methods were used for the estimation of accretionary growth rates in the

coral Montastrea annularis. These included permanent growth stations, which involve

repetitive measurements of stainless steel spikes implanted within live coral, and

sclerochronological measurements from two coral core samples collected during the 1995

field effort. Most permanent accretionary growth stations established during previous

studies and located in 1994 were found to be unusable. Therefore, a set of 20 new

stations were established within each site during this field effort. Estimates of

accretionary growth by this method were made during the 1994-1 995 period only.

Encrusting growth rates of the coral Diploria strigosa were estimated by

measurement of change along a specific coral-dead reef rock interface, or border, within

each permanent station. Similar to the case of accretionary growth stations, all

encrusting growth stations used during previous studies and located in 1994 were found

to be unusable. Therefore, 60 permanent stations were established at each site during

the 1994 field effort. Each station was marked with two spikes permanently affixed within

dead reef rock adjacent to the selected coral tissue border. These spikes were

positioned in such a manner to facilitate alignment of a camera close up framer device for

repetitive photography of the border area. Encrusting growth and retreat of the coral

tissue were estimated by superimposing the original coral border traces, made on sheets

of clear acetate, onto sequential photographs. Planimetric measurements were then

made of areas of growth and retreat, along with the border length over which these

changes occurred.

Forty permanent 8 m2 quadrat stations, established during the previous

monitoring study, were photographed during the 1994 and 1995 field efforts to monitor

changes in individual coral colonies. Photographs were taken using a camera attached to

a T-shaped frame, at a distance of 2 m (6.6 ft) from the bottom. Comparisons of these

photographs and those collected in 1992 (using transparency film) were made by

superimposing sequential images onto a baseline template, produced by tracing colony

outlines onto a sheet of paper, and comparing the dimensions of each colony. Counts of

coral growth, disease, bleaching, algae mediated or algae/sediment mat-mediated retreat,

and unexplained mortality were made from each station photograph. In addition,

estimates of percent coral cover and percent coral bleaching were made from each

photograph using a series of paper templates containing 100 randomly located crosses.

Two diver-held, repetitive video transects of 100 m (328 ft) length were filmed

at each site during the 1994 and 1995 field efforts: Each transect followed a specific

boundary line for scale reference and to provide some degree of repetition between field

sampling efforts. The boundary lines selected for video transects duplicated those used

during the previous monitoring study. Each video transect was filmed from approximately

2 m (6.6 ft) above the bottom and at an angle of 45°. A baseline working map of each

transect filmed during the 1994 field effort which depicted large or conspicuous coral

colonies and areas of coral disease or bleaching, sand flats, sponges, etc., was

constructed to provide a reference for changes observed in 1995 transects.

Ancillary measurements included the collection of recording thermographs on

each site which were programmed to record water temperature every two hours, daily

measurements of water temperature, salinity, dissolved oxygen, and ambient light from

near-surface (1 m (3.3 ftl depth) and near-bottom depths, and the deployment and service

xxi
of recording light meters at the two study sites and on the Mobil Hl-389 A platform near

the East Flower Garden Bank.

Acquisition of the recording light meters occurred subsequent to a contract

modification in August 1995. These instruments are designed to measure and record

Photosynthetically Active Radiation (PAR) in the 400 to 700 nm waveband. Data were

presented as total daily irradiance from each light meter and percent light transmission on

each site, by dividing underwater irradiance values by the surface reference values

collected by the surface meter on the Hl-389 A platform. Each underwater unit consisted

of a spherical (omnidirectional) quantum light sensor and datalogger, which was placed in

sealed, acrylic housings and secured on relatively flat areas of solid reef rock located in

proximity to the study site mooring buoys. The surface reference light meter consisted of

a surface quantum light sensor and datalogger. The surface sensor was fastened to the

Hl-389 A platforms helipad, an area that will be least affected by daytime shading from

the platform structure. Both underwater and surface reference light meters were

programmed to record ambient light readings on an hourly basis. At this frequency, the

internal memory of the dataloggers was filled in approximately three months. The three

meters were serviced and their datasets collected during 15-16 November 1995 and

2-3 March 1996.

CORAL COMMUNITY - STATUS AND TRENDS

The mean percent cover of all coral species (total coral cover) estimated from

random transects sampled during the 1992, 1994, and 1995 field efforts was significantly

greater at the East Flower Garden Bank study site than the West (48.2% and 44.1%,

respectively). Total mean percent coral cover was also significantly greater on transects

collected during 1995 and 1994 than those collected in 1992. In terms of percent cover

and relative dominance, M. annularis was the dominant species of coral at the two study

sites (28.3% on the East Flower Garden Bank and 25.9% on the West Flower Garden

Bank), followed by D. strigosa (6.9% on the East Flower Garden Bank and 7.5% on the

West Flower Garden Bank). Porites astreoides was the only species that showed a

significant difference in percent cover between study sites during certain years. Species

diversity and evenness based on coral colony counts was significantly greater on

transects sampled during 1992 than those sampled during 1995, but not significantly

different between study sites. Species diversity and evenness based on coral cover

showed no significant differences between years or study sites.

Data collected from the 1989-1 991 monitoring study reported total coral cover

of 46.0% and 46.5% at the East and West Flower Garden Banks study sites, respectively.

Estimates of percent cover of individual coral species during this study were similar to the

present study, with the exception that some differences between study sites. Unlike the

present study, species diversity and evenness estimates during the 1989-1991 study

showed significant differences between sites.

Comparison of data collected during the present study from stratified random

transects with those from previous studies indicated that the coral community structure of

the Flower Garden Banks has been stable pver time; there was no evidence of habitat

deterioration.

xxh
CORAL GROWTH - STATUS AND TRENDS

Estimates of accretionary growth rates of M. annularis between 1994 and 1995

using growth spikes at permanent stations averaged 5.7 and 5.5 mm/yr at the East and

West Flower Garden Banks study sites, respectively. Mean accretionary growth rates of

M. annularis from 1973-1 995, as determined from sectioned core samples collected from

the East and West Flower Garden Banks study sites, were 6.8 and 8.1 mm/yr,

respectively. These rates closely compare with the range of values collected during the

1989-1991 monitoring study. Estimates of accretionary growth rates during this period

averaged 7.0 and 6.0 mm/yr at the East and West Flower Garden Banks study sites,

respectively. Growth rates determined with coral core samples also compare with those

collected during previous studies.

Estimates of encn.isting growth rates of D. strigosa between 1991-1 992 and

1994-1 995 suggest favorable conditions of growth at the Flower Garden Banks. Relative

tissue growth (advance) and retreat rates during these two periods were comparable. Net

growth rates, defined as the mean rate of change of coral areas observed to advance or

retreat, were positive during the 1991-1992 and 1994-1995 periods. Net growth rates

were substantially lower during the 1991-1 992 period, indicating that greater numbers of

permanent stations during the 1994-1995 period had measurable growth than those

selected for analysis from the 1991-1 992 period. This may be explained by the fact that

over 60% of photographs collected for the quantitative measurement of encrusting growth

during 1992 were rejected for analysis, due to either the effects of natural changes

observed along coral tissue-reef rock borders in certain stations or the effects of

inconsistent camera angle. Because of these problems and the relative low resultant

sample size, it is possible that the differences may be an artifact of sampling error.

Retreat to advance ratios of encrusting growth for D. .strigosa also indicate net tissue gain

during both 1991-1992 and 1994-1995 periods.

Encrusting growth rates of M. annularis were estimated only from data

collected during 1992. Net growth rates during the 1991-1 992 period were negative

(-0.05 cm/yr) at the East Flower Garden Bank study site and positive (0.68 cm/yr) at the

West Flower Garden Bank study site. Overall net growth was positive (0.60 cm/yr) during

this period. Retreat to. advance ratios for this species indicate net tissue loss at both

study sites during this period. Due to aforementioned problems in data collected in 1992,

these results may also be an artifact of sampling error.

Encrusting growth rates that were estimated during the present study indicate

favorable growth conditions for D. strigosa at both study sites. Because of the problems

associated with the 1992 data, it is unclear that estimates of relative growth made during

this period are representative. From these data, it is apparent that the period of time over

which permanent stations for the measurement of encn.isting growth of corals may be

reliably used is finite.

CORAL BLEACHING

Coral bleaching, the expulsion of symbiotic algae (zooxanthellae) by corals

when under stress, was observed in repetitive quadrat photographs taken in 1992, 1994,

and to a much greater extent during 1995. The extent of bleaching within the study sites

was most pronounced in November 1995, when the two study sites were visited to
conduct periodic maintenance of recording light meters. Bleaching during these periods

coincided with periods of elevated bottom temperatures (above 30°C), which are not

uncommon during late summer. As observed in November 1995, the effects of bleaching

may appear to persist long after temperatures drop below 30°C. Other conditions

reported to cause bleaching in corals include high/low light levels, high levels of ultraviolet

radiation, high/low salinity, sub-aerial exposure, excessive sedimentation, storm shock,

and anthropogenic sources such as petroleum hydrocarbons and oil dispersants. Data

indicate that coral bleaching can affect calcification rates, metabolic functions, and in

severe cases lead to localized or widespread mortality of tissue.

Coral bleaching events have been documented on the Flower Garden Banks

on many occasions, although coral mortality associated with bleaching is low. Colonies

which exhibited bleaching usually sustained only minor tissue loss (1992 - 0.5%; 1994 -

0.2%; 1995 - 2.8%). Mortality appeared to be no higher in colonies which exhibited

recurrent bleaching than in other colonies.

CORAL DISEASES

Coral disease, resulting in the necrosis of coral tissue, remains the most

serious natural threat to corals at the Flower Garden Banks. The number of coral

colonies observed at repetitive quadrat stations affected by diseases were significantly

higher in 1995 than 1994 and 1992. Similarly, numbers of colonies affected in 1995

photographs were also appreciably higher than during the previous monitoring study,

which ranged from approximately 10 to 25 colonies per bank per survey. It is not known

whether the increased numbers of coral colonies affected by diseases can be attributed to

the same environmental conditions on the banks (e.g., elevated water temperatures

during the summer and early autumn) which led to significant coral bleaching during this

period. Despite the marked increase in bleaching observed in 1995, the number of

colonies exhibiting disease was low when compared to the 3,902 colonies analyzed in

quadrat photographs (6.0% occurrence).

INDUSTRIAL THREATS TO THE FLOWER GARDEN BANKS

Oil and gas exploration and production continues in the vicinity of the Flower

Garden Banks. Potential sources of petroleum input to the offshore marine environment

of the Flower Garden Banks include natural seeps, marine transportation, and offshore

operations for the exploration and production of hydrocarbons. Accidents related to

offshore operations that result in the release of oil include well blowouts and

transportation incidents.

Generally, oil spills at the Flower Garden Banks and their vicinity could

originate both at the surface and on the seafloor. Because of the banks' depths, surface

spills and resultant slicks would produce minimal to negligible impacts to major reef

constituents, such as scieractinian corals, other invertebrates, and reef fishes. Surface

winds and currents would carry spilled oil or fuel away from the vicinity of the banks in a

relatively short time period. Surface slicks could, however, impact marine mammals, sea

turtles, seabirds, certain pelagic fish, and floating marine plants. An oil spill occurring

during the annual coral reproductive spawning period could also severely impact or

entirely destroy the floating spawn. Modelling studies of the predicted effects of

subsurface spills originating from oil pipelines in the vicinity of the banks indicated

xxiv
minimal to non-existent effects on the sensitive benthic biota of the Flower Garden Banks

(Continental Shelf Associates, Inc., 1992).

Chemical dispersants are agents designed for reducing the surface tension of

spilled oil on the water surface. Surface oil treated with a dispersant mixes within the

water column as fine droplets and is dispersed by currents. Rationale for treating spilled

oil with chemical dispersants includes the prevention of a concentrated surface slick from

moving into biologically sensitive environments; a reduction of direct impacts of surface oil

to offshore natural resources such as marine birds, marine mammals, sea turtles, and

pelagic fish; or the prevention of surface oil from stranding onshore, thus reducing or

eliminating impacts to important coastal habitats, biological communities, or coastal

facilities. Because of the uncertainties associated with vertical transport of oil and

dispersant, the MMS has historically banned their use within the 1-Mile Exclusion Zone of

the Flower Garden Banks. This was felt to be an adequate mitigative measure for

unknown and unquantifiable impacts of the dispersed oil and dispersant to reef biota on

the banks. Recent studies (Fucik et al., 1994) have reported that the application of

dispersants to surface oil did not increase its toxicity to species indigenous to the Gulf of

Mexico. Furthermore, the application of dispersants served to dilute the concentration of

surface oil to approximately 0.1 ppm at depths of approximately 10 m (33 if). At this

dilution, the resultant dispersed oil plume is not considered acutely toxic. These data

have led to a decision by the Flower Garden Banks National Marine Sanctuary that the

application of dispersants may be advantageous to Sanctuary resources in the event of a

surface oil spill, as surface oil would be more harmful than dispersed and diluted oil to

certain pelagic fish, marine mammals, and sea turtles. Therefore, the Sanctuary

approves of the use of oil dispersants on the Flower Garden Banks when deemed

appropriate and conducive by the Federal On-Scene Coordinator.

Current National Pollutant Discharge Elimination System (NPDES) permits limit

oil and grease levels in produced waters, restrict flow rates, require chronic, static,

aquatic toxicity analyses of produced water effluents, and require monitoring of produced

waterdischarges. Regulations also require that all drill cuttings and drilling fluids must be

shunted through a downpipe which terminates at a distance of no more than 10 m (33 if)

from the seafloor. Presently there are no production platforms near enough to the Flower

Garden Banks to produce detectable impacts to the bank's biotic communities resulting

from the regulated discharge of produced waters and drilling fluids.

RECREATIONAL THREATS TO THE FLOWER GARDEN BANKS

Historically, all recreational diving activities on the Flower Garden Banks were

unregulated. Their distance from shore has made visitation to the banks very difficult and

costly for recreational divers. Negative impacts on the banks were associated with

activities such as the anchoring of boats on the live coral reef, spearfishing, collecting reef

biota, and physical damage to living corals from divers. Public awareness of the banks

subsequent to their designation as a National Marine Sanctuary has led to a marked

increase in numbers of recreational divers visiting the area each year.

Historically, the greatest physical impacts to the Flower Garden Banks

associated with recreational diving were due to the anchoring of vessels on live coral

areas of the banks. Permanent mooring lines with surface floats were installed in 1990

at several locations on the high diversity reef areas of both banks in an effort to reduce

xxv
anchor damage. Activities such as spearfishing, collections of reef biota, and destruction,

additions, or modifications to the seabed of the Sanctuary are also prohibited. Despite

the protection afforded to the Flower Garden Banks from regulations associated with

Sanctuary status, negative impacts resulting from physical contact between recreational

divers and sensitive reef biota remain an issue of concern. The use of mooring lines

tends to focus the numbers of divers within repetitively used areas and thus increases the

probability of localized damage caused by physical contact with corals and other reef

biota, and displacement of certain fish species. Currently, no studies have been

conducted to assess the impacts of recreational diving pressures within the area.

Utilization of several alternative mooring line sites for divers during alternate years may

serve to reduce localized pressure on recreational dive sites on the banks.

CONCLUSIONS

Present estimates of coral community structure and coral growth rates are

comparable to those made during the 1989-1 991 study, and reveal no significant

long-term changes in these communities or evidence of the deterioration of habitat

quality. Permanent accretionary and encrusting growth stations at both East and West

Flower Garden Banks study sites were found during the 1994 field effort to be in

unusable condition. It is recommended that these types of permanent study stations be

re-established when deemed necessary in order to minimize the possibility of sampling

error caused by the degradation of the station. No evidence of catastrophic coral

diseases such as band diseases were detected in permanent stations or video transects.

Coral bleaching was detected in the 1992, 1994, and 1995 data and appears to be an

annual event, presumably triggered as a result of elevated sea water temperatures.

Bleaching may persist for several months subsequent to recorded temperature maxima.

Bleaching, however, appears to result in minimal coral tissue mortality. No substantial

changes in coral communities on the Flower Garden Banks, attributable to human

activities, were detected during the present study. Protective regulations of activities on

the Flower Garden Banks, associated with their status as a National Marine Sanctuary,

have served to minimize impacts such as anchor damage, occurrence of debris on the

banks, and impacts to fish resources from commercial fishing and spearfishing.

xxvi
1.0 INTRODUCTION

1.1 OVERVIEW OF THE FLOWER GARDEN BANKS

The East and West Flower Garden Banks are located on the outer edge of the

Gulf of Mexico continental shelf, approximately 193 km and 172 km (104 nmi and 93 nmi)

respectively, southeast of Galveston, Texas (Figure 1). The banks are topographic

prominences of bedrock which have been uplifted and fractured by the intrusion of

underlying Jurassic evaporite salt deposits, or diapirs, which are located at a distance of

15 km (8 nmi) below the seafloor (Bright et al., 1984). The bedrock is capped with a

relatively thin layer of calcareous reef-building organisms. The Flower Gardens are the

two largest of more than 130 calcareous banks charted in the northwest Gulf of Mexico

that exhibit topographic elevation above an otherwise smooth continental shelf (Bright et

al., 1985).

The East Flower Garden Bank is located at 27°54.5' North latitude and

93°36.0' West longitude (Figure 2). The bank is pear-shaped and covers an area of

approximately 67 km2 (19.5 nmi2) (Rezak et al., 1985). Topographic relief is pronounced

on the east and south sides of the bank and gentle on the west and north sides due to

the asymmetric nature of the underlying diapiric core (Bright et al., 1985). The shallowest

depth on the East Flower Garden Bank is approximately 20 m (66 ft). Surrounding water

depths range from approximately 100 to 120 m (328 to 394 ft) (Rezak et al., 1985).

The West Flower Garden Bank lies 12 km (6.5 nmi) west of the East Flower

Garden Bank at 27°52.4' North latitude and 93°48.8' West longitude (Figure 3). The

bank is characterized by three main crests separated by grabens which are aligned

parallel to the long axis of the underlying diapiric core (Bright et al., 1985). The bank

covers an area of approximately 137 km2 (40 nmi2). The shallowest depth on the West

Flower Garden Bank is approximately 15 m (49 ft). Surrounding water depths vary from

100 to 150 m (328 to 492 ft) (Rezak et al., 1985).

The sediments found on the Flower Garden Banks are principally biogenic in

origin, consisting of calcareous sands and gravels. The hard bottom structure of the

banks has been formed from the skeletons of corals and other calcareous organisms.

Sediments surrounding the banks are principally terrigenous sands and muds (Rezak et

al., 1985). The presence of a series of brine seeps and a documented brine lake on the

Flower Gardens indicates the dissolution and removal of sizeable quantities of solid salt

from subbottom locations beneath the reef crests, and creates conditions of seafloor

instability and faulting in those areas (Rezak et al., 1985).

1.1.1 Habitat Description and Zonation

The Flower Garden Banks appear to constitute elements of a discontinuous

ring of reefal structures found on the Gulf of Mexico continental shelf. These reefal

structures, consisting of a combination of thriving coral reefs and scattered hard banks

and patches, bear elements of typical Caribbean reef biota (Bright et al., 1985). The

Flower Gardens, however, are unique in many respects. They are considered to be near

the northern physiological limits for tropical hermatypic (reef-building) corals in the Gulf of

1
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97. 95. 95. 94. 93. 9r 

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Figure 2. Topography and biotic zonation of the East Flower Garden Bank (From: Bright et al., 1985).

3

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I,. GULF OF MEXICO. TEXAS

THOMASJ.8GHT.STEPHENT.VIADA

and CHRISTOPHER L. COMCS

DEPARTMENT OF OCEANOGRAPHY

TEXAS A&M UNIVERSITY

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DATUM: SEA LEVEL

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Figure 3. Topography and biotic zonation of the West Flower Garden Bank (From: Bright et al., 1985).

4

, BIOTIC ZONATION

WEST FLOWER GARDEN

GULF OF MEXICO - tEXAS

COMPILED BY

THOMAS J. 8RIGHT. STEPHEN

and CHRISTOPHER L. COMBS DEPARTMENT OF OCEANOGRAPHY

TEXAS A&M UNIVERSITY

1987 CONTOUR INTERVAL: '0 METRES DATUM: SEA LEVEL

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Mexico and are thus the northernmost thriving tropical coral reefs on the North American

continental shelf (Bright et al., 1984; Rezak et al., 1990). Winter temperatures less than

50 km (27 nmi) to the north are too low for reef-building (Rezak et al., 1990). Because

of its latitude and relative isolation from other regional coral reefs, the biological

communities of the Flower Garden Banks are less diverse than typical western Atlantic

and southern Gulf of Mexico reefs (Bright et al., 1984). For example, only 18 of the 65

western Atlantic hermatypic coral species occur on the Flower Garden Banks (Gittings et

al., 1992). Acroporid scleractinians (including elkhorn and staghom corals) and shallow

water octocorals (sea fans, sea whips, and other gorgonians) which are common

constituents of other western Atlantic reefs at these depths are absent on the Flower

Garden Banks. Nevertheless, coral abundance and specific growth rates at the Flower

Garden Banks compare closely with those in more tropical locales at similar depths

(Rezak et al., 1985). The presence and extent of reef-building activity on the Flower

Garden Banks is due to favorable conditions of substrate, water depth, temperature,

salinity, and water clarity. At their location on the shelf edge, they are exposed almost

continually to tropical-subtropical, clear, oceanic water. Salinities in the area average

over 36 ppt, but have been recorded as low as 32 ppt at the surface and 34 ppt at the

reef tops. Above 25 m (82 ft) depth, water temperatures on the Flower Garden Banks

range annually from approximately 30°C (86°F). Water transmissivity is generally greater

than 75% per meter for white light and light penetration is generally 40% to 50% of the

surface light at 37 m (121 ft) depth (McGrail et al., 1982).

The ciosest coral reefs in the Gulf of Mexico off Cabo Rojo (Mexico) are more

than 600 km (324 nmi) from the Flower Garden Banks. The Flower Garden Banks may

have depended upon these reefs for their initial colonization (Rezak et al., 1985; Bright et

al., 1991; Gittings et al., 1992). Because of their isolated location, the reef corals at the

Flower Garden Banks rely on their own reproductive viability for successful colonization

and development of coral communities (Holland, 1991). Mass spawning, defined as the

synchronous release of gametes by multiple species has been documented annually at

the Flower Garden Banks since 1990 (Gittings et al., 1992). Corals species are either

dioecious "broadcasters" which release eggs or sperm into the water column for external

fertilization, or hermaphroditic "brooders" which release discrete gamete bundles. Mass

spawning observations, together with data collected from coral recruitment studies which

show routine reproduction by brooding corals, and recruitment activities of both

broadcaster and brooder species on nearby oil platforms, suggest that the coral

communities at the Flower Garden Banks are capable of both self-seeding following

disturbance and of supplying viable larvae for colonization of natural and artificial

substrates (Gittings et al., 1992).

Biotic zonation at the Flower Garden Banks is distinct and stringently depth

related (Figures 2 and 3). These biotic zones and their specific depth ranges in turn

correlate consistently with those of known sedimentological fades, though commonly

overlap or grade into one another to some degree (Rezak et al., 1985). Figure 4 is a

schematic depiction of biotic zonation on the southeastern part of the East Flower Garden

Bank. Flourishing coral reefs constitute the largest reefal component on the Flower

5
; D 6 . '- Figure 4 Schematic depiction of the biotic zones and conspicuous biota of the East Flower Garden Bank (From. Bright a
Garden Banks, occupying the crests of the banks at depths of 15 to 52 m (49 to 171 ft) in

some areas. Biotic zones on the banks that correspond to specific depth ranges have

been described as follows:

Diploria-Montastrea-Porites Zone, 15 to 36 m (49 to 118 ft);

Stephanocoenia-Millepora Zone, 36 to 52 m (118 to 171 ft);

Leafy Algae Zone and the Madracis Zone, 28 to 46 m (92 to 151 ft);

Algal-Sponge Zone, 46 to 88 m (151 to 289 ft);

Antipatharian Zone, 52 to 90 m (171 to 295 ft); and

Soft Bottom Zone, <88 m (<289 ft).

1.1.1.1 Diplosria-Montastrea-Porites Zone

The Diploria-Montastrea-Porites Zone extends from the reef crests to a depth

of approximately 36 m (118 ft), and includes an assemblage of 16 species of hermatypic,

or reef-building coral species. This relatively high-diversity zone is dominated by the

scleractinian corals Montastrea annularis, Dip/ode strigosa, Porites astreoides,

Montastrea cavemosa, Colpophyl/ia natan.s, Colpophyllia amaranthus, and the hydrozoan

coral Millepora alcicomis. This zone is platform-like with broad tops composed of

primarily hard substratum formed by hermatypic corals (85%) and carbonate sand and

gravel. Coral reefs within this zone are typically made up of closely spaced, massive

coral colonies, or heads, up to 3 m (10 ft) in both diameter and height. Percent coral

cover in this zone averages over 46% (Gittings et al., 1992). Historical data have shown

minor spatial variability in abundance of certain coral species at the East and West

Banks. However, it is felt that the high-diversity reef communities of the two banks are

essentially similar with respect to coral cover, species composition, dominance hierarchy,

diversity, and evenness. M. annularis is the most abundant hermatypic species, typically

covering from 20% to 40% of the hard substratum in this zone. No other coral species

cover more than 9% of the substratum (Bright et al., 1984). Calcareous sand and gravel

are commonly found in large flats and as isolated patches among the coral heads.

Evidence of extensive bioerosion of the coral heads is common. At least nine genera of

crustose coralline algae (Corallinaceae) are found at the Flower Gardens. Hydrolithon

spp. is most abundant in the Diploria-Monta.strea-Porites Zone. As a group, crustose

coralline algae are abundant within this zone, covering approximately 15% to 20% of the

hard substratum, and contribute substantial calcium carbonate to the reef substratum and

sediments. The algae tend to inhabit cryptic as well as exposed substratum and appear

to be pervasive opportunists, capable of rapid colonization of exposed substrate but

incapable of preventing subsequent encroachment by the dominant hermatypic corals.

Other conspicuous biota include sponges, which occupy a small portion of the

high-diversity reef, and leafy and filamentous algae. A total of 253 species of reef

invertebrates and 103 reef fishes were reported by Bright and Pequegnat (1974) from the

West Flower Garden Bank. Most of these species were collected from within the

Diploria-Montastrea-Porites Zone. Subsequent studies suggest nearly identical

community structure and diversity of associated reef invertebrates and reef fishes from

within this zone at the East Flower Garden Bank (Gittings et al., 1992).

1.1.1.2 Stephanocoenia-Millepora Zone

The Stephanocoenia-Millepora Zone is a narrow and relatively low-diversity

zone on both banks which ranges from approximately 36 to 46 m (118 to 151 ft), with

7
components to 52 m (171 if), and comprises 12 species of hermatypic scleractinian

corals. Eight varieties are conspicuous within this zone, and include Stephanocoenia

michelini, Millepora alcicomis, Montastrea cavomosa, Colpophyllia spp., Diploria strigosa,

Agadcia spp., Mussa angulosa, and Scolymia cubensis. Unlike the high-diversity zone,

the percent cover and relative abundances of corals within the Stephanocoenia-Millepora

Zone shows substantial spatial variability. Crustose coralline algae cover probably equals

or exceeds that of the corals in this zone, but the basic reefal substratum is coral (Bright

et al., 1984).

1.1.1.3 Leafy Algae Zone and the Madracis Zone

Two minor zones, the Leafy Algae Zone and the Madracis Zone are located

intermittently on the peripheral parts of the East Flower Garden Bank between 28 m

(92 ft) and 46 m (151 if) depth. These zones exist on large knolls made of thick deposits

of skeletal remains of the thin, branching coral Madracis mirabilis. These knolls of coral

gravel support thriving populations of leafy algae (Leafy Algae Zone) or living M. mirabilis

(Madracis Zone). Comparable knolls bearing Madracis Zone biotic communities,but not

Leafy Algae Zones, have been documented on the eastern extremity of the main reef

structure at the West Flower Garden Bank (Bright et al., 1985).

1.1.1.4 Algal-Sponge Zone

Hermatypic coral abundance tends to decrease with increasing depth, leading

to virtual dominance by coralline algae. The Algal-Sponge Zone ranges from

approximately 46 to 88 m (151 to 289 ft) in depth and includes a number of biotope

types, including an upper carbonate sand/rubble transition zone and a broad platform

covered with sand, rubble, rhodoliths, and partly drowned reefal structures. Rhodoliths, or

nodules formed by Lithotharnnium and Lithoporella, along with the encrusting

foraminiferan, Gypsina plana, range in size from <ito >10 cm (<0.4 to >4 in.) in diameter

and form a terrace which in most places covers 50% to 80% of the bottom (Bright et al.,

1985). The nodule terrace creates a biotope that harbors a diverse benthic community

which may be comparable in diversity to the shallower coral reefs. Associated organisms

include an abundance of algae dominated by Lithothamnium spp., Tenarea spp., and

Peyssonnelia spp.; boring, attached, and mobile invertebrates; and small fishes (Abbott,

1975). Also within this zone are found relic reefal structures termed "partly drowned

reefs" that now exist at depths in which hermatypic corals have limited capabilities for

growth. These reefs are predominantly covered with living crusts of coralline algae and

occasional veneers and heads of several species of hermatypic corals, such as Helioseris

cucullata, Agaricia spp., Madracis spp., and M. cavemosa. Deep-water octocorals,

primarily from the families Ellisellidae and Paramuriceidae, and several species of

sponges are abundant in the Algal-Sponge Zone. The most distinctive sponge species is

Neofibularia nolitangere, which forms crusts of approximately 1 m (3 if) in diameter on

nodules, sand, and exposed rock within the zone (Rezak et al., 1985). Numerous species

of fishes, mobile and sessile invertebrates, and plants also commonly occur within the

Algal-Sponge Zone. Many species are involved to varied extents in the formation of

carbonate substratum in this zone.

8
1.1.1.5 Antipatharian Zone

The antipatharian zone constitutes a transition zone between shallow-water

and deep-water assemblages on both banks and ranges from 52 m (171 ft) to more than

90 m (295 ft) in depth within the Algal-Sponge Zone. This zone is characterized by the

presence and abundance of white, loosely coiled antipatharians (Ciuhipathes spp.).

1.1.1.6 Soft Bottom Zone

At depths below 88 m (289 ft) sediments change from coarse carbonate sand,

mixed with an abundance of nonliving foraminifera (Amphistegina ) tests, to fine silt- to

clay-sized particles which are easily and commonly resuspended in the water column.

This area has been termed the Soft Bottom Zone. "Drowned reefs," which are at depths

too great for hermatypic corals to exist and for crustose coralline algae to thrive, are

found in areas of relatively fine sediment and are thus commonly covered with veneers of

fine sediment, with veneers being thicker on the deeper reefs. These relict structures are

typically covered with sponges, deep-water octocorals, comatulid crinoids, and

ahermatypic (nonreef-forming) scieractinian corals. -The drowned reefs also attract a

number of fishspecies, many of which are substantially different and of much lower

diversity than -that ofthe partly drowned reefs of the Algal-Sponge Zone and high diversity

coral reefs (Rezak et al., 1985).

1.1.2 Human Activities

Although known by turn-of-the-century fishermen, the Flower Garden Banks

were.first charted by the U.S. Coast and Geodetic Survey (C&GS) in 1936. Protective

lease stipulations were developed for the Flower Garden Banks by the U.S. Department

of the Interior (USD0!), Bureau of Land Management (BLM) in 1974. These included a

"No-Activity Zone" which was based on the 100-m isobath and corresponds roughly with

the edge of the banks; a "1-Mile Zone" around the No-Activity Zone in which all drill

cuttings and discharges were.requiredlobe:shunted.towithin 10 m(33 ft) of the-seafloor

and monitoring studies of the effects of operations on the biota of the bank were

performed; and a "4-Mile Zone," based on a 4-mile radius of the banks, where shunting of

all drill cuttings and discharges was required but not biological monitoring.

Present MMS regulatory zones for the Flower Garden Banks include the

No-Activity Zone and 4-Mile Zone. Exploration, development, and production of oil, gas,

or minerals are prohibited within the No-Activity Zone. However, geophysical surveys and

seismic exploration are allowed within this zone provided that seismic techniques do not

involve the use of explosives or the release of electrical discharges. The 1-Mile Zone has

been removed, as requirements for industry monitoring studies associated with production

activities inside of this regulatory zone have been lifted. Shunting of drill cuttings and

discharges to within 10 m (33 ft) of the seafloor is still required within the 4-Mile Zone.

Early research efforts on the Flower Garden Banks showed significant

mechanical damage to the high diversity coral reef zones as a result of vessel anchoring.

Consequently, BLM/MMS prohibited all anchoring of oil and gas industry vessels on these

biologically sensitive areas of the banks. However, no regulations were in effect to

prohibit the anchoring of recreational vessels or large merchant vessels such as freighters

and tankers on the banks. In 1982, an attempt was made to restrict vessel anchoring on

9
the banks through the National Marine Fisheries Service's Coral Fishery Management

Plan for the Gulf of Mexico. This attempt failed, as it was declared that vessel anchoring

did not constitute a fisheries issue. In 1986, the Flower Gardens were formally labelled

on National Oceanic and Atmospheric Administration (NOAA) navigational charts and

related publications as a "Protected Area," requesting that large vessels avoid anchoring

in the area. In 1990, local volunteers installed 12 buoys on the banks to provide moorage

for small vessels. Since their installation, these buoys have successfully mitigated

mechanical damage to the high diversity reefs by small vessel anchors (Gittings et al.,

1993).

In 1978, the Flower Garden Banks were nominated for National Marine

Sanctuary status by MOM but were withdrawn from consideration in 1982 amid

controversy over proposed sanctuary borders and the methods of disposal of drilling

effluents in the area (Bright et al., 1984). Following an incident involving anchoring by a

large tug in 1983, the Flower Garden Banks were again placed on the list of active

candidates for sanctuary designation. They were formally designated as a National

Marine Sanctuary on 17 January 1992. Sanctuary boundaries roughly correspond with

those of the MMS No-Activity Zone. Within Sanctuary boundaries, regulations prohibit

exploration, development, or production of oil and gas resources; anchoring of vessels

greater than 100 ft in length; possessingr collecting, injuring, and altering Sanctuary

resources; ailfishing other than by hook-and-line; most discharges; possessing or using

explosives; and releasing electrical discharges (Gittings et al., 1993). Figure 5 shows

MMS regulatory zones and Sanctuary boundaries around the Flower Garden Banks.

1.1.3 Historical Research

The first hydrographic survey of the Flower Garden Banks was conducted by

the C&GS in 1936. Stetson (1953) first proved the presence of Uving coral at the banks,

and presumed they were bioherms on top of salt diapirs. This theory was proved by L.L.

Nettleton (1957) after completion of a series of bottom gravity surveys of the West Flower

Garden Bank in 1957. In 1961 Dr. Thomas E. Pulley substantiated the fact that the

Flower Garden Banks were flourishing coral reef communities (Pulley, 1963). From 1961

to 1974, research at the Flower Garden Banks was conducted through Texas A&M

University and the Flower Garden Ocean Research Center at the University of Texas

Marine Biomedical Institute (Galveston, Texas). The BLM, and later the MMS began

funding studies on the topographic features of the Gulf of Mexico continental shelf,

including the Flower Garden Banks. in 1974. Due to their biological complexity and

sensitivity, studies of the Flower Garden Banks has been much more extensive than

those of the other banks. These studies focused on the collection of baseline biological

and geological data to assist in the establishment of policy for protective regulations to be

imposed on drilling operations near these banks. Techniques for the collection of

baseline data of coral community structure and growth rates were developed during this

period (Bright et al., 1981, 1982). These techniques were later used in damage

assessment (Continental Shelf Associates, Inc., 1984; Gittings and Bright, 1986) and

monitoring studies on the banks (Continental Shelf Associates, lnc;, 1985, 1990). The

present study involves analyses of photographic data collected in 1992 during a previous

monitoring study (Gittings et al., 1992), and collections and analyses of data collected in

1994 and 1995.

10
s Figure 5. Location of MMS regulatory zones and National Marine Sanctuary boundaries around the East and West Flowe

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1.2 STUDY OBJECTIVES

The primary objectives of the present long-term monitoring study at the Flower

Garden Banks were as follows:

provide relevant and timely environmental data to agencies which

develop policies concerning oil and gas exploration and development in

the vicinity of biologically sensitive habitats;

document acute and long-term changes in reef-building and other

associated communities within the high-diversity Dipthria-MontastreaPorites Zone at the Flower Garden Banks which may be attributed to

impacts of oil and gas exploration and development or other human

activities;

document natural variation in reef-building and associated communities

within this biotic zone on the banks; and

duplicate methodologies and, whenever possible, utilize study stations

developed during the previous long-term monitoring study in an effort to

maintain a continuous database of information on the banks.

Contract requirements for this study specified field data collections and analyses to be

completed in 1994 and 1995, and the analysis of photographic data which had been

collected in 1992 at both East and West Flower Garden Banks study sites by Texas A&M

University. The 1992 data set was collected between the 1989-1 991 and present contract

periods, and was representative of conditions on the Flower Garden Banks from 1991-

1992.

12
2.0 METHODS

2.1 FIELD LOGISTICS

Field sampling efforts were conducted during 11-16 September 1994

and 20-25 August 1995. Weather conditions during the 1994 field effort were generally

poor, greatly reducing the efficiency of field operations and at times creating potential

safety hazards for divers. Therefore, operations conducted in 1995 were scheduled

slightly earlier in the year to reduce the chances of encountering inclement offshore

weather conditions which are common during autumn months.

2.2 STUDY SITES

Field efforts in 1994 and 1995 were conducted within a previously established

100 m by 100 m study site on each bank. The East Flower Garden Bank site was initially

established by Texas A&M University investigators during the previous monitoring

program (Gittings et al., 1992). The West Flower Garden Bank site was initially

established by CSA during. 1988 for monitoring efforts conducted for Union Oil Co.

(Continental Shelf Associates, Inc., 1990) and later occupied by the Texas A&M

University investigators (Gittings et al., 1992). Figures 6 and 7 represent working maps

of the East and West Flower Garden Banks study sites, respectively.

During the previous monitoring study, permanent markers were deployed within

the two sites to facilitate their relocation and to demarcate their boundaries. Large,

stainless steel U-bolts were cemented within solid reef rock near the center of each site

for initial site location and moorage of the support vessel. A mooring line and large

surface float is kept affixed to each U-bolt during spring, summer, and autumn months.

These mooring lines and floats, and others located outside of the study sites and used for

recreational dive boats, are owned by the NOAA Sanctuary Office and maintained by

contract through Buoy Services, Inc. (Freeport, Texas). The four corners of both sites

have been demarcated using subsurface floats attached to small stainless steel eyebolts

cemented into areas of reef rock. During the 1994 field effort, plastic marker floats

painted with marine antifouling paint were permanently attached to the corner marker

bolts at a height of approximately I m (3 ft) off the seafloor. These floats were replaced

during the 1995 field effort to reduce their chance of loss by fish bites and abrasion. The

freshly painted floats also provide less water resistance (and thus resist drag frorn

currents) and higher visibility to divers than floats which become fouled.

During each field effort, the sites were clearly defined by extending color

coded, graduated polypropylene lines between the 100 m (328 ft) corner marker eyebolts,

forming an enclosed square. On the West Flower Garden Bank, additional site boundary

lines were extended between halfway marks on each line, forming four smaller squares,

or blocks within the site. Though tightened snugly when extended, the lines would tend to

float a meter or two above the reef contours, especially along the middle sections. This

increased the line's visibility and reduced abrasion across the tops of the reef contours.

All lines that extended North-South were yellow in color and those which extended EastWest were white in color. The color coding and graduations on boundary lines greatly

facilitated diver navigation and accurate mapping of all permanent study stations within

13
lOOm

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Figure 6. Map of the 100 mx lOOm study site at the East Flower Garden Bank, showing graduating boundary

lines, relative positions of permanent stations, and conspicuous features.

14
Figure 7. Map of the 100 m x lOOm study site at the West Flower Garden Bank, showing graduating boundary

lines, relative positions of permanent stations, and conspicuous features.

15

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and in proximity to the sites. The relative position of each station along a specific

boundary line was drawn onto a form printed on underwater paper that showed the site

boundary lines and distinctive features such as sand flats, mooring anchors, and various

debris found within the site. Whenever possible, station positions were also referenced to

a second perpendicular boundary line for improved accuracy.

2.3 RANDOM TRANSECTS

Population levels of reef coral communities within the two study sites were

estimated using stratified random photographic transect techniques. During each field

effort, fourteen, 10 m (33 ft) transects were photographed within each site. The

photographs were obtained using a Nikonos V underwater camera with 28 mm lens and

dual Ikelite 150 watt-second strobes, which were mounted on a rectangular stainless steel

camera frame. The bottom tubes of the camera frame were covered with foam pipe

insulation to minimize contact abrasion to corals during transect photography. Contact

pressure on corals from the camera frame was minimized by reducing its underwater

weight using small floats attached to the upper tubes (Figure 8).

16

Figure 8. Diver using camera and stainless steel rectangular frame to

photograph 10 m (33 if) random transects. East-West study site

boundary line is visible in the background.
Random numbers served as the prescribed compass direction and distance

from the photographer's initial descent point within the study site (measured as number of

flipperkicks) to the starting point of the first transect. The transect was then photographed

along this same compass direction, producing a continuous swath of non-overlapping

exposures. Seventeen exposures produced a transect swath of 10 m (33 ft) in length.

Thus, the use of 36-exposure print film enabled each diver to complete two transects per

dive. The end point of the first transect then served as a reference for the starting point

of the second transect, using a second set of random direction and distance numbers.

During all transects, areas of sandy bottom were bypassed or avoided to maximize the

amount of coral and hard bottom community data collected.

Population levels of corals and other associated reef biota were determined by

their areal coverage and abundance in transect photographs (Figure 9). Areal coverage

of corals, sponges, leafy algae, and reef rock were determined in the lab using a Hi-Pad

Plus electronic digitizing planimeter (Houston Instruments, Inc.) and EASYDIJ digitizer

program (Geocomp, Ltd.). Each transect photograph was analyzed separately. The

outlines of corals and reef biota within each transect photograph were traced on sheets of

clear mylar and assigned corresponding identification codes. Coral species were

identified to species level within transect photographs. The mylar traces provide a

permanent record of all species identifications used in subsequent analyses. The

outlines on the mylar traces were again traced using the calibrated planimeter and their

areas automatically calculated. The sum of areas for each coral species, and all

sponges, leafy algae, and reef rock traced on each set of transect photographs were

converted to values of relative percent cover. The areas and numerical densities of each

coral species were then used to calculate relative dominance (specific percent coral cover

relative to total percent coral cover), species diversity (H') (the natural log variant of the

Shannon Weaver Diversity Index), and species evenness (J) (species diversity divided by

the maximum possible diversity, i.e., the natural log of the total number of species

present).

The transect data were analyzed with a two-way factorial analysis of variance

design. Treatments in the analysiswere bank (East and West Flower Garden Banks) and

year (1992, 1994, and 1995). Response variables in the analysis were percent cover of

coral taxa, relative dominance of coral taxa, total coral cover, coral species diversity

(based on cover and count) and coral evenness (based on cover and count). An

arcsine-square root was used to transform data that were reported in percentages (cover

and relative dominance). This transformation is commonly used to help normalize

percentage data. Statistically significant main effects (bank and year) or interactions

between the main effects were examined a posteriori with Tukey's honest significant

difference test.

2.4 ACCRETIONARY GROWTH

Two methods were used for determination of accretionary growth rates in the

coral Montastrea annularis. These included permanent growth stations and

sclerochronological measurements from collected coral cores.

17
18

a

Figure 9. Example of a 10 m (33 ft) random transect photograph from the

East Flower Garden Bank. Seventeen sequential photographs

were equivalent to an overall transect length of 10 m (33 ft).

2.4.1 Permanent Growth Stations

Most accretionary growth stations used during the previous monitoring study

were found to be unusable during the 1994 field effort due to the following:

Sharpened stainless steel rods, or "growth spikes," had become loose

within the coral, introducing the potential for substantial sample error

during subsequent measurements.

Coral tissue around the growth spikes had receded and negated further

growth in the area.

Placement of the growth spike had altered normal coral growth

patterns, varying from a pronounced swelling, or hummock of growth

around the base of the spike to a thin veneer of growth up the spike. In

one case the coral had completely covered the spike and deposited fine

streamers of growth in an outward or perpendicular direction.

Spike was lost or previously removed.

Station was not found in the area designated on site maps made during

the previous monitoring study.
Therefore, a set of 20 new growth stations were established for the measurement of

accretionary growth of the coral M. arinularis (= M. faveolata) within both study sites

during the 1994 field effort (Figure 10). Masonry expansion bolts (1⁄4" X 2%") were used

for both growth measurements and station markers instead of the smooth stainless spikes

used during the previous study. This type of bolt is placed within a pre-drilled hole and

secured by a slight expansion of its base using a mallet. This method permits accurate

and reliable placement, with respect to both location and depth, and minimizes trauma to

surrounding coral tissue. These types of fasteners are also very secure when properly

set in reef rock. The holes for the expansion bolts were made using a in. drive

pneumatic drill attached to a compressed air (scuba) bottle. A single expansion bolt was

set within the upper surface of each selected colony and measured to the nearest

millimeter. As the coral continues to grow, calcium carbonate is deposited around the

stationary growth spike. Accretionary growth rates are thus estimated by the measured

decrease in the length of growth spikes over time. A second expansion bolt was then

placed in proximity to the growth spike and marked with a small fluorescent numbered tag

to serve as a station marker. The station marker bolts were placed in areas of the coral

colony which would be easily visible to divers for relocation and, whenever possible, in

areas of dead reef rock.

Figure 10.

.1

2.4.2 Sclerochronology

Determination of theaccretionary growth of M. annularis via measurement of

annual skeletal growth bands, or sclerochronology, was accomplished in 1995. This

method involves the collection of intact coral cores from the tops of large, symmetrical

lJe

Permanent station for determination of accretionary growth in

the coral Montastrea annular/s ( M. faveolata). Note station

marker tag and growth spike.

19
colonies, which are later slabbed along the axis of the corallites and x-radiographed to

illuminate banding (Hudson, 1981; Hudson et al., 1976). Two coral core samples were

collected from separate colonies of M. annularis (= M. faveolata) within each site during

the 1995 field effort using a 2.5cm (1.0 in.) diamond-tipped coring bit and a 1.25 cm

(0.5 in.) drive pneumatic drill (Figure 11). Core samples for sclerochronology must be

taken from areas of the coral which have experienced relatively straight or planar growth.

The core sample must be taken parallel to the plane of growth to obtain the most

uninterrupted growth information. Breaks in the core sample, though common, must also

be minimized to avoid loss of data. After removal of each intact core sample, the

resultant holes in the coral colonies were sealed using tightly fitting, tapered rubber

stoppers. The stoppers were positioned slightly below the level of the surrounding coral

tissue to permit the subsequent lateral growth of coral over the affected area. Core

samples were delivered to Mr. Harold Hudson (Reef Tech, Inc.), thin sectioned, x-ray

photographed, and annual growth bands labelled and measured.

20

4/

S

Figure 11. Diver using pneumatic drill and 2.5 cm (1 in.) coring bit to collect

core sample from the coral Montastrea annularis ( M.

faveolata) for determination of accretionary growth. Note

application of padded drill guide.

2.5 ENCRUSTING GROWTH

Encrusting growth rates of 60 colonies of the coral 0. strigosa were

determined from permanent stations within each site. Each station was composed of a

margin1 or border, of coral which lay adjacent to dead reef rock. A pair of station marker

spikes set into the reef rock and away from the actual coral border were used to align a

Nikonos camera and close-up framer for repetitive photography. During the 1994 field
effort it was found that lateral growth stations used during the previous monitoring study

were no longer useable. This was due to the following:

The coral border had shifted by either growth or recession beyond the

area viewed in the repetitive photographs.

The border had become three dimensional, or plateau-like, due to the

bioerosion of the reef rock area and/or accretionary growth of the coral

tissue. In this case, the growth border became perpendicular to the film

plane and therefore very difficult to view and determine minute changes

in growth and recession in station photographs.

Spikes used during the previous study were missing or had become

loose in the reef rock.

The station was not located in the area designated on site maps made

during the previous monitoring study.

Therefore, new stations were selected and photographed for the first time during the 1994

field effort. To maximize photograph repeatability, selected border areas were located on

relatively planar surfaces. Coral borders exhibiting areas of apparent coral disease and

intra- or inter-specific competition with other coral species for available space were

avoided. Two expansion bolts were placed within dead reef rock adjacent to the selected

coral border, using a Nikonos close-up framer as a guide for station position and

dimension. After placement, a numbered marker tag was fastened to one of the bolts for

station identification (Figure12).

Photographic data were collected in 1992 for estimates of encrusting growth of

both D. stdgosa and M. annulads. These photographs were compared with those

collected in 1991 during the 1989-1991 monitoring study for estimates of encrusting

growth during the 1991-1992 period. The coral-reef rock borders in 1991 and 1994

encrusting growth station photographs were traced on mylar sheets, along with a series of

corresponding and distinctive coral growth patterns to facilitate subsequent photograph

alignment. The 1992 and 1995 coral-reef rock borders were also traced onto their

corresponding mylar sheets, using a different color ink for clarity. The changes in area

along the border length of each photograph were calculated using the electronic digitizing

planimeter. In many cases, the 1995 border included sections of both growth and retreat,

forming a number of border segments. Each border segment was traced and its area

calculated separately. Growth and retreat rates for each station (expressed as cm/yr)

were calculated by dividing areal measures of change (cm2) by the total analyzed border

length of the station (cm). Net growth was determined by pooling growth and retreat

measurements. Each station provided a single estimate of each parameter (growth,

retreat, and net growth rates) regardless of the total number of border segments present.

21
22

Figure 12. Permanent station for determination of encrusting growth in the

coral Diploria strigosa. Note station marker tag on the right

station spike and left station marker spike at colony break at left

center of photograph.

2.6 REPETITIVE QUADRATS

Forty permanent quadrat stations established by either CSA or Texas A&M

University during the previous monitoring studies were utilized during the 1994 and 1995

field efforts. Each station was marked with a single stainless steel rod set vertically into

an area of reef rock (Figure 13). A plastic number tag was affixed to each post for

station identification. Single photographs were taken at each station using a I-shaped

camera frame equipped with a down-looking Nikonos V camera with 15 mm lens and two

Ikelite 225 watt-second strobes mounted on the upper horizontal bar, or crossmember,

and a 2 m (7 ft) vertical bar (Figure 14). The electronic strobes were attached to the

ends of the frame's crossmember and oriented vertically. Precision in the orientation of

subsequent photographs was ensured with the use of a compass and surveyor's

bubblelevel mounted on the camera frame crossmember. The frame's vertical bar was

placed directly against the station marker post, oriented to magnetic North, and positioned

in a level attitude prior to each photograph.
Figure 13. Permanent 8 m2 quadrat station marker. Note marker post at

center of photograph and station marker tag.

In the lab, the photographic transparency of each station was projected onto a

table top and adjusted to produce images of 25.2 cm by 37.9 cm (Figure 15). Working

templates of this size which were produced for each station during the previous study

consisted of the outlines of living and dead portions of all visible colonies on large paper

sheets. Temporal comparisons of each station were made by superimposing the current

photographic image onto the template and comparing colony borders individually.

Changes in borders were traced onto the templates using a different color pencil for each

year. These changes were then categorized using the following categories: growth,

algae-mediated or algae/sediment mat-mediated retreat, bleaching, and disease. Percent

coral cover and percent bleached coral cover in each photograph were determined using

identically sized paper templates containing 100 randomly located crosses. When

superimposed on these overlays, the percent cover of live coral and bleached coral at

each station were derived from the total number of crosses which were counted over live

coral or bleached coral, respectively. One estimate of percent cover of live coral and

bleached coral was made for each station

23
24

-tk

I- -a

.6

F' r

I .

Figure 15. Example of a 8 m2 repetitive quadrat photograph from the East Flower

Garden Bank. Dark line in the photograph is the T-frame vertical member.

1 tø

Figure 14. Diver using camera and aluminum 1-frame to photograph 8 m2 repetitive

quadrats. Note that the lower end of the vertical frame member is

positioned at the base of the station marker rod.
2.7 VIDEO TRANSECTS

Two diver-held, repetitive video transects were filmed at each site during the

1994 and 1995 field efforts. Each transect was 100 m (328 ft) in length and followed a

specific boundary line for scale reference and to provide some degree of repetition

between field sampling efforts. The general areas selected for video transects during the

1994 and 1995 field efforts duplicated those used during the previous monitoring study.

At the East Flower Garden Bank site, these included the northern boundary line, run from

west to east, and the eastern boundary line, run from north to south. At the West Flower

Garden Bank site, these included the southern boundary line, run from east to west, and

the western boundary line, run from south to north. Temporal comparability between

each transect was possible only near the ends of each line, due to variability in

positioning the line over rough topography of the reef top and displacement of the line by

bottom currents. Each video transect was filmed from approximately 2 m (7 ft) above the

bottom and at an angle of 45°. A 2 m (7 ft) weighted line suspended from the video

camera housing provided a reference for camera altitude and angle during the filming of

each transect. A baseline working map of each transect filmed during the 1994 field

effort which depicts large or conspicuous coral colonies and areas of coral disease or

bleaching, sand flats, sponges, etc., was constructed to provide a reference for changes

observed in 1995 transects.

2.8 ANCILLARY MEASUREMENTS

2.8.1 Recording Thermometers

Hobotemp (Onset Instruments, Pocasset, Massachusetts) and Ryan

TempMentor thermographs, deployed on both study sites during the previous monitoring

study and presently owned by NOAA, were retrieved, their data downloaded onto

computer, and redeployed during the 1994 and 1995 field efforts. These units are

programmed to record water temperature every two hours. The units are affixed to the

bottom in proximity to the mooring anchor at the EFG and in the northeast corner of the

WFG study site.

2.8.2 Water Profiles

During each field effort, daily measurements of water temperature, salinity,

dissolved oxygen, and ambient light were collected from near-surface (1 m (3 ft] depth)

and near-bottom depths. A Hydrolab Surveyor Ill water quality probe was utilized for

temperature, salinity, and dissolved oxygen parameters. A Licor 185B photometer was

used to calculate ambient light. Both instruments were calibrated daily prior to each

profile.

2.8.3 Light Recorders

Continuous recording light meters were installed during the 1995 field effort at

underwater locations on the two sites and a surface location on the Mobil Hl-384 A

platform (East Flower Garden Bank). The light meters are designed to measure

Photosynthetically Active Radiation (PAR) in the 400 to 700 nm waveband, and record

data expressed in units of pmoles s1m2 (lpmol = 6.022 x 1017 photons). Data are then

presented as total daily irradiance (mol m2day') from each light meter and percent light

25
transmission on each site, by dividing underwater irradiance values by the surface

reference values collected by the above water meter on the Hl-384 A platform. Each

underwater unit consists of a Licor LI-i 93SA spherical (omnidirectional) quantum light

sensor and LI-i 000 datalogger (Figure 16). The dataloggers were placed in 0-ring

sealed, acrylic housings and secured within stainless steel cages which were coated with

antifouling paint and equipped with zinc anodes (Figure 17). The underwater deployment

sites were selected on relatively flat areas of solid reef rock located in proximity to the

study site mooring buoys. The stainless steel cages were affixed to the bottom using four

in. masonry expansion bolts. The light sensors were secured to a projecting vertical bar

on the cages using heavy duty nylon cable ties. Commercially available 'ziplock" plastic

bags were fastened over the sensors to prevent biofouling and the subsequent scoring of

the sensor surfaces during cleaning. These protective covers will be replaced as needed

by divemasters aboard the vessels MN FLING or MN SPREE during scheduled sport

diving trips The surface reference light meter consists of a Licor Ll-210 SA terrestrial

quantum light sensor, 100 ft coaxial extension cable, and LI-i 000 dataiogger. The sensor

was secured within a PVC bracket and fastened to a section of the safety guard fencing

on the outer rim of the Hl-384 A platform's helipad. This area will be least affected by

daytime shading from the platform structure. The coaxial cable was fairleaded from the

platform helipad to the living quarters below and fitted through an electrical penetrator in

the outer wall to the main office quarters. The datalogger is equipped with a ii Ov AC

adaptor; internal batteries thus provide auxiliary power only in the event of platform

26

Figure 16. Layout of equipment used to record incident light at underwater

sites on the East and West Flower Garden Banks study sites.

These include a datalogger, spherical underwater sensor and

coaxial cable, and sealed acrylic housing.
/, ' a

Figure 17. Recording underwater light meter in position at the East Flower

Garden Bank study site. Note stainless steel containment cage

bolted to reef rock and protective plastic bag over spherical

sensor.

electrical power interruptions. Both underwater and surface reference light meters were

programmed to record ambient light readings on an hourly basis. At this frequency, the

internal memory of the dataloggers is filled in approximately three months, necessitating

service on a quarterly basis. The three meters were serviced and their datasets collected

during 15-16 November, 1995 and 2-3 March 1996. The service procedure included data

collection from dataloggers, datalogger battery replacement and overall check, cleaning

and servicing of acrylic housings, and the replacement of zinc anodes on the two

underwater stainless steel cages.

2.9 SEDIMENT COLLECTIONS

Sediment samples were collected during each field effort to be archived for

possible future hydrocarbon and trace metal analyses. Three replicate samples were

collected for both trace metal and hydrocarbon analyses from each site during each field

effort. At each site, pre-cleaned 250 ml glass jars filled with distilled water were carried

by diver to a sand flat. Each jar was then opened and filled with sand, skimming only the

upper 5 cm (2 in.). At the surface, approximately 5 cm (2 in.) of water and sand were

poured from each jar to prevent breakage during freezing. The jars were then labelled

and frozen. A separate jar filled with distilled water served as a trip blank during each

field effort. These blanks have also been archived for future analysis.

27
3.0 RESULTS

3.1 RANDOM TRANSECTS

Percent coral cover (per taxa and total), relative dominance of coral species,

and species diversity and evenness (calculated from both coral counts and coral cover)

were determined through analysis of the stratified random photographic transects.

Statistical comparisons were made between coral species, between the East and West

Flower Garden Banks study sites, and between the 1992, 1994, and 1995 field efforts

(years).

3.1.1 Coral Cover and Relative Dominance

The mean percent cover of coral taxa, reef rock, leafy algae, sponges, and

sand at each study site for data collected during the 1992, 1994, and 1995 field efforts is

graphically depicted in Figure 18. Tabte A.1 in Appendix A lists mean percent cover

estimates for coral taxa, combined coral taxa (total coral cover), reef rock, leafy algae,

sponges, and sand on transects collected during the 1992-1994, and 1995 field efforts on

both banks. M. annularis was the dominant reef component on the East and West Flower

Gardens Banks study sites, with estimates of 28.3% and 25.9% cover, respectively on the

transects. The closest species in terms of percent cover to M. annularis was D. strigosa,

with estimates of 6.9% and 7.5% cover at the East and West Flower Gardens Banks

study sites. Estimated total coral cover at the East and West Flower Gardens Banks

study sites was 48.2% and 44.1%, respectively.

Mean percent cover of reef rock over the 1992 to 1995 period on the East and

West Flower Gardens Banks study sites was 48.0% and 44.1%, respectively. Since sand

flats were avoided or bypassed during field data collection, its percent cover on transects

was understandably extremely low. The percent cover of leafy algae and sponges on

both banks was comparable to several coral species. Leafy algae comprised 1.88% and

2.52% of the transects on the East and West Flower Gardens Banks study sites. - Percent

cover of sponges at the East and West Flower Gardens Banks study sites were 0.88%

and 1.13%, respectively.

Comparisons of percent cover for individual coral taxa were made for each

year (with data from both study sites pooled) and bank (with data from all field efforts

pooled) with the bank by year interaction also included in the analysis. A synopsis of

these comparisons is displayed in Table 1. Among individual species, significant

differences in cover between years for pooled banks were observed for three of the

fourteen coral taxa. Cover of M. annularis and Siderastrea siderea was significantly

higher on 1995 transects than on both 1994 and 1992 transects. Cover of M. cavemosa

was significantly higher on 1994 transects than on 1992 transects. There were no

significant differences in coral cover for specific corals (years pooled) between banks.

Significant bank by year differences were observed in P. astreoides. Percent cover

estimates for P. astreoides at the East Flower Garden Bank study site were significantly

higher in 1992 than those on the West Flower Garden Bank study site in both 1992 and

1994. The 1994 East Flower Garden Bank study site estimates were significantly higher

than at the West Flower Garden Bank site in 1992.

29
(A) 0 Figure 18. Comparison of percent cover of corals, reef rock, conspicuous biota, and sand between the East and West F

sites during the 1992 to 1995 period (* indicates coral cover estimates which are significantly different betw

Montas tree annularis Diplorla strlgosa -, PonIes estreoldes * Montastrea cavernosa Colpophyllia spp. DEast Flower Garde

MIllepora spp. West Flower Garde

Agarlcla spp. Stephanocoenla michelini ) Madracis decactis 3 Sideras tree slderea Musse angufosa Scolymla cubensts Pofltes furcata - Madracis mirablils - TOTAL CORAL - Reef Rock - Leafy Algae a Sponges Sand 0 10 20 30 40 50
Table 1. Summary of the results of the statistical analysis of percent coral cover from

random transect data. Statistical analysis included year, bank, and bank by

year interaction. Statistical tests were performed at a confidence level of 95%

(a = 0.05).

NS = No significant difference. * = Significant interaction of bank by year precludes interpretation of main effects (i.e.,

year and bank).

31

Species

Coral Cover

Year

(banks pooled)

Bank

(years pooled)

Bank by Year

Interaction

Montastrea annularis 95 > 94, 92 MS NS

Diploria strigosa NS NS NS

Pon'tes astreoides * * EFG 92>WFG 92,

WFG 94; EFG

94>WFG 92

Agaricia spp. NS NS NS

Millepora spp. NS NS NS

Colpophyllia spp. NS NS NS

Montastrea cavemosa 94 > 92 MS MS

Stephanocoenia michelini NS MS NS

Siderastrea siderea 95 > 94, 92 NS NS

Madracis decactjs MS NS NS

Madracis mirabilis NS NS NS

Mussa angulosa NS MS NS

Scolymia cubensis NS MS MS

Porites furcata MS NS MS

Total Coral Cover 95, 94 > 92 E > W MS
Total percent coral cover (with all species pooled) was significantly different

between years and between banks. Mean percent coral cover was higher in both 1995

and 1994 than in 1992, and higher on the East Flower Garden Bank study site than the

West Flower Garden Bank study site.

The relative dominance of each coral taxa on each bank for data collected

during 1992, 1994, and 1995 is graphically depicted in Figure 19. Patterns in relative

dominance of coral taxa were similar to those observed in percent cover. M. annularis

was the dominant species observed in transects on both study sites, followed by

D. strigosa. Ratios were slightly higher for both species at the West Flower Garden Bank

study site.

Comparisons of relative dominance for each coral species were made for each

year (with data from both study sites pooled), bank (with data from all field efforts

pooled), and between bank by year. Table A.2 in Appendix A lists relative dominance

estimates, expressed in percent, for all coral taxa. A synopsis of these comparisons is

displayed in Table 2. No significant differences in relative dominance of coral taxa

between years (banks pooled) were observed. Significant differences in relative coral

dominance between banks (years pooled) were observed in three species. Relative

dominance of M.cavemosa was significantly higher in 1 994 than 1992, Stephanocoenia

michelini was higher in 1992 than 1995, and S. siderea was higher in 1995 than in both

1992 and 1994. As in the case of coral cover, P. astreoides showed significant

differences in comparative bank by year interactions. The relative dominance of

P. astreoides in 1992 at the East Flower Garden Bank study site was significantly higher

than in 1994 and 1995, and higher than the West Flower Garden Bank study site during

1992, 1994, and 1995.

3.1.2 Species Diversity and Evenness

Estimates of coral species diversity and evenness from the random transects

sampled during 1992, 1994, and 1995 at the East and West Flower Garden Banks study

sites are listed in Table A.3 in Appendix A. Table 3 is a synopsis of comparisons

between year (with data from both study sites pooled), bank (with data from all field

efforts pooled), and between bank by year (interaction). With data from both banks

pooled, values of species diversity and evenness based on coral counts were significantly

higher in 1992 than 1995. No significant differences in diversity and evenness were

observed between banks and the interaction between banks and years was not

significant.

3.2 ACCRETIONARY GROWTH

3.2.1 Permanent Growth Stations

Accretionary growth rates were determined from 20 stations established at

both the East and West Flower Garden Banks during the 1994 field effort. Data from 18

of the 20 stations at the East Flower Garden Bank and 15 of the 20 stations frorn the

West Flower Garden Bank were used to derive these measurements (Appendix B,

Tables BA and B.2). Aberrant data, indicative of sampling error, were not included in the

32
Figure 19. Comparison of relative dominance of corals between the East and West Flower Garden Banks study sites duri

(* indicates relative dominance estimates which are significantly different between banks at a 0.05). '1⁄4 Montarea annularis Diploria strigosa - Porltesastreo!des - * Montasrea caverno Colpophyilla qp. Millepora p Agaricia p. ft Stephanocoenla michelin! ft M adracis decactis Siderastrea siderea Mus angufosa ) Dst Rower Garden Bank Scolymia athensls West Power Garden Bank Porites furca ta Madracis mira bills

0 0.1 0.2 0.3 0.4 0.5 0.6
Table 2. Summary of the results of the statistical analysis of relative dominance of coral

taxa from random transect data. Statistical analysis included year, bank, and

bank by year interaction. Statistical tests were performed at a confidence level

of 95% (a = 0.05).

NS = No significant difference. = Significant interaction of bank by year precludes interpretation of main effects (i.e.,

year and bank).

34

Species

Relative Dominance

Year

(banks pooled)

Bank

(years pooled)

Bank by Year

Interaction

Montastrea annulafls NS NS NS

Diploria strigosa NS NS NS

Porites astreoides *

* EFG 92>EFG

94, EFG 95,

WFG 92, WFG

94, WFG 95

Agaflcia spp. NS NS MS

Mi/Jepora spp. MS MS MS

Colpophyllia spp. NS NS NS

Montastrea cavemosa NS 94 > 92 NS

Stephanocoenia michelini NS 92 > 95 NS

Siderastrea siderea NS 95 > 94, 92 NS

Madracis decactis NS MS NS

Madracis mirabilis MS NS MS

Mussa angulosa NS MS NS

Scolymia cubensis MS MS MS

Porites furoata MS NS MS
Table 3. Summary of the results of the statistical analyses of coral species diversity (H')

and species evenness (E) based on colony counts and percent cover.

Statistical analyses included year, bank, and bank by year interaction.

Statistical tests were performed at a confidence level of 95% (a = 0.05).

NS = No significant difference

35

H' (counts) E (counts) H' (cover) E (cover)

Year 1992>1995 1992>1995 NS NS

Bank NS NS NS NS

Bank by Year NS NS NS NS
data set. Table 4 is a synopsis of accretionary growth data collected during the 1994-95

period at both banks.

Table 4. Accretionary growth of Montastrea annu!afls from 1994-1995, measured from

growth spikes installed at the East and West Rower Garden Banks study sites.

These data are also graphically depicted in Figure 20. Mean growth rates during this

period were similar to those determined from the East and West Flower Garden Banks

during the previous monitoring study (7.0 and 6.0 mm/yr, respectively) (Gittings et al.,

1992).

3.2.2 Sclerochronology

The 1973 to 1995 accretionary growth records of two cores of M.. annularis

collected from each study site are listed in Appendix B (Table 8.3) and graphically

depicted in Figures 20 and 21. The mean accretionary growth rate during this period

from cores collected from the East and West Flower Garden Banks was 6.8 and

8.1 mm/yr, respectively. Individual annual growth estimates ranged from 5.3 to 11.7 mm

during this period. Mean accretionary growth of the cores during the 1994-1 995 contract

period was 8.0 mm (East Flower Garden Rank) and 8.5 mm (West Flower Garden Rank).

These rates fall within the range of measurements derived from permanent growth station

data during this period.

3.3 ENCRUSTING GROWTH

As discussed in Section 2.5, the physical condition of previously established,

permanent encrusting growth stations at both East and West Flower Garden Bank study

sites were determined to be unsuitable for continued use during the present contract

period. Consequently, a new set of permanent stations for the measurement of

encrusting growth of D. strigosa was established during the 1994 field effort. Estimates

of encrusting growth rates for this species are availible for the periods between

1991-1 992 and 1994-1995. Estimates of encrusting growth rates of M. annularis were

measured from 1992 station photographs, representing growth from 1991-1992.

In the lab, it was found that approximately 60% of the encrusting growth station

photographs of both 0. strigosa and Al. annu/aris taken in 1992 could not be analyzed.

This was due in most cases to 1) the effects of natural changes observed along coral

tissue-reef rock borders in certain stations (as described in Section 2.5), 2) the effects of

inconsistent camera angle, or 3) different species selected for permanent stations

(M. cavemosa or Coipophyi!ia spp.).

36

Bank Mean (mm/yr) Range (mm/yr) Number Standard

Deviation

East 5.7 0-8 18 0.5

West 5.5 4-9 15 0.5
12

10 -

8

6

4

2

EFG WFG

Permanent

Growth

Stations

Coral Cores

Figure 20. Comparison of accretionary growth rates of Montastma annularis during 1994 - 1995 from

permanent growth stations and coHected coral cores.

37

EFG WFG
Figure 21. Accretionary growth rates of Montastrea annularis measured from cores collected at the

East and West Flower Garden Banks.

38
Subsequent to the analysis of the acceptable 1992 photographs, it was

discovered that the estimates of net encrusting growth rates of D. strigosa during the

1991-1 992 period were substantially less than those estimated for the 1994-1 995 period.

Because of the problems with the 1992 data and the resultant low sample size, it is

possible that the differences may be an artifact of sampling error. Therefore, they are

compared only graphically and not statistically with the 1994-1 995 data set.

3.3.1 Net Growth Rates

Net growth rates are defined as the mean rate of change of coral areas

observed to advance (growth) or retreat, using pooled measurements from all stations.

For D. strigosa (Table 5), net encrusting growth rates at the East and West Flower

Garden Banks were positive during the 1991-1 992 period and 1994-1 995 period, and

averaged 0.05 and 0.20 cm/yr. respectively. Comparisons between the banks showed

comparable net growth rates within each sample period. The substantial differences in

net growth rates between sample periods may be an artifact of sample error or may

indicate that greater numbers of permanent stations in the 1994-1 995 period had

measureable growth than those selected for analysis from the 1991-1 992 period.

Measurements of encrusting growth rates of M. annularis were determined

from 1992 data (Table 6). Because the net growth rate estimated at the East Flower

Garden Bank during this period was negative (-0.05 cm/yr), net growth for the combined

banks during the 1991-1992 period was comparatively low (0.01 cm/yr). The net growth

rate at the West Flower Garden Bank during this period was estimated at 0.07 cm/yr. As

in the case of 0. strigosa, the estimates for M. annularis may be an artifact of sampling

error.

3.3.2 Advance and Retreat Rates

Separate mean advance and retreat rates and their corresponding standard

deviations for D. strigosa are shown in Table 7. The mean advance rates for both banks

during the 1991-1 992 and 1994-1 995 periods were 0.36 and 0.41 cm/yr. respectively.

Mean retreat rates and their standard deviations were somewhat higher than advance

rates during both sample periods.. This may be explained by the fact that whereas

encrusting growth of corals on the Flower Garden Banks proceeds at a relatively constant

rate, their tissue retreat or death, which can be attributed to a variety of causes, may

occur at a higher and more variable rate (Gittings et al., 1992). During the 1991 -1 992

period, both advance and retreat rates of encrusting growth in D. strigosa at the East

Flower Garden Bank were greater than at the West Flower Garden Bank. Comparative

advance and retreat rates for the combined banks during the 1994-1 995 period were very

close.

Mean advance and retreat rates for encrusting growth in M. annularis at the

East and West Flower Garden Banks are shown in Table 8. The mean advance rate for

the combined banks during the 1991-1 992 period was 0.34 cm/yr. As in the case of

0. strigosa, the mean retreat rate for the combined banks was somewhat greater for this

period (-0.46 cm/yr). Differences in both advance and retreat rates between the two

banks were small.

39
Table 5. Net growth rates of Dip/one strigosa.

Table 6. Net growth rates of Montastrea annulenis.

Table 7. Mean advance and retreat rates of Diploria strigosa.

Table 8. Mean advance and retreat rates of Montastrea annulanis.

40

Area Growth Rate (cm/yr) Standard Deviation

East Flower Garden Bank 1991-1992 0.05 1.04

West Flower Garden Bank 1991-1992 0.05 0.33

Both Banks 1991-1992 0.05 0.71

East Flower Garden Bank 1994-1 995 0.18 0.51

West Flower Garden Bank 1994-1995 0.21 0.50

Both Banks 1994-1995 0.20 0.51

Area Growth Rate (cm/yr) Standard Deviation

East Flower Garden Bank 1991-1 992 -0.05 0.52

West Flower Garden Bank 1991-1992 0.07 0.68

Both Banks 1991-1992 0.01 0.60

A rea Advance

Rate (cmiyr)

Standard

Deviation

Retreat Rate

(cmlyr)

Standard

Deviation

East Flower Garden Bank 1991 -1992 0.45 0.27 -0.70 1.16

West Flower Garden Bank 1991-1992 0.30 0.19 -0.28 0.16

Both Banks 1991-1992 0.36 0.24 -0.42 0.68

East Flower Garden Bank 1994-1 995 0.41 0.18 -0.58 0.69

West Flower Garden Bank 1994-1995 0.42 0.18 -0.55 0.82

Both Banks 1994-1995 0.41 0.18 -0.56 0.75

A rea

Advance

Rate (cmlyr)

Standard

Deviation

Retreat Rate

(cm/yr)

Standard

Deviation

East Flower Garden Bank 1991-1992 0.29 0.14 -0.53 0.44

West Flower Garden Bank 1991 -1992 0.40 0.25 -0.38 0.74

Both Banks 1991-1992 0.34 0.21 -0.46 0.59
3.3.3 Retreat to Advance Ratios

Retreat to advance ratios are useful for the determination of net tissue gain or

loss and are derived from mean retreat and advance rates. Values of retreat to advance

ratios above 1.0 are indicative of net tissue loss; those below 1.0 indicate net tissue gain.

Figure 22 shows the ratios of tissue lost to tissue gained forD. strigosa during the 1991-

1992 and 1994-1 995 periods and for M. anna/ails during the 1991-1 992 period.

Retreat to advance ratios for 0. strigosa during the 1991-1 992 and 1994-1995

periods were below 1.0 at both East and West Flower Garden Banks study sites,

indicating net tissue gained for this species at all permanent stations. During the

1991-1 992 period, the retreat to advance ratios for M. anna/ads at both sites were above

1.0, indicating net tissue loss at those stations selected for analyses. As mentioned in

Sections 2.5 and 3.3, these data may be a result of sampling error.

3.4 REPETITIVE QUADRATS

3.4.1 1992 Survey

A total of 72 stations from the East and West Flower Garden Banks were

analyzed in permanent 8 m quadrat station images collected in 1992. Percent coral

cover at the East Flower Garden Bank averaged 50.6% overall, and ranged from 14% to

82% (Table 9). Coral cover at the West Flower Garden Bank averaged 48.0% overall,

and ranged from 24% to 68% (Table 10). Bleaching was observed on colonies at both

banks. The mean percent cover of bleached corals at the East and West Flower Garden

Banks during 1992 was 3.4% and 3.8%, respectively. Observations of growth in identified

colonies far exceeded observations of retreat, bleaching, and disease (Table 11 and

Appendix C, Tables C.1 and C.2).

3.4.2 1994 Survey

A total of 76 stations from the East and West Flower Garden Banks were

analyzed in permanent 8 m2 quadrat station images collected during the 1994 field effort.

Percent coral cover at the East Flower Garden Bank coral coveraveraged 49.3% overall,

and ranged from 20% to 87% (Table 9). Coral cover at the West Flower Garden Bank

averaged 45.1% overall, and ranged from 15% to 83% (Table 10). Average percent

cover of bleached corals at the East and West Flower Garden Banks during 1994 was

3.0% and 3.4%, respectively. Observations of growth in identified colonies far exceeded

observations of retreat, bleaching, and disease (Table 12 and Appendix C, Tables C.3

and C.4).

3.4.3 1995 Survey

A total of 75 stations from the East and West Flower Garden Banks were

analyzed in permanent 8 m2 quadrat station images collected during the 1995 field effort.

Percent coral cover at the East Flower Garden Bank averaged 50.2% overall, and ranged

from 10% to 84% (Table 9). Coral cover at the West Flower Garden Bank averaged

47.4% overall, and ranged from 19% to 75% (Table 10). Average percent cover of

bleached corals at the East and West Flower Garden Banks during 1995 was 2.7% and

41
aP0 DEFG Montastre

WFG Montastr

EFG Diploria s

o WFG Diploria s

Figure 22. Retreat to advance ratios (total coral tissue lost divided by tota' tissue gained) of Montastrea annularis from 199

strigosa from 1991 - 1992 and 1994 - 1995 at the East and West Flower Garden Banks study sites. Dotted line 

where net tissue change between sample periods is zero. 1991-1992 1994-1 995
43

CSA

Station

No.

TAM U

Station

No.

% Coral Cover Change in %

Coral Cover

(1992- 1995)

% Bleached Coral Cover

1992 1994 1995 1992 1994 1995

I 173 76 20 51 -25 0 1 2

2 22 65 7 4

4 51 57 37 60 3 6 1 0

5 112 28 43 24 -4 2 5 I

6 61 53 54 50 -3 2 1 5

7 150 32 41 33 1 3 2 2

8 37 40 47 53 13 7 2 1 9 101 4g 3

10 58 34 60 61 27 3 3 4

11 70 44 60 54 10 2 1 4

12 33 47 32 49 2 1 0 2

13 49 25 71 18 -7 9 2 1 14 43 49 35 63 14 7 5 4

15 21 39 46 50 11 8 1 2

16 39M 66 65 67 1 0 2 2

18 18 61 49 68 7 3 1 1 19 19 81 43 65 -16 0 2 2

20 7 82 24 84 2 2 1 1 21 155 76 77 59 -17 1 2 3

22 14 71 46 68 -3 2 3 1 23 5 74 35 81 7 3 5 1 24 52 54 77 64 10 7 1 I

27 36 39 50 18 -21 27 6 9

28 36M 44 87 45 1 2 1 3

29 50 14 40 10 -4 4 2 2

30 67 35 67 25 -10 2 1 2

31 41 59 45 58 -1 2 3 3

32 26 38 53 26 -12 2 4 0

33 8 71 32 75 4 5 0 2

Table 9. Percent coral cover at East Flower Garden Bank repetitive 8 m2 stations during 1992,

1994, and 1995. Values were derived from one estimate per station per survey period.

Shaded areas were not used in calculations of mean cover, standard deviation, etc.,

because slides were missing or not useful in one of the data sets. Also shown is the

percent cover of bleached corals at repetitive stations during 1992, 1994, and 1995.
Table 9. (continued).

44

CSA

Station

No.

TAMU

Station

No.

% Coral Cover Change in %

Coral Cover

(1992-1995)

% Bleached Coral Cover

1992 1994 1995 1992 1994 1995

34 28 41 42 55 14 1 2 3

35 81 22 65 17 -5 2 12 7

36 82 44 57 43 -1 1 2 1 37 106 60 42 50 -10 0 11 9

38 134 50 42 58 8 3 6 2

39 151 50 41 40 -10 0 4 3

40 156 63 53 66 3 1 4 4

31 48 1 4 62 1 65 a 4 2

75 62 2

Mean 50,6 49.3 50.2 -0.3 3.4 3.0 2.7
Table 10. Percent coral cover at West Flower Garden Bank repetitive 8 m2 stations during 1992,

1994, and 1995. Values were derived from one estimate per station per survey period.

Shaded areas were not used in calculations of mean cover, standard deviation, etc.

because slides were missing or not useful in one of the data sets. Also shown is the

percent cover of bleached corals at repetitive stations during 1992, 1994, and 1995.

45

CSA

Station

No.

TAM U

Station

No.

% Coral Cover Change in %

Coral Cover

(1992- 1995)

% Bleached Coral Cover

1992 1994 1995 1992 1994 1995

1 149 55 60 44 -11 2 2 3

2 266 32 66 34 2 2 3 4

3 119 38 49 30 -8 6 11 2

4 31M 67 41 75 8 0 0 3

5 246 2 2

6 397 39 20 38 -1 2 5 1 7 247 26 78 20 -6 3 2 2

8 375 46 22 61 15 5 6 7

9 386 37 18 39 2 4 2 2

10 373 63 46 42 -21 3 3 0

11 341 55 32 58 3 4 4 4

12 329 47 23 51 4 3 7 8

13 332 36 38 36 0 9 8 6

14 32M 24 47 19 -5 7 5 2

15 232 3,3 8 2

16 239 49 51 45 -4 6 3 4

17 240 53 47 54 1 7 I 2

18 185 51 40 63 12 2 4 1 19 350 3 3

20 346 47 44 51 4 4 4 I

21 279 48 80 42 -6 5 3 4

22 243 59 38 49 -10 3 2 2

23 310 57 47 54 -3 0 4 7

24 249 52 38 55 3 3 3 4

25 226 68 55 64 -4 1 3 6

26 285 43 83 43 0 4 1 6

27 366 61 66 55 -6 12 5 4

28 368 '3 6 1 29 230 56 46 56 0 1 4 0
Table 10- continued)

* Stations not renumbered during the present study.

46

CSA

Station

No.

TAMU

Station

No-

% Coral Cover Change in %

Coral Cover

(1992-1995)

% Bleached Coral Cover

1992 1994 1995 1992 1994 1995

30 311 45 44 60 14 1 1 1 31 229 30 15 33 3 1 3

32 189 58 40 46 -12 0 2 2

33 349 44 45 50 6 9 8 3

34 333 50 51 51 1 2 5 1 35 215 41 19 .53 12 2 2 2

36 214 54 62 46 -8 3 4 0

37 NEW 40 2 11

38 NEW 49 46 1 0

39 NEW 26 1 40 NEW 31 3

* 231 55 51 -4 4 3

* WFGNT 56 2

Mean 48.0 45.1 47.4 -47 3.8 3.4 3.4
Table 11. Observations of growth, retreat, coral bleaching, and disease at permanent

8 m2 quadrat stations photographed during the 1992 field effort at the East and

West Flower Garden Banks. Data are in number of observations in all quadrat

stations without regard to the sizes of areas affected. "New disease"

occurrence is the number of colonies infected since the last sampling period.

Mortality is the number of colonies exhibiting mortality since the last sampling

period.

Table 12. Observations of growth, retreat, coral bleaching, and disease at permanent

8 m2 quadrat stations photographed during the 1994 field effort at the East and

West Flower Garden Banks. Data are in number of observations in all quadrat

stations without regard to the sizes of areas affected. "New disease"

occurrence is the number of colonies infected since the last sampling period.

Mortality is the number of colonies exhibiting mortality since the last sampling

period.

47

Change Cause Occurrence Mortality

Growth - 2,157 - Retreat, Bleaching,

and Disease

unknown cause 85 85

algae mediated 692 0

algae/sediment 28 0

new disease 1 1 bleaching 91 18

Change Cause Occurrence Mortality

Growth - 1,913 - Retreat, Bleaching,

and Disease

unknown cause 147 147

algae mediated 729 729

algae/sediment 28 28

new disease 0 0

bleaching 24 15
3.4%, respectively. Observations of growth in identified colonies far exceeded

observations of retreat, bleaching, and disease (Table 13 and Appendix C, Tables C.5

and C.6).

Table 13. Observations of growth, retreat, coral bleaching, and disease at permanent

8 m2 quadrat stations photographed during the 1995 field effort at the East and

West Flower Garden Banks. Data are in number of observations in all quadrat

stations without regard to the sizes of areas affected. "New disease"

occurrence is the number of colonies infected since the last sampling period.

Modality is the number of colonies exhibiting mortality since the last sampling

period.

3.4.4 1992 to 1995 Period

Coral growth was clearly identifiable in 8 m2 quadrat station images collected

during 1992, 1994, and 1995, and included examples of both unimpeded encrusting

growth and interspecific competition between several species. Numbers of observations

of coral growth far exceeded observations of coral bleaching, disease, and retreat during

this period. Occurrences of coral colony retreat, bleaching, and disease were evident in

quadrat images but causes were often difficult to conclusively identify due to the large

scale of the overall quadrat images and the length of time between sample photographs.

Occurrences of coral bleaching were much higher in quadrat images collected during the

1995 field effort than those from 1992 and 1994 (Figure 23). Mortality associated with

bleaching observed in 1992 and 1994 quadrats was minimal. The hydrocoral, Millepora

alcicomis, was the predominant species observed with bleached areas in 1992, 1994,

and 1995 quadrat images. Occurrences of coral disease were significantly higher in 1995

quadrat images than in 1992 and 1994 (Figure 24). This may be due to differences in

the interpretation of disease categories (Table 13) during analysis that were originally set

up during the previous monitoring program. This ambiguity was exacerbated when

examining very small colonies within the 8 rn2 quadrats.

3.5 VIDEO TRANSECTS

Video transects filmed during the 1994 and 1995 field efforts followed the

same 100 m (328 ft) study site boundary lines and relative directions as those filmed

during the previous monitoring study. Because of the displacement of the boundary lines,

due to prevailing currents and the rough topography of the reef, it was estimated that only

48

Change Cause Occurrence Mortality

Growth - 2,138 - Retreat, Bleaching,

and Disease

unknown cause 19 19

algae mediated 43 43

algae/sediment 0 0

new disease 317 234

bleaching 429 111
Figure 23. Coral bleaching observed in 8 m2 quadrats, 1992, 1994, and 1995.

49
250 - 200 - 0) Lii z0o 150 - C-) LL0 100 - z 50 - 1992 1994 1995 YEAR E Disease w

Disease w

Figure 24. Numbers of colonies in permanent Sm2 quadrat stations with disease during the 1992, 1994, and 1995 field effo

banks were combined.
20% (10 m [33 if] at each end) of the 100 m (328 if) transects were comparable between

the 1994 and 1995 field efforts.

3.5.1 East Flower Garden Study Site

The relative condition of the reef observed within these transects was good,

with no evidence of widespread coral disease or mechanical damage. Coral bleaching

was observed in both 1994 and 1995 transects. During both years, small bleached areas

on coral colonies were observed scattered throughout both transects. Some degree of

temporal variability in the extent of bleaching observed on individual colonies was noted.

Sections 3.5.1.1 and 3.5.1.2 are descriptions of affected areas observed on the two video

transects filmed during 1994 and 1995 field efforts.

3.5.1.1 Transect I - Northwest to Northeast Site Boundary Line

0 m: A D. strigo.sa colony had a central dead area in 1994; this area had

infilling growth and formation of a colony of P. astreoides in 1995.

1 through 92 m (3.3 through 302 ft): No significant changes in the coral

colonies were observed during 1994 and 1995. A bleached M. alcicomi,s

colony was similar in appearance in both surveys.

93 m (305 if) : A D. strigo.sa colony with a dead area and a bleached area

was observed on a colony of M. annularis. These affected areas appeared

to be similar in size in both 1994 and 1995.

94 through 100 m (308 through 328 if): No significant changes in the coral

colonies were observed during 1994 and 1995.

3.5.1.2 Transect 2 - Northeast to Southeast Site Boundary Line

0 through 9 m (0 through 29 ft): No significant changes in the coral

colonies were observed during 1994 and 1995.

10 m (33 if): A bleached area was observed on a colony of M. annularis in

1994. This affected area appeared to be very reduced in size in 1995.

11 through 15 m (36 through 49 if): No significant changes in the coral

colonies were observed during 1994 and 1995.

16 m (52 if): A paling area on a colony of M. annularis was observed in

1994. This affected area appeared to increase in size (bleaching) in 1995.

17 through 82 m (56 through 269 if): No significant changes in the coral

colonies were observed during 1994 and 1995.

83 m (272 if): A dead area in the center of a D. strigosa colony was

observed in both 1994 and 1995.

51
84 through 86 m (276 through 282 ft): No significant changes in the coral

colonies were observed during 1994 and 1995.

87 m (285 ft): A round paling area was observed on top of a colony of D.

strigosa in 1994. This area appeared to increase in size (bleaching) in

1995.

88 through 92 m (289 through 302 ft): No significant changes in the coral

colonies were observed during 1994 and 1995.

93 m (305 ft): Some bleaching and algae growth was observed on a colony

of M. annular/s in 1994. This affected area appeared to increase in size in

1995.

94 through 100 m (308 through 328 ft): No significant changes in the coral

colonies were observed during 1994 and 1995.

3.5.2 West Flower Garden Bank Study Site

Similar to the East Flower Garden Bankstudysite, the general condition of the

reef observed within the two video transects was good. Only 10% (5 m at each end of

the boundary lines) of the transects were comparable between 1994 and 1995. Scattered

bleaching was observed in both transects during both field efforts. From comparable

sections of the transects, both increased and decreased bleaching was observed between

1994 and 1995.

3.5.2.1 Transect I - Southeast to Southwest Site Boundary Line

100 through 95 m (328 through 312 ft): No significant changes in coral

colonies were observed during 1994 and 1995.

94 through 6 m (308 through 20 ft): Areas were not comparable between

1994 and 1995.

5 through 0 m (16 through 0 ft): No significant changes in coral colonies

were observed during 1994 and 1995.

3.5.2.2 Transect 2 - Southwest to Northwest Site Boundary Line

100 through 14 m (328 through 46 ft): No significant changes in coral

colonies were observed during 1994 and 1995.

13 m (43 ft): A bleached area was observed on a colony of M. alcicomis.

This affected area appeared to be similar in appearance and size in 1995.

10 m (33 ft): A dead area was observed on top of a colony of M. alcicomis

in 1994. This affected area increased in size along with complete

bleaching of the colony in 1995.

52
8 m (26 if): A bleached area was observed on top of a colony of D.

strigosa in 1994. In 1995, the bleached area appeared to moderate to a

pale area in 1995.

. 6 m (20 ft): A colony of M. alcicomi.s was completely bleached in 1995.

5 through 0 m (16 through 0 ft): No significant changes in the coral

colonies were observed during 1994 and 1995.

3.6 ANCILLARY MEASUREMENTS

3.6.1 Water Profiles

Discrete measurements of temperature, salinity, dissolved oxygen, and light

made from near surface (1 m [3.3 if]) and near bottom depths during the 1994 and 1995

field efforts are listed in Appendix D, Tables D.1 and D.2. In 1994, near surface and

near bottom temperatures were rather homogeneous and ranged from 28.8°C to 29.3°C.

Temperatures were slightly higher in 1995, ranging from 28.9°C to 30.3°C. Salinity and

dissolved oxygen measurements were relatively homogeneous during both field efforts.

3.6.2 Recording Thermometers

Water temperature profiles collected by recording thermometers at the East

and West Flower Garden Bank study sites are shown in Figure 25. Due to equipment

failure, data sets were incomplete at both sites. Minimum and maximum temperatures

recorded at both study sites are listed in Table 14.

Table 14. Minimum and maximum temperatures recorded on the East and West Flower

Garden Banks during 1993 - 1995.

a = East Flower Garden Bank data collected after 1 September 1993.

b = West Flower Garden Bank data collected after 28 February 1994.

c = West Flower Garden Bank data collected from January-March, 1995.

53

Year

Temperatures (°C)

East Flower Garden Bank West Flower Garden

Bank

Minimum Maximum Minimum Maximum

1993 18.7 29.11 n/a n/a

19.0 29.5 22.1 28.9

1995c 18.1 30.0 18.0 22.3
/ 28 - a) - .22- aE 2016 3028 a) .22 a. E20. 18 - 16 East Flower Garden Bank West Flower Garden Bank 0) a- wCl) 0 C., 0) >0z0 Figure 25. Seafloor temperature data on the Flower Garden Banks, September 1993 to August 1995.
3.6.3 Recording Light Meters

Total daily irradiance (expressed in mol m2 day1) at the two study sites and

the surface reference station (HI 389) during the period from 24 August to 12 November

1995 (Period 1) is graphically shown in Figure 26 and 17 November 1995 to 2 March

1996 (Period 2) in Figure 27. Temporal trends between the 3 m (10 ft) are quite similar,

with slightly lower irradiance values collected at the deeper West Flower Garden Bank

site. Mean percent transmission during Period 1 was 17.7% (East Flower Garden Bank)

and 12.7% (West Flower Garden Bank) (Figure 28). Data were not collected from the

West Flower Garden Bank site during Period 2 due to equipment failure. Mean percent

transmission for the East Flower Garden Bank site during this period was 8.7%

(Figure 29).

55
'6040- 2 30- C 20 Ct >1 0 0- Ct 0I Figure 26. Total daily irradiance on the East and West Flower Garden Banks from August to November 1995 (Period 1).
LI-COR LIGHT DATA - FLOWER GARDEN BA

Figure 27. Total daily irradiance on the East Flower Garden Bank from November 1995 to February 1996.
Figure 28. Percent of surface light transmission to the East and West Flower Garden Banks from August - November 1995
LI-COR LIGHT DATA - FLOWER GARDEN BA

Figure 29. Percent of surface light transmission to the East Flower Garden Bank from November 1995 to February 1996
4.0 DISCUSSION

The following section includes a discussion of results obtained during this

study and comparisons of these results with data collected during previous monitoring

studies on the Flower Garden Banks. Specific topics include coral reef community

structure and coral growth rates and patterns, loss of coral pigmentation (bleaching), coral

diseases, and present environmental threats to the banks from offshore oil and gas

activities, and recreational diving. Based on these impact producing factors, a

recommendation for a more extensive and effective water quality monitoring plan for the

Flower Garden Banks is included.

4.1 CORAL COMMUNITY STRUCTURE - STATUS AND TRENDS

Total percent coral cover, as estimated from stratified random photographic

transects at the East and West Flower Garden Banks study sites, was 48.2% and 44.1%,

respectively. These estimates are very similar to those from the 1989-1991 monitoring

study (46.0% on the East Flower Garden Bank and 46.5% on the West Flower Garden

Bank) (Gittings et al., 1992). Significant spatial and temporal differences in percent coral

cover were not measured in the 1989-1991 study. In the present study, total percent

coral cover was significantly greater at the East Flower Garden Bank compared to the

West Flower Garden Bank during 1992, 1994, and 1995. Total coral cover at both banks

combined was greater in 1994 and 1995 than in 1992.

Differences in results from the two studies were also observed in comparisons

of percent cover among individual coral taxa. For example, from the 1989-1991 study,

percent cover estimates of D. strigosa and S. siderea were greater at the West Flower

Garden Bank study site than the East Flower Garden Bank study site, and percent cover

estimates of P. astreoides and Agaricia spp. were greater at the East Flower Garden

Bank than the West Flower Garden Bank. From the present study, percent cover

estimates of only P. astreoides were shown to be significantly greater between banks

during various years (Table 1). Overall, the pattern of annual differences in percent

cover and relative dominance of corals on the Flower Garden Banks do not suggest

significant spatial or temporal changes in their population levels.

Coral species diversity and evenness based on colony counts were statistically

similar between banks. Mean coral species diversity and evenness were statistically

greater in 1992 compared to 1995. Diversity and evenness values collected during the

present study were generally similar to those collected during the 1989-1 991 study

(Gittings et al., 1992). Coral species diversity and evenness based on coral cover were

not statistically different between banks and years. Diversity and evenness values

collected during the present study were also generally similar to those collected during

the 1989-1991 study. These results indicated that there were no temporal trends within

the two study sites.

4.2 CORAL GROWTH - STATUS AND TRENDS

Mean accretionary growth rates of M. annularis, measured by growth spikes

within permanent stations, were very similar between the East and West Flower Garden

61
Banks (5.7 and 5.5 mm/yr, respectfully) during the 1994-1 995 survey period. Mean

estimates of accretionary growth rates of this species during the 1989-1991 monitoring

study (East Flower Garden, 7 mmlyr; West Flower Garden, 6 mm/yr) fell within the range

of values determined during the 1994-1 995 survey period.

Accretionary growth rates of M. annularis, as measured by linear growth

measurements of sectioned coral core samples collected during the 1995 field effort, were

comparable between the East and West Flower Garden Banks during the period between

1973 and 1995 (6.8 and 8.1 mm/.yr, respectfully). These data also fell with the range of

values determined from similar core samples collected during previous studies on the

banks (Table 15).

Table 15. A comparison of accretionary growth rates of Montastrea annularis estimated

from sectioned core samples collected during recent studies of the East and

West Flower Garden Banks.

* Measurements in this study were made by integrating annual growth increments using

planimetry rather than the standard linear measurement of single polyps along growth

axes.

During the 1994 field effort, it was discovered that the majority of permanent

growth stations which had been established during previous studies within both study

sites were unsuitable for further use. The rejection of encrusting growth stations was

primarily due to the dynamic nature of the coral-reef rock margins. In accretionary growth

stations, it was found that the growth spike had loosened within the corallum, the

surrounding coral tissue had died around the spike or encrusted over the spike. These

examples suggest that there may be a limit to the length of time that permanent stations

may be used for studies which involve either direct measurements or repetitive

photography.

Since all permanent encrusting growth stations were re-established during the

1994 field effort, encrusting growth data were not available for the 1992-1 994 period. In

addition, approximately 60% of the photographs of these stations collected during 1992

could not be analyzed. Because of the high variability in these data and their relative

small sample size, no statistical comparisons of entrusting growth between the 1991-

1992 and 1994-1 995 periods were attempted.

Net encrusting growth rates of M. annularis during the 1991-1 992 period and

D. strigosa during both 1991-1992 and 1994-1995 survey periods fell within the range of

measurements estimated during the 1989-1991 monitoring study for the combined East

62

Investigator Growth Period Mean Growth Rate # Cores

CSA (present study) 1973-1 995 7.4 mm/yr 4

Gittings et al. (1992) 1910-1 989 6.6 mm/yr* 4

Kraemer (1982) 1964-1980 7.6 mmlyr 4

Hudson and Robbin (1980) 1910-1 979 8.3 mm/yr 12
and West Flower Garden Banks (Gittings et al., 1992). Substantial differences in net

growth rates of 0. strigosa were observed between 1991-1992 and 1994-1 995 survey

periods at both East and West Flower Garden Banks. Because individual advance and

retreat rates were comparable, these data indicate that there were greater numbers of

coral borders within these growth stations which demonstrated retreat instead of advance

during the 1991-1992 period. These differences may be attributed to sampling error

caused by incorrect camera angle at the time of data collection and/or physical problems

with the growth station's coral tissue-reef rock border. Net growth rates were positive for

D. strigosa at the East and West Flower Garden Banks during the 1991-1 992 and 1994-

1995 survey periods. Net growth rates for M. annularis were negative at the East Flower

Garden Bank and positive at the West Flower Garden Bank during the 1991-1 992 period.

Individual coral advance and retreat rates were comparable between the two

survey periods and similar to rates estimated during the 1989-1991 monitoring study

(Gittingset al., 1992). From these data, it was found that coral retreat rates often

exceeded advance rates. This was also determined in previous studies on the Flower

Garden Banks and Florida Keys (Abbott, 1979; Gittings, 1988; Gittings et al., 1992).

Retreat to advance ratios for D. strigosa during this study were also

comparable to those observed during the 1989-1 991 monitoring study. Since all

permanent encrusting growth stations were re-established during the 1994 field effort, the

similar ratios calculated from the 1994-1 995 survey period indicate that encrusting growth

patterns for this species at both study sites have remained consistent. Retreat to

advance ratios forM. annularis were above 1.0 during the 1991-1992 period1 indicating

net tissue loss. Ratios calculated for this species during the 1989-1 991 monitoring study

were below 1.0. Since encrusting growth measurements for this species were only

required for data collected during 1992, it is not possible to ascertain whether these data

are correct or in error as a result of the condition of the permanent stations or incorrect

camera angle during the time of data collection.

4.3 CORAL BLEACHING

Coral bleaching is the localized or widespread loss of pigmentation in coral

tissues and is considered a stress response to one or more abnormal environmental

conditions (Figure 30). The loss of pigmentation is due to the loss of symbiotic algae

(zooxanthellae) by expulsion or migration of the algae out of the coral tissue, degradation

of the algae in situ, or by the loss of pigmentation of the algae itself. Conditions reported

to cause bleaching in corals include high/low temperatures, high/low light levels, high

levels of ultraviolet radiation, high/low salinity, sub-aerial exposure, excessive

sedimentation, storm shock, and anthropogenic sources such as petroleum hydrocarbons

and oil dispersants (Hagman and Gittings, 1992). The effects of bleaching on corals may

include loss of reproductive activity, significantly reduced growth rate, and tissue loss.

63
S

Figure 30. Coral bleaching in Montastrea annularis observed during the

1995 monitoring survey at the Flower Garden Banks.

Coral bleaching was observed in repetitive quadrat photographs taken in 1992,

1994, and to a much greater extent during 1995. The extent of bleaching within the study

sites was even more pronounced in November 1995, when the two sites were visited to

conduct periodic maintenance of recording light meters. Bleaching during these periods

coincided with periods of elevated bottom temperatures (above 30°C) which are not

uncommon during late summer. As observed in November 1995, the effects of bleaching

may appear to persist long after temperatures drop below 30°C. Coral bleaching events

have been documented on the Flower Garden Banks on numerous occasions. Data

collected during the 1989-1991 monitoring study showed that coral bleaching events

occurred following summer water temperature maxima when bottom temperatures

exceeded 30°C (Hagman and Gittings, 1992; Gittings et al., 1992). Temperature data

collected during the 1994 and 1995 field efforts also showed temperatures in excess of

30°C. This threshold temperature is also considered representative for reefs within the

tropical western Atlantic and tropical eastern Pacific. As in historical observations at the

Flower Garden Banks, the species most affected by the phenomenon were M. alcicornis

and M. cavernosa. Other bleached species included M. annularis, Agaricia spp., P.

a,streoides, and S. siderea.

Coral mortality associated with coral bleaching at the Flower Garden Banks is

low. Colonies that exhibited bleaching usually sustained only minor tissue loss (1992 -

0.5%; 1994 - 0.2%; 1995 - 2.8%). Hagman and Gittings (1992) found that bleaching often

recurred in certain colonies in similar patterns or areas within the colonies. Mortality,

however, appeared to be no higher in colonies which exhibited recurrent bleaching than in

other colonies.

64
4.4 DISEASES IN REEF BIOTA

Coral "disease, usually resulting in necrosis of the affected coral tissue,

remains the most serious natural threat to corals at the Flower Garden Banks. Data

collected from repetitive 8 m2 quadrat stations showed evidence of coral tissue necrosis

attributed to "ridge mortality" (Abbott, 1979), a progressive disease that first spreads

along the tops of ridges on brain corals, especially D. strigosa, and unidentified diseases.

No evidence of "black-band" or "white-band" diseases (Antonius, 1981), caused by the

spread of bacteria or viruses, were observed on corals during the contract period. This

was also noted during the previous monitoring study (Gittings et al., 1992). The

percentage of coral colonies observed on repetitive quadrat stations affected by diseases

were significantly higher in 1995 than 1994 and 1992. Similarly, numbers of colonies

affected in 1995 photographs were also appreciably higher than during the previous

monitoring study, which ranged from approximately 10 to 25 colonies per bank per

survey. It is not known whether the increased numbers of coral colonies affected by

diseases can be attributed to the same environmental conditions on the banks (e.g.,

elevated water temperatures during the summer and early autumn) which led to

significant coral bleaching during this period. Despite the marked increase observed in

1995, the number of colonies exhibiting disease was low when compared to the 3,902

colonies analyzed in quadrat photographs (6.0% occurrence).

4.5 PRESENT ENVIRONMENTAL THREATS

The Flower Garden Banks were officially designated as a National Marine

Sanctuary in January 1992. Regulations associated with National Marine Sanctuary

status have been designed to protect the banks from many impact producing factors.

Despite these regulations, certain environmental threats to the banks remain. These

include negative impacts resulting from accidental oil spills and chronic, low-level impacts

associated with increases in the numbers of recreational divers who visit the banks each

year.

4.5.1 Oil Spills

Oil and gas exploration and production continues in the vicinity of the Flower

Garden Banks. Potential sources of petroleum input to the offshore marine environment

of the Flower Garden Banks include natural seeps, marine transportation, and offshore

operations for the exploration and production of hydrocarbons. Accidents related to

offshore operations that result in the release of oil include well blowouts and

transportation incidents.

Blowouts are defined as the accidental and uncontrolled release of petroleum

hydrocarbons resulting from improperly balanced well pressures. Blowouts can occur

during any phase of oil development. Accidental oil spills can also occur during any

stage of exploration, development, or production, and can be attributed to many causes in

both the oil extraction process and support activities necessary for recovery and

transportation of the resource. In addition to crude oil spills, chemical, fuel oil, and other

oil-product spills can also occur (USD01, MMS, 1995). Most field studies concerning the

effects of petroleum hydrocarbons on coral reef communities conclude that oil imparts

significant negative impacts on shallow-water reef biota (Lewis, 1971; Johannes et al.,

1972; Reimer, 1975: Loya, 1976; Birkeland et al., 1976; Rinkevich and Loya, 1977, 1979;

65
Loya and Rinkevich, 1980; Peters et al., 1981; Bak, 1987; Jackson et al., 1989; Guzma'n

and Jackson, 1991; Keller and Jackson, 1991). Laboratory studies show some variability

in results with respect to effects of petroleum hydrocarbons and oil dispersants on corals

(Lewis, 1971; Reimer, 1975; Birkeland et al., 1976; Elgershuizen and de Kruijf, 1976;

Neff, 1979; Peters et al., 1981; Cook and Knap, 1983; LeGore et al., 1983; Dodge et al.,

1984; Knap et al., 1985; Wyers et al., 1986). Stress responses exhibited by corals to

direct exposure to oil are difficult to assess at sublethal levels, especially when measured

in the field (Fucik et al., 1984). In some cases, the effects or impacts are not evident for

some length of time subsequent to exposure. In general, corals exposed to oil may

reveal elevated susceptibility to mortality, bleaching and infection, and reduced growth

rates and fecundity (Brown and Howard, 1985).

Methods, or options, for responding to offshore spills include mechanical

containment and collection (e.g., skimmers and sorbents), the use of chemical oil

dispersants, and natural removal (involving no cleanup action). Other countermeasures

include burning, sinking, gelling, and enhanced biodegradation (bioremediation).

Generally, oil spills at the Flower Garden Banks and their vicinity could

originate either at the surface or on the seafloor. Because of the depth of the Flower

Garden Banks, surface spills and resultant slicks would produce minimal to negligible

impacts to major reef constituents, such as scleractinian corals, other invertebrates, and

reef fishes. Surface winds and currents would carry spilled oil or fuel away from the

vicinity of the banks in a relatively short time period. Surface slicks could, however,

impact marine mammals, sea turtles, seabirds, certain pelagic fish, and floating marine

plants. An oil spill occurring during the annual coral reproductive spawning period could

also severely impact or entirely destroy the floating spawn. Continental Shelf Associates,

Inc. (1992) conducted an analysis to evaluate potential effects of subsurface oil spilled

from a proposed pipeline in the vicinity of the Flower Garden Banks. Assumptions were

made based upon worst case scenarios from oil spills at three separate locations and

depths. Times chosen for the spill to reach the sensitive areas of the Banks were

selected to predict reasonable arrival times from corresponding current velocities for the

area. A comparison of the estimated water column oil concentrations to acute and

chronic toxicity data summarized in the literature indicated that the effects of an untreated

oil spill from a pipeline would have minimal to non-existent effects on the sensitive benthic

biota of the Flower Garden Banks.

4.5.2 Oil Spill Dispersants

Chemical dispersants are agents designed for reducing the surface tension of

spilled oil on the water surface. Surface oil treated with a dispersant mixes within the

water column as fine droplets and is dispersed by currents. Rationale for treating spilled

oil with chemical dispersants includes the prevention of a concentrated surface slick from

moving into biologically sensitive environments; a reduction of direct impacts of surface oil

to offshore natural resources such as marine birds, marine mammals, sea turtles, and

pelagic fish; or the prevention of surface oil from stranding onshore, thus reducing or

eliminating impacts to important coastal habitats, biological communities, or coastal

facilities.

The key constituents of oil spill dispersants are one or more surface-active

agents termed surfactants (or detergents), which contain both water-compatible and

66
oil-compatible fractions, and in most cases a solvent to reduce viscosity and facilitate

application and dispersal. The surfactants are also classed by chemical charge type,

including anionic, cationic, nonionic, and zwitterionic (containing both positively and

negatively charged groups). Generally, the addition of a dispersant to a slick greatly

reduces the natural energy required to break a surface oil slick apart into droplets. The

size distribution of dispersed droplets within the water column is an important measure of

dispersant effectiveness. Larger droplets tend to resurface, whereas smaller droplets

tend to remain suspended in the water column as a result of turbulent diffusion.

Suspended droplets are transported horizontally by subsurface currents and can diffuse

or be transported into deeper depths. They are eventually removed from the water

column by combining with suspended sediment and other abiotic particles, or becoming

bound to or ingested by biota such as plankton.

Because of the uncertainties associated with vertical transport of oil and

dispersant, the MMS has historically banned their use within the 1-Mile Exclusion Zone of

the Flower Garden Banks. This was felt to be an adequate mitigative measure for

unknown and unquantifiable impacts of the dispersed oil and dispersant to reef biota on

the banks.

Recent studies have reported that dispersed oil was not more toxic to species

found in the Gulf of Mexico than undispersed oil (Fucik et al., 1994; National Research

Council, 1989). Furthermore, studies on the behavior of dispersed oil within the water

column showed that oil was diluted to concentrations of approximately 0.1 ppm at depths

of 10 m (33 ft). At this dilution, the plume was not considered acutely toxic (Mackay and

Wells, 1983).

These data have led to a decision by the Flower Garden Banks National

Marine Sanctuary Office that the application of dispersants may be advantageous to

Sanctuary resources in the event of a surface oil spill (S.R. Gittings, 1995, personal

communication, NOAA). It is felt that an untreated surface spill would be more harmful

than dispersed oil to certain pelagic fish, marine mammals, and sea turtles, due to

elevated concentrations of hydrocarbon vapors associated with a surface spill,

consumption of spilled oil through respiration or ingestion, and direct oiling of animals and

plants. Therefore, the Sanctuary Office approves of the use of oil dispersants on the

Flower Garden Banks when deemed appropriate and conducive by the Federal On Scene

Coordinator. When applied, all efforts must be made to apply the dispersants in water as

deep as possible and as far from the Sanctuary as possible to promote dilution of

dispersed oil and to minimize effects on shallow-water biota. Other factors to be

considered include prevailing weather and sea state, water temperature, characteristics of

the spilled oil, history of the spill, and the risk of spill contact for particular biota. In some

cases, the use of oil dispersants may be avoided, such as during mass spawning periods

for corals and other species.

4.5.3 Operational Wastes

The major operational wastes of concern generated in quantity by offshore oil

and gas exploration and development include produced waters and drilling fluids and

cuttings. Other wastes generated during these activities include drilling waste chemicals,

fracturing and acidifying fluids, and well completion and workover fluids produced during

drilling operations; produced sand, deck drainage, and miscellaneous well fluids

67
generated during production operations; and miscellaneous minor discharges (USD01,

MMS, 1995).

4.5.3.1 Produced Waters

Produced water is defined as the water discharged from the oil and gas

extraction process. It is primarily composed of formation waters (those located in the

permeable sedimentary rock strata), injection water (when used), and various chemicals

added during the oil and water separation process. Because these waters are mixed with

petroleum, they contain variable concentrations of petroleum hydrocarbons, Naturally

Occurring Radioactive Material (NORM), and other toxic chemicals. Current NPDES

permits limit allowable oil and grease levels in produced waters, restrict flow rates, require

chronic, static, aquatic toxicity analyses of produced water effluents, and require

monitoring of produced water discharges (USD01, MMS, 1995).

Currently, there are no oil and gas production platforms close enough to the

Flower Garden Banks to pose a risk of impact from the discharge of produced waters.

Historic monitoring studies of the effects of a platform in the vicinity of the East Flower

Garden Bank showed no detectable effects on the shallow, high-diversity reef. Other

platforms in the area are in relatively deep water, where strong shelf edge currents serve

to disperse discharges. Platforms within the MMS 4-Mile Zone are required to shunt all

discharges to within 10 m (33 ft) of the seafloor as a means to further reduce potential

impacts.

4.5.3.2 Drilling Fluids and Cuttings

The major source of environmental contamination from drilling operations is the

discharge of drilling fluids and cuttings. Drilling fluids are defined as the suspensions of

solids and dissolved materials in a water or oil base which are used in rotary drilling to

remove cuttings from beneath the drill bit, to control well pressure, .to cool and lubricate

the drill string, and to seal the well. Drill cuttings are fragments of rock that are

generated during drilling operations and carried to the surface with drilling fluid.

According to MMS and National Marine Sanctuary requirements, persons

engaged in oil and gas exploration, development, and production in areas outside of the

established no-activity zones and within Sanctuary boundaries must shunt all drill cuttings

and drilling fluids through a downpipe which terminates at a distance of no more than 10

m (33 ft) from the seafloor (15 CFR, Part 922, Subpart L). Due to these regulations,

negative impacts to the Flower Garden Banks resulting from the discharges of offshore oil

and gas operational discharges have not been detected and do not pose a threat to the

bank's biotic communities.

4.5.4 Recreational Diving

Historically, all recreational diving activities on the Flower Garden Banks were

unregulated. Their distance from shore has made visitation to the banks somewhat

difficult and costly for recreational divers. Negative impacts on the banks were

associated with activities such as the anchoring of boats on the live coral reef,

spearfishing, collecting reef biota, and physical damage to living corals by divers

themselves.

68
Historically, the greatest physical impacts to the Flower Garden Banks

associated with recreational diving were due to the anchoring of vessels on live coral

areas of the banks. Permanent mooring lines with surface floats were installed in 1990 at

several locations on the high diversity reef areas of both banks in an effort to reduce

anchor damage. Current Sanctuary regulations prohibit anchoring or otherwise mooring a

vessel greater than 100 ft in length within the Sanctuary boundaries. Vessels less than

100 ft in length are prohibited from anchoring in areas where mooring lines are available.

In areas where there are no mooring lines, these vessels must minimize physical impacts

to the reef by reducing the length of chain or wire rope on ground tackle (15 CFR,

Part 922, Subpart L).

Activities such as spearfishing, collections of reef biota, and destruction,

additions or modifications to the seabed of the Sanctuary are also prohibited. Despite

the protection afforded to the Flower Garden Banks from regulations associated with

Sanctuary status, negative impacts resulting from physical contact between recreational

divers and sensitive reef biota remain an issue of concern. The Flower Garden Banks

have received a marked increase in publicity as a result of their Sanctuary status. This in

turn has brought about an increase in the number of recreational divers that visit the

banks each year. The use of mooring lines tends to focus the numbers of divers within

repetitively used areas and thus increases the probability of localized damage caused by

physical contact with corals and other reef biota, and displacement of certain fish species.

To date, no studies have been conducted to assess the impacts of recreational diving

pressures within the area. Utilization of several alternative mooring line sites for divers

during alternate years may serve to reduce localized pressure on recreational dive sites

on the banks.

4.6 WATER QUALITY PLAN

The physical location of the Flower Garden Banks poses logistical difficulties

for the systematic collection of water quality data. Historical water quality data at the

Flower Garden Banks typically involved discrete collections of water samples or hydrocast

profiles in different locations on the banks. Because of the continental shelf edge location

of the banks, measured concentrations of hydrocarbons, pesticides, and trace metals

from historic collections were typically very low to undetectable. These samples have

provided baseline data of water quality in the area but do not reveal temporal trends in

contaminant concentrations or show evidence of acute events such as spills. Collections

of the American thorny oyster (Spondylu.s arnericanus) were made during the 1970's from

the high diversity coral reef and the algal-sponge zones of the banks for determination of

biological accumulation of hydrocarbons and trace metals in bivalve tissues. These

bivalves are irregularly distributed within these zones and were at times difficult to locate

in sufficient numbers for analyses. Typically, collections were made using Texas A&M

University's submersible DIAPHUS in the deeper waters of the algal-sponge zone.

The design of a water quality monitoring plan for the Flower Garden Banks will

be limited by the budgetary constraints of the monitoring study contract. Field sampling,

as specified in the existing contract, is limited to annual visits. Plans involving extensive

water quality sampling at this frequency are ineffective and collections of live corals or

other reef fauna within the sanctuary boundaries for tissue analyses are not

recommended for long-term studies.

69
The recent installation of recording light meters on the Flower Garden Banks

has necessitated quarterly visitation to both study sites in order to download data and

service the instruments. This service schedule, conducted from a sport diving charter

vessel during a 2-day trip, could also permit cost effective, quarterly collections of water

samples for analyses of hydrocarbons, trace metals, pesticides, and nutrients.

Uncontaminated water samples could be collected using the charter vessel's inflatable

boat during dive operations on each bank. Also, a device for passive in-situ monitoring of

organic contaminants in water is available and suitable for use at the Flower Garden

Banks. This semi-permeable membrane device (SPMD) consists of a thin film of neutral

lipid which is enclosed in thin-walled layflat tubing made of low-density polyethylene.

Lipophilic chemicals such as petroleum hydrocarbons permeate the thin wall of the tubing

and partition into the lipid where they are concentrated. In this manner the SPMDs

function, or uptake contaminants, as an "artificial bivalve" with the exception that

accumulated chemicals are not metabolized. These devices have been successfully used

in studies within both coastal and offshore waters (Prest et al., 1992; Huckins et al., 1993;

Peven et al., 1996). For application at the Flower Garden Banks, a single SPMD would

be contained within a fabricated stainless steel rack at each study site. The racks would

be affixed to the reef rock with masonry bolts in proximity to the recording light meters.

The SPMD's could be collected and replaced at the same time that the recording light

meters are serviced, and thus provide quarterly qualitative records of organic

hydrocarbons (and pesticides) present on the Flower Garden Banks. Collected water

samples would provide single point collection data of concentrations of hydrocarbons and

pesticides to compare to those collected by the SPMD's. A one year feasibility study of

the SPMD's on the banks would determine their practicality and provide a year of

uninterrupted baseline data.

70
5.0 CONCLUSIONS

The results of the analysis of the random transect data collected in 1992,

1994, and 1995 do not suggest significant long-term changes in coral cover or diversity

parameters. Overall estimates of total coral cover, cover of individual species, relative

dominance of individual coral species, and species diversity and evenness are generally

comparable with previous studies within the same study sites. Specific differences in the

estimates made during the present study and previous studies on the banks appear to

result from spatial variability in coral communities and are not considered to represent

trends or deterioration of habitat quality.

Estimates of the growth rates of M. annular/s and 0. strigosa made on the

Flower Garden Banks indicate favorable conditions for both accretionary and encrusting

growth during the study period. Accretionary growth rates of M. annular/s during

1994-1 995 were comparable with estimates from previous studies. The poor physical

condition of all permanent growth stations located during the 1994 field effort necessitated

their re-establishment during this period. Growth estimates, therefore, are only available

for the 1991-1 992 and 1994-1 995 periods. In addition, a large percentage (over 60%) of

photographic data from permanent growth stations collected during the 1992 field effort

were not analyzed because of the condition of individual stations, sampling error caused

by inconsistent camera angle, and inconsistent species selection. As a result, statistical

comparisons of encrusting growth between data representative of the 1991-1992 period

and the 1994-1 995 period were not made. Overall, these observations indicate that

permanent growth stations typically have a finite useable lifespan and must be

abandoned and re-established as necessary to maximize accuracy of growth rate

estimates. Encrusting growth estimates made from re-established stations during the

1994-1 995 period were comparable to those of previous studies, and showed relatively

high rates of tissue advance and net tissue gain during this period.

Coral growth was also clearly identifiable in 8 m2 photographic quadrat stations

during the study period. The number of observations of coral growth far exceeded

observations of retreat at both study sites during this period.

Coral bleaching was observed on 8 m2 photographic quadrats collected during

1992, 1994, and 1995. The extent of bleaching observed at the two study sites was most

pronounced during the 1995 field effort. Minor coral bleaching events have been

documented on the Flower Garden Banks on numerous occasions. Both historic and

present documentation of bleaching events appear to coincide with periods of elevated

sea water temperatures of 30'C or above, which may be common during late summer.

Susceptibility to bleaching in corals also appears to be somewhat species-specific and

perhaps colony-specific. Data from 8 m2 photographic quadrats suggest that coral

bleaching may not necessarily result in coral tissue mortality. Colonies that exhibited

bleaching during the present study usually sustained only minor tissue loss (1992, 0.5%;

1994, 0.2%; 1995 2.8%).

Potential threats to the Flower Garden Banks associated with offshore

petroleum hydrocarbon exploration and development remain. These include oil spills

from tankers, platforms, and pipelines, associated spill clean-up efforts, and chronic

71
effects from the discharge of produced waters and drilling fluids. Accidents involving the

release of oil in the vicinity of the Flower Garden Banks represent the most serious threat.

Presently, it is the opinion of the Flower Garden National Marine Sanctuary management

that surface oil spills in the vicinity of the banks should be, under proper conditions,

treated with oil dispersants to promote the dilution of surface oil in order to mitigate

harmful effects to certain pelagic fish, marine mammals, and sea turtles. Public

awareness of the Flower Garden Banks, associated with their designation as a National

Marine Sanctuary, has increased the public demand for visitation and access by means of

recreational diving. Present threats associated with recreational diving on the Flower

Garden Banks include small boat anchor damage to corals and other reef biota, and

physical damage to the coral community by divers themselves. The maintenance of

mooring buoys for small vessels may reduce overall anchor damage to the banks but

tends to focus the number of divers within specific locations. Altemation of mooring buoy

availability may be the best solution for minimizing damage associated with recreational

diving.

72
6.0 LITERATURE CITED

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Garden Banks, northwest Gulf of Mexico. M.S. thesis, Texas A&M University,

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Western Atlantic Reefs. Bull. Mar. Sci. 34(3):461-476.

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Gardens: A compendium of information. U.S. Department of the Interior,

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Orleans, LA. OCS Study MMS 85-0024. 103 pp.

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Bright, T.J., S.R. Gittings, and R. Zingula. 1991. Occurrence of Atlantic reef

corals on offshore platforms in the northwestern Gulf of Mexico.

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incident at the East Flower Garden Bank coral reef. Report to Mobil Producing

Texas and New Mexico, Inc., Offshore Texas Division. The Woodlarids, TX.

25 pp.

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"A", Lease OCS-G-2759, High Island Area, South Extension, East Addition,

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Texas and New Mexico, Inc., The Woodlands, TX. 353 pp. + app.

Continental Shelf Associates, Inc. 1990. Environmental monitoring program for

Exploratory Well #1, Lease OCS-G-6264, High Island Area, South Extension,

East Addition, Block A-401, near the West Flower Garden Bank. Report to

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Texaco's proposed pipeline on the biota of the East Flower Garden, West

Flower Garden, Rankin, and MacNeil Banks. Report to Texaco, New Orleans,

LA. 27 pp.

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coral Diploria strigosa. Coral Reefs 3:191-198.

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to the stony coral Madracis mirabi/is. Mar. Poll. Bull. 7(2):22-25.

Fucik, K.W., T.J. Bright, and K.S. Goodman. 1984. Measurements of damage, recovery,

and rehabilitation of coral reefs exposed to oil, pp. 115-134. In: J. Cairns, Jr.

and A.L. Buikema, Jr. (eds.), Restoration of Habitats Impacted by Oil Spills.

Butterworth Publishers, Boston. 182 pp.

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species indigenous to the Gulf of Mexico. U.S. Department of the Interior,

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97 pp. + app.

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Gittings, SR. and T.J. Bright. 1986. Assessment of coral recovery following an incident

of anchoring damage at the East Flower Garden Bank, northwest Gulf of

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Aspects of Coral Reefs: Health Hazards and History. Miami, FL.

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major oil spill on Panamanian subtidal reef corals. Coral Reefs 10:1-12.

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five western Atlantic populations of the coral Montastrea annularis. MS.

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77
APPENDICES

79
APPENDIX A

STRATIFIED RANDOM TRANSECT DATA

A-i
Table A. 1. Mean percent cover estimates of corals reef rock, conspicuous biota, and

sand on random transects sampled during 1992, 1994, and 1995 field efforts

at the East and West Flower Garden Banks study sites.

A-2

Analyzed Reef Component

Percent Cover

East Flower Garden Bank West Flower Garden Bank

1992 1994 1995 All 1992 1994 1995 All

Montastrea annularis 24.12 26.93 35.65 28.30 23.02 24.95 31.00 25.89

Diploria strigosa 4.69 8.92 7.92 6.86 6.15 10.15 6.66 7.52

Porftes astreoides 4.57 3.89 2.71 3.83 1.49 2.55 2.44 2.09

Montastrea cavemosa 1.49 4.80 3.20 296 0.87 3.15 2.33 1.98

Colpophyllia spp. 2.14 1.59 3.78 2.46 3.11 2.82 0.97 2.41

Millepora spp. 1.30 2.49 1.66 1.75 0.80 1.91 1.87 1.44

Agenda spp. 0.50 0.89 0.32 0.57 0.36 0.42 0.46 0.40

Stephanocoenia michelini 0.52 0.97 0.14 0.54 0.63 0.37 0.75 0.59

Madracis decactis 0.53 0.37 0.05 0.34 0.19 0.25 0.34 0.25

Siderastrea siderea 0.22 0.07 1.07 0.42 0.39 0.00 4.13 1.34

Mussa angulosa 0.05 0.17 0.08 0.09 0.16 0.14 0.1ff 0.16

Scolymia cubensis 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.01

Porites furcata 0.00 0.07 0.01 0.02 0.01 0.02 0.00 0.01

Madracis mirabilis 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.00

TOTAL CORAL 40.15 51.17 56.61 48.16 37.20 46.74 51.14 44.10

Reefrock 54.46 47.31 42.15 47.97 56.56 51.08 45.85 51.16

Leafy algae 4.78 0.29 0.57 1.88 4.45 0.42 2.70 2.52

Sponges 0.74 1.23 0.67 0.88 1.53 1.58 0.27 1.13

Sand 0.00 0.00 0.00 0.00 0.26 0.17 0.03 0.15
Table A.2. Relative dominance estimates, expressed in percent, of all coral taxa on

random transects sampled during 1992, 1994, and 1995 field efforts at the

East and West Flower Garden Banks study sites.

A-3

Taxa

Relative Dominance

East Flower Garden Bank West Flower Garden Bank

1992 1994 1995 All 1992 1994 1995 All

Montastrea annularis 57.33 51.69 61.36 56.86 61.93 53.96 60.05 58.95

Diploria strigosa 12.06 18.17 14.81 14.64 16.15 21.27 12.68 16.72

Podtes astreoldes 12.77 8.37 5.14 9.25 4.07 6.13 4.81 4.91

Montastrea cavemosa 3.38 8.63 5.82 5.62 2.44 5.89 5.09 4.26

Colpophyllia spp. 6.41 2.94 6.65 5.47 8.12 5,71 1.92 5.61

Millepora spp. 3.23 4.81 3.10 3.65 2.38 4.09 4.01 3.37

Agaricia spp. 1.38 1.85 0.58 1.28 0.87 1.06 0.92 0.94

Stephanocoenia miehelini 1.41 2.04 0.24 1.25 1.97 0.85 1.60 1.52

Madracis decactis 1.41 0.76 0.09 0.84 0.55 0.64 0.63 0.60

Siderastrea siderea 0.47 0.13 2.02 0.82 1.04 0.00 7.90 2.68

Mussa angulosa 0.14 0.39 0.13 0.21 0.44 0.34 0.39 0.39

Scolymia cubensis 0.02 0.28 0.02 0.02 0.02 0.01 0.01 0.01

Porites furcata 0.00 0.17 0.02 0.06 0.02 0.05 0.00 0.02

Madracis mirabilis 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Table A.3. Species diversity (H') and species evenness (E) of corals observed on

random transects collected during 1992, 1994,. and 1995 field efforts at the

East and West Flower Garden Banks study sites. Shannon-Weaver diversity

and species evenness estimates are based on both colony counts and

percent cover.

A-4

Bank Year H' (count) E (count) H' (cover) E (cover)

EFG 1992 1.835 0.861 1.216 0.568

WFG 1992 1.866 0.844 1.113 0.501

EFG 1994 1.841 0.839 1.340 0.608

WFG 1994 1.758 0.812 1.200 0.554

EFG 1995 1.672 0.815 1.118 0.538

WFG 1995 1.724 0.829 1.136 0.540

EFG All 1.789 0.541 1.224 0.571

WFG All 1.792 0.530 1.146 0.529
APPENDIX B

ACCRETIONARY GROWTH DATA

B-i
Table B.1. Montastrea annularis accretionary growth data (spike length in mm) and growth rates

(mrn/yr) measured on growth spikes at the East Flower Garden Bank study site. Data

are shown only for stations and time periods that were used for analysis of growth

rates.

* Stations destroyed between 1994-1995 field efforts.

B-2

CSA

Station

Number

1994 1995

Length

(mm)

Growth

(mm/yr)

Length

(mm)

Growth

(mm/yr)

1 31 28.5 2.5

2 80 * 3 75 70 5

4 71 63 8

5 35 30 5

6 24 19 5

7 35 29 6

8 38 31 7

9 33 26 7

10 30 22 8

11 33 25 8

12 27 22 5

13 55 * 14 33 26 7

15 34 28 6

16 30 30 0

17 34 27 7

18 25 20 5

19 27 20 7

20 26 21 5

21

22

Mean Growth (mmiyr) 5.7

Standard Deviation 0.5

Number 18
Table B.2. Montast4rea annularis accretionary growth data (spike length in mm) and growth rates

(mm/yr) measured on growth spikes at the West Flower Garden Bank study site. Data

are shown only for stations and time periods that were used for analysis of growth

rates. Shaded areas were not used in calculation of accretionary growth due to

incorrect field measurement.

Mean Growth (mm/yr)

Standard Deviation

Number

5.5

0.5

15

B-3

CSA

Station

Number

1994 1995

Length

(mm)

Growth

(mmlyr)

Length

(mm)

Growth

(mmlyr)

1 32

2 24.5 15.5 9

3 27 21 6

4 75 68 7

5 27 23 4

6 27 23 4

7 31 26 5

8 27 21 6

9 30 28 2

10 31 27 4

11 30.5

12 29.5 24 5.5

13 28 19 9

14 31

15 30 23.5 6.5

16 28

17 31 26 5

18 25 20 5

19 30

20 35 30 5

21 24.5

22 21
Table B.3. Accretionary growth rates of Montastrea annuiaris measured from cores colLected at

the East and West Flower Garden Banks.

EFG(1): Collected 8/24/95 East Flowe Gardens Bank.

EFG(2): Collected 8/24/95 East Flowe Gardens Bank.

WFG(1): Collected 8/22/95 West Flower Gardens Bank.

WFG(2): Collected 8/22/95 West Flower Gardens Bank.

B-4

Years

Annual Growth Rates (mm)

EFG(1) EFG(2) WFG(1) WFG(2)

1994-1995 10.0 6.0 83 8.7

1993-1994 8.4 6.4 7.4 7.0

1992-1993 10.7 6.8 8.9 8.7

1991-1992 8A 6.8 7.7 7.5

1990-1991 7.5 5.9 9.4 8.9

1989-1990 7.1 7.2 7.3 8.9

1988-1989 7.1 6.9 7.7 11.1

1987-1988 6.9 7.0 7.2 12.1

1986-1987 7.2 6.0 9.3 8.6

1985-1986 7.5 5.5 7.8 9.3

1984-1985 10.4 6.2 7.4 11.7

1983-1984 6.8 5.3 6.1 6.9

1982-1983 6.9 7.9 5.7 8.4

1981-1982 4.2 5.8 8.6 8.1

1980-1981 4.9 5.9 7.7 7.5

1979-1980 4.5 5.4 7.7 6.9

1978-1979 4.4 5.7 7.5

1977-1978 6.8 7.4 6.6

1976-1977 6.8 6.8

1975-1976 8.7

1974-1975 8.1

1973-1974 6.8
APPENDIX C

REPETITIVE QUADRAT DATA

c-i
Table 0.1. Repetitive 8 m2 stations, East Flower Garden Bank, 1992,

Table C.2. Repetitive 8 m2 stations, West Flower Garden Bank, 1992.

Table 0.3. Repetitive 8 m2 stations, East Flower Garden Bank, 1994.

C-2

Change Cause Occurrence Mortality

Growth - 1,202 -

unknown cause 80 80

algae mediated 382 382

Retreat, Bleaching, and Disease algae/sediment 5 5

- new disease 0 0

bleaching 53 9

Change Cause Occurrence Mortality

Growth - 955 -

unknown cause 5 5

algae mediated 310 310

Retreat, Bleaching, and Disease algae/sediment 23 23

new disease I I

bleaching 38 9

Change Cause Occurrence Mortality

Growth - 995 -

unknown cause 78 78

algae mediated 330 330

Retreat, Bleaching, and Disease algae/sediment 28 28

new disease 0 0

bleaching 16 15
Table 0.4. Repetitive 8 m2 stations, West Flower Garden Bank, 1994.

Table C.5. Repetitive 8 m2 stations, East Flower Garden Bank, 1995.

Table C.6. Repetitive 8 rn2 stations, West Flower Garden Bank, 1995.

C-3

Change Cause Occurrence Mortality

Growth - 918 -

unknown cause 69 69

algae mediated 399 399

Retreat, Bleaching, and Disease algae/sediment 0 0

new disease 0 0

bleaching 8 0

Change Cause Occurrence Mortality

Growth - 1,195 -

unknown cause 17 17

algae mediated 26 26

Retreat, Bleaching, and Disease algae/sediment 0 0

new disease 165 97

bleaching 200 52

Change Cause Occurrence Mortality

Growth - 943 -

unknown cause 2 2

algae mediated 17 17

Retreat, Bleaching, and Disease algae/sediment 0 0

new disease 152 137

bleaching 229 59
APPENDIX D

ANCILLARY DATA

D-1
Table Dl. Ancillary measurements: temperature, salinity, dissolved oxygen, and ambient light data collected at near 

depths during the 1994 field effort. NA = Data not available. Bank Date Local Time Near Surface (1 m) Near Bottom 

Temperature (°C) Salinity (ppt) Dissolved Oxygen (mg/I) Ambient Light (pmol seC' m2) Temperature (°(3) Salinity (ppt) 

EFG 14 Sept. 1994 1540 29.1 34.9 6.2 NA 29.0 35.2 

EFG 15 Sept. 1994 1135 28.8 34.9 6.2 400 28.9 35.2 EFG 16 Sept. 1994 0900 28.8 34.6 6.1 300 28.9 35.0 

WFG 12 Sept. 1994 1344 29.1 35.0 6.4 120 29.2 35.0 WFG 13 Sept. 1994 1057 29.0 34.9 6,1 800 29.3 36.3 WFG 14 Sept. 1994 0940 29.0 34.6 6.2 700 29.2 35.1 
a Table 0.2. Ancillary measurements: temperature, salinity, dissolved oxygen, and ambient light data collected at near 

depths during the 1995 field effort. NA = Data not available. Bank Date Local Time Near Surface (1 m) Near Bottom 

Temperature (°C) Salinity (ppt) Dissolved Oxygen (mg/I) Ambient Light (pmol sec' m2) Temperature (°C) Salinity (ppt) D

EFG 23 Aug. 1995 -- 30.1 37.6 6.3 150 29.7 38.0 EFG 24 Aug. 1995 1042 30.3 37.3 6.2 800 29.5 37,4 

WEG 21 Aug. 1995 1618 30.0 36.3 6.0 NA 29.4 36.3 WFG 22 Aug. 1995 0900 29.9 33.2 6.2 NA 29.8 33.4 
The Department of the Interior Mission

As the Nation's principal conservation agency, the Department of the Interior has responsibility for

most of our nationally owned public lands and natural resources This includes fostering sound use

of our land and water resources protecting our fish, wildlife, and biological diversity; preserving the

environmental and cultural values of our national parks and historical places; and providing for the

enjoyment of life through outdoor recreation. The Department assesses our energy and mineral

resources and works to ensure that their development is in the best interests of all our people by

encouraging stewardship and citizen participation in their care. The Department also has a major

responsibility for American Indian reservation communities and for people who live in island territories

under U.S. administration.

The Minerals Management Service Mission

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS) primary

responsibilities are to manage the mineral resources located on the Nation's Outer Continental Shelf

(OCS), collect revenue from the Federal OCS and onshore Federal and Indian lands, and distribute

those revenues

Moreover, in working to meet its responsibilities, the Offshore MInerals Management Program

administers the OCS competitive leasing program and oversees the safe and environmentally sound

exploration and production of our Nation's offshore natural gas, oil and other mineral resources. The

MMS Royalty Management Program meets its responsibilities by ensuring the efficient, timely and

accurate collection and disbursement of revenue from mineral leasing and production due to Indian

tribes and allottees, States and the U.S. Treasury.

The MMS strives to fulfill its responsibilities through the general guiding principles ot (1) being

responsive to the public's concerns and interests by maintaining a dialogue with all potentially affected

parties and (2) carrying out its programs with an emphasis on working to enhance the quality of life for

all Americans by lending MMS assistance and expertise to economic development and environmental

protection.