Contractor Report

USGS/BRD/CR--1 997-0005

OCS Study MMS 96-0014

1L

Panama City

0

Apalachicola

2

Tallahassee

Cedar Key

Tarpon

Springs S

Northeastern Gulf of Mexico Coastal and Marine Ecosystem

Program: Data Search and Synthesis

Synthesis Report

U.S. Department of the Interior U.S. Department of the Interior

U.S. Geological Survey Minerals Management Service

Biological Resources Division Gulf of Mexico OCS Region

AL. Pensacola

Mobile
I S I

Contractor Report

USGS/BRD/CR--1 997-0005

OCS Study MMS 96-00 14

Northeastern Gulf of Mexico

Coastal and Marine Ecosystem Program:

Data Search and Synthesis

Synthesis Report

August 1997

Prepared under BRD contract

I 445-CT0009-95-004

by

Science Applications International Corporation

Raleigh, North Carolina 27605

in cooperation with the

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

This study was procured to meet information needs identified by the Minerals Management Service (MMS)

in concert with the U.S. Geological Survey, Biological Resources Division (BRD).

DISCLAIMER

This report was prepared under contract between the U.S. Geological Survey, Biological Resources Division

and Science Applications International Corporation. This report has been technically reviewed by the BRD

and the MMS, and has been approved for publication. Approval does not signify that the contents necessarily

reflect the views and policies of the BRD or MMS, 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

Telephone: (304) 725-8461 (ext. 675) Telephone: (504) 736-2519 or

1-800-200-GULF

Copies of this publication are available from the National Technical Information Service, 5285 Port Royal

Road, Springfield, VA 22161 (1-800-553-6847 or 703-487-4650). Copies also are available to registered

users from the Defense Technical Information Center, Attn: Help Desk, 8725 Kingman Road, Suite 0944, Fort

Belvoir, VA 22060-6218 (1-800-225-3842 or 703-767-9050).

SUGGESTED CITATION

Science Applications International Corporation. 1997. Northeastern Gulf of Mexico Coastal and Marine

Ecosystem Program: Data Search and Synthesis; Synthesis Report. U.S. Dept. of the Interior, U.S.

Geological Survey, Biological Resources Division, USGS/BRD/CR-1 997-0005 and Minerals

Management Service, Gulf of Mexico OCS Region, New Orleans, LA, OCS Study MMS 96-0014. 313

pp.

ACKNOWLEDGMENT

Although key authors are listed for each chapter, other members of the project team reviewed, edited, and

amended this report to enhance its content and clarity. This was a team effort.

U.S. Department of the Interior U.S. Department of the Interior

US Geological Survey Minerals Management Service

Biological Resources Division Gulf of Mexico OCS Region

Eastern Regional Office Public Information Office (MS 5034)

1700 Leetown Road 1201 Elmwood Park Blvd.

Kearneysville, WV 25430 New Orleans, LA 70123-2394
TABLE OF CONTENTS

Chapter Page

List of Figures ix

List of Tables xv

Chapter 1 - INTRODUCTION

iii

Chapter 2 - THE PHYSICAL ENVIRONMENT

2.1 Introduction 2-1

2.2 Meteorology 2-1

2.2.1 Introduction 2-1

2.2.2 Air and Sea Surface Temperature Climatology 2-2

2.2.3 Slope Processes 2-8

2.2.4 Shelf Processes 2-13

2.3 Physical Oceanography 2-19

2.3.1 Introduction 2-19

2.3.2 Loop Current 2-21

2.3.3 Slope Processes 2-27

2.3.4 Shelf Processes 2-28

2.3.4.1 Wind-Forced Circulation 2-28

2.3.4.2 Shelf Water Temperature and Salinity 2-34

2.3.4.3 River Flow and Buoyancy Forcing 2-43

2.3.4.4 Tides and Inertial Currents 2-45

2.3.4.5 Nearshore Processes 2-47

2.4 Literature Cited 2-47

1.1 Background 1-1

1.2 Project Organization 1-1

1.3 Program Activities 1-3

1.3.1 Information Collection 1-3

1.3.2 Information Synthesis 1-3

1.4 Program Participants 1-3

1.5 Report Organization 1-4

Chapter 3 - THE GEOLOGICAL ENVIRONMENT

3.1 General Geological setting 3-1

3.1.1 Origin of Florida Peninsula 3-1

3.2 Shoreline Geomorphology 3-1

3.2.1 Big Bend Marsh Coast 3-4

3.2.2 Panhandle Barrier Chain 3-6

3.3 Bathymetry 3-6

3.4 Sediments 3-11

3.4.1 Big Bend Area 3-14

3.4.2 panhandle Area 3-15
TABLE OF CONTENTS

iv

4.1.1 Physical Setting and Processes

4.1.2 Geologic Setting

4.1.3 biological Setting

4.2 Chemical Properties and Distribution

4-1

4-2

4-3

4-4

4.2.1 Shelf Characteristics 4-4

4.2.2 Dissolved and Particulate Constituents 4-4

4.2.3 Humics 4-5

4.2.4 Decomposition and the Formation of Biogenic Gases 4-5

4.2.4.1 Methane 4-6

4.2.4.2 Nitrous Oxide 4-7

4.2.4.3 Organic Sulfur Compounds 4-8

4.2.5 Trace Metals 4-8

4.2.6 Radioactivity 4-12

4.2.7 Pulp Mill Effluents 4-12

4.2.7.1 Hydrocarbons 4-13

4.2.7.2 Chlorinated Organics and Organophospates 4-16

4.2.7.3 Pulp Mill Effluents 4-18

4.2.8 Case Studies 4-19

4.2.8.1 Chattahoochee-Flint-ApalachicOla River and

Apalachicola Bay 4-19

4.2.8.2 Suwanee River 4-21

4.2.8.3 Bayou Texar/Pensacola bay 4-22

4.3 Chemical Cycles 4-22

4.3.1 Nutrient Cycling 4-22

4.3.1.1 Primary Production 4-23

4.3.1.2 Ochiockonee Bay 4-24

4.3.1.3 Hypoxia/Anoxia 4-24

4.3.2 Red Tides 4-25

4.3.3 Contaminant Cycling 4-25

4.4 Conclusions 4-27

Chapter Page

3.5 Sediment Dynamics 3-16

3.5.1 Coastal Sediment Transport 3-16

3.5.1.1 Big Bend Area 3-16

3.5.1.2 Panhandle Area 3-17

3.5.2 Shoreface and Shelf 3-18

3.6 Summary 3-20

3.7 Literature Cited 3-21

Chapter 4 - THE CHEMICAL ENVIRONMENT

4.1 Introduction 4-1
TABLE OF CONTENTS

V

Chapter Page

4.5 Literature Cited 4-28

Chapter 5 - THE BIOLOGICAL ENVIRONMENT

5.1 IN'I'RODtJCTION 5-1

5.1.1 Area Description 5-1

5.1.2 Data Gaps 5-6

5.2 Continental Shelf 5-7

5.2.1 Environmental Setting 5-7

5.2.2 Biology 5-7

5.2.2 1 Plankton 5-7

5.2.2.2 Benthos 5-9

5.2.2.3 Fish 5-11

5.2.2.4 Sea Turtles and Marine Mammals 5-14

5.2.3. Data Gaps 5-15

5.3. Estuaries 5-16

5.3.1 Environmental Setting and Characteristics of Florida

Panhandle Estuaries 5-17

5.3.1.1 Estuarine Climatic Features 5-17

5.3.1.2 Seasons 5-18

5.3.1.3 Temperature 5-18

5.3.1.4 Precipitation 5-19

5.3.1.5 Hurricanes and Storms 5-20

5.3.1.6 Seasonal Wind Patterns 5-20

5.3.1.7 Estuarine Circulation 5-20

5.3.1.8 Tides and Sea Levels 5-21

5.3.1.9 Data Gaps 5-22

5.3.2 Environmental Quality of Panhandle Estuaries 5-22

5.3.2.1 Estuarine Pollution 5-23

5.3.2.2 Nutrients 5-24

5.3.2.3 Metals 5-24

5.3.2.4 Sediment Contaminants 5-24

5.3.2.5 Data Gaps 5-25

5.3.3 Estuarine Habitats 5-26

5.3.3.1 Salt Marshes 5-26

5.3.3.2 Submerged Aquatic Vegetation (Excluding Algae) 5-30

5.3.3.3 Oyster Reefs 5-35

5.3.3.4 Data Gaps 5-38

5.3.4 Estuarine Organisms and Communities 5-39

5.3.4.1 Primary Production 5-39

5.3.4.2 Zooplankton 5-40

5.3.4.3 Benthic Macroinvertebrates 5-41

5.3.4.4 Fishes 5-50

5.3.4.5 Threatened and Endangered Species 5-51
TABLE OF CONTENTS

Chapter 6 - SOCIOECONOMIC CONDITIONS

6.1 Introduction 6-1

vi

Chapter Page

5.4 Florida Panhandle Estuaries 5-51

5.4.1 Pensacola Bay 5-51

5.4.1.1 Environmental Setting 5-52

5.4.1.2 Hydrography and Oceanography 5-55

5.4.1.3 Water and Sediment Quality 5-57

5.4.1.4 Biology 5-62

5.4.1.5 Data Gaps 5-70

5.4.2 Choctawhatchee Bay 5-71

5.4.2.1 Environmental Setting 5-71

5.4.2.2 Hydrography and Oceanography 5-73

5.4.2.3 Water and Sediment Quality 5-74

5.4.2.4 Biology 5-75

5.4.2.5 Data Gaps 5-78

5.4.3 St. ridrew Bay 5-79

5.4.3.1 Environmental Setting 5-79

5.4.3.2 Hydrography and Oceanography 5-79

5.4.3.3 Water and Sediment Quality 5-82

5.4.3.4 Biology 5-85

5.4.3.5 Data Gaps 5-89

5.4.4 Apalachicola Bay 5-90

5.4.4.1 Environmental Setting 5-90

5.4.4.2 Hydrography and oceanography 5-92

5.4.4.3 Water and Sediment Quality 5-92

5.4.4.4 Biology 5-93

5.4.4.5 Data Gaps 5-100

5.4.5 St. Joseph Bay 5-100

5.4.5.1 Environmental Setting 5-100

5.4.5.2 Hydrology and Oceanography 5-100

5.4.5.3 Water and Sediment Quality 5-102

5.4.5.4 Biology 5-102

5.4.5.5 Data Gaps 5-103

5.4.6 Apalachee Bay/Big Bend 5-104

5.4.6.1 Environmental Setting 5-104

5.4.6.2 Hydrography and Oceanography 5-104

5.4.6.3 Water and Sediment Quality 5-104

5.4.6.4 Biology 5-106

5.4.6.5 Data Gaps 5-108

5.5 Summary and Major Data Gaps 5-108

5.7 Literature Cited 5-113
TABLE OF CONTENTS

Chapter Page

6.2 Socioeconomic Indicators 6-1

6.3 The Export Base of the Region 6-4

6.4 The Socioeconomic Component of the Marine Ecosystem 6-7

6.5 Spending; Annual User Value and Asset value of Selected

Elements of the Marine Ecosystem 6-11

6.5.1 Annual Spending 6-11

6.5.2 Annual User Value 6-12

6.5.3 Asset Value 6-13

6.6 Evaluation of Water Quality 6-15

6.6.1 Escambia County of Wakulla County 6-15

6.6.2 Jefferson County to Levy county 6-16

6. .6.3 Levy County to citrus County 6-16

6.7 Literature Cited 6-17

Chapter 7 - CONCEPTUAL MODEL

7.1 Introduction 7-1

7.2 System Definition 7-2

7.2.1 Model Levels 7-2

7.2.2 Components and Model Representation 7-4

7.3 System Level One - Comprehensive Model of the Northeastern

Gulf of Mexico Ecosystems 7-4

7.3.1 Physical Processes 7-7

7.3.2 Biogeochemical Processes 7-9

vii

7.4 System Level Two - Representation of Biochemical Processes 7-10

7.4.1 Sedimentation Processes 7-10

7.4.2 Chemical Processes 7-12

7.4.3 Carbon-Oxygen Cycling 7-12

7.4.4 Nitrogen Cycling 7-15

7.4.5 Toxicant Cycling 7-15

7.4.6 Ecological Processes 7-20

7.5 System Level Three - Ecological Process Representation 7-20

7.5.1 Pelagic Trophic Dynamics 7-25

7.5.2 Benthic Trophic Dynamics 7-25

7.5.3 Nekton Life Cycles 7-27

7.5.4 Marsh-Estuarine Dynamics 7-27

7.6 Summary of Major Components of the Conceptual Model 7-31

7.7 Literature Cited 7-37
LIST OF FIGURES

Figure No. Caption Page

Figure 1-1. Map of the study area showing the general

bathymetry, study area boundaries and the location

of the six estuaries identified for special study 1-2

Figure 2-1. Monthly mean air temperature (°C), sea surface

temperature (°C), air-SST (°C) and sensible heat

flux (Wm2) for the period 1987-1994 for the NDBC

C-M station located at Dauphin Island, Alabama 2-9

Figure 2-2. Monthly mean air temperature(°C), sea surface

temperature (°C), air-SST (°C) and sensible heat

flux (Wm2) for the period 1987-1994 for NDBC buoy

42015 2-10

Figure 2-3a. Winter (December - March) wind roses for the

National Weather Service stations at Mobile,

Alabama and Pensacola, Florida 2-11

Figure 2-3b. Winter (December - March) wind roses for the

National Weather Service stations at Apalachicola,

Florida and Tampa, Florida 2-12

Figure 2-4a. Summertime (May - October) wind roses for the

National Weather Service stations at Mobile,

Alabama and Pensacola, Florida 2-14

Figure 2-4b. Summertime (May - October) wind roses for the

National Weather Service stations at Apalachicola,

Florida and Tampa, Florida 2-15

Figure 2-5. Wind speed (ms1) and direction (°True) for the

period 1987-1994 2-16

Figure 2-6. Summary of tropical cyclone activity for the

northeastern Gulf of Mexico for the period 1886-

1985 2-18

Figure 2-7. Map of the region showing bathymetry, various

features and key locations 2-20

Figure 2-8. Labeled satellite image showing Loop Current,

possible LC eddy separation, large boundary

filament over slope and outer shelf offshore of the

Big Bend Area 2-22

Figure 2-9. Contours of the temperature at 150 m depth clearly

showing the general depressed isotherm structure of

the relatively warm LC 2-23

ix
LIST OF FIGURES

Figure No. Caption Page

Figure 2-10. Normal velocities for an east-west transect shown

in Figure 2-9 2-24

Figure 2-11. Two realizations of Eddy B from hydrography (depth

of 20°C isotherm), Lagrangian drifters and daily

average 300-400 m measured current vectors 2-25

Figure 2-12. Simple illustrations of three types of LC/filament

interactions over the Mississippi/Alabama/Florida

Panhandle slope and shelf 2-29

Figure 2-13. Trajectories of two drifters with x" placed at a

daily interval 2-30

Figure 2-14. SST image showing an eddy over the upper slope on

the eastern wall of the De Soto Canyon 2-31

Figure 2-15. Monthly mean, maximum and minimum temperatures and

salinities computed from data taken at 150m on

Mooring C from the MMS-funded MANES project 2-32

Figure 2-16. Plot of surface salinity contours digitized from a

figure in Drenrian (1965). 2-33

Figure 2-17. Map with mooring positions shown 2-36

Figure 2-18. Near surface monthly mean temperatures for

indicated moorings 2-37

Figure 2-19. Changes in shelf water stratification due to

passage of a front and cold air outbreaks offshore

of the Florida Panhandle 2-38

Figure 2-20. Monthly means, maximums and minimums from Mooring B

(midshelf) offshore of Alabama 2-40

Figure 2-21. Monthly means, maximums and minimums from Mooring F

(rnidshelf) offshore of Fort Meyers, FL 2-41

Figure 2-22. Monthly means, maximums and minimums from Mooring C

(upper slope) offshore of Alabama 2-42

Figure 2-23. Monthly mean, maximum and minimum salinities

computed from data taken near the water surface 2-44

Figure 2-24. Currents measured at the NORDA/DeSoto Canyon

mooring duing passage of a hurricane 2-46

Figure 3-1. Location of the Suwannee Channel 3-2

x
LIST OF FIGURES

Figure No. Caption Page

Figure 3-2. Location of the Panhandle barrier chain and the Big

Bend marshy coast within the study area 3-3

Figure 3-3. The shoreline of a portion of the Big Bend marshy

coast, showing distribution of major morphologic

elements 3-5

Figure 3-4. General bathymetry within the study area 3-7

Figure 3-5. Contour map of Apalachicola Bay and the nearshore

region 3-9

Figure 3-6. Formation of karst terrain 3-10

Figure 3-7. Linear features are shown in the bathymetry for the

area off Choctawhatchee Bay between the 60 ft (18 m)

and the 110 ft (33 m) contours 3-12

Figure 3-8. sedimentary facies found in the study area 3-13

Figure 5-1. Map of the eastern Gulf of Mexico 5-3

Figure 5-2. Generalized circulation in the Gulf of Mexico 5-4

Figure 5-3. Western Florida Panhandle showing bay systems and

barrier islands 5-5

Figure 5-4. Beach and foreshore benthic macroinvertebrate

communities 5-12

Figure 5-5. shallow shelf benthic invertebrate assemblages 5-13

Figure 5-6. Energy flow in a generalized food web 5-33

Figure 5-7. Low salinity marsh and delta macroinvertebrate

communities 5-45

Figure 5-8. Schematic diagram of a characteristic oyster reef

community in Panhandle brackish waters 5-46

Figure 5-9. Bay and sound macroinvertebrate communities 5-47

Figure 5-10. Composite hard substrate community 5-49

Figure 5-11. Schematic map of the Pensacola Bay system 5-53

Figure 5-12. Schematic map of the Choctawhatchee Bay system 5-72

Figure 5-13. Schematic map of the St. Andrew Bay system 5-80

xi
IIST OF FIGURES

Figure No. Caption Page

Figure 5-14. Schematic map of the Apalachicola Bay and St.

Joseph Bay systems 5-91

Figure 5-15. Schematic map of the Ochlockonee Bay/Apalachee Bay

system 5-105

Figure 6-1. Map of the state of Florida indicating the 13

counties covered in this study 6-2

Figure 7-1. Map of the northeastern Gulf of Mexico showing the

boundaries of the study area and ecosystem core

regionS 7_3

Figure 7-2. Odurn energy-mass language symbols used in the

northeastern Gulf of Mexico ecosystem

conceptualization 7-5

Figure 7-3. A comprehensive conceptual representation of the

northeastern Gulf of Mexico ecosystem 7-6

Figure 7-4. A conceptual representation of sedimentation

processes in the region west of Cape San Bias in

the northeastern Gulf of Mexico ecosystem 7-8

Figure 7-5. A conceptual representation of sedimentation

processes in the Big Bend region of the

northeastern Gulf of Mexico ecosystem 7-11

Figure 7-6. A conceptual representation of carbon-oxygen

cycling for well-mixed water column conditions in

the northeastern Gulf of Mexico ecosystem 7-13

Figure 7-7. A conceptual representation of carbon-oxygen

cycling for stratified water column conditions in

the northeastern Gulf of Mexico ecosystem 7-14

Figure 7-8. A conceptual representation of nitrogen cycling for

well-mixed water column conditions in the

northeastern Gulf of Mexico ecosystem 7-16

Figure 7-9. A conceptual representation of nitrogen cycling for

stratified water column conditions in the

northeastern Gulf of Mexico ecosystem 7-17

Figure 7-10. A conceptual representation of toxicant cycling for

well-mixed water column conditions in the

northeastern Gulf of Mexico ecosystem 7-18

xii
LIST OF FIGURES

Figure No. Caption Page

Figure 7-11. A conceptual representation of toxicant cycling for

stratified water column conditions in the

northeastern Gulf of Mexico ecosystem 7-19

Figure 7-12. A conceptual representation of ecological processes

for well-mixed water column conditions in the

northeastern Gulf of Mexico ecosystem 7-21

Figure 7-13. A conceptual representation of ecological processes

for stratified water column conditions in the

northeastern Gulf of Mexico ecosystem 7-22

Figure 7-14. A conceptual representation of trophic processes in

the pelagic subsystem for well-mixed water column

conditions in the northeastern Gulf of Mexico

ecosystem 7-23

Figure 7-15. A conceptual representation of trophic processes in

the benthic subsystem of the northeastern Gulf of

Mexico ecosystem 7-24

Figure 7-16. A conceptual representation of the life cycles of

estuarine and estuarine-dependent nekton in the

northeastern Gulf of Mexico ecosystem 7-28

Figure 7-17. A conceptual representation of the life cycles of

estuarine-related and estuarine-independent nekton

in the northeastern Gulf of Mexico study area 7-29

Figure 7-18. A conceptual representation of the important

ecological features of Marsh-Estuarine dynamics in

the northeastern Gulf of Mexico study area 7-30
xv

LIST OF TABLES

Table No. Caption Page

Table 2-1. Long-term climatological data collectedatthe

Mobile, Alabama National Weather Service

(NWS)station 2-4

Table 2-2. Long-term climatological data collected at the

Pensacola, Florida National Weather Service

(NWS) station 2-5

Table 2-3. Long-term climatological data collected at the

Apalachicola, Florida National WeatherService

(NWS)station 2-6

Table 2-4. Long-term climatological data collected atthe

Tampa, Florida National WeatherService (NWS)

station 2-7

Table 4-1. Chemical characterization of Apalachicola and

Suwannee Rivers 4-6

Table 4-2. Median trace metal concentrations in oyster for

Gulf of Mexico and major embayments of the

northeastern Gulf of Mexico and clams (Corbicula

manilensis) from Apalachicola River 4-10

Table 4-3. Concentrations of polyaromatic hydrocarbons found

in snails (Thais haemostoma), Pensacola Bay

sediments and inf lowing stream sediments from

creosotecontaminated Super Fund site 4-15

Table 4-4. Median concentrations of organiccontaminants in

Apalachicola River sediments, detritus and whole

body tissue from the clam, Corbicula manilensis 4-17

Table 5-1. Clusters of macroepifaunal species assemblages

found in different depth zones on the panhandle

shelf 5-9

Table 5-2. Habitat-depth assemblages 5-15

Table 5-3. Listing of Florida Panhandle hurricanes from 1885

through 1995 5-21

Table 5-4. Summary of sediment contamination for Panhandle

estuaries by habitat 5-25

Table 5-5. Relative value of indicated marsh subsystems to

listed animals 5-27
LIST OF TABLES

Table No. Caption Page

Table 5-6. Relative importance of coastal marshes for three

life-history functions of the three principal

animal groups found in marshes 5-27

Table 5-7. Listing of some of the estuarine-dependent species

from the Gulf and southeastAtlantic coasts 5-28

Table 5-8. Common fishes found in salt marshes 5-29

Table 5-9. Distribution of seagrasses in the panhandle 5-32

Table 5-10. Acreage of scarred seagrasses to thenearest ten

acres in each Florida coastal county 5-36

Table 5.11. Percentage of scarred seagrasses by intensity level

within each Florida coastal county 5-37

Table 5-12. Percent of dominant fish species in Crystal River,

Cedar Key, Apalachicola Bay, and St. Andrew Bay

estuaries 5-52

Table 5-13. Comparisons of dimensions of Pensacola Bay subsystems 5-55

Table 5-14. Comparisons of sediment percentages in the

Pensacola Bay System 5-61

Table 5-15. MacroinvertebrateS found in the Pensacola Bay

System from January 1980 to the present, compared

with macroinvertebrates found by Cooley (1978) 5-64

Table 5-16. Sea-surface temperatures (°C) in the St. Andrew Bay

system 5-81

Table 5-17. Estimated nutrient loadings for the St. Andrew Bay

system 5-83

Table 5-18. Predicted concentration status for the St. Andrew

Bay system 5-83

Table 5-19. oyster reef coverage in the St. Andrew Bay system 5-89

Table 5-20. Fish community composition in St. Andrew Bay

System, based on the top ten species reported in

Florida from major individual studies 5-89

Table 5-21. Distribution of seagrasses in Apalachicola Bay 5-95

Table 5-22. Most abundant infaunal taxa in Apalachicola Bay,

Apalachee Bay and St. George Sound 5-96

xvi
LIST OP TABLES

Table No. Caption Page

Table 5-23. The distribution of oysters, Crassostrea virginica,

in Apalachicola Bay 5-97

Table 5-24. Fishes collected from East Bay and Apalachicola

Bay, Florida 5-98

Table 5-25. Otter trawl collections of epibenthic fishes

collected in various regions and habitats of the

Apalachicola estuary from 1972 through 1982 5-101

Table 5-26 The most numerous ten species of benthic

macroinvertebrates collected from 1971-1980 in

Apalachee Bay 5-107

Table 6-1. A Summary of Socioeconomic Characteristics for

Thirteen Counties in Northwest Florida, 1993 6-3

Table 6-2 .A Summary of the Principal Exportlndustries in the

Thirteen Counties of the Northwest Florida Area 6-6

Table 6-3. A Summary of the Principal EcosystemSensitive

Industries in the Thirteen Counties of the

Northwest Florida Area 6-9

Table 6-4. A Summary of the Principal Ecosystem Insensitive

Industries in the Thirteen Counties of the

Northwest Florida Area 6-10

Table 6-5. A Summary of Spending and Value for Marine

Resources in the Thirteen Counties in Northwest

Florida, 1993 6-12

Table 6-6. A Summary of User Value for the Marine Resource in

the Thirteen Counties in Northwest Florida, 1993 6-13

Table 6-7. A Summary of the Asset Value for the Marine

Resource in the Thirteen Counties in Northwest

Florida, 1993 6-14

xvii
Chapter 3. - INTRODUCTION

1.1 Background

With the possibility of oil and gas development and production and the

associated potential for ecological and environmental impacts, the

Biological Resource Division (BRD) of the United States Gelogical Survey

(USGS) initiated a phased sequence of studies which should produce a

comprehensive description of the dominant environmental processes, the

ecological communities, and their potential sensitivities to development in

the project study area (Figure 1-1). As the first phase in the process of

establishing a rational base for management and leasing decisions by the

Minerals Management Service (MMS), the present project conducted a

comprehensive search and integration of regional environmental information.

Specific project objectives are to gather environmental and socioeconomic

information related to the continental shelf ecosystem and associated

coastal and estuarine communities. This information was then be used to

describe elements of the ecosystem in the study area, establish an

understanding of the environmental processes that drive the system, and

identify those processes that are potentially sensitive to anthropogenic

activities, particularly oil and gas development and operations.

1.2 project Organization

As described below, planned project activities focused on the two primary

tasks:

(A) Information Collection -

Conducted literature searches to identify, review and annotate

citations and data relevant to the meteorological/physical

oceanographic, geological, chemical, biological and socioeconomic

conditions in the study area. The results of these searches were

compiled into separate Annotated Bibliographies for each of these

topical areas.

(B) Information Synthesis -

Developed the present Final Synthesis Report describing the above

environmental topics as they relate to the study area.

Information in these topical descriptions were used to develop a

multi-level Conceptual Ecosystem Model relating various compartments

of the ecosystem. The conceptual model provides a basis to help

organize requirements and activities in future studies as well as

identify important data gaps.

Site specific environmental material and descriptions are presented

describing six estuarine/nearshore areas: Pensacola Bay,

Choctawhatchee Bay, St. Andrew Bay, St. Joseph Bay, Apalachicola Bay,

and the Florida Big Bend Area (Figure 1-1)

1-1
89° W 31° N 300 N 29° N 28° N 27° N890 WNortheastern Gulf of Mexico Coastal and Marine Ecosystem Program: Data Search and Syn

88° W 88° W 87° W 87° W 86° W 86° W 85° W 85° W 84° W 84° W 83° W 

A = Pensacola Bay B = Choctawhatchee Bay C = St. Andrew Bay D = St. Joseph Bay E = Apalachlcola Bay F = Florida Big Bend & South 83° W 

Figure IL I . Map of the study area showing the general bathymetry, study area boundaries a

the six estuaries identified for special study.
1.3 Program Activities

1.3.1 Information Collection

The first key activity was to conduct a search for topically and

geographically relevant citations and data. Much of this was done

electronically using such on-line data bases available from DIALOG and

National Technical Information Service (NTIS) . The results of these

searches are presented in six separate Appendices (A-F) to this Synthesis

Report. Operationally, these appendices are inclusive such that some

citations will appear in more than one volume. This approach was taken

intentionally to reduce the need for a user to have to review the complete

set of appendices to identify information relevant to a particular topical

area. The results of these searches have been entered into a bibliographic!

citation data base manager called Papyrus. A copy of the Papyrus formatted

data base as well as a digital (word processor) version of each of the

appendices has been provided to the National Biological Survey to

facilitate both distribution and access to this information.

1.3.2 Information Synthesis

Principal Investigators for chapters in this report were selected for their

familiarity with the present study area. In defining the project team,

such a knowledge base was essential to efficient and timely development of

the overall synthesis. This reservoir of regional knowledge was

supplemented with the results of the Information Collection phase. The

authors had access to the relevant annotated bibliographies as the present

descriptive material was being developed.

For this study no original research little supplemental analysis was

conducted. One exception was Socioeconomics. Dr. F. Bell (FSU) was also a

Principal Investigator on a companion NBS study, being conducted

concurrently by Continental Shelf Associates, investigating fisheries with

the study area. Dr. Bell conducted additional analyses and associated

description which were supported by both this and the companion program.

1.4 Program Participants

Information is collection occurred at several levels. For time and cost

efficiency, the on-line/electronic bibliographic searches were conducted by

personnel in the SAIC Center for Technical Research, which specializes in

these activities. Lists of key words to be used in the search strategy

were developed in collaboration with the Principal Investigators for each

discipline. During the search process, PIs had opportunities to review

possible citations to help remove those having no obvious application to

the present program objectives. When a topical list of citations was

completed, it was imported into the database.

Those program participants having a key role in the Information Collection

phase are listed below with their associated activities:

1-3
Meteorology/Physical Oceanography - Dr. Evans Waddell and Mr. Paul

Blankenship (SAIC).

Geology - Mr. David Inglin (SAIC).

Chemistry - Ms. Margaret Murray (SAIC)

Biology - Dr. Sneed Collard (IJWF) and personnel with Barry Vittor and

Associates (BVA).

Socioeconomic - Dr. Fred Bell (FSTJ)

In addition, Dr. Sneed Collard visited many government, state and

university laboratories along the Gulf coast to identify appropriate

unpublished information relevant to the study area. Mr. Paul Blankenship

was the resident expert in the use and importing of citations into the

Papyrus software.

As described below, this report has a chapter for each of the topical

disciplines, and a chapter describing the Conceptual Ecosystem Model. The

decision was made not to integrate the various material around some other

organizing principle. Thus, material in each chapter is similar to that

submitted by the chapter authors. The authors are:

Meteorology - Dr. Robert Wayland

Physical Oceanography - Dr. Peter Hamilton and Dr. Evans. Waddell

Geology - Dr. Richard Davis and Mr. David Inglin

Chemistry - Dr. Jane Caffrey

Biology - Dr. Sneed Collard and Dr. Carl Way

Socioeconomics - Dr. Fred Bell

Conceptual Ecosystem Model - Mr. Steven Pace

The program is managed by Dr. Evans Waddell. Supporting the PM is the

Science Review Board which has as members Dr. William Schroeder (Dauphin

Island Sea Lab) and Dr. John Hitron (UWF). Dr. Hitron has the additional

responsibility of reviewing work being done by Continental Shelf Associates

in a companion study that focuses primarily on fisheries in the study area.

1.5 Report Organization

This report is organized into eight chapters as follows:

Chapter 1: Introduction - provides a general overview of the program

objectives, procedures and participants

Chapter 2: Meteorology and Physical Oceanography - describes many of the

general processes affecting local weather conditions and

1-4
circulation patterns. Also describes ecologically significant

physical parameters.

Chapter 3: Geology - describes the general geological conditions including

an overview of the geological history and aspects of sediment

dynamics.

Chapter 4: Chemistry - describes many of the key chemical concentrations

and cycles, especially those relevant to the regional ecosystem

Chapter 5: Biology - the largest chapter presents a description of many of

the key flora, fauna and biologically important conditions on

the shelf and in the six estuaries/nearshore areas identified

for special study.

Chapter 6: Socioeconomics - Describes many of the key marine related

economic patterns and conditions in the coastal counties in the

study area with a particular emphasis on the role of the marine

fishery, both commercial and recreational.

Chapter 7: Conceptual Ecosystem Model - presents conceptual ecological

relationships at three levels or tiers. The levels from 1 to 3

have increasing levels of detail and complexity.

Chapter 8: Summary - describes some of the key points and insights

developed in the various topical and process chapters.

The six appendices (A-F) containing the annotated bibliographies are

incorporated as separate documents. Appendix G of this report are a series

of Socioeconomic Summaries for each coastal country described in Chapter 6.
Chapter 2 - THE PHYSICAL ENVIRONMENT

by Dr. Peter Hamilton,

Dr. Evans Waddell

and

Dr. Robert Wayland

Science Applications International Corp.

2.1 Introduction

This chapter presents a general description of key meteorological and

physical oceanographic conditions and processes which are significant to

the ecosystem in the study area. The objective has been to use the existing

literature and published data to describe such things as patterns and

ranges of conditions, with some general discussion of responsible

processes. Specifically, the material presented is not meant to provide a

detailed understanding of the potential physical mechanisms. Rather, the

objective is to provide an ecologically meaningful framework within which

to view such things as energy paths, material transport, recruitment and

limiting environmental conditions. As will become apparent, there are a

number of physically important variables and processes in the study area

that are neither well-resolved nor understood, which point to the need to

expand the regional oceanographic data base with tailored measurement and

synthesis program(s).

Chapter 2 is split into two related primary sections, Meteorology

(Section 2.2) and Physical Oceanography (Section 2.3) . The Annotated

Bibliographies, appendices to the main report, are divided on this

same basis and are presented as two separate appendices, A and B,

respectively.

2.2 Meteoroloay

2.2.1 Introduction

Synoptic climatology of a geographic region is based primarily on the types

of air masses which seasonally dominate the local weather. In general,

mid-latitude locations are characterized by two distinct seasonal weather

patterns, which are linked synoptically by less well-defined transition

periods. Meteorological conditions found within the orthastern u1f Qf

exico (NEGOM) follow this generic scenario quite well and are

characterized by two distinct synoptic seasons: winter (December - March)

and summer (May - October) - Between these two dominant weather regimes are

brief transitional periods of approximately one month duration (e.g. April

and November) . The region does not experience the lengthier spring and

fall transitional periods, which characterize the mid-latitude continental

sections of the United States. The Gulf of Mexico has been divided into

eastern, central and western regions for previous oceanographic and

meteorological studies. The west Florida Shelf region, or eastern Gulf of

Mexico, is characterized by the persistence of warm, moist maritime

tropical (mT) air masses throughout most of the year. The central and

western Gulf of Mexico, while dominated by the warm, moist mT air masses in

the summer, are exposed to strong arctic intrusions of cold, dry

continental polar (cP) air masses during the winter season. The "collision

2-1
zone" between these two differing air masses in winter months is often

found in the northeastern Gulf of Mexico, causing it to be a prime location

for the formation and development of winter extratropical cyclones (low

pressure systems) . Additionally, the warm shallow shelf waters in summer

months, coupled with the warm Loop Current to the south of this region,

have also made the NEGOM the landfall target of several major tropical

systems over the past 30 years (Florida A&M University, 1988)

Several major global circulation features play a role in defining the

synoptic climatology of the Gulf of Mexico. However, the two dominant

circulation features influencing the region are the respective positions of

the polar front (e.g. polar jet stream) and the Atlantic sub-tropical gyre

(e.g. "Bermuda High"). The Atlantic sub-tropical gyre dominates the winter

circulation patterns of the eastern Gulf of Mexico, with its strong

clockwise circulation advecting warm tropical air into the region. This

circulation feature is responsible for the relatively mild winter

conditions observed along the southwestern and central Florida coast. The

other winter meteorological feature in the Gulf of Mexico is the southward

excursion of the polar jet stream. The high-amplitude patterns of the

winter polar jet stream bring strong, cold, dry continental air masses into

the region. These cold air outbreaks (CAO) provide a great deal of energy

to the marine atmospheric boundary layer (MABL) over the shallow inner

shelf regions of the northern Gulf. Fernandez-Partegas and Mooers (1975)

found these strong polar outbreaks to occur at 3- to 10-day intervals

during the period between October and March. Reviewing records for the

past 103 years in Louisiana, Mortimer et al. (1988) determined that

approximately every five years, the Gulf coastal region experiences severe

freeze conditions, resulting from a strong CAO. Dimego et al. (1976)

observed approximately 8-9 frontal passages per month in the northeastern

Gulf of Mexico during winter. The frequency of frontal systems decreases

markedly during the core summer months (e.g., 2 per month from June through

August), with slight increases on either end of this period (e.g., 3-5 per

month in May and September/October).

During the summer months, the northward migration of both the Atlantic subtropical gyre and the polar jet stream allow the Gulf region to be

influenced strongly by the northeast trade winds. The increased influence

of the trade winds on the region provides the steering mechanism for

tropical wind/pressure systems which form in the eastern Atlantic to find

their way into the Gulf. In past decade (1985-1995), the northeastern Gulf

has experienced an increase in the number of tropical systems, relative to

the previous 10-year period. However, although the region is subjected to

varying extremes of synoptic weather from hurricanes and extratropical

cyclones to cold air outbreaks, the relatively warm waters of the

surrounding Gulf of Mexico serve as a stabilizing influence, resulting in a

mean synoptic climatology which is mild (Florida A&M University, 1988)

The following sections will describe in detail the individual elements of

the synoptic climatology of the northeastern Gulf of Mexico: temperature,

winds and extratropical/tropical storms.

2.2.2 Air and Sea Surface Temperature Climatology

Mean annual variations in surface temperature at National Weather Service

(NwS) locations across the northeastern Gulf of Mexico region are similar.

2-2
Tables 2-1 through 2-4 summarize the mean monthly surface temperature

conditions at the NWS sites located in Mobile, Alabama; Pensacola, Florida;

Apalachicola, Florida and Tampa, Florida. The observations presented in

these Tables represent the long-term 30-year climatic mean. The greatest

variability in the temperature data is found during winter months (December -

March), where there is approximately a 5.6°C (10°F) temperature difference

between Mobile and Tampa during January. The northern tier cities show

little variation during the winter, exhibiting monthly mean temperature

differences less than 1.7°C (3°F) . However, Pensacola and Apalachicola,

Florida are slightly warmer (e.g. <1.1°C [2°F]) than Mobile, Alabama during

winter, which is attributed to their close proximity (nominally less than

16 km) to the warmer Gulf waters. Tampa is located far enough south that

only the strongest cold air outbreaks reach the region, leaving this area

considerably milder than the northern locations during winter.

During the summer months (May - October), variations in the north-south and

east-west surface temperature patterns are greatly reduced. All four of

these locations experience sea/land breeze circulations during summer. The

resulting daytime marine influence moderates extreme air temperatures at

these continental locations. The summer reduction in temperature

variability in the northeastern Gulf of Mexico is attributed to the

northward retreat of the polar jet stream, which results in a reduction in

frontal activity and the stabilizing influence of the increased presence of

the moderating northeast trade wind circulation. Florida A&M University

(1988) observed similar seasonal trends in temperature across the entire

Gulf of Mexico utilizing data collected over a 17-year period.

The sea breeze circulation, which flows inland at the coastline on fairweather days, is generated by the temperature differential between the

"hot" land mass and the relatively cool ocean region. This thermal

contrast increases during daylight hours (maximized in early to midafternoon) producing pressure differences in the lowest levels ( 300 m) of

the atmosphere, which causes the low-level "sea breeze" to occur. However,

during nightime hours, the pressure difference is markedly reduced and is

sometimes reversed, creating a much weaker land breeze (Simpson 1994)

The magnitude of the sea breeze and its inland/offshore extent are very

localized phenomena. In hot, tropical environments, where the synoptic

pressure gradient is relatively constant, sea breeze winds reach 6 to 7 rn s' on average. However, in mid-latitude locations the movement of other

synoptic phenomena (i.e. anticyclones and cyclones) often moderate the

spatial/vertical extent and magnitude of the local sea breeze. Hsu (1988)

has documented sea breeze circulations in the Gulf of Mexico with along

coast dimensions of approximately 200 km, which extend 30-40 km inland

during the strongest part of the events. The overall vertical extent of

sea breeze circulations systems in the Gulf can reach 3 km (i.e. -700 mb)

Of particular interest to oceanographic processes is the variation in mean

monthly sea surface temperature (SST) relative to the overlying air

temperature. This temperature differential is the mechanism which allows

the exchange of surface sensible and latent heat energy between the lowest

layers of the atmosphere and the ocean surface layer. Wayland and Rarnan

(1989, 1994) have documented large instantaneous sensible (200-300 Wm2)

2-3
Table 2-1. Long-term climatological data collected at the Mobile, Alabama National Weather Service (NWS) station for the interval 1951-1980. PARAMETER JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NO

TEMPERATURE (°F) Daily Max 60.6 63.9 70.3 78.3 84.9 90.2 91.2 90.7 87.0 79.4 6

DailyMin 40.9 43.2 49.8 57.7 64.8 70.8 73.2 72.9 69.3 57.5 4Monthly Mean 50.8 53.6 60.1 68.0 74.9 80.5 82.2 81.8 78.2 68.5 5

PRECIPITATION (inches) Monthly Mean 4.59 4.91 6.48 5.35 5.46 5.07 7.74 6.75 6.56 2.62 3

TsStorm Days 2.0 2.3 4.9 4.9 7.2 11.9 18.0 14.3 7.4 2.1 

PRESSURE (mb) 1012.811011.611009.311008.811007.511007.911009.311008.911008.51l010.61101Monthly Mean
Table 2-2. Long-term climatological data collected at the Pensacola, Florida National Weather Service (NWS) station for the interval 1951-1980. r PARAMETER JAN -FEB _MAR APR MAY JUN JUL AUG SEP OCT NO

TEMPERATURE (°F) Daily Max 61.2 64.1 68.9 76.8 84.2 89.0 89.7 90.0 86.3 79.9 6

Daily Mm 43.0 45.5 50.8 59.4 66.1 72.1 73.9 73.6 70.2 60.0 4Monthly Mean 52.1 54.8 59.9 68.1 75.2 80.6 81.8 81.8 78.3 70.0 5

PRECIPITATION (inches) Monthly Mean 4.37 4.69 6.31 4.99 4.25 6.30 7.33 6.67 8.15 3.13 3T'Storm Day 2.0 3.0 5.0 4.0 6.0 11.0 15.0 15.0 7.0 2.0 PRESSURE (nib) Monthly Mean '°'66I1016'V°'31I10135L101051'°122I'°127I'°'29V°5I10142I'°'
Table 2-3 Long-term climatological data collected at the Apalachicola, Florida Nationa

Weather Service (NWS) station for the interval 1951-1980. PARAMETER JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NO

TEMPERATURE (°F) DailyMax 61.1 63.1 67.6 75.0 81.8 86.4 87.5 87.7 84.7 78.3 6

DailyMin 46.3 48.5 53.8 61.5 68.0 73.6 75.2 75.2 72.4 63.3 5MonthlyMean 53.7 55.8 60.7 68.3 74.9 80.0 81.4 81.5 78.6 70.8 6PRECIPITATION (inches) MonthlyMean 3.07 3.78 4.70 3.61 2.78 5.30 8.02 8.07 9.00 2.88 2T'Storm Days 2.0 2.0 4.0 3.0 5.0 10.0 16.0 16.0 10.0 2.0 

PRESSURE (mb) Monthly Mean 1020.3 1020.4 1017.8 1017.5 1014.7 1016.5 1016.9 1016.7 1015.2 1017.0 101
Table 2-4. Long-term climatological data collected at the Tampa, Florida National Weather Service (NWS) station for the interval 1951-1980. PARANETER JAN FEB MAfl APR M7,Y JUN JUL AUG SEP OCT NO

TEMPERATURE (°F) DailyMax 70.6 71.9 76.1 82.4 87.5 89.9 90.1 90.4 89.0 83.9 7

Daily Mm 50.1 51.7 55.9 61.6 66.9 72.0 73.7 74.0 72.6 65.5 5

MonthlyMean 60.4 61.8 66.0 72.0 77.2 81.0 81.9 82.2 80.8 74.7 6

PRECIPITATION (inches) Monthly Mean 2.33 2.86 3.89 2.10 2.41 6.49 8.43 8.00 6.35 2.54 1

T'Storm Days 1.0 2.0 2.0 3.0 6.0 14.0 21.0 21.0 12.0 3.0 PRESSURE (mb) Monthly Mean 1019.711018.211017.7 10l5.41l016.5110l7.61l017.31l0l5.2110l6.5110l

1020.2
and latent heat (300-400 Wm2) fluxes over the shelf during extreme CAOs.

Huh et al. (1984) documented the effects of CAOs on shelf hydrography in

the northeastern Gulf of Mexico.

In an effort to document these processes for the northeastern Gulf of

Mexico, approximately eight years of meteorological data was obtained from

the National Data Buoy Center (NDBC) Coastal-Marine Automated Network (CMAN) station located at Dauphin Island, Alabama, and an additional four

years of data was also obtained for NDBC buoy 42015, which is located in

relatively shallow water just offshore of Dauphin Island.

Figures 2-la through 2-lc show the respective monthly mean SST time series

for surface air temperature, sea surface temperature, air-SST and the

sensible heat flux for the Dauphin Island data record. Similarly, Figures

2-2a through 2-2c display similar time series for NDBC buoy 42015. The

most noteworthy observation from these Figures is the tendency of the sea

surface temperature to follow the surface air temperature quite closely.

At both Dauphin Island and buoy 42015, the mean monthly SST is generally

(except for a couple of isolated occurrences) greater than the mean monthly

surface air temperature, indicating that the prevailing mean heat flux is

from the oceanic air-water surface layer into the marine atmospheric

boundary layer. The largest temperature differential at these shelf

locations occurs during the summer months (Figures 2-la and 2-2a), which is

attributable to the coastal location of the SST measurements. This result

differs from the earlier finding of Florida A&M University (1988), where

the deep water buoys across the central Gulf (-26°N) were analyzed. For

those deep water locations, the air-SST differential was maximized during

winter and minimized during summer.

2.2.3 Wind Climatoloqy

The wind climatology of the northeastern Gulf can be divided into two

distinct periods, winter and summer, just as can the temperature and storm

climatologies. Winter is characterized by frequent frontal incursions and

extratropical cyclones, which produce large shifts in wind speed and wind

direction in response to rapidly changing atmospheric pressure and thermal

gradients. In general, the summer is characterized by light and variable

winds originating from the northeast trade wind circulation. The reduced

influence of the Bermuda High and lack of frontal activity serves to reduce

mean pressure fluctuations across the region. In response to the strong

differential heating of the land and adjacent waters along the coast during

the summer months, significant sea/land breeze circulations develop (Sonu,

et al. 1971) . The summer months are subject to an occasional tropical

system, but these storms tend to move relatively rapidly through the

region, causing only a short-term, but at times intense, "pulse" to the

atmospheric and oceanographic systems.

Mean wind roses for the four National Weather Service stations discussed

above are presented in Figure 2-3a,b for the winter period (December -

March). The westernmost stations (e.g., Mobile and Pensacola) show the

seasonal dominance of the polar Jet Stream, while the easternmost stations

are dominated by the influence of the Atlantic sub-tropical gyre. At Mobile

and Pensacola, the influence of the polar jet results in a substantial

2-8
35

3025

20

15

10

5

2.5

2.0

1.5

1.0 0.5

0.0

-0.5

-1.0

-1.5

-2.0

-2.5

25.0

20.0

15.0

10.0

0

0

5.0

0.0

-5.0

-10.0

Dauphin Island, Alabama - NDBC C-MAN Station

12 24 36 48 60 72 84 96

Month ( Month 1 = 1(87)

Dauphin Island, Alabama - NDBC C-MAN Station

i HIiiFWIkbiL wtr

0 12 24 36 48 60 72 84 96

Month (Month 1 = 1(87)

Figure 2-1. Monthly mean air(°C), sea surface temperature (°C), air-SST

(°C) and sensible heat flux (Wm2) for the period 1987-1994

for the NDBC C-MAN station located at Dauphin Island, Alabama.

2-9

wiIIllflhIltIllIlUItIlt r-rriiirwraiii

_____________

AirrC) ----ssTrc)

£ 4 9 I

II " i" I I I

, I II

I

!1t'i*ri,gt

I i I

I %

II

II

S % I ' I 1,1 $ $. I % I AI 'I'I I, ç

'I 0 12 24 36 48 60 72 84 96

Month (Month 1 = 1/87)

Dauphin Island, Alabama - NDBC C-MAN Station
35

3025

10

5

45

40

35 E

30 x

25

20 z

C, U, 10

(I)

0

0

$

0

NDBC Buoy 42015

1r'

AirrC) -- SSTCC}

54

3

2

10

1

-2

-3

-4

-5 0

12 24 36 48 60

Month (Month I = 1187)

NDBC Buoy 42015

72 84 96

I'

0

Figure 2-2. Monthly

(°C), air-SST (°C) and sensible heat flux (Wm2) for the

period 1987-1994 for NDBC buoy 42015.

2-10

I A.

'

S

S -S

'S

12 24 36 48 60 72 84 96

Month (Month I = 1187)

NDBC Buoy 42015

96

U

U

12 24 36 48

Month (Month 1 = 1187)

60 72 84

mean air temperature (°C), sea surface temperature
1.3 CALM WINDS 2.85% NOTE f,eq.end,s idicase direalos from ,.*lcJ Ihe dod Is blosisS. N WiND SPEED (KNOTS) 7I0 11.16 1 2! +2! CALM WINDS 5.43% NOTE Freqoedes idicte di s-s cut Jr." ,.-hlch he s-id Is blowing NS WIND 

,. 4-6 

Figure 2-3a. Winter (December - March) wind roses for the National Weather Service st

Alabama and Pensacola, Florida. Data is for the nine-year period 1984-1992. Mobile, Al (Winter) Pensacola, Fl (Winte

December 1-March 31; Midnight-i 1 PM December 1-March 31; Midn
'.3 CALM WINDS 10.73% NOTE. Freq....de: I,.dfrale dkeafon /ro,. .61th ..M Is blow.g. S WIND SPEED (KNOTS) 740 11.16 17.21 +21 wCALM WINDS 5.77% NOTE Fcq.Mdes I,.dicase threctlo,. f,,, ..lpkh II,. s.v.d u bl.ss.*g. S WIND SPEE

Figure 2-3b. Winter (December - March) wind roses for the National Weather Service statio

Apalachicola, Florida and Tampa, Florida. Data is for the nine-year period except for Apalachicola, which is for the period 1988-1991. Apalachicola (Winier) Tampa. Fl (Winter) December 1-March 31; Midnight-lI PM December 1-March 31; Midnigh

N N
northerly component to the winter wind patterns. At more easterly

locations around the Florida Panhandle, the influence of frontal activity

is reduced and the increased importance of the Atlantic sub-tropical gyre

is observed. At Apalachicola, the predominant winter flow is off the ocean

from the southeast, while at Tampa, the mean circulation for this interval

is more easterly. This circulation pattern is indicative of a synoptic

wind pattern flowing clockwise around the Bermuda High. However, at all

four locations, there is considerable variability in the seasonal wind

rose, indicating the frequency of frontal passages, storm systems and other

perturbations in the synoptic flow.

The summer (May - October) wind roses for the four NWS stations are

displayed in Figure 2-4a,b. In general, these data show the decreased

influence of both the Atlantic sub-tropical gyre and the polar jet stream

on the wind climatology of the eastern Gulf of Mexico, and an increase in

the frequency of calm wind conditions. Data from Tampa also show increased

influence of trade winds, which results in a significant easterly component

during summer. The northern three stations are on the fringe of the trade

wind circulation, and thus do not display a significant trade wind

component. Additionally, each location shows an increase in onshore flow

during summer, which is attributable in part to the increased influence of

the sea breeze circulation systems.

The NDBC C-MAN station at Dauphin Island and Buoy no. 42015, located just

offshore of the island (e.g. 42015), show similar distinct seasonal wind

patterns as well (Figure 2-5) . The mean monthly time series that are shown

in Figure 2-5 indicate a similar increase in wind speed during winter,

followed by the expected decrease in magnitude during the summer months.

The mean monthly wind flow is from the south-southeast during winter, and

becomes southerly to southwesterly during summer.

2.2.4 torras

The Gulf of Mexico storm season climatology is affected by both

extratropical and tropical cyclone tracks. Florida A&M University (1988)

summarized both of these climatologies for the entire Gulf region. Thus,

for specific details the reader is referred to the earlier document;

however, a subset of this information which is relevant to the northeastern

Gulf of Mexico will be presented here.

Winter storm climatology for the Gulf of Mexico is dependent upon the

genesis and transit of extratropical cyclones within the region. Using a

100-year data set developed by Hayden (1981), an analysis of storm tracks

(based on 2° by 50 grid cells) indicates that the Texas-Louisiana shelf

has the highest occurrence (4.2 storms, ± 2.4) for extratropical cyclones

during winter (December - March) . The mean frequencies and standard

deviations decrease markedly to the east and south of this region. Below

approximately 25°N latitude, the mean winter storm frequency is generally

less than 1. Grid cells representing the northeastern Gulf of Mexico have

winter seasonal storm frequencies of 2.9 (±1.9) and 2.1 (±1.7),

respectively. In a more recent study, Johnson, et al. (1986) observed

similar patterns in a winter data set collected between 1977-1983. In that

study, approximately 80% of all winter cyclones in the Gulf region

2-13
CALM WINDS 5.71% NOTE: Freqo,des frdicgse direction fto, o9dth the ,tiM t, blowioS. '.3 WIND SPEED (KNOTS) 4.6 7.10 11.16 17-21 +21 CALM WINDS 9.10% NOTE: Freq.enc1ct indicete direction fro,n ,ti,ich she wind is bt.m4ng. '-3 S WIND SPEE

7-10 

Figure 2-4a. Summertime (May - October) wind roses for the National Weather Service st

Alabama and Pensacola, Florida. Data is for the nine-year period 1984-1992. Mobile, Al (Summer) Pensacola, F! (Summer) May 1-October 31; Midnight-Il PM May 1-October 31; Midnight-l

N N
NO7 Fre,'4., I,,dlcageIi,eciIo,i from roifriuh, iod 1, boomg. NO7 Froqror.cfrs iodkoie direction from '.uic ii,, .ctnd s bio.roog. Figure 2-4b. Summertime (May - October) wind roses for the National Weather Ser

Apalachicola, Florida and Tampa, Florida. Data is for the nine-year period 

for Apalachicola, which is for the period 1988-1991. Apalachicola (Sununer) Tampa, Fl Su,n,ner, May 1-October 31; Midnight-Il PM May 1-October 31; Midnight-i

N N S S CALM WINDS 14.96% WIND SPEED (KNOTS) CALM WINDS 8.11% WIND SPE
10

10

8

6

4

2

0

Dauphin Island, Alabama - NDBC C-MAN Station

NDBC Buoy 42015

0 12 24 36 48 60

Month (Month I = 1/87)

0 12 24 36 48 60 72 84

Month (Month I = 1/87)

Wind Speed (mis)

Wind Direction (T)

360

60

30

0

96

Figure 2-5. Wind speed (ms') and direction (°True) for the period 1987-

1994 for (a) the NDBC C-MAN station located at Dauphin Island,

Alabama, and (b) NDBC buoy 42015.

2-16

.vv

330

300

270

240

' 'I 120

I 90

60 Wind Speed (mis)

Wind Direction (°T) 30

0 a I i i a I I

330

300

270

240

0.

I II IIII I' 'I 'I a ' S 'I 210

180

I' S

-. 'I I- S. #,

II a'; a"

a:

a' '! 150

120

0

Is 90

72 84 96
developed in the west-central Gulf of Mexico (e.g., west of 90°W latitude),

leaving only 2O to develop in the central and eastern Gulf.

The north-central Gulf of Mexico, while not the major region of winter

cyclogenesis in the Gulf, is also an important location for extratropical

activity. In the northeastern Gulf, cyclogenesis generally occurs along

stalled or slow-moving frontal boundaries residing across the northern tier

of the region. Storms developing in the north-central Gulf region, which

are generally linked dynamically to stronger upper-level storm centers,

tend to track eastward along the frontal boundary (e.g., across the

northeastern Gulf of Mexico), crossing over the Florida Panhandle and

recurving northward along the Atlantic seaboard. Such systems are capable

of extracting large amounts of heat from the oceanic surface layer of the

NEGOM, and of generating sufficiently strong surface winds to create

vigorous mixing of the shallow shelf waters.

An analysis of the summer (May - October) cyclone data shows that the storm

frequency maxima shift towards the central and southeastern Gulf of Mexico,

reflecting the increased influence of tropical systems on the Gulf-wide

storm track climatology. Essentially, the summer storm track climatology

for the Gulf of Mexico is determined by the frequency and direction of

tropical cyclone systems. With the polar Jet Stream positioned well north

of the region, the opportunity for frontal incursions and subsequent

extratropical cyclogenesis events in the Gulf region is infrequent.

Neumann and Pryslak (1981) conducted a detailed analysis of tropical

cyclone activity for the North Atlantic basin, including the Gulf of

Mexico. This summary documented the frequency of occurrence (based on 2°

by 2° grid cells) for both tropical storms (e.g., sustained winds of 34

knots [39 mph or 18 rn/si) and hurricanes (e.g., sustained winds of 64

knots, [74 mph or 33 mIs]) in the basin. Their results indicate that the

southeastern and central Gulf of Mexico have the highest frequency of

occurrence for tropical storm systems. The Yucatan Channel is the most

likely entry point into the Gulf of Mexico for tropical storms forming in

the Caribbean and further east in the Atlantic Ocean. Tracks that storms

forming early in the hurricane season tend to move into the Gulf through

the Yucatan, while storms forming late in the season often recurve

northward, prior to reaching the Straits of Florida and the Gulf of Mexico.

The standard hurricane season begins on June 1 and ends on November 30.

When considering only storms that reach hurricane intensity, they have an

almost equal probability of entering the Gulf from either the Straits of

Florida or the Yucatan Channel.

Figure 2-6 summarizes decadal tropical cyclone activity in the northeastern

Gulf of Mexico over the past 100 years. The region has been divided into

two smaller areas: the Big-Bend area and the Panhandle area. The average

number of storms influencing the region has declined markedly over the

interval between 1976-1985, reaching an all-time low of 7 storms per

decade. Over most of the 20th century, the region has averaged 10-12

cyclones per decade. In general, the frequency of occurrence for cyclones

has tended to be out-of-phase between the Big Bend area and the Panhandle

region over much of the past century (e.g., increased activity in one area

is associated with decreased activity in the other)

2-17
z0

- 29.. .. - 28i

27.

26

-89

20

16

16

14 2

5

12

10

' 8 16

.420

-. Panhandle

.- Bg Bend

-0- Total

Tropical Storms & Hurricanes

(Sustained Wind Speed 18 mIs)

.200m

'S .is I u 4. ..

1900 1920 1940 1960 1980 Bedm9 Date cfO.oade

a a -88 -87 -86 -85 -84 Longitude (°W) -83 -82

Figure 2-6. Summary of tropical cyclone activity for the northeastern Gulf

of Mexico for the period 1886-1985. Data extracted from the

NOA/NCDC/Asheville HURDAT database.

2-18

-85 -84 -83 -82

31

30

29

IBI9 Bend Areal

Tampa

28

27

20m

Wi.

p. r 26

-89

31

-88 -87 -86

30_)

- ___

Alabama Florida

- Panhandle Areal
2.3 hysica1 Oceanograh

2 .3.1 Introduction

The study region includes the shelf, and upper slope and offshore of the

Florida Panhandle and the west Florida shelf north of Tampa Bay. The

natural division between the eastern and western Gulf of Mexico for

physical oceanographic process is about 90°W longitude, between the

Mississippi Delta and the Yucatan Peninsula. East of the Delta, the Loop

Current (LC) dominates the circulation of the eastern basin. West of the

delta, the circulation is dominated by large, westward and southwestward

propagating LC anticyclones which interact with the topography, existing LC

eddies, secondary cyclones and smaller scale anticyclones to generate

complex circulation patterns, Similarly, the northern shelf, east of the

delta, should be considered all one system because of shelf geometry and

major fresh water inputs from the Mississippi, Mississippi Sound and Mobile

Bay just west of the study area. Therefore, this review of circulation

processes will include some aspects of the Mississippi and Alabama shelf

waters east of the Mississippi Delta.

The shelf narrows from about 120 to 60 km from just east of the Chandeleur

Islands to the head of the DeSoto Canyon. There is an extensive area of

shallow water behind the barrier islands consisting of the Mississippi,

Chandeleur and Breton Sounds. The slope (200-2000 m) is fairly broad with

complex, rough topography between the Mississippi Delta and DeSoto Canyons

(Figure 2-7) . East of Pensacola, the shelf remains narrow until Cape San

Bias, where it abruptly broadens to about 200 km and becomes the Big Bend

area of the west Florida shelf. This area includes the very shallow, broad

inner-shelf waters of Apalachee Bay and waters further south off Cedar

Keys. Between the head of the DeSoto Canyon and 26°N latitude, the slope

becomes progressively steeper, particularly below bOOm. This very steep

slope is known as the Florida Escarpment.

This review of the physical oceanography is organized starting with the

deep eastern basin. The Loop Current (LC) and its variability is

discussed, then the effect of LC and related circulations on the slope and

outer shelf of the NEGOM. Other aspects of slope currents are also

explored, including secondary small-scale cyclones and anticycbones that

are believed to be prevalent over the NEGOM slope. Eddies and LC

intrusions are known to influence the outer shelf; however, the mid- and

inner-shelf circulations have important contributions from wind forcing and

the input of fresh water from the Mississippi and coastal rivers. The

latter has a strong east-west gradient, with most of the fresh water input

in the west. Mississippi River water flows onto the outer and middle

shelf, unlike the other rivers which discharge into sounds, bays or the

shallow nearshore zone. Coastal river plumes and fronts are likely to be

present in some inner-shelf areas.

wind-forced shelf circulation patterns are also likely to be complex

because of the changes in direction in the trend of the shelf isobaths, the

changes in shelf width and the existence of sharp corners in the coastline,

such as at Cape San Blas. Continental shelf waves are known to be a

significant factor in coastal sea-level fluctuations on the west Florida

shelf.

2-19
Figure 2-7. Map of the region showing bathymetry, various features and key

locations.
The following sections begin with a view of the Loop Current, and then the

conditions on the slope and shelf.

2.3.2 Loop Current

The Loop Current is a branch of the Gulf Stream system, which enters the

Gulf of Mexico through the Yucatan Channel and exits through the Straits of

Florida. The clockwise circulation of the LC extends northwards as a

quasi-stationary meander that shows considerable variability in the

northward extent and the shape of the front between the LC and the Gulf

waters (Vukovich, 1986) . In winter and spring, there is sufficient

contrast between the warm LC and Gulf surface waters that the LC is clearly

observed in cloud-free Advanced Very High Resolution Radiometer (AVHRR)

satellite images (Figure 2-8). In summer (June to November), high humidity

and almost uniform surface water temperatures across the Gulf make the LC

difficult to distinguish in AVHRR satellite data, Maximum surface current

velocities in the LC range from 100 to 200 cms'. Flows extend down to

about 800 m, which is the depth of the Straits of Florida sill. Below

1900 m, the depth of the sill in the Yucatan Channel, Gulf of Mexico is a

closed basin with a maximum depth of 3600 m. Figure 2-9 shows the

temperature structure of a moderately extended LC obtained from an AXBT

survey. Features to note are the closed temperature contours in the center

and the cold pools along the west Florida slope. Deployment of a drifter

in the LC in 1985 showed that closed anticyclonic circulation is present in

the center and that the LC can extend northwards from 24°N to 27°N latitude

in as short a time as two months (Lewis and Kirwan, 1987). The velocity

structure obtained from AXCPs on the east-west directed center line of this

survey is shown in Figure 2-10. Strong northward and southward surface

flows are seen near the western and eastern edges, respectively. Flows are

strongly sheared vertically and horizontally on the outer edges, but there

is a suggestion of more depth-independent solid body rotating type flows

over the upper 200 m at stations 8 and 12. This is similar to the velocity

structure measured across a warm anticyclonic eddy (Cooper et al., 1990).

Below the 800 m depth of LC flows, there is a suggestion of opposing

counter currents. The northward deep flows over the steep west Florida

slope have been confirmed with current meter observations (Molinari and

Mayer, 1982; Hamilton, 1990). When extended far to the north the LC can

shed a large warm anticyclone. Such a detached eddy, known as a LC eddy,

has a diameter of 200 to 300 km and subsequently moves westward and

southwestward into the western Gulf basin. Figure 2-11 shows hydrographic,

drifter and current meter data for the LC and a recently detached eddy

[eddy B or 'Fast" eddy (Lewis and Kirwan, 1987)] and its position 4 months

later. Numerical models of LC eddy shedding suggest that the detachment

process is quite slow and there are connecting circulations between the

eddy and the LC even after the center of the eddy has reached 90°W

longitude (a practical measure that the eddy is free of the LC and will

continue to propagate into the western Gulf) . There are many examples from

AVHRR imagery of LC eddies detaching and reattaching to the LC a number of

times over several months before finally being shed. There have been many

investigations of the frequency of LC eddy shedding. An early study (Maul,

1977) postulated an annual cycle for LC growth and retreat. Early

numerical models (Hurlburt and Thompson, 1980) suggested that a fundamental

period was about 14 months. However, recent studies of the northward

extension using approximately 12 years of AVHRR data supplemented by

2-21
Sea Surface Temperature - Eastern Gulf of Mexico

Large warm LC

boundary filament

overthe west

Florida slope

February 12,

NOAA-1

Sea Surface Temperarture

- : ' ..

Figure 2-8. Labeled satellite image showing Loop Current, possible LC eddy

separation, large boundary filament over slope and outer shelf

offshore of the Big Bend Area.

2-22
AXBT SURVEY FLIGHT 840511 5/11/84 TO 5/14/84

89°W 88°W 87°W 86°W 85°W 84°W 83°W 82°W

31°N I I 31°N

3 00 N

290 N

28° N

270 N

260 N

25° N

240 N

230 N

22° N

89°W 88°W 87°W 86°W 85°W 84°W 83°W

150 METER TEMPERATURE (DEG C)

Figure 2-9. Contours of the temperature at 150 m depth clearly showing the

general depressed isotherm structure of the relatively warm

LC. There were three relatively shallow cyclonic features

along the west Florida slope boundary of the LC.

2-23
111111 200 1 ) UU/1I" ;?' , , ,,,,ilruril 1⁄4. ,-\ '-,.- ._g-- 400 / , I'l / ) S - 0 -. - 11 600u L- Ui \/ lt h I' u-i ':; / 5 800 4\/ I' ' -I t I- 1000 3 : I 1200 - 1400 -I 1600 0 SECTION 2A STATION LINEAR INTERPOLATION - j. N 10 AXBT SURVEY FLIGHT 8

5/11/84 TO 5/11/84 STATIONS 5 TO 16 TRANSECT NORMAL VELO

MIN =-151.31 MAX = 158

CM/SEC I I 50 100 150 200 250 300 350 400 450 500 DISTANCE (KM) Current Meters Figure 2-10. Normal velocities for an east-west transect shown in Figure 2-9. These AXCP 

with the subsurface current meter observations.
DEPTH (M) OF 20 C ISOTHERM

98W97W9bW95W94 wg3wg2wgl W90W89W86W87 W86W65W64 W83W 30 N

... ..30 N

o.CTD

21N ii 21N

e g7 tJ96 U95 W94 W93 W92 W91 W90 W89 68 W87 W86 W85 tJB4 W83 W

Figure 2-11. Two realizations of Eddy B from hydrography (depth of 20°C

isotherm), Lagrangian drifters and daily average 300-400 m

measured current vectors (from Hamilton, 1990)

2-25
regular XBT transacts between the Mississippi Delta and the Yucatan Channel

(Hamilton, 1990; Brown et al. 1986; Brown et al. 1989) have shown that the

fundamental period is about 8-9 months (Sturges, 1992; 1994) . Significant

peaks are found at about 5 months and 14-16 months. These are thought to

be the result of modulations of the fundamental period by the annual cycle

of the transport in the Yucatan Channel, and by the Florida Current

(Sturges, 1992). The times of LC eddy separations are known to be highly

variable, and tabulations by Vukovich (1988, 1995) show that the period

between separation of successive eddies can vary from 6 months to 17

months. The description of the genesis of eddy B by Lewis and Kirwan

(1987) indicates that the LC can grow in a sufficiently short time for a

new eddy to be shed in as little as 5 to 6 months after the previous

shedding event. The extent of the northward penetration, and whether the

axis of LC is northward or deflected towards the Mississippi Delta, are

thought to be related to the position and angle of separation of the LC

front from the Yucatan shelf. The theory is based on simple conservation

of vorticity arguments (Reid, 1972) and there is evidence (Molinari and

Morrison, 1988) that the further north and the larger the westward

deflection of the front at the point of separation from the Campeche Bank,

the larger the area of the eastern Gulf is covered by LC water.

An extended LC often has a multitude of frontal features, including large

filaments of LC water extending from the front and cold cyclonic

circulations associated with frontal eddies. Figure 2-9 shows 3 pools of

cold water between the LC and the west Florida slope. These eddies are

similar in character to those found along the Gulf Stream front in the

South Atlantic Bight (Lee et al., 1981), both in dimensions and speed

(Paluszkiewicz et al., 1983). The eddies appear to propagate around the LC

front, from the Campeche Bank around to the Dry Tortugas, where they often

stall and grow. This Dry Tortugas eddy eventually moves into the Florida

Straits and can cause large deflections of the Florida current between Key

West and Cay Sal Bank (Lee et al., 1995). It is thought that similar

frontal eddies can exist on recently shed LC anticyclones. Over the deep

water of the eastern basin, the cyclonic circulations of the frontal eddies

can be quite vigorous, and appear to be part of the cause of the streamers

and filaments that are often found north of an extended LC. Filaments are

found over the outer west Florida shelf (Paluszkiewicz et al., 1983) where,

because of the shallow water, they become stranded and dissipate.

Deep currents in the eastern basin are also dominated by the LC. Hamilton

(1990) showed that periodic extensions of the LC caused energetic

fluctuations of currents below 1000 in, and that the deep water off the west

Florida shelf was a generation zone for Topographic Rossby Waves (TRWs)

These waves propagate westward towards the Mexican slope at a typical group

velocity of -9 kmday1. Thus, deep currents are not necessarily directly

related to upper-layer eddy circulations, particularly in the western

basin. Numerical models (Oey, 1995) suggest that a preferred region for

the generation of TRW5 is the northeast corner of the Gulf, in the deep

water at the base of the DeSoto Canyon. However, according to the

barotropic instability theory of Malanotte-Rizzoli et al. (1987), the energy

source for these waves is the fundamental period fluctuations of the LC.

Within the LC and major LC eddies, but away from boundaries, a consistent

T-S relationship is found which has a subsurface salinity maximum of about

2-26
36.65 ppt with a corresponding temperature of about 22.5°C at an

approximate depth of 125-150m (SAIC, 1988) . Outside of these core waters,

lateral mixing in the upper A150m dilutes salinities causing scatter in the

T-S relationship. As found in these studies as well as other surveys, for

water depths of 200m or greater ai-id temperatures of A16°C, the T-S

relationship in the Gulf has little scatter which allows temperature to be

an excellent surrogate for salinity.

2.3.3 Slope Procerses

Currents and water mass structures over the continental slope, between the

Mississippi Delta and the west Florida shelf off Tampa, can be expected to

be highly variable. An extended LC, or recently shed LC eddies, may affect

flows over the slope directly or indirectly through frontal eddies and

filaments. However, when the LC front is far to the south, strong current

events are still observed on the northern slope. These are thought to be

secondary cyclones and anticyclones, which seem to be ubiquitous in the

Gulf of Mexico. Little quantitative information is known about these

eddies over the NEGOM slope. Recent surveys of the Texas - Louisiana slope

have described incidences of these eddies (Hamilton, 1992), and there are

expected to be similarities between the two slope regions. Most of the

evidence for the existence of secondary eddies over the NE Gulf slope comes

indirectly from satellite imagery, which often shows LC filaments wrapped

cyclonically or anticyclonically around cold or warm eddies, respectively.

Current meter observations over the slope are sparse. However, the

indications are that strong eastward upper layer currents (-60 cms1) that

last for several weeks can occur between the Mississippi Delta and the

DeSoto Canyon (Molinari and Mayer, 1982; Ebbesmyer et al., 1982; Kelly,

1991). There is also nonpublic/proprietary data from a number of deep

water sites that show similar events. Most of these are accompanied by

higher temperatures and can be attributed to the direct impingement of the

LC or a recently shed LC eddy on the slope. It is expected that slope

sites closer to the delta are more likely to experience eddy events than

sites further to the east. On the west Florida slope, direct LC intrusions

are likely to be quite rare. Three years of current meter observations at

26°N latitude, south of the study area (SAIC, 1987) show only 2 (or

possibly 3) events of strong southward currents (>60 cm-s1 at the shelf

break) that can be attributed directly to the LC moving over the shelf

break. At a similar mooring at 27.5°N latitude, off Tampa, only one highspeed event was observed over 3 years of measurements. Thus, the upper

slope on the east side of the DeSoto Canyon is not expected to be impacted

directly by LC flows.

On the slope in the NE Gulf, indirect LC effects, such as filaments and

diluted LC-derived surface waters, have been observed to be advected over

the slope and outer shelf. Huh et al. (1981) describes an intrusion of LC

water up the DeSoto Canyon to within 8 km of the shore. Kelly (1991)

defines three types of intrusions onto the Florida-Alabama-Mississippi

shelf and slope: (1) filaments intrude up the axis or along the east side

of the DeSoto Canyon, similar to the event described by Huh et al. (1981);

(2) the exchange of outer shelf water with a frontal eddy on the northern

periphery of the LC [or recently shed LC eddy]; and (3) the northward

advection of diluted warm LC-derived waters directly onto the shelf. A

2-27
sketch of these three types of intrusions is given in Figure 2-12 (Kelly,

1991) . For a two-year long data set, Kelly (1991) estimates that LC

intrusion affects the slope and outer shelf by one of the three mechanisms

about 44's of the time.

The processes that advect filaments or LC derived intrusions onto the outer

shelf are not clear at the present time. They probably involve the

interaction of frontal eddies with secondary cyclones and anticyclones over

the slope. Typical current speeds of events that are not caused by the LC,

or by large LC eddies, are 20-30 cms, and can be eastward or westward

(Molinani and Mayer, 1982; Kelly, 1991) . Along-slope coherence between

observations is usually low for moorings separated by less than 50 km. On

the Louisiana - Texas slope, cyclones and anticyclones with diameters on

the order of 50 to 100 km have been observed a number of times. They tend

to be long-lived (6 months or more) and relatively stationary (Hamilton,

1992) . An explanation for the characteristics of non-LC flows observed

over the slope in the NE Gulf would probably involve similar eddies.

Figure 2-13 shows a drifter track on the Louisiana - Texas slope which

shows the existence of a number cyclones and anticyclones. Also shown in

this Figure is a drifter making two circuits of a similar-sized anticyclone

just southeast of the delta. The northern edge of the LC was at about 27°N

latitude at this time. An AVHRP. image for January 12, 1988 (Figure 2-14)

clearly shows a secondary cyclone just west of the DeSoto Canyon which is

separated from the northern LC front by more than 150 km. There is,

therefore, circumstantial evidence that secondary eddies, similar to these

observed further west of Louisiana and Texas, are also common on the slope

of the NE Gulf.

Figure 2-15 presents monthly mean, maximum and minimum temperatures and

salinities computed using in-situ, time series measured 150m below the local

water surface on the upper slope in the DeSoto Canyon during MANES (Kelly, 1991).

Allowing for some instrument error, these data are consistent with the

temperature and salinity relationship expected in LC eddies and slope water

masses below the seasonal thermocline. As such these provide a reasonable

indication of the range of conditions which might be expected at this depth on

the slope adjacent to the shelf break.

Drennan (1965) presented hydrographic survey data illustrating transport of

relatively high salinity water onto the upper slope and outer shelf in the

Panhandle portion of the study area. In Figure 2-16, surface salinities

measured during a spring cruise (March-April 1965) suggest the presence of

a cyclonic feature in the DeSoto Canyon which was drawing less saline water

off the shelf while high salinity, and possibly LC water (36ppt), moved

onshore. The scale of this feature and corresponding exchange incorporated

the slope and outer shelf on both the eastern and western flanks of the

DeSoto Canyon.

2.3.4 Shelf Processes

2.3.4.1 Wind-Forced Circulation

Wind stress on the water surface is often a key circulation producing!

forcing mechanism for shelf environments. In the present study area, some

2-28
Figure 2-12. Simple illustrations of three types of LC/filament interactions over the Mi

Florida Panhandle slope and shelf (from Brooks, 1991).
DRIFTERS 03353 ARGOS3351 3/20/85 TO 12/31/

97°W 96°W 95°W 94°W 93°W 92°W glow go°w 89°W 88°W 87°W 86°W 85°W 84°W 83°W 82°W 

31 °N - __________ 

30°N 29°N 28°N 27°N 2 6°N 25°N 24°N E0c,tI " c' 353 Go frZ i/1000 /120 i \ (I y' I 97°W g6°W 95°W 94°W 93°W 92°W glow go°w 8g°w 88°W 87°W 86°W 85°W 84°W 83°W 82°W 

Figure 2-13. Trajectories of two drifters with x" placed at a daily interval. No. 33

anticyclonic slope eddies offshore of Louisiana and Texas. No. 3351 smotion on most probably related to LC boundary features. This driftentrained in the LC and moves out of the Gulf.
30°O'O"N

28°O'O"N

26°O'O"N

240010uN

-

NOAA-lOCh4 January 12, 1988 OO53UTC

88°00"W 86°00"W

I

I

8800sOflW

---nIflUIUflhI

86°O'O"W 84°O'O"W 82°O'O"W

Temp (C)

84°OO"W 82°O'O"W

I I

2-31

L

Kilometers

200 0

Nautical miles

100 0 Figure 2-14. SST image showing an eddy over the upper slope on the

eastern wall of the De Soto Canyon.

10 15 20 25

Scale

3O°OO"N

28°OON

26°OO"N

24°OON
12/1/87 5/1/88 Date Mooring C MIss./Aia. Shelf (150m below surface) 6 1/1/90 

I I I 

Figure 2-15 Monthly mean, maximum and minimum temperatures and salinities computed from 

on Mooring C from the MMS-funded MANES project. Circles are salitemperature. (See Figure 2-17 for mooring location.) Mooring C/Mid-Depth -u Mean Temp. 12 -.- Mean Salinity -.- Max. Temp. - .- Max. Salinity -n- Mm. Temp. .o.- Mm. Salinity 10 I I I I I I I I i i i i I I I I I I 20 I I I I 

I I I I I I I I I I 3/1/89 I I I I 10/1/88 I I I 8/1/89
31.0 30.5 30.0 29.5 29.0 28.5 28.0-90.0 -89.5 -89.0 -88.5 -86.0 -85.5 Salinity (pptl5 -1015 -20 -25 - 30 -31 -32 -33 -34 -35 - 35.5 -36 - 36.5 + Sta. r:'- ,..- ' 36.5 ' "S - - :' - -. O00 000 m Surface Salinity: 31 March - 9 April, 1965 (from Drennan, 1965) 

Figure 2-16 Plot of surface salinity contours digitized from a figure in Drennan (1965) . 

surface salinity shows an cyclonic feature in the DeSoto Canyon transportinshelf water offshore onto the slope while more saline water moved onshore. -90.0 -89.5 -89.0 -88.5 -88.0 -87.5 -87.0 -86.5 -86.0 -85.5 

-88.0 -87.5 -87.0 -86.5
of the most vigorous wind forcing takes place in winter, when there are

strong fluctuations in the wind (several day periodicity) caused by

frequent incursions of cold fronts from the north. The northern Gulf of

Mexico shelf is an area of cyclogenesis for winter storms caused by the

meeting of cold, dry continental polar air with warmer, more humid subtropical air over the Gulf. Warm surface waters found seaward of the shelf

break in winter are a crucial component to the genesis of winter storms.

In summer, synoptic-scale winds are relatively weak and from the east or

southeast. A substantial sea-breeze system is present over shallower

inshore waters (Sonu et al. 1971). The calm conditions of summer are

sometimes interrupted by the passage of hurricanes or tropical storms. The

region of the Florida Panhandle, and Alabama and Mississippi coasts, has

often been severely impacted by tropical storms and their associated storm

surges, traveling north over warm Gulf of Mexico waters.

On the west Florida shelf, the wind-forced response of middle and inner

shelf waters has been studied by Mamorino (1982, 1983), Mitchum and Sturges

(1982) and Mitchum and Clarke (1986). Weather band (2-10 day periods) sealevel and current fluctuations increase in amplitude towards the north from

Key West. The explanation is in terms of a forced continental shelf wave

propagating southward with the alongshore wind stress fluctuations, and an

associated free continental shelf wave which cancels out the sea-level

response at the southern boundary (Mitchum and Clarke, 1986. At Florida's

Big Bend, the shelf narrows by a factor of 3 and wind-forced current

magnitudes increase by a factor of 2 between the same isobath off Cedar Key

and northwest of Cape San Bias (Mamorino, 1983) . Coastal sea level

response decreases slightly over the same region.

The nearshore and mid-shelf regions to the west of the DeSoto canyon have

been less studied as regards wind forcing. The delta obstructs the shelf

to the west, and shelf currents measured just south of the delta show weak

to intermittent fluctuating flows when not under the influence of the LC or

an eddy interacting with the slope topography (Wiseman and Dinnel, 1988).

Chuang et al. (1982) indicated that inshore waters respond to the local

alongshore wind. There has been little study of the connections between

the wind-forced continental shelf wave response on the wide west Florida

shelf and the more complex NE Gulf shelf. The effect of blocking by the

delta on wind-forced flow has also not been considered or modeled. Kelly

(1991) reports that hurricanes generate strong currents which promote

flushing of the shelf.

Current measurements at the shelf break on both the west Florida (Mamorinc,

1983; Niiler, 1976; SAIC, 1987) and the NE Gulf shelves (Kelly, 1991) show

very weak or no relationship to the local wind. The fluctuations tend to

be of longer period than wind-forced responses and more likely are caused

by LC or slope eddy activity as discussed above.

2.3.4.2 Shelf Water Temperature and Salinit\

Because of its ecological importance, as well as being a variable which

changes in response to important environmental and circulation-producing

mechanisms, mean temperature and variability in and adjacent to the study

area are discussed. To support this, search was made to identify and

2-34
acquire selected field observations which could be used to characterize

conditions and patterns that might be expected in this study area.

In terms of geographic locations and depths of measurements, the most

appropriate and representative observations were made as part of the

Mississippi/Alabama Continental Shelf Ecosystem Study (Kelly, 1991) and the

Gulf of Mexico Physical Oceanography Program, Years 1,2,4 and 5 (SAIC,

1987) . Measurements made during these two MMS-funded studies bracketed the

present study area. Observations discussed were derived from temperature

time series measured at current meters or an NDBC buoy (42015) . The

general locations of these shelf and upper slope moorings and the inner

shelf buoy, as shown in Figure 2-17, are just west or south of the present

study area boundaries.

Information presented is primarily the monthly mean and extreme (max. and

mm.) temperatures. These statistics were selected since they indicate

many of the key patterns as well as when certain ecologically important

temperature thresholds were or were not exceeded. While the overall data

sets are not all coincident, the general patterns are consistent with that

expected for the shelf in the northern Gulf of Mexico. Although the

observations taken west of the Mississippi Delta are well away from the

present study area, they are included to illustrate the broad regional

similarity of certain patterns on the shelf in the northern Gulf.

Temperatures measured near or at the water surface are shown in Figure 2-

18. There are concurrent observations from west of the delta and on the

Miss./Ala. shelf (A, B, and C in Figure 2-17) . Also shown are air (A) and

sea surface (5) temperatures measured at NDBC Buoy 42015. The annual cycle

of temperatures is clearly evident. During fall and winter an increasingly

strong cross-shelf temperature gradient develops, with warmer water near

the shelf break and colder surface waters near the shore. Following the

occurrence of minimum monthly means, near-surface-cross shelf temperature

gradients disappear as the surface waters warm, coincident with and

approximately equal to the increasing air temperature. Maximum surface

temperatures occur in late June through September. Following this, surface

waters cool with the shorter days and decreasing air temperature. Minimum

monthly mean near-surface water temperatures occur in January/February.

When minimum mean temperatures occur in the shallow nearshore region, nearsurface temperatures at the shelf break are -6°C warmer. Fairly

consistently for the inner shelf data, monthly mean sea surface temperature

remained higher than the adjacent air temperature, indicating that the mean

heat flux was from the water to the air throughout the year.

During fall, as air temperatures and surface waters cool, the general

vertical temperature stratification decreases as heat is removed from the

upper portion of the water column (Huh et al. 1984). As shown in Figure 2-

19 the entire water column is eventually overturned (transformed from

vertically stratified to vertically well mixed) due to the increased heat

flux from water to air during more vigorous CAOs. The specific timing of

this transformation can vary interannually and depends substantially on the

local wind speed, and cumulative and specific air-water temperature

differences during CAOs. These strong fronts, that are often associated

with developing atmospheric low pressure systems, can also provide a source

of mechanical energy to facilitate vertical mixing.

2-35
Temperature Data

Proximate

Moonng Locations

Figure 2-17. Map with mooring positions shown. Moorings A, B and C were

part of the Mississippi - Alabama Shelf Study. Moorings E,

F and MD were part of the Gulf of Mexico Physical

Oceanography Study.

2-36
3230... II

28-

26-

24- 22_

20

18

F!16............................ 14-

12-

10........................ 8

Temp. at top instrument

(on indicated moorinal

-A-. Buoy 42015 Air Temp.

-S- Buoy 42015 SST(lm)

-o- Miss/Ala. Mooring A (1 Om)

-o- Miss/Ala. Mooring B (lOm)

-a- Miss./Ala. Mooring C (20m)

-s- W. Flo. Shelf, Mooring DA (1 7m)

s W. Flo. Shelf, Mooring F (17m)

... W. Fla. Shelf, Moor. E (50m)

E. Louis. Shelf Mooring BB (1 Om)

Figure 2-18. Near surface monthly mean temperatures for indicated

moorings. Included are air and water temperatures measured

at NDBC Buoy 42015.

2-37

7/1/85 1/1/88

Date
tine of Stohons No. 3 ! December 1978

1 2 3

Figure 2-19. Changes in shelf water stratification due to passage of a

front and cold air outbreaks offshore of the Florida

Panhandle (from Huh et al., 1984)

2-38

0

20

C 30

C-o

. 0

tine of Stations Nc. 4 26 November 1978

1 2 3 21.9 Temperature 'C

22.0

22.5

, 34.1 Salinity %. 10

20

3° 10 km

34.2

/

34.6

I.
Figure 2-20, for Mooring B on the Mississippi/Alabama shelf from November

1988 to March 1989, the vertical water column continued to cool with

relatively weak vertical stratification as compared to the summer months.

Comparable observations just south of the study area showed essentially no

vertical stratification in the mean during winter (Figure 2-21). Figure 2-

20 also illustrates the more intense stratification of mean temperatures in

summer, which reached a maximum of -7°C in September during both years

shown.

The mean temperature pattern reflects the cumulative influence of higher

frequency changes, which produced the monthly extreme temperatures

(maximums and minimums) shown in other Figures. From an ecological

perspective, the magnitude and duration of the minimum temperatures may be

a significant limiting factor to habitat suitability.

For near surface waters the monthly range of temperatures (max. -mm.) was

-4°C, with maximum annual temperatures (-30°C) occurring in September in

1988 and 1989. Although generally somewhat less than near the water

surface, the range of monthly near-bottom temperatures was occasionally as

large or larger than further up in the water column. Minimum temperatures

at this mid-shelf location were approximately 15-16°C, usually in

February/March.

At Mooring C (Miss./Ala.), located just seaward of the shelf break in 459 m

of water, the warmer winter temperatures (Figure 2-22) moderated the

amplitude of the annual mean temperature cycle as compared to further

onshore (Figure 2-18) . However, the monthly range was on occasion

considerably larger, primarily due to the presence of much cooler water

(see minimum temperature of -21.5°C in July 1989.) At 150 m depth on

Mooring C, the mean temperatures had no recognizable seasonal pattern and

varied on the order of 2°C while the an annual range of measured

temperatures was -6°C.

Similarity of annual shelf temperature cycles across the northern Gulf of

Mexico and on the northern half of the west Florida shelf is not

surprising, since many of the controlling conditions are quite similar.

Water over the slope is a relatively constant reservoir of warm water

(heat) with weaker seasonal fluctuations. Many of the shelf sites are

affected by the same cold air outbreaks and associated atmospheric low

pressure systems. Certainly, from Mobile Bay eastward, sources of fresh

water are rather limited (see Section 4.3) so that the shelf density

structure is dependent in large part on the annual (and shorter interval)

changes in temperature.

As discussed previously, higher frequency and aperiodic processes such as

LC eddies/gyres on the slope and outer shelf can have more localized

impacts. Kelly (1991) identified regular temperature changes near the

shelf break which were directly related to the influence of the LC or

related features such as eddies and filaments. Images of sea surface

temperature patterns and in-situ observations suggest that some of the

warmer offshore waters move across the shelf break and extend part of the

way across the shelf. Satellite imagery often show that lower sea surface

temperatures in winter are at times correlated with water depth. Thus, off

2-39
3/1/88 7/1/88 11/1/88 3/1/89 7/1/89 11/1/89

Date

Figure 2-20. Monthly means, maximums and minimums from Mooring B

(midshelf) offshore of Alabama.

32- J...........................I........

Miss./Alo Shelf

Mooring B

(Max./Min./Mean) . . 28-

S 26

'S...

U0

S . S

aE . C) ' 20-

18-

16- -.-- Mooring B, Bottom

-o- Mooring B, Top

14 I I I I I I I I

I I I I
18

Monthly Mean Temperature

W. Florida Shelf (26°N)

Mooring F (50m)

-a-- Top (1 7m)

-a- Bottom (40m)

16 i i I I I I I I I I I I I I I I I I I I

2/1/84 7/1/84 12/1/84 5/1/85 10/1/85

Date

Figure 2-21. Monthly means, maximums and minimums from Mooring F

(midshelf) offshore of Fort Meyers, FL.

30

28-

26-

C) 0

24

0

E

0 20-

t i i i I}I IlIllilill
12-

Miss./Ala. Shelf

Mooring C 0 Top (20m)

-- Middle (150m)

I I I I

4 I I I 3/1/88 7/1/88 11/1/88 3/1/89 7/1/89 11/1/89

Date

Figure 2-22. Monthly means, maximums and minimums from Mooring C (upper

slope) offshore of Alabama.
the Big Bend area with its broader, more gently sloping shelf bottom,

temperature gradients were weaker than over the narrower shelf at the head

of DeSoto Canyon and east towards Appalachicola Bay (Figure 2-8)

Kelly (1991) used observations made during five MANES cruises to

reconstruct surface and near bottom salinity, temperature and dissolved

oxygen (Do) on the shelf just to the west of the present study area. Of

particular interest were patterns of DO which was almost always greater

than 5 mi/i with lower values being associated with near bottom water at

the shelf break and on upper slope. An exception to this was one cruise in

August 1988, when DO values of 4.5 mi/i were found over the mid-shelf

south of Mobile Bay associated high salinities (36.5 ppt).

As shown in Figure 23a,b monthly mean near surface salinities over the midto inner shelf were generally lower and had greater variability than

similar computed variables measured over the upper slope. The monthly and

annual range were similarly greater at the shallower location which was

closer to lower salinity estuarine discharges.

2.3.4.3 River Flow and Buoyancy ForcizW.

River runoff to the AlabamaMississippi shelf is highly visible. About

30 of the annual average discharge of 14,000 m3s of the Mississippi

River is thought to be discharged eastwards onto the outer shelf (Kelly,

1991). This is the largest freshwater source in the region and

significantly freshens the outer shelf regiox. The next-largest source is

the flow of the Alabama and Tombigbee Rivers into the Mobile

Bay/Mississippi Sound system. The average discharge is about 2,200 m3s'

into Mobile Bay and about 1,220 m3s1 into Mississippi and Chandeleur

Sounds. West of Mobile Bay, the average discharge is about 800 m3-s,

primarily from the Pascagoula and Pearl Rivers (Dinnel, 1988) . In the

Florida Big Bend region, the rivers are small (the Apalachicola and the

Suwannee) with annual average discharge of about 1000 m3s'. There is,

thus, a strong west-to-east gradient in buoyancy input to the shelf, and an

unusual situation in that as much fresh water input is discharged onto the

outer as the inner shelf.

Mississippi River water can become entrained in Loop Current and cyclonic

eddies in the region. An example of this process is shown in Figure 2-16

from Drennan (1965) which showed fresher surface water coming from the

delta and being incorporated in an outer shelf and slope cyclonic

circulation. Low surface salinities (2oppt) were found well seaward of

the Chandelier Islands. Note the very strong coastal front just offshore

of South Pass.

The overall effect of coastal and riverine discharge on the mean shelf-wide

circulation is unclear. It is generally believed that there is a cyclonic

gyre between the delta and the DeSoto Canyon. Evidence for this is based

primarily on hydrographic data and surface drift bottle studies (Chew et

al., 1962; Tolbert and Salsman, 1964). Outer-shelf current meter moorings

(Kelly, 1991) suggest eastward mean flow, which could be considered as the

southern part of the gyre. However, these records are dominated by LC or

LC eddy interactions with the slope. Thus, it is not clear if these are he

2-43
J) 30

I I I I I I I I I II I I I I I I I

I

I I I I 38-

36.

34.o

32-

30-

28--

26

38-

36 -

34-

0

32-

28-

0

In-Situ Salinity Obs.

I Mean

Maximum

o Minimum

Monthly Salinities MissJAla. Shelf

Mooring C (20m)

In-Situ Salinity Obs.

I Mean

I Maximum

o Minimum

Date

Monthly Salinities

Miss./Ala. Shelf

Mooring A (lOm)

I I I I II I I I I

I I I i I i i i I i i i

12/1/87 5/1/88 10/1/88 3/1/89 8/1/89 1/1/90

Date

26-

I I I I II I I I I I I I I I I I I I I I I 12/1/87 5/1/88 10/1/88 3/1/89 8/1/89 1/1/90

Figure 2-23. Monthly mean, maximum and minimum salinities computed from

data taken near the water surface. (a) data measured at

lOm depth on Moorings A located on the inner half of the

shelf; (b) data measured at 20m depth on Mooring C located

on the upper slope in 430m of water. (See Figure 2-17 for

mooring locations.)

2-44
normal conditions or if different circulation patterns exist when LC or LC

eddy influences are absent. The hydrographic data presented in Kelly

(1991) suggest that a wide variety of temperature and salinity

distributions can exist over the Mississippi-Alabama shelf, depending on

the fresh water discharge and whether LC-derived intrusions are present.

Equivalent analyses of the Florida Big-Bend region do not seem to have been

carried out, so mean flow patterns are not available. However, the

relatively low river discharge into the region, and the dominance of windforced fluctuating flows in the mid-shelf region, would indicate that only

weak buoyancy-driven mean flows are likely except in shallow nearshore

areas. 2.3.4.4 Tides and Inertial Currents

The majority of the Gulf of Mexico is dominated by the diurnal tides (K1

and °1) which are basically uniform in amplitude and phase across the Gulf.

1(1 and 1 constituents have amplitudes of about 16 cm. In the northeast

corner of the Gulf, however, the semi-diurnal tides dominate, with M2

amplitudes of about 35 cm in Apalachee Bay. In the Gulf, the small M2 tide

is mostly locally generated in the main basin by the astronomical tide

generating forces (Reid and Whitaker, 1981), and then amplified across the

wide west Florida shelf. The basic features of the M2 tide and tidal

currents are well explained by the shelf-tide theory of Battisti and Clarke

(1982a, b). The theory is also reviewed by Clarke (1991). The major axes

of the semi-diurnal and diurnal current ellipses are directed perpendicular

to the isobaths and have amplitudes of about 10 cms CM2), 7 cmOs' (K1)

and 4 cms' (01) (Mamorino, 1982; 1983) . West of Cape San Blas, where the

shelf is narrow, M2 tidal current amplitudes are smaller (3 cms') and the

K1 and 01 constituents begin to dominate the surface tide. In the

Mississippi sound region, tides are predominantly diurnal and current

amplitudes are small (3-4 cms1)

Inertial currents are internal waves with a frequency near "f", the

Coriolis parameter. In the study area the inertial period is approximately

24 hrs. Inertial currents can be characterized as a nearly horizontal

current vector rotating clockwise at a frequency near 'f". They are

generated by sudden changes in surface wind stress, and large rapidly

moving storms such as hurricanes generate inertial wakes. One such example

is currents measured in the DeSoto Canyon during the landfall of Hurricane

Frederic at Dauphin Island on September 13, 1979 (Figure 2-24). Inertial

surface currents with amplitudes of about 100 cms1 which persisted for

more than 5 days after the passage of the eye were observed in deep water

(Shay and Ellsberry, 1987)

The phase difference between orthogonal velocity components is clearly seen

in Figure 2-24a. In Figure 2-24b, cross isobath velocities at differing

depths are shown to illustrate the vertical structure of the horizontal

currents. Both the current amplitudes and relative phases vary with depth.

By approximately September 19, 1979, cross-isobath currents at 437 m were

greater than surface currents which had been generally decreasing with

after hurricane passage. From Figure 2-24b currents at increasing depths

were in directions different than surface currents.

2-45
0 50-

I

-50--

100

E5-0

150

100

-1501 I

-50

NORDA/DeSoto Canyon Mooring #3

NO ADA / DeSoto Canyon Mooring #3

-150 II

I

I

I I

Instrument Depth=21 meters

Water Depth=465 meters

- Across Isobath Velocity

Along Isobath Velocity

Across Isobath Component

Water Depth = 465 m

Instrument Depth 21 m

251 m

437 m

Figure 2-24. Currents measured at the NORDA/DeSoto Canyon mooring during

passage of a hurricane. (A) across and along isobath

current components; (B) across isobath currents at indicated

depth.

2-46

9/12/79 9/14/79 9/16/79 9/18/79 9/20/79

Date

9/14/79 9/16/79

Date

9/12/79 9/18/79 9/20/79
Inertial period currents are often vigorous at shelf break sites during the

summer when the water column is highly stratified. At 26°N latitude, on the

west Florida shelf, inertial currents of amplitudes -50 cms1 were quite

common during three summers of measurements (SAIC, 1987), and not related

to any strong wind events. It is possible that at this site, inertial

energy was being trapped in the cyclonic shear zone of the LC front.

However, strong inertial currents not related to hurricanes have been

observed on the Louisiana (SAIC, 1989) and the Alabama - Mississippi shelf

breaks (Kelly, 1991). The reasons for the strong inertial response of

outer shelf waters in the Gulf of Mexico are not known at the present time.

2.3.4.5 Nearshore Processes

The discharge of fresh water into the nearshore zone has not been studied

in any detail in the study region. Shallow regions of Apalachee Bay are

dominated by tidal currents and a discharge of brackish water which forms a

coastal frontal zone (CFZ) . This CFZ extends about 20 km offshore to the

20 m isobath. Vertical and horizontal mixing by tidal and wind-driven

currents generates offshore gradients of density which can drive two-layer

onshore-offshore flows that are comparable in magnitude to the alongshore

currents. Such diffuse CFZ5 have been primarily studied in the Georgia

Bight (Blanton et al., 1989) . There have been some models of these zones

(Garrett and Loder, 1981; Werner et al., 1993). In the Florida Big Bend

region, there are additional complications of the change in direction of the

coastline and changes in shelf topography. Interaction of the major river

outflows (Apalachicola and Suwanee) with this CFZ are likely to be highly

dynamic with the formation of multiple river plume fronts as the outflows

interact with tidal and wind-forced shelf currents (e.g., Garvine, 1991)

2.4 Literature Cited

Battisti, D.S. and A.J. Clarke. 1982a. Estimation of nearshore tidal

currents on nonsmooth continental shelves. J. Geophys. Res.

87(C9) :7873-7878.

Battisti, D.S. and A.J. Clarke. l982b. A simple method for estimating

barotropic tidal currents on continental margins with specific

application to the M2 tide off the Atlantic and Pacific coasts of the

United States. J. Phys. Oceanogr. 12:8-16.

Blanton, J.O., L.-Y. Oey, J. Amft and T.N. Lee. 1989b. Advection of

momentum and buoyancy in a coastal frontal zone. J. Phys. Oceanogr.

19(1) :98-115.

Brown, M., E. Waddell, J. Karpen and R.J. Wayland. 1986. Gulf of Mexico

ship-of-opportunity data report, January 1983 - October 1985. OCS

study/MMS. 86-0028. 632 pp.

Brown, M., E. Waddell and R.J. Wayland. 1989. Gulf of Mexico hip-ofopportunity data report, update: October 1985 - March 1988. OCS

Study/MMS 89-0013. 598 pp.

2-47
Chew, F., K.L. Drennan and W.J. Demoran. 1962. Some results of drift bottle

studies off the Mississippi Delta. Limrxology and Oceanography.

7(2) :252-257.

Chuang, W.S., W.W. Schroeder and W.J. Wiseman. 1982. Summer current

observations off the Alabama coast. Contrib. Mar. Sci. 25:121-131.

Clarke, A.J. 1991. The dynamics of barotropic tides over the continental

shelf and slope (Review). pp. 79-108. B.B. Parker, ed. Tidal

Hydrodynamics. John Wiley and Sons, Inc., New York.Cooper, C., G.Z.

Forristall and T.M. Joyce. 1990. Velocity and hydrographic

structure of two Gulf of Mexico warm-core rings. J. Geophys. Res.

95(C2) :1663-1679.

Dimego, G.J., L.F. Bosart and G.W. Endersen. 1976. An examination of the

frequency and mean conditions surrounding frontal incursions into the

Gulf of Mexico and Caribbean Sea. Mon. Wea. Rev. 104(6) :709-718.

Ebbesmeyer, C.C., G.N. Williams, R.C. Hamilton, C.E. Abbott, B.G. Collipp

and C.F. McFarlane. 1982. Strong persistent currents observed at

depth off the Mississippi River Delta. OTC. 4322(1982) :259.

Fernandez-PartegaS, J. and C.N.K. Mooers. 1975. A subsynoptic study of

winter cold fronts in Florida. Mon. Wea. Rev. 103:742-744.

Florida A&M University. 1988. Meteorological database and synthesis for

the Gulf of Mexico. OCS Study/MMS-88-0064. U.S. Dept. of the

Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Regional Office,

New Orleans, La. 486 pp.

Garvine, R.W. 1991. Subtidal Frequency Estuary-Shelf Interaction:

Observations Near Delaware Bay. J. Geophys. Res. 96(C4) :7049-7064.

Hamilton, P. 1990. Deep currents in the Gulf of Mexico. Journal of Physical

oceanography. 20(7) :1087-1104.

Hamilton, P. 1992. Lower Continental Slope Cyclonic Eddies in the Central

Gulf of Mexico. J. Geophys. Res. 97(C2) :2185-2200.

Hayden. B.P. 1981. Secular variation in Atlantic coast extratropical

cyclones. Mon. Wea. Rev. 109(1) :159-167.

Hsu, S.-A. 1988. Coastal Meteorology. Academic Press. San Diego. 260 pp.

Huh, O.K., W.J. Wiseman and L.J. Rouse. 1981. Intrusion of Loop Current

waters onto the west Florida continental shelf. J. Geophys. Res.

86(C5) :4186-4192.

Huh, K.H., L.J. Rouse and N.D. Walker. 1984. Cold air outbreaks over the

northwest Florida continental shelf: heat flux processes and

hydrographic changes. Jour. Geophys. Res. 89(C1):717-726.

Hurlburt, H.E. and J.D. Thompson. 1980. A numerical study of Loop Current

intrusions and eddy shedding. J. Phys. Oceanogr. 10(10) :1611-1651.

2-48
Johnson, G.A., E.A. Meindl, E.B. Mortimer, M.C. Koziara, W.L. Read and J.S.

Lynch. 1986. Winter cyclogenesis over Gulf of Mexico. NOAA/NWSFO.

Slidell, La. 7 pp.

Kelly, F.J. 1991. Physical oceanography/water mass characterization. pp.

862. J.M. Brooks, ed. Mississippi-Alabama Continental Shelf

Ecosystem Study: Data Summary and Synthesis, Technical Narrative.

Vol. II. U.S. Dept. of the Interior, Minerals Management Service,

Gulf of Mexico OCS Regional Office, New Orleans, LA. (OCSA Study MMS

91-0063)

Lee, T.N., L.P. Atkinson and R. Legeckis. 1981. Observations of a Gulf

Stream frontal eddy on the Georgia continental shelf, April 1977.

Deep-Sea Res. 28(4):347-378.

Lee, T.N., K. Leaman, E. Williams, T. Berger and L. Atkinson. 1995. Florida

Current meanders and gyre formation in the southern Straits of

Florida. J. Geophys. Res. (C Oceans). l00(C5):8607-8620.

Lewis, J.K. and A.D. Kirwan Jr. 1987. Genesis of a Gulf of Mexico ring as

determined from kinematic analysis. J. Geophys. Res. 92(Cll) :11,727-

11,740.

Malanotte-Rizzoli, P. D.B. Haidvogel and R.E. Young. 1987. Numerical

simulation of transient boundary-forced radiation. Part 1: The linear

regime. J. Phys. Oceanogr. 17:1439-1457.

Marmorino, G.O. 1982. Wind-forced sea level variability along the west

Florida shelf (Winter, 1978). J. Phys. Oceanogr. 12(5):389-405.

Marmorino, G.O. 1983. Variability of current, temperature, and bottom

pressure across the West Florida continental shelf, winter 1981-1982.

J. Geophys. Res. 88(C7):4439-4457.

Maul, G.A. 1977. The annual cycle of the Gulf Loop Current, Part I:

Observations during a one-year time series. J. Mar. Res. 35(1) :29-47.

Mitchum, G.T. and A.J. Clarke. 1986. Evaluation of frictional, wind-forced

long-wave theory on the West Florida shelf. J. Phys. Oceanogr.

16(6) :1029-1037.

Mitchum, G.T. and W. Sturges. 1982. Wind-driven currents on the west

Florida shelf. J. Phys. Oceanogr. 12(11) :1310-1317.

Molinari, P..L. and D.A. Mayer. 1982. Current meter observations on the

continental slope at two sites in the eastern Gulf of Mexico. J.

Phys. Oceanogr. 12:1480-1484.

Molinari, R.L. and J. Morrison. 1988. The Separation of the Yucatan Current

from the Campeche Bank and the intrusion of the Loop Current into the

Gulf of Mexico. J. Geophys. Res. 93(10) :10645-10654.

Mortirner, E.B., G.A. Johnson and H.W.N. Lau. 1988. Major arctic outbreaks

affecting Louisiana. Nat. Wea. Dig. 13(1) :5-13.

2-49
Neumann, C.J. and M.J. Pryslak. 1981. Frequency and motion of Atlantic

tropical cyclones. U.S. Department of Commerce, NOAA Technical

Report, NWS 26. washington, D.C. 64 pp.

Niiler, P.P. 1976. Observations of low frequency currents on the west

Florida continental shelf. Mem. Soc. R. Sci. Liege. 6:331-358.

Oey, Lie-Y. 1995. Eddy- and wind-forced shelf circulation. J. Geophys. Res.

(C Oceans). lOO(C5) :8621-8637.

Paluszkiewicz, T., L.P. Atkinson, E.S. Posmentier and C.R. McClain. 1983.

Observations of a Loop Current frontal eddy intrusion onto the west

Florida shelf. J. Geophys. Res. 88(C14):9639-9651.

Reid, R.O. 1972. A simple dynamic model of the Loop Current. pp. 157-162.

L.R.A. Capurro and J.L. Reid, eds. Contributions on the physical

oceanography of the Gulf of Mexico. Gulf Publishing Co., Houston.

Reid, R.O. and R.E. Whitaker. 1981. Numerical model for astronomical tides

in the Gulf of Mexico. Vol. I: theory and application. Tech. Report.

Department of Oceanography, Texas A&M University. College Station,

TX. 115 pp.

Science Applications International Corporation. 1987. Gulf of Mexico

physical oceanography program, final report: year 4. Volume II:

technical report. Minerals Management Service, OCS Regional Office.

New Orleans, LA. 226 pp. (MMS Contract No. 14-12-0001-29158, OCS

Report/!1S 87-0007 (SAIC Report No. SAIC-87/l027))

Science Applications International Corporation. 1989. Gulf of Mexico

Physical Oceanography Program, Final Report: Year 5. Volume II:

Technical Report. OCS Report/S-89-0068, U.S. Dept. of the Interior,

Minerals Management Service, Gulf of Mexico OCS Regional Office, New

Orleans, LA. 333 pp.

Shay, L.K. and R.L. Elsberry. 1987. Near-inertial ocean current response to

Hurricane Frederic. J. Phys. Oceanogr. l7(8):1249-1269.

Simpson, J.E. Sea Breeze and Local Wind, Cambridge University Press, Port

Chester, NY, 234p.

Sonu, C.J., S.P. Murray and W.G. Smith. 1971. Environmental factors

controlling the spread of oil. Nay. Res. Rev. 24(8):ll-19.

Sturges, W. 1992. The spectrum of Loop Current variability from gappy data.

Journal of Physical Oceanography. 22(11) :1245-1256.

Sturges, W. 1994. The frequency of ring separations from the Loop Current.

Journal of Physical Oceanography. 24(7) :1647-1651.

Tolbert, W.H. and G.G. Salsman. 1964. Surface circulation of the eastern

Gulf of Mexico as determined by drift bottle studies. J. Geophys.

Res. 69(2) :223-230.

2-50
Vukovich, F.M. 1988. Loop Current Boundary Variations. J. Geophys. Res.

93(C12) :15585-15591.Vukovich, F.M. 1995. An updated evaluation of the

Loop Current's eddy-shedding frequency. J. Geophys. Res. 100,8655-

8660.

Wayland, R.J. and S. Raman. 1989. Mean and turbulent structure of a

baroclinic marine boundary layer during the 28 January 1986 cold air

outbreak (GALE 86). Bound.-Layer Meteor. 48(3):227-254.

Wayland, R.J. and S. Raman. 1994. Mean and turbulent structure of the

marine atmospheric boundary layer during two cold air outbreaks of

varying intensities (GALE 86) . Bound.-Layer Meteor. 71(1-2) :43-66.

Wiseman, W.J., Jr. and S.P. Dinnel. 1988. Shelf currents near the mouth of

the Mississippi River. J. Phys. Oceanogr. 18(9) :1287-1291.
Chapter 3 - THE GEOLOGICAL ENVIRONMENT

by Dr. Richard Davis

University of South Florida

and

Mr. David Inglin

Science Applications International Corp.

3.1 General Geological Settinq

The area of interest is located in the northeast portion of the Gulf of

Mexico sedimentary basin. The study area includes two geologically and

geomorphologically distinct areas: the Big Bend area and the panhandle

coast. They are separated by Ochiockonee Bay. The Big Bend area is

characterized by open coast marshes that rest on a karstic Eocene limestone

surface. The panhandle coast is comprised of numerous estuaries with a

nearly continuous barrier/inlet system.

Peninsular Florida is underlain by a carbonate platform that contains

thousands of meters of Cenozoic (67 mya to present) marine limestones,

dolomites, sands, and clays overlying Pre-Cambrian (about 700 mya) to midMesozoic (about 150 mya) basement rocks. These marine sedimentary rocks

contain very little siliciclastic material below the Miocene, due to the

absence of input from terrestrial sources to the north before the Suwannee

Channel was closed. Since that time, siliciclastic sediments from the

Appalachians and the Coastal Plain have made their way south onto the

Florida peninsula. In contrast, the Gulf Coast contains a huge

accumulation of terrigenous siliciclastic sediments that were provided by

the Mississippi River and other fluvial systems.

3.1.1 Origin of Florida Peninsula

The Florida Platform is built on basement rocks which represent a fragment

of the African Plate left behind in the Mesozoic when the continents broke

apart. During its early geologic history, the platform was intermittently

covered by shallow seas, and cut off from the mainland by a seaway known as

the Gulf Trough or Suwarinee Channel (Figure 3-1). The Gulf Trough cut

through the study area in the area of Cape San Blas, connecting two ancient

depositional basins, the Southeast Georgia Embayment and the Apalachicola

Ernbayment. The majority of the marine sedimentary rocks and evaporites

were deposited during this time. During the early Miocene (-20 mya) there

was renewed uplift in the Appalachian Mountains which caused increased

erosion and a corresponding increase in sediment supply to the southeast

United States. This influx of sediment eventually caused the closing of

the Gulf Trough. After that time the carbonate sediments became mixed with

siliciclastic material from the Appalachian Mountain erosion. Eventually

the area became covered with siliciclastic sediments, which today dominate

the southern and western portion of the study area.

3.2 Shoreline GeomorpholQgy

The coast of the study area is comprised of two general regions (Figure

3-2): 1) the Big Bend marsh coast, and 2) the panhandle barrier chain

3-1
EVAPOR lflc.

GULF

OF

MEXICO

LITTORAL

CRSER CLASTICS

INNER SUBLITTORAL

FINER & CALCAREOUS CLASTICS

ITTI CARBONATES (CARBONATE BANK)

CARBONATES a EVAPORITES

OUTER SUBLITTORAL

77j FINER & CALCAREOUS CLASTICS

V/'l & CARBONATES

INFERRED DIRECTION OF

MINOR OCEAN CURRENTS

& LITTORAL DRIFT

INFERRED DIRECTION OF

MAJOR OCEAN CURRENTS

--5000 PRESENT-DAY SUBMARINE

CONTOUR

Figure 3-1. Location of the Suwamlee Channel, which created a barrier to

terrigenous sediment transport during the deposition of the

carbonate sediments on the Florida Platform until the early

Miocene (-20 mya, from McKinney, M.L., 1984).

3-2
Figure 3-2. Location of the Panhandle barrier chain and the Big Bend

marshy coast within the study area.
including the Apalachicola Delta area. Ochiockonee Bay effectively divides

these two regions. The geomorphic province known as the Gulf Coastal

Lowlands (White, 1970) dominates the geomorphology inland of the coast.

The lowlands contain marine terraces of various ages on the inland side.

In the seaward direction, the marsh coast is bounded by a broad, lowgradient continental shelf. A similarly gently-sloping shelf is present

off the Apalachicola Delta. The slope of the shelf increases markedly as

one moves to the west of this area.

3.2.1 ig Bend Marsh Coast

The Big Bend marsh coast is a very low-gradient shoreline with very limited

sediment cover. The 300 km shoreline of marshy coast is bounded on the

south by the west Florida Barrier Island Chain, begilining in northern Pasco

County, and to the northwest by Ochlockonee Bay. When compared to the

barrier coasts to the north and south, the marsh coast has had little study

(Hine et al., 1988) until a recently completed 5-year study conducted by

the US Geological Survey.

Historic upland geomorphology has played an integral role in creating the

present-day Big Bend coast. The guartz sands, whose ultimate source was

the Appalachian Mountains, were concentrated along the Brooksville Ridge to

the east, preventing them from being deposited on this portion of the

coast. Very few large streams capable of transporting this sediment to the

coast have formed along this part of Florida, and thus the area is starved

of sediments. There are numerous short spring-fed streams originating near

the coast but these carry little sediment. The only large river that

enters the Big Bend area is the Suwannee River (Figure 3-2), which drains a

mostly karst limestone terrain and thus carries little sediment (Wright,

1996) . Consequently, the Eocene limestones are either exposed, or thinly

covered by sediments, both at the shoreline and on the adjacent shelf. The

result of having limestone at or near the surface, exposed to weathering

and dissolution by ground water, is a karst topography and an extremely

irregular shoreline [Figure 3-3] (Hine et al., 1988; Davis et al., 1992).

Karst terrain exhibits a range of morphologic scales from small scale

variations (centimeters to meters) to regional scale features (kilometers)

In the Big Bend area, medium scale karst features are represented by tidal

creeks, created by dissolution and enlargement of joint features in the

underlying limestone, and islands, created in areas with less severe

erosion of the surface limestone. Embayments associated with the larger

streams of the area and marsh archipelagos in areas of higher elevation

represent the largest scale of karst features (Davis et al., 1992).

Embayments are created by increased dissolution due to the presence of

springs near the shoreline. These embayments provide a good habitat for

development of oyster bioherms, with lower salinities, strong tidal flows

and a rock substrate. These bioherms extend for several kilometers in a

north-south orientation, forming barriers and creating depositional basins

with distinct sedimentary processes. The oyster colonies have mostly died,

however, and the bioherms are being subjected to severe erosion. The marsh

archipelagos form on the limestone highs which lie between the embayments

3-4
Figure 3-3. The shoreline of a portion of the Big Bend marshy coast,

showing distribution of major morphologic elements (from Hine

et al., 1988).

3-5

GO'.. CRYSTAL RIVER E?.AYENT FIG 22'c.

0

'!i

'/ '__'4 "'

50

0

k

'

)

' N , . .'

....... '

. 7--

IIOMOSASSA / ..' EM8AYMENT '"

EMBAYeff -

f7

L.J 44i

'-..

... 6-? -28'40- --i '... 0

SHELF EMBAYMENT

(ASSOCIATED WITH SPRING)

=:ELAGo

182., WACHEE . EI.AYMENT - . MARSH PENINSULA

- BERM RIDGE MARSH -

./

-25

STUDY AREA -- --S PSTHLACHASCOTEE

'T' I

n,ve* -

0 5

ANCLO1EW I KEY8 ' KM

55' 45' 40' 82135'W
and are comprised of limestone-cored islands separated by creeks CHine et

al., 1988).

Along portions of this coast exposed to higher wave energies, quartz and

skeletal sand berm-ridge shorelines border the slowly eroding marshes.

During storms, and as sea-level rises, the sands from these beach segments

overwash onto the marsh surface, creating a transgressive berm-ridge

morphology (Hine et al., 1988).

3.2.2 panhandle Barrier Chaixi

The panhandle barrier chain is made up of a series of spits and islands

which extend from the eastern side of the Apalachicola River delta to the

mouth of Mobile Bay (Figure 3-2). Included in this chain, from east to

west, are Dog Island, St. George Island, St. Vincent Island, St. Joseph

Spit, Crooked Island, Shell Island, Alligator Point peninsula (across St.

Andrews Bay), Choctawhatchee peninsula, Santa Rosa Island, Perdido Key

peninsula, and Mobile Point peninsula.

The most-studied portion of this chain is the eastern portion associated

with the Apalachicola River delta and Cape San Bias (Donoghue, 1993; Otvos,

1992; Donoghue, 1992; Donoghue and Tanner, 1992; Arthur et al., 1989;

Schnable and Goodell, 1968; Stewart and Gorsline, 1962) . The Apalachicola

River represents the largest river on the west coast of Florida and one of

the only continuing sources of fine-grained sediments. Cape San Blas is a

classic example of a cuspate foreland including a barrier spit (St.

Joseph's Spit) . To the east are three barrier islands (Dog Island, St.

George Island, and St. Vincent Island), all with relatively complex

developmental histories. Beach-dune ridges with varying orientations are

found both on the barrier islands and on the mainland shoreline.

To the west of the Cape San Blas promontory the barrier spits, islands, and

some mainland beach areas form a gently curving shoreline. These barriers

are not unlike those of the Apaiachicola delta, with their primary

geomorphic features being beach-dune ridges. The shape of the barrier

features vary from east to west, with only limited barrier-spit formation

in the area closest to Cape San Blas and very long, narrow islands or

attached barriers near the mouth of Mobile Bay. This region also contains

four estuaries including St. Andrews Bay, Choctawhatchee Bay, Pensacola

Bay, and Perdido Bay (Figure 3-2). The rivers in the area discharge their

sediment loads into these bays, creating bayhead deltas.

3.3 Bathymetr

The bathymetry of the study area also exhibits a different nature across

this coastal region, particularly in the general slope of the various areas

(Figure 3-4) . To the east, the slope of the shelf averages 1:3 000 (Davis

et al., 1992), increasing to the west of the cape to an average of 1:1000

(Parker et al., 1992). The shelf break in the study area has a gradual

increase in slope over a wide area (Parker et al., 1992), but distinct

changes in slope of the shelf occur around 60 m and 130 m (Ballard and

Uchupi, 1970). One of the major bathymetric features within the study area

is the De Soto Canyon, which is located near the western extent of the

study area (Figure 3-4). The canyon is evident in the bathymetry from the

3-6
Figure 3-4. General bathymetry within the study area (depths in meters)
40 m contour seaward of Santa Rosa Island to greater than 1000 m. This

section will describe the smaller-scale features present within the study

area starting closest to shore and working seaward.

The bathymetry in the estuaries in the panhandle area is generally shallow

and smooth. Depths reported for Apalachicola Bay range from 2 to 4 m

[Figure 3-5] (Kofoed and Gorsline, 1963). In some areas of the estuaries

oyster bioherms are present, creating linear ridges. Inlets which empty

the estuaries range from about 2 m to 16 m in depth and have small (if any)

ebb-tidal deltas, and moderate to large flood-tidal deltas associated with

them (Hine et al., 1986).

Along the Big Bend coast, stream channels from spring-fed rivers are the

landward extent of the study area. These are relatively narrow channels

carved into the limestone, which may extend into the nearshore zone. The

Homosassa River, to the south of the study area, flows out into the

nearshore through a channel which has a relief of 5 m and a length of 9 km

(Hine et al., 1988) . Most of the stream channels in the area are not this

large. The major exception to this generalization is the Suwannee River,

which has its headwaters in the Okefenokee Swamp in southern Georgia. This

river extends for over 100 km and drains a large area of the northern

Florida peninsula. Although discharge is modest, there is a well-developed

Holocene delta at its mouth (wright, 1996)

The majority of the nearshore zone within the Big Bend area is typified by

an irregular bottom with few significant areas of relief. There is no

obvious surface pattern to this intricate bathymetry. These irregular

features are due to a karst terrain being overlain by a thin and

discontinuous veneer of Holocene sediments (Figure 3-6) . Many of the

larger karst features have been filled in by sediments, thereby masking

some of the irregularities (Hine et al., 1988; wright, 1995).

The Florida Middle Ground (FMG) (Figure 3-4) is one of the most significant

features within the Big Bend area. Located about 110 km south-southwest of

Apalachicola Bay, it consists of an area of 700 km2 with depths from 30 to

50 m. It was originally described by Jordan (1962) as an "old river

delta.. .flanked by embankments 50 feet high". The FMG is a coral reef

system that consists to two parallel ridges trending north-northwest

separated by a wide, flat central valley and a series of pinnacles to the

south of the main ridges (Brooks and Doyle, 1991). The ridges are 12 to 15

meters in height with their crests at 30 meters water depth. Recent work

by Mallinson, et al. (1996) indicates that the reef is built on a basement

of karstic limestone which is thought to be Miocene in age. Growth of the

FMG is believed to have begun during high sea-level stands of the

Pleistocene. The development probably was triggered by a combination of a

break in slope of the bathymetry and the convergence of circulation

patterns and water masses from the Florida Loop current, the West Florida

Estuarine Gyre, and Florida Bay Waters. This convergence in the

circulation may allow transport and settling of Caribbean reefal organisms

to the FNG (Brooks and Doyle, 1991). Another theory on the development of

the FMG suggests that the reef developed on bathymetric highs of river

banks formed during a sea-level low stand. The reef is thought to have

developed during the subsequent sea-level rise (Donoghue, 1993; Jordan,

1962)

3-8
j: 1

- ,0

SUBMARINE TOPOGRAPHY

CONTOUR INTERVAL

Figure 3-5. Contour map of Apalachicola Bay and the nearshore region (from

Kofoed and Gorsline, 1963)
A INITIAL FRACTURING OF LIMESTONE

0 MORE FRACTURE8 FEWER FRACTURES

0

24

SM B INCIPIENT KARSTIFICATION

MORE INTENSE

0 jl j 11 INIVI.IIIgl

R1 I I1Ifl

, . aui III,*UU uj..\..uii ui ii sJiuivai uinhII tiuiu. ..iIluauIa 1.111 ,__ I_._* a1 iJlwuiliUI.uuuIlII waUlII.IIIU ___uII__%i_IIi. i.IaIi uulNUIliJflI i. 1 IIIRUIIU III II I SM - C CONTINUING KARSTIFICATION

0 TOPOGRAPHIC LOW* i1i. 11 a 1 I_ - :;

. 1.UiI uiIuu.nui.i$ I_i t,ii.WIII -_

_I.0I

0

SM

500$

I II .l.l.uI.UII

IiIDIUIIiiIL1E1!II1IflII VU*IUIUUII iuuuuui WIHI1I1KW ii. UUIIUIuIIlIIIIII 1 II

TIDAL CREEKS

LESS INTENSE

HIGH

HAMMOCKS

LOW

Figure 3-6. Formation of karst terrain. Panel D illustrates the present

situation in the marshy coast (from Hine et al., 1988).

MARSH

SM D CONTINUING KARSTIFICATION

WITH SEDIMENTARY

VENEER
Within the panhandle portion of the study area, the nearshore zone is

covered with linear ridges [Figure 3-7) (Hyne and Goodell, 1967; Parker et

al., 1992), which are located around the 20 m isobath. Those ridges

described by Parker et al. (1992) on the western side of the study area

have an average height of 2 m, an average spacing of 0.5 km, and extend

between 300 m and 2.65 km laterally.

A series of shoals extends 60 km offshore from Cape San Bias and is evident

in the 60 m contour (Ballard and tJchupi, 1970). The genetic relationship

between these shoals and the cape will be discussed in the section on

Sediment Dynamics.

Ballard and Uchupi (1970) describe six ridge and valley complexes which

straddle the 60 in contour, with the northernmost ridge occurring at the

southern extent of the present study area. The slope of the shelf increases

around the 60 m contour from an average slope of 0.5 m-km1 to 2 mkm1

(Gould and Stewart, 1956). A series of protuiDerances is evident in the 60 in

contour westward from Cape San Bias, which correspond with the major rivers

along the coast (Ballard and Uchupi, 1970). ?nother set of ridge and

valley features lies across the 160 in contour. The northernmost ridge of

this series lies directly south of Cape San Bias.

3.4 Sediments and Surface Geoloav

The distribution and composition of sediments in the study area

demonstrates its transitional nature. The surface sediments of the study

area can be divided into several zones (Doyle and Sparks, 1980; Figure

3-8). The portion of the study area west of Cape San Bias is dominated out

to the 100 in contour by the relatively uniform MAFLA sand sheet. Within

this same depth zone (0 to 100 m) to the east of Cape San Bias, three

sedimentary facies are found, representing a transition from the nearshore

quartz sand-dominated environment to the offshore carbonate sand

environment. Below 100 m there is a transition to a fine-grained carbonate

facies (Gould and Stewart, 1956; Doyle and Sparks, 1980)

Generally, the nearshore quartz-rich sands within the region are relatively

uniform. The average mean grain size is 0.325 mm (medium sand) and varies

from 0.137 mm to 0.796 mm between Mobile Bay and Apalachee Bay. The

sediments are moderately well-sorted, indicated by the average standard

deviation of the grain-size distribution of 0.79c. The average amount of

fines (silt and clay particles) present in the rxearshore sands is about 2%

(Arthur et al., 1989).

There is no correlation between depth and sediment grain size, but there is

a correlation between the composition and grain size (Gould and Stewart,

1956) . The coarse to medium sands are composed of algal and phosphoritic

grains. Medium to fine sands are generally composed of quartz, shell,

colitic, algal, and foraminiferal grains.

Heavy minerals comprise an average of about 1% of the quartz-rich sediments

within the study area (Gorsline, 1966; Birdsall, 1979) with few, if any,

heavy minerals represented in the carbonate facies. The heavy mineral

suite present in the study area includes magnetite, ilmenite, rutile,

3-li
SUBMARINE TOPOGRAPHY CONTOUR INTERVAL 10 EEET Figure 3-7. Linear features are shown in the bathymetry for the area off Choctawhatchee B

ft (18 m) and the 110 ft (33 m) contours (from Hyne and Goodell, 1967)
ST. BERNARD PRODELTA

PRODELTA MAFLA SAND

ZONE MAFLA SAND SHEET

CARBONATE-QUARTZ TRANSITION

ZONES

WEST FLORIDA QUARTZ SAND B

CARBONATE SAND SHEET

Figure 3-8. Sedimentary facies found in the study area (from Doyle and

Sparks, 1980)
leucoxene, kyanite, staurolite, tourmaline, and zircon, with other minor

minerals. This suite is similar to that found in sediments from

Mississippi to Florida. Heavy mineral concentrations tend to be higher in

the west than in the east, with elevated concentrations in the area of Cape

San Bias (Arthur et al., 1986, 1989).

Clay minerals are present in small amounts within the sediments of the

region. Clay mineralogy is dominated by smectite and kaolinite, with a

small amount of illite. Smectite is characteristic of the Mississippi

River drainage system and is the dominant clay mineral on the west side of

the study area. East of Cape San Blas, kaolinite becomes more important,

indicating some influence from the rivers of northwest Florida (Doyle and

Sparks, 1980) . Mazzullo and Peterson (1989) came to the same conclusions

based on a study of the roundness and surface textures of the quartz silt

grains of the study area.

The offshore carbonate sand facies is made up of several sediment types

including broken shell, algal sand, ooid sand, and foraminiferal sand and

silt (Gould and Stewart, 1956). The lime-mud facies that lies at the

seaward limit of the entire study area is made up of foraminifera tests and

coccoliths. Small amounts of terrestrial clays from the Mississippi River

are found in these sediments, with higher amounts to the west due to the

closer proximity to the river.

3.4.1 i9 Bend Area

Little information has been found concerning the sedimentology of the Big

Bend portion of the study area. Doyle and Sparks (1980) provides an

investigation that covers the area with the most detail, but their study

area does not extend to the shoreline or intertidal zone. Gould and

Stewart (1956) provides an in-depth study of the central Florida west coast

and a reconnaissance look at the panhandle area. Hine et al. (1988)

provides a cursory description of the sediments in the shoreline and

nearshore zone, but their study area lies to the south of this review's

target area. The area examined by Arthur et al. (1986, 1989) extends into

Apalachee Bay, which covers the western portion of the Big Bend area.

The marshy, intertidal zone of the Big Bend area is dominated by a veneer

of peaty muds with numerous limestone outcrops. At the shoreline, some

beaches of shelly sand are present. The nearshore zone is sediment-starved

4-1-, ,-,,,1, 1-hi,- rf c,h1 1r r,1.ri7 TH mrkd by
with over 75% carbonate (Doyle and Sparks, 1980). The distribution of the

various sediment types is not uniform over wide areas. Rather, it is

patchy, with numerous bedrock outcrops (Doyle and Sparks, 1980)

The surface sediment cover at the FMG is patchy. About 50 percent of the

area covered by sediments and the remaining area is exposed reefal

materials. The ridge crests are predominantly coarse to very coarse sands.

Sediments generally become finer away from the ridges with fine and very

fine sands found in depressions within the ridges as well as adjacent to

the ridges. Carbonate content for sediments on and adjacent to the ridges

ranges from 70% to 99%, lower values occurring away from the ridge crests.

Fine grained quartz sand makes up the remainder of the sediments. Mollusc

shell fragments are the dominant type of carbonate grain making up an

average of 36% of the carbonate fraction. Additional major constituents of

the carbonate fraction include barnacles (8%), benthic foraminifera (3-4%),

annelid tubes (3-4%), bryozoa (3-4%), and coralline algae (2%) . Barnacle

fragments are a good sedimentological indicator because they are rare in

the sediments of the surrounding shelf. Clay minerals make-up less than 5%

of the sediments at the FMG. HydrobiOtite is the only clay mineral

detected. (Brooks and Doyle, 1991)

The FMG reef flanks are dominated by large blocks of reef material broken

from the reef structure. These blocks range from 1 to 3 meters on a side

Few lithoclasts were found in the sediments surrounding the reef indicating

that the reef material either breaks down to individual components, or they

are not broken down into sand-sized particles (Brooks and Doyle, 1991)

3.4.2 Panhandle Area

Fine sediments predominate in the estuaries along the panhandle, deposited

by the rivers that drain into them. Detailed investigations of the

sediment distributions within the estuaries of the Florida panhandle are

found in Kofoed and Gorsline (1963; Apalachicola Bay), Stewart and Gorsline

(1962; St. Joseph Bay), and Boone (1973; Mobile Bay). Considering that

similar sediment sources and mechanisms of deposition exist throughout the

panhandle area, it is safe to extrapolate the nature of the remaining

estuaries from these sources. Indeed, the descriptions of these estuaries

are very similar.

Sediments within Apalachicola Bay are made up of sand and silt. The bay is

surrounded by a margin of sandy beaches created through winnowing of fine

sediments by the higher energy present at the shoreline. Looking toward

the central portion of the bay, silt content increases until it is the

dominant sediment texture at depths greater than about 2 m. Shell gravel

and gravely sands are also found in the bay. Only small amounts of

carbonate sediments are found in ApalachicOla Bay, and they are

concentrated in shoal areas where oyster reefs are common. Organic matter

accounts for only 1 to 2% of the sediments by weight (Kofoed and Gorsline,

1963)

In contrast to the discontinuous sediment cover of the Big Bend area, a

fairly continuous blanket of quartz sand extends from the shoreline to

about 80 km offshore within the panhandle area (Gould and Stewart, 1956).

Sediments generally contain less than 25% carbonate within this facies that

3-15
Doyle and Sparks (1980) call the MAFLA sand sheet. An exception to this is

the Destin carbonate facies, an area of carbonate sands (>75% carbonate)

off Panama City (Doyle and Sparks, 1980). To the west of Mobile Bay, the

MAFLA sand sheet grades into the pro-delta and delta sediment of the

Mississippi River (Coleman et al., 1991). Thin veneers of fine-grained

sediments covering the sands of the inner shelf have been reported (Hyne

and Goodell, 1967; Stauble and Warnke, 1970)

At a smaller scale there is variation in the sediments present within the

area. Kofoed and Gorsline (1963) describe a basin in the area between the

Cape San Blas and Cape St. George shoals that is dominated by fine sands

and silts, which are transported to the basin from Apalachicola Bay. The

shoals themselves contain coarser sands and shell gravel.

3.5 sediment Dynamics

In general, the highest rate of sediment movement occurs along the coast

where wind, waves, and tides directly influence the sediments. The

variations in geomorphology and bathymetry result in varying levels of wave

and tidal energy input. This varying energy leads to distinctly different

processes within each of the two portions of the study area. Because of

the very low wave energy, the marshy Big Bend coast tends to be tidedominated, despite the small tidal range. The barrier/inlet coast tends to

be wave-dominated, with a smaller tidal range and larger waves than the Big

Bend area. Moving further offshore, the tidal forces and breaking waves

play a decreasing role. Here, shelf currents play an increasing role in

the movement of bottom sediments. This section will discuss the various

mechanisms within the study area that influence the movement of sediments.

3.5.1 Coastal Sediment Transport

There are several sedimentary environments within the study area. These

areas include rivers, deltas, estuaries, tidal inlets, beaches and salt

marshes. Each of these environments has specific processes that affect the

movement of sediments. The limestone substrate of the Big Bend area

creates a very different environment from the unconsolidated sandy

sediment/fluid interface of the Panhandle area.

3.5.1.1 ia Bend Area

The Big Bend area rivers drain an exposed limestone surface which erodes

through dissolution and provides very little sediment input. This is one

reason for the continued lack of sediment within this area. Sediment

sources for this area are transported into the area from adjoining areas

and carbonate producing organisms. Tanner (1960) indicates that this area

is a "Zero" energy coast due to the wide, shallow, and gently sloping

shelf, relatively low average breaker height, and limited tidal range.

This designation is actually incorrect, although it is widely used. There

have been many severe storms, including hurricanes, that have impacted this

coast and that have caused substantial change (e.g., Goodbred and Hine,

1995) . The lack of sediment is actually the most important factor in the

absence of beaches, barriers, etc. along this coast. These conditions

create a relatively stable area with limited sediment movement.

3-16
Much of the sediment movement in the area occurs during winter

extratropical storms. During these storms, wind-generated tides can reach

225 cm with 190 cm waves, much greater than the average spring tides of 90

cm and winter significant wave heights of 45 cm. Under storm conditions,

sand from the shoreline is transported into the marsh areas through

overwash (Hine et al., 1988) . In the shallow water areas the sediments are

moved about, resulting in uncovering of some limestone features and

blanketing of others.

Sediment transport in the marsh system occurs through a number of

mechanisms. During storms, the high-wind tides provide a route by which

sediment can be carried far up into the marshes. Suspended sediment is

carried by the water as it flows up into tidal creeks and across the marsh

surface, where it settles out as the flow velocity decreases around the

marsh grasses (Frey and Basan, 1985; Leonard, 1994) . Along the marsh

borders, the marshes retreat as waves cut into the base of the marsh

sediments and wash the sediments onto the marsh surface. Larger grain

sizes are introduced into the marsh by this overwash process.

Most of the large sediment particles are skeletal in origin, with the

majority of them being oyster fragments. It should also be noted that the

abundant benthic community includes many filter feeders. These worms and

bivalves ingest large amounts of suspended sediments and convert the Line

particles to sand-sized pellets. These pellets are fairly cohesive and are

difficult to transport. They comprise a large portion of the sediment in

the Suwanee River delta.

The processes that created the karst features described previously are

still active in the Big Bend in areas where springs are actively

discharging in the nearshore region. These processes include surface

dissolution from acidic pore waters from overlying marsh sediments, and

regional dissolution due to mixing-zone uridersaturatiofl (Hine et al.,

1988) . A result of these processes of dissolution is the collapse of the

limestone surface, creating sinkholes.

3.5.1.2 Panhandle Area

The coastal region in the western portion of the study area is a more

diverse and dynamic place than the Big Bend coast. It resembles a typical

coastal plain paralic system with well-developed fluvial/estuarine systems

and barrier/inlet systems. The steeper inner shelf results in more

sediment transport due to the increased energy.

Rivers in this area introduce some fine-grained sediments to the coastal

zone. Most of these sediments are trapped in estuaries. As the velocity

of the river flow decreases when entering the bay, the sediments settle out

and form bayhead deltas within the enclosed bays. Only a fractionof this

sediment is carried into the open Gulf. The Mobile River, one of 'the

largest rivers in the area, discharges about 4 x l0 kg of sediment annually

(Parker et al., 1992) into its bay, with only about 30% reaching the Gulf

(Parker et al., 1992). The other rivers in the area provide negligible

amount of sediment to the open Gulf.

3-17
The Apalachicola River carries an annual average of 1.5 x 1O9 kg of sediment

(Donoghue, 1993). This sediment is mostly deposited as a delta which

protrudes beyond the mainland coast into Apalachicola Bay, an estuary

protected by a series of four barrier islands. This sediment volume seems

small when compared to the 200 xlO9 kg of sediment discharged annually by

the Mississippi River. Donoghue (1993) indicates that the Apalachicola

River is the only river in the eastern Gulf of Mexico which is annually

discharging sufficient sediment to fill its estuary, considering the

present rate of sea level rise. Estimates of the vertical accumulation

rates for Apalachicola Bay average 8 mmyr1, and the rate of progradation

of the delta lobes averages 2.2 myr1 (Donoghue, 1993) . A substantial

part of this accumulation rate is due to the extensive oyster community

filtering suspended sediment and producing pelleted mud.

The small amount of sediment from the estuaries that is transported to the

open Gulf moves through tidal inlets. Depths of these tidal inlets range

from about 2 m at the mouth of Choctowhatchee Bay to 16 m at West Pass,

which empties Apalachicola Bay. In general these inlets lack welldeveloped ebb-tidal deltas because wave energy and longshore drift tend to

transport any sediment carried by the tidal currents down the coast. Some

fine-grained sediment is carried out onto the shoreface and shelf. Kofoed

and Gorsline (1963) describe a basin area, lying between the tidal inlets

that empty Apalachicola Bay, which contains deposits of silts and clays

apparently discharged from those inlets. This is one route by which

sediment is carried offshore from the shoreline to the continental shelf.

Longshore transport is one of the primary sediment transport mechanisms

along the shoreline. Longshore transport occurs through the interaction of

waves with the coastline Gorsline (1966) indicates that there is a net

longshore drift to the west within the panhandle area with transport rates

increasing from 50,000 m3yr' just west of Cape San Bias to 150,000 m3yr1

near Pensacola. Other researchers, examining specific portions of the

panhandle, have come to the conclusion that there are actually a number of

drift cells within the area, with little transfer between the cells (Stone

et al., 1992; Stapor, 1971). Both schools of thought submit values for the

volume of sediment transported along the coast each year that are within

the same range as Gorsline (1966)

3.5.2 Shoreface and Shelf

Waves provide the primary mechanism for sediment transport along the

shoreline. Further offshore, at a depth of about 10 m, direct movement of

sediment by waves becomes less important and movement of sediment by shelf

currents becomes more important. This area of transition is known as the

shoreface. Within the Big Bend area this zone extends several kilometers

from the shoreline. The limited energy and very gently sloping limestone

surface provide a distinct contrast to the classic shoreface zone of

terrigenous shelves.

Along the panhandle of Florida the shoreface extends to water depths of 15

to 18 m (Boone, 1973). This region is characterized by active and variable

sediment transport created by the interaction of waves and currents. Four

scales of bedforms are created by this transport: 1) wave-generated

3-18
ripples that change position with the orientation of waves (Vause, 1959),

2) megaripples with spacing of 2 to 3 m, 3) sand waves with spacing on the

order of 100 m, and 4) kilometer-scale sand ridges (Niedoroda et al.,

1985)

The presence of a ridge and trough topography along the upper shelf

provides an indicator of the sediment dynamics of this area. Parker et al.

(1992) conclude that they represent large-scale bedforms and that they are

genetically related to similar large-scale bedforms on other continental

shelves due to their similar shapes, and to the textural distribution of

sediments. Swift and Field (1981) postulate that the ridges on the north

Atlantic shelf are formed as the shoreface retreats. It is also thought

that they are produced by downwelling during storm flows (Niedoroda et al.,

1985) Offshore-directed currents are created through the piling up of

water at the shoreline by wind and waves. Sediment is eroded from the tops

of the ridges by wave agitation and transported offshore by these currents.

They demonstrate this by presenting an evolutionary succession of ridge

forms extending from nearshore to offshore. Following Swift and Fields

(1981) model, sediment is eroded from the onshore side of the ridges and

deposited on the offshore side as storm related currents flow from onshore

to offshore.

The primary sedimentary processes occurring further out onto the shelf,

beyond all but hurricane wave influence, are deposition of pelagic

sediments, slumping, and bioturbation. Foraminiferal oozes are deposited

as pelagic organisms settle to the shelf floor. Sedimentation rates

obtained from cores on the upper slope indicate accumulation as high as 20

cm per 1,000 years (Doyle and Holmes, 1985) . These rates are an order of

magnitude higher than deep-sea oozes of the same composition (Doyle and

Holmes, 1985)

The De Soto Canyon is a bathymetric anomaly, and seems to be an anomaly of

sediment accumulation as well, due to the large volume of sediments that

have been deposited there throughout the Quaternary Period. Antoine (1972)

speculates that there is some interaction between the bottom currents in

the area and the shelf. He presents some erosional features on seismic

reflection profiles that cross the canyon. Antoine concludes that since

there are no rivers associated with the canyon, there must be some erosion

by ocean currents.

The FMG also represents a bathymetric anomaly on an otherwise flat portion

of the shelf. The dominant process that occurs on the ridges of the FMG is

winnowing. This is indicated by the large size of grains and the thin

layer of sediments found on the tops of the reef structures. Fine-grained

sediments are being winnowed leaving the coarse grains made up mostly of

rnollusc shell fragments. Bathymetric control of the currents driving the

winnowing process account for the patchy distribution of sediments.in the

FMG. The bathymetric highs show the largest grain sizes while the low

lying central valley, which acts as a sediment sink, contains a larger

percentage of fine-grained materials. Sediment accumulations within the

low lying areas of the FMG are generally thicker than the surrounding shelf

indicate that the reefs provide some sheltering from the currents that

redistribute the sediments on the open shelf. The FMG acts to trap

sediments thus reducing the off-shelf movement of sediments much like a

3-19
shelf-edge reef. Sediment accumulation and reef growth at the FMG are

insufficient to keep pace with rising sea-level, therefore it is currently

being drowned (Brooks and Doyle, 1991).

3 . 6 Summary

The study area is located across a geologic and morphologic transitional

area. Ochlockonee Bay is the divide between the Big Bend coast to the east

and the panhandle area to the west. Geologically, the area represents the

transition from a sediment-starved carbonate platform (the Florida

Platform), represented in the Big Bend area, to the United States mainland

terrigenous sedimentary system, with a large supply of sediments (the Gulf

Coastal Plain), represented by the panhandle area.

The Big Bend coast is lined by marshes, with numerous tidal channels

extending into them, built directly on the limestone surface. The tidal

channels are formed by erosion along fractures in the limestone. The

continental shelf is wide, with an irregular, low-gradient limestone

surface with patchy sediment cover. These sediments are generally medium

sands with quartz dominating the nearshore and carbonate sands becoming

dominant offshore. Due to the low energy input to the area, the majority

of sediment transport occurs during storm events. During these events,

sediment is moved about on the shelf, erosion and overwash occur at the

shoreline, and deposition occurs in the marshes. The area continues to be

sediment-starved due to a lack of longshore drift into the area from

neigbboring regions and a lack of sediment-carrying rivers entering the

area. The panhandle coast is a smooth arcuate shoreline with a number of barrier

islands, spits, and mainland sandy beaches. Several estuarine systems line

the coast and effectively trap nearly all sediment currently being carried

by rivers. Thus, the sediments of the open coast are comprised primarily

of sands reworked from previous deposits present on the narrow shelf.

These sands are relatively uniform medium sands with small amounts of heavy

minerals, carbonate sediments, and clay. Their composition indicates that

they were transported to the coast by local rivers from the Appalachian

Mountains during times of lower sea level.

Increased wave energy in the panhandle area creates increased sediment

transport At the shoreline, overall sediment movement is generally to the

west, but many reversals in the longshore drift exist along the coast,

resulting in a compartmentalized coast with little net transport. On the

shoref ace and upper shelf, out to the 60 m contour, the sediment surface is

irregular, with large scale bedforms. Several authors have interpreted

these to indicate offshore transport of sediments during storm conditions.

Offshore of the 60 m contour, the distinction between the Big Bend and the

panhandle coast becomes less apparent. Contours generally flow smoothly

from the Big Bend area to the De Soto Canyon (the western edge of the study

area) . Overall, the energy input to the area is low. Carbonate sediments

composed of foraminifera tests and coccoliths are the dominant outer shelf

sediment.

3-20
Other features of interest within the study area include the De Soto

Canyon, Cape San Bias, and the Florida Middle Ground. The De Soto Canyon

is the western boundary of the present study area. The canyon represents a

drowned ancient river valley that is in the process of being filled in by

sedimentation. It is speculated that the feature is presently being

maintained by ocean currents eroding the sediments (Antoine, 1972) - Cape

San Bias is a cuspate foreland that is prograding to the east and is

experiencing rapid shoreline retreat on the south. A series of shoals

extends from the cape offshore with some expression as deep as 60 m. The

Florida Middle Ground is a coral reef system. The two primary ridges of

the reef complex are 15 m high in depths of 30 to 50 m. The shallow

portions support living coral reefs. Growth at the FMG is insufficient to

keep up with the current rise of sea-level, thus the reefs are being

drowned.

3.7 Literature Cited

Antoine, J.W. 1972. Structure of the Gulf of Mexico, pp. 1-34 In R. Rezak

and V.J. Henry, eds. Contributions on the geological and geophysical

oceanography of the Gulf of Mexico: Volume 3. Texas A&M University

Oceanographic Studies, Gulf Publishing Co., Houston, Tex.

Arthur, J.D., S. Melkote, J. Applegate and T.M. Scott. 1986. Heavymineral reconnaissance off the coast of the Apalachicola river delta,

northwest Florida. Florida Geological Survey report of investigation

No. 95. Florida Geological Survey, Tallahassee, Fla. 164 pp.

Arthur, J.D., S. Melkote, J. Applegate and T.M. Scott. 1989. Heavymineral reconnaissance off the coast of the Apalachicola river delta,

northwest Florida: a summary and new interpretations. Marine

Geology 90:51-57.

Ballard, R.D. and E. Uchupi. 1970. Morphology and quaternary history of

the continental shelf of the Gulf Coast of the United States.

Bulletin of Marine Science 20(3) :547-559.

Birdsall, B.C. 1979. Eastern Gulf of Mexico continental shelf phosphorite

deposits. M.S. Thesis. Univ. South Florida. St. Petersburg, Fla.

87 pp.

Boone, P.A. 1973. Depositional systems of the Alabama, Mississippi, and

western Florida coastal zone. Gulf Coast Assoc. of Geological Soc.

Trans. 23:266-277.

Brooks, G.R., and Doyle, L.J., 1991. Geologic development and depositional

history of the Florida middle ground: A mid-shelf, temperate-zone

reef system in the northeastern Gulf of Mexico. IN: Osbourne, P. H.,

From shoreline to abyss; contributions in marine geology in honor of

Francis Parker Shepard. SEPM Special Publication No. 46, SEPM,

Tulsa, Okla..
Coleman, J.M., H.H. Roberts and W.R. Bryant. 1991. Late Quaternary

sedimentation, pp. 325-352. In A. Salvador, ed. The geology of

North America, volume J, the Gulf of Mexico basin. Geological

Society of America. Boulder, Cob.

Davis, R.A., Jr., A.C. Hine and E.A. Shinn. 1992. Holocene coastal

development on the Florida peninsula, pp. 193-212. J F. Wehmiller

and C.H. Fletcher, eds. Quaternary coasts of the United States:

marine and lacustrine systems. SEPM Special Publication No. 48.

SEPM, Tulsa, Okla.

Donoghue, J.F. 1992. Late Quaternary coastal and inner shelf

stratigraphy, Apalachicola Delta region, Florida. Sedimentary

Geology 80:293-304.

Donoghue, J.F. 1993. Late Wisconsinan and Hobocene depositional history,

northeastern Gulf of Mexico. Marine Geology 112:185-205.

Donoghue, J.F. and W.F. Tanner. 1992. Quaternary terraces and shorelines

of the panhandle Florida region, pp. 233-241. In J.F. Wehmiller and

C.H. Fletcher, eds. Quaternary coasts of the United States: marine

and lacustrine systems. SEPM Special Publication No. 48. SEPM,

Tulsa, Okla.

Doyle, L.J. and C. Holmes. 1985. Shallow structure, stratigraphy, and

carbonate sedimentary processes of west Florida upper continental

slope. AAPG Bulletin 69(7) :1133-1144.

Doyle, L.J. and T.N. Sparks. 1980. Sediments of the Mississippi, Alabama,

and Florida (MAFLA) continental shelf. J. Sed. Pet. 50(3) :905-916.

Frey, R.W. and P.B. Basan. 1985. Coastal salt marshes, pp. 225-301. In

R.A. Davis, Jr., ed. Coastal sedimentary environments. SpringerVerlag, New York, N.Y.

Goodbred, S.L. and A.C. Hine. 1995. Coastal storm deposition: salt-marsh

response to a severe extratropical storm, March, 1993, west-central

Florida. Geology 23:679-682.

Gorsline, D.S. 1966. Dynamic characteristics of west Florida Gulf coast

beaches. Marine Geology 4:187-206.

Gould, H.R. and R.H. Stewart. 1956. Continental terrace sediments in the

northeastern Gulf of Mexico, pp. 2-20. In J.L Hough and H.W. Menard,

eds. Finding ancient shorelines, SEPM special publication No. 3.

SEPM, Tulsa, Okla.

Hine, A.C., D.F. Belknap, J.G. Hutton, E.B. Osking and M.W. Evans. 1988.

Recent geological history and modern sedimentary processes along an

incipient, low-energy, epicontinental-sea coastline: northwest

Florida. Jour. of Sed. Petrology 58(4) :567-579.
Hine, A.C., R.A. Davis, D.L. Mearns and M.P. Bland. 1986. Impact of

Florida's Gulf coast inlets on the coastal sand budget, final report

to Florida Dept. of Natural Resources, Division of Beaches and

Shores. Tallahassee, Fla. 108 pp.

Hyne, N.J. and H.G. Goodell. 1967. Origin of the sediments and submarine

geomorphology of the inner continental shelf off Choctawhatchee Bay,

Florida. Marine Geology 5:299-313.

Jordan, G.F. 1962. Reef formation in the Gulf of Mexico off Apalachicola

Bay, Florida. Geological Society of America Bulletin 63:741-744.

Kofoed, J.W. and D.

Apalachi cola

33(1) :205-223.

Leonard, L. 1994. Environmental and physical factors controlling sediment

transport and deposition in microtidal marsh systems: implications

for marsh stability. Ph.D. Dissertation. Univ. South Florida. St.

Petersburg, Fla. 201 pp.

Mallinson, D.J., A.J. Hine, and S.D. Locker. 1996. Paleocirculation and

paleoclimatic implications of the Florida Middle Ground reefs. GSA

Abstracts with Programs, 1996 Annual Meeting, Denver, CO.

Mazzullo, J. and M. Peterson. 1989. Sources and dispersal of late

Quaternary silt on the northern Gulf of Mexico continental shelf.

Marine Geology 86:15-26.

McKinney, M.L. 1984. Suwannee channel of the Paleogene coastal plain:

support for the "carbonate suppression model." Geology 12:343-345.

Niedoroda, A.W., D.J.P. Swift and T.S Hopkins. 1985. The shoref ace, pp.

533-624. Iz R.A. Davis, Jr., ed. Coastal sedimentary environments.

springer-Verlag, New York, N.Y.

Otvos, E.G. 1992. Quaternary evolution of the Apalachicola coast,

northeastern Gulf of Mexico, pp. 221-232. In J.F. Wehntiller and C.H.

Fletcher, eds. Quaternary coasts of the United States: marine and

lacustrine Systems, SEPM Special Publication No. 48. SEPM, Tulsa,

Okla.

Parker, S.J., A.W. Shultz and W.W. Schroeder. 1992. Sediment

characteristics and seafloor topography of a palimpsest shelf,

Mississippi-Alabama continental shelf, pp. 243-251. In J.F.

Wehmiller and C.H. Fletcher, eds. Quaternary coasts of the United

States: marine and lacustrine systems, SEPM Special Publication No.

48. SEPM, Tulsa, 0.

S. Gorsline. 1963. Sedimentary environments in

Bay and vicinity, Florida. Jour. of Sed. Petrology

Schnable, J.E. and H.G. Goodell. 1968. Pleistocene-recent

evolution, and development of the Apalachicola coast,

Geological Society of America Special Paper No. 112.

Society of America, Boulder, Cob. 72 pp.

3-23

stratigraphy,

Florida.

Geological
Stauble, D.K. and D.A. Warnke. 1974. The bathymetry and sedimentation of

Cape San Bias shoal and shelf off St. Joseph Spit, Florida. Jour. of

Sed. Petrology 44(4) :1037-1051.

Stapor, F.W. 1971. Sediment budgets on a compartmented low-to-moderate

energy coast in northwest Florida. Marine Geology lO:M1-M7.

Stewart, R.A. and D.S. Gorsline. 1962. Recent sedimentary history of St.

Joseph Bay, Florida. Sedimentology 1:256-286.

Stone, G.W., F.W. Stapor, J.P. May and J.P. Morgan. 1992. Multiple

sediment sources and a cellular, non-integrated, longshore drift

system: northwest Florida and southeast Alabama coast, USA. Marine

Geology 105:141-154.

Swift, D.J.P. and M.E. Field. 1981. Evolution of a classic sand ridge

field: Maryland sector, North American inner shelf. Sedimentology

28:461-481.

Tanner, W.F. 1960. Florida coastal classification. Transactions Gulf

Coast Association of Geologic Society 10:259-266.

Vause, J.E. 1959. Underwater geology and analysis of recent sediments off

the northwest Florida coast. Jour, of Sed. Petrology, 29:555-563.

White, W.A. 1970. The geomorphology of the Florida peninsula. Florida

Geological Survey Bulletin No. 51. Tallahassee, Fla. 164 pp.

Wright, E.E. 1996. Sedimentation and stratigraphy of the Suwannee River

marsh coastline. Ph.D. Dissertation. Univ. South Florida.

St. Petersburg, Fla.
Chapter 4 - THE CHEMICAL ENVIRONMENT

by Dr. Jane Caffrey

University of California, Santa Cruz

4.3. Introduction

This review provides a summary of what is known about the major inputs of

nutrients, metals and organics to the NEGOM study area, and the processes

affecting them in the estuarine and nearshore regions. The study area has

a low population density and therefore, problems associated with

urbanization and industrialization are less than other areas in the Gulf of

Mexico and along the Atlantic coast. This discussion will emphasize the

literature from Pensacola Bay to the Suwanee River, starting with a general

introduction to the physical, geological and biological setting, and

emphasizing riverine inputs to this region. Some literature from Mobile

Bay, Ala. and the blackwater Ogeechee River, Ga. is included to supplement

information gaps. Three case studies are provided. The Suwanee River

Basin is characterized by blackwater and spring-fed rivers, and has no

major urban centers in the watershed; some agricultural inputs are present.

The Chattahoochee-Flint-Apalachicola River system has urban inputs into the

Chattahoochee and Flint Rivers, while the Apalachicola River basin has

agricultural inputs. Bayou Texar is part of the Escambia/Pensacola Bay

system, which has significant urban inputs.

4.1.1 Physical Setting and Processes

The northeastern Gulf of Mexico is subtropical with average air

temperatures between 7-33°C, and average rainfall of 132-150 cmyf'

(Livingston, 1984; Crane, 1986). Temperatures in the rivers, estuaries,

and shallow coastal zone generally follow air temperature (see Chapter 2)

Average January surface water temperature along the nearshore coast is

16°C, increasing offshore to 19.5°C, while July surface water temperature

averages 30°C (NOAP, 1985). Salinity at the shelf break varies between 34-

36.5 psu (Nowlin, 1972; Nowlin and Hubertz, 1972), while nearshore regions

experience wider salinity variations, particularly in estuaries such as

Apalachicola Bay that have significant riverine inputs. Circulation in the

Gulf of Mexico is dominated by the Loop Current which brings water in

through the Yucatan Straits, flows in a clockwise direction, and exits

through the Florida Straits. In January, water also flows in a clockwise

direction along the coast, while weaker flows are reversed in July (NOAA,

1985). Mixing between the central Gulf of Mexico and the shelf is limited

except during upwelling along the shelf break (SAIC, 1988), meanders of

Loop Current (Tester et al., 1993) or during winter storm passage (Dagg,

1988) . In addition, hurricanes can greatly increase the exchange between

shelf and offshore waters (Ichiye, 1972).

Numerous small rivers and streams discharge into the northeastern Gulf of

Mexico, and from east to west include the Withlacoochee, Suwanee, Aucilla,

Fenholloway, Econfina, Wacissa, Wakulla, Sopchoppy, Ochlockonee, St. Marks,

the Chattahoochee-Flint-ApalaChicola system, Choctawhatchee, Yellow and

Escambia Rivers. Seasonal flow patterns depend on river type, with

alluvial rivers having high flow in spring and summer and low flow during

late summer and fall (Wharton et al., 1982). Blackwater rivers tend to

4-1
respond to local precipitation while spring-fed rivers show little

deviation over an annual cycle (Wharton et al., 1982). spring-f ed rivers

include the St. Marks, Wakulla, Wacissa, and Suwanee. The highest river

stages on the Suwanee usually occur after early spring rains, although

extensive flooding occurs following hurricanes (Crane, 1986) . Discharges

range from less than 50 m3s' by the Withlacoochee, Ochlockonee and Yellow

Rivers, to 844 m3s from the Chattahoochee-Flint-Apalachicola river system

and 100-300 m3s' from the Suwanee, Choctawhatchee and Escarnbia Rivers

(NOAh, 1985). Flow in the Chattohoochee-Flint-Apalachicola system is

regulated by a dam which forms Lake Seminole. The channel is dredged to

approximately 3 m to allow barge traffic upriver.

Estuarine systems along the coast vary from lagoonal systems like

Apalachicola Bay, that have relatively long retention times, to more open

systems like Apalachee Bay. The major estuaries are the Suwanee estuary,

Apalachee Bay, Apalachicola Bay, Choctawhatchee Bay and Pensacola Bay.

Embayments with insignificant freshwater inputs are St. Joseph Bay and St

Andrews Bay. The astronomical tide range is between 0.4-1 meter and can be

either diurnal or semidiurnal. Apalachicola Bay is a transition zone

between the diurnal tides of west Florida and the semidiurnal tides of the

Florida Peninsula (Livingston, 1984). Typical wind-forcing associated with

fronts can lead to water elevation changes on the order of 20-30 cm

(Marmer, 1954; Livingston, 1983). Hurricanes can cause severe tidal

surges. For example, Hurricane Agnes, in 1972, caused a two-meter tide

surge in Apalachicola Bay (Livingston et al., 1978).

4.1.2 Geologic Settinq

Formation of the modern coast occurred following sea level rise between 4-6

thousand years ago (Arthur et al., 1986; Donoghue and White, 1995). The

northeastern Gulf of Mexico can be divided into two segments, with the

dividing line at Cape San Blas. The western section is dominated by quartz

sands and fine clays such as smectite and kaolinite (Doyle and Sparks,

1980), while the eastern section is characterized by a limestone platform

with overlying carbonate deposits (Doyle and Sparks, 1980; NOAA, 1985).

Shelf sediments are a mixture of quartz sands inshore, carbonate sands

offshore, and patches of shell, calcareous algae, and coral fragments

(Doyle and Sparks, 1980).

Watersheds of the northeastern Gulf of Mexico are part of either the

northern physiographic zone or the central physiographic zone (Crane,

1986). The northern physiographic zone, located along the Florida

Panhandle, is a broad continuous upland region stretching inland from the

coast Crane, 1986) . The central physiographic zone, which occurs in north

central Florida, is comprised of a series of ridges and broad valleys

(Crane, 1986) . Karst features such as sinkholes, dry stream courses,

underground rivers, springs, caves and abandoned spring heads are common

through the central zone (Crane, 1986). The three-dimensional,

subterranean network characteristic of the central zone has been formed

from the dissolution of carbonate bedrock by organic and carbonic acids

continually enlarging open spaces and fractures in the rock.

The continental shelf off the northern zone is a depositional environment.

Weathering of the crystalline rocks of the Southern Appalachians occurred

4-2
during the Pleistocene when sea level was lower and was the source for most

of the inner shelf sediments (Arthur et al., 1986; Donoghue and Greenfield,

1991; Donoghue, 1992) . These sediments have been reworked, and offshore

sediment sources have also contributed to their makeup (Arthur et al.,

1986). Modern delta formation by the Apalachicola River began about six

thousand years ago, with development of barrier islands beginning about

four thousand years ago (Donoghue and White, 1995). currently, the delta

is prograding and filling in Apalachicola Bay (Donoghue, 1992). The

Apalachicola River carries 1.5 million metric tons of sediment per year on

average (Donoghue and Greenfield, 1991), although much of the upstream

sediment transport has been reduced following construction of the Jim

Woodruff Dam in 1954 (Arthur et al., 1986). The Chattahoochee-FlintApalachicola River system is typical of fluvial systems which flow onto

marginal seas like the Gulf of Mexico (Donoghue, 1992; Nittrouer and

Wright, 1994)

Hurricanes have a strong impact on barrier islands, which experience

washovers and sand loss during these storms. Increased development on

barrier islands makes them vulnerable to significant economic losses from

damage by hurricanes. In addition, the construction of marinas, jetties

and other structures on barrier islands or along the coast can alter

circulation and sediment transport, and increase pollution.

4.1.3 biological Settinq

The mild, subtropical climate supports rich and diverse biotic communities.

Blackwater rivers, swamps, saitmarshes, barrier island, soft bottom,

seagrass and coral reef communities make up the mosaic of the northeastern

Gulf of Mexico. Swamp forests and bottomland hardwoods are widespread

along the rivers. Cypress and tupelo are the major species in the swamps.

There are extensive saitmarshes along the coast, which are dominated by

Spartina alterniflora and Juncus romerianus. Net aboveground annual

production in saltmarshes around Apalachicola Bay is about 500 gm2yr'

(Livingston, 1984; 1985). Seagrass beds are widespread in the shallow

(water depth <4.5 m) nearshore region and can comprise between 5-25 of the

open water area (Deegan et al., 1986; Iverson and Bittaker, 1986). The

major seagrass species are Thalassia testudinurn, Syringoclium filiforme,

Halodule wrightii, Halophila decipiens, Malophila engelrnanni arid Ruppia

maritima (Iverson and Bittaker, 1986). Seagrasses in this region are

limited by light (Iverson and Bittaker, 1986). Seagrass production ranges

from 320-500 gm2yr1 in Apalachicola Bay (Livingston, 1984; 1985) . Small

and scattered coral reefs occur offshore in 40-lOOm of water (NOAA, 1985).

Phytoplankton production in the bays and estuaries ranges from 6 jg

C-l'hr' off the Econfina River to 40 g C-l1hr' in Apalachicola Bay

(Myers and Iverson, 1981) . Within Apalachicola Bay, integrated daily

production of phytoplankton ranges between 63-1700 mg Cm2-d' (Livingston,

1984) . Diversity of the vegetation on barrier islands is high, although

production may be limited by nutrient-poor beach sands (Barbour et al., 1987).

In contrast to most of the U.S. coastal zone, human population density in

much of the study area is low. Although 80% of the coastal counties have

less than 64 people per square mile (NOAA, 1985), the coastal counties of

western Florida are projected to have some of the largest population

increases in the entire Gulf of Mexico over the next two decades (NOAA,

4-3
1990). The major cities are Pensacola and Panama City. The total

population for the counties bordering the Gulf of Mexico (Escambia to

Citrus) was nearly 900,000 in 1993. Agriculture, particularly forest

production, is important, while manufacturing and other industrial

activities are a small percentage of the regional economy. As a result,

inputs of nutrients, heavy metals, and organics to the coast are low,

although there are some point sources which will be discussed below.

4.2 Chemical Properties and Distributions

4.2.1 Shelf Characteristics

The northeastern Gulf of Mexico can be divided into 2 provinces based on

salinity: estuarine and shelf. Estuaries are strongly influenced by

freshwater inputs and seasonal discharge characteristics. The shelf is

influenced by excursions of the Loop Current, which bring Gulf gyre water

onto the shelf. Gulf gyre water is typically very oligotrophic. Nutrient

concentrations have typical oceanic distributions with slightly higher

concentrations nearshore (0.5-0.8 /M NO3 , 0.2-0.4 M DIP, 4.7-13.4 M DSi)

than in the surface gyre (0.2 M NO , 0.1 M DIP, 3.2 M DSi), and high

concentrations at depth (25-35 /AM NO3 , 1.5-2 /.IM DIP, 20-30 M DSi) (ElSayed et al., 1972; SAIC, 1988) . Chlorophyll-a concentrations on the shelf

and in the gyre were usually low. Chlorophyll-a concentrations nearshore

were about 0.41 gl', about 0.2 g-l1 on the shelf and about 0.1 ig-l1 in

the Gulf gyre (El-Sayed et al., 1972; NOAP, 1985; SAIC, 1988). Primary and

secondary production on the shelf are enhanced following storm-induced

upwelling and vertical overturning that mixed nutrient-rich bottom water

with surface shelf water (El-Sayed et al., 1972; Dagg, 1988). Just south

of the study area on the west Florida shelf, dissolved oxygen

concentrations in November 1983 were about 6.4 mgl1 at the surface and

about 4 mg-l' in bottom water (SAIC, 1988).

Most studies of the shelf have focused on nutrient and carbon cycling in

the Mississippi River plume off Louisiana. Riverine discharge onto the

west Florida shelf is an order of magnitude lower than the Mississippi!

Atchafalaya discharge, so nutrient and contaminant inputs, as well as the

salinity regime, are radically different. Because the basic conditions on

the shelf are so different, most of the research in water chemistry from

the Mississippi shelf is not very applicable to the west Florida shelf.

For example, a recent study of bacterial dynamics in the Gulf of Mexico

found no consistent differences in bacterial numbers, biomass or production

between the west Florida shelf, slope and offshore stations, although

readings at a series of stations in the plume of the Mississippi River were

very different from those measured at eastern Gulf of Mexico stations

(Pomeroy et al., 1995). In addition, their experiments suggested that

bacterial production on the west Florida shelf was limited by phosphorus

and potentially carbon.

4.2.2 Dissolved and Particulate Constituents

Most of the numerous small rivers entering the northeastern Gulf of Mexico

can be characterized as either alluvial or blackwater. Each type has

different physical and chemical characteristics, particularly with respect

to inorganic ion and organic carbon concentrations. Alluvial rivers, such

4-4
as the Apalachicola, have dissolved inorganic ion concentrations about an

order of magnitude greater than total organic carbon concentrations

(Wharton et al., 1982). Most of the dissolved inorganic ions come from

minerals, leached from parent rocks and soils in the headwaters during

weathering, and include chloride, sodium, potassium, magnesium, calcium and

phosphate. Atmospheric deposition is not a significant source of these

inorganic ions (Winchester and Fu, 1992) . In contrast, blackwater rivers,

such as the Suwanee, are rich in refractory organic compounds such as

fulvic and humic acids and generally have a 1:1 ratio of dissolved

inorganics to total organic carbon (Wharton et al., 1982). Precipitation

dominates the water budgets of these rivers, which can have pH values as

low as 4, although this varies depending on flow (Wharton et al., 1982). A

comparison of dissolved inorganic ion and organic concentrations f or the

Apalachicola and Suwanee Rivers is given in Table 4-1.

4.2.3 gumics

Humic compounds are very complex and have varying composition. Humics from

acidic waters have a larger percent of oxygen and lower percent carbon

content than humics from neutral pH waters (Chlou et al., 1987). Humic

compounds from the Suwanee River have been widely used to examine the

properties of organic compounds. (Chlou et al., 1987; Serkiz and Perdue,

1990; Thorn and Mikita, 1992; Schlautman and Morgan, 1993) . Humics or

refractory dissolved organic carbon (DOC) can be a significant source of

carbon monoxide (CO) by photochemical oxidation (Valentine and Zepp, 1993).

Although CO is not a greenhouse gas, it is highly reactive with other trace

gases in the atmosphere (Valentine and Zepp, 1993). Carbon monoxide

production rates were much higher in the Suwanee River, which had higher

DOC concentrations than either the Intracoastal Waterway or a nearshore

island (Valentine and Zepp, 1993)

4.2.4 Decomposition and the Formation of Biogenic Gases

This section provides a brief overview of the major microbial processes

responsible for the decomposition of organic matter, emphasizing those

processes, such as methanogensis and denitrification, that result in the

formation of biogenic gases.

Decomposition of organic matter has not been measured in the northeastern

Gulf of Mexico, except for methanogenesis in a freshwater marsh and

denitrification in Ocklockonee Bay. Decomposition of organic matter

usually occurs through a sequence of electron acceptors. These electron

acceptors, in order from highest energy yields to lowest, are oxygen,

nitrate, oxidized manganese, oxidized iron, sulfate, and carbon dioxide

(methanogenesis) . The greatest energy yields are obtained from oxygen

(Fenchel and Blackburn, 1979), and aerobic respiration dominates in the

water column in moist (not saturated) soils, and at the sediment-water

interface. In sediments and saturated soils below the aerobic zone, other

pathways dominate. Dissimlatory nitrate reduction to either nitrogen gas

(denitrification) or ammonium usually represents between 8-37% of organic

matter mineralized (Sorensen, 1987) and is most important when nitrate

concentrations are high, or when nitrate production by nitrification is

high. Iron and manganese reduction occur after nitrate is depleted.

Sulfate reduction is most important in marine systems because sulfate

4-5
Table 4-1. Chemical characterization of Apalachicola and

Suwannee Rivers. Values for constituents in mg1'

(except for specific conductance, which is in

j.imhocm, and pH, which is in standard units).

a from Elder and Mattraw, 1982; Mattraw and Elder, 1984; Elder,

1985; and Winchester and Fu, 1992

b from Crane, 1986

concentrations are generally much higher than in freshwater systems (mM vs.

MM concentrations) . Hydrogen sulfide, produced during sulfate reduction,

is toxic to many organisms and complexes with metals such as iron,

manganese, cadmium, mercury and other trace metals. Methanogenesis is

normally the major route of decomposition in freshwater systems. Recent

interest in methane has increased because it is a greenhouse gas.

4.2.4.1 Methane

Wetlands are extremely active sites of mineralization, including methane

production, and may be responsible for about 40% of the atmospheric methane

4-6

Conatitient Apalachicolaa Suwanneeb

Stream water:

pH 5.7-7.8 3.9-7.3

Total dissolved solids 56-97

Specific conductance 68-127 155

CaCO3 alkalinity 20-49

chloride 2.9-4.7

sulfate 1.6-7.2

calcium 6.1-29

DO 4.8-11.4

TOC 6-9

DOC 6.7 30-80

TN 0.7-1.0

DON 0.6

TP 0.02-0.10

SPM 0.85

Groundwater:

pH 4.6-7.5 4.3-9.0

Total dissolved solids 18-34

Specific conductance 10-46 200-500

CaCO3 alkalinity - 100-300

chloride 1.9-3.6 0.6-10

sulfate - 0-50

calcium 37 0.1-494

DO - TOC 4.8-5.5

DOC 4-9

TN 0.3-0.8

DON 0.1-0.2

TP 0.01-0.20
flux (Cicerone and Oremland, 1988) . Plants enhance tnethanogenesis by

increasing organic carbon concentrations at the surface and at depth in the

root zone, or rhizosphere (Chanton and Dacey, 1991) . Organic carbon

collects at the surface by accumulation of abovegrourid biomass or the

trapping of allochthonous material within grassbeds. Release of DOC by

plant roots and rhizomes, as well as turnover of belowgrourid biomass,

contribute to organic carbon pools in the rhizosphere. Emergent plants can

also serve as conduits transporting methane from the rhizosphere (where it

is produced) to the atmosphere through plant lacunae (Chanton and Dacey,

1991; Chanton et al., 1993). Because of this enhanced methane transport,

vegetated sediments generally have lower methane concentrations and higher

dinitrogen gas concentrations than unvegetated sediments (Chanton and

Dacey, 1991). Rates of methanogenesis in freshwater marshes are much higher

than methane emission to the atmosphere because of methane oxidation

(Chanton and Dacey, 1991; Epp and Chanton, 1993) . In addition, methane

oxidation can be enhanced by plant processes (Chanton and Dacey, 1991; Epp

and Chanton, 1993) . Emergent and submersed plants can release significant

amounts of oxygen from roots and rhizomes, which can enhance aerobic

processes such as methane oxidation (Caffrey and Kemp, 1991; Chanton and

Dacey, 1991). Between 23-90% of methane produced was oxidized during

greenhouse and field experiments with several freshwater marsh species from

the northeastern Gulf of Mexico (Epp and Chanton, 1993). A complex

interaction of many factors such as water level, temperature, nutrient

loading, species composition, organic matter content of sediments, and

sediment oxygen consumption controls methane emission from wetlands

(Chanton et al., 1993). Although the significance of all of these

interactions is not understood, one unifying relationship is that methane

emission is about 3% of net ecosystem production over a wide range of

biomes, from the Arctic tundra to subtropical freshwater marshes in the

Everglades (Whiting and Chanton, 1992).

Methane production has not been measured in northeastern Gulf of Mexico

swamp forests or bottomland hardwoods. However, research in a similar area

in Georgia (Ogeechee River) suggested that swamp forests and flooded

bottomland hardwood forests were regions of enhanced methane flux to the

atmosphere. Pulliam (1993) found that methane flux only occurred at

flooded sites when temperatures exceeded 15°C and that about half of the

methane produced was oxidized in the water. Methanogenesis in the Ogeechee

River basin represented about 20% of the total soil respiration at flooded

sites, but only a small fraction (4%) of the total respiration of

aboveground leaf litter within the basin as a whole (Pulliam, 1993). A

model of methane emission within the basin suggested that changes in

precipitation which affect floodplain inundation and temperature have the

most significant effects on methane emission (Pulliam and Meyer, 1992)

4.2.4.2 Nitrous Oxide

Nitrous oxide formation occurs during nitrate reduction and nitrification,

so any increase in rates of these nitrogen transformations results in

increased nitrous oxide production (Vitousek and Matson, 1993). Nitrous

oxide fluxes are generally a very small percentage of denitrification

rates, usually <6%, and often less than 1% (Seitzinger, 1988) . Nitrous

oxide fluxes in Ochlockonee Bay were 0.02-0.05 imol Nm2hr1 and were less

than 0.1% of denitrification rates (Seitzinger, 1987) . Enhanced rates of

4-7
N20 flux have been measured from eutrophic sediments (Seitzinger, 1988) and

from agricultural soils (Vitousek and Matson, 1993)

4.2.4.3 Organic Sulfur Compounds

Dimethyl sulfide (DMS) and other organic sulfur compounds in the atmosphere

may affect climate and atmospheric chemistry, so the contribution of

oceanic fluxes of DMS and other organic sulfur compounds have been measured

(Kiene, 1993). DMS and dimethyl-sulfonium proprionate (DMSP), a precursor

of DMS, are produced by marine algae - both macroalgae, such as Ulva, and

phytoplankton, particularly prnnesiophytes (Iverson et al., 1989). DMSP

appears to be an osmotic regulatory agent (Iverson et al., 1989). Total

concentration of DMS in the water column was greatest in the freshwater

reaches of the estuary where chlorophyll-a concentrations were highest

(Iverson et al., 1989). However, DMS concentrations normalized to

chlorophyll-a increased with increasing salinity and were higher in

Ochiockonee Bay than in either Chesapeake or Delaware Bays (Iverson et al.,

1989). Their results suggested that DMS production per unit of

chlorophyll-a was higher in more saline regions. An oxidation product of

DMS, dimethylsulfoxide (DMS0), was highly variable in rainwater samples

collected from Mobile Bay, perhaps due to a combination of industrial

sources (paper mills) and biogenic sources such as wetlands and coastal

waters (Kiene and Gerard, 1994).

4.2.5 Trace Metals

Trace metal concentrations within the northeastern Gulf of Mexico are

generally low (Windom et al., 1989; Hanson et al., 1993). Metal inputs are

less than 0.018 g.m2-yr' from most of the Gulf counties, and less than

0.175 gm2yr1 for the four more urbanized Gulf counties (NOAA, 1985)

Metal concentrations in the environment are strongly dependent on the

source, whether physical and chemical weathering of silicate minerals and

metal oxides, or anthropogenic inputs (Windom et al., 1989). Grain size

distribution also has an important role in determining metal concentrations

in the environment because most metals are associated with clays, the finegrained fraction (Windom et al., 1989). organic matter content and metals

such as cadmium and mercury are often positively correlated (Lind.berg and

Harriss, 1974; Windom et al., 1989; Hanson et al., 1993). organic-metal

complexes are particularly important in controlling the availability of

metals in the environment (Bruland, 1983; Cross and Sunda, 1985; Kennish,

1992) . In sediments, complexation with hydrogen sulfide or polysulfates

can lead to high porewater concentrations of metals such as mercury

(Lindberg and Harriss, 1974). In addition, pH and the oxidation-reduction

condition (redox) of sediments has a significant affect on availability of

metals, which varies depending on the metal (Brannon et al., 1977; Gambrell

et al., 1980) . In Mobile Bay sediments, soluble levels of mercury were

highest under either acid (pH=5), reduced conditions or near neutral

(pH=8), oxidized conditions; the greatest recovery of radioisotope-labeled

lead occurred under oxidizing conditions, while most of the zinc seemed to

be associated with colloidal hydrous oxides (Gambrell et al., 1980) . The

role of acid volatile sulfide pools in binding the cationic metals cadmium,

copper, lead, nickel, and zinc has been demonstrated by DiToro et al.

(1991)

4-8
The geology of Florida is dominated by carbonate minerals, which are

relatively metal-poor. However, metal composition normalized to aluminum

concentrations from estuarine and marine sediments is similar to the

crustal composition except for arsenic, copper, manganese and nickel

(Windom et al., 1989). Arsenic-rich phosphate deposits in the region are

probably the source for higher arsenic levels, while copper, manganese and

nickel are depleted in coastal plain soils (Windom et al., 1989). Although

trace metal concentrations are generally low throughout this region, lead

and zinc in Pensacola Bay were elevated (between 15-50 ppm lead and between

60-280 ppm zinc), particularly near the port facility (Windom et al.,

1989). An analysis of trace metal contamination along Atlantic and Gulf

coasts also indicated metal contamination in Pensacola Bay, although the

level and frequency of occurrence was far less than heavily polluted sites

like Baltimore and Boston harbors (Hanson et al., 1993).

Much of these metal data and the organic contaminant data presented in a

later section were collected as part of the NQAA National Status and Trends

Program (NS & T). This program was designed to examine spatial and

temporal trends of contaminants in sediments and bivalves (oysters and

mussels) . Measurements were made over five years (1986-1990) at sites

along the Atlantic, Gulf and Pacific coasts. Median metal concentrations

in oysters from the Status and Trend sites for the first three years of the

program are listed in Table 4-2 (Presley et al., 1990). Choctawhatchee Bay

had much higher concentrations of silver, cadmium, iron, mercury, lead, and

zinc than the median value for the Gulf of Mexico. Arsenic concentrations

were high in St. Andrew, Apalachicola and Suwannee estuary oysters compared

to the median Gulf of Mexico value, while mercury in oysters from the

Suwannee estuary was higher than the median Gulf of Mexico value. In

Pensacola Bay, mercury and selenium were higher than median Gulf values.

Biota can be significantly affected by point sources of metals,

particularly epibiota on chromated-copper-arsenate (CCA) treated wood,

which was developed to replace creosote and PCP treated wood (Weis et al.,

1993). Algae (Cerarniurn sp.) collected from a CCA wood dock in Pensacola

Bay had significantly higher concentrations of copper and arsenic than

algae growing on rocks from the region (Weis et al., 1993). Barnacles

(Balanus eburneus) and mussels (Brachidontes recurvis) also had

significantly higher levels of these contaminants, particularly from an

area with restricted circulation, than animals from the reference site

(Weis et al., 1993).

Trace metal concentrations have also been measured in freshwater sediments

and biota from the Apalachicola River. Metal concentrations in

Apalachicola River sediments and clam tissues were generally low, and there

were no significant point sources of metals within the basin (Elder and

Mattraw, 1984) . Silver, mercury and molybdenum were below detection limits

(0.2, 1.0, 2.0 ppm respectively) in sediments, while the lowest detectable

concentrations were for cadmium (3 ppm); arsenic, beryllium, tin and iron

were also low (5 ppm), while chromium, copper, lead, cobalt, nickel and

zinc were intermediate (70 ppm) and high for manganese (1200 ppm) (Elder

and Mattraw, 1984) . Metal concentrations in the clam, Corbicula

znanilensis, were generally lower than sediment concentrations, about 0.1

ppm for arsenic, cadmium, lead and mercury, about 0.6 ppm for chromium, 8.7

ppm for copper and 20 ppm for manganese and zinc (Elder and Mattraw, 1984)

4-9
Table 4-2. Median trace metal concentrations in oyster for Gulf of Mexico and major embay

northeastern Gulf of Mexico (Presley et al., 1990) and clams (Corbicula inanileApalachicola River (Elder and Mattraw, 1984) . Values were calculated for each 

stations) over the three year sampling period (1986-1988), except for values f

n.d. - no data River which are median values from 1979-80. All values are which is ppb dry weight (Presley et al., 1990). ppm dry weight exc

Trace Metal Gulf of Mexico Pensacola Choctawhatchee Bay Bay St. Andrew Apalachicola Bay Bay Apalac

Riv

Silver 1.9 1.4 3.4 0.7 1.8 n

Arsenic 8.0 7.3 5.6 13.5 10.8 <0

Cadmium 3.8 3.0 5.2 0.9 2.6 <0Chromium 0.45 0.5 0.5 0.5 0.4 0

Copper 123 44 95 87 62.5 8Iron 252 345 368 100 322 n

Mercury 95 115 350 51 105 <100 Manganese 12.5 14 12.2 6.9 14.1 20 Nickel 1.6 1.7 1.2 2.0- 1.3 n

Lead 0.4 0.4 1.5 0.7 0.2 0Selenium 2.8 4.1 5.8 0.8 2.4 nTin <0.2 <0.2 0.2 0.2 nZinc 1730 1550 3550 710 525 20 
Elder and Mattraw (1984) observed no trends upstream or downstream, nor was

there any obvious seasonal pattern, although the seasonal sampling was

limited. Winger et al. (1985) also measured concentrations of metals in

the Apalachicola River in a variety of organisms (mayflies, Corbicula,

threadf in shad, channel catfish, largemouth bass, water snakes and little

green herons) and found generally low to moderate concentrations of

cadmium, mercury, arsenic, selenium and lead. In contrast to the study by

Elder and Mattraw (1984), Winger et al. (1985) found higher concentrations

below the confluence of the Apalachicola and Chipola Rivers than in the

upper Apalachicola River. The highest cadmium and lead concentrations,

0.63-1.01 ppm and 0.31-1.13 ppm, respectively, occurred in mayflies (Winger

et al., 1985). Arsenic levels were highest in threadf in shad and

Corbicula, 1.07 ppm and 1.75 ppm respectively (Winger et al., 1985).

Selenium concentrations were highest in the eggs from the largemouth bass

and channel catfish, 0.67-1.03 ppm and 0.78-2.08 ppm, respectively, while

mercury concentrations were highest in the herons, 0.67 ppm (Winger et al.,

1985). Metal concentrations higher than 0.5 ppm may be harmful (Winger et

al., 1985). The higher concentrations found in the downstream portion of

the Apalachicola River may be a result of contamination from battery

salvage operations in the upper Chipola River basin (Winger et al., 1985).

The NOAA NS&T Program has defined high metal concentrations as those

greater than the geometric mean of the national data set for any single

chemical plus one standard deviation. Sediment samples collected in the

northeastern Gulf containing "high" NS&T metal concentrations were found

in: Apalachicola Bay (As), Panama City (Zn), St. Andrew Bay (Hg, Pb),

Choctawhatchee Bay (As, Pb), and Pensacola Bay (As) (NOAA, 1991). The

Environmental Protection Agency's Environmental Monitoring and Assessment

Program (EMAP) sampled estuaries in the GOM from 1991-1994. EMAP

statistical summaries for the Louisanian Province have characterized

sediments as contaminated if concentrations exceed effects thresholds

established by Long and Morgan (1990) and Long et al. (1995) known as

Effects Range Low (ER-L) and Effects Range Median (ER-M). These thresholds

are based upon a national data set containing measured sediment chemical

concentrations and associated biological effects that include a wide range

of biological responses, e.g., toxicity, pathology, community composition,

diversity. ER-L values are those below which 10% of the effects data occur

and ER-M values are those above which 50% of the effects data occur.

Biological effects are not expected below ER-L concentrations and they are

predicted at concentrations above the ER-M. None of the metals measured in

1991-1993 exceeded the respective ER-M values. The following ER-L values

were exceeded: 1991 for Cr (<1% of the area of western Florida estuaries)

and Hg (15% of the estuarine area) Summers et al., 1993); 1992 for Cr, Ni,

Pb, and Sn in 7% of the estuatine area (MacauJ.ey et al., 1994); and in 1993

for As (30% area), Cr (20% area), Hg (7% area), and Ni (23% area) (Macauley

et al., 1995).

Not surprisingly, metal contamination is greatest in areas with the

greatest human activity (Hanson et al., 1993). The effect of metals on

organisms depends on factors such as which metal is considered, the

concentration, chemical speciation, the species of organism and the

developmental stage of the organism. Although a variety of factors affect

metal toxicity, in general, there is a trend of decreasing toxicity from

mercury to cadmium, copper, zinc, nickel, lead, chromium, aluminum, and

4-11
cobalt (Kennish, 1992). The results of these studies in the northeastern

Gulf of Mexico show that trace metals distributions are very different

between sediments and biota. The survey of metals in sediments suggests

that trace metal distributions generally follow the distribution expected

from weathering of crustal rocks, except in Pensacola Bay (Windom et al.,

1989; Hanson et al., 1993). In contrast, trace metal concentrations in

oysters show numerous "hot spots," particularly in Choctawhatchee Bay, that

are not correlated with either sediment concentrations or known

anthropogenic inputs (Presley et al., 1990).

4.2.6 Radioactivity

Significant anthropogenic sources of radioactive isotopes do not occur in

the northeastern Gulf. Uranium concentrations are often enhanced in

phosphate rocks and subsequent radioactive decay leads to the production of

radon and radium (Crane, 1986; Cowart and Burnett, 1994). Average activity

of radium in rivers ranges between 10-30 dpml00L' (Burnett et al,, 1990)

However, radium and radon activities are very high in groundwater and

spring fed rivers such as the Suwanee (226Ra = 210 dpmlOOL') (Crane, 1986)

West Florida shelf waters have much higher radium and radon activities than

other coastal waters (Fanning et al., 1982). Radium sources in estuarine

and marine waters can come from dissolved radium in river water, radium

desorbed from particles at the freshwater/estuarine interface and sediments

(Fanning et al., 1982; Cowart and Burnett, 1994). Measurements of radium

from the Suwanee River showed higher downstream activities than upstream,

as well as a significant variability over a seasonal cycle (Burnett et al.,

1990). This study suggests that discharge from submarine springs and seeps

may be a significant source of radium to offshore waters, as well as a

potential source of other constituents such as nutrients. Thus, radium and

radon may be useful tracers of groundwater and provide useful information

about groundwater inputs to estuarine and marine environments. Although

groundwater inputs to estuaries of the northeastern Gulf of Mexico have not

been measured, many studies over the last 10 to 15 years have shown that

groundwater can be a significant input of nutrients and freshwater to many

estuarine systems (Valiela et al., 1992).

4.2.7 Organic Contaminants

Organic contaminants include a wide range of compounds with varying

composition, reactivity, and sources. Polyaromatic hydrocarbons (PAH) and

chlorinated hydrocarbons (such as DDT and PCBs) will be the major focus,

although information about heterocycles (nitrogen, carbon, and sulfur) and

organophosphates (pesticides) will be included as available. In general,

inputs of organic contaminants are low in the northeastern Gulf of Mexico.

Lipid biomarkers have been used extensively to trace sources of organic

matter in sediments (Sever et al., 1972; Palacas, 1972). Organisms are

significant sources of hydrocarbons in the environment (Kennish, 1992)

There are several basic kinds of hydrocarbons: alkanes, which are linear

or branched chains of carbons with single carbon-carbon bonds; alkenes,

which are also linear or branched chains of carbons, with one or more

double bonds between carbon atoms; cycloalkanes, are rings with single

bonds between the carbon atoms; and aromatics, which are rings with double

bonds (benzene being the simplest example) . Biogenic hydrocarbons have a

4-12
distinctly different combination of compounds than do petroleum

hydrocarbons. Biogenic hydrocarbons are characterized by: alkanes with an

odd number of carbons greater than even-numbered alkanes (CPI); few

cycloalkanes and, when present, are 1-3 chain rings; simple aromatics with

on 1-2 alkyl group substitutions; while alkenes are very common (Kenrxish,

1992). The alkane, Cl7, is a hydrocarbon that is often found in blue-green

algae (Sever et al., 1972). Other biomarker ratios such as pristane/n-C17,

n-C18/phytane and pristane/phytane are useful for determining the likely

source of the hydrocarbons. High pristane/n-C17 ratios are characteristic

of bacteria, and some algal species, although low ratios have been found

from other benthic algae and phytoplankton samples (Palacas et al., 1972).

Concentrations of coprostanol, which is a biomarker indicative of

anthropogenic inputs from sewage or livestock, were less than the average

for the whole Gulf of Mexico (51 sites) at 6 of the 7 sites in the

northeastern Gulf of Mexico, with the higher than average coprostanol value

occurring in St. Andrew Bay (Wade et al., 1988).

4.2.7.1 Hydrocarbons

Hydrocarbon concentrations in Choctawhatchee sediments ranged from 6-SO ppm

in organic-poor sands (O.l5 organic carbon) to 60-470 ppm in organic-rich

mud (3.6's organic carbon) and 240-930 ppm in muddy bayou sediments (Palacas

et al., 1972). Pristane:n-C17 ratios were high and CPI (odd:even ratio)

was low in the sandy sediments, suggesting a marine source, while the high

CP1 in the muddy sediments indicated that terrestrial plants were the

likely source (Palacas et al., 1972). There was no indication of

hydrocarbon pollution in any of the samples. Hydrocarbon concentrations in

the west Florida shelf sediments ranged between 1.5 and 4.1 ppm, and

decreased with increasing water depth (Gearing et al., 1976; Lytle and

Lytle,, 1976). Low molecular weight alkanes (n-C17 and C18), which are the

main constituents of marine algae, dominated the hydrocarbon signal

(Gearing et al., 1976; Lytle and Lytle, 1976). Sediments along most of the

eastern portion of the Florida shelf had pristane/phytane ratios suggestive

of marine organisms, while sediments off of the Apalachicola River and

further west had signatures more typical of inputs from terrigenous organic

material and petroleum (Gearing et al., 1976).

Polyaromatic hydrocarbons (PARs) are a complex class of hydrocarbons that

are hydrophobic, but rapidly sorb to organic particles. Concentrations of

PARs in estuarine and marine environments are generally highest in

sediments, lowest in the water column and intermediate in the biota

(Keimish ,1992). In the northeastern Gulf of Mexico, inputs of PARS from

the watersheds are less than 0.09 gm2yr1 from most of the coastal

counties (NOAA, 1985) . Mean PAR in sediments from 51 Status and Trend sites

throughout whole Gulf is 0.5 ppm, with a range of <0.005 (limit of

detection), to 36.7 ppm (Wade et al., 1988). Based on the ratio of

phenanthrene:anthracene, Wade et al. (1988) suggested that the source of

the PAR was probably not fresh petroleum but may have been weathered

petroleum. Sediment PAR concentrations measured by NOAA NS&T exceeded the

'thigh" values in Panama City, St. Andrew Bay, and Choctawatchee Bay (NOAA,

1991, O'Connor and Ehier, 1991). EPA's EMAP detected exceedences of total

PAR ER-L values of 4,000 ppb in 5% of the area of western Florida estuaries

in 1991 (Summers et al., 1993) and 14% of the estuarine area in 1992

4-13
(Macauley et al., 1994), while PABs were not elevated in 1993 samples

(Macauley et al., 1995).

PAH concentrations in oysters were 0.5 ppm, with a range of <0.02 (limit of

detection), to 18.6 ppm throughout the whole Gulf with similar

phenanthrene:anthracene ratios (Wade et al., 1988). PAR body burden at S

stations along the northeastern Gulf of Mexico ranged between 0.02-13.3 ppm

over a four-year interval (Wilson et al., 1992; Jackson et al., 1994). The

highest concentrations (0.9-13.3 ppm) consistently occurred in St. Andrew

Bay oysters, while the lowest concentrations (0.04-0.4 ppm) generally

occurred at Cedar Key (Wade and Sericano,1989; Wilson et al., 1992).

Median values of PAR concentrations in oysters from the major embayments

over a five-year interval were 46 ppb for the Suwannee, 57 ppb for

Apalachicola Bay, 1800 ppb for St Andrew Bay, 429 ppb for Choctawhatchee

Bay, and 197 ppb for Pensacola Bay (Jackson et al., 1994). One potential

source for these high PAR concentrations in St Andrew Bay was a minor oil

spill (<10,000 gallons) in the 1970's (NOAA, 1985)

No oil development in the Florida coastal zone is currently allowed, so

direct local inputs associated with oil field production are not a problem

in Florida. However, new fields are rapidly being developed in Mobile Bay

and the Alabama shelf (Hagar, 1985; McCabe, 1985; Mancini et al., 1984).

Successful oil exploration in the Mobile Bay region has led to speculation

that significant oil and gas reserves may exist in comparable geologic

formations off of Florida (Hagar, 1985).

Pensacola Bay is the site of a long term (over 80 years) significant

anthropogenic input of PAHs from a creosote wood treatment plant, which is

now a Super Fund site (Elder and Dresler, 1988) . Creosote is a complex

mixture of polyaromatic hydrocarbons, phenols, and nitrogen heterocycles,

although PAils comprise about 90% of the total (Elder and Dresler, 1988).

Groundwater and stream sediments near the site are highly contaminated with

a variety of PAils (Table 4-3) including naphthalene at 200 ppb and

anthracene at 140,000 ppb (Rostad and Periera, 1987; Elder and Dresler,

1988) . Water samples from the stream and estuary near the plant, as well

as surf icial sediment samples, had no detectable concentrations of PAils

(Elder and Dresler, 1988) . Oyster drills (Thais hae.mastoma) and oysters

(Crassostrea virginica) near the creosote site accumulated phenanthrene,

fluoranthene and pyrene, while oysters also accumulated benzo[a]anthracene

and chrysene; neither accumulated naphthalene (Elder and Dresler, 1988)

The effect of PAils on organisms depends on chemical structure, molecular

weight, the organism, how easily the compound can be metabolized, and the

intermediate breakdown compounds (Kennish, 1992). Low molecular weight

PAils often cause acute toxicity, but are not usually carcinogenic (Kennish,

1992). On the other hand, high molecular weight PARs are not as toxic, but

are often carcinogenic, mutagenic or teratogenic (Kenrxish, 1992) . PAils can

become carcinogenic or mutagenic after being partially metabolized by

organisms (Kennish, 1992) . Toxicity tests of the groundwater, streamwater

and ultrafiltered groundwater from this site all caused a toxic or

teratogenic response in newly spawned inland silversides (Menidia

beryllina) [Middaugh et al., 1991] . However, when groundwater, streamwater

and ultrafiltered groundwater were diluted by 10:1 and 100:1, embryos in

the diluted ultrafiltered groundwater survived with a greater than 90%

hatching rate and most of the larvae appeared normal, while the other

4-14
Table 4-3. Concentrations of polyaromatic hydrocarbons found in snails

(Thais haeznostoma), Pensacola Bay sediments and inf lowing

stream sediments from creosote-contaminated Super Fund site.

Concentrations in gkg' (detection limit 40 gkg1 for

sediments)

a from Elder and Dresler, 1988

b from Rostad and Pereira, 1987

C n.a. - data not available

treatments showed a teratogenic or toxic response (Middaugh et al., 1991).

Although relatively low concentrations of PAH were found in the water,

sediments, or biota of the Pensacola Bay estuary, even these concentrations

may have a deleterious effect on biota (Middaugh et al., 1991).

Distributions of particular creosote-derived compounds are determined by

factors such as solubility and susceptibility to degradation, as well as

physical and hydrologic factors such as sediment resuspension and increased

flushing during storm events (Elder and Dresler, 1988). The phenolic and

heterocyclic components of creosote are rapidly and effectively

biodegraded, as are many of the Ps (Elder and Dresler, 1988). Elder and

Dresler (1988, p. 127) described 5 characteristics that determined the

likelihood of a contaminant being bioaccumulated:

"resistance to biodegradation;

resistance to chemical transformation reactions such as

photochemical oxidation;

capacity to be transported rather than deposited in non-mobile

forms;

bioavailability, or capacity to be incorporated into tissues of

the organism;

resistance to depuration, or tendency to remain in tissues of the

organism. IT

4-15

Compound Stream Sediment&

Pensacola Bay

Sedimenta Snailb

di-n-butyl phthalate

naphthalene

<40 - 2,000

200-300

<40-2,900

<40

C n.a.

C n.a. phenanthrene <40-12,000 <40 65 . 6 - 194 fluoranthene 17,000-62,000 <40 - 190 25.9 - 60.8

pyrene

benzoanthracene

11,000- 32, 000

5,000-15,000

<40 - 160

<40 - 75

22.7 -40.4

C n.a.

chrys ene 7,000-10,000 <40 - 100

acenaphthene 5,000- 19, 000 <40 2 . 06 - 8.08

fluorene 3,000- 32, 000 <40 1.34 - 6.28

anthracene 3,000- 140, 000 <40 9. 03 - 24. 7
For PARS, the number of rings and characteristics such as n-octonal/water

partition coefficients may be useful diagnostics of bioaccumulation in the

absence of direct experiments (Rostad and Periera, 1987; Elder and Dresler,

1988; Wade et al., 1988; Farrington, 1989).

4.2.7.2 Chlorinated Organics and Organophosphates

Organochlorines bind to suspended matter and are soluble in lipids (Nimmo

et al., 1971a), often accumulating in fatty tissues of organisms at 102_104

times the ambient concentrations (Kennish, 1992) . These properties have a

significant effect on their distribution in the environment. Common

examples of organochlorines include the pesticide DDT and degradation

products, DDE and DDD; dieldrin; chlordane; and PCBs. For the 51 Status and

Trend sites throughout the Gulf of Mexico, the DDT average was 6.19 and 44

ppb in sediments and oysters, respectively (Wade et al., 1988). A similar

trend of higher accumulation in oysters than in sediments occurred for PCB5

(9.84 ppb sediment, 172 ppb oyster) and a variety of chlorinated

hydrocarbons (chlordane 0.5 ppb sediment, 20.7 ppb oyster) (Wade et al.,

1988) - Sediment DDT concentrations measured by NOAA exceeded the NS&T

"high values in Panama City, St. Andrew Bay, and Choctawatchee Bay (NOAA,

1991). EMAP detected exceedences of the following pesticides and their

areal extent in western Florida estuaries: 1991 for chloradane (1%),

dieldrin (2%), endrin (1%), and DDE (1%) (Summers et al., 1993); 1992 for

dieldrin (32%) (Macauley et al., 1994); and 1993 for chloradane (8%),

dieldrin (28%), endrin (12%) (Macauley et al., 1995).

Measurements of DDT-R (DDT, DDE, DDD), PCB and Mirex in sediment and biota

from Lake Seminole (Apalachicola River headwaters) and Apalachicola Bay

over a four-year interval (1972-1976) showed rapid declines after the first

year of sampling (Livingston et al., 1978). By 1974, concentrations had

dropped to 34 ppb DDT and 55 ppb PCB in Rangia cuneata, 10-14 ppb DDT-R and

32-39 ppb PCB in Callinectes sapidus. In contrast, a later study (1978) of

organochlorine insecticides and PCBs found higher concentrations in a

variety of organisms in Apalachicola River than did this previous study

(Winger et al., 1985). organochiorine insecticidesand PCB concentrations

were measured in the Apalachicola River in mayflies, Corbicula, threadf in

shad, channel catfish, largemouth bass, water snakes and little green

herons, and were generally higher in animals from the upstream stations

compared to those at downstream stations (Winger et al., 1985). DDT

residue concentrations were highest in eggs from largemouth bass, water

snakes and herons, 1.86 j.g-g1, 1.01 j.g-g' and 1.1 g-g', respectively,

while PCB concentrations were high in herons, largemouth bass and eggs from

largemouth bass, 1.72 jgg1, 1.4 Lg-g' and 1.7 g-g1. Herons, largemouth

bass eggs and channel catfish had the highest concentrations of toxaphene,

1.28 JAg-g1, 0.83 Mgg' and 0.8 p.g-g1, respectively. Concentrations of

contaminants were generally higher in higher trophic levels. Winger et al.

(1985) concluded that organic contaminants in the Apalachicola River biota

are higher than recommended levels proposed by the National Academy of

Science. Another study was conducted in 1979-1980 and sediments,

particulate detritus and clam (Corbicula rnanilensis) tissues from the

Apalachicola River were analyzed for a series of organochlorine pesticides

(aldrin, chlordane, DDD, DDE, DDT, dieldrin, endosulfan, endrin,

heptachlor, heptachlor epoxide, lindane, methoxychlor, mirex, perthan,

strobane, toxaphene), organophosphate pesticides (diazinon, ethyl

4-16
parathion, ethyl trithion, methyl parathion, methyl trithion, ethion,

malathion), chlorinated phenoxy acid herbicides (silvex; 2,4-D; 2,4-DP;

2,4,5-T) and polychlorinated biphenyls (PCBs). These organic contaminants

were either undetectable or present at concentrations less than 20 ppb

(Elder and Mattraw, 1984). Only chlordane, PCB, DDD and DDE were above

detection limits (0.1 ppb) in fine-grained sediments (Table 4-4) . Organic

concentrations in detritus were generally higher than in sediments,

particularly chiordane, DDD, DDE, dieldrin and PCB. Highest concentrations

of organic contaminants were found in clam tissues. Elders and Mattraw

(1984) observed some temporal variability in organic contaminants, although

the resolution of their sampling program was not fine enough to determine a

seasonal pattern. They also observed that chlordane and PCB concentrations

in clam tissues generally decreased downriver, although concentrations at

the headwaters were highly variable. They concluded that nonpoint

discharges were the major source of organic contaminants to the

Apalachicola River.

Table 4-4. Median concentrations of organic contaminants in

Apalachicola River sediments, detritus and whole

body tissue from the clam, Corbicula rnanilensis,

tissue in ppb (Elder and Mattraw, 1984).

Herbicides, organophosphorus insecticides, aldrin, heptachior, lindane,

mirex, perthan, methoxychior were below detection limits (<0.1 ppb)

in all samples. Endrin, endosulfan, strobane and toxaphene were below

detection limits (<0.1, <0.1, <1, <10 ppb respectively) from all of

sediment and detritus samples and from over half of clam samples.

PCBs, specifically Arochlor 1254, have been a serious contaminant in

Escambia Bay following its accidental release from a chemical plant in 1969

(Nimmo et al., 1971a). Shortly after the release, water samples near the

plant had Arochior concentrations of 274 ppb. These declined to less than

5 ppb in the following months, and by 1974 only trace amounts could be

detected, or concentrations were below detection limits (Wilson and

Forester, 1978) . In the Escambia River near the plant outfall, sediment

concentrations were generally higher (about 486 ppm) than water

concentrations, although the sediment concentrations from further

downstream were lower, and decreased from 78 ppm in 1970 to about 1 ppm by

1972 (Nimmo et al., 1975; Wilson and Forester, 1978). In December 1971,

4-17

Compound Sediment Detritus Clam

chiordane <1.0 6.9 21.0

DDD 0.4 2.3 8.0

DDE 1.3 2.5 18.0

DDT <0.1 <0.1 3.0

dieldrin <0.1 0.5 2.0

heptachlor epoxide <0.1 <0.1 0.3

PCB 1.0 2.1 21.0
Arochlor 1254 concentrations in Escambia Bay waters ranged from

nondetectable (<0.03 ppb) to 8.6 ppb, while sediment concentrations ranged

from nondetectable (10 ppb) to 30 ppm (Nimmo et al., 1975). Arochior

concentrations varied depending on sediment type, with higher

concentrations in the silty compared to sandy sediments (Nimmo et al.,

197la)

Significant concentrations of Arochior were measured in a variety of

invertebrates following the spill: 14 ppm in several shrimp, Penaeus spp.,

and 0.45-1.5 ppm in fiddler crabs, Uca spp. (Nimmo et al., l97la). A long

term study of oyster populations in Escambia Bay showed that whole body

concentrations decreased over time, from 2.5 ppm to between 0.1-0.5 ppm

after 7 years (Wilson and Forester, 1978). Wilson and Forester (1978)

observed a strong seasonal variation in Arochior concentrations with higher

concentrations during spawning when lipid contents are highest in oysters.

No detectable Arochior concentrations were measured in Spartina or Zostera,

while concentrations were significant in higher trophic levels; even shrimp

from Pensacola Bay, about 35 km away, had significant concentrations (Nimmo

et al., 1975). In contrast, Arochlor was not detected in shrimp collected

from the adjacent Perdido or Choctawhatchee Bays (Nimmo et al., 1975).

Toxicity tests were done on shrimp collected from Pensacola and Tampa Bays,

and several other organisms common to the area. Arochlor 1254 was toxic to

juvenile shrimp, causing 51% mortality after 15 days exposure to 1 ppb

(Nimmo et al., 1971b) . Shrimp seemed to be affected during molting,

although adults were not as susceptible as juveniles (Nimmo et al., 1971b).

Arochior also reduced the growth of ciliates and caused mortality and/or

histopathological changes in shrimp, oysters and spot at 1 ppb

concentrations (Nimmo et al., 1975). PCB5 are very stable and persistent

compounds, with relatively slow degradation rates compared to other organic

contaminants (Kennish, 1992) . Bacteria can degrade PCBs but the rate

depends on the degree of chlorination (more chlorines, less degradation)

and the position of the chlorine (Kennish, 1992). PCBs tend to

bioaccumulate and are not easily metabolized. The estimated half-life of

these compounds in estuarine and marine environments is 8-15 years

(Kennish, 1992)

4.2.7.3 Pulp Mill Effluents

A number of pulp mills operate within the drainage basin of the

northeastern Gulf of Mexico (NOA, 1985). Effluent from pulp mills is a

complex mixture of organic acids, polythionates, lignins, sulf ides and

inorganic compounds (Zimmerman and Livingston, 1976). Chlorinated organic

compounds are a significant fraction of the Kraft process pulp mill

effluent, which appears to consist of a chlorinated thiolignin (30%) and

other high molecular weight chlorinated lignin compounds (70%) (Watts and

Locke, 1993) . In the 1970's, discharge of relatively untreated effluent

from Kraft process pulp mills into freshwater and estuaries led to low

dissolved oxygen concentrations, increased turbidity and color in the water

column and a reduction in seagrass and macroalgal biomass (Zimmerman and

Livingston, 1976) . Improvements in mill operations led to improved water

quality (particularly dissolved oxygen) and water color, and a partial

recovery of the seagrass beds (Livingston 1980) . Discharge of chlorinated

organic compounds continues to this day and is of local concern because

4-18
discharge from the mill is the predominant source of the water to the

Fenholloway River. Effluent from the mill has been implicated as the

source of contamination of residential drinking water wells in the region

(Watts and Locke, 1993) . A Kraft process pulp mill also discharges into

St. Andrew Bay (Grady, 1981), although no published studies of the effects

of this effluent on St. Andrew Bay were identified.

4.2.8 Case Studies

4.2.8.1 Chattahoochee-Flint-ApalachiCOla River and ADa].achicola Bay

The Chattahoochee-Flint-ApalaChicola River system is the largest river

system in the northeastern Gulf of Mexico. The watershed is 50,800 km2 and

drains parts of Georgia, Alabama and Florida. The headwaters of the

Apalachicola river begin at the Jim Woodruff Dam, where the Chattahoochee

and Flint Rivers join. There are 16 other lock and dam structures on these

two rivers. The Apalachicola River is 170 km long and drains 3,100 km2.

and is joined by the Chipola River which also has a drainage basin of 3,100

km2. The 454 km2 floodplain is regularly inundated during high flow

between February and April (Elder et al., 1988). Mean annual flow is 650

m3s1, while low flow is about 290 m3s' and high flow is greater than

2,910 m3s (Elder et al., 1988). Average annual rainfall is 147 cm and

evapotranspiratiOn is 114 cm. Mean air temperatures are-ll°C in January

and 27°C in July. The water budget for the Apalachicola River is dominated

by streamf low from upstream (80'E) and the Chipola River;

evapotranspiration, groundwater and precipitation are not significant terms

in the budget (Elder, 1985). Apalachicola river pH ranges between 5.7-7.8.

The forested floodplain is the largest in the state of Florida and has

about 211 different tree species, dominated by tupelo, gum, oak and cypress

(Leitman et al., 1983). Flooding restricts the species composition of the

forest to flood-tolerant species and has important impacts on

biogeochemical processes and productivity in the basin (Mitsch and

Gosselink, 1986) . With the advent of flooding in the basin, soils become

saturated and decomposition changes from mainly aerobic to anaerobic

processes, such as denitrification, sulfate reduction and particularly

methanogenesis. Flooding can supply nutrients to the forested floodplain

and flowing water enhances flushing, leading to increased oxygen and

decreased carbon dioxide and methane concentrations in soils. These

factors are partly responsible for the high productivity of forested

floodplains, some of which is exported as organic carbon and used by

downstream ecosystems (Mitsch and Gosselink, 1986) . Annual litterfall in

the Apalachicola basin was high, about 800 gm2, and represented an

important source of organic carbon (Elder and Cairns, 1982) . Decomposition

rates of litter were 300 kgha'yr' for nitrogen and 30 kgha'yr' for

phosphorus (Elder and Cairns, 1982) . Most transport of organic carbon

occurred (73 tons .yr') during peak spring runoff, but was also important

in the summer (45 tonsyr1) when primary production was high (Elder et

al., 1988). Most organic carbon in the system was dissolved (6.7 mgl'),

while only a small fraction was particulate (0.7 mg.l) [Mattraw and

Elder, 1984 . The finest particulate size (45-63 j.im) transported most of

the particulate carbon out of the floodplain (Elder et al., 1988).

Total nitrogen (TN) and phosphorus (TP) concentrations were not seasonally

variable and the TN:TP ratio was between 12 and 15 for most sites in the

4-19
main channel of the Apalachicola River (Elder, 1985) . TN:TP ratio for

precipitation data was near 10, while the small tributary streams had lower

concentrations of TN and TP and variable TN:TP ratios. In contrast,

dissolved inorganic nitrogen (DIN = nitrate + nitrite + ammonium) to soluble

reactive phosphorus (SRP) ratios in the river increased from 23 at the

headwaters to 40 at the mouth (Elder and Mattraw, 1982). In contrast to

the TN:TP ratios, these high DIN:SRP ratios, which represent available

nutrients, suggest that primary production in the river may be phosphoruslimited. Nitrate and dissolved organic nitrogen (DON) are the major

nitrogen species in the Apalachicola River. Nitrate concentrations are

generally lowest in late summer (0.02 mgl) and highest in late winter

(0.44 mgl), while DON increases during flooding from 0.20-0.25 mg11

(Elder, 1985) - Particulate organic nitrogen (PON) concentrations were

about 0.15 mg-l', while ammonium concentrations were about 0.05 mgl' and

decreased from headwaters to mouth (Elder, 1985). Soluble reactive

phosphorus (SRP) decreased from 15 mg-1' at the headwaters to 8 mg-l' at

the mouth with a concomitant increase in dissolved organic phosphorus (DOP)

from 0 to 13 mg-11 and particulate phosphorus from 35 to 40 mg-l' over the

length of the river (Elder, 1985).

The Apalachicola River has no significant anthropogenic sources; the few

municipal sewage treatment plants in the watershed serve small communities

and did not affect nutrient inputs (Mattraw and Elder, 1984). Mattraw and

Elder (1984) also developed a nutrient budget for the river which showed

that upstream nutrient inputs from Chattahoochee and Flint Rivers were the

major source of nutrients for the Apalachicola River, as was the Chipola

River was a significant source of nitrogen and phosphorus. Atmospheric

deposition, groundwater and evapotranspiration were smaller terms in the

total budget.

In contrast, atmospheric deposition was an important source of ammonium

within the basin (Mattraw and Elder, 1984). A regional analysis by

Winchester and Fu (1992) of atmospheric inputs of nitrate, sulfate and

ammonium suggested that the atmosphere was the principal source of these

constituents to the Apalachicola River. Their analysis suggests that

sulfate is a conservative tracer of acid deposition, but that nitrate and

ammonium are affected by burial, uptake and denitrification. In addition,

transformations of DIN to DON within the river may explain the increased

DON observed within the Apalachicola River basin. Measurements of nitrous

oxide or dinitrogen gas have not been made, although measurements of

nitrous oxide from other agricultural areas suggest that nitrous oxide

ef flux may be a significant component of the nitrogen budget (Winchester

and Fu, 1992; Vitousek and Matson, 1993). There is a seasonal cycle in the

transport of nutrients and detritus in Apalachicola River with 50% of

nitrogen and phosphorus and 60% of particulate detritus occurring within an

86-day interval during peak discharge (Elder and Mattraw, 1982). Elder and

Mattraw (1982) also observed that leaf decomposition was enhanced during

prolonged inundation. The Apalachicola River and forested floodplain seem

to act as a transformer, changing inorganic inputs to organic outputs.

Apalachicola Bay is 62,900 ha in size and has a well-mixed water column,

although some parts can be seasonally stratified (Livingston, 1984). In

the early 1980's, oysters made up 7% of the open water area, while

submerged grassbed represented 10% and marshes 14% of the area (Livingston,

4-20
1984). Apalachicola Bay, near the river mouth, had a highly variable

nutrient and salinity regime over the annual cycle and was characterized by

high secondary production, while stations in the adjacent St. George Sound

had little variability in salinity or organic matter (Federele et al.,

1986). Nutrient concentrations were generally higher in the bay in winter

than summer (Livingston, 1984) . Nutrient concentrations were greater near

the freshwater end, with peaks in 10 .iM nitrate and 0.8 j.LM phosphate in the

spring and an average of 3.3 j.iM nitrate and 0.37 M phosphate throughout

year (Myers and Iverson, 1981). Generally low concentrations occurred in

the oligotrophic reaches of St. George Sound where nitrate concentrations

averaged 0.55 M and phosphate concentrations averaged 0.19 M. Myers and

Iverson (1981) measured chlorophyll-a concentrations between 3-9 gl1

with a peak in late summer in the freshwater end. They also measured

higher phytoplankton productivity in the freshwater region, while both

chlorophyll-a concentrations and primary productivity were much lower in

the more saline and oligohaline region. Primary production in Apalachicola

Bay, as well as Ocklockonee Bay and the Econfina estuary, was limited by

phosphate (Myers and Iverson, 1981), although both nitrate and phosphorus

may limit production in Apalachicola Bay in the summer (Livingston, 1984).

The river is a source of nutrients to the bay (NOAA, 1985; Elder and

Mattraw, 1982) and can lead to enhanced microbial productivity and

secondary productivity within Apalachicola Bay (Livingston, 1980).

Nitrogen inputs to Apalachicola Bay were 560 mmol Nm2yr1 with only 2%

coming from sewage and phosphorus inputs were 14 mmol Pm2yr'

(Livingston, 1984). Increased development on St George Island,

particularly from seepage of nitrate from septic tanks, has the potential

to increase nutrient inputs to Apalachicola Bay. No studies directly

examining this impact were identified, although work from other marine and

estuarine systems suggests that groundwater inputs of nitrate from septic

tanks can have deleterious impacts (Capone and Batista, 1985; LaPointe,

1992; Valiela et al., 1992).

4.2.8.2 uwanee River

The Suwanee River originates in the Okefenokee Swamp, while the lower part

of the Suwanee River Basin receives much of its flow from the Florida

aquifer (Crane, 1986) . The whole drainage basin includes 28,600 km2 in

South Georgia and 11,000 km2 in Florida. A study of the groundwater

chemistry of the Suwanee River Basin showed that low pH values (4.3)

occurred in the northeastern part of the basin, and that pH increased to

6.5-7 in springs near the coast (Crane, 1986) . A similar gradient occurred

in the distribution of major ions which changed from dominance by calcium,

bicarbonate and magnesium in the upstream groundwater springs to increased

concentrations of sodium, chloride, potassium and sulfate in springs near

the coast (Crane, 1986) . Nutrient concentrations were generally low

(<36 M NO3 , 18 ,uM NI4 , 2 jM orthophosphate), except near septic tanks,

or agricultural sites where NO3 levels reached 1900 jIM. The Suwannee

River has extensive tidal wetlands, with freshwater tidal marshes and

swamps comprising 4615 ha and saltwater marshes making up 6720 ha of the

basin (Leadon and Wetterqvist, 1986). Wetlands in this area help to

maintain freshwater in the coastal aquifer which is susceptible to

saltwater intrusion following drainage of wetland (Leadon and Wetterqvist,

1986). Species diversity of both plants and animals is high (Leadon and

4-21
Wetterqvist, 1986, Mason et al., 1994). The river is considered pristine

because of the lack of urban development in the watershed (Burnett et al.,

1990), although there are some point and nonpoint sources of organic waste

and toxic contaminants (Mason et al., 1994).

Little is know about the cycling of organic matter within the Suwanee River

and estuary. Nutrient concentrations in the river are low (Mason et al.,

1994) . Studies in the Ogeechee River, a blackwater river in coastal

Georgia, may provide insight to the cycling of organic matter in blackwater

rivers like the Suwanee. The Ogeechee has a low algal biomass because of

light limitation, and high bacterial and protozoan densities, as well as

high macroinvertebrate densities (Carlough, 1994). About 96's of the organic

carbon is dissolved, while the particulate matter is very fine (<50 jtn)

amorphous material, rich in bacteria, extracellular organic material and

protozoans (Carlough, 1994) . Significant organic production can also occur

on snags which are covered with thick biofilms rich in bacteria (Couch and

Meyer, 1992). Bacterial production is fueled by uptake of DOC from the

water or leaching out of the wood (Couch and Meyer, 1992).

4.2.8.3 bayou Texar/Pensacola Bay

Bayou Texar is a subestuary of Pensacola Bay, although exchange between the

two is restricted. Extensive urban development in the watershed led to an

overloading of the waste treatment system in the region in the early 1970's

(Moshiri et al., 1981). That study, which provided this excellent overview

of the chemical status of the estuary, showed that the bayou received most

of the nutrient inputs from sewage and storm water runoff. Nitrogen

concentrations were high, particularly in the freshwater region where

average NO3 concentrations were 44 /.LM, but decreased downstream to 5 iM in

Pensacola Bay, while NH4 concentrations ranged between 1.8-7 j.M.

Phosphate concentrations were generally low, between 0.1-0.5 iM for PO43

and between 0.5 and 1.7 jM for total phosphate. Primary productivity was

highest at the freshwater end, with rates between 60-70 mg Cm3-h', while

rates near Pensacola Bay were between 30-40 mg Cm3h. As a result of

the high nitrogen inputs, development of intense algal blooms occurred

during warm, clear and calm weather and the degradation led to periodic low

oxygen events. In addition, blooms of Gymnodinium, a red tide

dinoflagellate, may have contributed to the numerous fish kills in Bayou

Texar. Improvements in water quality and reduction in the number of fish

kills occurred after several engineered changes were made to the flow

regime, which enhanced exchange between the Bayou with Pensacola Bay.

These included dredging the bayou to a uniform depth, dredging the channel

and removing structures which impeded flow between the bayou and bay,

building a storm water holding system, and slowing the flow of freshwater

from the major creek to the bayou. Subsequent studies comparable to

Moshiri (1984) for the status of this estuary in the 1980's and 1990's were

not located.

4.3 Chemical Cycles

4.3.1 Nutrient Cyclinq

Northeastern Gulf of Mexico estuaries are strongly influenced by nutrient

inputs from rivers. Agriculture, including silviculture, represents the

4-22
dominant nitrogen and phosphorus inputs. Because this region is generally

sparsely populated, particularly along the coast, sewage inputs are less

important, except near major cities such as Pensacola and Panama City. It

is difficult to make general statements or draw conclusions about the

current status of nutrient cycling within the northeastern Gulf of Mexico

because of the lack of data for some regions, including the Suwanee

estuary, Choctawhatchee Bay, St. Andrew Bay, St. Joseph Bay and the lack of

recent data (within the last 10-15 years) for otherregions, including

Apalachicola Bay and Pensacola Bay. Despite the lack of information, some

hypotheses can be examined based on information from other estuarine and

marine systems. It would be expected that there would be significant

differences between blackwater/spring fed systems like the Suwanee and

alluvial river systems like the Apalachicola. The Suwannee has low

nutrient concentrations and highly colored water, so phytoplankton

productivity would be expected to be lower due to a reduced euphotic zone

within the river, although bacterial productivity may be high. There have

not been any comparative studies of the Suwannee or Apalachicola Rivers to

examine whether phytoplankton productivity is light-limited and whether

differences between light attenuation by humics versus inorganic particles

is significant.

The role of physical processes has an important impact on nutrient cycling.

The effect of freshwater inputs to estuaries has been discussed previously.

Mixing of shelf and nearshore water is also important in controlling

concentrations of nutrients and contaminants. Because of low tidal energy

in the region, the effect of fronts and hurricanes can have an important

effect on mixing of nearshore and offshore water (Darnell, 1992) . Gulf of

Mexico water from the shelf and gyre has very low nutrient and contaminant

concentrations so it would dilute concentrations of these substances

nearshore.

4.3.1.1 Primary Productiozi

In estuaries, phytoplankton and seagrass production are often controlled by

light and nutrient availability. The most complete study of phytoplankton

production in the northeastern Gulf of Mexico showed that phosphorus often

limited summer phytoplankton productivity in several estuaries (Myers and

Iverson, 1981). The most productive areas found by that study were

brackish (mean salinity 3-12 psu) stations in Apalachicola Bay and

Ocklockonee Bay which had higher nitrogen and phosphorus concentrations,

but were more turbid than the other stations. This suggests that nutrient

inputs are more important than the light regime, which may be expected

since these are very shallow systems. In contrast, seagrass production in

the region is controlled by light limitation, with beds in Apalachicola Bay

occurring in less than 1 m water depth, compared to beds down to 4.5 m for

the rest of the region (Iverson and Bittaker, 1986) . Seagrass beds along

the northeastern Gulf of Mexico, as in other region, trap organic matter

(Grady, 1981). Higher organic inputs generally lead to greater rates of

decomposition and nutrient cycling. Thus, rates of nutrient cycling are

often higher in seagrass beds than unvegetated sediments, although

concentrations of nutrients in water and sediments may be low. Enhancement

of a variety of nutrient transformations, such as amrnonium mineralization,

nitrification, denitrification, and nitrogen fixation have been measured in

4-23
seagrass beds in other regions (O'Neill and Capone, 1989; Caffrey and Kemp,

1990)

4.3.1.2 Ochiockonee Bay

The most recent and complete information about nutrient cycling exists for

Ochlockonee Bay, which is a small, pristine system. Ochlockonee Bay is

similar to Apalachicola Bay in that the major input of nutrients is from

nonpoint sources (Kaul and Froelich, 1984; Seitzinger, 1987). Primary

production in the Bay is about 28 g Cl1h' and can be limited by either

nitrogen or phosphorus depending on sampling date, although there are not

enough data to resolve a seasonal pattern (Myers and Iverson, 1981) . This

contrasts with the results from Apalachicola Bay, which had slightly higher

productivity, 38 g Cl'.h1, and phosphorus limitation of production for

most of the experiments (Myers and Iverson, 1981). Nutrient budgets for

Ochlockonee Bay were calculated by Kaul and Froelich (1984) for silica,

nitrate and phosphorus. Riverine inputs of silica equaled estuarine

outputs and the internal cycle of silica was about 181 of the yearly

riverine input (Kaul and Froelich, 1984). Their budget also showed that

97.51 of the phosphorus inputs from the river were exported out of the

estuary, so only 2.5% of phosphorus inputs were buried in sediments. They

were not able to balance the nitrate budget because they did not measure

ammonium, nitrous oxide or dinitrogen concentrations, nor rates of

nitrification and denitrification which were probably significant.

Seitzinger (1987) found that denitrification rates in Ochiockonee Bay

averaged 73 mol Nm2hr' over an annual cycle, with benthic nitrogen

fluxes (mainly ammonium) able to supply about 20% of the nitrogen

requirements of the phytoplankton. Ammonium fluxes were greatest in the

June, while nitrate fluxes were greatest in March, and denitrification

removed about 541 of the nitrogen coming in from the river (Seitzinger,

1987) . For these relatively pristine estuaries, nutrient inputs and

outputs seem to be in balance, with none of the positive feedback loops

characteristic of more eutrophic estuaries like Chesapeake Bay (Kemp et

al., 1989). However, recent data are lacking for more urbanized areas such

as Pensacola Bay.

4.3.1.3 ypoxia/Anoxia

Hypoxia (water column oxygen concentrations <2 mg.1') and anoxia (water

column oxygen concentration = 0 mgl1) often occur in eutrophic systems

and are a severe problem in other areas of the Gulf, including Lake

Pontchartrain, Mobile Bay and the Mississippi River plume (May, 1973;

Turner et al., 1987; Darnell, 1992). Water column stratification, high

organic inputs, warm temperatures and calm conditions combine to promote

hypoxia/anoxia (Turner et al., 1987). For well-mixed estuaries such as

Apalachicola Bay, one would not expect hypoxia to be common. However,

areas with restricted circulation, particularly harbors, marinas and

canals, would be at risk; hypoxic events have occurred around St George

Island and the city of Apalachicola (Livingston, 1984). Bayou Texar, which

is a subestuary of Pensacola Bay, had summertime anoxia in the l97OTs

(Moshiri et al., 1974), although a series of changes to the flow regime and

inputs to the bayou appeared to reduce the problems (Moshiri et al., 1981).

However, the status of Bayou Texar over the last 15 years is unknown.

Hypoxic bottom water conditions were detected by instantaneous sampling in

4-24
the EMA.P western Florida estuaries in 1991, 1992, and 1993 in 1, 7, and 0%

of the estuarine area, respectively. Comparable figures for the estuarine

area experiencing dissolved oxygen <5 mgl were 13, 23, and 48%,

respectively (Summers et al., 1993, Macauley et al., 1994, Macauley et al.,

1995) . These data indicate that, while severe oxygen stress is minimal in

extent (<10% of the area), moderate stress may be widespread (i.e.,

approaching 50% of the area) in estuaries of the region.

Given the current low nutrient inputs, hypoxia does not seem to be a severe

problem in the region. However, because the same conditions (periodic

stratification, warm temperatures and calm weather) exist in the riverdominated estuaries of the northeastern Gulf of Mexico (Apalachicola Bay,

Choctawhatchee Bay, Pensacola Bay) as in estuaries in the central and

western Gulf of Mexico, hypoxia/anoxia could become a problem in the future

if nutrient or organic loading to these systems increases.

4.3.2 Red Tides

Red tides are common in the Gulf of Mexico and are caused by blooms of two

dinof1ae1late species, Gonyaulax monilate and Gymz2odinium breve (Darnell,

1992) . G. breve was widespread in nearshore, shelf and gyre waters during

the summer, but only occurred in warmer gyre waters during the winter

(Tester et al., 1993). G. breve blooms develop 18-74 km offshore, and most

remain offshore, although dense blooms (5 x107 cellsl') can occur inshore

when offshore water is transported inshore (Geesey and Tester, 1993)

Nitrogen and phosphorus limitation of these red tide species has not been

observed (Geesey and Tester, 1993), although iron may be important (Wells

et al., 1991) . Red tides such as G. breve can cause neurotoxic shellfish

poisoning and can irritate human respiratory systems (Tester et al., 1993).

4.3.3 Contaminant Cyclinq

Direct relationships between human activities and contaminant inputs have

been observed in many estuarine and coastal systems, where contaminant

concentrations usually seem to increase following population growth. What

happens to these contaminants varies, particularly within different

ecosystems. For example, one would expect that contaminant cycling would

be very different between alluvial and blackwater systems, or between

phytoplankton-domiflated and seagrass-dominated systems. In part, this is

due to the link between contaminant and organic matter cycling.

For metals, concentrations and reactivity are dependent on dissolved

organic carbon because of organic-metal complexation, particulate

concentrations, pH, and redox conditions. Many trace metals are particle

reactive, transported down rivers in particulate fractions, and deposited

in estuarine and nearshore sediments. In sediments, redox and the

formation of metal-sulf ides depends on organic loading, with lower redox

conditions occurring in organic-rich marine sediments, where sulfate

reduction dominates. Because of diagenesis reactions in sediment, metals

can be released back into the water column. The availability of ligands

such as organic carbon compounds and sulf ides, and environmental conditions

such as pH and redox, control metal speciation in the environment. Metal

speciation is the dominant factor controlling bioavailability of metals to

organisms (Cross and Sunda, 1985)

4-25
Organic contaminants can also be particle reactive. Degradation of these

compounds by bacteria is dependent on nutrient concentrations and redox.

Degradation is usually higher when nutrient concentrations are high, while

degradation of many toxic organics seems to be less efficient under

anaerobic conditions (Kexmish, 1992). Because of the lipophilic nature of

many organic contaminants, concentrations of these contaminants are highest

in the biota. Specific responses of some organisms to specific

contaminants have been described above. A general effect or response to

low levels or to complex mixtures of contaminants is difficult if not

impossible to separate from natural factors (M011er, 1985; Overstreet,

1988) . Pathological conditions such as parasites, parasitic diseases,

microbial infections, neoplasia and mortality have been linked to

pollution, although specific responses are affected by temperature,

salinity, pH, dissolved oxygen concentrations, resistance, genetic

predisposition and behavior (Overstreet, 1988) . A survey of disease among

oysters and fish from Mobile, Pascagoula and Pensacola Bays showed more

pathological conditions closer to river effluents and industry, although

none of the estuaries was severely unhealthy (Couch, 1985)

The effect of contaminants on communities and ecosystems is important, but

has not been addressed by most of the previously cited studies. Most of

these have focused on using bioassays such as the LD50 type toxicity test

to examine immediate and lethal effects of contaminants. Un-fortunately

many LD studies have critical flaws and these approaches can not be used

to determine the ecological effects of contaminants (Howarth, 1989) . Some

of the common problems with using these tests to determine the effects of

oil pollution are described by Howarth (1989). They are: (1) using

adults, although eggs and larvae are often more sensitive; (2) adding

particular oil concentrations, but not actually measuring the oil

concentration during the experiment, so that the concentration that the

organism is exposed to is unknown; (3) using species because they are easy

to culture in the laboratory, not because of their importance in a

particular ecosystem; (4) laboratory experiments usually do not have the

same UV radiation as in the environment and photo-oxidation by UV can

produce more toxic compounds (Howarth, 1989) . Contaminants can have

sublethal effects such as interfering with reproductive success, slowing

growth rates and altering behavior (Howarth, 1989). Lethal and sublethal

effects can have a impact on population abundances, community composition

and ecosystem processes, although it is difficult to attribute changes

directly to pollution because environmental factors can also have a

significant effect on populations, communities and ecosystems (Howarth,

1989; Kelly, 1989; Klerks and Levinton, 1989) . Decreases in species

composition have been observed in many polluted environments and are

usually attributed to a replacement of sensitive species with more

pollution tolerant species (Howarth, 1989; Klerks and Levinton, 1989) . The

pollution tolerance of some species may be a result of enhanced genetic

capability to become resistant to toxic substances. Klerks and Levinton

(1989) suggest that this capacity can limit the usefulness of standard

bioassay experiments because development of resistance can not be

incorporated into these kinds of experiments.

The goal of most research on toxic contaminants is to understand the effect

of contaminants on the environment, particularly the biota. One approach

is to use concepts from nutrient cycling and try to draw parallels between

4-26
nutrient cycling and contaminant cycling. A review by Farrington (1989)

applies some of these concepts by describing the different aspects of

organic contaminant cycling in the environment:

routes of entry of compounds to the environment and routes of

movement through ecosystems;

reactions of these compounds to the environment, either chemical,

photochemical or biological transformations/degradation;

rates of movement and reactions;

reservoirs of short-term (days-months) and long-term (years to

decades) accumulations."

Certainly most of the 4 R's are applicable to metal cycling as well.

Trying to develop tests of how contaminants affect ecosystems is quite

difficult, but not impossible (Howarth, 1989; Kelly, 1989) . Often

microcosms and mesocosms are useful tools for studying effects of

contaminants on ecosystems under more controlled conditions (Gearing, 1989;

Howarth, 1989; Kelly, 1989). For example, the effect of drilling muds on

Thalassia beds was tested with microcosms (Morton et al., 1986; Kelly et

al., 1987 [as cited in Kelly, 1989]) . The results of these experiments

showed that drilling muds reduced primary production by Thalassia and

decomposition of organic matter. In addition, chlorophyll-a concentrations

in Thalassia and epiphytic algae were reduced, as were numbers of the

dominant macrofauna (Kelly, 1989). These effects were observed in

treatments with drilling muds and with clay particles (at same SPM

concentration as drilling muds), suggesting that indirect effects, such as

physical disturbance and reduced light levels can be as important as toxic

effects (Kelly, 1989) . The power of these kind of approaches is that they

incorporate more of the complexity found in the environment, such as

interactions between trophic levels arid different processes, and indirect

effects can also be examined.

4.4 Conclusions

The estuarine and coastal zone of the northeastern Gulf of Mexico has a

rich biotic community, but a low population density. This results in

relatively low inputs of nutrients, heavy metals, and organics to the

coast, although some significant point sources of trace metals, PAHS, and

PCB5 have been found in sediments and biota in Pensacola Bay,

Choctawhatchee Bay and St. Andrew Bay. Spills of PCB5 and oil can account

for some of the high concentrations that have been found in sediments and

biota. However, the sources of elevated trace metal concentrations, such

as silver, cadmium, lead, mercury and zinc in Choctawhatchee Bay, are

unknown.

The EPA has recently produced a summary of the extent and severity of

sediment contamination in U.S. surface waters including estuaries (EPA,

1996) as part of its National Sediment Inventory (NSI). Using sediment

chemical concentration, tissue residue data, and information on sediment

toxicity the NSI established three tiers that classify watersheds as having

4-27
a high probability of adverse effects to aquatic or human health (Tier 1),

an intermediate probability of adverses effects (Tier 2), and no indication

of adverse effects (Tier 3) . Ninety-six water bodies in the continental

U.S. were identified to fall in Tiers 1 or 2. only one of these,

Choctawatchee Bay, is found in the northeastern Gulf region as a result of

metals, in particular mercury, and PAH contamination.

Although groundwater inputs have not been directly measured in the

northeastern Gulf of Mexico, some evidence suggests that it may be a source

of freshwater to estuaries and the coastal zone in this region. Thus,

contaminantion of groundwater with nutrients, metals or organic

contaminants could easily be transferred to the coastal zone. Rivers are

the other major source of freshwater and nutrients to estuaries and the

coastal zone. The Apalachicola River and forested floodplain appears to

transform inorganic inputs from upstream to organic outputs which are

exported to Apalachicola Bay and support high primary and secondary

production there. For the relatively pristine estuaries such as

Ocklockonee Bay, nutrient inputs are moderate, while recycling and losses

within the estuary seem to be in balance with no evidence of eutrophication

which is common in many other estuaries.

4.5 I,piterature Cited

Arthur, J.D., J. Applegate, S. Melkote and T.M. Scott. 1986. Heavy

mineral reconnaissance off the coast of the Apalachicola River delta,

Northwest Florida. Report of Investigation No. 95. Florida Bureau

of Geology. 61 pp.

Barbour, M.G., D.M. Rejmanek, A.F. Johnson and B.M. Pavlik. 1987. Beach

vegetation and plant distribution patterns along the northern Gulf of

Mexico. Phytocoenologia 15:201-233.

Brannon, J.M., J.R. Rose, R.

distribution of heavy

Alabama, pp. 125-150.

sediments. Ann Arbor

M. Engler and I. Smith. 1977. The

metals in sediment fractions from Mobile Bay,

In T.F. Yen, ed. Chemistry of marine

Science, Inc. Ann Arbor, Mich.

Bruland, K.W. 1983. Trace elements in seawater, chapter 45, pp. 157-220.

Ifl Chemical oceanography volume 8. Academic Press.

Burnett, W.C., J.B. Cowart and S. Deetea. 1990. Radium in the Suwannee

River and estuary, Spring and river input to the Gulf of Mexico.

Biogeochemistry 10:237-255.

Caffrey, J.M. and W.M. Kemp. 1991. Seasonal and spatial patterns of

oxygen production, respiration and root-rhizome release in

Potamogeton perfoliatus L. and Zostera marina L. Aquatic Botany

40:109-128.

Caffrey, J.M. and W.M. Kemp. 1990. Nitrogen cycling in sediments with

submerged macrophytes: microbial transformations and inorganic pools

associated with estuarine populations of Potarnogeton perfoliatus L.

and Zostera marina. Marine Ecology - Progress Series 66:147-160.

4-28
Capone, D.G. and M.F. Batista. 1985. A groundwater source of nitrate in

nearshore sediments. Nature 313 :214-216.

Carlough, L.A. 1994. Origins, structure, and trophic significance of

amorphous seston in a blackwater river. Freshwater Biology 31(2):

227-237.

Chanton, J.P. and J.W.H. Dacey. 1991. Effects of vegetation on methane

flux, reservoirs, and carbon isotopic composition, pp. 65-92. T.D.

Sharkey, E.A. Holland and H.A. Mooney, eds. Trace gas emissions by

plants. Academic Press.

Chanton, J.P., G.J. Whiting, J.D. Happell and G. Gerard. 1993.

Contrasting rates and diurnal patterns of methane emission from

emergent aquatic macrophytes. Aquatic Botany 46:111-128.

Chlou, C.T., D.E. Kile, T.I. Brinton, R.L. Malcolm, J.A. Leenheer and P.

MacCarthy. 1987. A comparison of water solubility enhancements of

organic solutes by aquatic humic materials and commercial humic

acids. Environ. Sci. Tech. 21:1231-1234.

Cicerone, R.J. and R. Oremland. 1988. Biogeochemical aspects of

atmospheric methane. Global Biogeochem. Cycles 2:299-327.

Couch, C.A. 1985. Prospective study of infectious and noninfectious

diseases in oysters and fishes in three Gulf of Mexico estuaries.

Dis. Aquat. Org. 1:59-82.

Couch, C.A. and J.L. Meyer. 1992. Development and composition of epixylic

biofilm in a blackwater river. Freshwater Biol. 27:43-51.

Cowart, J.B. and W.C. Burnett. 1994. The distribution of uranium and

thorium decay-series radionuclides in the environment - a review.

J. Environ. Qual. 23:651-662.

Crane, J.J. 1986. An investigation of the geology, hydrogeology and

hydrochemistry of the lower Suwannee River basin. Report of

Investigation No. 96. Florida Bureau of Geology. 205 pp.

Cross, F.A. and W.G. Sunda. 1985. The relationship between chemical

speciation and bioavailability of trace metals to marine organisms -

a review, pp. 169-182. N.L. Chao and W. Kirby-Smith eds.

Proceedings of the international symposium on utilization of coastal

ecosystems: planning, pollution and productivity (1982: Rio Grande,

Brazil). Ed. da Fundacao Universidade do Rio Grande; Duke University

Marine Laboratory.

Culliton, T.J., M.A. Warren, T.R. Goodspeed, D.G. Remer, C.M. Blackwell,

and J.J. McDonough. 1990. 50 Years of Population Change Along the

Nation' 5 Coasts 1960-2010. Second Report of a Coastal Trends Series,

NOAA NOS OMA, Rockville, MD.

4-29
Dagg, M.J. 1988. Physical and biological responses to the passage of a

winter storm in the coastal and inner shelf waters of the northern

Gulf of Mexico. Cont. Shelf Res. 8:167-178.

Darnell, R.M. 1992. Ecological history, catastrophism, and human impact

on the Mississippi/Alabama continental shelf and associated waters: a

review. Gulf Research Reports 8:375-386.

Deegan, L.A., J.W. Day, Jr., H.G. Gosselink, A. Yanez-Arancibia, G.S.

Chavez and P. Sanchez-Gil. 1986. Relationships among physical

characteristics, vegetation distribution and fisheries yield in Gulf

of Mexico estuaries, pp. 83-100. n D.A. Wolfe ed. Estuarine

variability. Academic Press.

DiToro, D.M., J.D. Mahoney, D.J. Hansen, K.J. Scott, M.B. Hicks, S.M.

Mays, and M.S. Redmond. 1990. Toxicity of cadmium in sediments: the

role of acid volatile sulfide. Environmental Toxicology and

Chemistry 9:1487-1502.

Donoghue, J.F. 1992. Late Quaternary coastal and inner shelf

stratigraphy, Apalachicola Delta region, Florida. Sedimentary

Geology 80:293-304.

Donoghue, J.F. and M.B. Greenfield. 1991. Radioactivity of heavy mineral

sands as an indicator of coastal sand transport processes. J. Coast.

Res. 7:189-201.

Donoghue, J.F. and N.M. White. 1995. Late holocene sea-level change and

delta migration, Apalachicola River region, Northwest Florida, U.S.A.

J. Coast Res. 11:651-663.

Doyle, L.J., and T.N. Sparks. 1980. Sediments of the Mississippi, Alabama

and Florida (MAFLLA continental shelf. J. Sedimentary Petrology 50:

905-916.

Elder, J.F. 1985. Nitrogen and phosphorus speciation and flux in a large

Florida river wetland system. Water Resources Research 21:724-732.

Elder, J.F. and D.J. Cairns 1982. Production and decomposition of forest

litter fall on the Apalachicola River flood plain, Florida. Water

Supply Paper 2196-B. U.S. Geological Survey. 42pp.

Elder, J.F. and P.V. Dresler. 1988. Accumulation and bioconcentration of

polycyclic aromatic hydrocarbons in a nearshore estuarine environment

near a Pensacola (Florida) creosote contamination site. Environmental

Pollution 49:117-132.

Elder, J.F. and H.C. Mattraw, Jr. 1982. Riverine transport of nutrients

and detritus to the Apalachicola Bay Estuary, Florida. Water

Resources Bulletin 18:849-856.
Elder, J.F. and H.C. Mattraw, Jr. 1984. Accumulation of trace-elements,

pesticides, and polychiorinated-biphenyls in sediments and the clam

Corbicula manilensis of the Apalachicola River, Florida. Archives of

Environmental Contamination and Toxicology 13 :453 -469.

Elder, J.F., S.D. Flagg and H.C. Mattraw, Jr. 1988. Hydrology and ecology

of the Apalachicola River, Florida: a summary of the river quality

assessment. U.S. Geological Survey, Water Resources Division,

Reston, Va. 54 pp.

El-Sayed et al. 1972. Chemistry, primary productivity and benthic algae

of the Gulf of Mexico. Amer. Geogr. Soc. of New York. Serial atlas

of the marine environment, folio 22. Amer. Geogr. Soc.

Environmental Protection Agency. 1996. The National Sediment Quality

Survey: A report to Congress on the extent and severity of sediment

contamination in the surface waters of the United States. EPA-823-D96-002, Washington, DC.

Epp, M.A. and J.P. Chanton. 1993. Rhizospheric methane oxidation

determined via the methyl fluoride inhibition technique. J. Geophys.

Research 98:18413-18422.

Fanning, K.A., A. Breland and R.H. Byrne. 1982. Radium 226 and radon 222

in the coastal waters of west Florida: high concentrations and

atmospheric degassing. Science 215:667-670.

Farrington, J.W. 1989. Bioaccumulation of hydrophobic organic pollutant

compounds, pp. 279-313. S.A. Levin, M.A. Harwell, J.R. Kelly and

K.D. Kimball, eds. Ecotoxicology: problems and approaches.

Springer-Verlag.

Federle, T.W., R.J. Livingston, L.E. Wolfe and. D.C. White. 1986. A

quantitative comparison of microbial community structure of estuarine

sediments from microcosms and the field. Can. Jour. Microbiol. 32:

319-325.

Fenchel, T. and T.H. Blackburn. 1979. Bateria and mineral cycling.

Academic Press. 225 pp.

Gambrell, R.P., L.A. Khalid and W.H. Patrick, Jr. 1980. Chemical

availability of mercury, lead, and zinc in Mobile Bay sediment

suspensions as affected by pH and oxidation-reduction conditions.

Environ. Sci. & Technol. 14:431-436.

Gearing, J.N. 1989. S.A. Levin, M.A. Harwell, J.R. Kelly and K.D.

Kimball, eds. Ecotoxicology: problems and approaches. SpringerVerlag.

Gearing, P., J.N. Gearing, T.F. Lytle and. J.S. Lytle. 1976. Hydrocarbons

in 60 northeast Gulf of Mexico shelf sediments: a preliminary survey.

Geochim. Cosmochim. Acta. 40:1005-1017.

4-31
Geesey, M. and P.A. Tester. 1993. Gymnodiniurn breve: ubiquitious in Gulf

of Mexico waters, pp. 251-255. .Iz T.J. Smayda and Y. Shimizu, eds.,

Toxic Phytoplankton Blooms in the Sea. Elsevier.

Grady, J.R. 1981. Properties of sea grass and sand flat sediments from

the intertidal zone of St. Andrew Bay, Florida. Estuaries 4:335-344.

Hagar, R. 1985. Mobile Bay shaping up as a major gas producing area. Oil

Gas J. 85:25-30.

Hanson, P.J., D.W. Evans and D. R. Colby. 1993. Assessment of elemental

contamination in estuarine and coastal environments based on

geochemical and statistical modeling of sediments. Mar. Environ.

Res. 36:237-266.

Howarth, R.W. 1989. Determining the ecological effects of oil pollution

in marine ecosystems, pp. 69-97. S.A. Levin, M.A. Harwell, J.R.

Kelly and K.D. Kimball, eds. Ecotoxicology: problems and approaches.

springer-verlag.

Ichiye, T. 1972. Circulation changes caused by hurricanes, pp. 229-257.

In L.R.A. Capurro and J.L. Reid, eds. Contributions on the physical

oceanography of the Gulf of Mexico, volume 2. Texas A&M University

Oceanographic Studies. Gulf Publishing Co.

Iverson, R.L. and H.F. Bittaker. 1986. Seagrass distribution and

abundance in eastern Gulf of Mexico coastal waters. Est. Coast Shelf

Sci. 22:577-602.

Iverson, R.L., F.L. Nearhoof and M.O. Andreae. 1989. Production of

dimethylsulfonium propionate and dimethylsulfide by phytoplankton in

estuarine and coastal waters. Limnol. Oceanogr. 34:53-67.

Jackson, T.J., T.L. Wade, T.J. McDonald, D.L. Wilkinson and J.M. Brooks.

1994. Polynuclear aromatic hydrocarbon contaminants in oysters from

the Gulf of Mexico (1986-1990) . Environ. Poll. 83:291-298.

Kaul, L. and R.N. Froelich, Jr.. 1984. Modeling estuarine nutrient

geochemistry in a simple system. Geochim. Cosmochim. Acta 48:1417-

1433.

Kelly, J.R. 1989. Ecotoxicology beyond sensitivity: a case study

involving "unreasonableness" of environmental change, pp. 473-496.

5.A. Levin, M.A. Harwell, J.R. Kelly, and K.D. Kimball, eds.

Ecotoxicology: problems and approaches. Springer-Verlag.

Kelly, J.R., T.W. Duke, M.A. Harwell and C.C. Harwell. 1987. An ecosystem

perspective on potential impacts of drilling fluid discharges on

seagrasses. Environ. Manage. 11:537-562.

Kemp, W.M., P. Sampou, J. Caffrey, M. Mayer, K. Henriksen and W.R. Boynton.

1990. Ammonium recycling versus denitrification in Chesapeake Bay

sediments. Limnology and Oceanography 35:1545-1563.

4-32
Kennish, M.J. 1992. Ecology of estuaries: anthropogenic effects. CRC

Press. 494 PP.

Kiene, R.P. 1993. Microbial sources and sinks for methylated sulfur

compounds in the marine environment, PP. 15-33. D.P. Kelly and

J.C. Murrell, eds. Microbial growth on Cl compounds, 7. Intercept.

Kiene, R.P. and G. Gerard. 1994. Determination of trace levels of

dimethyl sulf oxide (DMSO) in seawater and rainwater. Marine

Chemistry 47:1-12.

Klerks, P.L. and J.S. Levinton. 1989. Effects of heavy metals in a

polluted aquatic ecosystem, pp. 41-67. S.A. Levin, M.A. Harwell,

J.R. Kelly, and K.D. Kimball, eds. Ecotoxicology: problems and

approaches. Springer-Verlag.

LaPointe, B.E. and M.W. Clark 1992. Nutrient inputs from the watershed

and coastal eutrophication in the Florida Keys. Estuaries 15:465-

476.

Leadon, C.K. and O.F. Wetterqvist. 1986. Land acquisition criteria for

the Suwanee River Estuary, Florida. Coast. Zone Manage. 14:217-239.

Leitman,, H.M., J.E. Sohm and M.A. Franklin. 1983. Wetland hydrology and

tree distribution of the Apalachicola River flood plain, Florida.

Water Supply Paper 2186-A. U.S. Geological Survey. 52 pp.

Lindberg, S.E. and R.C. Harriss. 1974. Mercury-organic matter

associations in estuarine sediments and interstitial water. Environ.

Sci. & Tech. 8:459-462.

Livingston, R.J. 1980. The Apalachicola Experiment: research and

management. Oceanus 23:14-21.

Livingston, R.J. 1983.

Florida Sea Grant

Report Number 55.

Gainesville, Fla.

Livingston, R.J. 1984.

estuarine profile

Resource atlas of the Apalachicola estuary.

College Program. Sea Grant Project No. T/P-l.

Dept. of Biol. Sci. Florida State University.

64 pp.

The ecology of the Apalachicola Bay system: an U.S. Fish Wild. Serv. FWS/OBS 82/05. 148 pp.

Livingston, R.J. 1985. N.L. Chao and W. Kirby-Smith, eds. Proceedings

of the international symposium on utilization of coastal ecosystems:

planning, pollution and productivity (1982: Rio Grande, Brazil). Ed.

da Fundacao Universidade do Rio Grande; Duke University Marine

Laboratory.

Livingston, R.J., N.P. Thompson and D.A. Meeter. 1978. Long-term

variation of organochlorine residues and assemblages of epibenthic

organisms in a shallow north Florida estuary. Mar. Biol. 46:355-372.

4-33
Long, E.R. and L.G. Morgan. 1990. The potential for biological effects of

sediment-sorbed contaminants tested in the National Status and Trends

program. NOAA Tech. Mem. NOS OMA 52, Seattle, WA.

Long, E.R., D.D. MacDonald, S.L. Smith, and F.D. Calder. 1995. Incidence

of adverse biological effects within ranges of chemical

concentrations in marine and estuarine sediments. Environmental

Management 19:81-97.

Lytle, T.F. and J.S. Lytle. 1976. Assessment of hydrocarbon pollutants in

Gulf and estuarine environments. J. Miss. Acad. Sci. 21:128-147.

Macauley, J.M., J.K. Summers, P.T. Heitmuller, V.D. Engle, G.T. Brooks, M.

Babikow, and A.M. Adams. 1994. Annual Statistical Summary: EMAPEstuaries Louisianian Province - 1992. U.S. EPA Office of Research

and Development, EPA/620/R-94/002, Gulf Breeze, FL.

Macauley, J.M., J.K. Summers, V.D. Engle, P.T. Heitmuller, and A.M. Adams.

1996. Annual Statistical Summary: EMAP-Estuaries Louisianian

Province - 1993. U.S. EPA Office of Research and Development,

EPA/620/R-96/003, Gulf Breeze, FL.

Mancini, E.A., R.M. Mink and B.L. Bearden. 1984. Petroleum geology of the

Norphiet formation (upper Jurassic), S.W. and offshore Alabama. Oil

Gas J. 82:147-150.

Mason, W.T., Jr., R.A. Mattson and J.H. Epler. 1994. Benthic

invertebrates and allied macrofauna in the Suwannee River and estuary

ecosystem, Florida. Florida Scientist. 57:141-160.

Marmer, H.A. 1954. Tides and sea level in the Gulf of Mexico, pp. 101-

118. P.S Gaitsoff, ed. Gulf of Mexico, its origin, waters and

marine life. Fishery Bull. U.S. Fish and Wildlife Service.

Washington, D.C. 604 pp.

Mattraw, H.C., Jr. and J.F. Elder 1984. Nutrient and detritus transport

in the Apalachicola River, Florida. U.S. Geological Survey Water

Supply Paper 2196-C, 62 pp.

May, E.B. 1973. Extensive oxygen depletion in Mobile Bay, Alabama.

Limnol. Oceanogr. 18:353-366.

McCabe, C. 1985. Operators move to develop Mobile Bay gas fields. Ocean

md. 20:28-33)

Middaugh, D.P., R.L. Mueller, R.L. Thomas, M.H. Lantz, M.H. Hemmer, G.T.

Brooks and P.J. Chapman. 1991. Detoxification of pentachlorophenol

and creosote contaminated groundwater by physical extraction:

chemical and biological assessment. Archives. Environ. Contamin. &

Toxicol. 21:233-244.

Mitsch, W.J. and J.G. Gosselink. 1986. Wetlands. Van Nostrand Reinhold

Co. New York, N.Y.

4-34
Moller, H. 1985. A critical review on the role of pollution as a cause of

fish diseases, pp. 169-182. A.E. Ellis, ed. Fish and shellfish

pathology. Academic Press.

Morton, R.D., T.W. Duke, J.M. Macauley, J.R. Clark, W.A. Price, S.J.

Hendricks, S.L. Owsley-Montgomery and G.R. Plaia. 1986. Impact of

drilling fluids on seagrasses: an experimental community approach,

pp. 199-212. J. Cairns, ed. Community Toxicity Testing. ASTM STP

920, Philadelphia: Amer. Soc. for Testing and Materials.

Moshiri, G.A., D. Brown, P. Conklin, D. Gilbert, M. Hughes, M. Moore, D.

Ray and L. Robinson. 1974. Determination of a nitrogen-phosphorus

budget for Bayou Texar, Pensacola, Florida. Florida Water Resources

Research Center, Research Project Technical Completion Report. OWRR

Project Numbers B-016-FLA and B-019-FLA. 82 pp.

Moshiri, G.A., N.G. Aumen and W.G. Crumpton. 1981. Reversal of the

eutrophication process: a case study, pp. 373-390. B.J. Neilson

and L.E. Croniri, eds. Estuaries and Nutrients. Humana Press.

Myers, V.B. and R.I. Iverson. 1981. Phosphorus and nitrogen limited

phytoplankton productivity in northeastern Gulf of Mexico coastal

estuaries, pp. 569-582. B.J. Neilson and L.E. Cronin, eds.

Estuaries and Nutrients. Humana Press.

Nimmo, D.R., R.R. Blackman, A.J. Wilson and J. Forester. 1971a. Toxicity

and distribution of Arochlor® 1254 in the pink shrimp Penaeus

duorarum. Mar. Biol. 11:191-197.

Nimmo, D.R., P.D. Wilson, R.R. Blackman and A.J. Wilson. 1971b.

Polychlorinated biphenyl adsorbed from sediments by fiddler crabs and

pink shrimp. Nature 231:50-52.

Nimmo, D.R., D.J.

Lowe. 1975.

activity in

Toxic. 3:22-

Hansen, J.A. Couch, N.R. Cololey, P.R. Parrish and J.I.

Toxicity of Arochlor® 1254 and its physiological

several estuarine organisms. Arch. Environ. Contam. and

39.

Nittrouer, C.A. and L.D. Wright. 1994. Transport of particles across

continental shelves. Rev. Geophys. 32:85-113.

NOAA. 1985. Gulf of Mexico coastal and ocean zones strategic assessment:

data atlas.

NOAA. 1991. Second Summary of Data on Chemical Contaminants in Sediments

from the National Status and Trends Program. NOAA Tech. Mem. NOS OMA

59, Rockville, MD.

Nowlin, W.D., Jr. 1972. Winter circulation patterns and property

distributions, pp. 3-51. n L.R.A. Capurro and J.L. Reid, eds.

Contributions on the physical oceanography of the Gulf of Mexico,

Volume 2. Texas A&N University Oceanographic Studies. Gulf

Publishing Co.

4-35
Nowlin, W.D., Jr. and J.M. Hubertz. 1972. Contrasting summer circulation

patterns for the eastern Gulf-Loop Current versus anticyclonic ring,

pp. 119-137. L.R.A. Capurro and J.L. Reid, eds. Contributions on

the physical oceanography of the Gulf of Mexico, Volume 2. Texas A&M

University Oceanographic Studies. Gulf Publishing Co.

O'Connor, T.P. and C.N. Ehler. 1991. Results from the NOAA National

Status and Trends program on distribution and effects of chemical

contamination in the coastal and estuarine United States.

Environmental Monitoring and Assessment 17:33-49.

O'Neill, J.M. and D.G. Capone. 1989. Nitrogenase activity in tropical

marine sediments. Mar. Ecol. Prog. Ser. 56:145-156.

Overstreet, R.M. 1988. Aquatic pollution problems, southern U.S. coasts:

histopathological indicators. Aquat. Tox. 11:213-239.

Palacas, J.G., A.H. Love and P.M. Gerrild. 1972. Hydrocarbons in

estuarine sediments of Choctawhatchee Bay, Florida, and their

implications for genesis of petroleum. APPG Bull. 56:1402-1418.

Pomeroy, L.R., J.E. Sheldon, W.M. Sheldon, Jr. and F. Peters. 1995.

Limits to growth and respiration of bacterioplankton in the Gulf of

Mexico. Mar. Ecol. Progress Ser. 117:259-268.

Presley, B.J., R.J. Taylor and P.N. Boothe. 1990. Trace metals in Gulf of

Mexico oysters. The Science of the Total Environment 97/98:551-593.

Pulliam, W.M. 1993. Carbon-dioxide and methane exports from a

southeastern floodplain swamp. Ecol. Monogr. 63:29-53.

Pulliam, W.M., and J.L. Meyer. 1992. Methane emissions from floodplain

swamps of the Ogeechee River - long-term patterns and effects of

climate change. Biogeochem. 15:151-174.

Rostad, C.E. and W.E. Pereira. 1987. Creosote compounds in snails

obtained from Pensacola Bay, Florida, near an onshore hazardous-waste

site. Chemosphere 16:2397-2404.

Science Applications International Corporation. 1988. Gulf of Mexico

physical oceanography program, final report: year 3, volume II:

technical report. OCS study/MMS 88-0046. U.S. Dept. of the

Interior. Minerals Management Service. Gulf of Mexico OCS Region.

241 pp.

Schlautman, M.A. and J.J. Morgan. 1993. Binding of a fluorescent

hydrophobic organic probe by dissolved humic substances and

organically-coated aluminum-oxide surfaces. Environ. Sci. Tech. 27:

2523-2532.

Seitzinger, S.P. 1988. Denitrification in freshwater and coastal marine

ecosystems: ecological and geochemical significance. Limnology and

Oceanography 33 :702-724.

4-36
Seitzinger, S.P. 1987. Nitrogen biogeochemistry in an unpolluted estuary:

the importance of benthic denitrification. Marine Ecology Progress

Series 41:177-186.

Serkiz, S.M. and E.M. Perdue. 1994. Isolation of dissolved organic matter

from the Suwanee River using reverse osmosis. Water Res. 24:911-916.

Sever, J.R., T.F. Lytle and P. Haug. 1972. Lipid geochemistry of a

Mississippi coastal bog environment. Contrib. Mar. Sci. 16:149-161.

Sikora, W.B. and J.P. Sikora. 1982. Ecological charterization of the

Beuthic Community of Lake Poutchartrain. Louisiana Stat University

Center for Wetland Resources. Publ. LSU-CEL-82-05. 214 pp.

Serensen, J. 1987. Nitrate reduction in marine sediment: pathways and

interactions with iron and sulfur cycling. Geomicrobiololgy J.

5:401-421.

J.K. Summers, Macauley, J.M., P.T. Heitmuller, V.D. Engle, A.M. Adams, and

G.T. Brooks. 1993. Annual Statistical Summary: EMAP-Estuaries

Louisianian Province - 1991. U.S. EPA Office of Research and

Development, EPA/600/R-93/00l, Gulf Breeze, FL.

Tester, P.A., M.E. Geesey and F.M. Vukovich. 1993. Gymnodiniuxn breve and

Global warming: what are the possibilities, pp. 67-72. T.J.

Smayda and Y. Shimizu, eds. Toxic Phytoplankton Blooms in the Sea.

Elsevier.

Thorn, K.A. and M.A. Mikita. 1992. Ammonia fixation by humic substances:

a nitrogen-15 and carbon-13 NNR study. The Science of the Total

Environment 113:67-87.

Turner, R.E., W.W. Schroeder and W.J. Wiseman, Jr. 1987. The role of

stratification in the deoxygenation of Mobile Bay and adjacent shelf

bottom waters. Estuaries 10:13-19.

Valentine, R.L. and R.G. Zepp. 1993. Formation of carbon monoxide from

the photo degradation of terrestrial dissolved organic carbon in

natural waters. Environ. Sci. Tech. 27:409-412.

Valiela, I., K. Foreman, M. Lallontagne, D. Hersh, J. Costa, P.Peckol, B.

DeMeo-Andreson, C. D'Avanzo, M. Babione, C.H. Sham, J. Brawley and

K. Lajtha. 1992. Couplings of watersheds and coastal waters:

sources and consequences of nutrient enrichment in Waquoit Bay,

Massachusetts. Estuaries 15:443-457.

Vitousek, P.M. and P.A. Matson. 1993. Agriculture, the global nitrogen

cycle and trace gas flux, pp. 193-208. R.S. Oremland, ed.

Biogeochemistry of global change: radiatively active trace gases.

Chapman and Hall.

Wade, T.L. and J.L. Sericano. 1989. Trends in organic contaminant

distributions in oysters from the Gulf of Mexico. Oceans 89: The

Global Ocean 2:585-589.

4-37
Wade, T.L., E.L. Atlas, J.M. Brooks, M.C. Kennicutt II, R.G. Fox, J.

Sericano, B. Garcia-Romero and D. DeFreitas. 1988. NOAA Gulf of

Mexico status and trends program: trace organic contaminant

distribution in sediments and oysters. Estuaries 11:171-179.

Watts, G.B. and B.R. Locke. 1993. Nonpurgeable total organic halide

analysis and the characterization of river water quality adjacent to

the discharge from a kraft mill. Environ. Sci. Technol. 27:2311-2317.

Weis, P., J.S. Weis and E. Lores. 1993. Uptake of metals from chromated

copper arsenate (CAA)-treated lumber by epibiota. Mar. Pollution

Bull. 26:428-430.

Wells, M.L., L.M. Mayer and R.R.L. Guillard. 1991. Evaluation of iron as

a triggering factor for red tide blooms. Mar. Ecol. Prog. Ser. 69:

93-102.

Wharton, C.H., W.M. Kitchens, E.C. Pendleton and T.W. Sipe. 1982. The

ecology of bottomland hardwood swamps of the Southeast: a community

profile. FWS/OBS 81/37. U.S. Fish and Wildlife Service, Biological

Services Program, Washington D.C. 133 pp.

Whiting, G.J. and J.P. Chanton. 1992. Plant-dependent CH4 emission in a

subarctic Canadian f en. Global Biogeochem. Cycles 6:225-231.

Wilson, A.J. and J. Forester. 1978. Persistence of Arachlor 1254 in a

contaminated estuary. Bull. Environ. Contam. & Toxicol. 19:637-640.

Wilson, E.A., E.N. Powell, T.L. Wade, R.J. Taylor, B.J. Presley and J.M.

Brooks. 1992. Spatial and temporal distributions of contaminant

body burden and disease in Gulf of Mexico oyster populations: the

role of local and large-scale climatic controls. Helgol.

Meeresunters. 46:201-235.

Winchester, J.W. and J. Fu. 1992. Atmospheric deposition of nitrate and

its transport to the Apalachicola Bay estuary in Florida. Water, Air

& Soil Pollution 65:23-42.

Windom, H.L., S.J. Schropp, F.D. Calder, J.D. Ryan, R.G. Smith, Jr., L.C.

Burney, F.G. Lewis and C.H. Rawlinson. 1989. Natural trace metal

concentrations in estuarine and coastal marine sediments of the

Southeastern United States. Environ. Sci. Technol 23:314-320.

Winger, P.V., T.W. Siekman, T.W. May and W.W. Johnson. 1985. Residues of

organochlorine insecticides, polychlorinated biphenyls, and heavy

metals in biota from Apalachicola River, Florida, 1978. J. Assoc.

Off. Anal. Chem. 67:325-333.

Zimmerman, M.S. and R.J. Livingston. 1976. The effects of Kraft-Mill

effluents on benthic macrophyte assemblages in a shallow-bay system

(Apalachicola Bay, North Florida) . Mar. Biol. 34:297-312.

4-38
Chapter 5 - THE BIOLOGICAL ENVIRONMENT

by Dr. Sneed Collard

University of West Florida

and

Dr. Carl Way

Barry Vittor and Associates

5.1 Introduction

This chapter presents available information on the biology of a study area

encompassing the northeastern Gulf of Mexico continental shelf and Florida

panhandle estuarine waters. Detailed discussions of the physical

environment of the region may be found in Chapter 2 (Physical Oceanography

and Meteorology), Chapter 3 (Geology), and Chapter 4 (Chemistry).

The study area is relatively large geographically, but lacks identifiable

ecological boundaries. Consequently, ecosystems within the region can not

be considered to be members of a coherent ecological unit. The study area

is transitional with respect to its climate (Fernald and Purdum, 1992) and

the biogeographical affinities of its flora and fauna (Hedgpeth, 1953;

Briggs, 1973.: Britton and Morton, 1989) Nearshore estuarine and marine

communities throughout the region include species with temperate

("Carolinian") and subtropical-tropical ("West Indian") affinities, but the

former decrease, and the latter increase from west to east, from north to

south, and with depth and distance from shore (Collard and D'Asaro, 1973;

Lyons and Collard, 1974).

With some exceptions, descriptions of marine ecosystems in the ecologically

heterogenous northeastern Gulf of Mexico emphasize water quality conditions

and anthropically-related losses of large, abundant or commercially

valuable organisms from estuaries. Knowledge of shelf communities is

scanty, as is information on physicochemical and biological processes.

Because biological models use highly condensed information to identify

pathways of energy flow within ecological systems, it is essential to

recognize biases and gaps in the regional database. In addition to the

deficiencies noted, problems specific to individual geographic areas and/or

to ecosystems and communities within them are discussed in appropriate

subsections of the chapter. To the extent that the gappy database permits,

we attempt to characterize major biological features of the region by

describing those communities within ecosystems that share similar

ecological functions.

5.1.1 Area Description

The Gulf of Mexico is a marginal sea of the Western North Atlantic Ocean.

Darnell et al. (1990) reported the Gulf to have a maximum east-to-west

width of about 1,600 km, a maximum north-to-south length of about 900 km,

and a surface area of more than 500,000 km2. The Gulf has a maximum depth

of 3,850 m in the Sigsbee Deep. Continental shelves of the Gulf of Mexico

equal about 35% of its surface area, or about 200,000 km2 (Darnell et al.,

5-i
1990). The continental shelf off the Florida panhandle/Big Bend is widest

in the eastern part of the region. It narrows south of Choctawhatchee Bay,

where it deepens rapidly, via rugged terraces and rocky outcrops, into

DeSoto Canyon, the major physiographic feature of the eastern Gulf basin.

The canyon trends southwest as it widens and deepens (Figures 1-1 and 5-1).

Tropical water from the Caribbean Sea/Atlantic Ocean enters the Gulf of

Mexico through the Yucatan Channel. This water forms the Gulf of Mexico

Loop Current which affects circulation in the entire basin. The behavior

of the Loop Current is complex (see Chapter 2), and has a profound affect

on the distribution of salinity, energy and biota in the Gulf of Mexico, as

noted by, among others, Collard and Ogren (1990, Figure 5-2) . The Loop

Current may flow almost directly from the Yucatan Channel to the Straits of

Florida. More commonly, however, the current flows north into the eastern

Gulf basin, where it meanders, becomes unstable, and sheds one or more

anticyclonic rings or eddies. Water derived from the Loop Current or its

westerly translating eddies may cross the shelf boundary, advecting

tropical organisms (ichthyoplankton, meroplanktonic invertebrates, etc.)

into the neritic waters of the shelf.

According to Darnell et al. (1990), coastal waters annually receive some

i0'2m3 of fresh water from rivers. While the Mississippi River is the

largest source of fresh water, northeastern Gulf coast river- discharges are

significant. As a result of these river discharges and freshwater springs

located on the shelf, coastal waters of the Big Bend are brackish.

The Florida Department of Environmental Protection (FDEP, 1994) described

the coastline from Perdido Key east to Apalachee Bay as being characterized

by high energy barrier islands with sand beaches. From west to east these

islands (the "Gulf Barrier Chain" of Brooks, 1973) are: Perdido Key; Santa

Rosa Island; Shell Island; St. Vincent Island; Little St. George Island;

St. George Island; and Dog Island. Further along the coast Piney Island,

Jug Island, and the Cedar Keys exhibit some of the protective functions of

barrier islands; however, Fernald and Purdum (1992) consider Dog Island in

Apalachicola Bay to be the easternmost barrier island in the panhandle

(Figure 5-3). The coastal area from Apalachee Bay to Cedar Key is a low

energy, marsh-dominated shoreline. Fernald and Purdum (1992) describe this

area as almost featureless, with the lowest relief in the panhandle.

Tornbolos, spits, headlands, and offshore shoals provide the mainland

shoreline with varying degrees of protection from the full force of storm

winds and waves. From west to southeast, these coastal barriers include

Crooked "Island'T (two spits separated by "Hurricane Pass'T which opens St.

Andrew Sound to the Gulf of Mexico); St. Joseph Spit; a complex of bars and

shoals from Cape San Blas to Cape St. George; and Alligator Harbor Spit.

Major sand dunes on barrier islands and mainland beaches from Perdido Key

to Cape San Bias were severely eroded, and in some areas (e.g., Navarre,

Pensacola Beach, Fort Walton Beach to Destin, and Mexico Beach) were

virtually destroyed by Hurricanes Allison, Erin and Opal in 1995. The

severe damage and/or destruction of these large dunes left large areas of

northwest Florida's nearshore marine habitats (i.e., salt marshes)

vulnerable to further damage by storms. Santa Rosa Island is the longest

barrier island in the eastern Gulf of Mexico, extending some 50 miles from

5-2
89 88 87. 86 05 84 83 Sr ei Coastal Plain AU.. MISS. LPUHD - ._=id;-; s jIAIS,1 U1e C.,. 3.. 81.. 0 

Figure 5-1. Map of the eastern Gulf of Mexico (from Pyle et al., 1975).
7 1

souptlna o09

k Zone \ \.Region of Florida Offshore Advection : I P\ I jCurrent -

( I

iv Mexican Current t

'

Figure 5-2. Generalized circulation in the Gulf of Mexico (from Collard and

Ogren, 1990)

5-4
Penf ---- PK .1 / / I I c ( / -It. / J / '- T Florida Panhandle Bay Systems I = Pensacola Bay 2 Choctawhatchee Bay 3 = St. Andrew Bay 4 = St. Joseph Bay 5 = Apalachicola Bay 6 = Ochlockonee Bay 7 = Apalachee Bay SI CI -cJolco B..ch Pods sis\p.l.c cola CSB 5 SGI LSGI p

6AH

Figure 5-3. Western Florida Panhandle showing bay systems and barrier islands (from NOAA 1986). 

key; SRI=Santa Rosa island; NB=Navarre Beach; SI=Sheli Island; CI=Crooked Isla

Spit; CSB=Cape San Bias; SVI=St. Vincent Island; LSGI=Little St. George IslanIsaind; DI=Dog Island;and AHS=Aliigator Harbor Spit.
5-6

Pensacola Pass to East Pass Channel. According to Brooks (1973), Santa

Rosa Island receives longshore sediment drift from the Miramar-Grayton

Beach area to the east, and from the inner shelf between Pensacola,

Florida, and Morgan Point, Alabama. There are no barrier islands between

East Pass Channel and Shell Island off Panama City. The Apalachicola

barrier island chain (Dog, St. George, Little St. George, and St. Vincent

Islands), Cape San Bias and its associated bars and shoals, and St. Joseph

Spit were formed largely by the longshore drift of sediments deposited in

the Gulf by the Apalachicola River. West of St. Joseph Spit, "the 25 m

depth contour approaches shore and a considerable amount of sediment is

funneled into deep water" (Stout, 1984). The bathymetry of this area has

not been charted since Hurricane Opal in 1995; however, extensive shoaling

has been observed from the eastern end of Crooked TIIsland! to west of Cape

San Bias-St. Joseph Spit, and from an imaginary line connecting Cape San

Blas and the mainland (Port St. Joe-Mexico Beach-eastern Tyndall Air Force

Base).

Sea level on the northwest Florida coast has risen from 0.02-0.2 cm per

year during the past century (e.g., Gaitsoff, 1954; Fernald and Purdum,

1992), but there is general agreement that the shoreline has remained

relatively stable during this same period. Because of very low relief in

eastern portions of the panhandle, continued sea level rise will eventually

result in changes in the extent and/or distribution of estuaries and salt

marshes.

5.1.2 Data Gaps

Ogden's (1992) description of the West Florida Shelf applies to the mosaic

of physiographic and biological features present in the northeastern Gulf

of Mexico. Both areas consist of "a network of spatially and temporally

interconnected ecosystems. . ." Region-wide knowledge of the northeastern

Gulf is lacking in many areas, and we list only major, fundamental data

gaps with broad scope.

Nutrient sources, sinks and cycles. Effects of nutrient

enrichment.

Physical processes driving nutrient exchanges between

coastal ecosystems (estuaries, salt marshes, seagrass

meadows) and the shelf.

Transport and fate of toxic substances, nutrients and

organisms (microbes, meroplankton, fish eggs and larvae)

within and between estuaries and shelf waters.

Identification and distribution of primary and secondary

producers.

Levels of production in coastal and shelf waters.

Taxonomic and trophic structure of coastal and shelf

benthic microbial, plant and animal communities.

Coupling between water column and benthic communities, and

between estuary-shelf and shelf-ocean basin communities.

Impacts of fresh water on shelf ecosystems.

Impacts of catastrophic events (storms, toxic algae, toxic

spills) on community structure.

Impacts of coastal development, including pollution, on
estuarine and nearshore communities.

11. Status and trends in fisheries resources and management.

5.2 Continental Shelf

The following sections describe the general environmental setting and

biology of the continental shelf. Known data gaps are provided at the end

of the section.

5.2.1 Environmental Settina

Physiographically, the panhandle shelf is dominated by DeSoto Canyon. An

inner shelf drops off via a series of rocky terraces to an outer "shelfslope" region south of Destin. East and west of Destin, the shelf deepens

gradually to the shelf break at the head of the canyon. In broad overview,

inner shelf sediments of the panhandle west of Alligator Harbor are

predominantly quartz sands to approximately the 20 m isobath. From Crooked

Island to the east, this sandy, shallow depth zone becomes progressively

broader, extending more than 30 miles offshore in the Big Bend region.

Lyons and Collard (1974) described nearshore sediments east of Alligator

Harbor as comprised of a thin veneer of quartz sand and organic debris

overlying the limestone plateau of the Ocala-Middle Ground Arch. Limestone

outcrops protrude through this veneer and provide hard substrate. Hopkins

et al. (1979) described sediments off Pensacola as soft clastics, coarse

sand and shell rubble at depths of 30-35 m, with algal cemented nodules at

90-95 m depths. Rocky outcrops occur off Panama City in depths of about 20

m, and these increase in number on transitional terraces in depths of about

30-100 m, which divide inner and outer portions of the shelf in the western

panhandle. Rock pinnacles are common at depths of 30-100 m off Pensacola

and Choctawhatchee Bays (Collard, unpubl. data).

5.2.2 Bioloav

Information about eastern panhandle continental shelf biology is scarce

compared to knowledge of the West Florida or western Gulf of Mexico

shelves. The MAFLA Program (ississippi-labama-.iorid), which included

portions of the panhandle shelf, is the only major non-proprietary

investigation of the region accomplished to date (Alexander et al., l977a,

l977b; State University System of Florida, Institute of oceanography, 1978;

Dames and Moore, l979a, b, and c) . The use of information on the

distribution and abundance of benthic invertebrates gained during MAFLA and

subsequent, smaller-scale, investigations of the region (e.g. Hopkins et

al., 1979), provides the most useful and least equivocal basis on which to

base a brief biological characterization of the panhandle shelf.

5.2.2.1 Plankton

Primary production in panhandle shelf waters is influenced by nutrients in

pulse, seasonal or annual river and estuarine discharges into the Gulf of

Mexico. Apalachicola River water has been observed 160 miles offshore

(Livingston and Joyce, 1977), and St. Andrew, Choctawhatchee and Pensacola

Bay water often extends a considerable distance offshore. Mississippi

River water has been observed more than 50 miles offshore southeast of

5-7
Pensacola (Collard, unpubl. data). Bogdanov et al (1969) reported that

productivity was high on the northern part of the Florida shelf due, in

part, to upwelling in the vicinity of DeSoto Canyon. Steidinger (1973)

reported that phytoplankters in the northern Gulf were mainly cosmopolitan

species typical of temperate and subtropical waters. Productivity

generally decreased, and species diversity increased with distance from

shore.

The most comprehensive investigations of zooplankton in panhandle shelf

waters were accomplished by Maturo (water column), and by Collard (neuston)

during MAFLA cruises of 1975-1978 (Maturo et al., 1975; Collard, 1978,

1981; Dames and Moore, l979a, b, and c; State University System of Florida,

Institute of oceanography, 1978). During this period, a series of stations

were established from nearshore to near the shelf break off Pensacola, and

in the Big Bend region. A large suite of physical and chemical

measurements (e.g. temperature, salinity, pH, dissolved oxygen,

chlorophyll, sea state, light, etc.) were collected with plankton samples,

which were counted and identified to the species level. Identifications

also included larvae and subadult stages. Sampling intervals were dense,

and accounted for hourly, daily, seasonal and annual variations in species,

their relative abundances, and their geographic distributions relative to

oceanographic conditions and watermasses. More than 600 invertebrate

species were collected with neuston and plankton nets, and data were

analyzed for patterns. Zooplankton nets of varying mesh sizes were used in

collections and the ecologically very important gelatinous plankters were

significantly undersampled (Collard, 1978).

Results of more than 200 statistical analyses clearly showed that none of

the observed variation in species assemblages, biomass, numerical

abundance, or in time and space could be accounted for with respect to any

single or combination of the abiotic variables measured. Standard errors

of mean values in both parametric and nonparametric tests were often more

than l0 times larger than the mean. For this reason, we feel that the

inclusion here of quantitative values of either biomass or numbers would be

misleading (Collard, 1984)

In all samples, mero- and holoplanktonic crustaceans dominated the catch.

Of these, pontellid copepods were most abundant near the surface, and other

calanoid copepods dominated midwater catches. Other significant

zooplankters included larval fishes, chaetognaths, bivalve and gastropod

veligers, and occasionally, salps, doliolids, appendicularians, pteropods,

hydromedusae and siphonophores. As noted, gelatinous zooplankters were

undersampled. Cladocerans occurred in pulses, and sometimes nearly equaled

the larger species of copepods in numerical abundance. Annual zooplankton

abundance in panhandle shelf waters appeared to be greatest in frontal

zones associated with river plumes, watermass boundaries (e.g. Loop Current

eddys near the shelf break), and in upwelling areas near the head of DeSoto

Canyon. Seasonal variation in abundance varied from year to year (e.g.

Turner et al., 1979; Turner and Collard, 1980), but in most extra-estuarine

areas sampled, numerical zooplankton abundance was higher during winter and

spring.
5.2.2.2 Benthos

Descriptions of the benthos may or may not be representative of the Panhandle shelf as a whole. It is clear, however, that species richness is

relatively high, which suggests that water column and primary production is

relatively high. The following summarizes studies of benthic organisms

(macroepifaunal and macroinfaunal) including beach and outer shelf

communities found within the region.

MacxoepifaUfla

As reported in Dames and Moore (1979), the 25 most abundant macroepifaunal

taxa collected in shelf waters during the period 1975-1978 included eight

crustaceans (6 shrimp, 1 portunid crab, 1 hermit crab); five molluscs (2

squid, 2 snails, 1 scallop); eight echinoderms (2 brittle stars, 1 crinoid,

2 sand dollars, 1 seastar, 1 sea urchin, 1 basket star); and four

cnidarians (1 soft coral, 3 hard corals). Clusters of macroepifaunal

species assemblages occurred in the following depth zones (see Table 5-1)

Table 5-1. Clusters of macroepifaunal species assemblages found in

different depth zones on the panhandle shelf (from Dames and

Moore, 1979)

Hopkins (1979) continued work on the benthic macroinvertebrates of the

panhandle shelf, and reported collections of echinoderms roughly south of

Pensacola, as an area that is "enormously rich in species, and virtually

unknownTM (pers. comm.). Hopkins (1979) found, from collections made 25-50

km south of Pensacola in 1988-1989, 30 species of echinoderTns. Taxa

collected on coarse sand and shell rubble at depths of 30-35 m included

five asteroids, two ophiuroids and three regular echinoids. Taxa collected

on soft clastic sediments at the same depths included three asteroids and

two irregular echinoids. Hopkins reported a distinct increase in numbers

and species of echinoderms associated with "a unique habitat of algal

cemented nodules and coralline red algae" at depths of 90-95 m.

epth Zone Species Assentblage

33-50 m Chiamys benedicti

Laevicardium pictum

Sicyonia brevirostris

Solenocera atlantidis

Scyllarus chacei

Pylopagurus coralinus

Palicus alternata

Luidia clathrata

Ophiolepsis elegans

80-110 m Bebryce grandis

Paracya thus puichellus

Mesopenaeus tropicalis

Iliacantha subglobosa

Anthenoides piercei

170-190 m Turgurium caribaeurzi

Murex beauii

Aequipecten glyptus

Parapenaeus longirostris

Acan thocarpus al exandri

Myropsis quinquespinosa

Pyrornaia arachna

Gonyplax hirsut

Squilla heptacantha
Macroinfauna

During 1977-1978 MPFLA collections, over 1,200 macroinfaunal species were

identified (Dames and Moore, 1979). The one hundred most abundant species

were relatively ubiquitous (nearly 75% of the taxa were collected at more

than half of the stations.) Only six of the top 100 taxa were present at

less than 25% of the stations. Dominants included: 87 polychaetes; 10

crustaceans; and 3 molluscs. The ten most abundant taxa occurred in

densities of greater than 35 individuals rn"2 per station per sampling

period. The next 20 most-abundant taxa had average densities of greater

than 17 individuals rn", and most of the remaining 70 taxa occurred in

densities of less than 17 individuals rn"2. Overall, densities of

macroinfauna ranged from 138 to 15,583 individuals rn"2. The authors noted

that a density of 5. 9 individuals m"2 is equivalent to about one

individual in an area about the size of this page.

No latitudinal trends in numbers of species or in density of macroinfauna

were found, but highest densities were observed nearshore, and the lowest

densities of animals occurred offshore, as was the case with macroepifauna

and meiofauna (Dames and Moore, 1979) . In general, infaunal density

decreased with a combination of increasing percent fine sediments and

increasing depths.

More than 1,000 species of polychaetes were recovered from 1974 MPFLA

collections. These included about 750 different confirmed species, of

which at least 50 (from nearly 200,000 animals counted), were new to

science. Sixty families (including all major families) were identified, of

which seven were new to the Gulf of Mexico. The polychaetes, as a group,

represented a mix of cosmopolitan species (the smallest group), with some

25-30% (each) of the remainder representing Caribbean, Carolinian and

endemic Gulf of Mexico species.

Of about 10,500 crustaceans recovered from box cores during 1977-1978, more than 85% were identified to species level. Ninety families and 360 species

were represented in the collections, of which decapods and amphipods

accounted for 72% of the species and 65% of the total number of specimens.

Nearly one-third of the 360 species collected were new to science.

Beach Counities

Much of the mainland coast of the western Florida panhandle is protected

from heavy wave shock by barrier islands. Barrier island beach communities

experience only low to moderate energy wave shock, except during strong

storms, due to gentle foreshore slopes along all but the extreme western

panhandle area off Pensacola. Because beaches are comprised of unstable

quartz sands, however, intertidal macroinvertebrate species are adapted to

survive maceration by burrowing. The beach flea, Emerita, and the bivalve,

Donax, for example, can bury themselves almost instantaneously. This

ability enables them to live directly in the surf zone. The latter two

species have somewhat patchy distributions, but are found on sandy Gulf

beaches throughout the panhandle, where they migrate up and down the beach

with the tides.
A shallow trough running parallel to the shoreline usually occurs just

offshore of the sandy beaches of the western and central panhandle coasts.

Benthic invertebrates living in the trough are partially protected from

wave action during normal tide and surf conditions. Relatively stable sand

substrates in the trough result in the replacement of rapid burrowers by

whelks, olive shells, sand dollars, and the seastar, Astropecten. A second

(or third) sand bar usually occurs further off the beach, separated from

the first sand bar by a deeper, broader trough. Waves break on the shallow

surface of these sand bars, and Donax-Ernerita communities are again found.

Seaward of the sand bar, as the beach gradually slopes into deeper water, a

third group of animals, including Dinocardiurn, Encope, and the common

seastar, Luidia, are found. These assemblages are characterized in Figure

5-4.

Invertebrates in the zero to low energy beaches in the Big Bend region are

similar to the foreshore "trough communities" described above, with

increasingly subtropical affinities.

Shelf Counities

Beach and foreshore communities intergrade with the shallow shelf

community, which occurs at depths of about 10-30 m (Lyons and Collard,

1974) . Many species found in shallower water also occur at these and

greater depths (Figure 5-5). As depth increases, areas of mud, hard clay,

carbonate, and patchy rock and shell hash substrates become more common.

The species composition of otter trawl and Cape Town dredge collections

becomes progressively less predictable with distance from shore and with

depth, but the extreme variation observed in catches is speculated to

depend more on substrate type than either depth or distance offshore

(Millender, pers. comm.; Collard, unpubl. data) . Trawl collections from

depths of 30-400 m in the steeply terraced region near the head of DeSoto

Canyon may be dominated by ahermatypic corals, echinoderms, gastropods,

decapods, holothurians, or clumps of calcareous algae. Several hundred

trawls made in close proximity to each other (less than a nautical mile

apart) in this area during the period 1970-1994 exhibited enormous

variation in the numbers and species of animals caught (Collard, unpubl.

data) . Species diversity appears to be greater in water depths from 20-30

m to ca.lOO m, than in shallower water, and West Indian taxa become more

common with increasing depth. Clearly, however, shelf benthic communities

have not been sampled sufficiently well to permit even general

characterizations of species assemblages to be made.

5.2.2.3 Fish

Darnell's (1990) synopsis of regional demersal fish, based on collections

totalling in excess of 2,245,000 fish, includes the following. "Depth

related zonation reveals nearshore, mid-shelf, outer shelf, and trans-shelf

assemblages. Estuary related species are particularly prominent on the

northwestern Gulf shelf, while rock and reef related species are most

important in the fauna of the eastern Gulf shelf. Recognizable elements in

the shelf fauna also include species of tropical affinity; open ocean and

upper slope species; inhabitants of seagrass beds, mangrove swamps, and

carbonate rubble and shell hash; burrowers in soft bottoms; and inhabitants

5-li
BACKSHORE FORESHORE TROUGH BAR OFFSHORE

DUNE BERM

Coypods albcans (C)

Talo,vheslia longicomis (vc)

Orvheslia g!llus (tv)

MHWST MLWST

Caiianassa islagrat?de (vc)

HauSfO,'iuS sp. (vv)

Lysiosquffla exoavafnx (t

Batrillipes t7flJS (ye)

Arenasus cnbanus (C)

I BuSycon sp4ratum (C)

Conan vanabilis (ye)

Emedia talpoida (ye)

Terebra cnne,ea (c)

MHWST = mean high water spring tide

MLWST = mean low water spring tide

vc = very common

C = common

r = rare

Olive sayana (c)

Lepidopa benediali (I)

Mellita quinquiespeiforefa (vC)

Astropecien a,liculafus (C)

Poru,us gibbet? ('C)

Ovàlipes guaculpensis (C)

RelØlla mullen (ye)

Strdmbus pugilis OlafUS (r)

Phalium grenulatum (C)

At,!na serrata (C)

Oinoca,dium robusturn (I)

Oosinia discus (C)

Tellifla ve,sicolOr (vc)

Encape michelin! (vC)

Luidia c'ethiafa (c)

Metre atropos (ye)

Macrocallista nimbosa (c)

PereSphona punatata 0)

Sinun perspechvum (r)

Hepafus ephelitiouS (r)

Figure 5-4. Beach and foreshore benthic macroinvertebrate corrimunities

(after Collard and D'Asaro, 1973)

5-12
Oculina diffusa (C)

Pilumnus sa) (vC)

Leptogorgia virgulata (C)

L setacea (C)

Sairpeena grandis

Muricea pendula (C)

Astrangia solitana (C)

Phyllangie amencana (C)

Caodie gibbemSa (C)

Petrolisihes galathinum ('v)

vc = very common

c = common

r = rare

Sphecospongia vespana (Sc)

Axinella polycape!la (C)

Stenorynchus es2io3miS (,

lrania campana (Sc)

I. fasaculata (Sc)

Tubularia crocee (C)

Gonodactylus townsendi (C)

Spondylus amerscanus (c)

Echinochama comuta (c)

Sirierontma siderea (sv)

Argopecten gibbus (vC)

Scaphelia kiener, (,)

CenanthiopeiS amencanus (c)

ous commonis (r)

Tonna galea (r) Cassis magadascarensis (1)

Renilla mullen (vc)

Cardiomya gamma (c)

Clypeaster subdepressus (C)

Pie gb br,ssus grandis (r)

Amphipolie graCiIiima (Sc)

Figure 5-5. Shallow shelf benthic invertebrate assemblages (after Collard

and D'Asaro, 1973)

5-13

ROCK SAND
of the upper water column. The eastern Gulf shelf is inhabited by twice as

many fish species and eight times as many unique species as the northwest

shelf, reflecting the great diversity of habitat types in the eastern Gulf.

A few key species numerically dominate the ichthyofauna of the northwestern

shelf, but dominance is spread through many species in the east. Seasonal

shifts in species density primarily reflect inshore/offshore seasonal

migrations of estuary related species, but seasonal inshore/offshore

density shifts are also observed among the true shelf residents.

Trophically the shelf systems are supported by precipitated plankton and

organic detritus derived from rivers, bays and estuaries, seagrass beds,

and mangrove swamps, although attached algae are also important producers

in the east. Mollusks, polychaetes, and small crustaceans which feed upon

this material, in turn, support the demersal fish communities whose species

are generally short-lived. Larger long-lived predators are mostly seasonal

migrants which appear in the northern Gulf during the warmer months.

Bottom-feeding generalists are prominent in the northwest, while

specialists are in great evidence in the east."

According to Dames and Moore, (1979), the distribution of fishes on the

northern Florida shelf is "particularly homogeneous", and similar to the

ichthyofauna of northern and southern portions of the Gulf (see Table 5-2).

The authors remarked that similarities reflected the distribution of

calcarious substrates in the three areas. Trawl collections made from

1974-1978 comprised 292 species, "about half the species known from the

Gulf of Mexico, and nearly all of the demersal fish previously reported

from the Gulf".

5.2.2.4 Sea Turtles and Marine Ma2zmtals

The distribution and abundance of marine mammals and adult sea turtles in

panhandle shelf waters varies seasonally and from year to year. The

distributions of these animals is not well known, but may be related to

watermass preferences, food source availability and reproductive cycles.

Post-hatchling sea turtles are too rarely seen to discuss objectively, but

Collard and Ogren (1990) are of the (minority) opinion that small turtles

do not purposefully associate themselves with sargassum. They are found in

or near convergence zones where they fetch up (with or without sargassum

present) as buoyant plankters. Solitary loggerhead turtles are seen

everywhere in shelf waters during warm water months.

Most of the leatherback turtles and marine mammals (save porpoises)

observed by Collard on more than 40 cruises (1970-1994), were near

watermass boundaries where their presumed forage was also concentrated.

Tursiops truncatus and Stenella frontalis are the most common porpoises in

panhandle waters. Although there is little evidence to support this

speculation, the abundance of the latter species appears to be increasing

in rough proportion to an apparent decrease in numbers of the former.

Ziphius cavirostris (Cuvier's beaked whale), Physeter rnacrocephalus (sperm

whale), and Globicephala macrorhynchus (short-finned pilot whale) are

probably the most common species of large marine mammals in panhandle shelf

waters.
Table 5-2 Habitat-depth assemblages described by Dames and Moore,

(1979)

5.2.3 Data Gaps

1. Artificial reefs of various sizes and materials are being deployed

with increasing frequency on the inner shelf. Some of these reefs

are unstable during heavy storm conditions because of their small

size and/or placement in inappropriately shallow water depths. While

much has been written about the presumed benefits of artificial

substrates (increased productivity, etc.), relatively little work has

been done on assessing the possible negative impact of these

materials on natural communities. For example, it would be of value

to know whether the translocation and/or destruction of artificial

reefs during the three hurricanes of 1995 negatively impacted live

bottom communities in the vicinity of their original location.

5-15

Shallow Sand Indicative Species:

Dasyatis sayi [bluntnose stingray]

Eucinostomus gula [silver jenny]

Micropogon undulatus [Atlantic croaker]

Deep Reef Indicative Species:

Holocentrzzs bullisi [deepwater squirrelfish]

Chaetodon aya [bank butterflyfish]

Sponge Reef Indicative Species:

Apogon quadrisquarnatus [sawcheek cardinalfish]

Gobiosoma xanthiphora [yellowprow goby]

Shallow Reef Indicative Species:

Hypoplectrus puella [barred hamlet]

Evermannichthys spongicola [sponge goby]

Epinephelus mono [red grouper]

Rypticus mnaculatus [whitespotted soapfish]

Astrapogon stellatus [conchfish]

Mid-Shelf Sand Indicative Species

Synodus interinedius [sand diver]

Centropnistis ocyurus [bank seabass]

Syaciumn papillosum [dusky flounder]

Sphoeroides dorsalis [marbled puffer]
The long-term impact of artificial reefs on the abundance and

sustainable yields of recreationally and commercially important fish

species remains unknown, although a relatively large literature on

the subject is available.

n unknown, but possibly significant amount of military debris (e.g.

aircraft, missiles, ordnance) has accumulated in shelf waters of the

northeastern Gulf of Mexico. The short- and long-term ecological

impact of this material should be assessed.

Propagules of tropical organisms (zooplankton, benthic invertebrates,

fishes), are recruited onto the continental shelf during intrusions

of Loop Current, or Loop Current Transitional Water. The extent,

mechanisms, and impacts of nutrient and biotic coupling between Gulf

of Mexico basin and shelf waters (including coastal embayments)

should be documented.

The upwelling of nutrient-rich water south of Cape San Bias, and at

the edge of the West Florida Escarpment is apparently common.

Primary production in this water (the "Green River" seen in satellite

images of the northern Gulf) may have a major trophodynamic impact on

many or all water column and shelf ecosystems, and should receive

intensive investigation.

The distribution of sargassum and its associated organisms in the

eastern Gulf of Mexico has received scant attention. Remote sensing

of the distribution of "Gulf weed" (primarily Sargassum natans and S.

fluitans) may reveal valuable information about sea states and, more

importantly, the distribution and longevity of frontal zones and

frontal boundaries. Sargassum as an important habitat (e.g. for

larval fishes; hatchling and post-hatchling sea turtles) has not been

investigated in the eastern Gulf of Mexico.

The occurrence and impact of exotic invertebrate species introduced

to shelf and estuarine waters via the release of ballast water has

not been adequately investigated.

5.3 Estuaries

From Perdido Bay to Apalachicola Bay, much of the mainland coast is fronted

by a series of estuaries and associated sounds. East of Ochlockonee Bay,

the upper Big Bend coastline is entirely estuarine in terms of salinity,

biota and ecological function.

Of the major estuaries west of the Big Bend, Pensacola, Choctawhatchee, and

Apalachicola Bay-St. George Sound systems are coastal-plains drowned river

valleys. These systems receive water from one or more rivers and streams,

and discharge into coastal-trending sounds bounded by barrier islands.

Brackish water from these estuary-sound systems flows via one or more

passes between barrier islands into the Gulf of Mexico. St. ndrew Bay is

also a coastal plain (bar-built) estuarine system, but unlike those named

above, receives fresh water primarily from relatively small, non-f luvial

streams and land runoff. Econfina Creek, the largest stream in the St.

Indrew Bay watershed, enters the system indirectly via Deer Point Lake,

which was created by a man-made dam at the mouth of North Bay. St. Joseph

5-16
Bay, Alligator Harbor and St. Andrew (Crooked Island) Sound are marine

lagoons partially impounded by well-developed sand spits. St. Andrew Sound

became decoupled from the St. Andrew Bay system as a result of Hurricane

Eloise in 1975. All three marine lagoons have salinities near those of

open Gulf of Mexico waters.

5.3.]. Environmental Settina and Characteristics of Florida Panhandle

Estuaries

Ochiockonee Bay is the easternmost estuary in the panhandle that conforms

to conventional estuarine classification schemes (see Kennish, 1989)

Apalachee Bay is not impounded by land features, yet its brackish waters

and biota clearly qualify it as an estuarine ecosystem. Apalachee Bay lies

within the upper portion of the Big Bend region, and its geographical

boundaries vary with the quantity and distribution of fresh water

contributed by rivers, streams, springs and land runoff. Included among

the larger streams entering Apalachee Bay are the Anclote, Pithlachascotee,

Weeki Wachee, Homosassa, Chassahowitzka, Waccasassa, Ochiockonee, Aucilla,

St. Marks, Crystal, Withlacoochee, Spring Warrior, Econfina, Fenholloway,

Steinhatchee and Suwannee Rivers.

Pensacola, Choctawhatchee, St. Andrew and Apalachicola Bays are not unitary

estuaries, but estuarine systems. The components of these systems (i.e.,

connected bays and their associated bayous) exhibit non-trivial differences

in their physical, chemical, and biological characteristics and, therefore,

in their ecological functions. The Pensacola Bay System, for example, is

comprised of Escambia, Blackwater, East and Pensacola Bays. Significant

biological differences in these system components are attributable, in

part, to differences in water received from distinct riverine watersheds

and drainage basins. As an example, Blackwater Bay receives water from the

Blackwater and Yellow Rivers. The former is an Outstanding Florida Water

and the lower reaches of the latter are protected as an aquatic preserve.

The moderately polluted Escarnbia River empties into a more heavily polluted

Upper Escambia Bay. East Bay River discharges into East Bay which, until

the mid- to late 1980s, was relatively pristine. Pensacola Bay receives

water from, and is influenced by, each of these subsystems (i.e.,

watersheds, rivers, bays) comprising the Pensacola System. The kinds,

magnitudes of influence and interactions that component parts of the system

have on one another are likely to be significant, but have not been

described in detail (Collard, 1991)

5.3.1.1 Estuarine Climatic Features

Both local and regional climatic features influence the organization and

fundamental characteristics of estuarine ecosystems. The seasonal and, in

some cases, episodic impact of these abiotic variables on northeastern Gulf

of Mexico estuarine systems are briefly discussed in the following

paragraphs. A complete discussion of meteorological conditions within the

study region is provided in Chapter 2 (Physical Oceanography and

Meteorology)of this document.
5.3.1.2 Seasons

In the Florida panhandle, solar and biological "seasons" do not coincide,

and the division of a year into three-month-long seasons (winter, spring,

summer and fall) is not justifiable when evaluating seasonal changes in

estuaries of the region, Using data from 1924-1942, Moskovits (1955)

considered the following seasons to occur in the Pensacola region, based on

an analysis of average temperature maxima and minima (the authors have

modified his time intervals and terminology) : winter occurs from DecemberFebruary (or mid-March), for a duration of two and a half to three months;

spring is a transitional period from March-May (or mid-March to mid-May),

with a duration of two to three months; summer lasts from June-September

(or mid-May to September), a duration of four to four and a half months;

and fall, another transitional period, lasts from October-November, or for

about two months. Both "summer" and "winter" may be longer than indicated

in this scheme, and transition periods may be abrupt.

Fernald and Purdum (1992) suggested that from Pensacola through the middle

of Taylor County, winter begins on 1 November or earlier, with an average

maximum temperature of 75°F or lower. South of Taylor County, winter

begins between 1 November and 1 December. Spring (from Pensacola to about

Turkey Point) begins on 1 April or later, when the average maximum

temperature rises to 75°F or higher. South of Turkey Point, spring begins

between 1 March and 1 April. Summer (from Pensacola to about St. George

Island) begins on 1 June or later, when the average maximum temperature

reaches 88°F or higher. South of Apalachicola Bay, summer begins earlier,

between 1 May and 1 June. Fall (Pensacola to about Steinhatchee) begins on

3-4 October, when the average minimum temperature falls to 60°F or lower.

In the Cedar Key area, fall begins during the period 4 October to 1

November. The time of the first and last freeze of a given year are

variable. In the panhandle, dates of the first and last freeze are 15

November to 15 December, and 1 March to late March, respectively. Seasons

Florida panhandle coastal areas experience two major seasons: a lengthy

warm to hot summer, and an almost equally long cool to mildly cold winter.

Spring and fall transitional seasons while of short duration, are periods

of significant physical, chemical and biological change which are most

pronounced in estuaries of the western panhandle.

5.3.1.3 Temperature

Seasonal air temperatures divide the climatically transitional panhandle

into three "subregions" whose boundaries are discernable, but not

sufficiently distinct to be considered biogeographical zones (discussed

later in this chapter). The Pensacola Bay System, Big Lagoon, Santa Rosa

Sound and the lower reaches of Choctawhatchee Bay, support a largely

5-18

along the Florida panhandle coast are approximately as follows:

Season. Occurrence Duration

Spring March-April 2 months

Summer May-September 5 months

Fall October 1 month

Winter November-February 4 months
temperate fauna and flora year-round, and the incursion of tropical species

into this area is relatively uncommon. St. Andrew Bay and the St. Andrew

Sound lagoon are transitional warm-temperate embayments during cooler

months, and gain a fair number of subtropical-tropical species during hot

summer months, depending on upstream Gulf recruitment patterns (Hydroqual,

Inc. and Barry A. Vittor & Associates, Inc., 1993). Many subtropical and

all tropical invertebrates and fishes die during the winter. St. Joseph

Bay, the Apalachicola System (including St. George Sound), Ochiockonee Bay,

and Upper Apalachee Bay support a largely subtropical biota. Southern and

deeper portions of this Big Bend estuary are increasingly subtropical, and

some tropical species are present year-round (Myers and Ewel, 1990;

Livingston et al., 1974 et seq.; Lyons and Collard, 1974; Collard, 1992,

1993, 1995 unpublished data)

5.3.1.4 Precipitation

The amount of fresh water discharged into panhandle estuaries (as pulses or

average volumes per unit time) has a large impact on estuarine biota.

Local and watershed precipitation patterns control river output which,

along with winds, tides, and the strength of the pycnocline, influence

assemblages of stenotopic (species with low physiological tolerances for

changes in environmental conditions) sessile invertebrates and motile

invertebrates and fishes. Episodic flooding of several days duration may

cause mass mortalities of many species in any of the panhandle estuaries

and, less frequently, in coastal lagoons such as St. Andrew Sound and the

shallow portions of St. Joseph Bay.

Rainfall amounts vary in the panhandle from season-to-season, year-to-year,

over shorter time scales (e.g., during large storms), and over longer

periods of time (e.g., El Nine Southern Oscillation conditions). For this

reason, the use of seasonal and annual averages must be used with caution.

According to Fernald and Purdum (1992), the area from Pensacola Bay through

St. Andrew Bay receives roughly 60 inches of rain per year. Other forms of

precipitation (snow, hail, etc.) are rare and insignificant. Some 25-30

of the annual total rainfall throughout the region falls during September

storms and hurricanes. St. Joseph Bay receives 56-60 inches of rain each

year, and the rest of the coastal panhandle receives 52-56 inches of rain

annually. These figures should be used cautiously for modeling purposes,

for they are somewhat misleading. The total amount of fresh water entering

an estuary over a given period of time must be used to calculate the

magnitude of forcing functions. Total precipitation in watersheds as well

as runoff from rivers and the land surface, contribute very large volumes

of fresh water to panhandle estuaries. Estimates or measures of river

flows at the few gauging stations in the region provide accurate

information, but do not account for the very large variation in output

during even a single season. Thus, one of the most important abiotic

variables affecting the hydrology, chemistry and biota of panhandle

estuaries cannot be evaluated with acceptable levels of confidence.
5.3.1.5 Hurricanes and Storms

Williams et al. (1993) reported that from 1871-1922 (122 years) , 180 of

almost 1,000 North Atlantic hurricanes or tropical storms, "have struck,

passed immediately offshore or adjacent to the Florida coastline."

Historically, hurricane landfalls have been more frequent in the panhandle

and southwest Florida than in other parts of the State. The favored

statistic used in forecasting Florida hurricane landfalls is one per 10-15

years. Williams et al. (1993) have examined the possibility that

hurricanes occur in temporal patterns or cycles. Between 1870-1880, four

hurricanes struck eastern Florida from the east or southeast, and 17 struck

the western Florida coast or the panhandle. This pattern continued through

the turn of the century. From 1901-1930 there were fewer tropical storms

(22 hurricanes and 17 tropical storms) than during the previous 30 year

period, and more strikes came from the southeast. The worst of these

destroyed Pensacola in 1906, and the city was again damaged in July 1916,

October 1916, and September 1917. After 1919, the "cycle" of tropical

cyclone activity changed, and most hurricane landfalls occurred in south

Florida. Table 5-3 presents a list of Florida panhandle hurricanes

occurring from 1885 through 1995. Additional information concerning

tropical storms in the study area is presented in Chapter 2 of this report.

In addition to hurricanes and tropical storms, Florida experiences more

thunderstorms than any place on earth except East Africa (Williams et al.,

1993) . For example, thunderstorms occur some 70-80 days per year in St.

Andrew Bay. Winds associated with these convective storms promote

turbulent mixing in shallow bays, which increases near-bottom dissolved

oxygen concentrations.

5.3.1.6 Seasonal Wind Patterns

Prevailing winds are northeasterly in the Pensacola area during winter, and

northerly in the remainder of the panhandle. In spring, Pensacola area

winds are southeasterly, and southerly in the rest of the panhandle.

During summer months prevailing winds are southwesterly, becoming

southeasterly further to the east and south. In the fall, prevailing winds

are northeasterly throughout the panhandle (Fernald and Purdum, 1992).

During warm months, coastal winds in the panhandle are monsoon-like:

onshore during the day, and offshore as land areas cool more rapidly than

coastal waters (a sea-breeze system)

5.3.1.7 Estuarine Circulation

Accurate knowledge of water movements and their causes is fundamental to

understanding the fate and transport of gasses, dissolved and suspended

chemicals, plankton, and other biological conditions in estuarine systems.

Water movements and the distribution of salinity in estuaries are

influenced by river flow, tidal currents, seiching, Langmuir circulation,

advective processes, winds, basin geometry, and many other factors, such as

the semi-permanent gyres reported to occur in Tampa Bay and Upper Escambia

Bay. Knowledge of the complex and highly variable circulation patterns and

small scale, current and water column temperature/salinity profiling be
imprudent to attempt to describe "characteristic" circulation patterns in

any estuarine system using these data.

Table 5-3. Listing of Florida panhandle hurricanes from 1885-1995.

5.3.1.8 Tides and Sea Levels

Two general tidal patterns are observed in the panhandle: diurnal, from

Pensacola Bay to Cape San Blas; and mixed semidiurnal, from Apalachicola

Bay to Ochiockonee Bay. Tidal ranges along the panhandle coast have

amplitudes ranging from 0.4 - 1.2 m. Tidal amplitudes along the coast are

somewhat greater east of Cape San Blas; however, the tidal range

experienced on both the coast and within a given estuary is significantly

5-21

Date Primary Affected Area

1856 Choctawhatchee Bay

1885 St. Joseph Bay

1886 Apalachicola Bay (2)

1887 Choctawhatchee Bay

1888 Big Bend

1894 Apalachee to Apalachicola Bays

1895 St. Andrew Bay

1896 Big Bend (Dixie Co.)

1898 Apalachicola Bay

1906 Pensacola; St. Joseph and St. Andrew Bays

191]. Pensacola Bay

1915 Apalachicola Bay

1916 Pensacola Bay (2)

1917 Pensacola Bay

1924 St. Joseph; St. Andrew Bays

1926 Pensacola Bay

1928 Apalachicola Bay

1929 Apalachicola Bay

1935 Big Bend (Taylor Co.)

1936 Choctawhatchee Bay

1941 Apalachicola Bay

1949 Apalachicola Bay

1950 Cedar Key

1953 Between Choctawhatchee and St. Andrew Bays

1956 Choctawhatchee Bay

1966 Apalachicola Bay

1968 St. George Sound

1972 St. Andrew to St. Joseph Bays [Agnes]

1975 Choctawhatchee to St. Andrew Bays [Eloise]

1985 Big Bend [Elena] Pensacola to St. Joseph Bay [Kate, Juan]

1986 Apalachee Bay [Chancy]

1995 St. Joseph to Pensacola Bays [Allison, Enin, Opal]
influenced by wind velocity, direction and duration. Tidal currents in

panhandle estuaries are generally weak, except in lower reaches near passes

and channels communicating with the Gulf of Mexico (e.g. East Pass Channel

at Choctawhatchee Bay). These currents aid in mixing processes, but may

not result in net transport (e.g. of nutrients, pollutants, plankton) over

a tidal cycle. Circulation and diffusion in some estuaries (e.g. Pensacola

Bay) are too weak effectively to reduce pollutant concentrations through

mixing processes.

On the northeast Gulf coast, monthly sea level rises above the mean annual

level beginning in May, and remains above the mean level from June through

December. Higher sea levels coupled with southerly (i.e., monsoonal)

winds, result in increased marsh flooding even on neap tides (Stout, 1984)

Annual sea level cycles are ecologically important, particularly in shallow

relief regions of the panhandle (e.g., Apalachee Bay) where salt marsh

abundance may increase or decrease significantly in abundance over the

course of a year.

5.3.1.9 Data Gaps

Perhaps the single most important data gap in the northeastern Gulf

of Mexico database is the lack of knowledge of estuarine circulation

patterns, and how these vary with tides, river flows, seasonal

temperature changes, winds, and inner shelf currents. Detailed

information about currents and mixing processes in terms of local

forcing functions is prerequisite to understanding the fate,

transport and distribution of salinity, dissolved oxygen, nutrients,

toxicants, plankton, turbidity and other variables needed to create

useful models of these systems.

There is a significant need for knowledge about the extent and

importance of coupling (exchanges of nutrients, toxicants, suspended

materials) between estuaries and coastal waters.

Little is known about the amount or impact of watershed or local

stormwater runoff into northeastern Gulf estuarine systems. There

are far too few river gauging stations in place.

5.3.2 Environmental Oualitv of Panhandle Estuaries

Most of the physicochemical characteristics used to evaluate estuarine

quality are highly variable over relatively short time scales. Among these

characteristics are circulation patterns, the distribution of dissolved and

particulate substances, pollutant and nutrient loading, water and sediment

quality, stormwater and river runoff, chemical kinetics and human use

patterns. Because of variability, both "snapshot" assessments and trends

in estuarine environmental quality are often difficult to discern. For

example, when predictable low dissolved oxygen levels occur near the bottom

during summer months and a fish kills results, an estuary may be judged to

have poor water quality (Collard, 1991). In contrast, when industrial

wastewater discharges into panhandle estuaries decreased during the

economic downturn of the 1970s, a gradual improvement in water quality was

erroneously declared to be a trend. Many short-term changes (e.g., in

5-22
fishing pressure, occurrences of toxic algal blooms, dredging activities

and watershed precipitation) may incorrectly suggest that favorable or

unfavorable trends in estuarine quality have begun (Olinger et al., 1975;

Collard, 1991)

Population growth in the Florida panhandle has increased dramatically in

the past 20 years, particularly in urban areas surrounding the Pensacola,

Choctawhatchee, and St. ndrew Bay systems (Florida Statistical bstracts,

1994). Environmental impacts of this growth, which is forecast to

continue, are poorly understood and have been underestimated. Historical

descriptions of coastal environments that have significantly changed or no

longer exist (e.g. salt marshes, seagrass meadows, oyster reefs) as a

consequence of population growth and development must be used with caution.

Three hurricanes impacted shallow shelf, estuarine and salt marsh

environments of the panhandle during 1995. The last and most damaging

storm of the year, Hurricane Opal, struck the area in October 1995 as this

report was being written, and much of the pre-hurricane environmental

information being used to characterize coastal ecosystems became

problematic within a matter of hours. The impacts of these storms on

coastal and nearshore habitats and biota have not been published to date.

5.3.2.1 stuarine Pollution

Pollutants such as oil, heated water, nutrients, caustic substances and

poisons enter estuaries via urban, agricultural and construction site

runoff, domestic and industrial wastewater, land disposal and mining

operations. These, and other pollutants, may drastically affect estuarine

communities such as seagrass meadows. Species react in different ways to

pollution stress, depending upon their dispersive capability, stage of

development, numbers, tolerance limits and physiological state; and on the

type of pollutant and its concentration and residence time in the

environment.

As noted by Hand et al. (1994) in their review of panhandle estuaries, "The

assessment of public health and aquatic life impacts found several

concerns. Many of these problems are associated with estuaries and are of

a persistent nature." Examination of the literature suggests that most

panhandle estuaries are pollution sinks (e.g. McNulty, 1961), and it

appears that most estuaries have been anthropically impacted to some

degree. The extent to which individual estuaries, bayous, and lagoons are

"polluted" is only superficially discussed in the present review. The

amounts, distributions, residence times, interactions, and effects of

pollutant substances (in the broadest sense) or pollution conditions (e.g.

turbidity levels, color, dissolved oxygen concentrations, low/high pH,

elevated biological, chemical or sediment oxygen demand [BOD, COD or SOD,

respectively]; seagrass scarring; and habitat destruction) on species,

communities and ecosystems, are highly variable and (quantitatively) poorly

known. Symptoms of pollution, such as fish kills, algal blooms, turbidity,

declining fisheries, closed shellfish harvesting areas, and decreased

swimming and fishing activities are noted in subsequent sections where

recent data were available.
According to Paulic and Hand (1994), "Water quality problems are evident

around the densely populated, major urban areas such as... Pensacola..."

No other estuaries in the panhandle were mentioned. These authors found

that 63% of the total estuarine areas evaluated fully supported, and 33%

partially supported their designated uses. Paulic and Hand (1994)

concluded that the primary causes for water bodies not fully supporting

their designated uses varied by water body type. For estuaries, "[the]

primary causes are identified as algal blooms, nutrient enrichment,

suppressed dissolved oxygen levels, and turbidity." No estuaries in the

panhandle region were found to be "worse." "No change" was reported for

Apalachicola Bay and the mouth of St. Andrew Bay. Big Lagoon (between

Perdido and Pensacola Bays) was found to be "better" in terms of its

designated use.

5.3.2.2 Nutrients

The susceptibility of estuaries to nutrient discharges may serve as an

important indicator of the future condition of their habitats and faunal

assemblages. Pensacola Bay was found to have a "medium susceptibility" to

increases in the concentration of dissolved substances, and was in the

"medium range" for additional Total Kjeldahl Nitrogen (T}) and phosphorus.

Pensacola Bay was "not likely to be influenced by minor changes (< 20%) in

nutrient loadings." St. Andrew Bay also had a "medium" susceptibility for

dissolved substance concentrations, but was "in the low range for T and

phosphorus... [and] not likely to be influenced by minor changes (< 20%) in

nutrient loadings (Paulic and Hand, 1994). Other estuaries in the

panhandle had low susceptibility to increased nutrient loadings.

5.3.2.3 Metals

According to Paulic and Hand (1994), toxic metals in the water column of

panhandle estuaries included: As, Cd, Cr, Cu, Fe, Pb, Hg, Ni and Zn. Water

column concentrations of Hg, Fe and Pb were generally above Florida

standards, which are determined as a function of water hardness (*assumed

to be 100 mg/i as calcium carbonate) . Florida metals criteria (ppb) are:

As=50 Cd=1.i Cr=207*

Cu = 12* Fe = 1000 Pb = 3.2*

Hg = 0.012 Ni = 158* Zn = 106

5.3.2.4 Sediment Contaminants

Isphording (1983) stated that, "The true pollutant hazard of a bay or

estuary can ... be most accurately evaluated by analysis of the fine

particulate matter that occurs in the colloidal phase just above the

sediment-water interface." This latter type of information is not available

for the panhandle estuaries. However, information on contaminants within

sediments is presented as Table 5-4 (from Paulic and Hand, (1994)
Table 5-4. Summary of sediment contamination for panhandle estuaries by

habitat (from Paulic and Hand, 1994).

5.3.2.5 Data Gaps

"Water quality" monitoring in panhandle estuaries is generally

accomplished in the immediate vicinity of known industrial or

domestic effluent outfalls for compliance purposes. Many, perhaps a

majority, of these data are not entered into the STORET database

(Collard, 1991). Biannual 305(b) statewide assessments of

environmental conditions and quality, which are largely based on

STORET data, do not provide accurate status and trend reports on

panhandle estuaries, and may be misleading.

The assimilative capacity of nutrients and toxic substances in

panhandle estuarine water and sediments is not known in sufficient

detail. Until estuary-specific information on circulation and mixing

processes is understood, quantitative determinations of loading and

assimilative capacities can not be made.

Integrated, multidisciplinary, monitoring programs of estuarine

5-25

Habitat Contaminant

Suwanriee Sound PAR

Apalachee Bay PAR, PCB, Pesticides

Apalachicola Bay PAR, PCB, Pesticides

Choctawhatchee Bay

Boggy Bayou

Old Pass

Lagoon

PAR, Pesticides

PAR, Pesticides

PAR

Pensacola Bay

Bayou Grande

Bayou Chico

Escambia Bay

Pensacola Harbor

East Bay

Lower Pensacola

Bay

PAR, PCB

PAR, PCB, Cd, Cr, Hg,

PAR, PCB, Cd, Cr, Hg,

PAR, PCB

PAR, PCB

PAR

PAR, PCB

Pb, Zn

Pb, Zn

St. Joseph Bay Hg, Pb, Zn

St. Andrew Bay

Watson Bayou

Zn, Pb, Cu, PAR, PCB,

Cd, Hg, Zn, PAR, PCB,

Pesticides

Pesticides
physical, chemical, sedimentological and biological conditions are

needed to understand and evaluate environmental conditions and

trends in panhandle coastal environments.

5.3.3 Estuarine Habitats

This section provides a brief review of seagrass, salt marsh and oyster

reef communities because of their significant functional importance in

panhandle estuaries. Less well-known assemblages are described to the

extent that relevant information was available.

5.3.3.1 Salt Marshes

Salt marshes are complex coastal communities usually dominated by one or a

few species of relatively large, perennial, salt-tolerant, or halophilic

plants (e.g., Juncus roe.rnerianus, Spartina spp.), and the microbiota, flora

and fauna associated with them. Dominant plant species may be intertidal

(J. roemerianus, S. alterniflora), or live above mean sea level (MSL) with

their roots in hydric, salty soils (e.g., Spartina patens).

Distribution

According to Stout (1984), large, well developed, but discontinuous stands

of Juncus roeznerianus border the low-energy shorelines, sounds, lagoon and

bays from Cedar Key to the Pearl River estuary in Mississippi. South of

Cedar Key, mangroves begin to co-dominate with J. roemerianus. FDEP (1994)

reported that, "Salt marshes dominate the coastal landscape from

Apalachicola Bay to Tampa Bay... [but] West of Apalachicola Bay, estuaries

have few salt marshes." These apparently disparate assessments are

artifacts of perception. Salt marshes along the low-relief Big Bend coast

are more extensive in area than those in the western panhandle. However,

significantly large areas of non-urbanized, low-relief shorelines and river

floodplains of the panhandle support well-developed salt marsh communities,

as do barrier island sound-side shorelines (e.g. Crooked Island, Santa Rosa

Island). J. roemerianus dominates 31% of the marsh areas in the Florida

panhandle (Stout, 1984).

Ecological Functions

According to Stout (1984, and authors cited therein), salt marshes have

four major ecological functions. First, large quantities of organic matter

are produced per unit time. Some of this detritus remains in the marsh as

peat; some is recycled in marsh food webs; some is (passively or via

consumers) transported out of the marsh; and some is dissipated into

estuaries. Second, marshes are the exclusive habitat of several species of

algae and seed plants, a large variety of invertebrates and birds, and

numerous species of reptiles and mammals. A third function is that these

areas provide substantial protection to adjacent low-lying uplands from

saltwater intrusion, coastal erosion, drifting debris, and salt spray.

According to Stout (1984), marshes protect shores only in major embayments,

such as St. ndrew and Choctawhatchee Bays. However, J. roemerianus

marshes provided at least some protection to shorelines around Escambia

Bay, Santa Rosa Sound, St. Andrew Sound and St. Joseph Bay during Hurricane

5-26
Opal (unpubl. data). The fourth ecological function of salt marshes

described by Stout (1984), is their importance as nursery grounds for

commercial and sport species. Odum and Smith (1981) elaborated on this

function of marshes, noting that in fish and wildlife life history cycles,

marshes provide (1) sites for reproduction, (2) a conducive environment for

early life stages (i.e., they play a "nursery" role), and (3) areas where

young animals can find and utilize concentrated, high quality food.

Table 5-5 provides an estimate of the relative value of three subsystems of

coastal marshes (i.e., high marsh, intertidal marsh and tidal channels) to

various animal groups, without consideration of any indirect value of the

high marsh to fishes, such as the export of dissolved organic carbon.

Table 5-6 estimates relative importance of coastal marshes to the lifehistory functions of these same three principal animal groups, and Table 5-

7 presents a partial listing of some estuarine-dependent species from the

Gulf and southeast Atlantic coasts.

Intertidal Marsh Flats

It has been reported that the most abundant infaunal animals inhabiting

intertidal marsh substrates are crustaceans and polychaetes (Whitlach,

1982; Montague and Weigert, 1990). Marsh infauria are represented by the

following feeding guilds: surface deposit feeders; suspension feeders;

conveyor-belt deposit feeders and burrowing deposit feeders; as well as

herbivores, detritivores, carnivores and ornriivores. These animals serve as

forage for a large number of predatory animals, including birds, crabs and

fishes.

Table 5-5. Relative value of indicated marsh subsystems to listed animals

(from Table 1, Odum and Smith, 1981).

Table 5-6. Relative importance of coastal marshes for three life-history

functions of the three principal animal groups found in

marshes (from Odum and Smith, 1981).

5-27

Animal High marsh Intertidal

marsh

Tidal channels

Fishes Low-Moderate High High

Waterfowl High Mod.-High Mod.-High

Furbearers High High Moderate

Animal Groups Reproduction "Nursery" Feeding

Fisheries

Finfish

Shellfish

Low

High

High

High

High

High

Waterfowl Low-Moderate Low-Moderate High

Furbearers High High High
Table 5-7. Listing of some of the estuarine-dependent species from the

Gulf and southeast Atlantic coasts (from Odum and Smith,

1981)

(N = nursery dependence, F = feeding by juveniles and adults, and S =

spawning dependence)

Salt Marsh Microbial Co=unities

Within the spartina spp.-Juncus-DiStiChliS spicata communities of

Mississippi and Alabama, 60 species of fungi, yeasts and actinomycetes were

recorded (Stout, 1984) . Plate counts were always highest on the surface.

In below ground plates, counts were always lowest in Spartina alterniflora

areas. A survey of Florida panhandle salt marshes -- dominated by the same

plants -- would likely yield a similar diversity of microbes.

Salt Marsh Invertebrates

In her survey, Stout (1984) found the following invertebrates to be among

the common and abundant animals in salt marshes:

Meiofauna: nematodes, harpactacoid copepods

Insects: flies, bugs, beetles.

Polychaetes: Scoloplos fragilis; Neanthes succinea; Amphicteis

gunneri; Laeonereis culveri.

Molluscs: Littoraria irrorata; Polymesoda caroliniana; Neritina

5-28

Common Name Scientific Name Use

Menhaden Brevoortia spp. N,F

Mullet Mugil spp. N,F

Spotted seatrout Cynoscion nebulosus N,F

Grey seatrout C. regalis N,F

Sand seatrout C. arenarius N,F

Red drum Sciaenops ocellatus N,F

Tarpon Megalops atlantica N,F

Silver perch Bairdiella chrysura N,F

Croaker Micropogon undulatus N,F

Spot Leiostomus xanthurus N,F

Jacks Caranx spp. N,F

Summer flounder Paralichthys dentatus N,F

Striped bass Morone saxatilus S,N,F

Bluefish Pomatornus saltatrix N,F

Shrimp Penaeus spp. N,F

Blue crab Callinectes sapidus N,F

Oyster Crassostrea virginica S,N,F

Bay scallop Argopecten irradians S,N,F
Salt Marsh Birds

Stout (1984) reported that five orders and 41 species of birds were known

to nest, roost, forage or visit salt marshes of the northern Gulf of

Mexico. While her list is not repeated here, we note that birds are

trophically important components of salt marsh food webs: as consumers

(predators, scavengers, seed eaters); prey (eggs, young and adults are

eaten by raptors, mammals, snakes); and as contributors of nutrients via

their fecal deposits.

Data Gaps

The post-hurricane areal extent and species composition of salt

marshes has not been adequately assessed.

Except in general terms, nutrient cycling via microbial and detrital

food webs within salt marsh areas of panhandle coastal ecosystems

have not been sufficiently investigated.

usnea; Melarnpus bidentata; Cerithidea scariformis; Detracia

floridana.

Crustaceans: Halmyrapseudes bahamensis; Cyathura polita; Palaemonetes pugio; P. interrnedius; Callinectes sapidus; Uca spp.

Salt Marsh Fishes

Fishes species listed by Stout (1984) as common representatives of salt

marshes are presented in Table 5-8. As with most of the non-insect

invertebrates, most of the fishes listed are not salt marsh-limited, and

are frequently collected in nearby sand flat, seagrass and oyster reef

habitats.

Table 5-8. common fishes found in salt marshes (from Stout, 1984).

Conunon Nate Scientific Name - Status

tidewater Menidia beryllina permanent

longnose Fundulis sirnilis permanent

Gulf killifish F. grandis permanent

marsh killifish F. confluentis permanent

sheepshead Cyprinodon variegatus permanent

diamond Adinia xenica permanent

sailf in molly Poecilia latipinna permanent

spot LeiostornuS xanthurus nursery user

bluefin Lucania parva permanent

bay anchovy Anchoa mitchilli nursery user

striped mullet Mugil cephalus nursery user

pinfish Laqodon rhomboides nursery user
3. Trophodynamic coupling (i.e. import and export of organic carbon)

between salt marshes and estuaries is unknown, except in general

terms (see Data Gaps 1 and 2).

5.3.3.2 Submerqed Aauatic Veqetation (Exc].udina Alae)

The dominant forms of submerged aquatic vegetation (SAy) in brackish waters

are seagrasses. This taxonomic group of plants is emphasized in the

following discussion, along with two non-seagrass species, Vallisneria

americana, and Ruppia maritima. Vallisneria americana is found in

abundance in fresh to slightly brackish water environments (e.g. at the

mouths of rivers discharging into estuaries), and is ecologically important

in these areas. R. maritima is widely distributed in estuarine and

nearshore marine ecosystems, and is the ecologically functional equivalent

of the true seagrasses.

Seagrasses are salinity-tolerant flowering plants which form patchy beds or

meadows in estuarine and coastal marine waters at all but polar latitudes.

They are neither true grasses nor strictly marine (Humm, 1953) . Of

approximately 12 genera of seagrasses worldwide (Dawes, 1987) those from

the northern Gulf of Mexico include Thalassia testudinurn, Halodule

wrightii, Halophila spp. and Syringodiurn filiforrne.

Seagrasses play important roles in the ecology of estuaries, and changes in

their relative abundance can provide a direct measure of changes in the

biological "quality" of an estuary. The decline and ultimate disappearance

of seagrasses in the Pensacola Bay System during the l970s and 1980s, for

example, likely reflected declines in water quality, benthic animal

diversity, and fisheries yields (Collard, 1991). According to the Florida

Department of Natural Resources (1987), "Seagrasses are a valuable part of

Florida's marine environment but they are disappearing at an alarming rate.

Dredge and fill projects and degraded water quality, as well as other

activities, are responsible for their precipitous decline."

Distribution

Major factors which determine the distribution of seagrasses are climate,

salinity, light, and turbidity. These environmental factors and the

difficult-to-define variable known as "water quality" also regulate the

abundance, distribution and growth of seagrasses. Halodule wrightii is

usually found in waters of lO or greater, while Thalassia testudinum is

usually found in water with average salinities greater than 2O%. Ruppia

maritirna is often found in mixed stands with other submerged fresh and

saltwater species. Halophila spp. are usually found in abundance in waters

of near ocean-strength salinities.

In general, seagrass beds cover a greater area in the eastern than in the

western portion of the panhandle (Humm, 1953). Humm (1974) noted that,

"The seagrass beds between Tarpon Springs and Port St. Joe are probably the

most important community of the inner shelf in basic productivity.

Apparently they far exceed the basic productivity of phytoplankton in the

area they occupy, perhaps several thousand square miles of inner shelf
bottom. Humm (1974) also noted that, "Our lack of knowledge of these

seagrass beds is appalling."

BCM Converse, Inc. (1987) reported that, on an areal basis, St. Joseph Bay

contains more seagrass than any other bay in the [western] Florida

panhandle. In total acreage, the St. Andrew Bay system has more seagrass

than any of the other panhandle estuaries. In contrast, Pensacola Bay

effectively lost all of its once abundant seagrasses by 1976 (Collard,

1991). This estuarine system has, since approximately 1955, been one of

the most anthropically impacted estuaries in the Florida panhandle.

The distribution of Florida seagrasses is currently being mapped by the

Florida Marine Research Laboratory (FDEP, St. Petersburg, unpublished

data); their GIS-formatted maps should provide very accurate distribution

and abundance information. Table 5-9 summarizes the distribution of

seagrasses in the panhandle as of 1984.

Ecological Functions

In those estuaries and shallow shelf waters of the panhandle where they

occur, seagrass meadows, and to a lesser extent, smaller patches (seagrass

beds), have a number of critical ecological functions. According to

numerous authors (summarized in Wolfe et al., 1988), these include:

trapping and stabilizing bottom sediments; producing and exporting

photosynthate; serving as direct food sources for invertebrates, some

fishes and green sea turtles; producing large quantities of detritus and

dissolved organic matter; providing substrate for microbes, algae and

invertebrates that are a food source for other organisms; providing refuge

for small and/or young invertebrates and fishes from larger predators;

providing habitat(s) for epifauna, infauna and fishes; and linking trophic

dynamic-biogeochemical cycles of coastal areas. Numerous fishes (e.g.

speckled trout) and commercially important invertebrates (e.g. scallops)

have been reported to require seagrass as nursery areas and/or sources of

forage (e.g., Heck and Thoman, 1984; Zieman et al., 1984; Wooters, 1990)

Counity Structure

Kikuchi and Peres (1977) reported four sub-habitats associated with

seagrasses: sediment fauna; rhizome and stem animals (e.g. amphipods,

bivalves, polychaetes); leaf periphyton (microbiota, anemones, hydroids,

ectoprocts, crustaceans, echinoderms, nematodes, polychaetes, gastropods);

and nekton which swim among the leaves (e.g. crustaceans, fishes). In his

review of seagrass-associated invertebrate communities of thesoutheastern

United States , Virnstein (1987) reported considerable faunal diversity and

temporal variability within and between sites. Many species, especially

decapod crustaceans, were widely dispersed, but dominant species were

similar in most areas. Virnstein observed that while some combination of

crustaceans, gastropods and polychaetes dominated in all seagrass areas,

the structure of communities, even at nearby sites, was widely variable in

both space and time.

Certain species of macrofaunal predators such as Lagodon rhomboides and

Penaeus duorarurn, were found to have a significant impact on invertebrate

5-31
distribution and abundance. These species and others (Lytechinus variabilis, Fasciolaria spp., Busycon spp., etc.), are abundant throughout

Florida seagrass ecosystems.

Table 5-9. Distribution of seagrasses in the panhandle (from Savastano et

al., 1984).

Trophic Considerations

Su.bmerged plant communities trophically link terrestrial, intertidal and

aquatic communitie found in estuarine ecosystems. For example, seagrasses

are important primary producers, consumers of nutrients through both their

leaves and roots, and a source of energy in detrital food webs. Detritus

allows nutrients to be retained in sediments, or recycled by microbiallymediated chemical processes which provide the main source of nutrients for

seagrass growth (McRoy and Barsdate, 1970; McRoy et al., 1972; Zieman,

1987)

Seagrasses are slow to decompose, which may result in a "time release

mechanism" in the detrital cycle (Zieman, 1987) . Detritivores typically

assimilate nutrients associated with detrital microflora with efficiencies

of 50% to nearly 100%-. Cammen (1980), for example, found that 26% of the

carbon requirements, and 90% of the nitrogen requirements of depositfeeding polychaetes were met by their ingestion of microbial biomass

generated from plant detritus. Carbon is exported as particulate or

dissolved organic matter (Fenchel and Jorgensen, 1977; Lee, 1980) . A

generalized food web is depicted as Figure 5-6.

In a study in Texas bays, more than 340 animals were reported to consume

seagrass tissues (Fry and Parker, 1979). However, the energy flow models

of Stewart (1975) and Thayer et al. (1975) estimated that invertebrate

macrofauna consumed about 75% of net primary production. These authors (in

5-32

wacer oay bottom area eagrass

Alligator Harbor 1,637 261

St. George Sound 30,762 3,392

East Bay 3,981 1,434

Apalachicola Bay 20,960 1,125

St. Vincent Sound 5,540 10

St. Joseph Bay 17,755 2,560

St. Andrew Sound 1,906 151

East Bay [St. Andrew] 7,557 464

St. Andrew Bay 10,615 1,029

West Bay 7,118 626

North Bay 2,704 417

Choctawhatchee Bay 34,949 1,252

Santa Rosa Sound 9,947 1,897

East Bay [Pensacola] 14,906 0

Escambia Bay 9,754 0

Pensacola Bay 16,435 627
Toxicity.

Zoop ankton Oxygen

Dead

Bacteria &

Fungi

Detritus

Macrophytes &

Penphyton

Toxicity,

Nutrients

Water Qnality

Food Benthos

Toxi ',Oxygen

Nekton

Man-Induced

Waste Loads

Dead

Solar Radiation, Physical

Hthitat& Hydrodynamics

Supply

Food

Toxicity, Nutrients

A

Supply

Toxicity, Oxygen

Excretion

\xicity, Nutrients

Figure 5-6. Energy flow in a generalized food web (from Seaman, 1985)

5-33
Zieman, 1987) suggested that the predominant pathway of energy flow through

seagrass ecosystems occurs in the following sequence: senescent seagrass

leaves colonized with very large numbers of aufwuchs (fouling organisms)

fall off and drift to the bottom where they decay via microbial digestion,

and/or are eaten by invertebrates which recycle nutrients through the

microbial loop. In addition to the downstream drift of detrital particles,

some nutrient export into adjacent areas probably occurs via the fecal

deposits of motile herbivores (e.g. shrimp, sea urchins) and carnivores.

Stingrays and Propeller Scars

The progressive disappearance of seagrass meadows in the Florida panhandle

has been attributed primarily to dredge and fill projects and degraded

water quality (Florida Department of Natural Resources, 1987). The general

causes of seagrass declines were discussed in an earlier section of this

report (Estuarine Pollution) . Here, two additional causes of seagrass

damage are mentioned. The first (destruction by stingrays) is relatively

minor and biological in nature; and the second (propellor scarring) is a

major, anthropic cause of seagrass destruction that appears to be

increasing, but can be mitigated. Valentine et al. (1994) reported that

stingrays (Dasyatis americana) and sand dollars (Mellita

quinquiesperforata) did not damage the root-rhizome system of Thalassia in

St. Joseph Bay, but caused damage in Zostera beds. Collard (unpubl. data)

found that adult D. sabina and D. americana caused significant damage to

the root-rhizome system of Halodule wrightii in St. Andrew Sound. The rays

made hundreds of one- to two-meter-wide feeding depressions in shoal grass

beds that, during the period of observation (1992-1995) have not recovered.

Stingrays have also enlarged unvegetated patches created by bioturbating

organisms. Sand dollars have not been observed in the seagrass beds in St.

Andrew Sound, although they are quite abundant in su.btidal sand-flat

habitats. Stingrays enter the Sound by the thousands during spring, and

the cumulative impact of their feeding activities has been significant in

controlling the distribution and density of Halodule. It is believed that

stingrays may have a non-trivial impact on 1-lalodule and a lesser impact on

Thalassia in the panhandle estuaries and lagoons used as nurseries by these

animals. Sargent et al. (1995) summarized data on the impact of boat

propeller scarring in seagrass beds. An increase in recreational boating

accompanying recent population increases near panhandle estuaries has

accelerated the destruction of meadows already severely stressed by other

human activities. Most of the scarring observed in 1992-1993 aerial

surveys occurred in water less than 2 m deep. Most scarring was "light"

(less than 5% of the seagrass community was scarred) . The panhandle and.Big

Bend area had the least "medium" and "severe" (> 20%) scarred acreage, but

in western panhandle embayments, "medium to severe" scarring was prevalent

in the few acres of seagrasses still remaining. The authors observed that

in areas with little seagrass acreage, any scarring may have a critical

effect on habitat functions. Halodule was found to recover faster (0.9-1.8

years) than Thalassia (10 years, or never) because of the shallower

rhizome-root system in the former. Halodule is usually the first seagrass

species to recolonize an area.
Table 5-10 documents the acreage of scarred seagrasses to the nearest ten

acres in each Florida coastal county, and Table 5-11 presents the same

information as percentages.

Data Gaps

post-hurricane areal distributions of SAV have not been

documented.

The contribution to primary and secondary production by SAyassociated organisms (epiphytes, drift algae, motile invertebrate

species) is unknown for most of the region. For example, while St.

Andrew Bay, St. Andrew Sound, and St. Joseph Bay are geographically

close neighbors, SAV in each system supports significantly different

assemblages of epiphytes, which may be reflected in different

community trophic structure (Collard, unpubl. data).

Trophic coupling between SAy, marsh and oyster reef communities

has not been determined.

The meaning of "SAy-dependent", especially with respect to fishes

(e.g., Cynoscion nebulosus) is often unclear or problematic.

The true cause(s) of SAV die off s in most panhandle estuarylagoon systems have not been determined.

5.3.3.3 Oyster Reefs

Oyster reef communities form the structural and functional bases of the

preeminent hard-substrate faunal assemblages found in panhandle estuaries.

Crassostrea virginica is the keystone species of a reef biocenosis that

includes several hundred species (Wells, 1961). Because they inhabit

estuaries which are increasingly surrounded by people and their waste

products, these animals are particularly vulnerable to anthropic stressors.

Large, episodic swings in the health and abundance of oyster reefs are

relatively common, and localized mass mortality events are not uncommon.

Prolonged periods of low dissolved oxygen levels during periods of warm

weather and intense water column stratification, may severely stress, and

sometimes cause the death of oyster communities. The susceptibility of

oysters to microbial pathogens (Vibrio spp., Pseudomonas spp. and Perkinsus

marinus) also increases when water temperatures are high; P. marinus may be

the cause of mass mortalities in C. virginica. Oyster reefs may be

suffocated by excessive sedimentation from floods, storms, or dredge and

fill operations. The impact of dredging on oyster communities has long

been a subject of controversy (e.g. Florida Department of Environmental

Regulation, 1984; Isphording et al., 1984; Schropp and Windom, 1988;

Goldberg, 1990). Regardless of the method used to remove or displace

sediments, some increase in turbidity always occurs in the immediate

vicinity of the dredging site. Clearly, however, the degree to which

turbidity increases, length of time it persists, size of the affected area,

duration of time that non-particulate sediment constituents remain in the

water column, and sedimentation rates and fallout patterns, depend upon a

wide range of chemical (e.g. toxic substances in the sediments) and

5-35
Table 5-10. Acreage of scarred seagrasses to the nearest ten acres in each

Florida coastal county (after Sargent et al., 1995).

(Light scarring presence or scars in less trian ot tne ae.i.ini.0 pyci;

moderate scarring = 5-20%; severe scarring = more than 20%.

physical variables (e.g. local current patterns), as well as the relative

proximity of the dredge site to oyster reefs and co-occurrence of other

stressors. Since, in the aggregate, these variables are unique at and in

the vicinity of each dredging location, any speculation about the qeneral

impact of dredging on oyster communities would be frivolous. In a worst

case scenario, a relatively large volume of hopper-removed, contaminated,

fine sediments, dredged from a stressed (e.g. eutrophied, polluted) estuary

in mid-summer, near a stressed oyster reef, disposed overboard near the

reef, could suffocate and/or poison, and/or severely depress the health of

the community.

Increased turbidity would decrease downwelling light levels, and

algae associated with the reef would die;

Suspensionfilter-feediflg animals (including oysters, polychaetes,

ascidians and the like) would suffocate;

With the death of reef-associated organisms, biological and chemical

oxygen demand would increase, and depress dissolved oxygen levels;

5-36

CoUnty

Acreage

Total

Light

Scarring

Moderate

Scarring

Severe - ScarringMod/sev.

Scarring

Total

Scarring

Bay 10,530 4,050 820 80 900 4,950

Dixie 111,130 2,470 1,020 0 1,020 3,490

Escanibia 2,750 510 180 10 190 700

Franklin 19,840 440 370 0 370 810

Gulf 8,170 4,200 530 110 640 4,840

Jefferson 10,500 420 80 0 80 510

Levy 132,400 9,970 120 0 120 10,090

Okaloosa 3,450 310 80 0 80 390

Sta. Rosa 2,270 450 110 0 110 560

Taylor 162,860 8,100 60 0 60 8,160

Wakulla 29,630 2,060 730 0 730 2,790

Walton 710 10 0 0 0 10

State

Totals

2,658,290 109,870 48,630 15,470 64,100 173,960
Table 5-11. Percentage of scarred seagrasses by intensity level within each

Florida coastal county (after Sargent et al., 1995).

Dredging would, under these possib.Le, but unJUeJ.y circumstances,

or all of the following consequences:

individual animals, if not killed by the direct or indirect impacts

of sedimentation, would be highly stressed, more susceptible to

disease and predation, and unsuitable for human consumption;

The availability of hard substrate for recruiting spat would be

reduced;

6 .Reproductive success would decrease for all members of the

community;

7. The oyster community would be replaced by fugitive or opportunistic

species of polychaetes, small bivalves and amphipods.

The U.S. Army Corps of Engineers is well-aware of the consequences of

dredging under such conditions, and is required to avoid them when

possible. Contractors may not be as knowledgeable. The more likely

problem with dredging in estuaries is that: (1) the location and extent of

viable oyster reefs may not have been adequately documented prior to

dredging; (2) the health of oysters potentially threatened by dredging may

not have been recently assessed; (3) contaminants in sediments to be

5-37

coty

Percent

Total

Light

Scarring

Moderate

Scarring

Severe

Scarring

Mod/sev.

Scarring

Total

Scarring

Bay 10,530 3.7 1.7 0.5 1.4 2.8

Dixie 111,130 2.2 2.1 0.0 1.6 2.0

Escambia 2,750 0.5 0.4 0.1 0.3 0.4

Franklin 19,840 0.4 0.8 0.0 0.6 0.5

Gulf 8,170 3.8 1.1 0.7 1.0 2.8

Jefferson 10,500 0.4 0.2 0.0 0.1 0.3

Levy 132,400 9.1 0.2 0.0 0.2 5.8

Okaloosa 3,450 0.3 0.2 0.0 0.1 0.2

Santa Rosa 2,270 0.4 0.2 0.0 0.2 0.3

Taylor 162,860 7.4 0.1 0.0 0.1 4.7

Wakulla 29,630 1.9 1.5 0.0 1.1 1.6

Walton 710 0.0 0.0 0.0 0.0 0.0

State

Totals

2,658,290 4.1 1.8 0.6 2.4 6.5
dredged may not be known; (4) local current and mixing patterns may be

variable and/or unknown; and (5) pre-dredging assessments, monitoring, and

post-dredging assessment may be superficial, or not made at all. One or

more of these five (of several other possible) problems may have adversely

impacted oyster reef communities in panhandle estuaries, but there are no

published data with which the question can be answered.

Major predators of oysters include Busycon contrarium, Thais haemostoma,

Callinectes sapidus, Menippe rnercenaria, Melongena corona, Urosalpynx, many

other invertebrate predators, fouling and boring organisms, birds (e.g.,

herons, gulls), and mammals (e.g., raccoons, humans) . Predation is reduced

in salinities below about l5t, which excludes some snails (e.g., Thais)

and crabs (e.g., Menippe).

Since the ecological importance of oyster reefs is high, information on the

distribution and area occupied by these animals is desirable. However,

published estimates of area coverage must be used with caution, because the

impacts of 1995 hurricanes on oyster reef communities in panhandle

estuaries, while believed to have been extensive, have not been documented

(FDEP, pers. comm.) . Pre-hurricane (1993) data on some oyster harvesting

areas are summarized by Paulic and Hand (1994)

Apalachicola Bay supports the largest number of oyster reefs in Florida

and, despite periodic fluctuations as noted above, it is likely to retain

its viable oyster reef communities. Other estuaries in the panhandle also

had extensive oyster reefs, but their size has diminished greatly in the

past two to three decades. It is suspected that the magnitude of loss in

oyster reefs may be similar to that of seagrass meadows.

Depending on latitude, oysters in the northern Gulf generally spawn from

March through October, when water temperatures reach and remain above 20°C.

Mass spawning generally occurs at temperatures above 25°C. (U.S. Army Corps

of Engineers, 1982, 1984). According to these authors, larvae drift in a

westerly direction along the coast, and settle on any hard (or compact)

substrate available. Physical oceanographic data on longshore drift do not

entirely support the view of a general westward transport of planktonic

oyster larvae.

The volume of water filtered by oysters is prodigious. Estimates are as

high as 1500 times body volume per hour, independent of food, tide or time

of day (U.S. Army Corps of Engineers, 1982, 1984). As suspension-f ilterfeeders, oysters rival the benthic turiicates (Collard, 1993)

5.3.3.4 Data Gaas

Biological organisms associated with oyster communities (especially

microbes and algae) need to be assessed in terms of total community

production.

Quantitative post-hurricane damage assessments need to be made and

recovery rates monitored.

Inter-community trophic coupling needs to be assessed (e.g. SAy5-38
oyster reefs and bars; oyster reef-muddy bottom infaunal

communities).

5.3.4 Estuarine Oraanisms and Communities

5.3.4.1 Primary Production

Discussions of primary productivity or production conventionally begin with

taxonomic or narrative descriptions of producing communities, followed by

estimates of the relative contributions made by each taxonomic group (as

rates or yields) to the total amount of carbon fixed per unit area per unit

time. Such values, when measured over a lengthy period of time, using

multiple methods (to mitigate the inherent flaws of each method), are

useful when: (1) comparing the relative productivity of different

geographical areas or ecosystems; (2) evaluating the assimilative capacity

of a body of water for nutrient loading/processing; (3) using the

distribution and quantities of chlorophyll as indicators of physical

oceanographic processes (upwelling, frontal boundaries); or (4) using

chlorophyll as an indicator of stress in eutrophic estuaries.

Quantitative measures of productivity, in whatever form, and however

carefully obtained, are estimates that must be used with caution in energy

f low models.

Most surveys of primary producers in the water column emphasize large

organisms, the diatoms and dinoflagellates. While important to total water

column production, microflagellates, other naimophytoplankters and

picoplankters (prochiorophytes, photo- and chemosyrithetic bacteria) likely

produce more, or much more photosynthate (organic compounds) than the first

two groups.

In estuarine waters, there is often, but not always, a general increase of

primary water column production with increasing salinities (toward the

mouths of estuaries). Water column production is, however, considered by

most authors to be less, or much less than the total production of

seagrasses, their epiphytes, benthic algae, diatoms, bacteria, and

cyanophytes. Water color, turbidity, salinity, nutrient availability,

flushing rates, the presence/absence of toxic substances and herbivorous

zooplankton are some of the many variables that influence variation in

estuarine production. Primary production in nearshore shelf waters is also

variable, and depends on those factors mentioned, as well as distance from

shore. In general, nutrient levels and primary production decrease, and

species diversity increases with distance from shore, except in areas of

upwelling or frontal zones convergences. These latter regions, themselves

variable in location and intensity, concomitantly support higher numbers of

consumer individuals.

Data Gaps

i. Water column and benthic primary and secondary production are

coupled in complex, poorly understood ways. Peaks of benthic

secondary production may occur in the same area, or some distance

away from areas of high primary water column production. These

relationships require investigation.

5-39
Relationships between the microbial loop, water column, and benthic

primary production need to be elucidated.

Relationships between "water quality" (e.g. transparency, nutrients,

toxicants) and primary production need to be evaluated.

Relationships between levels of seasonal primary production and

benthic species diversity need to be assessed.

Primary producers other than diatoms, dinoflagellates and seagrasses

need to be assessed in terms of their contribution to total carbon

fixation.

5.3.4.2 Zoolankton

According to numerous authors (e.g. Hopkins, 1973), the copepod, Acartia

tonsa, is the principal holoplanktonic species in terms of biomass in

estuaries of the eastern Gulf. The zooplankton biomass peaks during summer

months, and increases with increasing salinities within estuaries (Hopkins,

1973) . Seasonal incursions of ctenophores and chaetognaths into higher

salinity estuaries, however, can result in rapid declines in zooplankton

species diversity and numbers.

Shelf waters of the Gulf of Mexico advect a wide variety of meroplankton

species into panhandle estuaries. These plankters fetch up in areas where

the watermasses in which they are embedded take them. When appropriate

biological, chemical or physical settlement cues and substrates are

present, meroplankters leave the water column, metamorphose and become

members of the benthos (Collard, 1991). Thus, whether or not a particular

benthic species is present or absent in a given estuary during a given

season or year, depends to a large extent on whether its pelagic larval

stage was transported into the estuary by currents.

As an example, Livingston (1984) reported that 92% of the eggs and 75% of

the larval ichthyoplanktofl in Apalachicola Bay were Anchoa mitchilii in

1975. Of the non-fish zooplankton, the copepod, Acartia tonsa, made up

92.5% of the catch in East Bay, and 68.2% in Apalachicola Bay. Barnacles

made up 11.7% of zooplankton catches. Menzel (1971) reported that the only

abundant zooplankters in Apalachicola Bay were the calanoid copepods

Acartia tonsa, Anomalocera ornata, Labidocera aestiva and Paracalanus

crassirostris.

The reported abundances of Acartia tonsa and Anchoa mitchilli in

Apalachicola Bay are not remarkable, and agree with the findings of, for

example, Hopkins (1966) in St. Midrew Bay. Labidocera aestiva and the

other calanoid species reported by Menzel (1971) were also found by Thrner

et al (1979) in shelf waters of the panhandle.

The apparent paucity of zooplankton species listed in the previous two

paragraphs should not be misinterpreted. Zooplankton assemblages of

Apalachicola Bay waters are very diverse, as evidenced by the diversity of

benthic species whose eggs and/or larvae are members of the meroplankton.
Data Gaps

The relationship between meroplankton and adult benthic communities

in estuaries has not been adequately investigated. Whereas the

water column may be of sufficient quality to support the eggs and

larval stages of species that metamorphose and become members of the

estuarine benthos as adults, sediment conditions may not support

them following this habitat shift. This information would provide a

much more accurate measure of estuarine conditions than is presently

available.

Seasonal recruitment and export of larvae into and out of estuaries

to/from coastal waters is poorly understood. It might be assumed,

for example, that estuarine species diversity is high/low because of

good/poor water/sediment conditions, when these measures of

biological quality are actually the result of good/poor recruitment

from shelf waters. This problem is one of a number of difficult,

but important questions that involve coupling between the embayments

(estuaries and lagoons) and shelf waters of the panhandle.

Flushing times under given tide and river flow conditions are not

accurately known for any of the panhandle estuaries. Average

flushing rates are of very little practical or theoretical value.

For example, planktonic stages of species that require a period of

time in brackish environments for development will perish

(regardless of water or sediment quality, or substrate suitability

and availability) if flushing rates are too slow, too rapid, or too

variable. In the latter instance, higher than predicted seasonal,

annual (or longer period) variability in benthic species assemblages

may occur.

The advection of large numbers of non-fish plankton predators (e.g.

chaetognaths, ctenophores, jellyfish, chondrophores) into an estuary

may rapidly reduce the diversity and abundance of other zooplankton.

Unless these predator "blooms" have been accounted for, reductions in

plankton abundance may be erroneously attributed to degraded water

quality conditions. When the inevitable dieoff of such predators

occurs, and their bodies sink and decay, biological oxygen demand

increases, and dissolved oxygen levels decrease, which may

precipitate not only fish mass mortalities, but benthic invertebrate

dieoffs. These occurrences have occurred in the Pensacola Bay

system (Collard, 1991), and were attributed to "pollution".

5.3.4 .3 Benthic Macroinvertebrates

Wolfe et al. (1988) stressed that, "The short and very arbitrary naming and

delineation of habitats are made with the following caveats: (1) the

environment is a continuum of habitats, each one unique (e.g. not each

oyster reef is exactly the same), each one dependent to varying degrees

upon the others, and (2) many organisms use multiple habitats during

different times of the day or different life stages and, therefore, cannot

be assigned precisely to a single habitat." This point should be regarded

as given throughout the following discussion.

5-41
Factors Controlling the Distribution of Benthic Invertebrates

Scanland (1966) noted that, "No single abiotic factor may be said to be

most influential in determining the absolute composition of a community."

Numerous abiotic factors and conditions influence the species composition

of benthic invertebrate communities and, as noted earlier, most of these

are highly variable, particularly in estuaries. Temperature, salinity,

turbidity and other environmental conditions (sediment chemistry, dissolved

oxygen, etc.) in a given region or estuary vary at different magnitudes and

at different time scales. We presumptively assume that abiotic variables

within a given habitat have different impacts on each species within the

habitat. Because neither the scale of overall variation nor the degree of

impact of these variables on species or communities are known, the

following discussion of habitats is general in scope.

Suitable abiotic environmental conditions are pre-conditions for the

presence or absence of each species found in a given habitat-type.

However, species richness, community structure and function are, in large

part, the result of complex biological interactions involving predation,

competition, physiological tolerance limits, and the attributive

characteristics of populations, including their fecundity and longevity.

Unfortunately, except for commercially important species (blue crabs,

oysters, scallops, penaeid shrimps, some hard clams), little is known about

the natural history or population biology of panhandle invertebrates. It

is assumed that representatives of the several feeding guilds (direct and

indirect deposit feeders, suspension-filter feeders, carnivores,

herbivores, omnivores) contribute to the production, consumption and

processing of energy in each of the estuarine and shelf habitats discussed.

It is not presently possible to provide quantitative information on the

contributions to energy flow made by individual species.

The physical and chemical characteristics of sediments play a crucial role

in the organization of benthic habitats and biological communities. In

estuaries, sedimentation rates are generally much higher than in the ocean,

and the transport and re-suspension of fine-grained sediments is more

frequent and of greater biological consequence.

The duration of annual minimum water temperature controls the

distributional limits of many benthic species. Seasonal temperature

fluctuations are larger in western than in eastern panhandle nearshore

environments, and variation in faunal abundance and species diversity

appear to be greater west of Cape San Blas than in the Big Bend area.

Hedgpeth (1954) suggested that as waters cool, there is a general exodus of

animals from estuaries into the Gulf. While motile species (e.g. Penaeus

spp.) may be cued by cooling water temperatures to migrate from estuaries

to the Gulf, other authors have reported that infaunal species diversity in

western panhandle estuaries reaches a maximum during cooler months

suggesting that there may be an inverse relationship between water

temperature and benthic invertebrate abundance in western panhandle

estuarine systems.

Salinity fluctuations of as much as 30 ppt occur episodically in panhandle

estuaries during periods of droughts and floods. Pulse or longer term

5-42
(days) elevations or decreases in salinity can result in mass mortalities

of sessile organisms.

Data Gaps

Most of the data gaps mentioned in the previous section

(zooplankton) apply to deficits in our understanding of benthic

invertebrates.

Difficult, and perhaps intractable problems exist in the general

area of translating (micro- or mesocosm) toxicity test results from

laboratory conditions to natural communities. This has been a muchdiscussed subject, and space does not permit a review here. The

major points to be made are: (1) species tested in laboratory

environments often do not (or can not) live in the environments for

which laboratory conditions are meant to be surrogates; (2)

elements, chemicals and compounds used in bioassay experiments are

often in different form (e.g. oxidation state, ligand-bound) in the

laboratory than in field conditions; (3) interactions with other

compounds are usually not accounted for in laboratory tests; and,

most importantly (4) marine organisms do not live in statistical

environments - they live in real ones.

Biogeographic Provinces

n unknown number of benthic macroinvertebrate species are distributed

throughout the estuaries and shelf waters of the Florida panhandle. Based

on species lists compiled by various authors, it is suspected that the

number is relatively large. BCM Converse (1987), for example, noted that

the polychaetes, Axiothella mucosa, Heteromastus filiforrnis, Laeonereis

culveri, Prionospio heterobranchia and Streblospio benedicti) are found in

shallow water sand and seagrass habitats from Miami to Apalachee Bay.

These species are also common in the western panhandle (e.g. Hydroqual,

Inc. and Barry A. Vittor & Associates, Inc., 1993) . The wide distributions

of such species, many of which are numerically abundant and ecologically

important, makes it difficult to identify distinct biogeographical

provinces in panhandle coastal waters, and brings into question the reality

of such boundaries or their geographical limits.

As a result of their work on benthic communities in Biscayne Bay, McNulty

et al. (1962) concluded that, "Clearly no generalization can be made from

the Florida data." .xnong the decapod crustaceans, Williams (1965) estimated

that only ten percent are disjunct at peninsular Florida. Abele (1970),

regards the Carolinian Province to be a transitional area, not a faunal

province or a biogeographical unit. It is recognized for heuristic

purposes, that certain estuarine and inner shelf habitats are putatively

West Indian, Transitional, or Carolinian, primarily in terms of their

correspondence to climatic (i.e., temperature) regions.

Benthic Invertebrate Comuriities

Panhandle brackish and marine benthic invertebrate communities are

identified and defined by their dominant species, which are recognized as

5-43
being diagnostic of and usually abundant in the community which they

characterize. Examples of these species are included in Peterson-like

habitat diagrams from Collard and D'Asaro (1973) shown in Figures 5-7

through 5-10. "Dominant" species are members of conspicuous and

comparatively well-studied taxa. Many numerically important groups (e.g.

nematodes, foraminiferans, platyhelminths, sponges, small crustaceans) are

poorly known in the panhandle and, except in general terms, their roles in

benthic communities are unknown. Noting the cautions written by Wolfe et

al. (1988)1 seven types of brackish-marine benthic macroinvertebrate

communities found in the Florida panhandle are identified. These

communities are not mutually exclusive and have fuzzy boundaries. However,

the assemblages summarized as habitat diagrams represent the major

recognizable benthic invertebrate habitats of the Florida panhandle.

Marsh and Delta [Low Salinity] Cossnunities

Marshes and deltas are characteristically low salinity, low energy

environments with organically rich bottom sediments. These conditions

exclude all but transient stenohaline species, and benthic communities are

comprised of a mix of freshwater and marine animals. Grass shrimp

(Palaemonetes), fiddler crabs (Uca spp.), and marsh snails (Littoraria

irrorata, Neritina reclivata) are common. Figure 5-7 depicts a cross- -

section of characteristic species found in low salinity areaa (marshes and

deltas) of the panhandle (Beccasio et al., 1982; Stout, 1984; Livingston,

1984; Myers and Ewe]., 1990; NOAP, 1990; Field et al., 1991; Hackney et al.,

1992). Salt marsh communities occur at the margins of most panhandle

estuaries and lagoons. True deltaic communities, while not as ubiquitous

as non-deltaic marshes along the panhandle coast, are common features of

the larger rivers (e.g. Yellow and Apalachicola Rivers)

Oyster Reef Conununities

Oyster shells and the spaces between their valves and shells provide a

complex, three-dimensional hard substrate habitat for many species that

would not be found in the absence of Crassostrea virginica, a keystone

species (Figure 5-8). Oyster reefs are most abundant in Apalachicola Bay.

Bay and Sound Counities

Bays and sounds are brackish water environments most of which, when not

significantly stressed by humans, support an abundant and diverse benthic

fauna. The benthic invertebrates of panhandle bays and sounds are characterized by oyster reefs, and mixed polychaete, peracarid crustacean

(amphipods, isopods, tanaids), molluscan (small bivalves and gastropods),

echinoderm (infaunal synaptid holothurians, epifaunal sea urchins and sand

dollars) and penaeid shrimp communities (Figure 5-9) . Seagrass meadow,

oyster reef and hard ("live bottom") habitats support the most diverse

assemblages of microbes, algae, microfauna, meiofauna, macrofaunal

invertebrates and fishes in bays and sounds. However, non-vegetated, nonreef bay bottoms (sand, mud, peat, shell hash) are also inhabited by very

large numbers and species of microbes, algae, invertebrates and fishes

whose ecological role in food webs is crucial to the function of bay and

sound ecosystems. St. Joseph Bay (arguably the least impacted bay-sound

5-44
vc = very common

c = common

r = rare

Liftenna jnv,aaa (nC)

UCa pugnax (C) Neritjna mdfivata (vC)

Uca pugifator (c)

Rangia cuneato (vc)

ModioluS demissus (vc) ) Macmbrach,um onion. (r)

Paiaemoneies pugio ()

P. vulgans (C)

N

Macoma togeIfforin (C) M. mitchefli (C)

Potynesoda carolin,ana (C)

Figure 5-7. Low salinity marsh and delta macroinvertebrate communities

(after Collard and D'Asaro, 1973).

5-45

A A

V.

ProcambaruS blandingi (uc)

MUD BANK TIDAL CHANNEL SPARTINA MARSH

lJca minmax (vC)
Figure 5-8. Schematic diagram of a characteristic oyster reef community in

Panhandle brackish waters (after Collard and D'Asaro, 1973)

5-46

Crassotrea virginica (vC)

Balanus amphitrite (vc)

B. ebumeus (vc)

Oostomia impresse (C)

StyloChus fronta!is (oc)

Menippe ma,00nana (C)

Mit,pJla lunate (c)

Anaphis ovate (vc)

A. obese (C)

Cliona vastifica (c)

Thais haemastoma (vc)

Ophiothiix angulata (vC)

- SAND

/

-

--.

.'.

rvr v-rJm.r,SjN,-S,

REEF

Anaara simplex (C) Neopanope texana (c)

Clibananus viftatus (C)

Bugula sp (C)

Membssnpom s (c)

Anomie simplex (C)

Ostma aquestns (c)

Crepidula plane (C)

C. fomicata (vc)

B,achidontes recu,vus (vC)

9. exustus (vc) Aiptasia pallida (vC)

SANfl

Polirnosa duplicatus (r)

Chione canoellata (r)

.

Neanthus sunea (c)

Polyriora websten (C)

. /

>

:

Magelona Corona (r)

vc = very common

C = common r = rare
FORESHORE TROUGH OFFSHORE

albicans (c)

MHWST NLWST

Ca&anassa er()

. canc.

Somna

Tag&us4ss.v) Tmo'rjcajmmusic.bim (tc) Ia4c) Anac) C$ui*oce(c

Pomis8,c

c.eftiptus sped.fls(c)

agunJsJpus

albanasius 1ffaWs (C)

Nassarnis vfbar(c) Fascoiwa hunf (C) m a,ab1e (vs)

lexana (a)

GRASS

Bu,eatella !i (C) Aipcea1sn inwi.ns (c LyteQà)uS va,aWs (

Biftium valium ()

Cascum nilidum (by)

C. puldIellum (by) blan*poea su,ea (C)

Melan,pus bWenWWS (C

Aiuduius modulue (C)

flgu'a fasnieta (C)

Anodcntj,alba (c)

Cebraluluslanieus(c)

Limulu$

1Y.apalracupleajbc) ACCi.0 Lhata(C) Onuptasnalgnafrc)

us (C)

Refuse canehculafa (c)

Abraaequalls(c) =CrblcuAbecta (c)

Nuaaftac,

.eidOta6*,eefa (c) r4*jm,e (

MLWST = mean low water spring tide

a = abundant

vc = very common

c = common

r = rare

Figure 5-9. Bay and sound macroinvertebrate communities (after Collard and

D'Asaro, 1973)

5-47
system in the panhandle), and other examples of this important community

are provided in characterizations of individual bay systems in subsequent

sections of this chapter.

Hard Substrate and Fouling Counities

Hard substrates (including oyster shells, man-made structures and trash)

evolve through increasingly complex successional seres into complex,

sheltered environments inhabited by annelids, nudibranchs, tunicates,

hydroids, turbellarians, shrimps, nemerteans and the vulnerable young

stages of many species. Such communities provide forage for predators

(e.g. stone crabs, drills, nereids, carnivorous gastropods), and

scavengers (e.g. Melongena, Callinectes, Pagurus, Petrochirus) . A

composite hard substrate community is shown in Figure 5-10. Fouling

communities are found at all depths in panhandle marine and brackish

waters. They are especially conspicuous in the lower intertidal and

subtidal portions of pier pilings in ports and marinas where salinities

average 20 ppt or greater. These communities are also found on

breakwaters, suspended ropes and cables, artificial reefs, oyster reefs,

discarded tires, abandoned crab traps, ship's hulls (including those with

copper sheathing) and, in a strict sense, on seagrass blades. Among the

most conspicuous year-round members of fouling communities in the panhandle

are the solitary tunicates, Styela plicata, and their colonial

relatives,Dideznnum spp., Distaplia berrnudensis, Diplosc'ma spp., and

Amouricium constellatuin, and the barnacle, Balanus eburneus. The bryozoan,

Bugula neritina, and various species of filamentous green algae are

abundant during cooler months.

Fouling assemblages are considered to be a sub-category of hard substrate

communities. As described by Wolfe et al. (1988), panhandle fouling

community development occurs in the following predictable sequence. The

first organisms to colonize clean substrates are slime-producing bacteria,

diatoms and cyanophytes. Depending upon the type of substrate (wood,

plastic, metal, etc.), water depth and temperature and, especially, larval

availability, this first sere may persist for periods of days to weeks

(Collard, unpubl. data).

After "processing" by microbes, substrates are colonized by barnacles,

gammarid and caprellid amphipods, bryozoans, tunicates, hydroids, young

gastropods and bivalves. Most of these organisms are suspension or filterfeeders. Again, depending on temperature, larval availability and,

perhaps, phytoplankton and meroplankton abundance (Collard, unpubi.), a

fairly rapid increase in species diversity may occur, followed by an

extended period of gradually increasing species settlement. Successful

animals (e.g. tunicates, bryozoans, sponges) often grow rapidly, decreasing

available space in some cases (e.g. on substrates dominated by colonial

tunicates with antifouling chemicals in their tests), or increasing space

with their own bodies, shells, etc. Following a sometimes rapid, sometimes

extended period of increasing complexity and density, stabilization of the

community occurs with the loss or decrease in abundance of some species.

Tunicates such as the common sea squirt, Styela plicata, may simply tear

away from vertical substrates because of their weight; other species are

preyed upon by fishes or invertebrates (e.g. crabs) . After full

5-48
Ano.ria simplex (,) Bunodcsoma emata (i

S41a pedb (C) S. Øce (C) cieXuia ftnta (c) clone W (iv) Tubulede eiodea (C) Rudenddum meum (c)

Pennaxia daelle (C) flaW

Cantha,us DncWs(C)

P.*,bmn!poi'a ap. (c) A,baaW puni4eta (by) Menippe me,nade (C) Pethea annefus (C) S*Bsbce. sidesa (c)

Mu,ax M,aoefle (c) Dmsida annsis(C) Anipht'teama (c) lvide$ us(C) Mulgule man (C) AoonapmWefa (c)

Imiflia fasricuieta (C)

Leptogora WVuIaW (vc)

Figure 5-10. Composite hard substrate community (after Collard and

D'Asaro, 1973).

5-49
development, fouling communities tend to be dominated by a few large,

persistent species such as sponges, solitary or colonial tunicates and

barnacles that support a continuously changing assemblage of sessile and

motile associated organisms (Collard, unpubl.data) . In western panhandle

estuaries and lagoons, seasonal temperature decreases result in the

disappearance of a majority of species and recolonization during spring

seems to follow the "broken stick" model of MacArthur.

5.3.4.4 Fishes

As a group, adult estuarine and marine fishes (including elasmobranchs) in

panhandle waters are much better known than the invertebrates. Most of the

fishes have been described taxonomically, and their distributions are

adequately known. However, detailed information about the natural history,

reproductive biology, population dynamics and trophic dynamics of most fish

species is scarce. This is especially true with respect to the biology of

sharks and rays, some of which are estuarine-dependent.

Comp and Seaman (1985) reported that, "Most estuarine-dependent species [of

fishes] are spawned in offshore coastal waters, then migrate to the

estuaries where a variety of habitats such as mangrove forests, marshes,

seagrass beds, oyster bars, and sand and mud flats offer food and

protection from predators." These authors also pointed out that (the same)

ten or fewer species of fishes were numerically dominant (70% or more of

the number of individuals, regardless of the total number of species or

individuals captured) in most of Florida's estuaries. The two most

abundant species collected in estuaries were the bay anchovy, Anchoa

mitchilli, and the pinfish, Lagodon rhomboides.

The diversity and abundance of fishes in a given panhandle estuary vary

seasonally and year to year. Species whose eggs or larvae are recruited

from Gulf waters via advective transport depend on favorable upstream and

local conditions (e.g. winds) that move them into or out of estuaries at

appropriate times in their life cycles. After entering estuaries, eggs,

larvae and adults require suitable environmental conditions (i.e., water

quality, salinity), forage (e.g. detritus, phytoplankton, zooplankton,

benthos), and habitat (e.g. salt marshes, seagrasses, oyster reefs) in

order to survive, grow and/or reproduce. In like fashion, eggs and larvae

produced in estuaries, must find egress via currents that transport them

offshore into suitable environments.

With respect to numerically abundant, widely distributed panhandle

estuarine species, Kobylinski (1979) reported that MicropogoniaS undulatus

(croaker) are omnivores, and feed on polychaetes, harpactacoid copepods,

detritus and bivalves. Leiostomus xanthurus (spot) forage chiefly on

polychaetes and detritus, Of the two most common species, the bay anchovy

(Anchoa rnitchilli) preferentially feeds on calanoid copepods but also

consumes other zooplankters. A. rnitchilli is in turn consumed by the

common species, Cynoscion arenarius. The pinfish, Lagodon rhornboides,

changes its preferred diet with age and, at various stages in its life

cycle, feeds on seagrasses, aufwuchs, grass shrimp and other small

invertebrates. Direct observation suggests that pinfish are opportunistic

feeders (Collard, unpubl.) . Table 5-12 summarizes the dominant species of

5-50
fishes in the Crystal River, Cedar Key, Apalachicola Bay and St. Andrew Bay

estuaries. Species reported to occur in individual panhandle estuaries are

treated in subsequent sections of this chapter.

5.3.4.5 Threatened and Endanqered Species

Endangered, threatened, rare, special concern, and other categories of

animal and plant species in Florida have been variously defined by federal

and state agencies, as well as by committees of professional biologists.

In the coastal panhandle region, as elsewhere in the state, many more

plants than animals have been identified as endangered or threatened in

some way; many more vertebrates than invertebrates have been so classified;

and more fresh water than marine species are recognized as under some

threat or potential threat of harm or extinction. U.S. News and World

Report (December 24, 1995, p. 28) listed the Florida panhandle coastal zone

as one of six regions in the country (including Alaska and Hawaii) where

wildlife is in the greatest danger.

An official list of endangered and potentially endangered fauna and flora

in Florida was published by the Florida Game and Fresh Water Fish

Commission (7 volumes, June, 1994)

Panhandle-region species having special status include: subspecies of the

Atlantic sturgeon; the green, hawksbill, Kemp's ridley, and leatherback sea

turtles (endangered); the loggerhead sea turtle (threatened in Florida);

West Indian manatee (especially in the Suwannee River); sperm whale (edge

of the continental shelf); Cuban snowy plover (a rare summer breeder on

outer beaches and bars); least tern (a summer resident), and the various

subspecies of beach mice found on barrier islands (Beccasio et al., 1982).

It appears that populations of subspecies of the beach mouse, Peromyscus

polionotus (i.e., west of Perdido Inlet, Perdido Key, Santa Rosa Island,

Destin to Panama City mainland, and St. Joseph Spit) were significantly

impacted during Hurricane Opal. Additionally, sea turtle eggs that had not

hatched prior to this hurricane were killed by salt water. Anecdotal

information suggests that some hatchling and post-hatchling turtles

perished by being cast ashore during the storm. Island and mainland

beaches in the western panhandle were so heavily impacted by storm surge

and waves that shorebird and sea turtle nesting areas were destroyed or

significantly reduced in size.

5.4 Florida Panhandle Estuaries

Thw following sections discuss the major Florida panhandle estuaries in

order from west to east. Of necessity the discussions under various

categories are not to the same level of detail for all estuaries. The

section headings are the same for each estuary. As in previous sections

data gaps are identified where appropriate.

5.4.1 Pensacola Bay

The discussion in this section is based largely on Collard (1991) except

where noted otherwise.
Table 5-12. Percent of dominant fish species in Crystal River, Cedar Key,

Apalachicola Bay, and St. Andrew Bay estuaries (from Comp and

Seaman, 1985)

5.4.1.1 Environmental Settinq

Pensacola Bay is the fourth largest estuarine system in Florida. The

estuary is about 126,000 acres in area and has a coastline of some 550

miles (Reidenauer and Shambaugh, 1986). Isphording (1989) calculated that

the volume of Pensacola Bay was 5.095 X 1011 cubic-feet. Extensive

watersheds feed each of the four major streams entering the system.

Isphording also reported that the drainage area of Pensacola Bay was 6990

square miles and that annual river flows were 11,600 cfs. The Escambia

River, the largest stream entering the estuary, forms an extensive

distributary delta before discharging into upper Escambia Bay. The Yellow

and Blackwater Rivers discharge into Blackwater Bay; and East Bay River

empties into the eastern portion of East Bay (Figure 5-11)

The Escambia River is the fifth largest river in Florida, with stream flows

ranging from about 500 to 50,000 cfs. The Blackwater River receives water

from three tributary streams: Big Juniper, Big Coldwater and Pond Creeks.

Stream flows range from about 100 to 6,000 cfs in Big Coldwater Creek, and

60 to 5,000 cfs in the Blackwater River. The Yellow River discharges

through an extensive delta system into the northeastern part of Blackwater

5-52

Dominant Fish Species

Estuary

Crystal

River

Cedar Key Apalachicola

Bay

St.

Andrew

Bay

Anchoa mitchilli 41

Fundulis similis 8 Menidia beryllina 28

Sygna thus scovelli 6 Eucinostomus argenteus 8 Orthopristis chrysoptera 13 18

Lagodon rhoznboides 27 46 22

Bairdiella chrysoura 19 5

CynosCion arenarius 9 Leiostomus xanthurus 11 10

Micropogon undulatus 31

Percent of Catch 70 75 81 76

Total Species 100 122 76 88
Figure 5-11. Schematic map of the Pensacola Bay system.
Bay with stream flows ranging from about 100 to 10,000 cfs. Discharge

volumes of the East Bay River have not been determined. Freshwater input

into the Pensacola Bay System is generally highest from February to April,

and lowest in October to November. High pulse inputs have been recorded

throughout the year, however, and wide month-to-month, season-to-season,

and year-to-year variation in discharge flows are characteristic of

tributaries. Escambia Bay receives about twice the volume of fresh water

than Blackwater-East Bays. Variation in riverine input into the system is

some 2-3 orders of magnitude between extreme low and high flows.

Five physiographic sub-systems are recognized in the Pensacola estuary: (1)

Upper Escambia Bay; (2) Lower Escambia Bay; (3) Pensacola Bay; (4)

Blackwater Bay; and (5) East Bay (Table 5-13). The Pensacola Bay System

drains the Western Highlands physiographic region of northwest Florida and

southeastern Alabama.

Based on its origin and geometry, Pensacola Bay is a broad, wedge-shaped,

drowned-river-valley estuary with a large width to depth ratio. Salinity

values range from 34-35 ppt near Pensacola Pass to 0.5 ppt or less in the

upper bays. Saltwater extends several miles upriver to the fall line in

the fluvial tributaries of Escambia and Blackwater Bays. Overall, the

system is a low relief, coastal plain estuary partly blocked by a barrier

island. The upper half of the system is a moderate relief, ITyTI shaped na,

and upper Escambia and Blackwater Bays are delta-front estuaries with

ephemeral distributaries (Escambia and Yellow Rivers) with interlobate

embayments. Santa Rosa Sound is a bar-built estuary bounded seaward by

Santa Rosa Island.

Sub-sections of Pensacola Bay conform to definitions of salt wedge,

partially mixed, vertically homogenous, or sectionally hornogenous estuaries

at certain times. Salt wedge conditions are present when the bay is

vertically stratified and river flow is high. A salt wedge is probably

present in Pensacola Bay most of the time because of its depth and

proximity to the Gulf of Mexico. During periods of low river flow, wind

mixing causes the halocline to break down or weaken in upper Escambia,

Blackwater and East Bays, which become partially mixed.

When river discharges into Blackwater and Escambia Bays are low, turbulent

wind mixing (e.g. during summer thunderstorms and winter frontal passages),

causes shallow portions of the upper bays to become vertically homogenous

for short periods of time. During the same conditions a vertical boundary

separates horizontal sections of the central portion of the system east of

Garcon Point, and the bay becomes, for probably short periods of time,

sectionally homogenous. According to the classification scheme of Odum and

Copeland (1974), Pensacola Bay is a natural temperate ecosystem with

seasonal programming (i.e. with seasonally predictable characteristics) as

well as an emerging new system associated with man.
Table 5-13. Comparisons of Pensacola Bay sub-systems (from Olinger et al.,

1975, and Reidenauer and Shambaugh, 1985).

5.4.1.2 Hvdoraphv and Oceanoarahv

Few physical oceanographic studies of Pensacola Bay have been accomplished,

and details of circulation patterns and mixing processes are poorly

understood. When winds are light, little energy is available for mixing,

and flushing rates tend to be slow in most portions of the system other

than lower Pensacola Bay. Materials entering the Pensacola Bay System via

tributaries and bayous tend to be trapped and remain in the system for

extended periods of time. Weak currents and tides, high river flows, and

intense solar heating in summer months contribute to conditions of intense

vertical stratification, low dissolved oxygen concentrations below the

pycnocline, and the accumulation of pollutants in the system. The

Pensacola Bay System is river-controlled much of the time, and turbulent

mixing is low in the absence of wind stress. When benthic biological

respiration and COD are unsatisfied, dissolved oxygen levels decrease with

depth, and DO may be exhausted in portions of the system where BOD, COD or

SOD are high. Diffusion of oxygen from the atmosphere and surface fresh

waters are insufficient to satisfy the sub-halocline oxygen demands of

phytoplankton and chemical processes. Low dissolved oxygen conditions have

precipitated fish kills and other mass mortalities in the bay.

Sub-system

Surface

Area (2)

Volume

(10' m3)

Average Depth

(m)

Pensacola Bay 135 800 6

Bayou Grande 4 10 2

Bayou Chico 1 2 2

Bayou Texar 1.5 3 2

Escambia Bay

Escambia Bay 95 225 2.5

Mulatto Bayou 1 1 1.5

Blackwater Bay

Blackwater Bay 25 50 2

Catfish Basin 1 1 1

East Bay

East Bay 110 260 2.5

East Bay Bayou 5 5 1
Tides

In a hypothetical estuary with no tides, winds, other energy inputs or

friction between fresh water near the surface and denser ocean water

beneath it, static conditions exist. Fresh water flows out to sea on the

surface and sea water extends upestuary to the fall line. The Pensacola

Bay System, for variable periods of time, effectively approximates this

zero energy-no motion condition.

The tidal prism in the Pensacola system is small (about 0.5 m), and tidal

currents are of importance primarily near the mouth of the system and in

bayous. Tidal cycles at Pensacola are diurnal most of the time. However,

during two-to-three-day periods when the moon crosses the equator,

semidiurnal tides occur (Marmer, 1942)

Based on records from 1923-1941, Marmer (1942) reported that, disregarding

equatorial tides, the mean tide range at Pensacola was 0.39 m (1.27 ft). A

maximum range of 0.43 m (1.4 ft) was recorded in 1932, and a minimum of

0.34 m (1.12 ft) was recorded in 1941 (a nine-year, half-cycle interval)

During the period of record, tides were highest in June and DecemberJanuary, and lowest in March-April and August-October. The former period

roughly corresponds to periods of high rainfall and river flow, and the

latter to the "dry" season. Provost (1971) observed that highest tides

occur every four years, when the moon is at perigee.

Sea Level

Marmer (in Gaitsoff, 1954) reported that between 1924-1950, sea level at

Pensacola rose by nearly (0.15 m (0.5 ft), or about half the tidal range.

During the period 1924-1941 sea level rose more than 0.03 m (0.1 ft) per

year, and from 1941-1950 the rate of sea level rise slowed to a little over

0.009 (0.03 ft) per year.

Circulation

Gallagher (1971) reported that Coriolis force directs high salinity water

into Pensacola Bay on the right (facing the direction of current flow), and

out of each subsystem (Blackwater, East and Escambia Bays) on the left.

Olinger et al (1975) reported that circulation in 1973-1974 varied between

a two-layer flow with entrainment and a two-layer flow with vertical

mixing. The latter condition was infrequently encountered, and the system

characteristically showed little vertical mixing.

Major current major current reversals due to wind stress have been reported

throughout the bay system (Edwards, 1976; Ketchen and Staley, 1979).

According to Ketchen and Staley (1979), wind velocities of less than 8 kn

for a period of time (not specified) could result in a complete reversal of

current directions at all depths. Gorsline (in Lauff, 1967) reported that,

"Slicks, foam lines and debris lines are common [in Pensacola Bay]; they

separate tidal water masses of slightly different composition which move in

variable directions in the estuary. .

Olinger et al. (1975) reported that flushing was more rapid in Pensacola

Bay than in other parts of the system. A model based on average river flow

5-56
and average tides indicated that flushing of the Pensacola Bay System

should take on the order of 34 days, but a 60-day reduction in flushing

time may occur with tidal mixing. In conditions of low flows and weak

tidal mixing, flushing of the Pensacola Bay System may take as long as 200

days. Under certain wind conditions current reversals occur. Surface

currents flow landward and deeper currents flow seaward. When current

reversals occur, wastes are sometimes transported to the north and remain

in the system (Upper Escambia Bay) for longer periods of time than

calculated flushing rates may indicate. Ross (1973) postulated that a

semi-permanent cyclonic gyre was present in Upper Escambia Bay, and if

true, water would tend to be recirculated within this subsystem. Data

indicate that substances in waters entering Upper Escambia Bay are retained

within the bay for extended periods of time, and Stursa (1973) stated that,

"Much of Escarnbia Bay is considered to be a 'dead' estuary."

Coupling

Corcoran (1973) reported that shelf currents and Pensacola Bay water

coupling occurs. His data showed that a large tongue of water moves to the

east from either Mobile Bay or Mississippi Sound, suggesting that some of

the chemical compounds and trace metals (e.g. Cd, Zn) found at higher than

expected concentrations in Pensacola Bay may have entered from shelf

waters. Indications of nitrate enrichment in the bay from shelf waters was

reported by La Rock (1973).

5.4.1.3 Water and Sediment Oualitv

Moskovits (1955) was the first investigator to report that water quality in

the Pensacola Bay system had deteriorated due to the commencement of

operation for several industrial operations. Facility discharges increased

nutrients, toxic waste products and BOD into Bay waters. A series of

investigations during the period 1955-75 (Olinger et al., 1975) concluded

that water quality continued to worsen in wetern portions of the system

through the study interval. This study was the only comprehensive

ecological investigation of the Pensacola Bay system undertaken.

Commensurate with a nationwide economic downturn, industrial effluents

decreased, and water quality within the system appeared to increase and was

considered to be the beginning of an improving trend. Collard (1991)

however, reviewed all water quality investigations undertaken for the

system through 1990 and concluded that water quality progressively worsened

during the period 1955-75 and has remained essentially unchanged since that

time, as evidenced by the total disappearance of once huge seagrass meadows

and productive oyster reefs.

Olinger et al. (1975) distinguished three major habitats based on sediment

type in Pensacola Bay: (1) a broad central plain of mud; (2) a transition

zone close to shore with steep slopes and sediments grading from mud to

sand and, (3) a sandy shelf around the bay margins. In addition, eight

benthic habitats, eight benthic habitats based, in part, on non-sediment

characteristics were identified. These included: (1) sand shelf (25 % of

the Pensacola Bay System); (2) transition zone (a narrow band paralleling
the shore between predominantly sand and mud sediments); (3) mud plain (70%

of the bay bottom, consisting of a thin, flocculent, soupy-sticky, gel-like

layer about 15 cm thick); (4) oyster bed (undersampled); (5) submerged

aquatic vegetation (SAy) (no seagrasses were found during the 1973-74

sampling period, but brackish-freshwater Vallisneria americana beds were

sampled in Escambia, East, and Blackwater Bays); (6) sewage treatment plant

(STP) discharge (primarily sand); (7) industrial outfall (included all

three major sediment types in northeastern Upper Escanthia Bay near Air

Products and American Cyanamid), and (8) deep water mud (primarily silt and

clay).

Eastern margins of the Pensacola Bay System had the widest shelves,

shallowest slopes, and provided the best habitat for oysters in the system.

The mud fraction of sediments increased everywhere with increasing depth.

Total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC)

also increased with increasing depth (with increases in fine sediments)

TP and TN concentrations were higher and TOC was lower in Escambia than in

East Bay. TP, TN, and TOC were higher in Choctawhatchee and St. Andrew

Bays than in Escambia Bay. The presence of toxic compounds was not

determined. Volatile organic compounds (VOCs) were highest in deep water;

similar concentrations occurred in Escambia and East Bays in like

sediments, and were higher in Pensacola than East Bay. It was concluded

that volatile organics in Escambia Bay resembled concentrations found in

other estuaries.

An area of higher BOD (biological oxygen demand) occurred in Escambia Bay

at the zone of maximum mixing between salt and freshwater due to

flocculation of dissolved riverine organic materials. Highest BOD levels

occurred in Escambia Bay in general, but values were not considered

remarkable except near industrial outfalls.

PCBs were found throughout the system, but concentrations were highest in

muds, in channels, and near industrial outfalls in the northeast portion of

Upper Escambia Bay. PCBs were estimated to have decreased about 90% per

year from 1969 to 1974. Of 21 pesticides tested, only Dieldrin was

detected in Escanthia Bay. Eleven of 12 trace metals sampled for were

present in higher concentrations in fine sediments. Seven metals were

found in the same concentrations in Escambia and East Bays; four were

higher in Escambia than East Bay; and one (titanium) was uniformly

distributed throughout the Pensacola Bay System. Mercury was found in very

low concentrations. The dredged channel in Escambia Bay was considered to

be a sink for clay, fine organically rich sediments, nutrients, trace

metals, and PCBs. "Black, gelatinous sludge" has been reported by numerous

FDEP biologists (pers. comm.) in the eastern portions of the bay.

Brazzell (cited in Stith et al., 1984) characterized Upper Escambia Bay

sediments as comprised of "black carbonaceous mud" containing 7.8-11.6%

volatile organic solids. Brazzell stated that such sediments when

resuspended had high BOD and long settling times. These sediments

contained PCBs and trace metals and had a strong smell of hydrogen sulfide.

REMOTS® (SAIC, 1986) sediment profiling in Pensacola Bay in 1985 consisted

of 200 images obtained from 104 locations. These techniques (described by

5-58
Germano and Rhoads, 1984), produced important information concerning depths

of the apparent reduction potential discontinuity layer, or RPD. This is

the sediment depth where redox values become approximately zero, as

measured by Eh or as visually indicated by an often rust- or dark-colored

band or layer in sediments. RPD depths of 10-20 cm are characteristic of

uncontaminated, oxygenated sediments often colonized by Stage iii

successional seres (head-down feeders, bioturbators, biological

bulldozers). Shallower RPD depths indicate that the reducing environment

is close to or at the sediment-water interface (e.g. as a result of

sediment overenrichrnent, toxic substances or chronically low bottom Do).

Such benthic environments are able to support primarily surface suspension

and/or deposit feeders of the types most frequently reported by FDER

environmental staff (opportunistic polychaetes, tube-dwelling amphipods,

and small bivalves). See Collard (1989) for details.

In general, SAIC REMOTS® findings agreed with the sediment descriptions of

Olinger et al. (1975), and concluded that the majority of the bay bottom

had RPD depths of between 4 and 10 cm. Deepest RPD depths were in high

energy areas corresponding to Olinger's shallow sand substrate habitats.

Shallowest RPD depths were found in "quiet" (low energy) areas, as

expected. SAIC concluded that, "This suggests that the RPD depth is not

strongly mediated by chemical stress factors [but the] area around the Port

suggests both physical disturbance and anthropogenic disturbances."

Chemical stress factors mentioned by SAIC included toxic substances and

high BOD/COD, while "anthropogenic disturbances" included organic loading

from discharges and dredging, reducing sediments, and high BaD/COD.

Sediments profiled north of the Port suggested that the area had not

recently been disturbed but had been so in the past, probably by dredging.

Sediments around the Port and at the mouth of Bayou Chico were viewed as

stressed due to "known organic inputs in these areas". Based on an

organism-sediment index (051) low values calculated in shoal areas near

Fair Point were attributed to natural physical disturbances (e.g.

currents) . In general, it was concluded that Pensacola Bay sediments were

not overly stressed.

George (1988) summarized changes in sediments during the period 1965-1985:

(1) the percentage composition of sand decreased by more than 50% in East

Bay; (2) silt and clay-sized sediments were more than twice as abundant in

East Bay; (3) grain sizes and percent sand increased seaward and toward the

mouths of rivers in all segments of the Pensacola Bay System; (4) sediments

changed from well-sorted to a more poorly-sorted, finer-grained condition

throughout the Pensacola Bay System [Horvath (1968) reported mean grain

size to be 4.1 (phi units) and George (1988) reported mean grain size to be

6.4]; (5) shoreline configurations had changed little; (6) carbonates had

decreased by more than 50% in Pensacola Bay, and almost doubled in East

Bay; (7) the cause(s) of fining of sediments in Blackwater Bay was unknown,

but tentatively attributed to private damming of tributaries, or to the

long-term effects of hurricanes; (8) an increase in coarser sediments in

Upper Escambia Bay was tentatively attributed to 1985 quarrying activities

in the Escambia River, and the increase in "fines" in the eastern portion

of Pensacola Bay (eastern Upper Escambia Bay) was attributed, in part, to

the action of submerged L&N railroad ties acting as a "snow fence", thus

trapping finer sediment particles; (9) the percentages of surface sediment

5-59
clay in the Pensacola Bay System ranged from 0.5% to 90.4%, with an average

of 37.8%; the clay fraction increased northward from Santa Rosa Island, and

toward the central, deeper portions of bays in the system; and (10)

Blackwater Bay sediments were the most poorly sorted in the Pensacola Bay

System [sorting was best in the southwest portion of Pensacola Bay near

Pensacola Pass]

George (1988) reported organic carbon concentrations of zero to 7.5%

(average 2.4%) in Pensacola Bay System sediments; the second highest levels

in any northeast Gulf of Mexico estuaries, except for Mobile Bay.

Blackwater Bay was lowest in sediment organics. The eastern shore of

Pensacola Bay, off Garcon Point, had lower concentrations than the western

shore, and organics were found to be high at the mouth of the Escambia

River. No unusually high concentrations of organics were found in

Blackwater Bay, East Bay, or Escambia Bay except in the center of the

system, at the confluence of East and Pensacola Bays. Isphording et al.

(1989) calculated that the estuary received an average annual sediment load

of 1.08 million tons per year, and an average sediment input of 154.5 tons

yr' mi-2 of drainage area.

Sediment grain size changes in subsystems of the Pensacola Bay System (see

Table 5-14) can be postulated to have resulted in substantive changes in

water column turbidity; changes in the distribution and diversity of

benthic invertebrates and submerged vegetation; changes in the

concentrations and distributions of chemical (toxic and nutrient)

substances throughout the system; and changes in the flushing rates and

residence times of chemicals sequestered in fine sediments.

Data collected and interpreted by Young (1982), Ryan et al. (1984),

Isphording (1985), SAIC (1986) and FDER (1988) were different, in some ways

significantly so. In contrast to conclusions reached by Brazzell (1984),

the overall quality of sediments in the Pensacola Bay System has apparently

not significantly improved during recent decades.

Escarnbia Bay sediment characteristics and currents were compared during low

river flow conditions in 1969, and high flow conditions in 1970 (USEPA,

1971) . In Upper Escarnbia Bay, unconsolidated sediments from less than two

to greater than six feet thick were found. Forty-five percent of these

sediments were found to contain greater than 0.2% total organic nitrogen,

and 35% of the sediments contained total phosphorus concentrations greater

than 0.3%. Total sediment oxygen demand in the samples ranged from 25-100

g kg2 (dry weight), and 30% of the sediments had a total oxygen demand

greater than 100 g kg'. Organic content increased to 5% near the mouth of

the Escambia River and was lowest (2.3%) in the southeast portion of Upper

Escambia Bay, above the L&N trestle off Mulatto Bayou. It was concluded

that most total organic carbon (72.6%) entered Upper Escambia Bay "via

rivers in which Monsanto and Container Corporation discharge." Based on

current measurements it was concluded that wastes discharged into the

northeast portion of Upper Escambia Bay flow to the north and accumulate in

the central and western portions of upper and lower Escambia Bays.
Table 5-14. Comparisons of 1968 and 1988 sediments in the Pensacola Bay

System (George, 1988).

These authors also suggested that a cyclonic gyre may be a common feature

of Upper Escarnbia Bay waters regardless of river flow conditions.

Sediment microbial activity was estimated to be similar in all sections of

the Pensacola Bay System, including sewage treatment plants (STPs) and

industrial outfalls. Microbial activity increased with increasing

volatile organic concentrations until the latter reached 1%, at which time

no further microbial activity increase was observed.

In connection with an oyster bed restoration project during the period

March 1972 - June 1973, bottom conditions in most of Escambia Bay were

characterized as flocculent, organic, anaerobic muds (Little and Quick,

1976). This qualitative description was in general agreement with sediment

conditions reported in 1949, 1955, 1969, 1973 and 1974.

A special monitoring survey conducted in Pensacola Bay from the fall of

1987 to the summer of 1988 (FDERI 1988), compared conditions in the bay to

those reported by Olinger et al. (1975). The six stations sampled for

sediments and benthos provided reasonable coverage, but some station

locations were different than those sampled by Olinger et al., (1975).

With respect to sediments the FDER (1988) study reported that five of six

stations were "heavily polluted" by arsenic, iron, and chromium; one of six

was heavily polluted with copper, and one of six with mercury (near the

Main Street STP) . Five of the six stations sampled were found to be

"heavily polluted" with volatile solids.

Sediments in Bayous Texar and Chico are reported to be of low biologicalchemical quality. Sediments in the bayou are chronically over-enriched, as

expected in heavily populated areas where bayous have historically been

used as domestic or industrial sewers. Sediments are impacted by pulses of

stormwater runoff from Carpenter's Creek and numerous (>65) stormwater

5-61

Comparison - Pensacola

Bay

- Escambia

Bay

East Bay Blackwater

Bay

AVG. SD PERCENT

Horvath 58 48 59 -- George 49 46 22 35

AVG. SILT PERCENT

Horvath 17 22 17 - - George 21 23 25 28

AVG. CLAY PERCENT

Horvath 29 27 22 -- George 30 30 53 37
drains. Hoffman, Woodland, and Gilmore Bayous appear to have the same

basic problems as Bayou Texar. Recent information is not available for

Mulat-Mulatto Bayou, Catfish Basin, Indian, Trout or Raccoon Bayous.

5.4.1.4 Bioloav

This section describes the salt marhes and submerged aquatic vegetation,

benthos and fish communities found in Pensacola Bay

Salt Marshes and Submerged Aquatic Vegetation

Seagrass changes within the Pensacola Bay System were documented by Rogers

and Bisterfield (1975), based on an analysis of aerial photographs taken

from 1949-1974. At the time of writing the authors' stated that the

Pensacola Bay System had productive "grass" beds in all bays of the system.

Their finding, however, is not in agreement with those of other authors.

The three most abundant species of SAV reported to occur in the Pensacola

Bay System were Thalassia tea tudinum (marine-brackish, to about 2 m depth),

Halodule wrightii (marine-brackish), and Vallisneria americana (freshbrackish). The authors reported that Ruppia maz-itima, "is also fairly

common in the fresh to brackish waters of the area". Rogers and Bisterfield

(1975) concluded that: (1) Escambia Bay had extensive grassbeds along its

entire shoreline in 1949; (2) seagrass losses occurred from 1949-1966. (3)

declines accelerated from 1966-1968, and were still declining in 1968-1974;

(4) seagrasses were mostly gone by 1970; (5) all SAV had disappeared from

Escambia Bay except for a small patch of Vallisneria along the upper

western shore, where there was a significant influence from the Escambia

River; and (6) SAV had decreased in East Bay and Blackwater Bay by 1974,

but some, including Thalassia, remained. The authors attributed declines

in Pensacola Bay System SAV to sewage and industrial effluents, dredge and

fill, beachfront operations, and changing watershed characteristics.

Seagrass beds along the southern shore of Pensacola Bay disappeared by

1974. Meadows in East Bay disappeared completely by 1976 and have not reestablished themselves. Seagrasses have not disappeared, but have

decreased in the Santa Rosa Sound portion of the Pensacola Bay/Gulf Breeze

area. About a 50& reduction in seagrass area coverage occurred in beds

around the Gulf Breeze Peninsula between November 1982 and November 1986.

Beds of seagrass around Sabine Island remained about the same between 1982

and 1986.

Benthos

Based on the documents reviewed, benthic macroinvertebrate species

diversity in Pensacola Bay is low, and has probably not changed

significantly during the past 30-40 years. Low dissolved oxygen levels

occur seasonally in northeastern Upper Escambia Bay and in most bayous.

Sediments with high organic content occur in deep mud areas of the bay, in

many or all of the bayous, in parts of Upper Escambia Bay, and

(aperiodically), elsewhere in the system. Even though samples of the

benthos have been collected on an irregular basis and have emphasized

point-source locations, a sufficient number of samples have been collected

to show conspicuous differences in species diversity within the system

5-62
after differences due to salinity have been filtered out (Olinger et al.,

1975)

During the period 1961-1990, more than 400 taxa of (primarily sessile)

benthic macroinvertebrates were reported from Pensacola Bay; 145 taxa were

collected in Escambia Bay, and a total of 82 taxa were known from East and

Blackwater Bays. A large fraction of the total number of taxa known from

Pensacola Bay was collected in 1986, during sampling of the aircraft

carrier turning basin in lower Pensacola Bay. As many as 50-60% of the

total number of species historically collected from all parts of the

estuary were associated with either seagrass meadows, which disappeared by

1974-1976, or with oyster reefs, which have declined in abundance.

The benthic fauna of a large portion of the Pensacola estuary, except in

well-flushed, high salinity areas, resemble pioneering communities (Rhoads

and Germano, 1986) . These communities consist of small, opportunistic,

near-sediment surface tubiculous polychaetes, amphipods and bivalves, or

their ecological equivalents. The most abundant and widely distributed

species in the Pensacola estuarine system are polychaetes, the amphipod,

Carinoma tremaphoros, and the small clam, Tellina texana. A comparison of

macroinvertebrate species collected in the system by Cooley (1961-1963),

the Florida Department of Environmental Protection (1980-1988); and the

U.S. Navy (spring 1986) is presented as Table 5-15.

olinger et al. (1975) reported that samples from 11 sand shelf stations

showed an average of 13 species per station (18.5 in winter, 13 in summer)

A total of 36 species were collected from this habitat in summer, and 24 in

winter. A three-fold increase in numbers of organisms was collected during

winter. Summer samples were dominated by the following species: the

amphipod, Grandidierella bonnieroides, in numbers as high as 1000 m2, the

clam Mulinia lateralis (60% of the total number of animals collected),

Laeonereis culveri, Odostomia sp., the clam, Tagelus plebeius, and

Haustorius sp. Haustoriid amphipods comprised as much as 89% of the number

of individuals in some samples. Winter samples were also dominated by G.

bonnieroides, which occurred in larger numbers than Mulinia lateralis. The

two other winter dominants were Neanthes succinea and Monoculoides

edwardsi. Sand substrata were considered to have been undersampled. No

statistical differences were found in numbers, biomass or species with

respect to north, south, east or west sides of the system.

Ten transition zone stations were sampled by Olinger et al. (1975),

yielding a total of 34 species and an average of 9.8 species per station.

Numerical dominants were Mulinia lateralis and Parandalia fauveli. These

and five other species accounted for 80% of the total number of animals

collected. Species composition remained essentially the same in summer and

winter, with a ten-fold increase in numbers of organisms in winter. The

number of species/station in winter was 19.5, and in summer, 8.5. No

differences in faunal assemblages were found in different areas of the

transition zone.
Table 5-15. Macroinvertebrates found in the Pensacola Bay System from

January 1980 to the present, compared with macroinvertebrates

found by Cooley (198). DER = samples taken by the Florida

Department of Environmental Regulation, Navy = samples taken by

the U.S. Navy (U.S. Department of the Navy, 1986), EB = East

Bay, PB = Pensacola Bay, UEB = Upper Escambia Bay, +" =

present, = absent.

Syllidae + - - - + Brania clavata + - - Nereis sp. -

- + + Nereis succinea + + + - + Laeonereis culveri + + + + + Nephtyidae - - + + Nephtys sp. - - - + + NephtyS picta + - - + Aglaophamus verrilli - + -

Goniadides carclinae - + Progoniada sp. + - - - Diopatra cuprea + - + Lumbrineris tenuis + + + - Lumbrineris ernesti - - + Lumbrineris verili - + Lurnbrineris culveri - + - Arabella sp. + -

5-64

GENtJ SPECIES DER

+

DEE

+

DER ___

Navy

£ COOLEY

PLATYHELMINTHES

RHYNCHOCOELA

Stylochus ellipticus + + Carinoma tremaphoros + + + Cerebractulus lacteus + + - + Tetrastemrna candiduzn + + + POLYCHAETA

Polynoidae - - + + Lepidonotus sp. - + - + Sthenelais sp. + + + + Sthenelais boa + - - Pisione sp. - + - Bhawania heteroseta + - Chxysopetalurn occidentale - + - - - Phyllodocidae - + + Anaitides sp. - - + + Eteone heteropoda + + + + + Phyllodoce arenae - + + - Hesionidae - - + + Gyptis brevipalpa + + - - - Heteropodarke lyonsi -

- + - Pilargidae + - + + Sigambra tentaculata - - + - Sigambra bass.i + + + - - Parandalia ap. - - + Parandalia americana -

- + -

Glycera americana -

- + + Glycera dibranchiata + + + + + Glycinde sp. + + + - - Glycinde solitaria - - - + - Gonaiada sp. + + -

Protodorvillea kefersteini

LeitoscolopluS sp.

- -

- - + HaplosColoplOS foliosus + + + + HaploscolOploS fragilis + - + - + Leitoscoloplus fragillis - + + + Scoloplos rubra -

- + + Orbibia sp. - - +
Table 5-15. Macroinvertebrates found in the Pensacola Bay System

from January 1980 to the present, compared with

macroinvertebrates found by Cooley (1978) continued.

DER DER DER Navy

ENTJS SPECIES PB COOLEY

Ariciedea sp. - + - - A.ricidea cerruti - - - + An cidea taylori - + Cinrophorus sp. - - + Spionidae - - + + Polydora socialis - - - + + Polydora ligni + + - - Polydora webs ten + + + + Polydora cornuta - - - + + Pnionespio sp. - - - + - Pnionospio heterobranchia - + - - + Pnionospio criStata - - -+ - Apoprionospio pygmaea - - - + - Prionospio dayi + - - - Spiophanes sp. - - + - Spiophafles bonibyx - + + + + Parapnionospio pinnata + + + + + Streblospio benedicti + + + + - Dispio unciata - + - - Scolelepis squarnata + + - - Magelona sp. - + + + Spiochaetopterus costarurn + - - Mesochaetopterus sp. + - Cirratulidae - + + Tharys setigera + - - - Tharyx Cf. annulosus - + Tharyx setosus + - - - Chaetozone sp. -

- + - Cossura delta + - - Arrnandia agilis - + - - + Arrnandia maculata - -

- + - Travisia hobsonae - + - - Capitella capitata + - + + + Heteromastus filiformis - + - - + Notornastus sp. - - + + Mediomastus ambiseta + + + - Maldanidae - - + + Axiothella mucosa + - + Pectinaria gouldi + + + Hobsonia florida + + + + - Sabellides sp. - - + Chone cf. americana + - - Potainilla cf. renifozinis - + - - Fabniciola trilobata - + MOLLUSCA

GASTROPODA

Nenitina virginea + + - - Nenitina reclivata + + - + Neritina usnea + Littonina lirieolata - - + Zebina browniana - + Bittium vaniurn + - Cenithium flonidanum + - - Epitonium rnultistriatuin - - + + Crepidula maculosa - + + Natica pusilla - - + + Polinices duplicatus + + Polinices cf. hepaticus + - - - Mitrella lunata + - + Anachis translirata - + - - - Anachis lafresnaya - + 5-65
5-66

Macoma Cf. tenta

Tellina lineata

Tellina cf. texana

Tellina sybaritica Tagelus plebeius Tagelus divisus Polymesoda caroliniana

+

-

-

+

-++

+

-

-

-+

-

-

-+

-

--+

+

-+

+

-++

+ Verieridae + + Anomalocardia cuneimeris + + + - - Corbula Cf. contracta + - - Lyonsia hyalina - + - - + CRUSTACEA:

CIRRIPEDIA

Balanus eburneus + + - + PERACARIDA - -MYSIDACEA

Mysidopsis bigelowi + + Mysidopsis bahia + Bowznaniella floridana + + - PERACARIDA - CUMACEA

Leucon sp. - + Oxyurostylys srj,ithi + + + + + Cyclaspas sp. + - - PERACARIDA - TANAIDACEA

Leptochelia rapax + + + + Leptochelia signyi + - PERACARIDA - ISOPODA

Xenanthura brevitelson - - + Cirolana sp. + Sphaeroma quadridenta turn + - - + Edatea triloba - + - Munna reynoldsi -

- +

Table 5-15. Macroinvertebrates found in the Pensacola Bay System

from January 1980 to the present, compared with

macroinvertebrates found by Cooley (1978) continued.

DER DER DER Navy

GENUS SPECIES EB PB B PB COOLEY

Nassarina vibrex - - + - Cantharus cancellarius - + + Nassarius vibe.x - + - Nassarius acutus - - - + + Nassarius albus - + - Olivella pusilla + - Olivella sayana - + - Turbonilla conradi - - + + Pyramidella fusca + - + - - Acteon punctostriatus - - + + Retusa canaliculata + + + - - Cylichna bidentata + - - Bulla striata + - - + BIVALVIA

Nuculana acuta - + + Nuculana concentrica + - - + Anadara transversa - + - + Modiolus demissus - + + - Modiolus americanus + - - + BranchiodonteS recurvus - + - + Amygdalum papyrium - + - + PazviluciZ2a multilineata - - - + + Anodontia alba - + - - Crassinella lunulata - + - Laevicardium mortoni - + - - + Mulinia lateralis + + + + Mulinia caroliniana - - + - Rangia cuneata + + + - + Ervilia concentriCa - + - Ensisminor + + + - +
Table 5-15. Macroinvertebrates found in the Pensacola Bay System

from January 1980 to the present, compared with

macroinvertebrates found by Cooley (1978) continued.

DEP. DER DER Navy

GENTJS SPECIES EB UEB COOLEY

PERACP.RIDA - NPHIPODA

EUCP.RIDA - DECAPODA

Maj idae

Megalops

INSECTA - ODONATA

Ampelisca sp. Ampelisca abdita Ampelisca Cf. verrilli Ampelisca aggassizi Cyrnadusa cf. cornpta

Parainetopella tejcensis Orchestia sp. Eudevenopus honduranus Caprella sp.

Automate evermanna

Penaeus sp. Tnachypenaeus cons tn ctus Sicyonia breviros tnis

Acetes sp. Palaemonetes pugio Ogynides alphaeros tris Pagurus sp. Pagurus longicarpus

Pagurus gymnodactylus Clibanarius vi ttatus

Albunea pare tii

Call inectes sapi dus Callinectes similis

Eurypanopeus depressus Panopeus herbstii Rhi thropanopeus harni si Pinnixa chaetopterana Pinnixa sayana Pinnixa flonidana

Zschnura sp.

5-67

- - - + + + + + +

- - + + +

+

+

Le.znbos sp. - - + Lembos srnithi + + Mi crodeu topus gryl 10 talpa - + Cerapus tubularis - + Corophiurn sp. - + Corophiuni tubercula turn - + Corophium cf. louisianum + + + + Grandidierella bonnieroides + + + + Elarnopus levis - - - + Garnrnarus macrornucrona tus + + + Megal uropus rnyersi - - + Melita nitida + Meli ta longisetosa + Delichiella appendiculata + Acanthohaustorius sp. - - + Acanthohaustorius intermedius - + AcanthohauStOriuS milisi - + Neohaustorius sp. + ProtohausCorius sp. + Haustorius sp. + Photis macromanus + Mi croprotopus raneyi + Listriella barnardi - + - + Monocul odes edwardsi + + + + Synchel i di urn amen canum - + Metharpinia flonidana +
SIPUNCTJLA PHORONIDA

ECHINODERMATA

Ophiuroidea

CEPHALOCHORDATA

Palpomyia sp. - - - + Chironomus sp. - - - + Polypediluzn illinoense - - + Polypedilurn scalaenum - - - + Dicroendipes neomodestus - - + Phascolion sp. - - - + + Phoronis sp. - + + + + Ophiodez7na brevispina + - Mellita quinquiesperforata + + Leptosynapta sp. + - Leptosynapta tenuis - + Branchiostoma caribaeuzn - + .4. + Fourteen mud-plain habitat stations were sampled by Olinger et al., which

was characterized as being covered with a 15 cm thick layer of gel-like

flocculent, soupy material. Dominant species in this habitat were the

polychaetes, Siga.rnbra bassi (18.3%) and Paraprionospio pinnata (17.5%).

These and five other species accounted for 85% of the community. In

summer, an average of 5.5 species per station was collected, and in winter

the number increased to 14.5 species per station. The number of

individuals collected per station during winter was twice as high as the

number collected in summer. No significant differences were found in

dominant species between mud stations.

Olinger et al. (1975) collected 35 species of invertebrates from oyster

beds, nine of which accounted for 89% of the number of individuals. Most

of the species recovered from oyster beds were also found elsewhere in the

bay. Twenty-eight of 35 species were collected only in Escambia Bay, and

16 species occurred in both East and Escambia Bays. The authors considered

oyster beds to have been under-sampled.

Vallisneria americana was the only species of submergent vegetation

sampled. Twenty-three species of invertebrates were collected in Escambia

Bay, 24 in Blackwater Bay and 26 in East Bay. Industrial- discharge faunal

assemblages were comprised of 25 species and an average number of 778

individuals per station. Species richness was not influenced by the sewage

treatment (transitional sand-mud substrate), and samples were dominated by

Paraprionospio pinnata. The industrial discharge habitat was

indistinguishable from other habitats with primarily sandy substrates.

Samples were dominated by three polychaetes (L. culveri, P. pinnata, and P.

fauveli), Mulinia lateralis and G. bonnieroides. Species collected from

mud substrata near the industrial outfall were similar in diversity and

numbers to those collected from similar substrates in other parts of the

system. At deepwater mud stations, eight species were collected with

average total densities of 52 m2. Samples were dominated by polychaetes, a

cumacean and a small clam.

5-68

Table 5-15. Macroinvertebrates found in the Pensacola Bay System

from January 1980 to the present, compared with

macroinvertebrates found by Cooley (1978) continued.

DER DER DER Navy

GENUS SPECIES ___ COOLEY

INSECTA - DIPTERA
Results of olinger et al. (1975) benthic macroinvertebrate collections are

summarized as follows:

No north-south gradients of changes in community structure were found

in the Pensacola Bay System.

Whereas many assemblages within the system could be discerned, they

were all interrelated.

North-south salinity gradients within the system were not reflected

by changes in biological community structure or species composition.

There were no biological trends within comparable habitats regardless

of east-west salinity differences.

CH2M Hill (1985) reported that over 97 of all invertebrates at all

stations in winter were polychaetes and bivalves. Capitella capitata,

Tellina texana and haustoriid amphipods were dominants at all five

stations, including Vallisneria beds. As suggested by Collard (1989) the

bay benthos may not be successional, and these functional groups may be the

dominant benthic organisms of the Pensacola Bay System.

Rakocinski et al. (1993) sampled macrofauria from 36 stations located along

four 800 m seaward transects at Perdido Key. All collections changed

markedly with distance from shore. Species richness ranged from 40 m2 in

the swash zone, to as many as 800 per m2, 800 m offshore. The total

density of animals ranged from 2,000 m2, in the swash zone, to 20,000 m2,

800 m offshore.

Species recorded from subsystems of the Pensacola estuary were also

recorded from Pensacola Bay proper. Dominant animals in all years sampled

were polychaete worms, amphipods, and small bivalve molluscs. The presence

of echinoderms (mostly brittle stars) was an indication of higher salinity

water near Pensacola Pass. Polychaetes were clearly dominant in species

and numbers, followed by bivalves and arthropods Of the arthropods,

amphipods dominated assemblages.

About one-fourth as many species were collected in Escambia Bay (145) as in

Pensacola Bay (466) . Fourteen and 27 species, respectively, were

identified as indicator species in Pensacola and Escambia Bays. In East

and Blackwater Bays, during the decade 1974-1984, the number of benthic

invertebrate species and the number of individuals varied considerably less

than in Pensacola or Escambia Bays. Polychaetes and bivalves clearly

dominated the assemblages sampled, and in 1980, occurred in sufficiently

high numbers to indicate stressed conditions in East Bay. The high number

of species collected by Olinger et al. in 1974 was reduced by half in the

nine succeeding years. Seventeen of 82 species reported were considered to

be potential indicators, a much higher proportion than in the other

subsystems or their bayous.
Fishes

Finfish and invertebrate fisheries have declined in the Pensacola Bay

System according to Reidenauer and Shambaugh (1986), NWFW (1990) and the

Marine Fisheries Commission (FDNR, 1974 et seq.) . Presumptive evidence of

long-term fisheries declines has been reported by, among others, the Bream

Fishermen's Association (pers. comm.), and mass media reports of polluted

conditions in the system. Fisheries are discussed in Chapter X of this

report. among the principal indicators of declines in the biological

quality of the Pensacola Bay system, are seagrass losses, episodic massive

fish kills (particularly of the alewife, Alosa pseudoharengus), and reduced

abundances of shrimp, crabs and oysters.

Using seines and trawls, 57 species of fishes representing 32 families were

collected by Olinger et al. (1975) . No significant increases in catch vs.

ef fort (about one fish per hour) were noted to have occurred in the

Escambia River or delta as a result of improved water quality, but fish

kills decreased in the river by 86% between 1970 and 1974. Fish kills

decreased in the Pensacola Bay System by 75% during the same period. The

authors speculated that causes of fish kills in the system were due to

nutrient excesses, PCBs, sewage, oil, phenols, toxic metals, pesticides,

and "Other" industrial by-products. Olinger et al. (1975) reported that

diversity in Escambia Bay was similar to or higher than in many other

northern Gulf coast estuaries.

5.4.1.5 Data Gaas

Currents in the whole of the Pensacola Bay System require careful,

long-term study. Without such information, fate and transport of

nutrients, dissolved and suspended water column substances, and the

distribution of plankton can not be known.

The bathymetry (and as a consequence, circulation patterns and

flushing rates) in the Pensacola estuary may have been altered by

Hurricane Opal, and should be re-charted.

Hurricanes impacting Pensacola Bay in 1995 re-distributed sediments

and substances (nutrients, pollutants) sequestered in them. A

comprehensive sediment survey is needed to determine the redistribution of sediments types, which, if extensive, will affect the

distribution of invertebrate communities, SAy, oyster reefs and

fishes. It is possible that the resuspension of contaminated

sediments and their subsequent export out of the bay during the three

major storm events of 1995 improved the overall quality of the

system.

It is erroneous to assume that a consistent, direct relationship

between benthic secondary productivity and the number of species of

macroinvertebrates will persist between sampling intervals in a given

place, time or habitat-type. There is rarely a predictable,

invariable relationship between the numbers of large sessile animals

supported by a habitat and the numbers of smaller or larger sessile

and motile organisms living in it. The variety and numbers of

5-70
resident species in a given habitat are directly and indirectly

influenced by transient species (wide-ranging predators, for

example), whose numbers and types have been undersampled in the

Pensacola and the other estuarine and shelf regions discussed in this

report.

5. Little information exists on fisheries by-catch species composition

or abundance, and less in known about the recruitment of fishes into

the system, or their residence times. The suitability and abundance

of Pensacola Bay System invertebrate species as forage for

commercially important predatory fishes is unknown, as is the

carrying capacity of the system for fishes in general, and for

schooling fishes in particular.

5.4.2 Choctawhatchee Bay

5.4.2.1 uvironmerzta1 Settiria

Choctawhatchee Bay is an east-to-west trending coastal basin 48 km long and

1.6-2.4 km wide in the Gulf Coastal Lowlands physiographic province of the

Florida panhandle. With a surface area of 1,190 km2, Choctawhatchee Bay is

the largest drowned river valley estuary in the panhandle, and the third

largest on the Gulf coast of Florida (Blaylock, 1983; Livingston, 1987;

FDEP, 1994) . Choctawhatchee Bay and its bayous are shown in Figure 5-12.

Choctawhatchee Bay communicates with the Gulf of Mexico through a shallow

channel (East Pass) at Destin, Florida. Water in eastern portions of Santa

Rosa Sound commingle with Choctawhatchee Bay water near Ft. Walton Beach.

It is suspected that very little mixed Santa Rosa Sound-Choctawhatchee Bay

water enters the Gulf of Mexico through Pensacola Pass 69 km to the west.

The intracoastal waterway is a 32.2 km-long, man-made canal that connects

Choctawhatchee Bay to West Bay in the St. Andrew Bay system.

The eastern portion of Choctawhatchee Bay near the Choctawhatchee River is

shallow, with depths of 0.1 to 3 m (FDEP, 1994) . Water depth progressively

increases to 9 m, and reaches a maximum of 13-14 m northeast of East Pass

(Blaylock, 1983; Wolfe et al., 1988; FDEP, 1994). The average depth of

Choctawhatchee Bay is about 3 m (Sonu and Wright, 1975). Shoaling is

achronic problem at East Pass Channel, which is periodically dredged to

maintain controlling depths of 4 m (Collard, 1976). Choctawhatchee Bay

receives about 95% of its fresh water inflow from the highly alluvial

Choctawhatchee River (Seaman, 1985) . Thirteen smaller streams, including

Alligator, Black, Peach, Rocky, Turkey, Holmes, Camp Branch, Sandy, West

Sandy and Bruce Creeks also discharge into the bay. The largest of these

is Alaqua Creek (Blaylock, 1983) . Base flow in the bay is high due to

seepage from the Sand and Gravel Aquifer (Wolfe et al., 1988).

FDEP (1994) noted that the Navarre Bridge Causeway divides Santa Rosa Sound

into nearly equal sized eastern and western portions, and contributes to a

bi-directional tidal flow in the estuary. Santa Rosa Sound is nearly

uniform in depth and salinity with mean annual values of 2.7 m and 24 ppt,

respectively. Although Santa Rosa Sound and Choctawhatchee Bay are

connected, their physical boundaries and water quality characteristics are

5-71
Figure 5-12. Schematic map of the Choctawhatchee Bay system.
quite different (FDEP, 1994) . Bottom salinities at least in western

portions of Santa Rosa Sound approach zero frequently. USEPA data (unpubi.

data) suggest that average near-bottom salinities are about 15 ppt.

5.4.2.2 Hvdroqrahv and OceanocwaDhv

Choctawhatchee Bay is a low energy estuary with a non-storm tidal range of

0.2 m or less within the bay, and 0.4 m in the Gulf at East Pass (FDEP,

1994) . Both eastern (Choctawhatchee River), and western (East Pass) ends

of the bay are shallow relative to the central bay, and are at opposite

ends of the salinity spectrum (0 and 34 ppt, respectively). Low tidal

energy, a bowl-like bathymetry, and a single major point source of fresh

water input result in a two-layered bay, in some ways reminiscent of a

hypothetical estuary. Livingston estimated that salt water exchange was

about 14 ppt during each tidal cycle, and that the overall flushing rate of

Choctawhatchee Bay may exceed one year.

Whereas the friction of riverine fresh water flowing over deeper, saltier

water causes some vertical, seaward-flowing entrainment of salt water and

development of a mixed layer of variable, but generally shallow thickness,

Choctawhatchee Bay is known to be strongly stratified (e.g. Collard, 1976;

Blaylock, 1983; Livingston, 1986; FDEP, 1994) . Livingston (1986) reported

the presence of an extremely strong halocline, where salinity increased by

14 ppt with a two foot increase in depth. He recorded a maximum salinity

below a halocline of 36.9 ppt LaGrange, Alaqua and Basin Bayous in eastern

sections of the bay have relatively low salinities. Joe's, Indian, Horseshoe and Hogtown Bayous have low to moderate salinities; and Upper Rocky

and Boggy Bayous have moderate salinity at depth. Old Pass Lagoon, and

Gamier Bayou have relatively high salinity according to Livingston (1986).

Horizontal, and to a somewhat lesser extent, vertical salinity gradients,

depth of the mixed layer, and the depth and strength of the pycnocline are

a function of river flows and wind mixing. A strong halocline seems to be

present most of the time, throughout most of Choctawhatchee Bay. Collard

(1976) reported that the western two thirds of the bay was highly

stratified, and the eastern third was weakly stratified year round.

Livingston (1986) reported that deeper bay waters were among the most

highly stratified in the panhandle.

During warm summer months isohaline and slightly mixed upper water in the

bay becomes even less dense, and a strong thermocline develops at

approximately the same depth as the halocline. These two factors result in

a strong pycnocline that resists turbulent mixing, and may result in

drastically reduced dissolved oxygen concentrations in bottom waters

depleted of the gas by HOD, COD and SOD.

Sonu and Wright (1975) studied the interactions between tides, water

density distribution, longshore currents, waves and winds associated with

East Pass. Pollutants moving with undiluted offshore water can approach

the inlet for most of the tidal cycle. Sonu and Wright reported that,

"During flood tides, a wave-induced longshore current is readily entrained

into the inlet, whereas an ambient cross current, either driven by tide or

sea breeze, tends to bypass the inlet by deflecting seaward at the jetty.

5-73
During ebb tide, these currents can still operate in strength in the

underlayer, by-passing the inlet beneath the buoyant jet or approaching the

inlet under a laterally expanding effluent along the adjacent surf zone.

The effluent discharging with the jet can undergo strong buoyant expansion

into the adjacent coast, forming a partially diluted effluent pool against

the shore under a sea breeze. The land breeze and the instability at the

density boundary between this nearshore effluent pool and the undiluted

offshore water are the two most important factors affecting the eventual

dispersion and diffusion of the tidal inlet effluent."

5.4.2.3 Water and Sediment Oualitv

Livingston (1986) described the development of Choctawhatchee Bay from its

almost lake-like condition in the early 1920s, to the late 1980s. His

historical account of modifications made to the estuary are useful in

understanding its present characteristics. According to Livingston (1986)

the first major modification of the bay occurred in 1929, when a new,

direct channel was cut from the bay to the Gulf of Mexico at Destin. Prior

to that time, flushing of the bay was much less than at present; water

level was much higher; and overall salinity was (probably) much lower.

Livingston (1986) suggested that a second major modification was made to

the bay itself, with construction of a causeway across the eastern part of

the bay. The causeway modified circulation patterns and altered the

movement and deposition of sediment carried into the bay from the

Choctawhatchee River. The most recent, and continuing major modifications

of Choctawhatchee Bay are the result of, "considerable growth of

agricultural land use" in the Choctawhatchee River basin, along with

accelerating municipal development in western portions of the bay

(Livingston, 1986)

Paulic and Hand (1994) assessed water quality in choctawhatchee Bay as

"generally good" (i.e. met its designated use), but threatened due to

development in Destin and Fort Walton Beach. The occurrence of

eutrophication and fish kills in Old Pass Lagoon at Destin was mentioned as

a problem area. Water quality was assessed as "fair" in Jose, Rocky,

Indian, LaGrange and Boggy Bayous and in Peach Creek and Jolly Bay at Black

Creek. Water quality problems in these bayous and streams were attributed

primarily to development and Waste Water Treatment Plant (WWTP) discharges.

Paulic and Hand (1994) determined from available data and professional

judgement that the Choctawhatchee River was of "generally good water

quality", but several tributary systems (Alligator, Holmes, Camp Branch

Creeks, West Sandy Creek and Bruce Creek) had problems with domestic or

industrial discharges.

FDEP (1994) reported that nitrogen levels were highest in western portions

of Choctawhatchee Bay (Cinco, Gamier, lower Rocky and Boggy Bayous) due to

stormwater runoff from Destin Peninsula and adjacent developed areas. Low

primary productivity in the bay was attributed to low concentrations of

dissolved phosphorus.

Choctawhatchee Bay sediment characteristics vary from east to west with

distance from the Choctawhatchee River (and smaller streams) and East Pass,

respectively; and from shallow marginal areas to deeper depths in the

5-74
central basin of the estuary. Fine sediments containing relatively high

TOC and heavy metals are found in much of the eastern, Choctawhatchee

River-dominated portions of the estuary, in some bayous (e.g. La Grange,

Basin, Lower Rocky, Boggy, Gamier, Indian, and Hogtown Bayous), and in

deeper portions of the basin, where silts and clays accumulate (e.g.

Livingston, 1986; FDEP, 1994)

Livingston (1986) reported a fringe of medium- to well-sorted quartz sand

from shore to the 6-8 foot depth contour in Old Pass Lagoon, and in Alaqua

and Upper Rocky Bayou. The shelf drops sharply to a transition zone of

silty sand, followed by a second shelf-slope transition zone where

sediments become predominantly clay-silt in deeper water of the central and

western portions of the estuary. Relic quartz sand characterizes the far

western end of the bay, and fine sediments dominate eastern portions

(Livingston, 1986)

SOD is reported to be fairly high in fine sediments because of hypoxia

(oxygen concentrations < 2 mgl'), relatively high nutrient concentrations

and in some areas, the likelihood of high BOD (Livingston, 1986; Paulic and

Hand, 1994; FDEP, 1994) . Livingston (1986) did not find significant

concentrations of toxic organic agents (pesticides, herbicides) in

Choctawhatchee Bay sediments.

Using FDER guidelines for assessing metals concentrations in sediments

(i.e. aluminum-to-metal ratios), (Ryan et al., 1984), Paulic and Hand

(1994) and Livingston (1986) reported that fine sediments in some portions

of urbanized western bayous (particularly Boggy Bayou) and deeper portions

of the central and eastern bay basin were "enriched" or "possibly enriched"

with several metals, including Al, As, Cd, Cu, Fe, Pb, Ni and Zn. The

concentration and distribution of metals was patchy and attributed to

natural processes, including river flow, basin physiographic

characteristics, and anthropogenic activities such as urbanization and

stormwater runoff. It was suggested that at least copper and lead, and

possibly zinc and cadmium enrichment were associated with urban stormwater

runoff and marina development in western portions of the bay. River

influence was most evident for As, Cu and Ni. Urban runoff and marina

activities explained in part elevated concentrations of Cu, Pb, Zn, Cd in

Old Pass Lagoon sediments.

5.4.2.4 Bioloav

Livingston (1987) characterized Choctawhatchee Bay as an important nursery

area for marine organisms and supported an active fishing industry. He

noted, however, that productivity of the bay was perceived to be lower than

in the recent past (i.e. early 1980s). This impression is widely held by

biologists at Okaloosa Community College (Hamilton, pers. comm.), local

commercial and sports fishers (pers. comm.), local residents (pers. comm.)

and the mass media.

As is the case with the Pensacola estuary, Santa Rosa Sound, and St. Andrew

Bay, Choctawhatchee Bay is increasingly exposed to, and undergoing adverse

changes caused by anthropic stressors. Poorly flushed, urbanized bayous,
in particular, appear to be changing at rates too rapid for accommodation

by historically abundant transient and resident animals and plants.

Salt Marshes and Submerged Aquatic Vegetation

Choctawhatchee Bay exhibits a submerged vegetation coenocline, with fresh

water species (e.g., Cladiurn jamaicense) dominant near freshwater sources.

Species tolerant to slightly brackish water (e.g., Vallisneria americana)

are found in shallow water with increasing distance from fresh water

sources, and Ruppia maritima is the only submergent vascular plant found in

brackish waters of the estuary (Livingston, 1987). True seagrasses are not

supported in Choctawhatchee Bay because of low salinities in the bay's

eastern reaches, high turbidity in deeper, saline portions of the bay, and

current scouring of sand sediments in the vicinity of East Pass (Collard,

pers. comm.). Fringing fresh-to-salt marsh dominants include, from east to

west (fresh to more saline), the exotic Phragmites australis, Spartina

spp., and Juncus roemerianus (Livingston, 1987). Fishes associated with

SAV are discussed below.

Benthos

Livingston (1987) reported that as of 1968, a total of 110 species of

benthic macroinvertebrate species (including freshwater taxa) had been

recorded from Choctawhatchee Bay. Collard (1976), however, reported that

otter trawl and grab samples taken during the summer suggested that the

bottom of the bay was "biologically barren." All recent investigators (e.g.

Collard, 1976; Taylor Biological, 1978; Livingston 1986; Livingston, 1987;

FDEP, 1994), found that species diversity decreased to the east, with

decreasing salinity.

In the most comprehensive investigation of Choctawhatchee Bay accomplished

to date, Livingston (1987) found, based on collections made during 1985-

1986, that benthic abundance and species composition was highly variable,

but that Carolinian species predominated. Livingston reported that the

lowest number and biomass of infauna occurred in mid-bay and in various

bayous (Boggy, Lower Rocky and Gamier). Deep, mid-bay silt-clay

substrates were dominated by the opportunistic polychaete, Medic'mastus

ambiseta, which was a numerical, but not a biomass dominant in the bay as a

whole. The polychaete, Carazziella hobsonae, was numerically dominant in

Old Pass Lagoon.

Livingston's 1985-86 collections showed that the highest number and biomass

of the benthic biota occurred in shallow seagrass areas, and in deeper

sections of the western portions of the bay. Such areas were dominated by

tubiculous worms, Mediomastus ambiseta, Aricidia philbinae, A. taylori, and

Carazziella hobsonae. In contrast, areas of the bay comprised of silt-clay

sediments with high organic and metals concentrations were depauperate.

Livingston (1987) stated that, "In any case, for the bay's size, the

Choctawhatchee Bay infaunal biota can be characterized as depauperate in

numerical abundance, dry weight biomass, and species richness."

Livingston (1986) described the trophic guild structure of the benthos as

follows: Overall, below-surface browsers, scavengers and grazers were

5-76
dominant at deep, mid-bay stations, but not in the metals-enriched western

bayous or in Old Pass Lagoon. In the latter, above-surface feeding types

dominated collections. Livingston suggested that this type of foraging

could explain, in part, the high densities of animals observed, in spite of

the presence of polluted sediments. Livingston (1987) concluded that, "the

overwhelming bay-wide majority of such [epibenthic] organisms are

detritivorous omnivores, and that "herbivory was also somewhat common".

Two guilds clearly dominated in the Choctawhatchee Bay benthos: omnivorous

scavengers of limited dispersal, and deposit-feeding omnivores having wide

dispersal. A disproportionate fraction of all "guilds" were dominated by

so-called opportunist indicator species (Livingston, 1987) . "Clearly, the

biological features of the infaunal macroinvertebrates were primarily

associated with the various aspects of the sediments and, secondarily, with

depth" (Livingston, 1987)

Over 30% of the benthic infatinal macroinvertebrates in Rocky Bayou were

reported to be oligochaetes by Livingston (1987). Infaunal polychaetes

were represented by Mediomastus ambiseta, Aricidea philbinae, Streblospio

benedicti, Fabricio sp., Prionospio heterobranchia, Lepidactylus sp.

Chione duneri and Laeonereis culveri. The macroepifauna of Rocky Bayou was

dominated by Penaeus duorarura, P. setiferus, P. aztecus, Callinectes

sapidus and Lolliguncula brevis.

Wolfe et al. (1988) reported that benthic collections near Fort Walton

Beach showed a fairly healthy macroinvertebrate community, but that there

was a significant decline in species diversity in the bay, near Piney

Point. These observations support those of Livingston (1987) that species

diversity decreased east of East Pass inlet.

Fi ches

FDEP (1994) reported that a total of 330 species of fishes were collected

from Choctawhatchee Bay, Pensacola Bay and Santa Rosa Sound during the

period 1972-1992. Of the species collected in Choctawhatchee Bay, more

than 91% of the catch was represented by only six species. During spring,

1994, a total of more than 302,000 individuals representing 117 taxa of

fishes were captured in the bay using beach seines, offshore seines,

gilinets, and trawis. Leiostomus xanthurus, Lagodon rhomboides, Menidia

spp., and Brevoortia spp. accounted for 81.6% of all beach seine

collections, and of these, twice as many L. xanthurus were captured as

either L. rhomboides or Menidia spp. Lagodon rhomboides was the most

abundant species collected in offshore seines (67.5% of the catch),

followed by Leiostornus xanthurus (10.1%) . Four numerically dominant taxa

(75.2% of the total catch) were collected with experimental gillnets: Anus

felis (52.1% of the total); Cynoscion nebulosus; Mugil spp.; and

Opisthonema oglinum comprised the remainder. Trawl catches were dominated

by Leiostomus xanthurus (84.2%), which together with Brevoortia spp. and

Anchoa spp. made up 91.5% of all trawl catches.

Fishes were also collected by FDEP during fall 1994 with the same types of

gear used during their spring sampling. Catch results are summarized

below. Beach seine dominants (90.1% of the total) were LeiostornuS

xanthunus, Menidia spp., EucinOstoinUS spp. and Anchoa spp. Menidia spp.

5-77
were most common (25.8% of the total) in offshore seine catches, and 77.4%

of experimental gillnet takes were comprised of Leiostomus xanthurus

(49.6%), Anus felis and Brevoortia spp. Trawl hauls were dominated by

Leiostomus xanthurus (34.5%), Anchoa spp., Penaeus spp. and Eucinostomus

spp. At fixed beach seine stations, the numerically most abundant species

caught was Lagodon rhornboides, followed by Leiostomus xanthurus, and the

invertebrates, Callinectes sapidus and Penaeus spp. Anchoa spp. was most

abundant (84.6% of the total) in offshore seine collections. Anchoa spp.,

L. xanthurus and Mugil spp. together made up 94% of the total offshore

seine collections. Most of the numerically abundant species were dominant

in all habitats.

Many seasonal tropical species occur at or near the Destin jetties. These

include cocoa damsels (Pornacentrus vaniabilis), angelfishes

(Pomacanthidae), parrotfishes (Sparidae), spadefishes (Ephippidae) and

butterflyfishes (Chastodontidae). It is likely that the young stages of

many tropical species are advected to panhandle coastal environments, but a

lack of suitable habitat (i.e. extensive rubble mounds) prevents them from

becoming established during warm water months.

5.4.2.5 Data Gape

The impact of Hurricanes Erin and Opal (August and October, 1995) on

the water quality of Choctawhatchee Bay and its bayous has not been

evaluated. However, the high storm surge and pulse of ocean water

into Choctawhatchee Bay during this hurricane may have flushed a

significant volume of resuspended fines out of the system. Sand

dunes between Destin and Ft. Walton Beach were completely destroyed

during the storm, permitting a free exchange between Gulf of Mexico

and Choctawhatchee Bay water.

Environmental impacts of Hurricanes Erin and Opal on Choctawhatchee

Bay water and sediment quality; flushing rates; bathymetry;

nutrients, toxic chemicals and heavy metals pulse loadings; and

suffocation of sessile benthic invertebrates (e.g. oysters) by

sediments are not known. Based on personal observations, however, we

speculate that the storm's impact on some or all of the variables

mentioned may have been significant over short (weeks to months) and

intermediate (months to several years) time scales.

A considerable quantity of military-related debris (bombs, bullets,

etc.) may contribute to elevated levels of certain metals in

Choctawhatchee Bay. n effort should be made to assess the

distribution of submerged ordnance, as well as the overall impact of

Eglin Air Force Base on the bay's ecology.

Primary productivity-production throughout the bay, and its

distributional relationship with primary sources of nutrients (i.e.

Choctawhatchee River, nutrient-rich bayous, marinas) needs to be

assessed in order to determine food web relationships between

organisms in the system.
5. Because of very rapid population growth in the area surrounding

Choctawhatchee Bay, a monitoring program should be implemented to

assess likely increases in levels of adverse anthropogenic impacts on

the bay's ecosystems.

5.4.3 St. Andrew Bay

5.4.3.1 Environmental Settina

The St. Andrew Bay coastal plain estuary is a large bilobate embayment

located in the Gulf Coastal Lowlands physiographic region of the central

Florida panhandle. West and North Bays form the western lobe, and East Bay

forms the eastern lobe of the embayment. St. Andrew Bay proper lies

between the eastern and western portions of the estuary, and connects the

Gulf of Mexico with West, North and East Bays (Figure 5-13). Panama City

lies between East and West Bays (Saloman et al., 1982; Wolfe et al., 1988;

Paulic and Hand, 1994). The estuary is approximately 31 miles (19.2 krn)

long, arid trends from northwest to southeast parallel to the coast. North

Bay extends inland approximately 13.5 miles (21.7 km) to Econfina Creek,

its major freshwater source (Young et al., 1987).

St. Andrew Bay has a surface area variously estimated to be between 94 mi2

and 108 mi2 (Pristas and Trent, 1978), with a total volume of 3.13 X l0°

ft3 (about 829,000 acre-feet) at mean high water (Saloman et al., 1982;

NOA/EPA, 1989) . The estuarine drainage area of the system is 1,130 m12,

with an average daily inflow of 4,500 cfs. Econfina Creek, with an average

flow about 500 cfs, is the principal point-source of fresh water (via Deer

Point Lake) into the system. For most of the year base flow in Econfina

Creek is maintained by ground water from springs fed by the Floridan

Aquifer (Musgrove et al., 1968). Unlike other major estuaries in Florida,

the St. Andrew system has no fluvial streams, and its watershed lies

entirely within the state. The St. Andrew Bay Resource Management

Association (1992) described the bay system as having an average depth of

5.2 m (17 ft) and a maximum depth of 19.8 m (65 ft). Because natural

tributaries that discharge into the system are clean, and several are

spring-fed, St. Andrew Bay has clear water throughout most of its reaches.

In addition to Econfina Creek, Wolfe et al (1988) consider the main

tributaries in the St. Andrew Bay coastal drainage area to be Wetappo

Creek, Sandy Creek, Bear Creek and Big Cedar Creek. Except for Econfina

Creek, streamfiows are unknown.

5.4.3.2 HvdroQrahv and Oceanoqrat,Iiv

The St. Andrew Bay system communicates with the Gulf of Mexico through two

passes. West Pass, constructed by the Army Corps of Engineers in 1934, is

a 10 to 20 m deep, 152 m (500 ft) wide channel located about seven miles

northwest of East Pass. It is, relative to the latter, of little

significance to circulation patterns or flushing rates. East Pass is (or

was, prior to October 1995) over a mile wide, and relatively shallow over

most of its width (depths range from 2-8 m). A sand bar forms at the

seaward opening of East Pass (due to longshore drift), and it must be

dredged every 12-18 months.
Figure 5-13. Schematic map of the St. Andrew Bay system.
Saloman et al. (1982) noted that as a result of low volumes of freshwater

inputs and good flushing rates in most of the system, St. Andrew Bay has

relatively clear, high salinity water. They found that Secchi depths are

generally 6 m or more near Gulf passes, and nearly always greater than 1.8

rn in North, West, and East Bays. Saloman et al. (1988) attributed clear

waters of the system to: (1) clear incoming tidal and tributary waters; (2)

forested uplands; (3) locally porous, sandy soils with a low silt-clay

fraction; and (4) natural filters in the form of abundant tidal marshes and

submerged aquatic vegetation that collect and stabilize suspended sediments

and particulate detritus.

Under average conditions the salinity at the surface and bottom in North,

West, and East Bays is about 10-30 ppt Surface salinity in East Bay falls

as low as 5 ppt, the halocline is deeper, and turbidity is higher than in

the other subsystems. Salinity in St. Andrew Bay rarely falls below 30 ppt

at the surface and is usually 33 ppt or higher (Saloman et al., 1982).

Following heavy rains, the salinity frequently falls below 10 ppt in the

upper parts of North, West, and East Bays. At such times a well-defined,

strong halocline may develop between relatively fresh surface waters and a

lower wedge of highly saline water (Saloman et al., 1982). When heavy

rainfall is of unusually long duration (several days) surface salinities of

0 ppt may occur throughout the system. Collard (unpubl. Data) measured

salinities of 0 ppt at the surface, and 21 ppt in the bottom waters of

central St. Andrew Bay during September 1994. Fernald and Purdum (1992)

reported mean seasonal salinities in the system to be 35 ppt in winter, 34

ppt in spring, 35 ppt in summer, and 36 ppt in the fall.

There is disagreement with Naughton and Saloman (1978), who reported that,

"Salinity stratification is minimal except in bayous and creeks during

rainfall periods". Baskerville-Donovan, Inc. (1991) suggested that, "A

strong halocline may often occur, but thermoclines are generally weak, with

differences of only a few degrees Celsius."

Saloman et al. (1982) reported that summer water temperatures fluctuate

between 26.7CC and 32.2CC. Spring and fall water temperatures average

about 2l.lC, and winter temperatures fall to l2.8eC or less. Thermoclines

are common, but seldom exceed a surface to bottom temperature difference of

more than a few degrees. Surface water temperatures are summarized in

Table 5-16.

Table 5-16. Sea-surface temperatures (CC) in the St. Andrew Bay system

(after Saloman et al 1982).

Although surface water temperatures are mild or warm most of the time, in

most years; ice occasionally forms at the edges of quiet inlets and bays

5-81

Winter Spring - Summer Fall

Maximum 24.4 (76F) 28.9 (84SF) 30.0 (86°F) 26.7 (80°F)

Minimum 16.7 (62°F) 23.3 (74°F) 26.7 (80°F) 18.9 (66°F)

Mean 17.8 (64°F) 25.6 (78°F) 28.9 (84°F) 22.2 (72°F)
(e.g., Bureau of Submerged Lands and Preserves, 1991). Surface water

temperature ranged between 5C and l6C in January, 1996 (Collard, unpubl.

data).

Tides in the St. Andrew Bay system were reported by Saloman et al. (1982)

to be diurnal, with a tidal range generally less than 1.2 m. Wave heights

are usually less than 0.3 m, and tidal currents are generally less than 1

knot. The highest storm surge measured in the system was 5 m above mean

sea level (MSL) (Saloman et al., 1982). Collard (unpubl. data) measured

the October, 1995, storm surge in St. Andrew Sound as between 2.0 and 2.5 m

above MSL.

Based on the analysis of tide gauges at six stations during the period

August 1991 to January 1992, HydroQual, Inc. and Barry A. Vittor &

Associates, Inc. (1993) reported that a spring-neap tidal cycle with an

approximate period of two weeks, was clearly evident. The daily average

water level at each location also varied with time, primarily due to

varying hydrodynamic conditions in the Gulf of Mexico.

A circular current often develops in East Bay, when tides are flooding in

the tidal inlets at a maximum rate. This creates a zone of poor

circulation at the upper (northeast) part of the bay. The current in East

Bay, however, maintains relatively good circulation in the rest of the bay.

Whereas West Bay directly receives little fresh water from runoff or

streams, it receives water from Deer Point Lake driven by strong tidal

currents in St. Andrew Bay. Saloman et al. (1982) described the mass

balance of water in the system. The net flow of water at the surface is

northwest into West Bay; south from North Bay; northwest out of East Bay

and to the Gulf of Mexico from the system as a whole. Mass balance for the

lower layers of water (i.e. below the halocline) are northwest into West

Bay; north into North Bay; southeast into East Bay; and north into the

system from the Gulf of Mexico.

5.4.3.3 Water and Sediment Oualitv

Paulic and Hand (1994) stated that, "The St. Andrews (sic)Bay system

generally exhibits good water quality. The major inflow, Econfina Creek,

is nearly pristine, and most of the urbanized area is concentrated where

the bay is better flushed by the Gulf. However, the bay is threatened, not

only by the growth-induced nonpoint source pollution, but also by several

important domestic and industrial point-sources." Watson and Beatty Bayous

were judged to be degraded by urban stormwater and historic waste water

treatment plant (WWTP) discharges. Watson Bayou was also reported to have

high sediment concentrations of lead, mercury, cadmium, zinc, DDT,

Chiordane, PCBs and polycyclic aromatic hydrocarbons (PAHs). Metals found

in St. Andrew Bay included zinc, lead and copper.

NOAA (1989) evaluated the pollution susceptibility of St. Andrew Bay and

predicted that its dissolved substance concentration potential was 0.76 mg

1', and its particle retention efficiency was 0.22 mg 11 (volume to

inflow) . Both of these values correspond to "medium class" pollution

susceptibility. The NOAA study estimated nutrient loadings for the system

(Table 5-17)and its predicted concentration status (load in tons per year

required to change its concentration class) [see Table 5-18]

5-82
Sources of TKN were calculated to be about 24-25% from point-source WWTPs,

about 60% from point-source industrial facilities, about 20% from nonpoint

agricultural ruriofn, and less than 5% from nonpoint urban runoff (about 75%

from point source WWTPs and industry, and about 25% from nonpoint

agriculture and urban sources). About 80% of phosphorous inputs were

calculated to come from point-source WWTPs and industry, and about 20% from

nonpoint agriculture and urban sources (NOAh, 1989).

NOAA (1989) estimated that St. Andrew Bay had a medium susceptibility for

concentrating dissolved substances: "This dissolved concentration potential

combined with the estimated nutrient loadings results in predicted

concentrations within the low range for both nitrogen and phosphorous.

Table 5-17. Estimated nutrient loadings for the St. Andrew Bay system (from

NOAA, 1989)

Table 5-18. Predicted concentration status for the St. Andrew Bay system

(from NOAA, 1989)

In St. Andrew Bay, the low nitrogen concentration classification may be

influenced by a minor increase (< 20%) in nitrogen loading."

Ferrario (1990) reported that a site in St. Andrews (sic)Bay had a

phenanthrene to anthracene ratio of 144 and showed high levels of alkylated

PAHs, indicative of contamination by non-combusted petroleum products.

Ratios were greater than 50, thus the sources of PAH5 were not from rain or

stormwater runoff, but likely from municipal, agricultural or industrial

waste. Ferrario (1990) also reported that the highest concentrations of

total DDTs in estuaries were usually associated with major river outfalls.

However, St. Andrews (sic) Bay and Panama City, Florida, which receive no

major river effluents, have not only the highest concentrations of total

DDT but also the highest concentrations of PARs, evidence of human impact

on these areas.

5-83

Sources

Nutrients

TKN

(tonsyr)

Phosphorous

(tonsyr)

Point 271 42

Nonpoint 872 61

Upstream 0 0

Concentration Increase By Decrease By

Nutrient (mg1') Class Load % Load

Nitrogen 0.087 (L) 173 15 N/A N/A

Phosphorous 0.008 CL) 29 28 N/A N/A
The St. Andrew Bay Resource Management Association (SABRMA (1992) reported

that point-source pollution discharges exceeded 30 rngd, and that secondary

domestic and industrial wastewater inputs were gradually increasing

pollution levels in the system. Other causes for concern mentioned in the

report were chronic stack emissions and a virtual lack of stormwater runoff

or treatment controls. The SABRMA (1992) report concluded that the St.

Andrew Bay system was still in generally good condition, but some of its

bayous were deteriorating as evidenced by fish kills and seagrass losses.

Baskerville-Donovan, Inc. (1991) calculated that there were currently

approximately 30 major point-source discharges into the St. Andrew system.

Young et al. (1987) reported that West Bay received discharges from the

West Panama City Beach WWTP, and thermal effluents from the Lansing Smith

Power Plant at Warren Bayou. Saloman et al. (1982) calculated the Gulf

Power thermal effluent to be some 200,000 gallons per minute, and the

SABRNA (1992) reported that water temperatures from the outfall in Warren

Bayou exceeded 40°C, higher than the upper lethal temperature of many

estuarine species. Low DO levels were reported in the vicinity of the

Panama City Beach WWTP by Hand and Paulic (1992).

According to Young et al. (1987), East Bay (connected to Lake Wimico and

Apalachicola River by the Intracoastal Waterway) drained a number of acid

sand-bottom streams, including Sandy, Wetapo, and Calloway Creeks.

Environmental problems in East Bay included domestic and industrial

wastewater discharges, sand mining in Cook's Bayou, non-point source

impacts from Tyndall Air Force Base, stormwater runoff from surrounding

urban areas, and draining of wetlands for pine tree silviculture.

In lower St. Andrew Bay, Young et al. (1987) reported that water quality

degradation sometimes occurred in areas of tidal and wind concentration of

the wastewater from outfalls at Gulf inlets and along beaches.

Duke and Kruczynski (1992) reported that St. Andrew Bay was impacted by

high coliform contamination from combined urban and nonurban sources. Hand

and Paulic (1992) reported that water quality was depressed in an area

around a paper mill, and that water in both Beatty and Watson Bayous was

degraded by urban stormwater and historic WWTP discharges. Wolfe et al.

(1988) reported that in 1984 Bay County showed elevated levels of As, Ba,

Cr, small amounts of Pb, Se, F, N, and turbidity in untreated public water

supplies.

Sediments in most of the St. Andrew Bay system are medium fine quartz sands

about one foot thick (Wolfe et al., 1988; Fernald and Purdum, 1992).

Clayey sands are found north and in the eastern portions of East Bay (Wolfe

et al., 1988). Saloman et al. (1982) characterized shallow water sediments

of the estuary as comprised of shell fragments and fine to course quartz

sand. Substantial amounts of silt and clay sediments are present in many

bayous, and in open bay areas at depth greater than 6.1 m (Saloman et al.,

1982) . Sediments around the margin of the bay system were reported by

Baskerville-Donovaxi, Inc. (1991) to be predominantly quartz sands with

shell hash. Grady (1981) reported that the average organic and carbonate

content of sediments in seagrass beds were 1.9-fold greater than in sand

flats. Tidal stream sediments were sandy silts containing moderate amounts

of organic material. The total organic carbon content of these sediments

ranged from l0 in shallow waters to 15% in deep waters.

5-84
In conjunction with biological sampling Saloman et al. (1982) reported that

sediments consisted of moderately sorted fine sand, with finer sediments in

quiet waters. Coarser sediments and shells were associated with oyster

beds and reefs. Saloman et al. (1982) determined average sediment TOC to

be slightly less than 1%, of which 70% consisted of plant detritus, and 30%

of shell fragments and animal remains.

Ferrario (1990) reported the concentrations of 18 PAH compounds from 153

sediment and 145 oyster samples collected from 50 locations within the St.

Andrew system. PAH5 were detected in 89% of the sediment and 78% of the

oyster samples (Wade et al., 1988). The total PAH concentration in both

sediment and oysters ranged from about 10 ppb to 18,000 ppb, with

fluoranthrene and pyrene generally accounting for more than 25 percent of

the total. The highest value in both sediment and oysters was from

Watson's Bayou in St. Andrew Bay. PARs are reported to be carcinogenic,

mutagenic, and/or teratogenic.

Baskerville-Donovan, Inc. (1991) reported that sediments in both St. Andrew

and North Bays contained moderate amounts of contaminants such as heavy

metals, hydrocarbons, and excess organic compounds and nutrients.

Baskerville-Donovan (1991) stated, however, that, "These data indicate that

estuaries in the St. Andrew Bay system contain lower sediment contaminant

levels than most other estuaries in the northeastern Gulf of Mexico."

5.4.3.4 Biology

The biology of the salt marsh and submerged aquatic vegetation, benthos and

fish in St Andrew Bay and St. Andrew Sound is discussed in the following

paragraphs.

Salt Marshes and Submerged Aquatic Vegetation

St. Andrew Bay was reported by NOAA (1991) to have a total of 251,100 acres

of coastal wetlands. Included in this total were 8,500 acres of salt marsh

and 3,500 acres of tidal flats. Hand and Paulic (1992) noted that a

dieback of salt marsh cordgrass (Spartina spp.) had occurred along the

inner perimeter of St. Andrew Bay, but did not furnish quantitative

information on causes or loss rates. Wolfe et al. (1988) noted that the

shores of St. Andrew Bay are protected by marshes. It was not possible,

however, to evaluate the degree of erosion mitigation or other protection

actually provided by salt marshes in our post-Hurricane Opal observations

of St. Andrew Bay.

Wolfe et al. (1988) reported that the St. Andrew Bay system contained the

largest total acreage of seagrass stock in the panhandle. According to

Brusher and Ogren (1976), the estuary had about 7,900 acres of submerged

aquatic vegetation (SAy) . Vallisneria americana was found in the fresher

waters of lower Econfina Creek, and Ruppia rnaritima occurred near bayhead

tidal streams. Of the true seagrasses, Halodule wrightii was also found

around bayheads, and in shallow waters inshore of Thalassia testudinurn.

Grady (1981) observed that Thalassia testudinurn was the dominant seagrass

in unpolluted parts of the system. Halodule wrightii replaced Thalassia in

polluted waters (Grady, 1981). In the high salinity waters of upper West

Bay, SAV was reported to be primarily Ruppia raaritirna and Halodule

5-85
wrightii, with only patchy beds of Thalassia testudinum (Young et al.,

1987)

It was not possible to distinguish major changes in the distribution of

seagrass meadows in St. Andrew Bay from visual and photographic

observations made during an overflight of the area two weeks after

Hurricane Opal (Collard, unpubl. data).

Seagrass meadows in St. Andrew (Crooked Island) Sound, a shallow marine

lagoon bounded by Tyndall Air Force Base, were studied from mid-June to

mid-August 1992. The study site was located at the narrowest part of the

Sound about 3 km from its eastern origin. Seagrass meadows were

monocultures of Thalassia testudinum and Halodule wrightii. Beds of the

two species were often contiguous, with little or no overlap in

distribution. Water temperatures during the study period ranged from 29.9

to 34.4 C; salinity ranged from 30.1 to 36.0 ppt At the deepest station

water depth ranged from 40 to 118 cm. A pycnocline was often present at

mid-depths in deeper water. Currents in the Sound are complex, and react

instantaneously to wind stress. Seagrass densities ranged from 951 leaves

m2 at the shallow T. testudinum to 2078 leaves m2 at the deepest T.

testudinurn site. Reliable measures of H. wrightii densities were not

obtained. Growth rates ranged from -0.3 cm day' to 2.5 cm day-1 Fish and

macroinvertebrate species diversity were high compared to o-ther seagrass

communities described in the literature. During a three day period a total

of 57 species of fishes were collected using a small trawl and a crab

scrape. This compares to a total of 128 species caught during both day and

night trawl hauls over a one year period in the entire St. Andrew Bay

estuarine complex. Heat and low tide exposure stress caused short-term

diebacks in the shallowest beds, and contributed to a mass mortality of the

sea urchin Lytechinus variegatus. Dominant macroepibenthic invertebrates

included sea urchins, the Florida crowned conch, the horn shell, Bittiurn

varium, blue crabs, hermit crabs, paleomonid shrimp, pink shrimp, mud

crabs, hermit crabs, and arrow shrimp. Preliminary lists of species are

included in the report. Infaunal species were inadequately sampled, and

epiphytes were not sampled. Macroalgae were not found in or near the

sampling area, an unusual, if not singular characteristic of the seagrass

community in Crooked Island Sound. Damage to seagrass meadows in the

sampling area was caused by boat propellers, recreational scallop

harvesting and intrusive sampling by the author. No direct or presumptive

evidence of pollution from anthropogenic activities in the area was

detected. Compared to other coastal ecosystems in the northern Gulf of

Mexico Crooked Island Sound is relatively undisturbed and biologically

diverse.

Benthos

Saloman et al. (1982) identified benthic macroinvertebrates from 149

stations in the St. Andrew estuary during the summer of 1974. At a

majority of stations they obtained one sample from an unvegetated sand

substrate and one from a seagrass meadow. Samples were collected from

Military Point, several bayous, and in central portions of the system.

Collections from East Bay extended only to Pitt Bayou, and no collections

were made in North or West Bays. Collections were also analyzed for

sediment characteristics and carbon chemistry. Saloman et al. recorded a

5-86
total of 242 species from their collections, which included 96 species of

annelids (35% of the total species and 65% of the total number of animals);

89 species of crustaceans (33% of the total species and 23% of the total

number of animals); and 69 species of molluscs (26% of the total number of

species and 9% of the number of animals) collected. Ten taxonomic groups

comprised the remainder of the catch (6% of the species and 9% of the

individuals) . Saloman et al. (1982) concluded that coelenterates and

echinoderms may be limited, and that nemerteans, phoronids and

cephalochordates may be favored in portions of the system that were

sampled.

The most recent community analysis of benthos in the St. Andrew Bay system

was accomplished by HydroQual, Inc. and Barry A. Vittor & Associates, Inc.

(1993) during four seasonal sampling periods from May 1991 to May 1992.

The following paragraphs refer to results of this work.

Of the ten most abundant species collected, eight were polychaetes

and the remaining two were an amphipod and a tanaid. The ten most

widely distributed species included an unidentified nemertean, seven

polychaetes, one mollusc and one species of isopod. Not

surprisingly, the ten "most abundant" and ten "most widely

distributed" species were not identical.

The polychaetes, Syllis cornuta and Nereis pelagica; the amphipod,

Lepidactylus sp., and the tanaid, icalliapseudes sp., were among the

ten most abundant species, but not among the ten most widely

distributed. In contrast, Glycinde solitaria, Heterornastus

filiforrnis, Anodontia alba, and a nemertean were listed among the ten

most widely distributed species, but were not members of the most

abundant group.

The fewest species and number of individuals recovered during the

investigation were obtained from samples collected in unvegetated

sediments. Most of the 89 unvegetated sediment samples were taken in

brackish water, in areas of higher than average currents/waves, in

emergent spoil areas, or from polluted areas. The third highest

number of species and individuals were recovered from 23 collections

made in pure stands of Halodule wrightii, and the second highest

number of species and individuals were recovered from 28 samples

collected in mixed meadows of H. wrightii and Thalassia testudinum.

The largest number of both species and individuals was collected from

pure stands of T. testudinurn.

Within seagrass habitats, the number of species and individuals

collected increased with increasing salinity; the lowest numbers were

collected in lower salinity areas of East and West Bays.

Seasonal collection comparisons revealed significant variability in

infaunal macroinvertebrate abundance and diversity. May 1991

collections yielded 416 taxa (from 9 to 137 per station), and both

numerical abundance and density varied widely, from 106 to 10,211

individuals per m2. In September 1991, 385 taxa were recovered, and

lower species abundance occurred at 20 of 29 stations (from 8 to 135

taxa per station) . December 1991 collections recovered 414 taxa.

5-87
The May 1992 collections yielded the greatest number of taxa (455),

and the highest and most variable between-station species abundances

of the four sampling periods.

The total number of taxa collected during the HydroQual, Inc. and

Barry A. Vittor & Associates, Inc. (1993) study was 675. Of these

taxa, polychaetes accounted for 61.5% of all infaunal individuals;

arthropods comprised 20.5% of the total number of individual animals

collected; and molluscs made up 13.5% of the individuals collected.

Echinoderms and "other" taxa contributed only 4.4% of the total.

Whereas polychaetes were most numerous, arthropods were the most

speciose taxon with 41.5% of the total number of species. One third

of all species collected were annelids, and 21.5% of the higher taxa

were molluscs. When possible redundant taxa were excluded, sampling

over all four seasons produced a total of 469 species; 169 annelids;

168 arthropods; and 112 molluscs.

The polychaete, Fabricinuda trilobata, was the most abundant taxon

collected during all four seasons, and equaled 18.7% of all organisms

from the four surveys combined. F. trilobata was especially abundant

in May 1992, when it accounted for 26% of the infauna.

To summarize, the ten most abundant species collected in the HydroQual,

Inc. and Barry A. Vittor & Associates, Inc. (1993) survey accounted for

41.7% of the total infaunal taxa recovered. Nine of the ten species (five

polychaetes, four molluscs, one crustacean) were among the numerical

dominants during each survey.

Species assemblages were associated generally with depth (i.e. with similar

substrata) rather than sample location. These data supported the findings

of other workers who reported that East Bay had lower species diversity and

numerical abundances than the rest of the system. East Bay, as noted

above, is the most strongly stratified of the four subsystems in the St.

ndrew estuarine system. A strong pycnocline is commonly associated with

low dissolved oxygen levels and depauperate benthic communities.

HydroQual, Inc. and Barry A. Vittor & Associates, Inc. (1993) data showed

that the benthic macroinfauna was diverse and abundant throughout the study

area. The number of taxa was much higher than reported for other northern

Gulf coast estuaries. Species abundance was highest in shallow waters, and

correlated with depth, sediment texture and organic content. The lowest

infaunal species diversity and abundance occurred in September 1991, a

period of maximum thermal and salinity stratification throughout the

system.

Prochaska and Mulkey (1983) reported that while Franklin County typically

accounts for 90% of the statewide total of the annual Florida commercial

oyster harvest, other counties, including Bay County "support some

oystering". prochaska and Mulkey (1983) stated that, "recreational data

apparently do not exist... and whether the geographic distribution of

effort parallels the commercial fishery [for oysters] is not known." Table

5-19 presents oyster reef coverage as of 1972. There is no reliable

current information on the areal coverage of oyster reefs in the system.

5-88
Table 5-19 Oyster reef coverage in the St. Andrew Bay system (from McNulty

et al., 1972).

Fishes

Ogren and Brusher (1977) trawied the deeper portions of the St. Andrew Bay

system and collected 128 species of fishes. Seine samples collected within

the St. Andrew estuary and along adjacent coastal beaches yielded 88

species (Naughton and Saloman, 1978) (see Table 5-20). Discussions of

seasonal trends in distribution and abundance were provided in both papers.

Table 5-20. Fish community composition in St. Andrew Bay System, based on

the top ten species reported in Florida from major individual

studies (based on Naughton and Saloman, 1978).

5.4.3.5 Data Gags

1. Hurricane Opal struck the panhandle coast on 4 October, 1995. Based

on observations and personal communications with state and federal

agency personnel, the environmental impacts of this large storm on

the coastline between Pensacola Beach and St. Joseph Spit-Cape San

Bias were significant and, in some respects, extreme. Island and

mainland beaches in the vicinity of St. Andrew Bay (including Crooked

"Island and Shell Island), sand dune, beach, and foreshore sediment

translocation was so great that volumes can not be reliably

5-89

Bay Area (acres)

St. Andrew Bay 0 East Bay 46

West Bay 7 North Bay 6

St. Andrew Sound 0

Dominant Species Total Nwnber of

Fishes (%)

Fundulus sirnilis (longnose

killifish)

8 Menidia beryllina (inland

silverside)

28

Eucinostomus argenteus

(spotf in mojarra)

8

Lagodon rhomboides (pinfish) 22

Leiostomus xanthurus (spot) 10

Percentage of Catch: 76
estimated. Although magnitudes are not known, some salt marsh vegetation

(Juncus, Spartina), seagrass beds (Halodule, Thalassia), supratidal (e.g.,

Ocypode), intertidal (e.g., Donax, Ernerita), foreshore, and estuarine

infauna were destroyed or covered with sediments. It is likely that sof tbodied epifauna and infaunal animals exposed to wave shock (but not storm

surge, per se) may have suffered large, probably temporary reductions in

abundance. With the destruction of dune barriers separating estuarine

areas from the open Gulf (particularly in western Choctawhatchee Bay, St.

Andrew Sound, St. Andrew Bay inlets, and St. Joseph Bay), these areas have

become very vulnerable to further storm damage. Ecological damage, and

risk assessments should be made.

High levels of some contaminants are not readily explained by

"sources of municipal and industrial waste". It is possible that St

Andrew Bay has received (as noted in the section on Choctawhatchee

Bay) wastes and/or debris as the result of historical military

activities. Such sources may explain, in part, elevated levels of

uncombusted petroleum products and (some) metals.

The distribution and areal coverage of oyster reefs and bars needs to

be assessed.

5.4.4 Apalachicola BaY

5.4.4.1 Enviroxunental Settina

Apalachicola Bay is a wide, shallow, 210 mi2 estuary located on the eastern

panhandle coast of Florida (Figure 5-14). The estuary lies at the mouth of

the Apalachicola-Chattahootchee-Flint River system, and is separated from

the Gulf of Mexico by a nearly complete semicircle of barrier islands: St.

Vincent, Cape St. George, St. George and Dog Islands (Gorsline, 1963; FDNR,

1992; Donoghue, 1993). The bay communicates with the Gulf of Mexico

through Indian, West and East Passes, and through St. George Sound and

Sikes Cut, which is a man-made channel (Edmiston and Tuck, 1987). The

Apalachicola River is the 2l largest river in the conterminous United

States, with a mean annual flow of 25,000 cfs (Edmiston and Tuck, 1987).

The river accounts for 35 of the total runoff from the west coast of

Florida, and farms an extensive, compound, lobate-birdfoot delta which is

gradually prograding into Apalachicola Bay (Wolfe et al., 1988; FDNR,

1992)

The Apalachicola Bay system is divided into four subsystems, based largely

on their bathymetry (FDNR, 1992): (1) East Bay (north and east of the

delta) has an average depth of about 1 m, and is surrounded by extensive

marshes and swamps; (2) St. Vincent Sound, which has an average depth of

about 1.2 m, and supports numerous oyster bars [this sound separates St.

Vincent Island from the mainland, and communicates with the Gulf of Mexico

by Indian Pass, which is about 4 m deep]; (3) Apalachicola Bay proper,

which occupies the central and widest portion of the estuary, and is 2-3 m

deep at mean low water; and (4) St. George Sound, which averages 3 m in

depth, and is connected to the Gulf of Mexico through East Pass, separating

Dog and St. George Islands (FDNR, 1992).

5-90
N 98 (p IStJoe NdRd9OGULF CO\UNTY 71 SI Vincunc Sound uSflCI tnnd. 65 4 nI Apatachicol _-°- çu FRANKLIN COUNTY Figure 5-1.4. Schematic: map of the Apalachicola Bay and St. Joseph Bay systems.ello 98
About 60% of Apalachicola Bay is a National Estuarine Research Reserve

(NERR) consisting of 80,000 acres of mostly submerged land extending from

the eastern tip of St. Vincent Island, to a line across St. George Sound at

East Point to St. George Island. The reserve includes both East Bay and

the Apalachicola River delta. The NERR and Apalachicola Bay have received

continuous investigative attention for more than 25 years by Livingston and

his students (Livingston, 1972 et seq.)

While located adjacent to the Apalachicola estuary, the coastal area

between Ochlockonee Bay and the Apalachicola River is not well known (Wolfe

et al., 1988). This 1,440 km2 poorly drained area consists of two regions:

an eastern portion of 830 km2 drained by the New River and its tributaries

which discharge into St. George Sound at Carabelle; and a western portion

known as Tate's Hell Swamp, which drains into East Bay (Wolfe et al.,

1988)

5.4.4.2 Hydroaraphv and Oceanoqraphv

Apalachicola Bay has mixed tides of 0.30 to 0.61 m (1 to 2 ft), with

maximum winter tides reaching 0.91 m (3 ft) (FDNR, 1992). Water movement

in the bay is complex, and controlled by wind, currents and tides

(Livingston, 1989) . The FDNR (1992) report stated, "Over a typical year,

river output can vary over tenfold." circulation, mixing and stratification in the system are influenced, to a large extent, by this

variation in riverine inputs. Winds, tides and fresh water flows each play

important, and varying roles in current forcing. Because of its mean

shallow depth, Apalachicola Bay is usually well-mixed and, with a maximum

transport during ebbing tides of about 20,000 m3s', flushing of the system

is good (FDNR, 1992). Deeper water areas of the bay may become stratified

with the development of a halocline (FDNR, 1992) . Salinity is related to

up-basin rainfall, resulting in a bottom salinity distribution of 0 to 35.6

ppt in various parts of the bay (Livingston, 1984). Circulation inside the

barrier islands involves a net movement of water into the bay on the east,

with major outflows to the west (FDNR, 1992).

5.4.4.3 Water and Sediment Oualitv

According to FDNR (1990), Hand and Jackman (1992) and Paulic and Hand

(1994), the Apalachicola estuary and its tributaries have generally good

water quality. However, Scipio Creek, at the mouth of the river is

impaired by shrimping and marina activities, and by historic wastewater

loading. Apalachicola Bay has very good water quality; and St. George

Sound, at the eastern end of Apalachicola Bay, has good water quality

except in the Carrabelle area which is improving. Water quality in St.

Vincent Sound has not been evaluated in recent years.

Apalachicola Bay and the Apalachicola River are extremely productive

ecosystems as evidenced by their designation by UNESCO as an International

Biosphere Reserve. The river and bay are also Outstanding Florida Waters,

and the largest of the 41 National Estuarine Research Reserves. The bay is

also an Area of Critical State Concern, a State Aquatic Preserve, and a

Priority Florida SWIM (Surface Water Improvement and Management) waterbody.

5-92
The Apalachicola River delta and Bay receive sediments from a watershed of

more than 50,000 km2 with average accumulation rates of about 4.3 mm yr1

over the last century (Donoghue, 1993). Sediments entering Apalachicola

Bay are generally unpolluted and contribute minimal nutrient loading to the

system (Donoghue, 1993; FDNR, 1992). Muddy, soft bottom substrates cover

some 78 of the open-water bottom of the bay, and form the dominant benthic

habitat type (Livingston, 1984). The remaining sediments found in the

system include sand, clay, sandy clay, clayey sand and carbonates from

oyster shells. Apalachicola Bay sediments contain little silt (FDNR,

1992) . It has been reported that terriginous sediments dominated the shelf

off Apalachicola Bay.

Sediment metals to aluminum ratios suggest that only Cd, Cr and Zn are

enriched in the bay (FDNR, 1992). Livingston (1989) reported that heavy

minerals from 24 km off Apalachee Bay to offshore Pensacola Bay increased

westward through the study area. Donoghue (1993) found that heavy, mineral

rich sands concentrated by wind and waves produced significant gamma

radioactivity in beach berms and coastal dunes on the barrier islands

ringing Apalachicola Bay. The source of radioactivity was determined to be

the detrital products of southern Appalachian crystalline rocks. Heavy

mineral sand deposits were reported by Donoghue (1989) to be highly mobile,

based on the distribution of radionuclides (uranium and thorium in monazite

and zircon)

5.4.4.4 Bioloav

The Apalachicola Bay system is widely considered to be one of the few

remaining relatively unpolluted, highly productive estuaries in Florida.

Its temperate-subtropical climate, well-mixed and well-flushed waters

produce rich fisheries yields, and its oyster reefs and organically rich,

muddy substrates create a complex, highly diverse ecosystem.

FDNR (1992) summarized conditions in Apalachicola Bay. Overall high water

quality coupled with seasonal flooding, nutrient and detrital export, and a

variable salinity regime, provide ideal living conditions for estuarine

biota and a highly productive system. The estuary is also surrounded by

wetlands which interdict and remove toxic substances which enter the

system.

Salt Marshes and Seagrasses

Marsh vegetation and river input are the major nutrient sources for food

webs in Apalachicola Bay, which has an estimated annual production of about

103,080 metric tons C. yr (Livingston, 1983; 1991).

Livingston (1983) estimated that seagrasses were present in about l0 of

the total water area (30,480 ha) of Apalachicola Bay. Fringing beds of

Halodule wrightii grew around St. George Island, and in the area from

approximately Eastpoint to Carrabelle on the mainland. Mixed beds of

Halodule wrightii Thalassia testudinum and Syringodiurn filiforrne fringed

the sound side of Dog Island, and covered Dog Island Reef, and Turkey Point

Shoals. These beds also occurred as fringing stands on the mainland from

Carrabelle to Alligator Harbor. Fringes of seagrass beds were reported to

be fairly narrow and occupied a small portion of the estuary. The

5-93
relatively small area coverage of seagrasses was not attributable to water

depth, according to Livingston (1983). Wolfe et al (1988) suggested that

high turbidity and sedimentation from river runoff decreased light, and

produced an unsuitable substrate for seagrass growth in most areas of the

bay.

Edmiston and Tuck (1987) reported that the densest seagrass beds (H.

wrightii and T. testudinum) occurred along the northeast shoreline of St.

George Island. No seagrasses were found in St. Vincent Sound. Large beds

of seagrasses were reported to occur along the northern shore, on Bay Mouth

Bar (at the entrance to the harbor), and in the eastern third of Alligator

Harbor (Wolfe et al., 1988) . These authors also reported the presence of

extensive, continuous beds of seagrasses along the northern shore of the

eastern half of St. George Sound. The distribution of seagrasses in the

Apalachicola Bay system as reported by Livingston (1984) is summarized in

Table 5-21.

Benthos

Livingston (1983) reported that the most abundant infaunal macroinvertebrates in Apalachicola Bay were the polychaetes, Mediomastus

ambiseta and Streblospio benedicti, and the tanaid, Hargeria rapax. Other

abundant species were amphipods (Corophium, Ampelisca, Grandidierella

bonnieroides, GammaruS mucronatus), and the snail, Neritina reclivata.

Federle et al. (1983) determined that microbial community structure in St.

George Sound sediments was controlled by epibenthic predators, whose

abundances were, in turn, controlled by physical factors (i.e. the

influence of the Apalachicola River on Apalachicola Bay).

Based on monthly infaunal collections made in Halodule wrightii beds during

1975-1976, Sheridan et al (1983) recovered a total of 58 species, an

average of 35 per month. Sixteen species accounted for 84% of the total

number of animals, and 89% of the total biomass. Numerical dominants were

one amphipod, one tanaid, one polychaete and one clam (Arnpelisca vadorurn,

Hargeria rapax, Heteromastus filiformis and Aric.iclea fragilis,

respectively) . Biomass dominants were three molluscan and one amphipod

species (Tagelus plebeius, Neritina reclivata, Ensis minor and

Haploscoloplos fragilis, respectively)

Samples collected by Livingston (1984) in East Bay were dominated by

Mediomastus ambiseta, Streblospio benedicti, Heteromastus filiforrais,

Ampelisca vadorum, Hobsonia florida, Hargeria rapax, Grandidierella

bonnieroides and Paraprionospio pinnata. Most of these infaunal species

were associated with seagrasses. Leaf-litter dominants reported by

Livingston (1984) were Neritina reclivata, Palaemonetes spp., Corophium

louisianum, Garamarus spp., Grandidierella, Melita spp. and Munna reynoidsi.

The most abundant infaunal macroinvertebrates collected in Apalachicola Bay

by FDNR (1992) were Grandidieriella bonnieroicles, Dicrotendipes sp. (a

larval chironomid), Laeonereis culveri, one nematode, Mediomastus

californiensis, and Arnphiteis gunneri. Peak numbers were recovered during

September to March, and minimum numbers of individuals were collected from

May to August. A biomass peak was observed during May through August, and

5-94
Table 5-21. Distribution of seagrasses in Apalachicola Bay (after

Livingston, 1984)

a minimum occurred during August to September. Seventy-eight percent of

the samples collected by FDNR (1992) were from soft sediments, where the

dominant animals were mostly polychaetes and amphipods. Menzel (1971)

reported that the most abundant infaunal taxa Apalachicola Bay, Apalachee

Bay and St. George Sound were as shown in Table 5-22.

It should be noted that Menzel's list of decapods contains planktonic

species (e.g. Lucifer faxoni), intertidal species (e.g. Uca spp.), hermit

crabs (e.g. Clibanarius vittatus), swimming and spider crabs (e.g. Portunus

gibbesi and Libinia dubia), and seagrass-associated species (e.g. Tozeuma

carolinensis) . This suggests that most habitats were sampled using a

variety of collection devices.

Tunicate species are identical to the list of "most common" tunicates found

in St. Andrew Sound (Collard, unpubl. data), and quite different (except

for the solitary species, Styela plicata and Molgula occidezitalis) from

those recovered in Alligator Harbor.

Apalachicola Bay produces 90% of the Florida oyster crop, and 10% of the

nation's harvest (the bay is a major breeding ground for blue crabs, shrimp

and finfish). The temperature, salinity, plankton and turbidity levels are

optimum for oysters in Apalachicola Bay. Oyster bars covered about 7% of

the bottom in Apalachicola Bay intertidal and subtidal sand and firm mud

substrates in 1917 (FDNR, 1992) . In their Shellfish Harvesting AreasSurvey

(1990) [data from July 1979 to July 1989), Apalachicola Bay was determined

to have 105,788 acres of "Conditionally Approved" and 6,798 acres of

"Prohibited" oyster grounds. Winter harvesting areas totaled 76,188 acres,

and summer areas totaled 29,000 acres. Table 5-23 gives approximate areas

of oyster beds in Apalachicola Bay.

Water Body Area (Ha) Grassbeds (Ha)

St. Vincent Sound 5,540 10

Apalachicola Bay 20,960 1,125

East Bay 3,981 1,434

St. George Sound (W) 14,747 624

St. George Sound (E) 16,016 2,767

Alligator Harbor 1,637 261

Total 62,881 6,211

Total Area I 100 I 10
Table 5-22 Most abundant infaunal taxa in Apalachicola Bay, Apalachee Bay

and St. George Sound.

Polychaetes:

Arenicola cristata Dexiospira 3 spp.

Diopatra cuprea Heteromastus filifonnis

Laeonereis culveri Neanthes succinea

Onuphis eremita 0. rnagna

Polydora webs ten

Sixteen other polychaete species were reported to be "common".

Mo].lusca:

None of the molluscs were listed as abundant, but 80 species of bivalves and

89 species of gastropods (virtually all of the species collected) were

listed as "common".

Arthropods:

Barnacles: Chtharaalus fragilis (on seagrass)

Amphipods: None were "abundant'

Decapods: Lucifer faxoni Penaeus duorarum

P. setiferus Hippolyte pleuracaritha

Synaipheus to'ic-isendi Thor flonidanus

Tozeuma carolinensis Callianassa islagrande

Clibananius vittatus Emenita talpoida

Pagurus (4 species) Petrolisthes armatus

P. gala thinus Porcellana sayana

Callinectes sapidus Eunypanopeus depressus

Eurytium limosum Hexapanopeus angustifrons

Libinia dubia Menippe rnercenaria

Neopanope packardii Panopeus herbs tii

Pelia rnutica Pilumnus sayi

Portunus gibbesi Sesarrna cinereurn

Uca pugila ton Uca pugnax

IEchinoderms:

Arbacia punctulata Encope rnichelini

Lytechinus vaniagatus Mellita quinquiesperforata

Moira atropos Arnphipolis gracillirna

Ophiolepis elegans Leptosynapta crassipatifla

Urochordata/Tunicata: (27 species reported)

Botnyllus schlosseni Clavelina picta

Diplosoma rnacdonaldi Styela plicata

Didemnurzi candidum Molgula occidentalis
Table 5-23 The distribution of oysters, Crassostrea virginica, in

Apalachicola Bay (Livingston, 1984).

Although conditions in Apalachicola Bay are normally optimum for the growth

and reproduction of oysters, major storms and pandemic diseases

occasionally cause mass mortalities. For example, Hurricane Elena

destroyed 80-100% of the oysters in Cat Point and East Hole, the most

productive (eastern) part of the bay (FDNR, 1992). Recovery of the

population was rapid, however. Lowery (1992) suggested that Apalachicola

Bay exports sediments during hurricanes, which increases water quality and

oyster production. In contrast, Wilber (1992) observed that low river

flows were followed two years later by decreased oyster production.

Apalachicola River flows greater than 30,000 cfs for 100 days or more also

decreased production. Environmental stress, perhaps exacerbated by

anthropic stressors caused mass mortalities of oysters due to a stressinduced outbreak of the parasite, Perkinsus marinus ("Dermo" disease)

(FDNR, 1992)

Pi.thlic health concerns have increased in recent years because oysters are

reservoirs of several human pathogens including Vibrio cholerae, V.

parahaernolyticus, hepatitis "B", and several other parasites (Hood, pers.

comm.).

Oysters and mussels are known to accumulate heavy metals in their tissues

and shells, and are used as biomonitors of environmental quality. FDNR

(1990) reported the following trace metal concentrations in Apalachicola

Bay oysters collected from unpolluted areas of the bay (mean g' wet

weight, whole organism) : Al 27.8; Cu 11.48; Fe 70.86; and Zn 111.26.

Apalachicola Bay supports a major fishery for stone and blue crabs; and all

three species of penaeid shrimps (Penaeus aztecus, brown shrimp; P.

setiferus, white shrimp; and P. duorarum, pink shrimp). White shrimp are

the most abundant swimming macroinvertebrate in the bay, making up about

40% of trawl catches in low salinity areas (Livingston, 1983) . Pink shrimp

make up about 5% of the annual trawl catches in high salinity areas during

spring and summer. Brown shrimp catches are 2-3% of trawl catches in

variable salinities (Livingston, 1983)

Water Body Area (ha) - Oyster Beds (ha)

St. Vincent Sound 5,540 1,097

Apalachicola Bay 20,960 1,659

East Bay 3,981 67

St. George Sound (W) 14,747 1,489

St. George Sound (E) 16,016 3 Alligator Harbor 1,637 37

Total 62,881 4,352

Total Area (%) 100 7
Fishes

According to Livingston (1984), epibenthic marsh-associated, and open water

fish assemblages in the Apalachicola estuary are characterized by

relatively low species diversity, and numerical dominance by relatively few

species. The three most numerous species (Anchoa mitchilli, Micropogonias

undulatus and Leiostomus xanthurus) account for 70-8O of catches year

round, but have different seasonal distribution patterns, probably related

to salinity and life-history stage (Livingston, 1984). The bay anchovy (A.

mitchilli), is the numerically dominant species in the system. This

species is abundant throughout the estuary during January and February, but

concentrates in the upper portions of East Bay during spring and early

summer. In fall, A. mitchilli is most abundant around the mouth of the

Apalachicola River and in portions of East Bay. "In contrast, the Atlantic

croaker [M. undulatus] spawn near passes during fall and early winter; the

juveniles occupy the estuary in peak numbers during late winter and early

spring when salinities are usually less than 10-15 ppt. Spot [L.

xanthurus] also spawn near passes, and peaks of abundance in the estuary

generally coincide with those of the Atlantic croaker." (Livingston, 1984).

Young sand seatrout (Cynoscion arenarius), another abundant species, enter

the estuary in May, where they concentrate in lower salinity areas. They

remain in these areas (near the river mouth, in East Bay, and northern

regions of Apalachicola Bay) through June, but from July through September

the species is found in greatest abundance at the river mouth. During the

fall, numbers of sand seatrout decrease, their distribution within the

estuary becomes dispersed, and they are not found in collections by winter

or early spring (Livingston, 1984). Due to large numbers of juvenile spot

and Atlantic croaker which spend their early developmental stages in

brackish waters, peak numbers of fishes in Apalachicola Bay are recorded

during the period February through April.

The standing crop of fish in Apalachicola Bay is about an order of

magnitude higher than in other estuaries in the region according to

Livingston (1991) . Fishes commonly collected with seines in oligohaline

waters of East Bay and mesohaline (Apalachicola Bay) marshes of the

estuarine system are summarized in Table 5-24 (from Livingston and

Thompson, 1975). Otter trawl collections of epibenthic fishes collected in

various regions and habitats of the Apalachicola estuary from 1972 through

1982 are summarized in decreasing order of their abundance in Table 5-25

(Livingston (1984)

Table 5-24. Fishes collected from East Bay and Apalachicola Bay, Florida

(after Livingston and Thompson, 1975).

East Bay Species

5-98

Scientific Name Common Name

Ictalurus natalis yellow bullhead

Micropterus salmoides largemouth bass

Lepomis raicrolophus redear sunfish

Lepomis punctatus spotted sunfish

Poecilia latipinna sailfin molly

Adinia xenica diamond killifish

Cyprinodon variegatus sheepshead minnow

Fundulus grandis Gulf killifish
Table 5-24. Fishes collected from East Bay and Apalachicola Bay, Florida

(after Livingston and Thompson, 1975) continued.

East Bay Species

Scientific Name

Fundulus confluentus

Fundulus similis

Not emogonus cxysol eucas

Lucania parva

Lucania goodei

Notropis sp.

Lepisosteus osseus

Cyprinus carpio

Anguilla rostrata

Poinoxis nigrornaculatus

Menidia berylliria

Anchoa rnitchilli

Brevoortia patronus

Mugil curema

Mugil cephalus

Micropogonias undulatus

Bairdi ella chrysoura

Stellifer lanceolatus

Cyz2osciOfl arenarius

Paralichthys lethostigma

Trinectes maculatus

Eucinostomus gula

LutjanuS griseus

Gobiosoma bosci

Microgobius gulosus

Archosargus proba tocephalus

Apal achi cola

Anchoa mitchilli

Anchoa hepsetus

Menidia beryllina

Eucinostomus gula

Synodus foe tens

Strongylura marina

Lucania parva

Fundulus similis

Syngnathus floridae

Lagodon rhomboides

Leiostomus xanthurus

Bairdiella chrysoura

Cynoscion nebulosus

Mugil cephalus

Orthopri s ti s chrysoptera

Opsanus beta

Examination of Table 5-25 suggests that gear bias may have influenced the

frequency-of-capture of some taxa (e.g. larger elasmobranchs and oysterreef-associated species) . However, there is strong support for

Livingston's observation that ichthyofaurxal species diversity in the

Apalachicola estuary is rather low.

5-99

Common Name

marsh killifish

longnose killifish

golden shiner

rainwater killifish

bluefin killifish

shiners

longnose gar

common carp

Imerican eel

black crappie

inland silverside

bay anchovy

Gulf menhaden

whit mullet

striped mullet

Atlantic croaker

silver perch

star drum

sand seatrout

southern flounder

hogchoker

silver jenny

gray snapper

naked goby

clown goby

sheepshead

Bay Species

bay ancovy

striped anchovy

inland silverside

silver jenny

inshore lizardfish

Atlantic needlefish

rainwater killifish

longnose killifish

dusky pipefish

pinfish

spot

silver perch

spotted seatrout

striped mullet

pigfish

Gulf toadfish
5.4.4.5 Data Gaps

Apalachicola Bay has received more long-term investigative effort than any

estuary in Florida. While a case can justifiably be made that more work

needs to be done in such areas as microbial ecology and process-related

trophodynamics, no major data gaps were recognized.

5.4.5 St. Joseph Bay

5.4.5.1 Environnkental Setting

St. Joseph Bay is located off the city of Port St. Joe in the central

Florida panhandle (Figure 5-14). The bay is partially impounded by St.

Joseph Spit. As one of only two coastal embayments in the eastern Gulf of

Mexico that are not diluted by the inflow of fresh water (the other is St.

Zndrew Sound), Saint Joseph Bay is not an estuary, but a protected marine

lagoon with open-Gulf salinities. The lagoon-like embayment has a surface

area of about 73,000 acres, a mean depth of 7 m, and a maximum depth of

about 12 m near the northern tip of St. Joseph Spit (FDNR, 1992).

St. Joseph Spit is connected to the mainland by a three mile long, narrow

(less than one mile wide) arm extending eastward from Cape San Blas. The

spit bends sharply at the Cape and extends about 15 miles northward in a

gentle, convex-seaward arc (FDNR, 1992) . Eagle Harbor, midway up the spit,

may once have been an ancient pass (FDNR, 1992) , and this area was breached

during Hurricane Opal. Cape San Blas and St. Joseph spit have been

lengthening due to the northward and westward erosion of sand from their

western shores (FDNR, 1992) . According to Balsillie (1975), the southern

five miles of St. Joseph Spit was eroding at a rate of -9.4 meters per

year, the largest historical, long-term erosion rate recorded in Florida.

Cape San Blas and St. Joseph Spit were heavily impacted by Hurricane Opal

in October 1995. The Cape lost as much as 50% of its high sand dunes, and

was breached in two places by storm surge and waves. Water from the Gulf of

Mexico entered St. Joseph Bay carrying with it an unknown, but probably

large amount of sand and silt. During an overflight, gross shoaling of the

region was noted, from outside and west of St. Joseph Spit to the eastern

"end" of Crooked Island (i.e. Mexico Beach-Tyndall Air Force Base), but

significant changes were not detected within the bay itself.

The following observation warrants emphasis in light of Hurricane Opal:

"Although the St. Joseph Spit is lined with dunes facing the Gulf of

Mexico, these dunes almost without exception show signs of severe scarp

erosion. Blowout conditions exist in some of the high dune areas on the

spit. The topography is also low in the areas north and east of the cape.

Therefore, in an event of 100 year frequency storm or hurricane, most

coastal areas of Gulf County are subject to flooding" (FDNR, 1992) . Most

of coastal Gulf County was flooded in 1995.

5.4.5.2 Hvdroloav and Oceanoqraphv

Tides in St. Joseph Bay are best described as irregular; they are a "mix"

of diurnal tides to the west, and semidiurnal tides to the east. The tidal

5-100
range varies from less than 0.06 to 0.76 m (0.2 to 2.5 ft), and differs in

time and magnitude from predictions (Tanner, 1966)

Surface water hydrology in St. Joseph Bay is influenced primarily by tidal

exchange with the Gulf of Mexico (FDNRI 1992). During flood tides, a

Table 5-25. Otter trawl collections of epibenthic fishes collected in

moderately strong current sweeps around St. Joseph Spit into the bay, and a

counter-clockwise circulation pattern is established in the central portion

of the system. This semi-permanent gyre is disrupted only at maximum flood

tide. At the ebb, water flows out of the lagoon via a channel at the point

of St. Joseph Spit, and across a shoal in the vicinity of the navigation

5-101

various regions and

1972 through 1982

Species

habitats of the Apalachicola estuary from

(after Livingston, 1984).

1. Anchoa mitchilli 41. Archosargus probatocephalus

2. Micropogonias undulatus 42. Microgobius gulosus

3. Cynoscion arenarius 43. Bagre marinus

4. Leiostomus xanthurus 44. Menidia beryllina

5. Polydactylus octonemus 45. Monacanthus ciliatus

6. Anus felis 46. Caranx hippos

7. Chloroscoznbrus chzysurus 47. Centropristis rnelana

8. Menticirrhus americanus 48. Sygnathus floridae

9. Symphurus plagiusa 49. Ancyclopsetta quadrocellata

10. Bairdiella chzysura 50. Chilornycterus schoepfi

11. Etropis crossotus 51. Diplectrum forrnosurn

12. Trinectes maculatus 52. Ictalurus catus

13. Prionotus tribulus 53. Sciaenops ocellatus

14. Stellifer lanceolatus 54. Astroscopus y-graceum

15. Anchoa hepsetus 55. Hippoca.mpus erectus

16. Porichthys porosissirnus 56. LepisosteuS osseus

17. Prionotus scitulus 57. Lucanis parva

18. Eucinostomus gula 58. Lutjanus griseus

19. Paralichthys lethostigma 59. Opsanus beta

20. Synodus foetens 60. Paralichthys albigutta

21. Eucinostomus argenteus 61. Ophidion beani

22. Dasyatis sabina 62. Aluterus schoepfi

23. Cyrioscion nebulosus 63. Diplodus hoibrooki

24. Microgobius thalassinus 64. Gobionellus hastatus

25. Urophycis floridanus 65. Hypsoblennius hentzi

26. Lagodon rhomboides 66. Meriticirrhus saxatilis

27. Gobiosoma bosci 67. Myrophis punctatus

28. Chaetodipterus faber 69. Ogilbia cayorum

29. Orthopristis chrysoptera 70. Oligoplites saurus

30. Brevoortia patronus 71. Pomatomus saltatrix

31. Dorosorna petenense 72. Rhinoptera bonasus

32. Peprilus burti 73. Scoraboromorus znaculatus

33. Peprilus paru 74. Selene vonier

34. Stephariolepis hispidus 75. Sphyraena borealis

35. Sphaeroides nephelus 76. Sphyrna tiburo

36. Ophichthus gomesi 77. Sardinella anchovia

37. Syngnathus louisianae 78. Caranx bartholomaei

38. Sygnathus scovelli 79. Mugil sp.

39. Gobionellus boleosorna 80. Gymnura micrura

40. Harengula pensacolae
channel into the bay. While (FDNR, 1992) reports that there are no

currents at the southern end of St. Joseph Bay, it would seem that the high

water clarity characteristic of the entire lagoon may be maintained by

flushing currents induced during tidal exchanges.

During high flows, the Apalachicola River may feed St. Joseph Bay through

the 5.5 mile long Gulf County Canal which connects the Gulf Intracoastal

Waterway (ICWW) with Lake Wimico and St. Joseph Bay.

5.4.5.3 Water and Sediment Oualitv

As evidenced by the abundance of salt marsh vegetation and dense stands of

SAV; clear water; and abundant and divers finfish, infaurial and shellfish

communities, water quality in St. Joseph Bay is considered possibly to be

of the highest quality of all panhandle embayments.

St. joseph Bay has no fluvial streams and , therefore, sediment input is

low. In addition, the Bay is well flushed and anthropic loadings from

discharge and construction activities are relatively minor.

Sediments in St. Joseph Bay are predominantly quartz sand, with patches of

clayey silt, clayey sand, and sand-gravel mixtures. Clay is found in the

deep central portion of the lagoon. Sand enters the lagoon from the east,

and the remaining sediments are of in situ biogenous origin. Sedimentation

rates are slow (FDNR, 1992).

5.4.5.4 Bioloqy

St. Joseph Bay is located in a transitional climatic zone between the semitropical climate of peninsular Florida and the subtropical climate of

southern Florida. This ecotone is reflected in the species composition of

St. Joseph Bay's flora and fauna.

While information on the animal taxa inhabiting St. Joseph Bay are not

available, observations of P. Hamilton, C.N. D'Asaro and R. Heard (pers.

comm.), among others, strongly suggest that species diversity and abundance

in St. Joseph Bay are very high. The lagoon supports numerous species

representative of both Carolinian and West Indian faunal provinces

(Collard, unpubl. data).

Salt Marshes and Submerged Aquatic Vegetation

According to FDNR (1992) , Juncus roemerianus and Spartina spp. marshes

occur in a narrow band around St. Joseph Spit, and widens near Pig Bayou.

Salt marshes are a prominent feature of the shallow areas of the southern

and southeastern portions of the bay, and extend for hundreds of feet into

the bay. The intertidal zone include mud flats and a few tidal creeks

(FDNR, 1992)

Five species of seagrasses cover about one-sixth of the bay bottom (FDNR,

1992) . Thalassia testudinum is the most abundant species, but Halodule

wrightii and Ruppia maritima are common and often occur in mixed stands

with turtle grass. Halophila englemanni (star grass) is patchy throughout

the bay, and Syringodium filiforme (widgeon grass) occurs in patches on the

5-102
eastern side of the bay. St. Joseph Bay is reported to have the densest

seagrass meadows on the northern Florida coast (FDNR, 1992)

Because of weak tidal currents, the bay is reported to function as a moreor-less a closed system. Therefore, the nutrient budget and food web of

the bay are largely dependent upon the primary productivity of the bay

itself (FDNR, 1992)

Benthos

The longshore current pattern described below by Tanner (1966) has

biological implications that may explain, in part, observed differences in

the macroinvertebrate faunas of St. Joseph Bay and St. Andrew Sound which

are physiographically similar, and located only a few miles from each other

(Collard, unpu.bl. data) . "Waves are refracted around the Cape San Bias

shoals in such a manner to arrive nearly parallel to the beach. This

results in a bi-directional littoral drift system [and embedded

rneroplankton] which runs northward along the northern half of the spit, and

southward along the southern portion."

The principal shellfish harvested in St. Joseph Bay include hard shell

clams, Mercenaria spp., the sunray venus, Macrocallista nirnbosa, bay

scallops, Argopecten irradians and blue crabs, Callinectes sapidus.

Valentine and Heck (1993) reported that the annual infaunal

macroinvertebrate production of Mc'diolus a.mericanus beds in St. Joseph Bay

ranged from 229 to 429 g ash-free dry mass (AFDW) m2. In comparison,

production in pure stands of Thalassia testudinurn was 145 to 245 g AFDW rn

2; 84 to 180 g AFDW m2 in Halodule wrightii beds; and 20 to 42 g AFDW rn2

in unvegetated sand flats.

Fishes

Little information exists concerning fish populations within St. Joseph

Bay. Among the major fishes taken by recreational fishers are spotted

seatrout and Spanish and king mackerel.

5.4.5.5 Data Gaps

Although St. Joseph Bay is widely known by marine biologists as

perhaps the only pristine coastal embayment remaining on the Florida

panhandle, surprisingly little has been published about its biota.

As a "semi-closed system", the bay's microbial communities, drift

algae, seagrasses and associated organisms, benthic invertebrates,

plankton, nekton, and diverse, numerically abundant transient

avifauna may be trophodynamically closely coupled. Primary and

secondary production within the bay, and export into surrounding

coastal waters (largely to the west?), warrant investigation.

The impact(s) of recreational fishing (scallops, finfish) and shell

gathering (e.g. live Pleuroploca gigantea), while not adeguately

documented, may be significant.

5-103
3. St. Joseph Paper Company has recently been bought, sold, and shut

down for variable periods of time. The immediate and longer-term

ecological consequences of mill activity should be

documented/monitored for several years.

5.4.6 Analachee BayIBi Bend

5.4.6.1 Environmental Settinq

Lyons and Collard (1974) characterized the Big Bend area (i.e. Apalachee

Bay) as, "a huge, seagoing estuary extending from near Anclote Key to the

vicinity of Alligator Harbor (Figure 5-15). Oyster reefs are common

parallel to the shore, and vast beds of seagrasses are characteristic of

the area. A thin veneer of quartz sand and organic debris overlies the

limestone plateau of the Ocala-Middle Ground Arch. Occasional limestone

outcrops protrude through this veneer to provide hard substrate. Species

composition is predominantly the same found in estuarine seagrass or oyster

reef communities. The shoreline receives only low energy waves." Zimmerman

and Livingston (1976) described Apalachee Bay proper as a broad, shallow

estuary lying between Alligator Point and Cedar Key, extending about 15 km

offshore.

5.4.6.2 Hvdroqrahv and Oceanoqranhy

Livingston (1990) described the region from the knclote Keys north to the

Ochlockonee River as a massive, open estuarine system supplied by

freshwater from the Anclote, Pithlachascotee, Weeki Wachee, Homosassa,

Chassahowitzka, Crystal, Withiacoochee, Waccassa, Suwannee, Steinhatchee,

Spring Warrior, Fenholloway, Econfina, Aucilla, St. Marks, and Ochlockonee

Rivers. Livingston calculated the combined stream discharge of fresh water

into Apalachee Bay to be approximately 1 X l0 gal day'. Unlike central

and western regions of the Florida panhandle, coastal waters of the Big

Bend region are shallow and unprotected by barrier islands. The mainland

shoreline gradually merges into the sea, and beaches are absent.

5.4.6.3 Water and Sediment Oualitv

Hand et al. (1994) summarized water quality conditions in the Big Bend area

in very general terms. Water quality was evaluated as "good" in the

following drainage basins and rivers: Suwannee River confluence; Aucilla

River Basin; Econfina Creek/Steinhatchee River Basin; Econfina River to the

Gulf of Mexico; Steinhatchee River to the Gulf of Mexico; Suwannee River to

the Gulf of Mexico (manatees frequent the lower reaches of Suwannee River);

Ochlockonee River Basin-Ochlockonee Bay to the Gulf of Mexico at Panacea;

Waccasassa River Basin to the Gulf of Mexico; New River Basin; St. Marks

River Basin; and Apalachee Bay, from Lost Creek through the St. Marks

River. Much of Apalachee Bay water quality was evaluated as "excellent".

According to Hand et al (1994) Ochlockonee Bay has high nutrient levels and

low macroinvertebrate diversity due to construction activities, clear

cutting and (possibly) septic tank leachates. Using FDEP water quality and

trophic state indices, waters at the mouth of Spring Warrior Creek were

judged to be "fair" (Hand et al., 1994). The Fenholloway River was

5-104
\W A K U L L A AIIigaIor Harbor Och1ockdnee Bay nd Apalachee Bay TA' O

Qf 1;J £ Figure 5-15. Schematic map of the Ochiockonee Bay/Apalachee Bay system.
assessed as "poor", the only Class V water body (industrial use only) in

the state.

5.4.6.4 Bioloqy

The paucity of information in the following paragraphs does not reflect the

biological richness of the Big Bend estuary. In all important respects

this brackish, shallow, quiet water open system supports complex, diverse

assemblages of microbiota, invertebrates and fishes. It is widely

recognized that the region should not be viewed as a simple, or single

ecosystem, but as a mosaic of habitat types difficult to characterize in

summarial fashion. For modeling purposes, it is reasonably prudent to

suggest that Apalachee Bay and surrounds may be considered the functional

ecological equivalent of a low energy, temperate-subtropical, composite

oyster reef-seagrass estuary.

Salt Marshes and Submerged Aquatic Vegetation

Paulic and Hand (1994) reported that salt marshes dominate the coastal

landscape from Apalachicola Bay to Tampa Bay. Juncus and Spartina marshes

are characteristic of the headwaters and floodplains of a majority of the

small rivers and streams entering Apalachee Bay from the St. Marks River to

the Withiacoochee River.

Benthic macrophytes collected in Apalachee Bay by Zimmerman and Livingston

(1976) were mainly warm temperate species, but included many eurythermal

tropical species. Some species (e.g. Polysiphoriia harveyi) has a disjunct

distribution and a temperate origin. Thirty-nine species of macrophytes

were recorded, but collections were dominated by 17 species of red algae,

and the seagrass, Thalassia testudinum. The authors considered algal

diversity to be low with respect to estuarine areas in Texas and Louisiana,

but did not mention other panhandle estuaries. Species with warm-temperate

distributions included Halimeda incrassata, Digenia simplex, Laurencia

poitei, Halophila engelrnanni, Caulerpa, Penicillus, Udotea and Padina

species.

During the Florida Big Bend Seagrass Habitat Study (Continental Shelf

Associates/Martel Laboratory, 1985) 3.7 x 106 acres (1.5 x 106 ha) of

seagrass beds and meadows were mapped using aerial photography. Groundtruthing was accomplished by divers. Sixteen percent of seagrass areas

were characterized as dense, 33% as sparse, and 19% as patchy seagrass

beds. Results of the survey were plotted on a composite 1:250,000 scale

map) . According to the authors, TSpecies zonation patterns were similar to

those observed elsewhere in Florida and the Caribbean." Commonly, a

nearshore zone of pioneer or fringing species (primarily Halodule wrightii,

and occasionally Halophila decipi ens), was replaced by a zone of dense,

bed-forming Thalassia testudinum and Syringodium filiforme in deeper

subtidal waters. A fringe of Halophila decipiens and Halophila engelmanni

with some H. wrightii in shallow areas formed an offshore zone. The unique

feature of the Florida Big Bend area seagrass zonation pattern is the

extended nature of an offshore fringing zone. Offshore fringing (or

pioneer) species grow from a depth of 10 m to depths greater than 20 m. Seagrasses showed transitional tolerances to low salinity and temperature.

5-106
B en tho a

Dugan and Livingston (1982) compared selected macroinvertebrate taxa of

Apalachee Bay based on collections made in the lower reaches of the

Fenholloway and Econfina Rivers during the period 1971-1980. Decapods

comprised 95& of the total number of individuals collected during the

study; molluscs accounted for 4, and echinoderms made up l of the

collections. Dugan and Livingston (1982) reported that the percentage

composition of the samples was relatively constant, but numbers of

individuals in the Fenholloway River were approximately twice those of the

Econfina River estuary (Table 5-26). According to Hand et al. (1994), the

Fenholloway River is biologically degraded, in contrast to the Econfina

which was reported to have "good" water quality. Papermill-derived

pollution abatement in the Econfina River began in 1975.

Wolfe et al. (1988) reported that Ochiockonee Bay, west of Bald Point had

consistently high benthic macroinvertebrate diversity. In contrast, Hand

et al. (1994) reported that Ochlockonee Bay has high nutrient levels and

low macroinvertebrate diversity due to construction, clear cutting and

(possibly) septic tank leachate. While it is not possible to explain the

apparent discrepancy between the assessment of Hand et al. (1994), and

Wolfe et al. (1988) with confidence, it is possible that: (1) sampling

methods accounted for the differences observed; (2) the drift of

Ochlockonee Bay water was to the east; (3) Wolfe et al. (1988) reviewed a

different data set; or (4) "high diversity" meant different things to the

different authors. Other interpretations are possible, including the most

parsimonious, and probably correct, conclusion that the differences

observed were real, and reflective of unremarkable variation in estuarine

benthic population demographics.

Table 5-26. The most numerous ten species of benthic macroinvertebrates

collected from 1971-1980 in Apalachee Bay (from Dugan and

Livingston, 1982)

5-107

Econfina River Estuary Fenhol].oway River Estuary

1 Palaernon floridanus 1 Pagurus n. sp.

2 Pagurus n. sp. 2 Neopanope texana

3 Tozeuma carolinense 3 Paiaemon floridanus

4 Neopanope texana 4 Tozeurna carolinense

5 Palaernonetes intermedius 5 Palaemonetes internieditis

6 Hyppolyte pleuracanthus 6 Periclemenes longicaudatus

7 Periclemenes longicaudatus 7 Hy-ppolyte pleuracanthus

8 Neopanope packardii 8 Neopanope packardii

9 Penaeus duorarurn 9 Penaeus duorarurn

10 Thor dobkini 10 Callinectes sapidus
Fish

Menzel (1971) listed seven shark, ten ray, and 140 bony fish species

associated with Apalachee Bay. Investigations of St. Mark's estuary and

Wakulla marshes within the Bay resulted in a total of 55 fish species

overall (comp and Seaman, 1985). In general, the dominant fish species

found in Apalachee Bay are similar to those observed in other panhandle

estuaries (e.g., anchvy, pinfish spot and mullet).

5.4.6.5 Data Gaps

1. The nature and magnitude of physical and biogeochemical coupling

processes between riverine, brackish water and marine communities in

the region may provide information of value in understanding fate and

transport processes in the whole of the northeastern Gulf of Mexico.

2 The Big Bend includes northwestern portions of the West Florida

Shelf and the eastern panhandle. This "open estuary" is ecologically

unique in the Gulf of Mexico, and as indicated by the biogeographically mixed affinities of its biota, it appears to be an

ecoregional transition zone. Production levels in, and energy export

from the Big Bend should be assessed, as downstream flows may

significantly impact the trophodynamic structure of communities to

the south and west.

5.5 Summary and Malor Data Gaas

The portion of the northeastern Gulf of Mexico (NEGOM) discussed in this

chapter extends from the Florida-Alabama border to Citrus County, Florida,

and from the shoreline to the continental shelf-slope boundary. The major

physiographic feature of the NEGOM is DeSoto Canyon, which dominates the

eastern Gulf of Mexico basin. The major coastal feature of the region is

Cape San Blas, which lies northeast of the canyon (Figure 5-1). The shelf

is relatively narrow near the head of DeSoto Canyon, and progressively

broadens to the east and southeast. The panhandle, from Perdido Bay to

eastern Apalachicola Bay-St. George Sound, is a moderate-to-low energy,

sandy coast, characterized by an almost continuous chain of barrier islands

and embayments. There are no barrier islands east of Ochlockonee Bay, which

marks the western boundary of the low energy, brackish water Big Bend

region.

Basin circulation in the NEGOM (Chapter 2) is dominated by the Loop

Current, which brings warm, salty, oligotrophic water and tropical

organisms into the eastern Gulf of Mexico. The behavior of the LC and its

eddies is complex, and the extent and biological consequences of coupling

between shelf and basin watermasses and currents are not clear. Periodic

incursions of LC-derived water transport subtropical-tropical species into

shelf and nearshore environments where, given suitable substrates and warmwater conditions, they form minor components of panhandle species

assemblages. The role of shelf currents with respect to the fate and

transport of nutrients, meroplankton (e.g., larval fishes, developmental

stages of benthic invertebrates), pelagic organisms (phytoplankton,

zooplankton, fishes), and toxic substances, such as crude oil and trace

metals, is poorly known. Net transport of sediments and larval organisms

5-108
in nearshore/longshore currents is southeast from the eastern side of Cape

San Bias, and northwest from the western side of the Cape. Circulation in

panhandle estuaries is highly variable, and depends upon river flow, tides,

basin geometry, bathymetry, winds and other factors. Regional estuaries

are shallow, drowned river valleys, and may be well-mixed or highly

stratified and hypoxic during summer months. Sediments, nutrients and

pollutants are retained within these embayments.

The water quality of regional estuaries is reported to be generally good.

However, some of the poorly flushed bayous and backwaters of most panhandle

estuaries show evidence of degraded water and sediment quality attributed

to pollution. Seagrasses have entirely disappeared from the Pensacola Bay

system, and sediments in some areas of this estuary are heavily polluted

from chronic exposure to industrial and domestic effluents.

Inner and middle shelf sediments west of Cape San Blas are predominantly

sandy (Chapter 3) with patches of shell rubble and algal nodules. Fines

accumulate in pockets between sand ridges. East of St Vincent Island in

Apalachicola Bay, sediments are described as sandy near shore, transitional

carbonate-quartz on the inner shelf, and carbonaceous on the middle shelf.

Limestone outcroppings in the Big Bend, and rock pinnacles near the steeply

terraced head of DeSoto Canyon provide hard substrates habitats. Species

assemblages characteristic of unconsolidated, oxygenated sands dominate

benthic shelf communities inshore of DeSoto Canyon. Sediments in water

deeper than 100 m are comprised of compact clays, and the fauna of these

substrates is depauperate.

As discussed in Chapters 2 and 4 of this report, nutrients are contributed

to shelf waters via large fresh and brackish water discharges from the

Mississippi River and Mobile Bay, respectively. In contrast, nutrient

enrichment of shelf waters from western panhandle estuaries is relatively

low. Numerous small rivers enter the Big Bend "open estuary" although their

nutrient contribution to shelf waters is apparently minor. Upwelling along

eastern portions of DeSoto Canyon, south of Cape San Blas, and along the

northern portions of the West Florida Shelf brings deep, nutrient rich

water into the euphotic zone.

Primary productivity in the NEGOM increases from offshore to coastal waters

as a function of nutrient availability. Shelf phytoplankton production is

highest in upwellirig areas and coastal frontal zones, and may impact

production rates downstream from these areas. However, neither the fate

and transport of energy nor the relationship between water column primary

production and benthic secondary production on the shelf have been

investigated. Estuarine primary production is high or very high, and many

of the region's estuaries have reached or exceeded their assimilative

capacity for nutrients. Salt marsh, seagrass and benthic algal production

varies considerably between different panhandle estuaries, but a majority

have experienced decreases in marsh and submerged aquatic vegetation

habitats during the past two to three decades. Losses of these two

community types are accompanied by significant decreases in fish and

invertebrate diversity, and are symptomatic of degraded environmental

quality.

5-10 9
Although knowledge of benthic invertebrate communities on the NEGOM

continental shelf is limited, epifaunal and infaunal species assemblages

vary, as do the fishes, with depth and substrate type. In decreasing order

of their numerical abundance and species diversity, polychaetes, decapod

and amphipod crustaceans dominate shelf habitats. One fourth to one third

of the polychaetes collected on the shelf were allied with either West

Indian or Carolinian faunal provinces, some 25-3O were Gulf of Mexico

endemics, and a somewhat smaller number of species were cosmopolitan.

Outer shelf invertebrate collections suggest that tropical species become

more common with increasing depth. The composition of estuarine benthic

communities is regulated by a large suite of environmental variables.

Among the most important of these are substrate type and quality, depth of

the redox layer, salinity and water quality, including dissolved oxygen

levels.

In general, the diversity of shelf and coastal fish communities is high and

remarkably uniform throughout the region. The NEGOM shelf is reported to

be inhabited by twice as many species and eight times as many unique

(endemic) species as the northwestern Gulf shelf. Differences in the

composition of fish assemblages on the shelf are related to depth and

substrate type, and exhibit variation corresponding to developmental and

reproduction-related movements from one habitat to another (e.g. open ocean

to estuary). Estuaries in the NEGOM support similar fish faunas, with the

same or very nearly the same ten numerically dominant species.

Hypoxia, anoxia, thermal and osmotic stress, pollutants and toxic algal

blooms may contribute to, or cause the episodic mass mortality events

reported from all of the region's embayrnents and large stretches of coastal

waters. Decreased diversity within benthic invertebrate and fish

communities as a result of the progressive disappearance of salt marsh and

seagrass habitats constitute perhaps the least equivocal and most easily

visible indicators of environmental degradation available. With reference

to these indicators, it is speculated that a decrease in the overall

environmental quality of panhandle embayments and coastal waters has

occurred over the past 20-30 years. Continued growth of human populations

in the panhandle coastal zone may promote a continuation of this trend

which, although more difficult to discern, may eventually influence the

quality of shelf habitats as well.

Previous sections have identified data gaps in specific areas. The

following identify the major data gaps affeting knowledge of the shelf

ecosystems as a whole and suggest topics for further study.

1. The frequency, duration, scale and physical-chemical characteristics

of upwelled water in northern portions of the West Florida Escarpment

(the "Green River"seen in satellite images of the northern Gulf) , at

the head of DeSoto Canyon, and in the region south of Cape San Blas,

warrant investigation and documentation. Short-term, episodic

upwelling in these, and possibly other areas associated with the

NEGOM shelf-slope boundary, may bring nutrient-rich water to the

surface, and periodically increase local and downstream primary

productivity. If upwelling is a frequent occurrence in some or all

of the areas mentioned, nutrient enrichment in the euphotic zone may

influence patterns of water column production over relatively large

5-110
areas of the NEGOM and may, via trophic coupling (e.g., developmental

migrations, fecal pellet "fallout"), turbulent mixing, and

downwelling at frontal boundaries, significantly impact secondary

production in benthic communities of the shelf.

As discussed in Chapter 7 of this report, physical oceanographic

processes in NEGOM shelf waters are complex. Knowledge of the

origin, fate and transport of nutrients, toxic substances and pelagic

organisms (primary producers, holozooplankton and meroplanktonic

invertebrates and fishes) depends to a large extent on knowledge of

episodic and "on average" interactions among coastal, shelf and Loop

Current (or LC-derived) watermasses. The sources, pathways and sinks

of energy flow within and between ecosystems and their major

biological components is a fundamental ecological question. While

some understanding of salt marsh, estuarine and nearshore

trophodynamics in the NEGOM has been acquired, very little is known

about ecological processes on the continental shelf. Lacking more

detailed information on physical oceanographic processes, biological

processes can neither be described nor understood.

Significant amounts of particulate and dissolved organic material,

other nutrients, suspended sediments and fresh water discharged from

the Mississippi River and, to a lesser extent, from Mobile Bay, enter

NEGOM shelf waters. Water column and benthic communities of the

outer shelf west of DeSoto Canyon may be influenced by Mississippi

River water, while inner shelf community structure may be influenced

by eastward flowing water from Mobile, and perhaps Perdido Bays. The

physical-chemical and consequent biological significance of these two

major freshwater discharges into western portions of the NEGOM have

not been assessed.

The distribution of sand substrata on western portions of the middle

shelf may not be uniform (see Figure 3-8). Echinoderms and other

taxa characteristic of fine, clastic, carbonate, and hard substrates

have been reported, and the distribution and areal extent of these

non-sandy patches requires further documentation.

Biological communities of the Big Bend continental shelf and their

trophodynamic interactions with coastal, West Florida Shelf, Loop

Current, and upwelled basin water are poorly understood. This region

of the NEGOM seems to be physicochemically and geologically unique,

which may be reflected in the structure of its benthic biological

communities. Because the biological importance of shelf communities

of the Big Bend has not been adequately assessed, a multidisciplinary

investigation of the area is warranted.

The quasi-seasonal occurrence of tropical pleuston (e.g., Physalia,

Velella, Porpita) , macroplankton (e.g., salps, pteropods) and reef

fishes (e.g., Chaetodon spp., Pomacanthus spp.) in panhandle coastal

waters suggests that intrusions of subtropical-tropical water may

reach nearshore environments. While the occurrence of surfaceassociated organisms such as Sargassum spp., and some of the

chondrophores, jellyfishes and ctenophores stranded on beaches or

transported into estuaries can be explained by wind drift, subsurface

5-ill
species are likely to have been advected inshore by currents.

Presumptive evidence that the young stages of tropical species are

advected to coastal waters is provided by observations of scuba

divers and sportsfishers, who report that tropical invertebrates and

fishes are commonly encountered on and near artificial "reefs".

These reefs are commonly deployed on sandy (i.e., soft) bottoms

unsuitable for colonization by "live-bottom" epifaunal animals. The

presence of tropical benthic adults on hard-substrates suggests that:

(a) planktonic stages of subtropical-tropical species are not

uncommon in shelf waters; (b) the predominance of soft substrates in

the western portion of the NEGOM may limit the distribution of adults

of these species in benthic shelf communities; and (C) benthic

species assemblages characterized from trawl catches may not reflect

the species composition and diversity of potential benthic

communities, which are controlled by substrate type rather than by

recruitment constraints. This speculative arguement has significance

when, as is often the case, epibenthic species diversity is used as a

surrogate indicator of environmental quality. The distribution of

hard substrates in the NEGOM requires further investigation, and

biological collections of shelf communities should accompany

geological-sedimentological sampling.

The distribution of sargassum and its associated organisms in the

eastern Gulf of Mexico has received scant attention. Remote sensing

of the distribution of "Gulf weed" (primarily Sargassurn natans and S.

fluitans) may reveal valuable information about sea states and, more

importantly, the distribution and longevity of frontal zones and

boundaries. Sargassum as an important habitat (e.g. for larval

fishes; hatchling and post-hatchling sea turtles) has not been

investigated in the eastern Gulf of Mexico.

Artificial reefs of various sizes and materials are being deployed

with increasing frequency on the inner shelf. Some of these reefs

are unstable during heavy storm conditions because of their small

size and/or placement in inappropriately shallow water depths. While

much has been written about the presumed benefits of artificial

substrates (increased productivity, etc.), relatively little work has

been done assessing the possible negative impact of these materials

on natural communities. For example, it would be of value to know

whether the translocation and/or destruction of artificial reefs

during the three hurricanes of 1995 negatively impacted "natural"

live bottom communities in the vicinity of their original location.

The long-term impact of artificial reefs on the abundance and

sustainable yields of recreationally and commercially important fish

species remains unknown, although a relatively large literature on

the subject is available.

An unknown, but possibly significant amount of military debris (e.g.

aircraft, missiles, ordnance) has accumulated in shelf waters of the

northeastern Gulf of Mexico. The short- and long-term ecological

impact of this material should be assessed. Should a Theater Missile

Defense (TIv) program be initiated by DoD as planned, combusted and

non-combusted accelerants and other debris will fall into NEGOM shelf

waters. At the present time, no assessment of the potential

5-112
environmental impact of the program on shelf or nearshore waters have

been made.

5.7 Literature Cited

Abele, L.G. 1970. The marine decapod crustacea of the northeastern Gulf of

Mexico. Master's Thesis. Florida State University, Tallahassee, FL.

136 pp.

Alexander, J.E., T.T. White, K.E. Turgeon, and A.W. Blizzard. 1977a.

Baseline monitoring studies, Mississippi, Alabama, Florida, outer

continental shelf, 1975-1976, Volume III, Results. Final report

prepared for U.S. Department of the Interior, Bureau of Land

Management, Washington, DC. Report No. BLM-ST-78-32, Contract No.

08550-CT5-30.

Alexander, J.E., T.T. White, K.E. Turgeon, and A.W. Blizzard. 1977b.

Baseline monitoring studies, Mississippi, Alabama, Florida, outer

continental shelf, 1975-1976, Volume IV, Discussion. Final report

prepared for U.S. Department of the Interior, Bureau of Land

Management, Washington, DC. Report No. BLM-ST-78-33, Contract No.

08550-CT5-30.

Balsillie, J.H. 1985. Long-term shoreline change rates for Gulf County,

Florida: A first appraisal. Florida Dept of Natural Resources,

Beaches and Shores Special Report No. 85-3.

Baskerville-Donovan, Inc., 1991. Pre-Draft Environmental Document for

the Bay County Bridge Authority. Prepared in association with Sandy

Young, Environmental Consultant; Vittor & Associates, Inc.; and New

World Research, Inc. for Figg Engineers, Inc.

BCM Converse, Inc. 1987. St. Andrew Bay system environmental database.

BCM Converse, Panama City, FL. Various pp.

Beccasio A.D., N. Fotheringhani, A.E. Redfield, R.L. Frew, W.M. Leviton,

J.E. Smith and J.O. Woodrow. 1982. Gulf coast ecological inventory.

User's guide and information base. U.S. Fish and Wildlife Service,

Office of Biological Services. Washington, D.C. 191 pp.

Blaylock, D. 1983. Choctawhatchee Bay: Analysis and Interpretation of

Baseline Environmental Data. Florida Sea Grant College. Technical

Paper No. 29. University of West Florida: Institute for Statistical

and Mathematical Modeling. Pensacola, Fla. Northwest Florida Water

Management District.

Bogdanov, D.V., V.A. Sokolov, and N.S. Khromov. 1969. Regions of high

biological and commercial productivity in the Gulf of Mexico and

Caribbean Sea. Oceanology 8:371-381. (Trans. NSF)

Brooks, H.K. 1973. Geological oceanography. Pages lIE-i to 49 in A

summary of knowledge of the Eastern Gulf of Mexico. State University

System of Florida. Institute of Oceanography, St. Petersburg.

5-113
Brusher, H. A., and L. H. Ogren. 1976. Distribution, abundance, and size

of penaeid shrimps in the St. Andrew Bay system, Florida. Fishery

Bulletin 74(1) :158-166.

Bureau of Submerged Lands & Preserves. 1991. St. Andrews State Park

Aquatic Preserve Management Plan. Florida Department of Natural

Resources, Division of State Lands. Tallahassee, FL

Cammen, L.M. 1980. The significance of microbial carbon in the nutrition

of the deposit feeding polychaete Nereis succinea. Mar. Bid. 61:9-

20.

CH2M Hill 1985. Effluent mixing study. Final report. Air Products and

Chemicals, Inc. Escambia Plant, Pensacola, Florida.

Collard, S.B. 1976a. Biological, Chemical, Geological, and Physical

Parameters Essential to Estuarine Management in Choctawhatchee Bay.

15 pp. Sea Grant Project R/EM-5 Annual Progress Report.

Collard, S.B. 1976b. Neuston of the MAFLA lease areas. Bur. Land Manage.,

84p.

Collard, S.B. 1978. Neuston of the eastern Gulf of Mexico. Bur. Land

Manage., 23 p.

Collard, S.B. 1981. Neuston of the MAFLPA lease areas. Final Report. Bur.

Land Manage., 91 p.

Collard, S.B. 1984. Pleustonic metazoans of the continental shelf of the

eastern Gulf of Mexico. Internat. Symp. Mar. Zooplankton, Shimizu,

Japan (Abstract).

Collard, S. B. 1989. Sorting and identifying macroinvertebrates, St.

Andrew Bay. Unpublished, unpaged.

Collard, S. B. 1991. Surface water improvement and management (S.W.I.M.)

program. Northwest Florida Water Management District, Water Resourc

Spec. Rep 91-3.

Collard, S. B. 1992. Characteristics of seagrass meadows in St. Andrew

(Crooked Island) Sound, northern Gulf of Mexico: preliminary

findings. University of West Florida, Pensacola, FL. 19 p.

Collard, S.B. 1993. Styela plicata and Molgula occidentalis (tjrochordata:

A.scidiacea: Stolidifera) in St. Andrew Sound, Florida. Final Rep.

AFOSR 19:1-20.

Collard, S.B. and C.N. D'Asaro. 1973. Benthic invertebrates of the

eastern Gulf of Mexico. J.I. Jones, R.E. Ring, M.O. Rinkel and

R.E. Smith, eds. A summary of knowledge of the eastern Gulf of

Mexico. University System of Florida, Institute of Oceanography, St.

Petersburg, FL.

5-114
5-115

Collard, S. B. and Larry H. Ogren 1990. Dispersal scenarios for pelagic

post-hatchling sea turtles. Bull. Mar. Sci. 47(1) :233-243.

Continental Shelf Associates, I. 1985. Florida Big Bend Seagrass Habitat

Study Photographic Atlas. Minerals Management Service. Metairie,

LA. 17 pp.

Comp, G.S. and W.Seaman, Jr. 1985. Estuarine habitat and fishery

resourcces of Florida. In: Florida Aquatic Habitat and Fisheries

Resources, W. Seaman, Jr. (ed.), pp337-411.

Cooley, N.R. 1978. An inventory of the estuarine fauna in the vicinity of

Pensacola, Florida. Florida Mar. Res. Publ. 31:1-119.

Corcoran, E.F. 1973. Chemical oceanography. Section 2C. In: A summary

of knowledge of the eastern Gulf of Mexico 1973 (J.I. Jones, R.E.

Ring, M.O. Rinkel, and R.E. Smith, eds.). State Univ. Sys. of

Florida. Inst. Oceanogr.

Dames & Moore. 1979. Mississippi, Alabama, Florida outer continental

shelf baseline environmental survey; MAFLA, 1977/78. Vol. II:

Compendium of work element reports. Final report prepared for U.S.

Department of the Interior, Bureau of Land Management. Contract No.

AA550-CT7-34.

Darnell, R.M. 1990. Mapping of the Biological Resources of the

Continental Shelf. Amer. Zool. 30:15-21.

Dawes, C.J. 1987. The dynamic seagrasses of the Gulf of Mexico and

Florida coasts. In Proceedings of the symposium on subtropicaltropical seagrasses of the Southeast United. States. M.J. Durako,

R.C. Phillips, and R.R. Lewis, III, eds., Florida Marine Research

Publication 42, pp. 25-38.

Donoghue, F.F. 1988. Evaluation of sediment loading processes in the

Apalachicola Bay, Florida: NOAA Technical Memorandum Series NOSMEMD-17, 72 pp.

Donoghue, J. F., and W. T. Cooper. 1993. Contaminant history of the

sediments of Apalachicola Bay. Florida Dept. of Nat. Resour. 45 pp.

+ figures.

Dugan, P.J. and R.J. Livingston. 1982. Long-term variation of

macroinvertebrate assemblages in Apalachee Bay, Florida. Estuarine,

Coastal and Shelf Science. 14(4) :391-403.

Duke, T. and W.L. Kruczynski (eds.) 1992. Report on the status and trends

of emergent and submerged vegetated habitats of Gulf of Mexico

coastal waters, U.S.A. Preliminary Rept., U.S. Environ. Protection

Agency, Gulf of Mexico Prog., Habitat Degradation Comm. EPA/800-R92-003.
Edmiston, H.L. and H.A. Tuck. 1987. Resource Inventory of the

Apalachicola River and Bay Drainage Basin. Florida Game and Fresh

Water Fish Commission.

Edwards, N.C. Jr., 1976. A Study of the circulation and Stratification of

Escarnbia Bay, Florida During the Period of Low Fresh Water Inf low.

Tallahassee, FL: Florida State University. Thesis.

Federle, T.W., R.J. Livingston, D.A. Meeter, and D.C. White. 1983.

Modifications of estuarine sedimentary microbiota by exclusion of

epibenthic predators. J. Exp. Mar. Biol. Ecol. 73:81-94.

Fenchel, T., and B. Jorgensen. 1977. Detritus food chains of aquatic

ecosystems: the role of bacteria. Pp. 1-58 in M. Alexander, ed.

Advances in Microbial Ecology. Plenum Press, New York.

Fernald, E.A. and E.D. Purdum. (eds.) 1992. Atlas of Florida. Inst. Sci.

Public Affairs, Univ. Presses Florida. 280 p.

Ferrario, J.B. 1990. Toxic substances and pesticides in the Gulf of

Mexico. Pp. 29-39. In: The environmental and economic status of

the Gulf of Mexico (G. Flock, ed.). Gulf of Mexico Prog., Stennis

Space Center, Stennis, Mississippi. Unpubl. Conf. Rept. 196 p.

Field, D.W., A.P.. Reyer, P.V. Genovese, and B.D. Shearer. 1991. Coastal

wetlands of the United States. U.S. Dep. Commerce, Natl. Ocean.

Atmosph. Admin. Spec. NOAA 20th Anniversary Rep. 59 p.

Florida Department of Natural Resources. 1992. Apalachicola Bay Aquatic

Preserve Management Plan. Division of State Lands, Florida Dept.

Nat. Resour. 163 pp.

Florida Department of Environmental Protection. 1984. Final report.

Deepwater ports maintenance dredging study: Results, interpretations

and recommendations. Ports of Jacksonville, Tampa, Manatee and

Pensacola. Vol. 1. Tallahassee, FL.

Florida Department of Environmental Protection. 1994. Strategic

Assessment of Florida's Environment: SAFE. Florida State

University. Tallahassee, FL. 287 pp.

Florida Department of Environmental Regulation. 1988. A special

monitoring project basin survey: Biological physicochemical

assessment of Pensacola Bay 1987-1988. Northwest Dist, Biol. Sect.,

Pensacola, Florida. 67 p.

Florida Department of Natural Resources. 1990. Guide to the natural

communities of Florida. Florida Natural Areas Inventory and Florida

Department of Natural Resources, Office of Land Use Planning and

Biological Services. Tallahassee, FL.

Florida Department of Natural Resources. 1987. St. Joseph Bay Aquatic

Preserve Management Plan.

5-116
Florida Department of Natural Resources. 1974. Proceedings of the Florida

red tide conference 10-12 October 1974, Sarasota, Florida. Florida

Dept. Nat. Resour. 8:1-17.

University of Florida. 1994. 1994 Florida Statistical Abstract, 28th

Edition. Bur. Econ. Business. Reg., Coil. Bus. Admin. Univ.

Florida. Univ. FL Press, 794 p.

Fry, B. and P.L. Parker. 1979. Animal diet in Texas seagrass meadows:

8l3C evidence for the importance of benthic plants. Estuarine and

Coastal Marine Science 8: 499-509.

Gallagher, R.M. 1971. Preliminary Report on the Hydrography of the

Pensacola Bay Estuary, Florida. St. Petersburg, FL: Florida Dept.

of Natural Resources, Marine Research Lab. 36 p. (Spec. Sci. Rept.

29)

Galtsoff, P.S. 1954. Gulf of Mexico: its origin, waters and marine life.

U.S. Fish and Wildlife Service, Fishery Bulletin. Vol. 89 No. 55. p.

604.

George, S.M. 1988. The sedimentology and minerology of the Pensacola Bay

system. M.S. Thesis, Univ. So. Mississippi, Hattiesburg,

Mississippi, 95 p.

Germano, J.D., and D.C. P.hoads. 1984. REMOTS® Sediment Profiling at the

Field Verification Program (fvp) disposal site. Proceedings of the

Conference on Dredging '84, Waterway, Port, Coastal and Ocean

Division, American Society of Chemical Engineers. Nov. 14-16, 1984.

Clearwater Beach, Florida.

Goldberg, E.D. 1990. Environmental quality and useless numbers. Sea

Technol., August, 1990:89.

Gorsline, D. S. 1963. Oceanography of Apalachicola Bay, Florida. In: Essays

in Marine Geology in Honor of K. 0. Emery; Pp. 69-96. Los Angeles:

University of Southern California Press.

Grady, J. R. 1981. Properties of sea grass and sand flat sediments from

the intertidal zone of St. Andrew Bay, Florida. Estuaries 4(4) :335-

344.

Hand, J. and D. Jackman. 1982. Water quality inventory for the State of

Florida (305b report). Florida Department of Environmental

Regulation, Tallahassee. 207 pp.

Hand, J., J. Col and E. Grimison. 1994. Northwest Florida District Water

Quality Assessment 1994 305(b) Technical Appendix. Bureau of

Surface Water Management. Florida Department of Environmental

Protection. 155 pp.

Heck, K.L., Jr. and T.A. Thoman. 1984. The nursery role of seagrass

meadows in the upper and lower reaches of the Chesapeake Bay.

Estuaries 7:70-92, March, 1984.

5-117
Hedgpeth, J. W. 1954. Bottom communities of the Gulf of Mexico in Gulf of

Mexico, its origin, waters, and marine life. Fishery Bulletin, U.S.

Fish and Wildlife Service, 55(89): 203-214.

Hopkins, T.S. 1979. Chapter 17. Macroepifauna. pp. 789-835. The

Mississippi, Alabama, Florida outer continental shelf baseline

environmental survey. Bureau of Land Management, Washington, D.C.

Hopkins, T.S. 1973b. Zooplankton. J.I. Jones, R.E. Ring, M.O. Rinkel

and R.E. Smith, eds. A summary of knowledge of the eastern Gulf of

Mexico. State University System of Florida, Institute of

Oceanography, St. Petersburg, FL.

Hopkins, T.L. 1966. The plankton of the St. Andrew Bay system, Florida.

Univ. Texas, Pul,1. Inst. Mar. Sci. 11:12-64.

Horvath, G.J. 1968. The sedimentology of the Pensacola Bay system,

northwestern Florida. M.S. Thesis. Florida State University,

Tallahassee. 89 pp.

Humm, H.J. 1974. Seagrasses. Pp. 149-151. In: Proceedings of marine

environmental implications of offshore oil drilling: eastern Gulf of

Mexico (Smith, R.E., ed.) State Univ. System of Florida, Inst.

Oceanogr., St. Petersburg, FL.

Humm, H.J. 1953. Notes on the marine algae of Florida. II. Flora of the

rocky bottom off St. Mark's Light, Wakulla County (Gulf of Mexico).

Phycol. Society News Bulletin. 6:8.

Hydroqual, Inc. and Barry A. Vittor & Associates, Inc. 1993. St. Andrew

Bay Environmental Monitoring Program 1990-1992. Bay County Utilities

Department. Panama City, FL.

Isphording, W.C. and J.A. Stringfellow. 1983. Environmental implications

of metal contamination levels in Crassostrea virginica from Mobile

Bay, Alabama and St. Louis Bay, Mississippi, 7 p.

Isphording, W.C., F.D. Imsand, and G.W. Isphording. 1984. Identification of

short-term changes in depositional rates: Importance in environmental

analysis and impact investigations. Trans. Gulf Coast Assoc. Geol.

Soc. 34:69-84.

Isphording, W.C., F.D. Imsand, and G.C. Flowers. 1989. Physical

characteristics and aging of Gulf Coast estuaries. Trans. Gulf Coast

Assoc. Geol. Soc. 39:387-401.

Isphording, W.C., J.A. Stringfellow, and G.C. Flowers. 1985. Sedimentary

and Geochemical Systems in Transitional Marine Sediments in the

Northeastern Gulf of Mexico. Trans. Gulf Coast Assoc. Geol. Soc.

35:397-408.

Kennish, M.J. 1989. Practical handbook of marine science. CRC Press,

Boca Raton, Florida, 710 p.

5-118
Ketchen, G.H, and R.C. Staley. 1979. A Hydrographic Survey in Pensacola

Bay. Tech. Rep., Dep. Oceanogr., Florida State Univ., Tallahassee,

Florida. 117 p.

Kikuchi, T. and J.M. Peres. 1977. Consumer ecology of seagrass beds. Pp.

147-193. ID,: Seagrass ecosystems. A scientific perspective (McRoy,

C.P. and C. Helfferich, eds.). Marcel Dekker Inc., N.Y.

Kobylinski, G.J. and P.F. Sheridan. 1979. Distribution, abundance,

feeding and long-term fluctuations of spot, Leiostornus xanthurus, and

croaker, Micropogonias undulatus, in Apalachicola Bay, Florida,

1972-1977. Contrib. Mar. Sci. 22:149-161

Lauff, G., 1967. Estuaries. American Assoc. for the Advancement of Science,

Pullication 83.

Lee, J.E. 1980. A conceptual model of marine detrital decomposition and

the organisms associated with the process. Pp. 257-291 In M.R. Droop

and H.W. Yannasch, eds. Advances in Microbial Ecology. Academic

Press, New York.

Little, E.J., and J.A. Quick. 1976. Ecology, resource rehabilitation, and

fungal parasitology of commercial oysters, Crassostrea virginica

(Gmelin), in Pensacola Estuary, Florida Florida Department of

Natural Resources, Marine Research Laboratory. St Petersburg. 89 pp.

Livingston, R.J. 1991. Historical relationships between research and

resource management in the Apalachicola River estuary. Ecological

Applications. 1(4) :361-382.

Livingston, R.J. (ed.) 1987. Distribution of toxic agents and biological

response of infaunal macroinvertebrates in the Choctawhatchee Bay

System. Florida Dep. Environ. Regul., Office Coast. Manage., 40 pp.

Livingston, R.J. 1986. The Choctawhatchee River-Bay System. Center for

Aquatic Research and Resource Management, Florida State University.

Tallahassee. 1,075 pp.

Livingston, R.J. 1984. The ecology of the Apalachicola Bay system: an estuarine profile. U.S. Fish and Wildlife Service FWS/OBS-82/05.

Livingston, P..J. 1989. A photographic atlas of north Florida estuarine

phytoplankton and summarization of life history relationships and

associations with various environmental conditions. Center for

Aquatic Research and Resource Management, Florida State University,

Tallahassee.

Livingston, R.J., and E.A. Joyce. 1977. Proceedings of the Conference on

the Apalachicola drainage system, 23-24 April 1976. Gainesville,

Florida. Florida Mar. Res. Pubi. 26.

Livingston, R. J. 1983. Resource atlas of the Apalachicola estuary.

Florida Sea Grant College Publication. 64 pp.

5-119
Livingston, R. J. 1977. Estuarine and coastal research in Apalachee Bay

and Apalachicola Bay. Pp. 7-11 In Coastal Zone Management Symposium,

University of West Florida. Pensacola.

Livingston, R.J., R.L. Iverson, R.H. Estabrook, V.E. Keys and J. Taylor,

Jr. 1974. Major Features of the Apalachicola Bay System:

Physiography, Biota, and Resource Management. Fla. Sci. 37 (4) :245-

271.

Livingston, R. J., et al. 1972. The effects of dredging and

eutrophication on Mulat - Mulatto Bayou, Research No. 111308016.

Florida State University. Tallahassee, FL. 172 pp.

Lowery, T.A. 1993. Derivation and use of Gulf Coast estuary watershed and

population estimates (1960-2010) . Northeast Gulf Science. 73(1) :35-

41.

Lyons, W.G. and S.B. Collard. 1974. Benthic invertebrate communities of

the eastern Gulf of Mexico. In R.E. Smith, ed. Proceedings, Marine

Environmental Implications of Offshore Drilling in the Eastern Gulf

of Mexico Conference/Workshop. (Contribution No. 233, FDNR/MRL)

State University System of Florida, Institute of Oceanography, St.

Petersburg, FL. Pp. 157-165.

Marmer, H.A. 1942. Tide at Pensacola. Proc. U.S. Naval Inst. 68:1427-

1431.

McNulty, J.K., R.C. Work, and H.B. Moore. 1962. Level sea bottom

communities in Biscayne Bay and neighboring areas. Bull. Mar. Sci.

Gulf Caribb. 12:204-233.

McNulty, J. K., 1961. Ecological effects of sewage pollution in Biscayne

Bay, Florida: sediments and distribution of benthic and fouling

macro-organisms. Bulletin of Marine Sciences, 11:394-447.

McNulty, J. Kneeland, W. N. Lindall Jr., and J. E. Sykes. 1972.

Cooperative Gulf of Mexico estuarine inventory and study, Florida:

Phase I, Area description. U.S. Dept. of Commerce, NOAA Technical

Report NMFS Circ-368, 126 p.

McRoy, C.P., and R.J. Barsdate. 1970. Phosphate absorption in eelgrass.

Limnol. Oceanogr. 15:14-20.

McRoy, C.P., R.J. Barsdate and M. Nebert. 1972. Phosphorous cycling in an

eelgrass (Zostera marina) ecosystem. Limnol. Oceanogr. 17-58-67.

Menzel, R. W. 1971. Checklist of the fauna and flora of the Apalachee Bay

and the St. GeorgeTs Sound area. Third edition. Florida State

University, Tallahassee. 126 pp.

Moskovits, G. 1955. Literature survey of Lake Charles, LA. Gulfport,

Miss., Mobile, Ala., and Pensacola, Florida., and their approaches.

Vol. 2. Pp. 91-94. Marine biology. Agricult. Mech. Cell., Texas,

Dep. Oceanogr., College Station, Texas.

5-120
Musgrove, R. H., J. B. Foster, and L.G. Toler. 1968. Water resource

records of the Econfina Creek Basin area, Florida. Florida State

Board of Conservation, Div. of Geology, Tallahassee, FL, Information

Circular No. 57, 127 p.

Myers, R.L., and J.J. Ewel. 1990; Problems, prospects and strategies for

conservation. Pages 619-632 in R.L. Myers and J.J. Ewel, eds.

Ecosystems of Florida. Gainesville, FL.

Naughton, S.P., and C.H. Saloman. 1978. Fishes of the nearshore zone of

St. Andrew Bay, Florida and adjacent coast. Northeast Gulf Science

Vol. 2(1) pp. 43-55.

NOAA. 1991. The 1990 National Shellfish Register of classified estuarine

waters. U.S. Dept. of Commerce, National Ocean Service, Rockville,

MD, 100 p.

NOAA. 1989. A summary of data on tissue contamination from the first

three years (1986-1988) of the mussel watch program. U.S. Dept. of

Commerce, National Ocean Service Technical Memorandum NOS OMA 49,

var. pag.

NOAA. 1986. Eastern Gulf of Mexico Regional Map. National Ocean Service,

Riverdale, MD.

Odum, W.E. and T.J. Smith. 1981. Habitat value of coastal wetlands. Pp.

30-35. In: Proceedings of a workshop on coastal ecosystems of the

southeastern United States (Casey, P.S., P.S. Markovits, and J.B.

Kirkwcod, eds.). U.S. Fish Wildl. Serv. FWS/OBS-80/59.

Odum, H.T., B.J. Copeland, and E.A. McMahan, eds. 1974. Coastal

ecological systems of the United States. The Conservation

Foundation, Washington, D.C. 4 vols.

Ogren, L. H., and H. A. Brusher. 1977. The distribution and abundance of

fishes caught with a trawl in the St. Andrew Bay system, Florida.

Northeast Gulf Science 1(2) :83-105.

Olinger, L.W., R.G. Rogers, P.L. Fore, R.L. Todd, B.L. Mullins, F.T.

Bisterfield, and L.A. Wise. 1975. Environmental and recovery

studies of Escambia Bay and the Pensacola Bay System, Florida. EPA

904/9-76-016. EPA, Region 4. Various paging.

Paulic, M. and J. Hand. 1994. Florida Water Quality Assessment 1994 305

(b) Report. Bureau of Surface Water Management. Florida Department

of Environmental Protection. 261 pp.

Pratt, T.R., P.G. Weiland, J.H. Cason, J.M. Starnes-Smith, W.K. Jones, D.J.

Cairns, and L.P. Simoneaux (eds). 1990. The Pensacola Bay System

Surface Water Improvement and Management Plan. Northwest Florida

Water Management District.

5-121
Pristas , P.J., and L. Trent. 1978. Seasonal abundance, size, and sex

ratio of fishes caught with gill net in St. Andrew Bay, FL. Bulletin

of Marine Science. Vol. 28 PP. 581-589.

Prochaska, F.J. and D. Mulkey. 1983. The Apalachicola Bay oyster

industry: some economic considerations. pp. 47-52. In: S. Andree

(ed.) Apalachicola oyster industry. Florida Sea Grant Col. Rept. No.

57. Gainesville, FL.

Provost, M.W. 1971. Mean high water mark and use of tidelands in Florida.

Florida Sci. 36(2) :50-64.

Rakocinski, C.F., R.W. Heard, S.E. LeCroy, J.A. McLelland, and T. Simons.

1993. Seaward change and zonation of the sandy-shore macrofauna at

Perdido Key, Florida, U.S.A. Estuarine, Coastal and Shelf Science.

36:81-104.

Reidenauer, J. and C. Shambaugh. 1986. An analysis of estuarine

degradations within the Pensacola Bay system and their relationship

to land management practices. Florida Dep. Commun. Affairs. Draft,

132 pp.

Rhoads, D.C. and J.D. Germano. 1986. Interpreting long-term changes in

benthic community structure: A new protocol. Hydrobiol. 142:291-

308.

Rodriguez, J. A., P.E. and T. Wu. 1990. Initial Analysis of Circulation

and Flushing Characteristics of the St. Andrew Bay System. Water

Resources Special Report 90-1. Northwest Florida Water Management

District. 105 pp. and appendices.

Rogers, R.G., and F.

the Pensacola

Conference on

FL. Lewis,RR

T. Bisterfield. 1975. Loss of submerged vegetation in

Bay system 1949-1974. Proceedings of the Second Annual

Restoration of Coastal Vegetation in Florida, Tampa,

(ed.) . pp. 35-51.

Ross, B.E. 1973. The hydrology and flushing of the bays, estuaries, and

nearshore areas of the eastern Gulf of Mexico. Section 2D. Ina; A

summary of knowledge of the eastern Gulf of Mexico 1973 (J.I. Jones,

R.E. Ring, M.O. Rinkel, and R.E. Smith, eds.). State Univ. Sys. of

Florida, Inst. Oceanogr.

Ryan, J.D., F. D. Calder, and L.C. Burney. 1984. Deepwater ports

maintenance dredging and disposal manual. Florida Department of

Environmental Regulation. Internal Publication.

Saloman, C.H., S.P. Naughton, and J.L. Taylor. 1982. Benthic Fau.nal

Assemblages of Shallow Water Sand and Seagrass Habitats, St. Andrew

Bay, Florida. U.S. Fish and Wildlife Service, Division of Ecological

Services. Panama City, FL. 27pp.
Sargent, F.J., T.J. Leary, D.W. Crewz and C.R. Kruer. 1995. Scarring of

Florida's Seagrasses: Assessment and Management Options. FMRI

Technical Report TR-l. fl Marine Research Institute, St. Petersburg,

Florida. 37 p. plus appendices.

Savastano, K.J., K.H. Faller, and R.L. Iverson. 1984. Estimating

vegetation coverage in St. Joseph Bay, Florida, with an airborne

multispectral scanner. Photogramm. Eng. Rem. Sens. 50: 1159-1170.

Scanland, T. B. 1966. A description of the community associated with two

Arks, Arca zebra and Arca imbricata (Pelycopoda: Arcidae) in the

offshore northeastern Gulf of Mexico. M.S. thesis, Florida State

University, Tallahassee.

Schropp, S.J. and H.L. Windom. 1988. A guide to the interpretation of metal

concentrations in estuarine sediments. Florida Dept. Environ. Regul.,

Coast. Zone Manage. Sect., 43 p.

Science Applications International Corporation. 1986. REMOTS survey of

Pensacola Bay, Florida. Florida Department of Environmental

Regulation. Internal report No. SAIC-86/7500&99.

Seaman,W., Jr. (ed.) 1985. Florida aquatic habitat and fisheries

resources. Am. Fish. Soc., Florida Chapt. 543 p.

Sheridan, P.F and R.F. Livingston. 1983. Abundance and seasonality of

infauna and epifauna inhabiting a Halodule wrightii meadow in

Apalachicola Bay, Florida. Estuaries 6:407-419.

Sonu, J.C., and L.D. Wright. 1975. Mass transport and dispersion of of a

tidal inlet. Pp. 489-4981n: Seventh Annual Offshore Technology

Conference, May 5-8, 1975, Houston, Texas. Volume III, No. OTC 2383.

St. Andrew Bay Resource Management Association. 1992. Lake/Baywatch. A

citizen volunteer water quality monitoring program for Bay County,

Florida. Rep. No. 2 (1991-92), June 1992. 180p.

Steidinger, K.A. 1973. The biological environment: Phytoplankton, pp. 1-

17. In: J.I. Jones, R.E. Ring, M.O. Rinkel, and R.E. Smith (eds.),

A Summary of the Knowledge of the Eastern Gulf of Mexico, Vol. III.

State University System of Florida Institute of Oceanography.

Stith, L., J. Barkuloo, and M.S. Brim. 1984. Fish and wildlife resource

inventory for Escambia navigation project Escambia and Santa Rosa

Counties, Florida. U.S. Fish Wildl. Serv. DIV. Ecol. Sd., Panama

City, Florida. 44 p.

Stout, J.P. 1984. The ecology of irregularly flooded salt marshes of the

northeastern Gulf of Mexico: a community profile. U.S. Fish Wildl.

Serv. Biol. Rept. 85(7.1). 98 p.

Stewart, H.H. 1975. Distribution and summer energetics of invertebrate

epifauna in an ellgrass (Zostera marina) bed. MS. Thesis. North

Carolina State Univ., Raleigh, N.C. 76 p.

5-12 3
Stursa, M.L. 1973. Environmental quality problems. : A summary of

knowledge of the eastern Gulf of Mexico. J.I. Jones, R.E. Ring, M.O.

Rinkel, and R.E. Smith (eds). Pubi.: State University System of

Florida, Institute of Oceanography. St. Petersburg, FL

Tanner, W.F. 1966. Late Cenozoic history and coastal morphology of the

Apalachicola River region, western fla. In, Deltas and their

geologic framework, M. Shirley editor, pp. 83-97.

Taylor Biological Company. 1978. Environmental summary and benthic

investigation - Choctawhatchee Bay, Florida. Lynn Haven, FL. 55

pp. and appendixes.

Thayer, G.W. and J.F. Ustach. 1975. The impact of man on a seagrass

system. American Scientist. 63:288-296.

Thompson, R., V. Brooks, J. Gunter, and E. Barnett. 1990. Comprehensive

Shellfish Harvesting Area Survey, Apalachicola Bay, Franklin County.

Florida Department of Natural Resources.

Turner, J.T., S.B. Collard, J.C. Wright and P. Steele. 1979. Summer

distribution of pontellid copepods in the neuston of the eastern Gulf

of Mexico continental shelf. Bull. Mar. Sci. 29(3) :289-297.

Turner, J.T. and S.B. Collard. 1980. Winter distribution of pontellid

copepods in the neuston of the eastern Gulf of Mexico continental

shelf. Bull. Mar. Sci. 30(2) :526-529

U.S. Army Corps of Engineers. 1982. Water quality management studies of

Lake Seminole, February - December, 1979. Phase II, ACR 80-11,

Mobile District.

U.S. Army Corps of Engineers. 1984. 1984 water assessment for the

Apalachicola-Chattahootchee-Flint River basins, Vol. 1. Mobile

District. 88 pp.

U.S. Army Corps of Engineers. 1955. Perdido Pass (Alabama Point),

Alabama, Beach Erosion Control Study. In: 84th Cong., 2nd Sess.,

House Doc. 274. 30 p.

U.S. Department of Commerce, National Oceanic and Atmospheric

Administration. 1990. Estuaries of the United States: Vital

statistics of a national resource base. Spec. NOAA 20th Anniversary

Rep. 79 p.

U.S. Department of the Navy. 1986. Draft environmental impact statement:

United States Navy gulf coast strategic homeporting. Appendix IV.

Pensacola, Florida. Southern Division, Naval Facilities Engineering

Command, Charleston, SC.

U.S. Environmental Protection Agency (EPA). 1971. Circulation and benthic

characterization studies: Escambia Bay, Florida. Southeast Water

Quality Laboratory, Athens, GA. 32 pp.

5-12 4
Valentine, J. F. and K.L. Heck Jr. 1993. Mussels in seagrass meadows:

their influence on macroinvertebrate abundance and secondary

production in the northern Gulf of Mexico. Mar. Ecol. Prog. Ser.

Vol. 96:63-74.

Valentine, J.F., K.L. Heck Jr., P. Harper, M. Peck. 1994. Effects of

bioturbation in controlling turtlegrass (Thalassia testudinum) from

field enclosures and observations in the northern Gulf of Mexico. J. Exp. Mar. Biol. Ecol. 178(2) :181-192.

Virnstein, R.W. 1987. Seagrass-associated invertebrate communities of the

southeastern U.S.A.: A review. Pp. 90-116. In: Proceedings of the

symposium on the subtropical-tropical seagrasses of the southeastern

United States, 12 August 1985 (M.J. Durako, R.C. Phillips, and R.R.

Lewis, III, eds.) . Florida Mar. Res. Publ. 42.

Wade, T.L., E.L. Atlas, J.M. Brooks, and M.C. Kennicutt, II. 1988. NOAA

Gulf of Mexico Status and Trends Program: trace organic contaminant

distribution in sediments and oysters. Estuaries 3:171-179.

Wade, T.L., E.L. Atlas, J.M. Brooks, and M.C. Kennicutt, II. 1988. NOAA

Gulf of Mexico Status and Trends Program: trace organic contaminant

distribution in sediments and oysters. Estuaries 3:171-179.

Wells, H. W. 1961. The fauna of oyster beds, with special reference to the

salinity factor. Ecological Monographs, 31(3) :239-266.

Whitlach, R.B. 1982. The ecology of New England tidal flats: a community

profile. U.S. Fish Wildl. Serv. Biol. Serv. Prog. FWS/OBS-81/Ol.

125 pp.

Wilber, D.H. 1992. Influence of Apalachicola River flows on blue crab

Callinectes sapidus, in north Florida. Fish. Bull. 92:180-188.

Williams, A. B. 1965. Marine decapod crustaceans of the Carolinas. U. S.

Fish Wildlife Service, Fishery Bulletin, 65(1) :1-298.

Williams, S.L. and N.H. Ruckelshaus. 1993. Effects of nitrogen

availability and herbivory on eelgrass (Zostera marina) and

epiphytes. Ecology. 74(3), pp. 904-918.

Wolfe, S.H., J.A. Reidenauer and D.B. Means. 1988. ?n ecological

characterization of the Florida panhandle. FWS Biol. Rep. 88(12),

OCS Study MMS 88-063, U.S. Dept. Interior, Fish Wildl.

wood, D.A. 1986. Official lists of endangered and potentially endangered

fauna and flora in Florida. Florida Game FreshwaterFish Commiss.,

Tallahassee, Florida. 19 p.

Wooters, J. S. 1989. Ecology of vision in the bay scallop: Argopecten

irradians (Pectinidae: Bivalvia). M.S. Thesis. Univ. of W. FL. 57

pp.

5-125
Young, W.T., G.L. Butts, L.W. Donelan, and D.H. Ray. 1987. Biological

and physicochemical assessment of St. Andrew Bay Estuaries 1986-1987.

Special Monitoring Project Basin Survey, Florida Department of

Environmental Regulation, Northwest Distr., Biol. Sect. 24 pp.

Young, W.T., G.L. Butts, L. Donelan, and D.H. Ray. 1982. A biological

water quality and sediment survey of the Choctawhatchee River Basin

and estuaries. Florida Dep. Environ. Regul., Northwest Distr. Spec.

Monitor. Proj., Fiscal Year

Zieman, J.C. 1987. A review of certain aspects of the life, death, and

distribution of the seagrasses of the southeastern United States

1960-1985. Pp. 53-76. : Proceedings of the symposium on

subtropical-tropical seagrasses of the southeastern United States.

12 August 1985. (Durako, M.J., R.C. Phillips and R.R. Lewis, III,

eds.). FL Dept. Nat. Resour., Bur. Mar. Res. Pubi. No. 42, 209 p.

Zieman, J.C., R.L. Iverson, and J.C. Ogden. 1984. Herbivory effects on

Thalassia testudinurn leaf growth and nitrogen content. Mar. Ecol.

Prog. Ser. 15:151-158.

Zimmerman, M.S. and R.J. Livingston. 1976b. Seasonality and

Physiochemical Ranges of Benthic Macrophytes from a North Florida

Estuary, Apalachee Bay, Florida. Bull. Mar. Sci. 20:33-45.
Chapter 6 - SOCIOECONOMIC CONDITIONS

by Dr. F. Bell

Florida State University

6.1 Introduction

This study is an intensive analysis of the socioeconomic characteristics of

northwest Florida that are related to the marine ecosystem. As Figure 6-1

indicates, northwest Florida includes 13 coastal counties, starting with

Escambia County (i.e., a dot indicates a county that is part of this study)

in the extreme northwestern part of Florida to Citrus County, just north of

the Tampa metropolitan area. These coastal counties exhibit a great range

of economic activities and marine ecosystem processes. As will be

indicated, the economies of these counties depend greatly on and interact

with the marine ecosystem; therefore, the emphasis of this report is to

identify the extent and nature of this interaction. Since OCS activities

must be analyzed within the context of the existing onshore and offshore

economic activities, a baseline socioeconomic characterization of such an

area as northwest Florida is important in identifying positive and negative

potential impacts on the marine environment.

This summary, which reflects material from the individual county summaries

in Appendix G of this report, is composed of five parts. First, key

socioeconomic characteristics of the 13 counties are reviewed. Second,

each county has critical industries which are defined as the export base,

or those industries that derive income from outside the county. Such

industries are the driving force behind the economic growth or decline of

the region. Third, aspects of the local economies can affect the marine

ecosystem. Industries can create environmental externalities which are

linked in a negative way to the ecosystem by such things as wetland

destruction, pollution and altered water flows. Such industries are named

"ecosystem-sensitive" in that the level of economic activity in an industry

has a direct bearing on the well-being of the marine environment. Those

industries that are relatively independent of the ecosystem are identified

and characterized as "ecosystem-insensitive." Discussion of this third

part provides an indication how sensitive the marine environment is to the

regional (county) economies. Fourth, the marine ecosystem directly

supports key industries in the counties under analysis. Four such

industries are analyzed:

commercial fishing,

recreational fishing,

saltwater beach use, and

marine recreational boating.

In addition, wetlands support the fishing industries as part of their

economic function, and the saltwater marshes are reviewed in terms of their

economic contribution to these industries.

6-1
%-; _&TSI

,

S-IA

£ p

NBS Study Area

-- --.tWrr'.

a

II

STATE PLANNING REGIONS

1993

VIII

ILW I -, au.

nfl

S

\;

Ix _J____

IV

ST. LU x

XI

Figure 6-1. Map of the state of Florida indicating the 13 counties covered

in this study.
The fifth part of this summary presents a review of water quality, which is

critical to the marine ecosystem; this subject is related back to

industries that contribute to negative impacts.

6.2 Soàioeconomic Indicators

Table 6-1 shows key economic indicators reflecting the relative economic

size and welfare of the 13 coastal counties in northwest Florida. Escambia

County is the largest in terms of population, personal income, wages and

employment, with nearly 271,000 inhabitants and nearly 144,000 workers.

This is in marked contrast to Franklin County, which has but 10,000

inhabitants and slightly over 4,000 workers.

Table 6-1. A Summary of Socioeconomic Characteristics for Thirteen

Counties in Northwest Florida, 1993

Counties Population Personal Wages by Employment Per Capita

Source: BEA, USDC

As shown in Table 6-1, there is a great disparity in economic size from

county to county. In second and third place in terms of population and

employment are Okaloosa and Bay Counties, respectively. The three mostpopulated counties are concentrated in the extreme western part of the 13-

county region. One of the main reasons for this is their sandy beaches

which attract tourists and retirees, coupled with their proximity to

natural resources (e.g., forestry) and good transportation. In addition,

these counties are close to Alabama, a rapidly growing state.

The 13-county region has a population of nearly 900,000 people1 which is

6.6 percent of the 1993 state population. Although this is a large coastal

area, the population density is less than the Florida average. There is

still much open space in this area of Florida. In general, the population

concentration declines from the extreme northwest area and around the Big

Bend. It is not until Citrus County, on the southern edge of the study

area, that population reaches over 100,000 people. This contrasts with Bay

6-3

(000) Income

($000)

Place of

Employment

Income

Escambia 270.4 $4,569,565 $3,439,195 143,673 $16,899

Santa Rosa 94.5 1,564,823 1,964,348 30,741 16,556

Okaloosa 1573 2,863,026 629,336 89,337 18,202

Walton 30.4 429,411 203,184 11,652 14,128

Bay 137.2 2,311,669 1,564,044 74,228 16,852

Gulf 12.0 174,258 109,891 4,692 14,482

Franklin 9.5 136,900 63,323 4,020 14,458

Wakulla 16.1 238,807 80,375 4,581 14,816

Jefferson 11.8 172,176 69,470 4,453 14,575

Taylor 17.3 236,255 170,156 7,541 13,690

Dixie 11.4 172,176 63,482 3,570 10,334

Levy 28.1 367,532 145,228 9,021 13,062

Citrus 101.9 1,558,130 641,140 32,585 15,295

Total 897.9 $14,794,728 $9,143,172 420,094 $16,477
County in the western portion of the region, where the tourist mecca of

Panama City exists. The sparsely-settled counties do not have the

attractive beaches, infrastructure and other amenities that characterize

the more populated counties in the study area.

Jnother key economic indicator is per capita income, which is an economic

welfare indicator and a gauge of relative affluence. The most western

counties in the region also show the highest per capita income with

Okaloosa County exhibiting the highest ($18,202 per person). Per capita

income is lowest ($10,334 per person) in Dixie County. In general, there

is a positive correlation between economic size and the level of affluence

as measured by per capita income.

The marine ecosystem plays a dramatic role in enhancing the economic

capabilities of each county. For example, Escambia County has a deep water

port, while the region from Santa Rosa County to Bay County has some of the

most attractive beaches in the world. These marine resources have been

instrumental in increasing the population and attracting tourists and

retirees to these areas. Also, military air bases help raise per capita

income in these areas (i.e., the high percent of officers at such bases).

Thus, it is not surprising that the economic size and affluence is

prevalent. Other counties such as Franklin have marine resources, but do

not have the resource variety found in the northwest counties. Franklin

County's economy is dominated by commercial fishing of oysters and shrimp

(see county summary in Appendix G). Relative to the state of Florida, the

region's per capita income of $16,477 is below the state average of

$20,828, due in part to a number of low-wage industries (i.e., services,

paper manufacturing, etc.) and a lack of "high-tech" industries such as

those found in central and southern Florida (i.e., Harris, McDonnell

Douglas, IBM) . In summary, there is a great variance in economic size and

level of affluence among the 13 counties under study (a more detailed

analysis can be found in the individual county reports in Appendix G).

6.3 The Export Base of the Region

When analyzing a regional economy, it is important to identify the

principal reason(s) for any economic growth or decline. The export base

theory is widely used to analyze this issue. In effect, there are two

kinds of industries in a region or county. Those that depend on demand

outside the county are what are called "export industries". These export

industries either sell products outside the county or attract individuals

into the region who in turn inject money into the local economy. Good

examples in northwest Florida are exports of paper products and tourism.

In these cases, money is injected into the local economy and undergoes a

multiplier effect as workers spend money on "local industries;" workers in

these local industries in turn spend money on other local industries.

Examples of local industries are usually found in the retail and service

sectors. The multiplier effect is limited since there is leakage from the

spending process because goods need to be imported. Most northwest Florida

counties must import consumer durables such as autos, TV sets and washing

machines.

6-4
In the county reports, export industries were identified by using what is

called a "location quotient." This technique is simple and is usually

fairly accurate in identifying the critical export industries in an area

which are the driving force behind a region's growth. The degree to which

the marine ecosystem interacts with export industries will be important in

this analysis. For example, if an export industry, such as a pulp and

paper plant, discharges toxic chemicals into estuaries, this might have an

adverse impact on estuarine-dependent fisheries which form the basis for

commercial and recreational fishing. Placing restrictions on the pulp and

paper mills may raise prices, thereby making the company less competitive.

This could in turn have negative multiplier effect on the region.

Therefore, the identification of the export base through location quotients

is important for this socioeconomic profile.

The location quotient is defined as follows:

Location quotient (LC) = % of Wages in industry in the region

% of Wages in industry in the U.S.

In computing the percent of wages, the base is either total wages or

personal income in the region and in the United States. For example,

assume the paper industry is 10% of personal income in a particular county,

but only 1% at the national U.S. level. The LC would be 10, indicating an

unusually high concentration of paper production in the region. The

inference is that most, if not all, of the paper produced in the region is

for export. Thus, an export industry has been identified. The simple

formula for identifying how much paper is exported from the region is as

follows:

% Exported = (1 minus 1/LQ)

In our example, the percent exported would be (1 -1/10) or 90%. The

balance is presumed to be consumed locally. In reality, LQ's higher than

2 are good indicators that possibly all the product is exported, especially

if it is an intermediate product such as phosphoric acid or ammonia which

is used by manufacturers outside the region. Thus, a LQ can be considered

as an indicator, rather than a precise calculation of how much is exported

and how much is consumed locally. This technique was used for all of the

13 counties in northwest Florida. The results are shown in Table 6-2,

along with the total wages generated by that industry in 1993.

The far western part of the study area, from Escambia County to Franklin

County, has been compared with a stool with two thick legs - the military

and tourism - and one thin one which is industrial. It has been said that

this area depends on beaches and bases. This is only partly true (Table 6-

2). Escambia County is dominated by the military (i.e., Pensacola Naval

Air Ease) and tourism, but also has a substantial manufacturing export base

of paper and printing. This county is also diversifying into being a

regional health center for many counties both in Florida and Alabama.
Table 6-2. A Summary of the Principal Export Industries in the Thirteen

Counties of the Northwest Florida Area.*

* Earnings in thousands of dollars

6-6

Escambia ($3,439,195) Santa Rosa ($629,336)

Health Services ($466,890)

Federal Government, Civilian (384,120)

Military (296,766)

Water Transportation (194,425)

Tourism (103,456)

Paper & Allied Products (80,966)

Printing & Publishing (23,871) f

Chemicals & allied products ($40,056)

Military (65,927)

Federal Civilian (25,245)

Textiles (15,060)

Food & Kindred (5,064)

Tourism (19,208)

Bedroom Community (488,438)/1,564,823

Okaloosa ($1,964,348) Walton ($203,184)

Military/Federal Government ($704,335)

Tourism (129,840)

Engineering Services (119,802)

Transportation Equipment (36,008)

Real Estate (28,144)

General Building (23,558)

Electrical Machinery (16,695)

Construction ($15,691)

Food Stores/Tourism (8,234)

Hotels/Tourism (22,014)

Eating & Drinking Places!

Tourism (9,097)

Real Estate (4,400)

lpparel (1,896)

Lumber/Wood (1,259)

Bay ($1,564,044) Gulf ($109,891)

Military ($170,262)

Federal Employees (137,088)

Construction (103,232)

Retail (220,661)

Eating & Drinking Places (71,855)

Hotels & Lodging (42,606)

Real Estate (24,222)

Paper Products ($35,961)

Chemicals (5,827)

Railroad Transportation (2,717)

Fishing (388)

Forestry (200)

Franklin ($63,233) Wakulla ($80,375)

Health Services ($9,212)

Fisheries (3,329)

Building (2, 303)

Food Stores (2,806)

Eating & Drinking Places (2,330)

Lumber & Wood (1,783)

Railroad Transportation (926)

Food Stores ($2,858)

Food & Kindred (1,735)

Fisheries (1, 176)

Petroleum Products (415)

Chemicals (19,000)

Water Transportation (402)

Jefferson ($69,470) Taylor ($170,156)

State & Local Governments ($20,215)

Agricultural Services (3,867)

Utilities (3,798)

Lumber & Wood (3,607)

Apparel (1,624)

Lumber & Wood ($11,387)

Fabricated Metals (6,833)

State & Local Government (3,359)

Fisheries (573)

Paper & Allied (52,000)

tixie ($63,482) Levy ($145,228)

State & Local Governments ($21,143)

Lumber & Wood (13,239)

Fishing (1,151)

Forestry (612)

Lumber & Wood ($3,993)

Agricultural Services (3,359)

Fishing (838)

Machinery (323)

Citrus ($641,140)

Construction ($66, 524)

Retirement (315,763)/1,558,130

Printing (4,179)

Fisheries (945)

Utilities ( )
As shown, the military export industry generated nearly $297 million, or

8.7 of the $3.439 billion in wages generated in Escambia County. This

does not include the multiplier effect of this injection of money by the

federal government. As a general rule, for every dollar injected by an

export industry into a small area like a county in northwestern Florida, an

additional $.50 is generated. Thus, the military would generate nearly

$446 million ($297 times 1.5) when the multiplier is taken into account, or

7.7 of total Escambia County wages. The reader can analyze the other

counties with this illustration for the largest county in the region as

measured by population and personal income, as discussed previously.

A group of industries present in most counties in northwest Florida is

forestry, wood processing, paper production and printing. Of the 13

counties, nine have these industries as an important part of their export

base. The reason for this is the abundance of forest products in this

area. Recently, there has been less optimism about the future of northwest

Florida lumber. In Dixie County, Georgia-Pacific's Chip-N-Saw plant, which

produces lumber for the building industry, has resorted to week-long

furloughs for employees. The lumber business is extremely weak in response

to Canadian competition. Because of government subsidies, Canadian lumber

can be imported into Florida at cheaper prices than those charged for

products from the study area.

Santa Rosa County is really a "bedroom community" for Escambia County, as

nearly two-thirds of its wages are generated by those commuting to Escambia

County (Table 6-2). Okaloosa County is a high-income county and depends

more than any other county on high-wage industries such as engineering

services, transportation equipment and electrical machinery. Eglin Air

Force Base is also a great part of this county's export base. Walton

County is heavily dependent on tourism, which depends on sandy beaches as

an attractive natural resource. Bay County extends the features of Walton

County in terms of tourism, but adds Tyndall Air Force Base as an important

export industry. The tourism theme falls off for Gulf County, which is

heavily dependent on St. Joe's Paper Company or the forestry resource in

the area. Franklin County is largely a single-industry area, with most of

its export base still centered around the fisheries, especially oysters and

shrimp. Wakulla County is similar to Franklin County with commercial

fishing being an important export industry; however, Wakulla is the home of

the manufacturing of gun powder (Olin Corporation) and is an important area

for the arrival, at St. Marks, of crude oil imports from other Gulf states.

Jefferson County has only about 10 miles of coastline and limited marine

activities. Taylor County is highly dependent upon the forestry resource,

except for the presence of a state facility. Finally, Levy and Dixie

Counties continue the general theme of wood products and fisheries as the

foundation for their export base. Notice that a large tourism component to

the economic base really ends in Bay County. To the east of Bay County,

the attractive sandy beaches are minimal or nonexistent, especially from

Taylor to Citrus Counties.

6.4 The Socioeconomic Component of the Marine Ecosystem

For purposes of this analysis, industries are divided into two functional

groupings to investigate the relation between the industry and the marine

ecosystem. The first grouping is ecosystem-sensitive industries. By this,

6-7
we mean industries that have been historically, or are presently, in

conflict with the natural processes of the ecosystem. Such industries,

including the household sector, create point or nonpoint discharge of

substances that are biodegradable and/or non-biodegradable. In either

case, there are negative externalities (i.e., damage to elements of the

ecosystem such as fish or wetlands) that impact water quality, which is

central to the viability of the marine ecosystem. Thus, an ecosystemsensitive industry is defined as one that, without proper regulation, will

have a negative impact on one or more elements of the marine ecosystem.

Table 6-3 shows the ecosystem-sensitive industries for the 13 county areas

under study. These industries are not necessarily export industries as

discussed in the last section. For example, local industries, such as

stores in a shopping center, may produce nonpoint source pollution through

extensive storm runoff. But, in the main, point source polluters are

usually in manufacturing, which also tends to be part of the export base as

defined in the last section.

In Escambia County, there is a deep-water port that produces many

effluents. Also, paper and printing manufacturing have historically

discharged toxic chemicals into streams leading into bays and inlets. As

with all the other counties, this is described in some detail in the

separate county reports in Appendix G. Santa Rosa County also has

manufacturing industries - chemicals, textiles and food processing - that

contribute to diminished marine water quality. In counties that are

growing rapidly, the general building industry produces, as a byproduct of

its activities, a lot of non-porous surfaces as well as homes with septic

tanks which produce nonpoint source runoff and leaching, respectively.

Thus, we have included this "industry" in Okaloosa County along with two

manufacturing industries

In Walton County, construction of homes for retirees and corresponding

shopping areas are sources of nonpoint source water pollution. The apparel

and lumber industries also contribute point source pollution in this

county. Bay County has little manufacturing, but does have rapid growth -

construction - that is associated with nonpoint source pollution. Gulf

County is dominated by one paper company. Paper companies have come into

great conflict with the marine ecosystem, as discussed in Appendix G.

Franklin County, emerging from its sole dependence on the commercial

fishing industry, is becoming attractive for tourism and retirement;

therefore, Table 6-3 lists various development industries that have

produced high coliform or bacterial counts in Apalachicola Bay, thereby

preventing the harvest of oysters. In Wakulla County, the principal source

of pollutants has been at St. Marks, where oil is imported into Florida.

Thus, water transportation comes into conflict with the marine ecosystem.

Other manufacturing industries are not consistent with the optimal marine

environment, but do appear to be less of an ecological threat.

Jefferson County is largely rural, and depends on primary natural resources

such as crops and timber for its economic base. However, the shortness of

its Gulf coastline does not place Jefferson County in great conflict with

the marine environment. Taylor County contributes its share of pollutants

from industrial point sources, contributed primarily by manufacturing of

6-8
Table 6-3. A Summary of the Principal Ecosystem-Sensitive Industries in

the Thirteen Counties of the Northwest Florida Area.*

* Earnings in thousands of dollars

lumber and wood products. This theme can be extended to Dixie and Levy

Counties. Finally, Citrus County is just north of the Tampa area and

population growth has produced nonpoint source pollutants. This county

also contains the Crystal River electric facility, powered by atomic

energy, which is an ecosystem-sensitive facility.

Table 6-4 shows the ecosystem-insensitive industries for the coastal

counties under discussion. Some clarification is needed. If any industry

is based upon the resources of the marine ecosystem, we have designated

this industry as an ecosystem-insensitive industry since it is not usually

in conflict with the ecosystem. This may be too simplistic in that such

industries can contribute to pollution. The commercial fishing industry is

a good example. To the degree that growth is regulated, tourism is

generally not in conflict with the marine ecosystem, since tourists use

this system for recreational fishing and beach use. Also, the military,

such as Eglin Air Force Ease, is generally considered a 'clean' industry as

6-9

Escambia ($3,439,195) Santa Rosa ($629,336)

Water Transportation (194,425) chemicals & allied products ($40,056)

Paper & Allied Products (80,966) Textiles (15,060)

Printing & Publishing (23,871) Food & Kindred (5,064)

Okaloosa ($1,964,348) Walton ($203,184)

Transportation Equipment ($36,008) Construction ($15,691)

General Building (23,558) pparel (1,896)

Electrical Machinery (16,695) Lumber/Wood (1,259)

Bay ($1,564,044) Gulf ($109,891)

Construction ($103,232) Paper Products ($35,961)

chemicals (5,827)

Franklin ($63,233) Wakulla ($80,375)

Building ($2,303) Food & Kindred ($1,735)

Food Stores (2,806) Petroleum Products (415)

Eating & Drinking Places (2,330) chemicals (19,000)

Lumber & Wood (1,783) Water Transportation (402)

Railroad Transportation (926)

Jefferson ($69,470) Taylor ($170,156)

Agricultural Services ($3,867) Lumber & Wood ($11,387)

Utilities (3,798) Fabricated Metals (6,833)

Lumber & Wood (3,607) Paper & Allied (52,000)

Apparel (1,624)

Dixie ($63,482) Levy ($145,228)

Lumber & Wood ($13,239) Lumber & Wood ($3,993)

Forestry (612) Agricultural Services (3,359)

Machinery (323)

Citrus ($641,140)

Construction ($66, 524)

Printing (4,179)

Utilities (N/A)
Table 6-4. A Summary of the Principal Ecosystem-Insensitive Industries in

the Thirteen Counties of the Northwest Florida Area.*

* Earnings in millions of dollars

far as the marine ecosystem is concerned. Finally, state government is

considered ecosystem-insensitive. In many areas in northwest Florida,

prisons are being built, and they pose no threat to the marine environment.

These are the kinds of industries that are listed in Table 6-4. The reader

can review these industries and see the common theme, as discussed above,

regarding ecosystem-insensitive industries. Admittedly, the line between

the two kinds of industries is not always clear cut; however, for our

purposes, we can identify those industries that should be considered when

analyzing economic activities that come in conflict with and are not a

natural part of the marine ecosystem.

Escambia ($3,439,195) Santa Rosa ($629,336)

Federal Government ($384,120)

Military (296,766)

Health Services (466,890)

Military

Federal Civilian

Tourism

($65,927)

(25,245)

(19,208)

Tourism (103,456) Bedroom Community (488,438) /1, 564,823

Okaloosa ($1,964,348) Walton ($203,184)

Military/Federal Government ($704,335) Food Stores/Tourism ($8,234)

Tourism (129,840) Hotels/Tourism (22,014)

Engineering Services (119,802) Eating & Drinking Places/

Real Estate (28,144) Tourism (9,097)

Real Estate (4,400)

Bay ($1,564,044) Gulf ($109,891)

Military ($170,262) Railroad Transportation ($2,717)

Federal Employees (137,088) Fishing ($388)

Retail/Tourism (220, 661)

Eating & Drinking Places!

Tourism (71,855)

Hotels & Lodging/Tourism (42,606)

Real Estate (24,222)

rranklin ($63,233) Wakulla ($80,375)

Health Services ($9,212) Food Stores ($2,858)

Fisheries (3,329) Fisheries (1,176)

Jefferson ($69,470) Taylor ($170,156)

State & Local Government ($20,215) State & Local Government ($3,169)

Fisheries (573)

Dixie ($63,482) Levy ($145,228)

State & Local Governments ($21,143) Fishing ($838)

Citrus ($641,140)

Retirement ($315,763)/1,558,l30

Fisheries (945)
6.5 Spending; Annual User Value and Asset Value of Selected Elements of

the Marine Ecosystem

6.5.1 nnual Spendinq

To estimate the economic magnitude of the marine ecosystem in northwest

Florida, available secondary data, both published and unpublished, was used

to estimate annual spending by tourist and residents on the following

economic activities: (1) recreational fishing, (2) recreational saltwater

beach use and (3) recreational marine boating. In addition, the dockside

value of commercial fishery landing by county was estimated. Thus, three

critical resources in the marine ecosystem are evaluated: (1) marine

fisheries, (2) saltwater beaches and (3) water areas. Finally, a critical

resource of the marine ecosystem is saltwater marsh or wetlands, which

perform many economic functions such as a support for marine fisheries

(Appendix G). Table 6-5 shows the results of our analysis for the 13-

county region.

The ex vessel or dockside landings were valued at $48.29 million dollars

for the thirteen counties. By far, Wakulla County was the largest producer

of commercial fisheries in northwest Florida, with over 25 of the total

value of this region's landings. In terms of the value of landings this

county was followed by Bay, Dixie, Okaloosa and Levy Counties. Every

county except Jefferson showed landing of commercial fisheries. Thus, the

commercial fisheries provide widespread income to practically every coastal

county in our study area.

The other user of fishery resources in the region is the recreational

angler. Recreational anglers include both residents and tourists. With

the limited data available (see individual reports), it was estimated that

saltwater anglers spent nearly $85 million dollars on travel, supplies,

bait, food, lodgings and fishing equipment while fishing off the Gulf coast

in the 13 counties in 1993. Okaloosa, Bay and Citrus Counties were about

equal in spending and together accounted for over 38 of the saltwater

angler spending in the region. In contrast to commercial fishing value,

this spending is all at the retail level. Thus, the fishery resources off

the coast of the study area produce a considerable amount of spending.

Environmental damage to these resources would result in a loss in revenue

and, of course, jobs in this area. This estimate of the recreational

fishery is believed to be conservative.

Generally, there is no direct spending on saltwater marsh, which has a key

input to many marine ecosystem elements, including the support of

estuarine-dependent fishes. However, there is no organized market for

wetlands as a support for fisheries. The owners of wetlands cannot collect

revenue from fishermen for the contribution of their land. So, wetlands

are filled in for other uses, such as hotels and marinas, which do have

economic value in an organized market. This does not mean that the marsh

has no economic value to fishermen. This concept will be discussed later,

and is mentioned here to explain why spending for saltwater marsh was not

placed in Table 6-5.

6-11
Table 6-5. A Summary of Spending and Value for Marine Resources in the

* Insignificant

**No Significant Beaches

Source: See County Economic Prof ile.

One of the largest economic activities in the western part of the study

area is tourism. Tourists usually mention Florida's beaches as a primary

attraction. Table 6-5 shows an estimate of resident and tourist spending

for beach-related goods and services (e.g., lodgings, food, travel, etc.)

Of note, total spending at retail amounted to nearly $135 million in 1993

as a very conservative estimate. Because there are no major beaches from

Wakulla County to Citrus County, spending estimates are negligible. This

area is covered with wetlands rather than beaches, so tourism has been much

slower to develop in this portion of the study area. Bay County showed the

largest spending, nearly $60 million dollars, on beach-related goods and

services, or 44 of all spending in the 13-county region. There were no

estimates for spending on recreational boating in the Gulf of Mexico.

There is, of course, an overlap between the general activity of

recreational boating and offshore saltwater recreational fishing.

6.5.2 nnua1 User Value

Practically all of the marine ecosystem resources discussed above are

common property resources. This means that there is no overt price charged

for their use, even though there are associated expenditures and values as

shown in Table 6-6. A day at the beach or a day engaged in recreational

fishing may have no overt price, but still the recreationalist derives

value from this experience. It is true that sometimes a license is

required, but this is a nominal price per day of recreation. The concept

of user value comes into play for such common property resources.

6-12

Thirteen Counties in Northwest Florida, 1993 ($Millions).

Counties Ex Vessel Recreational Saltwater Saltwater Marine

Fish Fishing Marsh Beach Boating

Landings Spending Spending

Escarnbia $2.5 $8.]. N/A $22.4 N/A

Santa Rosa 1.2 5.1 N/A 22.4 N/A

Okaloosa 6.0 10.2 N/A 21.3 N/A

Walton .1 1.5 N/A 5.6 N/A

Bay 6.7 11.0 N/A 59.6 N/A

Gulf 3.8 3.7 N/A 2.5 N/A

Franklin 12.3 6.5 N/A .7 N/A

Wakulla 2.8 5.9 N/A ** N/A

Jefferson * .9 N/A ** N/A

Taylor 1.3 7.3 N/A ** N/A

Dixie 2.1 5.2 N/A ** N/A

Levy 3.1 8.1 N/A ** N/A

Citrus 6.4 11.2 N/A ** N/A

Total $48.3 $84.6 N/A $134.5 N/A
**No Significant Beaches

Source: See County Economic Profile

Estimates of user value may be obtained by the travel cost and contingent

value methodologies (CV method) discussed in Appendix G. User value is a

flow of value from the use of a common property resource. In Table 6-6, it

is given on an annual basis for recreational fishing, beach use and

boating. For saltwater recreational fishing, the user value generated in

the 13-county region was nearly $60 million in 1993, with the largest value

of $10.4 million generated in Bay County.

Because the beach area is limited to the western part of the study area and

beach value per day are also significantly less than recreational fishing,

user value from beaches was nearly $20 million, but less than recreational

fishing. The user value of boating as a generic recreational activity was

only $5.6 million in 1993. Such values would be of significant use in

estimating losses if there were environmental damages to marine resources.

6.5.3 Asset Value

In Table 6-7, we estimated the asset value of four critical marine

resources. Since the user value is a flow over time, then the asset value

or the worth of the resources can be computed by use of the following

formula:

Asset Value of a Resource = User Value/Yr.

r where "r" is the discount rate. In effect, the above expression yields the

6-13

Table 6-6. A Summary of User Value for the Marine Resource in the Thirteen

Counties in Northwest Florida, 1993 ($Millions).

Counties User Value User Value User Value

Recreational Saltwater Marine

Fishing Beaches Boating

Escambia $5.40 $2.85 $1.l50

Santa Rosa 3.40 2.85 .390

Okaloosa 6.20 2.71 .845

Walton .92 .72 .156

Bay 10.40 7.61 .867

Gulf 2.10 3.11 .169

Franklin 3.37 .09 .131

Wakulla 3.55 ** .305

Jefferson .64 ** .040

Taylor 4.30 ** .219

Dixie 3.60 ** .138

Levy 6.00 ** .198

Citrus 8.00 ** .991

Total $57.88 $19.94 $5.6
Table 6-7. A Summary of the Asset Value for the Marine Resource in the

Thirteen Counties in Northwest Florida, 1993* ($Millions)

*Va].ues in Table 6 divided by .03 = Asset Value. See text for a discussion.

**No Significant Beaches

Source: See County Economic Prof ile.

value of an asset if the user value (i.e., profits for a private

corporation) flows into perpetuity - forever or a long period of time. The

real discount rate is about 3% so all the user values in Table 6-7 were

divided by .03 to yield their asset value. The asset value of recreational

fishing is over $1.8 billion, with the highest values in Bay and Okaloosa

Counties. The saltwater beach resource has an asset value of one-half

billion dollars even though the beaches are restricted to the western part

of they study area. Bay County has an asset value of over one-quarter of a

billion dollars. Generic recreational boating had an asset value of over

$186 million.

Finally, the saltwater marsh also has a user value to commercial and

recreational fishermen, and this value was estimated using the marginal

productivity theory discussed in Appendix G. The asset value to the

fisheries alone is over $889 million and is larger for the southeastern

part of the study area where saltwater marsh is more abundant.

These asset values would answer a critical question in environmental damage

cases, either naturally occurring or anthropogenic in origin. For example,

if 10 percent of the saltwater beach area in northwest Florida were

permanently destroyed, how much asset value was destroyed and what might

the damage be. In this example, it would be $180 million. These baseline

estimates will be of assistance in further policy problems regarding the

coastal and marine ecosystem in northwest Florida.

6-14

Counties Asset Value Asset Value Asset Value Asset Value

Recreational Saltwater Saltwater Marine

Fishing Marsh Beach Boating

Escambia $180.0 $6.9 $95.0 $38.45

Santa Rosa 113.3 34.0 95.0 13.0

Okaloosa 207.0 1.6 90.0 28.2

Walton 30.7 14.3 23.4 5.2

Bay 346.0 43.6 253.0 28.9

Gulf 70.0 14.9 10.0 5.6

Franklin 112.0 98.0 3.0 4.4

Wakulla 118.0 98.8 ** 10.2

Jefferson 21.0 20.2 ** 1.3

Taylor 143.0 115.8 ** 7.3

Dixie 120.0 108.0 ** 4.6

Levy 200.0 188.0 ** 6.6

Citrus 145.0 145.0 ** 33.1

Total $1,806 $889.1 $569.4 $186.85
6.6 Evaluation of Water Ouality

6.6.1 Escainbia County to Wakulla County

In general, rivers in this region have good water quality, with a number of

near-pristine water bodies. The major pollution sources in the area

include agricultural, silvicultural, and construction runoff.

Additionally, several low-volume waste water treatment plants, especially

in rural areas, are overloaded and/or poorly operating. Rapid coastal

economic development threatens bays and lagoon waters. Finally, some high

volume point source discharges, particularly from pulp and paper mills,

adversely affect water quality.

The Perdido Bay basin has water quality problems in two major areas:

Elevenmile Creek and Bayou Marcus Creek. Champion Paper Company discharges

into both of these creeks. Dioxin contamination is a concern, as fish

taken from the creek have had tissue levels of dioxin ranging from 8.1 to

25.7 parts-per-trillion. The EPA-recommended maximum level is 7 parts-pertrillion. Bayou Marcus Creek receives urban runoff and discharge from a

waste treatment facility. The bay is threatened and partially degraded due

to these point and nonpoint pollution sources. Perdido River has good

water quality except for the area near its mouth that is affected by poorer

quality bay waters.

The Escambia, Blackwater, and Yellow Rivers all drain into Pensacola Bay.

They generally have good water quality except for localized areas

downstream of point sources. In the Escambia River, these areas are in the

northernmost reaches, with mostly domestic discharges, and in the

southernmost reaches where there are industrial discharges. Trammel Creek,

in the Yellow River basin, shows degraded conditions due to domestic

discharge. The waste water treatment plant in that area has a history of

discharge violations, with one of the more recent resulting in a large fish

kill. Though the general water quality of Escambia, Blackwater, Yellow,

and Perdido Rivers appears to be good, all four rivers have mercury

contamination at high enough concentrations in the tissue of largemouth

bass to warrant issuing limited consumption advisories.

The Pensacola Bay basin has water quality problems associated with

urbanization around the City of Pensacola. The western bay receives the

bulk of the treated wastewater and urban runoff, while Escambia Bay had

industrial discharges. Fish kills have been a persistent problem in both

Pensacola and Escambia Bays and their tributary bayous. Although the

Choctawhatchee River generally has good water quality, it has a moderate

degree of impact from agricultural runoff (turbidity, nutrients,

pesticides, etc.). Additionally, several of the tributary systems within

the basin have problems associated with domestic or industrial discharge.

West Sandy Creek and Bruce Creek, in the western basin, receive discharge

from DeFuniak Springs waste water treatment plant and the Showell Farm

poultry processing plant, respectively. Most of these small treatments

plants have been upgraded, or are in the process of being upgraded through

Consent Orders. Choctawhatchee Bay has good water quality, but is

threatened by development of its watershed. Of particular concern are

spray field and/or urban runoff from developed areas at Ft. Walton Beach

and Destin.

6-15
St. Andrews Bay has fairly good water quality, except for an area around a

paper mill discharge. Most of the rest of the basin has good water quality

except Beatty Bayou. High concentrations of lead, mercury, DDT, chlordane,

PCB's, and polycyclic aromatic hydrocarbons have been found in sediments in

Watson Bayou. Also, Deer Point Lake, the drinking water source for Panama

City, has nutrient and aquatic weed problems. Both Ecofina Creek and Deer

Point Lake have largemouth bass contaminated with mercury, resulting in

limited consumption advisories. St. Josephs Bay has excellent water

quality except for an area around its paper mill discharge.

Apalachicola Bay has very good water quality and supports Florida's largest

commercial oyster fishery, although within this basin there are localized

problems due to nonpoint source pollution from fish houses and marinas.

The New River basin, which drains into the eastern end of Apalachicola Bay,

has very good water quality. Little of this basin's area has been

developed. At the eastern end of Apalachicola Bay is St. George Sound. In

general the sound has good water quality with exception of the area near

Carrabelle. The City discharged primary treated wastewater, but has

recently made significant upgrades in its treatment.

The St. Marks, Wakulla, and Aucilla Rivers have excellent water quality

except for a small stretch in the lower St. Marks that has oil-polluted

sediments from oil spills, historic Seminole Asphalt discharge and marina

activities.

6.6.2 Jefferson County to Levy County

The Steinhatchee River basin's major water quality problem area is the

Fenholloway River, which is seriously affected by the effluent from a large

paper mill. Although the discharge quality improved in the early 1970's,

the river still has high nutrients and color, and low DO and biological

diversity. An EPA study indicated impacts to the bay at the mouth of the

Fenholloway. The Florida Department of Environmental Protection conducted

a use attainability study of the river, and has changed its classification

from Industrial (Class V) to Recreation (Class III). The upper and lower

Suwannee River basins, which receive a considerable quantity of groundwater

spring flow, have good water quality. Other direct threats to the Suwannee

include agricultural and silviculture runoff, septic tank leachate, and

nitrates from dairy farms. Major tributaries of the Suwannee are generally

of good quality, but are threatened by local pollution sources.

6.6.3 Levy County to Citrus Count

The water bodies in this basin are typically clear, high transparency

waters which are major recreational and economic attractions. For example,

Crystal River is one of the south's most popular diving sites and a

wintertime manatee refuge. Crystal River and Kings Bay are designated as

"Outstanding Florida Waters." The rivers along the west coast of Florida

from the Waccassa River to the Anclote River are mostly small, spring-fed

streams and generally have good water quality. However, problems of high

nutrient inputs and high bacteria counts exist for many of these rivers.

High total coliform counts in the Weeki Wachee River resulted in the

closure of Rodgers Park to swimming. The only large river basin in this

stretch of the west coast, the Withlacoochee River, originates in Green

6-16
Swamp, but also has significant groundwater inflow. This basin generally

has good water quality.

The spring-fed rivers in the northern basin generally have very good water

quality. Crystal River has relatively high nutrient input and, because of

its high transparency, it is subject to dense aquatic weed growths in the

Kings Bay area. Historical sources of nutrient input are the Crystal River

waste water treatment plant discharge, spring discharge, septic tanks and

stormwater runoff. The City of Crystal River has completed construction of

a new inland spray field and has eliminated the surface discharge from

their wastewater treatment facilities. In addition, the Homosassa River

has a history of bacterial problems of unknown source, possibly residential

canals and septic tanks. Also, the Weeki Wachee has some bacteria

problems. Rodgers Park on the river has been closed since summer 1989

because of high coliform bacteria counts. The source of the bacteria is

unknown. The lower Pithlachascotee and Anclote have also had some bacteria

problems, presumably from septic tank drainage and/or urban runoff.

6.7 Literature Cited

Bell, F.W. 1989. Application of wetland valuation theory to Florida

fisheries. Florida Sea Grant College. SGR-95.

Bell, F.W. 1993. Current and projected tourist demand for saltwater

recreational fisheries in Florida. Florida Department of Natural

Resources and Florida Sea Grant College Program.

Bell, F.W. 1995. Estimation of the present and projected demand and supply

of boat ramps for Florida's coastal regions and counties. Florida Sea

Grant College Program. TP-77.

Bell, F.W. and V.R. Leeworthy. 1986. An economic analysis of the

importance of saltwater beaches in Florida. Florida Sea Grant

College. SGR-82.

Bell, F.W., P.E. Sorensen and V.R. Leeworthy. 1982. The economic impact

and valuation of saltwater recreational fisheries in Florida. Florida

Sea Grant College. SGR-47.

Bureau of Economic Research. 1995. Unpublished computer runs, 1969-93.

U.S. Department of Commerce. Washington, D.C.

Florida Department of Environmental Protection. 1994. Unpublished

commercial fishery landings. Tallahassee, Fla.

Florida Department of Natural Resources. 1980. Florida commercial marine

landings. Tallahassee, Fla.

Hall, R. 1994. Gold and green: can we have good jobs and a healthy

environment? Institute for Southern Studies Publications. Durham,

N.C.

6-17
Leeworthy, V.R., N.F. Meade, K. Drazek and D. Schruefer. 1989. A

socioeconomic profile of recreationists at public outdoor recreation

sites in coastal areas: volume 3. NOAA, U.S. Department of Commerce.

Lester, W. 1995. "Toxic Troubles" A five part series by the Associated

Press. Tallahassee Democrat. November.

Milon, J.W. and E.M. Thunberg. 1992. A regional analysis of current and

future Florida resident participation in marine recreational fishing.

Florida Department of Natural Resources and Florida Sea Grant College.

NOAP. 1991. Coastal wetlands of the United States, A special NOAA 20th

anniversary report. U.S. Department of Commerce.

University of West Florida. 1985a. Unpublished report on saltwater beach

statistics in Florida for Florida Department of Environmental

Protection.

University of West Florida. l985b. Sandy beaches of Florida.
Chapter 7 - CONCEPTUAL MODEL

by Steven Pace

Science Applications International Corp.

7.]. Introduction

This conceptual model of the northeastern Gulf of Mexico (NEGOM) study area

is an abstract, qi.ialitative representation of ecosystem components and

their interactions with one another. It is designed to help managers

understand the system and facilitate the development of testable

hypotheses. The NEGOM model identifies the major components of this

ecosystem (physical, chemical, biota and human influences) and the

processes which link the components (energy and material transfers, and

physical and biological interactions). The model also provides a framework

for information synthesis activities and identification of data gaps that

may be addressed in future research activities.

This model is built upon the Tuscaloosa Trend regional model (Barry A.

Vittor and Associates, 1985), since some of the continental shelf processes

in these adjacent areas are governed by large-scale physical and geological

processes common to both. Modification of the existing model followed the

collection of data, synthesis of information, and identification of

different subsystems in this NEGOM study area.

Previous sections of this report discussed the physical oceanographic

meteorological, chemical biological and socioeconomic elements of the

ecosystem.

While clean-cut boundaries separating elements of the NEGOM ecosystem may

not exist, for purposes of this discussion two areas, separated by a

transition zone, may be defined.

The panhandle area west of Cape San Blas characterized by estuaries

behind barrier islands, a narrow continental shelf dominated by DeSoto

Canyon, significant fresh water input from the Mississippi River and

other rivers flowing into the estuaries, and relatively large sediment

load;

Transition zone from Cape San Blas eastward to Ochlockonee Bay

characterized by low-energy barrier islands, broadening shelf, river

input from the Apalachicola River, and sediments of quartz and

feldspar sands;

Big Bend [Ochlockonee Bay to Citrus County] characterized as an open

brackish estuary with a broad continental shelf, low sediment load,

and carbonate outcrops. This is also referred to as the west Florida

shelf.

This chapter proceeds with definition of model levels, model components and

methods of representations; discussion of the three model levels; followed

by a discussion of the major areas of the model where data are missing or

inadequate.

7-1
7.2 Systen Definition

7.2.1 Model Levels

Three levels of the model were developed to accommodate the large range of

spatial and temporal scales present in this ecosystem. Modeling the

ecosystem on a large or regional scale requires information occurring over

larger spatial and temporal scales than functions which operate on small

scale or lower level ecosystem components. The Marine Ecosystem Analysis

(MESA) approach (McLaughlin et al., 1975) was used to model the NEGOM. It

consists of:

. Level 1 - a comprehensive ecosystem representation;

Level 2 - a depiction of major processes (sedimentary,

biogeochemical and biological); and

Level 3 - specific ecological applications (pelagic trophic

dynamics, benthic trophic dynamics, nekton life stages,

and marsh-estuarine interactions)

Each level "rolls upTi into the one above it, with Level 3 representing the

finest scale (resolution) of ecological interactions, Level 2 representing

intermediate-scale processes and Level 1 incorporating all of the processes

describing the entire ecosystem.

The boundary of the NEGOM ecosystem model also takes into account the

relationship between the study area and adjacent interrelated ecosystems.

The NEGOM shelf exchanges materials and energy with the atmosphere,

adjacent estuaries, terrestrial and freshwater ecosystems, adjacent upcoast

and dowricoast continental shelf ecosystems, and with the deep ocean located

seaward of the shelf break (approximately the 200 m isobath). The choice

of the 200 m isobath as the seaward boundary of the system is a matter of

convenience. On the west Florida shelf this isobath marks a location where

bottom slope changes abruptly In the panhandle region this is not

necessarily the case. Nonetheless, the 200 m isobath is used throughout

this study as a convenient definition of the shelf break. The boundaries

and exchange processes of the region are depicted in the map shown in

Figure 7-1. Specifically, the NEGOM study area includes the inshore and

slope waters of the Florida panhandle and the west Florida shelf south to

Citrus County. The area is in bounded on the west by Mobile Bay

(Tuscaloosa Trend study area) and on the south by the southern portion of

the west Florida shelf.

The subdivision of the ecosystem into homogeneous units (discretization)

was accomplished by determining where natural discontinuities in the

system's structure and functioning exist (e.g., the shelf break). Physical

factors or features, such as solar radiation, salinity, water layers,

bathymetry and geomorphology define how discretization is carried out,

since clear-cut boundaries do not often separate subsystems in the NEGOM.

Discretization involved dividing the ecosystem along major (large or steep)

habitat gradients, such as segmenting the water column on a pycnocline, if

present.

7-2
.Fusca!oosa Trend Warm Slope Eddy Panhandle EBtuarine Systems Florida Big Bend Mixing U - Possible Upwelling 4-+- Exchange 4 - Input 

ot the northeastern Gulf of Mexico showing the boundaries of the study area and ecosystem 

 regions. Major physical exchange paths and forcing mechanisms are indicated schematically.
Though input and output controlling factors were identified and modeled,

they could not be calculated, because comprehensive quantitative data to

support the movement of materials, energy or chemicals across the

boundaries do not exist. Simple mass-balance models have not been provided

to identify materials that may be imported into, accumulated or exported

from the NEGOM study area.

7.2.2 Components and Model Representation

The NEGOM conceptual model comprises four components:

inputs and outputs;

compartments;

processes (physical, chemical, geological and ecological); and

regulators (salinity, temperature, advection, turbulence [nonsteady flow having a very broad time and spatial scale] and

others)

Inputs and outputs define relationships of the subject ecosystem to

adjacent ecosystems. Compartments in the model are either biotic or

abiotic functional entities. These compartments include producers,

consumers, decomposers, particulate detritus, and organic and inorganic

material dissolved in the water column. Functional relationships among

these entities are represented by the flows connecting them, which are, in

turn, controlled by environmental regulators. Ecosystem components are

represented graphically by symbols developed for marine ecosystem modeling

by Odum (1972). The flow "language" provides a way of representing basic

structural and functional components of ecosystems so they can be related

in a modeling context (Figure 7-2) . Sources of energy and materials are

represented by circles. Biotic compartments are defined by how they feed

or fit into a trophic breakdown of the biological community. Producers

(plants) are separated from consumers (animals) . A.biotic storage

compartments, such as particulate and dissolved material in the water

column, and seafloor sediments, are represented by storage tanks. Energy

or mass flow is represented by an arrow, defining the direction of flow.

The flows represent physical, chemical, geological and ecological processes

in the model and are controlled by regulators like advection and

turbulence. The regulators are represented as unidirectional or bidirectional hollow arrows. The "grounding" symbol associated with the

regulators represents energy loss associated with the work done by the

flows.

7.3 System Level One - Comprehensive Model of the Northeastern Gulf

of Mexico Ecosystems

The simplest conceptualization of the NEGOM ecosystems includes

representations of both the physical and biogeochemical processes. As in

Figure 7-3, the left-hand side presents the dominant physical oceanographic

processes while the right-hand side shows important biogeochemical

processes.

7-4
roTwflA1 ENEOY CONtOI.1ING FACTOR INPUT I UNECNONM. CONTXOIIING FATO ,el.rUECTION.ALCOMBINED STORAGE COMPARTMENTS REPRESENTS A COMBINATION OF TWO ORMORE STORAGE COMPARTMENTS ACTING AS A SINGLE FUNCTIONAL UNIT. ENERGY OR MASS SOURCE MAY REPRESENT THE FOLLOWING ENERGY FORILS: MECHANICAL (RINETIC OR POTENTIAL) SOLAR CHEMICAL GRAVITATIONAL AS WELL AS A MASS STORAGE SUCH AS SEDIMENT PASSIVE STORAGE STORAGE OF EITHER ENERGY OR MASS. NO NEW POTENTIAL ENERGY GENERATED UY STORAGE FUNCTION ENERGY OR MASS FLOW PATH FLOW OF ANY TYPE OF ENERGY OR MASS I3ETWEEN STORAGE OK SOURCE UNITS. DIFFERENT LINES MAY REPRESENT PIFFEREN I FORMS OF ENERGY OK MASS. ENERGY LOSS ENERGY DISSIPATION (ENTROPY INCREASE) ASSOCIATED WITH FUNCTION. DIFFUSION. OK IRREVERSIBLE SACEFOECLES ALONG ENERGY FLOW PATHS. POTENTIAL GENERATING ENERGY STORAGE COMUINATION OF ENERGY STOKAGE AND LOSS WHICH INCREASES POTENTIAL ENERGY THE SYMSOL IS AN ANALOG FOR WATER STORED (AGAINST GRAVITY) IN AN ELEVATED TOWER. REGULATOR REPRESENTS REGULATION OF AN ENERGY MASS FLOW Y AN AUXILIAK CONTROL FACTOR. ENERGY LOSS SYMBOL IS USED IF THE CONTROL PROCESS DISSIPATES ENERGY OR INCREASES ENTROPY ANALOGOUS TO A VALVE. US5.EUP2T TE5PIATIOTL RESPIRATiON UNDIRECTIONAL GATE ALLOWS ENERGY OR MASS FLOW ONLY IN THE DIR

INDICATED 13Y THE ARROW () ANALOGOUS TO AELECTRONIC DIODE. UNSPECIFIED FUNCTION USED TO PROVIDE FOR COMPLEX OK POORLY FNOWFUNCTIONS WHICH MODIFY ENERGY OR MASS FLOHYSTERESIS OR THRESHOLD EFFECTS ARE 1YPICEXAIIPLES). DETAILS MAY DE INDICATED INSIDE 1

SWITCH REPRESENTS REGULATION OF AN ENERGY OR MA

FLOW IN A DISCRETE MANNER I3Y AN AUXILIARY SWITCHING FACTOR. ENERGY LOSS SYM6OL IS UIN THE SWITCH. PROCESS DISSIPATES ENERGY OR INCREASES ENTROPY ANALOGOIJS TO AN ELECTLIGHt SWI1CIL. PLANT POPULATION RIPKI:SLNTS A SELF-MAINTAINING (AUTOTROPIIIC) PRODUCER WHICH IS AITLEi TO ALTI:KNATIiLY STOKE Awl) UTILIZE SOLAK ENERGY MAYOR MAY NOT PIE PLANE1ONIC. ANIMAL POPULATION REPRESENTS A SF.L.F MAINTAINING (HETEKOIROPHIC) CONSUMER WHICH MUST O[3TAIN IrS ENERGY FROM COMPLEX ORGANIC TIOLECUIES. MAYOR MAY NOT ITE PLANKTONIC. BIOLOGICAL COMMUNITY REPRESENTS A SYSTEM OF PLANTS AND ANIMALS ACTING AS A SINGLE FUNCTIONAL COIIPARTMENT. N

Figure 7-2. Odum energy-mass language symbols used in the northeastern Gulf of 

conceptualization.
ESTUARINE A OCEANIC BOUNDARY NEAT OUTFLOWS ESTUARINE & OCEANIC BOUNDARY OUTFLOWS SALUIITY ©TO REGULATORS ®TO REGULATORS DENSITY a= f (TS) HYDIXAIA.IC PRESSURE I000NOARY SEA LEVEL) ATMOSPHERIC PRESSURE POTENTIAL ENERGY 0 REGULATORS ATMOSPHERIC EXCHANGE BOUNDARY SHEAR FORCES = WIND © = DENSITY =ADVECTION = TURBULENCE = TEMPERATURE © SALINITY - = REPRODUCTION MATURATION HEAT ENERGY (WATER COLVIAN) KINETIC (NE RO V ENERGY EXCHANGE L ESTUARINE AND OCEANIC BOUNDARY O&JTF1GWS REGULATORS EROSION. RESUSPENSION & DREDGING PARTICILATE MATERIAL (INCLUDING MARSH DEPOSITS & SHOREFACE SANDS) SEDIMENTATION LOOP PARTICUlATE MATERIAL REFRACTORY (SUBSTRATE) LOSSES AND BOUNDARY OUTFLOWS RENTRIC COB KIlN IT S BOUNDARY ®(.jOUTPLOWS GRAIN SIZE DISSOLVED MATERIAL DEPOSITION HARVES TWO ESITJARINE AND OCEANIC MIGRATION DETRITUS A EXCRETED MATER

, 

REPROOUCT

TURATION

Figure 7-3. A comprehensive conceptual representation of the northeastern Gulf of 

(modified from McLaughlin et al., 1975). eVIOLOGICAL, GEOLOGICAL, AND CHEMICAL OCEANOGRAPHY PHYSICAL OCEANOGRAPHY
7.3.1 Physical Processes

As in the conceptual model developed for the adjacent Tuscaloosa Trend

study area, physical processes in the NEGOM study area regulate many of the

biogeochemical processes. Current advection (mean transport) and

dispersion (mixing) provide the primary means by which biogeochemical

components are transported and dispersed in the ecosystem, while water

temperature and photoperiod regulate the rates of biological and

geochemical processes (Figure 7-4) . Temperature also influences advection

and turbulence through its effect on density and stratification of the

water column.

Physical processes in the NEGOM are dependent on energy exchanged across

atmospheric and oceanic boundaries. Potential and kinetic energy flowing

across the estuarine and oceanic boundaries of the study area are

associated with tidal forces, winds, and riverine inputs. All of these are

especially important for the estuaries and nearshore areas where mixing of

brackish water by tidal and wind-driven currents generate pycnoclines

(e.g., density gradients), and produce onshore-offshore, two-layer flow.

Tidal currents and discharges of brackish water from small rivers and

streams bordering the estuaries may form transient coastal fronts.

Proximity of the Mississippi River inflow provides the largest addition of

freshwater in the region, which can be entrained by the Loop Current in the

western portion of the study area. Potential energy is also introduced to

the ecosystem by way of barometric and gravitational pressure fields

(baroclinic forcing and gravity flow). The combination of local and

regional processes determines advection and turbulence, which in turn

regulate the inputs and outputs of the ecosystem as well as the materials

and energy within it

On the west Florida shelf portion of the study area, long-term circulation

patterns of advective transport are determined by ocean boundary conditions

and seasonal cross-shelf density gradients. Transient west Florida shelf

currents driven by wind-forced shelf waves also contribute to overall

advective transport, as do such episodic events as hurricanes and storms.

In the western section of the NEGOM study area, Loop Current waters in the

form of frontal eddies and filaments may intrude onto the shelf in the

DeSoto Canyon region and other areas along the shelf break.

Dispersion in the study area is dominated by tide- and wind-induced mixing

and storm events. Mixing in the upper layer of the water column is caused

by wind stress while internal waves can provide mixing forces throughout

the water column. Mixing between shelf waters and Gulf of Mexico waters

results from Loop Current and eddy interactions with the shelf, storms, and

hurricane events.

In the conceptual model of physical oceanic processes, heat energy is

transported across estuarine and oceanic boundaries by advective and

turbulent flows. Boundary conditions also exist at the air-sea interface

where solar radiation seasonally warms the ocean's surface, and sea surface

temperatures in turn warm the air, contributing to the generation of winter

storm fronts in the NEGOM. Heat energy from the atmosphere can also affect

7-7
ESTUANINE I LX TRANSPORT EROSION DREDGE SPOil, I1iARINE I DAEDGE SPOIL I LOOP AVERAGE OSURFACE FLOW. ESIUARINE ASGRE. SUSPENDED GAllON SEGMENTS FINE COURSE ,DETRITUS DREDGING /' - (I) ESIUARUAE REFRACTORY BOTTOM SEDIMENTS LOSSES (PRIMARILY COARSE) 000 BENIHIC A I LOOD4 I=JJ, BENIHIC UPTAKE COMI.RJNIIY I ESTUARY DUMPED & DISCHARGE WASTE (SHELF) SHELF DREDGE SPOIL LOOP DREDGING SHELF EROSION AND RESUSPENSION N SHELF SUSPENDED SEGMENTS (FINE S COURSE) SHELF TRANSPORT LOOP -I, REFIDACTORY LOSSESUPTAKE TO TURRIDITY REGULATORS ROSIn DEPOSITS SANDS OCEANIC BOUNDARY OUTFLOWS 0 DEPOSITION SLAtE YOLK 050 5SBEN THIC LOOP I BENTHIC COMMUNITY (INCLUDING BACTERIA) GRAIN SIZE DISSOLVED MATERIAL 0000 WATER COL

WA1ER-SUINTERFACE O = TEMPERA© = SALINITY = TOXICIT

o = TURBIDI

Figure 7-4. A conceptual representation of sedimentation processes in the region west of 

the northeastern Gulf of Mexico ecosystem. (from McLaughlin et al., 1975). DOnOR I GO9I I I p ESTUASINE -SHELF TRANSPORT LOOP PELAGIC LOOP 

PELAGIC COM LAIN I

(INCLUDINBACTERIA

GRAIN SIZE -I. jOEPOSITIONI
the structure of the water column by warming surface waters and creating a

less-dense layer over a cooler, heavier layer.

Density differences in the water column, generated by heating/cooling and

fresh water inputs, represent important regulators of flow patterns in the

NEGOM. Water in the NEGOM is transported across estuarine and oceanic

boundaries by both riverine discharge (fresh water) and incursions of the

Loop Current (saline water) . Salinity is influenced by seasonal

precipitation and evaporation patterns. Salinity and temperature determine

the density of a water mass and regulate advection and turbulent transport

of materials and energy.

The energy exchange loop shown in the conceptual model represents the

endless cycle of kinetic-to-potential-to-kinetic energy conversion,

occurring in NEGOM. Kinetic energy moves water masses around and through

the NEGOM study area by advection and turbulence, while the loop itself is

regulated by the distribution of water mass densities.

7.3.2 iogeochemical Processes

The right-hand side of the comprehensive model depicts the biological,

chemical and geological processes in the NEGOM study area (Figure 7-4)

The regulators of the processes are those previously described in Section

7.3.1. As in the Tuscaloosa Trend, the NEGOM model shows a pelagic and a

benthic habitat. The separation and unique identity of each depends on

such physical phenomena as density gradients. During mixing events, when

wind mixing produces a homogeneous water column, pelagic and benthic

functioning may be similar and the division between them poorly defined.

Both pelagic and benthic habitat types contain biological communities,

dissolved chemicals and particulate sediment load. These habitats receive

input from oceanic boundary inflow, dumping and discharging of wastes, land

runoff, estuaries and the atmosphere. Both communities utilize the

dissolved and particulate loads of the water column, which involve organic

carbon, oxygen, inorganic nutrients (nitrogen, phosphorous and silica)

toxicants (trace metals, hydrocarbons and pesticides) and trace organics.

Both habitat types exchange materials through the following processes: a sediment deposition or resuspension loop, detrital rain from the pelagic to

the benthic habitat, movement of animals (fishes, portunid crabs, shrimp)

from the water column to the bottom, and transport of living material from

one habitat to the other during the reproduction and maturation processes.

The sedimentation loop, which is routinely regulated by turbulence and

advective transport in the western section of the NEGOM study area, does

not function substantially in the Big Bend area, except when storm waves

and surge erode marshland and estuarine deposits.

Both benthic and pelagic communities in the NEGOM study area contain

primary production components, due to the availability of light for

photosynthesis and solid substrate for attachment of macrophytes.

Components of both benthic and pelagic communities are outputted' through

harvesting by man or exported to estuarine or oceanic boundary outflows and

migrations. Dissolved and particulate materials are also lost to the

7-9
system through ocean boundary exchanges or are buried by sediment accretion

within the system. Volatile materials, such as dissolved gasses and the

lighter fractions of hydrocarbons, are also lost to the system through

exchanges with the atmosphere.

7.4 ystexn Level Two - Representation of Biochemical Processes

Level 2 representations of the biological processes within the NEGOM study

area include separate models for sedimentation, chemical and ecological

cycles. The sedimentation processes at work in the NEGOM are presented for

both estuarine and shelf environments in two diagrams, while those

depicting chemical processes are divided into three major categories

(carbon-oxygen, nitrogen and a prototype toxicant) . The ecological

processes are illustrated by a generalized representation in the second

level.

7.4.1 sedimentation Processes

Dynamics of particulate material movement within the NEGOM study area are

represented in Figures 7-4 and 7-5. Within the estuarine and shelf

domains, the benthic and water column subsystems are separated by the

sediment-water interface. The representations contain four to five

sediment storages: a pair of suspended sediment and deposited sediment

storages in each of the domains and a marsh and shorefast sand deposit in

the shelf domain. Water columns in both domains receive inputs from land

runoff and rivers, dumped and discharged wastes, ocean boundary inflows and

the atmosphere. Suspended material export occurs through estuarine and

oceanic boundary outflows.

Sedimentation processes within the western half of the NEGOM, with its many

small rivers and shallow water embayments, are portrayed in Figure 7-4,

while the processes within the Big Bend estuary are depicted in Figure 7-5.

The difference between the two regions is reflected in the feedback loops,

which represent the sediment transport processes in the model. The

estuaries to the west of Cape San Bias depend on the shoreface sand

transport loop to maintain barrier islands. The Big Bend estuary does not

show substantial evidence of this component of sand transport. Instead,

its banks are composed of marsh deposits which are not exposed to

substantial littoral drift or erosion except during severe storms or

hurricanes.

Other feedback loops involve erosion and deposition of sediments under nonstorm conditions and are regulated by advection and turbulence, sediment

grain size and bottom topography. They include the dredge material

disposal loops and benthic loops in both estuarine and shelf domains, as

well as individual estuarine and shelf transport loops and the estuarineshelf transport loop. The estuarine-shelf loop linking exchange of

sediment across a common boundary is regulated by advective and turbulent

transport generated by tidal forces and local winds. Estuarine and shelf

dredge material transport loops incorporate dredging material from both the

estuaries and their entrances and disposal of this material in the water

column and on the shelf seafloor. A majority of dredged material enters

the shelf transportation loop through deposition, while turbulence and

advection may transport a small fraction off-site.

7-10
PRECIPITATION I-[1ARINE DREOGE SPOIL LOOP ,- , '_) :' ESTUARINE TRANSPORT EROSION LOOP DREDGING DREDGE SPO(L_ AVERAGE SURFACE FLOV YB/ OFT TUS ESTYJARIN REFRACTORY BOTTOM SEDIMENTS LOSSES (PRIMARILY CO NSF) 000 UPTAKE lIEN IHIC L. BEN 11KG COMMUNITY ESTUARY.nrsg flowSUlFATE I .ovBcflcohS DISflRSDII I sonGs I ADVEUSOFI £T OEPOSITION ESTUARINE SHELF TRANSPORT LOOP SHELF DREDGE SPOIL LOOP EROSION AND RESUSPENSION DREDGING SHELF SHELF SUSPENDED SEDIMENTS FINE & COURSE) SHELF fl TRANSPORT II LOOP,, CI 5- UPTAKE OCEANIC BOUNDARY OUTFLOWS TO TURBIDITY REGULATORS 40 OK POSIT ION I.HENTHIC LOOP 1 BEN THIC COMMUNITY (INCLUDING BACTERIA) DID SOLYEO MATERIAL PELAGIC LOOP -

PELAGIC COMMJNI

INCLUDINBACTERIA

WATER COLWA1ER-SU

INTERFACE o = TEMPERA

= SALINIT= TOXICIT

o = TURBIDIT

Figure 7-5. A conceptual representation of sedimentation processes in the Big Ben

northeastern Gulf of Mexico ecosystem. (from McLaughlin et al., 1975)
In the shelf and estuarine domains, both pelagic and benthic loops absorb

and release particulate organic and inorganic materials. Most suspended

particulate matter is transported to the shelf seafloor in the shelf

transport loop or to estuaries through the estuarine-sheif loop or across

oceanic boundaries in the pelagic loop. The pelagic loop contains

shoreface sand and marsh deposit transport loops adjacent to the barrier

island estuaries. The shoreface sand and marsh deposit loop is most active

during storm conditions, when barrier island dunes can be eroded and the

seafloor sediments of protected estuaries are resuspended and advected into

shelf waters. The shoreface and marsh transport loop is regulated by

littoral drift and turbulence driven by wave energy and storm surge.

7.4.2 Chemical Processes

Representations of chemical processes within the NEGOM study area include a

well-mixed water column, and a two-layer water column with a pycnocline

separating the warmer, less-dense upper layer from the cooler, denser lower

layer. Within the estuaries, water column structure is also influenced by

freshwater input from rivers. During the spring and summer wet seasons,

stratified conditions predominate in the estuaries west of Cape San Blas.

During the drier seasons the water column is well mixed in the estuaries,

simplifying the model to a single layer. In the shelf domain solar warming

creates density differences in the water column by heating well-mixed

surface waters, effectively isolating the cooler, denser waters and their

retinue of chemical constituents from exchange with the atmosphere. Solar

heating and strong theroclines are of perhaps even greater importance in

estuaries with respect to biological function. Even in shallow area,

diffusion of oxygen through the thermocline may not be rapid enough to

prevent near bottom hypoxia.

7.4.3 Carbon-Oxygen Cyclinq

The three storage compartments present in both single-layer and two-layer

models of carbon-oxygen cycling are organic carbon, oxidizable inorganic

material and dissolved oxygen (Figures 7-6 and 7-7). In both representations, dissolved oxygen is replenished from the atmosphere-water

interface by wind mixing, by photosynthesis in either the phytoplankton or

benthic epiflora, and by inputs across ocean boundaries.

Throughout the water column, dissolved oxygen is taken up during both

biological respiration and organic and inorganic oxidation, while organic

carbon resulting from excretion, egestion and death can, depending on size,

fall to the bottom and be recycled there; be recycled in the water column

and fall through the pycnocline; or be transported across oceanic

boundaries. In the shelf domain, net flux of organic carbon is downward

across the pycnocline to the detritus-based benthic food web. The presence

of a strong pycnocline, conthined with slow advection and much reduced

vertical and horizontal mixing (dispersion), can adversely affect dissolved

oxygen concentrations in the lower water column. Organic material may

"rain from the pelagic community, especially in embayments, in such

quantity that the benthic community, which is stimulated to metabolize the

detrital food source, depletes the dissolved oxygen levels to hypoxic

conditions. Hypoxia at the water-seafloor interface would create anaerobic

conditions in the sediments, which are not conducive to the survival of

7-12
BOUNOARY INFLOWS ATMOS. PHERIC INPUTS DUMPED & DIG. CHARGED WASTES LAND RUNOFF ESTUHIRNE INFLOW ORGANIC CARD ORREFRACTORY LOSSES & BOUNDARY OUTFLOWS DETRITUS & EXCRETED ORGANIC CARBON BIOLOGICAl 0 OEMRNO PELAGIC COMMUNITY DENTHIC COMMUNITY ATMOSPHERIC EXCHANGEEXPIRED CO. .\ ESTUARINB BOUNDARY INFLOW BOUNDARY. OUT © =ADVECTION © TURBULENCE ® TEMPERATURE =WINDENERGYOXIDIZED 000MIICN OXIDIZABLE IRORSANICS CHEMICAL 0 DEMANDBOUNDARY OUTFLOWS / DISSOLVED 0, PHOTOSYNTHETIC 0, PITODUCT ION DI

Figure 7-6. A conceptual representation of carbon-oxygen cycling for well-mixed water co

the northeastern Gulf of Mexico ecosystem (from McLaughlin et al., 1975).
OSICIZED INORGANICS ESTUARINE OCEANIC BOUNDARY OUTFLOWSf VERTICAL I TRANSPORT I OF OXIDIZABLE INORGAN IC S ONDIZA&E WORGABACS (UPPER WATER COLUMN) OIBOIZABIE INORGANIC S (LOWER WATER COLUMN) S ORGANIC CARBON UPPER WATER COLUMN) t VERTICAL I TRANSPORT I OR PARTICULATE CARSON AND DETRITUS CHEMICAL 0. DE MANSDETRITUS A EXCRETED ORGANIC CARBON OCEANIC BOUNDARy PLANATONIC CO. OUTFLOWS UPTAKE CHEMICAL 0, OEM AND REFRACTORY LOSSES & 00050MW OUTFLOWS BIOLOGICAL 0 DEMANd OCEANIC BOUNDARY OUTFLOWS PELAGIC COMMUNITY (INCLUDING BRA / S.) I DISSOLVED 0 J (LOWER WATEIA COLUMNI ESTUARINE A OCEANIC BOUNDARY OUT FALL S ATMOSPHERIC EXCHANGE ..3./ '._J I DISSOLSEDO I (UPPER WATE1A 0 COLUMNS ORGANIC ORGANIC CARBON CARBON (LOWER UPTAKE RENTHIC COMMUNITY WATER COLUMN (INCLUDING A SUBSTBATE) DUCTEXIRI V 00 .F1ESPIAEO CO. I PHOTOSYNTHETIC 0, PRODUCTION VERTICAL TRANSPORT OF DISSOLVED 0, ESTTJARINE BOUNDARY INFLOW OCEANIC BOUNDARY INFLOWS LOWER WATER COLUMN AND SUST

RESPIRED CO.UI'I'ER WATER COLUMN F'YCNOCUNE = ADVECTION © = TURBULENCE © = TEMPERATURE = WIND ENERGY PIPOT

Figure 7-7. A conceptual representation of carbon-oxygen cycling for stratified water co

the northeastern Gulf of Mexico ecosystem (from McLaughlin et al., 1975). DETRITUS £ EXCRETED ORGANIC CARBON BIOLOGICAL 0, DEMAND
aerobes (virtually all benthic macrofauna and epifauna) . Note, however,

that many benthic animals have mechanisms (siphons, etc.) to obtain oxygen

above a thin hypoxic or anoxic layer at the sediment water interface while

some nematodes and meiofauna/microfauna are facultative anerobes. Sessile

and motile benthic fauna, with the notable exception of the blue crab, tend

to stay in the area affected and die, further increasing the detrital mass.

Anaerobic conditions would change the chemical state to a reducing

environment, releasing phosphorous from the sediments. Once aerobic

conditions returned to the lower water column, the released phosphorous

would restimulate primary production.

7.4.4 nitrogen Cyclinq

Depictions of nitrogen cycling have two storage compartments, the

particulate and dissolved nitrogen pools. These represent the processes in

the single-layer and two-layer systems of the estuarine and shelf domains,

respectively (Figures 7-8 and 7-9) . These representations do not show

ammonia, nitrite, nitrate or the dissolved organic species. Instead, both

dissolved and particulate nitrogen are exchanged between the biological

communities and the water column. Primary producers absorb dissolved

nitrogen from the water column, while detritivores filter nitrogenous

organic materials. A major source of nitrogen for benthic animals is

ingestion of microbial biomass by direct and indirect deposit feeders.

Both dissolved and particulate nitrogen are cycled back to the water column

by biological communities.

7.4.5 Toxicant Cyclinq

Two storage compartments, ambient toxicant and biomass toxicant pools, are

rendered for the single-layer and two-layer models of the estuarine and

shelf domains (Figures 7-10 and 7-11). Representations include sources,

transport mechanisms and fluxes of a typical prototype toxicant, as well as

anthropogenic system inputs. Sources of toxicants are boundary inflows,

toxic algal metabolites, atmospheric inputs, dumped and discharged wastes,

land runoff, and riverine input. The relative importance of inputs will

vary with the contaminant and environment. On the west Florida shelf,

transport of atmospheric contaminants across the air-water interface could

represent a major flux of trace metals, while in the estuarine domain the

same input would be minor except in heavily industrialized regions where

sources are close to the estuary (Pensacola Bay, for example) in comparison

to riverine input and discharged wastes.

Chemical characteristics of contaminants are important in determining

transport, fate and residence times in the ecosystem. The chemical state

of a toxicant depends on its affinity for the surface of particles as well

as the oxidation-reduction state of the medium, which determines the path

that a toxicant cycles through the system. Trace salinities (<2ppt) and pH

(from acid rivers to basic estuaries) can significantly alter solubility

and ionic states of chemicals. Those with strong sorption characteristics

will be accumulated by sediments, while dissolved forms are likely to be

transported out of the ecosystem by turbulent and advective forces. The

oxidation-reduction status of the water column and sediment also determines

the availability of toxicants, as changes in the redox potential may

7-15
OCEANIC BOUNDARY HFLOWS DUMPEOD DIS- CHARGED WASTES ATMOR- PHE N IC INPUTS LARD RUNOFF ESTUARINE INFLOW REFRACTORY LOSSES & BOUNDARY OUTFLOWS PARTICULATE NITROGEN UPTAKE DETRITUS & EXCRETED PARTICUT ATE NITROGENESTUARINE I OCEANIC ROUNDARY OUT LOWS OCEANIC BOUNDARY NP 10 WY ATMOS- PHERIC INPUTS LAND RUNOFF ESTURRINE INFLOW DUMPED & DIS- CHARGED WASTES - OCEANIC BOUNDARY INFLOWS ATMOS- PHERIC INPUTS LAND RUNOFF ESTUABINE INFLOW DUMPED £ DIS- CHARGED WASTES F'ARTICU LATE NITROGEN IN 12U IS DISSOLVED NITROGEN INCLUDES AMMONIA (NH,) NITRITE (NOj NITRATE (NO) DISSOLVO c3RGANIC FORMS OCEANIC BOUNDARY OUTFLOWS PARTICOLATE NITROGFN PARTICLUATE NITROGEN DETRITUS & EXCRETED OYCANIC CARBON FE LAG IC COMMUNITY INCLUDING TACTE Bin OCEANIC BOUNDARY OUTFLOWS ISSOLVED NITROGEN DISSOLVED - NITROGEN I EXCRETED I DISSOIYEO NITROGEN EXCRETED DISSOlVED NITROGEN PISSOLVE NITROG

IN F'U IS = ADVECTION © = TURBULENCE = TEMPERATURE Figure 7-8. A conceptual representation of nitrogen cycling for well-mixed water column 

northeastern Gulf of Mexico ecosystem. (from McLaughlin et al., 1975).
I'ARTICU LATE NITROGEN IN FU IS FYCNOCLINE DISSOLVED NITROGEN INCLUDES AMMONIA (NH5) NITRITE (NO) NITRATE (Nd) DISSOLVED oRGANIC FORMS PARTICIAATE NITROGEN (UPPER WATER COLUMN)OCEANIC BOUNDARY OUTFLOWS on I PARTICULATE NITROGEN (TOWER WATER COLUMN AlAS SUBSTRATE) REFRACTORY LOSSES & BOUNDARY OUTFLOWSDEIRIISJS & EXCRETES ORGANIC CARSON PARTICULATE NITROGEN UPTAKE PPELAGIC COMMUNITY (INCLUDING BACTERIA OCEANIC BOUNDARY OUTFLOWS ESTUARINE & OCEANIC BOUNDARY OUTFLOWS IL) 1ÔISSOLVEO NITROGEN JPPER WATER COLUIAl)) DISSOLVED NITROGEN (LOWER WATER COLUMN) BEN TH IC COMMUNITY (INCLUDING BACTERIA) DETRITUS £ EXCRETED PARTICULETF NITROGEN IEXCRETED I DISSOLVED NITROGEN EXCRETED DISSOLVED NITROGEN PISSOLVEP NITR

IN I7UTS = ADVECTION = TURBULENCE = TEMPERATURE UPFER WATER COLUM

LOWER WATER COLUM

& SU eISTRA

Figure 7-9. A conceptual representation of nitrogen cycling for stratified water column 

northeastern Gulf of Mexico ecosystem. (from McLaughlin et al., 1975).
EROSION ARE. SUSPENTION OCEANIC DISSOLVED NITROGEN INCLUDES AMMONIA (NH,) NITRITE (NO,) NITRATE (NO) DISSOLVED 6RGANIC FORMS LOSSES DUE TO CHEMICAL TRANSFORMATIONS (eg. PHOTOSYNTHESIS) OCEANIC BOUNDARY ATMOSPHERIC OUTFLOWS EXCHANGE AMBIENT TOSICANT CONCENTRATION DISSOLVED, SUSPENDED. OR FLOATING) LOSSES DUE TO CHEMICAL TRANSFORMATIONS (e.g., WEATHERING) TOXICANT RELEASE THROUGH EXCRETION. EGESTION & RESPIRATION DEPOSITION j DIAGENE XIS BIOLOGICAL UPTAKE voTOXICANT CONCENTRATION IN BIOUASS (REISULATOP®) SURFAE EFFECTS I TROPHIC UPTAKE MIGRATIONHARVESTING TOXICANI RELEASE THROUGH EXCRETION. EGESTTON, RESPIRATION. & BIOTURBATION 4 'N BE NT HIC COMMUNITY (INCLU DING BACTERIA MIORATION TOXICANT CONCENTRATION IN BIOMASS (REGULATOR®) UF'rER WATER COLUM

PYCNOCL

LOWER WATER COLUM

& SU STRA

Q = ADVECTION PARVESTING = TURBULENCE 0 = TEMPERATURE o = TEMPERATURE Figure 7-10. A conceptual representation of toxicant cycling for well-mixed water column 

northeastern Gulf of Mexico ecosystem (modified from McLaughlin et al., 1975

BOUNDARY OUTFLOWS 4 / REFRACTORY LOSSES A BOUNDARY OUTFLOWS AMBIENT TON IC AN T CONCENTRATION (DISSOLVED. SUSPENDED. OR FLOATING)
TOXICANT RELEASE THROUGH EXCRETION. EGESTION & RESPIRATION EROSION & RE. SUSPENTION OCEANIC BOUNDARY OIJTFLOWS DISSOLVED NITROGEN INCLUDES AMMONIA (NH1) NITRITE (NO) NITRATE (NO) DISSOLVED dAGANIC FORMS LOSSES DUE TO CHEMICAL TRANSFORMATIONS (eQ ,PHOTOSYNTHESIS) OCT AN IC BOUNDARY ATMOSPHERIC OUTFLOWS EXCHANGE AMBIENT TOSICANT CONCENTRATION DISSOLVEO. SUSPENDED. OR FLOATING) LOSSES DUE TO CHEMICAL TRANSFORMATIONS (g . WEAThERING) BIOLOGICAL UPTAKEDEPOSITION DIAG E N E S IS AMBIENT TOXICANT CONCENTRATION REFRACTORY (DISSOLVED. SUSPENDED. LOSSES OR FLOATING) & BOUNDARY OUTFLOWS PELAGIC SURFACE COMMUNITY EFFECTS - TOXICANT CONCENTRATION IN SIOMA5S (REGULATOR®) TROPHIC UPTAKE / HARVESTING MIGRATION TOXICANT RELEASE THROUGH EXCRETION. EOESTION. RESPIRATION. 6 BIOTUABATION BE NTH IC COMMUNITY (INCLUDING BACTERIA) SURFACEEfEETS MIGRATION TOXICANT CONCENTRATION IN BIOMASS (REGULATOR®( 0 = ADVECTION 'S HARVESTING ® = TURBULENCE = TEMPERATURE 0 =TEMPERATURE Figure 7-11. A conceptual representation of toxicant cycling for stratified water column 

northeastern Gulf of Mexico ecosystem (modified from McLaughlin et al., 1975
release those previously bound to particles in the water column ant

sediments. The presence or absence of plants (algae and tnacrophytes) may

have a large influence on what contaminants are found in the water column

and sediments.

Toxicants find their way into living organisms through ingestion of food

and respiration. They are returned to the water column and sediments

through the metabolic processes of excretion, egestion and death. Toxic

materials can become concentrated in consumers through food chain

biomagnification. In the two-layer model (Figure 7-11) death or egestion of

planktonic organisms make concentrated toxicants available to the benthic

community once carcasses and fecal pellets fall through the pycnocline and

are consumed by the detrital-based food web. In the single-layer model

(Figure 7-10) of toxicant cycling, benthic filter feeders in the estuaries

accumulate above ambient concentrations of toxic materials from their

planktonic food sources and through sorption of dissolved materials.

Turbulence, diagenic reactions and redox state are among the processes

determining the fate of adsorbed toxicants in the sediments. Storms may

resuspend contaminated sediments and homogenize the distribution of

toxicants throughout the water column and the sediment profile, making

previously buried toxicants available to both plankton and benthic

communities. In dynamic benthic communities, reworking of the sediments

during feeding activities may mix the upper 10-20 centimeters. Both of

these mixing mechanisms would tend to keep toxicants in surficial sediments

where advective forces may disperse them to previously uncontaminated

(pristine) areas. Toxicants are also lost from the ecosystem by transport

across oceanic boundaries and across the air-water interface. Within the

ecosystem, toxicants may degrade to non-toxic states through chemical

transformation in biologically mediated water columns and sediments.

7.4.6 Ecological Processes

The ecological conceptualizations include both a single-layer model and a

two-layer model (Figures 7-12 and 7-13) . Light, turbulence and density

stratification of the water column are critical factors in determining the

distribution of primary productivity. Fluxes across the pycnocline are

accomplished through settling of organic material; dispersal of eggs,

ichthyoplankton and meroplankton; and migration of juveniles including the

developmental migrations of meroplankters that make a habitat shift from

the water column to benthic habitats. In the following section, several

Level 3 representations of major ecological patterns are developed from the

generalized models.

7.5 $ystem Level Three - Ecological Process Representation

Detailed descriptions of trophic processes of pelagic and benthic

subsystems in the NEGOM ecosystem are discussed in Chapter 5. In both

conceptualizations, biological communities have been separated into several

entities (Figures 7-14 and 7-15) . A species may occupy several trophic

levels during its lifetime as feeding relationships change with size and

stage of development. Similarly, individuals such as members of the

benthic community may occupy different trophic compartments based on their

7-20
ocEmIc BOUNDARY INFLOWS MUON. PHERIC INPUTS LAND RUNOFF ESTUARINE INFLOW DUMPED A DIN. CHARGED WASTES ATMOSPHERIC EXCHANGEDE. CONPOSERS SOLAR ENERGY DETRITUS & EXCRETED MATERIAL ZOOPLANKTON PUTT OP LANK TON MAC ROFAU N A RESPIRATION MORTALITY HARVESTING NEKTONHARVESTING PARTICULATE MATERIAL U AC R OPH VT ES IIARVES SING II MATURATION U ORATIONSEllER SAL RESPIRATION & MORTALITY 0 =ADVECTION = TURBULENCE = TEMPERATURE O = TOXICITY © = SALINITY o = TURBIDITYA o

RESPIR

MORT

Figure 7-12. A conceptual representation of ecological processes for well-mixed water co

the northeastern Gulf of Mexico ecosystem (from McLaughlin et al., 1975).
AIOAOS PIIERIC INPUTS DUMPE S N D'S- CHAROED WASTES LAND RUNOFF ESTUARINE INFLOW OCEANIC BOUNDARY HF LOWS ESTTJ. ARINE & OCEANIC BOUNDARY IN F 10 PART DILATE MATERIAL SUSPENDED)ESTUARRIE A OCEANIC 9OUNOARY OUTFLOWS UPOSEBS SOLAR ENERGY - ZOOPLAMKT:IN PHYT0PLANK1CV 0 DETRITUS U JXCRETED MATERIALOCEANIC BOUNDARY INFLOWSRESPIRATION & MORTALITY RESPIRATION & MORTALITY PYCHOCLINE EROSION RESUSPENSION N DREDGINGPARTICULATE MATERIAL SUBSTRATE REP RACTORY LOSSES & BOIJNOARY OUTFLOWS DISSOLVED MATERIAL ATMOSPHERIC EXCHANGEMPOSEAS DISSOLVED MATERIAL SE P0 S IT ION DETRITUS A EXCRETED MATERIAL 000 GROWTH ESTS)ARINE & OCEANIC MIGRATION PLANETONIC COMMUNITY RESPIRATION A MORTALITY ESTUARINE & OCEANIC BOUNDARY OUTFLOWS PREDATION 'I RE PRODUCTION,'. 'j/TURATION ESTUARBIES OCEANIC MIGRATION I = ADVECTION = TURBULENCE TEMPERATURE = TOXICITY SALINITY 0 = TURBIDITYI DETR

IA AN

4 REM

REPO

Figure 7-13. A conceptual representation of ecological processes for stratified water co

the northeastern Gulf of Mexico ecosystem (from McLaughlin et al., 1975). HRBVESTING S 00
NUT A IE NT UPTAKE (i BACTERIA DISSVED MATERIAL ltTl PAPTI' CUEATE MATERIAL BOUNDARY EXChANGE \\.rLHYTOPLAMcT0N DEAlING GRAZING O = TEMPERATURE O = TOXICITY = SALINITY o = TURBIDITY DEATH A EXCRETION GRAZING ZOOPL AN K S ON BOUNDARY EXCHANGE MUCUS NET FEEDERS DETRIAI. FEEDING & GRAZING BOUNDARY BOUNDARY EXCHANGE EXCHANGE RE DATION PREDATORY ZOOPL ANY TON DEATH A EXCRETION HARVESTING MIGRATION S PLA NE T IV OROU S NIX I ON DEATH. EXCRETION. EGESTION & REPRODUCTION PREDATION PIlE OAT ION DOUNOVRY EG CV A ND E TEN XACUI,ATE FEEDING ZOOPE AK V TON EKTIVORES EGESTION & REPRODUCTION ,1 REPO

Figure 7-14. A conceptual representation of trophic processes in the pelagic subsyst

water column conditions in the northeastern Gulf of Mexico ecosystem (from 1975) MIGRATION MIGRATION HARVESTING 5 HARVESTING $
0043 DTAITAL FEEDING S OEAVI, EXCRETION. SUSPENSION SEDIMENTS ITICI'TENTAI FEFflINO p PISODISTON GROWTH PREDATION GROWTH IItIEATH. EXCRETION, SE S I ION ISUSPENSOIX PREDATION 0 AT H. E MCXCI ON SEGEST ION SUSPE S S ON REPROOIICT rECTA P1015105 'H. 00 ADVECT ION TURBULENCE TEMPERATURE 0. TOXICITY SALINITY 0TURGIDITY DEATH. EXCRETION. EGESTIOX.REXHSPENHON 

ESTUAPINE OCEANIC MIGRATION REPOR

Figure 7-15. A conceptual representation of trophic processes in the benthic subsystem o

Gulf of Mexico ecosystem (from Vittor & Associates, 1985)
feeding behavior. The conceptual representations show growth and predation

on the same path, even though they are different processes.

7.5.1 Pelagic Trophic Dynamics

The pelagic food chain is based on primary production, which occurs within

estuaries and on the shelf. Phytoplankton production is controlled

primarily by light, nutrients, density stratification, turbulence and

temperature (Figure 7-14). Nutrient (nitrogen and phosphorous)

availability within estuaries limits primary productivity, although

panhandle estuaries do not appear to be nitrogen/phosphorus limited.

Infusion of nutrients is linked with industrial, urban and agricultural

runoffs; municipal and domestic wastewater discharges; and river input to

the estuaries, which may form coastal frontal zones bounding the shelf

domain. On the shelf domain, the availability of light and nutrients

limits primary productivity. Photosynthesis decreases in proportion to

decreased light intensity. The compensation depth (bottom of the euphotic

zone) occurs where the rate of photosynthesis equals the rate of

respiration, and depends also on the type of plant being considered.

Correspondence between the upper water column and the euphotic zone depends

upon the relative positions of pycnocline depth and compensation depth.

During upwelling conditions at the shelf break of the DeSoto Canyon,

primary production is rapidly stimulated by waters rich in nutrients

reaching the photic zone. It is possible that an important, but patchy,

regulator of primary production, especially near the shelf break, is the

density of saips.

The pelagic food chain includes consumers - zooplankton which graze upon

the photosynthetic phytoplankton. Grazing zooplankters are prey for

predaceous zooplankton, planktivorous nekton and tentaculate-feeding

macroplankton (Figure 7-14). Predatory plankton include cheatognaths,

copepods, ctenophores and jellies as well as temporary plankton such as

meroplankton (benthic forms) and ichthyoplankton (nektonic forms). The

mucus net-feeding and tentaculate-feeding macroplankton are important in

detritus production and as a habitat for microbial decomposers.

7.5.2 Benthic Trophic Dynamics

The benthic food web is primarily based on microbially-mediated (or

processed) detrital sources of energy. Within the NEGOM the benthic

community includes hardbottom (rock, oyster reef, wood), beach and

nearshore sand, soft sediment and marsh habitats. All of these include

substantial dependence on assimilation and recycling of detrital energy

sources. For the purposes of this ecosystem model, "detritus" refers to

the complex of organic and inorganic particulates including attached

microorganisms (chief source of organic molecules) that enter the system.

While the exact components of the energy sources in detritus are not clear,

it is widely recognized that an influx of detritus is critical to the

maintenance of benthic production in most ecosystems. The principle source

of detrital particles is primary productivity (planktonic and shallow

benthic) . Some members of the benthic food. web (clams, oysters, tunicates,

etc.) feed directly on phytoplankton and may dominate in some estuaries.

While in others this is a small fraction of the total flow and largely

contributes to the rnaceration and breakdown of plant materials. Few

7-25
species feed directly on seagrasses but many animals graze on organisms

attached to the seagrasses. Much of the detritus which enters the NEGOM

ecosystem is either transported across the pycnocline by gravitational

settling or resuspended and advected from estuarine and shelf environments

during storms. In general, detrital sources external to the ecosystem

(land-derived) decrease in importance with increased distance from shore.

As distance offshore increases, the benthic community becomes more

dependent on production in the upper layers of the water column. On most

continental shelves, benthic standing stock and productivity, decrease with

distance offshore, presumably due to decreased food resource availability,

while species diversity often increases (albeit with fewer individuals per

species) . In the western portion of the present study area (and associated

material transport), this general cross-shelf pattern is modified by

outflow of the Mississippi River to the mid to outer shelf.

In recent years, considerable attention has been paid to deducing the

nutritional value of detritus. However, it is fair to say that "deposit

feeders satisfy their nutritional requirements from the organic fraction of

ingested sediment't (Levinton, 1989) . This organic fraction includes a

startling variety of forms, including dissolved and particulate non-living

organic matter and microorganisms. The role that benthic deposit feeders

(or detritivores) play in assimilation, breakdown and remineralization of

organic matter is crucial in assessing the recycling or stor-age of

ecosystem energy as well as contaminants. Deposit feeding activities (from

microheterotrophic exudates to megafaunal irrigation) have profound

consequences on physical and chemical properties of sediments, which in

turn affect resuspension and transport of sediments and organic

particulates. The nature and rate of supply of organic material to benthic

environments and the density and metabolic efficiency of benthic deposit

feeders are significant variables in determining trophic dynamics.

The detrital food web has two distinct loops, one external (sedimentation

and advection of detritus) and one internal (recycled detritus) . The

external loop can develop complex coupling of trophic relationships between

the pelagic trophic system and the benthic trophic system. The nature and

specific dynamics of this coupling in the NEGOM are poorly understood. The

internal loop can be described in general terms common to most shallow

estuarine and shelf ecosystems (Figure 7-15)

Detrital particles are generally a complex combination of living and nonliving organic matter and mineral components. They contain large numbers

of microorganisms (bacteria, fungi, rnicroheterotrophs) that can constitute

a complete trophic cycle in themselves. Microorganisms decompose and

remineralize organic matter and sorb dissolved organic matter, and exchange

exudates and metabolic products freely. Large microheterotrophs ingest

bacteria and fungi and are, in turn, ingested by larger meiofauna and

macrofauna. In simple terms, microheterotrophs reside on detritus

particles, meiofauna reside between particles, and macrofauna move the

particles out of their way.

The particulates with their associated communities may be collected from

the near-bottom water column by attached suspension feeders or ingested by

surface and subsurface deposit feeders. As the eggs and larvae of

macroinvertebrates grow, their functional role may change from meiofaunal

7-26
to macrofaunal and from highly prized food source to detritivore to

predator. Benthic macroinvertebrates are preyed upon by infaunal and

epifaunal invertebrates, nekton and demersal fish. The larger epifauna,

fish and nekton are in turn preyed upon by top carnivores or harvested.

7.5.3 Nekton Life Cycles

Types of nekton life cycles depicted for the NEGOM study area are based on

their dependence on the estuary environment. Taxa which spend their entire

life cycle in the marsh-estuary environment are classified as estuarine,

while estuarine-dependent species spend at least part of their early life

cycle in the estuary. Estuarine-related taxa are sometimes present, but

estuarine-independent are exclusive to shelf waters. The estuarine life

cycle is depicted on the left-hand side of Figure 7-16, while the remainder

shows the estuarine-dependent type of life cycle. Figure 7-17 shows both

the estuarine-related and estuaririe-independent nekton life cycles.

Early larval stages of estuarine and estuarine-dependent species are both

dependent on the marsh-estuary habitats. The post-larvae of estuarine

species drift and swim to the marshes, where they are nurtured through

their early life stages (Figure 7-16). The amount of habitat available to

the post-larvae depends on the salinity and temperature of the water and

the taxa's response to these regulators. The post-larvae and juveniles of

menhaden, shrimp, seatrout and drums are estuarine-dependent species, which

spawn on the shelf and advect into the estuarine environment as larval

stages. These species depend on wind-driven and tidal currents to disperse

and transport early larval stages from the shelf into the estuaries along

the NEGOM study area. Providing that the seasonal cohorts are advected

into the estuary, early life stages are similar to that of the estuarine

species. Early life stages are spent in the marsh habitat, gradually

migrating into the estuary and then the shelf through their phases of

development.

Neither the estuarine-related nor the estuarine-independent nekton taxa

require the support of estuaries to complete their life cycles. The

estuarine-independent taxa have no relationship with the estuaries and

spend their entire life cycle on the shelf, while the estuarine-related

species make occasional use of the estuaries to feed (Figure 7-17)

Estuarine-independent taxa include groupers, snappers, and billfish.

Bluefish and mackerel are estuarine-related species which are prone to use

the estuaries when high salinity conditions permit.

7.5.4 Marsh-Estuarine Dynamics

In the detailed representation of marsh-estuarine trophic processes, two

major links exist between the habitats. One involves the two-way transport

of dissolved and particulate materials between the marsh and estuary, while

the other depicts the migration of juvenile shellfish and finfish (Figure

7-18) . In the first, dissolved and suspended particulates are moved by

advection and turbulence associated with the tidal exchange of brackish

water. Flood tides inundate the marsh with estuarine water, suspending

detritus which becomes the food base of the linked habitats. Ebb tides

then transport suspended material from the marsh to the estuary, and may

effect net flow of detritus into the estuary. The question of net flow

7-27
BOUNDARY OUTFLOWS 0 = TURBULENCE TEMPERATURE DENSITY SALINITY 0 = TURBIDITY = REPRODUCTION MATURATION EXCRETION & DEATH HARVESTING ADULTS I ESTUARIES MATURATION EXCRETION I & DEATH HARVESTING JUVENILES ESTUARIES PREDATOR MIGRATION PREDATOR MIGRATION ESTUARY/MARSHPREDATORS PREDATORS SHELF PREDATOR I EXCRETION MIGRATION DEATH MATURATION JUVENILES "Y JUVENILES OFFSHORE I PREDATORS ESTT.IARINE HATCHINGPHOTOP ROW HARVESTING SPAWNING CUES EGOS IOPFSHOREIMIGRATION INTO £ OUT OF THE NEOOM REGIONPRE

MIGR

/PREDA

BOUNDAROUTFLOW

IDEAN

'I

Figure 7-16. A conceptual representation of the life cycles of estuarine and estuarine-d

the northeastern Gulf of Mexico ecosystem (from Vittor & Associates, 1985)
ES1UAgYIMASH = ADVECTION © = TURBULENCE = TEMPERATURE = DENSITY SALINITY = TURBIDITY = REPRODUCTION MATURATION I100ATION IN TO $ OJT OF TOE NEOFU qEOIO

$

Fi9ure 7-17. A conceptual representation of the life cycles of estuarine-related and estu

nekton in the northeastern Gulf of Mexico study area (from Vittor & Associat
= ADVECTION TURBULENCE 0 - TEMPERATURE 0 TOXICITY SAUNITY = TURBIDITY = REPRODUCTION MATURATION U ARSIA -K ST 0DM INE (SCHMIDT DISSOLVED & lUTE Mini 00LANK- ON REPRODUCTIVE REGILATOMS AT MO S. PHERIC IN PU I S DUN P EO AND OIS. ODAMOEO WASTES TERR(STRIAI. & PRESIOWATER AERIAL OOUPED AND DIS- CHARGED WASTES AEFRACTORY LOSSES & ROUSDARV OLIDLOWSRESPIRATION U MORTALITY TS DETRITUS A EDCRETEOUATERIDU IMRSII.ESTUAAINE MIGRATION PH V TO- PLANKTON SSOCIATED AURA EN TAOS AUTOMAT &IF

Figure 7-18. A conceptual representation of the important ecological features of Marsh-E

in the northeastern Gulf of Mexico study area (from McLaughlin et al., 1975)

SlUGS- PITERIC MEPR000CIT

MARSH ESTUARY
into the estuary is still being debated. The second transport mechanism

between habitats shows the movement of post-larvae and juvenile forms into

the marsh, and their subsequent migration into the estuary as subadults.

Juveniles feed on particulate material while in the nurturing environment

of the marsh, and move into the estuary as they make dietary shifts.

Among the several primary producers found in an estuary, seagrasses are an

important link in the flow of detrital-based foods between the marsh and

estuary. Seagrass beds pump oxygen into the sediments and function as

sediment traps, which collect suspended detritus advected from the marsh.

They also provide substrate for the microbial decomposition of detritus,

and the production of dissolved organic material. In addition to

contributing to the reduction of detritus advected from the marsh, and

their own productivity, seagrass beds also produce photosynthate, and

provide refugia for juvenile forms and habitat for macrofauna and fish.

7.6 Suiiunary of Major Components of the Conceptual Model

Ecosystem models are mathematical or graphical depictions (maps) of energy

sources, sinks, and (implied) trophodynamic processes of areas within

arbitrarily or geographically defined boundaries. Unpopulated conceptual

models are similar because fundamental trophodynamic processes in large

ocean areas are similar. In contrast, quantitative (i.e., populated) models

summarize and describe specific trophodynamic processes within specific

ecosystems or regions. An effective means of assessing the depth and

quality of information about a specific region involves (1) creating a

conceptual ecological model of the area of interest (in the present case,

the NEGOM), (2) gathering all reliable information available about the

area, and (3) using this information, populating the conceptual model.

Chapters 1-7 summarize the results of this approach. Major data gaps in

knowledge of the NEGOM (discussed by discipline in Chapters 2-6) clearly

show that population of the conceptual model (step 3) can not be

accomplished based on present knowledge. The following paragraphs

summarize, in a general way, what is known about the NEGOM, what kinds of

information must be acquired in order to understand it within acceptable

levels of confidence, and why the information needs to be gathered.

From shore to the continental shelf-slope boundary, geological,

sedirnentological, chemical, hydrological, physical oceanographic and

biological features of the Florida panhandle (Perdido Key to Cape San

Bias), and the Big Bend (Ochlockonee Bay to Cedar Key), are sufficiently

different to be considered core subregions of the northeastern Gulf of

Mexico. A transition zone located between Cape San Bias and Ochlockonee

Bay with fuzzy physical and ecological boundaries lies between western and

eastern core subregions. Based on limited information, it is expected that

forcing functions (sediments, chemistry, circulation patterns), and the

relative contributions of major biological players (producers, consumers,

decornposers) differ between these NEGOM core subregions, and that some of

the characteristics of the transitional zone between them may be unique to

that area.

In general terms, nutrients (C, N, P, Si) and photoperiod drive levels and

rates of primary production form the proximate or ultimate basis of food

webs. Turbidity, toxic substances and other factors secondarily influence

7-31
production. Primary nutrient inputs into the NEGOM are from rivers,

estuaries and upwelling. Nutrient contributions are also made from land

runoff, atmospheric fallout and basin-to-shelf water exchanges. Winds,

water, and biological waste product fall-out transport nutrients from their

sources to where they are used by producers (phytoplankton and benthic

plants for the most part); and water movements also transport oxygen,

producers and their corpses and by-products to areas where they are

consumed by microbes and other consumers. Sediment composition and quality

(the chief abiotic organizing determinants of benthic biological

communities) depend upon circulation patterns, water chemistry and

biogeochemical processes. Biotic characteristics (communities and species

assemblages within them) are consequences of: (1) chemical, physical and

geological-sedimentological conditions, events, and processes; and (2)

recruitment patterns, competition, space availability, and highly variable

factors that require measurement rather than conceptualization.

Water mass characteristics reflect the complex interaction of transport and

mixing as well as the source and characteristics of those waters found on

the shelf in this NEGOM study area. In the panhandle, fresher estuarine

water is provided primarily by the Mississippi River (by volume) and other

local sources such as Mobile Bay and the Apalachicola River and Bay. The

net transport of fresh water from these is part of a two-way exchange that

contributes to movement of material and organisms into and out of the area's

estuaries. The freshwater contribution also changes over time, with the

largest occurring in spring with high discharge from the Mississippi River

from South Pass, Pass a Loutre (North Pass) and Main Pass. Discharges from

other estuaries with more local drainage basins respond to local and

generally higher frequency variations in precipitation. The other key

source of shelf water results from exchange across the shelf break which, at

the head of the DeSoto Canyon, can be as close as 30-50 km from the

shoreline. Shelf break processes generally exchange consistently warmer and

more saline water with the shelf. Linkage of the slope water to the Loop

Current provides a pathway between this mid-latitude shelf and tropical

waters of the Caribbean Sea. Shelf waters result from mixing of estuarine

water and slope waters with in-place modification on the shelf by the

overlying atmosphere, particularly by heat and wind energy. Circulation

patterns on the shelf study area are affected by buoyancy (gravitational)

forces, wind stress acting on the water surface, tides and exchanges due to

slope circulation patterns, such as cyclonic and anticyclonic eddies.

In the Big Bend area, the shelf is considerably wider than on the

panhandle, hence the body of warmer, more saline slope water is further

offshore; in addition, the number and cumulative magnitude of freshwater

sources is smaller. The breadth of the slope would seem to help isolate

the mid- to inner shelf from shelf break exchange dynamics. At those times

when the Loop Current (LC) is extended northward, LC-related eddies can

affect the shelf break and result in the transport of material onto this

broad, more gently sloping shelf. An example of the role that physical

transport mechanisms can have occurs in the Big Bend area. It is known

that DeSoto Canyon is an important spawning area for many commercially

important fishes. The larvae of these fishes spend their early development

stages in the seagrass beds of the Big Bend coast. The mechanisms and

events that contribute to the transport of larvae across the wide west

Florida Shelf are not at present understood.

7-32
Many key processes affecting the shelf conditions have consistent annual

patterns. Wind stress and temperature patterns (the march of seasons) are

relatively consistent from year-to-year. The Mississippi River flow can

change interannually, however, with a large annual discharge generally

occurring in late spring (March-May) . Slope processes dependent on the

proximity of the Loop Current do not exhibit an annual pattern, given that

the eddy shedding cycle can vary from 6 to 14 months.

For this study area, little systematic, regional-scale information exists

on water mass characteristics and hydrography as it changes annually and

interannually. Clearly, information concerning the distribution of

physical oceanographic conditions relative to other governing variables,

such as the presence of soft or hard bottoms and seagrass beds, will be

fundamental in understanding the range and distribution of various species

throughout their life cycles.

To understand the presence and distribution of water mass characteristics

requires as yet unavailable concurrent documentation of hydrography and

currents. Currents reflect the dynamic processes that result in along- and

across-shelf mixing. Concurrently, hydrography reflects the results of the

dynamic mixing processes. These are interrelated and mutually dependent,

since buoyancy forces are dependent on the changing spatial distribution of

the density field (i.e. water mass distribution).

Considerable historical meteorological information is available for the

study area, however, its importance in driving circulation patterns and

modifying the underlying water column requires that it be documented

concurrently with any measurement of currents, dynamics and hydrography.

Processes controlling shelf-slope exchange are not well documented,

although recent insights to slope dynamics have helped focus on eddies as

likely features affecting the outer shelf circulation and transport

patterns.

In summary, relatively few coordinated measurements are available

concerning specific regional and subregional scale physical oceanographic

conditions and processes occurring in this northeastern Gulf of Mexico

shelf area. Although a conceptual basis exists for helping define

processes of importance, little systematic information is presently

available to allow observationally-based descriptions of ecologically

significant physical oceanographic conditions and patterns/processes.

In the NEGOM biologically significant and often linked aspects of the

geological setting for the panhandle and Big Bend regions include:

Bottom type, composition and coverage

Location and types of estuaries

Sediment dynamics

Bathymetry

7-33
A detailed description of bottom sediments is not possible based on

presently available results of field sampling. However, based on spatially

nonuniform sampling, coarse-scale generalizations are possible. The study

area is composed of two major geologic regions each having a certain degree

of internal consistency. They are the Florida panhandle and the Big Bend

areas as shown in Figure 7-1. The separation or transition between these

is in the general vicinity of Ochlockonee Bay. To the south or east is the

more sediment starved carbonate region. To the west is the more

terrigenous sediment rich region.

The panhandle coast consists of an almost continuous series of barrier

islands forming relatively shallow estuaries which are receiving waters for

local watersheds and the associated load of relatively fine grain material.

In contrast, the Big Bend coast is generally marshy with small quantities

of sediment being provided by smaller streams draining the adjacent

carbonate platform. The exception to this is the Suwannee River which

transits to the Gulf coast from the Okefenokee Swamp in Georgia.

On the shelf, in water depths of less than 60-80 meters, bottom sediments

reflect the availability and type of coastal sediments. In the more gently

sloping Big Bend area, sediments are generally characterized as being an

intermittent veneer overlying an irregular carbonate platform. In the

panhandle, shelf sediments reflect a mixture with components coming from

relic, largely quartz sands, more recent fine terrigenous and organic

sediments mixed with shell fragments.

With a more limited sediment supply, a broader, shallower shelf and thin

sediment layers on the shelf, sediment dynamics are less of a factor

affecting the ecosystem than in the panhandle where riverine and estuarine

sources continue to discharge generally fine textured sediments to the

estuaries, with some transiting out of the estuaries to the shelf. On the

basis of occasional or anecdotal information, the presence of the

relatively large Mississippi River outflow onto the Mississippi and Alabama

shelves has been suggested as a possible explanation for nepheloid layers

that are at least occasionally vertically extensive. These could inhibit

the depth to which biologically important light can penetrate the water

column.

Types of geological information which would enhance populating an ecosystem

model for the present study area include:

The depth at which combined waves and currents can expect to move or

resuspend the actual sediment population. This information can be

related to the intensity and track of storm events that might disrupt

bottom communities in the study area.

Finer scale resolution of the sediment thickness, composition and

texture throughout the study area. Given the size of region, this

information may be better established in conjunction with sampling

schemes needed to characterize the biologically significant benthic

and epibenthic communities.

7-34
Shelf water chemistry is a cumulative reflection of (1) the material being

contributed to the shelf via rivers and estuaries and exported from the

shelf over the shelf break or to adjacent shelf areas, (2) transport and

mixing (dilution) of these materials by the shelf circulation patterns, and

(3)chemical reactions and modifications with time and in reaction with

other material on the shelf. This framework defines information needed if

shelf chemistry is to be understood.

Material being contributed to the shelf should be well documented as to

source, quantity and timing. Since estuaries are the primary pathway for

non-ambient materials reaching the shelf, the location, quantity and type

of material coming from the estuaries should be documented. As discussed

in Chapter 4 of this document, a modest sampling program has or presently

exists for some the estuaries in the panhandle. As this region becomes

more developed and industrialized (see Chapter 6), the resulting type and

quantities of material may change. Consequently, documentation of

estuarine contributions should be maintained and adjusted to changing

patterns of discharge.

Relative to an ecosystem model, the availability of nutrients is a key

factor. The distribution of nutrient materials is governed by biochemical

processes, and transport and mixing identified in the discussion of

physical processes. If shelf water masses, and mixing and transport

processes are documented and understood, it remains to understand the

utilization and contributions of nutrients coming from geological and

biological conditions on the shelf. Practically, this calls for

documenting local nutrient levels in conjunction with water column and

bottom/sub-bottom biological sampling.

Dissolved oxygen (Do) concentrations are basic to chemical and ecological

conditions in the study area. There have been some suggestions that low DO

levels may occur within or immediately adjacent to the present study area.

However, the durability, vertical and horizontal locations and factors

contributing to hypoxia have not been well documented. Limited and

sometimes anecdotal information on low dissolved oxygen levels is primarily

from the Florida panhandle, with little information from the Big Bend area.

Since oxygen utilization by sediments and organisms is a continuing

processes, oxygen replenishment is largely dependent on vertical and

horizontal mixing processes and primary production which are highly

variable at least on a seasonal basis. Again, knowledge of both mixing and

transport processes along with patterns of primary production are basic to

an understanding of this key chemical variable. Documenting the

distribution and pattern of DO levels should be an integral part of any

biological, physical, geological or chemical sampling conducted on the

shelf.

Conceptually, the condition of an ecosystem at any given time reflects the

cumulative influence of conditions prior to the time of sampling. The

response or recovery time of the system determines the degree of dependence

on prior conditions. Knowledge of water mass characteristics and mixing

and transport processes, sources and sinks of constituents, and important

forcing functions, such as light penetration for primary production, should

provide a basis for estimating the range and expected chemical conditions

that might occur at various locations in the study area.

7-35
Clearly, understanding the water chemistry in the region is intimately

linked to understanding material sources and their movement, and biological

and sediment utilization of these materials. These components are not well

understood or well documented in the study area.

Species and trophic guilds comprising biological assemblages are

consequences of the physical, chemical and geological attributes of the

communities which they partially reflect and define. Communities are

biological units that, by their existence, provide information about many

of the abiotic features of regions or ecosystems, and can be used partially

to characterize, compare, or discriminate between them. As discussed in

Chapter 5 of this report, recent detailed knowledge of the structure,

density, diversity and distribution of pelagic and benthic communities is

relatively scanty in most estuarine-coastal areas of the NEGOM and, for all

practical purposes, this information is not available for shelf areas. In

order to gain the kind and depth of knowledge needed to understand the

biology and trophodynamic structure of the NEGOM, coordinated,

multidisciplinary studies of keystone sites within the region should be

conducted.

Nutrient loads imported into estuaries and the fraction exported onto the

shelf should be documented. Phytoplankton, salt marshes, benthic algae

(including diatoms), microbes, and submerged aquatic vegetation capture and

release nutrients in estuaries. This seasonal import-export variation

should be determined. Nutrients in shelf waters are transported downstream

or, through mixing processes, become available for assimilation in benthic

food webs. Thus, currents and mixing patterns should be documented at the

same time and locations as nutrient sampling. In order to determine

background concentrations and assimilation rates of nutrients,

phytoplankton samples (or chlorophyll surrogates) should also be collected

with nutrient and water mass data, again on a seasonal (winter-summer)

basis. The simultaneous collections of organisms which, at increasingly

higher trophic levels participate in water column energy exchanges should

include zooplankton and larger pelagic organisms, including crustaceans,

cephalopods and fishes.

The structure of benthic communities depends upon substrate characteristics

as well as water column processes. Thus, sediments (which are not

uniformly distributed in the NEGOM) and benthos (microbes, meiofauna,

macrofauna) should be sampled concurrently with water column variables.

The conceptual ecosystem model for the NEGOM study area is complex.

Estuaries to the west of Cape San Blas are often stratified, while those to

the east have good exchange with shelf waters and are typically well mixed.

The shelf region west of the Southwest Cape (Alligator Harbor) have

sufficient energy inputs and alluvial sources of sediment to form the

barrier islands typical of the region. By contrast, blackwater sources of

riverine input and sands of autochthonous origin are the dominant

components in the nearshore region of the Big Bend estuary and the western

Florida shelf.

Evidence supporting biological variability in the NEGOM ecosystem is

missing. Data gaps exist for distribution and abundance information along

the entire shelf region and in the estuaries east of Apalachicola Bay.

7-36
This is especially true for the Big Bend area where trends in species

richness, community standing stocks, estuarine dependence and

relationships, and benthic-pelagic coupling are not understood in the

context of either longshore or onshore-offshore variability.

Major changes in ecosystem structure in an onshore-offshore direction

typical of continental shelf regions are not known for this study area. In

continental shelf systems, sediment grain size, hydrographic variability,

tidal influences, nutrient concentrations, detrital input, community

standing stocks and benthic-pelagic trophic coupling would all be expected

to decrease with increasing water depth and distance from the shore, while

depth of euphotic zone, and importance of biological interactions would

increase with distance from shore. Classification analyses conducted on

biological community data and sediment data collected in the Southern Texas

OcS study area showed that habitat groupings were based on distance

offshore and depth (Flint and Rabalais, 1981). Little information is

available describing the nearshore and offshore biological communities in

the NEGOM study area.

7.7 Literature Cited

Flint, R.W., and N.N. Rabalais. 1981. Environmental studies of a marine

ecosystem, south Texas outer continental shelf. University of Texas

Press. Austin, Tex.

Levinton, J.S. 1989. Deposit feeding and coastal oceanography. In G.

Lopez, G. Taghon and J. Levinton, eds. Ecology of marine deposit

feeders, lecture notes on coastal and estuarine studies No. 31.

Springer-Verlag, New York, N.Y. 322 pp.

McLaughlin, D., J.A. Elder, G.T. Orlob, D.F. Kibler and D.E. Evenson.

1975. A conceptual representation of the New York Bight ecosystem.

NOAA Technical Memorandum ERL MESA-4. Boulder, Cob.

Odum, H.T. 1982. i energy circuit language for ecological and social

systems: its physical basis, pp. 140-202. B.C. Patten, ed.

Systems analysis and stimulation in ecology, Vol. II. Academic

Press, New York, N.Y.

Vittor, B.A. and Associates, Inc. 1985. Thscaloosa trend regional data

search and synthesis study, final report, Vol. I: synthesis report

Submitted to Gulf of Mexico Regional OCS Office, MNS, U.S. Dept. of

the Interior. Contract No. 14-12-0001-30048. Metairie, La.
U.S. Department of the Interior

U.S. Geological Survey

Biological Resources Division

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

responsibility includes fostering the sound

use of our lands 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 enjoyment

of live 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.