WATER POLLUTION CONTROL
OIL AND HAZARDOUS MATERIALS PROGRAM SERIES OHM 72 05 001
FATE AND EFFECT STUDIES OF
SHELL OIL SPILL-DECEMBER 1970
OFFICE OF WATER PROGRAMS
ENVIRONMENTAL PROTECTION AGENCY
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Studies and Investigations of the Fate and Effect
of the Shell Oil Spill, Platform B, Block 26,
South Timbalier Bay
(December 1, 1970-November 30, 1971)
Final Report
January 1972
Under Contract Number 68-01-0051
Prepared For:
Environmental Protection Agency
Washington, D.C.
Prepared by:
RESOURCES TECHNOLOGY CORPORATION
1275 Space Park Drive, Suite 111
Houston, Texas 77058
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402- Price$1.25
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EPA Review Notice
This report has been reviewed by the Water Quality Office, EPA, and
approved for publication. Approval does not signify that the contents
necessarily reflect the views and policies of the Environmental Protection
Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
11
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FORtfORD
Under the provisions of Sections 11 and 12 of the Federal
Water Quality Improvement Act of 1970 (PL 91-224) and Presidential
Executive Order 11548, dated July 20, 1970, the United States
Environmental Protection is charged to carry out specific functions
regarding spills of oil and hazardous materials. These functions
include contingency planning, response activities, .and prevention
and control. The Division of Oil and Hazardous Materials, Office
of Water Programs of EPA, is responsible for carrying out such
functions. In early 1970 the Division planned, developed, organized
and implemented a program which facilitated a rapid response to spills
of oil and hazardous materials throughout the United States.
Experienced and well trained oil and hazardous materials program
staff located among the ten EPA regional offices execute spill program
requirements.
This report represents a formal documentation of selected
field study activities for one major spill incident which initially
occurred offshore Louisiana on December 1, 1970 and lasted until
April 16, 1971. The report is based on data and information obtained
through three field surveys undertaken by EPA. The field studies
and activities were coordinated through the State of Louisiana's
Wild Life and Fisheries Commission and Stream Control Commission.
The purpose of these field studies was to determine the
areal extent of the spilled material, the fate of the spill, and the
effect of the material on the biota. They were:
t The Caminada Bay - Barataria Bay physical, chemical and
biological sampling conducted by EPA Region VI personnel
assisted by the State of Louisiana.
• The offshore physical, chemical and biological sampling
conducted by EPA regional personnel.
• Oceanographic and remote sensory survey by Texas
Instruments, Inc.,
• The joint physical, chemical and biological sampling
conducted by EPA and contractor (Resources Technology Corp.).
In order to supplement EPA resources in biological, chemical
and physical disciplines, several contractors located throughout the
United States were selected through a competitive elimination process,
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to assist EPA regional staff on spills of oil and hazardous materials.
Resources Technology Corporation is one of those contractors selected
to provide technical assistance to EPA during spill emergencies in
the Gulf of Mexico area.
This report prepared by the contractor describes the efforts
of the United States Environmental Protection Agency to document the
post spill conditions in the vicinity of the spill incident. There
are a total of four volumes to the complete report. Volume I is a
brief Executive Summary; Volume II is a summary report of the entire
effort; Volume III is data compilation of all sources, and Volume IV
is detailed data compiled for use in the comparative background
analysis. Because of the large amount of data, it was decided to
print Volume II only. Copies of Volumes I, III, and IV are available
for review in the Surveillance and Analysis Division, EPA Region VI,
1600 Patterson Street, Dallas, Texas.
H. D. Van Cleave
Division of Oil and Hazardous Materials
Office of Water Programs
Environmental Protection Agency
Washington, D. C. 20460
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ACKNOWLEDGMENTS
RESOURCES TECHNOLOGY CORPORATION gratefully acknowledges
the hard work and dedication of the many individuals who contributed
to the study program and to the writing and preparation of this re-
port. Particular appreciation is extended to Mr. Emory V. Dedman,
Vice President, RESOURCES TECHNOLOGY CORPORATION, who served as the
principal editor.
Dr. William George Blanton, Texas Wesleyan College, and
Mr. Michael C. Robinson, Tarrant County Junior College; both affil-
iated with the RESOURCES TECHNOLOGY CORPORATION Fort Worth Operations,
were instrumental to the success of this study and prime contributors
to the data contained in this report.
Invaluable direction, guidance and assistance was afforded
by staff members of the many federal, state and local agencies and
industrial concerns, who, because of their numbers, cannot all be
acknowledged here. However, among those to whom RESOURCES TECHNOLOGY
CORPORATION is especially indebted are Messrs. Russell H. Wyer and
H. D. Van Cleave, of the Division of Oil and Hazardous Materials, and
J. Thornhill and R. Forrest of the Environmental Protection Agency's
Region VI Office, whose administrative direction and technical guid-
ance contributed greatly to the success of this program. Mr. E. H.
Douglas of the Environmental Protection Agency in Baton Rouge, Louisi-
ana provided much valuable technical assistance and aided inmeasurably
in effecting coordination and information exchanges with contributing
agencies. The earlier study efforts and information provided by the
Environmental Protection Agency, Ada, Oklahoma, served as valuable
basis for study data and planning of the program. Analyses of many
of the biological and chemical samples were accomplished and reported,
and assistance provided in analytical techniques, by the Environmental
Protection Agency Laboratories of Edison, New Jersey, Cincinnati, Ohio;
and Baton Rouge, Louisiana. The efficiency with which efforts were
coordinated, the expediency of support provided, and the cooperative
spirit of individuals of these geographically dispersed organizations
was a tribute to the Laboratories and the Environmental Protection
Agency.
Finally, grateful acknowledgment is made of the many con-
tributions of the other participating staff members of RESOURCES TECH-
NOLOGY CORPORATION who worked many long, hard and dedicated hours to
the preparation and publication of this report.
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Table of Contents
1.0
2.0
Section
2.1
2.2
'2.2.1
2;2.2
2.2.3
2.2.4
2.3
2.3.1
2.3.2
2.3.2.1
2.3.2.2
2.3.3
2.3.3.1
2.3.3.2
2.3.3.3
2.3.3.4
Title
Introduction
Geological and Historical Review
of the Study Area
Geological and Historical
Nature of the Coastline
Gulf of Mexico
i
Coastal Plain and Continental Shelf
Marine Marshes
Dynamic Process
Climate
Average Conditions
Unusual Tides and Storm Surges
Lunar Tides
Storm Surges
Hydrol ogy
Rainfall and River Discharge
i
Water Temperature
Bay Salinities
Oceanic Currents Associated with the
Study Area
Biological and Zoogeographical Review
Page
1-1
2-1
2-1
2-3
2-3
2-3
2-6
2-6
2-6
2-6
2-8
2-8
2-8
2-11
2-11
2-11
2-11
2-17
3-1
3.0
of the Study Area
iii
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Table of Contents
(Continued)
Section Title Page
3.1 Description of the Northern Gulf and 3-1
Ecological Factors Affecting the Fauna
3.2 Faunal Diversity and Species Ranges 3-2
4.0 Data Analysis 4-1
4.1 Hydrocarbons in Living Organisms and 4-2
Natural Sediments
4.1.1 Distribution and Ecological Significance 4-8
of Observed Hydrocarbons
4.1.1.1 Water-Dispersable Hydrocarbons 4-8
4.1.1.2 CCI-4 Extractable Hydrocarbons 4-10
4.1.1.2 Ecological significance 4-10
4.1.2 Species Diversity 4-17
4.1.3 Distribution of Fauna in Study Area and 4-17
Possible Ecological Effects of Hydrocarbons
4.1.3.1 Results of Biological Sampling 4-17
4.1.3.2 Interpretation of Biological Catch Data 4-30
4.2 Histological Comparisons of Branchial Gill 4-40
Filaments Taken from Fishes
4.2.1 Introduction 4-40
4.2.2 Experimental Procedure 4-41
4.2.2.1 Specimen Selection 4-41
4.2.2.2 Control Specimens 4-41
i,
4.2.3 Discussion 4-48
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Table of Contents
(Continued)
Section Title
5.0 Conclusions 5-1
5.1 Fate of Spilled Oils 5-1
5.2 Effect of Spilled Oils 5-2
5.2.1 Species Diversity 5-2
5.2.2 Distribution of Fauna 5-2
5.2.3 Verification of Effects 5-6
6.0 Bibliography 6-1
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Table of Contents
Section T1tle Page
1.0 Introduction 1-1
2.0 Geologic, Climatic and Oceanographic Setting 2-1
of the Area in the Vicinity of South Timbalier
Bay
2.1 Geology--Geomorphology 2-1
2.2 Climate 2-1
2.3 Hydrology 2-2
3.0 Biological and Zoogeographical Description 3-1
of the South Timbalier Bay Area
4.0 Bases for Analysis of Data and Techniques 4-1
Employed
5.0 Conclusions 5-1
VI
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List of Figures
(Continued)
Figure Number Title
4.4 Current and Wind Data and Oil-Slick Orientation, 4-6
16 January 1971, EPA Spill Surveillance
4.5 Sediment Hydrocarbon 4-9
4.6 Distribution of Carbon Numbers in a Sample 4-11
of Shell Crude
4.7 Movement of Spilled Oil 4-12
4.8 Distribution of N-Paraffin Carbon Numbers 4-14
4.9 Distribution of N-Paraffin Carbon Numbers 4-15
from Caminada Bay near Andre Island
4.10 Distribution of N-Paraffin Carbon Numbers 4-16
4.11 Sediment Distribution of Hydrocarbons 4-16
4.12 Composite Megafaunal Diversity 4-18
4.13a Taxonomic Diversity of Invertebrates 4-19
4.13b Taxonomic Diversity of Invertebrates 4-20
4.13c Taxonomic Diversity of Invertebrates 4-21
4.14a Numerical Abundance of Invertebrates 4-22
(1/25 m2 Van Veen Grab)
4.14b Numerical Abundance of Invertebrates 4-23
(1/25 m2 Van Veen Grab)
4.14c Numerical Abundance of Invertebrates 4-24
(1/25 m2 Van Veen Grab)
4.15a Numerical Abundance of Fish (20 min. trawl) 4-25
4.15b Numerical Abundance of Fish (20 Min. trawl) 4-26
4.15c Numerical Abundance of Fish (20 min. trawl) 4-27
4.15d Numerical Abundance of Fish (20 min. trawl) 4-28
vi 1
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List of Figures
Figure Number Title
2.1 Regional Geo-oceahographic Classification, 2-2
Shorelines and Coasts, Gulf of Mexico
2.2 Sedimentary Provinces of the Gulf of Mexico 2-4
2.3 Location of Landmarks 2-5
2.4- Schematic of Climactic Zones 2-7
2.5A Hurricane Wave Height Frequency 2-9
2.5B Hurricane Wave Period Frequency 2-10
2.6 Monthly Rainfall 2-12
2.7 Daily Range of Water Temperature 2-13
2.8 Mean Monthly Temperature 2-14
2.9 Average Sea Surface Temperature for February 2-15
2.10 Average Sea Surface Temperature for August 2-16
2.11 Surface Ocean Currents, December 2-19
2.12 Surface Ocean Currents, June 2-20
2.13 Gulf Stream in Gulf of Mexico 2-21
3.1 Abundance of Oyster Reefs 3-3
3.2 Representative Habitats-Fauna! Succession 3-13
4.1 Comparison of UV Analysis and Visual Observa- 4-3
tion in Vicinity of Shell Platform B
4.2 Current and Wind Data and Oil-Slick Orientation, 4-4
13 January 1971, Texas Instruments Surveillance
4.3 Current and Wind Data and Oil-Slick Orientation, 4-5
14 January 1971, EPA Spill Surveillance
viii
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List of Figure
(Continued)
Figure Number Title Page
4.16 Composite Grab Catch Data 4-19
4.17 Composite Meiofaunal Mean Counts 4-29
4.18 Composite Megafaunal Mean Counts 4-31
4.19 Trawl Cath Data Counts Per 20 Minute Drag 4-32
4.20 Trawl Catch Data Counts P (Luidia clathrata) 4-34
4.21 Luidia. clathrata taken in 20 min. trawls 4-35
4.22 Bottom Water Salinity (ppt) Along Sample 4-36
4.23a Typical Tel cost Branchial Filament 4-43
4.23b Example of Branchial Filament which has lost 4-43
some tissue
4.24a Normal Branchial Filament from Ancyclopsetta 4-44
4.24b Branchial Filament from Ancyclopsetta. taken 4-45
near Shell Platform
4.25a Normal filaments from Micropogon. Structures 4-46
seen are identical to those in Figure 2a.
Epithelial cells (arrows), mucous cells (M),
pillar cells (P) and acidophils (A).
4.25b Note washed-out appearance due to sloughing 4-47
(arrows) and swollen filaments (S).
4.26a Normal Etropus from Aransas Bay. Note many 4-49
mucous cells (M), acidophils (A), Epithelium (E).
4.26b Shell sample Etropus. Note swelling (arrows), 4-50
fewer mucous cells (M).
4.27a Prionotus - South transect from shell platform. 4-51
Acidophils (A), mucous cells (M), Pillar cells
(P) - intact.
IX
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List of Figure
(Continued)
Figure Number Title Page
4.28a Chloroscombrus - South transect. All cells 4-53
Acidophils (A), Mucous (M), and Pillar cells
(P).
4.28b Chaetod-ipterus - South transect. All cells 4-54
intact. Acidophils (A), Mucous (M) and
Pillar (P).
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List of Tables
Table Number Title Page
3.1 Sequential Macro-organismal Faunal Successions 3-6
4.1 Test Specimens 4-42
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1.0 Introduction
On December 1, 1970, a blow out occurred on Shell Oil
Company's Platform B in Block 26, approximately seven miles off-
shore of South Timbalier Bay. Eleven of the twenty-two producing
wells were involved in the incident. While control, containment and
clean-up efforts were underway, a series of field surveys were under-
taken by the Environmental Protection Agency to determine the areal
extent of the movement of the spilled material, the fate of the crude
spilled, and the effect of the material on the environment.
The first of these was a study of the physical, chemical
and biological conditions in the Caminada-Barataria Bay areas and in
the Gulf in the area of the burning platform. Field sampling and stu-
dy was conducted from December 13 to 18, 1970, and analytical work con-
tinued through November, 1971.
A second field study was conducted by Texas Instruments,
and involved collection, correlation and analysis of oceanographic
and remotely sensed data in the area of Platform B. The field survey
was conducted from January 10 to 17, 1971; and the results were pre-
sented in the Texas Instruments final report entitled "Oceanographic
and Remote Sensing Survey in the Vicinity of the Shell Spill, Gulf of
Mexico, January 1971." This report was published bearing the date
March 25, 1971.
The third study was the joint effort of the Environmental
Protection Agency field team in Caminada and Barataria Bays and RE-
SOURCES TECHNOLOGY CORPORATION, offshore with field sampling and study
conducted from June 1 to 10, 1971. RESOURCES TECHNOLOGY CORPORATION
participation was under Basic Ordering Agreement Number 68-01-0051.
This document reports the results of the study by RESOURCES
TECHNOLOGY CORPORATION; and in addition, incorporates the results of the
first and second studies. Surveys have been conducted to compile and
evaluate background information from a multiplicity of sources to yield
meaningful bases for comparison of the information gained during the
studies from December 1970 through June 1971. These comparisons form
the bases for many of the conclusions reached in this report.
The report is so structured as to facilitate review and as-
simulation of the data contained.
Section 2.0 defines the geologic, climatic and oceanographic
parameters of the study area and the impact of these factors on life
forms under study in the environment. In Section 3.0, a Biological and
Zoogeophysical description of the study area is presented. Data and
analyses presented in this section were based on data from all three
studies. These detailed input data are presented in Appendices I and II
1-1
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as data sheets, field logs, trip reports, study plans, sampling and
analytical procedures; and background faunal data compiled for the
periods 1950 to 1960.
In Section 4.0 of this report, the results of the studies
are presented. Again, the reader need refer to the Appendices I and
II for detailed discussions of data sources and techniques employed.
The significant conclusions drawn from this study are pre-
sented in Section 5.0. Section 6.0 contains a Bibliography of these
publications from which much valuable information and data were drawn
in the conduct of this study.
1-2
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2.0 Geological and Historical Review of the Study Area
Description of the Area (General)
The study area lies in the coastal region between Ver-
million Bay on the west and the southwestern margin of the Missis-
sippi Delta. The area is characterized by marshes (660 square miles
associated with the Atchafalaya River below Morgan City and about
470 square miles below the levees associated with the Mississippi
River). Also associated with these systems are vast areas of es-
tuarine and marine waters. The coastline is characterized by numerous
bay systems, communicating through natural and artificial passes, and
with fresh water distributaries of the Atchafalaya River. The lower
Atchafalaya Basin exhibits an intricate system of lakes and channels.
The Mississippi River, being leveed almost to its mouth, permits lit-
tle drainage to the west below Baton Rouge to the Atchafalaya Basin.
2.1 Geological and Historical
The lower Mississippi River Basin consists mainly of
alluvium deposited during the final cycle of the most recent gla-
ciation. During the last glacial stage when the sea level was much
lower, the lower valley became deeply eroded and entrenched between
the valley's walls. The rise in sea level which accompanied the melt-
ing of glacial ice caused the valley to fill with gravels and coarse
sand in the lowest strata. The subsequently deposited alluvial plain
'consists primarily of sand and silt, grading to fine sand and silt
in the lower portion of the basin with extensive deposits of clay
scattered through the sand and silt deposits.
Since distributaries are usually a shorter distance from
the Gulf and the gradient is steeper, the percentage of flow in the
main channel decreased until the old channel became abandoned. Pre-
vious routes of the Mississippi River have covered most of southern
Louisiana. The Atchafalaya River is presently the only major distri-
butary of the Mississippi.River. The Atchafalaya River was formed
during very recent geologic times and was a minor stream until about
1900. Developments for navigation and flood control have aided a
natural tendency for the river to enlarge.
An extensive delta has formed at the extreme lower por-
tion of the Mississippi River. The formation of natural levees of
heavy sediments near the stream bank resulted in drainage away from
the stream to low ground near the basin walls. These natural levees
on both sides of the river resulted in the extension of a delta into
the Gulf of Mexico. The delta is geologically recent in origin. Figure
2.1 illustrates the geo-oceanographic regional classification into which
2-1
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94e
90e
86C
82C
30*
26'
22<
18°
30°
26C
22'
94s
90°
86'
82°
I8C
Figure 2.1 Regional geo-oceanographic classification, shore-
lines and coasts, Gulf of Mexico: 1, alluvial
coasts; 2, drowned limestone plateaus; 3, young
orogenic coasts; 4, biogenous (organic) devel-
opment on various coasts. Sub-sectors: 1.1,
deltaic coasts with 1.11, unentrenched simple
deltaic plain, and 1.12, entrenched and embayed
compound deltaic plain. 1.2, terraced deltaic
coastal plain; 2.1, unsimplified to little sim-
plified drowned karst; 2.2, limestone karst
with beaches; 3.1, erosional, and 3.2, depo-
sitional, orogenic coasts; 4.1, broad shelf;
4.2 shelf absent to narrow; 4.3 lesser bio-
genous development (more extensive than shown).
The two southerly Mexican 3.1 Sectors are vol-
canic salients.
(Gulf of Mexico, its origin, waters, and marine
life; U. S. Dept. of Interior; Fish and Wild-
life Service Fishery Bulletin 89).
2-2
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the study 1s fitted and Figure 2.2 shows the sedimentary provinces
of the Gulf of Mexico (Riley, 1937-38).
2.2 Nature of the Coastline
An attempt has been made to characterize the shoreline
of the north central Gulf of Mexico. In this characterization, a
more detailed discussion of the study area will be fitted. Shore-
line type, bottoms, relief, and dynamic mechanisms presently active
in shaping this coastline are considered.
2.2.1 Gulf of Mexico
The Gulf of Mexico has a surface area of approximately
600,000 square miles and is connected with the Caribbean by the
Yucatan Passage (100 miles wide and about 1,000 fathoms deep) and
with the Atlantic Ocean by the Florida Straits (less than 100 miles
wide and less than 300 fathoms deep). The distance across the Gulf
varies from 500 to 1,000 miles, depending on the route. The shoreline
from Cape Sable to Yucatan is roughly 5,000 miles long, not considering
bays and islands. That part of the Gulf Coast under consideration
(western vicinity of the Mississippi Delta) possesses the following
geomorphological features: a coastal plain, marshes, bays, river del-
tas, alluvia and a highly irregular coastline. Figure 2.3 shows the
locations of the important landmarks of the system under study.
2.2.2 Coastal Plain and Continental Shelf
The characteristic inland feature of the study area is
the gently sloping coastal plain. This plain is continuous in the
east with the South Atlantic coastal plain and extends southward to
Mexico just south of Brownsville, Texas. The plain slopes at a rate
of five feet per mile into tidal marshes just inland from secondary bays
and is characterized by numerous lakes and channels. As the coastal
plain reaches the Gulf shoreline the slope increases from 8 to 12 feet
per mile, except in the immediate vicinity of the delta.
2-3
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ro
"r" *"* """" r~\""i i i* °"''i
— ^— -^ ^^ i ' i i.i i i • i
----------.." I li.it,.
Figure 2.2 Sedimentary provinces of the Gulf of Mexico. Data
compiled from many sources (U.S.D.I.; F.W.S. 1954),
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ro
i
en
•ULF or MIXICO
SlMt 26
90
Bd-
Figure 2.3 Location of landmarks
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2.2.3 Marine Marshes
Marine marshes lie on the shoreward periphery of the
shallow bays and are formed by precipitated sediments from land
runoff and by dead lignacious materials. These marshes are char-
acteristically covered with vegetation and represent highly pro-
ductive zones of the ecosystem. The alternate exposure and in-
undation of these marshes by wind and lunar tides contribute to
the overall productivity of associated bays. Some of the mechan-
isms which may be active in the enrichment and productivity of
these marsh areas are discussed by Oppenheimer and Ward (1963).
2.2.4 Dynamic Processes
Some disagreement exists between various authorities
concerning classification of coastlines or even the need for a
classification system (Johnson, 1919; Russell, 1949; Hedgpeth,
1953). However, for the purpose of characterizing various coast-
lines for this study, some classification system is required. Be-
cause no uniform system has been accepted, the classification pre-
sented herein is arbitrarily chosen from those available as best
suited to the needs of this study. On this basis and because of
previous documentation of a particular system to the Department
of the Interior (Pequegnat, Blanton, Bottom, and Bright, 1967),
the classification system of Gilluly, Waters, and Woodford (1959)
was chosen.
According to this system the coastline of the study
area is classified as "emergent" or depositional. Dynamic pro-
cesses such as river discharge, delta formation and wave action
have lead to an extension of the coastline into the Gulf of Mexico.
2.3 Climate
2.3.1 Average Conditions
The climatic zones bordering the Gulf of Mexico are
shown in Figure 2.4. The study area lies within the temperate
mesophytic (humid) zone. This zone is characterized by rainfall
of from 40 to 80 inches per year, temperature from 5° to 32° C
(41 to 89°F) and bay salinities from 0% to 32%. The predominant
2-6
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ro
l»40-»0'
k S'C - SZ'C
a 0%. - SS%.
II ..LOW
». LOW
III. TERRIGENOUS - SOS AND CLAYS
IV DEPOSIT
V. LECITHITROPHIC PREDOMMATES
VI WFAUNAL PELECYPOO AND OYSTER REEFS
... 30'-50"
-S2-C
. I2X. - MX.
I • INTERMEDIATE
k NTERMEDIATE
III TERRIGENOUS - SANDS
IV MIXED
V MIXED
VI MKED EPI- AND MFAUNAL
OYSTER REEFS RARE
•.»%.- 55%.
II • LOW TO NTERMEMATE
k LOW TO NTERMEDIATE
III TERRIGENOUS-SAND-SILT-CLAYS
IV DEPOSIT PREOOMMATES
V. MIXED
VI. INFAUMAL AND OYSTER REEFS
k 56%.- IOOX.
IU VERY LOW
kVERY HIGH
III. TERRIGENOUS-SAND
IV. BOTH SUSPENSION AND
DEPOSIT
V. PLANKTONK
VI. RAPID TURNOVER MFMMA
IV MIXED
V MIXED
VI MFAUNAL
t 15 X. - 36X.
II .
» MEDHJM
IM MIXED TERRIGENOUS AND
CALCAREOUS SANDS AND
MUDS
PELAGIC REALM
GULF OF MEXICO
DCSCRPTION KEY
COASTAL PLAIN
2OO« CONTOUR
CLIMATE
MOISTURE (INOCS OF RAMF&LL)
TEMPERATURE TO
SALINITY (XJ
NVERTEBRATE POPULATIONS
DIVERSITY (SPECCS)
NUM6ER OF NOIVIDUALS/^
PREDOMNANT SEDHKNT
PREDOMNANT FEEDTM TYPE
OF INVERTEBRATES
V. WVERTEBRATE DEVELOPMENT TYPE
VI COMMUNTTY TYPE
> HIGH
CALCAREOUS* SANDS (SOME MUDS)
IV SUSPENSION
V PLANKTON4C
VI EP1FMINAL REEFS
SEDIMENT TYPE
Figure 2.4
Schematic of climatic zones and ecosystem components for
the coastal zone of the Gulf of Mexico (Parker and Blanton,
1970}.
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sediment in bays of this area is terrigenous (silt and clay).
The predominant feeding types found among benthos are deposit and
suspension feeders, associated with infaunal pelecypod and oyster
reef communities. The mean annual precipitation of the area
ranges from 35 to 54 inches and the temperature ranges from mean
lows of -7.2 to 6.7°C (19 to 44°F) in January to mean highs of
from 29.4 to 32.8°C (85 to 91°F) in July (FWPCA, 1969).
2.3.2 Unusual Tides and Storm Surges
2.3.2.1 Lunar Tides
In the Gulf of Mexico, tidal action is damped and the
range of the tide is reduced, averaging 2 to 3.5 feet. Tidal cur-
rents in narrow inlets affect the migration of organisms through pas-
ses. The tides in the Gulf are of two types; tropical and equatorial.
Tropical tides are those of maximum range occurring as the moon rea-
ches its maximum declination north and south. These are daily tides
with one high and one low each 24 hour period. Equatorial tides are
those of minimum range, occurring as the moon passes the equator.
These are semi-daily tides with two highs and two lows each 24 hour
period.
2.3.2.2 Storm Surges
Figures 2.5A and 2.5B depict the frequencies of occur-
rence of hurricane waves of specific significant heights and periods
at the 100 fathom curve off Gilchrist which lies to the west of the
study area on the northeastern Gulf of Mexico. The isolines give
the frequency (1 in h years); the polar co-ordinates represent wave
heights and the radial lines represent approach direction toward the
shore station.
As waves progress toward the coastline their heights
are reduced by shoaling, refraction, and friction. A particularly
detrimental feature of hurricanes is the storm tides caused by
barometric suction and wind stress on the sea surface. These result
in a "piling up" of water near the coast. Storm tides in excess of
15 feet are not uncommon and have made tragic depredations upon the
Gulf and east coast seaboards.
2-8
-------
ENE
wsw
ISE
SE
sw
SSE
ssw
Figure 2.5A
Hurricane wave height frequency (deep water offshore
station) .... 100 fathom depth contour.
Plot 1 - 1 in 1% years frequency
Plot 2 - 1 in 2 years frequency
Plot 3 - 1 in 5 years frequency
Plot 4 - 1 in 10 years frequency
Plot 5 - 1 in 20 years frequency
Plot 6 - 1 in 50 years frequency
Plot 7 - 1 in 100 years frequency
2-9
-------
ENE
wsw
ESE
SE
sw
SSE
ssw
Figure 2.5B Hurricane wave period frequency (deep water offshore
station) . . . .100 fathom depth contour
Plot 1 - 1 in 1% years frequency
Plot 2 - 1 in 2 years frequency
Plot 3 - 1 in 5 years frequency
Plot 4 - 1 in 10 years frequency
Plot 5 - 1 in 20 years frequency
Plot 6 - 1 in 50 years frequency
Plot 7 - 1 in 100 years frequency
2-10
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2.3.3 Hydrology
2.3.3.1 Rainfall and River Discharge
The Mississippi water shed covers about 1,243,600
square miles. For the period of time between 1920 and 1949,
a maximum discharge rate of 1,360,000 Cfs and a minimum
discharge of 49,200 Cfs were observed. Rainfall in the
vicinity of Barataria Bay ranged from a monthly average of
3.5 to a monthly average of 7.0, with a monthly mean of 5.18
inches. Since these data cover a time span of nearly 30 years
they should serve well as baseline values for the study area.
Relative seasonal fluctuations in monthly averages are typified
in Figure 2.6 which shows monthly rainfall in Barataria Bay for
1949.
2.3.3.2 Water Temperature
The daily range of water temperatures in lower
Barataria Bay is shown in Figure 2.7. These data were compiled
for the 1948-1949 period from 100,000 measurements. The
maximum range within one 24 hour period was about 8°C. The
range of temperature over the full seasonal cycle was from
35°C in July to 7.5°C in February or a total range of 27.5°C.
From these data we can deduce that water temperatures may
vary significantly within the span of any one day or from
season to season. The mean monthly water temperature
maxima and minima for Barataria Bay during the period 1920-
1947 are presented in Figure 2.8. The temperatures of
coastal waters appear to be controlled by large scale thermal
regimes from the Gulf of Mexico. "Typical" surface isotherms
are shown in Figure 2.9, winter, and Figure 2.10, summer. Thermal
gradients are generally increasing from the northern Gulf
southward to Yucatan. These gradients become more pronounced
during the winter spanning a range of about 18°C in the
study area to about 25°C in the Yucatan Straits. The winter
temperatures in the study give way to summer temperatures of
about 28°C.
2.3.3.3 Bay Salinities
Bay salinities of the area are influenced by many
of the same factors which operate on bay systems elsewhere
2-11
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ro
i
*-•
ro
10
2
RAINFALL, BAR/J77\RIA
JAN. FEa MAR APR MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.
Figure 2.6 Monthly rainfall, Barataria Bay Area, 1949
(Mackin and Hopkins, 1961).
-------
ro
DAILY RANGE OF WATER TEMPERATURE
LOWER BAR ATARI A BAY
STATION 51-A
JIH.V l*4« TtmOUCH AUGUST l«4»
3EPTEMBCB OCTOBER
1948
Figure 2.7 Daily range of water temperature - lower Barataria Bay July 1948
through August 1949 (Hewatt, 1953).
-------
MEAN MONTHLY TEMPERATURES (°C), BARATARJA BAY AREA
( 1 MAXIMA •• MINIMA
ro
30 -
20 -
I 0 -i
JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.
Figure 2.8 Mean monthly temperatures (°C), Barataria Bay Area
(Mackin and Hopkins, 1961).
-------
ro
i
en
Figure 2.9 Average sea surface temperatures for February
(after Fuglister, 1947).
-------
ro
i
»-•
o\
Figure 2.10 Average sea surface temperatures for August
(after Fuglister, 1947).
-------
on the Gulf coast. Some of these factors are lunar tidal -
currents, wind tides, wind driven currents, rainfall, sand-
bar islands (barrier islands), evaporation, and to a high
degree the discharge rates of the Mississippi River and
its distributaries. Modifications of the lower Mississippi
for flood control purposes have greatly altered the various
bay ecosystems within the study area.
Historically speaking, the protozoan (Dermoeystidiwn)
has been considered the most damaging oyster predator. Conversations
with members of the Louisiana Wildlife and Fisheries Commission,
however, reveal that the principal oyster predator in Louisiana
Bays is now the oyster drill (Urosalpinx) and occasionally the
starfish (LuidLa olathratah This change has resulted from blockage
in the lower Mississippi distributaries and the resultant ele-
vation of bay salinities. As fresh water sources are diminished,
salt water from the Gulf has intruded further into the bays and
oyster production extended further up into bayhead areas.
An associated problem accompanying the blocking of
distributaries by flood control and navigation measures is the
reduction of sediment recruitment from upstream sources. This
has caused the area to shift toward a new deposition-erosion
equilibrium. This shift has introduced excessive erosion
to certain delta areas.
Although not as well studied, Timbalier and Terrebone
Bays in the study area possess similar geomorphological and
hydrological features to Barataria Bay. Most of the statements
concerning Barataria Bay may be applied to Timbalier and Terrebone
Bays as well.
Within the bays, salinities may vary from near 0 to
35 parts per thousand(°/oo) depending on rainfall and evaporation.
The mean salinity for lower Barataria Bay is about 20%>o. Coastal
salinities may range from normal Gulf salinities near 34°/oo
to lower salinities depending on location of Mississippi River
discharge. During periods of upwelling, salinities in excess
of 34%>o may occur within a few miles offshore.
2.3.3.4 Oceanic Currents Associated with the Study Area
It must be noted that the characterization of
inshore currents of the study area was hampered by scarcity
of available information. This is apparently the general
case for other sections of the United States coastline
as well (Pequegnat, et al, 1967). The current studies
performed by Texas Instruments under Contract 68-01-0017
for the Environmental Protection Agency reveal that near
2-17
-------
shore currents may be influenced by local winds. At this
point, any predictions of nearshore currents would be
largely speculative in nature and unsuitable for baseline
comparisons. The assumption can be made, however, that
surface currents are of major importance, because of
controlling depths (60').
Certain data are available concerning offshore
and Gulf surface currents compiled from U. S. Navy Hydrographies
Office pilot charts and published in Fisheries Bulletin 89,
1954. These schematics are shown in Figures 2.11, 2.12, and
2.13.
2-18
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IN)
I
I—»
10
Figure 2.11 Surface ocean currents in the Gulf of Mexico in December
-------
ro
8
Figure 2.12 Surface ocean currents in the Gulf of Mexico in June
-------
ro
i
ro
Figure 2.13 Gulf Stream in the Gulf of Mexico shown by Soley's chart, 1914.
The currents as they exist during the different seasons.
-------
3.0 Biological and Zoogeographic Review of the Study Area
3.1 Description of the Northern Gulf and Ecological Factors
Affecting the Fauna
The northern Gulf of Mexico may be characterized as an
area of temperate and subtropical climates, with a mean surface
water temperature range of 18° - 30°C and meteorological areas
ranging from xerophytic (arid) to mesophytic (humid). Ecological
factors throughout the northern Gulf are quite varied. The eastern
portion of the Gulf and the southwestern coast of Mexico are
uniformly subtropical, while the northcentral and northwestern coast-
lines range from subtropical in the summer to temperate in the winter.
As would be expected in a region of such variation, the faunal as-
semblages of the northern Gulf are subjected to severe ecological
stresses and populations are maintained largely through recruitment.
Strictly endemic forms constitute less than 10% of the native popu-
lations (Hedgpeth, 1953), while the distribution of the populations
is dependent upon prevailing current patterns within the Gulf. A
brief discussion of the ecological significance of the climatological
factors and current patterns follows.
The ecological characteristics of each segment of the Gulf
coast vary greatly, both from each other and in absolute values
within segment. As previously shown in Section 2.0 the temperature,
salinity, precipitation, and sedimentary types are noticeably
disjunct between the northcentral and northeastern Gulf coast. For
instance, the temperature ranges in the eastern portion of the Gulf
coast vary from 12 - 32°C (55-90°F), while the remainder of the
northern Gulf coastline temperature range from 5 - 38°C (40-100°F).
Temperatures of the inshore and nearshore waters change from warm,
subtropical in the eastern portion of the Gulf to cooler, more tem-
perate fn the central and northwestern regions. The surface water off
Texas and Louisiana west of the Mississippi delta frequently reach
temperatures less than 5 C°(40°F) in winter. This distinct tempera-
ture gradation between the eastern and northcentral regions of the
Gulf implies that the two regions lie in different zoogeographic
realms or provinces. This supposition is supported by the fact that
a definite break in the distribution patterns of several temperate
species occurs in Florida (Ekman, 1953). Such commercially valuable
organisms as the oyster, Crassostrea virginiaa* and shrimp, Penaeus
sp. display behavioral as well as distribution anomalies throughout
the eastern Gulf. These resultant zoogeographic provinces have
been characterized as temperate-subtropical (Texas and Louisiana
west of the Mississippi delta) and subtropical (Florida and the
northeastern Gulf coastline).
3-1
-------
The diversity of climatic and other ecological factors
in the Gulf have resulted in a wide diversity of faunal assem-
blages. The high productivity of the Gulf coastline as shown in
Figure 3.1 is evidenced by the abundance of oyster reefs, shrimp
ground, sponge beds and serpuloid reefs. Inshore and nearshore
faunal communities are often subjected to the stress of variable
ecological conditions. A brief discussion of the population
recruitment mechanism is therefore in order. Circulation patterns
in the waters of the Gulf appear to be of primary importance in
governing the dispersal of marine organisms and their larvae.
The principal current patterns have been charted by Leipper (1954),
Hedgpeth (1953) and Curray (1960). The chartings establish that
the primary current inflow enters through the Yucatan Straits
which is, in turn, derived from the western Caribbean currents with
some influx from the Atlantic Gulf stream along the southern coast
of Cuba. Upon entering the Gulf, the Yucatan current separates off
the Mississippi delta into eastward and westward currents as shown
in Figures 2.1 and 2.12 of Section 2.0. The eastward current
feeds the eastern Gulf and eventually leaves through the Florida
straits. The westward current splits into two major subdivisions,
one along the central and northwestern coasts and one through
the Gulf of Campeche. Both reunite in the vicinity of Padre
Island. During the vernal and the autumnal equinox, the currents
off Padre Island also show divergences eastward below the mouth
of the Mississippi delta. During these fall and spring periods,
when larval production is at its peak, large influxes of animals
occur. Those animals entering during the spring will find environ-
mental conditions very similar to those of their normal habitats.
Those entering during the fall, however, encounter the vicious
winters so characteristic of the Gulf coast. Animals entering
this period, however, frequently establish themselves and even-
tueally spawn when conditions again become favorable. Since the
currents upon which recruitment depends may flow eastward with-
out a reverse pattern and since significant zoogeographical
limits exist between the eastern and central portions of the
Gulf, it might be expected that a stronger correlation would
exist between the northwestern and northcentral areas of the
Gulf coast than between either of them and the Florida coast.
This may be seen in the disjunct distribution patterns between
Florida and the remainder of the Gulf and in the fact that native
faunal populations in Florida are frequently not shared in toto with
the rest of the Gulf coast. Those populations which are shared
are often less hardy in the Florida region.
3.2 Faunal diversity and Species Ranges
Much of the indigenous fauna of the northern Gulf of
Mexico have been investigated only in restricted geographical
areas. Specific catch records and data are particularly scarce
when compared to the remainder of the continental coastlines
3-2
-------
Serpuloid reefs
I SHRIMP GROUNDS: •":
-fSPON&E GROUNDS:;;
CORALS:
reefs / patches * -
Figure 3.1 Abundance of oyster reefs, shrimp grounds, sponge beds
and sepuloid reefs in the Gulf of Mexico.
3-3
-------
of the United States. One comprehensive collecting program for
the Gulf has been undertaken during recent years: the explora-
tions by the National Marine Fisheries Service (then Bureau of
Commercial Fisheries) U. S. Department of Commerce* during the
years 1950-1960. Additional investigations are currently under-
way by the Hourglass cruises of the Florida Board of Conservation,
but these data are not yet available. Therefore, in the compilation
of background data for this report, the 1950-1960 data of the NMFS
was used. In compiling this data, it was found that data on most
of the smaller groups were incomplete. Accordingly, only those
data pertaining to crustaceans, mollusks, and fishes have been
included in the compilation as used for analytical purposes.
In this report, information has been assembled and
data compiled into a checklist of species, comparative between
the three principal provinces of the northern Gulf Coast-Texas,
Louisiana west of the Mississippi delta, and Florida. In each
instance, the relative abundance of a particular species within
a given area has been recorded. However, the summary background
data, for reasons previously noted, has been restricted to those
data from the Central Gulf Coast area; the area of interest
to this study.
Background data were compiled for the selected species
in the following manner. First, the total number of sites where
the species were taken was tabulated. From those sites, the
sites located within the area of interest of this study were
identified. Due to volume, these data, are not presented in this
section but are included in Appendix II of this report, with specific
site locations identified by latitude and longitude, and then
positioned on a map which is also included.
From the data thus compiled a scale was developed
which quantified the relative abundance of species in the locales
of interest. These data are also presented in detail in Appendix
II. As a final step in establishing "normal" populations in the
study area, the data were refined to 1) identify, by species and
relative quantitative populations, the species to be used for
correlation with results of sampling conducted during this
study and 2) to assign these species to their representative
habitat in the inshore and nearshore environments. These
data, representing the "normal" background data for purposes
of analyses conducted in this study, are tabulated in Table 3-1.
Figure 3.2 charts the habitatal areas classified with respect
to the study area.
3-4
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Table 3-1
Sequential Macro-Organismal Faunal Successions
for the Central Gulf Coast
Sequential checklist of major invertebrate species distribu-
tional patterns illustrating faunal succession of microhabi-
tats within the study area.
X = absent, not reported or doubtful in area
R = rare, seldom recorded
0 = occur, usually encountered in small numbers
C = common, usually encountered in large numbers
A = abundant, always encountered throughout entire
area.
3-5
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Table 3-1
Sequential Macro-Organismal Faunal Successions
for the Central Gulf Coast
Freshwater/Brackish Water Assemblages (0-5 °/oo)
Gastropoda
LittoTina irrorata A
Neritina reolivata A
Crustacea
Uoa pugilitor C
Cambarus sp. A
Low-salinity Assemblages (0-10 °/oo)
Pelecypoda
Rangia ouneta C
Rangia flexuosa 0
Rangia oarolinesis O
Maooma mitchelli, C
Gastropoda
L-ittoridina sphinctostoma O-C
Crustacea
Callinectes sapidus C
Macrobrachium sp. O
Intermittent Variable-salinity Assemblages (5-30 °/oo)
Pelecypoda
Rangia euneata O-C
Rangia flexuosa O-C
Maooma mitchelli R
Crassostrea virginica A
Petrieola pholadiformis C
Gastropoda
Littordina sp. O
Amnioola sp. O
Variable-salinity Oyster Reef Assemblages (10 - 30 °/oo)
Pelecypoda
Crassostrea virginioa A
Brachidontes recurvus C-A
3-6
-------
Variable-salinity Oyster Reef Assemblages (continued)
Gastropoda
Crepidula plana 0-C
Crustacea
Balanus eburneus C
Balanus amphitrite 0-C
Variable-salinity Non-reef Assemblages (10 - 30 °/oo)
Pelecypoda
Nuoulana aouta R-0
Nuoulana concentrica C
Mulina lateral is A
Tagelus plebius C
Ensis minor C
Gastropoda
Retusa oanaliculata R-0
Echinodermata
Amphiodia limbata C
Intermediate-salinity Inshore Coastal Assemblages (20 - 40 °/oo)
Pelecypoda
Aequipeotern irradians A
Tvaohycaifdi-um muricatum A
Mercenaria mercenaria A
Ch-ione cancellata C-A
Tagelue divisus A
Gastropoda
Nassari-us vibex C
Neritina virginea R-0
Melampus bidentatus C
Intermediate-salinity Inshore Shallow Water Assemblages (20-40 °/oo)
Pelecypoda
Abra aequalis A
Corbula oontvaota C
Diplodonta punctata R-O
Mulina lateral-is A
Nuoulana oonoentvica C
Pandora trilineata R-O
Periploma fragile R-O
V N
3-7
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Intermediate-salinity Inshore Shallow Water Assemblages (continued)
Gastropoda
Nassarius acutus C
Retusa canaliculate. O-C
High-salinity Oyster Reef Assemblages (34 - 45 °/oo)
Pelecypoda
Anomia simplex C
Brachidontes exustus C
Diplothyra smithi 0
Ostrea equestris A
Gastropoda
Anachis avara C
Anaehis obesa C
Mitrella lunata C
Thais haemostoma floridana O-C
Crustacea
Crangon heterochelis C
Menippe mercenaria 0
High-salinity Non-reef Assemblages (34-45 °/oo)
Pelecypoda
Amygdalum papyria C
Anomalocardia cuneimeris A
Laevicardium mortoni C
Phacoides peotinatus R-O
Pseudocyrena floridana C
Gastropoda
Bittium vaTium A
Caecum pulchellum C
Cerithidea pliculosa C
Cerithium variabile C
Haminoea succinea R-O
Modulus modulus R
Tegula fasciata R-O
Vermicularia fargoi C
3-8
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Inshore/nearshore Inlet and Pass Assemblages
Pelecypoda
Atrina seminuda R-0
Crassinella lunulata C
Lucina amiantus C
Lucina orenella C
Tellidora oristata C
Gastropoda
Anaohis avava R-0
Pol-inioes duplioatus C
Sinum perspeetivum R-0
Scaphoda
Dentalium texasianum O-C
Echinodermata
Arbacia punotulata 0
Hemipholis etongata R-0
Luidia clathrata 0
Mellita quinquiesperforata C
Ophiolepis elegans C
Coelenterata
Astrangia astve-iform-is C
Crustacea
Dromid-ia antillensis R-0
Heterocrypta granulata R-O
3-9
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Nearshore and Offshore Facies
Intertidal Surf Zone
Pelecypoda
Donax variab-ilis var-iab-il-is A
Donax variabilis texasiana A
Donax tumida C
Gastropoda
Olivella mut-ica C
Terebra cinerea A
Crustacea
Emerita talpoida A
Octpode alb-Loans C
Constant-salinity Littoral Zone
Pelecypoda
Atrina serrata C
Chione intapurpurea C
Dinocardium robustum C
Dosinia discus C
Dosinia elegans R
Labiosa pl-icatella R-O
Solen viridis C
Spisula solid-issima C
Tellina tayloriana A
Gastropoda
Architeetonica nob-Llis C
Busyoon plagiosum C
Oliva sayana C
Phalium granulatum C
Terebra dislocata A
Echinodermata
Lu-idia olafh^ata C
Mellita quinquiesperforata A
Variable-salinity Littoral Zone (15 -36 °/oo
Pelecypoda
Abra l-Loica A
Maooma tageliformis C
Mul-ina lateralis C-A
Nuculana concentrica C
3-10
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Variable-salinity Littoral Zone (continued
Gastropoda
Anachis avara C
Nassarius aoutus C
Polinioes duplioatus C
Crustacea
Povtunus g-ibbesi. O-C
Squilla empusa C-A
Offshore Littoral Zone - Soil or Mud Bottom
Pelecypoda
Nucula proximo. C
Nuoulana concentrica C
Pandora bushiana C
Pitor cordara C
Varicorbula operoulata A
Gastropoda
Anach-is saintpairiana A
Nassarina glypta C
Nassarius ambiguus C
Offshore Littoral Zone - Sandy Bottom
Pelecypoda
Aequipecten gibbus C
Aequipeoten muoosus C
Chione clenchi A
Chione grus C
Gouldia cerina A
Laevicardium laevigatum R-0
Luoina sombrerensis C
Peoten vaveneli R
Phylloda squamifera C
Quadrans lintea C
Semele purpurescens C
Solecurtus eurningianus R-0
Tellina georgiana C
Gastropoda
Antilliphos candei C
Distorsio clathrata C
Murex fulvescens C
Murex pomum C
Strombus alatus R-0
Tonna galea R-O
3-11
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Figure 3.2
Representative habitats illustrating faunal successions
in the inshore and near shore environments.
1. Freshwater/brackish biotope (0-5 °/oo)
2. Low-salinity biotope (0-10 °/oo)
3. Intermittent variable-salinity biotope (5-30 °/oo)
4. Variable-salinity oyster reef biotope (10 - 30 °/oo)
5. Variable-salinity non-reef biotope (10 - 30 °/oo)
6. Intermediate-salinity inshore coastal biotope (20 - 40 °/oo)
7. Intermediate-salinity inshore shallow water biotope
(20 - 40 o/oo)
8. High-salinity oyster reef biotope (34 - 45 °/oo)
9. High-salinity non-reef biotope (34 - 45 °/oo)
10. Inshore/nearshore inlet and pass biotope
11. Intertidal surf zone
12. Constant-salinity littoral zone
13. Variable-salinity littoral zone
14. Offshore littoral zone - soil or mud bottom
15. Offshore littoral zone - sandy bottom
3-12
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GO
I
u>
Figure 3.2 Representative habitats illustrating faunal successions
-------
4.0 Data Analysis
The analysis of data collected in the three post-
spill studies and from literature sources is discussed in this
section. To the extent data limitations permit, analytical studies
were performed in an attempt to identify the fate and effects of
the crude oil spilled as a result of the Shell Incident in December
of 1970.
The Gulf Coast area is dynamic both physically and
biologically, and does not lend itself to easy determination
of the existence of environmental stresses. This is further
complicated by the extensive development of the a-rea in
petroleum production. Within the constraint of such a system,
this study was conducted to determine deviations from normal
conditions within the area of the spill which first identifies
anomalies and then correlates these anomalies to the existence
of crude oil within the water column, sediments, and the biota.
Shortly after the spill incident, Texas Instruments
conducted a remote sensing and oceanographic survey in the
vicinity of Shell Platform B.
The area! survey which was made between January 10-17,
1971 used ultraviolet and infrared imagery. The first survey
utilized ultraviolet imagery only and mapped areas of slick
(6.2 square miles), rainbow (8.6 square miles) and sheen (22.2
square miles). Three days after the first survey the area was
again flown and the oil spill area mapped with only infrared
imagery showing a total area of spill of 4.9 square miles and
42.8 linear miles of oil stringers. Thus, the conclusion was reach-
ed by Texas Instruments that the infrared detects primarily oil
slick whereas the ultraviolet detects all of the oil spill ma-
terial that is present, be it slick, rainbow or sheen.
The surveys conducted by Texas Instruments from January
10 through 17, 1971, and supplemented by visual observations for
January 10, establish that spilled oil movements for this period
were mostly in a northeasterly direction with some movement to
the north and southwest but, in no instance.across transect ,
stations beyond the two (2) mile station on the south transect.
1. See report entitled "OCEANOGRAPHIC AND REMOTE SENSING SURVEY
IN THE VICINITY OF THE SHELL SPILL, GULF OF MEXICO", January
1971, prepared by Texas Instrument, Inc., under Contract no.
68-01-0017, and dated 25 March 1971.
4-1
-------
The reported locations and concentrations of pollutants is pre-
sented in Figures 4.1, 4.2, 4.3, and 4.4 which have been extract-
ed from the report prepared by Texas Instruments, Incorporated.
The results of the remote sensing overflight experiment indicate
that such devices can yield valuable data for both predictive
and historical purposes.
The flights represented only a portion of the air-
borne surveilance of the incident in that daily flights by USC6-
EPA-USGS-Shell mapped the oil slick and showed that during the
incident "the oil was moved in every direction" from the Plat-
form.
4.1 Hydrocarbons in Living Organisms and Natural Sediments
Hydrocarbons found in natural recent sediments were
derived from the components of former living things. As the sediment
matures, the composition of the organic debris changes. Some of
the major compounds from the biotic matter are partially or completely
eliminated while other compounds of little importance in the life
cycle of organisms become enriched.
A new group of compounds which are generally absent in
organisms can be generated as the result of action of microbes and/or
inorganic processes. It should be noted that anaerobic conditions
at the water-sediment interface is preferred, if not prerequisite,
to the preservation of the organic matter contributed to the sedi-
ments. In the presence of oxygen, hydrocarbon-oxidizing bacteria
would make short work of the debris. If oxygen is absent the hydro-
carbons are preserved and part of the non-hydrocarbon organics can
be transformed by anaerobes into hydrocarbons. Recent analysis of
food materials from the sunken and recovered research submarine ALVIN
indicate that microbial degradation is 10 to 100 times slower at
greater depths even in the presence of adequate oxygen.
As early as 1954, it was substantiated that liquid parafin-
ic, naphthenic and aromatic hydrocarbons were present in recent
sediments in a variety of salty, brackish and freshwater deposits.
There are conflicting views on the general natural concentration of
hydrocarbons in sediments, with reported ranges of a few tenths of
hundredths ppm to a range of 9 to 11,700 ppm. Degens, in 1965,
reported that a 300 ppm hydrocarbon concentration found in an
ancient shale is 5 to 10 times higher than recent sediments. From
these data a normal level of 30 to 60 ppm may be extrapolated as
a reasonable natural range. However, because the study area is
located in a highly developed oil production area with continuing
minor spillage and seepage, the pre-spill levels probably exceed
the normal levels of 30 to 60 ppm, which is not, therefore, used for
analytical purposes.
4-2
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KEY
OIL SLICK
RAINBOW
SHEEN
LAND
VISUAL OBSERVATIONS
EPA SURVEILLANCE
GRAND ISLE
90*K>'
• Z9'00'
NAUTICAL MILES
I 1/2 O I 2 3
STATUTE MILES
I 1/2 0
LYSIS OF ULTRAVIOLET IMAGERY
IN THE VICINITY OF THE
SHELL OIL PLATFORM B FIRE
GULF OF MEXICO
PREPARED FOR
ENVIRONMENTAL PROTECTION AGENCY
BY
TEXAS INSTRUMENTS'INCORPORATED
SERVICES GROUP
DATE: 10 JANUARY 1971 TIME: 1322-1522 HRS
Figure 4.1 Comparison of UV Analysis and Visual Observa-
tion in Vicinity of Shell Platform B
4-3
-------
Tl MBALIER
BAY
Percent of Readings
/ 5 mph Wind
10 mph
Figure 4.2 Current and Wind Data and Oil-Slick Orientation, 13 January 1971,
Texas Instruments Surveillance
-------
I
en
STATUTE MILES
0 5
r~ • i 1 f —t
MAUTICAL MILES
Scole i 250,000
Commodo Pass
T I MB ALIER
BAY
EAST T,MBA
SLANJCJ
Percent of Readln
20 cm/sec Current
Figure 4.3 Current and Wind Data and Oil-Slick Orientation, 14 January 1971,
EPA Spill Surveillance
-------
Percent of Readings
5mph Wind
/ 10 mph
20 20 cm/sec Current
Scale I 250,000
, -Cominoda Pots
T I iVI B A L I E R
BAY
FAST TiMBALILR
AMD
TlMBAUIER
SUAMO
Figure 4.4 Current and Wind Data and Oil-Slick Orientation, 16 January 1971,
EPA Spill Surveillance
-------
Present day organisms and natural recent sediments lack
light hydrocarbons in the C$ to Cu range. In the Cjr range, normal
recent sediments show a marked preference of odd numbered over even
numbered paraffins, probably resulting from the preferential oxi-
dation of even numbered hydrocarbons by microbes.
Preference varies widely in living organisms. Petroleum
paraffins exhibit no odd or even preference in the 0^5 + range and the
hydrocarbons in the €3 to (^4 range are not only present but con-
stitute 50% of the average crude.
Saturated hydrocarbons from Cj to 059 make up a substantial
fraction of crude oils as do the naphthalenes and aromatic hydro-
carbons. The lowest molecular weight n-alkane reported in plants
is n-heptane (Cy HIS) anc' the heaviest reported is n-dohedracontane
(Cg2 ^125). n's °kvious tnat hydrocarbons are much more universally
distributed in nature than was previously thought. They are synthe-
sized by most if not all organisms and certain compounds are stable
to the extent that they can be used to determine feeding habits and
ranges of some fishes and mammals.
Distinction between oil and natural hydrocarbons requires
careful detailed analysis of the characteristic differences in
molecular size and type distribution. Crude oils are vyide range
mixtures containing molecules of different sizes in fairly even
distribution while organisms are limited to certain biogenic path-
ways which produce hydrocarbons in preferred size ranges.
4-7
-------
4.1.1 Distribution and Ecological Significance of Observed
Hydrocarbons
4.1.1.1 Water-Disperable Hydrocarbons
Examinations of sediments and waters near Shell Platform
B, Block 26, reveal that water-dispersable hydrocarbons have been
dissipated from the sediments immediately surrounding the subject
platform (reference Figure 4.5). These data indicate that no
seepage of oil from the incident location occurred for some time
prior to these investigations. The exact time cannot be estimat-
ed because of the absence of information related to dissipation
rates. There can be little doubt, however, that water-dispersable
fractions (probably aromatic compounds) from the crude oil were
transported through the water column and deposited in sediments
even at considerable depths (601 observed). These deposits appear
to become rapidly redispersed into the overlying waters. Results
of this study indicate that significant residuals of these dis-
persable hydrocarbons remain in the sediment for some time prior
to their redispersal. This depostion and redispersal is discussed
in later portions of this report.
Many data from these analyses repeatedly verified that
water-dispersable fractions of crude oil from this spill found their
way to the sediments underlying the oil slicks and sheens. A clear
example of this vertical dispersion was observed in association with
the oil sheen observed 4 to 6 miles north and northwest of Platform
B. The vertical dispersion and deposition of water-dispersable hydro-
carbons in sediments is shown in Figure 4.5 on the N and NW transects.
Variations in sediment hydrocarbon concentrations indicate the sheen
was progressing from south to north in response to prevailing winds.
In Figure 4.5, North Transect, at miles 2 through 4, it is
noted that increased sedimental water-dispersable hydrocarbons were
observed and to mile 7 where the absence of similar data occurred
across the northermost front of the sheen. After passage of the
sheen, a rapid dissipation back to the water apparently occurred,
indicated by decreased sedimental water-dispersable hydrocarbons
from miles 6 to 5, 5 to 4, and 4 to 3.
Data discussed and presented are limited to these data acquired by
sampling during the period from June 1-10, 1971. No baseline data
are available and samples taken during earlier studies of the area
(Dec 1970) showed anomalies attributable to the effects of the spill
See also Appendix II.
4-8
-------
350
SEDIMENT HYDROCARBON
SEDIMENT
(4.5 PPT) NORTH
TRANSECT
H2O DISPERSABLE
350
NORTHWEST
300
250
200
150
100
HYDROCARBON
(4.5 PPT)
TRANSECT
MILES FROM RIG
2345
MILES FROM RIG
350
SEDIMENT
H2O
O
CD
CC
<
O
O
CC
Q
CL
CL
300
250
200
150
100
HYDROCARBON
SOUTH
TRANSECT
DISPERSABLE
C-CL4
EXTRACTABLES
MILES FROM RIG
Figure 4.5 Sediment Hydrocarbon
4-9
-------
4.1.1.2 Carbontetrachloride Extractable Hydrocarbons
(Aliphatic and Isoprenoid Hydrocarbons)
Significant quantities of CC1. extractable crude oil frac-
tions reached bottom sediments at depths down to 60'. This fact
was revealed through the analyses of sediments near the subject
platform where sampleswere found to contain concentrations which
averaged 4.5 ppt compared to about 300 ppm one mile from the plat-
form on all transects. Levels dropped to between 50 and 100 ppm
four miles from the platform on all transects. A chromatographic
analysis of a sample of crude oil from Platform A revealed that
carbon compounds with carbon numbers between 15 and 31 predominated
with the highest concentrations occurring in the smaller compounds
near and including 15 carbons (Figure 4.6). The major concentrations
of crude fractions lie within carbon numbers less than 24 with a
comparatively minor distribution above this length.
In the vicinity of the oil sheen as previously discussed
sedimental CC1. extractables rose rapidly indicating a relatively
free movement of these substances through the water column. Like-
wise, on the south transect, at miles 2 and 3 south of the plat-
form at depths near 60' there was again evidence of significant
concentrations of CC1, extractables. (These data may have been
influenced by quantities of oil dispersants to the extent they
may have been used for safety purposes during the "spill"). Con-
sequently the vertical dispersion of both the water dispersable and
CCK extractable crude oil fractions may have been unduly augmented
by these artificial conditions. These data, the distribution of
sediment hydrocarbons south of Platform B, correspond with data
presented by Texas Instruments regarding the direction of the movement
of oil during the early phases of the incident.
4.1.1.3 Ecological Significance
The water-dispersable components of crude oil probably
represent aromatic compounds which have been cited as being more
toxic than aliphatic hydrocarbons. These compounds are more soluble
in salt water than in fresh water thus increasing their biological
1. See Texas Instrument Inc. report entitled "Oceanographic and
Remote Sensing Survey in the Vicinity of the Shell Spill, Gulf of
Mexico, January 1971."
4-10
-------
•H
I
O
*
a
o
H
1
w
u
13
O
U
350
300
250
200
SHELL CRUDE
PLATFORM A
BAY MARCHAND FIELD
15 18 21 24 27 30
PARAFFIN CARBON NUMBER
Figure 4.6 Distribution of Carbon Numbers in a
Sample of Shell Crude
4-11
-------
i
i—•
ro
INFRARED IMAGERY - SHELL OIL PLATFORM-B FIRE, GULF OF MEXICO
1
PREPARED FOR ENVIRONMENTAL PROTECTION AGENCY
i:i .v.A'-fx wi,
i »; f I \ \ S I S S I U I M L N TS
Figure 4.7 '\ovenent of Soilled Oil
-------
accessibility in the marine environment and hence, their potential
toxicity. The apparent cycling of water-soluble and dispersable
petroleum fractions from the water column to the sediments and back
to the water is therefore potentially damaging to the ecosystem.
Benthic populations may be damaged by these transient mater-
ials which, because of their redispersability, may not be detectable
a short time later. Likewise, pelagic organisms may be adversely
influenced by the above processes since only a fraction of the
water-dispersables would ultimately reach the sediments and be
deposited. The remaining water-borne fractions would then constitue
a significant level in the water column, 1.3, ppm total hydrocarbons
were measured from bottom water samples taken near the sheen area
while concentrations near zero were found in similar samples three
miles south of the sheen.
A comparison of Figure 4.6 with Figure 4.8 reveals a
preference of "uncontaminated" megafauna for aliphatic hydrocarbon
compounds from 22 through 30 carbons in length. This distribution
.corresponds closely with the data cited earlier in Section 3.0.
Analysis of these data also revealed that organisms of different
types tend to reflect the same aliphatic hydrocarbon background
levels in the same environment. Note the similarities between the
shrimp, crab, oyster, and fish from the same general location on
Caminada Bay near Andre Island (Figure 4.9). A definite preference
is shown for even numbered short chain hydrocarbons 16, 18, 20, and
22 carbons in length. The odd numbered carbon chains were almost
entirely absent in these organisms presenting two distinct possi-
bilities: (1) the odd numbered hydrocarbon chains are not absorbed
by endemic organisms, or, (2) they are degraded by the organisms in
such a way as to yield even numbered chains. Insufficient data
are available at this time for a definitive answer to this question.
These data do not relate directly to the offshore spill but
are considered significant since they will prove valuable in future fate
and effects studies. Based upon a literature survey and this study,
it now appears that the significant aliphatic hydrocarbon chain
lengths lie between 15 and 22 carbons. Shrimp taken between 4 and
6 miles northwest of Platform B were relatively free of hydrocarbons
in the 15 to 21 range, indicating their uptake of petroleum products
was low or insignificant at the time of sampling (Figure 4.10).
In view of the foregoing discussions concerning the vertical
migrations of both water-extractable and CCl.-extractable petroleum
products between the water column and sediments, it is difficult not
to recognize that both must come into direct contact with all forms
of aquatic life throughout the ecosystem. This supposition is rein-
forced by data from hydrocarbon analyses of bottom water samples in
which levels of 3.8 ppm concentrations were found both near the surface
4-13
-------
ISOLATE
816
2.40
2.00
S
* 1.60
o
Si.20
I
O
1
80
40
15 18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
i
o
H
EH
W
2
O
u
18
15
12
9
6
ISOLATE 805
(OYSTER)
15 18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
2
O
u
2.40
2.00
1.60
1.20
.80
.40
ISOLATE
(CRAB)
806
15 18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
Figure 4,8 Distribution of N-Paraffin Carbon Numbers
4-14
-------
350
cu
I
H
W
u
z
o
u
15 18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
15 18 21 24 27 30
N-PARAFFIN CARBON NUMBER
ISOLATE
(OYSTER)
18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
a
ft
^ 5
O
g 4
u
13
o 2
u
ISOLATE
(FISH)—
818
15
18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
Figure 4.9 Distribution of N-Paraffin Carbon Numbers
from Caminada Bay near Andre Island.
4-15
-------
2.40
ISOLATE
(SHRIMP)
800
15 18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
S3
ft
ft
§
W
U
§
U
ISOLATE 801
(SHRIMP)
18 21 24 27 30 33 36
N-PARAFFIN CARBON NUMBER
Figure 4.10 Distribution of N-Paraffin Carbon Numbers
o
CO
tr
<
o
o
cc
0
QL
CL
350
300
250
200
SEDIMENT HYDROCARBON
C-CL4 EXTRACTABLES
( A . 5 PPTt
150
100
23456
MILES FROM RIG
Figure 4.11 Sediment Distribution of Hydrocarbons
4-16
-------
and in near bottom waters five miles south and 1.3 ppm hydro-
carbons was found in both surface and bottom waters four miles
south of Platform B. These data correspond closely with the sediment
analysis data presented in Figure 4.11.
4.1.2 Species Diversity
Very poor correlation was observed between Van Veen grab
numerical catch data and simple diversity (number of species
present as shown in Figure 4.12. No trends could be established
between these data and any other parameters. However, a very poorly
defined direct relationship appears to exist between dominance
diversity (Figure 4.12) and hydrocarbon concentrations in sedi-
ments. These data are of questionable significance, however,
and must be viewed with caution because of the usual shortcomings
of diversity computations.
4.1.3 Distribution of Fauna in the Study Area and Possible
Ecological Effects of Hydrocarbons
4.1.3.1 Results of Biological Sampling
Biological sampling near the rig and in adjacent waters was
conducted along three distinct transects with samples being taken at
one mile intervals. Samples were taken from the sediments by grab
sample, off the bottom and just above the bottom by trawl, and near
the rig by divers. A survey of the composite catch results for
biologically significant organisms may be seen in Figures 4.13 through
4.15. The detailed catch records are contained in Appendix II.
Figures 4.16 through 4.17 delineate the meiofaunal and
megafaunal catches. Both meiofaunal and megafaunal organisms appear
to show the same numerical trends.
Generally speaking, fauna! counts.from bottom sampling
wece uniformly low at stations nearest the rig, comprising 13 X
10 /m or less at stations on the one mile radius. Counts along the
three transects showed a general numerical increase between the one
and two mile stations. The south transect-exhibited its highest
fauna! count at the two mile mark (32 X 10 /m organisms). ..Counts
along the north transect reached a maximum of about 48 X 10 /m organ-
isms at the four mile mark. Beyond the four mile mark, there was a
steady and marked decrease in the number of organisms. At the extreme
end of the North transect (nearshore), this decrease may be attributable
4-17
-------
H
LO
H
Q
W
M
CO
28
24
20
16
12
8
4
A
COMPOSITE
MAGAFAUNAL S
,DIV.
\
2345
MILES FROM RIG
><
H
H
°3
CJ
M
Q
§
2.5
2.0
1.5
1.0
0.5
0
COMPOSITE
MEGAFAUNAL D. DIV.
SOUTH
i
23456
MILES FROM RIG
Figure 4.12 Composite Megafaunal Diversity
4-18
-------
8
7j
6
5
4
MILES —>ocjjk bi—>ou«.o,»'Nj-»o<
C.oel enterota
Ctenophora
Nemertea
Echinodermata Ophiuroidea
Figure 4.13a Taxonomic Diversity of Invertebrates
-------
I
ro
o
MILES I
FROM
RIG S
N NW
N NW
N NW
N NW
N NW
Holothuroidea Polychaeta Erranfia Polychaeta Sedentaria Gastropoda
Pelecypoda
Figure 4.13b Taxonomic Diversity of Invertebrates
-------
8
7
6
5
4
3
2
1
MILES I
FROM
RIG S
N NW
N NW
N NW
N NW
Sfomatopoda
Decopoda
(shrimp)
Decopoda
(crabs)
Cephalopoda
Figure 4.13c Taxonomic Diversity of Invertebrates
-------
no
ro
ro
NW
NW
Coelenterata
Nemertea
Ophiuro idea
Polychaeta
Figure 4.14a Numerical Abundance of Invertebrates
2
(1/25 m Van Veen Grab)
-------
rioo
ro
CO
1*11 i i
NW S N NW
Gastropoda
Pelecypoda
Stomatopoda
Decopoda
(shrimp)
Figure 4.14b Numerical Abundance of Invertebrates
2
(1/25 m Van Veen Grab)
-------
NW
NW
Decopoda
(crabs)
Cephalopoda
Figure 4.14c Numerical Abundance of Invertebrates
2
(1/25 m Van Veen Grab)
-------
ro
tn
NW
Engraulidae
Synodontidae
Ari idae
Ser ran idae
Carangidae
Figure 4.15a Numerical Abundance of Fish (20 min. trawl)
-------
"
-p*
ro
NW
N NW
N NW
N NW
Gerridae
Sciaenidae
Sparidae
Ephippidae
Trichiur idae
Figure 4.15b Numerical Abundance of Fish (20 min trawl)
-------
I
ro
Tr'i g I idae
Pol y nem i da e
Bothidae
Sole i dae
Cynogloni dae
Figure 4.15c Numerical Abundance of Fish (20 min. trawl)
-------
50 •
45 -
40 -
35-
30-
25-
20.
15-
10 -
5
N NW
Tetraodontidae
Figure 4.15d Numerical Abundance of Fish (20 min. trawl)
-------
o
o
o
*
CO
co
H
O
O
60
50
40
30
20
10
COMPOSITE
VAN VEEN GRAB CATCH DATA
COUNTS PER SQ. M
MILES FROM RIG
Figure 4.16 Composite Grab Catch Data
o
o
o
CO
S
CO
o
A
o
COMPOSITE
MEIOFAUNAL MEAN
COUNTS PER SQ. M
II
10
23456
MILES FROM RIG
Figure 4.17 Composite Meiofaunal Mean Counts
4-29
-------
to changes in salinity and sediment type, but intermediate stations
are probably under the influence of some other limiting factor. Pop-
ulations along the northwest transect were intermediate in numbers,
but altered in population diversity and distribution. Again, it is
probable that the extreme terminal stations of the transect exhibit
alterations due to the influence of Timbalier Bay, but the middle
stations are under the influence of other factors.
Without exception, megafaunal counts taken from grab
samples were reduced as they approached the platform from all three
directions, north, northwest, and south. A comparison of Figure 4.11
and Figure 4.18 suggests a general inverse relationship between mega-
faunal counts per square meter and the concentration (ppm) of sedi-
mental hydrocarbons (CC1* extractables). Within the first three miles
along the north transect, where the highest sedimental hydrocarbon
concentrations were found (highest in all three transects) the
lowest megafaunal (grab megafauna) counts of all transects were
found. In the northwest transect, where sedimental hydrocarbons
were present in intermediate amounts, observed grab megafaunal
counts were found to be intermediate to the other two transects.
Finally, along the south transect where sediment hydrocarbons were
the lowest of the occupied transects, organism counts from grab
samples were the highest.
4.1.3.2 Interpretation of Biological Catch Data
It must be recognized that the study area is located in
a region of extensive oil production and that intensive activity
preceded this study. Such activity included high noise and vibration
levels associated with relief well drilling and control and contain-
ment of the spill (December 70 to March 1971) and removal of debris
during and subsequent to that time. Extensive movements of surface
vessels also occurred and there can be no doubt that these factors
exerted some indeterminable degree of stress on the environment
in the study area.
However, at the time the field sampling (on which most
of the analysis in this report is based) was conducted, heavy
activity was restricted to the immediate vicinity of the platform.
Biological samples were taken at distances of one mile and more
from the platform, a distance considered sufficient to buffer ef-
fects which might be attributable to such causes.
Examination of the catcfi data from trawl samples revealed
a series of distinctly anomolous distribution and density patterns for
the scavenger starfish, Lu-idia clatfoata. As shown in Figure 4.20
distributional patterns are fairly similar along the northwest and
south transects, but the distribution along the north transect
4-30
-------
o
o
S
en
o
A
o
35
30
25
20
COMPOSITE
MEGAFAUNAL MEAN
COUNTS PER SQ. M
23456
MILES FROM RIG
Figure 4.18
4-31
-------
o
o
H
O
TRAWL CATCH DATA
COUNTS PER 20 MINUTE DRAG
2345
MILES FROM RIG
Figure 4.19
4-32
-------
is different. The numerical density of Luidia is highest along the
northwest transect, with the numerical density along the south tran-
sect, although still high, moderately reduced. It was, again,
along the north transect that anomolies occurred. For example
miles 2 and 4 along the north transect exhibit the highest con-
centrations of Luidia, while mile 3 is totally devoid of the
starfish. It is evident from Figures 4.20 and 4.21 that the numerical
density of Luidia are being controlled by some external factor.
The conditions governing population density of Luidia and
its closely allied cousin Astropecten, have been cited as principally
salinity, sediment type, and availability of food. When the concen-
trations of Luidia are compared to the bottom salinity readings
(Figure 4.22) several anomolies appear. Concentrations of Luidia
along the south transect are very close to the normal expected
populations for the biotope. Along the northwest transect, however,
the numerical abundance far exceeds that expected, and along the
north transect, the numbers are below the expected norm, in spite
of an apparent compatibility to recorded salinities. Maloeuf (1937)
suggests that the surface of starfish is freely permeable to water
and any significant decline below some minimal figure in salinity
will result in massive water uptake and death.
Loosanoof (1945) has shown that once above the minimum
salinity range salinity ceases to be a significant factor in
determining population density. In other words, drastic reduc-
tions in salinity will result in drastic reductions in population
density, but drastic increases in salinity will have little or no
effect upon increasing the size of the population.
It is of some interest to note that Luidia are frequently
found along with the sand-dollar, Mellita quinquiesperforata, and
seem to prefer the same biotopic conditions. The minimal salinities
for Mellita, Luidia, and Astropeoten have been studied and appear
to fall into the 20 - 23°/oo salinity range. As may be seen in
Figure 4.21, the recorded salinities along all three transects fall
well within the minimal tolerance limits of Luidia. The disjunctive
distributional patterns, however, do not appear to reflect the
salinity patterns.
Along the northwest transect, the numerical density far
exceeds that expected, but the population is centered within the
first four miles out from the rig. Beyond the 4 mile mark, Luidia
all but disappear in spite of the fact that salinities are compat-
ible. It would appear, then, that the concentration of Luidia within
the four miles around Platform B and their peripheral scarcity are
due to some factor other than salinity.
The numerical concentrations of Luidia along the North tran-
sect are the most disjunct found in any transect with a small peak
4-33
-------
o
o
w
S
w
H
8
o
TRAWL CATCH DATA
COUNTS P (Luidia clathrata)
23456
MILES FROM RIG
Figure 4.20
4-34
-------
CO
en
300-
200
1 00
LUIDIA CLATHRATA taken in 20min. trawls
800
Figure 4.21 Luidia clathrata taken in 20 min. trawls
-------
36,
I
CO
^ 26
Bottom water salinity (ppt)
along sample transects
M
38
Figure 4.22 Bottom water salinity (ppt) along sample transects
-------
2 miles north of the platform and a secondary peak 4 miles north.
Between these two peaks, however, no Luidia were taken. At each of
these stations, the recorded salinities were within the preferential
ranges for Luidia. It would seem, therefore, that the populations
along the north transect were being actively depressed by some agent
and it is unlikely that the causal agent was salinity.
^ Hyman (1955) and MacGinitie and MacGinitie (1968) found
that Luidia and Astropecten show a marked preference for sandy
bottom sediments, but modifications of their tube-feet enable them
to move about on silt and clayey-mud bottoms. The sediments in
the immediate vicinity of the rig are silted mud with a moderate
amount of sand deposition from the Mississippi delta mouth to the
south and from the inshore bays to the north and northwest (see
Section 2.0, this report). It appears, therefore, that sediment
type is not a limiting factor on the Luidia populations.
The possible effect of food availability upon the Luidia
distributions must be considered from two standpoints - (1) food
selection based upon digestive characteristics of Luidia and, (2)
the occurrence of preferential food sources in situ. The latter
preferences are based largely upon the anatomical and behavioral
characteristics of the starfish. Luidia is a scavenging carnivore,
but it lacks the eversable stomach of the typical starfish. It also
lacks any crushing or grinding mechanism, consequently, Luidia crawl
about ingesting large quantities of sediment and benthic organisms
and utilize all available organic material contained therein. The
undigestable material is then regurgitated. The species for which
Luidia has shown a preference include other echinoderms, especially
ophiuroids, foraminfera, and molluscs. Analyses of stomach contents
made by other investigators indicate a good preference of Luidia for
gastropod molluscs over pelecypods, an almost direct contradiction
to the preference seen in most other starfish. This stands to
reason, however, since Luidia lack the eversible stomach necessary
for the successful predation of bivalve pelecypods. The ability of
Luidia and any other asteroid echinoderm to locate prey is dependent
largely upon luck, but starfish possess a strong attractant mechanism
whereby they are drawn to potential prey by concentrations of prey-
emitted chemicals in concentrations as small as parts per billion.
It has also been shown that increased amounts of the chemical will
significantly increase the attraction of the starfish to the prey.
Blumer (1969) has suggested that the longer chain, higher boiling
aliphatic hydrocarbons mimic natural attractant stimuli.
The extreme abundance of Luidia along the northwest transect
may possibly have been due to the attraction by ophiuroid echinoderms
and gastropod molluscs. However at the time of the study population
depletion as may be seen in Figures 4.14 and 4.22 resulted in
concentrations of Luidia which were inversely proportional to the
population densities of both ophiuroids and gastropods.
4-37
-------
The presence of high concentrations of long chain aliphatics
in the sediments along this transect add another possibility. If the
theory proposed by Blumer (-ibid. 1969) is true, it is then possible
that these starfish may have been drawn by false chemical stimuli.
If such is indeed the case, then the low taxonomic diversity shown
in Figure 4.13 for the northwest transect would appear to indicate a
probable stress on the environment for the transect. The numerical
resurgence along this transect (Figure 4.14) would then indicate the
possible beginnings of a recovery phase.
North transect catch data exhibits an extreme anomoly. Both
ophiuroid and gastropod populations show a numerical increase away
from the rig, but the expected higher numerical concentrations of
Luida, although minimally present at mile 2, fail to materialize
(Figure 4.19). At the mile 3 station, the life zone is almost devoid
of any species and Luida, ophiuroids, and gastropods are completely
absent. Normal benthic inhabitants, such as polychaete annelids
and the pelecypod molluscs, are also greatly reduced (Figure 4.14).
A possible explanation for this apparent distribution anomoly may
be found in Figure 4.5. Between the platform and the mile 3 station,
the long chain aliphatic hydrocarbons were present in the sediments
in quantities sufficient to be potentially toxic. These concentrations
decrease sharply between the mile 3 and mile 4 stations. At
about this same location, the incidence of aromatic hydrocarbons
and a noticeable surface sheen were observed. The toxicity of aro-
matic hydrocarbons has been repeatedly documented and one would
expect a depression in both numerical populations and taxonomic diver-
sity. As may be seen in the Figures 4.13 and 4.14, this is. indeed the
case.
Stomatopod populations are another valuable indicator of
differential environmental stress, since the adults are burrowing
benthic organisms, while the larvae are planktonic in the water
column above the bottom. The stomatopods (adult and larval forms)
are almost uniformly absent from the north transect, as might be
expected from the heavy hydrocarbon concentrations previously
discussed. Along the northwest transect, however, the increase in
numerical abundance of stomatopods is quite noticeable (Figure 4.14).
It should be noted, however, that all of the stomatopods taken within
4 miles of the rig were larval and no evidence of either settling
of larvae or indigenous adults in the sediments could be found. This
is in contrast to the large numbers of adults found in the sediments
farther out along the transect. The absence of stomatopods in the
sediments within 4 miles is a strong indication of severe environmental
stress in the area, since they occur in all surrounding sediments
and are quite numerous beyond the "sterile" zone. The presence of
larval stomatopods in such large quantities in the water column
above these "sterile" sediments, however, is an indication that this
portion of the transect is normally subject to larval dispersal and
repopulation. The failure of successful repopulation evidenced by
the absence of adult stomatopods in these sediments indicates a con-
tinuing environmental stress in the sediments. The presence of
4-38
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stomatopod larvae, however,'attests to the potential recovery possi-
bilities, since the low-boiling aromatic hydrocarbons - the toxicants
that would be present in the water-column - are particularly toxic
to planktonic larvae. These toxicants were therefore reduced or
absent.
Pelecypod molluscs were not abundant along any of the north
and northwest transects but were nominally present along the south
transect stations. The predominant pelecypod near the rig was
Corbula swiftiana. Farther out along the south transect, however,
Corbula populations were gradually replaced - first, by Nuolana
and then by Tellina (see Appendix II). This represents a
fairly normal faunal succession from clay to sandy bottoms.
Along the northwest transect, the pelecypod populations were
uniformly low (Figures 4.3 and 4.14), but it appears the tendency was
for Tellina to increase as the transect neared shore. Along the
north transect, there was essentially no pelecypod population near
Platform B (Figure 4.14), but the numbers tended to increase with
increasing distance from the platform. At miles 3, 4, and 5, the
predominant pelecypods were Tellina^ with the population peak at
mile 4. Beyond the 5 mile station, the Tellina populations appear to
be replaced by Nassarius and Mulinia. Both of these latter species
are euryhaline organisms with a habitat preference for sandy-mud
bottoms and are characteristic of inshore and bay entrance biotopes.
The significance of the pelecypod populations is related to
the habitat selection and behavioral feeding responses characteristic
of Tellina. Tellina maintains a definite sphere of influence and,
when crowded, will migrate to less dense areas or, if unable to do
so, will exhibit growth anomolies. The Tellina is typically a sandy
bottom inhabitant but will move into partial mud bottoms when forced
to do so. A fairly hardy organism, the Tellina will actively move
away from its neighbors v/henever the population density is lessened
in an adjacent region.
Since normal concentrations of Tellina have been shown to
be approximately 250/m2 and, since the numbers of Tellina collected
along the north transect fall on or above this value (while numbers
of other species are reduced), these numbers would tend to indicate
that Tellina had migrated into the area. This possibility is also
supported by the fact that the substrata in which they were found
was mud or sandy mud, a substrata that is not one of preference for
Tellina. One would normally expect to find Maooma or Mulinia to be
the predominant organism in this area.
This was the case at the extreme end of the transect
indicating the Mulinia was the normal inhabitant. For some
reason, it had disappeared and been replaced by Tellina.
Significant conclusions regarding the fish populations in
and around the study area were not possible to derive because of
4-39
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their natural mobility and seasonality, and because of the possible
impact of noise and activity levels on the populace. It is of
interest to note, however, that those areas along the transects which
theoretically showed environmental stress exhibited fish populations
lower than areas showing lesser stress. The area immediately
around the platform was almost devoid of fish (Figure 4.15).
It has been established that various petroleum fractions
are, in general, toxic to pelagic marine species. Because the
investigation of sediment hydrocarbons revealed relatively high
concentrations, and such concentrations corresponded with the
location of observed surface sheens, it was hypothesized that
significant quantities of hydrocarbons would be found throughout
the water column in these locations. This resulted in the decision
to conduct histological examinations of fish taken from the study
area; with such examinations validated with control specimens
taken from Aransas Bay, Texas; an area comparable, both physically
and biologically, to the study area.
4.2 Histological Comparisons of Branchial Gill Filaments
Taken From Fishes
4.2.1 Introduction
In higher fishes, the gill pouch is a passageway from the
pharynx directly to the outside through gill slits or through a
gill chamber covered by the operculum. The mucous membranes of
the anterior and posterior walls of each gill pouch are raised
into a number of horizontal ridges called branchial filaments.
The branchial pouches consist of an arch bearing the posterior
filaments of one pouch and the anterior filament of the next.
(Lagler, Bardach, and Miller, 1962). The fundamental histological
structure of branchial filaments consists of a low, single-layered
epithelium surrounding the basic filament. The blood vessels
are lacuna (round) or sinusoidal (irregularly-shaped) in nature,
and are supported (kept open) by connective cells called "pillar
cells." Mucous-secreting cells are common and are scattered along
the filament. (Patt and Patt, 1969). Covered pseudobranchs
contain many acidophilic secretory cells which are presumed to be the
sites of production of carbonic anhydrase-like enzymes. These acido-
phi Is are located on the side of the branchial filament supplied by
afferent capillaries (Andrew, 1959). In addition, those fish adapted
to sea water possess an "excretory vesicle" at the free surface of
the epithelial cell (Bevelander, 1935).
4-40
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4.2.2 Experimental Procedure
4.2.2.1 Specimen Selection
Specimens were collected from three transects radiating out-
ward from Shell Platform B, Block 26. The transects ran south, north,
and northwest from the platform. Representative specimens from seven
species of fish were randomly selected from each transect station
near the platform. Thin section tissue slides of the first gill
arch from each specimen were prepared using mictrotome techniques
and a paraffin mount. The preparations were stained with Oela-
fields Hematoxylin and counterstained with Eosin. These histolo-
gical slides were compared with preparations of similar tissue taken
from specimens from a control location (Aransas Bay, Texas).
4.2.2.2 Control Specimens
Gill filaments were considered to be of greatest importance
since they are sensitive to environmental stress. Table 4.1 lists the
species and place of capture of the test and control specimens examined,
The specimens from the south transect exhibited no apparent
abnormal loss of gill tissue compared to control specimens. Certain
abnormalities were found to occur, however, in fish from the north
and northwest transects. These abnormalities are illustrated in
Figures 4.23A and 4.23B.
The specimen from SPMW-17 (161A) Anaylopsetta, showed a loss
of: (1) epithelial, (2) mucous-secreting cells and (3) some acidophils
(Figure 4.24A). "Normal" branchial filaments are ragged in appearance,
as is shown in the control specimen (Figure 4.24B). The control
exhibits loosely arranged cells between each filament. In the
specimen from the spill zone these cells are absent or significantly
reduced in numbers. The loss of these cells is termed "sloughing"
and could result in certain physiological changes discussed
later. The remaining cells in the damaged filament appear to
be slightly swollen and caused the "blurred" photographic response.
Specimens of Miaropogon (Figure 4.25A,B) exhibited similar
cellular alterations as those found in Ancylopsetta Again, the
tissue from the control fish was normal with a typical ragged
appearance (Figure 4.25A). However, the specimen from the spill area
(SPNW-16, sample no. 154B) exhibited the following abnormalities:
(1) swollen branchial filaments, (2) definite loss of epithelial
cells and (3) noticeably fewer mucous cells (Figure 4.25B). This
loss of cells was not as pronounced as that found in Ancylopsetta
4-41
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Table 4-1
Test Specimens
SPECIES
COLLECTION SITE
Ancylopsetta quadrocellata
MioTOpogon undulatus
Etropus orossotus
Prionotus tribulus
Chloroscombrus chrysurus
Chaetodipterus faber
Aransas Bay
SPNW-17-161A
Aransas Bay
SPNW-16-154B
Aransas Bay
SPN-8-144B
Aransas Bay
SPS-1-36
SPN-8-114
SPN-1
4-42
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Blood cells i
lamellar vessels
Epithelial cells
Pillar cells
Blood cells in
capillaries
Acidophil
Cells
Mucous Gland
Cell
Figure 4.23A Typical Telcost Branchial Filament
Note loss of
Epithelial
Cells
Blood cell
Figure 4.23B Example of Branchial Filament which
has lost some tissue
4-43
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••
'
-
I
Ancylopsetta quadrocellata
Aransas Bay
Figure 4.24A Normal branchial filament from Ancyclopsetta.
Note cells between each filament(arrows),
mucous cells (M), pillar cells (P) and
acidophilis (A).
4-44
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s
X V
.-•
. ,.&"
Ancylopsetta quadrocellata SPNW-17- 161 A
Figure 4.24B Branchial filament from Anayclopsetta taken
near Shell Platform.
Note loss of epithelial cells (sloughing)
between the filaments, giving a rather
"clean" appearance. Also, note swollen
Filaments (S).
4-45
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,
• , i '
, :
*• •
\~f
I
*
.-»•
t •
•
I
-
"
-
. v.
V
t
- , • v • "•
* '*£• '>' : * ..-'
^a^i -».' -v*^ : ••. * - -;; • »
*^^ ' • X
-X^Xf^ v v
' - ^^, ~* 'v- - " - ^ ^ V
<•:<"*'>•'"*•$ .r .
-
'-
-------
" ^.
'
V
Micropogon undulatu'-
SPNW 16-154 B
Figure 4.25B Note washed-out appearance due to sloughing (arrows)
and swollen filaments (S).
4-47
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(Figure 4.24B). Mioropogon is a fast-swimming, shallow or mid-water
fish capable of moving away from adverse conditions. Anoylopsetta
is a slow-swimming bottom-fish easily affected by environmentally
induced physiological stress. The loss of tissue was evident in
both specimens.
Another bottom-dwelling fish, Eutropus erossotus, was exam-
ined from Station SPN-8 (sample 144B). A control specimen of this
species from Aransas Bay showed no gill damage (Figure 4.26A,B).
Swelling coupled with loss of epithelial cells was also observed.
Mucous cells were present in reduced numbers and the filament had a
"smeared" appearance as though it were soft from degeneration.
A specimen of Prianotus tribulus was taken from the south
transect of the oil spill area. No pathological alterations were
observed in histological preparations from this specimen (Figures
4.27A.B).
Finally, specimens of Chloroscombrus (Figure 4.28A) and
Chaetodipterus (Figure 4.28B) were examined histologically and found
to be normal; with the possible exception of slight swelling and
minor epithelial sloughing in Chloroscombrus.
4.2.3 Discussion
Specimens 114 A and 114 B were taken from station SPN-8 lo-
cated 3 miles north of the Shell Platform B in the wake of the oil sheen.
Spill data indicated that the oil was being redispersed to the water
column from sediments in this area hence, bottom swimming fish would
be in contact with these redispersed petroleum fractions. Histo-
logical preparations from the gills of these two specimens were com-
pared with those of the same species taken from Aransas Bay, Texas
(control specimens). Gill filament epithelium from the fishes taken
near the Shell Platform had sloughed away in several areas.
The filament taken from Eutropus crossotus in Aransas Bay
was intact and showed no apparent sloughing. Preparations from fish
gills near the Shell Platform exhibited a definite loss of acido-
philic and mucous cells. Control and experimental specimens of
Miaropogon widulatus (154B, from station SPNW-16, 4 miles northwest
of the platform in the vicinity of the oil sheen and a specimen from
Aransas Bay) yielded similar data; a loss of epithelial tissue; how-
ever, other cell losses from this specimen were not evident and the
control specimen was unaltered. Specimens examined from the south
transect near the Shell Platform where there was no evidence that
redispersion was occurring showed no apparent cell loss.
The alterations of branchial filaments discussed herein
may produce certain physiological malfunctions. The loss of sufficient
4-48
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Figure 4.26A Normal Etropus from Aransas Bay.
Note many mucous cells (M) , acidophils (A) ,
Epithelium (E).
4-49
-------
•
V
Etropus crossotus
SPN 8 144 B
Figure 4.26B Shell sample Etropus. Note swelling (arrows),
fewer mucous cells (M) .
4-50
-------
M
x
•
•
Priontus tribulus
Aransc s Bay
Figure 4.27A Prionotus - South transect from shell platform
Acidophils (A) , mucous cells (M) , Pillar cells
(P) - intact.
4-51
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Prionfus tribulus
—. SPS 1-36
Figure 4.27B Prionotus - Aransas Bay, Acidophils (A), mucous
cells (M), pillar cells (P) - all intact.
4-52
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A
X
Chloroscrombus chrysurus SPN 8-1
Figure 4.28A Chloroscombrus - South transect. All cells intact,
Acidophils (A) , Mucous (M), and Pillar cells (P) .
4-53
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1
•
„
Chaetodipterus faber
SPN-l
'"*>
Figure 4.28B Chaetodipterus - South transect. All cells intact.
Acidophils (A), Mucous (M) and Pillar (P)
4-54
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acidophlls will reduce the production of carbonic anhydrase-like
enzyme (secreted by these cells). This enzyme deficiency may lead
to pH changes in the blood and tissue fluids (acidosis or alkalosis)
through a reduction in the rate of dissociation of carbonic acid into
C02 and hence a malfunction of the blood-buffer system.
Loss of mucous cells may result in the clogging of
the filaments with detretus. Resultant irritation of the filament
may produce epithelial sloughing as that seen in test specimens.
These data are not conclusive with regard to the impact of
petroleum fractions on pelagic megafauna because of the migratory
nature of these animals; however, the observed damage raises certain
critical questions which deserve further investigations under con-
trolled laboratory conditions. Laboratory studies using sublethal
quantities of oil and histological techniques should be incorporated
into studies on the fate and effects of marine oil spills. Standard
T^M tests coupled with autopsies of terminal animals and histological
procedures are also indicated. Such studies would establish direct
cause-effect relationships and establish correlations with such alter-
natives as viral, fungal, bacterial or parasital contributions
(including possible inducement by effects of oil).
4-55
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5.0 Conclusions
From the data acquired and the analyses conducted, a
number of meaningful conclusions can be drawn. From these con-
clusions and experience gained in the performance of this study,
the following can be accomplished:
• Achieve better understanding of the specifics of
the fate and effects of the incident under study;
t Extend the body of knowledge of the fate and ef-
fect of such spills, in the areas affected, and,
in the Marine Environment as a whole;
• Enhance the value of future studies of this nature
by refinement of techniques and procedures.
Analysis and evaluation of data, acquired during this
study on the fate and the effects, of the Shell incident at Plat-
form B, Block 26, has been discussed in Section 4.0 of this re-
port. Specific conclusions reached in the performance of the
analyses and data gathering are summarized in this section.
5.1 Fate of Spilled Oils
Data presented in Section 4.1 of this report suggests
that water-dispersable fractions (probably aromatic compounds)
from the crude oil spilled were transported through the water
column and deposited in sediments at least to the observed depths
of sixty feet (601). It has also been established that these
deposits become redispersed into the overlying waters. Correlation
has been established between the locations of these sedimentary deposits
and the surface locations of slicks and sheens throughout the areas
of migration of the spill oil.
The sedimentary deposits of crude oil contained signif-
icant quantities of Carbontetrachloride Extractable Hydrocarbon
(CC1* extractables) as represented by the Aliphatic Hydrocarbons.
In fact, sediments near the platform (source of the spill) were
found to contain in excess of 4.5 ppt compared to about 300 ppm
one mile from the platform and between 50 and 100 ppm at a dis-
tance of four miles. However, in the area of an observed sheen,
as far as 7 miles from the source, sedimental CC1* extractables
were again found at levels of concentration in excess of 300 ppm.
These data may be influenced by oil dispersants to the extent
dispersants were introduced during the spill.
5-1
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The water dispersable Hydrocarbons were probably aromatic
compounds, highly soluble in salt water and therefore more bio-
logically accessable. Although representing only a small percen-
tage of the released aromatics, the majority of which dissipated prior
to settlement, the apparent cycling from the water column to sediments
and back to the water is potentially damaging to the ecosystem.
Benthic populations may be damaged by these transient
materials which are redispersable and may not be detectable within
brief periods after deposit. Similarly, pelagic and benthic organ-
isms may be adversely effected by these processes of free movement
of both the aliphi tics and water dispersable hydrocarbons. Both are
potentically toxic to the pelagic and benthic communities.
5.2 Effect of Spilled Oil
Assessment of the effect of the spilled oil was based
on an evaluation of the sampled (or observed) ecosystem; a compari-
son of species diversity, and distribution; and examination of
specimens, both in the field and in the laboratory. To the ful-
lest extent possible applicable background data available in
literature and data acquired during earlier studies in the area of
Platform B (December 1970 studies) have been utilized in the
studies reported herein. The results of these investigations and
the conclusions reached are summarized in this Section.
5.2,1 Species Diversity
Data yielded by Van Veen grab sample resulted in little
or no 'correlation of the numbers of species present with any
other parameters. The single exception of this was a direct,
although poorly defined, relationship between dominance diversity
and hydrocarbon concentrations in sediments. This is reflected
by the increased, simple diversity of megafauna found in samples
in the South and Northwest transect over the North transect
which corresponded to the direction of movement of the spill.
5.2.2 Distribution of Fauna (Meiofaunal and Megafaunal)
Fauna! counts from bottom sampling were low at and
immediately around the rig with 13,000 per square meter of less
within a one mile radius. Between one and two miles, general
5-2
-------
numerical increases were found. In the South transect, the
highest faunal count of 32,000 per square meter occured at the
two mile mark. In the North transect, a high count of 48,000
per square meter was found at the four mile mark, with a steady
and marked decrease at greater distances. In the Northwest tran-
sect, intermediate numbers were encountered, however, distinct
alterations in population diversity and distribution was noted.
Grab sample megafaunal counts significantly diminished
from all directions as they approached the platform. A generally
inverse relationship between megafaunal counts per square meter
and the concentrations (ppm) of sedimental hydrocarbons (CC1.
extractables) was found. Within the first three miles along the
North transect where the highest sedimental hydrocarbon concentrations
of the three transects were found, the lowest grab megafaunal were
recorded. In the northwest transect, where sedimental hydrocarbons
were present in the intermediate amounts, grab megafaunal counts were
intermediate to the other two transects. Finally, along the south
transect where sediment hydrocarbons were the lowest, organism
counts were the highest.
Examination of trawl sample catch data revealed dis-
tinctly anomolous distribution and density patterns for the
scavenger starfish, Luidia Clatfoata. Distribution patterns
remained similar in the south and northwest transects; with
higher densities in the northwest and moderately reduced den-
sities in the south. However, in the north transect significant
anomalies occur. These anomalies; typified by the highest con-
centrations at miles 2 and 4 with a population void at mile 3,
establish that concentrations are being controlled by some ex-
ternal factor.
Analyses of these phenomena reveal that the relatively
uniform concentrations along the south transect are very close to the
normal expected populations. Along the northwest transect, the
density far exceeds that normally expected while the numbers en-
countered in the north transect fell below the normal population.
Because salinity is known to affect the density of Luidia; an
analysis was conducted and the recorded salinity ranges of all
areas studied were found to fall within the tolerance range of
the Luidia. This factor was thus dismissed as a possible cause
of the anomalies.
Since salinity was not determined to be the depressant,
other possible causal factors were considered. The bottom sedi-
ments in the study area were found to be silted mud with a mod-
erate amount of sand deposition; again within the tolerance,
range of the Luidia. This was, therefore, also discounted as a
limiting factor on the populations.
5-3
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The possible effect of food availability was considered
in terms of food preference as opposed to the occurrence of
preferential foods in the sampling area. The Luidia feeds.by
ingesting large quantities of sediment and benthic organisms
and utilizing all available organic material so ingested; sub-
sequently regurgitating the undigestables. Preferences include
other echinoderms, especially ophuiroids, foramenfera, and mol-
luscs; with a sharply defined preference for gastropod molluscs
over pelecypods. Although primarilly locating prey by chance
encounter in its foraging; prey-emitted chemicals appeal to a
strong attraction mechanism and entice the Luidia to the better
feeding grounds. An extension of this concept opines that longer
chain, higher boiling aliphatic hydrocarbons mimic natural at-
tractant stimuli and thus attract the Luidia to areas of higher
than normal hydrocarbon concentrations.
Based on these premises, an evaluation of the impact
of food availability on areal densities was made. This eval-
uation led to the following conclusions:
1) The extreme abundance of Luidia along the north-
west transect is inversely proportional to the population den-
sities of both ophiuroids and gastropods. The presence of high
concentrations of long chain aliphatics in the sediments along
this transect was revealed by sampling thus, based on the premise
that Luidia are attracted by prey-emitted chemical stimuli
which is mimicked as false chemical stimuli by long chain aliphatics,
the low taxonomic diversity for the northwest transect would
appear to indicate an oil induced stress on the environment for
the transect. The numerical resurgence at greater distances
along this transect would then indicate the beginnings of a
recovery phase.
(2) North transect catch data exhibits an extreme
anomaly. Both ophiuroid and gastropod populations show dra-
matic increases at greater distances from the rig, but the
expected higher concentration of Luidia* although minimally
present at mile 2, fails to materialize. At the mile 3 station,
the life zone is almost devoid of any species and Luidiat
ophiuroids, and gastropods are completely absent. Normal
benthic inhabitants, such as polychaete annelids and the pelecypod
molluscs, are also greatly reduced. A possible explanation for
this depressed state may lie in the concentrations of long
chain alipatic hydrocarbons in the sediments; quantities suf-
ficient to be potentially toxic. These concentrations decrease
sharply between the 3 and 4 mile stations where the incidence
of aromatic hydrocarbons and noticeable surface sheen were ob-
served to terminate. Because the toxicity of aromatic hydro-
carbons has been established a depression in both numerical pop-
ulations and taxonomic diversity can be expected.
5-4
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3) Stomatopod populations were also evaluated and found
(in both adult and larval forms) almost uniformly absent from the
north transect. This is as expected in view of the heavy hydrocarbon
concentrations. Along the northv/est transect, however, the
increase in numerical abundance of stomatopods is quite marked.
However, all stomatopods taken within 4 miles of the rig were
larval and no evidence of either settling of larvae or indigenous
adults in the sediments could be found. This is in contrast to
the large numbers of adults found in the sediments farther out
along the transect. The absence of stomatopods in the sediments
within 4 miles is a strong indication of severe environmental
stress in the area. The presence of larval stomatopods in such
large quantities in the water column above '"sterile" sediments
is an indication that the area is normally subject to larval
dispersal and repopulation. The failure of successful repopu-
lation evidenced by the absence of adult stomatopods indicates
a continuing environmental stress, although the presence of larvae
attests to a potential recovery.
4) Pelecypod molluscs were not abundant along any of
the north and northwest transects but were nominally present to
the south. The predominant pelecypod near the rig was Corbula
swiftiana. Farther out along the south transect, however,
Corbula populations were gradually replaced - first, by
Bucula and then by TelHna.
Along the northwest transect, the pelecypod populations
were uniformly low with a tendency for TelHna to increase nearer
shore. Along the north transect, there was essentially no
pelecypod population near Platform B with increasing numbers
farther from the platform. At miles 3, 4, and 5, the predominant
pelecypods were TelHna, with replacement by Nassarias and Mulinia
beyond the 5 mile point.
Because the major anomalies evolved around the TelHna,
analysis involved its habitat selection and behavioral feeding
responses. The TelHna maintains a definite sphere of influence
and, when crowded, will migrate to less dense areas. Typically
a sandy bottom inhabitant, the TelHna will move into partial
mud bottoms when forced to do so. Normal concentrations of
TelHna have been shown to be approximately 250/m . Since the
numbers collected along the north transect were equal to or greater
than normal (while numbers of other species are reduced), the
conclusion can be drawn that TelHna had migrated into the area.
This conclusion is also supported by the fact that bottom sediments
were mud to sandy-mud, not a preferred habitat of the
TelHna. Thus TelHna replaced the Macoma or Mulinia\ normally
the predominant organism in the area.
5) Significant conclusions regarding fish populations
"were not practical because of their natural mobility and seasonality.
5-5
-------
However, those areas along the transects in which other
evidence showed environmental stress exhibited very low fish
populations, while the area immediately around the platform was
almost devoid of fish.
5.2.3 Histological Data
On the basis of the significant evidence resulting
from the analyses previously discussed, it was concluded that an
oil-induced stress of unknown origin existed in the environment partic-
ularly in the vicinity of oil sheens at 4 to 6 miles north and
northwest of the platform. To test this conclusion, histological
examinations were conducted to determine if fish taken- from the
vicinity of the oil sheens would show signs of gill damage. A series
of histological studies were performed on the gills of different
species of fish in both a control group taken outside the spill
area and on specimens captured at the sampling stations located
at the scene of the spill. The gill filaments of fish are con-
sidered important because they are sensitive to contaminants
and thus are reliable indicators of environmental stress. Thin
section tissue slides were made of randomly selected specimen
fish collected along the three transects.
Specimens examined from the south transect exhibited
no abnormalities when compared to control specimens. Tissue
slides of fish specimens from the north and northwest transects,
however, showed loss of cells, "sloughing" and swollen branchial
filaments, symptoms of environmental stress. Because of the direct
correlation between sedimental hydrocarbon content and locations
of observed surface oils and the locations where test specimens were
taken; it is highly probable that the indicated environmental stress
is the result of toxic hydrocarbon fractions within the water column.
5-6
-------
6.0 Bibliography
In the performance of sampling and analyses, and in
the compilation of this report, numerous findings and data
from previous publications have been used. Those publications
are listed, alphabetically, in this section.
6-1
-------
Andrew, W. 1959, Textbook of Comparative Histology. Oxford
University Press. New York.
Attaway, D. and P. L. Parker. 1970. Sterols in recent marine
sediments. Science. 169: '674-75.
Barnes, R. D. 1968. Invertebrate Zoology. 2nd. ed. W. B. Saunders
Co., Philadelphia.
Bell, B. M. and R. W. Frey. 1969. Observations of ecology and the
feeding and burrowing mechanisms .of Mellita quinquiesperforata.
J. Paleon. 43(2):553-60.
Bevelander, 0. 1935. A comparative study of the branchial
epithelium in fishes, with reference to extrarenal
excretion. J. Morph. Vol. 57 (2). pp. 335-51.
Blanton, W. G., T. J. Culpepper, H. W. Bischoff, A. L. Smith, and
C. J. Blanton. 1971. A study of the total ecology of a secondary
bay (Lavaca Bay). Alcoa Project # TA-691350.
Blumer, M. and W. D. Snyder. 1965. Isoprenoid hydrocarbons in recent
sediments. Presence of pristane and probable absence of phytane.
Science. 150: 1588-99.
Blumer, M. and D. W. Thomas. 1965. Phytadiences in zooplankton.
Science. 147: 1148-49.
Blumer, M. and D. W. Thomas. 1965. "Zamene" Isomeric C,g monoolefins
from marine zooplankton fishes and mainmals, Science. 148:370-71.
Blumer, M. 1967. Hydrocarbons in digestive tract and liver of a
basking shark. Science. Vol. IV. 390-91.
Blumer, M. 1969. Oil pollution of the ocean, in. Oil on the Sea3
ed. by D. P. Houlte. Plenum Press, New York: pp. 5-13.
Blumer, M, G. Souza, and J. Sass. 1970. Hydrocarbon pollution of
shellfish. Marine Biology 5: 195-202.
Blumer, M. 1971. Man's Impact on Environment. McGraw-Hill, N. Y.
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