x>EPA
United Slates
Environmental Protection
Agency
Office of
Water Procjram Operations
Washington, DC 20460
EPA 430 9- 79-014
Water
Oil Spill
Bahia Sucia, Puerto Rico
18 March 1973
Environmental Effects*
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OIL SPILL
BAHIA SUCIA, PUERTO RICO
18 MARCH 1973
ENVIRONMENTAL EFFECTS
Contract 68-10-0542
TRC Project 62284
July, 1975
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EPA REVIEW NOTICE
This report has been reviewed by the Office of Water Programs, EPA, and
approved for publication. Approval does not signify that the contents
necessarily reflect the views and policies of the Environmental Protec-
tion Agency, nor does mention of trade names or commercial products con-
stitute endorsement or recommendation for use.
ii
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ABSTRACT
The following surveys were done to assess the impact of oil that was
spilled in the vicinity of Cabo Rojo, Puerto Rico. The first survey be-
gan within a week of the spill and the second was done three months later.
There was a pattern to the behavior of the oil and its effect. Regard-
less of ecological domains, e.g., mangroves or Thalassia beds, the oil
first affected the epibenthic and intertidal communities. The oil pene-
trated the sediments shortly after the spill but the impact on the benthic
infauna was not clearly seen until three months following the spill.
This report was submitted in fulfillment of Contract 68-10-0542, Order
No. 68-01-1116, under the sponsorship of the Oil and Special Materials
Control Division, Office of Air and Water Programs, Environmental Protec-
tion Agency.
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FOREWORD
This report is the product of a scientific investigation conducted
to determine the short term impact of a major oil spill at Caho Rojo,
Puerto Rico. It is part of a series of reports on major oil spill inves-
tigations funded by the Environmental Protection Agency. A principal
objective of these investigations is to develop a background of knowledge
and understanding of methods and tools used in assessing the environ-
mental damage which can ultimately be applied for setting environmental
priorities in spill response and cleanup.
The Caba Rojo study provides an indication of some of the gross
effects which were observed within certain biological communities;
however, it points out the problems associated with not having ecological
baseline information available to use in assessing the impact of the oil
on biological populations. The report emphasizes the need for initiating
damage assessment activities immediately following an oil spill to detect
the immediate effects, particularly for tropical and subtropical marine
communities.
Hopefully, this report will provide insight for future impact assess-
ment activities to be conducted in accordance with the 1977 Amendments
of the Federal Water Pollution Control Act.
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CONTENTS
SECTION PAGE
ABSTRACT ill
CONCLUSIONS 1
RECOMMENDATIONS 3
INTRODUCTION 5
GENERAL OBSERVATIONS 9
Rocky Shores 10
Beach Areas 11
Mangroves 14
Thalassia 17
Hydrographic Conditions 17
Cleanup Operations 17
METHODS 19
Thalassia Beds 19
Mangroves 21
Statistical Methods 21
Chemical 22
RESULTS 23
Thalassia Beds 23
General Ecology 23
Epibenthic Community 23
Benthic Infaunal Community 30
Mangroves 30
General Ecology 30
Prop Root Communities 34
Benthic Infaunal Community 42
Fiddler Crab Habitats 42
Chemical Analyses 42
DISCUSSION 49
Thalassia Beds 49
Mangroves 50
Beach Cleanup Operations 50
REFERENCES 53
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FIGURES
FIGURE PAGE
1 Map of S. W. Puerto Rico 6
2 Location of Oil-Contaminated Sampling Stations .... 7
in Bahia Sucia, Puerto Rico
3 Photo of a Boat Path through Oil-covered Water .... 9
in Bahia Sucia
4A The Rocky Shore Zone at Cabo Rojo 10
4B The Rocky Shore Zone at Cabo Rojo 11
5 Beach Scene in Bahia Sucia - Survey I 13
6 Northward View of Beach Area during Survey II .... 13
7A Oil Film on the Water Near Mangroves 14
7B Intertidal Region of Prop Root Zone of the Red .... 15
Mangrove
8A Oil in Red Mangroves at Station G (Silt Mangrove) . . 15
Survey I
8B Characteristic Condition at the Thalassia and .... 16
Mangrove Control Stations
9 Trench-pit System for Oil Recovery 18
10 Sampling Station in Short Thalassia Beds - 19
Survey I
11 Thalassia Beds During Survey II 33
B-l Calibration of Infrared Spectrophotometer Using ... 59
Dilutions of Crude Oil from the Beach at Bahia
Sucia
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TABLES
TABLE PAGE
1 Physical Parameters of the Water at the Various ... 20
Stations
2 Summary of Density and Diversity 24
3 Survey I Macroinvertebrate Communities 26
Thalassia Stations Sampled by Walking Survey
of 39.0 mz
4 Survey II Macroinvertebrate Communities of .... 27
Thalassia Stations Sampled by Walking Survey
of 39.0 m2
5 Survey I Epibenthic Communities of Thalassia ... 28
Beds
6 Survey II Epibenthic Communities of Thalassia . . 29
Beds
7 Survey I Benthic Infaunal Thalassia Communities . 31
per 3,063 CM3
8 Survey II Benthic Infaunal Thalassia Communities . 32
per 3,063 CM3
9 Survey I Macroinvertebrate Community for 35
Mangrove Prop Roots
10 Survey I Microscopic Survey of Mangrove Prop ... 36
Roots
11 Survey II Macroinvertebrate Community for .... 38
Mangrove Prop Roots
12 Survey II Microscopic Survey of Mangrove Prop . . 39
Roots
13 Survey I Benthic Infaunal Mangrove Communities . . 41
per 3,063 CM3
14 Survey II Benthic Infaunal Mangrove Communities . 43
per 3,063 CM3
vii
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TABLES (Continued)
TABLE PAGE
15 Mortalities at Fiddler Crab Habitat, Survey I 44
16 Field Survey I - Total Hydrocarbon Concentrations ... 45
in ppm of Oil in Samples
17 Field Survey II - Total Hydrocarbon Concentrations . . 46
in ppm of Oil in Samples
viii
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CONCLUSIONS
1. The epibenthic communities in the Thalassia beds and in the man-
groves, and intertidal communities of mangrove prop roots were among
the first to show the effect of the oil by an initial mortality to
the population. Three months later there was a noticeable recoloni-
zation in the epibenthic communities of the Thalassia and a slight
recolonization in the mangroves.
2. Benthic communities under Thalassia and mangrove were affected
initially by the oil, and showed major losses of individuals and
diversity three months after the oil spill.
3. The appearance of beach sand indicated that the beach cleanup opera-
tions were partially successful. However, oil remained below the
beach surface and oil sheens were still visible on the water near
the beach after three months.
4. In Survey I, the heavy losses of crabs indicated that the oil dis-
turbed their habitat. A census made three months later on the site
indicated that fiddler crabs of various sizes were repopulating the
area.
5. Infrared analysis showed that during the three-months between sur-
veys, there was a considerable reduction in hydrocarbon concentra-
tion at all stations, except in the sediments of the Thalassia beds,
in the sediments of the north and south mangrove areas, and in the
mangrove silt.
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RECOMMENDATIONS
1. Trenching and pits are efficient methods of oil recovery, and can be
improved by lining the trenches and pits to prevent oil seepage into
subsurface sand.
2. More boom should be employed to prevent oil drifting with unexpected
wind shifts, and to corral the oil as quickly as possible.
3. Beach harrowing and sorbents are very inefficient and possibly det-
rimental to biota.
4. Short-term biological assessment should begin promptly after a spill,
and must be followed by later assessments to determine if immediate
effects are important or lasting.
5. Follow-up studies should be done to determine the long-term effect
of oil on the various communities in the Cabo Rojo area.
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INTRODUCTION
On 18 March 1973 a major oil spill occurred near Cabo Rojo, Puerto Rico.
The area where the spill was detected is designated by the X on Figure
1. VAST/TRC was requested by the United States Environmental Protection
Agency to carry out two field surveys to assess the acute biological dam-'
age caused by the oil in the two major ecological communities in this re-
gion: the Thalassia beds and the mangroves. The first study was done be-
tween 24 March and 17 May, 1973, while the second occurred between 30
June and 17 July, 1973, Since the oil came ashore in Bahia Sucia (see
Figure 2), this area was the principal study area.
The following is a chronological summary of events1 that transpired be-
tween the time when the accident was first reported and the arrival of
VAST/TRC personnel. The events are presented in a tabular form in Appen-
dix A.
At 1041 hr, 18 March 1973, local police advised the Captain of the Port
(COTP), San Juan, that the motor vessel, Zoe Colocotronis, had run
aground in the vicinity of La Paraguera, Puerto Rico. By 1430 hours,
the vessel's exact location was determined to be 17°54' N, 66°59' W,
close to a shoal area. At this time, a large oil slick was spotted ex-
tending from this position to a point two miles east of Cabo Rojo and
drifting towards the beach (see Figure 1). At 1145 hours that day, the
vessel's agent advised the COTP, San Juan, that the vessel had freed it-
self with no damages and was no longer spilling oil. The vessel was con-
tinuing to Guayanilla, ETA 1430 hrs, 18 March 1973. However, at the
same time, a U.S.C.G. helicopter observed that the vessel apparently dis-
charged oil to lighten its load. The vessel had stopped discharging oil
and was afloat under her own power. The approximate position was three
miles offshore from Phosphorescent Bay, a popular tourist attraction in
Puerto Rico. The vessel proceeded to the Commonwealth Oil Refining Com-
pany (CORCO) terminal and commenced offloading. The vessel, under char-
ter to Mobil Oil, was carrying 180,000 BBLs of crude oil from Venezuela
to CORCO. The oil was expected to come onshore somewhere between Cabo
Rojo and Punta Tocon some time during the evening of 19 March 1973. The
regional response team and local government officials were alerted. COR-
CO advised the COTP, San Juan, that Mobil Oil agreed to accept all clean-
up costs. Mobil Oil, however, failed to confirm this, so a pollu-
tion contingency fund contract number was assigned, pending positive as-
sumption of cleanup responsibility by one of the companies involved.
The Commonwealth of Puerto Rico planned to require the vessel to post
bond. At 0015 hrs, 19 March 1973, a USCG helicopter observed a very
thick oil slick ashore from Bahia Sucia to Cabo Rojo and offshore oil ex-
tended from La Parguera to El Combate. Winds were easterly at ten knots,
seas moderate. Cleanup operations involving ten men from Commonwealth
Public Works Department and 180 bags of sorbent were underway. At 0805
hrs, 19 March 1973, Captain Ramsey of Mobil Oil reported from Hess that
Mobil would pay all costs incurred and that he would be on the scene dur-
ing the afternoon of 19 March. By 0815 hrs, 19 March 1973, On-Scene Co-
ordinator (OSC) from COTP, San Juan, arrived with 100 extra bags of
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:S ."" ""70
Arrecife Tourmali
Bajas Gallardo'y
62 © 8 @| ,3 X
X - Siting of tanker after
the oil spill
Y - Thalassia controls
Z - Mangrove controls
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A Short Thalassia
B Thalassia flats
C Long Thalassia
D-l Main Beach area
D-2 Small Beach area
F South mangrove
G Silt mangrove
H North mangrove
L-l Western lagoon
L-2 Crab lagoon
M Upper mangrove area
R Rocky shore
S Shark Bay
Figure 2: Location of Oil-contaminated Sampling Stations
in Bahia Sucia, Puerto Rico
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sorbent and a 640 ft boom.
At 0915 hrs, 19 March 1973, the slick was sited on two shore locations:
(a) at the cliff face (67°11.0T W) and (b) east of Cabo Rojo between
67°11.6' W and 67°11.5f W, 17°57.6' N. Between 0940 and 1000 hrs on
the 19th, officials from the Commonwealth's Environmental Quality
Board (EQB) and the Department of Natural Resources made separate over-
flights. Regional EPA representatives arrived and were transported to
the scene at 1700. During the 19th, cleanup operations continued and
the vessel posted bond. However, the company had not accepted the re-
sponsibility. At 1630 hrs, 19 March 1973, a U.S.C.G. overflight revealed
that the slick moved north, parallel to the west coast of Puerto Rico.
On 20 March 1973, cleanup operations continued. The vessel's master,
crew, and logs were subpoenaed and a complaint against the captain,
M. Michalotoulis, was filed in U.S. District Court by EPA lawyers. An
arrest was to be made following EQB hearings. These hearings, which
were to determine the damage caused by the spill, began on 22 March
1973. The vessel's captain was arrested on the 23rd of March and was
released on bail that same day.
The VAST/TRC field survey team was activated by EPA Region II on 21
March 1973. On the following day, representatives of this team met with
Mr. Richard Dewling and Dr. Royal Nadeau for a briefing on the situation
at Cabo Rojo. The scope of the field survey, including chemical pro-
cedures, was outlined. The field team departed for Puerto Rico on 24
March 1973 and established a field base at the Nuclear Science Center,
University of Puerto Rico, Mayaguez.
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GENERAL OBSERVATIONS
A preliminary survey to determine the extent of oil contamination in the
Cabo Rojo area was made by our survey team on 24 and 25 March. The sur-
vey included the entire coastline between Cabo Rojo and La Parguera
(Figure 1). We observed that the heaviest concentrations of oil were
confined to the western portion of Bahia Sucia and that small amounts of
oil were washing ashore on the western side of Shark Bay, S in Figure 2.
Figure 3 demonstrates the general condition in Bahia Sucia. The dark
Figure 3: Photo of a Boat Path through Oil-covered Water in
Bahia Sucia. The photo was taken during the after-
noon of 31 March 1973. The dark line is oil-free
water. This view is towards Punta Molina.
line is a trail made in the otherwise oil-covered water by a small boat.
The view is across the Bahia towards Punta Molina. Some weathered oil
could be seen at the high tide line on the eastern side of Punta Molina.
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Rocky Shores
The rocky shore zone, R in Figure 2, along the seaward section of the
western shore of Bahia Sucia is primarily limestone cliffs. The rock
rubble at the base of the cliffs is both pitted and eroded (Figure 4A).
Figure 4A: The Rocky Shore Zone at Cabo Rojo. Photo taken
on 25 March 1973. Pitted rock rubble at the
base of the cliffs.
An oil-free zone extended along this shore from the tip of Cabo Rojo to
a point 400 m north along Bahia Sucia. Beyond this point, the vertical
faces of the cliffs were covered with a thick band of oil. The width of
the band varied from one to three meters, depending on the extent of the
splash zone. Figure 4B illustrates the conditions along the oiled rocky
shore line.
The surface of the water washing the rocks in the oiled zone was heavily
coated with oil. The oiled rocks were devoid of visible signs of life,
except for subtidal algae. It was not clear whether this condition
resulted naturally from the exposed nature of the habitat, or from the
presence of oil.
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Figure 4B: The Rocky Shore Zone at Cabo Rojo. Photo taken
on 25 March 1973. Oiled rocks in the north end
of the rock zone.
Beach Areas
The major beach area around Bahia Sucia was located at Dl on Figure 2.
The southern half section of beach confronted the largest concentrations
of floating oil in the entire Bahia Sucia. It was here where the effort
of oil recovery took place. (See Cleanup Operations section). This
beach was made of white, calcareous sand sloping gently up to the upper
end of the intertidal zone where there was a sand-filled narrow detrital
seagrass step about 20 to 30 cm. high. The terrain above this step was
sandy and mostly covered with sea grape. During the cleanup operations
large sections of sea grape vegetation were demolished to provide an
access road about 20 m. wide along the length of the oil-covered beach.
The intertidal beach section, as well as the offshore waters, were
thoroughly covered with oil during the duration of Survey I (Figure 5).
During Survey II (three months later) oil sheens could still be seen on
the water and oil-soaked sand was observed starting at 10 to 15 cm. be-
low the intertidal beach surface.
Biologically, the beach was considered to be less productive than the
mangroves or Thalassia beds and thus not selected as a sampling location
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due to the project's limited resources and the difficulty in finding an
area undisturbed by cleanup operations. However, physically the beach
probably became a significant storage and continuous, long-term, small
source of hydrocarbon to the offshore waters and the environs.,
North of the rocky shore near Cabo Rojo was a small beach area, D2 in
Figure 2. This beach had a narrow intertidal zone that was covered with
wrack (mostly detrital sea grasses). The beach itself had a shallow
berm which contained numerous crab burrows and some scrub vegetation.
The latter was comprised mostly of red and white mangrove, sea grape,
grass, and Badis. At the time of the first survey wind-driven oil had
completely covered the water along the beach shore for a relatively
short time, leaving a narrow band of oil, about 0.5 m. wide, along the
beach. We also observed a surface sheen of oil extending far offshore,
as well as tarry deposits on sandy shallows. Cleanup operations on this
beach consisted of raking and use of sorbents.
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Figure 5: Beach Scene in Bahia Sucia - Survey I. Photo
taken on 26 March 1973. There is extensive
litter and oil-covered water just off shore.
Figure 6: Northward View of Beach Area during Survey II.
Photograph taken on 1 July 1973.
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Mangroves
In Survey I, the water along the western shore of Bahia Sucia was
covered with a visible film of oil (Figure 7A). Oil penetrated a man-
Figure 7A: Oil Film on the Water Near Mangroves.
taken on 26 March 1973.
Photo
grove area situated along this shore (F, G, and H in Figure 2) and a
layer of oil covered the prop roots of these mangroves. Figure 7B
shows the oiled prop roots of the red mangroves in this area. There was
no visible sign of life on the intertidal portion of these prop roots
and the oil floating on the water surface was too thick to allow sub-
tidal observations (Figure 8A).
There was a lagoon located behind this mangrove area, L-l in Figure 2.
Oil penetrated this lagoon and covered both the water surface and the
intertidal zone. This zone was densely packed with crab burrows. We
did not observe any dead crabs nor were there any signs of fresh dig-
gings at the mouths of the burrows. Unoiled mangroves and Thalassia
beds were selected east of Bahia Sucia. These areas are designated by
Z and Y in Figure 1. Conditions in this control region are shown in
Figure 8B.
In Survey II the intertidal regions of the oiled mangroves were littered
with plant debris and were heavily silted. Deposits of dead Thalassia
had accumulated on the bottom adjacent to the South mangrove site. Many
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Figure 7B: Intertidal Re-
gion of Prop
Root Zone of
the Red Man-
grove . Survey
I at Station H.
Photo taken on
26 March 1973.
Figure 8A: Oil in Red Mangroves at Station G (Silt Mangrove),
Survey I. Photograph taken on 27 March 1973.
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Figure 8B: Characteristic Condition at the Thalassia and
Mangrove Control Stations.
March 1973.
Photo taken on 26
hydroids and sponges could be seen in this area and the latter were
attached to both the prop roots and substrate. There were many dead sea
urchins at this location. The calcareous alga, Halimeda, was abundant
on the bottom nearby the mangroves.
The benthos near the "silt" mangroves (G), was also littered with dead
Thalassia by Survey II. However, oil-coated Manatee grass (Syringonium
sp.) at this location was rooted and green; as were green algae and
Halimeda. There were still oil slicks evidenced on the water surface
and prop roots.
Field observations at the northern mangroves (H) suggested that oil
penetrated the sediments because our walking squeezed oil up from the
sand. Some dead Thalassia also accumulated in this location. However,
there was not a large accumulation of Thalassia detritus at the man-
grove control stations.
There is a second mangrove area in Bahia Sucia, M in Figure 2. During
the early stages of Survey I, this area was clear of oil. However,
during the first of April, there was a wind shift and oil was carried
from the southwest portion of Bahia Sucia north to this mangrove area.
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The oil penetrated the canals which intersected the shoreline, and
covered the banks of these canals. These banks had broad intertidal
zones which were densely packed with crab burrows. Consequently, the
intertidal zones were covered with oil. Heavy mortalities among at
least four species of crabs were then observed.
Thalassia
Shallow water (mostly less than 1/2 meter in depth) extended about 100
meters offshore from the beach (D2, Figure 2) to a small Porites reef.
The subtidal areas between the reef and the beach were covered with
turtle grass (Thalassia) interspersed with several other varieties of
sea grasses. Near the reef was a diverse faunal community associated
with the coral nodes. Organisms in this community included starfishes,
sea urchins, brittlestars, snails, limpets, and hermit crabs.
Within 50 meters of the beach the grass beds were occasionally broken
with sandy depressions which harbored schools of anchovies and small
wrasses. No starfish were seen in this zone. Several recently dead sea
urchins and some live ones which were losing their spines were picked up
along the shore. Within the intertidal area a dead oil-soaked sea cucum-
ber and a small dead lobster were found. The adjacent beach did have
some live hermit and sand crabs.
Hydrographic Conditions
Offshore water currents in the Cabo Rojo region are part of the North
Equatorial Current, and run westward, parallel to the coast. The annual
average magnitude is 0.14 m/sec. with small annual variations of approx-
imately 0.02 m/sec. One high and one low tide occur daily. The inter-
tidal zone is thus very small due to the tidal range of less than one
foot (30 cm ). Observations made at Bahia Sucia indicated a longer
duration of flood tide over ebb (the flood ran north and ebb ran south
at about the same magnitudes on the west shore), suggesting a possible
CW net flow along the shores of the bay.
The offshore water salinity varies 2 or 3 ppt. during the year and
averages 35.4 ppt. Surface water temperatures have a very small range
from 25°C to 32°C.
Winds in the semiarid Cabo Rojo region are from the southeast or east
southeast. The average annual rainfall is 30 inches (76 cm ), offset by
an annual average evaporation rate of 80 inches (203 cm ).
Cleanup Operations
There were two phases to the beach cleanup operations: (1) containment
by oil booms, and (2) recovery by a trenching-pumping method. During
containment, booms were deployed perpendicular to the beach. The oil
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would be corralled near the beach instead of drifting eastward along the
shore. However, on 1 April, there was a wind shift and the oil moved
south out of Bahia Sucia. The booms were relocated off the mangroves
along the west shore of Bahia Sucia to keep the oil in the mangroves
from spreading out into the bay.
The removal procedure consisted of trenches cut into the beach at right
angles to the shoreline. Oil flowing into these trenches was pumped
directly into tanker trucks (Figure 9). This method was an effective
and ingenious way of removing a large portion of floating oil blown
against the beach by prevailing winds.
Minor cleanup efforts with particulate sorbent materials were relatively
ineffective due to the small percentage recovery of the sorbent, and the
higher affinity of sand particles for the oil.
Figure 9: Trench-pit System for Oil Recovery. Photo taken
on 26 March 1973.
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METHODS
The west shore of Bahia Sucia was chosen for intensive study in Surveys
I and II. The specific study areas shown in Figure 2 include short
Thalassia beds (A), Thalassia flats (B), long Thalassia (C), and the
south (F), silt (G), and north (H) mangroves which were mentioned in the
previous section. The corresponding control areas were located well
east of the westward drifting oil (Y,Z Figure 1). Physical parameters
of temperature, salinity, dissolved oxygen, and specific gravity were
measured at each station (see Table 1).
Thalassia Beds
The three Thalassia study areas represented the seagrass beds typical of
Bahia Sucia. The southernmost station, Figure 2, was dominated by short
Thalassia. The grass was at an average depth of 15 cm below the surface
(Figure 10). Station B, the Thalassia flats, had numerous sandy depres-
Figure 10: Sampling Station in Short Thalassia Beds - Sur-
vey I. Photo taken on 27 March 1973.
sions and the area was partially exposed at low tide. The grass at this
location was short but it did not appear to be the same variety seen at
Station A. The third station, C, was in approximately one meter of
water. The substrate here was level and supported a tall Thalassia com-
munity. Two comparable control stations were established on an island
offshore from Isla Cueva (Z, Figure 1).
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TABLE 1
PHYSICAL PARAMETERS OF THE WATER AT THE VARIOUS STATIONS
o
LOCATION
Short
Thalassia 0
Short
Thalassia C
Long
Thalassia 0
Long
Thalassia C
Thalassia
Flats 0
North
Mangrove 0
North
Mangrove C
South
Mangrove 0
South
Mangrove C
Silt
Mangrove 0
Silt
Mangrove C
SURVEY I
SALINITY
0/00
38.5
39.6
37.5
38.0
36.8
39.0
37.3
30.5
37.3
39.0
38.4
TEMPERATURE
(°C)
31.0
30.6
30.5
30.0
30.0
32.1
27.0
31.2
27.0
32.5
30.0
DISSOLVED
OXYGEN
(ppm)
12.2
12.9
8.2
12.9
4.4
8.0
9.8
8.0
7.9
6.9
SPECIFIC
GRAVITY
1.024G
1.0250
1.0237
1.0240
1.0234
1.0246
1.0245
1.0249
1.0245
1.024:;
1.024')
SURVEY II
SALINITY
' 0/00
37.5
37.3
37.5
37.5
37.4
30.8
38.5
37.9
37.1
37.9
37.8
TEMPERATURE
(°C)
29.3
28.3
29.0
29.0
29.5
30.8
31.2
30.5
31.8
30.2
30.0
DISSOLVED
OXYGEN
(ppm)
9.2
13.8
8.8
12.4
8.8
9.3
13.8
13.9
13.9
12.4
10.9
SPECIFIC
GRAVITY
1.0240
1.0242
1.0240
1.0242
1.0240
1.0246
1.0240
1.0245
1.0240
1.0245
1.0244
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A stake marked the center of each station (see Figure 10). Macrofauna
and flora were identified and counted while walking or snorkling over a
six meter diameter around the stake. All macro-organisms within the
station were counted and identified. Smaller epibenthic organisms were
sampled by random placement of wire grids (25 cm x 19 cm). Organisms
within six such grids were collected and preserved for identification
and enumeration. All preservation was done by first fixing the sample
in 10% formalin for 24 hours, then transferring the sample to 70%
isopropyl alcohol. Infauna were sampled by taking three cores (10 cm
diam. x 13 cm deep) at each station, then screening through two mesh
sizes (1.5 and 1 mm). The coarse fraction (1.5 mm) was wet weighed and
sorted in the field laboratory. The fine fraction (1 mm) was stained
with Rose Bengal solution, preserved in 70% isopropanol and sorted under
dissecting microscopes in the laboratory.
Samples for chemical analysis at each station included one liter of
water (sampled at mid-depth and acidified in the field with 5 ml 1:1
H^SO,), one sediment core (6.5 cm diam. x 12 cm deep) of each grassy
area, and a sample of Thalassia. All samples were collected in glass
containers prepared by washing in carbon tetrachloride (nanograde MCC).
These samples were extracted in the field laboratory using the method
outlined in Appendix B. They were returned to the TRC chemistry labo-
ratory for infrared analysis.
Mangroves
The three stations were established in the oil-saturated mangrove com-
munity on the western shore (see Figure 2), two on the exposed side and
one in the leeward side of a mangrove island shown in Figure 7A. Com-
parable control stations were located near Isla Cueva (Y, Figure 1). At
each mangrove station, three prop roots which were not yet imbedded were
wrapped in aluminum foil to keep the root community intact. The roots
were cut off above the water level and sealed in plastic bags. At the
field station, the prop roots were soaked in alcohol, wrapped in alcohol-
soaked cheesecloth, and transported back to the laboratory where they
were frozen within 48 hours of collection. Infauna was sampled by
taking three benthic cores at each station and treating them as de-
scribed in Thalassia methods. One mid-depth water sample and one sedi-
ment core from each station were collected and analyzed as in the
Thalassia methods.
Statistical Methods
Our assessment of the effects of the spilled oil are based on compari-
sons of diversity and abundance both between the oiled and control stady
areas as well as between surveys. However, the taxonomic keys that were
available did not enable us to identify all our faunal and floral
samples to the same level of taxonomic specificity. In order to settle
on a taxonomic unit that would be applicable to all the communities we
studied, we developed the faunal group. This unit was the basis of our
-21-
-------
comparisons of faunal diversity observed at the various areas. We
define the faunal group as the most specific taxon that is common to all
animals that clearly belong to a particular taxonomic group. In most
cases, the faunal group was at the "family" taxonomic level.
The statistical comparisons of faunal group diversity between oiled and
control communities and between surveys are based on a test of dif-
ferences between the mean number of faunal groups observed at the re-
spective communities. The difference is used to calculate a statistic
called the student's "t." This statistic has a Gaussian or normal dis-
tribution similar to the distribution of observations about the mean of
a population and it is a tool to determine whether two independent
groups of observations are the same. To apply this test we lumped
all possible sources of variation in the biological communities, i.e.,
migration, seasonal changes, and the invasion of oil into the control
areas. A particular limitation on this statistical test is the sample
size. As will be seen in the following section, there were three
samples taken from a given community. Although this can introduce
errors into statistical comparison, it cannot affect the field observa-
tions. Consequently, our conclusions and recommendations are based on
the observed faunal diversity and abundance in the various communities.
Chemical
The methods used in our chemical analysis are summarized in Appendix B.
-22-
-------
RESULTS
Thalassia Beds
General Ecology
Thalassia or turtle grass is a common seagrass found along the Gulf
shore of Florida, down through the Florida keys and on the islands of
the Caribbean Sea. Its growth generally begins at the mean low spring
tide level and extends out to depths ranging from 20 to 75 m3. Local
distribution patterns suggest that this grass is limited by exposure to
environmental stresses. Jackson^ observed that Thalassia on back reef
areas on the north coast of Jamaica had shorter leaves than the grass in
protected deeper adjacent locations. This observation coincides with
Humm's-" conclusion that seagrass serves as a sediment trap and stabi-
lizes the bottom substrate.
The calm waters and high solar radiation associated with this grass
allow the growth of various algae genera, i.e., Penicillius, Halimeda,
Udotea, Dictyota, Valonia, and Caulerpa. -1 Algae are known for their
ability to secrete materials which stabilize sediments. »' The general
bottom stability combined with excessive sedimentation can lead to a
series of successive changes that eventually result in an invasion by
mangroves. -*
The Thalassia is the basic producer for a wide variety of herbivorous
animals such as sea urchins, parrot fish, sea turtles, and Manatees.
The grass also provides protection and camouflage for its endemic filter
feeders and deposit feeders.
Epibenthic Community
Tables 2, 3, and 4 summarize our observation of the macro-epibenthic
organisms at the Thalassia stations during Surveys I and II. A total
area ty 28 m^ was examined at each station. In the first survey, the
oiled long Thalassia and oiled Thalassia flats had a paucity of faunal
groups (Table 3). However, the oiled short Thalassia and all the con-
trols had a similar faunal composition. Sea urchins were most common,
followed by decapod arthropods (i.e., shrimp), and sponges.
During the second survey in July, there was a slight increase in the
number of faunal groups in the oiled long Thalassia and in the oiled
Thalassia flats (Table 4), but the abundance was low. No particular
faunal group seemed to dominate these two stations. The control areas
and the oiled short Thalassia showed a general decline in the number of
faunal groups and abundance between surveys. However, the sea urchins
(Echinoidea) did persist in the oiled short turtle grass.
Close analysis of the epibenthic organisms in six grids (each 19 x 25 cm)
taken from each of the grass stations during Surveys I and II are sum-
marized in Tables 5 and 6. The faunal pattern seen in the macro-study
-23-
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TABLE 2
SUMMARY OF DENSITY AND DIVERSITY
MANGROVE BENTHIC COMMUNITY
HABITAT
Mangrove-North
Mangrove-South
Mangrove-Silt
Mangrove-Nor th
Mangrove-South
Mangrove-Silt
STATION
H-Oily
F-Oily
G-Olly
Control
Control
Control
SURVEY I
SURVEY II
NUMBER OF FAUNAL GROUPS
PER 3,063 CM3
2
5
4
0
4
9
4
0
2
5
4
5
SURVEY I
SURVEY II
NUMBER OF INDIVIDUALS
PER 3,063 CM3
12
28
6
0
5
39
4
0
3
12
e
6
"t" TEST OF FAUNAL
GROUPS H = (P=0.95)
Oil - Control : Accept
Oilj « Control :Accept
Control = Control_T :Accept
MANGROVE PROP ROOT COMMUNITY
Mangrove-North
Mangrove-South
Mangrove-Silt
Mangrove-North
Mangrove-South
Mangrove-Silt
Mangrove-North
Mangrove- South
Mangrove-Silt
Mangrove-North
Mangrove-South
Mangrove-Silt
H-Oily
F-Oily
G-Oily
Control
Control
Control
H-Olly
F-Olly
G-Oily
Control
Control
Control
NUMBER OF FLORAL AND
FAUNAL GROUPS PER
3 X 2 CM2*
4
2
2
12
15
8
13
4
2
9
8
9
NUMBER OF FAUNAL GROUPS
PER ENTIRE PROP ROOT**
1
4
0
9
9
11
7
6
1
4
6
4
NUMBER OF INDIVIDUALS
PER 3 X 2 CM2*
1 + algae
3 + algae
algae
32 + algae
17 + algae
21 + algae
23 + algae
6 + algae
2 + algae
33 + algae
63 + algae
9 + algae
NUMBER OF INDIVIDUALS
PER ENTIRE PROP ROOT
1
8
0
172
169
136
24
32
1
53
53
16
Oil - Control :Reject
Oil Control : Accept
Control *- Control : Reject
Oilj - Control :Reject
Qiljj Control _: Accept
Control - Control :ReJeci
-24-
-------
TABLE 2
(continued)
SUMMARY OF DENSITY AND DIVERSITY
Thalassia Beds
short
Thalassia Beds
Long
Thalnp.sid FJots
Thalassia Beds
short
Thalassia Beds
Long
A-Olly
C-Oily
B-Oily
D-Control
E-Control
Thalassia Beds
short
Thalessla Beda
Long
Thalassia Flats
Thalassia beds
short
Thalasaia Beds
Long
A-Olly
C-Olly
B-Oily
D- Control
E-Control
THALASSIA EPIBENTKIC COMMUNITY
SURVEY I
SURVEY II
NUMBER OF FLORAL AND
FAUNAL GROUPS PER
6 X 475 CM2
4
0
2
6
5
9
10
6
6
10
THALASSIA BENTHIC
NUMBER OF FAUNAL GROUPS
PER 3,063 CM3
12
24
13
12
7
13
7
5
8
10
SURVEY I
SURVEY II
NUMBER OF INDIVIDUALS
PER 6 x 475 CM2
17
0
30
10
19
19
e
30
25
COMMUNITY
NUMBER OF INDIVIDUALS
PER 3,063 CM3
***
55
90***
***
52
****
24
19
40
15
45
29
24
Oil- » Control : Accept
011T, "= ControlTI : Accept
Control * Control :Accept
Oilj Oilrl: Accept
Oil- - Control :Accepc
Oil-- " Control :Accept
Control Control :Accept
Based en microscopic survey of 3 x 2 cm.
Based on visur.l survey of the whole nuingrove prop root.
Primarily worms.
Primarily molluscs and echlnoderma.
-25-
-------
TABLE 3
SURVEY I MACROINVERTEBRATE
COMMUNITIES OF THALASSIA STATIONS
SAMPLED BY WALKING SURVEY OF 39.0 m
ANNELIDS
Polychaetea
ARTHROPODS
Decapoda
CNIDARIA
(COELENTERATES)
Anthozoa
CHORDATES
Tunicata
ECHINODERMS
Crinoidea
Echinoida
(sea urchins)
Holothuroidea
MOLLUSCS
Bivalva
Gastropoda
PORIFERA
(Sponges)
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
LONG THALASSIA
OILY
0
0
CONTROL
2
5
1
1
14
2
1
7
26
SHORT THALASSIA
OILY
5
3
9
2
2
6
6
27
CONTROL
1
6
12
1
12
5
1
5
8
43
FLATS
OILY
6
1
6
-26-
-------
TABLE 4
SURVEY II MACROINVERTEBRATE
COMMUNITIES OF THALASSIA STATIONS
SAMPLED BY WALKING SURVEY OF 39.0 m
ANNELIDS
Polychaeta
Hermodice?
Type K
ARTHROPODS
Decapoda
Pagnridea
Brachyrhyncha
Penaeidea
Sty 1.1 ar idea
COELENTERATES
Anthozoa
ECHINODERMS
Echinoidea
Asteroidea
Holothuroidea
Ophiuroidea
MOLLUSCS
Polyplacophore
Bivalvia
SPONGES (Porifera)
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
LONG THALASSIA
OILED
1
*
1
1
1
*
4
4
CONTROL
1
1
2
*
3
4
SHORT THALASSIA
OILED
1
2
1
*
7
4
11
CONTROL
1
2
2
3
4
8
FLATS
OILED
1
*
2
?.
3
Present b^l not quantified or inclucej
in totals.
-27-
-------
TABLE 5
SURVEY I EPIBENTHIC COMMUNITIES OF THALASSIA BEDS
TOTALS OF SIX (19 x 25 CM) GRIDS PER STATION
GREEN ALGAE
Halimeda sp.
Penicillus capitatus
ARTHROPODS
Decapods
Brachyrhyncha
Kajidae
COELENTERATES
Zoanthidea
CHORDATES
Tunicate
ECHINODERMS
Ophiuroidea
Helothuriodea
MOLLUSCS
Gastropoda
TOTAL FLORAL AND
FAUNAL GROUPS
TOTAL INDIVIDUALS
(FAUNA)
SHORT THALASSIA
OILED
8
2
1
14
4
17
CONTROL
"
4
1
U.Og
6
2
17
6
30
LONG T!'ALASSIA
OILED
0
0
CONTROL
15. Og*
3
14. Og
2
6
5
11
FLATS
OILED
4
1
2
1
Wet weight, not included in totals of individuals
-28-
-------
TABLE 6
SURVEY II EPIBENTHIC COMMUNITIES OF THALASSIA BEDS
TOTALS OF SIX (19 x 25 CM) GRIDS PER STATION
CLASSIFICATION
ALGAE
Brown Algae
Dictyota sp.
Padina sp.
Green Algae
Halimeda
Penicillus capitatus
ANNELIDS
Polychaete Families
Serpulidae-Type A
Terebellidae -Type 0
ARTHROPODS
Amphipoda
Decapoda
Paguridea
Acarina
ECHINODERMS
Ophuitoidea
Echinoidea
MOLLUSCS
Bivalvia
Polyplacophora
Gastropoda genera
Astraea
Cantharus
Cerithium
Columbella
Modulus
Morum
Tegula
Turbo
SPONGES (Porifera)
TOTAL FLORAL AND FAUNAL
GROUPS
TOTAL INDIVIDUALS
(FAUNAL)
SHORT THALASSIA
OILED
*
1
1
1
6
4
1
3
4-
9
19
CONTROL
*
1
6
1
16
6
6
30
LONG THALASSIA
OILED
*
*
1
1
7
1
6
1
1
1
10
19J
CONTROL
1
1
1
1
1
2
9
1
6
2
10
25
FLATS
OILED
*
*
*
2
2
2
6
6
present but not quantified, not included in totals
-29-
-------
in Survey I was valid for the grid analysis. The oiled long Thalassia
and oiled Thalassia flats showed the lowest number of groups and the
lowest abundance (Table 5). The control areas and the oiled short
Thalassia were similar in faunal composition with gastropods the most
frequently observed group.
In the second survey, there was a general increase in diversity and
abundance at all but the short Thalassia control area (Table 6). The
oiled long Thalassia grids contained six genera of gastropods while in
the previous survey, there were none. The other areas, which showed an
increase in diversity between surveys, were uniform in the types of
faunal groups.
Benthic Infaunal Community
Observations of infaunal communities contained in a benthic grab
(3063 cm ) taken from each station during Surveys I and II are sum-
marized in Tables 7 and 8. During the first survey the communities did
not show any depletions that could be related to the oil spill. All
the areas showed a uniform mix of faunal groups that are available in
the Cabo Rojo region (Table 7). The oiled long Thalassia had the
greatest abundance and number of faunal groups.
However, in Survey II there was a reduction in numbers of faunal groups
in the oiled long Thalassia and oiled Thalassia flats (Table 8). Al-
though the infauna at the control long Thalassia slightly increased in
abundance and diversity, there was a 3fold decrease in numbers of
groups of organisms (diversity) and a 4fold decrease in numbers of
individuals in the oiled long Thalassia benthic community. The most
substantial depletion occurred in the bivalve and polychaete groups. The
numbers of groups and abundance of infauna decreased in Survey II in the
oiled Thalassia flats; however, there was an exceptional increase in
numbers of one family of polychaetes, the Onuphidae. This pattern is
reminiscent of the disproportionate increase in numbers of Capitellidae
in response to the Falmouth Oil Spill in Massachusetts.-^
Between surveys there appeared to be a general decline in the appearance
of the oiled Thalassia beds. It appeared that a large amount of the
grass had died and had been washed away, leaving more numerous and exten-
sive pits of loose sand than were present on the first survey. The
death of turtle grass was evident by the extensive windrows of dead
blades washed up on the beaches and lying on the bottom at the edges of
the mangroves on Survey II. Furthermore, exposed roots and rhizomes
lined the edges of the sand pits suggesting that a great deal of erosion
had taken place with the death of the grass following the oil spill.
Mangroves
General Ecology
The mangroves are the culmination of coastal succession in the tropical
-30-
-------
TABLE 7
SURVEY I BENTHIC INFAUNAL Til ALAS SIA COMMUNITIES
PER 3,063 CM3
ANNELIDS
Polychaete Families
Arabellidae-Type L
Amphinomldae
Capitelltdae-Type B
Eunicae
Glycerldae-Type M
Nephytidae-Type F
Onuphidae-Type I
Polynoidae-Type N
Syllidae-Type K
Terebellidae-Type 0
Species Unknown-
Type P
Mutilated*
ROUNDWORMS
Nematoda
ARTHROPODS
Amphlpoda
Decapoda
Paguridea
Brachyrhyncha
Pycnogonida
Isopoda
COELENTERATES
Anthozoa
CHORDATES
Tunlcata
ECHINODERMS
Ophluroldea
MOLLUSCS
Blvalvla genera
Anomalocardla
Brachlodontes
Chlone
Codakla
Macoma
Gastropoda genera
Anarchls
Astrea
Marginella
Nassarius
Ollvella
Polinices
Retusa
Rlssonia
Tegula
Truncatella
Turbo
Unknown
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
SHORT THALASSIA
OILED
5
1
1
32
31
1
4
1
1
2
5
1
1
12
55
CONTROL
1
1
2
1
1
4
3
3
1
3
4
1
1
12
2*
LONG T1IALASSIA
OILED
16
7
1
1
4
7
23
33
3
2
1
2
6
2
1
1
1
4
1
1
1
2
1
1
1
24
90
CONTROL
1
2
1
__
1
7
3
4
7
19
FLATS
OILED
1
8
1
2
1
7
12
2
14
1
1
1
1
13
52
*Not included in total of faunal groups or individuals;
cause of mutilation unknown.
-31-
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TABLE 8
SURVEY II BENTHIC INFAUNAL THALASSIA COMMUNITIES
PER 3,063 CM3
ANNELIDS
Polychaete Families
Capitellidae-Type B
Flabelligeridae, Type U
Hermodice?-Type K
Nereidae-Type Q
Onuphidae-Type I
Sabellidae-Type S
Terebillidae-Type 0
Unknown-Type R
Mutilated, Type
Unknown*
ARTHROPODS
Amphipoda
Decapoda
Brachyrhynclia
Ma j idea
Isopoda
ROUNDWORMS
Nematoda
ECHINODERMS
Ophiuroidea
Echinoidea
Holothuroidea
MOLLUSCS
Bivalvia
Polyplacophora
Gastropoda
Aspidobranchia
Nudibrahchia
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
SHORT THALASSIA
OILED
2
1
3
9
2
1
1
2
5
1
11
2
1
1
13
40
CONTROL
1
1
1
1
5.
1
16
1
3
8
29
LONG THALASSIA
OILED
1
1
2
3
2
5
1
7
15
CONTROL
1
4
3
4
2
1
5
1
4
1
1
1Q
24
FLATS
OILED
1
2
40
1
1
3
5
45
*Not included in totals of faunal groups or individuals.
-32-
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environment. They became established on the silt and detritus of cal-
careous algae that are associated with Thalassia beds.5 The mangroves
modify the physical nature of a coast line in two ways:3 (1) they
absorb the impact of waves during storms, and (2) the organic debris
which accumulates among the prop roots is converted to peat which then
provides a substrate for terrestrial succession.
Zonation is frequently observed in mangrove stands through the tropical
areas of the world.^ In Puerto Rico there are three types of mangroves:
Figure 11: Thalassia Beds During Survey II.
on 1 July 1973.
Photo taken
the red (Rhizophora mangle), a seaward or pioneer form; the black
(Avicennia nitida), a germinous type; and the white (Laguncularia
racemosa), more terrestrial in nature.
Through a tidal cycle the prop roots, particularly of the Rhizophora
can be completely exposed and completely inundated. Consequently, the
mangroves must tolerate daily extremes of environmental stress. The
Rhizophora are one of several mangrove genera that have lenticels, or
-33-
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pores in the roots for gas exchange. These lenticels facilitate root
respiration. Oxygen in these roots is consumed when the roots are
covered with water and is replenished when the roots are exposed.^
The mangroves provide habitats for a wide variety of organisms including
barnacles, crustaceans, algal grazing snails, bees, and reptiles. The
submerged roots provide shelter and a substrate for filter feeders, such
as tunicates, hydroids, tube dwelling annelids and sponges, and mangrove
oysters.^
Prop Root Communities
There was observable disturbance in both the benthic and prop root com-
munities (See Table 2). In the first survey (Tables 9 and 10), the oil
affected both the macroinvertebrate and microinvertebrate communities in
the prop root regions and the benthic infaunal communities (See Table
13).
The macroinvertebrate and microinvertebrate prop root communities from
the three oiled mangroves, (F, G, and H in Figure 2) showed less than
half as many faunal groups as was observed in the control areas. The
abundance of organisms at the oiled area was also less than half of the
control regions (see Tables 9 and 10). The macroscopic organisms in the
oiled areas were essentially missing, while the control areas showed a
community comprised mostly of tanaids and amphopods. Smaller organisms
on the three prop root zones were mainly algae (Table 10). The upper-
most zone of the roots in the oil and control areas had the least algae
coverage. Regardless of the effects of oil, this upper zone in both
areas is most likely to experience extremes in temperature and desicca-
tion stress. Consequently, the impact of oil on the epifauna is not
clear. In addition, the oil may have clogged the lenticels and stressed
mangrove respiration. However, in the lower zones the algal coverage in
the oil and control areas showed differences that may be related to the
spilled oil. The,maximum algal coverage of 6 cm^ in the oiled areas was
30% (1.8 cm^) and* this was in the lowest prop root region of the north
mangroves, Station H. The control areas had algal coverage ranging from
25% to 75%.
Three months later in Survey II, animals were returning to the mangrove
areas. This is shown in Tables 11 and 12. The macroinvertebrates in
the north (Station H) and south (Station F) had representatives from
several polychaete and arthropod groups. The silt area (Station G) was
still devoid of animals. The control areas were dominated by Arthropods,
particularly the amphipods and tanaids.
The microinvertebrate community in the middle and bottom regions of the
prop roots increased in diversity, but it was still dominated by algae
(Table 12). Maximum algal coverage in the oiled area reached 90%: this
was in the silt mangrove area. However, this area did not show the
increase in faunal diversity seen at the two adjacent oiled mangroves.
The northern oiled mangrove showed the greatest diversity of faunal
-34-
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TABLE 9
SURVEY I MACROINVERTEBRATE COMMUNITY
FOR MANGROVE PROP ROOTS
CLASSIFICATION
ANNELIDS
Polychaete Families
Hermodice?-Type K
Nephtyidae-Type Q
Sabellidae-Type S
Flabelligeridae-
Type U
Unknown-Type P
Unknown-Type V
Unknown-Type X
Mutilated*
ARTHROPODS
Amphipoda
Cirripedia*
Decapods
Brachyrhyncha
Majidae
Caridea
Isopoda
Tanaidacea
COELENTERATES
Hydrozoa*
MOLLUSCS
Bivalvia
Gastropoda
Aspidobranchia
SPONGES (Porifera)
CHORDATES
Tunicata-.
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
NORTH
OILED
1
--
1
1
CONTROL
1
4
5
24
3
130
3
1
1
5
9
172
SOUTH
OILED
1
2
4
2
1
4
8
CONTROL
6
3
1
3
21
3
124
2
5
4
9
169
SILT
OILED
0
0
CONTROL
3
1
1
74
2
2
4
28
2
10
9
11
136
Denotes presence of the organism, but no quantification;
not included in totals.
-35-
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TABLE 10
SURVEY I MICROSCOPE SURVEY
OF MANGROVE PROP ROOTS.
A TOTAL OF 3 (2cm ) GRIDS.
CLASSIFICATION
ALGAE
Bostrichia sp.
Filamentous Type A
ANNELIDA
Polychaete Family
Serpulidae (tube)
White calcareous
substance
ARTHROPODA
Cirripedia
Isopoda
COELENTERATA
Hydrozoa
ALGAE
Bostrichia sp.
Caulerpa racemosa
Filamentous Type A
Filamentous Type B
Filamentous Type C
ANNELIDA
Polychaete Family
Sabellidae (Tubes)*
Serpulidae (Tubes)*
ARTHROPODA
Amphipoda
Cirripedia
Isopoda
CHORDATES
Colonial Tunicata
White calcareous
substance
COELENTERATES
Hydrozoa
MOLLUSCS
Gastropoda
PORIFERA (SPONGES)
Encrusting tan sponge
NORTH
OILED
CONTROL
SOUTH
OILED
CONTROL
SILT
OILED
CONTROL
TOP ZONE
2 cm2a
1.5 cm22
.02 cm a
0.1 cm2
--
~~
0.02 cm2a
29
1.6 cm2a
__
2.0 cm
9K
2.8 cm2b
^
4
0.20 cm2a
0.1 cm2a
15
1
MID ZONE
0.04 cm2a
0.04 cm,a
0.88 cm.
0.40 cm
__
3
1.22 cm2b
0.34 cm2c
7-
1.8 cm23
3
__
2.1 cm2b
0.1 cm.
0.4 cm
1
0.06 cm
1
1
0.2 cnTa
__
__
-, c/ 2c
3.54 cm
16
2
0.10 cm2a
_
3
continued
-36-
-------
TABLE 10
(continued)
SURVEY I MICROSCOPE SURVEY
OF MANGROVE PROP ROOTS.
A TOTAL OF 3 (2cm2) GRIDS.
CLASSIFICATION
NORTH
OILED
ALGAE
Bostrichia BP.
Filamentous Type A
Filamentous Type B
Filamentous Type C
ANNELIDA
Polychaete Family
Sabellidae (Tube)*
Mutilated*
ARTHROPODS
leopoda
CHORDATES
Tunicata
Colonial
Solitary
COELENTERATES
Hydrozoa.is
ROUNDWORMS
Nematode-Type A
PORIFERA (SPONGES)'
Encrusting tan
sponge
TOTAL FLORAL AND
FAUNAL GROUPS
TOTAL FAUNAL
INDIVIDUALS
1.84 em2:0
--
._
ft
1
CONTROL
SOUTH
OILED
BOTTOM ZONE
0.80 em2.3
2.02 em
--
0.34 cm2°
12
32
_
0.20 cm2a
..
2
3
CONTROL
SILT
OILED
, o" 2a
1 . 8 cm,,
i , 2a
1.6 cn_
i i 2a
1.1 cm
2
8
3
0.40 cm2a
15
17
0?6 cn,2b
0.4 en.
2
0
CONTROL
0.21 cm2b
0.70 cm2"
.8
21
*Not included in total of faunal groups or individuals.
aCoverage in 1 out of 3 zones
Coverage in 2 out of 3 zones
Coverage in 3 out of 3 zones
-37-
-------
TABLE 11
SURVEY II MACROINVERTEBRATE COMMUNITY
FOR MANGROVE PROP ROOTS
CLASSIFICATION
ANNELIDS
Polychaete Families
Arabellldae - Type L
Hermodice? - Type K
Polynoidae - Type N
Sabellldae - Type S
Serpulidae - Type A
Unknown - Type V
ARTHROPODS
Amphipoda
Decapod a
Caridea
Brachyrhyncha
Tanaidacea
Isopoda
CHORDATES
Fish larvae
Tunicata
MOLLUSCS
Bivalvia
Gastropoda
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
NORTH
OILED
2
2
1
1
6
11
1
7
24
CONTROL
31
,
20
.
1
1
4
53
SOUTH
OILED
2
13
4
8
3
__
2
6
32
CONTROL
1
2
15
5
18
12
__
6
53
SILT
OILED
--
__
1
1
1
CONTROL
2
4
1
9
4
16
-38-
-------
TABU 12
SURVEY II MICROSCOPE SURVEY OF MANGROVE PROP ROOTS
A TOTAL OF 3 (2 CM23) GRIDS.
CLASSIFICATION
NORTH
OILED
CONTROL
SOUTH
OILED
CONTROL
SILT
OILED
CONTROL
TOP ZONE
ALGAE
Filamentous Type A
Filamentous Type B
Red Filamentous Type C
ANNELIDS
Polychaete Family
Serpulidae-Type B
ARTHROPODS
Cirripedia
MOLLUSCS
Bivalvia
White Calcareous
Substance*
4
1.0 cm23
1.0 cm/a
0.04 cm
31
6
MID ZONE
ALGAE
Bostrichia sp.
Encrusting algal mat
Filamentous Type A
Filamentous Type C
ANNELIDS
Polychaete Family
Serpulidae-Type A
ARTHROPODS
Cirripedia
Isopoda
COELENTERATES
Hydrozoa
4.0 cm,
0.2 cm
1
11
1
3
2.o"cm2b
2
0.2 cm2a
2.0 cm2a
2
54
0.04 cm2a
3.0 cm2b
2
5
i
1.0 cm2a
0.6 cm,
0.3 cm
___
2
continued
-39-
-------
TABLE 12
(continued)
SURVEY II MICROSCOPE SURVEY OF MANGROVE PROP ROOTS
A TOTAL OF 3 (2 CM23) GRIDS.
CLASSIFICATION
NORTH
OILED
CONTROL
SOUTH
OILED 1 CONTROL
1
sip
OILED | CONTROL
1
BOTTOM ZONE
ALGAE
Filamentous Type A
Filamentous Type B
ANNELIDS
Polychaete Families
Arabellidae
Sabellldae (tube)
Serpulidae (case)
Mutilated
ARTHROPODS
Amphipoda
Decapoda
Caridea
Tanaldacea
CHORDATES
Tunlcata
Red Calcareous
encrustation*
COELENTERATES
Hydrozoa
MOLLUSCS
Gastropoda
PORIFERA (SPONGES)
TOTAL FLORAL AND
FAUNAL GROUPS
TOTAL INDIVIDUALS
(FAUNAL)
4.2 cm2c
1
4
7
1
:
L.O cm2a
i.8 cm2a
13
28
3.0 cmfa
1.0 cni
«>_
1.2 em2*
..
0.8 cm2a
9
33
3.3 cm2c
1.0 c*2a
4
6
4.0 cm2b
4
1
1
3
2
1
10
63
5.4 cm20
2
2
2.3 cm2"
7
1
1.06 cm2a
9
9
Not Included in totals.
Coverage in one out of three zones.
Coverage in two out of three zones.
Coverage in three out of three zones.
-40-
-------
TABLE 1.3
SURVEY I BENTHIC INFAUNAL MANGROVE COMMUNITIES
PER 3,063 CM
CLASSIFICATION
ANNELIDS
Polychaete Families
Arabellidae - Type L
Hermodice? - Type K
Glyceridae - Type M
Terebellidae - Type J
Unknown Type F
Mutilated*
NEMATODA (Roundworms)
ARTHROPODS
Amphipoda
Isopoda
Unidentified Larvae
COELENTERATES
Anthozoa
ECHINODERMS
Ophiuroidea
MOLLUSCS
Bivalvi a
Gastropoda
Aspidabranchia
NEMERTINA (Ribbonworms)
SPONGES (Porifera)
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
NORTH
3ILED
1
1
11
--
--
--
--
2
12
CONTROL
~
0
0
so
OILED
12
U
1
9
1
3
5
28
ITH
CONTROL
-2
1
1
1
4
5
STTT
OILED
__
1
1
7
--
2
2
--
4
6
CONTROL
3
3
3
22
4
1
1
1
3
1
--
9
39
Not included in totals.
-41-
-------
groups; various arthropod representatives were most frequently observed
at all three depths.
Benthic Infaunal Community
Table 13 summarizes the faunal composition we observed in the benthic
infaunal community during Survey I. There was no clear pattern that
related to the movement of oil as described in the summary of events
(Appendix A). The oiled northern mangroves, Station H in Figure 2,
was dominated by anthozoans. The other two oiled mangrove stations,
F and G, contained nematodes and polychaete worms. Only the silt con-
trol area showed a fairly diverse community, but it was also dominated
by one faunal group: amphipods.
In the second survey, we noticed a decline in abundance at all three
oiled mangrove stations, and there was a marked reduction in the number
of faunal groups at the south oiled mangrove location (Table 14). The
anthozoans and polychaete groups seen in March and April were missing
and no particular group moved into these areas during the three months
between surveys.
The control areas changed between surveys. However, there was no clear
trend in the controls that can be attributed to seasonal variations or
contamination of the control areas by oil.
Fiddler Crab Habitats
There were lagoons located inland from the mangroves on the western
shore and on the northern shore of Bahia Sucia. The respective lagoons
are designated L-l and L-2 in Figure 2. The southern-most lagoon (L-l)
was visited in our first survey during March. We did not observe any
signs of crab mortality that could be attributed to the spilled oil.
However, the wind shift on 1 April 1972, which drove the oil northward
into the canals associated with lagoon L-2, did result in extensive
mortalities in at least four species of crabs in this area. The total
area affected was approximately 0.6 km^. Table 15 represents a summary
of our observations. The fiddler crab suffered the greatest number of
deaths.
By Survey II, oil was still present. However, an increase was noted in
numbers and species of crabs. The main members were ghost crabs
(Ocypode albicans) and fiddler crabs (Uca sp.) of all sizes.
Chemical Analyses
The results of the chemical analyses of oil in Surveys I and II are sum-
marized in Tables 16 and 17. The infrared spectroscopy technique used
determines total hydrocarbon content. The infrared peak, 2930 cm~^>
which we used to interpret the infrared absorption spectra, is con-
sidered to encompass oil and oil-related compounds.9
-42-
-------
TABLE 14
SURVEY II BENTHIC INFAUNAL MANGROVE COMMUNITIES
PER 3,063 CM3
CLASSIFICATION
ANNELIDS
Polychaete Families
Capitellidae-Type B
Hermodice?-Type K
Nereidae-Type Q
Onuphidae-Type I
Mutilated*
ARTHROPODS
Amphipoda
Decapod a
Panuridea
ECHINODERMS
Ophiuroidea
MOLLUSCS
Bivalvia
Gastropoda
PORIFERA (SPONGES)
TOTAL FAUNAL GROUPS
TOTAL INDIVIDUALS
NORTH
OILED
3
1
1
1
1
4
4
CONTROL
2
1
1
1
7
5
12
SOUTH
OILED
1**
--
0
0
CONTROL
2
3
1
1
~
2
4
8
SILT
OILED
1
--
2
2
3
CONTROL
1
1
2
1**
1
1
5
6
**
Not included in totals.of faunal groups of individuals.
*
Fragment
-43-
-------
TABLE 15
MORTALITIES AT FIDDLER CRAB HABITAT, SURVEY I
AREA £ 0.6 KM2
DATE
3 April 1973
7 April 1973
SPECIES
Uca sp.
Ocypode albicans
Callinectes ornatus
Uca sp.
Cardisoma guanhumi
Callinectes ornatus
Ocypode albicans
NUMBER DEAD
62
7
3
198
3
3
12
-44-
-------
TABLE 16
FIELD SURVEY I
TOTAL HYDROCARBON CONCENTRATIONS IN PPM OF OIL IN SAMPLES
HABITAT
Thalassia,
short
Thalassia,
long
Thalassia,
flats
Thalassia
Mangrove,
south
Mangrove,
silt
Mangrove,
north
Mangrove
Blanks
STATION
A
Oily
C
Oily
B
Oily
Control
F
Oily
G
Oily
H
Oily
Control
WATER
2.70
0.92
2.17
0.40
0.40
0.70
0.72
N.D.
N.D.
SEDIMENTS
254.7
151.8
5360.1*
274.5**
N.D.
33.6
43.6
68.0
6.0
GRASS
1130.2
6160.0
134342.0
56.3
* (0 - 5 cm depth)
** (6 - 12 cm depth)
N.D. - Not detectable,
limit of detection
-45-
-------
TABLE 17
FIELD SURVEY II
TOTAL HYDROCARBON CONCENTRATIONS IN PPM OF OIL IN SAMPLES
HABITAT
Thalassia,
short
Thalassia,
long
Thalassia,
flats
Thalassia
Mangrove,
south
Mangrove,
silt
Mangrove,
north
Mangrove
STATION
A
Oily
C
Oily
B
Oily
Control
F
Oily
G
Oily
H
Oily
Control
WATER
N.D.
N.D.
N.D.
***
0.20
0.20
0.20
0.20
SEDIMENTS
21.3
39.7
3.4*
3.5**
N.D.
25.0
215.8
27.8
3.1+
4.8++
GRASS
30.2
12.3
25.0
4.8
BLANK BROKEN IN TRANSPORT
* (0 - 6 cm depth)
** (6 - 12 cm depth)
*** Missing
+ Silty Sediment
++ North Sediment
N.D. Not Detectable,
Limit of Detection
-46-
-------
Analysis of water samples collected during Survey I showed hydrocarbons
at two of the three Thalassia stations (Table 16). Grass samples were
analyzed for hydrocarbon. Samples taken from the Thalassia flats had
the greatest hydrocarbon content; the long grass was second and the short
Thalassia was third. The pattern was also seen in sediment samples
taken from the various areas.
The hydrocarbon content in the water in the oiled mangroves was less
than 1.0 ppm (Table 16). However, substantially higher levels were
detected in the sediments of these oiled stations. We did not detect
hydrocarbons in the 2930 cm"-'- range in the sediments from the control
mangroves.
In the second survey, there was a general improvement, i.e., decrease in
hydrocarbon content, at all the oiled stations (Table 17). In many in-
stances, there was an order-of-magnitude reduction in the levels of hy-
drocarbons in the 2930 cm~l range. A notable exception was the sedi-
ments from the oiled silt mangroves, Station G. Here the hydrocarbon
concentration had doubled between surveys. Also the hydrocarbon con-"~
centration in the water and sediment at the central mangrove station
increased from non-detectable to 0.20 ppm and 3 to 4 ppm respectively.
-47-
-------
DISCUSSION
The biological and chemical data show a sequential change in the biota..
of Bahia Sucia that can be related to the observed movement of the oil
and the long-term behavior of spilled oil.-'-'-'> H The organisms which
were first affected by the oil either occupied the intertidal areas of
the mangroves or were associated with the epibenthic community in the
Thalassia. The benthic organisms in both areas seemed to be unaffected
by the oil, although it had penetrated the sediments. During the three
months following the spill there was some recovery in the intertidal and
epibenthic communities, but there was a marked depletion of faunal
groups in the benthic communities.
A similar sequential pattern was observed by Sanders, et. al. in the
first three months following the oil spill at West Falmouth, Massachu-
setts. This pattern was also noted at the site of the Casco Bay, Maine,
oil spill. The scope of our impact studies was three months following
the spill; however, we feel that the disturbance in the benthic com-
munities will last at least one year.
Thalassia Beds
The Thalassia beds showing the greatest impact of oil in Survey I were
the long Thalassia and the Thalassia flats. These two areas have fewer
faunal groups and higher hydrocarbon concentrations than the oiled short
Thalassia and the control areas (Tables 3, 4, 16). The short seagrass
beds were closer to the open sea than the other two oiled seagrass beds.
Consequently, the short grass area may be subjected to wave action more
frequently than the other two; this is a likely cause for the reduced
impact that was seen in the short grass.
The epibenthic community showed an increase in the number of faunal
groups between surveys. Molluscs particularly increased in the oiled
long Thalassia during the three months following the spill. The com-
position of epibenthic communities in all three areas was similar to
that expected for a tropical lagoon.1^
The benthic infaunal community in the Thalassia declined between surveys,
particularly in the long grass and in the flats. In Survey I, sediments
from both of these areas had particularly high concentrations of hydro-
carbons. It appears that the effect of oil on organisms in the sedi-
ments proceeds at a slower rate than in the water column.
The qualitative change in the appearance of the Thalassia may be caused
by a natural phenomenon as well as by oil. Sea urchins are known to
graze on turtle grass and grazing by the sea urchin, Diadema antillarum
has been known to cause extensive damage to sea grass beds in the U. S.
Virgin Islands.-^ Our general field observations have shown that
sea urchins were dying or losing their spines; there were none in long
Thalassia nor Thalassia flats and only sparsely represented in short
Thalassia. Thus, damage to Thalassia is probably not attributable to
-49-
-------
sea urchins.
Mangroves
The initial impact of oil in the mangroves was a disturbance to the
organisms in the upper root zone of the mangrove community. This is
expected since this is the area most likely to be covered with oil that
is floating on water. Eventually the oil penetrated the sediments. The
chemical analyses of hydrocarbons (Table 16) shows this pattern. The
decrease in hydrocarbon content at two sites (Table 17) between surveys
indicates that these sediments lost oil, but only additional future ob-
servations would determine the removal rate. The increase in hydro-
carbon at the mangrove silt area may be related to the smaller flushing
rate and consequent deposition of fine particles in this area, compared
with higher flushing rates and sediment erosion at the other mangrove
stations.
At the present time we have no way of determining the long-term (greater
than three months) effect of spilled oil on the health of the mangrove
plants themselves. The plants are major contributors to the biological
and physical characteristics of the community. A serious long-term
deterioration of the mangrove plants can lead to extensive modification
in patterns of coastal succession and in a reduction of habitats avail-
able to organisms in the Bahia Sucia. The magnitude of these problems
can best be measured by future resurveys of this area.
Beach Cleanup Operations
Visual observations indicated a general improvement in the Bahia Sucia
area between the first and second surveys. This was due to the combina-
tion of beach cleanup operations and natural factors, such as weathering
and tidal action.
The concept of a trenchpit system to remove oil from the beach area
appeared to be effective. Trenches dug perpendicular to the shoreline
convey floating oil into the pits from which the oil is pumped into
trucks. This is a simple method and oil recovery appears to be high.
However, lining the trenches and pits with plastic sheeting may be wise
to prevent seepage of oil into the subsurface sand or to keep subsurface
water from mixing with oil. Perhaps a system of trench liners and port-
able cisterns can be adapted for this purpose.
Harrowing sorbent into the sand to soak up oil can lead to further mix-
ing the oil through the sand. The sand particles do as well as, or
better than, the sorbent particles in adsorbing the oil and the harrow-
ing or raking produces a small percentage recovery of the sorbent
material. Thus, the method is fairly ineffecient. Also, little is
known about the effect of the sorbent material on organisms.
On the whole, the beach area was cleaned on the surface but oil was
-50-
-------
still present below the sand surface. This oil probably does slowly
leach out into the water and becomes a source of long-term pollution in
Bahia Sucia.
-51-
-------
REFERENCES
1. Pollution Reports Nos. 1-9, 19-23 March, 1973.
2. Duncan, A. J., Quality Control and Industrial Statistics, Irwin,
Inc., Homeward, Illinois, 1959, 114-116.
3. Humm, H. F., "Seagrasses and Mangroves," A Summary of Knowledge
of the Eastern Gulf of Mexico, Institute of Oceanography, State
University System of FloridaM973-
4. Jackson, J. B. C., "The Ecology of the Molluscs of Thalassia Commun-
ities, Jamaica, West Indies," Marine Biology. 14:304-337 (1972).
5. Matthews, B. M., "An Ecological Guide to the Littoral Fauna and
Flora of Puerto Rico," Department of Education Press, San Juan,
Puerto Rico, 1967.
6. Aller, R. C. and Dodge, R. E., "Animal-Sediment Relations in a
Tropical Lagoon, Discovery Bay, Jamaica," J. Mar. Res., 32:209-
232 (1974).
7. Frost, J., J. Sed. Pertol. (1974).
8. Walter, H., Ecology of Tropical and Subtropical Vegetation, Van Nos-
trand Reinhold, New York, 1971, 150-166.
9. M. Gruenfeld, personal communication.
10. Sanders, H. L., The West Falmouth Oil Spill, Woods Hole Ocean-
ographic Institute, Woods Hole, Massachusetts, 1973.
11. VAST, Inc., Oil Spill, Casco Bay, Maine,.July 22, 1972. Environ-
mental Effects, final report for the Office of Water Programs,
Environmental Protection Agency, October, 1973.
12. Collard, S. B., and D'Asaro, C. N., "Benthic Invertebrates of the
Eastern Gulf of Mexico," A Summary of Knowledge of the Eastern Gulf
of Mexico, Institute of Oceanography, State University System of
Florida, 1973.
13. Ogden, J. C., et. al., "Grazing by the Echinoid, Diadema antiliarurn
Philippi: Formation of Halos around West Indian Patch Reefs,"
Science, 182:715-717 (1973).
14. Georg, Wust. Stratification and Circulation in the Antillean-
Caribbean Basins, Part One.
15. Almy and Carrion. "Shallow water Stony Corals of Puerto Rico, Carib.
Journal of Science, vol. 3, no. 2, 1963.
16. Coker and Gonzalez. Hydrographic Conditions near Parguera, 1960,
pp. 11-16.
-53-
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APPENDICES
APPENDIX
A A Chronological Summary of the Events
Immediately Following the Accident
B Chemical Methods
-55-
-------
APPENDIX A
A CHRONOLOGICAL SUMMARY
OF THE
EVENTS IMMEDIATELY FOLLOWING THE ACCIDENT
TIME
DATE
ACTION
1041
1145
1430
0015
0805
0615
0915
0940
to
1000
1630
1700
18 March 1973
18 March 1973
18 March 1973
18 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
19 March 1973
20 March 1973
20 March 1973
22 March 1973
23 March 1973
24 March 1973
Police advised the Commander of the Port (COTP), San Juan, that
the vessel, Zoe Colocotronia, ran aground In the vicinity of La
Parguera, Puerto Rico.
The vessel's agent notified the COTP that the ship ran aground,
was afloat with no damages, was no longer spilling oil, and was
proceeding to Guayanilla.
A U.S.C.G. helicopter observed that the vessel apparently dis-
charged oil to lighten its load and had ceased discharge of the
oil and was under way. The vessel proceeded to CORCO.
Vessel was located a't 17°54' N and 66°59' W. Oil slick extended
from this position to two miles east of Cabo Rojo.
Oil expected to come ashore between Cabo Rojo and Punta Tocon on
19 March 1973. The regional response team and local officials
were alerted.
COTP advised by CORCO that Mobil Oil agreed to accept all cleanup
costs. This was not confirmed by Mobil Oil and a cleanup
contingency fund was set up.
The Commonwealth of Puerto Rico planned to require the vessel to
post bond.
U.S.C.G. overflight observed that the slick came ashore from Bahia
Sucia to Cabo Rojo and extended offshore from La Parguera to El
Corabate.
Cleanup crews from Commonwealth Public Works Department were
under way.
Captain Ramsey of Mobil Oil reported that Mobil Oil will pay all
costs incurred.
Two U.S.C.G. helicopters were on-the-scene and the OSC had obtained
sorbent from Sun Oil and 640 ft of boom.
Oil was located ashore at the cliff face (67°11.0' W) and east of
Cabo Rojo between 67°11.5' W and 67°11.5' W, 17°57.6' N.
Overflight by officials of the Commonwealth Environmental Quality
Board and Department of Natural Resources.
Transport of EPA Region II strike force to the scene. Containment
operations in progress.
Commonwealth requires vessel to post additional bond.
U.S.C.G. overflight reveals that slick has moved north parallel to
the west coast of Puerto Rico.
Vessel posts bond but company has not yet accepted responsibility.
EPA strike force transported to the scene.
Cleanup operations in progress.
Cleanup operations in progress. West of England P & I Club assumes
contracting responsibilities.
Ship's master, crew, and logs subpoened by local EQB. A complaint
is filed against the vessel Captain H. Mlchalotoulla. Arrest will
be made following EQB hearings.
EQB hearings begin and the U. S. Attorney filed a complaint in the federal
District Court against the ship's captuin
Ship's captain arrested and released on ball.
TRC personnel arrive in Mayaguez, Puerto Rico, to begin surveys
-56-
-------
APPENDIX B
CHEMICAL METHODS
Field Extractions
All extractions were carried out using Spectrograde CCl^. All glassware
used for extractions was rinsed three times with Spectrograde CC11+, ex-
cept where noted. Spectrograde CCl^ cannot be obtained on short notice
in Puerto Rico, so for some extractions the glassware was rinsed in re-
agent grade CCli^ to conserve Spectrograde supplies for the extractions.
The blanks reflect this method of preparation.
Water
Water collected and acidified in the field with 5 ml 1:1 E2SO^ was placed
in a separating funnel and tested for pH of 3 or lower by bringing the
wetted stopper of the separating funnel into contact with pH-sensitive
paper. Hydrocarbons were extracted by shaking the water with 25 ml CCli+,
allowing the phases to separate, and draining off the lower phase (CClif
+ hydrocarbons) into a 100 ml volumetric flask. Three additional extrac^
tions were performed, rinsing the sample bottle each time with the 25 ml
portion of CCl^ to be used in the extraction and adding the extract to
the volumetric flask. The stoppers were fitted snugly into the flasks,
covered with aluminum foil, and taped down to seal them for shipment to
the TRC laboratory.
Sediment
Approximately 50 gm wet weight (later increased to 100 gm) of sediment
from a thoroughly mixed core sample was placed in a 250 ml beaker and
stirred with four separate portions (25 ml each) of CCl^, each portion
being poured off into a single 100 ml volumetric flask which was sealed
for shipment as specified under Water.
Grass
Samples of grass (40 to 60 gm) were wet weighed and extracted following
the procedure described under Sediment.
Oil
Five ml of oil collected from the beach area at Cabo Rojo was diluted to
100 ml in a volumetric flask and sealed as specified under Water.
Blank
The blank was prepared by adding 100 ml of CC14 to a volumetric flask
prepared in the field.
-57-
-------
Laboratory Analysis
Samples from the field laboratory were passed through a funnel containing
one inch of anhydrous sodium sulfate to remove all water and returned to
the original volumetric flask where their volume was brought to 100 ml
with additional CClit (Spectrograde) . After mixing, the extract was
scanned in the range of 4200 cm -1 to 2600 cm * using a silica cell (1 cm)
in a Perkin-Elmer Model 727 Infrared Spectrophotometer with CCl^ in the
reference beam.
Dilutions of 2.0, 4.0, 10.0, 16.0, 20.0, and 30.0 mg per 100 ml (Figure
B-l) were used to calibrate the instrument on the same day that the sam-
ples were run. The concentration of oil in the samples was then read
directly from the standard curve. The standards were tested before and
after passing them through the anhydrous sodium sulfate to test the re-
covery rate which was found to be 100 percent.
-58-
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0.9
0.8
0.7
0- 6
0.5
I
Ui
VO
I
0.4
0.3
0.2
0.1
y = 0.0297 X - 0.02960
r= 0.992
n= 6
Sy. v=0.03i7
o
0.0
8 10 .12 14 16 18 20 22 24 26
CRUDE OIL" t,1s PER 100ml
28 30
Figure &-1: Calibration of Infrared Spectrophotometer Using Dilutions
of Crude Oil from the Beach at Bahia Sucia
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