vvEPA
United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97330
Research and Development
EPA-600/S3-81-018 July 1981
Project Summary
Some Effects of
Petroleum on Nearshore
Alaskan Marine Organisms
D. G. Shaw, L E. Clement, D. J. Mclntosh, and M. S. Stekoll
The overall objective of this project
was to better understand the effects
of chronic, low-level oil pollution on
nearshore Alaskan marine organisms.
The bivalve mollusc Macoma bahhica
accumulated hydrocarbons during
180 days of continuous exposure to
Prudhoe Bay crude oil in flowing
seawater dispersions with nominal
concentrations of 0.03 mg/l~1, 0.3
mg/r1 and 3.0 mg/l*1. The animal's
ability to concentrate oil from seawater
increased with decreasing oil in water
concentration. Decreases in Mbahhica's
oil burden began after 30 to 120 days
(depending on the oil concentration)
and continued for at least 60 days
after oiling ceased. Alipathic and
aromatic hydrocarbons were fraction-
ated in markedly different ways by the
animal. Branched and cyclic aliphatics
in the range dodecane through hexa-
decane were preferentially retained
over their higher homologs, whereas
larger and more substituted aromatics
were selectively concentrated.
Macoma balthica showed a number
of physical, behavioral, physiological
and biochemical changes during oil
exposure. An oil in seawater concen-
tration of 3.0 mg/r1 caused severe
dysfunction in the clams including a
decreased burial rate, increased respi-
ration rate, and inhibition of growth
leading to very high mortalities. The
lowest concentration of oil tested,
0.03 mg/r1 will in time lead to popula-
tion decreases.
This Project Summary was devel-
oped by EPA's Environmental Research
Laboratory, Corvallis, OR , to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Understanding and predicting the
cumulative impacts of chronic, low level
petroleum discharges are particularly
difficult because the environmental
changes induced are generally gradual
and often extremely difficult to distin-
guish from natural environmental fluc-
tuations. This project was an effort to
improve our scientific understanding of
the fate and effects of long term, low
level petroleum exposure on marine
organisms. This extremely broad topic
was narrowed to a tractable investiga-
tion by setting the following conditions:
• We were principally concerned
with invertebrate intertidal animals
common to Alaskan and other
northern waters.
• We wish to focus on sublethal
physiological and biochemical
changes which might effect the
viability of populations, rather than
on processes of hydrocarbon me-
tabolism.
• We wanted to investigate animals
exposed to environmentally realistic
oil concentrations.
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• We would monitor the kinds and
amounts of hydrocarbons to which
the animals were exposed and
which they incorporated in order to
correlate petroleum burdens with
biological effects.
After a series of preliminary investi-
gations we determined that the most
promising approach would be to work
with the small deposit feeding clam,
Macoma balthica, under controlled con-
ditions in the laboratory. Although this
species has no common name, it is
circumpolar in distribution and occurs
abundantly in intertidal and shallow
subtidal areas of fine grained sediments
north of about 40° latitude. We felt that
the stresses caused by bringing the
clams into the artificial environment of
the laboratory were offset by our in-
creased ability to manipulate and moni-
tor oil exposure in a controlled setting.
In order to provide a realistic simula-
tion of chronic exposure of marine
animals to oil-in-seawater dispersions
in the laboratory, we constructed a
continuous-flow system capable of
simultaneously delivering dispersions
with nominal oil in water concentra-
tions of 0.03 mg/r1,0.3 mg/l"1 and 3.0
mg/l"1. Through the course of our
experiments we quantitatively mea-
sured the concentrations of various
aromatic and aliphatic petroleum hydro-
carbons in the clams and the seawater
to which they were exposed. For this we
used the techniques of gas chromato-
graphy and computerized gas chromato-
graphy-mass spectrometry. We exposed
clams for six months to oil and in
seawater dispersions and maintained
another group of clams free of oil but
otherwise under identical conditions in
the laboratory, to serve as controls.
Numerous biological parameters were
monitored during the six month oil
exposure test and for an additional two
months afterwards.
Results
Figure 1 shows the total hydrocarbon
burden of oil exposed and control clams
during and for two months after the
experiment. These data reveal two
important facts:
• Clams exposed to each oil concen-
tration began to reduce their body
burden of petroleum before the end
of exposure.
• Although the "high exposure"
clams were in water containing
70,0001-
7,000 -
f
•*w
1
1
•9
I
100
Figure 1.
"72CT
Days of Exposure
Macoma balthica tissue concentrations of total hydrocarbons during
180 days of exposure to oil in seawater dispersions and 60 days of
recovery. Bars show the range of duplicate determinations; dots are
single determinations.
100 times as much oil as the "low
exposure" clams, after six months
oil exposure, the body burdens of
clams from the two exposure levels
differed by only about a factor of
four.
Chemical analysis showed that not all
of the constituents of petroleum were
taken up or retained by the clams to the
same extent. For the aliphatic hydro
carbons we found, as have other;
previously, retention by the animals is
greatest for ring compounds, less foi
branched compounds, and least fo
straight chains. We also found tha
within the cyclic and branched aliphatic
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Hydrocarbon series, lighter molecules
were retained more strongly than their
heavier cogeners. Aromatic hydrocarbons
as a group were taken up in preference
to aliphatics but for these compounds
heavier homologs were selectively
accumulated.
Table 1 gives a summary of the bio-
logical condition of clams exposed to oil
for six months as compared to unexposed
controls. Clearly the animals subjected
to the two higher oil in water concentra-
tions, 0.3 mg/r1 and 3.0 mg/l"1, were
adversely affected in numerous ways;
feeding decreased, mortality increased,
weight and growth decreased, gonads
appeared abnormal and enzyme activities
were altered. Clams exposed to 0.03
mg/l"1 oil were in most ways not signifi-
cantly different from controls. However,
in two critical respects these clams
differed from the control group. These
exposed clams grew only 20% as much
as the controls. This difference is highly
significant according to standard statis-
tical tests. In addition microscopic
examination of these exposed clams'
gonads showed that reproductive mate-
rials were being resorbed rather than
brought to maturity for spawning. It
seems clear that conditions which
impair functions as basic as growth and
reproduction threaten the viability of a
population.
This work suggests that sublethal
exposure of Macoma balthica to petro-
leum results in two distinct groups of
adverse effects. The first group includes
several alterations of behavior which
indicate that oil exposed clams are
sluggish and disoriented. These effects
include decreased burial rate, decreased
feeding rate and decreased general
activity. The onset of these behavioral
changes occurs within one week of
initial oiling. Similar effects have been
reported in numerous short term acute
oiling effects studies. The second group
of adverse effects appears to be related
to a negative energy balance in the oil
exposed animals. These effects include
decreased dry weight, abnormal and
resorbed gonads and decreased carbo-
hydrate content. These effects begin to
appear only after 60 days of exposure
and appear not to be simply a conse-
Table 1. Summary of the Effects of Six Months of Oiled Seawater on Various
Parameters of Macoma balthica
Level of oil in exposure tanks
Parameters measured
0.03 mg/l
0.3 mg/l
3.0 mg/l
1. Behavior
general activity
burying rate
% unburied
feeding rate
2. Mortalities
3. Respiration rate
4. Physical
wet weight
dry weight
dry/ 'wet ratio
growth
condition index
5. Morphology
gonads
gills
6. Biochemical
protein
carbohydrate
lipid
DNA
RNA
Mg^-ATPase
Na*-K*-ATPase
5'-nucleotidase
phosphodiesterase
normal*
normal
normal
normal
normal
normal
normal
normal
normal
decreased
increased
reabsorbed
normal
normal
normal
normal
normal
normal
normal
increased?
normal
decreased
decreased
increased
decreased
increased
normal?
normal
decreased
decreased
decreased
decreased
abnormal
normal
decreased
normal
normal
normal
normal
normal
increased?
normal
decreased
decreased
increased
decreased
increased
increased
decreased
decreased
decreased
decreased
decreased
abnormal
normal
decreased
increased?
normal
normal
decreased
normal
increased?
increased
quence of decreased feeding activity.
Bivalves normally offset a decrease in
food intake by decreasing their meta-
bolic rate and thus are able to endure
prolonged periods with little or no food.
However, in the oiled M. ballhica the
decrease in feeding was compounded
by an increase in metabolic activity as
measured by respiration rate. It appears
that these two effects together are
responsible for the negative energy
balance in the oiled clams. Certainly
each of these groups of effects will
adversely impact Macoma balthica,.
affecting the viability of exposed indi-
viduals and populations.
References
Portions of this research have been
published:
Clement, L.E., M.S. Stekoll, and D.G.
Shaw. Accumulation, fractionation
and release of oil by the intertidal
clam Macoma balthica. Marine Biol-
ogy 57, 41-50 (1980).
Stekoll, M.S., LE. Clement, and D.G.
Shaw. Sublethal effects of chronic oil
exposure on the intertidal clamMacoma
balthica. Marine Biology 57, 51-60
(1980).
^normal, decreased, increased - are levels relative to those in the controls.
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D, G. Shaw, L. E. Clement, D. J. Mclntosh, andM. S. Stekollare with the Institute
of Marine Science, University of Alaska, Fairbanks, AK 99701.
Barry Reid is the EPA Project Officer fsee below).
The complete report, entitled "Some Effects of Petroleum on Near shore Alaskan
Marine Organisms," (Order No. PB 81-159 147; Cost: $9.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Corvallis, OR 97330
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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