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Executive Summary
OVERVIEW
The study of petroleum pollution in the ocean deals with two potentially
opposing aspects of man' s activities: on the one hand is pollution
arising from activities undertaken to meet man's needs--the extraction,
transpor t, and use of petroleum for energy and chemical feedstocks--and
on the other hand is the strong desire to preserve living mar ine
resources both for current uses and for a legacy for future generations.
In this examination of marine petroleum pollution we recognized
this dual ity and attempted to examine it from a broad and, at times,
somewhat distant perspective, without bias whenever Possible, so as to
avoid pitfalls of misinterpretation.
Petroleum is a naturally occurring
substance, derived from organic materials once living but since trans-
formed into a complex mixture of chemicals, consisting mainly of
hydrocarbons and small amounts of other organic compounds. A small
amount of petroleum has seeped into the world's oceans for at least
centuries and probably millions of years, and portions of the oceans
have accommodated long-term influx of some petroleum into their
communities and ecosystems.
The modern influx of petroleum into the marine environment is on a
different scale, occurring more rapidly and over a wider area, and
probably is of a different k ind . The product enter ing the oceans
today, both from chronic effluent release and runoff and from sudden
catastrophic spills, represents a sudden and significant input of
contaminants when viewed against the much longer, but much lower,
continuous presence of seepage petroleum. Also, the chemical composi-
tion of this modern petroleum input often differs from that of the
seepage oil, the latter being altered by the degradation processes,
both physical/chemical and microbial, occurring in the marine sediments
and crustal layers. In this context it must be noted that inputs of
petroleum are not the only sources for many of the compounds of
concern. For example, combustion of coal yields several polyouclear
aromatic hydrocarbons similar to or also found in petroleum. Finally,
modern petroleum input to the oceans is no longer restricted to the
seep locations but now includes many waters formerly held unpolluted
and pristine. Even those areas themselves free of oil exploration and
-
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production activity are nonetheless subject to potential pollution
resulting from petroleum tanker traffic.
Our mandate from the Ocean Sciences Board (now the Board on Ocean
Science and Policy) was to review the accomplishments since the 1975
NRC Repor t, Petroleum in the par ine Environment, to err ive at
conclusions on the basis of our newer understanding of the behavior and
fate of petroleum in the marine environment, and in the end to make
recommendations concerning possible further research. We recognize
potential environmental problems requiring further study as well as
areas where much less concern is required, either as a result of new
findings or because investigations are essentially completed.
Inevitably, the potential impact of petroleum as part of, or
together with, other contaminants in the marine environment was
considered. While in some instances petroleum itself is readily seen
as the identif table pollutant, as for example, in tanker spills or in
known cases of chronic petroleum pollution, there are many regions
where petroleum hydrocarbons are thought to form part of a more general
pollution threat to the health of those environments. Waters near or
receiving the effluent of urban and industrial regions serve here as
primary examples.
GENERAL ADVANCES: 19 73-1983
Progress in oil-pollution-related research during this past decade has
been impressive. Knowledge and understanding of its problems have come
about in each of the areas identified in the 1975 NRC report. Most
significant of the advances in these areas are the reduction in the
uncertainties regarding the rates of input and amounts of marine
petroleum pollution, the increasing sophistication of the analytical
methodology appl fed to chemical and biological studies, clearer
identif ication of the various processes acting on petroleum in the
oceans, and the clear identification of problem areas in the effects of
petroleum on biota.
Inputs
There is now a better understanding of the data base with respect to
input of petroleum into the world's oceans, especially for urban
runoff, which is a major source. Progress has been made also in the
design and implementation of procedures for measurement of atmospheric
inputs of petroleum hydrocarbons to the marine environment, although
more data are needed. In addition, over the past 8 years there has
been a better definition of the various sources of input, which has led
to the recognition and elimination of the problem of double bookkeeping,
i.e., including a particular source in more than one category in pre-
vious estimates. These advances came as a result of the discussion and
deliberations of the 1973 workshop, the recommendations from which were
carried forward to the present effort.
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Methods
Underlying the progress made in the area of inputs are the improvements
in chemical methods. Several new sampling methods and dev' ces ,
including specialized water samplers that avoid contamination from
surface film, have been developed and have led to greater confidence in
subsequent data. The analysis of petroleum hydrocarbons, pyrogenic
hydrocarbons derived from the atmosphere and resulting from incomplete
combustion of oil, coal, wood and gas, products of metabolic alteration
of petroleum by organisms, and products of chemical and biochemical
transformation after oil enters the sea (e.g., metabolites and photo-
chemical oxidation products), has made great strides, especially with
the parallel development of glass capillary gas chromatography, high-
pressure liquid chromatography, and glass capillary gas chromatography/
mass spectrometry computer systems. AS a result, there exists today an
improved capability to analyze a wide range of petroleum compounds,
including volat lie components, in water, sediments, and organisms ,
that was not possible or was achieved only with difficulty at the time
of the first workshop (1973~. The intercomparability of data from
different laboratories is more reliable as a result of several quality
control exercises and workshops for intercalibration.
Fate
Describing the fate of petroleum in the marine environment is possible
in a way that was not conceivable in 1973. Methods of modeling are now
approaching the level of sophistication where they are of potential use
in spill impact prediction. Much more is now known of the various
environmental processes acting on petroleum, and much has been added to
our understanding of the properties and factors relevant to the fate
and effects of oil. For example, whereas the process of photochem~cal
oxidation was only recognized at the time of the first report, today it
is being actively researched.
A major advance since the last report is the interactive biological/
chemical approach to studying petroleum in the marine environment, i.e.,
recognition of the need of these two disciplines to work intimately on
this problem. Indeed it is rare to find studies involving one without
the other. As a direct result, the role of biological alteration of
petroleum is much better understood. Such processes as microbial
degradation are now recognized as significant to the fate of petroleum
in the marine environment, and work on establishing rates of microbial
degradation for different environments is now being done. The broad
outlines of metabolic pathways of petroleum degradation are being
developed for bacteria, phytoplankton, and higher animals, and con-
siderable work is being carried out on specialized detoxification
mechanisms where these are known. It has also been shown that animals
exposed to sublethal dosages take up hydrocarbons, but in most cases
are able gradually to alter the various petroleum components, in some
cases by conversion to compounds that are more soluble and more readily
excreted, although a few of these are themselves highly toxic. Hence,
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accumulation by itself, under conditions of low concentrations, may not
be severe. Indeed there is very 1 ittle evidence of increased accumula-
tion in the higher predatory members of the food web. In terms of human
health the available data do not indicate that consumption of oil-
polluted seafood is a widespread problem, although we caution against
complacency in the application of broad generalizations to individual
local situations.
Effects
Studies on the biological effects of petroleum have benefited greatly
from improvements in experimental study design, from the application of
modeling made available by computer technology, and from the develop-
ment of specialized experimental equipment. A major step forward has
been the move away from lethal studies to sublethal studies, using
specialized flow-through systems and the concomitant measurement of
petroleum compos ition and concentration.
In terms of the measurement and evaluation of the impact of petrol-
eum, advances have been made along several lines of study--cellular,
organismic, population, and ecosystem. Much of this advancement is due
to a better understanding of the interaction of petroleum or of its
components with water, sediment, and tissues and to the specialized
analytical procedures developed over the last 8 years. These in turn
have led to a better predictive ability to anticipate and evaluate the
potential impact of oiling, whether acute (as from spills) or chronic.
Extensive studies on a var iety of marine organisms have been carried
out on the toxic effects of petroleum and on selected individual com-
ponents. These include laboratory experiments and observations in the
field made after oil spills. Significant differences In the tolerance
of individual species and of different life stages in a given species
have also been recorded, so that a better understanding of possible
impact is available.
FINDINGS AND RECOMMENDATIONS
Major Findings
The authors of this report conclude, based upon the evidence
available, that there has been no evident irrevocable damage to
marine resources on a broad oceanic scale, by either chronic inputs
or Occasional major oil spills. However, specific information that
would enable unequivocal assessment of the impact of oil on the
environment does not yet exist, particularly, with regard to certain
specific environments and conditions. We, therefore, recommend
further research in a number of areas as discussed below.
Despite the considerable advances made in the past 10 years, as
detailed in the preceding pages, a number of significant questions
remain unanswered. Frequently, the evidence on which conclusions
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regarding petroleum impact are based is either circumstantial or
insufficient. The former may occur, as in the situation where a
conclusion regarding the fate or effect of a given hydrocarbon compound
has to be based on data obtained for a similar or related compound,
because the relevant information is not available. In some cases,
impact on one marine species must be inferred from observations made on
a different but perhaps related species. The evidence is often
insufficient, as when data are available for only a single life-cycle
stage in an organism that normally has several such stages, each with
potentially differing susceptibilities. On the other hand, assembling
information on each and every organism or life-cycle stage would require
an extreme effort that might not be justifiable. It therefore appears
to us that more data on a number of select species would be preferable
to a large amount of scattered and possibly nonintegrated data on
several species.
In reviewing the past 10 years, it is probably fair to say that
these years have yielded a much improved understanding of the general
impact of petroleum on the marine environment. Furthermore, we conclude
on the evidence available that there has been no evident irrevocable
damage to marine resources on a broad oceanic scale, by either chronic
inputs or occasional major oil spills. Lacking, however, is the
specific understanding relating to details that would enable unequivocal
assessment of such impact. That understanding does not yet exist. We
therefore recommend further research in a number of areas as discussed
below. This recommendation stems from the many findings that very low
levels of petroleum, below 0.1 mg/L, can affect such delicate biological
entities as fish larvae.
Continued research will result in a much improved capability to
predict and assess the impact of both sudden and chronic petroleum
pollution, especially in those coastal regions where oil exploration
and production activities coincide with harvestable marine resources.
Such further research should also lead to a better understanding of
the apparent link between the polycyclic aromatic hydrocarbons, some of
which may be coming from pyrolytic sources, and the more general problem
of what seem to be pollution-related diseases found in commercially
important fish stocks in waters receiving a mixture of contaminants.
Input of Petroleum
Major Finding
The estimated range for the total input of petroleum from all
sources is between 1.7 and 8.8 million metric tons per annum (mta),
with a best estimate of 3.2 mta.
We believe that this range, rather than a single-number estimate,
is a more accurate summary of the state of knowledge, and reflects the
uncertainties that exist in all source data. Calculations of the total
input of petroleum are complex, for there are many sources, and in many
cases those data that are available are minimal for the purpose. There
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are also wide geographical gaps in information on sources, particularly
in the southern hemisphere and tropics.
This range of 1.7-8.8 mta includes the single-number estimate of
6.1 mta made in the 1975 NRC report. The difference (decrease) between
that earlier estimate and the current best estimate of 3.2 mta does not
necessarily represent a decline in annual input of petroleum hydrocar-
bons into the marine environment during this period but indicates a
better estimating of individual inputs.
Assessment of the available data on inputs and sources of petroleum
entering the marine environment confirms the earlier conclusions of the
1975 NRC report that a considerable portion of marine petroleum pollu-
tion is due to non-gas- and oil-related activities, and originates from
other human activities (see Table 2.22~. These include river and
terrestrial runoff from municipal, urban, and industrial sources as
well as from seeps and through atmospheric transport. A significant
source of petroleum pollution originates from bilge cleaning.
If we are concerned over the continuing health of our oceans and if
we are to develop a better understanding of the cycling and transport
processes of contaminants in the marine environment, then we suggest
the following steps to narrow these existing uncertainties in the
inputs of oil.
1. Improved documentation of continental margins to determine the
extent of submarine seepages, and to more accurately gauge their flow
rates.
2. Continued monitoring of all facilities discharging petroleum
hydrocarbon containing effluent.
3. Better methods for distinguishing petroleum hydrocarbons from
the "oil and grease. and naturally generated hydrocarbons currently
applied to municipal and industrial effluents.
4. A better accounting of petroleum inputs for the southern
hemisphere, where currently there is great uncertainty as to amounts
and rates of input to the oceans.
Major Recommendation
It is recommended that atmospheric transport of petroleum
hydrocarbons, particularly by rainwater, be given priority status
for research.
Rain scavenging of atmospheric particles is commonly thought to be
the major pathway for petroleum into the oceans from the atmosphere.
Unfortunately, today there exists little or no scientific evidence or
information on this potentially significant pathway. Concurrent with
this is the need to determine the various processes and reactions
affecting these compounds as they are transported from sources through
the atmosphere into the oceans.
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Study Methods: Chemical
Major Finding
Marked progress has been made in the application and development of
analytical methods to quantify petroleum components in air, water,
sediments, and biota of the sea and to distinguish these components
from other sources of hydrocarbons.
While the purpose and main thrust of this report are an examination
of petroleum in the seas, reaction products and other sources of hydro-
carbons also require attention in order to provide more accurate and
meaningful measurements in support of research and monitoring on inputs,
fates, and effects of petroleum. These products and other sources
include (1) products of metabolic alteration of petroleum by marine
organisms; (2) products of chemical and photochemical alteration after
oil enters the oceans; and (3) pyrogenic hydrocarbons produced during
combustion of oil, coal, and other carbonaceous materials. Some of
these compounds are toxic or biologically active in ways that may be
deleterious to natural resource populations or to man.
At the time of the 1975 report, existing analytical methods were
inadequate to deal effectively with this problem, but marked progress
has been made in the intervening years. Thus it is the general con-
sensus that at the present time, chemical methods are available to make
useful measurements on metabolites, reaction products, and nonhydrocar-
bon constituents of petroleum.
Study Methods: Biological
Major Finding
Techniques for experimental exposure of organisms to petroleum have
advanced significantly. The use of controlled environment systems
(mesocosms) in particular has been a significant step toward under-
standing the impact of petroleum on communities.
More experiments need to be conducted in the field to coordinate
laboratory and field components and to validate laboratory findings.
Biological interactions of different species are complex, and the
presence of degradation products of petroleum in the natural environ-
ment adds to the complexity, creating a gap between field-work observa-
t~ons and laboratory results.
Physical/Chemical Fate of Petroleum
Major Findings
Considerable progress has been made toward r igorously defining the
var. ious processes at fecting the movement of spilled oil, and its
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ultimate fate. It is now estimated that evaporation can account
for the loss to the atmosphere of from one- to two-thirds of the
oil spilled onto the sea surface.
Present knowledge suggests that almost all of the evaporated oil
becomes photochemically oxidized in the atmosphere. Photochemical
oxidation has also been identified as a significant process acting
on of] at the sea surface.
Modeling of the drift of spilled oil remains a complex and cliff icul.
problem, in part because of the wide spectrum of oil types and the
changing environmental conditions occurs ing dur ing a spill. The best
estimate at the present time for dr if t velocity still is between 3 and
49e of the wind speed. It appears now that dissolution into the water
column is considerably less important than evaporation in determining
the ultimate fate of spilled oil, because of the low aqueous solubility
of most components.
Considerable work has been devoted in the past decade to developing
a better understanding of the interaction of spilled oil with the water
column, including "mousses formation, oil droplet entrainment into the
water column, and sedimentation of spilled oil through eventual sorp-
tion onto particulate matter in the water column.
Major Finding
For all these processes, the relationship between chemical
composition and the formation and stability of oil-water emulsions
and of the sorption characteristics between oil and organic
particulate matter are only poorly known.
If there is to be a better understanding of the physical and
chemical behavior and fate of petroleum hydrocarbons in the marine
water column, then more basic research and experimentation in this area
are needed. This will yield useful information for quantitative models
of greater ability for assessing the fate of petroleum inputs in
various areas of the world's oceans.
Biological Fate of Petroleum
Major Findings
Uptake of petroleum by animals, and apparently by plants, from food
and/or water is universal. However, animals and, apparently ,
plants are able to clear their tissues by releasing the accumulated
petroleum back into the water after the removal of the pollution
source (s) .
There appear to exist in those living systems examined various
enzymatic mechanisms capable of metabolically transforming a range
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of petroleum hydrocarbon compounds. One notable exception appears
to be the bivalves.
In many cases, as in low level contamination, metabolic degradation
and/or the clearing of petroleum from the tissues back to the water
can balance uptake, without significant bioaccumulation of these
compounds in the tissues.
Microbial degradation is a major clearing mechanism for removal of
petroleum pollutants from marine environments. Environmental parameters
affecting the rate of biodegradation are now being defined, and some
progress has been made in measuring rates of biodegradation in the
oceans. Refinement and standardization of methodology are required
before rate projections will be sufficiently reliable.
Despite marked progress in the study of biological fates, some
important aspects remain to be clarified. Thus much less is known
about the fate of petroleum in marine plants, including macro-algae and
phytoplankton, than in animals.
As well, little is known of either the distribution, fate, or
turnover of the metabolic products of petroleum hydrocarbon, after
their formation within the tissues of marine organisms. It has been
demonstrated that some of these derivatives may be either toxic or
mutagenic.
Major Recommendation
It is recommended that further studies be encouraged to examine the
formation and fate of metabolic derivatives of petroleum hydro-
carbons taken up by marine organisms.
Amounts of Hydrocarbons in the Oceans
Several U.S. agencies, including the Bureau of Land Management, the
National Oceanic and Atmospheric Administration, and the Environmental
Protection Agency, as well as agencies of other countries, have actively
supported studies on the amount of petroleum found in the water column,
sediments, and organisms in the oceans. These studies yield the follow-
ing major findings.
Major Findings
Petroleum hydrocarbon concentrations in the water column can vary
by several orders of magnitude and are generally related in their
amount to the proximity of petroleum sources, e.g., offshore and
shore-based coastal production and refining activities, and to
transportation routes and accidents.
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Tar balls and other floating oil residues also vary by orders of
magnitude, with highest concentrations associated with tanker
shipping lanes and some mid-ocean gyres such as the Sargasso Sea.
Significant decreases in these concentrations have not been
observed.
Petroleum hydrocarbon contamination (PHC) of marine sediments
parallels that for the water column, with PHC concentrations
directly related to the proximity of sewage and industr ial
outfalls, dumping sites, and accidental discharges .
Relatively little information is available on PHC concentrations in
pelagic organisms, mainly because of analytical problems, that is, in
differentiating between PHC and hydrocarbons produced by organisms in
nature and micro tar balls caught in plankton net tows made in heavily
traversed oceanic areas. PHCS are usually detected in samples of
benthic organisms collected from polluted areas, but not from areas
free of spills or other sources of input.
Although the more immediate concerns are in the coastal areas that
receive the major amounts of petroleum inputs, the paucity of data for
the larger open ocean areas requires attention because it is a handicap
to our understanding of the long-term fate of petroleum in the marine
environment on a global scale.
Effects
Prior to the 1975 report, much of the work on effects was focused on
establishing toxic and lethal thresholds and on the assessment of
hydrocarbon concentrations in environmental samples.
Major Finding
Research since 1975 has resulted in considerable advances in the
understanding of the toxicities of various petroleum components, of
the effects on organisms and their life-cycle stages, and on the
relative vulnerability of various mar ine ecosystems.
This information has come both from experimental studies in the
laboratory and from the examination of spill situations. Much has been
learned, for example, regarding the impact of petroleum on intertidal
and coastal ecosystems and about the effects of petroleum on various
metabolic and physiological processes, especially in fish and in
invertebrates such as mollusks and crustacea.
Major Finding
Little is known about the impact of petroleum on pelagic organisms
and populations. There are also obvious gaps in our understanding
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of oil impact on macro-algae, on larval fish, and on polar and
tropical organisms.
In addition, research activity has broadened to include work on the
site of action of petroleum compounds, regarding their effects as
dynamic processes affecting the living organism at its var. ious levels--
enzymatic, metabolic, ultrastructural, and molecular . This has become
evident from the breadth of studies brought together in this report, a
range of effects extending from the ecosystem level down to the
chromosomal .
Effects-related research in recent years can be character ized
according to two signif icant advances: a shif t toward gaining an
understanding of the sublethal toxicities of petroleum, and recognition
that both species and life-cycle stages vary widely in sensitivity and
response. An increasing scientific awareness of a need to obtain and
interlock chemical, physiological, and ecological data has provided
additional momentum. AS a result, the trend is toward studies of
petroleum pollution on a solid basis of chemical and biological data.
However, increased depth of understanding of the effects of
petroleum in the marine environment can be gained through work in
certain areas, as outlined below.
.
Mutagenicity/Tumorigenicity. Only a small amount of information is
available on the occurrence, kinds, and detection of mutagenic and
tumorigenic problems in marine invertebrates and vertebrates and in
marine plants.
Alteration of Behavior. Perturbation of normal behavior at very low
_
concentrations of petroleum (less than 0.1 mg/L) is of particular
concern. Change in or cessation of feeding is an early indication of
oil's toxic effects in many test animals. Yet most available data are
largely anecdotal, and at least in higher organisms, ef feats on
behavior are only poorly understood.
Mechanisms of Toxicity. A focus of research on perturbations of physio-
logical processes is recommended. While respiration, photosynthesis,
AIP production, carbon assimilation, 1 ipid formation, and related
processes are known to be affected by individual hydrocarbons such as
naphthalene, the ultimate site, or sites, of toxic action of these
compounds have yet to be determined.
Polar and Tropical Environments. The polar environment poses a special
problem because of almost year-round ice cover and relative inacces-
sibility, compounded by large gaps in the basic data base on polar
biology. While some information exists on oil and the polar environ-
ment, the potential impact of a major oil spill on polar ecosystems
cannot be estimated with confidence at this time.
With respect to tropical regions, rather limited data are available
on the effects of oil on tropical ecosystems including mangroves, coral
reefs, and their associated biota. Nonetheless, these ecosystems
represent a large part of the tropical coastline and are often very
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near heavy tanker traffic or petroleum activity. They are also bio-
logically highly productive and are of great economic and cultural
importance. The preliminary data that do exist indicate these tropical
systems are as sensitive to oil as, if not more sensitive than,
temperate coastl ines .
Synergistic Toxicity. The interaction of petroleum with other non-
petroleum contaminants is not well understood. Further work is needed,
especially as chronic pollution of inshore waters often involves more
than one contaminant.
Ecosystem Effects. Population changes caused by an oil spill or by
chronic pollution inevitably result in additional effects by altering
food web relationship and interspecific competition in the ecosystem as
a whole. Each situation is different, and the effects of any given
spill or input can be quite unexpected. Underlying these concerns are
the various findings that low concentrations (less than 1 mg/L) of
petroleum hydrocarbons can apparently interfere with the normal behavior
of marine organisms, especially the more fragile components such as the
larval and juvenile forms of the marine foodchain. Continued study of
a few key examples of recovery after oil spills or from well-defined
chronic input sources, with adequate controls, is essential if eco-
system effects and their economic significance are to be well-defined.
Major Recommendations
Study the effect of low concentrations of petroleum hydrocarbons on
the behavior of marine organisms, particularly larval and juvenile
forms.
Conduct studies to examine the apparent coincidence between elevated
concentrations of mutagenic/carcinogenic petroleum hydrocarbons
(PAHs) and pollution-related diseases in certain fish from waters
receiving a mix of contaminants.
Conduct research into impacts of petroleum on polar and tropical
environments.
Finally, a major problem throughout this report has been the
difficulty of transferring information from laboratory studies to field
conditions, i.e., the difficulty in predicting impact in the field from
experimental data. Little is known of the effects of petroleum on
zooplankton and ichthyoplankton and of the potential impact on larval
fish stocks. Nonetheless, the potential exists that under certain
conditions of prolonged exposure, such impact could become significant.
Also, one of the most difficult aspects of this problem has been to
assess the potential impact of spills on commercially important stocks
of fish and shellfish.
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Major Recommendation
We recommend that research into the effect of petroleum on fish
stocks, including larval and juvenile stocks, be extended so as to
enable sensible assessment of the impact on these marine resources.
The major uncertainty preventing such assessments, as with most
ecosystem effects, is a limited understanding of natural fluctua-
tions in populations and ecosystems. We think that major progress
in determining the effects of petroleum, by itself and in concert
with other contaminants, on populations and ecosystems will largely
depend upon an increased understanding of short-term (years} and
long-term (decades) natural fluctuations in populations and
ecosystems.
SUMMARY AND CONCLUSIONS
Where oil has had an effect, subsequent monitoring has shown biological
recovery taking place. Hydrocarbons from seeps and pyrolytic sources
are part of the long-term evolution of the oceans, and results of
observations made to date indicate that most living organisms can
co-exist with hydrocarbons when concentrations are very low (less than
0.1 mg/L) and when the oil is weathered.
It is also revealing that, of the petroleum hydrocarbons entering
the marine environment, an estimated 39% derives directly from oil and
gas production and transportation. However, more than 45% originates
from other shipping activities and from industrial, municipal, urban,
and river runoff.
There is no clear indication so far that commercially important
fish stocks have been severely disrupted by either chronic or catas-
trophic oiling of their environment. However, present census techniques
remain too crude to provide clear knowledge of standing fish stocks,
while natural variabilities in the stocks probably mask such impact
from petroleum as may exist. The fragmented evidence on the effects of
petroleum on some larval fish and fish eggs from a few laboratory and
field studies indicates that such impact is possible, although it has
not been rigorously examined. This inability to transfer information
obtained from laboratory studies to field conditions has been an
intractable problem throughout this report.
Petroleum can have a seriously adverse affect on local environ-
ments, persisting, in some cases unaltered, for decades. Moreover,
some petroleum compounds are carcinogens and/or mutagens and can bind
to nucleic acids. Metabolic products of petroleum degradation also can
be potentially hazardous. However, the data are not available to
indicate that such a hazard has occurred in populations in affected
environments.
The greatest impact due to oiling clearly occurs in coastal areas,
especially those with shallow water, and in areas where local current
systems tend to contain or entrain the contaminant. Of special concern
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are situations of local chronic oil ing where there is low level (less
than 1 mg/L) but continuous exposure, as in waters near industrialized
or heavily populated coastal regions. There is a clear need to
continue research on these local situations, not only because of the
intrinsic toxicity of petroleum, but also because of its poorly
understood but suspected synergistic impact with other contaminants.
Particular concern is expressed about the potential impact of oil
on tropical coastal environments--mangrove systems and coral reefs.
These represent a major part of the coastline in tropical and
subtropical regions and are highly significant in terms of fisheries
and other resources. They have unique physical and biological
characteristics that make them highly vulnerable to the effect of
oiling. On for tunately, the research effor t on these ecosystems has
been confined to comparatively few studies.
Representative terms from entire chapter:
petroleum hydrocarbons
