tion, life span, growth rates, predators, and community ecology), however, is nonexistent.

Chemosynthetic seep communities are considered prevalent between 300 and 1000 m water depth on the northern Gulf of Mexico slope. Commonality, however, is not a reason for relaxing criteria for acceptable impact without knowledge of the ability of undamaged or damaged fauna to ultimately repopulate any impacted areas. Some organisms that inhabit the cold seep communities may be extremely old, and damaged communities would be slow or unlikely to recover. Hard bottom communities with highly diverse biogenically-structured communities are afforded protection from drilling operations in the Gulf of Mexico, and any chemical spills that approximate these types of effects would be expected to produce similar harm to live-bottom communities.

Summary

Since the compilation of the 1985 NRC report, Oil in the Sea, great progress has been made in identifying the toxic effects of petroleum hydrocarbons in a wide variety of organisms. We have also gained considerable knowledge of the effects of oil on various marine habitats through laboratory experiments, mesocosm experiments and practical experience with spills. Our knowledge of the effects of produced waters has expanded for inshore and offshore production fields and for multiple mixtures of oil and other contaminants in confined water bodies such as harbors. We now have first-hand experience with spills in coral reefs, mangroves, seagrass beds, and high-latitude cold-water environments. We are now in a better position to assess risks to individual organisms and habitats from the production, transport and consumption of petroleum than we were in 1985.

Assessing the effects of any particular spill and recovery from its effects has proven more complicated than was anticipated in 1985. We know that the natural variability of marine ecosystems and the open nature of marine communities, in which recruitment of young may be dependent on planktonic larvae transported from great distances, creates a substantial challenge in assessing both the effects of a spill and recovery from those effects. Although we now know much more about the toxicity and sublethal effects of petroleum hydrocarbons to organisms, we still have great difficulty in assessing the population, community, or ecosystem effects of pollution events. To assess the effects of oil in the sea and recovery from impacts, we need new information on the population structure of these marine organisms that is critical for the function of their communities. In addition, appreciation of the influence of decadal-scale and longer climate change means that we cannot expect communities or ecosystems to return to the state in which they were at the time of a pollution incident. Given the various time-scales of ecosystem change, before-after and control-impacted (BACI) designs for assessing damage are valuable, but they are no substitute for an up-to-date time series from a well-designed monitoring program. Based on an improved understanding of change in the marine environment, there is great value in having time series for detecting change and for pointing to processes critical for understanding change.

The effects of oil in the sea depend greatly on the season, place, and the types of organisms present. Although for a given habitat at a given time, a large amount of oil is likely to create more damage than a small amount, small amounts in sensitive environments or where there are populations at risk can have devastating effects.

Reducing the Threat to the Marine Environment

Ecosystems and their components vary at time-scales from seasons to decades and longer. Therefore, in the absence of on-going monitoring it is exceedingly difficult to quantify the effects of oil in the sea, or to establish when recovery from a pollution event is complete. Establishment of monitoring programs in selected regions with an elevated risk of petroleum spills or discharges would enhance the ability to determine effects and recovery, and to understand the processes controlling ecosystem responses to pollution. Existing databases on the distribution, frequency and size of petroleum spills and existing petroleum and distribution routes could be used to identify locations most appropriate for monitoring. Federal agencies, especially the USGS and EPA, should work with state and local authorities to establish or expand efforts to monitor vulnerable components of ecosystems likely to be exposed to petroleum releases.

There are demonstrable effects of acute oiling events at both small and large spatial-scales. These effects result from physical fouling of organisms and physiological responses to the toxic components of oil. Although there is now considerable information on the toxicological effects of individual components of oil, there is a lack of information about the synergistic interactions within organisms between hydrocarbons and other classes of pollutants. This problem is particularly acute in areas subject to chronic pollution, e.g., urban runoff. Research on the cumulative effects of multiple types of hydrocarbons in combination with other types of pollutants is needed to assess toxicity and organism response under conditions experienced by organisms in polluted coastal zones. Federal agencies, especially the USGS, NOAA, and EPA, should work with industry to develop or expand research efforts to understand the cumulative effects of multiple types of hydrocarbons in combination with other types of pollutants on marine organisms. Furthermore, such research efforts should also address the fates and effects of those fractions that are known or suspected to be toxic in geographic regions where their rate of input is high.

There are demonstrable sublethal physiological effects of long-term, chronic releases of hydrocarbons into the marine environment. These have been found in areas affected by



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