significant source, are two-stroke engines. Collectively, land runoff and two-stroke engines account for nearly three quarters of the petroleum introduced to North American waters from activities associated with petroleum consumption. This is particularly significant because, by their very nature, these activities are almost exclusively restricted to coastal waters. In fact, the estuaries and bays that receive the bulk of the load are often some of the most sensitive ecological areas along the coast. Federal agencies, especially EPA, should continue efforts to regulate and encourage the phase-out of older, inefficient two-stroke engines, and a coordinated enforcement policy should be established. Unfortunately, the estimates for land-based sources of petroleum are the most poorly documented, and the uncertainty associated with the estimates range over several orders of magnitude. Federal agencies, especially EPA, USGS, and NOAA, should work with state and local environmental agencies to develop and implement a system for monitoring the input of petroleum to the marine environment from land-based sources via rivers and storm- and waste-water facilities. Again, VOC are released during consumption activities and contribute to the total load of hydrocarbon input to the sea. Like VOC released by other sources, these compounds rapidly volatilize into the atmosphere and thus appear to have a short residence time in marine waters.
As discussed briefly above, the effect of a release of petroleum is not directly related to the volume. It is instead a complex function of the rate of release, the nature of the released petroleum (and the proportions of toxic compounds it may contain), and the local physical and biological ecosystem exposed. Progress has been made in understanding some basic processes affecting the fate of released petroleum. Much more needs to be learned about how petroleum interacts with marine sediment and how it is transported or dispersed by ocean and coastal processes such as waves and currents. Federal agencies, especially NOAA, MMS, U.S. Coast Guard, and the USGS, should work with industry to develop and support a systematic and sustained research effort to further basic understanding of the processes that govern the fate and transport of petroleum hydrocarbons in the marine environment.
Although the VOC released during the extraction, transportation, and consumption of petroleum appear to have short residence times in the marine environment, their impact on air quality may be significant. Federal agencies, especially the U.S. Coast Guard, MMS, and EPA, should work with the International Maritime Organization to assess the overall impact of VOC on air quality from tank vessels and other sources, and establish design and/or operational standards on VOC emissions where appropriate.
Studies completed in the last 20 years again bear out the significant environmental damage that can be caused by spills of petroleum into the marine environment. No spill is entirely benign. Even a small spill at the wrong place, at the wrong time, can result in significant damage to individual organisms or entire populations. With a few notable exceptions (e.g., the Exxon Valdez, North Cape, and Panama spills), there have been a lack of resources to support studies of the fates and effects of spilled oil. Much of what is known about the fate and effect of spilled oil has been derived from a very few, well-studied spills. Federal agencies, especially the U.S. Coast Guard, NOAA, and EPA, should work with industry to develop and implement a rapid response system to collect in situ information about spill behavior and impacts.
Despite the significant progress made in understanding the behavior and effect of petroleum spills on the marine environment and on preventing their occurrence in the first place, relatively little work has progressed on understanding the threat posed by small, chronic releases of petroleum from all sources. Insights have been made from long-term studies of sites of major spills or polluted harbors, but to a large degree the significance (in terms of environmental damage) of the large inputs from land-based sources or other chronic releases is not known. Recent studies, however, suggest that PAH, even in low concentrations, can have a deleterious effect on marine biota. Furthermore, 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 EPA, NOAA, NSF, USGS, and MMS, should work with academia and industry to develop and implement a major research effort to more fully understand and evaluate the risk posed to the marine environment by the chronic release of petroleum (especially the cumulative effects of multiple types of hydrocarbons present in these kinds of releases).
Finally, although there is now good evidence for the toxic effects of oil pollution on individual organisms and on the species composition of communities, there is little information on the effects of either acute or chronic oil pollution on populations or on the function of communities or ecosystems. The lack of understanding of population-level effects lies partly in the fact that the structure of populations of most marine organisms is poorly known. Such information is imperative if the impacts of individual spills or chronic releases in local areas are to be evaluated against the health of entire populations, species, or ecosystems. The U.S. Departments of Interior and Commerce should identify an agency, or combination of agencies, to prioritize and support continued research on the effects of releases (chronic and catastrophic) of petroleum on wild populations.