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2. Principles of Assessment
Pages 27-40

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From page 27...
... Marine ecosystems are complex, and many of the interactions within their biotic communities and between biotic communities and the physical environment are poorly understood, so estimation of risk and impact assessment cannot be very precise. Although the ESP is not primarily an ecological research program, many of its projects have provided useful data on the functioning of marine ecosystems, and ad its results must be interpreted In an ecosystem context.
From page 28...
... Vrl] ES Continental shelf habitats of North America contain diverse communities and constitute important economic assets; they are extremely productive and support some of the world's most important commercial harvests of fish and shellfish.
From page 29...
... For example, if a test for increased mortality of some benthic species shows no effect, one needs to Mow what increase could have been detected; if a mortality increase of 50% could not have been `detected, then the test has low power. Because of natural variability and other factors, tests for the effects of pollutants In nature often have low power.
From page 30...
... ~us, to understand the Impact of anthropogenic activities on components of continental shelf habitats, we need to define the mechanisms of resistance, elasticity, and recoverability of such communities, as wed as the various successional pathways In operation within the many assemblages of pelagic and benthic species. The past decade has seen considerable advances in both our understanding of the potential impacts of OCS development (Boesch et al., 1987)
From page 31...
... Within a species selected for study, geographical populations or breeding colonies should be selected for study according to the forgoing criteria: · Representativeness. To the greatest extent feasible, the populations selected for study should include populations that represent different ecological circumstances, e.g., large and small breeding colonies, dense and sparse feeding aggregations, inshore and pelagic locations and central and peripheral parts of a range.
From page 32...
... It requires study of the relationships between the distribution of marine species and oceanic features on various scales (Hunt and Schneider, 1987; Winn et al., 1987~. On the largest scales, the distributions of individual species are related to broad physical and chemical oceanic characteristics such as temperature, salinity, and nutrient concentrations and to the abundance of prey species, which themselves depend on these oceanic characteristics; seasonal distributions and migrations of marine species are related to seasonal changes An temperature, insolation, ice cover, and food availability.
From page 33...
... Specific OCS Impacts Effects of External Oiling Marine birds, mammals, and turtles can encounter oil while swimming at the surface of the water, while diving or when they come ashore on oil-coated beaches, rocks, or other
From page 34...
... Trophic Effects ~ addition to direct effects on animals that come into contact with oft OCS activities might affect birds, mammals, and endangered species indirectly, by changing or contaminating populations of their prey or of predators. Hypothetical examples of such effects include effects on populations of zooplankton, fish, or benthic organisms that are used as food by birds or mammals and effects on populations of predators that may otherwise control populations of marine birds and mammals.
From page 35...
... Assessment of the potential effects of noise and disturbance must be carried out case by case, and results of short-term studies are not necessarily predictive of long-term ejects. 35 Other Potential Effects Other potential ejects of OCS activities on birds, mammals, and endangered species include degradation of salt marshes by construction of pipelines and disposal areas, changes In tidal currents resulting from construction of islands and causeways, and secondary effects of residential development.
From page 36...
... , in his review of OCS benthic monitoring programs, concluded that none of the studies conducted before 1985 could define a anon what they were looking for; therefore, they could not use optimal design techniques. Although some intense point-source impacts of anthropogenic activities might be unambiguously recognized without a need to understand the sources of natural variability in benthic processes, detection of most anthropogen~c activities requires an understanding of both the magnitude and the natural causes of variation in the absence of human intervention.
From page 37...
... With regard to specific, subtle, pervasive impacts of anthropogenic activities, study of physical and geochemical processes is necessary for deciphering the mechanisms of natural biological variation in benthic populations. The benthic zone of the inner shelf from the beach or surf zone to a depth of about 30 m is poorly studied but crucially important because it is here where oil spins wiD encounter land.
From page 38...
... MMS has used two broad classes of models to assess the effects of OCS activities: descriptive models, In which observational data are fitted to statistics, and statistical parameters are derived for use In prediction or hypothesis testing; and process models of complex ecological systems, which are constructed from submodels with data derived Tom process studies. Empirical parameters derived Tom descriptive models of ecological processes are often used to set parameters for process models, which can then be used to predict the response of the system to external perturbations (e.g., Ford et al., 1982~.
From page 39...
... In ecology, functional systems of classification are often preferable to taxonom~c ones, and a failure to recognize this relationship can lead to difficulties. The results of the surveys and process studies discussed In the previous sections wid ultimately be used for either of two purposes: to predict the consequences of hypothetical oil spills or other OCS activities, or to interpret and assign causes to observed changes in patterns of distribution and abundance.


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