Ecosystem modeling of Prince William Sound Alaska

The largest oil spill in United States history (40 million liters) occurred when the Exxon Valdez super tanker struck Bligh Reef in Prince William Sound, Alaska in the early spring of 1989. The oil spread throughout the western portion of this 8,800 km2 coastal marine ecosystem before spreading to the Gulf of Alaska, Kodiak Island, and along the Kenai and Alaska Peninsulas. It covered rocky shorelines and beaches, and initially killed large numbers of birds, mammals, and marine invertebrates, including endangered and declining species. In addition, the Exxon Valdez Oil Spill severely jeopardized the health and food-gathering activities of indigenous communities and commercial fishing communities of the region.

Revealing the full impacts of the Exxon Valdez Oil Spill commands persistent focus by involved communities, the fishing industry, scientists, resource managers, and the courts fully nine years after the catastrophe. Determining the effects of the spill has proven difficult since Prince William Sound was not thoroughly studied prior to the 1989 spill. Scientists at the Fisheries Centre are constructing models of the Prince William Sound food web to synthesize ecosystem information collected since the spill into a coherent description of the ecosystem as a whole (the estimated 'amount' of each species group, the amount of food that group eats, and the amount of that group that is eaten are all compared with all other groups in the ecosystem to determine the energetic likelihood of given population and community estimates, thus refining overall knowledge of the system).

Oil spills and other human activities can change populations and the structure and function of marine ecosystems. 'ECOPATH' trophic models of Prince William Sound can be constructed for the periods before and after the oil spill to help reveal its impacts. These models can also be used in dynamic simulations (ECOSIM) to simulate the effects of oil spills, fishing activities, and marine protected areas. Such simulation models can be a useful tool for understanding, even predicting, effects of such human activities. Further advances have given the ECOPATH approach spatial and seasonal realism ( ECOPATH with ECOSIM 4.0 ).