EXXON VALDEZ Oil Spill Restoration Project Final Report. Monitoring of Oiled Mussel Beds in Prince William Sound and the Gulf of Alaska. Restoration Project 00090

摘要

Exxon Valdez oil trapped in intertidal sediment in Prince William Sound degraded slowly, was biologically available for at least a decade, and was toxic for at least 9 years. Habitat condition controlled the biological availability of oil. Exposure duration was short (months) where mussels were only exposed to oil in water and long (6 to 10 years) at locations where oil remained in sediment. Limited evidence suggests some oiling extended outside previously reported slick boundaries; polynuclear aromatic hydrocarbon (PAH) sources were verified with three independent models. After an initial peak, oil concentrations typically declined in sediment and mussels, although distribution was non-uniform and variability was often high. Oil may persist in some intertidal sediment for >50 years, but declines in mussel tissue suggest it became less available to surface organisms. Attempts to manually accelerate hydrocarbon loss from mussel beds were equivocal, demonstrating that removal of oil from intertidal sediment is difficult. Exposure to residual oil may explain why some vertebrate populations (pigeon guillemots, Cepphus columba, and sea otters, Enhydra lutris) that forage in the most heavily impacted areas have not yet fully recovered from the spill.