CHANGING PERSPECTIVES ON OIL TOXICITY EVALUATION

摘要

Recent advances in oil toxicity research may well alter the way oil spill response decisions are made. Those responding to spills should be aware of the limitations surrounding the use of acute toxicity data to predict even short-term oil effects. Many animals previously classified as tolerant of short-term oil exposure, such as fish eggs and benthic organisms, are just as or much more sensitive than pelagic fishes to chronic exposures. Toxicity bioassays proved to be of limited value in predicting the long-term damage from the Exxon Valdez oil spill because such toxicity information only measured mortality to water-accommo-dated fractions of fresh oil over a 96-hour period. During the spill, many of the aquatic organisms were exposed to weathered oil resolubilized from nearshore sediments rather than to fresh oil in the water column. Oil allowed to sequester in the sediments of streams, mussel beds, and estuaries provided a persistent source of contamination in natal and nursery fish habitats over several years. Eggs, larvae, and juveniles that inhabit these habitats are especially sensitive to long-term exposure to sediment accommodated weathered oil. Spill response should be geared toward preventing oil from reaching streams, fine sediment beaches, and estuaries that serve as critical fish habitats rather than solely toward reducing initial mortalities.