grounded on Bligh Reef in northern Prince

William Sound, Alaska, shows that current practices for assessing ecological risks of oil in the oceans and, by extension, other toxic sources should be changed. Previously, it was assumed that impacts to populations derive almost exclusively from acute mortal-ity. However, in the Alaskan coastal ecosystem, unexpected persistence of toxic sub-surface oil and chronic exposures, even at sublethal levels, have continued to affect wildlife. Delayed population reductions and cascades of indirect effects postponed recovery. Development of ecosystem-based toxicology is required to understand and ultimately predict chronic, delayed, and indirect long-term risks and impacts. Before the Exxon Valdez oil spill, infor-mation available for constructing riskassessment models to predict ecologi-cal impacts of petroleum hydrocarbons was limited to selective, largely short-term monitoring after previous oil spills and to tests of acute toxicity in laboratory-tolerant taxa (1). After the tanker Exxon Valde