Evaluation of the toxicity of oil residues in shoreline sediments following the Exxon Valdez oil spill

The grounding of the Exxon Valdez resulted in the oiling of approximately 16% (487 miles) of shorelines in Prince William Sound (PWS) with weathered North Slope crude oil. Shortly after the spill an extensive program was initiated to evaluate the fate and effects of this oil on shorelines using the benthic amphipod, Rhepoxynius abronius. Analytical characterizations for saturate (GC/FID) and aromatic (GC/MS/SIM) hydrocarbons were conducted on samples taken concurrently with toxicity test samples. During the 3 year study period, more than 1,600 sediment samples were taken from more than 60 sites in PWS and the northern Gulf of Alaska ranging from the upper intertidal to subtidal. A range of toxic responses, consistent with sediment hydrocarbon content, was observed; however, toxic residues were generally confined to the upper intertidal zone. The 2 and 3-ring aromatic hydrocarbons are implicated as responsible for the majority of the observed toxicity. Toxicity, and hydrocarbon residues, decreased substantially one year after the spill, indicating that natural processes and shoreline clean-up efforts were effective in removing toxic hydrocarbon residues