Pink Salmon Spawning Habitat is Recovering a Decade after the Exxon Valdez Oil Spill

Abstract

Intertidal sediment surrounding many spawning streams for pink salmon Oncorhynchus gorbuscha in western Prince William Sound, Alaska, was contaminated by the Exxon Valdez oil spill in 1989. Biochemical and egg-dig evidence suggested that oil reduced the survival of pink salmon embryos for several years. Previous research also demonstrated that dissolved oil can be transferred to developing embryos from surrounding oiled sediment via drainage of interstitial water as a result of tidal cycling and hydraulic gradients. In this study, completed a decade after the spill, we sampled stream water for the presence of oil using passive membrane sampling devices, collected sediment and pink salmon eggs for hydrocarbon analysis, and examined alevins for induction of cytochrome P4501A (CYP1A). Polynuclear aromatic hydrocarbons (PAHs) consistent with Exxon Valdez oil were present in the water of one of six heavily impacted streams; total PAH concentrations in the stream were greatest in the lower intertidal zone. Similarly distributed total PAHs in a second stream suggested possible contamination. Oil was not detected in the remaining four streams. Induction of CYP1A in pink salmon alevins from the two contaminated streams was lowest in water above mean high tide and increased downstream. Because our samples were all selected from heavily oiled streams, we infer that most pink salmon spawning habitat either has recovered or is recovering.