Distribution of hydrocarbon-degrading microorganisms in sediments from Prince William Sound, Alaska, following the Exxon Valdez oil spill

Biodegradation by naturally occurring populations of microorganisms is a major mechanism for the removal of petroleum from the environment. Therefore, measurements of microbial populations are an important component of contaminated site assessment studies. Over a 3 year period following the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, we counted numbers of hydrocarbon-degrading microorganisms in intertidal and subtidal sediments affected by the spill. We found significantly higher numbers of hydrocarbon-degrading microorganisms at sites within the path of the oil slick than at reference sites, indicating rapid acclimation of the resident microbial populations. In offshore surface sediments, we saw a temporal increase in numbers of hydrocarbon-degrading microorganisms. Our data suggest that microbial measurements are good indicators of exposure of sediments in Prince William Sound to hydrocarbons and of mobilization of oil to surface sediments offshore over time.