ENVIRONMENTAL-INFLUENCES ON THE MICROBIAL-DEGRADATION OF EXXON-VALDEZ-OIL ON THE SHORELINES OF PRINCE-WILLIAM-SOUND, ALASKA

Biodegradation was a major mechanism for removing oil resulting from t he Exxon Valdez oil spill in Prince William Sound, Alaska. For three f ield seasons, we examined the hexadecane, phenanthrene, and naphthalen e mineralization potentials of hydrocarbon-degrading microorganisms an d the accompanying hydrocarbon concentrations from intertidal and shal low subtidal sediments. We found that mineralization potentials were n ot directly dependent on sediment substrate concentrations, but enviro nmental factors influenced the ability of microbial populations to min eralize polycyclic aromatic and aliphatic compounds. These factors inc luded the intensity of physical mixing experienced, the treatments rec eived, and the availability of alternative carbon sources. In 1989, wh en the Exxon Valdez oil was relatively unweathered and before shorelin e treatment was begun, the mineralization potentials of aromatic hydro carbons were high at many sites even in the presence of alkanes at hig her concentrations. However, by 1990, mineralization potentials for al kanes were greater than those for aromatics at oiled sites exposed to terrestrial bio-waxes or fatty acids from the bioremediation process. Therefore, our study shows that sediment chemistry data alone cannot p redict the persistence of hydrocarbons following the Exxon Valdez oil spill and demonstrates the need for systematic ecosystem-level studies of the abiotic and biotic factors influencing biodegradation.