Hydrocarbon Monitoring: Integration of Microbial and Chemical Sediment Data, Prince William Sound, Alaska (1995)

Biodegradation was a major mechanism for removing oil resulting from the Exxon Valdez oil spill in Prince William Sound, Alaska. For three field seasons, we examined the hexadecane, phenanthrene, and naphthalene mineralization potentials of hydrocarbon-degrading microorganisms and the accompanying hydrocarbon concentrations from the intertidal and shallow subtidal sediments. We found that mineralization potentials were not directly dependent on sediment substrate concentrations, but environmental factors influenced the ability of microbial populations to mineralize polycyclic aromatic and aliphatic compounds. These factors included the intensity of physical mixing experienced, the treatments received, and the availability of alternative carbon sources. In 1989, when the Exxon Valdez oil was relatively unweathered and before shoreline treatment was begun, the mineralization potentials of aromatic hydrocarbons were high at many sites even in the presence of alkanes at higher concentrations. However, by 1990, mineralization potentials for alkanes were greater than those for aromatics at oiled sites exposed to terrestrial biowaxes or fatty acids from the bioremediation process. Therefore, our study shows that sediment chemistry data alone cannot predict 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.

Restoration Project 95026 (continued as 97026) was initiated as part of a detailed study plan in 1994. The project was a synthesis of data collected from prior projects including: (1) NRDA Air/Water Study Number 2 Petroleum Hydrocarbon-Induced Injury to Subtidal Marine Sediment Resources (changed to Subtidal Study Number 1 in 1991). The final reports for Subtidal Study Number 1 (including NRDA Air/Water Study Number 2 data) were submitted in June 1992 (microbiology) and July 1994 (chemistry). (2) Restoration Study Number 93047 Exxon Valdez Restoration Proiect: Subtidal Monitoring. The results of this project are found in two reports, Microbiology of Subtidal Sediments: Monitoring Microbial Populations (Project 93047-2) Recovery of Sediments in the Lower Intertidal and Subtidal Environment (Project 93047-1). A journal article from the current study (Restoration Project 95026) was published in 1997: Sugai, S.F., J.E. Lindstrom and J.F. Braddock. 1997. Environmental Influences on the Microbial Degradation of Exxon Valdez Oil on the Shorelines of Prince William Sound, Alaska. Environmental Science & Technology. 31:1564-1572.