The Deepwater Horizon drilling rig explosion resulted in the largest accidental oil spill in world history. The ecological consequences of this oil spill are still largely unknown. Although biodegradation of petroleum hydrocarbons has been studied extensively in controlled biodegradation experiments, our experiences with large-scale oil spills are limited to those occurred near rocky shorelines, e.g., the Exxon Valdez oil spill in Alaska.There are still significant knowledge gaps in the basic chemical, physical, and biological processes governing the fate of released oil and the recovery of the Gulf ecosystem. Although polycyclic aromatic hydrocarbons (PAHs) comprise a relatively small fraction of the total hydrocarbon content of crude oil, they persist in the environment and many of them are mutagens and carcinogens. PAHs are the primary determinant of oil toxicity.
In this project, we propose to study the responses of microorganisms in the intertidal zone sediments to PAHs. By selecting sampling sites with and without prior oil impact, we hope to assess microbial functional differences resulting from the selection pressure imparted by crude oil. We will use naphthalene and its methyl homolog as model PAH compounds to determine the potential rate and extent of PAH mineralization and the dynamics of naphthalene dioxygenase gene abundance during the biodegradation process. The recovery of the sensitive Gulf ecosystem depends on microbial degradation of residual oil. This study will help estimate the potential rate and extent of PAH degradation in the intertidal zone of Alabama shoreline ecosystem. It will also provide a better understanding of the responsiveness of indigenous PAH-degrading bacteria to future oil spills.