AFTER THE SPILL: METAL CYCLING IN GULF COAST WETLANDS

The Deepwater Horizon explosion (April 20, 2010) and subsequent oil spill contaminated hundreds of miles of Gulf Coast wetlands. It was expected that this influx of organic matter would serve as an electron donor to the system, thereby increasing biogeochemical activity and causing metals, as terminal electron acceptors, to be reduced and mobilized. Increased arsenic mobilization and mercury methylation are of special concern due to the toxicity of these elements. Arsenic may be mobilized by its reduction from As(V) to As(III), the more mobile form. Mercury may be methylated, and thereby bioaccumulate, due to the activity of sulfur reducing bacteria. Sediment cores and porewaters from ten Alabama, Mississippi, and Louisiana wetlands were collected and analyzed to examine this hypothesis. Initial data indicate that evidence of oil contamination is present over a large spatial extent and that strongly reducing conditions were attained, as indicated by high reduced sulfur concentrations. However, porewater metal concentrations remain low and evidence of altered metal cycling is limited. Explanations for this will be explored using both aqueous and solid phase analyses.