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Polycyclic aromatic hydrocarbons (PAHs) are common contaminants in terrestrial and aquatic environments and can represent a significant constituent of the carbon pool in coastal sediments. We report here the results of an 18-month seasonal study of PAH biodegradation and heterotrophic bacterial production and their controlling biogeochemical factors from 186 sediment samples taken in a tidally influenced freshwater estuary. For each sampling event, measurements were averaged from 25-45 stations covering ∼250 km 2. There was a clear relationship between bacterial production and ambient temperature, but none between production and bottom water dissolved oxygen (DO) % saturation or PAH concentrations. In contrast with other studies, we found no effect of temperature on the biodegradation of naphthalene, phenanthrene, or fluoranthene. PAH mineralization correlated with bottom water DO saturation above 70% (r 2 > 0.99). These results suggest that the proportional utilization of PAH carbon to natural organic carbon is as much as three orders of magnitude higher during cooler months, when water temperatures are lower and DO % saturation is higher. Infusion of cooler, well-oxygenated water to the water column overlying contaminated sediments during the summer months may stimulate PAH metabolism preferentially over non-PAH organic matter. © Springer Science+Business Media, Inc. 2005.

The objective of the project is to determine the extent to which intrinsic bioremediation is occurring in groundwater contaminated with gasoline (benzene, ethylberizene, toluene, and xylenes; 3TEX), methyl-tertbutyl ether (MTBB), and trichloroethylene (TCE). Preliminary findings suggest that the comingled contaminant plumes have significant bacterial productivity and contaminant mineralization rates. Rapid bacterial production and benezene turnover rates at wells, which are down gradient of the other BTEX plume(s) suggests that the natural bacterial assemblage has the capacity to inhibit migration of the plume towards Noisette Creek.