Experimental investigation of the effects of polynuclear aromatic hydrocarbons on an estuarine sediment food web

The influence of polynuclear aromatic hydrocarbons (PAH) on a benthic estuarine sedimentary salt-marsh food web was examined using a microcosm system to simulate natural conditions. Microcosms were dosed with sublethal concentrations of PAH-contaminated sediment collected from a produced-water site at Pass Fourchon, Louisiana, USA (final PAH concentrations ranged from 0.3 to 3 mg PAH/kg dry sediment). Bacterial activity, physiological condition and abundance were not influenced by PAH, but microalgal activity and physiological condition were. Grazing by meiobenthic copepods on benthic microalgae was not significantly influenced by PAH concentration, nor was the physiological condition of copepods, as determined by their lipid-storage material. Meiofaunal community composition was influenced by PAH, as nematodes became disproportionately abundant, and the nauplius/copepod ratio increased in High-PAH treatments. Overall, however, sublethal effects of PAH were not pronounced at the concentrations examined. Considering that coastal Louisiana has been exposed to chronic contamination by petroleum hydrocarbons for decades, it is suggested that the sedimentary microbial/meiofaunal community may have adapted to elevated PAH concentrations.