Polycyclic aromatic hydrocarbons and microbial community structure in the Mahoning River bank sediments

Abstract

Sediments in the Lower Mahoning River are among the most polluted in the United States. Polycyclic aromatic hydrocarbons (PAHs) are the most extensively found contaminants posing the greatest human and ecological risks in the Mahoning River sediments. Fatty acid methyl esters (FAMEs) were used to determine microbial community structure in bank sediments and to determine possible correlations among microbial biomass, microbial activity, PAHs and physical sediment characteristics. Nine sediment cores were collected from two sites (top core samples were taken at 5 centimeters and bottom core samples were taken at 2 meters) from the Mahoning River banks during March 2005. Leavittsburg was a no-to-low PAH site and Lowellville was a high PAH site. There were PAHs detected in all samples and all depths but, they were only quantifiable in highly contaminated sediments from Lowellville. Both bottom locations had very similar biomass and FAMEs, with 27-37% of the microbial community structure being composed of sulfate reducing and other anaerobic bacteria. The highest measured PAH concentration found in Lowellville bottom sediments (61.8 ug/g g-1) correlated with the highest measured microbial activity (195nmol INTF g-1), indicating potential for bioremediation. Multivariate ordination (Principal Components Analysis) indicated opposite loadings (negative vs. positive). Sediment samples tended to cluster by core depth, more than by site.