Biochemical Characterization of Estuarine Benthic Microbial Communities for Use in Assessing Pollution Impacts

Abstract

Monitoring the benthic microbial community offers a means of assessing biological changes in response to pollutants at the base of the estuarine food web. Traditional methods of microbial community analysis are inadequate because they require removal of the microorganisms from their habitat for culture on laboratory media, resulting in bias. Biochemical techniques, however, allow the microbial community structure to be analyzed without removing the microorganisms from their habitat. We have used analyses of phospholipid fatty acids (PLFA) to characterize benthic microbial community structure in Biscayne and Pensacola Bays, FL, and to relate changes in microbial community structure to sources of metal pollution. Sediment samples were obtained from clean and contaminated areas of each bay system. PLFA were analyzed by capillary gas chromatography after modified Bligh-Dyer extraction and silicic acid column chromatography. Principal components analysis was used to distinguish geographic areas, and stations within these areas, from one another based on either geochemical or microbial PLFA data. Canonical correlation was used to construct a linear relationship between metal concentrations and microbial PLFA characteristics, but was confounded by sediment grain size. Polluted stations were generally characterized by high metal concentrations, fine-grain sediments, high lipid phosphate, high trans/cis fatty acid ratios, high bacterial PLFA, and low eucaryotic PLFA.