A Comparison Study of Microbial Enzyme Activities and Coliforms in the Sediments of a Fecally-Contaminated Tennessee Stream Relative to Season and Land Use

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Enzymes react quickly to environmental stress and can serve as sensitive indicators of environmental change. Microbial enzyme activities (MEA’s) can be a useful tool to evaluate the health of an aquatic ecosystem. In this study we compared the trends of MEA’s (µg/g) to total and fecal coliform concentrations (CFU/g) in sediments from a stream in Northeast Tennessee that had an approved fecal coliform Total Maximum Daily Load (TMDL). The comparisons were based on season and land use through which the stream flowed. Triplicate grab samples of stream sediments were collected monthly for 29 months at 14 sites located in agricultural, urban, and forest regions. Dehydrogenase, acid phosphatase, alkaline phosphatase, galactosidase and glucosidase activities were determined using specific colorimetric analyses. Total coliforms and fecal coliforms were determined using the membrane filtration method. There was significant positive correlation (p<0.05 Pearson) between the total coliform concentrations and all five enzyme activities in the winter (January, February and March). A positive correlation was also seen with alkaline phosphatase in the summer. Fecal coliform concentration was positively correlated with dehydrogenase activity in the winter and spring (April, May and June), and with galactosidase activity in the winter, spring and summer (July, August and September). Fecal coliforms were also positively correlated with acid phosphatase in the summer. Only those sediments located in the urban region showed a positive correlation between total coliforms and dehydrogenase, acid phosphatase, alkaline phosphatase and glucosidase. DHA also showed a positive correlation between total coliforms and the forest region. The only correlation between fecal coliforms and region was with acid phosphatase in the urban region. A strong inverse relationship existed with the ratio of each specific MEA over the fecal coliform concentration versus both the seasons and regions. These correlations show that elevated activities of these five microbial enzymes can serve as another indicator of stream impairment.

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This document was originally published by the ETSU College of Public Health.

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