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Microbial metabolism reacts quickly to environmental conditions. These reactions are dependent on the need for nutrients and respiration and can be measured using an assay of individual microbial enzyme activities (MEA’s). In this study, we measured MEA’s in the sediments of a stream in northeast Tennessee that had an approved fecal coliform Total Maximum Daily Load (TMDL). These values were compared to biochemical oxygen demand (BOD), phosphate concentration and nitrate concentration in the water column of this stream. Comparisons were grouped by season and land use. Stream sediments and water were collected monthly for one year and then quarterly for an additional two years at 14 sites located in agricultural, urban and forest regions. Dehydrogenase (DHA), a measure of microbial respiration, along with acid phosphatase (AcidPA), alkaline phosphatase (AlkPA), galactosidase (GalA) and glucosidase (GluA) activities were measured using colorimetric assays. BOD was determined using the standard 5-day BOD test (BOD5). Nitrate and phosphate concentrations were measured using colorimetric procedures. There were significant positive and negative correlations (p5, DHA vs. nitrate concentration, and DHA vs. phosphate concentration. Also in the fall months there were significant negative correlations between GalA and GluA vs. BOD5, and concentrations of nitrate and phosphate. There was also a negative correlation between AcidPA and BOD5. In the warmer months of spring and summer, there were positive correlations between AcidPA, AlkPA, GalA and GluA vs. the BOD5 ’s, and the concentrations of nitrate and phosphate. The only negative correlation in a warmer season was in the summer between AlkPA vs. BOD5 and phosphate concentration. No significant correlations were found by land use type. Results indicate that significant relationships may exist between MEA’s and other water quality measures (e.g. BOD5, nitrate concentration, and phosphate concentration) that could make it possible to use MEA’s as another tool for water quality assessment.

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