ACTIVITY OF MICROBIAL PEPTIDASES, OXIDASES, AND ESTERASES IN LAKE WATERS OF VARYING TROPHIC STATUS

The range and activities of microbial enzymes present in lake water we re assessed directly in cells concentrated by tangential flow filtrati on. A total of 108 enzymes were assayed in this study, which included tests for 60 peptidases, 20 oxidases, and 10 esterases, and 18 miscell aneous tests. In general, no trends in the range of enzymes were assoc iated with trophic status of the lakes. However, one lake that was hyp ereutrophic had a greater range of enzymes than the other lakes tested . An increase in total enzyme activity (activity/mL) was recorded with an increase in trophic status of the water. The relationship between the physical and chemical attributes of each lake and microbial enzyme activities was investigated by principal component analysis. Quantita tive changes between lakes in 11 of the 21 variables were shown to be closely related to changes in the enzyme activities of the lakes; tota l organic carbon, particulate carbon, particulate nitrogen, pH, and ch lorophyll a showed the closest relationships.