PRODUCTION AND ENZYMATIC DECOMPOSITION OF ORGANIC-MATTER BY MICROPLANKTON IN A EUTROPHIC LAKE

This report presents studies on temporal variations of phytoplankton a nd bacterioplankton production and the kinetics of bacterial enzyme ac tivity (aminopeptidase, beta-glucosidase and lipase) in the littoral a nd pelagial sampling sites of a highly eutrophic lake. Bacterial and a lgal production correlated well in pelagic water, but in the littoral there was no significant correlation between these processes. The high est activity of bacterial enzymes occurred during phytoplankton blooms (except beta-glucosidase). The rates of enzymatic decomposition of or ganic matter in the littoral and pelagial sampling sites were similar. Turnover time of enzymatic hydrolysis of the studied biopolymers in l ake water was the shortest for proteins and lipids during phytoplankto n blooms in both sampling sites. The most dynamic changes in turnover time displayed were for the hydrolysis of polysaccharides by beta-gluc osidase in the littoral samples. The significance of organic matter fo r bacterial production and enzyme activity, and the role of enzymes in bacterial processing of biopolymers in a lake ecosystem are discussed .