Extracellular enzyme activity at the air–water interface of an estuarine lake

Variations in hydrolytic activity of eight extracellular enzymes in surface and subsurface waters in estuarine Lake Gardno were measured. The ranking of potential activity rates of the assayed enzymes was the same in both surface and subsurface water, i.e. esterase O lipase O aminopeptidase O phosphatase O b-glucosidase O a-glucosidase O chitinase O b-lactosidase. The vertical activity profiles show that esterase, aminopeptidase, a-glucosidase, b-glucosidase and b-lactosidase reached the highest values in surface layer, whereas lipase, phosphatase and chitinase showed maximum activity in subsurface water. Significant differences in enzyme activity between different parts of the studied lake were demonstrated, with higher values in the seawater zone, and lower values in the freshwater zone.