Stratification of selected hydrolytic enzyme activities in the sediment in two lakes in Finland

To investigate the stratification of hydrolytic enzyme activities and importance of subsurface layers in depolymerization of detritus biopolymers, nine hydrolytic enzyme activities involved in the cycling of carbon, phosphorus, nitrogen and sulphur were measured in various sediment layers and their extracts at Kyläniemi in Lake Saimaa in southern Finland and in Lake Ahvenjärvi in northern Finland. The results show that for each lake all nine hydrolytic enzyme activities were higher in all sediment layers than in comparable sediment extracts indicating that the major part of enzymes was bound to the sediment particles in all layers in both lakes. Carbohydratase, β-cellobiosidase, activities did not show any gradient with sediment depth at Kyläniemi in Lake Saimaa indicating that there was rapid turnover of carbohydrates in the entire sediment column. The activities of acetate esterase, butyrate esterase, phosphomonoesterase, aminopeptidase, N-acetyl glucosaminidase, sulphatase and β-glucosidase in the deepest layers were 19–53% of those in the surface sediment indicating that depolymerization of biopolymers involved in the cycling of carbon, nitrogen, phosphorus and sulphur was substantial in subsurface sediment.