Kinetics of alkaline phosphatase in lake sediment associated with cage culture of Oreochromis niloticus

Variations in kinetics of alkaline phosphatase occurring in different sites of sediment associated with cage culture of Oreochromis niloticus in a sha llow Chinese freshwater lake (Lake Donghu) were described. In addition, the kinetic parameters of each 2.5-cm stratum in the sediment from the surface down to 37.5 cm were analyzed. Horizontally, the V-max values of alkaline phosphatase in surface sediments increased markedly at sites immediately un der and adjacent to the cage that would be subjected to the deposition of f ish feces. Peak V-max values in the top 5 cm of the sediment under the cage were also observed relative to their deeper control. After a treatment whe re the fish feces were added over 12 days, the sediment in deeper layer exh ibited a significantly higher V-max value, thereby corroborating the relati onship between V-max values of alkaline phosphatase and fish feces in sedim ents. The fish feces exhibited a remarkable alkaline phosphatase activity ( APA). Thus, it is indeed a source of the enzyme. Effects of the fish feces were dose- and time-dependent. The V-max values in sediments were always st imulated, but the K-m values showed much more variability. (C) 2001 Elsevie r Science B.V. All rights reserved.