ARYLSULFATASE AND ALKALINE-PHOSPHATASE (APASE) ACTIVITY IN SEDIMENTS OF LAKE-KINNERET, ISRAEL

Arylsulfatase and APase activities were monitored in the upper sedimen t layer, of Lake Kinneret Israel, a warm, freshwater, monomictic lake characterized by a heavy spring bloom of the dinoflagellate Peridinium gatunense. Activity of both enzymes varied with depth and season. Hig hest activity was measured in July and high activities were monitored during the stratified period. Low values were observed in winter, when oxic conditions prevail in the water column and no organic sedimentat ion occurred. The values for APase ranged from 14-438 nmol PNP g(-1)h( -1) and for arylsulfatase from 103 to 843 nmol PNP g(-1)h(-1). Highest APase activity was recorded at 29 degrees C, and most of it took plac e on mud particles and not in the interstitial waters. There were diff erences in enzyme activity at different stations in the lake, correspo nding to differences in nutrient pore water concentrations. Enzymatic activity in Lake Kinneret sediments was related to lake trophic status , water levels, and climate conditions, all of which have an impact on the amount of organic matter reaching the sediments.