SULFATE-REDUCTION PROCESS IN SEDIMENTS OF LAKE KINNERET, ISRAEL

Monomictic Lake Kinneret is stratified during summer and autumn, resulting in a hypolimnion rich in H2S (3-7 mg l-1). In winter and spring every year a bloom of dinoflagallate Peridinium gatunense produces an average biomass of 150000 ton wet weight. Part of this biomass sinks to the hypolimnion and sediments where it is decomposed and mineralized, with some of the mineralization due to the activity of sulfate-reducing bacteria (SRB). The sulfate-reduction potential of the upper sediment layer at the deepest part of the lake (42 m) was measured. The activity of the enzyme arylsulfatase was also monitored. Rates of sulfate-reduction ranged from a minimum of 12 nmoles SO42- reduced cm-3 day-1 in December before lake overturn to a maximum of 1673 nmoles SO42- reduced cm-3 day-1 in July during stratification. These rates are considerably higher than those recorded from other freshwater lakes in the world and are probably limited more by the availability of organic matter than by sulfate concentrations.