Sulfate reduction in Lake Agmon, Israel

Lake Agmon, a newly reflooded water body in the southern part of the Hula valley is characterized by a clear phase period in winter with almost no blooms of phytoplankton. Dense macrobenthos and algal blooms form in the lake during summer and autumn. High primary production and chlorophyll-a concentrations were measured in April and during the summer of 1997. Fresh organic matter in the sediments from the degradation and decomposition of the blooms together with high sulfate concentrations, allowed microbial sulfate reduction to occur. Sediment cores taken from different sites (peat and marl) during various seasons in 1997, showed high sulfate reduction rates in June in the marl region, and in September in the peat region (842 and 2834 nmol SO₄^-2 reduced ml^-1 day^-1, respectively). In February, corresponding to the development and decline of macrophytes and algal blooms, lower rates of sulfate reduction were recorded (11 nmol SO₄^-2 reduced ml^-1 day^-1). Sulfate reduction is limited by the supply of organic matter and is one of the major processes contributing to the mineralization of organic matter in this lake.