Enzymatic and microbial degradation of organic matter in Lake Hongfeng, Guizhou Province, China

Abstract

In this work, enzymatic and microbial degradation of organic matter in Lake Hongfeng, Guizhou Province, is described in terms of variations in DNA, α-glucosidase and sulfatereduction bacteria (SRB). Organic matter is degraded by microbes and extracellular enzymes excreted by the former, to a relatively low content below the 11-cm sediment depth. The distribution of DNA indicated that microbes are very active at the 9-cm sediment depth, where organic matter is degraded by microbes intensively. The contents of α-glucosidase are highest in suspend layer (0.75 μmol · min−1· g−1 dry sediments), showing that starch and hepatin in organic matter have been degraded intensively. α-glucosidase activity weakens with sediment depth. At the 11-cm depth where the degradation of organic matter started to slow down, α-glucosidase activity has been reduced to 0.17 μmol · min−1 · g−1 (dry sediment). Molecular biological research indicated that sulfate reduction bacteria (SRB) are distributed mainly at the upper 7-cm sediments in Lake Hongfeng. Combined with the results of research on the variations of organic matter and SO 4 2− , it is indicated that SO 4 2− is unlikely to become an important electron acceptor and sulfate reduction is not limited by the supply of organic matter in Lake Hongfeng.