Acetate-Oxidizing Sulfate Reduction in Anoxic Marine Sediments

Abstract

The contribution of acetate-oxidizing sulfate reduction to decomposition of organic matter in anoxic marine sediments was estimated by the sediment slurry system and the rates of sulfate reduction in the sediment were measured. Acetate and propionate were oxidized completely by sulfate reduction. Formate, however, was decomposed by both sulfate reduction and other processes. Most of lactate was fermented to acetate, propionate, and formate. Half of the added glucose was mineralized by sulfate reduction through fermentation including production of some kinds of low molecular fatty acids. Using fluoroacetate as an inhibitor of acetate metabolism, about 40% of glucose mineralization was estimated to be derived from acetate. The rates of sulfate reduction in an anoxic surface sediment were about 50-60nmol·g^-1·day^-1 during the summer stratified season. Fluoroacetate inhibited this activity by 65-71%. These results suggest that sulfate reduction plays an important role in the mineralization of organic matter and that acetate is a major substrate for sulfate reduction in anoxic sediments.