Abstract
Chemical and biological characterization of anaerobic sediments of a eutrophic brackish lake Barato, Sapporo were performed with emphases on sulfur cycle in the sediment. Vertical distributions of sulfide compounds (FeS, FeS2 and S0) were measured and related to sediment oxygen demand (SOD). The SOD was divided into biological and chemical components by using specific inhibitors. The chemical SOD was further separated by ferrous, sulfide and manganous demands. The experimental results indicated that SOD ranged 0.3-1.4 mgO2/cm3 and the major component was ferrous demand accounting for 29-75%(avg.=55.4%). The content of sulfide compounds accounted for 1-2% of total dry weight of the sediment, which was responsible for about 40-50% of total SOD. Sulfate reduction and methane production in the sediment were limited by fatty acid (i. e., acetate) production. The addition of molybdate and chloroform to inhibit sulfate reduction and methanogenesis, respectively, gave a quantitative measure of fatty acid utilization rates by sulfate reduction and methane production. The experimental results revealed that acetate, propionate and n-butyrate accounted for approximately 60%, 25%, and 10%, respectively, of the electron donors of the sulfate reducing bacteria in this sediment. Acetate accounted for 40-60% of the electron donor of methane producing bacteria. These experimental results imply that the oxidation of sulfide, generated by microbial sulfate reduction is a key process in the biogeochemistry of brackish sediments. The detail information on the sediment of lake Barato will be useful for development of a new means to improve the overlaying water quality.
