HYDROGEN AS A SUBSTRATE FOR METHANOGENESIS AND SULFATE REDUCTION IN ANAEROBIC SALTMARSH SEDIMENT

H2 stimulated sulfate reduction in a saltmarsh sediment and the importance of H2 transferred from organotrophic bacteria to the sulfate-reducers is discussed. .beta.-Fluorolactate inhibited sulfate reduction whether lactate, ethanol or H2 was being used as growth substrate. When added to sediment .beta.-fluorolactate inhibited sulfate reduction with a consequent increase in methane production. Addition of H2 stimulated methanogenesis in sediment and this stimulation was greater if CO2 was also present. H2 availability was the primary limitation of methanogenesis but the low concentration of dissolved CO2 in seawater may limit methane production even if H2 is available. The removal of inhibition of methanogenesis by the use of fluorolactate to suppress sulfate reduction or by the provision of H2 indicates competitive inhibition of methanogens by sulfate reducers utilizing transferred H2.