Dimethylsulfoniopropionate as a potential methanogenic substrate in Mono Lake sediments

Abstract

A high concentration of dimethylsulfoniopropionate (DMSP) was found in the water column (0.1–1.8 µM particulate plus dissolved) of Mono Lake, CA, an alkaline, hypersaline waterbody. The dense Artemia monica population contained high levels of DMSP (1.7–2.5 mmol.g -1 wet weight), presumably as an osmolyte. Death of these brine shrimp caused accumulation of DMSP along the shoreline of the lake, where concentrations peaked at 7–13 jumol.cm -3 sediment. DMSP was also associated with the phototrophic microbial population in microbial mats close to the shoreline. Chemical hydrolysis of DMSP caused by the high pH value of the water (9.7–10.0) competed with biological consumption. Flux chamber experiments suggested that part of the dimethylsulfide (DMS) generated by hydrolysis escaped to the atmosphere. Vertical profiles of DMSP and DMS in the sediment correlated well. Methane and DMS also had similar distributions. Additional inhibitor studies showed that a major biological sink for DMS(P) is methanogenesis, although monooxygenase-containing bacteria also contributed to its consumption.