The cycling of climatically active dimethyl sulfide (DMS) in the marine euphotic zone: Biological and chemical constraints on the flux to the atmosphere

In this study, the author used a series of linked carbon-sulfur budget models to examine possible constraints on DMS production and sea-air flux. The results suggest that the cycling of DMS within the water column is complex and still poorly understood, with multiple biological processes controlling its production from DMSP, and rapid biological consumptions as well. It appears that there is often a much larger cycling of DMS within the water column than is evident from its flux to the atmosphere. Approximately 0.5% of the sulfate-S originally assimilated by phytoplankton was lost to the atmosphere as DMS. Although the constraint on DMS abundance may involve a near-balance between its biological production and consumption, there is still not adequate data to demonstrate this, and production of DMSP and its conversion to DMS remain one of the key rates to be measured in situ. 14C-DMS was consumed biologically with CO2 and particulate (cell) material the main products, in ratios typically about 2:1, suggestive of methylotrophy. Saturation was not observed up to 20 nM. Compared to a chloroform-inhibition method this method gave somewhat lower rate estimates. It was used to confirm that chloroform addition inhibits DMS consumption by 70-90%. The author found no evidence for production of methane or other volatile gases from DMS, and 100 μM trimethylamine did not appear to inhibit consumption