Turnover of dimethylsulfoniopropionate and dimethylsulfide in the marine environment: a mesocosm experiment

The production of dimethylsulfoniopropionate (DMSP) by marine phytoplankton and the fate of the produced DMSP and dimethylsulfide (DMS) were studied in 4 pelagic mesocosms during an algal bloom over a period of 1 mo. Bacterial numbers, concentrations of particulate and dissolved DMSP, DMS, and chlorophyll a were monitored, as well as the turnover rates of DMS and DMSP. Of the total amount of DMSP produced, only a fraction could be detected as DMS in the water column. DMS production in the water column did not necessarily correlate with algal senescence, but also occurred during the maximum of the algal bloom. The flux of DMS to the atmosphere played a minor role as a sink for DMS. Evidence is presented that shows bacterial consumption to be a major sink for DMS, under conditions of both high and low DMS water concentrations. DMSP was degraded either via cleavage or via demethylation; the results indicate a predominant role for the latter route.