DMSO: a significant compound in the biogeochemical cycle of DMS

Dimethylsulfoxide (DMSO) in seawater is thought to arise from photochemical and bacterial oxidation of dimethylsulfide (DMS) and is likely to be a key compound in the marine biogeochemical cycle of sulfur. DMSO was measured using a new highly specific method (12). This involves removal of DMS from samples by purging; DMSO is then reduced to DMS using the enzyme DMSO reductase purified from the photosynthetic bacterium Rhodobacter capsulatus. This technique has been used to measure DMSO concentrations during three field campaigns: in coastal and shelf waters of the North Sea during a cold and cloudy April, the equatorial Pacific inside and outside the nutrient rich plume in the vicinity of the Galapagos Islands, and the Arabian Sea along a transect from up welled eutrophic to oligotrophic waters. Results for DMSO concentrations have been compared with those for DMS and dimethylsulfoniopropionate (DMSP), in surface waters and throughout the water column. These data are used to establish the significance of DMSO in marine waters.