Dissolved and Particulate Dimethylsulfoxide in the South China Sea During Winter

The distributions of particulate and dissolved dimethylsulfoxide (DMSOp, DMSOd) were studied for the first time in the surface water of the South China Sea (SCS) in January 2010. The concentrations of DMSOp ranged from 2.6 to 56.8 nmol L−1 with an average of 11.1 ± 2.2 nmol L−1, and those of DMSOd ranged from 11.8 to 335.1 nmol L−1 with an average of 50.0 ± 16.5 nmol L−1. DMSOd dominated over both dimethylsulfide (DMS) and dissolved dimethylsulfoniopropionate (DMSPd) by 1–3 orders of magnitude and represented the major dissolved dimethyl sulfur pool. In addition, DMSOp/chlorophyll-a ratios varied from 2.7 to 180.7 mmol g−1 with an average of 30.5 ± 9.6 mmol g−1. DMSOd concentrations displayed a significant negative relationship with sea surface temperature (SST) and sea surfaces salinity (SSS) in the whole study area. The distribution of DMSOd in the coastal waters was obviously influenced by the Pearl River discharge, with high concentrations appearing around the river mouth. In the offshore waters, a significant correlation was observed between the DMSOp and DMSOd concentrations, suggesting that DMSOd was mainly from the diffusion of intracellular DMSO rather than from the photochemical and biological oxidation of DMS.