Variation of biogenic dimethylated sulfur compounds in the Changjiang River Estuary and the coastal East China Sea during spring and summer

The biogeochemical cycle of biogenic dimethylated sulfur compounds in oceans has received significant attention because of their critical role in the global climatic and atmospheric processes. The behavior of biogenic dimethylated sulfur compounds including dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) was measured in the waters of the Changjiang River Estuary and the coastal East China Sea during two cruises from 7 to 20 March 2016 and from 4 to 16 July 2016. The concentrations of DMS, particulate DMSP (DMSPp), dissolved DMSP (DMSPd), particulate DMSO (DMSOp) and dissolved DMSO (DMSOd) in the study area showed significant spatial and seasonal variation, with higher values in summer. DMS displayed significant relationships with DMSPp, DMSPd and DMSOp, and the dimethylated sulfur compound distributions showed similar patterns with that of chlorophyll a (Chl-a). The seasonal variation in DMSOd was inconspicuous compared to other sulfur compounds and its concentration inside the estuary was relatively high, suggesting an impact by anthropogenic activities and riverine inputs. Phytoplankton biomass and water mass mixing (upwelling and the Changjiang diluted water) played an important role in controlling the distributions of dimethylated sulfur compounds in the Changjiang River Estuary and the coastal East China Sea. The mean sea-to-air fluxes of DMS in this study area were 3.21 and 20.73 μmol m−2 d−1 in spring and summer, respectively. The study area was a net source for atmospheric DMS. [Display omitted] •DMS distribution was influenced greatly by phytoplankton and water mass mixing.•Diatoms and dinoflagellates dominate phytoplankton communities in the study area.•DMSOd was influenced by anthropogenic activities and riverine inputs.•A significant correlation was observed between pH and DMS concentrations in summer.•DMS emission in the study area had a great contribution to the global DMS budget.