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Temporal and spatial variations of three dimethylated sulfur compounds in the Changjiang Estuary and its adjacent area during summer and winter
The spatio-temporal distribution patterns of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), and chlorophyll a (Chl-a), as well as the oceanographic parameters influencing the concentrations of DMS, DMSP, and DMSO, were measured in the Changjiang Estuary and its adjacent area during two cruises from February 21 to March 10, 2014 and from July 10 to 22, 2014. The concentrations of DMS and DMSP showed a significant seasonal variation, i.e., higher values in summer than in winter. This result corresponded well with the seasonal change in Chl-a in the study area. The distribution of dissolved DMSO (DMSOd) conspicuously decreased offshore, suggesting a primary source of terrestrial and riverine inputs. The seasonal variations of both DMSOd and particulate DMSO (DMSOp) were weaker than other sulfur compounds. Significant relationships were observed between DMS (r = 0.579, P < 0.01 in winter; r = 0.832, P < 0.01 in summer), particulate DMSP (DMSPp) (r = 0.582, P < 0.01 in winter; r = 0.797, P < 0.01 in summer), DMSOp (r = 0.605, P < 0.01 in winter; r = 0.918, P < 0.01 in summer), and Chl-a, suggesting that phytoplankton biomass plays an important role in controlling the distributions of DMS, DMSP, and DMSO in the study area. The positive relationship between DMSPp and DMSOp (r = 0.606, P < 0.01 in winter; r = 0.771, P < 0.01 in summer) suggested similar sources and cellular functions in algae, whereas the oxidation of DMS to DMSOd appeared to be a dominant source of DMSOd in winter in the adjacent area of the river mouth. The average sea-to-air fluxes of DMS in the Changjiang Estuary and its adjacent area were 0.37 and 1.70 Âµmol mâ2 daysâ1 in winter and summer, respectively; these values were much lower than those in other continental shelf seas.
EN16158 Accepted 18 December 2016
© CSIRO 2016