Temporal variations of dimethylsulfide and dimethylsulfoniopropionate in the southern Yellow Sea in spring and autumn

Abstract

Temporal distributions of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) were studied in the southern Yellow Sea (SYS) during April and September 2010. The mean concentrations (range) of DMS, dissolved and particulate DMSP (DMSPd and DMSPp) in the surface waters in spring are 1.69 (0.48-4.92), 3.18 (0.68-6.75) and 15.81 (2.82-52.33) nmol/L, respectively, and those in autumn are 2.80 (1.33-5.10), 5.45 (2.19-11.30) and 30.63 (6.24-137.87) nmol/L. On the whole, the distributions of DMS and DMSP in spring are completely different from those in autumn. In the central part of the SYS, the concentrations of DMS and DMSP in spring are obviously higher than those in autumn, but the opposite situation is found on the south of 34 degrees N, which can be attributed to the differences in nutrients and phytoplankton biomass and composition between spring and autumn. Besides, the seasonal variations of water column stability and the Changjiang diluted water also have significant impact on the distributions of DMS and DMSP in spring and autumn on the south of 34 degrees N. DMS and DMSPp concentrations coincide well with chlorophyll a (Chl a) levels in the spring cruise, suggesting that phytoplankton biomass may play an important role in controlling the distributions of DMS and DMSPp in the study area. Annual DMS emission rates range from 0.015 to 0.033 Tg/a (calculated by S), respectively, using the equations of Liss and Merlivat (1986) and Wanninkhof (1992). This result implies a significant relative contribution of the SYS to the global oceanic DMS fluxes.