A multiple year‐round study of atmospheric dimethyl sulfide (DMS) (from December 1998 to April 2003) as well as sulfur‐derived aerosols (methanesulfonic acid (MSA) and non‐sea‐salt sulfate) (from March 1991 to February 2003) was conducted at Dumont d'Urville, coastal Antarctica. The three sulfur‐derived species exhibit a seasonal cycle characterized by maxima in midsummer (January). Whereas the interannual variability of winter levels remains low, a strong interannual variability is shown in summer, particularly for DMS and MSA, and to a lesser extent for non‐sea‐salt sulfate. Over the 1998–2003 time period, January 2002 stands out with high values for all sulfur species. These interannual variabilities of atmospheric summer levels are examined in the light of seawater chlorophyll a content derived from Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) data (themselves compared to field measurements made south of 60°S), oceanic DMS levels estimated from chlorophyll a SeaWiFS data, and various sea‐ice indices.

.[1] We present the first direct measurements of dimethylsulfide (DMS) emissions from Antarctic sea ice to the atmosphere during the seasonal warming period obtained using a chamber technique. Estimated DMS fluxes measured over the snow and superimposed ice (ice formed by the freezing of snow meltwater) were from 0.1 to 0.3 mmol m À2 d À1. The DMS fluxes measured directly over the sea-ice slush layer after removal of the snow and superimposed ice, ranged from 0.1 to 5.3 mmol m À2 d À1 , were large compared to those measured over the snow and superimposed ice. The DMS concentrations in slush water ranged from 1.0 to 103.7 nM. The DMS fluxes increased with increasing DMS concentrations in slush water. Our results indicate that the potential DMS flux measured over the slush layer occurred originally from the slush layer, and was dependent on the DMS concentrations in slush water. However, snow accumulation and the formation of superimposed ice over the slush layer significantly blocks the diffusion of DMS to the atmosphere, with the result that DMS tends to accumulate in the slush layer although the removal process of DMS by photolysis reaction can modify the DMS flux from the slush layer. Hence, the slush layer has the potential to release the DMS to the atmosphere and ocean when the snow and superimposed ice melts.

The role of zooplankton grazing on dimethylsulfide (DMS) and dissolved dimethylsulfoniopropionate (DMSPd) production was investigated in the Antarctic Ocean in January and February 2002. Dominant herbivorous macrozooplankton of this region, the Antarctic krill Euphausia superba and the tunicate Salpa thompsoni, were used in shipboard incubation experiments. The concentration of DMSPd + DMS increased in the water during incubation with krill. The production rate was 2.96 ± 2.78 nmol DMSPd + DMS·krill–1·h–1 (mean ± SD). In addition, the DMSPd + DMS production rate was linearly related to the ingestion rate of krill (r2 = 0.664, p ≤ 0.01). Addition of salps to natural surface water, however, did not change the DMSPd + DMS concentrations. During the experiments, both animals fed on phytoplankton cells. The fecal pellets of krill contained broken phytoplankton cells, whereas those of salps contained unbroken cells. These results suggest that sloppy feeding by krill is a more likely mechanism for producing DMS and DMSPd than the direct ingestion of phytoplankton cells by salps. The decrease of DMS concentrations in the upper 200 m of the water column from January to February may be explained, in part, by changes in the composition of the macrozooplankton community.