Vernal distribution of dimethylsulphide, dimethylsulphoniopropionate, and dimethylsulphoxide in the North Water in 1998

From April to June 1998, as a part of the International North Water Polynya Study (NOW), concentrations of dimethylsulphoxide (DMSO), dimethylsulphoniopropionate (DMSP), and dimethylsulphide (DMS) were determined in samples collected from the water column of the North Water, northern Baffin Bay. These compounds also were determined in ice algae and in under-ice water samples that were in close contact with the ice-algal communities. DMSO and DMSP concentrations were measured in both the dissolved phase and particulate material. The data presented here are the first reported for DMSOp in the water column of any polar sea. Water-column DMSOp and DMSPp concentrations varied from 0 to 16.9 nmol l−1 and from 0 to 9.53 nmol l−1, respectively. In April, phytoplankton biomass in the polynya was relatively low but increased considerably in May and June, reaching maximum values of 18.7 and 15.9 μg Chl a l−1, respectively. The phytoplankton community was dominated by diatoms, resulting in very low DMSPp:Chl a ratios. The behaviour of DMSOd differed from that of the other dimethylated-sulphur components in that concentrations were generally high throughout the water column and for the duration of the NOW expedition (13.1–106 nmol l−1). With the exception of a few peak values, mean water-column concentrations of DMS (0.17 nmol l−1 in April, 0.65 nmol l−1 in May, 1.08 nmol l−1 in June) and DMSPd (0.64 nmol l−1 in April, 2.12 nmol l−1 in May, 2.95 nmol l−1 in June) were low. The DMS measurements were considerably lower than those predicted by existing models for the distribution of DMS at high latitudes. These results call for a reassessment of the importance of DMS emissions in polar regions, which may have been overestimated. DMSPp and DMSOp concentrations associated with the ice-algal community were 8.66–987 and 1.35–102 nmol l−1, respectively, and were higher than water-column values due to the generally higher biomass of the ice-algal communities (4.01–2000 μg Chl a l−1). Monthly averages for total DMSPd+DMS at the ice-water interface were typically higher than water-column values for either DMSPd or DMS (6.79 nmol l−1 in April, 6.68 nmol l−1 in May and 7.30 nmol l−1 in June). Conversely, the range of DMSOd levels at the ice-water interface was generally similar to water-column concentrations (20.0–116 nmol l−1).