Spatial and vertical distribution of particulate dimethylsulphoniopropionate (DMSP) during spring in the Atlantic sector of the Southern Ocean

Dimethylsulphoniopropionate (DMSP) concentrations in relation to phytoplankton biomass and species composition were investigated on four transects between 47°S and 60°S along 6°W during the SO-JGOFS cruise ANT X/6 of R.V. Polarstern in October/November 1992. Particulate DMSP concentrations at 20 m depth in the three pelagic regimes, Polar Frontal Zone, southern Antarctic Circumpolar Current and the northern rim of the Weddell Gyre, were about 25–66, 5 and 3–14 nM, respectively. DMSP:chlorophyll a ratios for the three zones were 32–92, 10–35 and 25 nmol (μg chi a)−1, respectively. In the Polar Frontal Zone, the majority of DMSP was found in the 5–20 μm size fraction. Some DMSP was produced by algae > 20 μm (mainly diatoms), but the contribution of algae < 5 μm was negligible. As such, the Antarctic phytoplankton community sampled in the open Southern Ocean cannot be considered especially active DMSP producers compared to temperate and tropical algae.