SPATIAL AND VERTICAL-DISTRIBUTION OF PARTICULATE DIMETHYLSULPHONIOPROPIONATE (DMSP) DURING SPRING IN THE ATLANTIC SECTOR OF THE SOUTHERN-OCEAN

Dimethylsulphoniopropionate (DMSP) concentrations in relation to phyto plankton biomass and species composition were investigated on four tra nsects between 47 degrees S and 60 degrees S along 6 degrees W during the SO-JGOFS cruise ANT X/6 of R.V. Polarstern in October/November 199 2. Particulate DMSP concentrations at 20 m depth in the three pelagic regimes, Polar Frontal Zone, southern Antarctic Circumpolar Current an d the northern rim of the Weddell Gyre, were about 25-66, 5 and 3-14 n M, respectively. DMSP:chlorophyll a ratios for the three zones were 32 -92, 10-35 and 25 nmol (mu g chl a)(-1), respectively. In the Polar Fr ontal Zone, the majority of DMSP was found in the 5-20 mu m size fract ion. Some DMSP was produced by algae >20 mu m (mainly diatoms), but th e contribution of algae <5 mu m 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. (C) 1997 Elsevier Science Ltd.