Abstract - 1. Distribution of phytoplankton biomass was controlled by physical factors during Jan/Feb 1985 in the southeastern Weddell Sea. Microplankton mostly dominated phytoplankton biomass. Protozooplankton corresponded to 10-25% of autotroph biomass. 2. Nitrate decrease during the investigations was converted to new production of 11 and 13 gC m-2 for coastal and oceanic waters, respectively. Total measured production was in the same range. 3. Seasonal nitrate depletion was comparable to that in many mid-latitude environmaenst, and was equivalent to new production of 26 and 33 gC m-2 for coastal and oceanic waters. 4. It is suggested that new production is high during brief periods, when biomass accumulation is enhanced by transient reduction of vertical mixing. 5. Sedimentation of organic matter amounted to 2.4 gC m-2 for the investigation period and was dominated by zooplankton faeces. 6. Trap collections probably underestimated vertical flux. 7. Sampling strategies in relation to time-space scales of pelagic processes are discussed.