Size-differential regimes of phytoplankton production in the Northeast Water Polynya (77°–81° N)

Environmental control and potential fate of phytoplankton production were investigated in the Northeast Water Polynya (77° to 81° N), from 23 May to 31 July 1993. Sampling covered a mosaic of conditions ranging from open to fully ice-covered waters. Three regimes of phytoplankton production are identified, on the basis of the contribution of phytoplankton size fractions (>5 μm and 50 %) areas and was characterized by biomass and production dominated by small phytoplankton. The 2 other production regimes were found in open waters and/or mixed ice conditions. (2) In one case, surface stratification was strong, nutrients were abundant, biomass and production were dominated by large phytoplankton, and maximum chlorophyll a (chl a) was located near the surface. (3) In the other regime, the surface layer was strongly influenced by melt water, the pycnocline was relatively deep (>10 m), the biomass was dominated by large phytoplankton, production was shared by small and large phytoplankton, and maximum chl a was associated with the pycnocline. The dominant taxa in the 3 production regimes were flagellates, pennate diatoms and centric diatoms, respectively. The different primary production regimes reflect different export characteristics and could correspond to different pelagic food webs.