Spatial variability of phytoplankton, nutrients and new production estimates in the waters around Svalbard

Phytoplankton dynamics and carbon input into Arctic and sub-arctic ecosyste ms were investigated around Svalbard, in summer 1991. Phytoplankton biomass , species composition and dissolved nutrient concentrations were analysed f rom water samples collected along seven transects, Phytoplankton biomass wa s low especially to the north (Chlorophyll-a mean 0.3 mug l(-1)), where fla gellates dominated the communities and only ice-diatoms were present, To th e west, the phytoplankton composition was representative of a summer Atlant ic community, in a post-bloom state. Zooplankton grazing, mainly by copepod s, appeared to be the main control on biomass to the west and north of Sval bard. In the Barents Sea least of Svalbard), an ice edge bloom was observed (Chlo rophyll-a max, 6.8 mug l(-1)) and the ice edge receded at a rate of approxi mately 11 km day(-1). The phytoplankton community was represented by margin al ice species, especially Phaeocystis pouchetii and Chaetoceros socialis, South of the ice edge, Deep Chlorophyll Maxima (DCM) were observed, as surf ace waters became progressively nutrient-depleted, In these surface waters, the phytoplankton were predominantly auto- and heterotrophic flagellates, Carbon production measurements revealed high net production (new and regene rated) to the north of the Barents Sea Polar Front (BSPF); it was especiall y high at the receding 1.44 g C m(-2) day(-1)). To the south, a low level m aintained, mainly through regenerative processes.