Surface water distribution of pico- and nanophytoplankton in relation to two distinctive water masses in the North Water, northern Baffin Bay, duringfall

Distribution of pico- and nanophytoplankton in surface waters was investiga ted in relation to environmental factors at 10 stations in the North Water (NOW), northern Baffin Bay, and at 4 more southerly stations in Baffin Bay in fall 1999. Water temperature (T), salinity (S), dissolved inorganic nitr ogen (DIN), phosphate concentrations and pico- and nanophytoplankton abunda nces were measured in the surface waters in the studied area. A clustering analysis was performed on these data and allows 2 major ecological regions to be distinguished. An eastern region was characterized by warmer, more sa line, surface waters (T> -0.04 degreesC, 31.1 < S < 32.7) where the picophy toplankton (eukaryotic flagellates, prasinophyte) were more abundant (700 t o 4000 cells ml(-1)). The distribution of picophytoplankton in the NOW was directly correlated with the surface water rand S. Another region, the nort hwestern, was characterized by colder, less saline, surface waters (T < -1. 2<degrees>C, 29.3<S<31.0), can be divided into northern and western sub-reg ions. Nanophytoplankton (mostly diatoms) were more abundant (>3000 cells ml (-1)) in the northern sub-region and their distributions followed the chang e in DIN concentrations. DIN and phosphate concentrations were higher in th e northern sub-region than in the eastern region and the western sub-region , although DIN and phosphate concentrations were low in the NOW, with value s ranging from 0.1 to 1.0 and 0.09 to 0.69 muM, respectively. Based on thes e ecological results, it is hypothesized that a surface current flows north ward along the western coast of Greenland in fall, bringing warm, more sali ne water to the eastern part of the NOW. In contrast, surface Arctic water (colder, less saline) coming from the Kane Basin flows southward along the western part of the NOW. These 2 distinct water masses, with their differen t physical and chemical characteristics, govern pico- and nanophytoplankton distributions in the NOW during the fall.