Distribution and activity of bacterio-plankton in the marginal ice zone of the Weddell-Scotia Sea during austral spring

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Abstract
The distribution and metabolic activity of bacterioplankton were examined in relation to biological, chemical and physical factors in the marginal ice zone south of the confluence of the Weddell-Scotia Sea during austral spring, 1983. Melt water produced by the seasonal retreat of the ice edge resulted in regions of water with reduced salinity and increased vertical stratification, which in turn increased average irradiance levels for phototrophic growth. The enhanced stability of the water column apparently influenced distributions of biomass and physiological activities of both autotrophs and heterotrophs. Elevated biomass and productivity of phytoplankton and bacterioplankton coincided spatially, with maxima occurring from 100 to 250 km seaward of the ice edge. Bacterial abundance and biomass in ice-covered and open water regions averaged 0.7 .times. 1011 cells m-3 and 1.8 mg C m-3, and 1.6 .times. 1011 cells m-3 and 3.7 mg C m-3, respectively. Bacterial biomass represented only about 3% of the total particulate organic carbon, but bacterial production integrated over the euphotic zone averaged about 11% of primary production. Our results suggest that bacterioplankton production in the marginal ice zone of the Weddell-Scotia Sea contributes significantly to the enhanced biological activity of the region.