Microbial communities from the sea ice and adjacent water column at the time of ice melting in the northwestern part of the Weddell Sea

Abstract

Microbial composition-including microalgae, bacteria and protozoans- and potential metabolic activity of its autotrophic compartment were measured in December 1988 in several micro-environments that characterise the North-West Sector of the marginal area of the Weddell Sea; infiltration and band assemblages of ice floes and adjacent waters were investigated. At the time of ice melting, a shift from a diatom dominated population (ice) to a flagellate dominated population (water column) was observed. Nevertheless, this shift was not due to an “inability” of the ice-diatoms to grow in the water colum. Macro-grazing and/or sedimentation are suggested as possible causes of the disappearance of diatoms during ice melting. The remaining small autotrophic forms released by the ice would constitute a significant seeding stock for the growth of ice-edge blooms.