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Abstract: To investigate the fate of ice algae released from sea ice, we investigated the abundance, species composition, and sinking flux of diatoms in the water column under fast ice near Syowa Station, Antarctica during the summer of 2005/2006. The diatom assemblage in the water column consisted of chain-forming planktonic species, in contrast to the under-ice assemblage dominated by pennate species reported from this site in the past; this dissimilarity suggests the presence of an unconsolidated platelet ice layer under the congelation ice, within which planktonic species can bloom. Among the dominant diatoms, Porosira pseudodenticulata and Pseudo-nitzschia cf. turgiduloides were dominant in the water column, and their water column stocks were higher than their mass sedimentation. These species apparently maintain their populations in the surface layer, as their production remains in the water column. In contrast, Fragilariopsis kerguelensis and Thalassiosira australis were scarce in the water column but rich in the flux, indicating active sinking and export of their production to the benthic ecosystem. This distinction in buoyancy control and sinking characteristics of the dominant diatoms on release from the fast ice influences the diatom species composition and carbon flow under the ice. [Copyright &y& Elsevier]

Abstract: We investigated the morphological features, vertical sinking fluxes, and number densities of the resting cells of ice-associated microorganisms in the 20–100μm fraction of natural marine sediments collected from ice-covered and ice-free areas around Syowa Station, Lützow-Holm Bay, East Antarctica. We identified the resting cells of various taxonomic groups, including the spores of a diatom, cysts of three dinoflagellates, cysts of five oligotrich ciliates, and the eggs of a mesozooplankton. This is the first report of oligotrich ciliate cysts from Antarctic waters. The resting spores of Thalassiosira australis (diatom), cysts of Polarella glacialis (dinoflagellate), and egg type 1 sink to the bottom sediment during summer. Our results suggest that some planktonic and ice-associated microorganisms in Antarctic coastal areas send their resting cells to the bottom sediments as seed populations for the following generation. [Copyright &y& Elsevier]