Diversity in Zooplankton and Sympagic Biota during a Period of Rapid Sea Ice Change in Terra Nova Bay, Ross Sea, Antarctica

Sea ice is a major driver of biological activity in the Southern Ocean. Its cycle growth and decay determines life history traits; food web interactions; populations many small, ice-associated organisms. The regional ocean modelling system (ROMS) for sea western Ross has highlighted two modes duration: fast-melting years when water temperature warms quickly early spring melts out mid-November, slow-melting remains below 0 °C persists through most December. Ice-associated pelagic biota Terra Nova Bay, Sea, were studied intensively over 3-week period November 1997 as part PIPEX (Pack-Ice Plankton Experiment) campaign. environment exhibited features year, cover measured 0.65 m late November. Phytoplankton abundance diversity increased second half November, concomitant with warming air temperatures, melting progressive deepening still weak pycnocline. Water column phytoplankton was dominated by planktonic species, both diversity, although there also some input from benthic species. Pelagic zooplankton typical nearshore Antarctic system, cyclopoid copepod Oithona similis representing at least 90% total abundance. There an increase numbers coinciding thinning. Conversely, species such calanoid copepods Stephos longipes Paralabidocera antarctica decreased time found low once temperatures increased. Stratified sampling under ice, to 20 m, revealed that P. mainly close association under-ice surface, while S. longipes, O. similis, Metridia gerlachei dispersed more evenly.