Energetics of the Adults and Larvae of the Antarctic Krill Euphausia superba

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This research on the energetics of the adults and larvae of the Antarctic krill, Euphausia superba, is focused on quantification of the role of ice biota in winter-over survival of krill larvae. Observed interannual differences in physiological condition of the larvae during the winter could lead to differences in survival of the young-of-the-year, and thus in the strength of any one year class. Processes underlying such differences during early and late winter will be studied. Low food availability in the fall after the summer phytoplankton blooms suggests that larvae in early winter will have experienced several months of near starvation conditions. Without an additional food source such as ice biota in the underside of the sea ice these larvae may not survive the winter. However, larvae under the ice in late winter of a heavy ice year will have had this additional food source, and may be in better physiological condition than the beginning of the winter. Environmental conditions in open water and under ice will be compared and will be sampled to determine their physiological condition. The nutritional contribution of the ice biota to total energy demand of the larvae on two month-long cruises to the Southern Ocean will be quantified. The proposed research will address several significant questions about the winter-over energetics of larval krill, in particular the role of ice biota in winter-over survival and subsequent recruitment.