Sea Ice: An Important Seasonal Habitat for Marine Invertebrate Juveniles in Arctic Fast Ice Systems?

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A large fraction of Arctic coastal seas currently exhibits a sea ice cover for at least several months per year. This ice serves as a habitat for highly specialized, distinct communities inside and at the underside of the ice. The ice-related food web extends to higher trophic levels such as sea-floor dwellers, seals, and polar bears and, therefore, closely ties the sea ice, pelagic and benthic realms together. The quality and duration of the sea ice cover varies significantly on decadal time scales. In order to predict how future variations in ice cover might affect arctic ecology, a better knowledge of the present role of sea ice is needed. Therefore, funds are provided to enhance understanding of the role of near-shore Arctic sea ice in the life cycle of marine benthic invertebrates with a focus on polychaetes.Hypotheses to be tested concern three issues:1. Believing that sea ice is the preferred habitat for young stages of certain polychaete species in the Arctic nearshore, the PIs will test the hypothesis that polychaetes occur in the same densities in sea ice and the water columnthroughout the sea ice season.2. Believing that sea ice provides better growing conditions for young stages of certain polychaete species than the water column, they will test the hypothesis that polychaetes have the same growth and feeding rates in sea ice and the water column throughout the sea ice season.3. Believing that the effects of extreme environmental conditions prevailing in the sea ice brine channel system are outweighed by better overall growing conditions relative to the water column, they will test the two hypotheses that a) polychaete mortality at ambient salinities present in sea ice is equal to that at normal seawater salinity, and b) the sum of growth and mortality is the same in polychaetes inhabiting the water column and the sea ice.