Standing crop of algae in the sea ice of the Weddell Sea region

Abstract

Physical and biological measurements were made of sea ice cores taken fron 68° to 78° S in the Weddell Sea. Fluorescence measurements indicated an algal community that was strongly associated with salinity maxima within the ice. Maximum concentrations of chlorophyll a ranged from 0.31 to 4.54 mg m −3. Comparisons with standing crops in the water column indicate that the standing crop within the ice can represent a minor but significant fraction of the total standing crop for the region. The sea ice algal community is apparently distinct from others that have been described for land-fast ice in McMurdo Sound, sea ice in the Arctic, and pack ice off East Antarctica. The highest concentrations of biological material are found in the bottom or top samples from those regions, whereas the Weddell Sea maxima are concentrated at intermediate depths (0.65 to 2.15 m) within the ice. A qualitative model indicating the relationship between thermally induced brine migration and subsequent algal growth is presented. The model indicates that the distribution of algae within the ice depends on the thermal and physical setting for Weddell Sea pack ice where brine drainage is initiated by spring and summer warming but is not carried through so completely as in other regions. It is concluded that the ecological significance of the release of ice algae is greater for the community in the Weddell Sea than elsewhere.