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Plankton tows taken within the Antarctic sea ice in late October through November 1981, as part of the US-USSR Weddell Polynya Expedition contain numerous varieties of polycystine and tripylean radiolarians. Fifteen tows at nine sites sampled the zooplankton at specific intervals within the water column along a north-south transect extending over 300 km (190 mi) within the ice.
Although chlorophyll A levels were relatively low (<= 0.1 mg/m3) in samples taken under the ice, the total number of polycystine and tripylean radiolarians per cubic meter of filtered seawater ranged from 20 to 50% of that reported from open-ocean sites. At several of the ice stations, the number of radiolarians per cubic meter of filtered seawater was similar to that recorded at the ice edge, even though ice-edge chlorophyll levels were 100% higher than levels at sites in the ice. The relatively high number of radiolarians found under the ice is even more unusual considering that the region has been completely ice-covered for a minimum of 4 months prior to sampling.
Although most species were found living above and below the thermocline/halocline, specific species such as Spongotrochus glacialis Popofsky and Lithelius nautiloides Popofsky were most abundant in tows which sampled the water column above this oceanographic boundary. Comparison of this plankton-tow data with that from Antarctic surface-sediment samples shows, that with few exceptions, the relative abundances of specific polycystine species in the water column are comparable to those found in the surface sediments.
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