| Abstract: | A study was made of the standing crop and primary productivity of the marine phytoplankton and nutrient elements, in a transect along 150° E longitude from 64° S to 40° S latitude, during U.S.N.S. Eltanin Cruise 38 (March-May, 1969). Based on the hydrographic data collected, the areas investigated were divided into four regions: Antarctic, Antarctic Convergence (Polar Front), Subantarctic and Subtropical Convergence. Higher temperatures, lower dissolved oxygen concentrations, and a substantial decrease in silicate values were noted as the Antarctic Convergence was crossed (at 58° S) from south to north. During this cruise, the Subtropical Convergence was located at approximately 40° S latitude off the east Australian continental shelf. The standing crop of the phytoplankton, in terms of chlorophyll a, was generally low throughout the regions investigated, except in the northern areas of the Subantarctic region and at the Subtropical Convergence where relatively high amounts of chlorophyll were measured. Chlorophyll maxima found in the euphotic zone were observed either to coincide with or to be slightly above the thermocline. Phaeophytin maxima occurred at the same depth as the chlorophyll maxima or were slightly deeper. Peaks of phaeophytin suggested grazing of algal cells by zooplankton. ... |
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