The use of the fluorescent microscope in recent years has changed 

 many of our concepts of the composition of phytoplankton in the Southern 

 Ocean. It has been shown that, considering the microflagel lates , its 

 total population reaches I-5'IO^-^ indiv./m^, with nanoplankton making 

 up as much as 99% of the total number of cells (Walsh, 1969). However, 

 the distribution and duration of existence of these concentrations are 

 still not known. 



The composition of plankton changes with time. Extensive cruise 

 collections (Hart, 1934) have allowed an attempt to be made to classify 

 the most abundant species in accordance with their seasonal abundance 

 and to distinguish: vernal forms; forms which rrake up the maximum in 

 the spring, but are retained in large numbers throughout the entire 

 season; species which participate in the formation of the spring and fall 

 maxima, and species which form the maximum in late summer and fall. 



Further investigations have resulted in the detection of a succession 

 in species composing the peak during its seasonal shift to the south. In 

 addition to species which are present everywhere, others have been found 

 which are significant only in the northern or only in the southern latitudes 

 (Steyaert, 1974). Forms have been described which increase their number 

 during the decrease in the total quantity of phytoplankton. However, in 

 spite of the great qualitative variety of flora, we should not expect to 

 find a rigid succession of dominant forms, particularly since the degree 

 of connection of certain species of algae with others through the metabolite 

 path varies from obligate symbiosis to complete independence (Lukas, 

 1964). 



Let us emphasize the most important specifics of the phytoplankton 

 of the Southern Ocean: great amplitude of quantitative changes during 

 the course of the year and regional differences in maximum abundance; 

 brevity of the maximum; a general shift in the zone of the bloom during 

 the course of the season from the north to the south; significant local 

 variations in the time of onset of the maximum, related to local hydrologic 

 and meteorologic conditions; a seasonal succession of the composition 

 of the phytoplankton. 



4.2 Zoocenes . 



Life cycles . The main peculiarity of cold-water ecosystems, the 

 discontinuity of the process of primary production, has its maximum 

 influence on the mode of life of the main groups of animals in the Southern 

 Ocean. The cycles of herbivorous interzonal copepoda of the Antarctic 

 and Subantarctic occur practically identically and consist in successive 

 changes of the physiologic state, abundance, age composition, vertical 

 structure and distribution of the numbers of the populations. During 

 the biologic spring, sexually mature crustaceans accumulate in the narrow 

 surface layer, richest in phytoplankton. Their total number during this 

 period is usually not great, but local concentrations may be significant. 

 They feed, mature and breed here. All representatives of the families 

 Calanidae and Eucalanidae are characterized by a broad feeding spectrum, 

 and in all stages of their development, begltining with the first copepodite 

 stage, they consume all species of algae measuring from 5-300 pm in diameter. 



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