a result of pollution of the water along the coast of Japan (Lee, Williams, 

 1974). 



3.2 Planktonic Communities of the Boreal Atlantic 



The pelagic communities of the Boreal waters of the North Atlantic are 

 related in their distribution to the superficial subarctic water mass 

 (Mamayev, 1960; Jaschnov, 1961; Grainger, 1964; C. W. Beklemishev, 1969). 

 Within this area, a number of large regions can be distinguished, differing 

 in their latitudinal position, the presence of a more or less closed system 

 of water circulation and, as a result, the structure of the planktonic 

 communities and the dynamics of seasonal processes. These relatively 

 independent regions include the Norwegian Sea with its circulation formed 

 by the system of Norwegian and East Iceland Currents; the Labrador Basin, 

 with the circulation of the West Greenland and Labrador Currents; the open 

 portion of the North Atlantic, to the north of the main flow of the North 

 Atlantic Current, with its less clear circulation formed by the peripheral 

 streams of the North Atlantic Current, the Irminger Current, and the eastern 

 branch of the Labrador Current.* One general regularity in the hydrologic 

 mode of these regions is the predominance of cyclonic water circulation. 

 Cyclonic flow also predominates in the movement of air masses here (Bulatov, 

 1971). This creates favorable conditions for upwelling of deep water, rich 

 in biogenic elements, and, therefore, for abundant development of plankton 

 and the formation of concentrations of commercial fish. 



The taxonomic composition of the zooplankton of the Norwegian Sea, the 

 Labrador Basin and adjacent waters in the open North Atlantic is similar 

 in its main features, the difference resulting from the intrusion of 

 warm-water elements with the waters of the North Atlantic Current and 

 cold-water forms with the Arctic waters. 



The predominant role is that of the copepods, particularly the most 

 abundant species, C alanus finmarchicus s.l. During some seasons in the 

 Norwegian Sea and the Labrador Basin, these crustaceans may represent more 

 than 90% of the biomass of all zooplankton. The growth and development of 

 C_. finmarchicus from egg to the older copepodite stages produces the 

 summer increase in total biomass and the maximum concentrations of plankton. 

 The population of C^. finmarchicus in the 0-200 m layer decreases in the 

 fall, as a result of intensive predation by planktophagous fish, and also 

 due to the gradual descent of the fourth and fifth copepodite stages into the 

 depths, where they spend the winter. 



Due to the existence of more or less closed systems of water circulation, 

 the Labrador Basin and Norwegian Sea support large, independent populations 

 of C. finmarchicus s.l. It is more difficult to determine the nature of 

 the population of the species inhabiting the open waters of the North 

 Atlantic. Doubtless, it is supplemented by constant intrusion of a portion 



*In accordance with the purpose of the present monograph, primary 

 attention will be given to oceanic plankton communities, while the regions 

 of the North Sea, the Grand Banks and the Gulf of Maine will not be analyzed, 



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