QUALITATIVE COMPOSITION AND DISTRIBUTION 



OF PLANKTON 



Before proceeding to an analysis of the data we must first sketch the geographical features 

 of the Greenland and Norwegian Seas. 



One feature of the Greenland and Norwegian Seas is the presence of very deep depressions 

 in their central area. In the eastern area, there is a broad continental plateau with a steep shelf. 



The latest work of PINRO (B. V. Istoshin and A. P. Alekseev, 1950-1) has considerably 

 supplemented and improved the accuracy of the current chart of the Norwegian and the Greenland 

 Seas. 



It has been established that the Norwegian current entering the Norwegian Sea from the 

 south by way of the Faroe -Shetland channel splits up into three branches, which give a series of 

 offshoots as they travel north. 



The cold Arctic waters enter the Greenland Sea from the north. The polar East Greenland 

 current and its eastern branch, the East Icelandic current, are of great importance. 



The East Greenland current brings enormous quantities of ice from the Arctic into the 

 western areas of the Greenland and Norwegian Seas, and this results in a constant cooling of the 

 surface waters . 



This current does not pass into the central regions of the Greenland and Norwegian Seas, 

 but under the pressure of the warm Atlantic waters passes round Jan Mayen and comes into close 

 contact with the western branch of the Norwegian current on its way to the Faroes . 



The zone of contact between the warm and cold waters is called the "polar front" (10). The 

 optimum conditions for the development of animal and plant organisms occur here. 



At the point where the warm and cold waters meet, the mass of water is enriched with 

 organic matter as a result of the destruction of large quantities of organisms which are unable to 

 adapt themselves to the abrupt change in temperature. In addition, owing to the fact that the water 

 masses are well mixed at the places where the warmer and more saline waters coming from the 

 south meet the colder and less saline northern waters, abundant quantities of mineral salts rise 

 and all the layers of water are saturated with oxygen . 



Owing to the great expanse of the Norwegian and Greenland Seas from south to north, the 

 hydrologlcal conditions in the individual areas of these seas have a unique character, and con- 

 sequently plankton begins to develop at different times in different areas and the length of each 

 biological season also varies . 



The diagram showing the lengths ^ . reasons for these seas at various latitudes 



has been prepared by Bogorov (2), and Pavsn. .^ ,-:>oZ) has determined the times at which the princi- 

 pal plankton groups develop in the Norwegian and Greenland Seas . 



The development of biological processes in the Norwegian Seas begins in the south and grad- 

 ually moves northward following the paths of the Norwegian current. This is due to the fact that 

 the southern areas are more affected by the warm Atlantic waters with their high salinity (35 /oo 

 and more) and their surface temperature of 10-15 C. These waters carry with them the typical 



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