52 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



The existence of a single phytoplankton maximum, as Bogorov noted, is 

 characteristic of the normal cycle of plankton development in the seas of the 

 high Arctic sub-region. There is no autumn maximum there, as there is in the 

 seas of the lower Arctic region and in more southerly seas. 



This led Bogorov (1938, 1939) to the idea of using the seasonal state of 

 plankton as an indicator of ice conditions and, in particular, for ice forecasts 

 for Arctic passages ; he has repeatedly done this with great success. 



A number of investigators both at home and abroad have taken a keen 

 interest in luxuriant plankton development near the fringe of polar ice. The 

 names of Gran, V. Bogorov, P. Usachev, P. Shirshov and others may be 

 mentioned. 



Usachev (1935) saw that the mass development of phytoplankton at the 

 fringe of melting ice was caused by the special concentrations of carbonates 

 formed as a result of melting. N. Zubov (1938) points out the possibility of the 

 influence on seaweed development of 'trihydric' molecules abundant in 

 melt water. Shirshov (1936, 1937) and Bogorov consider the mass develop- 

 ment of phytoplankton as a temporary, seasonal condition in the regions of 

 melting winter ice. 



In the course of a year plankton passes through distinct successive stages. 

 'When light penetrates into water a rapid growth of algae begins. In polar 

 seas this occurs during the light period of the year, when the surface of the 

 sea is free of solid ice. This phase of biological spring is followed by the 

 summer phase, which in its turn passes first into the autumn and then the 

 winter phases. The succession of the biological seasons is a definite pheno- 

 menon' (V. Bogorov, 1939). 'The phytoplankton bloom among the ice is not 

 at all a direct function of its melting; it is the usual spring maximum' 

 (P. Shirshov, 1937). 



Phytobenthos 



Among the bottom macrophytes of the Arctic Ocean there is a certain pre- 

 dominance of the orders Laminariales (Laminaria and Alaria) and Fucales 

 (Fucus, Ascophyllum) among the brown algae and Ulvacea (Enteromorpha 

 and Monostroma) among the green ones. These algae attain their highest 

 growth in the warmest parts of the Arctic basin — the southern part of the 

 Barents Sea and the southeastern part of the Chukotsk Sea. In other parts of 

 the Arctic the bottom macrophytes are only slightly developed largely owing 

 to the weak development or even absence of the littoral population and of the 

 population of the upper level of the sublittoral. 



Qualitatively the Arctic basin macrophytes lack individuality. They all 

 belong to the typical Atlantic flora which has penetrated into the cold regions 

 of the north. The same may be said about the fauna of the littoral and the 

 upper level of the sublittoral. The peculiar characteristics of the fauna in- 

 crease with the depth of its habitat. 



This phenomenon can be explained by the fact that the deterioration of 

 climatic conditions in the Ice Age naturally had more effect on the popula- 

 tion of the shallows, all of which inevitably perished ; in deeper layers the 

 fauna could more easily endure harsh conditions and survive. 



