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



B. ciliatum, Bela morchi, Dendronotus frondosus v. dalli and some others) is 

 also of great interest. 



Sharp seasonal fluctuations of temperature in the Cheshskaya Guba, its 

 severe winter, and comparatively warm summer have led to the development 

 mainly of a eurytopic stable fauna. 



Some peculiarities of benthos distribution. With the changes of the Barents 

 Sea conditions from west to east, a vertical displacement of either the zones 

 or individual forms is observed in its fauna range. In the White Sea the 

 boundaries of the vertical zones rise upwards considerably as compared with 

 those of the Barents Sea. 



A number of typical Murman littoral forms in the eastern part of the Barents 

 Sea and off the coast of Novaya Zemlya go down into the upper levels of the 

 sublittoral. This is caused by severe climatic conditions, and chiefly by the 

 grinding effect of ice in winter. This was noted by a series of workers, begin- 

 ning with Stuxberg (1882, 1887). Thus in the Cheshskaya Guba Mytilus edulis 

 and Balanus crenatus form thick growths at depths down to 30 m. The poly- 

 chaete Fabricia sabella, so typical for the littoral, sinks down to a depth of 5 

 to 10 m in Belushja Guba. On the other hand, many forms typical of the sub- 

 littoral lower horizons move upwards in the eastern parts of the Sea. Ushakov, 

 for instance, caught (1931) in Matochkin Shar at a depth of 3 to 7 m such 

 forms as Yoldia hyper borea, Leda pernula, Pec ten groenlandicus, Pandora 

 glacialis, different species of Astarte and other forms which thrive at great 

 depths in the western parts of the Sea. The asterid Asterias panopla and the 

 mollusc Cardium ciliatum become also comparatively shallow-water forms in 

 the east. According to Stuxberg Gammarus locusta lives in the Kara Sea at a 

 depth of 6 m and Ophiura sarsi, Ophiocten sericeum and Asterias panopla 

 which in the Kola Inlet live in deep water are here encountered at 10 to 20 m. 

 This sinking down of the littoral fauna in deep inlets is due not only to the 

 above-mentioned cause, but may also be the consequence of a considerable 

 loss of salinity in the surface waters. The rise of the boundaries of the other 

 zones is controlled in the east by the low temperature of the surface layers 

 of the Sea, which allows the rise of cold-water bathypelagic fauna to higher 

 levels. This explains the migration of the many Barents Sea forms into the 

 colder deeper layers as they travel towards the more southerly parts of the 

 Atlantic. But observers have also noted the withdrawal to considerable 

 depths of the sublittoral of a number of typical littoral forms of the north- 

 western European shores, as they travelled into the Barents Sea {Pycnogonum 

 littorale, some species of Chiton, Margarita helicina, M. groenlandica, Anomia 

 squamula and others). K. Derjugin was inclined to explain this, as yet incom- 

 prehensible, phenomenon by biocoenotic correlation. 



The warm-water fauna travelling from the west differs from that of the cold 

 local waters of the Barents Sea. It has been shown by K. Derjugin his colla- 

 borators that the distribution of a number of forms in the warm and cold 

 waters can be established by collecting the bottom fauna along the Kola 

 meridian. 



The dominant forms in the warm waters consist of the coral polyps 



