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



The medium and shallow depths of the Kara Sea are populated mainly by 

 a typical, sublittoral, Arctic circumpolar and east-Arctic fauna. In his analy- 

 sis of the propagation of the molluscs Portlandia arctica and Pecten groen- 

 landicus in the Siberian seas, G. Gorbunov (1941) suggests that the absence 

 of the first of these molluscs in the Vilkitsky and Schokalsky Straits is an 

 indication that these deep passages are filled at the lower levels with typical 

 sea waters, mainly from the Laptev Sea side. A mass development of the 

 second mollusc in Vilkitsky Strait, and its absence from the Schokalsky 

 Strait, bear witness to a considerable penetration (from the east) into the 

 Schokalsky Strait of the intermediate layer of warmer Atlantic waters, and 

 of the absence of them in Vilkitsky Strait. 



The zone of brown muds is populated by a most original community of 

 bathypelagic animal forms. As has been mentioned above, the physico- 

 chemical conditions (constant low temperature and salinity, weak supply of 

 nutrient substances, an inadequate vertical circulation, and the unfavourable 

 mechanical and chemical properties of the soils) lead first of all to a marked 

 qualitative impoverishment of the fauna. Whereas the bathypelagic life off the 

 shores of Novaya Zemlya and Baydaratskaya Guba is varied, farther into the 

 depths, where the brown muds begin, the fauna becomes much more uniform 

 and the number of species decreases sharply. A comparatively small selection 

 of forms remains unaltered throughout the whole extent of the brown muds. 

 The diversity of the molluscs, polychaetes and crustaceans decreases especi- 

 ally markedly and the preponderance of the echinoderms comes out more 

 sharply. 



There is a considerable preponderance of large echinoderms — Urasterias 

 lincki, Icasterias panopla, Pontaster tenuispinus, Heliometra glacialis, Gorgo- 

 nocephalus arcticus, Trochostoma sp., Ophiopleura borealis, and Ophiocten 

 sericeum in the deeper central part of the Sea. 



The polychaetes are distributed more evenly, but they too show an increase 

 in the central part of the Sea in respect of the large Onuphis conchylega, Pecti- 

 naria hyperborea, Nephthys longisetosa, N. malmgreni, Ampharete arctica, 

 Owenia fusiformis and others. In shallower places Thelepus cincinnatus, Pista 

 maculata and Maldane sarsi are also found in large numbers. A reverse picture 

 to that of echinoderms is obtained for the quantitative distribution of bi- 

 valves — the large forms live in the shallows on grey sandy mud: Astarte 

 borealis placenta, Serripes groenlandicum, Astarte montagui, Macoma cal- 

 carea, M. moesta and Portlandia arctica. In the northern part of the Sea, the 

 biomass increases to 100 to 200 and even to 300 g/m 2 in respect of Astarte 

 crenata crebricostata, in the southern part — of Cardium ciliatum. In the 

 area of the Novaya Zemlya Trench the bivalves form a biomass of about 

 1 g/m 2 , mainly in respect of Axinus orbiculatus, Thyasira ferruginosa, Dacri- 

 dium vitreum, Yoldiella frigida, Y.fraterna, Y. lenticula which are all of small 

 size. Foraminifera are highly developed in the Kara Sea (Z. Shchedrina, 

 1938) and adapted mainly to the bathymetric part of the sea; hence the num- 

 bers of Foraminifera increase with the increase of the brown mud areas and 

 decrease of benthos biomass. Sand Foraminifera are greatly predominant in 

 the deeper parts occupied by brown mud, while the lime Foraminifera are 





