GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 61 



certain depths being full of warm waters from the Atlantic which in part 

 reach the surface in the shallows of the Siberian Seas carrying their fauna with 

 them.' 



The greatest variety of species was found here near the fringe of the shallow 

 plateau of the Siberian Seas. Gorbunov notes that one of the Sadko stations 

 obtained more than 200 species of different animal forms at the fringe of a 

 shallow bank of the Kara Sea, at a depth of 698 m. 



A considerable number of more thermophilic forms penetrated into the 

 Arctic from the Atlantic Ocean during the warm phase of the Littorina 

 period, and a part of them survives in the Arctic as relicts, as for example the 

 sea grass Zostera in the White Sea. 



Bathyal and abyssal fauna of the Arctic basin 



The collections of the latest Soviet polar expeditions have made it possible for 

 us to look into the interesting and hitherto closed world of the bathyal and 

 abyssal fauna of the Arctic basin. 



The bathyal fauna has risen so much at the shallow northern fringe of the 

 Siberian Seas that at depths of 100 to 200 m, as has been pointed out by 

 G. Gorbunov (1946), the fauna has a completely bathyal character. 



In the Barents Sea there is pseudo-abyssal fauna at depths of more than 

 200 m, while in the Novosibirsk shallows it rises to 40 to 50 m. 



The Novosibirsk shallows have a rich fauna of more than 800 species 

 mainly of the foraminifera, polychaetes, bryozoa, amphipoda and molluscs. 

 As has been noted by G. Gorbunov (1946) this fauna consists mainly of high 

 Arctic, Arctic and Arctic boreal forms. In this region it is very difficult to draw 

 the line between the abyssal and the bathyal, and between this latter and the 

 sublittoral, since for a variety of reasons that have been discussed, the sub- 

 littoral forms go down more easily into the bathyal and the abyssal and the 

 bathyal fauna rise easily to the sublittoral. 



Collections made at 300 to 400 m and sometimes higher should (according 

 to G. Gorbunov, 1946) be included in the bathyal fauna of the Arctic Ocean, 

 owing to a general rise to higher levels. 



In the bathyal fauna of the high-latitude collections made by the Sadko 

 and Sedov expeditions Gorbunov includes 528 species of bottom animals ; 

 hence, in general, it contains four times more forms than the abyssal one. 

 With the exception of some groups, this author gives the analysis of bathyal 

 fauna of the Siberian shallows set out in Table 25. 



Hence the bathyal fauna contains 72 per cent of sublittoral forms ; 80 of 

 these are really bathyal forms and 59 are endemic forms of the Arctic Ocean. 

 Gorbunov includes the typical bathyal forms Leucon spinulosus among the 

 Porifera, Umbellula encrinus among the Octocorallia, Phascolosoma glaciale 

 among the Sipunculids. As regards Amphipoda these are represented by 

 Halirages elegans, Cleppides lomonosovi, Amathillopsus spinigera, Bythocaris 

 payed ; there are Poliometra prolixa from the Crinoidea, and as regards fish 

 Lycodes eudipleurosticus. On the whole the fauna of the bathyal part of the 

 Siberian sector of the Arctic can be considered as 81 per cent endemic and 

 genetically linked with the abyssal fauna of the Atlantic Ocean but, unlike 



