THE CHUKOTSK SEA 267 



faeniculaceus, Desmarestia aculeata, Laminaria saccharina, L. bongardiana, 

 Antithamnion borealis and others). 



The fauna populating the shallow sand floor (7 or 8 m) off Wrangel Island 

 is similar in its composition to that inhabiting similar floors and depths off 

 Novaya Zemlya. The benthos biomass in this zone is a few dozen grammes 

 per m 3 . 



The population of the chief, mud-covered areas, 30 to 50 m deep, is very 

 similar to that of the southeastern parts of the Barents Sea, and apparently 

 to that of all the shallow Siberian seas. The basic forms here are Macoma 

 calcarea, Nucula tenuis and Terebellides stromi. Apart from them the most 

 usual among the polychaetes are : Lysippe labiata, Nephthys ciliata, Chaeto- 

 zone setosa, Scoloplos armiger, Capitella capitata, Scalibregma inflata and 

 Sc. robusta; among the molluscs : Yoldia sp. and Axinus flexuosus var. gouldi; 

 among the crustaceans : Ampelisca eschrichti, Amp. macrocephala, Acantho- 

 stepheia malmgreni, Byblis gaimordi ; and among the echinoderms : Ophiura 

 sarsi, Myriotrochus rinkii, Ctenodiscus crispatus and Ophiocten sericeum. 

 The ratio between the individual biomass groups is also similar to that of 

 the southeastern part of the Barents Sea {Table 118). 



Table 118 



Vermes 35-2 g/m 2 Gastropoda 20 g/m 2 



Crustacea 31-8 g/m 2 Lamellibranchiata 114-6 g/m 2 



Echinodermata 16-2 g/m 2 Varia 14-4 g/m 2 



Mean biomass 214-2 g/m 3 



Cirripedia, hardly represented in the Kara Sea, and so far not discovered 

 in the Laptev Sea, appear again after a long break in the Chukotsk Sea. 



Benthos biomass (Fig. 112) varies usually from a few dozen grammes to 

 100 to 200 g/m 2 , increasing only at the most southern part of the Sea and in 

 the Bering Strait, mainly in respect of the epifauna (up to 500 g/m 2 and more). 

 The numerical distribution of the bottom fauna in the Bering Strait and the 

 Chukotsk Sea is given by groups in Fig. 1 12. 



As has been pointed out by Ushakov, the main part of the bottom fauna of 

 the Chukotsk Sea consists of Arctic-boreal, eurybiotic, widely distributed 

 forms, as for instance, the amphipods Ampelisca macrocephala, A. eschrichti, 

 Pontoporeiafemorata, the polychaetes Chaetozone setosa and others. However, 

 a boundary can be drawn between the areas characterized by a preponderance 

 of typically Arctic forms, which are peculiar for all parts of the Arctic basin, 

 and those with a preponderance of Pacific Ocean boreal forms, which pene- 

 trate through the Bering Strait. The influence of the Pacific Ocean waters on 

 the local Arctic ones is clearly indicated by these two groups of forms (Fig. 

 113). 



Ushakov specifies the following forms as the most characteristic Arctic 

 and high Arctic forms — Foraminifera : Elphidium gorbunovi ; hydroids : Peri- 

 gonimus yoldiae arcticae; polychaetes: Melaenis loveni, Gat ty ana amundseni ; 

 bryozoans : Eucratea loricata var. cornuta, Notoplites sibirica ; amphipods : 



