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



130 species (64-6 per cent) and 30 genera (90 per cent) of the family Lamina- 

 riales, 84 species and 27 genera are known in the northern part of the Pacific 

 Ocean (mainly along the Asian coast) ; in the northern part of the Atlantic 8 

 species and 5 genera are known. Thirty-five species of Laminariales are known 

 for the Bering Sea, 40 for the Sea of Okhotsk and 32 for the Sea of Japan 

 (4 species only are known for the Yellow Sea). 



P. Ushakov (1953) points out 'that the occurrence in many groups of 

 "bunches" or "fans" of numerous very similar and, in most cases, not suffi- 

 ciently distinguished new subspecies and varieties is a distinctive feature of 

 the Far Eastern fauna. It bears incontestable witness to very violent contem- 

 porary processes of the formation of new species. These processes, moreover, 

 are most intensive in the Sea of Okhotsk.' 



Indeed, this phenomenon of the specific richness of the flora and fauna of 

 the northwestern area of the Pacific Ocean (within the limits of the boreal 

 region) is observed not only in the Far Eastern Seas but also in the composi- 

 tion of the deep-water fauna of the adjacent part of the Pacific Ocean. 

 Echiuroidea, Cephalopoda, Amphipoda, Isopoda, and especially Pogono- 

 phora (A. Ivanov, 1959) and Pisces may serve as examples. This is possibly 

 due partly to the insufficient investigation of this region of the Ocean ; but 

 mainly it is the result of the considerable antiquity and great variety of the 

 physico-chemical conditions of the northwestern part of the Pacific and of 

 some specific geochemical peculiarity. 



Some fauna groups of the northwestern part of the Pacific display an 

 abundance of species both in the shallow and deep-water fauna. Foramini- 

 fera, Radiolaria, Polychaeta, Amphipoda, Mollusca, Echinodermata, Pogo- 

 nophora, Pisces and Mammalia belong to these groups. Note that the last 

 three belong to these groups ; Pogonophora is particularly indicative in this 

 respect. Half of all the known species of this group have been recorded for the 

 northwestern part of the Pacific; not only the species but likewise the 

 genera, families and orders (Fig. 337). In contrast, as yet only one representa- 

 tive of the genus Siboglinum, out of 1 1 genera and a large number of species, 

 has been found in the Altantic Ocean. 



Plankton 



The group Calanoida occupies an exceptionally dominant position in the 

 oceanic plankton of the temperate zone (boreal region). Among the great 

 choice of species of this group the most significant in the Far Eastern Seas are 

 the following: Pseudocalanus elongatus, Calanus tonsus, Eucalanus bringii, 

 Calanus cristatus, Metridia pacifica, Scolecithricella minor and Pareuchaeta 

 japonica. C. cristatus, C. tonsus, E. bungii, P. japonica, M. pacifica, Sc. minor 

 var. orientalis and others are endemics of the Far Eastern Seas (K. Brodsky, 

 1955). The boreal aspect of this group of Calanoida is accentuated by the 

 close resemblance of many of the above-mentioned forms to the boreal 

 Atlantic forms. 



The boreal Far Eastern plankton is replaced by the tropical plankton in the 

 zone where the waters of the currents of Kuroshio and Oyashio meet. This 

 group is predominant in the upper layer of the Bering and Okhotsk Seas ; a 



