THE SEA OF JAPAN 773 



the brittle star Amphioplus macraspis, the mollusc Yoldiella derjugini, the 

 Amphipoda Syrrhoe crenulata, Socarnes bidenticulatus, Anonyx nugax and 

 others. The mean biomass of this biocoenosis is 80 to 90 g/m 2 , with the 

 number of specimens about 1,000 per m 2 . The mean biomass throughout the 

 shelf of Peter the Great Bay is 170 to 200 g/m 2 . 



In the lower horizon of the bathyal down to 2,000 m the following bio- 

 coenosis is equally widely distributed: the lily Thaumatometra tenuis, with 

 starfish Ctenodiscus crispatus and Luidiaster tuberculatus, the coral Primnoa 

 resedaeformis pacifica (Gorgonaria) (reaching 2 m in height), some single 

 madrepore corals Caryophyllia clavus, the hydroid Lafoeina maxima, the 

 brachiopods Terebratulina coreanica, the polychaetes Nephthys longisetosa, 

 Harmothoe impar and Jasmineira pacifica, the decapods Nectocrangon dentata, 

 Spirontocaris biunguis and Chionoecetes elongatus bathyalis, the Gephyrea 

 Phascolosoma spp., and the molluscs Leda sp., Buccinumsp., and Pectenrandolfi. 



At depths below 2,000 m life becomes qualitatively and quantitatively poor. 

 Derjugin gives the benthos of the abyssal as comprising one single biocoenosis, 

 owing its composition not to the abyssal fauna, but to the bathyal or even the 

 sublittoral. It contains many species of Rhizopoda, Hyper ammina friabilis, 

 Haplophragmoides canariensis, and others; the hydroid Lafoeina maxima, 

 the polychaetes Harmothoe derjugini, H. impar, Scalibregma inflatum, 

 Chaetozone setosa, Nephthys malmgreni and others ; the brittle star Ophiura 

 leptoctenia ; the molluscs Pecten randolfi, Axinus fiexuosus gouldi (?), Cylichna 

 alba corticata; the amphipods Tmetonyx cicada, Anonyx ampulloides; the 

 isopods Eurycope spinifrons, Gnathia elongata ; and the ascidian Goniocarpa 

 coriacea. 



A considerable admixture of cold-water species is characteristic of the 

 biocoenoses living even at depths of 50 to 80 m in Peter the Great Bay. Many 

 of these are well known as dominant mass forms in Arctic bodies of water : 

 Maldane sarsi, Harmothoe imbricata, Pelonaja corrugata, Byblis gaimardi, 

 Lembos arcticus, Hap/oops tubicola, Scoloplos armiger, Chaetozone setosa, 

 Lysippe labiata, Rhodine gracilior, Macoma calcarea, Crenella decussata, 

 Lacuna divaricata, Margarita helicina, Natica clausa, Venus fluctuosa and 

 Ophiopholis aculeata. All these species are present as dominant or characteristic 

 forms in the bottom-living biocoenoses of the Barents Sea. 



At depths below 80 to 100 m a number of similar species such as Ophiura 

 sarsi, Ctenodiscus crispatus, Heliometra glacialis, Ophiocantha bidentata, 

 Stegophiura nodosa, Travisia forbesi, Lysippe labiata, Polycirrus medusa, 

 Myriochele oculata, Lumbriconereis fragilis and others are also included. On 

 the other hand, in the upper horizons, there is an admixture of tropical species 

 such as the crustaceans Blephariposajaponica, Calianassa sp. and Upogebia sp., 

 Charybdis japonicus, the molluscs Alaba sp., Alectrion sp. and others. 



K. Gordeeva (1949) added to Derjugin's description of biocoenoses some 

 supplementary data on the eastern part of Peter the Great Bay. A selection is 

 given in Table 311. 



The bottom-living fauna of the Sea of Japan becomes markedly poorer in 

 species with increasing depth. Only fifty-three species of macrobenthos are 

 known for depths of 1,000 to 2,000 m, twenty-five for 2,000 to 3,000 m and 

 only five below 3,000 m (21 in the Sea of Okhotsk). Similarly the corresponding 



