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



bullata and L. japonica) and red algae, together with a series of their 

 own biocoenoses. Derjugin distinguishes among them the biocoenosis of 

 Laminaria thallus, the rhizoid biocoenosis, and the biocoenosis of the soil with 

 a large number of Polychaeta {Maldane sarsi, Scoloplos armiger), brittle stars 

 (Ophiura sarsi var. vadicola, Amphiodia craterodmetd), Holothuria (Cucu- 

 maria japonica, Stichopus japonicus), starfish {Asterias amurensis, Distolasterias 

 nipon), Mollusca (Pecten swift, Modiola modiolus, Yoldiajohanni, Be/a erosa, 

 Philine japonica) and a series of other biocoenoses with a rich and varied fauna. 

 K. Derjugin and N. Somova (1941) have given a quantitative description of 

 some of these biocoenoses. In Peter the Great Bay the biocoenosis [Maldane 

 sarsi -{-Ophiura sarsi var. vadicola-\-Nucula tenuis-^- Philine japonica (Fig. 383)] 

 is widely distributed at a depth of 14 to 40 m on a sandy silt soil. 



Among the Polychaeta, which make up more than half the biomass, the 

 most abundant, apart from M. sarsi, are Polydora coeca and Sosane gracilior. 

 The total biomass of this biocoenosis is from 50 to 262 g/m 2 . After the Poly- 

 chaeta the second and third places are occupied by Echinodermata and 

 Mollusca. 



At a depth of 25 to 45 m, also on siltysand soil, the biocoenosis Turitella for- 

 tilirata-\- Amphiodia crater odmeta-{-Magelona longicornis-\-Yoldia johanni-\- 

 Axinopsis orbiculata is commonly found. The biomass of this biocoenosis is 

 100 to 200 g/m 2 (Fig. 383). 



On sandy floors, at depths of 50 to 80 m, one of the most widely distributed 

 biocoenoses in the Bay is that of Venus fluctuosa-\-Ampelisca macrocephala-\- 

 Haploarthron laeve-\- Yoldiella derjugini (Fig. 383). 



On purer sand they become the dominant form. Crustaceans are pre- 

 dominant (70 to 95 per cent of the biomass) in this biocoenosis. Apart from 

 the four forms mentioned the following are characteristic for this biocoe- 

 nosis : the Ascidians Pelonaja corrugata and Pareugyrioides japonica ; the 

 Crustacea Byblis gaimardi; the Polychaeta Scoloplos armiger, Prionospio 

 steenstrupi, Euchone olegi; the Mollusca Macoma calcarea, Montacuta sp., 

 Axinopsis sp., Crenella decussata and many others. The mean biomass of this 

 biocoenosis is about 1 50 g/m 2 , with the number of specimens per 1 m 2 up 

 to 15,000, mainly Crustacea. 



At greater depths (80 to 200 m) the biocoenosis Venus fluctuosa-Ampelisca 

 macrocephala is replaced by that of Salariella varicosa, S. obscura-{- Myriotro- 

 chus mitsukuri-\-Stegophiura nodosa, St. brachiactis (Fig. 383). The total bio- 

 mass is considerably less (80 to 85 g/m 2 ) and there is qualitative impoverish- 

 ment. The following should be noted in this biocoenosis apart from the above 

 mentioned brittle stars : Amphiodia craterodmeta, the holothurian Eupyrgus 

 pacificus, the Mollusca Yoldiella derjugini, Venus fluctuosa, Verticordia nadina, 

 the Amphipoda Ampelisca macrocephala, the Polychaeta Scoloplos armiger, 

 Travisia forbesi, Asychis punctata and others. 



On the uppermost horizon of the bathyal, on firm sand and boulders, a 

 biocoenosis of the Heliometra glacialis maxima -f Ophiura sarsi with the mol- 

 lusc Verticordia nadina is widely distributed (Fig. 383). It contains also the 

 peculiar Foraminifera Bathysiphon, the Polychaeta Travisia forbesi, Amage 

 anope, Lumbriconereis fragilis, L. japonica, Scalibregma robusta and others, 



