770 



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



Life is much more abundant on the soft soils of the littoral ; the biocoenosis 

 Arenicola cristata, Mya arenaria, Laternula kamakurana is found everywhere 

 there. Throughout the littoral there is a large number of the jumping Amphi- 

 poda, Orchestia sp. ; they frequently travel far from the coast into the fields 

 and forests. 



Four horizons may be distinguished in the sublittoral zone : (7) A transi- 

 tional horizon with its characteristic Corallina, Laurensia and Chordaria 



Fig. 382. Distribution of main bottom-living biocoenoses in Peter the Great Bay 

 (Derjugin, 1939). 1 Harmothoe derjugini + Pecten randolphi; 2 Primnoa+Luidiaster 

 +Thaumantometra; 3 Heliometra + Ophiura sarsi; 4 Solariella + Eupyrgus + 

 Stegophiura; 5 Venus +Yoldiella + Plicifusus + Ampelisca; 6 Laminaria; 7 Mal- 

 dane + Scoloplos + Raeta+Theora; 8 Obelia + Ophiura + Philine ; 9 Echinarachnius 

 parma; 10 Turitella+ite/a erosa; 11 Solen + Pelonaja + Pareugyrioides; 12 Macro- 

 callista; 13 Echinocardium ; 14 Balanoglossus + Labidoplax ; 15 Zostera; 16 Cor- 



bicula fluminea. 



on the rocky bottom, and Arenicola pusilla, Echiurus pal 'lasi and Mya arenaria 

 (down to 0-5 to 1-0 m); (2) a Zostera horizon (down to 12 or 16 m); (5) a 

 Laminaria horizon mainly L. bullata (down to 30 to 50 m) and (4) the hori- 

 zon of the sand plateau (50 to 200 m). 



Fields of the sea grass Zostera (Z. marina on silt sand, Z. pacifica on purer 

 sand) give shelter to abundant fauna. Phyllospadix scoulleri, closely akin to 

 Zostera, forms dense growths on cliffs and rocky sea-floors. Biocoenoses 

 inhabiting the leaves and those living in the sea-bed and roots can be dis- 

 tinguished for both Zostera and Phyllospadix. Each of these groups can, in 

 their turn, be divided into two — animals sessile on leaves and animals swim- 



