THE SEA OF OKHOTSK 



797 

 with 



Macoma baltica, 275 specimens ; Amphipoda, 625 specimens per 1 m 

 a mean biomass of no less than 1 kg/m 2 . 



The upper horizons of the Sea of Okhotsk sublittoral are covered with 

 large sea-weed beds with their accompanying fauna. In the bays at depths of 

 to 5 m grow the Sargassum sea-weeds Cystophyllum and Zostera. Lami- 

 naria (L. agardti, L. bullata, L. saccharina, L. digitata, Alaria esculenta, A. 



Fig. 397. Echinarachnius parma colonies in La Perouse Strait at a depth of 40 m 

 (photographed by Zenkevitch). 



membranacea, A. ochotensis, Lessonia laminarioides) form dense growths 

 somewhat deeper (5 to 20 m). 



All these vegetation beds are populated by a varied fauna of Bryozoa, 

 Hydroidea, Mollusca, Polychaeta and Crustacea. Still deeper (from 15 to 

 30 m) red sea-weeds become significant {Phycodrya simosa, Ph. fimbriata, 

 Odonthalia dentata, O. ochotensis, and various Polysiphonia sp. and Ptilota 

 sp.) with a fauna of Hydroida, Bryozoa, Polychaeta, Crustacea, Echinodermata 

 and Ascidia. At depths below 30 m the macrophytes gradually disappear, and 

 growths of Porifera, Hydroidea and Bryozoans become significant. The ori- 

 ginality of the bottom fauna of the Sea of Okhotsk is reflected in some details 

 of its composition and distribution. 



The uncommon biocoenosis of Echinarachnius parma on pure fine-grain 

 sands at depths of 20 to 60 m (Fig. 397) occupies a special place in the fauna 



