146 



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

 Table 58 



Porifera are Geodia baretti, Craniella cranium and Thenea muricata. It is 

 interesting to note that these Porifera usually lie free on the bottom and there- 

 fore can develop in masses on a comparatively soft floor (sand and silty sand). 

 Many mass forms of the previous community are of secondary significance 

 here (Waldheimia, Retepora, Placostegus, Eunice, Asyches and others). More- 

 over among the characteristic forms here one may note Astarte crenata, 

 Nephthys coeca, Ophiocantha bidentata, Maldane sarsi, Lumbriconerbis fragilis, 

 Ophiura sarsi and a number of asterids Ceramaster, Leptychaster, Cribrella, 

 etc. This particular group has the following composition {Table 58). 



Farther east, in the Rybachiy Peninsula shallow, the admixture of cold-water 

 forms, such typical inhabitants of the Barents Sea as Myriochele oculata, 

 Macoma calcarea, Spiochaetopterus typicus and others, is felt even more 

 strongly. 



The Waldheimia and Porifera communities described above are gradually 

 replaced by the Brisaster fragilis community which inhabits silty sand bottoms 

 (200 to 300 m deep), with a mass Foraminifera Astrorhiza and Rhabdammina. 

 High salinity (35 to 35-5% ) and a temperature of 3° to 4° turn it into a 

 suitable habitat for a large number of warm-water forms. The average bio- 

 mass of this community is not high — 37 g/m 2 (from 20 to 80 m deep). The in- 

 fauna there already accounts for a biomass of about 90 per cent of the whole 

 fauna with a sharp preponderance of echinoderms and polychaetes {Table 59). 



Table 59 



Group 



Biomass 



g/m 2 



Percentage of 

 total biomass 



71 6 



13-5 

 6-4 



2-5 

 60 



Total biomass 



36-6 



100 



