THE BARENTS SEA 145 



this community passes over gradually into the communities Placostegus- 

 Modiola barbata, and farther on, at Lofoten, into the community of the madre- 

 porarian coral Lophophelia prolifera. The average biomass of the Waldheimia 

 cranium community is 133 g/m 2 (from 60 to 400 m.) Epifauna is sharply pre- 

 dominant in this community forming about 94 per cent of the total biomass 

 {Table 57). 



Table 57. Composition of the Waldheimia cranium 

 community according to groups 



The above-mentioned community in various places passes to the west, 

 north and east into the Porifera community, which frequently forms 95 to 

 98 per cent of the total benthos biomass. Proceeding from west to east one 

 observes that the thermophilic forms of this community are replaced by the 

 less thermophilic ones. Only the three areas of the greatest accumulation of 

 Porifera are marked on the chart ; lesser gatherings are met everywhere off 

 Finmark and the Murman coast on mixed rock bottoms. On bottom sectors 

 occupied by this community the work of trawlers is made difficult since Pori- 

 fera fill the trawl sometimes up to many tons and spoil the fish. On the other 

 hand, hunge amounts of dead Porifera spicules mix with the bed deposits in 

 such quantities that it becomes almost completely unfit for infauna habitation ; 

 after a little washing it appears as a compact felt made of spicules (the silica— 

 Porifera floor). Here infauna forms usually 1 to 3 per cent of the total fauna 

 biomass. 



The development of other representatives of epifauna is also restricted by 

 the mass growth of Porifera, since these latter, loose powerful filters, are the 

 first to take out of water all the nutrient substances (detritus and plankton 

 and, possibly, the dissolved organic substances). Manteufel (1938) has sug- 

 gested that the warm-water plankton brought from the west and destroyed at 

 the entrance to the Barents Sea may serve as a considerable source of food for 

 Porifera off the shores of Finmark and the western Murman coast, and cause 

 its luxuriant development. 



The biomass of the Porifera community reaches 5 to 6 kg/m 2 , and on the 

 average on the huge patch opposite Nordkyn, 350 g/m 2 . The mass forms of 



