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



The most dense population is found on the rocks and cliffs in the middle 

 horizons of the intertidal zone. 



The succession of the maximum development of individual forms proceeds 

 in the order given in Table 48. 



Table 48 



Like the western Murman coast the littoral is inhabited by a large number 

 of gammarids which serve as food to the numerous fish during low tide; 

 their numbers, however, have not been estimated so far, owing to the diffi- 

 culty of collecting them. When the stones under which they hide during 

 low tide are turned over they scatter with astonishing speed and agility. 



The biomass is somewhat lower (647-34 g/m 2 ) on the cliffs and rocks of 

 the littoral entirely exposed to the pounding of the waves on Kharlovsky 

 Island. As before, Mytilus edulis, Balanus balanoides and Littorina rudis are 

 preponderant, but the dominant role is transferred to Mytilus edulis (forming 

 about 67 per cent of the total biomass). In the inlets on the southern side 

 of this island which are protected from the action of the swell, the littoral 

 fauna biomass increases sharply from 1-3 to 9-3 kg/m 2 ; this is contributed by 

 Mytilus edulis and Balanus balanoides. 



Littorina rudis, which inhabits the upper horizon of the littoral, is found in 

 the supralittoral too. This is one of the most enduring forms of the intertidal 

 zone. It can exist for a long time without water and easily tolerates fresh 

 water. Littorina rudis prefers to inhabit cliffs and rocks. Balanus balanoides 

 also thrives in cliffs and rocks ; however, it does not rise beyond the limits 

 of the littoral. Downwards it extends farther than Littorina. The third and 

 most typical form of the intertidal zone sea mussel is usually found in the 

 shape of brushes or bunches and is adapted mainly to the lower part of the 

 littoral. The number of sea mussels decreases from west to east. According 

 to Wollenberg the amount of sea mussels on the mussel grounds of Helgo- 

 land reaches 75 kg/m 2 ; in the western Murman coast it is only 30 to 40, and 

 in the eastern it does not exceed 8 to 9 kg/m 2 . The amount of it in the White 

 Sea is smaller. 



Algal biomass increases in the littoral and the quantitative ratio of its 

 groups and forms changes as we move into the inlets of the eastern Murman 

 coast. T. Gurjeva (1948) provides demonstrative material derived from experi- 

 ments for the Dal'ne Zelentzkaya Guba {Table 49). 



