208 



BTOLOGY OF THE SEAS OF THE U.S.S.R. 



only to 40 to 50 m. Accordingly the upper layer of this zone (the former 

 'litoral' of Derjugin) is also raised from 60 to 70 m to 12 to 16 m. Mytilus 

 edulis and Fucus serratus descend from the littoral into the upper layers of 

 the sublittoral; in the White Sea the holothurian Chiridota laevis descends 

 from the upper layer of the sublittoral to great depths ; and there rise upwards 

 from below the red sea-weeds, poriferae, the hydroids and bryozoans, so 

 characteristic on the Murman coast of the lower horizons of the sublittoral. 

 The vertical distribution of the bottom fauna of the White Sea makes it 



Table 91. Comparison of littoral fauna of western Murman Peninsula and White Sea* 



* The absence from the table of Hydrobia ulvae and Rissoa aculeus from the Kola 

 Inlet and of the gammarids from the White Sea is explained by a deficiency in the col- 

 lection of material. 



possible to distinguish here the same zones and horizons as in the Barents 

 Sea. 



Derjugin takes as the lowest limit of the sublittoral a depth of 150 m, 

 although usually vegetation disappears by a depth of 40 to 56 m. The littoral 

 flora and fauna of the White Sea moves, without any sudden leap (as happens 

 on the Murman coast), into the sublittoral ; and most characteristic of the 

 upper horizon of the sublittoral are Fucus inflatus, and F. serratus on rocky 

 bottoms, and Chorda filum and Zostera marina on soft ones. Lower still there 

 extends a great belt oi Laminar ia sac char ina, L. digitata, Alaria, Ahnfeltia and 

 others. 



The upper division of the sublittoral, extending to 40 to 45 m, begins on 

 soft bottoms with Zostera growths which here attain luxuriant bloom (in- 

 dividual stems are as much as 3 m long), or Chorda filum, which attracted to 

 itself partly littoral fauna {Mytilus edulis, Littorina rudis, L. palliata, Rissoa 



