THE WHITE SEA 



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aculeus, Hydrobia ulvae, Skenea planorbis, Macoma baltica, Priapulus caudatus, 

 Halicryptus spinulosus, Arenicola marina, Lineus gesserensis and others) and 

 partly sublittoral {Ophelia limacina, Asterias rubens, Polydora quadrilobata, 

 Chiridota laevis and others). Zostera extends as far as 5 to 6 m in depth. The 

 belt of Laminaria may, on scattered boulders, reach the lower edge of the 

 littoral, and at spring tides is partly exposed. Besides the Laminaria, which 

 compose the main mass of vegetation, there are here always many other 

 different brown and red algae, partly epiphytes. Corallina and cork Litho- 

 thamnion may likewise attain a high stage of development here. At a depth 



Fig. 89. Bottom biocoenoses of the lower stage of the sublittoral 

 and pseudolittoral of the White Sea (Zenkevitch, 1927). Boxed 

 numerals refer to the isobaths; the other numerals denote bio- 

 mass (g/m 2 ) (61, 21, 17, 5 and 18). Different shading indicates 

 the various bottom biocoenoses: 1 Leda pernula, Yoldia hyper- 

 borea, Astarte montagui; 2 Portlandia arctica, Leda pernula, 

 Asterias lincki; 3 Astarte montagui, Leda pernula, Ophiocantha 

 bidentata; 4 Astarte borealis, Yoldia hyperborea, Leda pernula; 

 5 Portlandia arctica, Yoldia hyperborea, Pectinaria hyperborea; 

 6 Mesidothea entomon, Macoma baltica. 



of approximately 10 m the belt of Laminaria comes to an end (on the Mur- 

 man coast it goes down to 15 m and more, the biomass of sea- weeds falls 

 sharply, and the red algae become predominant: Prilota, Phyllophora, 

 Odonthalia and others). 



As on the Murman coast, so here also thallus and rhizome Laminaria give 

 shelter to a luxuriant and quite analogous fauna. On the thallus Laminaria 

 there settle in quantities the gasteropod molluscs Margarita helicina and 

 Lacuna divaricata ; Lucernaria quadricomis, and Haliclystus octoradiatus which 

 give special peculiarity to the sublittoral of the White Sea ; the bryozoans 



