THE BLACK SEA 443 



H. Caspers supplements the picture of the biocoenosis range of the Black 

 Sea bottom-living fauna given by Zernov with data related to the Gulf of 

 Varna (Fig. 213). He distinguishes the following biocoenoses: a littoral one, 

 with Pachygrapsus zostera ; a sandy one with Corbula ; that of the cliffs with 

 Sabellaria and Pectinaria ; and that of the central part and shell gravel. 



/• • * 



Sand community 



= Corbula biocoenosis 



Rocky ground community 

 = Saballaria biocoenosis 



re community 

 Pachygrapsus biocoenosis 



Mud community 



= Upogebia — Mellina — biocoenosis 



Fig. 213. Distribution of main bottom communities in Gulf of Varna 



(Caspers, 1957). 



M. Bacesko (1957) has given a detailed description of the Corbulomya maeo- 

 tica biocoenosis off the Rumanian coast of the Black Sea on littoral sand at 

 depths of 1 to 20 m. This biocoenosis provides the basic stock of food for ben- 

 thos-eating fish : Acipenseridae, flatfish, Mugilidae, bullhead, etc. The average 

 biomass of this biocoenosis is 360 g/m 2 (with fluctuations from 280 to 

 1 ,034 g/m 2 ), and the number of Corbulomya specimens reaches 1 45,000 per m 2 . 

 Besides Corbulomya, which sometimes furnishes up to 97 per cent by weight 



