THE ARAL SEA 



665 



(1935) and I. Kulichenko (1944). The most recent comprehensive study was 

 undertaken by E. Yablonskaya (1959), who has distinguished seven main 

 biocoenoses. Practically the whole Sea is encircled (Fig. 315, 1) at little 

 depth (2 to 10 m) by a zone of vegetation. Dreissena polymorpha is the pre- 

 dominant form. The mean mass of charial algae is 67T58 g/m 2 ; among the 

 Zostera in the Maloe More— 22-255 g/m 2 ; among the soft macrophytes 



И r 



Fig. 315. Main benthos biocoenoses of the Aral Sea in 1954 to 

 1957 (Yablonskaya). See text for interpretation. 



(Potamogeton and others) — 10-874 g/m 2 . This zone is followed by the sandy 

 zone, which has a predominance of Adacna minima (Fig. 315,2) with a bio- 

 mass of 6-181 g/m 2 . Still deeper (10 to 24 m) on the silty sand (Fig. 315, 3) 

 the Dreissena and Adacna biocoenosis develops with a biomass of 15 to 

 14 g/m 2 . Chironomid larvae are the dominant form on the mud soil of 

 Adzhibai Inlet (Fig. 315, 4), producing a biomass of up to 16-2 g/m 2 . All 

 the central part of the Sea, with depths down to 27 m, on sand and grey mud 

 soils is populated by the Chironomus, Dreissena and Adacna biocoenosis 



