THE BLACK SEA 



455 



sp. relicta, Vivipara vivipara, Theodoxus danubialis, Unio tumidus, Ponto- 

 gammarus maeoticus, Corophium volutator, С nobile, Balanus improvisus, 

 Oligochaeta, Tendipedidae, Hypaniola invalida, Nereis spp., Mytilus gallo- 

 provincialis. Half of them are 'Caspian' and 2 or 3 fresh-water forms. The 

 average biomass of the bottom biocoenoses is from a few grammes to 1 kg 

 per m 2 . 



The bentho-nectic biocoenoses are formed of 'Caspian' mysids; fresh- 

 water Rotifera and crustaceans are greatly preponderant in the plankton, the 

 Caspian fauna in them being represented only by Eurytemora velox. 



The Dniester inlet is only slightly smaller in size than the Dnieper-Bug 



Fig. 217. Distribution of isohalines (CI - , mg/1.) 



in the Dniester inlet, 27 June to 1 July 1950: 



1 Surface ; 2 Bottom layer (Markovsky). 



inlet (377 km 2 according to Markovsky) ; its salinity decreases gradually from 

 south to north (Fig. 217), undergoing considerable fluctuations under the 

 influence of the weather and the season of the year. 



Yu. Markovsky writes (1953) that zooplankton of the inlet consists mainly 

 of 'Caspian' crustaceans . . . which are represented in the Dniester inlet by 

 fresh-water populations with a few purely fresh-water forms. 



As in the Dnieper-Bug inlet, the plankton benthos of the Dniester inlet 

 has a pronounced preponderance of 'Caspian' mysids with some admixture of 

 'Caspian' Cumacea and amphipods. 



The bottom population of the inlet consists mainly of 'Caspian' forms. 

 According to Yu. Markovsky (1953) their number decreases as one approaches 

 the sea. If the inlet is divided into fresh-water, transitional and brackish- 

 water parts, the fauna of the first two comprises 66 to 67 per cent of the 



