532 



BIOLOGY OF THE SEAS OF THE U.S.S.R. 



BOUNDARIES OF DISTRIBUTION 

 "PECTINARIA NEAPOLITANA 



LORIPES RETUSA AND SPIONODAE 



NEMERTINI AND SYNCESMA 



CARDIUM EDULE 1DOTHEA 

 G. IOCUSTA AND 

 NEREIS DIVERSICOLOR 



HYDROBIA 

 ►-•-•- OSTRACODA 



CHIRONOMIDAE 



^^CLADOPHORA 



EPHYDRA 



ARTEMIA SALINA 



Fig. 252. Limit of distribution in the 



depth of the Sivash of some Azov-Black 



Sea forms (Vorobieff). 



Fig. 253. Northern boundary of distri- 

 bution of ultrahaline forms in the Sivash 

 (Vorobieff). 



Vorobieff gives the number of animal and plant species inhabiting various 

 parts of the Sivash as in Table 221. 



Of the 40 species of zoobenthos in the Sivash 18 (39-9 per cent) are Novo- 

 Euxine relicts, 5 (11-1 per cent) are ultrahaline forms, 19 (42-2 per cent) are 

 Azov-Black Sea forms and 3 (6-7 per cent) are ancient Euxine relicts. 



Of the 75 species of zooplankton 6 (7-98 per cent) are Novo-Euxine relicts, 

 9 species (12-9 per cent) are ultrahaline forms, 59 (79-4 per cent) are Azov- 

 Black Sea forms and 1 (1-33 per cent) is a Novo-Euxine relict. The occasional 

 drying up by the wind of large areas of the bottom is a characteristic pheno- 

 menon of the Sivash ; one part of its fauna perishes, while another develops 

 the ability to survive the dry periods by burrowing into the sea-bed. 



Plankton 



Plankton distribution, according to Vorobieff, is as set out in Table 222. 

 Plankton biomass throughout the Sivash comprises 22,440 tons in February, 



