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



Table 220. Change in the chlorine coefficients of the waters of the ocean, Black and 

 Azov Seas, and the Sivash (P. Danilchenko and A. Ponizovsky, 1954) 



Sea of Eastern 

 Coefficients Ocean Black Sea Azov Sivash 



Ca 2+ 



cF xW0 



Mg 2 + 



CI 



(so 4 ) 2 - 

 ci- 



(НСОз) 



xlOO 

 -xlOO 

 xlOO 



ci- 



CP XW0 



Na + 

 _x,00 



K + 

 -x,00 



Sum of salts 



cF 



MgS0 4 



m^ci; 



M. Bozhenko (1935) determines the sum total of the stock of salts in the 

 Sivash as 190 million tons, including 309,000 tons of elemental bromine and 

 7-1 million tons of magnesium. 



Temperature 



The shallow waters of Sivash become considerably warmed in the summer 

 (up to 30° to 35°). On the other hand in the winter their temperature falls to 

 — 1 ° or — 2° (and even to — 3 ° in the southern part), and the northern and some 

 of the central Sivash is covered with ice. 



According to Vorobieff either a mass extinction or a migration of animals 

 into the deeper parts of the Sivash occurs as a result of the sharp seasonal 

 temperature fluctuations and of a partial freezing of the whole column of 

 water. 



Oxygen 



Oxygen content decreases sharply from north to south. A litre of water in the 

 north of the Sivash contains 5-51 cm 3 of oxygen, in the central part 40 cm 3 , 

 and in the south 1-88 to 1 -75 cm 3 . The phenomenon of bottom-fauna suffo- 

 cation occurs more readily in calm summer weather in the Sivash than in the 

 Sea of Azov ; this is due to the shallow depth of water and to the large amounts 

 of oxygen used in the decay of organic substances. 



