!78 



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



^TEMPERATURE <^ 



Fig. 119. Changes of temperature at different depths of Danzig depression 

 during the period from 1902 to 1907 (Schulz). 



waters of the Baltic Sea which affects the entire set of conditions of the Sea 

 and the distribution of life in it. 



As is shown in Fig. 121, the surface salinity falls off to the east and to the 

 north very sharply in the area of the straits and more gradually in the rest of 

 the Sea. The surface salinity of the main basin of the Sea is 2 to 8% . The 

 salinity conditions of the deep layers of the Baltic Sea (Fig. 122) result pri- 

 marily from its bottom topography and from its water-exchange with the 

 North Sea through the straits. A great difference in the salinity of surface 

 water — discharge Baltic current — and that of the lower layers — the deep 

 compensating current from the North Sea to the Baltic — is observed all the 

 year round in the straits connecting these two Seas. The salinity changes are 



Fig. 120. Temperature range at different depths round Gotland Island in July 1922 



(Schulz). 





