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



the Kola Inlet are on the whole more severe than those of the well-washed, 

 comparatively shallow Motovsky Bay. 



The northern part of the Kola Inlet has depths down to 350 to 380 m, the 

 middle part down to 200 m and the southern part has depths mostly less than 

 50 m. The precipitous rocky, granite shores (to 150 m) frequently lead under 

 water into steep bottom slopes and the type of environment of submarine 

 cliffs is very prominent indeed. 



Almost all the deep parts of the bay are filled with ooze, sandy bottoms 

 appear only in the southern and middle parts of it. Rocky floors strewn with 

 large boulders are widely distributed over the whole inlet. 



Everywhere, especially in the north of the inlet, there are extensive beds of 

 several species of calcareous algae or of the Lithothamnion genus (red algae 

 group) which are found in individual patches. Branching Lithothamnion 



Fig. 47. Murmansk Biological Station of the Petersburg Society of Naturalists 



(1914). 



grows only in places where there are rapid currents, on steep cliff slopes, on 

 the cliff barriers at the mouth of the bay, and in narrow channels. 



The considerable north to south extent of the Kola Inlet, the inflow of two 

 large rivers — Kola and Tuloma — into its southern part, and additionally the 

 heating effect of the warm Atlantic waters (Ruppin branch) flowing along the 

 Murman coast make the Kola waters heterogeneous both in their salinity and 

 temperature. 



In summer the temperature in the northern part of the inlet is 5° to 13-5° 

 on the surface, and at a depth of 300 m it is only 1-3° to 2-0°. The temperature 

 falls rapidly from the surface to a depth of 50 to 100 m (down to the thermo- 

 cline layer) ; at greater depths it changes but little. 



A homothermic state (0° to Г) is established by the end of the coldest 

 season of the year. The ' hydrological summer' comes to the surface layers of 

 Kola Inlet waters in July and August and the winter in January and February. 



In summer there is a characteristic fall of salinity in the surface layer of the 

 Kola Inlet waters. Even in the northern part of the inlet up to 8-3% salinity 

 has been observed. However, even at a depth of 5 m salinity is never below 

 30% ; it increases still more lower down (up to 30 to 34-5% ), and its seasonal 

 changes in the deep zones are negligible. In winter the surface waters also 



