70 The Sea-water and its Physical and Chemical Properties 



Table 26. Average vertical distribution of t, S and Hydrogen Stdphide in the Black Sea 



Depth (m) 







100 



200 



300 



500 



1000 



1500 



2000 



Temp. {°C) 

 Potential temp. (°C) 

 Salinity (%«) 



13-80 



7-95 



7-94 



20-36 



8-69 



8-67 



21-35 



8-80 



8-76 



21-73 



8-83 



8-77 



22-09 



8-93 — 



8-81 — 



22-24 22-31 



9-00 



8-75 

 22-34 



HjS content ml/1, 

 (standard pressure 

 and C) 



0-0 



00 



0-45 



1-42 



3-45 



5-55 



6-09 



6-24 



inner end and access to the open ocean only over a bar or a very shallow sill. They have 

 recently been reviewed in detail by Munster (1936). Of 30 fiords on the western 

 and southern coasts, 16 showed hydrogen sulphide in the bottom layers; the other 

 14 had very low oxygen values varying between 0-22 and 5-47 ml/1. The ventila- 

 tion of the deeper layers depends in the first place on the sill depth and the width of 

 the passage to the free ocean. In some fiords changes in the hydrogen sulphide content 

 were found which must be due to the addition of ocean water. 



The formation of hydrogen sulphide is only possible in closed or very poorly ven- 

 tilated deep basins. The Baltic which has a much lesser depth than the Black Sea 

 shows very similar hydrographic conditions, although the deep water in the Baltic 

 is renewed occasionally by the spasmodic entry of masses of North Sea water (Watten- 

 BERG, 1941) so that it is only in stagnant periods that the oxygen content is depleted by 

 the respiration of animals and by the oxidation of organic material in the water and 

 on the bottom. Table 27 shows typical conditions at a summer station in the middle of 

 the Baltic. 



Table 27. Gotland Basin (57^24' N., 19°52' E.); ''Skagerrack'' 

 Station Alf. 96, 31 July, 1922 



The temperature minimum caused by winter cooling is at 60 m depth. The oxygen 

 content falls from the well-ventilated upper layer with 7-8 ml/1, to less than 2 ml/1, 

 a little above the bottom where it reaches only 30% of saturation. The carbon dioxide 

 content here is 3-3 ml/1., which is eight times the normal concentration (Schulz, 1924), 



