. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. 554 BIOLOGY OF THE SEAS OF THE Caspian. In 1934 even at the greatest depths there was some 0-13 to 0-64 cm3/l. of oxygen. According to N. M. Knipovitch's data (1914-15) for the Central Caspian, at a depth of 700 m oxygen was disappearing and hydrogen sulphide appearing (up to 0-3 to 0-4 cm3/l.). A smaller amount of hydrogen sulphide was recorded in the Southern Caspian. In 1934 S. Brujevitch recorded some small amounts of hydrogen sulphide (about 0-2 cm3/l.) in the Southern Cas- pian at a
. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. 554 BIOLOGY OF THE SEAS OF THE Caspian. In 1934 even at the greatest depths there was some 0-13 to 0-64 cm3/l. of oxygen. According to N. M. Knipovitch's data (1914-15) for the Central Caspian, at a depth of 700 m oxygen was disappearing and hydrogen sulphide appearing (up to 0-3 to 0-4 cm3/l.). A smaller amount of hydrogen sulphide was recorded in the Southern Caspian. In 1934 S. Brujevitch recorded some small amounts of hydrogen sulphide (about 0-2 cm3/l.) in the Southern Cas- pian at a depth of 700 m. As in the Black Sea, the hydrogen sulphide is mainly the result of anaerobic. SOUTHERN CASPIAN Fig. 264. Oxygen content (percentage saturation) of the Central Caspian in cross section (Brujevitch, 1934). reduction of sulphates due to the activities of bacteria of the Microspira type. Moreover A. Pelsh (1936) discovered in the Caspian Sea a new group of bacteria (Hydrogenthiobacteria) capable of synthesizing hydrogen sulphide from solid sulphur and gaseous hydrogen. In contrast to that of the Black Sea, animal life in the Caspian Sea penetrates to the greatest depths. Suffocation phenomena of the type found in the Sea of Azov have not been recorded in the Caspian Sea. If they do exist in the Northern Caspian they are probably local and limited; this is confirmed by the absence from the Caspian of zones of blackened shell gravel, so typical of the Sea of Azov. This is ex- plained by the wide distribution of sand and large-grain soils in the shallows encircling the Caspian depths, which indicates a sufficient aeration of the bottom layer in shallow areas. It is different in the shallows with mud-accu- mulations, where a very marked shortage of oxygen (4 to 20 per cent of satu- ration) has been recorded at times. A mass accumulation of soft mud-beds in protected regions and bottom hollows, however small, is due to abundant. Please note that these images are extracte
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