. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. THE BLACK SEA 395 amount of nitrogen in the photosynthetic zone of the ordinary sea is either zero or very small; it increases, however, with depth. In the depths of the oceans the amount of nitrogen in the form of nitrates usually does not exceed 006 to 0-07 mg/lb; at the surface it may rise to 0-11 to 0-16 mg/lb. The amount of nitrate nitrogen in the seas is usually expressed in microgrammes per pound. The ammonia content of the upper layer of the Black Sea is also practically the same as that of
. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. THE BLACK SEA 395 amount of nitrogen in the photosynthetic zone of the ordinary sea is either zero or very small; it increases, however, with depth. In the depths of the oceans the amount of nitrogen in the form of nitrates usually does not exceed 006 to 0-07 mg/lb; at the surface it may rise to 0-11 to 0-16 mg/lb. The amount of nitrate nitrogen in the seas is usually expressed in microgrammes per pound. The ammonia content of the upper layer of the Black Sea is also practically the same as that of the open seas and oceans; it increases, however, with depth,. 1000 2000 3000 4000 5000 6000 YEARS Fig. 190. Reconstructed course of the alteration of salinity in the Black Sea after the break-through of the Bosporus waters (Wodjanitzky, 1948): A Salinity at sur- face ; ? Mean salinity. and at 1,500 to 2,000 m the amount of ammonia nitrogen is 1-10 to 1-46 mg/lb. The content and distribution of nitrates and phosphates in the Black Sea were first investigated by Danilchenko and Chigirin in 1929 and 1930. Twenty years later their work was repeated by V. Datzko, and considerable deviations from the earlier data were found. Lately M. Dobrzanskaja (1958) has investi- gated the distribution and changes of phosphates throughout the Black Sea column of water. This author notes the frequent absence of phosphates from the upper region of the water (50 to 60 m) in spring and summer, although in some years phosphates are present throughout the year in the upper layer of the whole Sea during the periods of marked deficiency of nitrates. In some areas of the Sea there is a pronounced increase in phosphate content as a result of the off- and on-shore winds and the phenomena resulting from them. Within the halistatic areas the phosphate iso-surfaces rise, and off-shore they sink, with fluctuations of 50 to 100 m {Table 156).. Please note that these images are extracted from scanned page images
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