. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. 86 BIOLOGY OF THE SEAS OF THE homothermic conditions. At that time the amount of nitrates in the water varies from 150 to 250, and of phosphates from 40 to 60 mg/m3. The nitrate and phosphate contents increase slightly from south to north and in the northern parts of the Sea the amount of nitrates in bottom layers reaches 450 to 460 mg/m3. The off-shore waters are, on the contrary, appreciably poorer in nutrient salts. Their nitrate content may fall to 100 mg (and below) and that of phosp
. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. 86 BIOLOGY OF THE SEAS OF THE homothermic conditions. At that time the amount of nitrates in the water varies from 150 to 250, and of phosphates from 40 to 60 mg/m3. The nitrate and phosphate contents increase slightly from south to north and in the northern parts of the Sea the amount of nitrates in bottom layers reaches 450 to 460 mg/m3. The off-shore waters are, on the contrary, appreciably poorer in nutrient salts. Their nitrate content may fall to 100 mg (and below) and that of phosphates to 14 to 15 mg/m3. The Arctic waters are on the whole richer in nutrient salts than the Atlantic ones. Careful all the year round observation has allowed Kreps and Verzhbinskaya not only to draw a full picture of the annual cycle of nutrient salts but to come to some interesting conclusions on biological productivity. First of all it was found possible to determine the total amount of phosphorus used up during the multiplication period of 1930—31 in the region near the Kola meridian. Knowing the amount of phos- phorus contained in phytoplankton (0-15 per cent of the wet weight) it is possible to calculate the amount of phytoplankton which could develop at the expense of a given amount of phosphates. It was estab- lished that 3,000 to 5,000 tons of the wet mass of phytoplankton could be formed for each square kilometre of sea surface at the expense of the phosphates present through the whole depth of the Barents Sea. This amount is about double that of the annual phytoplankton production cal- culated by Atkinson for the English Channel (1,400 tons) and for the Oslo- fjord by Gran (1,600 tons/km2). Interesting data on the distribution of nitrites in the Barents Sea are given by S. P. Brujevitch (1931). In summer nitrites are absent from the photo- synthesis layer; the largest amount is accumulated under it, at a depth of 50 m or more. The amount of nitrites is rarely abov
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