Spatial and temporal variability of the ratios between the nitrate and phosphate concentrations in the Sea of Okhotsk

The relation between the nitrate and phosphate concentrations in the Sea of Okhotsk and the bordering waters of the Pacific Ocean were studied. The surveys were carried out in the autumn, spring, and summer of 2001-2002. For the deepwater part of the sea, the relation [NO^sup -^^sub 3^] = ((14.88 ± 0.07) × [PO^sup 3-^^sub 4^] - 5.46 ± 0.17) was found. The coefficients in the equation given are statistically different from those in the similar equation for the Pacific waters: [NO^sup -^^sub 3^] = (16.05 ± 0.15) × [PO^sup 3-^^sub 4^]-(7.23 ± 0.36). In the northern part of the sea; on the shelf; in the slope area; and, especially, in the deep waters of the TINRO Depression, the linear dependence between the phosphate and nitrate concentrations was distorted. This feature was described in terms of nitrate deficiency. The maximum values of this deficiency were found in the near-bottom waters. The principal processes that might cause the nitrate deficiency were considered: the difference in the oxidation rates of the nitrogen and phosphorus organic compounds, the matter transfer between the continent and the sea, the different efficiency of the biogenic burial of nitrogen and phosphorus in the bottom sediments, and the denitrification in the upper layer of the bottom sediments. It was shown that the most probable cause of the nitrate deficiency was the denitrification. The loss of inorganic nitrogen owing to the supply of the waters of the Sea of Okhotsk to the Pacific Ocean was estimated as 2.5 × 10^sup 11^ mol N/year.[PUBLICATION ABSTRACT]