On the Distribution and Variation of Nutrient Salts in the Adjacent Water to the Aleutian Islands in the North Pacific

Abstract

Abstract The author was engaged in the oceanographical observations carried out in a region adjacent to the Aleutian Islands in 1952 and obtained a number of data, on which the present discussions are based. As the results, slight differences in distributions of nitrate-nitrogen, phosphate-phosphorus and silicate-silicon were found between the northern and southern areas separated by the Aleutian Ridge, although distributions are almost the same in the two areas. Characteristic features in distributions of these nutrient salts are that the high concentrations were found even in the surface layer, increasing further with maximum gradients in depths within 100–300m. The ratios of N:P in the region under study are lower than the normal ratio given by Cooper; and deficiencies in dissolved oxygen were recognized in the subsurface layers. These facts seem to be related to the characteristics of the decomposition processes in the Aleutian region. On the basis of the rate of phosphate consumption in the upper layers, the net production rate has been computed by introducing some simplifying assumptions; and has obtained the value of 56 mg. C/m3/day. This value is considered to be reliable, since it coincides with that derived from Riley’s data and with that calculated from the data concerning the diurnal variations of dissolved oxygen.