Primary Production in the Northwestern Pacific Ocean

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Abstract
The primary production in the northwestern Pacific waters was measured during the cruises in August 1957 and in May, July-August 1958. The standing crop of phytoplankton was measured on the basis of its chlorophyll content, and the photosynthetic rate of phytoplankton was determined by the 14C method. The average chlorophyll value in euphotic layers was found within the range from 0.4 to 0.7 mg. /cu. m. for the Oyashio area and from 0.1 to 0.2 mg. /cu. m. for the Kuroshio, except for the coastal water. Furthermore, it was observed in euphotic layers that a linear relationship exists between transparency of water and average chlorophyll content. The photosynthetic capacity of water taken from various depth of the sea was measured under an optimal light condition and at temperature of water in situ. On evaluation of photosynthetic capa-city, the Oyashio area gave values 1-4 mg. C/cu. m. /hr., and the Kuroshio area from 0.1-0.7 mg. C/cu. m. /hr., respectively. The production was estimated by means of the tank and chlorophyll methods. The calculated value of the daily production rate was 0.2-0.4g. C/sq. m. /day for the Oyashio area as well as the littoral region of the Kuroshio, and 0.05-0.1g. C/ sq. m. /day for the pelagic area of the latter.

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