756 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



II. FLORA AND FAUNA 



Four hundred and fifty different plants have been identified in the plankton 

 of the Sea of Japan (Y. Kiselev, 1937, 1947), among them 306 diatoms and 

 133 peridinians. In contrast with the northern part of the Sea of Okhotsk 

 the phytoplankton of the Sea of Japan has two maximum blooms — a spring 

 (March- April) diatom bloom and an autumn (September-October) peridinean 

 bloom. 



Primary production in the Sea of Japan and the adjacent part of the Pacific 

 was estimated in the spring of 1957 (Yu. Sorokin and O. Koblents-Mishke, 

 1958) by the carbon tracer method. In the area surveyed primary production 

 fluctuated within the limits of 2 to 5 g of organic carbon in a column of water 

 of 1 m 2 cross section. Before the spring bloom carbon production was 2 to 

 6 mg of carbon under 1 m 2 along the western side of the Sea of Japan, which 

 is subject to the effect of the cold Primor'e current, and in the central part of 

 the Sea between 41° and 42° N latitude. In the same area carbon production 

 during the greatest bloom was between 200 and 1 ,900 mg of carbon. The corres- 

 ponding values in the eastern part of the Sea were 50 and 115 mg under lm 2 . 

 The highest production was recorded in the Ocean east of Hokkaido Island 

 within the zone of the convergence of warm and cold waters, where 5,000 mg 

 of carbon was reached. South of 40° N latitude production did not rise above 

 100 to 150 mg of carbon under 1 m 2 . Naturally the size of the primary pro- 

 duction depends on the bloom phase and is governed by the presence of 

 phosphates and by conditions to the north. 



Zooplankton in the Sea of Japan is fairly varied, including no fewer than 

 70 or 80 organisms, among them about 50 species of Copepoda (36 species of 

 Calanoida Cyclopoida, 9 species of Harpacticoida), 4 species of Euphau- 

 siaceae, and 9 species of Hyperiidae. 



The main forms of surface plankton in the Sea of Japan are : Paracalanus 

 parvus, Pseudocalanus elongatus, Oithona similis, Calanus pacificus, Metridia 

 lucens, Calanus tonsus, C. cristatus, Microcalanus pygmaeus and Oncaea 

 borealis. 



The plankton of the Sea of Japan changes considerably both qualitatively 

 and quantitatively with depth. Cold-water forms are predominant in the 

 upper horizons in winter ; plankton composition changes sharply in summer. 

 Only eurythermic forms (for example Oithona similis) are found here all the 

 year round. There are many Foraminifera and Radiolaria in the plankton of 

 the surface layer during the cold season of the year. Below 500 m Micro- 

 calanus pygmaeus (K. Brodsky, 1941), the radiolarian Challengeron spp. and 

 the ostracoda Conchoecia become the main forms {Table 305). 



As is shown by the data of Table 305, deep-water plankton species are 

 extremely scarce in the Sea of Japan. 



In contrast with the northwestern part of the Pacific Ocean (K. Brodsky, 

 1952) where the number of species of Copepoda increases more than ten 

 times with depth, their number in the Sea of Japan is barely doubled with 

 depth. As regards the number of specimens down to 1,000 m the decrease is 

 five times more rapid in the Pacific Ocean than in the Sea of Japan. This may 



