GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 



707 



another 31-8 per cent. The 4 km layer of the deep waters of the trench held 

 only 2 per cent of the plankton biomass of the 8 km deep-water column. The 

 plankton biomass of the to 50 m layer varies from 100 to 1,100 mg/m 3 in 

 different places and at different hours of the day. A pronounced decrease of 

 plankton biomass, followed by a consecutive increase in the 200 to 300 m 

 layer, is characteristic of the cold intermediate layer of the Kuril region. 

 Farther down the biomass decreases rapidly to between 1,000 and 1,200 m, 

 after which its rate of fall decreases ; but at a depth of 6 to 8-5 km it falls to 

 0-5 mg/m 3 . Within the trench itself at this depth there is only 1-2 g/m 2 of 



Fig. 341. Average diurnal production of carbon, 



mg/1, in the northwestern Pacific. August to 



October 1954, determined by the oxygen method 



(Bogorov and Beklemishev). 



plankton biomass. Some species of Copepoda, Amphipoda and Ostracoda 

 are characteristic of the ultra-abyssal plankton. Many planktons there lose 

 their red colour, which is typical of the deep-water plankton, and acquire a 

 dirty grey colour. Apparently (V. Bogorov and L. Vinogradov, 1955) the 

 differences in the quantitative development of plankton in the boreal and 

 tropical regions of the northwestern part of the Pacific are retained even with a 

 transition to the deep floor (Fig. 342), hence the suggestion that the organic 

 substances of the production zone are carried away in the vertical direction 

 more than they are in the horizontal. Life phenomena which develop in the 

 surface zone of the Ocean influence bottom fauna and the organic components 

 of the sea-bed. The distribution of silica in the soils of the northwestern part 

 of the Pacific Ocean, corresponding to the abundant development of plankton 

 diatoms in the surface layer, is a good illustration of this correlation (Fig. 326). 

 M. Vinogradov (1954) has established some curious phenomena of the 



