GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 



723 



Table 295. Changes in benthos biomass with depth (Ya. Bir stein and G. Belyaev, 1955) in 



northwestern part of Pacific Ocean 



The considerable difference between the variations of the biomass of plank- 

 ton and of benthos, either in the direction from the coast to the open ocean 

 or from the surface into its depths, is due apparently to the multiplication of 

 benthos being more closely dependent on the shore than is that of zooplank- 

 ton. The latter depends much more on phytoplankton, the development of 

 which in its turn is determined by the nutrient salts, the system of vertical 

 mixing which brings them from the depths to the surface, and by the general 

 conditions of lighting. 



Two diagrams may serve to illustrate this ; first the qualitative distribution of 

 life through a cross section of the Kuril-Kamchatka trench (Fig. 349). 



The amount of plankton decreases from 400 to 30 mg/m 3 from the neretic 

 zone to the oceanic (I). The increase (to 500 mg/m 3 ) corresponds to the in- 

 crease of plankton biomass towards the zone of convergence of the cold and 

 warm waters. Throughout the same field the benthos biomass (II) decreases 



Fig. 349. Diagram of quantitative changes in plankton and benthos south-east of 

 the Kuril chain (Zenkevitch). / Plankton; // Benthos; /// Bottom topography 

 (cross section of Kuril-Kamchatka trench). 



