Changes in the Biomass of the Seston in the 0-100 m. Layer (mg. /m.^) 



The changes in the plankton content in the 

 upper 100-m. layer can be illustrated by the 

 above table. 



Thus, in spring the plankton biomass is 

 usually about twice as great as in the summer. 



We have analogous data for the Bering Sea 

 (Vinogradov 1955). In spring (in May-June) 

 the average zooplankton biomass in the central 

 parts of that sea in the 0-100 m. layer was 747 

 mg. /m."", and at the end of summer (August- 

 September) it was 326 mg. /m.^. 



At the end of May and the beginning of June 

 we observed in waters with a surface tempera- 

 ture above 3°C. abundant "blooms" of various 

 diatoms. In August-September massive accu- 

 mulations of phytoplankton have almost nowhere 

 been found in the waters of the boreal zone. 

 Only small "patch" accumulations of phyto- 

 plankton are noted at that time close to the 

 coast of Kamchatka. 



A splendid development of phytoplankton 

 (predominantly Thallasiothrix) was discovered 

 between 155°E. and 170°E. longitude in the 

 zone of impingement of the boreal waters on the 

 waters of the Kuroshio. This is probably a 

 constant blooming in response to the steady 

 mixing in a zone of contact of different waters 

 (fig. 3). 



The available data testify that the months 

 of May and June are the spring biological sea- 

 son in the plankton of the boreal waters of the 

 northwestern part of the Pacific Ocean, and 

 that August-October is the summer season. 



In relation to the fact that the same 

 biological season for plankton at different lati- 

 tudes begins in different calendar months 

 (Bogorov 1938), the different parts of the ocean 

 simultaneously go through different biological 

 seasons. Thus, the spring enrichment of the 

 surface layer plankton in the southern part of 

 the Japan Sea, under the influence of the warm 

 Tsushima Current, occurs in March 

 (Meahcheriakova 1954), in the northern half of 



the Japan Sea in May (Brodskii 1941, 

 Kusmorskaia 1950), and in the cold Kurile 

 waters at the end of May or beginning of June 

 (according to L. A. Ponomareva's data). At 

 about the same time (May- June) it occurs in the 

 central areas of the Bering Sea and somewhat 

 later (June- July) in the northern Bering Sea 

 shallows and the Gulf of Anadyr (according to 

 data of M. E. Vinogradov), On the other 

 hand, the sharp autumn decline in the plankton 

 begins earlier in the northern areas and there- 

 after extends southward. Thus, for example, 

 the Anadyr Gulf area of the Bering Sea in Octo- 

 ber is in the stage of biological autumn, while 

 in the Komandorsky Islands area at that time 

 the plankton is in a summer condition. 



It is obvious that whales, in their feeding 

 migrations, keep to the areas of greatest con- 

 centration of plankton in the surface layers and 

 abandon these areas when the concentrations of 

 food decline. The feeding link between whales 

 and plankton arises either directly or through 

 small schooling fishes and squid. 



According to data of M. M. Sleptsov, the 

 whales appear in the northern part of the Japan 

 Sea and in the area of the southern Kurile 

 Islands and Sakhalin in April and May, that is, 

 in the period of the spring biological season of 

 the plankton. In May and June the whales arrive 

 at Kamchatka and the Komandorsky Islands. At 

 this time the plankton of these areas is also 

 characterized by the spring biological season. 

 In July the whales pass through the Bering 

 Strait into the Chukotsk (Chukchi) Sea, appear- 

 ing there in the period of the spring biological 

 season in the plankton. Since the summer bio- 

 logical season in the plankton of the polar seas 

 is very short (Bogorov 1938), in Septennber the 

 whales have already begun their return migra- 

 tion through the Bering Strait. In September 

 they appear in the area of the Komandorsky 

 Islands, toward the end of the biological summer 

 in the plankton, and in the Kurile Islands area 

 they appear again in October, also before the 

 end of the biological summer of the plankton. 

 Such links between plankton abundance and the 

 distribution of whales are hypothetical and 



14 



