Figure 3. --Distribution of the plankton in the 0-100 meter 

 layer in August-October 1954, 1 - above 50C mg. /m. ; 

 2 - 250-500 mg. /m.^; 3 - 100-250 mg. /m.^; 4 - less 

 than 100 mg. /m.^; 5 - areas of "blooming". 



The geographical distribution of C. cristatus 

 in the 0-200 m. layer (fig. 4) shows its strict 

 adaptation to the waters of the boreal region, 

 the boundary of which coincides well with the 

 southern boundary of its distribution in the sur- 

 face layers. At depths greater than 200-500 m. 

 it penetrates considerably farther south and 

 was discovered by us in the 500-1, 000 m. layer 

 at 30°52'N. 



The vertical distribution of the plankton 

 biomass is not the same in the various parts of 

 the area investigated. In the moderately cold 

 waters of the boreal region, in the area adjacent 

 to the Kurile Islands, under the influence of 

 waters from the Okhotsk and Bering seas and 

 characterized by the stratification found in them, 

 in the presence of a cold intermediate layer, the 

 relatively slightly warmed (to 10O-12°C.) sur- 

 face waters are richest in plankton. In the 

 0-25 m. layer the biomass nnay sometinnes 



reach 2 g. /m.^, and it fluctuates on the average 

 from 200 to 1 , 000 mg. /m.^, increasing in the 

 spring and decreasing in the autumn. The 

 25-50 m. layer is almost as rich, and in it is 

 sometimes observed just as high a plankton 

 biomass. In the 50-100 m. layer the biomass 

 diminishes, but it is especially low in the 100- 

 200 m. layer, below which it again increases. 

 Thus, the cold intermediate layer is the poorest. 



The standard stratification of the levels at 

 which samples were collected somewhat ob- 

 scures the poverty of the cold intermediate laye_r 

 and at the same time diminishes the /_apparent/ 

 magnitude of the biomass maximum lying below 

 it, for the 50-100 m. and 100-200 m. levels 

 take in, in addition to the waters of the cold in- 

 termediate layer, waters rich in plankton which 

 lie above and below this layer. A more differ- 

 entiated selection of samples in the cold inter- 

 mediate layer and in the layers adjacent to it 



11 



