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



20000000л 



щц/хшшшахшш! v ш a z и ш щ 



1938 1939 



Fig. 199. Seasonal alterations in the quantity of diatoms and 



peridinean algae in the plankton of the Black Sea and Bay of 



Sevastopol (Morozova-Wodjanitzkaja). 



greater that it must be defined according to an entirely different order of 

 values. Apart from annual fluctuations in the number of plankton specimens 

 a pronounced variety is observed in the time of mass development and the 

 significance of individual forms. In April and May 1939 about 300 milliard 

 cells were recorded under 1 m 2 in a column of water down to 15 m in the Bay 

 of Sevastopol. In the summer this amount was reduced to 0-8 to 1-5 milliard 

 cells, and in winter to 700 to 800 million cells. Phytoplankton biomass in the 

 Bay of Sevastopol under 1 m 2 surface area reaches 1 33 g in the spring. In 

 June it was found to be 70 or 80 g, and in autumn and winter it dropped to 



Table 164. The seasonal shift of the dominant forms of phytoplankton in Black Sea 



(Coast of Crimea) 



