The values of the concentration function of plankton in 

 relationship to a number of elements are quite great. For example 1 g 

 of plankton ash concentrates in itself a quantity of boron equal to its 

 content in 32 ml of sea water, along with a quantity of aluminum equal 

 to its content in 300 1 of sea water. 



Plankton also quite actively concentrates P, Cu, Cd, Ti, Cr and 

 other elements. Significant concentration of radionuclides by pelagic 

 crustaceans occurs during the first hours after the beginning of 

 exposure. For example, the Copepoda, during the first three hours, 

 usually accumulate from one third to one half of the quantity of Mn and 

 Co°^ which they accumulate over the next two days. Our attention is 

 drawn by the nonuniformity of accumulation of radionuclides by different 

 individuals of the same species. Usually, the young members of the 

 species concentrate these elements more rapidly than mature members. 

 This phenomenon has been specially studied from the standpoint of its 

 significance for the formation of absorbed doses of ionizing radiation 

 from the radionuclides accumulated by hydrobionts (Ivanov, Parchevskaya, 

 1975). 



Radioactivity of the environment and its significance in the life 

 of hydrobionts . --A comparison of the absorbed doses of various 

 radionuclides in the tissues of a number of animals of the Sea of 

 Okhotsk and the Bering Sea (herring, seal, whales) shows that the 

 primary contribution is made by K^^, with artificial radionuclides 

 (Cs^-^ , Sr^^, Y^^) playing a secondary role. 



A comparison of the doses accumulated in the Sea of Ireland by 

 phytoplankton and zooplankton, mollusks and crustaceans, benthic and 

 pelagic fish, from the natural background, global radioactive fallout 

 and the dumping of radioactive wastes in the vicinity of Windscale has 

 shown that the global fallout usually does not exceed the contribution 

 of the natural background radiation. However, the wastes dumped into 

 the Irish Sea by the Windscale enterprises create a dose level which is 

 higher than the natural background: for phytoplankton by a factor of 

 something over 10, for zooplankton by a factor of over 100, for the 

 benthos and fish--by a factor of up to 100. 



Various organisms differ sharply in their sensitivity to ionizing 

 radiation. „Most sensitive are certain crustaceans and fish. Beginning 

 with an SR^^-Y^^ concentration of 10'^ curies/1 or higher, the frequency 

 of nuclear disorders in a number of marine fish increases (Tsytsugina et 

 al., 1973). The sensitivity of the larvae of two species of sea 

 urchi ns- -Pseudocentrotus depresus Anthoci dari s crass i spi na- -to the 

 concentration of tritium differs by a factor of 10"^ (Akita, Shiroya, 

 1970). 



Due to experimental difficulties, there has been insufficient 

 material gathered to draw general conclusions in the area of the effects 

 of radioactive pollutants on the populations and ecosystems in the seas 

 and oceans. This is a matter which should be taken up in the near 

 future, considering the rapid rates of growth of nuclear power 

 engineering. 



420 



