82 



[chap. 3 



0.31 ~ 0.42 [JL[Jt.c/g of Ca in 1959. In the fish bones 90 Sr content ranged from 

 0.19 [i.[xc/g of Ca to 0.7 \i\icjg of Ca. In a composite sample of plankton, Nakai 

 et at. (1960) reported values as high as 6 y.\xc of 90 Sr per 1 g of Ca collected in 

 the coastal waters of Japan in 1959. The maximum value of 90 Sr in benthos 

 was 14.3 [Xfxc/g of Ca in Ccelenterata collected at the ocean bottom near Hachijo- 

 jima Island. These results showed the remarkable enrichment of the dissolved 

 or particulated forms of the radionuclide in marine products. 



Observations carried out by the Japanese Bikini Expedition (1954, 1956) 

 indicated that the gross activity was from 1000 to 10,000 times more con- 

 centrated in zooplankton than in water when compared on a weight basis. 



Table IV 



Approximate Concentration Factors of Different Elements in Members of the 



Marine Biosphere. The Concentration Factors are Based on a Live Weight Basis 



(Krumholz, Goldberg and Boroughs, 1957) 



a Values from Laevastu and Thompson (1956). 



According to Harley (1956), the radioactivity was on the average 470 times 

 higher in plankton than in sea-water collected west of the Bikini area. Such an 

 enrichment in plankton provides a detection device for the presence of radio- 

 activity in sea-water. Ketchum and Bowen (1958) suggested that organisms 

 may modify the distribution of radionuclides in the sea once living matter has 

 accumulated the radioactivity. Following their death, the organisms will sink 

 toward the bottom and carry with them radionuclides within the organic or 



