- 7 - 



Seymour, et_al. , 19^7) ai^d the movement of plankton with water 

 currents Is particularly useful in following the movement of 

 radioactivity in the sea. Laboratory tests employing marine phy- 

 toplankton have demonstrated the great variety of radioactive 

 materials accumulated and may provide Information allowing quan- 

 titative estimation of particular radionuclides in the water. 

 The plankton, however, drift with the water and may not remain 

 in the contaminated area long enough to accumulate the maximum 

 possible concentrations of radio elements. 



The fact that many bottom dwelling invertebrates are sessile 

 or have limited migration may prove advantageous since they will 

 be bathed constantly in the contaminated water. Many of these 

 concentrate elements of sea water to remarkably high levels. A 

 species of benthic foraminlfera has been shown to concentrate 

 Zr95 and Rul06 ^o a marked degree (Martin, 19^7) and bottom 

 dwelling pelecypods concentrate many of the minor elements, par- 

 ticularly trace metals, such as Zn°5 (Chipman et_al, , in press) 

 and Co^O (Gong et al .^ 19^6) » The calcareous shells of molluscs 

 and the skeletal structures of fish have been suggested as a 

 means of calculating water concentrations of Sr9D (Hiyama, 1957) 

 arid may be useful for estimation of water concentrations of 

 other bone-seeking radionuclides. It is anticipated that par- 

 ticular organisms of a marine environment will be of special 

 use for such bioassay procedures and exact concentration fac- 

 tors for many radionuclides are now being investigated, 



A number of the radio elements - especially the rare earths - 

 are very surface active and may be expected to adsorb strongly 

 on silts and clays in'the water and in the bottom sediments. Any 

 monitoring system should include extensive analyses of the bottom 

 sediments - especially if a method can be devised for collection 

 of the upper few centimeters to avoid dilution with old un- 

 affected sediments. 



