Chapter 8 



LABORATORY EXPERIMENTS ON THE UPTAKE, ACCUMULATION, AND 

 LOSS OF RADIONUCLIDES BY MARINE ORGANISMS ^ 



Howard Boroughs, Hawaii Marine Laboratory, University of Hawaii, Honolulu, Hawaii 



Walter A. Chipman, Fishery Radiobiological Laboratory, 

 U. S. Fish and Wildlife Service, Beaufort, North Carolina 



Theodore R. Rice, Fishery Radiobiological Laboratory, U. S. Fish and Wildlife Service, 



Beaufort, North Carolina 



What happens to radioactive materials that are 

 introduced into the oceans may be studied by a 

 marine biologist from at least two points of 

 view. As a physiologist, he will be interested in 

 the uptake, accumulation, and loss of radioele- 

 ments as a function of the element, and its con- 

 centration; in the physical factors of tempera- 

 ture, light, and salinity; and in differences 

 between species of organisms, as well as their 

 age and sex, to mention some of the most im- 

 portant parameters. As an ecologist, he will be 

 interested in these same parameters under a 

 steady-state condition. The physiologist would 

 profit most by exposure of the organism to a 

 single dose of radioactive material, while the 

 ecologist must concern himself with the results 

 of chronic exposure. 



Both types of biologists may be interested in 

 tracing the history of an element through the 

 food webs of the various trophic levels. Un- 

 fortunately, the experimental data involving the 

 metabolism of radionuclides by marine organ- 

 isms is extremely meager. In this section some 

 experiments will be described on the uptake, 

 accumulation, and loss of radionuclides by vari- 

 ous marine organisms in the three trophic levels. 

 It must be emphasized that the results of these 

 few experiments must be extrapolated with ex- 

 treme caution in predicting what may happen 

 to radioactive materials introduced into the 

 oceans from nuclear reactor plants, bomb deto- 

 nations, or from any other sources. 



^ Work performed at the Fishery Radiobiological 

 Laboratory of the U. S. Fish and Wildlife Service and 

 the Hawaii Marine Laboratory (Drs. H. Boroughs, 

 S. J. Townsley, and R. W. Hiatt). 



Contribution No. 95, Hawaii Marine Laboratory. 



In discussing the uptake of radionuclides by 

 marine organisms, it is sometimes difficult to 

 state exactly what constitutes a single or a 

 chronic exposure. For a unicellular alga, a few 

 hours may represent chronic exposure, while a 

 few weeks may be insufficient for a fish to reach 

 a steady-state condition. No long-term repeti- 

 tive feeding experiments have been done, so for 

 the purpose of this report, we will discuss the 

 metabolism of the various radionuclides solely 

 on the basis of the trophic level concerned. 



The term uptake implies passage through a 

 membrane. Radioactive material may be pres- 

 ent in the gut of an organism, but until it enters 

 the organism through a membrane, it can play 

 no role in the metabolism of that organism ex- 

 cept by producing radiation effects or by inter- 

 fering with a chemical reaction occurring within 

 the gut. In some of the experiments to be de- 

 scribed, particularly those involving phytoplank- 

 ton, it was not established whether or not the 

 radioisotope was actually incorporated into the 

 organism, or merely adsorbed to the surface. 

 For simplicity, we will therefore discuss uptake 

 in the sense that the radioisotope is associated 

 with the organ or organism in question. 



Isotopes of a given element usually have 

 similar chemical behavior, so that in tracing the 

 path of most elements in biological systems, it 

 can be assumed that a radioactive atom will be- 

 have in the same way as a non-radioactive atom 

 of the same species. The only parameters to be 

 considered in the discussion to follow will be 

 the species and age of the organism, the ele- 

 ment, the concentration of the element, the tem- 

 perature, and the duration of exposure or treat- 

 ment. No work using radioisotopes has been 



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