394 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



they be concentrated thousands of thnes in tissues of marine organisms 

 and remain in the tissues for much longer times than the cations. 



The fission-product isotopes, strontium 90 and cesium 137, that are 

 of great concern in land contamination from fallout, appear to be of 

 substantially less concern in the ocean where the biological demand 

 is apparently met by stable isotopes of the same or related elements. 

 Although there was a great uproar in 1954 when a Japanese ship, trans- 

 porting newly caught tuna, was discovered to have been in the path of 

 radioactive fallout from a weapons test, it later developed that the par- 

 ticles of radioactivity were on the surface of the fish and that they could 

 be removed by surface washing. No hazard has been fomid from 

 uptake of radioactivity by tuna. 



Only one example is known of marine organisms being destroyed 

 as a result of the uptake of radioactive isotopes. Following the deto- 

 nation of nuclear devices in the Marshall Islands in 1958, Aubrey 

 Gorbman, then of Columbia University, found evidence that herbivor- 

 ous fishes concentrated radioiodine which had already been concen- 

 trated by seaweeds. These high concentrations of radioiodine were 

 again concentrated to destroy the thyroids of carnivorous fishes which 

 fed on the herbivorous ones. Such carnivorous fishes were collected, 

 with death apparently due to destruction of thyroid tissues. Although 

 radioactive iodine may be concentrated by marine organisms, it is of 

 little serious concern except in cases of close-in fallout since its radio- 

 active decay rate is relatively rapid and since some dilution is present 

 from stable iodine in the ocean. 



Information is being accumulated that will provide basic infor- 

 mation on the uptake and concentration of isotopes near waste out- 

 falls. Less information is available and little useful data has 

 appeared to answer the question of biological effects of radiation 

 during the lifetime of individual marine organisms. 



A particularly interesting project now underway at the University 

 of Washington exposes salmon eggs and fingerlings to low-level 

 gamma radiation over the first 3 months of their existence. On 

 release they will go to sea to return in from 2 to 5 years. Comparisons 

 of return rates of irradiated versus unirradiated controls should give 

 some indication of the nature of the problem. 



In considering the uptake and effects of radioactive isotopes on 

 marine biota, attention must be given to the location of elements in 

 different organs of the body. Strontium 90 may be concentrated in 

 the skeletons of clams, scallops, oysters, and Kadiolaria of the suborder 

 Acantharia. Cesium 137 is concentrated about thirty to fifty times 

 more in the muscles of clams than in sea water. Zinc 65 may be concen- 

 trated several thousand times more in the muscles of oysters, clams, and 

 scallops than in sea water. Marine fishes concentrate zinc 65 espe- 



