Chapter 13 



LARGE-SCALE BIOLOGICAL EXPERIMENTS USING 

 RADIOACTIVE TRACERS^ 



MiLNER B. SCHAEFER, hiter-American Tropical Tuna Commhsion, Scripps Institution of 

 Oceanography, La Jolla, California 



One of the major difficulties in evaluating 

 the probable results of the introduction of radio- 

 active materials into the sea is the lack of ade- 

 quate knowledge respecting the effects of the 

 organisms in the sea on the distribution and 

 transport of such materials. Some information, 

 which has been reviewed in earlier sections of 

 this report, has been obtained on the uptake 

 and excretion of elements by different kinds 

 of marine organisms. This information is, 

 however, not sufficiently extensive. The even 

 more important problems of the quantitative 

 interrelationships and movements of the popu- 

 lations of organisms at the several trophic levels 

 are among the least understood biological phe- 

 nomena of the oceans. These, together with 

 physical factors, will determine the fluxes of 

 the radioactive materials. 



Measurements of the fluxes of materials 

 through physical-biological systems, or ecosys- 

 tems in the sea are of vast and fundamental 

 importance not only for evaluating the probable 

 distribution of radio-active products introduced 

 into the sea, but also as a basis of evaluating 

 the sea as a source of food and other biological 

 products for the use of mankind. With the 

 approaching full utilization of the land, in- 

 creasing attention is being directed to the sea 

 as a source of such products, but the basic bio- 

 logical knowledge for realistic evaluation of the 

 potential harvest of the sea is quite inadequate. 



The availability of rather large quantities of 

 radioactive materials, as by-products of the de- 

 velopment and utilization of nuclear energy, 

 makes possible the study, in situ, of the biologi- 

 cal and ecological processes in the sea by the 

 use of tracer techniques. A start has been made, 

 in connection with the introduction of radio- 

 isotopes into the marine and fresh waters by 



1 Contribution from the Scripps Institution of 

 Oceanography, New Series, No. 903a. 



weapons tests and by the disposal of low-level 

 wastes, but the opportunities for obtaining use- 

 ful information by these means have not been 

 fully exploited. Also it should be possible by 

 introducing radioisotopes in a planned, con- 

 trolled, and purposive fashion to obtain even 

 better information than is possible through ob- 

 servation of introductions ancillary to opera- 

 tions having a different primary purpose. 



Observation in connection with weapons tests 



Observations in connection with weapons 

 tests have the advantages that (1) very large 

 quantities of radioisotopes are introduced into 

 the sea, sometimes over a rather large area, so 

 that radioactivity is sufficiently high to be de- 

 tected in the sea waters and organisms over a 

 considerable time after the event, and (2) the 

 difficulty of being certain that the organisms 

 have actually remained in the water containing 

 the isotopes is minimized. On the other hand, 

 the determination of exact amounts of isotopes 

 introduced, of their spatial distribution, and 

 of their physical state presents some difficulty. 



Biological studies, in connection with the 

 various weapons tests in the Western Pacific 

 ocean, have been primarily directed toward de- 

 termining the concentration of gross activity in 

 different organisms, the localization of such 

 activity in different parts of the organism, and 

 the rates of decline of activity with time. There 

 has also been limited determination of the 

 isotopes concerned. The most extensive data 

 are from the lagoons of the atolls at and near 

 the test sites. In the open sea, outside the 

 lagoons, usually only limited collections of or- 

 ganisms have been made, incidental to other 

 operations. 



Following the test series of 1954, however, 

 two rather extensive surveys were made of the 

 distribution of activity in the sea, and in organ- 



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