Chapter 13 



Large-Scale Biological Experiments with Tracers 



135 



With the exception of hmited work at Han- 

 ford and Oak Ridge, it appears in all these cases 

 that primary attention has been concentrated 

 on monitoring aspects, that is measurement of 

 the quantity and distribution of radioisotopes 

 to insure against hazards to human or other 

 animal populations. The work of Richard Foster 

 and others on the radiophosphorus cycle in the 

 Columbia River, and the work of Louis A. 

 Krumholz on seasonal variations in quantities 

 of fission products in different groups of organ- 

 isms, indicate however, that locations where 

 wastes are being continuously introduced into 

 aquatic environments offer a good opportunity 

 to study the ecological processes of the aquatic 

 populations through the tracers provided by the 

 introduced isotopes. It may be expected with 

 the development of the fission industry in the 

 next few years, that there will be disposal of 

 some low-level wastes into marine waters, which 

 will provide opportunities to investigate the 

 ecology of estuaries and inshore ocean waters 

 by these means. 



These introductions also constitute large-scale 

 experiments on both the direct and genetic 

 effects of long-term exposure of marine organ- 

 isms to atomic radiations. It is important that 

 these eflFects be carefully investigated, because 

 it is possible that the larger organisms in the 

 sea, which are subjected to much lower rates 

 of natural radiation than terrestrial forms (due 

 to the shielding effects of water on cosmic 

 rays, as well as to the low gamma-ray activity 

 per unit volume of sea water compared with the 

 rock and soil of the land), may show propor- 

 tionally a greater genetic effect from a given 

 amount of radiation. 



Planned experiments 



Much useful information may be obtained by 

 well conceived biological observations in con- 

 nection with weapons tests and routine disposal 

 of industrial atomic wastes. Much more pre- 

 cise information could be obtained, however, 

 by planned experiments introducing measured 

 quantities of known isotopes into the marine 

 environment in a controlled manner. Further- 

 more, it is evident that the fluxes of different 

 elements through the ecosystem vary according 

 to their abundance in the sea and their physio- 

 logical roles in the organisms. Some of the 

 most important elements biologically are not 

 fission products, nor are they present in wastes 

 in appreciable quantity. The outstanding ex- 



ample is carbon. The energy which supports 

 most of the life in the sea, as on the land, is 

 fixed as chemical energy of complex carbon 

 compounds synthesized by plants. To study the 

 flux of energy through the different trophic 

 levels of the ecosystem it is necessary, therefore, 

 to measure directly or indirectly the flux of 

 carbon. One of the most promising possibili- 

 ties, discussed further below, is the use of radio- 

 carbon in tracer experiments on a scale larger 

 than the present laboratory-type experiments. 



The need for large scale experiments under 

 natural conditions arises because we require 

 knowledge concerning the quantitative interre- 

 lationships of the various populations of or- 

 ganisms, and it is not possible to reproduce 

 natural marine communities, especially the pe- 

 lagic elements, in the laboratory. It is probably 

 not possible yet to study some aspects of open- 

 sea communities by radioactive tracers, either, 

 but it may be possible to improve on present 

 techniques by larger scale in situ experiments 

 than have been attempted. 



Large scale experiments, employing either 

 mixed fission products or single isotopes iso- 

 lated from mixed fission products, appear feasi- 

 ble (at least in selected locations in the open 

 sea) to determine what organisms take up 

 which elements and the quantitative aspects of 

 how these elements are passed through the food 

 chain. It may also be feasible to introduce 

 sufficient quantities of radioisotopes in particu- 

 lar situations to make possible a study of the 

 transport of such elements by migrations of 

 organisms. In general, however, in the open 

 sea, it will be necessary to confine attention to 

 those elements which are naturally present in 

 seawater in very small concentrations, so that 

 the organisms may be expected to take up a 

 relatively large fraction of the isotope in ques- 

 tion. In the case of elements such as carbon, 

 only a small fraction of which is taken up by 

 the organisms, experiments in unconfined vol- 

 umes of open sea would appear to require 

 larger quantities of the radioisotope than are 

 feasible on a cost basis, and experiments there- 

 fore will have to be limited, in the near future 

 at least, to small enclosed arms of the sea or 

 artificially bounded volumes of water in the 

 open sea. 



In order to conduct experiments in the open 

 sea it is necessary to (1) introduce the radioiso- 

 topes into an area sufiiciently large so that it 

 can be located and followed, to insure the or- 



