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Discussion 
The retention or rejection of a given radioactive ele- 
ment by the organisms in the contaminated area of the ocean 
is determined by several factors, many of which also function 
in the distribution of naturally occurring elements of the 
sea. The effects of some of these factors are known; others 
are not. A better understanding of the unknown effects may 
be attained by observations on the accumulation of individual 
radioactive elements from fallout within the trophic levels 
of the contaminated biosphere. By observing which radioele- 
ments are concentrated in the phytoplankton, the zooplankton, 
and the nekton and relating these observations to (a) the 
known characteristics of the fallout elements before and 
after entry into the sea; (b) the half lives of the radio- 
isotopes, the amounts produced at detonation, and their 
distribution with respect to fallout particle size; and (c) 
the known biological factors involved in the uptake and re- 
tention of different elements, the eventual fate of the major 
fallout radioisotopes in the sea may be determined. 
In the waters of the open Pacific Ocean the naturally 
occurring trace elements, zinc, cobalt, ruthenium, manganese, 
cesium, strontium, and possibly zirconium and cerium, in the 
water are present mainly in solution. The small amount of 
naturally occurring iron occurs in the colloidal and particu- 
late form. All of the above named elements, however, except 
