536 TRANS URANIC ELEMENTS IN THE ENVIRONMENT 



using only one species of a rather large macroplankton whose particulate products (molts, 

 fecal pellets, and carcasses) would be expected to reach depths at fairly rapid rates. The 

 microzooplankton, which constitutes by far the larger portion of the biomass at trophic 

 level II (herbivores), most certainly contributes to this process, yet the basic biological 

 data concerning fecal-pellet and molt production rates under varying food conditions 

 comparable to data obtained for selected macrozooplankton species have yet to be 

 formulated in a way that could be used to refine vertical transport estimates for the 

 transuranics. Finally, the importance of the food vs. water pathway for uptake of 

 transuranics by marine biota has been established for only a very few species, and even 

 fewer definitive experiments have investigated direct uptake from labeled sediment. Until 

 substantial progress is made in each of these areas, our understanding of the behavior of 

 transuranics in the biotic component of the marine environment and its attendant 

 influence on the movement of these elements in the ocean, including transport back to 

 man, will continue to be inadequate. 



Acknowledgments 



We have attempted to select information that would give the reader a general overview of 

 the field and the directions that are being followed by researchers in the discipline. There 

 are Ukely omissions of some of the work of our colleagues, and for this we apologize. The 

 interested reader is urged to consult the articles cited to gain further insight into the 

 complexities of the subject as well as a full appreciation of the arduous tasks ahead. 

 Support for this work has been received from the U. S. Department of Energy under 

 contract Ey-76-5-06-2227, Task Agreement No. 30, and from a cooperative agreement 

 between the U. S. Department of Energy and the National Marine Fisheries Service. 



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