=\} 
Of GboOULIEORS) tanta Shishi (Tilapia). In the case of fish bone 
and scales, however, the concentration factors may be higher. 
In the croaker (Micropogon undulatus) concentration factors 
for strontium in vertebrae and scales were 2.5 and 2.1 re- 
spectively those of sea water. 
In addition to the above mentioned factors, isotope 
dilution by stable strontium would result in reduced uptake 
of $r99 by marine organisms. Stable strontium is present in 
the sea at a level 6 to 1300 times that of the naturally oc- 
curring forms of the other elements represented in fallout 
(Table 3, column 2). Thus the discrimination against radio- 
strontium as a consequence of the presence of stable stron- 
tium in sea water would be 6 to 1300 times that to which 
the other radioelements would be subjected because of the 
presence of their stable counterparts. 
Further discrimination against the uptake of radiostront ium 
in these organisms may be caused by the scavenging action of 
calcite formed from coral aragonite in fallout material. In a 
simple experiment by the author, pulverized coral was sprinkled 
onto and allowed to settle through sea water contaminated with 
gr39 Clo. Approximately 11 per cent of the radionuclide was 
removed from solution the first hour. No reduction in activity 
was noted in a parallel control experiment. Suito, Takiyama 
and Uyeda (22) reported that the ashes from the March 1, 1954 
weapons test at Bikini which fell on the No. 5 Pukuryu Maru 
consisted of white granules of calcite approximately 
