ete yy te te em ae ae oy oe ge . ~ wo Ea ela Manet “fig 1 OT PEE te oF tee * ‘wok Stet. 8 ]aaa ett nae= we The source of 6005 for the tuna must be Bikini Atoll and not worldwide fallout because we analyzed tissues from 214 tuna, including 75 yellowfin tuna, taken from the Japanese tuna fishery during 1968 and 1969, and found no 60n6 (NVO-269-7, Annual Report). In contrast, the 5° re concentrations in the dark muscle of the tuna from the Japanese fishery ranged from 3.3 to 1600 pCi/g ary, most of the values fell in the range of 101 to 500 pei/g dry. It appears, therefore, that a major amount of the 5 ne in the Bikini tuna is from worldwide fallout. One of the principal sources of radionuclides at Bikini is Bravo Crater in the reef adjacent to and southwest of Nam I. Figure 1 shows a gamma-ray spectrum of sediment taken from a depth of 160 feet. Clearly, £906 and 207 85 predominate among the gamma emitters. In most soils, 137K. is the most abundant radionuclide. An intermediate condition exists at the southwestern end of Eneman I., where a low area is occasionally overwashed by seawater, and at the high tide line, where the 137as is being leached from the soil. The retention of 6066 and 207 54 by the sediments is reflected in the fact that the bottom-feeding goatfish in the vicinity of the craters contain ten times more °c than the herbivorous convict surgeonfish and plankton feeding mullet. However, some 60K is being transported eastward by the bottom current in the lagoon either in solution or associated with fine (colloidal?) particles, because the difference in 60.6 con- tent between convict surgeonfish and mullet in the vicinity of Bravo Crater and 16 miles eastward near Bikini I. is only by a factor less than two. of Enetay pepartne an’s Qifice piston? RRCHIVES