T. M. neal, E._E. HELD and R. M. CONARD 1961-1962tests were maximal." Speeds of surface currents in both the California and North Equatorial Currents are sufficiently large to accountfor transport of waters from 30 to 40°N latitude to Rongelap Atoll!”in the time period 1961-1963; similarly, maximum surface de- position of 55Fe occurred in 1963," and thus the data ofTable 2 probably reflect contributions from both sources. The higher specific activity noted in goatfish liver in August 1963 may reflect morenearly the specific activity ofwaters at Rongclap Atoll than does the sample of March 1963. Liversfrom immature goatfish were used in the August specimen, while the | 249 species important in the Rongeizres¢ diet. The fact that livers from mature gc2:ish contzin between 2-3 times as much stable iron per urit wet weight as do livers of mazure selmon! is consistent with this argument. Second, Jenntres) and more recently Pazsvoxl® have suggested that large amounts cf *°Fe were introduced into the northern hemisphere 2s tropospheric fallout during the 1661-1052 test series and that deposition may have occurred in rather narrow latitudinal bands (maximum input at .60°-70°N (Preston). Josepx ef c/.©) suggest that subsequent stratospheric depesition of *5Fe from these tests was similar to that observed for March sample was obtained from mature fish. %Sr, i.e. maximum ceposition at =3°N. TransRecent measurements of the specific activity port of Fe from these high ladiruces by major ‘ofimmature and mature goatfish liver collected ocean current systems feecing the North at Johnston Atoll in 1968 showed that immature fish livers contained less stable iron and more *5Fe per unit wet weight than did livers from mature fish. We assume that the immature Equatorial Current (in e2ddision to bioicgical and physico-chemical factors; will deplete northern waters of this radionuclide. As discussed earlier, transit time for these waters from fish are in the process of forming their iron high. latitudes to Rongelap Azcil is measured in stores and therefore more nearly reflect the - year, and itis therefore possible that the higher environmental specific activities than do the. §5F'c¢ body burdensin the Rongelapese reflects 2 mature fish whose iron stores. are already - formed. In thelatter case, exchange rates may _ be slow. so Our measurements of ®5Fe in soils collected from the samesites between 1959-1963 do not “lag’’ time between the 55Fe specific activities of Northern Pacific and Southern Pecifc Ocean biota due to this transport. Finally it is possible that the high **Fe Rongelapese bedy burdens relative to the Japanese donors results from a clarify either of the input sources mentioned combination of dietary intake and uptake and above; the changes in concentrations are greater retention differences for iron bemveen the awo than can be accounted for by physical decay. groups sampled. Unfortunately precise dietary Natural processes which remove ®5Fe from the” information for both groupsis lacking and httle upper 2.54 cm of soil may preclude its use as a is known about the 55Fe specitic actvities of the ~ precise collector, and therefore the results are foods eaten by both groups. The Rongelapese useful only to indicateorder ofmagnitude values -do not suffer from iron deficiency anemia, so of 55Fe soil concentrations present at the collec- enhanced uptake of iron from the ciet is tion time. . probablyinconsequential. Itis clear that further Unfortunately it is not possible to offer a measurements of the specific activities of 55Fe in - Clear argumentin explanation of the 55Fe body. -the diets of the Rongelapese and other maritime burdens of the Rongelapese presented here, at cultures and the effective haiZiive thev display this time. Samples from 1963 through 1969. for this radionuclide will be needed to clarify would have shed light on the problem, but the questions raised here. none are available for analysis. In a speculative vein, several explanations can be advanced. First, the possibility of Rongelap lagoon acting 23 a nutrient and trace-clement “trap” similar to estuaries"® is intriguing. Removal and retention within the lagoon of both stable iron and ®Fe from the North Equatorial Current could lead to high specific activities of 55Fe in So - oe SULZ 1 eb Acknowledgement—We thans Mr. T. A. Joxrta for technical assistance and Dr. M. Feorra ior kindly arranging for the blood specimens ‘rom Tokai-mura, Japan. Dr. A. H. Seyvmocr and Mr. E. E. Parmer provided helpful discussions during preparation of the manuscript. Supported by AEC uncer Contract No. AT(45-1)-2225-14 and AT {70-15-259.