13 Six species of fish were collected from three sites in the lagoon at Rongelap Atoll. Naturally occurring 40K was the predominant radionuclide detected. Concentrations of 40Kbee89 10 pci/g. Values of the three fallout radionuclides measured, 37Cs, except for the viscera of mullet which had and 20Sr were less than 1 pCi/g, 20Sr levels of 1.1 and 2.7 pCi/g. Tridacna clams from the lagoon off Rongelap and Kabelle Islands con- tained 6UCo as the only significant fallout radionuclide. Cobalt-60 levels were highest (11 pCi/g) in the kidney and low in the mantle and muscle. Potassium-40 in the tissues of these clams averaged 7.8+1.4 pCi/g. aoants behhRongelap contained 137c5 and 29Sr in greater quantities than 4 13he cgncentration in Pandanus leaves was 4.4+1.8 pCi/g while the !37cs and QSr concentrations were 33419 and 30+17 pCi/g (dry), respectively. Pl nts from 5 e northern islands of Lukuen and Lomuilal had higher levels of Osr and 13/cs than did similar plants from Rongelap Island in the southern part of the atoll. Soil samples were collected from six islands ip ,Rongelap Atoll. Five gamma-emitting radionuclides, ©0Co, '25sb, 137cs, T55Eu and 41am, were measured in most samples. Strontium-90 and 239, A0p, were also easily ggasured in the samples analyzed for these radionuclides. Cesium-137 and Sr were the most aguncant ofFghe above radionuclides as shown in Figure 4. Americum-241, 239:240py, and 19°Eu were the next most abundant radionuclides. phey were, gommonl y resent in concentrations between 10 and 50 pCi/g while 9¢o and 1 3 5Sb values were Tess than 10 pCi/g. At Rongelap Atoll, soil from the northern islands of Lomuilal, Lukuen and Gejen had the highest radio- nuclide values of the six islands sampled. The amounts of radionuclides in soil from Rongelap Island were about a factor of ten lower than amounts in soil from the northern islands. Bikini Atoll Samples were collected at Bikini Atoll in April and December 1974 and in April 1975 for analysis in our Laboratory. One coconut crab, Tridacna clams, nine species of fish, plants, and extensive soil protlesos werg taken for gammaspectrum analysis. Selected samples were analyzed for 90Sr, or Pu. Results of these analyses are shown in Appendix Table 6 (csconut crabs), 14 (Tridacna clams), 22 and 23 (fish), 24 and 25 (plants), and 26 through 37 (soil 1. Animals and plants A single coconut crab captured on Bikini Island by an inhabitant of the jgiand was gpurchased by us in 1974. In the muscle from this large crab the 7cs and 905r yalues were 380 and 16 pCi/g of dry weight, respectively. Sixteen hundred pCi of 7¥Sr per gram were found in the exoskeleton of this crab. Plutonium-239, 240 concentrations in the three tissues analyzed were. about 0.02 pCi/g. Few coconut crabs remain on Bikini Island due to the destruction of the native vegetation during the rehabilitation of the island. Tridacna clams from the lagoon near Bikini Istand contained 60¢o in kidney tissue in amounts up to 322 pCi/g of dry weight. Cobalt-60 concen- trations in the other tissues from this clan were | 5 5 5nan 20 pCi/g. for other fallout radionuclides including 7“Sr and Values Pu were Tess than