. 2.) Cycling of Radionuclides in the Atoll Ecosystem Radionuclides are still present in the atoll ecosystems because they are incorporated into plants and soil and are continuously cycled through the plant/soil system. Smal] fractions of the total radionuclide inventory on an island are slowly transported down the soil column into the ground water system. Therefore, it is important to determine the mechanisms and controlling features of radionuclide cycling as a function of climatic conditions, season of the year and the agriculture and irrigation practices in order to better direct remedial actions for reducing radionuclide uptake and/or radionuclide inventory. Determining the movement of water in this ecosystem is a critical part of the study because it is essentially the soluble fraction of tne total inventory that i$ available to the food crops and transport to the groundwater system. Similarly, radionuclide transfer and cycling between the sediment, water column and marine species is of importance in the marine environment to predict the long term dose effects from that pathway and the ultimate turnover time of radionuclides in the marine ecosystem. Some of this research is currently being conducted in DOE funded programs, at Enewetak and Bikini but these studies should be extended to include Rongelap and Utirik. Also with increased funding, expertise on the role of soil microorganisms in radionuclide accumulation and cycling could be included in ongoing studies. Any new studies conducted independent of the current Programs would necessarily have to include the atolls of Enewetak and Bikini and at least partially duplicate or supplement the ongoing DOE programs at these atolls. 36