32 of all radionuclides, except spt?5 and sr°°, at the surface of the young soil is associated with the algal crust. The obser- vation that mosses and lichens collected from trees at Rongelap Atoll in 1961 show essentially the same gamma-ray spectra as the algal crust lends supporting evidence to this assumption. The retention of radionuclides by algal crust, mosses and lichens must be related to adsorptive surfaces or to the metabolism of the organisms, although it is impossible to determine from the field data the mechanism or combination of mechanisms involved. Similar observations have been made with arctic lichens (Palmer et al. 1964). Since the algal crust at Rongelap Atoll has retained the radionuclides for nine years and from all indications will continue to do so for years to come, it is possible that it also retains a variety of mineral nutrients, thus providing a reservoir of nutrients in otherwise barren areas. This reser- voir might be tapped upon invasion of the areas by higher plants and the concomitant activity of animals in mixing the upper layers of the soil. Distribution of the radionuclides in the old soils arises from a combination of processes which are difficult to delineate, No doubt much of the movement is due to leaching and readsorption 4.