1. INTRODUCTION The fate of radioactive materials introduced into the world's oceans continues to be a topic of considerable interest to marine scientists. Research in this field has included investigations of the mechanisms of the regional and global dispersal of radionuclides, the physical-chemical behavior of radioactive pollutants in the sea, the use of artificially produced radioisotopes as tracers of environmental processes, and the uptake and concentration of radfonuclides by biota. In addition, these studies have stimulated additional measurements of concentrations of naturally occurring radionuclides and their use as tracers of environmental processes. In spite of the interest in these areas, only limited data are available from in situ observations of the physical-chemical properties and behavior of artificially produced radionuclides introduced into the seas. It is not surprising, therefore, that a recent trend in marine geochemical and radicecological research is directed toward the study of the specific processes that control partitioning, speciation, transport and concentration of chemical elements in the different physical-chemical environs of the marine biosphere. Bikini Atoll was one site for nuclear weapons testing between 1946 and 1958. In the seventeen years since cessation of testing, physical decay and environmental processes have significantly removed or reduced in concentration many of the radionuclides which resulted from the nuclear transmutation processes. Because of their relatively long physical half-lives, several fission and neutron-induced radionuclides, such as 90 Sr 207,. 137 Cs, 60 Co, 55 ~~Fe, 155 Fu and Bi, can still be measured easily in sediments, soils and some biota at Bikini. However, the parent materials of uranium and plutonium-239, as well as many of the neutron-induced transuranium radionuclides such as americium and neptunium, have physical half-lives of 10°-10 9 years, and have not been