. at earlier times, however, estimates based -nly on exponential loss would not take into account possible retention and cycling of Sone within the lagoon, or the time lag between deposition and maximum specific activity in the aquatic biota. The increase in specific activity of goatfish liver between _ late 1961 and mid 1963 reflects the increased environmental concentrations of S56 resulting from testing nuclear devices in 1961-62, Introduction of this radionuclide to Rongelap Atoll can occur both by atmospheric fallout and by water transport of radioactivity from oceanic regimes. the westward-moving North ' Equatorial Current is comprised of waters from northern latitudes ‘where fallout from the 1961-62 tests were maximal (14). Speeds of surface currents in both the california and North Equatorial Currents are sufficiently large to account for transport of waters from 30-40° N latitude to Rongelap Atoll (15) in the time period 1961-63; similarly, maximum surface deposition of 3556 occurred in 1963 (14) and thus the data of Table 2 probably reflect contributions from both sources. (16). | Our measurements of > Fe in soils collected from the same sites between 1959-1963 do not clarify either of the input sources mentioned above; the change in concentrations are greater than can be accounted for by physical decay. Natural processes which remove >> re from the upper 2.54 cm of soil may preclude its use as a precise collector, and therefore the results are