Artificial radionuclides in marine organisms in the northeast Pacific Ocean off Oregon, U.S.A.

Although /sup 65/Zn is found in all groups of animals in the pelagic and benthic environments, in higher concentrations in some animal groups than others, the highest levels measured are still very much below hazard levels. Highest concentrations of /sup 65/Zn in the fauna usually were found near the Columbia River, a point source. However, pelagic organisms further to the south showed high concentrations during the summer. Bathymetric, seasonal and diurnal effects on the distributions of radionuclides in the biota are interconnected, particularly in the macroplankton and nekton. Zinc-65 stratified in the pelagic organisms in the summer, was uniformily distributed with depth in the winter. Concentrations were higher in the macroplankton and nekton in surface waters at night, and decreased with depth in the benthos. Zirconium-95-Niobium-95 were found at all depths, though in the pelagic fauna they were in higher concentration in surface waters. Zinc-65 was found throughout the food chain, while /sup 95/Zr-/sup 95/Nb decreased rapidly after the first two trophic levels.