Transfer of Cobalt-60 from Phytoplankton to the Clam (Mercenaria mercenaria)

Abstract

The transfer of cobalt-60 from phytoplankton (primary producer) to clams (primary consumer) was investigated to obtain additional information about the movement of cobalt-60 in the marine ecosystem. The retention (%) of cobalt-60 in the clams after feeding radioactive phytoplankton varied with size of the clams and cell density and species of phytoplankton fed to the clams. At high cell densities (2×10⁸ and 5×10⁸ cells/l), the retention of cobalt-60 by the clams was reduced with increasing cell density and size of the clams. More than 43% of the radioactivity which was introduced into the pallial cavity of the clams with the diatom (Nitzschia closterium) at cell densities less than 5×10⁷ cells/l was retained in the clams two days after feeding.