Biomagnification of cadmium in an aquatic food chain

Accumulation rates for the salts of five locally important heavy metal pollutants (Mn, Zn, Ni, Hg and Cd) were determined by bioassay in the common mosquitofish Gambusla affinis. Analyses for metal content in whole fish were performed by dry ashing and atomic absorption spectrophotometry. Cadmium was further investigated for evidence of magnification by monitoring uptake in the larvae of Culex piplens and feeding these larvae to G. affinis. Comparison of the rates of accumulation between larvae-fed fish, starved fish and fish fed on an uncontaminated food source showed that fish fed contaminated larvae had significantly higher cadmium content than fish fed on uncontaminated food. It was therefore concluded that biomagnification of cadmium may occur in fish feeding on food, organisms which concentrate cadmium from the environment.