Bioaccumulation of 137Cs and 60Co by a tropical marine teleost Epinephelus sp.

Abstract

As part of a project on the behaviour of radionuclides released by the Angra Nuclear Power Station in the marine environment, laboratory experiments were performed to study cesium and cobalt accumulation by juvenile groupers ( Epinephelus sp.). The fishes were kept in aquariums equipped with gravel-bed filters spiked with 60Co (150 KBq/1) and 137 Cs(75 KBq/1). Uptake was only via water since the fishes received only non-radioactive food during the 4 months of experiment. Cesium accumulation in muscle was higher than in any other organ, reaching concentration factors (CFs) of 5 (fresh weight basis). Cobalt, in contrast, was concentrated mostly in the liver, gut and skin and scales. Cobalt CF in muscle tissue was 8 × 10 −2, lower than any previously reported figure. Chromatographic analysis of the water at the beginning and end of the experiment showed that cobalt had been completely converted from 60CoCl 2 to non-cationic forms, most probably through complexation with organic ligands, mediated by the intense microbial activity of the filter bed. This conversion apparently enhanced cobalt bioavailability since a second experiment performed with this aged seawater yielded CFs for muscle tissue higher by a factor of 2.5.