Experimental comparison of the bioaccumulation of anthropogenic radionuclides by egg and juvenile life stages of a small shark.

This study compared the bioaccumulation of anthropogenic nuclides (Zn, Cs, Co and Am) between the egg and juvenile life stages of a small shark (Scyliorhinus canicula), based on previously published experimental data. Rates of accumulation over 15 days were derived and summed for the transfer pathways which were specific to these two life stages. Radionuclide transfers to the egg and its embryo & yolk were quantified for i) the maternal pathway following her uptake of radionuclides via food and seawater and ii) from seawater following its oviposition. For the juvenile, the transfer of radionuclides were measured for aqueous & dietary pathways. The results show that, compared to juveniles, eggs have equivalent rates of accumulation of Zn and Cs but enhanced accumulation of Am by a factor of five and of Co by two orders of magnitude. The radiological exposure of the embryo due to radionuclides maternally transferred to the embryo & yolk is also enhanced for the alpha-emitting Am. This enhanced accumulation of Am and Co, as well as the equivalent accumulation of Zn and Cs, suggest greater likely vulnerability to radiation damage in eggs as compared to juveniles. Radiological dose assessment confirmed highest doses to the egg which is predominantly due to accumulated Am.