Speciation, uptake and toxic effects of Cadmium on developing stages of Atlantic salmon (Salmo salar)

Cadmium (Cd) is well known as one very toxic trace elements for aquatic organisms including fish. Uptake and toxic effects of Cd in embryo of Atlantic salmon was studied from fertilization to hatching stage. Eggs from Atlantic salmon were exposed from fertilization to hatching to four different concentrations of Cd (10μg/L, 30μg/L, 100μg/L including control, respectively). Cd uptake and distribution of Cd was determined in whole egg compared to inside egg content only, and in whole alevin compared to yolk sac only. The long-term body concentration of Cd was followed in swimup after end of exposure. Sub lethal and lethal effects were followed by swelling, time of hatching, DNA damage, growth, deformity and mortality, respectively. Cd was taken up in embryos, however surprisingly no significant lethal effects were identified at the relative high concentration tested. No toxic effect was observed on degree of swelling by Cd. However, the hatching time was altered by initiation of premature hatching which was followed by extended period of hatching in 10ugCd/L. However, 30ugCd/L and 100ugCd/L showed only extended hatching time. Comet assay results showed some DNA damage in Cd treated groups. More over Cd with all three concentrations did not show any significant effects on growth of alevins. Body malformations were also recorded low in number. Compared to previous study this study demonstrate that the toxic effects of Cd is highly dependent upon life stage of exposure. Acute lethal effects of Atlantic salmon juveniles has been demonstrated at 0.5 μg/l while this study demonstrate significantly lower effects when exposure of Atlantic salmon embryos to Cd at 100 μg/L in similar water quality. Low chorion penetration of Cd could explain low effects.M-ECO