Toxicity and bioaccumulation of Cadmium, Copper and Zinc in a direct comparison at equitoxic concentrations in common carp (Cyprinus carpio) juveniles

Abstract

AbstractThe individual toxicity and bioaccumulation of cadmium (Cd), copper (Cu) and zinc (Zn) towards common carp juveniles was evaluated in a direct comparison in two experimental setups. First, the fish were exposed for 10 days to different metal concentrations. Accumulated metals were quantified and showed a positive dose dependent uptake for cadmium and copper, but not for zinc. Toxicity was in the order Cd>Cu>Zn with 96h LC50 values (concentration where 50% of the animals dies within 96h) for Cd at 0.20±0.16 μM, Cu at 0.77±0.03 μM, and Zn at 29.89±9.03 μM respectively, and incipient lethal levels (concentration where 50% of the animals survives indefinitely) at 0.16 μM, 0.77 μM and 28.33 μM respectively. Subsequently, a subacute exposure experiment was conducted, where carp juveniles were exposed to 2 equitoxic concentrations (10% and 50% of LC50 96 h) of the three metals. The gill metal content was quantified after 1, 3 and 7 days, and was correlated to electrolyte levels and structural damage of the gill tissue and associated pathological effects. Again a significant dose-dependent increase in gill cadmium and copper, but not in zinc, was observed during the 7-day exposure. Copper clearly affected the sodium levels in the gill tissue, while zinc and cadmium did not significantly alter any of the gill electrolytes. The overall histopathological effects (e.g. hyperemia and hypertrophy) of the metal exposures were mild for most of the alterations, and no metal specific pattern was elucidated for the tested metals except oedema of the primary epithelium which typically occurred in both levels of Zn exposure.