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The hardness of freshwaters varies depending on geographical locations and calcium is the most important element determining water hardness. Thus, the present study focused on responses of oxidative stress biomarkers in the liver and ATPase activities in the gill of freshwater fish (Oreochromis niloticus) after acute and chronic cadmium exposures in differing calcium levels (30, 60 and 120 mg Ca/L). Fish were exposed to Cd for acute (25 µM, 3 days) and chronic (5 µM, 30 days) durations. There were significant (p 0.05) in the responses of biomarkers. Data also showed that alterations in biomarkers were highest at the lowest calcium levels. Present data emphasised that calcium protected the fish against the toxic effects of cadmium and suggested that metal toxicity varies depending on the chemical quality of waters from different geographical areas.
Canli et al. (Thu,) studied this question.