Biochemical and Genotoxic Effects of Iron and Manganese in Oreochromis Niloticus (Teleostei: Cichlidae)

Abstract The Doce River, southeastern Brazil, in 2015 received iron mining tailings after the Fundão (MG) dam burst, which resulted in the leakage of about 50 million cubic meters of tailings mud, which have iron (Fe) and manganese (Mn) as main components, causing much damage to health to aquatic organisms, including death. Since exposure of aquatic organisms to metals can cause genotoxic damage and induce the generation of reactive oxygen species, causing oxidative damage to biomolecules, the present study aimed to evaluate the toxicity of the association between Fe and Mn in Oreochromis niloticus through genotoxic (micronucleus test and comet assay), and biochemical (CAT and GST enzymes) assays. The tested treatments were T1 = control group, T2 = 3.81 mg/L of Fe + 0.5 mg/L of Mn, and T3 = 7.62 mg/L of Fe + 5.23 mg/L of Mn, during 96-h bioassays. All animals exposed to the metals showed a significant increase in erythrocyte micronucleus frequency and DNA damage. The hepatic GST activity increased two times in animals exposed to T3 compared to control group. The results indicate that Fe + Mn caused genotoxic and biochemical changes in exposed fish. Therefore, excess metals in ecosystems, even those essential for organisms, can be dangerous for the local biota due to the risk associated with high concentrations of these metals.