Using antioxidant changes in liver and gonads of Oreochromis niloticus as biomarkers for the assessment of heavy metals pollution at Sharkia province, Egypt

The work was aimed to assess the heavy metals concentrations in the Sharkia Governorate, Egypt. The determination of heavy metal bioaccumulation and their antioxidant alterations on Oreochromis niloticus were considered. The gonads and the liver of the fishes were analyzed for essential metals (Cu, Mn, Fe & Zn) and non-essential metals (Pb) levels seasonally and their bioaccumulation factors. The results revealed that concentrations of the metals differ significantly between the gonads and the liver of the sampled fishes. During summer, liver bioaccumulation of the metals was in the order of Mn > Pb > Fe > Zn > Cu at area I and Mn> Pb> Zn> Fe > Cu at area II. However, the degree of tissue alterations in the gonads can accumulate the heavy metals in the following order Mn >Zn>Pb >Fe>Cu and Mn> Pb >Zn> Fe at the same season, for the areas I and II, respectively. The bioaccumulation of heavy metals in the liver tissue was higher than in the gonads of the O. niloticus. The antioxidant changes in the liver and gonads were mildly and moderately damaged, respectively. These indicated that Zn, Cd, Pb, and Fe polluted the Sharkia Governorate in the two selected areas. Elevation of lipid peroxidation in fishes was parallel with increasing the activity of endogenous antioxidants that could be to compensate for the stress. [Display omitted] •Bioaccumulation of heavy metals in liver of fishes more than gonad.•The variation of bioaccumulation differed seasonally.•The lipid peroxidation and antioxidant increased by as the effect of heavy metals.•Wastewaters must be treated before discharge into the aquatic systems.