Assessment of water quality of selected rivers in the Niger Delta region of Nigeria using biomarkers in Clarias gariepinus.

Petroleum exploration has continued to impact negatively the Niger Delta region of Nigeria. Oil spills from petroleum exploration contaminate both the aquatic and non- aquatic environments and destroy the ecosystem which makes people in these regions to be prone to diseases such as cancer, cardiovascular diseases, neurodegenerative disease, infertility, and sterility and also poverty. Some oxidative stress markers of the liver and muscle of fish (Clarias gariepinus) from Apata, Araromi, and Mahin rivers (located in the Niger Delta region) were compared with those of fish samples from a clean fish farm (control) in order to assess the level of pollution of the rivers. A significant increase in malondialdehyde level and myeloperoxidase (MPO) activity as well as alterations in antioxidant status (glutathione peroxidase, superoxide dismutase, reduced glutathione, and glutathione S-transferase) was observed in the organs of fish samples from Apata, Araromi, and Mahin rivers compared with the control. A significant increase in the frequency of micronucleated polychromatic erythrocytes (MnPCEs) was also observed in the fish samples from these rivers in comparison with the control. Based on results of our research, we can conclude that these rivers are polluted mainly by oil spillage and other industrial activities; therefore, the consumption of aquatic organisms from these rivers and the use of water from the rivers for domestic activities might be unsafe.