Increasing number and amount of industrial, agricultural and commercial chemicals discharged into the aquatic environment have led to various deleterious effects on the aquatic organisms. Aquatic pollution is a major contributor to oxidative stress in fish resulting from the redox cycling of pollution. This study aimed to evaluate heavy metal concentrations and enzymatic biomarker of two fish species (Sarotherodon melanotheron and Tilapia guineensis) from the Mahin Lagoon, Ondo State, Nigeria. Heavy metals (Zinc, Lead, Cupper, Chromium, Cadmium, Nickel and Cobalt) in fish tissues were analysed with GBC Savant AA Sigma flame atomic Absorption Spectrometer (AAS). Antioxidant enzyme (catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), Glutathione-S-Transferase (GST)) activities were evaluated in the livers of both fish species using standard methods. Observed mean level of heavy metals was in the order Zn > Fe > Cu > Ni > Cr > Cd > Co > Pb. When compared with the World Health organization (WHO) limit, the heavy metals were higher in all tested fish samples. There was significant difference (p>0.05) in the activities of the antioxidant enzymes across stations and seasons. Elevation in the activities of SOD and GST were observed. While the activities of CAT and GSH were observed to be inhibited. This study provides evidence that enzymatic biomarkers of oxidative stress can be sensitive indicators and biomarker of aquatic pollution.
Key Words: Pollution, health risk, Food safety and security, Biomarker, Heavy metals