Physicochemical characteristics, animal species diversity and oxidative stress responses in dominant fish from an impacted site on the Lagos Lagoon, Nigeria
The evaluation of biomarkers in resident fisheries of aquatic ecosystems is important for risk assessment of such ecosystems. In this study, surface water and sediment physicochemical characteristics, macrobenthic invertebrate and fish species diversity and oxidative stress of dominant fish were evaluated at an anthropogenic-impacted site (Iddo) as well as a reference site (after the Third Mainland Bridge) of the Lagos lagoon, Nigeria, over a period of three (3) months. Surface water analysis result showed that the Total dissolved solids (TDS) (5.54±2.85 mg/L), Salinity (5.09±2.56 o/oo), Conductivity (6.51±4.54 µS/cm), Nitrates (4.70±1.49 mg/L), Phosphates (3.03±0.60 mg/L), Biochemical oxygen demand (BOD) (18.62±3.77 mg/L) and Chemical oxygen demand (COD) (463.44±65.83 mg/L) were significantly higher at the test site compared to the reference site. The COD of the sediment were significantly higher (p<0.05) at the test site compared to the reference while the other sediment physicochemical parameters except pH were higher at the test site compared to the reference site. Macrobenthic invertebrate species diversity were slightly higher (1.70) at the reference site compared to the test site (1.66) while species richness were higher at the test site (1.43) compared to the reference site (1.26). Fish species diversity (1.95) and richness (1.79) were higher at the test site compared to the reference site. Dominant fish species at the test and reference sites were Ethmalosa fimbriata (Bonga shad) and Sarotherodon melanotheron (Blackchin Tilapia) respectively. There were increased levels of antioxidant enzymes and biomolecules- glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH) and malondialdehyde (MDA) in the gills and liver of E. fimbriata indicative of oxidative stress. Further studies on biomarkers at lower levels of biological organisation are recommended for holistic evaluations and evidence-based intervention if necessary. This will support the achievement of the United Nations Sustainable Development Goal 14 (life below water).