Heavy Metals Accumulation and Enzymatic Biomarker in Commercially Important Fish Species (Hemichromis fasciatus and Chrysichthys nigrodigitatus) at the Landing Site, Bariga, Lagos Lagoon

Abstract

2 Abstract: Pollution of the aquatic environment is a serious and growing problem. 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.Heavy metals level of lead (Pb), cadmium (Cd),iron (Fe), mercury (Hg), chromium (Cr), zinc (Zn) and copper (Cu) were determined in two commercially important fishes (Hemichromis fasciatus and Chrysichthys nigrodigitatus) from the Bariga landing site, using Atomic Absorption spectrophotometer. Physicochemical parameters were investigated by determining the level of dissolve oxygen (DO), biological oxygen demand (BOD), pH, temperature among others for the water samples. The activities of superoxide dismutase (SOD), Glutathione (GSH) and malondialdehyde (MDA) were also determined. Heavy metals were accumulated in the flesh of the fishes to varying extent. The trend of accumulation of the metals in each fish is as follows: Hemichromis fasciatus-Zn>Fe>Cu>Cr>Pb. Hg and Cd were not detected; Chrysichtys nigrodigitatus-Zn>Cu>Fe>Cr>Pb.Hg and Cd were not detected. SOD activities in the liver of Chrysichthys nigrodigitatus, with the highest concentration of 69.73% and SOD activities in the gill of Chrysichthys nigrodigitatus, with highest value of 45.83%.SOD activities in liver of Hemichromis fasciatus, with highest concentration of 29.21%.SOD activity in gill of Hemichromis fasciatus, with highest concentration of 53.77%.MDA concentration in liver of Chrysichthys nigrodigitatus, with highest concentration of 43.7%.while in it gill, the highest concentration of 36.82%. Concentration of MDA in liver of Hemichromis fasciatus, with highest concentration of 29.21%. Likewise MDA, in gill with highest concentration of 37.91%.Furthermore, GSH concentration in the liver of Chrysichthys nigrodigitatus with highest concentration of 0.54%. Also in it gills, with the highest concentration of 0.33%. In the liver of Hemichromis fasciatus, GSH has concentration of 0.54%. Similarly In gill having highest concentration recorded 0.35%. The result demonstrates that alteration in the antioxidant enzymes and induction of lipid peroxidation reflects the presence of heavy metals which may cause oxidative stress in Hemichromis fasciatus and Chrysichthys nigrodigitatus from the Lagos Bariga landing site of the Lagos Lagoon. The study therefore, provides a rational use of biomarkers of oxidative stress in biomonitoring of aquatic pollution.