Bioaccumulation of heavy metals in gills and muscles of selected fish species from Owerrinta section of Imo River

Abstract

Bioaccumulation of heavy metals in aquatic organisms had been known to occur naturally. Over the years the levels of these accumulations keep increasing due to various human activities which make it detrimental to the life of aquatic organism and humans. The study assessed bioaccumulation of some heavy metals in the gills and muscles of some fish species. Fish samples were collected for a period of 4 months, identified and stored for further analysis. The following heavy metals: Zinc (Zn), Copper (Cu), Iron (Fe), Lead (Pb) and Cadnium (Cd) were assessed on the fish gills and muscles using standard procedure. Results showed that the fish species sampled (Clarias gariepinus, Tilapia zilli, Oreochromis niloticus, Alestes baremose and Pareutropius buffei) showed some levels of metal accumulation both in the gills and muscles. Levels of Zn in muscles of A. baremose, P. buffei, C. gariepinus, T. zilli and O. niloticus were 3.63±0.12, 1.45±0.26, 4.27±0.15, 4.03±1.42 and 2.00±0.15mg/kg respectively. The highest level of Zn (3.44±0.15mg/kg) in the gills was observed in T. zilli. Other results showed that P. buffei had the highest Pb concentrations (0.48±0.22mg/kg in muscle) and (0.17±2mg/kg in gills) while T. zilli had 2.24±0.54mg/kg and 1.46±0.65mg/l as the highest concentration of Fe in muscles and gills respectively. The levels of Zn, Cu, Fe and Pb recorded in the fish muscles where below the World Health Organization (WHO) and Food and Agricultural Organization (FAO) standards while Cadmium levels in all the fish sampled were above the recommended standard of 0.5mg/kg. This high cadmium accumulation in fish samples calls for concern considering the adverse effect it may cause if transferred to humans through fish consumption. There is therefore need to intensify efforts in mitigating some of the activities that amplify the levels of bioaccumulation of these metals in the aquatic environment towards a healthier environment.