Monitoring of metals in Tilapia nilotica tissues, bottom sediments and water from Nworie River and Oguta Lake in Imo State, Nigeria
Tilapia (Tilapia nilotica), bottom sediments and water were collected from Nworie River and Oguta Lake. The muscle, liver and gills of the fish as well as the bottom sediments and water were analysed for Al, Cr, Cd, Pb, As, Zn, Mn, Co, Se, Cu, Ni and Fe using atomic absorption spectrophotometer to highlight the importance of tissue selection in monitoring research, contamination studies and human health risk assessment. Higher concentrations of metals were found in the gills and muscle tissues than in liver, except for Fe and Ni in the liver of T. nilotica from Nworie River and Fe in the liver of T. nilotica from Oguta Lake. Fe was the highest accumulating metal in the gills of fish samples collected from the two study areas, while Mn was the lowest. All metals were found to be below the international permissible limits. In water samples and bottom sediments, none of the metals exceeded the legal limits for the protection of the aquatic biota. The estimated daily intake (EDI) was below the reference dose (RfD) established by the US-EPA and the hazard quotient values indicated that there was no carcinogenic risk to humans.
Key words: Bottom sediment, water, metals, Tilapia nilotica, River Nworie, Oguta Lake.