Bio-tolerance potential and environmental risks assessment of Oreochromis niloticus and Ipomoea aquatica in Agodi Reservoir, Nigeria

The concentration of nine heavy metals in Oreochromis niloticus and Ipomoea aquatica inhabiting Agodi reservoir, Oyo State, Nigeria were investigated for twelve months. The concentrations of the metals were carried out using PG990 Atomic Absorption Spectrophotometer. The Ecological Risk Quotient (ERQ) was calculated using standard methods while the tolerability was determined with Box Plot analysis. The metal bioaccumulation in O. niloticus and I. aquatica followed the order Mn > Fe > Zn > Cu > Co > Pb > Cd > Cr > Ni and Fe > Zn > Mn > Cu > Pb > Cd > Co > Cr > Ni respectively. The results revealed O. niloticus to bioaccumulate the metals more than I. aquatica. Most of the examined metals were higher than the safety limit for the metals concentration in O. niloticus and I. aquatica. Also, I. aquatica had higher tolerability for heavy metals than O. niloticus. In O. niloticus, metal concentration, as well as ERQ, was higher in the wet season while no particular order was observed for I. aquatica. The ERQ result revealed that Cd, Fe, Mn, Zn, Cu and Pb exhibited a high level of ecological risk to both the aquatic flora and fauna as the ERQ values were above the risk limit of one (1). Thus, there is a significant environmental risk associated with heavy metals in the water body.