Assessment of heavy metal pollution in water and its effect on Nile tilapia (Oreochromis niloticus) in Mediterranean Lakes: a case study at Mariout Lake

Mariout Lake is one of the Northern Nile-Delta Lakes in Egypt that receives agricultural, industrial and domestic effluents through several drains. The present study aims to evaluate the levels of some heavy metals (HMs) in water and edible parts of Oreochromis niloticus in Mariout Lake, in addition to studying several pollution indices and potential human health risks. The levels of the studied HMs in water were in the order of Fe > Zn > Mn > Pb > Cu > Ni > Cd. However, results of the pollution index, that concerns the effect of individual metal, concluded that Cd and Pb in water had serious pollution effects for aquatic life, while Cu, Fe, Mn, Ni, and Zn had not any pollution effects at different locations in the lake. The indices of the composite effects of all HMs (Metal Index and Heavy Metal Pollution Index) indicated the high pollution of Mariout Lake water, which may cause adverse effects on fish and different aquatic organisms. On the other side, the bioaccumulation factors of HMs in edible parts of O. niloticus were in the order of Zn > Cd > Cu > Ni > Pb > Mn > Fe. Although the target hazard quotient for all metals was less than the non-hazardous limit (THQ < 1), the non-carcinogenic hazard index (HI = 1.24) was classified in the moderate hazard risk level (1 < HI < 10) indicating low potential adverse effects on the exposed population due to consumption of O. niloticus caught from Mariout Lake.