Bioaccumulation of heavy metals in water, sediment and fish (Oreochromis niloticus and Clarias anguillaris), in Rosetta branch of the River Nile, Egypt
Rosetta Branch of the River Nile is exposed to high input of agricultural drainage water, sewage and industrial water that affect living organisms like fish. In the present study, some heavy metals such as iron, copper, lead, cadmium and zinc (Fe, Cu, Pb, Cd and Zn) were seasonally determined in some tissues of tilapia (Oreochromis niloticus) and catfish (Clarias anguillaris), water sediment and in Rosetta branch of River Nile at the following areas: El-Kanater El-Khairya (I), El-Rahawy drain (II), Tamaly (III) and Kafer El-Zyate (IV), which are an important water source for irrigation and drinking in Egypt. The highest levels of heavy metal accumulated in the liver of C. anguillaris were Fe, Cu, Pb, Cd and Zn than accumulated in O. niloticus. In gills of C. anguillaris, the highest accumulation of metal levels were Zn, Fe, Pb, Cd and Cu than accumulation in gills of O. niloticus. In muscles of C. anguillaris, the highest accumulation of metal levels were recorded for Fe, Zn, Cd and Cu except Pb was highest in O. niloticus muscles. Bioaccumulation factor (BAF) of all heavy metals in organs of C. anguillaris was higher than O. niloticus. Heavy metal levels in water, sediment and fish samples were analyzed by using atomic absorption. The order of heavy metal accumulation in water was Fe > Pb > Cu > Zn > Cd. Maximum metal index (MI) recorded at station IV for Fe, Cu, Pb and Zn were 2.7, 0.3, 62 and 0.17 mg/L, respectively and Cd was 15.333 mg/L at station III. The order of heavy metal accumulation in sediment was Fe > Zn > Cu > Pb > Cd. It was discovered in the present study that fish can bioaccumulate heavy metals from a polluted environment and could be a risk factor for accumulation of heavy metal in humans after a long time that would lead to dangerous diseases.
Keywords: Heavy metals, metal index (MI), bioaccumulation factor (BAF), Oreochromis niloticus, Clarias anguillaris, gills, liver, muscles