Assessment on level of selected heavy metals in Nile Tilapia and Barbus fish species and water samples from the Southern parts of Lake Tana, Ethiopia

Metals released in to the aquatic ecosystem may be accumulated in aquatic organisms through the cumulative effects of bio-concentration, and bioaccumulation via the food chain pathway and become toxic when concentration reaches a considerably high level. The aim of the present study was thus to determine the levels of As, Cd, Pb, Cr, Fe, and Zn in muscle and liver parts of market available Nile tilapia, and Barbus fish species and water samples from three selected sites of Lake Tana. Concentration of the studied metals in the water, and liver and muscle parts of the two fish species were quantitatively determined using inductive coupled plasma optical emission spectroscopy. Recovery results in water sample in the range 82.0–110.2%, muscle fish part in the range of 86.7–96.5%, and liver fish part in the range of 82.9–114.3% validated the method for determination of the metals in real samples. Although Pb was below the limit of detection in the muscle of both fish species and water samples, the other metals were more or less detected quantitatively as: As (ND–0.98), Cd (ND-0.192), Cr (0.08–2.83), Zn (6.53–627.08), and Fe (14.23–164.77) in the muscle; As (1.58–4.94), Cd (0.7–1.633), Pb (2.65–6.12), Cr (1.95–4.5), Zn (227.38–769.67), and Fe (997.0 -6935.0 mg/kg dry mass) in the liver. Cd and As being not detected in water samples, levels (mg/L) of the remaining metals were in the range of Fe (0.197–0.557), Zn (0.012–0.021), and Cr (0.011). The level of the studied metals in general was higher in the liver fish part than the respective levels in the muscle fish part and water samples from the same sampling site. Moreover level of heavy metals, in water samples being not detected or very low, their levels in tissues of fish species with some exceptions were above the recommended level necessitating monitoring of contaminate pollutants from different sources.