Bioaccumulation Study of Cadmium, Copper, and Zinc in the Waters of the Main Drain River Using Nile Tilapia Oreochromis aureus as Bioindicators of Pollution in Al-Nasiriyah City

Abstract

Bioaccumulation of cadmium, copper, and zinc in the waters of the Main Drain River in Thi-QarProvince was assessed using Nile tilapia, Oreochromis aureus, as a bioindicator, alongside analysis of the physical and chemical parameters affecting water quality. The results revealed marked seasonal variation in environmental factors. Water temperature ranged from 17.3 to 27 °C which inversely influenced dissolved oxygen concentrations that varied between 7.8 and 10.8 mg/L, with the highest values recorded during the colder months. The pH values ranged from neutral to slightly alkaline 7.07–8.5 which is suitable for fish growth. Turbidity total dissolved solids, and electrical conductivity showed elevated levels in certain months, reflecting the influence of agricultural drainage water and waste discharge on water quality. Concentrations of cadmium and copper showed seasonal fluctuations, with the highest levels occurring during months influenced by agricultural and industrial activities, whereas zinc remained relatively stable. Cadmium poses the greatest risk due to its high toxicity even at low concentrations, while copper and zinc are essential at trace levels but become toxic at elevated concentrations. The results indicate that Nile tilapia serve as an effective bioindicator for monitoring heavy metal pollution due to their capacity for bioaccumulation. The data also point to significant environmental pressure in the Main Drain River resulting from human activities. It is recommended to strengthen regular monitoring and reduce untreated discharges to preserve aquatic ecosystems and support the sustainability of fish farming.