Ecological Risk Assessment of Surface Water Through Heavy Metal Contamination in the Fish Spawning Tetulia River Estuary of Bangladesh

Estuaries worldwide have been severely degraded and become reservoirs for many types of pollutants, such as heavy metals. Hilsa shad (Tenulosa ilisha) is Bangladesh’s most important single-species fishery that contributes to 12% of total catch and employment for millions of people. An important natural breeding area for hilsa in Bangladesh, the Tetulia River, is the subject of this study’s evaluation of heavy metal pollution. Surface water samples were collected during four periods July, August 23, February, and March 24 to analyze the concentrations of seven trace elements (Cd, Cr, Mn, Fe, Ni, Cu, and Pb) and assess metal toxicity. In the dry season, the average concentrations of Cu, Cr, Ni, Cd, Mn, Fe, and Pb were 0.06, 0.09, 0.06, 0.08, 0.30, 3.93, and 0.19 mg/L, respectively, while in the wet season, they were 0.05, 0.18, 0.05, 0.07, 0.17, 3.20, and 0.08 mg/L, respectively. The concentrations of Cr, Cd, Fe, and Pb exceeded the recommended safe limits for drinking water and freshwater aquatic life protection. The ecological risk index indicated contamination levels ranging from low to high. This study highlights the need for effective policies to safeguard valuable, productive, and diverse coastal ecosystems, particularly concerning water pollution. Further investigation to explore specific source of metals in coastal areas are warranted.