Effects of the urban runoff on fish in the Ikpoba River: heavy metal contamination and brain pathology

Abstract

This study investigated the ecological impact of urban runoff on fish fauna in Ikpoba River, Benin City, Nigeria. In particular, we focused on heavy-metal contamination and its effects on brain tissue pathology. During a three-month period (June–August 2023), water, sediment, and fish samples were collected from two locations with varying effluent attributes. Atomic Absorption Spectrophotometry was employed to determine the heavy metal concentrations (Cr, Co, Cd, Ni, and Pb) in the samples. Our findings revealed fluctuating heavy metal levels in the water and sediment samples. Notably, Ni exhibited the highest concentration in the sediment during July. The brain tissues of Clarias gariepinus and Tilapia 279illi demonstrated metal accumulation, with Nickel, Chromium, and Cobalt being prevalent. Histopathological analysis indicated progressive changes, including mononuclear exudates in the granular layer of the brain tissues of C. gariepinus by August, suggesting an inflammatory response. Urban runoff has emerged as a significant source of heavy metal pollution in the Ikpoba River, leading to bioaccumulation in fish and alterations in the brain tissue. Comprehensive monitoring and management strategies are crucial for mitigating the impact of runoff on aquatic ecosystems and safeguarding fish and human health. These results provide valuable insights into effective water resource management policies and enhance our understanding of the effects of urban pollution on freshwater environments.