Abstract

Heavy metals such as chromium are significant aquatic pollutants due to their bioaccumulation and potential to disrupt antioxidant defense systems in fish. Catalase, a key antioxidant enzyme, protects cells from oxidative damage by decomposing hydrogen peroxide. This study evaluated chromium accumulation in Clarias gariepinus and its effect on catalase activity. Clarias gariepinus were exposed to four different concentrations of chromium (1, 2, 3, and 4 mg/L) for seven days. Chromium accumulation in fish tissues was quantified using Atomic Absorption Spectrophotometry (AAS), while catalase activity was measured using spectrophotometer. Chromium accumulation increased proportionally with exposure, from 0.059 mg/kg at 1 mg/L to 0.149 mg/kg at 4 mg/L. Catalase activity also rose with chromium exposure, reaching 0.906 µmol/min at 2 mg/L and 0.853 µmol/min at 3 mg/L. However, at the highest exposure (4 mg/L; 0.149 mg/kg accumulated), catalase activity dropped sharply to 0.097 µmol/min. The study demonstrates that chromium accumulation in C. gariepinus stimulates catalase activity at low to moderate concentrations as part of the oxidative stress defense mechanism. However, excessive chromium exposure suppresses catalase activity, impairing the fish’s antioxidant response. These findings highlight the ecological risks of chromium contamination in freshwater ecosystems and underline the importance of monitoring heavy metal pollution to safeguard aquatic life.