Acute Toxicity and Genotoxic Responses in African Mud Catfish, Clarias gariepinus, Exposed to Biocides and Aqueous Ammonia

Document Type : Original Article

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Department of Zoology Faculty of Science University of Lagos

Abstract

Oil and gas industrial wastewater pose significant threats to aquatic organisms when discharged into the environment without proper treatment. This study aimed to assess the acute toxicity and genotoxic responses in African mud catfish, Clarias gariepinus, exposed to biocides and aqueous ammonia, aligning with the objectives of the UN Decade of Restoration and the Sustainable Development Goals (SDGs). The study commenced with a 96-hour acute toxicity assay to determine the 96 h LC50 values. Subsequently, chronic toxicity evaluation was conducted over 28 days using 1/10th, 1/100th, and 1/1000th of the 96-hour LC50 values to assess the ability of the test chemicals to induce oxidative stress and genotoxic effects in C. gariepinus. Key antioxidant stress enzyme activities, including Superoxide dismutase (SOD), Catalase (CAT), and reduced Glutathione (GSH), were examined. The results of the acute toxicity study revealed that the derived 96 h LC50 values of aqueous ammonia (1.358 mg/L) were slightly more toxic to C. gariepinus than biocides (1.586 mg/L). Furthermore, the biochemical assay indicated a significant inhibition of GSH levels in the liver of C. gariepinusexposed to the highest sublethal concentrations (1/10th of the 96-hour LC50) of both biocides and aqueous ammonia (P<0.05). The activity of SOD was significantly altered in the liver of fish exposed to sublethal concentrations of biocides compared to the control. Similarly, the activity of CAT was significantly modified in the liver of fish exposed to 1/10th of the 96-hour LC50 concentrations of aqueous ammonia (P<0.05). Increased levels of lipid peroxidation product, malondialdehyde, were observed in C. gariepinus exposed to 1/10th of the 96-hour LC50 concentrations of both biocides and aqueous ammonia compared to the control (P<0.05). Notably, the exposed fish displayed significant red blood cell nucleus abnormalities, including micronuclei (M.N.), binuclei (B.N.), and lobed-shaped nuclei, compared to the control. These findings emphasize that even sublethal concentrations of aqueous ammonia and biocides pose threats to the health of aquatic organisms. Thus, regulating their use and disposal is crucial to safeguard the sensitive aquatic biota in oil-producing communities and align with ecological restoration efforts and the SDGs.

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