Effects of Exposure to Bauxite Residue Leachates from Short-Term Revegetation on Oxidative Stress and DNA Damage in Zebrafish (Danio rerio)

Abstract

Revegetation is widely recognized as a promising strategy for the large-scale bauxite residue management and disposal. However, its potential ecotoxicological risks, particularly the ecotoxicity of treated bauxite residue leachate on aquatic organisms, remain largely unknown. This study assessed the effects of exposure to bauxite residue leachates from short-term revegetation on oxidative stress and DNA damage in zebrafish (Danio rerio) tissues. The results revealed significant variations in the activities or levels of superoxide dismutase (SOD), catalase (CAT), acetylcholinesterase (AChE), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) in zebrafish liver, brain, gill, and muscle tissues after 7, 14, 21, and 28 days of exposure to bauxite residue leachates. The integrated biomarker response (IBR) index indicated that leachate from treated residue exhibited greater toxicity to the liver, gills, and muscle compared to untreated residue, whereas brain tissue exhibited the opposite trend. Correlation analysis revealed significant positive and negative correlations between pH, EC, Al, Na, As, and V in leachates and oxidative stress/DNA damage biomarkers in zebrafish tissues. Despite the neutral pH (7.44 ± 0.26) and low concentrations of Al (0.67 ± 0.01 mg·L⁻¹), As (4.65 ± 0.20 mg·L⁻¹), and V (0.01 ± 0.00 mg·L⁻¹) in the treated residue leachate, the relatively higher Na concentration (22.33 ± 3.61 mg·L⁻¹) and other contaminants introduced by amendments and bauxite residue likely played a key role in inducing oxidative stress and DNA damage in zebrafish tissues. These findings highlight the importance of carefully selecting amendments for revegetation to support plant establishment while minimizing secondary contamination risks. This study provides valuable insights into the environmental risks of short-term bauxite residue revegetation, contributing to the development of more effective and sustainable revegetation strategies.