<b>Assessment of Oxidative Stress Markers <i>in Tympanotonus fuscatus</i> Exposed to Solid Waste Composite Leachate</b>

Leachate generated from municipal solid waste landfills contains high concentrations of organic matter, inorganic ions, nutrients, heavy metals, xenobiotic compounds, and pathogenic microorganisms, making it a significant source of environmental pollution when inadequately managed. This study evaluated oxidative stress biomarkers in the West African mud creeper, Tympanotonus fuscatus, following laboratory exposure to leachate collected from the Olusosun municipal solid waste landfill, Lagos, Nigeria. A 96-h laboratory bioassay was conducted using graded concentrations of landfill leachate to assess alterations in antioxidant defence mechanisms and oxidative damage. Reduced glutathione (GSH) levels decreased significantly (p < 0.05) from 9.29 ± 0.37 to 5.44 ± 0.31 µmol mg⁻¹ with increasing leachate concentration. Similarly, superoxide dismutase (SOD) activity declined from 7.69 ± 0.13 to 4.25 ± 0.04 µmol mg⁻¹, while catalase (CAT) activity decreased from 47.65 ± 0.20 to 32.62 ± 0.02 µmol mg⁻¹. In contrast, malondialdehyde (MDA), an established biomarker of lipid peroxidation, increased significantly (p < 0.05) from 31.34 ± 0.05 to 50.66 ± 0.03 µmol mg⁻¹, indicating enhanced oxidative damage to cellular membranes. The concomitant depletion of antioxidant biomarkers and elevation of MDA demonstrate that exposure to Olusosun landfill leachate induced significant oxidative stress in T. fuscatus. These findings highlight the susceptibility of T. fuscatus to landfill leachate and support its use as a sensitive bioindicator for monitoring leachate-induced toxicity in aquatic ecosystems. Furthermore, the study underscores the need for effective landfill leachate management, improved municipal solid waste disposal practices, and continuous environmental monitoring to mitigate ecological degradation, reduce contaminant transfer through aquatic food webs, and protect public health.