Antioxidant Enzyme Responses to Lead Exposure in Daphnia magna

Abstract: Lead (Pb), a pervasive environmental contaminant, poses significant toxicological risks to freshwater ecosystems. Daphnia magna, a widely used model organism in aquatic toxicology, provides valuable insights into the sublethal effects of heavy metal exposure. This study investigated the effects of Pb exposure on antioxidant defense mechanisms in D. magna. Test organisms were exposed to aqueous Pb solutions at varying concentrations (0, 10, 20, 30 μg/L) for 96 h. The enzyme activities of glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD) were measured using enzyme-linked immunosorbent assay (ELISA). SOD activity did not differ significantly between the exposed and control groups. However, CAT activity showed a significant decrease in all Pb-exposed groups compared to controls. GPx activity exhibited a non-significant decrease. In conclusion, Pb exposure may induce oxidative stress by generating reactive oxygen species (ROS) and inhibiting the function of sulfhydryl-containing antioxidant enzymes. Changes in antioxidant enzyme activity may serve as early biomarkers in ecotoxicological assessments of Pb pollution in aquatic environments. It is suggested that future studies incorporate molecular-level endpoints and chronic exposure scenarios to better elucidate the long-term impacts of Pb on aquatic invertebrates.