Abstract

The study aimed to assess the lethal and sublethal toxicity effects of heavy metals, Cobalt (Co) and Lead (Pb), on Aquatic oligochaete Tubifex tubifex, which is an essential environmental indicator. Experiments indicated that the median lethal concentration (LC50) was 998.2 mg/L for Co and 207.5 mg/L for Pb after 48 h of exposure, reproducing the higher toxicity of Pb compared to Co. The study also detected the effect of exposure to sublethal concentrations (680 mg/L for Co and 95 mg/L for Pb) over 7 and 14 days. The results showed a significant reduction in the activity of antioxidants. For Cobalt, the activity of superoxide dismutase (SOD) decreased from 98 U/mg on day 7 to 73 U/mg on day 14, while the concentration of glutathione (GSH) decreased from 20 μg/mL to 13 μg/mL. Upon exposure to lead, SOD activity decreased from 95 U/mg on day 7 to 68 U/mg on day 14, and GSH concentration declined from 18 μg/ml to 8 μg/ml. These results highlight the crucial role of antioxidants in counteracting oxidative stress induced by heavy metals, making them real biomarkers for monitoring environmental pollution. The study highlights the serious need to develop sustainable environmental strategies to reduce the effect of these pollutants on aquatic ecosystems.