Toxicity of Thiobencarb on Green Freshwater Alga and the Mitigating Role of Ozone

Toxicity of the formulated thiobencarb (50%, EC) on the growth of green freshwater alga, Pseudokirchneriella subcapitata was evaluated after 96 hours, both individually and in combination with a concentration of 100 ppm of ozone. The effective median concentrations (EC50) were determined to be 0.004 for thiobencarb and 0.9 ppm for thiobencarb in combination with ozone (O3). Algal biomass, growth rate, growth inhibition percentage, algal growth response, and the rate of division/day were decreased, while the generation time was increased in a concentration-dependent manner. Biochemical analysis of EC50 concentration of thiobencarb alone on microalga showed a reduction in protein, carbohydrate, and pigments (chlorophyll-a, chlorophyll-b, and carotenoids). In contrast, there was an increase in the activity of catalase, ascorbate peroxidase, superoxide dismutase and reduced glutathione content, lipid peroxidation, sucrose and free proline. However, when EC50 concentration of thiobencarb was in combination with 100 ppm of O3, most of these biomarkers showed improvement, indicating that the ozone treatment can mitigate the adverse effects of thiobencarb. Microalga can serve as bioindicators for this herbicide toxicity in water, while the measured biochemical parameters may be candidates for biomarkers for thiobencarb exposure in microalga. Additionally, the use of O3 as an eco-friendly technology is recommended for reducing thiobencarb contamination in water bodies.