toxic effect of bisphenol a causes oxidative stress in cyanobacterium gloeocapsopsis crepidinum

Microalgae are good tools for toxicity indicators in aquatic habitats. the present study was carried out to evaluate the toxicity of bisphenol a at different concentrations (1, 5, 10, 20, 50, 75, 100) mg/l and the oxidative response induced by this exposure using the cyanobacterium gloeocapsopsis crepidinum. the results showed a decrease in the algal biomass rate with increasing concentrations of bisphenol a, while the half inhibition concentration (ic50) of bpa was 2.68 mg/l. the chlorophyll-a and carotenoids recorded highest value in the control group, which were 0.96 and 0.56 µg/ml, while the concentrations of these pigments decreased with increasing concentrations of bpa, their lowest value being recorded at (0.54 and 0.35) µg/ml at a concentration of 100 mg/l. the results showed that catalase (cat) and ascorbate peroxidase (apx) enzymes recorded a higher value of (0.34 and 4.66) u/g at 100 mg/l bpa, while the lowest values of these enzymes recorded 0.10 and 3.7 u/g in the control group respectively. while the superoxide dismutase (sod) enzyme recorded a high value of 22.22 u/g at 1 mg/l bpa and decreased with a lower value of 19.46 u/g at 100 mg/l. in addition, glutathione (gst) showed lower values of 5.413 µmole/g in the control group and increased at higher values at a concentration of 100 mg/l which reached to 18.68 µmole/g. nevertheless, the indication of cell damage such as malondialdehyde (mda) and reactive oxygen species (ros) recorded lowest values of 0.13 and 14.153 µmole/g in the control group, while higher values recorded with increasing concentrations of bpa were recorded at 3.487 and 74.4 µmole/g at 100mg/l bpa, respectively. all treatments were statistically analyzed with p ≤ 0.05 as significant differences were found between all treatments.  this study concluded that cyanobacteria g. crepidinum have the ability to resist the toxic effects of bisphenol a by increasing antioxidant production in their bodies, so they can be considered biological tools to eliminate toxic compounds in aquatic environments.