Impacts of ZnO nanoparticles on growth and antioxidant enzymes of the green alga Scenedesmus obliquus

The growing passion for new industrial technology, using innovative materials such as nanoparticles (NPs) which reached water bodies as wastewater, heavily influenced aquatic organisms and consequently the human life. Physiological characteristics of the micro-green alga Scenedesmus obliquus can be used as biomarker to evaluate the effects of the newly invited zinc oxide nanoparticles (ZnO NPs). S. obliquus was exposed to different concentrations of ZnO NPs. The recorded results clarify not only an obvious inhibition in growth but also disturbance in the production of the tested antioxidant enzymes, where both Glutathione reductase (GR) and Glutathione peroxidase gradually increase with ZnO NPs concentration giving its maximum within 100 μg Zn NP.L–1 at the end of the experiment (562 and 0.42 μg.μg–1 respectively). However, in the case of Glutathione (GSH), Glutathione S-transferase (GST) and catalase (CAT) the gradual increase recorded only during the first 24 h, while Superoxide Dismutases (SOD) started to decrease within concentration of 50 μg L–1ZnO NPs. Scanning electron microscope clarifies abnormalities in the cytomorphological characteristics of the treated cells where the cells tended to aggregate in a cluster and take elongated and spindle-shaped and/or wrapping. The various responses to ZnO NPs concentrations reflected, the disposal of ZnO nanoparticles in the environment affecting growth, morphological, and physiological characteristic of the cell.