| With the mass production and widespread use of nanomaterials, the potential for their release into the environment is increasing. The potential risks and ecological effect to human health and ecological environment has become a new field of scientific research. In this study the impact of nano-ZnO and nano-TiO2 on aquatic ecosystems has been investigated using microalage Scenedesmus oblignus as a model. Microalgae S. oblignus were exposed to nano-ZnO and nano-TiO2 at different doses（0.01, 0.1, 0.5, 1, 5, 50 mg·L-1 and 1, 5, 10, 50, 100, 200 mg·L-1） for 96 h. Response of the growth, photosynthetic pigments and antioxidant enzyme activities were selected as assessment indicators. The results indicated that the effect of nano-ZnO within the concentrations of 0.01, 0.05, 1 mg·L-1 on the growth of S. oblignus showed a significant improvement（P<0.05） but no significant difference on protein content compared with control. However, when the concentration was increased to 5 mg·L-1, nano-ZnO started to bring an evident stress to the growth and protein content, and high concentrations of 50 mg·L-1 significantly inhibited the growth and protein content, while the inhibitation of photosynthetic pigments, and superoxide dismutase（SOD） and peroxidase（POD） activities was observed in lower concentrations. Similarly, dose-effects of nano-TiO2 was also observed in S. oblignus, being found to promote the growth at low concentrations of 1 mg·L-1, which could increase the content of photosynthetic pigments, especially the content of the chlorophyll b and protein. As the concentration increased, the stimulative effect was reduced and the inhibition effect was enhanced. The influence on the activities of SOD and POD was consistent with that of cell growth. These studies suggested that nano-ZnO and nano-TiO2 at high concentrations induced toxicological effects. |
