Response of submerged macrophytes and leaf biofilms to different concentrations of oxytetracycline and sulfadiazine

Oxytetracycline and sulfadiazine were widely used and they entered the environment through various channels such as domestic sewage, medical wastewater and agricultural wastewater, causing significant ecological risk. To determine the effects of different antibiotic concentrations on submerged macrophytes , Vallisneria natans was exposed to solutions containing different concentrations of oxytetracycline and sulfadiazine (0.1 mg/L、1 mg/L、10 mg/L、50 mg/L). After 20-days exposure, we found that 10 mg/L groups had a significant effect on Vallisneria natans . Under high antibiotic concentrations, the growth of Vallisneria natans was inhibited, chloroplasts were deformed, the chlorophyll content was reduced, and antioxidant enzyme activities , such as superoxide dismutase and glutathione , were increased. There was no significant difference between the control group and groups with low antibiotic concentrations (≤1 mg/L). The N-acyl- l -homoserine lactone concentration tended to increase with increasing antibiotic concentrations. The presence of antibiotics also affected the microbial community structure of biofilms on the submerged macrophytes. For example, the higher the concentration of antibiotics, the higher the proportion of Proteobacteria. These results suggest that high concentrations of oxytetracycline and sulfadiazine can disrupt homeostasis , induce effective Vallisneria natans defense mechanisms and alter biofilms in aquatic ecosystems .