Physiology responses of Nannochloropsis oculata and Pseudokirchneriella subcapitata to antibiotic pollution and their removal effects

The widespread use of antibiotics has caused potential risks to aquatic ecological environment.In order to investigate the physiology responses and their removal effects of algae to antibiotic pollution, three kinds of antibiotics erythromycin, norfloxacin and sulfadiazine, seawater algae Nannochloropsis oculata and freshwater Pseudokirchneriella subcapitata, were chosen for the study.Among three antibiotics, erythromycin was the most toxic.Lower concentrations of erythromycin stimulated the growth of algae, but its higher concentrations inhibited the growth of algae.The values of half maximal effective concentration (EC₅₀) at 72 h to Nannochloropsis oculata and Pseudokirchneriella subcapitata were 6.13 mg/L and 27.7 μg/L, respectively.With the increased concentration of erythromycin, the photosynthetic pigments of both algae decreased significantly (p < 0.05).The activities of superoxide dismutase and catalase of two algae were significantly enhanced when erythromycin was at the low concentrations, but with the increased concentrations of erythromycin their activities gradually decreased (p < 0.05).Results indicated that the studied two algae were capable of removing the residual antibiotics to some extents.After 144 h of culture, 57.0% of norfloxacin and 78.3% of sulfadiazine were removed by Nannochloropsis oculata, 51.2% of norfloxacin and 8.3% of sulfadiazine were removed by Pseudokirchneriella subcapitata after 120 h of culture.