Abstract:

Quinolones and tetracyclines are prevalent antibiotics in aquatic environment, posing potential ecological risks to the aquatic environment. However, the biochemical harm of these antibiotics to Chlorella pyrenoidosa has not been studied, and studies on the mechanism of their toxic effects in green algae are relatively few. In this work, three common quinolone antibiotics （ofloxacin （OFX）, enrofloxacin （ENR） and ciprofloxacin （CIP）） and two tetracycline antibiotics （tetracycline （TC） and oxytetracycline （OTC）） were used as target contaminants. Their inhibition rates on algal cell growth and their physiological and biochemical responses to chlorophyll, superoxide dismutase （SOD）, catalase （CAT）, total protein （TP） and trace malondialdehyde （MDA） at 96 h exposure were studied. The results showed that, the effects of growth inhibition for these five antibiotics were all positively correlated with Chl a; the MDA content was increased with increasing concentrations under antibiotic exposure except for CIP; the exposure to two tetracyclines enhanced SOD activity, while the exposure to quinolone antibiotics reduced SOD activity. CIP promoted the growth of Chlorella pyrenoidosa at low concentrations but inhibited it at high concentrations. The maximum promotion was 17.39%, which was ascribed to the accelerated photosynthetic rate and the enhanced CAT activity in algal cells when exposed to CIP. All these five antibiotics showed some promotion effect on TP. This work could provide reference for assessment of the potential risks of these five antibiotics on aquatic ecosystems.

Key words: quinolone, tetracycline, Chlorella pyrenoidosa, toxic mechanism