Abstract:The toxic effects of two antibiotics, enrofloxacin and erythromycin thiocyanate, on the growth and physiology of Microcystis aeruginosa are studied. The results show that both enrofloxacin and erythromycin thiocyanate inhibited the growth of M. aeruginosa, and their 96h-EC50values for M. aeruginosa were 84.6μg/L and 48.2μg/L, respectively. The chlorophyll fluorescence and photosynthetic pigment of Microcystis aeruginosa were also inhibited by the antibiotics, and the inhibition effects increased with the increasing concentrations of enrofloxacin and erythromycin thiocyanate. The soluble protein content of M. aeruginosa was promoted in the presence of low concentrations of antibiotics (£0.02mg/L), and was inhibited by high levels of antibiotics (30.05mg/L). The content of lipid peroxidation (malondialdehyde, MDA) presented a strong positive correlation with the levels of antibiotics. The study indicated that enrofloxacin and erythromycin thiocyanate both hindered the photosynthesis process of M. aeruginosa and the synthesis of soluble protein, thus inhibiting the growth of M. aeruginosa.