Three species of marine bait microalgae: Chlorella vulgaris.

Isochrysis galbanastrain 8701 and Nitzschia closterium were subjected to three antibiotics

Chloramphenicol（Cm）

Geneticin（G418） and Penicillin at the different concentrations to test their responses to the three antibiotics in terms of growth（cell quantity

Chlorophyll-a levels）.Results showed that: Cm had no significant effect on growth of C.vulgaris when the concentration was below 100 mg·L-1（p> 0.05）.Cm at low concentration（<25 mg·L-1） can stimulate the growth of I.galbanastrain 8701 but showed an inhibitory effect on its growth at high concentration（100 mg·L-1）.Cm had an inhibitory effect on the growth of N.closterium at all concentrations.G418 significantly inhibited the growth of three microalgae.Low concentration of Penicillin（<100 mg·L-1） increased the growth of C.vulgaris

I.galbanastrain 8701 and N.closterium but the relative growth rate（K） decreased steadily with the increasing concentration.Penicillin demonstrated slightly inhibitory effect on N.closterium at higher concentration

though insignificantly（p>0.05）.Our results also indicated that the optimal concentrations of Cm on the three microalgal growth were C.vulgaris: 200 mg·L-1;I.galbanastrain 8701:100 mg·L-1;N.closterium: 50 mg·L-1 respectively

and Penicillin on the three microalgal growth were C.vulgaris: 200 mg·L-1;I.galbanastrain 8701:200 mg·L-1;N.closterium: 100 mg·L-1 respectively.