Abstract: In this paper,the growth of two kinds of marine microalgae,acid phosphatase（ACP）,alkaline phosphatase （AKP）,catalase（CAT） and malondialdehyde（MDA） were used as indicators to study the responses of Chlorella vulgaris and Pyramidomonas delicatula to the toxic effects of benzo[k] fluoranthene in water environment and to reveal the importance of polycyclicaromatic-hydrocarbons for water pollution. The results showed that benzo[k] fluoranthene had inhibitory effect on the growth of two kinds of marine microalgae, and the inhibition rate of benzofluoranthene to C. vulgaris was up to 62%,and there was dose effect. The proper concentration of benzo[k] fluoranthene had a short time stimulating effect on P. delicatula,while high concentration of benzo[k] fluoranthenes had a strong inhibitory effect on P. delicatula,and its maximum inhibition rate was 89%. Two kinds of microalgae were prepared by adding fixed concentration（9 μg/L） of benzo[k] fluoranthene,the results showed the ACP of C. vulgaris reached the maximum at 72 h,which was 32% higher than that of the control group,while the ACP activity of P. delicatula reached the maximum at 48 h and increased by 105%. The trend of AKP activity was consistent with that of ACP. The CAT activity in C. vulgaris reached the maximum at 72 h,which was 2.3 times higher than that in the control group,and the activity of CAT was up to 48 h,which was 2.5 times of that of the control group. The content of MDA in two kinds of microalgae increased with the exposure time of benzo[k] fluoranthene. Compared with the control group,the contents of MDA in C. vulgaris and P. delicatula were increased by 73% and 81% at 72 h respectively. There was a difference in the toxic effects of benzo[k] fluoranthene on marine microalgae,and the toxic effects on P. delicatul were serious on C. vulgaris.

Key words: benzo[k] fluoranthene, Chlorella vulgaris, Pyramidomonas delicatula, toxic effects