Research Of Toxic Effects Of Different Modes Of Nonylphenol Exposure On Marine Microalgae

Nonylphenol (NP) is a typical environmental hormone that has been widely used in industrial and agricultural production and the production of consumer goods. It may release into the natural environmental system and cause environmental。pollution. This environmental hormone also disturbs growth and reproduction of organisms. In the present study, two marine microalgae, Phaeocystis globosa and Phaeodactylum tricornutum were used, and three experimental groups with different types of NP exposure were set up to evaluate the ecological toxic effects of NP on the two marine microalgae. In the first experimental group, the concentrations of NP were 0,0.1,0.2,0.3,0.4,0.5 and 0.6 mg-L-1 for P. globosa, and 0,0.2,0.4, 0.6,0.8,1.0 and 2.0 mg·L-1 for P. tricornutum, and the toxic effects of NP on the growth rate, contents of photosynthetic pigment, soluble protein, malondialdehyde (MDA), and maximal photochemical efficiency of PSII(Fv/Fm) were evaluated. In the second experimental group, the marine algae were treated by NP with the concentrations of 0,0.1,0.2 and 0.3 mg·L-1 for P. globosa, and 0,0.2,0.4 and 0.6mg·L-1 for P. tricornutum for one day, and the changes of growth rate, soluble protein content, photosynthetic pigment content, and MDA content were examined. In the third experimental group, seven NP treatments with different exposure duration and frequency were set up to investigate the growth rate, soluble protein content, photosynthetic pigment content, and MDA content in P. tricornutum under those different exposure modes. The results are as follows. (1) NP exposure resulted in toxic effects on the growth of two marine microalgae, and the values of 96 h EC5o were 0.42 mg·L-1 for P. globosa and 0.84 mg·L-1 for P. tricornutum. Besides, NP had hormesis effect on P. globosa. (2) Short-term exposure of NP had obvious toxic effects on the growth of P. globosa and P. tricornutum, but the toxic effects gradually disappeared after the exposure of NP was stopped. (3) The exposure duration and frequency of NP could influence the growth of P. tricornutum. Duration exposure treatments of NP had more significant toxic effects on P. tricornutum than the intermittent exposure treatments. The OD values in the groups of intermittent treatment during the same exposure period were increased 43.8%,41.2% and 211.7% as compared with the groups of duration treatment; in addition, the contents of chlorophyll a, carotenoids and soluble protein were increased significantly. (4) NP exposure could induce significant change of MDA content in the two marine microalgae. MDA content in two marine microalgae was significantly and positively related with the concentration of NP. High concentration of NP exposure could significantly increase MDA content of both P. tricornutum and P. globosa. The promotion effect of duration exposure on MDA content in P. tricornutum was more significant than of the intermittent exposure during the same exposure period.