Abstract: To explore toxic effects of F^- and Cl^- on growth of Chlamydomonas reinhardtii for comparison, algal biomass, specific growth rate and growth inhibition rate as affected by concentration of F^- or Cl^- were determined with the Erlenmeyer flask cultivation method and model analysis. Results show that F^- in the range of 5-80 mg·L^-1 was toxic to C. reinhardtii, inhibiting its growth and the growth inhibition rate increased with increasing exposure time and F^- concentration, but its maximum growth inhibition rate dropped below 62% on D 10, which suggests that C. reinhardtii is quite tolerable to F^- below 80 mg·L^-1 in concentration. By contrast, Cl^- could either promote or inhibit growth C. reinhardtii of  depending on Cl^- concentration. When Cl^- concentration was up to 12800 mg·L^-1, its growth inhibition rate reached as high as 96%. F^- and Cl^- differs in effect on growth of C. reinhardtii, which is reflected mainly in the laws of the functions of the growth effect models varying with F^- or Cl^- concentration. Besides, in terms of EC₅₀ under the same exposure time  F^- (18.0 to 56.4 mg·L^-1) was far too lower than Cl^- (1 074 to 2 360 mg·L^-1). That is to say, F^- is more toxic to C. reinhardtii than Cl^-，but the ecological risk of Cl^- in the environment may not be ignored, either.

Key words: fluoride ion (F^-), chloride ion (Cl^-), Chlamydomonas reinhardtii, growth, inhibition, model