Abstract: The purpose of this paper is to investigate the effects of different atrazine and thifensulfuron on the population dynamics of Euplotes vannus, Uronema marinum and Pseudokerono psiscarnea by calculating the population density, growth rate and generation time of Euplotes vannus, Uronema marinum and Pseudokerono psiscarnea. The results showed that the atrazine and thifensulfuron to Euplotes vannus concentration of 6 mg/L, the maximum population density was higher than other experimental groups. There were differences in population growth rate and generation time for each concentration of Euplotes vannus. The atrazine and thifensulfuron to Uronema marinum concentration of 6.5 mg/L, the population growth was obviously inhibited. The population growth rate and generation time of Uronema marinum at different concentrations were quite different. Atrazine to Pseudokeronopsis carnea concentration of 6.5 mg/L and thifensulfuron to Pseudokerono psiscarnea concentration of 7.5 mg/L, the population growth was obviously inhibited. The population growth rate and generation time of Pseudokerono psiscarnea at each concentration were significantly different.

Key words: atrazine, thifensulfuron, Euplotes vannus, Uronema marinum, Pseudokerono psiscarnea, population dynamics