The results show that, firstly, the cell number of the testing groups is significantly larger (P < 0.05) than that of the controlled group from the fourth day and at a 1.65 - 6.60 mg/L concentration of the rare earth elements. The cell concentration of the testing group is raised by 23.2% at a 4.95 mg/L concentration of the rare earth elements, compared with the controlled group. However, rare earth elements reduce the culture of Isochrysis galbana if the concentrations are higher than 9.9 mg/L. Secondly, the cell concentration of the testing group was significantly larger (P < 0.05) than that of the controlled group from the 4th day, when the ratios of nutrient salts N:P:Fe in the testing groups were 30:2:0.5 mg/L, 15:1:0.25 mg/L, 10:0.67:0.17 mg/L and 7.5:0.5:0.13 mg/L, respectively, in which the concentration of the rare earth constituents was 4.95 mg/L. Thirdly, when the rare earth was added on the 1st, 2nd ,3th and 4th day, the cell concentration of the testing groups was significantly larger (P < 0.05) than that of the controlled group from the second day after the rare earth was added; however, on the 5th day there was no significant different between the testing groups and controlled group. Finally, the chlorophyll content of the testing groups is raised by 19.9% - 45.2% for 1.65 - 6.60 mg/L concentrations of the rare earth elements, compared with the controlled group.

Hence, the mixed rare earth elements have a significant effect on the enhancement of the growth and chlorophyll synthesis of Isochrysis galbana. There is no relationship between the enhancement effect and the concentration of other nutrient salts. Further, such an effect is not related to the time when the rare earth was added during the exponential growth period of Isochrysis galbana.