The effect of urea concentration in a range of 25–300 mg L1
showed that Thalassiosira sp. needed 1 d for adaptation (Fig. 1C).
Maximum cell density in a range of 4.6–6.6 106 cell mL1 was
observed at the end of exponential phase (6th day). The F test value
of 0.26 was less than Fcrit value at the 99% confidence level of 2.45,
indicating no significant difference in biomass production obtained
from different urea concentrations in the culture medium.