As shown in Fig. 2a and Fig. 3a, Fv/Fm of C. muelleri and D. salina
cultured in f/2 medium was above 0.6 over the 12-day period.
However, Fv/Fm of the two microalgae cultured in the medium deprived
of different nutrients fell to below 0.6 on day 9 and continued
to decrease in the following days. Deprivation of nitrogen
reduced Fv/Fm of C. muelleri and D. salina by the greatest amount,
followed closely by deprivation of complete nutrient, phosphate
and iron. These results indicate that when the two microalgae were
cultured in f/2 medium, there was no notable stress during the
experiment time, but when they were cultured in nutrient deprivation
conditions, they were under physiological stress on day 9 and
the degree of the stress became more severe. Also, deprivation of
nitrogen gave the greatest physiological stress to the two microalgae,
followed closely by deprivation of complete nutrient, phosphate
and iron.