Figure 4

Mean effective PFD at different threshold values of daylight useable for the growth of the microalgae. PFD values above the threshold value were set to the threshold value, i.e. if PFD values above 300 μmol m^-2 s^-1 are recognised as having no effect, the effective PFD was set to 300 μmol m^-2 s^-1.