PSB increased in the beginning 24 h, and
then the pigment contents stopped increasing. It might be
explained that at the beginning, the PSB biomass was too low to
provide mutual shading. As a result, the ‘actual light intensity’
imposing on the PSB cells was very high, leading to a rapid increase
in pigment contents in the cells. After 24 h, the PSB biomass was
high enough to provide mutual shading and the pigment contents
stabilized. A similar phenomenon was observed in microalgae
growth, where photo-inhibition also more likely occurred at a
low microalgae concentration, such as during start-up