In the following few days (i.e. day 7–13),
reduced light intensity of 6000 lux could completely meet the
needs of microalgae growth. Decreased metabolism rate might
lead to the reducing demand for light. The light intensities of
2000 and 4000 lux were too weak to reach the photosynthesis
requirements of microalgaeChlorellasp. for light. Insufficient irradiation limited the increase of growth rate and photosynthesis, the
same result as was reported by Wahidin et al.[38]. Low light irradiation could not penetrate dark areas formed by the cells and
medium, which actually limited the microalgae cell proliferation.