Measurement of microalgal photosynthetic activity depending on light intensity and quality

A system that can precisely measure light-dependent microalgal photosynthetic activity was developed and successfully used to obtain the photosynthesis-irradiance responses at different concentrations of algal cells, and intensities of various light sources. The measurement system was designed to finely control both the intensity and spectrum of illuminated light. In order to test reproducibility of the measurement system, Haematococcus pluvialis was used as a model microalgal strain. As a result, the photosynthetic activity, in terms of the oxygen evolution rate, was consistently measured within errors less than 5%. When light sources were changed, the red light was more effectively utilized for algal photosynthesis than green light and even simulated daylight, which is likely to occur because H. pluvialis possesses a special pigment (i.e., Chl a) which enables it to harvest red light region.