We're beginning to realize spectral quality plays important role in the health and growth of corals' zooxanthellae and hence the coral host. More importantly, we are starting to understand why and how light quality affects zooxanthellae and host pigmentation.
Wang and his group of researchers exposed zooxanthellae isolated from the stony coral Euphyllia glabrescens to differently 'colored' light in order to examine the effects of spectral quality on the symbionts' reproductive cycles. LEDs provided essentially pure 'blue', 'red' and 'infrared' light. (Note that these results are probably not just applicable to light generated by LEDs, but to any essentially monochromatic light). See Figures 6-9.
In a nutshell, 'blue' light and a mixture of 'blue' 'red' and 'infrared' wavelengths were about the same in promotion of normal zooxanthellae reproduction (although the 'blue' light seems to be slightly more effective).
Exposure to only 'red' light significantly inhibits the productive cycle (is this the reason for the slightly less efficiency of the 'mixed' light?). Infrared light apparently plays no part in regulation of zooxanthellae reproductive cycle, and the algal cells remain in the G1 Phase with no DNA synthesis or mitosis.
