[MCsaxmaster]

Hi Tyler,

That explanation might make sense if these were photosynthetic pigments, but they are not. Zooxanthellae, with their chl a and chl c2 as well as several accessory pigments, absorb light strongly in a broad region from about 400 - 500 nm and then again at aroun 660 - 680 nm with less absorption (which is not NO absorption) outside of these ranges. Zoox. can and do use all visible wavelengths (and far violet), but photosynthetic pigments absorb best in the blue and red. Overall this pattern gives the zoox. a brownish or golden brown coloration.

Any color in a coral besides brown is due to coral pigments which have nothing to do with harvesting light. A blue coral vs. a red coral vs. a yellow coral vs. a green coral is not using any of those pigments to absorb light for photosynthesis. This is done entirely by the zoox. which are brown. These other pigments are produced by the coral for potentially a variety of reasons, many of which have nothing to do with the fact that these proteins interact with light. Interacting with light may just be a harmless side effect of the utility of these proteins. Some of these pigments may indeed be produced to absorb light and thereby shield the zoox. from intense sunlight. In this case, pigments that are red, blue, purple, or whatever color are simply absorbing light to shade the zoox. Think of them as like tinted glasses.

Chris