You realy need to careful on that statement. There are peak fwave lenghts that the photosynthetic chemicals absorb and there are other wave lenghts that are not used by them at all. Different photosynthetic chemicals use different wavelenghts of light.
Where I see the biggest confusion is with some of the florescent chemicals. In nature there purpose is to take the available wave lenght of light and convert it to a wave lenght that the other chemicals in the corals can readily use. These florescent chemicals have been found to be activated by nmany different wave lenght reaching from 420 nm to well over 600nm. But each of these chemicals again are unique and only is activated by one or two specific wave lenghts.
My fear is that so many of us are concentrating on the specific wave lenghts between 420 nm and 460 nm that we are completly ignoring the longer wave lenghts. Yes our corals are adapting to this light change we are giving them. But through several generation of corals will we be changing there chemical proportions where they will no longer have the color we are used to seeing from them.
As Sanjay Joshi pointed out to me, the following two graphs show that even the least absorbed wavelengths are still absorbed at a rate of 50%. This illustrates that the corals are utilizing all wavelengths in some way, shape or form.
Absorption/reflectance curves are valuable, but many people run with those peaks and think that there is no limit to how much of that light a coral can take. Excess blue light can cause corals to heat up as the extra energy is absorbed. This is a major cause of bleaching with new (blue) LED fixtures. The PAR value may be low, yet bleaching still occurs.
This study shows many such absorption peaks that we are all familiar with. They also show the varied photopigments and their significance in each respective coral. It isn't a simple matter of matching an absorption peak of chl a or c, such as ß-carotene, peridinin, neo-paradinin, diadinoxanthin, dinoxanthin, neodinoxanthin, & xanthophyll. Do I completely comprehend all of this? Absolutely not
and this is why I shrug when people focus on just one buzz word like chl c and it's absorption peak. I get it... peaks are cool and obviously mean something
The charts in the study show absorption peaks in the blues (400s) and in the reds (600s), but there are also some in the greens (500s), specifically 582-582, for those who worship peaks
http://www.biolbull.org/content/135/1/149.full.pdf
Below is another good paper on the photo-adaptation you have mentioned (TropTrea). They found that corals collected at 9m had a better photosynthetic response to full spectrum light than corals collected at 40m which responded better to blue light. I guess a good question would be which corals were more colourful. At 40m depth the presentation would be poor, but the pigmentation may be great. On the other hand, the corals at shallow depth could just as easily be more colourful and have better reflective colour as well.
I don't know if it is fair to assume that the shallow water corals are living in the "proper/natural" lighting conditions, and the deep water corals are adaptive to the missing spectra of the depths? or are the shallow water corals adaptive to the extra spectra?
There is a reflectivity graph in this study as well, and no wavelengths are entirely reflected, so the full spectrum is used. The deeper water corals have a lower reflective percentage, but they have adapted to absorb whatever they can get in a darker environment.
I really don't think that a few years in a reef tank will devolve corals of this adaptation. With millions of hears of evolution, they can't lose the ability to adapt that quickly. Corals fall off of shallow reefs and fall to deeper depths on a constant basis. They do not however, travel upwards. Perhaps adaptation to blue light comes quicker than adaptation to full spectrum light as a result?
http://jeb.biologists.org/content/213/23/4084.full.pdf
