giving corals the light that they do not need

I was wondering, if we give a coral, that has red pigments, light heavy in the 'red' part of the spectrum, then would it color up by producing more red pigments in an effort to keep that part of the spectrum out?

Edited by sshm - January 22 2007 at 12:00pm

Red was just an example, but the article does give good insights. I was wondering in the line that a pigment of a certain color will absorb every color in 'white' light except its own color which is why it shows up. So if the purpose of pigmentation in corals is to 'reject' that specific part of the spectrum (not talking about photosynthetic growth since that requires a specific spectrum) then can we encourage more pigmenbtation by giving it more light in the spectrum that it rejects?

It's certainly a good argument, but I don't think we know why corals are the color they are...

Many coral pigments fluoresce which is absorbing one wavelength of light and emitting a longer wavelength one. This is one reason to add actinics, and this can change the color you see. I believe it is highly unlikely coral pigments actually bending light.

Well, I am no authority on corals and coral physiology but if I can speculate on why coral fluoresce it would be as a way to reduce incident energy. As adam said corals fluoresce under blue light, blue light has higher energy so when the incident energy is high, the coral will absorb some of it and give out a reduced energy by fluorescing, thereby in a way reducing the incident energy on it.
Also, the purpose of pigmentation could also be to reduce incident energy for one. The second could be in response to the environment, which is unique since water acts as a filter. So the colors we see could be different from the colors that are, at the depth at which the coral occupies. A 'red' coral that is at more than 100m below the surface may n ot be visible at all since there is no red light around there.

Another way to ask the question is, if we have a coral that is predominant in 'red' pigmentation, and we only gave it light below 450nm range, i.e. only blue light, would it lose its red pigmentation (with the assumption that it doesnt need it anymore?)



Edited by sshm - January 22 2007 at 6:17pm

I guess I have always thought the pigments were to protect the coral from damaging UV radiation. Maybe the corals that don't have these fluorescing pigments have developed other means of dealing with the damaging rays. Certainly other saltwater organisms have developed fluorescing proteins for a specific purpose. I would love to hear if there are any prevailing theories on the purpose of these pigments.

Well, uniformity was never a halmark of nature. Not all mammals need to be able to run at 70mph to get the next meal. I guess what Im trying to say is that if one coral exhibits fluorescence to protect against UV or other hi-energy wavelengths, its not implied that all of them would need to do it.

I would think that some deep water fluoresce since they are only receiveing highly filtered and penetrative blue light which have 3 times the energy of light in the 'red' spectrum. For the ones that do not fluoresce, I wonder if that is a significant source of their energy, do many deepwater corals appear blue in normal light?

So when it comes to fluorescing, there is either a purpose to it and that purpose is more from natural selection (either to protect themslevs from UV or to attract prey or distort their shape - since if they absorb blue and fluroesce in green they wont show up in deep water) i.e. those that fluoresce have survived better than their counterparts that did not (and we probably wont find or know for sure if we do find their fossils) or they havve acqquired fluorescing pigments from a foreign source, secondary to whatever it is, so in those cases they fluoresce for no reason probably.

Adam Blundell wrote: SSHM- ready for another?  Okay with all those things you mentioned then let me ask you this.... so why is it that you can take a montipora capricornis, frag it, grow two pieces in the ocean side by side, and have one fluoresce and one not fluoresce?   Stumped yet?  If not feel free to keep playing... I do it all the time Adam

Well in that case (without knowing details on where the corals were placed, for how long and how many times the experiment was repeated) I wonder if the gene that encodes for the fluorescing protein exists in some corals but is expressed randomly. If not, then the source is foreign. I am not surprised that two monti caps side by side would behave differently, I must say whoever did that experiment was clutching at straws since the experiment is far from controlled. Is there any data where someone has put two say caps in a tank with controlled water parameters and get the same result? In that case, the source is probably not in the water but it is within. I am guessing that this was done before, and there was never a result where a coral would begin fluorescing (without showing any flourescence before) after a time in a controlled environment, so we can either rule out a latent gene or conclude that the conditions exist only in the ocean so that some corals can randomly express a latent gene. Then there are two more possibilities, some corals either randomly acquire the components from the water to synthesize the flurescing protein, or acquire the protein itself from a foreign source, by either trapping and injesting or as a symbiotic relationship. I guess once the how's become a little more clear, the why's become easier to speculate on.

Edited by sshm - January 23 2007 at 10:11am

Well nobody has tested that in a controlled tank.  Actually the best chance of that happening is my lab

Brian-