Euphyllia pigmentation

[Arthur1]

Just curious, I have not read about coral pigmentation in many years but know that there is a myriad of factors affecting them. This post concerns orange torch corals. I bought a single orange head about a year ago, have it under Kessils and there are probable 30 heads or so now, but they are more golden than orange. With LPS corals, how much of the light influences pigmentation in contrast to certain nutrients? None, minimal or in this case, much?

[Tripod1404]

Coral pigmentation depends largely on light intensity. They use pigments(not always a correct term as most so called "pigments" are actually fluorescent proteins) for photo protection and to a lesser extend to fight against the reactive oxygen generated by Zooxanthellae. Some of these proteins and pigments also require certain co-factors to be active or the enzymes that produces them require the cofactor. Most co factors are trace elements (more specifically metals) and vitamins. That is where nutrition and trace elements have a role in.

Edit1; I just wanted to add something, in addition to protection, corals also use pigmentation to adjust the growth of Zooxanthellae. Basically pigments absorb the excess light at a certain wavelength (mostly bluer wavelengths as they are most useful for photosynthesis) and either radiate it back at another wavelength (this is called fluorescence) or the energy is dissipated as heat. Most common fluorescence is green color because the pigment absorbs every wavelength except for the wavelength that cannot also be absorbed by chlorophyll and either reflect it back or radiate it at greener wavelengths. We see organisms with chlorophyll green (such as plants) because chlorophyll cannot use green wavelengths and reflect it. That reflected wavelength comes to our eyes and we see them green. Coral use this to their advantage in a very smart way, they basically produce pigments that compete with chlorophyll and by adjusting the amount of these pigments, they can regulate the amount of light accessible to Zooxanthellae and accordingly their numbers.

One reason why corals bleach with increased temperature is because most of these protein pigments are not heat-stable, when those proteins cannot be maintained, corals lose control over the Zooxanthellae . Zooxanthellae multiply and reach to an unmanageable number and as a last resort coral expels all of the Zooxanthellae.

Unfortunately corals do not have direct control over their photosynthetic aparathus (Zooxanthellae) like plants have (chloroplast). Chloroplast was once also a free living organims (like Zooxanthellae but bacteria based), over billions of years plants assimilated it into an organelle and now have direct control over it. They can directly control its number, growth and division. This is why plants do not bleach with excess light, they mostly become pale green ,due to reduction in number of chloroplast. For some reason corals could never developed this degree of control, which is interesting.

[Arthur1]

Tripod, thank you for the thorough response. I was actually going to use the term metals instead of nutrients but wasn't sure if going that direction was 100 percent correct. You mentioned light intensity, rather than wavelengths, which I can understand some people using them one in the same. Thank you jarring some old facts loose in my head as well, as I didn't not even remember your comment about plants, chlorophyll and green. That's what happens when you don't get to use your brain anymore lol. The energy being released as heat, never knew but it makes complete sense. Ok, back to the "topic". Concerning wavelengths and light intensity with the orange color that we, as humans perceive, would a lower kelvin rating be more conducive to accentuating this particular color or a stronger light intensity in the spectrum that it is currently receiving?

[Tripod1404]

Arthur1, about the orange color, my first question is; Was the coral orange when you got it? One issue with many online retailers is that they saturate the colors of their corals using computer software. This ranges from simple contrast manipulation to full scale Photoshop. So if you never saw it orange in person, that gold color might be its true color. But if you are sure it was orange at one point, here comes the rest.

About the way accentuating this particular color, to make a reliable prediction we need to know what is the source of that color. Meaning is it florescent protein (and the wave-length it it absorbs light and emits light) or is it a reflective pigment. If it is florescent I would guess higher kelvin light (more blue) would cause it to fluoresce more. Most of the time florescence is most visible to us under lower wavelength (actinic) lights. The reason for this is; our eyes are not very sensitive to actinic light but they are very sensitive to the wavelength of light that florescence happens. This cause us to not clearly see the bright background actinic light and but see the floureced light very clearly and this gives us the sensation that the coral is glowing. For an organism whose eyes are sensitive to lower wavelength lights (such as birds), the coral would not look particularly bright.
If it a reflective pigment, it will show its colors best under conditions here it is not washed out by other colors. If your bulbs are too blue, that orange might be mixing with blue. If this is the case a whiter light or perhaps slightly yellow light might work better. But keep in mind those generally do not grow corals well.
You should also consider the intensity of light in addition to the wavelength, like I said most of these proteins are produced to regulate the amount of light the tissue receives. If the amount of light is already weak, they wont need to produce pigment to counter that.

I think the best option is to ask someone who has one of these orange Euphyllias and learn their lighting conditions and additives they use.

[jrhupp]

Originally Posted by Tripod1404

Edit1; I just wanted to add something, in addition to protection, corals also use pigmentation to adjust the growth of Zooxanthellae. Basically pigments absorb the excess light at a certain wavelength (mostly bluer wavelengths as they are most useful for photosynthesis) and either radiate it back at another wavelength (this is called fluorescence) or the energy is dissipated as heat. Most common fluorescence is green color because the pigment absorbs every wavelength except for the wavelength that cannot also be absorbed by chlorophyll and either reflect it back or radiate it at greener wavelengths. We see organisms with chlorophyll green (such as plants) because chlorophyll cannot use green wavelengths and reflect it. That reflected wavelength comes to our eyes and we see them green. Coral use this to their advantage in a very smart way, they basically produce pigments that compete with chlorophyll and by adjusting the amount of these pigments, they can regulate the amount of light accessible to Zooxanthellae and accordingly their numbers.

The statement in bold is not correct in a few ways. Fluorescence is a process of dissipating energy from absorbed light, and as such it requires that the transition be from higher to lower energy. So to have something that emits a photon that appears green via fluorescence the photon that was originally absorbed would have to have been at a shorter wavelength. For something that appears green because it reflects green light, that does not automatically imply that it absorbs light at all other wavelengths. The statement as to why plants appear green is not entirely correct either. But I will leave that for another day.

[Tripod1404]

jrhupp, I have been working on photosynthesis for almost a decade. All chlorophyll based photosynthetic organisms have structures called light harvesting complexes. Energy harvested from numerous chlorophyll molecules on these light harvesting complexes are funneled (resonates) to the central chlorophyll at the reaction center of photosynthesis. So basically,energy harvested from many lower energy photons can be concentrated and if energy is excess, it can be fluoresced. Actually, two main process of getting rid of excess energy are chlorophyll florescence and non-photochemical quenching. I must also point out that blue light (lower wavelength) is already more energetic then green light (higher wavelength) so there is no violation of energy conservation for something absorbing blue light to flounce in green. Nevertheless, I wasn't trying to say a single molecule absorb light in all wavelength and radiates it back in green spectrum. There are many photo-protective molecules all with their specific absorption spectrum's. Some of these dissipate energy by radiating back to photons at specific energies and other just heat up and vibrate to release that heat. Of course it is not possible to absorb lower energy photon and radiate a higher energy one, unless there is a energy concentration mechanism like the one I explained above. There are other molecules with photo-protective properties that have this energy concentration mechanism.

About why plants appear green. They appear green because chlorophyll absorbs blue (actually all the way to UV) and red light quite well but not green.
Green light is reflected and since only photons with that "green" wavelength arrives to our eyes, they appear green. Now if you purifier chlorophyll and put it under white light with a broad visible spectrum, it will appear green. Because like I said it absorbs everything but green. On the other hand, if you repeat this experiment with UV light, chlorophyll will appear red. The reason for this is UV has no green element and chlorophyll is already good at absorbing it. The energy absorbed by the chlorophyll molecules excites its electrons and pushes them to higher energy state. As electron return to their ground state, they release that energy as a photon in red wavelength. Immigae I attcahed shows this.

The reason why most corals fluoresce in green is this reason, that is the wavelength that is not "absorbable" by chlorophyll.

[activecactus]

If I could bring out the orange in my torch and octopus without using 20k bulbs, I would love to know.

I have mine under 14k with blus+ and my orange looks tan. Only when the blues are on do the corals show a peach color and a hint of orange.

[jrhupp]

Tripod, I wasn't trying start anything. Just trying to correct some information that was clearly mixing up several processes.

As to my comment regarding why plants appear green, it warrants some clarification. What you say is mostly correct and follows how we teach this; even at the college level. But its an over simplification that I would really like to see corrected in general in the way we talk about plants. I apologize if I offended. Let me explain:

Chlorophylls are what we generally think of as the pigments involved in photosynthesis, and it is true that they reflect light in the green and act as the reaction center of the light harvesting complexes (LHC). But that is only a part of the story. The LHCs are not purely made of chlorophyll molecules, there are a number of other accessory pigments associated with them. These can serve in both energy capture and dissipation. This is why we define PAR the way we do; because you will find that if you measure photosynthesis using a narrow band light source across the visible spectrum (termed an action spectrum: see McCree 1970) that more then the just the wavelengths at which the chlorophylls absorb at drive photochemistry. This includes green light. Likewise, if you simply measure light absorption at the leaf level, you find that leaves do indeed absorb a significant amount of green light (though generally not as strongly as at other wavelengths), and they only absorb a portion (though quite large; ~70 to 90%) of the light in the red and blue where chlorophylls have their absorption peaks. The flip side of this is the device we use to perceive plants, our eye. Which does not have an even spectral response, and responds most strongly to light in the green (refer to the photometric curve). So my comment was based merely on the fact that a significant part of the reason that plants appear green has to do with our eye responding most strongly to green light, not just because chlorophylls don't absorb in the green.

It is good to see people with similar professional interest on here, as I too work on photosynthesis (among other larger scale processes; but I guess that is the nature of ecophys).