Lighting Wavelengths

<a href=showthread.php?s=&postid=14620030#post14620030 target=_blank>Originally posted</a> by greenbean36191
High flow doesn't lessen the photoinhibition- it lowers oxidative stress from high levels of photosynthesis. And yes, the need for high levels of flow is related to the high levels of light the corals are receiving.
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Yeah, I had some weird experiences with a huge acro I had chunks of in at different levels in my tank. With lower light the staghorn colored up better in the upper part of the tank and when I went with a more intense fixture the upper part of the coral lost color but I noticed one branch that was getting what I think was too much flow kept it color. It was about 5" away from a Maximod 900 pointed right at it after I had knocked the pump out of position and didn't notice it right away.
 
<a href=showthread.php?s=&postid=14610714#post14610714 target=_blank>Originally posted</a> by MCsaxmaster
The intensity of light required to reach photosaturation is highly variable among corals depending on the coral species, the type of zooxanthellae the coral is hosting, photoacclimation, and likely individual differences among genetically distinct individuals.

For example, due to photoacclimation Stylophora pistillata collected from the same reef at a couple of meters depth and ~30 m depth have been found to reach photosaturation at ~400 and 80 umol photons/m2/s, respectively (early work by Muscatine et al.).

However, all of this gets much, much more complicated when considering branching corals as compared to massive corals, or when comparing tissues in coenosarc and different spots of the corallite in corals. Branching corals inherently self-shade. Most of the light gets absorbed in the outer tissues and, sometimes within a few cm into the colony, you're down to light so dim it can barely sustain photosynthesis. For instance, we determined the light extinction coeficient in a branching Caribbean coral, Madracis mirabilis (rather similar to Stylophora or Pocillopora), in the field a couple of summers ago. At ~10 m depth the light intensity on a clear day was ~350 umol photons/m2/s during midday. Within 5-7 cm the light intensity inside a colony was down to less than 5 umol photons/m2/s--too little to support normal photosynthesis. Not surprisingly, below 5-7 cm at this depth the tissues naturally die back.

A lot of corals, regardless of growth form, will have a combination of very blanched and darker tissues in very shallow water. The tissues that are most exposed to sunlight tend to be very light, almost bleachy. At the very high light levels those corals often see during midday very little photosynthetic pigment is needed, and much of it gets destroyed daily anyway. In the deeper tissues (and remember, we're talking about around corallites--a few mm or less difference) the tissues are much darker and have much more photosynthetic pigment. These deeper tissues are more shaded. They require more photosynthetic pigments to capture sufficient light, and less pigment is destroyed daily by excessive light.

I suppose the point I'm really trying to make is that one size does not fit all, these issues are far from simple, and generalization can easily lead to overgeneralization. In particular, assuming that light tolerances or needs are similar among "sps" corals is totally and completely wrong. Different species of corals that we would call "sps" corals are tolerant of both the highest and lowest light levels generally tolerated by photosynthetic corals. Designations like "sps" mean absolutely squat about a corals' light needs or tolerances...really.

For most corals I think 200-300 umol photons/m2/s is a reasonable target light intensity. Some would be fried by that and some would be undersaturated but many will do quite well indeed. As for higher light intensity of say 500 umol photons/m2/s: many aquaria with strong lights probably have a few spots in the tank that bright, but very few tanks have more than small portion of the tank that bright. As for 1000 umol photons/m2/s: while I'm sure they exist, VERY few tanks are getting that kind of intensity essentially anywhere in the tank. While many corals can tolerate intensities that high for a few hours a day, it can cause significant photoinhibition in the outer tissues in many corals. That would not be a wise regime in captivity ;)

Chris
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If a coral is getting enough light to reach saturation then how long does it take to reach photoinhibition? how much light at the saturation point does it need?

thanks
 
Photoinhibition doesn't take longer to reach than Photosaturation, they are both entirely about intensity not duration. And they both happen almost instantly.

The point of onset photosaturation is where throwing more light at a coral does not increase photosynthesis while the onset photoinhibition point means that "from this point, more light brings a decrease in photosynthesis".

The intersection between the white and red lines represent the point of "onset photosaturation". ~400 PAR

medium


A similar point to the right of the curve (symetrical) represents the point of 'onset photoinhibition'. For this purple porites that looks to be around ~800 PAR. In other words this coral can take up more light than most corals.





This article was linked near the start of this thread but worth linking again:

http://www.advancedaquarist.com/2007/3/aafeature1/view?searchterm=too much light


I'm sure MCsaxmaster /Greenbean will have better information for you about the negative affects that photo-inhibiting light levels can cause. I'm sure you could damage a coral with even sub-saturating light levels if you left the lights on for long enough without a rest.
 
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Exactly as Ryan says above, the onset of photosaturation and photoinhibition (under otherwise normal and constant environmental conditions) depend on light INTENSITY. The light dependent reactions in photosynthesis happen so quickly (fractions of a second) they are effectively instantaneous for our purposes. To attain photosaturation or photoinhibition the parameter of importance is light intensity.

Hence, if the light intensity is subsaturating you could leave the light on 24/7 and you will NEVER attain photosaturation nor photoinhibition. Constant light may screw up other aspects of the organisms' biology, but higher light intensity is required to reach photosaturation or photoinhibition.

At or below saturating light intensity the quantity of net carbon fixation (net primary production) does depend on photoperiod. For instance, if X light intensity is at or below photosaturation then a photosynthetic organism will fix more C in 12 hrs than in 6 hrs. Exactly how much depends on where we are on the P/E curve. The RATE of photosynthesis depends on light intensity, the net total daily carbon fixation (NPP) depends on the 1) the rate of photosynthesis and 2) the photoperiod.

Photoinhibition occurs when the photosynthetic apparatus (collection of a photopigments and a variety of proteins) becomes damaged. Usually this happens through the production of excessive reactive oxygen species, which happens at high light intensity. The more ROS are produced the more photocenters are damaged and the more of them there will be that need replacement/repair. Again, the RATE of photodamage depends on light intensity (all else equal), the net daily amount of photodamage depends on 1) the rate of photodamage and 2) the photoperiod.

It all comes back to where we fall on a P/E curve though. We want light intensity bright enough that we are getting a sufficiently high rate of photosynthesis, but we don't want so much light we are causing photoinhibition (and significant photodamage). If we have enough light, but not too much, we should be able to run a good, long photoperiod, thereby getting lots of carbon fixation and ultimately happy, healthy, fast-growing critters.

cj
 
Thanks guys that is really helpful. I feel I actually understand now. well almost :D

so if photosaturation can be almost instant how to we know how long photoperiod we should give our corals?
 
Photosaturation will not even occur if the intensity does not reach that point. So, the magic that we need is to know what the correct intensity is for our given animals, then we can worry about photoperiod. Correct?
 
Thanks for clarifying Chris

In another thread about flow this came up:

medium


http://www.advancedaquarist.com/2006/9/aafeature2/view?searchterm=lighting flow

This seems to suggest that the levels of saturation/inhibition are not absolute per coral but depend on the levels of flow and other factors. Is that true or am I misintepreting? They were only measuring oxygen, is that test at all comparable to tests with a PAM?


Also, would you say that a photoinhibited coral is kinda like Wolverine at the end of Xmen3 when he kills JeanGray? constantly being damaged and rehealing??? :D
 
I don't know about the rehealing but heck of an example!

Yes, increased flow can raise the photoinhibition threshold according to Jake Adams. He gave a good talk at our recent event.
Oxygen production is what causes the damage in a over saturation problem.
 
:lol: nice. I skimmed all three parts of that series quite some time ago... back when I knew even less than I do now. I'd love to give them a thorough read later when I have time for it.

Strange that this isn't something you hear repeated very often, that a coral requires more flow to deal with more light. That's huge; no wonder people have such varying results with super intense lighting. People of course always say more flow but the why is lost.

always funny coming back to older articles, often I had no idea what certain parts were talking about and the re-read months later reveals all sorts of things and I spot more familiar terms.
 
Teh LED technology is making headways including aquarium lighting. The white LED's (6500K) have reasonable output (110lm/W) but the blue LED's are much less efficient (30 Lm/W). Soundwave and others are doing grreat work on another forum but in all cases have a 50% mix of white and blue LED's in a concentrated matrix. The spectral distribution of the cool white's have a high output in the blue wavelenghts and reasonable emission thru the visible spectrum. Finally my question: why not use only white LED's thereby lowering the cost for hardware & energy usage? [A distributed grid of LED's coupled with selected optics allows for efficient light control].
Thanks for some great information on selecting the best lighting system for reef tanks. I'm new at the hobby and am impressed on the technical support provided on this and other forums.
Jim
 
Re: Lighting Wavelengths

<a href=showthread.php?s=&postid=13600390#post13600390 target=_blank>Originally posted</a> by snaza
Just wondering if there is a perfered wavelength for SPS. I'm using T5s and most bulbs have lots of 400-450nm. I understand Natural sunlight users 400-760nm but is there a percentage of each?

Just for argument sakes, just say i had 1000PAR, what wavelength would be best? 1000PAR at 400-450nm or 1000PAR of 500-600nm.

Does this make sense? :D

Aaron
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<a href=showthread.php?s=&postid=13603396#post13603396 target=_blank>Originally posted</a> by greenbean36191
. . . intensity is indeed much more important to photosynthesis than than spectrum, which is nearly irrelevant. Aquarium lights are blue because blue light produces more fluorescence. . .
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Based on my reading of this thread I am left with the impression that the answer to Aaron's original question was given as and accepted as - NO.


But isn't coral coloration of greater importance to the vast majority of reefers rather than the rate of growth? And is not the overwhelming proof in favor of "violet" spectral light as having an HUGELY greater effect on the most favored pigmentations?

Q.E.D. The color of your bulb matters a lot if you care about the color of your coral.



Aaron, the answer to your question is: YES there is most definitely a preferred wavelength if you want the most colorful SPS possible!





Just a quick table taken from Dana Riddle's most recent article on lighting and coloration:


How to Make Corals More Colorful: Part Two


Table.tiff
 
Re: Re: Lighting Wavelengths

Re: Re: Lighting Wavelengths

<a href=showthread.php?s=&postid=14698324#post14698324 target=_blank>Originally posted</a> by JPMagyar
Based on my reading of this thread I am left with the impression that the answer to Aaron's original question was given as and accepted as - NO.


But isn't coral coloration of greater importance to the vast majority of reefers rather than the rate of growth? And is not the overwhelming proof in favor of "violet" spectral light as having an HUGELY greater effect on the most favored pigmentations?

Q.E.D. The color of your bulb matters a lot if you care about the color of your coral.



Aaron, the answer to your question is: YES there is most definitely a preferred wavelength if you want the most colorful SPS possible!





Just a quick table taken from Dana Riddle's most recent article on lighting and coloration:


How to Make Corals More Colorful: Part Two


Table.tiff
Click to expand...


Thanks for that. Great article, reading it now
 
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