Lighting, photosaturation, photoinhibition

[spanko]

Not gonna pretend I understand completely the physiology regarding zooxanthellae and the above subjects. However I would like to start a discussion about it to see what the populace here knows.
Photosaturation is the point where the zooxanthellae in this case, the photosynthetic organism in coral, has its photosynthesis cranking as hard as it can. No matter how much more light you pour to it at this point it will not work faster. We know that the photosynthesis is part of the symbiotic relationship between the coral and the algae and that it provides "food" to the coral which the coral uses and the by product is some food back to to the algae. That can be another discussion but let's leave it at that basic idea.
So if the algae is photosaturated then we can assume that it is growing a maximum potential and providing food to the coral at its maximum potential. A good thing for us reefers as our coral is growing fast.
Tomorrow, because it is 11:00 pm here in Michigan and I am tired, we can talk some about how fast does this photosaturation happen, what is required, and what it means in how long we can run our lights.
Anyone with more info on this or any correction to what I understand about it please jump in. Everyone else, jump in too just because!!!!

 

[geoj]

Me found big word

Photoinhibition
Several laboratory studies using high UV-B exposures have demonstrated damage to a primary molecular complex that all plants use for photosynthesis, photosystem II (PSII). However, field studies with algae grown under natural exposure conditions (solar irradiance) have found little or no effects on the perfomance of PSII in algae (Vincent & Neale 2000). An integral part of algal defense against UV is rapid repair of damaged photosynthetic complexes.
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[t316]

What have you been smoking...

 

[geoj]

Where I think Spanko is going is how much light is enough

 

[spanko]

Ding Ding Ding, we have a winner!!!!
I am trying to determine through all of this whether or not we can same some bucks on electricity costs and still provide to our coral what they need for continued growth, color and overall good health.

 

[reefkprz]

the problem being photosaturation levels for each coral are different. aka corralomorphs reach the point of photosaturation a lot sooner than say a shallow water acropora.
it seems, through the mass reading I have done and my own personal expirience, that the best bet for reaching or nearing photosaturation in a coral isnt always one super high powered bulb but a few medium to strong bulbs thus multiple light sources reaching the coral providing more even lighting over the entire surface of the coral. especcially in the case of branching corals or plating corals that may partially sdhade themselves from a direct point light source (eg a single halide) IMO 2 175w halides would be better than one 400w the light intensity is increased in the overlap zones and the two angles of light will more evenly reach various parts of the coral. even thought the total output of the 175's are lower. of course the par rating of the 175's is much lower so the effect is limited to a shallower reach.
photosaturation is/has beena goal of mine for years. over all its bnearly impossible for your average hobbyest to know whether or not the point of photosaturation has been reached.
I would suffice to say, that providing the most powerful lighting that a given species will acclimate to is about as close as most can come. you can acclimate most (some corals wont adapt to super intense lighting) corals from originating in low light to quite intense conditions. (eg; I have discosomas growing 8 inches directly under a 250w 10k halide) and they flourish, as much as I hate them, even though they are considered a low light coral they do adapt to very high light conditions.. one adaptation is that the discosomas turn their face at an angle to the light kind of like a back slash /, thus controlling how much light actually hits them directly, if the lighting is too intense they tend to slide around the rock to an off angle to the light source or release completly to land elsewhere.
most corals just build up various strains of Zooxanthellae that are more high light tolerant, whereas a lower light specimen of the same coral will have a different dominant strain of zooxanthellae that can achieve photosaturation at a lower level of light. so when you adapt a coral to higher light its actually making it harder for you to provide more light beyond the point of photosaturation. (up to a certain point)
I have more to say on this but I am out of time and would like to hear some opinions and thoughts from others on this topic.

 

[t316]

A lot of big words here but I see where you are going. So, understanding that there is some point of saturation (maxing out the amount of "needed" light), are we actually doing harm by going beyond that said point?
Another factor to consider is that some people don't run lights for the sole purpose of coral growth and/or for the benefit of the tanks occupants, but rather for visual beauty for viewers. I know I have purposefully allowed actinic bulbs to go way beyond their listed useful life, knowing that it is having no positive impact on my tank inhabitants, but simply because the thing still works and looks okay...

 

[reefkprz]

Originally Posted by T316
http:///forum/post/3175363
So, understanding that there is some point of saturation (maxing out the amount of "needed" light), are we actually doing harm by going beyond that said point?
not really, we just arent doing them any more "good" aka no additional benifit from exceeding the point of photosarturation, there is no evidence of harm to stemming from it.
Originally Posted by T316
http:///forum/post/3175363
Another factor to consider is that some people don't run lights for the sole purpose of coral growth and/or for the benefit of the tanks occupants, but rather for visual beauty for viewers. I know I have purposefully allowed actinic bulbs to go way beyond their listed useful life, knowing that it is having no positive impact on my tank inhabitants, but simply because the thing still works and looks okay...%%
this is actually close to one of the other points I want to make. lots of people want "the best growth, and viewing color" they seem to be mutually exclusive if you want the best possible growth run 65k bulbs, they contain the most amount of utilizable light for photosynthesis. this isnt appealing to most people even when balanced with actinic its "too yellow" well you cant have it both ways. if you want photosaturation, run a wide spectrum bulb, and do your best with additional actinics to achieve the viewing color you want, and the actinic light DOES promote photosynthesis, so your not doing harm by runnign extra actinics.
I feel the need to point this out again, most people think that actinics are for looks only, THIS COULDNT BE FURTHER FROM THE TRUTH corals photosynthsize in the 420 to 460nm wavelenght. changing these bulbs regularly are important to zooxanthellae that require the low end of the spectrum (aka deeper water corals, though shallow water corals require it too) deeper water corals are adapted to using the blue end of the spectrum because thats the only light that reaches them in the depths of the wild. thus maintaining you actinics when reaching for the photosaturation point of midwater to deepwater corals should play a key part in this goal. unfortunatly in bulbs the blue end of the spectrum burns out the fastest, thus changing your actinics should actually be done more often than say a higher spectrum builb like a 65k you lose very little of the wavelength in a 65k bulb after a year (because there is such a wide amount of wavelengths provided by a 65k bulb), after a year on an actinic the thing is only good for looks because such a limited range of utilizable light is provided, and the phosphers that provide that spectrum burn out the quickest leving visible light but little in the range corals can use), because most of the proper wavelengths have burnt out of the bulb.
this is also a reason a lot of bulbs seem to lose their luster over time, the blue end of the light that seems so appealing to us fades out while the upper end of the spectrum remains.
I have seen LPS grown under NOTHING but actinic bulbs.

 

[spanko]

Alright Houston we have lift off. I am so glad to see others with some knowledge of this joining in.
Originally Posted by reefkprZ
http:///forum/post/3175354
the problem being photosaturation levels for each coral are different. ...the best bet for reaching or nearing photosaturation in a coral isnt always one super high powered bulb but a few medium to strong bulbs thus multiple light sources reaching the coral providing more even lighting over the entire surface of the coral. ........over all its nearly impossible for your average hobbyist to know whether or not the point of photosaturation has been reached.
I would suffice to say, that providing the most powerful lighting that a given species will acclimate to is about as close as most can come.. ..... most corals just build up various strains of Zooxanthellae that are more high light tolerant, whereas a lower light specimen of the same coral will have a different dominant strain of zooxanthellae that can achieve photosaturation at a lower level of light...
Great points here especially the fact that photosaturation occurs at differing light intensities, wavelengths, etc. Also worth noting here are the other variables in our systems. Bulb-ballast combination's, turbulence-flow in the tank, nutrients in the water, CO2, O2, UV, temp can all affect photosynthesis. However in terms of providing enough light for photosaturation think about how things are in the wild. The sun rises and increases in intensity to the point where some time in the late morning there is enough light for the coral to reach photosaturation. In our tanks we flip a switch and the max intensity is there within a minute. Photosaturation is attained instantly. See the coral does not take time to photosaturate, it is for our discussion an instantaneous occurrence providing the light is there available.
Originally Posted by T316
http:///forum/post/3175363
...So, understanding that there is some point of saturation (maxing out the amount of "needed" light), are we actually doing harm by going beyond that said point? Another factor to consider is that some people don't run lights for the sole purpose of coral growth and/or for the benefit of the tanks occupants, but rather for visual beauty for viewers. I know I have purposefully allowed actinic bulbs to go way beyond their listed useful life, knowing that it is having no positive impact on my tank inhabitants, but simply because the thing still works and looks okay...

Good point here too. If the light intensity is enough to reach photosaturation,the TIME left there does not cause damage (within some reason). More on this later though when we start talking about photoinhibition.
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Originally Posted by reefkprZ
http:///forum/post/3175383
not really, we just aren't doing them any more "good" aka no additional benefit from exceeding the point of photosaturation, there is no evidence of harm to stemming from it.
this is actually close to one of the other points I want to make.... if you want photosaturation, run a wide spectrum bulb, and do your best with additional actinics to achieve the viewing color you want, and the actinic light DOES promote photosynthesis, so your not doing harm by running extra actinics.
I feel the need to point this out again, most people think that actinics are for looks only, THIS COULDN'T BE FURTHER FROM THE TRUTH corals photosynthesize in the 420 to 460nm wavelength. changing these bulbs regularly are important to zooxanthellae that require the low end of the spectrum (aka deeper water corals, though shallow water corals require it too) deeper water corals are adapted to using the blue end of the spectrum because that's the only light that reaches them in the depths of the wild. thus maintaining you actinics when reaching for the photosaturation point of mid water to deep water corals should play a key part in this goal. unfortunately in bulbs the blue end of the spectrum burns out the fastest, thus changing your actinics should actually be done more often than say a higher spectrum bulb like a 65k .........
I have seen LPS grown under NOTHING but actinic bulbs.
I am not knowledgeable enough here to talk to the life of the different spectrum bulbs and will leave that to the reefkprZ. I will add to his comment here though that photosaturation occurs with light and his point on the actinics adding to the mix is correct. As for zooxanthellae adapting I would submit to you verification of what the reef man has said. Take a look at the following pictures.
First is Acropora coral at a depth of 249 feet.

Next Leptoseris at a depth of 386 feet. Leptoseris is known to inhabit water as deep as 540 feet, making it the deepest known photosynthetic coral.

 

[reefkprz]

I cant really quote exact times for phospher burn out in bulbs but its been long understood that the blue end of the specturm in bulbs fades the fastest simply because of the nature of the phophers reactive half life is far shorter than those of phosphers that generate the red spectrum.
here is a great article on the spectral analysis for 400w halides.
http://www.personal.psu.edu/sbj4/aqu...lideLamps1.htm
the part I would draw attention to is the pie charts and the wave lenght outputs for various bulbs and what percentages are in supplied. you can see how a 60-65k bulb could be optimal for growth as they provide the most even distribution through the entire specrtrum available. where as all others have higher concentrations in one area or another. leaving spectral gaps so to speak.
its my opinion that providing the widest spectrum allows for the highest combination of various zooxanthellaes to produce peak growth in corals. I can only point to the fact that almost all comercial growers use 60-65k because of the rate of growth provided, instead of the aesthetic purposes of other bulbs. I consider this anecdotal evidence at best but you cant argue with the results.
Like I have said before and I continue to stand by it, reaching both peak growth and best aesthetics is going to be just about mutually exclusive, though you can come close with heavy use of actinics to balance out the looks of yellower bulbs. reaching maximum possible growth rate with a 14k bulb is not going to happen except possibly in deeper water corals as they are optimized to grow in their naturally occuring depths, but even in them you may find you can get a better growth rate at a higher spectrum.
as for reaching the point of photosaturation, that is only possible when using a bulb/bulb type coupled with the correct distance from the bulb to provide the enough intensity of photosynthetic supporting light for a given specimen.
it is possible to reach photosaturation in a discosoma with metal halide at a much further distance than it would be possible to reach photosaturation in the same discosoma with Ro flourescents, though in theory it may be possible to reach photosaturation in that discosoma with the RO flourescents at a distance of an inch or two in very shallow water.
this is by far one of the most interesting subjects when it comes to closed system lighting due to the extremely wide range of combinations possible due to various coral and lamp types. unfortuantly I learned early on when delving into this subject. there is a lot more to it than I originally thought. there are still more questions than answers and there are few easy answers except to say that all evidence (anecdotal and otherwise) shows photosaturation is generally easiest to achieve with the widest spectrum of light at a sufficient intensity..... probably the main reasson metal halides are currently still one of the best "results" type of lighting available, both intensity and range of useable spectrum.

 

[reefkprz]

as for photoinhibiton...... this is a tough subject. and generally not going to be a problem in your average tank. though you may expirience spot problems, aka sudden coral bleaching. let me see if I can put this out there in laymans terms. be aware this is not a subject I am very strong in, some input from others would be nice here.
all light spectrums can cause photoinhibition, but UV light is the most damaging, since we sheild our tanks from UV light (when running HQI a uv blocking glass is used, when using mogul based bulbs the bulb lens itself is a UV blocker) serious photo inhibition isnt a major concern.
however, in the case of sudden increases in light for a low light acclimated coral to a brighter location photoinhibition can occur. this is when the zooxanthellae is damaged by a lack of photoprotection by the amount of light it is recieving. if enough zooxanthellae is damaged you can expirience bleaching.
selective photoinhibition is actually the term for acclimating our corals to brighter light, by exposing them to higher levels gradually, we are doing a little damage through photoinhibition and the strains that are repaired are either better shielded from light or a a different zooxanthellae strain replaces it that is more capable of withstanding the light, often this is the reason for color morphing among our corals as the different strains are of a different color, either slightly different or massively different. think of it as working with your hands to build callouses, at first your hands are sensitive and cant handle much physical labor without damage (blisters), the more you do the tougher the skin gets to withstand a full days work without blistering. your hands are adding layers of protection. the zooxanthellae in a coral responds much the samne way, adding varied color zooxanthellae or denser amounts of to protect itself from the increase light. in some cases the denser colonies can produce more energy for growth in others the zooxanthellae just darkes to sheild itself from uneeded amounts of light lowering the input its recieveing by darkening. in some cases the coral wont open its polyps to protect itself from the excess light, or will only open for short periods as is receives damage begins to recover and acclimates.
this can work both ways either increse or decreasing light drasticly rto get bleaching only in the case of a decrease its not phtoinhibition but you can still get bleachign from sudden decreases because the coral is so used to a brighter level of light it doesnt have the capability of utelizing low levels and has to eject the zooxanthellae that is either blocking light or requiring higher light. leaving behind only the ones that can use the low level of light. some times this is almost none at all giving the bleached look.

 

[spanko]

Yup, my understanding too. Light above what is enough to saturate photosynthesis that the cells cannot purge themselves. Best analogy I saw was a sunburn. You can get when where you are uncomfortable but your skin darkens over time and you are able to stay out in the sun better without burning. Someone else may get a burn that puts them in the hospital ER for treatment.
Okay now we have a bsic (and I do mean basic, this physiology stuff will absolutely ummmmm.......burn your brain) we should move onto the ultimate discussion here. The reason that I wanted to start the thread and that would be photoperiod, that never ending question, "How long should I leave my lights on"?

 

[reefkprz]

Originally Posted by spanko
http:///forum/post/3177486
The reason that I wanted to start the thread and that would be photoperiod, that never ending question, "How long should I leave my lights on"?
hehehehe. there is no one answer to this. if you want serious growth....
my reccomendation is. 12-14 hours a day. I dont know any grower that runs a longer photoperiod because longer than that and you wind up with diminishing returns. AKA cost of operating versus growth achieved. though most commercial growers whenever possuible try to utelize natural light and only use mechanical lighting to supplement.
You may also find if you contact commercial growers they wont tell you what they do, they tend to consider their methods a trade secret. unfortunatly all this does is promote ignorance in the hobby. I have ran into this brick wall more than once. even SWF.com wont show their grow facilities, or share their methods because they dont want their competition to know what or how they do stuff. I cannot condone such behaviour, but it is infact a reality. in a competetive market, if a company has an edge they dont want the competition finding out how to mimic their results, though I do see that point of view, it dismays me that the all mighty dollar reigns over the sharing of knowledge. any given company that you contact may make reccomendations to you but overall you never know if that is infact what they do, or just similar enough to keep your stuff alive but not reach the same levels of growth that they may or may not be achieving.
you more likely to get your best answers from research programs at universities, or serious hobbyests.

 

[spanko]

Yeah, I don't fault the commercial vendors not sharing what they consider processes that may give them an edge in the market. Tis what capitalism is all about. I thing there are plenty of research, academic, clubs and such information to help move the hobbyist along. What I have found are a couple of things.
1. "There was though to be come type of circadian rhythm causing a depression of photosynthesis during the middle of the day separate from any effects of photoinhibition."
2. "However, a study by Moya et al., from a few months ago found no circadian rhythm at all."
3. "They found that the rate of photosynthesis was constant throughout the day at a saturating light intensity (they determined what was saturating beforehand). In order to test for a circadian rhythm in terms of calcification/photosynthesis they modulated the photoperiod from the normal 12:12 light:dark to 16:8 and 20:4 light:dark and vice versa. Calcification in light was about 3 times faster than dark calcification (well-known in many corals) but occurred at a continuous rate at either the fast, light rate or the slow, dark rate depending simply on the lighting. In other words, with a 16 or 20 hr light period the corals calcified at the fast rate for as long as the light was one. With a 16 or 20 hr dark period they calcified at the slow rate for as long as the light was off."
So your recommendation for 12 - 14 hours per day for serious growth coincides with the thinking from this study.
However now the question comes to mind;
Are we saying that we should run our halides from 12 - 14 hours?
Or can we run the halides 8 - 9 hours and the actinics from 12 - 14 hours?
My thoughts, you gotta balance;
How fast do you want your coral to grow, versus how much do you want to spend in electricity costs to get there.
Now for me, I have found that I don't want to pay for faster growth because I have a 29 gallon biocube that I don't want to overrun with coral. I like to see good - health - colorful - polyps extended SPS coral. I will frag when I have to but would like to sit back and not do too much of that. Sooooooooo.........I run 7.5 hours on the halides and 9.5 hours on the actinics. The balance of the time the moonlights are on.
If I were to graph it, it may look look something like this, note the graph is never touching the bottom which would represent zero photosaturation, because there is some level even with the moonlights.

Moya et al., 2006. Study of calcification during a daily cycle in the coral Stylophora pistillata: implication for 'light-enhanced calcifcation." J Exp Biol. 209: 3413-3419.

 

[spanko]

Here is something else to verify that even the actinics and led moonlights provide some level of photosaturation.
"Excerpt from Advanced Aquarist, May 2009
Effects of Altered Light Spectral Qualities
We're beginning to realize spectral quality plays important role in the health and growth of corals' zooxanthellae and hence the coral host. More importantly, we are starting to understand why and how light quality affects zooxanthellae and host pigmentation.
Wang and his group of researchers exposed zooxanthellae isolated from the stony coral Euphyllia glabrescens to differently 'colored' light in order to examine the effects of spectral quality on the symbionts' reproductive cycles. LEDs provided essentially pure 'blue', 'red' and 'infrared' light. (Note that these results are probably not just applicable to light generated by LEDs, but to any essentially monochromatic light). See Figures 6-9.
In a nutshell, 'blue' light and a mixture of 'blue' 'red' and 'infrared' wavelengths were about the same in promotion of normal zooxanthellae reproduction (although the 'blue' light seems to be slightly more effective).
Exposure to only 'red' light significantly inhibits the productive cycle (is this the reason for the slightly less efficiency of the 'mixed' light?). Infrared light apparently plays no part in regulation of zooxanthellae reproductive cycle, and the algal cells remain in the G1 Phase with no DNA synthesis or mitosis.
Figure 6. Over 50% of zooxanthellae are reproducing (that is, in mitosis) at Hour 23 when maintained under 'pure' blue light for 12 hours. Lamps were off between Hours 12 and 24. After Wang et al., 2008."

 

[reefkprz]

Originally Posted by spanko
http:///forum/post/3177548
However now the question comes to mind;
Are we saying that we should run our halides from 12 - 14 hours?
Or can we run the halides 8 - 9 hours and the actinics from 12 - 14 hours?
12-14 means the halides for best growth. your not going to hit photosaturation on all your halide acclimated corals with just actinic. you will begin some photosynthesis running your actinics but your not going to hit photosaturation.

 

[reefkprz]

Originally Posted by spanko
http:///forum/post/3177548
If I were to graph it, it may look look something like this, note the graph is never touching the bottom which would represent zero photosaturation, because there is some level even with the moonlights.

your mis-using the word photosaturation. let me see if I can clarify it a bit.
you either have photosaturation or you dont there is no partial. what your showing on your graph is photoexposure (even at your peak amount of light you may not be reaching saturation), or rather your showing when light is available for photosynthesis and in what amounts. photosaturation is only the point of maximum photosythesis possible for the creature, the point where increased light wont increse photosynthesis. photosaturation is one point, it doesnt scale back when your actinics come on. there is no Lesser photosaturation.

 

[spanko]

I am thinking in terms of the level of saturation in the total available zooxanthellae. Cannot some of them be photosaturated and some of them not be?
Again the physiology of this is something I am just trying to grasp. I do know that in hemoglobin oxygen binding sites some can be "occupied" while others are not and that oxygen saturation levels are the measurement of the percentage that are.

 

[reefkprz]

useing the term photosaturation only applies to when they have reached that point.
some photosaturate at a lower level, thats for sure. but when you apply the term to a low level of light its incorrect. even with your halides running there is a pretty good chance quite a few of your corals arent photosaturated.
they are photosynthesizing. not saturated. saturation is the end point. the chances of photosaturating a coral with actinics is virtually impossible. while photosynthaesis continues at the lower level of light its not photosaturation.
I'm thinking for clarity we should avoid using "photosaturation" unless we are actually meaning that end point. otherwise this conversation about photosaturation could get very confusing.

 

[spanko]

Originally Posted by reefkprZ
http:///forum/post/3177662
useing the term photosaturation only applies to when they have reached that point.
some photosaturate at a lower level, thats for sure. but when you apply the term to a low level of light its incorrect. even with your halides running there is a pretty good chance quite a few of your corals arent photosaturated.
they are photosynthesizing. not saturated. saturation is the end point. the chances of photosaturating a coral with actinics is virtually impossible. while photosynthaesis continues at the lower level of light its not photosaturation.
I'm thinking for clarity we should avoid using "photosaturation" unless we are actually meaning that end point. otherwise this conversation about photosaturation could get very confusing.
Check!