Question on photosynthesis data from Dana Riddle articles

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@Dana Riddle

Hello Mr. Riddle.
I need help to better understand ETR and photosynthesis graphs in the articles you published in the past.
In the PPFD interval ranging from zero to photosynthesis saturation point, is it right to assume that the energy produced linearly increases until the saturation point? in other words, is the best option to deliver PPFD level at saturation point?

Did You ever measure ETR under sunlight? Could it be that the unexpectedly low ETR saturation point is due to a narrow peak radiation? More practically, 250umoles could be the saturation point with a specific lamp, while with sunlight the saturation point could be higher? (this would mean saturation point is spectrum specific).

Thanks in advance.

 

[Dana Riddle]

@Dana Riddle

Hello Mr. Riddle.
I need help to better understand ETR and photosynthesis graphs in the articles you published in the past.
In the PPFD interval ranging from zero to photosynthesis saturation point, is it right to assume that the energy produced linearly increases until the saturation point? in other words, is the best option to deliver PPFD level at saturation point?

Did You ever measure ETR under sunlight? Could it be that the unexpectedly low ETR saturation point is due to a narrow peak radiation? More practically, 250umoles could be the saturation point with a specific lamp, while with sunlight the saturation point could be higher? (this would mean saturation point is spectrum specific).

Thanks in advance.

Many good questions! The electron transport rate is a hyperbolic tangent until the saturation point is reached but this point is confused by the method used to calculate saturation (it is linear.) Yes, delivering PPFD to reach the saturation point would be best and is easily realized when the coral surface area is flat. When we consider branching corals, the side pointed towards the light will obviously receive more light than the shaded portions. So, it is OK to deliver more light to the exposed part. Interestingly, the expression of colorful proteins is achieved at and above the saturation point (likely as a tool in the arsenal of photoprotection.) I never measured ETR in sunlight for two reasons - first, my PAM fluorometer cost $4,000 compared to ~$15,000 for the Walz Underwater PAM and this was simply out of my lab's budget. Second, calculation of ETR is best done when the light intensity is stable and I never figured out how to control the sun. Yes, the light source can definitely impact ETR; so much so that Walz now offers a PAM fluorometer with multi-colored LEDs as the actinic light sources. I'm beginning work on a project now. Sunlight (in the case of the limited measurements made so far) has a PUR score of ~0.63, while a violet LED scores 0.87. BTW, call me Dana. Mr. Riddle makes me feel as old as I really am.

 

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Thanks Dana.
What about photoperiod? I've read some articles, one in particular about growth on galaxea fascicularis - sadly that's not an acropora- whose results show that 8h light with 150PPFD (light: KZ coralight T5 10000K) produced the same growth as 12h. With an equivalent DLI, 12h 150 umoles seems to be better than 8h 225 umoles.

https://www.researchgate.net/profil...n-an-aquarium-setting-A-matter-of-photons.pdf

In Your experience, aquarists (and You of course) do have better results with warmer light or bluer one? Me and many italian aquarists have always preferred warmer light to achieve better coral growth (I'm always speaking about SPS), while in the last years all across europe is diffusing bluer light over our tanks.
I personally have had poor results with ecothec radion LED fixtures, especially reducing white, red and green intensity. A bit better results with all channels 100%. But when shifted back to T5, tanks really started to improve.
In particular, I've observed that with bluer light, there is quick formation of bacterial-algal powder-like film on glass, that is spiked up by alkalinity. The more is quick and intense the formation of this film, the more is associated with polyp retraction and STN-RTN. Lowering alk to 6,5dKh help to reduce this phenomenon, but is just palliation. Raising alk to something like 8dKh makes easy to observe increased water turbidity (I assume there is bacterial-algal bloom, they are photreactive) and is more associated with diffuse RTN, if this condition is kept for some days (I tried that more than one times - with both LED or T5 light, using mostly actinic ATI T5 tubes). I find very hard to add food to tank (even to fishes): it increases again the issue.
A warmer light (10-14.000°K T5 or MH lamps) seems to prevent this phenomenon and allow to keep high alk level and add large amount of food. No quick formation of powder-like film on glasses, but just common algae. No RTN-STN.
Any information about this?

Thanks.

Luca

 

[Charlie’s Frags]

Following

 

[Dana Riddle]

Your questions cover a lot of territory - light (intensity & spectrum), photoperiod (DLI), water chemistry... I reviewed the article in your link and found it interesting that the authors listed light intensities observed to produce good growth in various corals (determined by various researchers.) It would be interesting to review these works and look the lighting sources used.
As far a Galaxea, I looked at my database and found this coral is contain generalist zooxanthellae clades C1, C3, and another, C21. The generalist clades are highly adaptable to light, but are generally thought to reach photo-saturation at light intensity less than some other clades.
As for the bio-films observed, I saw an outbreak of some sort of growths (I think maybe diatoms, maybe) when I switched my lighting over to all blue light generated by actinic fluorescent tubes. As far as coral growths, I published an article here: https://www.advancedaquarist.com/2015/4/corals
The RTN/alkalinity observation has been observed by many, and I believe it is due to alkalinity acting as a turbo-fuel for photosynthesis, and probably generates may oxygen radicals, overwhelming natral defenses and burning tissues.

Thanks Dana.
What about photoperiod? I've read some articles, one in particular about growth on galaxea fascicularis - sadly that's not an acropora- whose results show that 8h light with 150PPFD (light: KZ coralight T5 10000K) produced the same growth as 12h. With an equivalent DLI, 12h 150 umoles seems to be better than 8h 225 umoles.

https://www.researchgate.net/profil...n-an-aquarium-setting-A-matter-of-photons.pdf

In Your experience, aquarists (and You of course) do have better results with warmer light or bluer one? Me and many italian aquarists have always preferred warmer light to achieve better coral growth (I'm always speaking about SPS), while in the last years all across europe is diffusing bluer light over our tanks.
I personally have had poor results with ecothec radion LED fixtures, especially reducing white, red and green intensity. A bit better results with all channels 100%. But when shifted back to T5, tanks really started to improve.
In particular, I've observed that with bluer light, there is quick formation of bacterial-algal powder-like film on glass, that is spiked up by alkalinity. The more is quick and intense the formation of this film, the more is associated with polyp retraction and STN-RTN. Lowering alk to 6,5dKh help to reduce this phenomenon, but is just palliation. Raising alk to something like 8dKh makes easy to observe increased water turbidity (I assume there is bacterial-algal bloom, they are photreactive) and is more associated with diffuse RTN, if this condition is kept for some days (I tried that more than one times - with both LED or T5 light, using mostly actinic ATI T5 tubes). I find very hard to add food to tank (even to fishes): it increases again the issue.
A warmer light (10-14.000°K T5 or MH lamps) seems to prevent this phenomenon and allow to keep high alk level and add large amount of food. No quick formation of powder-like film on glasses, but just common algae. No RTN-STN.
Any information about this?

Thanks.

Luca

 

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Ok, but how could it be that in my experience, using blue-actinic light, 7dKh is already causing RTN-STN? (even with natural seawater level of nitrogen and phosphate). While with warmer light, alk can be kept at much higher levels and I can feed much more with no issue?
Excess of photosynthesis because of very efficient light (with the bluer one)? So should we keep much lower PAR if we use a very blue-UV light?

Thanks

Luca

 

[Dana Riddle]

Ok, but how could it be that in my experience, using blue-actinic light, 7dKh is already causing RTN-STN? (even with natural seawater level of nitrogen and phosphate). While with warmer light, alk can be kept at much higher levels and I can feed much more with no issue?
Excess of photosynthesis because of very efficient light (with the bluer one)? So should we keep much lower PAR if we use a very blue-UV light?

Thanks

Luca

I intend to investigate PUR values of various lights. A hypothesis: Intense blue light promotes photosynthesis better than warmer light and could overwhelm protection provided by carotenes and xanthophylls. I'll have to give the nutrient issue some thought. Hopefully someone will jump in with some thoughts on this.

 

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That's exactly what I'm thinking about. Bluer light could better promote PS. 100 umoles of blue photons could be more efficient than 100 umols of "full spectrum" photons.
It could be that my previous setup with 13 ati actinic + 5 ati purple tubes just above water level for 12 hours caused photoinhibition. Reduction of alk at a level insufficient to make PS could prevent coral harming from PS excess, but also affected growth.
A few weeks ago I have shifted to 12 ATI aquabluespezial tubes, 40cm above water level for 8h. Polyps are now very well expanded and growth is a bit better, but still poor. But no more biofilm on glasses and water crystal clear. PAR now stay in the range 180-280umoles. I suspect now PS is obviously present, but not optimal.
Today I have shifted again to 6 aqabluespezial + 6 actinic. I'll see what is the effect. And I plan to progressively increase light intensity (lowering the fixtures) and eventually shift back progressively to more actinic tubes, in order to see if I can improve coral growth, without have previous issues.
Maybe this could help providing some more data to discuss on.

Thanks.

Luca

 

[rushbattle]

I intend to investigate PUR values of various lights. A hypothesis: Intense blue light promotes photosynthesis better than warmer light and could overwhelm protection provided by carotenes and xanthophylls. I'll have to give the nutrient issue some thought. Hopefully someone will jump in with some thoughts on this.

I have an interesting anecdote: a number of experienced and successful reefkeepers have told me that "white" LED light "fries" coral tissue and that only blue, or almost all blue spectra is better for coral growth and health (holding for PPFD). In other words, blue LED light is less likely to bleach and harm coral tissue. The conversation above would lead me to believe it would be blue, narrow-wavelength LED would more likely "fry" coral than phosphor based LEDs. Others have said something else curious, white light with equivalent PPFD from MH or T5 is less likely to bleach coral than white LED.

Do y'all have any idea how these two ideas might be opposed, related, or just let me know I am way off track?

 

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rushbattle, in 20 years dealing with SPS, I have had great success with MH lamp. Good results with T5. Awful results with radion ecotech G3 pro. But I tried led only for 6 months. A friend of me, with a remarkable experience, tried Hydra52 with my same results. We both switched back to T5. I know a few old aquarists, that recently came back to MH. All italian MH users, always said me 10000°K lamps were better to grow healthy corals (XM 10000°k and BLV 10000°k were the most used; no radium users in Italy). Every time in the past (believe me, I tried it many times) i shifted to bluer light, I didn't succeed with SPS. In the last year I tried keeping blue-actinic light, but it has been a war. Too many casualties.
I would like to find answers. It's two decades I'm looking for certainties. I don't think I have any. The more experience I collect, the less I'm sure about what is better.

Luca

 

[Dana Riddle]

You have managed to confuse an old man (me) - doesn't take much. Is blue light good or bad in your opinion?

 

[rushbattle]

rushbattle, in 20 years dealing with SPS, I have had great success with MH lamp. Good results with T5. Awful results with radion ecotech G3 pro. But I tried led only for 6 months. A friend of me, with a remarkable experience, tried Hydra52 with my same results. We both switched back to T5. I know a few old aquarists, that recently came back to MH. All italian MH users, always said me 10000°K lamps were better to grow healthy corals (XM 10000°k and BLV 10000°k were the most used; no radium users in Italy). Every time in the past (believe me, I tried it many times) i shifted to bluer light, I didn't succeed with SPS. In the last year I tried keeping blue-actinic light, but it has been a war. Too many casualties.
I would like to find answers. It's two decades I'm looking for certainties. I don't think I have any. The more experience I collect, the less I'm sure about what is better.

Luca

That experience seems to be quite common, I’m wondering the causation. Seems like a photon is a photon at any given wavelength. I can think of a number of reasons the technologies are different and how that might effect the photons delivered to the coral tissue, but I am sure it is something more complex than what I am thinking.

 

[rushbattle]

Referencing Dana's post above

I am not sure what or whom you are referring to, but I can answer the question you ask. My answer is I don't have any idea.

I have had success with MH with T5 supplement, success with MH alone with very large reflectors, and not a whole bunch of success with LEDs that are very high coverage area over the tank. I'd love to know what factors were important in that difference, but quantum physics are completely beyond me. Dana you are my only hope. I do like the low heat output and controllability of light output with LEDs.

 

[Dana Riddle]

I am not sure what or whom you are referring to, but I can answer the question you ask. My answer is I don't have any idea.

I have had success with MH with T5 supplement, success with MH alone with very large reflectors, and not a whole bunch of success with LEDs that are very high coverage area over the tank. I'd love to know what factors were important in that difference, but quantum physics are completely beyond me. Dana you are my only hope. I do like the low heat output and controllability of light output with LEDs.

In case you haven't seen this article... Note that red LEDs and blue LEDs produced the highest rate of photosynthesis. Oddly, there was no protection by xanthophylls when exposed to red light (possibly bad to very bad to the health of zoox/corals.) What needs to be done now is an examination of photosynthesis when there is exposure to light generated by metal halide/T5 lamps.

 

[Dana Riddle]

Oops! Here's the link:
https://www.advancedaquarist.com/2014/5/aafeature

 

[rushbattle]

In case you haven't seen this article... Note that red LEDs and blue LEDs produced the highest rate of photosynthesis. Oddly, there was no protection by xanthophylls when exposed to red light (possibly bad to very bad to the health of zoox/corals.) What needs to be done now is an examination of photosynthesis when there is exposure to light generated by metal halide/T5 lamps.

I have seen this article, wonderful work thank you! Actually, this is what is confusing me. In your experiment the more orange and green as a fraction of total flux, the lower the photosynthesis. This makes perfect sense to me and you point out why in the article. What I don't understand is orange and green light from metal halide bulbs and T5 bulbs doesn't seem to be a problem, but the phosphor LEDs with output at those same wavelengths have a reputation for causing issues. Seems like if it isn't spurring xanthophyll protection or photosynthesis, it should just reflect off of the coral tissue and not have much impact on coral health.

 

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Dana,
can You tell if have any experience/observation about how long it takes coral to retract their polyps in case of photoinhibition?
In the past, I think I've observed that a poor man sign of photoinhibition could be polyp retraction (or at least not optimal polyp extension - I know polyp can retract for thousand combined motivations). It typically happened in my tank within 2-3 hours from photoperiod start, but I don't know if this effect requires long time adaptation (days), or it is immediate (the first time coral is exposed to excessive light).

As I said, my previous t5 tubes combination was 13 actinic + 5 purple. I could have missed guessing actinic tubes were the problem, while instead purple ones where delivering too much red light harming corals.
I'm now shifting back progressively from aquabluespezial tubes to actinic and blueplus, avoiding purple tubes.
My question is practical: how many days it takes before corals retract their polyps if light is harmful? the same day new light is applied? or it could takes more days? (alk is kept steady at 7 dKh).

Thanks.

Luca

 

[Dana Riddle]

Dana,
can You tell if have any experience/observation about how long it takes coral to retract their polyps in case of photoinhibition?
In the past, I think I've observed that a poor man sign of photoinhibition could be polyp retraction (or at least not optimal polyp extension - I know polyp can retract for thousand combined motivations). It typically happened in my tank within 2-3 hours from photoperiod start, but I don't know if this effect requires long time adaptation (days), or it is immediate (the first time coral is exposed to excessive light).

As I said, my previous t5 tubes combination was 13 actinic + 5 purple. I could have missed guessing actinic tubes were the problem, while instead purple ones where delivering too much red light harming corals.
I'm now shifting back progressively from aquabluespezial tubes to actinic and blueplus, avoiding purple tubes.
My question is practical: how many days it takes before corals retract their polyps if light is harmful? the same day new light is applied? or it could takes more days? (alk is kept steady at 7 dKh).

Thanks.

Luca

I don't think that there is a simple answer here. Many observations I've made were without the benefit of analyses via instrumentation. In some cases, corals responded positively to what I believe was light intensity enough to cause photoinhibition, and a day or two later polyps failed to expand. Was this a case of lack of an insufficient xanthophyll pool, or a case of chronic photoinhibition where polyp retraction is an effort to self-shade the zoox? In addition, water motion comes into play. I read a research paper years ago that suggested corals would not expand polyps if they sensed insufficient food particles and conserved energy by not expanding polyps.

 

[dantimdad]

I think part of the issue you are having with switching to a more blue light is one we have been covering in other threads (hence the need for a central thread to discuss spectrum related to PUR/PAR). That is that many commercial lights try to shotgun hit a bunch of spectrums to look good to the human eye. They constantly include equal amounts of white/Royal blue/windex blue which is silly and wasteful.

This causes people to lean very heavily on just RB. This, in turn, causes a huge amount of energy around one chlorophyll peak and thus, bleaching as in your experience.

I have come up with an array that has been built by theatrus and is on it's way to me to be tested that include NO white light at all.

I am betting that I will get a much more even spread across the growth spectrums and look really nice doing so.

It will take a while, obviously to get the results, but, it also took quite a few years of my time to come up with a spectrum that I think will work.

The other thing I am hoping is that, with few channels and less complication, this will in the long term make a commercially viable setup that is much less expensive than the options available today and will last a lot longer due to not having to be overdriven to reach PAR/PUR goals.

 

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Dana,
is it right that using a light source made only of a narrow spectrum as for 450nm LED, ora maybe ATI actinic t5 tube (not so narrow as LED, but not full spectrum as an aquabluespezial tube) photosynthesis can be saturated as well (I mean reaching maximum ETR, photosynthesis yield)?
And if theory is correct, a blue light is "safer" because there is the energy shunt (in case of excess of light) that lacks for red light?

Sorry if my terms are uncorrect or poor... but I'm trying to detangle myself in a field I only know thank to your articles and in a foreign language.

Thanks.

Luca