Par intensity versus duration

[Acroporaaddict]

I remember @Ryanbrs mentioned something in the Par meter comparison video about Ecotech comparing par intensity versus duration. For example 6 hours at 200 par could be the equivalent of 3 hours at 400 par. Has any research been completed on this? @Dana Riddle any thoughts or insight?

 

[Dana Riddle]

It depends upon the photosynthesis saturation point of the zooxanthella species/clade, plant, or alga. The saturation point is when increasing light intensity no longer promotes a higher rate of photosynthesis. The figure below show the rate of photosynthesis (the Electron Transport Rate, or ETR) of the zooxanthella found in the stony coral Montipora capitata. The numbers on the y-axis is the number of electrons (in micromole) moving between Photosystem II and Photosystem I. The x-axis is light intensity (PPFD, or PAR, if you will.) As can be seen, The rate of photosynthesis is at a maximum at a PAR value of about 200. Technically, the saturation point is at about 134 (this is the method used by phycologists in determining that point.) There are other roadblocks to directly comparing light intensities, but this is the easiest example.

 

[Dana Riddle]

It depends upon the photosynthesis saturation point of the zooxanthella species/clade, plant, or alga. The saturation point is when increasing light intensity no longer promotes a higher rate of photosynthesis. The figure below show the rate of photosynthesis (the Electron Transport Rate, or ETR) of the zooxanthella found in the stony coral Montipora capitata. The numbers on the y-axis is the number of electrons (in micromole) moving between Photosystem II and Photosystem I. The x-axis is light intensity (PPFD, or PAR, if you will.) As can be seen, The rate of photosynthesis is at a maximum at a PAR value of about 200. Technically, the saturation point is at about 134 (this is the method used by phycologists in determining that point.) There are other roadblocks to directly comparing light intensities, but this is the easiest example.

I remember @Ryanbrs mentioned something in the Par meter comparison video about Ecotech comparing par intensity versus duration. For example 6 hours at 200 par could be the equivalent of 3 hours at 400 par. Has any research been completed on this? @Dana Riddle any thoughts or insight?

I should have explained further. If you're simply looking at the number of photons falling upon a surface, then, yes, 6 hours of 200 PPFD is equivalent to 3 hours at 400. But if the Saturation Point is 200, then additional intensity is not beneficial and in fact could be harmful.

 

[User1]

So not to hijack but in the corals native environment there are tides then sunrise and sunset. How is that factored into the equation?

Controllers can probably replicate that somewhat better by ramp up, down, parabola's, etc. Some don't use them and just say at 0800 On 2100 Off, etc. Or does it not really matter.

 

[Acroporaaddict]

How does photoperiod play into saturation point? I'm sure if you light the coral under the saturation point, you can light it for too long is that correct? I was watching one of your presentations on lighting and you talked about DLI and if I remember correctly, the porites in the aquarium you were measuring was at 12.5. Is that a good number to shoot for for all corals or is it species specific? Do you happen to have saturation point numbers for some of the more popular acropora such as tenuis, millepora, granulosa etc?

On another note, the same presentation I mentioned above, you briefly spoke about the Purple Monster Acropora and how it was a super slow grower, but you had great color. Do you think having it under lower par would have produced better growth but poorer color? Or do you think the spectrum from the Iwasaki bulbs was the problem and that the Purple Monster would have grown faster at the same par but with a different spectrum?

 

[hart24601]

I should have explained further. If you're simply looking at the number of photons falling upon a surface, then, yes, 6 hours of 200 PPFD is equivalent to 3 hours at 400. But if the Saturation Point is 200, then additional intensity is not beneficial and in fact could be harmful.

How about when it comes to coloration? Does the 200 PAR for twice as long promote the same shift in colors, possibly due to stress, that many people such as myself notice in acros when putting them under quite high par?

 

[Dana Riddle]

How about when it comes to coloration? Does the 200 PAR for twice as long promote the same shift in colors, possibly due to stress, that many people such as myself notice in acros when putting them under quite high par?

If the coral can handle high intensity light (M. capitata - the Rice Coral - can't and was almost always bleached in shallow Hawaiian environments) light intensity/duration (best defined as the Daily Light Integral) can promote the coral's production of colorful proteins. Interestingly, color production seems closely tied to the photosynthetic Saturation Point in *at least some* corals.

 

[hart24601]

If the coral can handle high intensity light (M. capitata - the Rice Coral - can't and was almost always bleached in shallow Hawaiian environments) light intensity/duration (best defined as the Daily Light Integral) can promote the coral's production of colorful proteins. Interestingly, color production seems closely tied to the photosynthetic Saturation Point in *at least some* corals.

So there is no difference with production of colorful proteins between say 600 par for 4 hours or 200 par for 12 since the DLI is the same on a coral species that can handle that much light?

 

[Acroporaaddict]

So there is no difference with production of colorful proteins between say 600 par for 4 hours or 200 par for 12 since the DLI is the same on a coral species that can handle that much light?

I could be wrong, but I think at 600 par on some corals you will probably be close to photo inhibition which can be fatal.

 

[hart24601]

I could be wrong, but I think at 600 par on some corals you will probably be close to photo inhibition which can be fatal.

I meant really just for examples but I personally have kept quite a few types or coral around 600 PAR. More in the range of 500 though. Some lps at 300-400.

 

[Dana Riddle]

So there is no difference with production of colorful proteins between say 600 par for 4 hours or 200 par for 12 since the DLI is the same on a coral species that can handle that much light?

It seems that in may cases the Saturation Point must be exceeded before colorful proteins are produced. 200 for 12 hours won't do it, while 600 for 4 likely will (at least in my experiences dating back to the late 90's when we realized the amount of light required for colorful Acroporas held in the coral farm.)

 

[Dana Riddle]

I could be wrong, but I think at 600 par on some corals you will probably be close to photo inhibition which can be fatal.

In some cases that much light will prove detrimental. Depends upon the zoox clade/species and their tolerance of high (or low) light intensity.

 

[Acroporaaddict]

It seems that in may cases the Saturation Point must be exceeded before colorful proteins are produced. 200 for 12 hours won't do it, while 600 for 4 likely will (at least in my experiences dating back to the late 90's when we realized the amount of light required for colorful Acroporas held in the coral farm.)

Would that be lights on for only 4 hours at 600 par and then turned off? Or could you run 12 or so hours low par with a 4 hour window of 600 par. Speaking of an Acropora only tank

 

[hart24601]

It seems that in may cases the Saturation Point must be exceeded before colorful proteins are produced. 200 for 12 hours won't do it, while 600 for 4 likely will (at least in my experiences dating back to the late 90's when we realized the amount of light required for colorful Acroporas held in the coral farm.)

Thank you!

 

[User1]

I can probably google this but what sort of par are we talking about in some of the waters we keep coral from and at what depth? Just trying to see what 300 par in our reef tank middle is or compares to a coral at 25 foot depth on a typical sunny day off an Hawaiian beach...or is that not apples to apples.

 

[Dana Riddle]

These measurements were taken at noon at Honaunau, Big Island at noon.

 

[User1]

These measurements were taken at noon at Honaunau, Big Island at noon.

Thanks. That is what I was wondering and it is pretty interesting. While I don't think it directly correlates I was checking to see how the peak sun hour map compared that is typically used for solar power generation, etc. It says Kailuo-Kona is about 5 hours. At 40 feet you are still exceeding 500 par...

 

[oreo54]

[q

I remember @Ryanbrs mentioned something in the Par meter comparison video about Ecotech comparing par intensity versus duration. For example 6 hours at 200 par could be the equivalent of 3 hours at 400 par. Has any research been completed on this? @Dana Riddle any thoughts or insight?

Up to a certain light level DLI is strongly and positively related to the photosynthesis of a leaf, the relative growth rate of a whole plant and the productivity of a crop. Each type of plant has a different DLI optimum for growth. DLI also changes leaf morphology, allocation of biomass to leaves, stems and roots morphology, and the timing of flowering. DLI is directly correlated with plant quality, and a minimum amount of DLI is required for marketable horticultural plants. Measuring DLI over a growing season and comparing it to results can help determine which varieties of plants will thrive in a specific location.[5]

https://en.wikipedia.org/wiki/Daily_light_integral#cite_note-5

no reason to suspect much differences w/ corals..within reason


https://en.wikipedia.org/wiki/Daily_light_integral

 

[Dana Riddle]

Here's a quick exercise I did. If we take the maximum PPFD seen in the previous chart and assume a 12-hour photoperiod, it looks like this:

I then calculated the DLI for each 30-minute photoperiod, summed it and then worked the formula backwards. A continuous PPFD of 366 for a 12-hour photoperiod will match the photon flux a coral at this depth would experience. But there are caveats...

 

[JDowns]

But there are caveats...

Oh you and the cliff hangers!