For Advanced Hobbyists - Importance of Green Light in Photosynthesis

[rockskimmerflow]

Hi

Together with David and Björn (from the Maritime Museum & Aquarium Gothenburg) can I present some rather primary results according to oxygen production of three different species hard corals. The oxygen production is a result of photosynthesis; hence you can use production during a certain time as an estimate of photosynthesis rate. We use small enclosed plastic containers with water and corals inside. Before closing – oxygen level was measured. The container was placed below 6 monochrome LED sources (400, 420, 450, 530, 630 and 660 nm) and below a white LED of 6500 K. PAR level for all 7 tests was adjusted to 90. After 2.5 Hour – The containers was open up, and a new measure of oxygen take place. For Seriatopora hystrix and S. caliendrum the weight was taken and for Montipora – the area was calculated. From this – an oxygen production per weight and hour (S. hystrix and S. caliendrum) was calculated and for Montipora sp oxygen production per square cm and hour was calculated. The result are shown in the graphs below.

Interesting test. I appreciate you contributing the data and research. I am curious, however, if the fact that the PAR was adjusted to be equivalent across all monochromatic and the single blended white LED sources somehow skewed the actual amount of light energy greatly between the light types. I can imagine a 400nm LED was absolutely blasting the sample with photon energy compared to the 6500k LED adjusted to that same 90 PAR set point. Since PAR is already a scale that weights light spectra differently based on a preset photosynthetic response curve, wouldn't using it as part of the baseline metric when testing monochrome LED sources undermine the magnitude of any contrasts we were hoping to see between the spectra.

Were all lamps driven at the same wattage? Or was their height above the same simply adjusted to achieve desired PAR level for the test? Any spectrometer data on the lamps used as well? I'd be super interested to see what sort of bandwidth a 400nm LED actually covers. It's always important to know how much real spectral range we're working with despite the sticker on the lamp that might say 400nm etc.

 

[Sallstrom]

Interesting test. I appreciate you contributing the data and research. I am curious, however, if the fact that the PAR was adjusted to be equivalent across all monochromatic and the single blended white LED sources somehow skewed the actual amount of light energy greatly between the light types. I can imagine a 400nm LED was absolutely blasting the sample with photon energy compared to the 6500k LED adjusted to that same 90 PAR set point. Since PAR is already a scale that weights light spectra differently based on a preset photosynthetic response curve, wouldn't using it as part of the baseline metric when testing monochrome LED sources undermine the magnitude of any contrasts we were hoping to see between the spectra.

Were all lamps driven at the same wattage? Or was their height above the same simply adjusted to achieve desired PAR level for the test? Any spectrometer data on the lamps used as well? I'd be super interested to see what sort of bandwidth a 400nm LED actually covers. It's always important to know how much real spectral range we're working with despite the sticker on the lamp that might say 400nm etc.

The white 6500K is done only because we can do it

We tested PAR under all lamps and adjusted them to 90. We also meassured wattage for each lamp, they are not on the same wattage. We wanted to see O2/g/W also.

I think Heliospectra ( which is our partners in this project and we use their research lamps) have the teh curves for each LED type in the lamps.

This is just preliminary results.

/ David

 

[rockskimmerflow]

The white 6500K is done only because we can do it

We tested PAR under all lamps and adjusted them to 90. We also meassured wattage for each lamp, they are not on the same wattage. We wanted to see O2/g/W also.

I think Heliospectra ( which is our partners in this project and we use their research lamps) have the teh curves for each LED type in the lamps.

This is just preliminary results.

/ David

Ahh thank you for confirming. I worry that setting the PAR equivalent rather than radiant watts will make the results much less valuable in terms of observed spectral photosynthetic preference in the given hard coral specimens. To my mind using a radiant watt measurement in the 360nm-700nm and setting each lamp to equivalent radiant watts in that spectral range would be the most 'objective' way to observe spectral photosynthetic bias in this type of experiment.

Best of luck with the future of your research. I enjoy hearing the results of unique tests such as this.

 

[Lasse]

We use a Li-Cor PAR meter in the test and it will give the right values of photon flux in the range 400 - 700. We are adware of the problem in the 400 nm where we have an underestimation of the photon flux. But - in spite of this - the 400 give lower oxygen production than expected.

This is not the report - it will come later on - but findings is important in this thread that deals with green wavelengths - that´s the reason why we publish the graphs before the report.

Sincerely Lasse

 

[Lasse]

I´m nor sure that watts/m2 is the best way of handle this according to photosynthesis. For me - its more interesting to know how many photons that reach the surface. (umol/squaremeter and second) These energy packets needs to be converted to the energy quanta of 680 and 700 nm in order to have the photosynthesis to work. I think that our charts show this - in spite of the fact that photons of the shorter wavelengths have higher energy quanta - the photosynthesis of different wavelengths is rather alike. As I see it the lost energy from a photon of 400 nm in the converting process to an energy quanta equal with 680 or 700 is waste energy (heat energy) As I know - no photon will be split into two energy packets (read photons) in this process. I wish it should be that way - cause it should be easier to explain some things - but I have never heard about it.

However - it could be good to be able to measure umol/square meter and second between 360 and 800 nm

Sincerely Lasse

 

[Stigigemla]

For me it is natural to use the photon flux for such measurements. I am not surprised to see the results. There were some results around about year 2000 showing similar results.
Now I want to see how the corals adapt to different light spectra. How they do grow after 2 months adaption time in the different spectra?

 

[Dana Riddle]

My 2 cents worth - I appreciate these researchers using PPFD, as this is more meaningful to hobbyists. The energy level of the photon matters not in photosynthesis.

 

[oreo54]

For me it is natural to use the photon flux for such measurements. I am not surprised to see the results. There were some results around about year 2000 showing similar results.
Now I want to see how the corals adapt to different light spectra. How they do grow after 2 months adaption time in the different spectra?

As interesting as that is doing monochromatic long term studies is somewhat pointless from a practical sense..
nobody would run monochromatic light sources.
Secondly, and using terrestrials, even bi-chromatic (660/560) light has already shown to be "insuffient" in many areas..

BTW if PAR was adjusted to 90 for every band the 400 is even worse, since a portion of PAR is un-recorded..

Once they start pairing some of these together.. that will be more "practical"..

Sadly.. ignored cyan again...

 

[Lasse]

BTW if PAR was adjusted to 90 for every band the 400 is even worse, since a portion of PAR is un-recorded..

We know - the photon flux was probably the dubble for 400 nm.

Sincerely Lasse

 

[rockskimmerflow]

I´m nor sure that watts/m2 is the best way of handle this according to photosynthesis. For me - its more interesting to know how many photons that reach the surface. (umol/squaremeter and second) These energy packets needs to be converted to the energy quanta of 680 and 700 nm in order to have the photosynthesis to work. I think that our charts show this - in spite of the fact that photons of the shorter wavelengths have higher energy quanta - the photosynthesis of different wavelengths is rather alike. As I see it the lost energy from a photon of 400 nm in the converting process to an energy quanta equal with 680 or 700 is waste energy (heat energy) As I know - no photon will be split into two energy packets (read photons) in this process. I wish it should be that way - cause it should be easier to explain some things - but I have never heard about it.

However - it could be good to be able to measure umol/square meter and second between 360 and 800 nm

Sincerely Lasse

Yes a umol/m^2/s would be a measurement Id be interested in seeing. Also maybe try driving the lamps all at the same wattage and distance from the sample, then recording the disparities between the photosynthesis rates. This would really expose the weakness in certain spectra when provided with equal input wattage across the board. Of course, this assumes similar physical construction across all your LED emitters. Id be curious to see those results. Thank you for the explanation of the intial test methodology.

 

[Lasse]

Yes a umol/m^2/s would be a measurement Id be interested in seeing.

It´s exactly that PAR gives but only for wavelengths between 400 and 700 nm. If we take 450 nm LED – the PAR will reflect all a umol/m^2/s – the same for all other except for 400 and a small part of 420 nm LED. We also use a PAR meter that show right values in the blue spectra

Sincerely Lasse

 

[rockskimmerflow]

It´s exactly that PAR gives but only for wavelengths between 400 and 700 nm. If we take 450 nm LED – the PAR will reflect all a umol/m^2/s – the same for all other except for 400 and a small part of 420 nm LED. We also use a PAR meter that show right values in the blue spectra

Sincerely Lasse

Yes, it's just that the 400nm LED might not be accounted for when we're only looking at a range from 400nm and up in a PAR type measurement. I just think if we're going to include a sample spectra we may as well be able to measure it's output additionally so that the PAR system does not underrepresented the amount of energy it's emitting with regard to a given photosynthesis measurement. I agree that the 90 PAR setting actually helps it appear more favorably in this test and I'd be curious to know what sort of radiant energy total we'd be looking at compared to the 450 nm which is clearly captured in the PAR range.

 

[Lasse]

We will try to publish the work later on in a special thread - we can take all of these discussion there. I published it here just in order to stress the importance of green wavelengths - the issue of this thread - so let us go back to that for this thread.

Sincerely Lasse

 

[oreo54]

Just in case it wasn't noted earlier.. Thanks for the work. Much appreciated..

 

[taricha]

that's pretty fantastic that you could show that green 530 wiggles the light harvesting complex of those corals in a way that's not insignificant compared to the "important" wavelengths.
It makes me think of papers I've seen where people were trying to show that coral fluorescence was beneficial in that it kicks light around into other wavelengths that could be used by the coral. But it seemed like they failed to find evidence of the usefulness of emitted fluorescent light to the coral.
Or maybe I'm misremembering.

 

[Lasse]

that's pretty fantastic that you could show that green 530 wiggles the light harvesting complex of those corals in a way that's not insignificant compared to the "important" wavelengths.
It makes me think of papers I've seen where people were trying to show that coral fluorescence was beneficial in that it kicks light around into other wavelengths that could be used by the coral. But it seemed like they failed to find evidence of the usefulness of emitted fluorescent light to the coral.
Or maybe I'm misremembering.

Thank you - and your have a good memory - see attached file - its new

Sincerely Lasse

 

[taricha]

Thank you - and you have a good memory - see attached file - its new

Sincerely Lasse

Nice! Still got that fresh research smell.
Eye-opening too!
It looks like the argument from green leaves actually holds up quite well: but tweak the analogy - instead of green leaves allowing green light penetration deep in the tissue, brown zooxanthellae allow "brown" light (green, red, and between) to go deep in the tissue.

Much better tissue penetration from 520 to 640nm.
It's really cool that it's worth it to a coral struggling in weak blue light to have fluorescent proteins that intercept some of the precious blue and kick it down to the longer wavelengths.
I also love that it took two years in low blue light to show that having this fluorescence was a survival advantage over the colonies that lacked it and died.

 

[ksed]

Am I reading this correctly? Therefore green red and between will make a coral look brown due to the enhanced brown zooxanthellae hence this is why we see the fluorescence pigmentation when running blue?

 

[Dana Riddle]

Some fluorescent proteins are excited by green light hence its penetration into coral tissues asks a bunch of questions. Lasse - do you have any corals plating to glass/acrylic/flat surface that could be chipped off and your leaf experiment repeated?

 

[mcarroll]

Nice! Still got that fresh research smell.
Eye-opening too!
It looks like the argument from green leaves actually holds up quite well: but tweak the analogy - instead of green leaves allowing green light penetration deep in the tissue, brown zooxanthellae allow "brown" light (green, red, and between) to go deep in the tissue.

Much better tissue penetration from 520 to 640nm.
It's really cool that it's worth it to a coral struggling in weak blue light to have fluorescent proteins that intercept some of the precious blue and kick it down to the longer wavelengths.
I also love that it took two years in low blue light to show that having this fluorescence was a survival advantage over the colonies that lacked it and died.

Jibes nicely with the results from The in situ light microenvironment of corals as well:

In situ spectral scalar irradiance at the upper surface of faviid corals—Spectral scalar irradiance at the upper surfaces of faviid corals (E
0) differed markedly from the incident downwelling irradiance (Ed; Fig. 3). Depending on the wavelength in the PAR region, the E0:Ed ratio varied between 0.8 and 2.4, with the most pronounced enhancement at wavelengths 500–640 nm and >680 nm (Fig. 3a–c).

That's roughly from Cyan to Orange....green and everything around it. Plus far red, obviously.

Also from the article (p.921), so you can see the "enhancement" they recorded from inside: