Post About Wasteful Spectrum in LEDs

[jda]

I was browsing threads last week and swear that I saw some posts about some studies and findings that there is a lot of wasteful spectrum in LEDs... something about a Kessil having 300 PAR, but 100 of it was waste?

My memory is horrible and I apologize if I misremembered all of this, but does this ring a bell to anybody? I have searched through a few pages (quickly, albeit) and did not find anything.

TIA

 

[oreo54]

There are not really "wasted" photons w/ most normal photosynthetic organisms..though some spectral components are more efficient than others..
Probably saw a Seneye PUR vs PAR type discussion..

There are a lot of assumptions made in such discussions..some valid.. some just fluff.

That said.. PAR is a "standard" not an "absolute"... used to compare things using similar "rules"...
Has no relation to true biologic activity..

You could also say Kessil has 33% less PUR than PAR but so will any similar spectrum light based on some "decided upon" weighing of wavelength vs efficiency..
Depending on the organism it could be true... or not..

 

[jda]

Thanks. That is not exactly what I saw, but this is helpful.

I totally understand PAR, all of it's nuances, downfalls and everything... and take a lot of garbage for telling people to use it a tool, not the tool.

 

[mcarroll]

The numbers are always true. The implications are usually quite debatable. Folks like a horse race a lot more than a debate.

That said, I've never heard anyone argue there was waste light in "LED spectrum". (Which LED?? )

I've only heard that applied to the IR and heat generated by halide and T5 lights.

The funny thing about the whole concept is that most of the light that hits a coral can more or less be considered waste....for the most part they get their "fill" in a few hours and then spend the rest of the day defending themselves from light-inundation.

 

[Big E]

I'm going to preface what I posted below as how it relates to Acropora dominant systems.

I'm not sure waste is the right definition but in these white leds anything above the red straight line is waste.........the corals don't need it. The conundrum is you need it for our eyes in LED only setups so the whole tank doesn't look blue.

As you turn those whites up to meet the ambient level look you run the risk of frying corals. This has been an issue from day one with LED only setups. If you like the windex/ black light poster look then it's not an issue. It's why I believe overly blue dark tanks have become more popular with new reefers.....they had to run them that way to keep corals alive, growing & colorful.

It's also why hybrid LED/T5 setups are popular right now..........you can create what the corals want and satisfy the ambient look at the same time and it's easier to hit the sweet spot without trashing corals.

The best LED only tanks I've tracked seem to have the fixtures very high and run the blue, white, violets at 100%. At those levels the overall plot will look similar to a Radium bulb.

Another option is months of minor adjustments so the corals adapt. I'm not sure you can create the same results as the other system setups I mention above.

Bulbs can create the white look to our eyes because of tighter peaks in specific areas while still providing what the corals need.

Cree XPE white (blue line)

Cree XTE white (blue line)

There have been some LED manufacturers that have tried to do no white LED fixtures to alleviate this issue. Red, Green, blue mixed right can create the spectrum corals need and give a nice bright white/blue look.

 

[oreo54]

RGB mixed = white...
White LED are blue pump emitters (mostly) and red/yellow/green emitting phosphors.. Ratios of which determine K value..and spectrum spread.

Economy-minded hobbyists and coral farmers may find this especially useful. It appears that light intensity and relatively simple light measurements alone adequately judge lamp efficiencies within the context of zooxanthellae photosynthesis. This should not be construed to mean that all light sources are adequate for reef aquaria use.

The spectral signatures obtained with the spectrometer demonstrate that these two metal halide lamps are full spectrum (though the 12,000° K lamp output is skewed towards the blue portion of the spectrum) and most resembles the "white light" category defined by Kinzie et al. (1984). Results garnered with the PAM meter suggest these two lamps are more or less equally efficient in the promotion of photosynthesis when PPFD values are the same.

It is inappropriate to claim that there are no major differences among the plethora of lamps available and their abilities to promote photosynthesis. Certainly the depreciation of overall lamp light output (PPFD) should be considered and readers are encouraged to review the works of Joshi and Morgan (1998; 1999, 2000) and others. Future experiments involving spectral quality and its effects should include more data points, different lamps and perhaps different coral species. Clearly, more work is required before we have an answer to the "best lamp" question. For now, it appears that spectral quality might be subordinate to lamp intensity

don't "need" is not the same as "can't use"...................

 

[oreo54]

The funny thing about the whole concept is that most of the light that hits a coral can more or less be considered waste....for the most part they get their "fill" in a few hours and then spend the rest of the day defending themselves from light-inundation.

not to mention photon "efficiency".. Only a few are "captured".
the lower the energy (blue,higher..red,lower) the more likely it's "trapped"...
at least that is how I understand it:

 

[jda]

I have heard a few people argue that there is waste spectrum LEDs, similar to what is described above with peaks that are too high. When we put Radion G3 and Kessil in an Integrating Sphere, the blue spikes/peaks were many times higher (like 12-14x higher) than ones for the 20K Radium and 14K Phoenix. When I saw this phantom post that must of imagined (or saw on a different board), this came back to me and I wondered if this was just waste. I wish that we would have put them on the same graph and overlayed them - separate, they look similar with peaks in the same places when scaled to fit. We did find about 2% UV wasted (over 720) in the 20K Radium, but the machine stopped at about 2000nm. There were flat out gaps of 10-40 nm in both of the panels. Man, I need to go back the next time that I am at the Alma Mater and have another take at this.

 

[oreo54]

for fun...

http://onlinelibrary.wiley.com/doi/10.4319/lo.2006.51.6.2702/epdf

http://onlinelibrary.wiley.com/doi/10.4319/lo.2000.45.1.0076/epdf

see fig 4

and:

Yentsch (1982) demonstrated no stimulation of photosynthe-
sis (PSII fluorescence) when short-wavelength UV radiation
is absorbed. It is highly unlikely that the observed differ-
ences in the concentration of UV-absorbing compounds with
depth or between species are a result of any photoacclima-
tization strategy to capture photons in the UV portion of the
spectrum to drive photosynthesis.
Differences in photosynthetic

 

[Dana Riddle]

Funny you should ask. I have partially completed testing of a Kessil AP700. This luminaire has 9 spectrum settings on its keypad. In addition to spectral quality, PAR is different at each level. Now, if we measure PUR (with a Seneye unit, based on red-green-blue content if I understood Matthew correctly) we see PUR drop from about 80% (blue spectrum) to 65% (white spectrum.) To take this further, if we multiply PAR by PUR (in percent) we arrive at a better idea of how this lamp performs. This just done yesterday, so I don't any comparisons made with other light sources. There is a rub here however. UV LEDs (with some their output falling into a range not sensed by the quantum sensor but still usable in photosynthesis) skew these results.

 

[Dana Riddle]

 

[oreo54]

True UV doesn't contribute to photosynthesis.. much..
though the point is arguable..

will def defer to your info though..
But for discussion:

Additionally, work on dinoflagellates in culture by Yentsch and
Yentsch (1982) demonstrated no stimulation of photosynthesis (PSII fluorescence) when short-wavelength UV radiation is absorbed. It is highly unlikely that the observed differences in the concentration of UV-absorbing compounds with
depth or between species are a result of any photoacclimatization strategy to capture photons in the UV portion of the spectrum to drive photosynthesis.

not sure of their def of short wavelength UV though..Certainly will change pigments though..

 

[oreo54]

UV .. the slippery slope..
http://www.scielo.sa.cr/scielo.php?script=sci_arttext&pid=S0034-77442010000100008

A second treatment group was exposed to ultraviolet light (predominantly UV-B but including all UV-A wavelengths) using 6x8W UVR fluorescent lamps (λmax=310 nm, 5.23 Wm-2; Ultra- Violet Products, Ltd, UK). This group was covered with a 20x20cm cut-off filter which was used to attenuate the shorter wavelengths. The UVR value was similar to the average recorded in the morning on a clear day at the study site (5.7Wm-2), during the month prior to collection measured using a Mannix UV-340 ultraviolet light meter (290- 390nm).

However, the UVR-treated corals had relatively low levels of carotenoids relative to Chl a concentrations, indicating that UVR caused damage to both the light-harvesting photosynthetic apparatus and the enzymes involved in carbon fixation (Warner et al. 1999, Jones et al. 2000). The CPs/Chl a ratios were lower in the UVR-treated corals, which could indicate a relatively high degree of photooxidative damage (Hendry & Price 1993, Gonçalves et al. 2001). Thus, low ratios in this treatment may be related to the progressive decrease of carotenoid pigments (Table 1); this decrease could be a non-enzymatic first line of defense against the pro-oxidant activity of ROS. Carotenoids not only destroy singlet oxygen (1O2), which causes oxidative damage to various biomolecules, but also prevent the formation of chlorophyll triplets in Photosystem II due to high radiation (Douglas 2003). This may represent a molecular strategy to prevent damage to diverse molecules, as well as the photosynthetic membranes.

One a side note.. UV levels in all current lights is probably quite low as to be relatively insignificant.. for photosynthesis or damage..

 

[Dana Riddle]

Sorry to the photo size - this from Jeffrey et al. Phytoplankton Pigments in Oceanography (1997.) Chlorophyll a and peridinin show similar absorbance. I, too, wonder about Yentsch's protocol. The instrumentation in the 80's is crude by today's standards (standard fluorometer v. PAM.) I know of a lab that bought a fluorometer in the late 80's (maybe early 90's) to detect chlorophyll in water and they found the instrument to be unreliable. Perhaps Yentsch's protocol/results were spot on, but I would like to see the paper.

 

[jda]

UV is not insignificant in nearly all 14K+ MH bulbs and True Actinic VHO and T5 bulbs, if the charts are be believed. This is a pretty significant amount of their output. Anecdotally observed by many, the color changes quite a bit on the coral when introduced to these spectrums.

 

[Dana Riddle]

UV .. the slippery slope..
http://www.scielo.sa.cr/scielo.php?script=sci_arttext&pid=S0034-77442010000100008





One a side note.. UV levels in all current lights is probably quite low as to be relatively insignificant.. for photosynthesis or damage..

Agreed. The UV output of LEDs in aquaria lamps is low, but I'm not ready to say it doesn't have an impact (however small) on photosynthesis. I'll measure the impact of blacklight on coral photosynthesis using a PAM fluorometer when I get a chance.

 

[Dana Riddle]

Quote: We did find about 2% UV wasted (over 720) in the 20K Radium, but the machine stopped at about 2000nm.
I'm not quite following this statement. Help the old man out and explain please

 

[jda]

I took a Kessil 360, Gen 3 Radion, 14K Phoneix and 20K Radium (both run on M80) to use an integrating sphere at the Engineering School at the Alma Mater since I cannot afford one to just keep around the home - I mostly wanted to know the radiated watts of each vs the wall-power. The output in radiated watts of the 20K radium over 720nm was 2% of the total. The Phoenix was a bit more at like 3%. Both of the panels were about .4-.5%. The sphere was only 36", so we did not test any T5s.

 

[Dana Riddle]

There are not really "wasted" photons w/ most normal photosynthetic organisms..though some spectral components are more efficient than others..
Probably saw a Seneye PUR vs PAR type discussion..

There are a lot of assumptions made in such discussions..some valid.. some just fluff.

That said.. PAR is a "standard" not an "absolute"... used to compare things using similar "rules"...
Has no relation to true biologic activity..

You could also say Kessil has 33% less PUR than PAR but so will any similar spectrum light based on some "decided upon" weighing of wavelength vs efficiency..
Depending on the organism it could be true... or not..

That graph is one I copied from a reference into an Excel file years ago. I think Apogee uses it on their website, and I've seen it floating around elsewhere. It grew legs...

 

[Dana Riddle]

To muddy the aquarium water a little, spectrum cannot be separated from photosynthetic photon flux density - If intensity increases to the point that the protective xanthophyll cycle (dynamic photoinhibition) kicks in, some wavelengths that are beneficial at low PPFD are wasted (photosynthetically speaking.) If light intensity is so intense that the photosynthetic apparatus is destroyed, then all wavelengths are wasted. But that is not the intent of this thread's question, is it? We're discussing the impact (or non-impact) of, say, yellow wavelengths on photosynthesis?