taking a break from LED

[newenglandreef]

This would help determine the true light output and efficiency of the light. Of course looking at the spectral curves is good to, but is tough it becomes tough to make quantitative comparisons.

this is an issue that I've posted up on RC and haven't really gotten a good answer from. We know that coral are getting enough energy--because just about everyone reports excellent coral growth with LED's--in many cases, better than MH/T5. But many experience problems with color. So if the coral are getting sufficient energy, and we're compensating for any missing reflective spectrums, then what's missing? What are corals not getting that they are getting from MH/T5?

 

[Pat02026]

Forgive my ignorance, but this came to mind brought about by newenglandreef's last post; the depth of water at any given point does what to the source lights spectrum? Does it filter out certain colors that are only capable of penetrating to a certain depth, or does it have the ability to alter the spectrum either higher or lower, favoring the blues/greens? Or is it that both and more of these things are happening.

The majority of our tanks' water level remains constant throughout the day. In nature, the water level varies with tide. Even though corals in the wild receive the "same" spectrum of the sun on a daily basis, how much does that change with the change in water depth of the daily tide cycles. Sorry if I'm being a little basic or off topic from this thread but its a good read and I feel it's a productive conversation.

Edit: you guys are too quick for me lol I was referencing post #99 fwiw

 

[inverted]

this is an issue that I've posted up on RC and haven't really gotten a good answer from. We know that coral are getting enough energy--because just about everyone reports excellent coral growth with LED's--in many cases, better than MH/T5. But many experience problems with color. So if the coral are getting sufficient energy, and we're compensating for any missing reflective spectrums, then what's missing? What are corals not getting that they are getting from MH/T5?

One thing to consider is coral color and growth are somewhat separate. This all starts to get pretty confusing, but light effects coral zooxanthellae and this can gives the coral more energy. This can be good, but can also be a source of stress as zoox byproducts aren't always tolerated well by corals. So, a lot of pigments seem to be to prevent zooxanthellae from growing too fast and working too efficiently. Certain environmental stress too, such as competition between corals for space though, can initiate growth in corals. So, there's all sorts of factors going on, sometimes these are good and other-times, the same factors may be bad.... Whether or not the coral can "handle" it I guess depends on the corals "health" which may be another factor all together.

 

[newenglandreef]

Many divers (myself included) report that corals are nowhere as brilliant in the ocean as in our tanks. If you ever dive, unless you use flash photography, everything looks blue/green, and I've learned when I was dive certified, that at least visually, mostly only green and blue penetrate to an atmosphere of depth. Here's a photo I took with a crappy underwater (disposable) camera with no flash at about 90 feet of depth last Spring in the Bahamas:

Large Image Link (272 kB)

 

[inverted]

Forgive my ignorance, but this came to mind brought about by newenglandreef's last post; the depth of water at any given point does what to the source lights spectrum? Does it filter out certain colors that are only capable of penetrating to a certain depth, or does it have the ability to alter the spectrum either higher or lower, favoring the blues/greens? Or is it that both and more of these things are happening.

The majority of our tanks' water level remains constant throughout the day. In nature, the water level varies with tide. Even though corals in the wild receive the "same" spectrum of the sun on a daily basis, how much does that change with the change in water depth of the daily tide cycles. Sorry if I'm being a little basic or off topic from this thread but its a good read and I feel it's a productive conversation.

Edit: you guys are too quick for me lol I was referencing post #99 fwiw

I posted this before. It discusses spectral qualities and changes in light with tide etc...
http://www.advancedaquarist.com/2009/5/aafeature

Also, another thing to consider is turbidity, sort of the amount of "stuff' in the water. This kind of "dust" can also change spectral qualities of light and varies on different reefs.

Here is sort of a general graph of light you may expect on a reef. Interestingly intense "red" is basically gone by about 3 meters. Also UV drops off pretty quick. Blue penetrates the furthest. So, yeah, most reefs are pretty monochromatic.

 

[newenglandreef]

One thing to consider is coral color and growth are somewhat separate. This all starts to get pretty confusing, but light effects coral zooxanthellae and this can gives the coral more energy.

so you're saying that, even if all factors other than lighting appear to remain constant, that it's still difficult to assess the affect that LED has on coral color and growth, because factors we cannot measure may be adversely affecting the coral?

 

[inverted]

so you're saying that, even if all factors other than lighting appear to remain constant, that it's still difficult to assess the affect that LED has on coral color and growth, because factors we cannot measure may be adversely affecting the coral?

Well, in the scientific world, we have repeatability and reproducibility. Kind of sort of, this means that we want to be able to hold as many variables constant as possible and obtain results, on repeated measurements, that are the same (or statistically the same). And also want to see that they are reproducible, on different trials, by different scientists, with changes in environmental variables. Tougher to do in the hobby though, but the more people that detail their experience the better certainly.

 

[newenglandreef]

I guess what I just don't understand--and there may not yet be an answer to this--is, if a light source is only providing energy in the form of a wave--and nothing more--then what could the MH/T5's be providing that the LED's are not? Is it the specific spectral recipe the corals are used to, which would imply that the coral will eventually acclimate to the LED's? Or is there something other than waves of energy? Is it possible that LED's are providing far more PUR than the corals are used to, which is causing the fading? I know that I've read many--mostly anecdotal--reports of identical systems (including nutrient load) that have much different coloration between MH/T5's and LED's. There may not be an answer to this, I understand.

 

[dz6t]

I will stay away when quantum physic is brought up...just kidding.

The way LED generate light is very different from metal halide.

Metal halide generate thermo radiation (same as the sun) which produce continous spectrum.

LED generate light by electroluminescence and the color of the light is determined by the energy gap of the semiconductor (which is a fixed value for a given LED), which produce very narrow band of spectrum as it should.

In theory, LED can mimic metal halide closely...with hundreads of them each at a single wavelength.

 

[dz6t]

I want to bring up a point that seems lost in all the discussion:
A lot of coral are highly adaptable to light. If you want pretty color and don't care how fast they grow, LED is a perfect choice.

If your goals is to grow corals, metal halide is still the best choice right now until may be the continous wavelength LED chips become afforable.

LiveAquaria claimed to be the largest aquaculture operation in US. They use metal halide in their facility.

 

[dz6t]

In this hobby, the PAR meter is an "unscientific" device. For example, one can design a LED light that can zap the PAR meter to death but it does not mean the light is better for coral. Another thing is the TDS meter, but that is another can of worm to open.

 

[inverted]

LED generate light by electroluminescence and the color of the light is determined by the energy gap of the semiconductor (which is a fixed value for a given LED), which produce very narrow band of spectrum as it should.

This is only partially true. It is true of colored LEDs, such as Blue, Royal Blue, Green, etc... This is not true of "White" LEDs, which produce light almost identically to fluorescent lights and even use the same phosphors. So, "White" LEDs are basically equivalent to "White: fluorescents as far as spectrum.

Heck, you will never find a MH in the hobby with a wide spectral output, like this CREE Neutral White (Blue Line).

 

[inverted]

if a light source is only providing energy in the form of a wave--and nothing more--then what could the MH/T5's be providing that the LED's are not?

Most likely just different spectral output.

Is it the specific spectral recipe the corals are used to, which would imply that the coral will eventually acclimate to the LED's?

In my experience, yes. At least shallow water corals, to narrow light. However, I think there is more to lack of light, sometimes, I think there is too much light. Corals can produce pigments to protect against light, but not necessarily if they are from an environment that is too deep to get certain spectrums. Danna Riddle, also did some work, and came up with his "red light" hypothesis. That was that certain corals have no protection against red light, because it is mostly filtered out within the first 3 meters of water. So, these deeper water corals are more easily damaged by red. LEDs, don't usually have much red, but the white LEDs (as the graph above shows) can have a lot more green and yellow than most metal halides used in the hobby. Is this a problem? Who knows, everyone keeps regurgitating the line that LEDs have a narrow spectral response LOL (not when your talking about white LEDs, with the exception of violet and some dark red)...

Or is there something other than waves of energy?

Some people think that the direction of light can be a problem. With a light, like a T-5, you get more diffuse light and more of the corals tissue may be exposed to light. So, maybe some of the tissue dies off when under LEDs, as it is no longer illuminated. I guess this decaying tissue could also lead to infections, and weakening of the coral as it adjusts. Although, halides are also pretty directional (but still not as much), so again, tough to say.

[/QUOTE] Is it possible that LED's are providing far more PUR than the corals are used to, which is causing the fading? [/QUOTE]

Maybe, PUR varies by coral though, you can't generalize PUR to all corals, as it depends on the zooxanthellae clade and the zooxanthellae pigments, as well as the corals pigments. This will vary by coral and the same coral can even have different zooxanthellae, sometimes it can even change zooxanthellae.

 

[inverted]

This article discusses the "red light" hypothesis.
http://www.advancedaquarist.com/2004/7/aafeature

 

[me2003]

There is a lot of misinformation in this thread. This is partially because not all the answers are known.
MAA involved with UV protection are clear and I have never seen a dinoflagellate in coral that was not
golden brown. This is a good article to get a start on where the research is

mycosporine-like amino acids
Gene Expression in the Scleractinian Acropora microphthalma Exposed to High Solar Irradiance Reveals Elements of Photoprotection and Coral Bleaching

http://www.aslo.org/lo/toc/vol_44/issue_7/1667.html


MAAs comprise a family of some 20+ small, colourless, cytosolic compounds containing either cyclohexenone or cyclohexenimine, UV-absorbing chromophores conjugated with the nitrogen substituent of an amino acid or imino alcohol. MAAs have been isolated from marine cyanobacteria, unicellular algae and intertidal seaweeds, as well as a wide range of sessile invertebrates having diverse photosymbionts, including symbiotic corals


http://www.aslo.org/lo/toc/vol_44/issue_7/1667.html


Initial results from PCR amplification using sequence-specific primers are remarkable because they suggest that enzymes to complete MAA biosynthesis are located not in the algal (dinoflagellate) endosymbiont as would be expected from MAAs having a precursor from the iconic shikimic acid pathway known in plants and microorganisms, but rather in the coral host. That is, essential MAA-biosynthetic genes identified in the symbiome of A. microphthalma appear lacking in cultured Symbiodinium symbionts (clade D) but were found in the spermatozoa of the congeneric coral A. millepora (Figure S3). Only symbiotic dinoflagellates of clade A synthesize MAAs on exposure of cultures to UVR [36], although Symbiodinium spp. of all clades do contain MAAs when in symbioses with cnidarians

 

[me2003]

If you want to measure spectral response of light this spectrometer and optic cable is a good deal.
http://www.vernier.com/products/sensors/spectrometers/svis-pl/
http://www.vernier.com/products/accessories/svis-fiber/
You can also use the spectrometers in chemical test as a color meter.
Although you would have to calibrate with standards

 

[inverted]

There is a lot of misinformation in this thread. This is partially because not all the answers are known.
MAA involved with UV protection are clear and I have never seen a dinoflagellate in coral that was not
golden brown.

MMAs are clear. GFP isn't and is involved in clenching radicals and high energy electromagnetic radiation, such as UV. But the key is it isn't limited to UV. Also, dinofallegellates are golden brown, but to be fair, cyanobacteria may not be and in some cases, seems to be involved in symbiosis with corals, such as montastrea sp. I wish you wouldn't have posted the spectrometer though, too many things to spend money on....

 

[jselzler1]

Has there ever been any research on our lights polarization effect on corals. It is true that LED, MH, flourescent, and sun all emit random polarization of light. However any reflector added to the system tends to polarize the light in some manner. Any impacts?

Plus the light from scatteres in the sky is polarized. Many animals use this to navigate, sense time of day, etc. cam corals 3 - 30 m deep sense the sky polarization and if so, any reaction?

 

[me2003]

I don't know the answer to this question. It seems that the UVA range is important UVA 400 – 315 nm
for coloration. There are many variables by species etc. This seems to have a good short explanation.
http://www.reefresilience.org/Toolkit_Coral/C3b1_Genetic.html

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007298

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007995
Dan Riddles article seem to rule out MAA in the UVA region
http://www.advancedaquarist.com/2007/2/aafeature

I just bought a vernier spectrometer for the school may try on a cree xp-g over break

 

[me2003]

"Has there ever been any research on our lights polarization effect on corals"
I believe there is some research on the effects of glitter lines on corals
Ex.
http://www.advancedaquarist.com/2006/5/aafeature

This is a major difference between MH and T5
LEDs are a little more complex You can get LED as a point source (like MH)
ex http://www.ecoxotic.com/cannon-led-pendants.html
or
as a distributed source (like t5)
Ex http://www.marinedepot.com/Ecoxotic..._Fixtures-Ecoxotic-XX08102-FILTFILDLK-vi.html

And Ecotech is somewhere between these two.

There is also some discussion about the rainbow effect with LEDs