Do actinics provide any value to corals?

[junkitu]

I have a modified aquapod 24 with 40W dual actinic and 40W daylight. Are the actinics purely aesthetic in value or do coral benefit from the light spectrum that they provide?

[$aint]

Taken from Drs. Foster & Smith, should help you out...

 

Natural conditions have caused all corals and invertebrates to adapt to bluer light. Therefore, most lighting systems include bulbs that focus specifically on blue wavelengths. Fluorescent systems, for example, offer blue bulbs called actinic bulbs. While most corals and invertebrates thrive under blue light, most people find blue-lit reef aquariums rather unattractive. This aesthetic dilemma can be solved by combining an actinic light with a white light. Most reef aquariums thrive under a half-and-half blue/white light combination in which the white lights give light in the range of 8000 to 12000 K. This lighting combination gives corals and invertebrates the spectrum necessary for growth, in addition to the spectrum necessary for accurate color rendering within the aquarium.

[Mr. Fosi]

^-- Good quote. Drs. F&S aren't always right, but I agree with them on this one.

[shaggydoo541]

For all intents and purposes actinic is purely aesthetic. It may provide a slight benefit for coral growth but actinics are mainly there for our viewing pleasure. They make the coral colors pop whereas the whiter/yellow light makes the corals grow.

[junkitu]

Sounds like mixed reviews on the replies. Any other opinions out there?

[proraptor2]

All opinions will be mixed on the subject...Ive seen comparisons in coral health that have showed that they do help but Im not so sure I believe them...

[junkitu]

All opinions will be mixed on the subject...Ive seen comparisons in coral health that have showed that they do help but Im not so sure I believe them...

Interesting. It seems like a fairly straightforward thing to study/test.

[supernip]

i think its kind of out of the scope of most members of this board. Its a matter how how the chloroplast uses different wavelengths of light to perform photosynthesis. I'd ask a biologist

[Mr. Fosi]

I'd ask a biologist

 

Agreed.

 

If I knew the spectrum that the lamp put out I could say more. The chloroplasts in zooxanthellae are attuned to blue(er) light (by using certain chlorophylls and accessory pigments). You can infer this not only from the depths to which they can live, but also by the absorption spectrums of the photopigments found in them.

[FateX9]

photosynthesis is affected by other factors not just light

paper written by dennison and barnes "Effect of water motion on coral photosynthesis and calcification" even with a little water motion growth increases by 65% compared to no motion

Also another paper by Reynaud et al "Effects of light and temperature on calcification and strontium uptake in the scleractinian coral Acropora verweyi"

they looked at intensity and temperature and found that higher intensity and temp resulted in higher growth (temps experimented were at 20, 25, and 29 celcius)

i dont have any papers on spectrum but ill look into it

[Keith_Man]

There will be enough of the blue spectrum in your daylight lamps for your corals. so for your purpose, the actinics is purely for aesthetics

[brshriver]

In “The Reef Aquarium, Volume 1” they talk about zooxanthellae in coral being most adapted to use the blue spectrum for photosynthesis because blue light penetrates water deeper than longer wavelength light. Blue actinic lights are targeted for this spectrum so they should help stimulate photosynthesis in zooxantellae. This is not to say that your 10K lights will not have enough of the blue spectrum in them for growth as indicated by Keith Man. I think $aint sums up why we use daylight spectrum lights quite well. His summary alines with what is written in “The Reef Aquarium, Volume 1”.

 

Fortunately, fluorescence in coral is triggered best by light in the blue/green range, which is why actinic lights cause corals to fluoresce more. The local marine society had a guest speaker this past month who studies this for a living (great work if you can get it - night diving with blue flashlights in the Caribbean ). He was showing off blue led flashlights combined with yellowish glasses that made the coral fluoresce like crazy with night viewing. The yellowish brown glasses filter out the blue light (yellow/brown is also the dominate color of zooxanthellae as well – which is why they absorb blue light so well) from the flashlight allowing you to see the light emitted by the fluorescing corals much better. The results are amazing. See attached pic of a doughnut coral and zoos in my tank using the blue led light and filter. This is one reason that actinic lights cause coral’s color to seem more colorful than straight daylight.

[shaggydoo541]

The reason I state that it is mainly for aesthetics is twofold. First, actinics put out a very narrow band of wavelengths that do make corals look better but do not in any way simulate natural sunlight. Since these corals have adapted to use sunlight (in its entire spectrum), shooting a narrow wavelength at them is obviously not going to get them everything they receive in nature; which ultimately is what we are trying to duplicate in our homes.

 

Second, look at people who use 20K bulbs (very similar to actinics in the amount of blue light they produce). Growth is almost always reported as lacking. If blue light was really what corals were 'fine tuned' to receive for photosynthesis than 20K bulbs should produce massive growth. The idea that corals need mostly blue light is bogus. Are red wavelengths absorbed first as light filters through water? Yes. Does that mean corals are only using blue light since the red light gets filtered out? Obviously not.

 

The fact of the matter is there are two many unknowns to really answer this question absolutely. But if you look at what is reported around the hobby it becomes fairly obvious that coral growth requires the full spectrum of light (white light) and that people who have the blue actinics/bulbs are using this blue light to enhance the coloration of their livestock not to promote the growth/health of said livestock.

[brshriver]

This link from the folks at wetwebmedia contains a lot of debate on the topic. Note that there are inconsistencies amongst the people at wetwebmedia on the issue. Most say that actinic lights are for aesthetics only and even go as far as to say not to count their wattage in your watts per gallon calculations. Others say that they are valuable because they help emphasize the blue spectrum – mentioning how zooxanthellae like the blue light waves. However, all opinions indicate that you need daylight bulbs for optimal growth. What is missing is a link to a controlled study comparing growth in tanks with just daylight spectrum bulbs to those with supplemental actinic bulbs. And as mentioned above by multiple people, 10K bulbs alone can light a successful reef aquarium.

 

http://www.wetwebmedia.com/marine/setup/li...actinicfaqs.htm

[Mr. Fosi]

photosynthesis is affected by other factors not just light...

 

Can you finish the citations on those (like journal title and year)? I'd like to read them and it'd be easier to find them in full-text format if I had that info.

 

Also, I am not sure that anyone claimed that there weren't other influencing factors. Obviously water flow, temp, and micro/macronutrient concentrations matter.

 

The origional question was:

 

I have a modified aquapod 24 with 40W dual actinic and 40W daylight. Are the actinics purely aesthetic in value or do coral benefit from the light spectrum that they provide?

 

The answer is: no, actinics are not purely aesthtic and yes, your corals will glean some benefit from them. In addition, the main reason that they are used is for aesthetic purposes, but this certainly does not cancel the fact that they are a source of some photosynthetically active (or availible) radiation.

 

If there is disagreement with this, data should be presented to back up those opinions.

 

EDIT: This is not a flame, it is a correction so please don't get mad. This statement: "Since these corals have adapted to use sunlight (in its entire spectrum), shooting a narrow wavelength at them is obviously not going to get them everything they receive in nature; which ultimately is what we are trying to duplicate in our homes." is patently incorrect.

 

Firstly, the corals are not adapted in any way to use sunlight. Corals are animals that are heterotrophes and it is their endosymbionts that have such photoautotrophic adaptations. This is more than a symantic argument because various corals are known to expell their crop of zooxanthellae and aquire ones that were previously not found in their tissue (Hughes et al 2003). It has also been hypothesized that corals be bleach and aquire endosymbionts that better fit conditions, such as higher temps (Buddemeier 1993). This means, that it is not a static light capture mechanism that we are discussing.

 

Secondly, many (I would go so far as to say most) corallite endosymbionts are not adapted to using the full spectrum of sunlight, because all but the blue, green, and purple wavelengths are attenuated within the first 4-5 meters of the water column. I think you know that most coral reefs composed of corals with photosynthetic endosymbionts have living, thriving corals deeper than 5 meters. IMO, so-called "full spectrum" or "daylight" lamps are just as much for aesthetics as actinics, for two reasons: 1) we like to see growth over short periods of time (weeks-months, not years) and 2) such lamps allow us to see all the pretty colors that we would not see if we were diving a reef at 20 meters.

 

Also, deep water coral growth is slow in the wild, of course it would be slow in a tank sporting only blue light. Yes, their endosymbionts will use more wavelengths of light if you give it to them, but they don't need it.

 

I know that this is a little esoteric, but a pic really is worth 1000 words. This is an amalgamation of two slides from the lecture from one of my current classes:

 

 

 

 

This particular class is taught by a phycologist. Not only does she know oodles about light in the ocean, but this information is all fairly common knowledge in oceanography and limnology circles. As you can see, water effectively attenuates the higher wavelengths from 700nm down to about 550nm (though that spectrogram is different from the ones I have seen in other oceanography and limnology books). You can also see that phytoplankton, of which zooxanthellae can rightly be considered a part of, absorb most efficiantly in the blue region.

 

I am not pretending to be an expert, I am only reporting the things that I have heard from experts. If I have to come up with papers to support this I will, but this is all basic oceanography info.

 

Hughes, T. P. Baird, A. H. Bellwood, D. R. Card, M. Connolly, S. R. Folke, C. Grosberg, R. Hoegh-Guldberg, O. Jackson, J. B. C. Kleypas, J. Lough, J. M. Marshall, P. Nyström, M. Palumbi, S. R. Pandolfi, J. M. Rosen, B. Roughgarden, J. (2003) Climate Change, Human Impacts, and the Resilience of CoralReefs. Science, Vol. 301. no. 5635, pp. 929 - 933

 

R. W. Buddemeier & D. G Fautin (1993) Coral beaching as an adaptive mechanism. Bioscience Vol. 43. No. 5 pp320-326

[shaggydoo541]

Can you finish the citations on those (like journal title and year)? I'd like to read them and it'd be easier to find them in full-text format if I had that info.

 

Not sure if this is the article he was referring to but this one applies to the statements made.

 

http://www.advancedaquarist.com/2006/9/aafeature2

 

You state that corals have not adapted to sunlight and this is true. They can and have been show to expel and uptake endosymbionts and these endosymbionts are in fact doing the majority of photosynthesis. But that is just dodging the question. These emdosymbionts have adapted to use the full spectrum (in the form of sunlight) so therefore there hosts require the full spectrum. Are there some endosymbionts that probably use just the blue light? Yes. Is it possible that there is an endosymbiont that utilizes each wavelength respectively? Biologically it only makes sense.

 

So naturally, if we provide a wide array of wavelengths we give more endosymbionts the energy needed to jumpstart photosynthesis and give the corals more options to survive. I highly doubt that every coral has the ability to envelop every symbiont and therefore if we provide only blue light what are the chances we have symbionts available to use the blue light??? On top of that, what about the chances our corals being able to take in said symbionts?

 

Again I will state there is not enough information to answer this question scientifically. There are way too many unknowns... what symbionts are compatible with what corals? What wavelengths provide stimulation to start photosynthesis in what symbiont? etc etc etc. So we can only rely on our experiences as hobbyists. Has anyone ever run an actinic only tank and had long term success? If so I have never heard of it.

[Mr. Fosi]

... these endosymbionts are in fact doing the majority of photosynthesis.

 

No, they are doing all the photosynthesis.

 

But that is just dodging the question. These emdosymbionts have adapted to use the full spectrum (in the form of sunlight) so therefore there hosts require the full spectrum.

 

How then do you account for corals with photosynthetic endosymbionts living at depths where only blue light is found? If they required the full spectrum they would die. In this case, any corals below several meters requiring photosynthetic supplimentation would be unable to survive or reproduce.

 

The attenuation curve of light in the ocean isn't something you can debate about. Too much evidence is stacked against you. As is the evidence of corals living at depths to which nothing but blue light penetrates.

 

Are there some endosymbionts that probably use just the blue light? Yes. Is it possible that there is an endosymbiont that utilizes each wavelength respectively? Biologically it only makes sense.

 

I never they only used blue light. I said that blue light is what they most efficiantly process.

 

So naturally, if we provide a wide array of wavelengths we give more endosymbionts the energy needed to jumpstart photosynthesis and give the corals more options to survive.

 

Of course, but survivability has never been in question, which makes this a distracting strawman argument.

 

I highly doubt that every coral has the ability to envelop every symbiont and therefore if we provide only blue light what are the chances we have symbionts available to use the blue light??? On top of that, what about the chances our corals being able to take in said symbionts?

 

Another strawman.

 

So we can only rely on our experiences as hobbyists. Has anyone ever run an actinic only tank and had long term success? If so I have never heard of it.

 

It is untrue that we have only experience to rely on. If that were the case, why reference the article you did in which experience plays virually no role?

 

Of course you haven't seen an actinic only tank, who would want one? If you can't see the colors of the corals, why keep them? Hence, daylight lamps are as much for aesthetics as anything.

[yomamaphat]

Woohoo for Mr. Fosi and the scientific method.

 

The endosymbionts should be responsible for all of the photosynthesis, or corals have chloroplasts, but why would they need xooxanthellae then? I would doubt there is an endosymbiont specializing in a single wavelength of light, even a narrow range of say + or - 25nm would be very odd I think, the environment doesn't provide a narrow range like this, therefore it shouldn't have been naturally selected for. Although I'll admit I'm not familiar with the diversity, in that respect, of the marine environment.

 

I think no one has run an actinic only tank because of aesthetics! I'd start to have acid flash backs (and I've never even done acid) after staring at my blatantly blue tank for hours. I think other wavelengths are needed too, I don't know all the reasons though. Most of the time things make sense from an evolutionary standpoint though. Since the ocean didn't evolve under a blue sun then its inhabitants may have evolved to rely on spectra other than blue.

 

And as always, to prove anything I've said we'd need to employ the scientific method .

 

EDIT: I replied as you did Fosi, I'd believe you over me, I'm a land scientist (budding) and you're a marine one. We both said aesthetics.

[junkitu]

Truly facinating! I really appreciate the thorough posts. I started this thread because I was worried that I may have been unknowingly making a tradeoff with respect to my corals health. After reading these posts I feel like there is likely some tradeoff but probably not enough to worry about as a hobbyist. Now if I were a biologist or aquaculturist maybe...

 

I'm curious, has anyone reading this thread ever run a tank both with and then without actinics for some period of time? For example, using two daylight bulbs in an aquapod instead of one daylight and one dual actinic. If so, did you notice any qualitative difference in your corals?

[brshriver]

Well, here is an article that is the closest thing that I could find to a scientific study on the topic:

 

http://www.advancedaquarist.com/issues/feb2002/Feature.htm

 

And I bet the person that asked the original question wanted a simple yes or no answer ;-)

 

The article suggests that intensity is more important than spectrum.

 

The summary paragraphs from the experiement follow:

 

This experiment’s results suggest information potentially valuable for hobbyists - that rates of photosynthesis were essentially the same under these two distinctly different light sources. Other than aesthetic value, there appears to be no advantage, photosynthetically speaking, in using high Kelvin lamps.

 

The implication of these results should be of interest to hobbyists; it suggests that lamp selection (with due regard to lamp intensity) may be based on appeal, whether that is price or the "look" it gives to a tank, without fear of hindering photosynthesis. 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.

[Mr. Fosi]

Since the ocean didn't evolve under a blue sun then its inhabitants may have evolved to rely on spectra other than blue.

 

Indeed, but the world is blue under the water.

 

I also agree that intensity is more important than spectrum, with one caveat: other, less desirable things may take advantage of lamp that puts out significant amount of red to orange light (read: cyanobacteria and other microalgaes). There is a reason, other than aesthetics, that people use 10000K lamps instead of 6700K over their SW aquaria.

 

Aquarium lamps (fluorescent and MH) are designed to emit different specra than your regular "cool" or "warm" white lamps because of both aesthetics and the desire to supress unfavorable photosynthetic organisms in the tank. MH lamps are much the same, but you would also have a hard time getting your typical coral or macroalgae to grow under a plain HomeDepot sodium or mercury lamp.

 

EDIT: Many people probably won't see a huge burst in growth when using both actinic and 10000K/14000K lamps in conjunction. In your case, you have only 80W total over a fairly deep 24g, so you need all the light you can get. If you want the tank to look brighter, you can add a 10000K lamp, but I wouldn't bother.

[FateX9]

Sorry for leaving out the journal info

didn't think anyone on here really read this stuff

Dennison and Barnes. "Effect of water motion on coral photosynthesis and calcification." J. Exp. Mar. Bio. Ecol. 1988. 115; 67-77

I haven't read papers in a while but I think the journal is Journal of Experimental Marine Biology and Ecology.

Reynaud, Ferrier-Pages, Boisson, Allemand and Fairbanks. "Effect of light and temperature on calcification and strontium uptake in the scleractinian coral A. verweyi." Marine Ecology Progress Series. 2004. 279; 105-112.

the main reason i said what i said is because it seems that people automatically think when keeping corals, lights are the most important thing, and even though they are extremely important they are useless in it self

maybe my assumptions were out of place but thats how i see it

here is also a little figure of light absorption

[Mr. Fosi]

the main reason i said what i said is because it seems that people automatically think when keeping corals, lights are the most important thing, and even though they are extremely important they are useless in it self

 

Conceded.

 

In case you are interested: http://www.nano-reef.com/forums/index.php?...c=87797&hl=

[shaggydoo541]

It is untrue that we have only experience to rely on. If that were the case, why reference the article you did in which experience plays virually no role?

 

That article had nothing to do w/ my post but a previous poster mentioned the effects of water movement vs light.

 

In order for me to believe that actinics are providing a major benefit to our corals I would need to see some documentation specifically regarding the question asked by the op. Which has not been produced because there have been no studies specifically taylored to this question. It makes sense that deep water corals do rely on blue light because this is the only light available. But who is to say that the wavelengths produced by the various actinic bulbs correctly simulates the same wavelengths produced by the sun at these lower depths? For all we know most actinics could provide the exact wavelength necessary or they could be a fraction off and be worthless to most corals.

 

Mr Fosi, your ideas are sound and I wouldn't be surprised if they are 100% true. But the research is not there to answer this question with any degree of authority. The unknowns are staggering. What wavelengths are most efficiently processed? Blue you say, but that is only at lower depths in the ocean... not in our aquariums. Who is to say that there are not some symbionts that more efficiently process the red spectrum vs the symbionts that use the blue, allowing the red absorbing symbionts to produce a higher yield of energy for the coral? Then, who knows if, when the red spectrum is present, corals will release the less efficient blue using symbionts and absorb their red counterparts because the red can give the coral more energy? Biologically it only makes sense to have the coral use the most efficient energy source based on the available spectrum, but what is the most efficient symbiont under various spectrums? All these questions plus thousands more would have to be answered before a definitive answer could be reached if we were relying solely on scientific studies.

 

Turn on your actinics in your tank and your corals will respond. Therefore they are definitely absorbing something from these lights. Therefore it would be safe to assume they are getting some benefit from the actinics or else they would not bother wasting the energy to react. But where is the majority of the growth reported in home aquariums? White light. Therefore what should we consider the most beneficial? White light. Could a study be presented to me that undeniably points to actinic lighting as being the ultimate lighting solution to our home aquariums? I'm open to this idea. Could we one day be lighting our tanks with a majority of actinics and only a small amount of white light purely for aesthetics? Sure, this hobby is changing everyday but I would let others test this new idea before I implemented it over my tank

[Mr. Fosi]

Therefore it would be safe to assume [corals] are getting some benefit from the actinics or else they would not bother wasting the energy to react. But where is the majority of the growth reported in home aquariums? White light. Therefore what should we consider the most beneficial? White light.

 

We agree then.

 

I never they only used blue light. I said that blue light is what they most efficiantly process.

 

... coral growth is slow in the wild, of course it would be slow in a tank sporting only blue light. Yes, their endosymbionts will use more wavelengths of light if you give it to them, but they don't need it.

 

Why would you want to see a study that "that undeniably points to actinic lighting as being the ultimate lighting solution to our home aquariums"? This is not an argument that has been made in this thread...

 

Let's not forget that efficiancy doesn't mean better, it means competency in performance.