Lower light coral growth discussion

[Aqua Pro Builder]

...

As for the growth, we know that corals have a window of tolerances (in regards to the light portion of this). They occur at a range of depths which could represent different types of aquarium lighting. Whenever I add a coral I usually wedge it into the rock around where I want it or use just enough glue to hold it so it can be moved later. If it isn't doing as well as I would like I move it somewhere else until I find a good spot for it. Sometimes even if you move a frag a few inches in any direction a new growth pattern can emerge or growth can accelerate. I'm inclined to say that I don't think it's the coral as much as the tank. If you take a frag and put it in another tank in the exact same spot I doubt it would respond the exact same way every time. Flow and water quality play a huge role and I think they trump the importance of light if they can be kept at an optimal level for the specimen. Light is only present for a portion of the day but the coral is always in contact with the water and currents. I'm not saying light isn't important, just that there are other more important factors.

AGREED.

When the parameter of the water change, the coral may die in hours. The light part is much less a factor.

There is a REDOX ratio to tell the minimum a coral may need to survive. So one element change in the formula can be supplemented by and varing another elements in the equation. As long as the swing is not too crazy, many coral can adjust to survive.

 

[nycmat]

everyone should keep this thread going.
personally i agree with pratt about the research that is available. i have been waiting and reading up on this for a while now, nothing says for sure that this is the way to go (LED that is) or that it is better then MH's other then wattage usage. although i have heard from certain people who already had a good system added LED's to there established tank and that there was growth. how much i dont know.

 

[House of Laughter]

I'll skirt the LED discussion as I have little practical experience using them on tanks, and others are better to comment there. However, as Randy says above, some corals do definitely get overlit in tanks, and some will take as much light as we can, practically speaking, give them.

One of the big problems with discussing lighting needs for corals is that folks so, so often oversimplify IME. There is a huge amount of diversity in the photosynthetic properties of various zooxanthellae (these are dinoflagellates--"algae"--not bacteria), and this diversity is further modified by the corals themselves. For instance, whether a coral is an "sps" or "lps" tells you squat about it's lighting needs and tolerances.

For example, the most abundant corals around Coconut Island, where I work, are Porites compressa (a branching Porites species) and Montipora capitata (encrusts, branches, and forms plates, depending on environment and maaaaaybe genetics). Both species grow from the surface of the water to the base of the reef (~50 ft at the deepest). Hence, both can survive in really bright light (~1200 umol photons/m2/s--about 1/2 the intensity of surface sunlight), and relatively dim light (<100 umol photon/m2/s). However, if you measure rates of photosynthesis, growth, proxies of photodamage, etc. you'll see that the Porites just gets happier and grows faster the more light you give it, up to at least 1200 umol photons/m2/s. To put into perspective, that's the light intensity you might see 6-10" from a 400 watt metal halide bulb. It's bright, and way brighter than we generally expose corals to in captivity. On the other hand, the Montipora maxes out growth, photosynthesis, etc. in the neighborhood of 300-500 umol photons/m2/s, and gets progressively less happy at brighter light levels. We can easily reach values of 300-500 umol photons/m2/s with halides in captivity. They're both "sps" and they can both survive and grow in suboptimal light conditions, but they have very different preferences.

Different corals really do have very different preferences. Since a lot of the equipment that would help to figure this out is a bit pricey for the average hobbyist (say $18K for a PAM fluorometer), it takes a little bit of educated guessing, and trial and error. Some corals are going to do the things we want them to do best in really bright light, and others are going to freak out, not do what we want, and potentially die. This is one reason getting captive-grown frags from other hobbyists over wild-collected colonies can be a good idea: a lot of the trial and error is already figured out

Chris,

is there any research on the properties of the Zx in these corals (similar to pigmentation in skin) and whether or not they can convert energy to food faster or slower? Maybe it's in the skin is what I am saying and NOT in the light source?

What does the research show if available?

Jim

 

[Alex]

everyone should keep this thread going.
personally i agree with pratt about the research that is available. i have been waiting and reading up on this for a while now, nothing says for sure that this is the way to go (LED that is) or that it is better then MH's other then wattage usage. although i have heard from certain people who already had a good system added LED's to there established tank and that there was growth. how much i dont know.

I don't believe we are saying that LED is a better choice, however for some it is an option that they have ventured on.

I believe that Pecan2phat, a member on this site, has had Led lights for some time and has experienced some good growth. Then we have the T5 users who will also show great growth. And so on for the MH users.

I can say that I've used all three, at present LED, and have experienced growth for all. What I can say is that with the use of LED's and T5 you have more control over the color and intensity of the light without having to change much.

Back to topic, I have seen where I've placed a broken frag of a colony on a different level and have seen a completely different coral emerge. At present I have a frag that I picked up at Aquatic Obsession, when placing it in the tank I accidentally broke off a piece and I decide to put one in my DT and the other in my smaller tank. What I have seen is that they have changed appearance. The frag in the DT is at a higher level with a good flow and direct LED light, this coral is lighter and growing. Now the other frag is at about the same distance from the light, but is not in direct light and the flow is a bit indirect. this frag has kept its original color but does not seem to have much growth. I'll try to post a pic. I also have another coral I got from James, in james' tank it was very pale with specks of green, In my DT under direct light its darker with a more vibrant green polyp and it has also grown nicely by encrusting on the frag plug.

 

[DREUTZ]

The frag in the DT is at a higher level with a good flow and direct LED light, this coral is lighter and growing. Now the other frag is at about the same distance from the light, but is not in direct light and the flow is a bit indirect. this frag has kept its original color but does not seem to have much growth.

I wonder if running a "cloud cover" type scenario (decreasing the intensity for a duration of time) with the LED's randomly throughout the day would affect the color (and possibly growth).

 

[lfsmarineguy]

This subject is something that I have always thought about to some degree. Since this thread popped up it's been on my mind more. While taking my vitamin D supplement this morning it hit me, "If sunlight is only used as a source of food for corals than it would stand to reason that that source could be offset by increasing or introducing other sources of nutrients". That thought also made me wonder if that were the case than photosynthetic corals could theoretically be raised in complete darkness as long as other food sources were increased and flow and parameters stayed the same. But then, one thinks about how sunlight is important to even nonphotosynthetic life on earth and if the same is true for corals. Does sunlight do more than just allow zooxanthellate corals to produce food, does it also play a role in creating other necessary compounds in the tissue like vitamin D in vertebrates? If it does do more than just facilitate photosynthesis than there must be some process by which azooxanthellate corals are creating these compounds on their own in the absence of sunlight, assuming they have similar physiological needs.


Just some thoughts I was kicking around that I thought would be worth sharing here.




P.S. as for LEDs, I haven't personally tested any yet but from all the claims, their PAR ratings seem to be much higher than similarly sized MH or T5 bulbs. I recently spoke to Ike at Ecoxotic about the 100W cannon LEDs I am considering for an installation I have coming up and he said that at 12" the PAR is at 2,000 and at 30" it is at 100. That's a little higher than a good 400w bulb with a 98% reflective fixture. When we get the lights and I have a chance to test them I plan on doing a review of them with some numbers I get myself, so we'll see.

 

[Alex]

P.S. as for LEDs, I haven't personally tested any yet but from all the claims, their PAR ratings seem to be much higher than similarly sized MH or T5 bulbs. I recently spoke to Ike at Ecoxotic about the 100W cannon LEDs I am considering for an installation I have coming up and he said that at 12" the PAR is at 2,000 and at 30" it is at 100. That's a little higher than a good 400w bulb with a 98% reflective fixture. When we get the lights and I have a chance to test them I plan on doing a review of them with some numbers I get myself, so we'll see.

That sounds like a lot of PAR, will you also be testing any of their other products as a comparison ?

 

[lfsmarineguy]

Not right now but I do plan on thoroughly testing the 100w floods and mapping their PAR over depth and spread. These LEDs are in an elliptical reflector so they have a 3' x 1' spread so they did say we should use 6 units in two rows of three for a 6' x 3' footprint. We decided to go with two rows of two set further back in the tank to give it even more depth and to save a little on the install. So we should see 4,000 PAR under each row just below the surface and 200 PAR at the bottom if the numbers are correct. I also plan on keeping records of coral growth and PAR reduction over time to compare to another all MH 300gal tank I service.

 

[Chris Jury]

Chris,

is there any research on the properties of the Zx in these corals (similar to pigmentation in skin) and whether or not they can convert energy to food faster or slower? Maybe it's in the skin is what I am saying and NOT in the light source?

What does the research show if available?

Jim

Jim,

Different zoox. definitely show different patterns of productivity and different rates of translocation of photosynthate to the coral hosts. This is an area we have only started to touch on in the last few years. There are a bunch of different major clades of zoox. (A through J, if I recall--clades A, B, C, and D are normally found in corals) and within each of these major clades are many, many subclades, e.g., C1, C2, C3, C1a, C3a,b are a few in clade C. At this point it's not so clear if these are different species, subspecies, genera, or what, but they appear to be different genetically, physiologically, and ecologically.

Zoox. from clade C dominate in the Pacific/Indian, and are somewhat less common in the Caribbean. Most of them are highly productive, but also somewhat sensitive to stress, especially temp stress. There is a lot of variation though, and they certainly don't all behave the same way, especially in different corals. Clade D is often more stress tolerant, especially temp tolerant, but genearlly less productive. Hence corals with mostly clade D zoox. often grow slower than those with clade C, but they also survive temp stress better than those with clade C of the same coral species.

Some really interesting recent work here by Ruth Gates' lab has shown some funky stuff happening with Acropora up in the NWHI. The collected samples from healthy-looking Acros (most of them) and those that looked diseases or otherwise unhealthy. When they genotyped the zoox. they realized that almost all of the unhealthy looking ones were hosting zoox. from clade A whereas all the healthy looking ones (again, most of the corals) were hosting some from clade C. It turns out the clade A zoox. (common in the Caribbean, weird in the Pacific) are from introduced Upside-down jellyfish. They tested to see how much photosynthate the zoox. were giving the corals, and the ones from clade A were giving up nada. Hence the corals are getting waaaay less food than normal, and are probably much more susceptible to disease as a result.

We don't know much more than this at this point, and this is just scratching the surface. How and why the different zoox. behave so differently we largely don't know, and other than in a few cases, we don't really know how all the different types of zoox. really effect what the corals are doing. We know a little bit, but there's a lot left to figure out.

Some corals and some zoox. can acclimatize to very different light levels, and some just don't, and that's that. There are good reasons for these, but we largely don't have the details yet.

Hope that helps,

cj

 

[Chris Jury]

I wonder if running a "cloud cover" type scenario (decreasing the intensity for a duration of time) with the LED's randomly throughout the day would affect the color (and possibly growth).

Very likely yes on growth, really depends on the specifics (i.e., sometimes yes, other times no) on color. Either way not a very good approach IMHO. If decreasing the lighting increases growth or improves coloration, that means the coral was overlit to begin with. Continuing to overlight it for part to the day wastes electricity, and makes the coral unhappy. On the other hand, reducing lighting on a happy coral will end up reducing growth, and might negatively effect coloration. Ideally one would find the sweet spot, and apply that

cj

 

[Chris Jury]

This subject is something that I have always thought about to some degree. Since this thread popped up it's been on my mind more. While taking my vitamin D supplement this morning it hit me, "If sunlight is only used as a source of food for corals than it would stand to reason that that source could be offset by increasing or introducing other sources of nutrients". That thought also made me wonder if that were the case than photosynthetic corals could theoretically be raised in complete darkness as long as other food sources were increased and flow and parameters stayed the same. But then, one thinks about how sunlight is important to even nonphotosynthetic life on earth and if the same is true for corals. Does sunlight do more than just allow zooxanthellate corals to produce food, does it also play a role in creating other necessary compounds in the tissue like vitamin D in vertebrates? If it does do more than just facilitate photosynthesis than there must be some process by which azooxanthellate corals are creating these compounds on their own in the absence of sunlight, assuming they have similar physiological needs.

It's not entirely clear how, but photosynthetically active zooxanthellae (i.e., those exposed to light) do seem to benefit corals beyond the fact that they provide food. You can actually keep some zooxanthellate coral species long-term in the dark by feeding them plenty of zooplankton, for instance. In fact, some of the earliest experiments doing exactly that were conducted about a century ago on the GBR. However, some corals aren't this flexible, and will simply die when deprived of light, regardless of how much food you offer. Even for very adaptable zooxanthellate corals, however, giving them light tends to increase their growth beyond what you can get by feeding them. Some recent work points to the oxygen they produce as very important for supporting high rates of calcification. Hence, they benefit corals by producing food AND by producing O2. There might be some other benefits too, but it's a technically difficult system to study.

There probably isn't much going on in corals that is analagous to the production of vit. D3 in the skin of vertebrates, but they have numerous endogenous responses that are governed by light (both sunlight and moonlight), as do most organisms that live where there is or can be light.

cj

 

[lfsmarineguy]

Chris, you wouldn't happen to have links or know where I can find those studies do you? I wouldn't even know where to start searching for those. I was just using the process of D production as an example of a process created by light.

 

[Chris Jury]

Chris, you wouldn't happen to have links or know where I can find those studies do you? I wouldn't even know where to start searching for those. I was just using the process of D production as an example of a process created by light.

Yes, however.... A few bits of information come from specific studies (e.g., clade A zoox. in Acropora from Ruth's lab--link below) whereas some others are sorta my synthesis of many studies. Is there something in particular you're interesting in?

Stat, Morris, and Gates. 2008. Functional diversity in coral-dinoflagellate symbiosis. PNAS

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2453720/pdf/zpq9256.pdf

cj

 

[lfsmarineguy]

I'm more interested in the part about what light adds beyond the actual food production in zooxanthellae. To be honest though, I'll read anything I can get my hands on about corals, it all fascinates me.

Thanks for the quick links!

 

[Chris Jury]

This is behind a pay wall, but it's a good start. If you want the paper I could email it as an attachment.

http://www.springerlink.com/content/w46733677604qp76/

cj

 

[House of Laughter]

Jim,

Different zoox. definitely show different patterns of productivity and different rates of translocation of photosynthate to the coral hosts. This is an area we have only started to touch on in the last few years. There are a bunch of different major clades of zoox. (A through J, if I recall--clades A, B, C, and D are normally found in corals) and within each of these major clades are many, many subclades, e.g., C1, C2, C3, C1a, C3a,b are a few in clade C. At this point it's not so clear if these are different species, subspecies, genera, or what, but they appear to be different genetically, physiologically, and ecologically.

Zoox. from clade C dominate in the Pacific/Indian, and are somewhat less common in the Caribbean. Most of them are highly productive, but also somewhat sensitive to stress, especially temp stress. There is a lot of variation though, and they certainly don't all behave the same way, especially in different corals. Clade D is often more stress tolerant, especially temp tolerant, but genearlly less productive. Hence corals with mostly clade D zoox. often grow slower than those with clade C, but they also survive temp stress better than those with clade C of the same coral species.

Some really interesting recent work here by Ruth Gates' lab has shown some funky stuff happening with Acropora up in the NWHI. The collected samples from healthy-looking Acros (most of them) and those that looked diseases or otherwise unhealthy. When they genotyped the zoox. they realized that almost all of the unhealthy looking ones were hosting zoox. from clade A whereas all the healthy looking ones (again, most of the corals) were hosting some from clade C. It turns out the clade A zoox. (common in the Caribbean, weird in the Pacific) are from introduced Upside-down jellyfish. They tested to see how much photosynthate the zoox. were giving the corals, and the ones from clade A were giving up nada. Hence the corals are getting waaaay less food than normal, and are probably much more susceptible to disease as a result.

We don't know much more than this at this point, and this is just scratching the surface. How and why the different zoox. behave so differently we largely don't know, and other than in a few cases, we don't really know how all the different types of zoox. really effect what the corals are doing. We know a little bit, but there's a lot left to figure out.

Some corals and some zoox. can acclimatize to very different light levels, and some just don't, and that's that. There are good reasons for these, but we largely don't have the details yet.

Hope that helps,

cj

This is exactly what I am saying (in English of course).

I am wondering how certain Zx accelerate growth (given conditions remaining generally the same) verses those that are more stress-tolerant.

My analogy is to those who tan better than others where their skin is more tolerant to the various rays/spectrum and others are not so much. There is definitely a parallel there for me. Additionally, I am sure there are regional (or not so regional) diseases both are more prone to. A weird parallel, I know.

I am also wondering that perhaps purposefully transplanting acropora from around the world to regions that are more endearing toward certain Zx clades will perpetuate the health and successes of the reefs - similar to developing cycles of harvest and rotation of land-based crops. This would be a rotation of crops in the ocean to further specific types of acropora that are otherwise endangered by global warming and other non-naturals that affect the suffering reefs.

Sometimes I think .. . . .

House

 

[Alex]

Very likely yes on growth, really depends on the specifics (i.e., sometimes yes, other times no) on color. Either way not a very good approach IMHO. If decreasing the lighting increases growth or improves coloration, that means the coral was overlit to begin with. Continuing to overlight it for part to the day wastes electricity, and makes the coral unhappy. On the other hand, reducing lighting on a happy coral will end up reducing growth, and might negatively effect coloration. Ideally one would find the sweet spot, and apply that

cj

Chris I understand this and to a certain degree agree with this theory. however let me pose this question, what about cloud cover or storms. As we all know reefs are usually unobstructed from the intensity of the sun throughout the day, but what about those reefs that have a constant cloud cover or rainy days ? The intensity of the sun is diminished when this occurs ,yet the corals still continue to do well. Is it that the corals have adapted to this and have come to flourish regardless or does something else take place when the intensity is decreased or filtered as in the case of cloud cover?

 

[lfsmarineguy]

Cloud cover is only temporary, sometimes a few minutes up to a few days. It isn't like the coral doesn't get any light when that happens it's just filtered and somewhat less than it was but radiation still penetrates so the corals are still going through photosynthesis. It's not like a massive temperature or PH swing it's just lower light and not that detrimental over the short period (what happens at night?). I'd imagine that polyp extension probably increases during during prolonged periods of lower light to aid in increasing food capture like at night. You also have to consider that corals, like terrestrial plants can't go through photosynthesis 24/7, they need rest periods in between bouts of photosynthesis or they get badly stressed.

 

[batt600]

Cloud cover is only temporary, sometimes a few minutes up to a few days. It isn't like the coral doesn't get any light when that happens it's just filtered and somewhat less than it was but radiation still penetrates so the corals are still going through photosynthesis. It's not like a massive temperature or PH swing it's just lower light and not that detrimental over the short period (what happens at night?). I'd imagine that polyp extension probably increases during during prolonged periods of lower light to aid in increasing food capture like at night. You also have to consider that corals, like terrestrial plants can't go through photosynthesis 24/7, they need rest periods in between bouts of photosynthesis or they get badly stressed.

lfsmarineguy this is a waste of time your 100% right but some people here are to big headed to agree .

 

[Alex]

Cloud cover is only temporary, sometimes a few minutes up to a few days. It isn't like the coral doesn't get any light when that happens it's just filtered and somewhat less than it was but radiation still penetrates so the corals are still going through photosynthesis. It's not like a massive temperature or PH swing it's just lower light and not that detrimental over the short period (what happens at night?). I'd imagine that polyp extension probably increases during during prolonged periods of lower light to aid in increasing food capture like at night. You also have to consider that corals, like terrestrial plants can't go through photosynthesis 24/7, they need rest periods in between bouts of photosynthesis or they get badly stressed.

You are correct but we can all agree that the SUN is not the lighting in our tanks. and therefore when it comes to our tanks, other factors must then be taken into account, ex..feedings, chemistry etc...

My point is that although light is important, I think the difference is made up by the husbandry that we as reefers put into our tanks. This can account in part for color change,form and at times growth.