Is shading BS?

[madweazl]

Was just scrubbing the algae off the back of the tank and noticed a response from a few of the corals. The image is purposely over exposed (I'm no Photoshop guru, sorry) so you can see the polyps in the shaded areas better but they sure did open up to grab hold of whatever may be coming their way.

 

[mcarroll]

No real answers here....consider this a really wordy BUMP for an interesting thread. Deserves as much attention as it can get.

just how much nutrition can a coral uptake from the water column without adequate light?

Whether a coral can recover from bleaching is an interesting point in this context. I haven't read up specifically on that, but I know it seems to be a relatively common occurrence. And I can't say I recall reading about any corals being incapable.

Speaking of "without adequate light", I also know that corals were originally more or less deep-sea predators. Eating "particles" or things is their main method. The rest of their feeding methods that we know are adaptations. Neither light, nor dissolved nutrients would seem to matter in that context. However feeding becomes just that much more important without those adaptations. Our tanks are notoriously barren of particulate foods due to all the filtration and limited environment.

Not really an answer, but maybe at least more interesting stuff!

A previous statement about the die off contributing to the building of the reef structure was another interesting point. Is there an innate response from the coral to do such?

Something else I've never looked specifically into, but I can't recall hearing that as a thing. Coraline algae are usually credited as the main reef builders in the things I've read that have touched on it. Where coraline cannot grow, the reef doesn't last. Storms are the main factor I think....a non-coraline-cemented reef will become suspended in the rush of the storm and just wash away in a million little pieces. It's also a risky move as it can potentially allow unfriendly epiphytes to grow on them.

I'd love to know if there is anything to the original point though!!! Maybe there's a context where they "contribute" bare skeleton purposefully.

 

[madweazl]

Dinner time!

 

[McMullen]

Great looking tank!

 

[tsav87]

I think @mcarroll is likely right in that starvation is the cause of die off but this begs the question, just how much nutrition can a coral uptake from the water column without adequate light? Anemones that have completely bleached are capable of surviving if fed directly and can return to a normal state of being once provided adequate lighting again. Can an acropora do the same?

I understand. But I don't think that it is possible to put your finger on ONE contributing factor. I think it has to be a multitude of factors, including lighting, flow, and water chemistry. But as someone mentioned earlier, the photo you posted earlier shows low PE in the shaded area. For whatever reason it is doing it, we know that the flow and water chemistry at that location is the same as the rest of the coral, only difference being the lack of light. I would suspect that as the coral gets larger, that area of low PE may die off due to lack of contribution of energy to the coral as a whole. The growth may stop there so that the coral can invest the energy in other areas the meat the trifecta of light, flow, and water chemistry. Just a thought, I'm only a hobbiest.

I said it first, but I guess my comments are not taken seriously.

 

[madweazl]

Are you looking for a pat on the back instead of engaging in conversation? Just because I don't interpret what you're saying as being the same thing (starvation vs contribution of energy to the colony) doesn't mean I discredit your statement as having no value.

On topic, how much sharing of energy happens within the coral? If a polyp consumes a source of nutrition, how far can does that energy migrate across the coral?

 

[tsav87]

Are you looking for a pat on the back instead of engaging in conversation? Just because I don't interpret what you're saying as being the same thing (starvation vs contribution of energy to the colony) doesn't mean I discredit your statement as having no value.

On topic, how much sharing of energy happens within the coral? If a polyp consumes a source of nutrition, how far can does that energy migrate across the coral?

Lol, no, no patting of the back, thanks. Just if we are going to have a discussion, let's have a discussion. Back on topic, agreed.

Yeh so I would imagine, just as @mcarroll stated about land plants, the corals may be using their entire bodies for one common goal, food (energy). So if one section is no longer able to to contribute, in this case unable to photosynthesize, the coral may purposely cut off support for the shaded portions. Seems like a reasonable reason as to why shaded areas die. If true, it would give good reasoning why you see more die off from LEDs than you do from T5s, for instance. The T5s are able to fill our tanks with light as opposed to spot lighting our tanks like LEDs do.

 

[madweazl]

I still think we're getting too hung up on the light source verse the shading itself. Shade is shade right? If PAR is equal in the shaded areas (impossible to know in these examples but they're both obviously shaded), what does it matter if it were created by T5/florescent, MH, LED, or the sun?

Why are these two corals growing into areas of shade...

... but this one isn't?

What is responsible for that difference and how do we promote it to continue happening? I don't use amino acids, phytopheast, or any other products in the tank. I don't set wavemakers to feed mode, I don't turn off the skimmer, carbon reactor, or return pump. I generously feed LRS (Reef and Herbivore Frenzy) twice a day; it takes about five minutes for the food to be consumed by the fish and/or sump after a feeding.

 

[alton]

LED users need to stop comparing themselves to T5's or making the statement " I need to add T5's". I don't have issues with shadowing with my Build My Leds and who ever uses the New Orphek will not have issues with shadowing. Most of the issues come from using spot light LED fixtures which Kessil is #1 on the list. They grow coral fine, they just are true spot light fixtures with the leds all on one small area.

 

[tsav87]

Maybe the coral actually explores a bit. As in it does not know for certain that there is more or less light on the other side of the shade but it's willing to try? I know that's not scientific, but neither are we as hobbyists....lol.

 

[tsav87]

what does it matter if it were created by T5/florescent, MH, LED, or the sun?

The sun has the advantage of a rotating earth

 

[Dana Riddle]

Interesting thread. To throw a bit of a curve here, Australian researchers found that Acroporas possess one zooxanthella clade when young and switch to another as they mature. I'd have to do some digging to find that reference. I'll stir the pot some here - I've had a nagging feeling that tissue loss at the base of *some* Acroporas is due to flow issues, but I don't want to hijack this thread.

 

[tsav87]

Interesting thread. To throw a bit of a curve here, Australian researchers found that Acroporas possess one zooxanthella clade when young and switch to another as they mature. I'd have to do some digging to find that reference. I'll stir the pot some here - I've had a nagging feeling that tissue loss at the base of *some* Acroporas is due to flow issues, but I don't want to hijack this thread.

Now that is interesting!

 

[madweazl]

Interesting thread. To throw a bit of a curve here, Australian researchers found that Acroporas possess one zooxanthella clade when young and switch to another as they mature. I'd have to do some digging to find that reference. I'll stir the pot some here - I've had a nagging feeling that tissue loss at the base of *some* Acroporas is due to flow issues, but I don't want to hijack this thread.

Oh, that is interesting. I wonder how that applies to frags from existing colonies (not sure how exactly this plays into the maturity level of captive acropora)?

Additionally, your thoughts on the tissue loss is relevant to the thread so I certainly wouldn't consider it a hijack.

 

[McMullen]

As I said before, confirmation bias.

I posted a large (for my tank) acro colony with dead tissue on part of the nether regions. The entire colony is above my rockwork (mounted via magnet) and gets strong pulsing flow (wave mode). When I cut several frags and the dead part that had not been receiving light is again receiving light, the tissue grows back. Anecdotal N of 1? Yes, but as pointed out on this thread by others, fairly common. This is not the only reason for acros to undergo some type of die off. However, to the original question and the original question only, shading is a real "thing." Maybe this simplistic real answer isn't as interesting as nutrients, flow, and metabolism, but it is still true.

 

[Graffiti Spot]

Yea good thread guys. Dana please share your thoughts, they seem to be perfectly on topic.

I won't use LEDs but I have seen a few friends switch back to halides because of shading issues and also color issues on a couple corals. The tanks that had shading on the bottom of large corals were apparent that the lack of good light was the cause. I have only seen the shading become an issue when colonies are large.

Have the medical marijuana growers started using only LEDs to light their plants yet? I wonder what the difference they see in their finished product is if they use all LEDs...

 

[Dana Riddle]

Yea good thread guys. Dana please share your thoughts, they seem to be perfectly on topic.

I won't use LEDs but I have seen a few friends switch back to halides because of shading issues and also color issues on a couple corals. The tanks that had shading on the bottom of large corals were apparent that the lack of good light was the cause. I have only seen the shading become an issue when colonies are large.

Have the medical marijuana growers started using only LEDs to light their plants yet? I wonder what the difference they see in their finished product is if they use all LEDs...

Medical marijuana - Yes, the pot growers are the reason BML got out of the aquarium market and now concentrate on agriculture.

 

[Dana Riddle]

The effects of light and flow on photosynthesis are not mutually exclusive. A coral colony large enough to self-shade also has the ability to restrict flow. I published this info back in the 90's when Aquarium Frontiers was still around, but here's a primer. Coral colonies (or any benthic object for that matter) restrict flow and create an area of high pressure (such as a ship's bow creates high pressure when moving through the water. Of course, for our purposes, it is flow moving against a stationary object.) Water moving over the top of the colony picks up speed and creates an area of low pressure (according to Bernoulli's Principle) hence water moves from the area of high pressure upwards to the area of low pressure. This is the reference:

Chamberlain, J. and R. Graus, 1975. Water flow and hydromechanical adaptations of branched reef corals. Bull. Mar. Sci., 25(1):112-125.
Crude drawing of the principle:
I'm of the opinion that crashes of mature coral colonies in aquaria are due to impacts of poor flow and, yes, light (but to a lesser degree.)

 

[madweazl]

I had never considered how the structure of the coral could promote flow within itself. So many fascinating aspects to reef keeping!

 

[BoomCorals]

The effects of light and flow on photosynthesis are not mutually exclusive. A coral colony large enough to self-shade also has the ability to restrict flow. I published this info back in the 90's when Aquarium Frontiers was still around, but here's a primer. Coral colonies (or any benthic object for that matter) restrict flow and create an area of high pressure (such as a ship's bow creates high pressure when moving through the water. Of course, for our purposes, it is flow moving against a stationary object.) Water moving over the top of the colony picks up speed and creates an area of low pressure (according to Bernoulli's Principle) hence water moves from the area of high pressure upwards to the area of low pressure. This is the reference:

Chamberlain, J. and R. Graus, 1975. Water flow and hydromechanical adaptations of branched reef corals. Bull. Mar. Sci., 25(1):112-125.
Crude drawing of the principle:
I'm of the opinion that crashes of mature coral colonies in aquaria are due to impacts of poor flow and, yes, light (but to a lesser degree.)

Good stuff.