PAR...how is it weighted? and other ??'s

[hahnmeister]

<a href=showthread.php?s=&postid=13321882#post13321882 target=_blank>Originally posted</a> by MCsaxmaster
Hmmm, but UV-A isn’t blue light. It’s invisible to us, hence it has no color. However, it is nearest deep violet, not blue. Again though, I’d have to see the data to entertain the notion that blue light causes measurably more photoinhibition in corals than red or green of the same intensity.

Sorry, I should have said 'bluer light'... the conversation was with regards to the UV-A that the Giesemann true actinics put out. The warning was that while UV-A is used by some corals (stags) for photosynthesis, that it is more able to cause photoinhibition as well, so watch it. Ask Dana... its that simple.

Nnnnoo, no no, that’s not how photosynthesis works. That would only work if the organism were at low light intensity (subsaturating) for the entire day. The photosynthetic response under a naturally varying light cycle due to solar precession is not the same as it is under constant light intensity. A coral exposed to 12 hrs of light at 300 umol photons/m2/s would probably be near the point of photosaturation, but for most corals wouldn’t be getting nearly enough light to cause significant photoinhibition. A coral exposed to a max intensity of 1000 umol photons/m2/s is going to be photoinhibited during that day. During the early morning and late evening it will be well undersaturated with light. NPP, GPP, photodamage, etc. will all be different between these scenarios.

Well, if thats not how photosynthesis works, then you had better tell Borneman and Wyatt because their research does not agree with you, and they seem to have some other scientists backing them up. When calculating the 'daily intake', if the integral under that curve for the parabolic variation of light intensity from daylight matches the integral under the flat line that represents a constant source like a bulb, then the daily productio of carbon is the same, and it ties into the next part regarding internal coral chemistry.

Huh? What do you mean waiting for the night cycle to process the carbon? Why would they wait for night to utilize the carbon they’ve fixed?

This is why their daily storage of carbon from light throughout the day reaches a 'full charge' and then the rest is useless. They are nitrogen limited, right? The polyps are out during the day, capturing prey and getting just the right amount of light to match. They dont actually digest what they catch though until night though. They cant.

Think about that though: you’re saying that production (e.g., NPP) is governed simply by the number of photons the corals are exposed to per day. So, at 300 umol photons/m2/s X 3600 s/hr X 12 hrs/day = 12.96 mol photons/m2/day. If we ramp up the intensity substantially and adjust down the photoperiod we can get the same number of photons hitting the corals with intensity of 3000 umol photons/m2/s for 1.2 hrs. If we expose the corals to light intensity 150% the intensity of unfiltered sun, do you think they’re going to do well? We can easily get that sort of light technology out of specialty bulbs, should we be doing that? No, were we to try that, the corals would fry during those 1.2 hrs.

They would have to photoadapt differently... most likely expell and take in some new types of zooanthelle(bleaching) to cope, but to suggest that corals cant do this is absurd... otherwise they wouldnt exist in nature. Corals that experience photoinhibition under say, 300 micromol/m2/s can take peaks that are much higher than that... at least thats what the research presented at MACNA suggests. Our corals in captivity are more limited in their carbon uptake anyways since if they dont have the nitrogen to go with it, its useless. Even if we fed our corals 4x a day, we couldnt keep up, so as a consequence, the coral has to dump all the carbon it cant use. You want to make your corals grow faster, you need to feed more, like 100x more, and provide more flow... or else all that extra light is just going to waste. And I never recall saying anything about how photosynthesis actually works...

No, that’s not how photosynthesis works.

Nnnooo, carbon fixation is only N-limited to the extent that N-limitation could reduce the production of photosynthetic reaction centers and/or associated proteins. Corals lose a lot of photosynthetically fixed carbon in mucus, but that’s no reason to think that they are using mucus production simply as a mechanism to dump excess fixed carbon. They lose a lot of fixed carbon to gametes too. Should we suggest that gamete production is a means to simply purge excess carbon?

 

[hahnmeister]

Slime to dump excess carbon was pretty much the main discovery presented by Borneman. If you think he is wrong, go talk to him. [ /COLOR]

In addition, corals tend to eat a fair amount in nature. Counting photosynthetically fixed carbon AND carbon intake from feeding, most corals are getting 200-300% of their daily metabolic expenditure worth of energy per day. Of that 200-300%, 100% goes to metabolism, about 50-100% goes to mucus production, and the rest goes to gametet production, growth, defense, tissue repair, etc.

Why wouldn’t they be able to store that fixed carbon until the next day?

Blasting them with more light does little good IF they are already photosaturated. Corals that grow at depth where light availability is low grow much, much more slowly than those in shallow water. It’s not an either or sort of thing though: corals that receive ample light, food, etc. grow fast. Those that don’t…don’t. I’d be the first to agree that most corals are woefully underfed in captivity though.

I suppose the main idea to consider would be that the protein and nitrogen that solid foods offer can raise the ability of the coral to handle more light (which makes sense). A starved coral will be more sensitive to light because it cant spend the energy on the pigments to protect it, and it wont be able to hande the extra carbon (store it where? How? The coral can only take in calcium so fast after all, so using calcium carbonate as energy storage isnt possible. Where else does the coral store the carbon? What else can it do other than dumping it? These arent trees that can pack it up into cellulose. I think that fills in the question you ask next as well. The slime doesnt JUST provide a form of carbon dumping... but its one of its convenient uses. The additional benefit is that potential pathogens and parasites are simply 'shed' faster than they can invade the coral.


1) What would be the purpose of wasting huge amounts of energy-rich food?

2) Where’s the evidence? Corals lose a lot of N in their mucus too, not just C. If mucus production is a mechanism for dumping excess fixed carbon, then why is their so much investment in it in terms of N, specialized proteins, etc.?

[COLOR=green Hey, Im just a messenger... ask Tom Wyatt if you want his data. He's the one with the lab. If you want to challenge what he has said... go for it. [/COLOR

Oh [I]reaaally[/I]? Well, since my MS deals heavily with skeletogenesis in corals, I’d be very interested to hear how or why the skeleton is used as a repository for inorganic carbon

Chris

That last part was kind of the 'ORLY?' moment of Borneman and Wyatt's presentations. The evolution of corals suggests that the primary reason for the development of calcium carbonate isnt so much structural advantage (it is, but that wasnt the primary evolution reason) as a means of energy storage. The calcium carbonate is a way of energy storage.

I think the transcripts for the lectures at MACNA are supposed to be posted soon... might be something to check out. But hey, maybe Borneman and Wyatt are wrong...

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
Sorry, I should have said 'bluer light'... the conversation was with regards to the UV-A that the Giesemann true actinics put out. The warning was that while UV-A is used by some corals (stags) for photosynthesis, that it is more able to cause photoinhibition as well, so watch it. Ask Dana... its that simple.

Ha, ok, I’ll have to ask Dana about that. No dispute that elevated UV (or even normal UV) can cause photoinhibition, but the process is different than I think you’re suggesting here. Within the visible spectrum, I don’t believe there’s any evidence that shorter frequency light is any more able to cause photoinhibition than longer wavelength light.

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
Well, if thats not how photosynthesis works, then you had better tell Borneman and Wyatt because their research does not agree with you, and they seem to have some other scientists backing them up. When calculating the 'daily intake', if the integral under that curve for the parabolic variation of light intensity from daylight matches the integral under the flat line that represents a constant source like a bulb, then the daily productio of carbon is the same, and it ties into the next part regarding internal coral chemistry.

If that were true, then there would be no such thing as photosaturation. What you’re suggesting is that photosynthetic rate increases linearly as a function of light intensity. That is only true at low light intensities. Eventually the rate of photosynthesis levels off (photsaturation) and at high light intensity begins to drop (photoinhibition). NPP is not simply governed by integrated daily photon flux.

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
This is why their daily storage of carbon from light throughout the day reaches a 'full charge' and then the rest is useless.

Why? If we take in calories in excess of our needs, we store much of the excess as fat. Are we to suggest that corals don’t have lipid reserves?

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
They are nitrogen limited, right? The polyps are out during the day, capturing prey and getting just the right amount of light to match. They dont actually digest what they catch though until night though. They cant.

1) Most prey capture is done at night in corals.

2) Why wouldn’t they be able to digest prey until night???

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
They would have to photoadapt differently... most likely expell and take in some new types of zooanthelle(bleaching) to cope, but to suggest that corals cant do this is absurd... otherwise they wouldnt exist in nature.

See Iglesias-Prieto et al. (2004) Different algal symbionts explain the vertical distribution of dominant reef corals in the Eastern Pacific. Proc R Soc Lond B 271:1757-1763.

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
Corals that experience photoinhibition under say, 300 micromol/m2/s can take peaks that are much higher than that... at least thats what the research presented at MACNA suggests.

Sure, they can certainly survive that. If they couldn’t, most corals in shallow water would be in trouble

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
Our corals in captivity are more limited in their carbon uptake anyways since if they dont have the nitrogen to go with it, its useless.

What do you mean they are limited in carbon uptake? Do you mean DIC uptake from sea water? If so, why??? Why is fixed carbon useless without nitrogen? How are you assessing that?

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
Even if we fed our corals 4x a day, we couldnt keep up, so as a consequence, the coral has to dump all the carbon it cant use.

Why can’t the corals use carbon they’ve fixed? What indication do you have that they aren’t using it?

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
You want to make your corals grow faster, you need to feed more, like 100x more, and provide more flow... or else all that extra light is just going to waste.

One of the surest ways to slow down growth significantly is deprive corals of light. Yes, clearly they need food, and clearly they need appropriate water flow, but not to the exclusion of light by any stretch of the imagination. Is calcification/linear extension higher in shallow water or deeper water on coral reefs?

<a href=showthread.php?s=&postid=13322153#post13322153 target=_blank>Originally posted</a> by hahnmeister
And I never recall saying anything about how photosynthesis actually works...

Ha, well, perhaps that’s the problem You’re making assertions about how photosynthesis and coral physiology is affected by x, y, and z without taking into account the physiological mechanisms involved in photosynthesis. One cannot describe how a physiological process is affected by something while ignoring how that process works.

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
Slime to dump excess carbon was pretty much the main discovery presented by Borneman. If you think he is wrong, go talk to him.

I’d be happy to talk with Eric

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
I suppose the main idea to consider would be that the protein and nitrogen that solid foods offer can raise the ability of the coral to handle more light (which makes sense). A starved coral will be more sensitive to light because it cant spend the energy on the pigments to protect it, and it wont be able to hande the extra carbon (store it where? How?

Sure, sure, starved corals are going to have neither the energy nor resources to repair tissue damage, such as photodamage to the photosynthetic apparati. But saying that they DO need food is very different than making many of the claims discussed above.

What do you mean “handle the extra carbon”? What about a bunch of glycerol makes it something that must be dealt with?

Excess calories are stored mostly as lipids in the corals’ tissues, just as with any other animal…

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
The coral can only take in calcium so fast after all, so using calcium carbonate as energy storage isnt possible.

Agreed, given that there is no mechanism by which to store metabolically accessible energy in CaCO3 or to retrieve it later

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
Where else does the coral store the carbon?

In lipids…

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
What else can it do other than dumping it?

Store it as lipids, use it for tissue repair, use it for growth, use it for gamete production, etc…

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
These arent trees that can pack it up into cellulose.

No, they’re animals, they store energy as lipids…

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
I think that fills in the question you ask next as well. The slime doesnt JUST provide a form of carbon dumping... but its one of its convenient uses. The additional benefit is that potential pathogens and parasites are simply 'shed' faster than they can invade the coral.

I’ll ask again,

1) What would be the purpose of wasting huge amounts of energy-rich food?

2) Where’s the evidence? Corals lose a lot of N in their mucus too, not just C. If mucus production is a mechanism for dumping excess fixed carbon, then why is their so much investment in it in terms of N, specialized proteins, etc.?

If corals are purposefully dumping huge amounts of fixed carbon everyday, why not simply put a smaller investment into photosynthetic reaction centers thereby fixing less carbon, wasting less in resources (energy and especially N) thereby having more available for reproduction, growth, etc.? Wasting huge amounts of energy makes no sense. Just because fixed C is lost in mucus does not mean the corals are “dumping” the C.

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
Hey, Im just a messenger... ask Tom Wyatt if you want his data. He's the one with the lab. If you want to challenge what he has said... go for it.

Ha, I don’t have his contact info, but I’m very curious to hear more about what he presented.

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
That last part was kind of the 'ORLY?' moment of Borneman and Wyatt's presentations. The evolution of corals suggests that the primary reason for the development of calcium carbonate isnt so much structural advantage (it is, but that wasnt the primary evolution reason) as a means of energy storage. The calcium carbonate is a way of energy storage.

Ok, I’ll have to follow up on this, but consider: how in the world could corals store energy in CaCO3? Metabolically accessible energy is stored in lipids, carbohydrates, etc. Metabolism produces and uses ATP from lipids, carbohydrates, amino acids, etc. CaCO3 is no more an energy source for metabolism than are diamonds.

<a href=showthread.php?s=&postid=13322202#post13322202 target=_blank>Originally posted</a> by hahnmeister
I think the transcripts for the lectures at MACNA are supposed to be posted soon... might be something to check out. But hey, maybe Borneman and Wyatt are wrong...

I’ll have to talk with Eric. I’ll see if I can catch up with what Tom Wyatt had to say.

Chris

 

[91yota]

i can already tell that by the time i get to check this again its going to be 5000000 posts long... very interesting topic and i'll be tagging along

 

[hahnmeister]

"how in the world could corals store energy in CaCO3?"

That was what Wyatt's talk was all about.

 

[greenbean36191]

Are you sure he wasn't talking about CaCO3 as a sink/source for atmospheric carbon rather than fixed carbon? I don't know of any research even suggesting that any organism might store energy in CaCO3. It would be an extremely inefficient way to do that since there are no high energy bonds in the molecule.

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=13324838#post13324838 target=_blank>Originally posted</a> by hahnmeister
"how in the world could corals store energy in CaCO3?"

That was what Wyatt's talk was all about.

Forgive me as I remain skeptical here. I've asked one other person that was in attendance about this subject, and it didn't ring a bell to them. I somehow doubt Tom Wyatt dedicated an entire presentation to a faulty premise

As I said though, there is no way for an organism to store energy in CaCO3 or to access it later. Suggesting so is somewhat like saying that a squirrel could make diamonds to use as a food source during winter hibernation

 

[GoBigOrGoHome]

Okay, so forgive me, as I'm not quite up to the level as you guys are on photosynthetic activities of zooxanthellae, but I have a few questions that this debate has raised.

If zooxanthellae are capable of using photons of light of all visible wavelengths, then what is causing the reflected light that we see? The zooxanthellae, or the corals themselves?

Energy storage in CaCO3 would probably mean that the coral would shrink a tiny bit every time it came up short on the day's energy intake, am I right?

So these corals store excess energy in lipids, just like other animals. Does this mean that as we perfect our reef-keeping methods, we might actually have obesity issues in reef tanks??

From what I've heard, although C is much more abundant than N, isn't the main limiting factor here Fe??

I'm not buying that excess C at the end of the day is just thrown out like yesterday's newspaper. If I make too much money in a day, I don't just toss it because my wallet is too full...

If one of you could just post something explaining the meaning of all the acronyms you are using, especially APP and GPP (I have no idea what those are), it would be much appreciated.

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=13378879#post13378879 target=_blank>Originally posted</a> by GoBigOrGoHome
Okay, so forgive me, as I'm not quite up to the level as you guys are on photosynthetic activities of zooxanthellae, but I have a few questions that this debate has raised.

If zooxanthellae are capable of using photons of light of all visible wavelengths, then what is causing the reflected light that we see?

Only something that is black is not reflecting light (and most things we consider black still reflect a small amount of light, just very little). Zooxanthellae are brownish or golden brownish. Some amount of just about any wavelength is reflected from corals. From the zoox. the reflected spectrum is heavy in the green, yellow, and orange and weak in the blue, violet, and red.

<a href=showthread.php?s=&postid=13378879#post13378879 target=_blank>Originally posted</a> by GoBigOrGoHome
The zooxanthellae, or the corals themselves?

Both the zoox. and the corals can reflect light. The spectrum reflected from the zoox. is heavy in green, yellow, and organge (= brown). The spectrum from a coral will depend heavily on the presence or absence of various non-fluorescing pigments (a lot of the pink, red, blue, and purple colors we see). In addition, there are also various fluorescing proteins in corals (e.g., GFP, green fluorescent protein) and you get scattering from the skeleton and such.

<a href=showthread.php?s=&postid=13378879#post13378879 target=_blank>Originally posted</a> by GoBigOrGoHome
Energy storage in CaCO3 would probably mean that the coral would shrink a tiny bit every time it came up short on the day's energy intake, am I right?

Don’t try to wrap your mind around itâ€"it’s biologically impossible

<a href=showthread.php?s=&postid=13378879#post13378879 target=_blank>Originally posted</a> by GoBigOrGoHome
So these corals store excess energy in lipids, just like other animals. Does this mean that as we perfect our reef-keeping methods, we might actually have obesity issues in reef tanks??

Ha, in fish perhaps, in corals, probably not

<a href=showthread.php?s=&postid=13378879#post13378879 target=_blank>Originally posted</a> by GoBigOrGoHome
From what I've heard, although C is much more abundant than N, isn't the main limiting factor here Fe??

Limiting for what, photosynthesis? Fe can be limiting, but that certainly doesn’t imply that it is limiting.

<a href=showthread.php?s=&postid=13378879#post13378879 target=_blank>Originally posted</a> by GoBigOrGoHome
I'm not buying that excess C at the end of the day is just thrown out like yesterday's newspaper. If I make too much money in a day, I don't just toss it because my wallet is too full...

Agreed, and another caveat that I think is important to consider is what is in the mucus. There’s a lot of N in that, and loss of mucus is a major mechanism of N loss in corals. Mucus production is metabolically expensive. I don’t buy the argument that they are dumping excess C into mucus to get rid of it because we could just as easily apply the same argument to N. That makes no sense.

<a href=showthread.php?s=&postid=13378879#post13378879 target=_blank>Originally posted</a> by GoBigOrGoHome
If one of you could just post something explaining the meaning of all the acronyms you are using, especially APP and GPP (I have no idea what those are), it would be much appreciated.

I think you mean NPP and GPP. NPP is net primary production and GPP is gross primary production.

Chris

 

[GoBigOrGoHome]

Haha... as I was thinking about the acronym thing, I was like N,G..... probably Net and Gross. Then I proceeded to figure out that it was primary production. Thanks for fillin me in though! I haven't been able to get on here for about the last 36 hours or so.. Not sure why, but anyway, I hope this debate isn't over, it is quite interesting.

 

[MCsaxmaster]

:thumbsup:

If you have questions I'd be happy to try to answer, but I'm otherwise I'm not sure I have much else to say here