Just heard a new word yesterday about measuring light output instead of lux.  I guess I'm an idiot because I have never even heard of it before.  Am I spelling it right?  So what is it anyway?

Read through this....

http://www.utahreefs.com/forum/forum_posts.asp?TID=6547 - http://www.utahreefs.com/forum/forum_posts.asp?TID=6547

Adam

These may help as well....

http://www.advancedaquarist.com/2005/7/review - http://www.advancedaquarist.com/2005/7/review

http://www.advancedaquarist.com/2005/8/lines - http://www.advancedaquarist.com/2005/8/lines

Adam

I believe it stands for Photosynthetic Active Response.

This is an attempt to measure and evaluate the intensity (lux or lumens) and wavelength (spectrum) of light which is most beneficial for coral. Even the brightest lights have different PAR values.

Also note, coral are not all the same in their response to light. They each respond to their own best light, depending on depth, water turbidity, etc.

It's actually Photosynthetically Active Radiation.  Meaning some wave of energy that can be used in photosynthesis.

Adam

Argh! I missed a lighting thread!

Does it mean the same as PAR?

Yes and no.  PAR is the amount of radiation falling between 400 and 700 nm wave length.  Remember from your science class that light is both a wave and a particle.  This means we can measure that energy as a wave (called irradiance) or you can just count the number of light particles called photons (giving each photon the same energy value).  PPFD just counts the number of photons but it equates a red photon with a blue photon, while on an energy basis, the red photon is only about 60% as "energetic".

PAR on a wave energy basis would have units of Joules/(sec m2), while PAR on a photon basis would have units of photons/(sec m2).  But most times, rather then using photons/(sec m2) you'll see microEinsteins/(sec m2).  1 microEinsteins = 6.022 x10^17 photons

I already know what the following questions are going to be.  I'll PM them to Jon just to see if I'm right.  Then I'll wait and see where this conversation goes.

Adam

So does the energy level of the photon really make much difference in the photosynthesis of our corals.

As a general rule, photosynthetically I think it does.  But our corals use blue light better then any other wavelength.  The molecules involved in capturing the energy from light (chlorophylls, carotenes, etc.) are "tuned" to specific wavelengths of light.  As a matter of fact they don't absorb hardly any green light (except the carotene's).  An einstein of blue light (6.022 x 10^23 photons) has 278 kJ of energy while the same number of red photons only has 179 kJ.  So a molecule of chlorophyll will have to absorb more red photons to get the same energy as from blue.

I could be totally off base here but it seems photosynthesis can only capture so much energy per photon, thus making the number of photons more important than there actually energy levels.

I've never read that.  Where can I read more?  If that's the case, how does the plant shed off all the excess energy from the blue light?  I know that excess energy is shed from accessory pigments in corals as florescences, but how does chlorophyll shed it?  I do know that if a plant is over illuminated (too many photons absorbed...red or blue) the photosystem can shut down and actually damage the photosynthesis pathways.

microEinsteins  

I think they all look like "mini me" from Austin Powers!

Here's the absorbance (photo activity) of chlorophyll:

And here is zooxanthellae:

But our corals use blue light better then any other wavelength

So are you saying we would see better growth with more actinics in our setups? 

Jon-
I disagree a little.  I don't think our corals use blue light better.  They grow way fast with red light.

I've never read that.  Where can I read more?  If that's the case, how does the plant shed off all the excess energy from the blue light?  I know that excess energy is shed from accessory pigments in corals as florescences, but how does chlorophyll shed it?  I do know that if a plant is over illuminated (too many photons absorbed...red or blue) the photosystem can shut down and actually damage the photosynthesis pathways.

Yes, they do shed off excess energy.  It's one of the boring parts of class I somewhat tuned out of many times over the years.  Do you think corals fluoresce to rid excess energy from light?  I'm very curious to know.  Also the very next sentence you said how does chlorophyll shed it...  well chlorophyll really fluoresces.  All the time, everywhere.  It's fluorescing more than corals do.

And yes, too much light kills plants, often by "burning up" the photosynthetic pathway.

Adam

They grow way fast with red light.

hmmm... I thought it was just the opposite.  Dana Riddle did an experiment where he exposed Pocillopora to a narrow blue band of light and a narrow red band of light http://www.advancedaquarist.com/issues/nov2003/feature.htm - http://www.advancedaquarist.com/issues/nov2003/feature.htm .  What he saw was that the area exposed to blue light was healthy and turned pink while the section exposed to red light bleached.  Dana doesn't come to any specific conclusion as to why this happens.  He offers a couple explanations: 

It is interesting to note that those pigments involved in photoprotective dynamic photoinhibition (i.e. xanthophylls diadinoxanthin and diatoxanthin) absorb blue wavelengths and not red wavelengths. Hence, coral zooxanthellae do not possess an ability to rapidly deal with red light and might bleach when suddenly exposed to increased amounts of red radiation.

and

It is possible that the red LED produced insufficient radiation to drive PS I, resulting in destructive pressure on PS II.

But others have shown that red light resulted in poor coral growth:

Kinzie et al (1984, 1987) reported effects of different spectra (including blue, white, green, blue-green and red) on two Hawaiian corals (Pocillopora damicornis and Montipora verrucosa - now M. capitata). The results of these experiments suggest that red light promoted poor coral growth and zooxanthellae growth/reproduction.

Dana adds:  Interpreted by some to mean that red light is inefficient in the promotion of photosynthesis, it could be that exactly the opposite is true � that bleaching (either loss of algal cells or reduction in pigmentation) was caused by an exposure to elevated levels of more photosynthetically efficient red light.

So I get the feeling that Dana feels a lot like you do and feels red light is getting undeserved bad press.

Do you think corals fluoresce to rid excess energy from light?

Yes.  It's all over in the literature isn't it?

hmmm... maybe Jared is right and it doesn't matter that a photon of blue has more energy then a photon of red???

Do you think corals fluoresce to rid excess energy from light?

Yes.  It's all over in the literature isn't it?

NO!!!!!  In fact if Dana heard me say that he'd be here slappin' me upside the face.  As of right now, why do corals fluoresce.... we have no idea.  If it was to get rid of excess energy then we'd assume that all corals would do it, or at least all corals near the water surface.... but that isn't the case. 

Dana knows more about this than I do, so I usually ask him for help.  He asked me if I wanted to help him with a project comparing blue corals to brown corals and looking at fluorescence.  So far I haven't had the time, nor do I have the blue corals.

Adam 

Side note- obviously a photon can have too much energy for photosynthesis.  Otherwise we could grow plants and corals by sticking them in the microwave.

Adam

NO!!!!!

Huh?  What do these statements mean?

Dana:  Fluorescence or non-radiant heat transfer can dissipate energy harvested by photopigments, or certain pigments can cause dynamic photoinhibition, where light energy is diverted from PS II altogether.

Adam:  Yes, they do shed off excess energy.  It's one of the boring parts of class I somewhat tuned out of many times over the years.  Do you think corals fluoresce to rid excess energy from light?  I'm very curious to know.  Also the very next sentence you said how does chlorophyll shed it...  well chlorophyll really fluoresces.  All the time, everywhere.  It's fluorescing more than corals do.

Sorry- Fluorescence certainly does shed off excess light and energy.  I guess what I meant was that we don't know why corals do that.  Why get rid of the excess?  Why do it through fluorescence?  Do healthy corals fluoresce and unhealthy corals not? 

That is where the big NO comes from.  I guess fluorescence by definition really is taking high energy and kicking out low energy.  But why do that?

I just didn't say that well, sorry.

Adam

Here is what I said.

Do you think corals fluoresce to rid excess energy from light?  I'm very curious to know.

Here is what I should have said.

Why do you think corals fluoresce?  I'm very curious to know.

Adam

Okay, I've read a little more and I'm now keen on Jared's statement that a photon of red would supply the same energy (to photosynthesis reaction centers) as a photon of blue.  But the photo pigment still needs to shed the excess energy from absorbing the blue photon (and likely even the red).  And from what I've read, it sheds this either thermally (gets hotter) or fluoresces (emits light energy at a lower frequency).

I guess what I meant was that we don't know why corals do that.

Don't all photo pigments do that?  Isn't it just a function/fact of photosynthesis?

Why get rid of the excess?

As you've already stated, excess energy in either of the photosystems can shut down and damage the chemical pathways to photosynthesis.  Wouldn't it be more amazing if corals could harvest this excess energy to do something more worthwhile then fluorescing? 

However if some of that energy is first lost to heat or used in a chemical reaction, the falling electron will emit a photon of a longer wavelength that that of the original photon.

I believe that is what happens in photosynthesis.

Wouldn't it be more amazing if corals could harvest this excess energy to do something more worthwhile then fluorescing? 

Keep going.... your onto my theory now. 

Don't all photo pigments do that?  Isn't it just a function/fact of photosynthesis?

Oh, and one more question Jon.... so do you think that non-photosynthetic corals fluoresce?

Adam

Oh, and one more question Jon.... so do you think that non-photosynthetic corals fluoresce?

No, I wouldn't expect them to fluoresce since they do not contain photo pigments.  But they might fluoresce for reasons not related to photosynthesis such as camouflage or attraction for other critters that might "see" certain wave lengths better then others. ??

If this is true then the number of photons would be the determining factor in photo sythesis and the energy levels of the photons would be the determining factor in florecens.

Which is why most corals flouresce most strongly in the blue or green spectrum (blue absorbed light... high energy to dissapate).  The red light that is absorbed will floresce in red or infared(?).

I hope you guys know I'm just egging you on here.

One more question- so if Isn't it just a function/fact of photosynthesis? is true, then why don't all corals fluoresce???

Or to get back to the basics (which is still way off from the original post)
WHY do some corals fluoresce, but others don't.

Adam

Jon- I have another question for (I'm full of them today)
 And from what I've read, it sheds this either thermally (gets hotter) or fluoresces (emits light energy at a lower frequency).

So do you think corals are heating up, and parts of them may be water temp while other parts of them are warmed up?

Adam

then why don't all corals fluoresce???

Which one's don't?

The tree outside (ok... if it was summer) is fluorescing isn't it?  It doesn't glow but the chlorophyll must be fluorescing, right?  Perhaps that is what corals which don't appear to be glowing fluoresce?

Nope, lots of corals do not fluoresce.  Talk about weird huh?  I'm going to say (just guessing off the top of my head without any data here) that 50% of corals fluoresce.

Adam

Are you ready for me to really throw the monkey wrench?
So why do some fish fluoresce, and others don't?

I'm still lost on all of this.

Adam

Jared-
That is quite possibly the best answer I've ever seen.  Next time someone asks me why their gobies fluoresce but not their tangs I'm just going to copy and paste your post.

Adam

JON-

Okay so I checked into it a little more.  Based upon my tank at home I'd change my answer to about 80% fluoresce.  That happens to be a better guess because I'm told (Mazel) that the percentage of corals that fluoresce is about 75%.

To directly answer your questions- corals that I own that do not fluoresce include Cladiella, Clavularia, Anthelia, a couple acros.

Adam

To directly answer your questions- corals that I own that do not fluoresce include Cladiella, Clavularia, Anthelia, a couple acros.

Do you mean they don't fluoresce when stimulated with blue light?  Or are you saying that you would not get a reading off you Cladiella if using a PAM chlorophyll fluorometer?

Ooh, I don't know.  Okay how to word this...

The coral does not fluoresce.  At least not by blue light, uv, nor common excitation wavelengths.  However, with a PAM meter you would get readings because of the minor fluorescent effects of the zooxanthellae or chlorophyll.  Maybe not on all those corals, but certainly on some.

Adam

This is all conjecture on my part...
If the light gathering part of photosynthesis follows the photoelectric effect, then it stands to reason that all photo pigments will fluoresce.  Blue light more then red.  Adam, what color do houseplants fluoresce when illuminated with blue light?  The PAM meters all use red actinic (650-660 nm) for illumination and detect fluorescence up around 700 nm don't they?  That fluorescence is near the limit of human vision (maybe past).  Maybe the corals you listed fluoresce at a wave length you're not looking at?

Jon and Jared-
It is possible, that is why asked Mazel, who confirms that they are not fluorescing.  He may be wrong, but since he is the world authority here I'll trust him.
So corals (in general) that fluoresce take blue light and give off green.  But zooxanthellae and chlorophyll take blue light and give off red.  So house plants glow red, cabbage does, trees do, algae does.  So it is really easy to see what is fluorescing from chlorophyll.

It is possible that we just aren't seeing it, and yes corals do fluoresce at other wavelenghts.  But I'd say about 98% of the coral fluorescence is taking blue, giving off green and orange. 

But I still can't figure out why corals fluoresce.  Is there an advantage to it, and what is that advantage?

Oh, and I'm still wondering if anyone believes that corals are emitting energy as heat and are therefore warm on side of the coral (near the light) but cool on the other side (bottom or shaded side).

Adam

My knowledge of photosynthesis is spent at this point .  Have you done a literature search?  Google shows lots of hits:  http://scholar.google.com/scholar?hl=en&safe=off&q=coral+fluorescence&spell=1 - http://scholar.google.com/scholar?hl=en&safe=off&q=c oral+fluorescence&spell=1  but I'm sure the searches at the university would be even better.

On that google search, I've probably read the first 20 articles it lists.  Although that was a year ago, and I've only read a couple new papers since.  Most of my new info is from Mazel and Dana. 

Like Jon, I'm out of info knowledge, but still can't answer my own questions.

Adam

Jared wrote: At least the topic question got answered.

Yeah...sorry I asked.    I mean, thanks.