Zooxanthellae Light Levels

[invincible569]

Some points to consider by Dana Riddle

http://www.masla.com/reef/lightingbasics.html

Zooxanthellae have a minimal light requirement called the Compensation Point. This is the point at which the oxygen produced by photosynthesis is equal to the oxygen requirement of the zooxanthellae. If light intensity is too low, a zooxanthella will not produce enough oxygen to meet its respiratory requirements and probably will not use enough of the coral’s waste products to be of any use. So, an increased photo period (the amount of time that the lamps are on) will not make up for an insufficient amount of light. Bottom line: The amount of light must exceed the Compensation Point!

Zooxanthellae also have a maximum light level - this is called Saturation Point. Exceeding the Saturation Point is senseless, as increasing the amount of light will not enhance the rate of photosynthesis.

Just one last term - Photoinhibiton. Photoinhibiton is when there is so much light that the photosynthetic process begins to shut down. In essence, too much light is just as bad as too little, resulting in the same effects. There is some debate as to whether this actually happens in aquaria. My personal opinion is that it happens a great deal. Two examples: Try to get some of the pretty red calcareous algae (Peyssonnelia, for instance) to grow directly under a 400 watt metal halide lamp. Try the same with some of the "Mushroom Corals" (Discosoma species). The calcareous algae will die within a few days’ time; the Mushroom Coral will react in a negative fashion and will shrivel in an attempt to hide from the light and will often die

[Aged Salt]

Good ponts, Edward, as once pohotosaturation is met photosynthesis is shut-down. The trick here is finding the up-to-saturation point as different corals have different light photosynthetic requirements, w/o photoinhibition. This will vary in our individual tanks even those with the same light intensity/photoperiod. Bob

[reefplayer]

I agreed with Edward. Every species has different needs and that is in the wild. Not to mention in our tank where we put all sps corals together, some do well, others may not. Not to mention when tanks with mix reef.

I always think that mix reef is far more difficult than sps nominated tank.

[mesocosm]

Greetings All !

Edward ... GREAT STUFF!

For anyone interested in some more detailed explanations of some of the essential terminology ... IMO ... that Edward referenced, and how it is specifically connected to photosynthesis, you might want to check out:

Lighting Technical Data
http://www.coralreefecosystems.com/l...nical_data.htm

These emergent concepts (... at least on the "hobbyist level" ...) are so vital that I just can't resist ...

Compensation Point is usually defined as the minimum amount of light required for oxygen production to meet the zooxanthellae/coral host respiratory requirements. Corals have the ability to absorb oxygen from the surrounding water (as they do in darkness); however, insufficient light energy may also result in low production of photosynthetic lipids. During periods of prolonged darkness (or inadequate light) zooxanthellae will then use their energy reserves until they are depleted and a sort of starvation occurs, usually resulting in irreversible damage or death. Compensation points vary from specimen to specimen and often depend upon their light history. Compensation points in low light adapted corals may be just a few µMols·m2·sec or much higher in high light adapted corals (350 µMols·m2·sec or ~17,500 lux; see Kirk, 1983). It should be understood that light intensity should exceed the zooxanthella’s compensation point.

Saturation Point Photosynthetic rates are proportional to light intensity only to a certain point. The Saturation Point has been met when photosynthesis is at a maximum, and increasing light will no longer increase the rate of photosynthesis. Saturation occurs when the photosynthesis electron transport systems are operating at full capacity. Exceeding the saturation point is pointless, and from a practical standpoint, results in needlessly high electric bills. If light energy greatly exceeds the saturation point, Photoinhibition may occur.

Photoinhibition is generally defined as any occurrence interrupting the normal electron flow in photosynthesis. There are two types of photoinhibition – dynamic and chronic. The first is chronic photoinhibition that involves irreversible damage to Photosystem II and were synthesis of new “photosynthetic proteins” must occur before normal photochemistry may resume (Brown et al, 1999). Dynamic photoinhibition involves reversible photochemical reactions that divert excess light energy away from Photosystem II through thermal dissipation. This “quenching” of photosynthesis involves reversible changes in xanthophylls diadinoxanthin and diatoxanthin. Dynamic photoinhibition protects the zooxanthellae (through absorption of violet through yellow-green wavelengths of 400-550 nm) from high levels of photosynthetically produced oxygen radicals, including hydrogen peroxide. Not all strains of zooxanthellae have the ability to produce xanthophylls and therefore may have little resistance to the effects of high light intensity.

Extracted from:
Lighting Technical Data
http://www.coralreefecosystems.com/l...nical_data.htm

Every species has different needs and that is in the wild. Not to mention in our tank where we put all sps corals together, some do well, others may not. Not to mention when tanks with mix reef.

Well said ...

There's some interesting literature emerging which begins to document a wide variety of potential factors, and the complexity of their interactions. Some examples include ...

Photoinhibition in shallow-water colonies of the coral Stylophora pistillata as measured in situ
Gidon Winters, Yossi Loya, Rüdiger Röttgers, Sven Beer
Limnol. Oceanogr., 48(4), 2003, 1388–1393
http://aslo.org/lo/toc/vol_48/issue_4/1388.html

Size-Dependent Differences in the Photophysiology of the Reef Coral Porites astreoides
Peter J. Edmunds, and Ruth D. Gates
http://www.biolbull.org/cgi/content/full/206/2/61



Even the big kids have trouble sorting it all out ... ... for example ...

For example, conspecifics belonging to different size classes may harbor distinct "types" of symbiotic zooxanthellae (7), each with the physiological characteristics and functional limits most suited to the ontogenetic rigors facing corals of a particular size. Alternatively, the symbionts harbored by size I and size II juvenile corals might be identical, but the communication between the symbiotic partners might be tailored to meet the unique demands of their specific developmental stage, such as the rapid growth necessary for small juveniles to escape the risks of overgrowth and predation (8). Or perhaps allometric scaling of biological traits (9) mediates the differences in photophysiology. For example, size-dependent changes in coral tissue biomass and thickness (9) could create variable shading of zooxanthellae through behavioral responses (10), and rapid protein metabolism in fast-growing small corals could reduce the nitrogen limitation of the symbiotic algae, thereby enhancing the efficiency of photochemical conversion (11). Regardless of the mechanisms underlying our results, we believe that further investigation of size-dependent variation in juvenile corals is likely to be valuable in understanding the environmental thresholds and biology of these complex symbiotic organisms.

Extracted From:
Size-Dependent Differences in the Photophysiology of the Reef Coral Porites astreoides
Peter J. Edmunds, and Ruth D. Gates
http://www.biolbull.org/cgi/content/full/206/2/61

Yeah, I had to read it a couple of times too ... ...


But all is not lost ... there are suggestions emerging in the literature regarding how to mediate the mechanisms of photoinhibition. Consider ...

The results of this suite of tests suggest that bleaching is a mechanism that the corals use to get rid of zooxanthellae when environmental conditions are such that the zooxanthellae are producing too much reduced oxygen. By expelling zooxanthellae, the corals are in effect, controlling the rate of photosynthesis so that it can be matched to the production of natural antioxidants.

The use of antioxidants showed that by artificially increasing the ability of the coral to deal with the higher concentration of oxygen radicals bleaching could be prevented. Does this mean that antioxidants could be a 'cure' for bleaching in corals? Cure would probably be the wrong word as this implies bring the coral back from an unhealthy state to a healthy state - this was not demonstrated in the Lesser study.

Antioxidants would be better described as a preventative. So how could they be used in the aquarium? That question is not answered yet. Perhaps they could be added at the first sign of stress but again the effectiveness of this has not been tested.

Extracted from:
Is There a Treatment for Coral Bleaching in the Future?
by Timothy A. Hovanec, Ph.D.
http://www.marineland.com/science/re...tCorBleach.asp

If you're not familiar with any of Dr. Hovanec's work ... it's great stuff ... IMO.


Just trying to fill in the data set ...

[invincible569]

Greetings All !


If you're not familiar with any of Dr. Hovanec's work ... it's great stuff ... IMO.

gary, on the last quote.. could this be the case of ZEOspur? An Antioxidant? or am i thinking of this backwards?

[mesocosm]

Greetings All !

Antioxidants would be better described as a preventative. So how could they be used in the aquarium? That question is not answered yet.

One possibility ... to my warped little mind at least ... ...

is "gut-loaded" microflora and microfauna (.... although limited by their "acceptability/applicability" to specific coral consumers, of course ...).

Another is the obvious ... direct supplementation into the saltwater medium. Think about it.

Then again ... maybe someone else already has. I wonder what the anti-oxidant profiles of ZEOvit products look like ... hmmm.

Let's not all be too surprised ... yes?

Just trying to fill in the data set ...

[invincible569]

After reading that article, I meant to say oxidant.. as quoted from the article:

" it can oxidize (basically dissolve) tissue"

[fkadir]

For photoinhibition to occur, does it take too strong an intensity or does it take too long a lighting duration? or both?

[invincible569]

The other good thing about this article is that it states that minimal bleaching is healthy for the coral.

"bleaching, at least in some cases, may be healthy for corals as it allows them to compensate for less than optimal conditions."

Farish, both. A perfect example of this is when you leave your lights on accidentally for too long and you see your corals shrivel up. Just like humans, we need both night/day times to survive on planet earth. Or think of it this way... when you are in a dark area and you are watching a movie.. but when you walk out the theater, its very bright and you have to squint. Your eyes have to adjust. Too much light is not good.

[mesocosm]

Greetings All !

I'm still trying to figure out why the reliable and replicated observations and photo-documentation of a large group of seriously experienced and advanced reefkeepers have been so blithely dismissed ... go figure. We're a funny species, aren't we?

What else is new? ...

And yet, it might be useful to those of us who are using the ZEOvit methodology to remember that, within the context of scientific empiricism, hands-on, experienced-based practical application and husbandry only goes so far ... powerful though that experienced-based practical application and husbandry has proven to be. Once you cross over into the land of proposing specific ... and in some cases even generalized ... chemical and biochemical pathways, you'd better have a pretty good understanding of the reactants you're dealing with ... otherwise you're just frolicking in the swamp of jibberish nonsense ...

...

... could this be the case of ZEOspur? An Antioxidant?

It's one thing to post some "generalized" literature extracts which pertain to reefkeeping in general, and coral growth specifically. It is a completely different thing to apply those extracts to the behavior of unspecified proprietary chemical solutions in a marine aquarium.

My statement ("Then again ... maybe someone else already has. I wonder what the anti-oxidant profiles of ZEOvit products look like ... hmmm") was made to SUGGEST the POSSIBILITY that IF ZEOvit products are DEMONSTRATED to contain anti-oxidants, they MAY serve to mediate photosynthetic pathways in corals. This possibility ... if operant ... might help to explain some of our experience-based, practical observations, yes? Just a thought ... .

Just trying to fill in the data set ...

[reefplayer]

Wow, Gary? very technical and valuable info. Thanks for sharing. Will print out to read it.

[nyfireman3097]

i agrree i shut my 10k 400 to 4 hours a day and everything looks awesome since ive done it and seem to be growing more
Nick