Inorganic Carbon to Reduce Phosphate & Nitrate?

[mesocosm]

Greetings All !

Originally posted by Redfish
... The problem is that we can't control the export once the something is inside the aquarium. ... Tell me what you are thinking from a practical standpoint.

Fair enough. If we're talking about precision control of export ... I agree completely. But on a "gross" level, I think we're already there ... on two levels.

The evolution of aquarium protein skimmers during the last 20 years has been nothing less than extraordinary. It seems to me that (... if we're willing to plunk down the cash ...) there are more than a few brands which are more than capable of "stripping" as much POM & bacterioplankton from the water column as we might safely generate. Adjusting the hours of skimmer operation presents a reasonable opportunity for "gross" export control. It seems to me that there are more than a few folks playing around with this husbandry tactic for a while.

The other opportunity has to do with bacteriplanktonic systems which incorporate some form of culture vessel. For this kind of configuration ... the characteristics & volume of media, the flow rate through the vessel, rate of violent disruption of the media, and on-off cycling of the pump operating the vessel are all indirect opportunities to control export (by influencing "production").



JMO

[jake2045]

I for one must say that this has to be the best thread I have read on RC in a long time. However, most of it is over my head but I can see the big points. Any opinion on why the alk has to be strictly maintained on some of the bacteriaplankton systems?(6-7.5 dkh)

[Canarygirl]

I read one person's opinion on this on the Zeovit forum recently. He said that in the ultra low nutrient environments, zooxanthella in the coral is reduced (this creates the nice colors); but with those reduced and their associated food source, corals can't sustain new growth at the accelerated rates that higher alkalinity promotes. Instead, they tend to burn out/die. That is one person's theory in non-scientific terms but it makes sense to me.

[stony_corals]

Canarygirl, there are a lot of theories... the answer is unknown. jake, the reason is that many experience burnt tips when higher than NSW levels are kept. Unfortunately, it's not the root cause. I've experienced it a few times....

[MCsaxmaster]

Originally posted by jake2045
Any opinion on why the alk has to be strictly maintained on some of the bacteriaplankton systems?(6-7.5 dkh)

I've gotta say, that is one of the odder things I've ever heard. I haven't any idea what might be going on there, but if this is a real phenomenon (I've heard of this from enough people to make me think that there really is something going on there) than it is an indirect and unfortunate side effect using whatever it is those folks are using in their systems. If you raise the alkalinity of real sea water (same stuff the corals are growing in) they calcify faster. If this causes adverse reactions in captivity, then there is something "off."

I read one person's opinion on this on the Zeovit forum recently. He said that in the ultra low nutrient environments, zooxanthella in the coral is reduced (this creates the nice colors); but with those reduced and their associated food source, corals can't sustain new growth at the accelerated rates that higher alkalinity promotes. Instead, they tend to burn out/die. That is one person's theory in non-scientific terms but it makes sense to me.

Unfortunately, this thinking makes some false assumptions. Firstly, the population density and growth rate of the zoox. in a lot of corals in captivity is probably not that much different from those in nature. Significant nutrient enrichment can cause increased zoox. growth rate and density, but most aquaria without persistent and obvious nutrient issues probably do not fall into this category. It is also possible to reduce zoox. density and growth rate due to nutrient starvation due to a lack of prey. Corals kept in systems that have little food input and mega-filtration likely have reduced populations of zoox. The population density of zoox. is only one part of the puzzle which helps to determine the coloration of the coral.

Second, increased alkalinity (which will increase the DIC) will reduce carbon limitation of the zoox. (though they probably aren't C-limited in most corals at fastish current speeds) and therefore increased alkalinity would increase the availability of photosynthate to both the corals and zoox., increasing their energy budgets. However, that is only true if the zoox. are C-limited, which they may be in relatively slow water motion, but probably are not on real reefs, or if they get sufficient water flow in reef tanks.

Third, calcification and photosynthesis are correlated, but not necessarily coupled (in fact, they are easy to decouple). Increased alkalinity increased the supply of DIC to calcification. Since calcification in most corals is likely C-limited this will increase calcification. If the coral calcification exceeds the rate of growth of the zoox. you'll get lighter colored tissue in the areas of growth. For some corals, this is the typical growth form. For instance, Acropora have zoox.-free axial coralites, yet this is the fastest growing part of the colony. There has to be some good regulation of the population and distribution of zoox. in the corals though, because a similar pattern is maintained even with widely variant rates of calcification. Corals in shallow water and corals in deep water maintain similar populations of zoox. even though they might be growing at very different rates.

More than anything though, I think it is worth considering what happens to corals out in nature that we know are living in low-nutrient water and in a relatively healthy setting. As I mention above, increased alkalinity means increased calcification (at least for the corals studied thus far).

Chris

[majesticangelfish]

Originally posted by jake2045
Any opinion on why the alk has to be strictly maintained on some of the bacteriaplankton systems?(6-7.5 dkh)

Gary was kind enough to send this information rich article. It’s a great read for low alkalinity, bacterioplanktonic reefing. (large file.. 7MB). Very interesting discussion on pg 30....

Geochemical Perspectives on Coral Mineralization
Anne L. Cohen & Ted A. McConnaughey
http://www.whoi.edu/science/GG/peopl...ralization.pdf

HTH

[Redfish]

Assuming the article is correct (I am not questioning it) there are some real one sentence zingers in there, particularly from page 28 on.

You could take some of those single sentences and spend years following up.

[mesocosm]

Greetings All !

Originally posted by Redfish
... there are some real one sentence zingers in there, particularly from page 28 on. ...

This is just too true ...


From the article ...

If corals calcify largely to help the zooxanthellae obtain nutrients, one might expect corals to calcify more (despite the metabolic expense) when the zooxanthellae need more nutrients. Experimental evidence to this effect surfaced a quarter of a century ago (Kinsey and Davies 1979), and subsequent experiments confirm that corals calcify more even though they photosynthesize less when phosphate, nitrate, ammonium, and iron are scarce (Marubini and Davies 1996; Marubini and Thake 1999; Ferrier-Pages et al. 2000, 2001) (Fig. 22).

This one was for the folks who've reported growth spurts in the SPS specimens in their ZEOsystems as the water column moved into phase 2 ...

... you're not hallucinating ...

BTW ... read the section previous to this quote (page 30) and you'll see the potential for an increased electrochemical gradient in the membrane to attract stuff like ... NH4 and Fe.



I dug the Cohen & McConnaughey one up because of a post by JWRE (... in another cyberspace far, far away). He reported that a group of German reefkeepers have been introducing CO2 in an effort to lower pH because they believe their corals (presumably SPS, but it was unspecified) demonstrate better nutrient uptake with the pH drop.

Those crazy Germans. You've got to love 'em ...

Cohen & McConnaughey also wrote this ...

The hypothesized connection between calcification and nutrient uptake may help to answer some the great conundrums of reef biology and geology: How do reefs flourish in some of the most nutrient deficient regions of the planet? Most corals feed on plankton, providing a source of nutrients beyond the reach of most plants. Corals also place their algae in a fixed location, often of high turbulence, enhancing their access to nutrients advected by in the ocean. But perhaps more importantly, corals generate protons through prolific calcification. The need for protons remains as long as the algae need nutrients. Corals therefore calcify year after year, long after they have built satisfactory skeletons. The same applies to calcareous algae.

That took me here ...

Photosynthesis and Calcification at Cellular, Organismal and Community Levels in Coral Reefs: A Review on Interactions and Control by Carbonate Chemistry
JEAN-PIERRE GATTUSO, DENIS ALLEMAND and MICHEL FRANKIGNOULLE
American Zoologist 1999 39(1):160-183; doi:10.1093/icb/39.1.160

Full Article
http://intl-icb.oxfordjournals.org/c...t/39/1/160.pdf


This article presents stuff like this ...

Goreau (1977) estimated, from stable isotope data, that approximately 40% of the carbon supply is from seawater DIC and 60% from recycled metabolic CO2.

Recycled metabolic CO2, as opposed to seawater DIC ... hmmm.


And this ...

There is no information available on the value of intracellular pH in coral cells and its control by seawater pH but it is well established that changes of external pH alter pH, and regulate numerous cellular process (e.g., Busa and Nucitelli, 1984). ...

... A decrease in external pH increase anionic permeability (reviewed by Madshus, 1988). Cell acidification can also increase the intracellular calcium concentration (e.g., Neglescu and Machen, 1990), which can, in turn, trigger numerous events such as exocytosis, kinase activation, and stimulation of cell membrane transport (Carafoli and Penniston, 1985).

pH, alkalinity, and metabolic "control" ... oh my ! ...



JMO

[mesocosm]

Greetings All !

Originally posted by jake2045
... Any opinion on why the alk has to be strictly maintained on some of the bacteriaplankton systems?(6-7.5 dkh)

Photoacclimation.



JMO

[Canarygirl]

Photoacclimation.

What about it? How does that relate to Alk level and Alk stability? Or are you joking and I don't get it....(wouldn't be the first time)

[MCsaxmaster]

The McConnaughey and Whelan hypothesis (which Cohen and McConnaughey follows up on) of calcification enhancing photosynthesis is contentious, to say the least. It seems pretty likely that calcification (if calcifcation produces protons, which it likely does, although that is a whole set of assumptions...) could aide photosynthesis, but ONLY if photosynthesis is C-limited in corals. At reasonable current speeds, zoox. in corals seem saturated at concentrations somewhat below NSW levels, so calcification likely is not significantly affecting photosynthesis in corals (neither helping nor hindering). This seems especially likely considering that it is easy to decouple the processes. Add nutrients and photosynthesis will go up while calcification will go down AT NSW LEVELS OF C. If you raise the DIC increased nutrients can actually increase both photosynthesis AND calcification.

Also, I think the argument that corals calcify to increase nutrient uptake for their zoox. is incredibly weak. The primary limitation on nutrient uptake by corals and other benthic reef denizons is the rate of mass transfer from the water column. This is controlled primarily by the rate of water flow over/around the organisms, not by electrostatic interactions. If there are German aquarists that are dropping the pH of their tanks in an effort to increase nutrient uptake and calcification...they would be best to read some more of the primary literature on the subjects. A higher pH and another water pump would likely serve them much better (as a side note, I've seen some surprising responses to altered sea water chemistry in some of my work lately...)

The best supported model for the effect of nutrients on calcification is C-limitation of calcification due to increased C-fixation by the zoox. While photosynthesis CAN increase calcification, the two can be decoupled easily as well. Calcification likely doesn't impact photosynthesis much. Light-enhanced calcification is well-supported, while calcification-enhanced photosynthesis has been at least partially refuted (all with respect to corals, of course).

Greetings All !



quote:
--------------------------------------------------------------------------------
Originally posted by jake2045
... Any opinion on why the alk has to be strictly maintained on some of the bacteriaplankton systems?(6-7.5 dkh)
--------------------------------------------------------------------------------

Photoacclimation.



JMO

Explaind if you would

Chris

[mesocosm]

Greetings All !

Originally posted by Canarygirl
... Or are you joking and I don't get it....(wouldn't be the first time)

Apologies if my alleged humor doesn't translate well through the cyber-ethers. You wouldn't be the first that I've annoyed with well intentioned, but failed efforts ...

... not by a long shot.

Originally posted by Canarygirl
What about it? How does that relate to Alk level and Alk stability? ...

I would ask your patience and forebearance ... from Chris and others as well ... there is much contention with this stuff, and I choose to move slowly. It is not my intention to be coy, or to play trail-of-breadcrumbs games ... there are some fascinating (and arguably complex) variables in play, and as Chris has already pointed out, not even the academic research community is in agreement as to what's going on with them.

Even so ...

Yes indeed, inorganic carbon must be taken up in large amounts by corals. Models of carbon isotope balance that I pubished in 1976 show that a significant fraction of the carbon used in the skeleton must be derived from uptake of inorganic bicarbonate from the ocean as well as from respiratory carbon. This confrms the T. F. Goreau calcification mechanism and model from the 1950s, in which alkalinity generated by photosynthetic CO2 removal drives coral calcification. As I pointed out in an earlier posting, you cannot derive coral organic carbon uptake from oxygen balance becauase most of the carbon translocated by zoocanthellae is immediately released as mucus, so coral must get most of their carbon from zooplankton feeding.


Thomas J. Goreau, PhD
http://coral.aoml.noaa.gov/pipermail...ly/003469.html

The "issues" associated with low alkalinity in bacterioplankton systems have to do with the growth of scleractinian corals, do they not? Alkalinity level, calcification, and photosynthesis are all dynamically entangled with the growth of scleractinian corals. All I've asserted is the notion that photoacclimation is part of that dynamic.

Is there really any question about this?




JMO

[mesocosm]

Greetings All !


Before I post another word ... you're a pleasure to talk with Chris. Many have commented on the quality of this thread, and your contributions are a large part of it. Nicely done, everyone ... many thanks for all the wonderful enrichment opportunities that you have provided.

The McConnaughey and Whelan hypothesis (which Cohen and McConnaughey follows up on) of calcification enhancing photosynthesis is contentious, to say the least.

Nolo contendre, but I'm not alone. For example ...

As for the -HCO3 issue, you may want to check the article by TA MacConnahaughy around 97 in Earth Sciences Review, title is something like "Calcification generates protons for nutrient capture." The article deals with a multitude of mechanisms for calcification as a means of capturing inorganic carbon rather than being solely a protective or structural development in terms of evolution of corals in an oligotropic niche.


Tom Wyatt
http://coral.aoml.noaa.gov/pipermail...ly/001113.html

... if photosynthesis is C-limited in corals ...

I do not content that photosynthesis is C-limited in marine aquaria. This is NOT where I'm going.

... This seems especially likely considering that it is easy to decouple the processes. ...

You've pointed this out before, and I hope others are taking note of it. This IS where I'm going.

... I think the argument that corals calcify to increase nutrient uptake for their zoox. is incredibly weak ...

Agreed, although I would comment that it's an interesting evolutionary tangent. My interest is that nutrient uptake does increase, along with the creation of a proton gradient ... as opposed to the notion that calcification is done to effect an increase.

The primary limitation on nutrient uptake by corals and other benthic reef denizons is the rate of mass transfer from the water column.

ROTFL ! ... hehe ... are you kidding me? You and Jake were the ones that convinced me of this last year. I went through post-gradient/diffusion concept withdrawals for months.

Old belief systems die hard, don't they? ...

... not by electrostatic interactions.

We need to talk ... the effects of osmoregulation and chemoelectric gradients is one of the components of where I'm going. Not in terms of the contrast with mass transfer ... your point with regards to nutrients is entirely well taken ... but rather in terms of PSII shutdown, electron flow sinks, the dynamics of intracellular CO2, and the enzyme regulation of oxidative stress.


Here's one for you ... do you think that what folks are reporting is a "chemical toxicity" phenomena, or, a "bleaching" phenomena? I come down on the "bleaching" side of the fence ... hence "photoacclimation".

From a different angle ... am I reading you wrong when I infer that you think it's a "toxicity" thing ("... it is an indirect and unfortunate side effect using whatever it is those folks are using in their systems")? If so, we have something else to discuss. I view the ease of remediation as a compelling demonstration against "toxicity".

If there are German aquarists that are dropping the pH of their tanks in an effort to increase nutrient uptake and calcification ... A higher pH and another water pump would likely serve them much better.

Fair enough ... but it is intruiging.

... While photosynthesis CAN increase calcification, the two can be decoupled easily as well ...

Indeed ... I have great hopes for this turn in the thread. It seems to me that getting a better handle on how to manipulate this dynamic would be of benefit to ALL reefkeepers ... whether they'd rather eat detritus than use a bacterioplankton system or not.

Light-enhanced calcification is well-supported, while calcification-enhanced photosynthesis has been at least partially refuted (all with respect to corals, of course).

ROTFL ... The calcification-photosynthesis stuff with regards to phytoplankton gets in the way of my data-mining adventures all the time. Even so, I'm not going towards light vs. dark cycles.

Explaind if you would

Not until we discuss the role of amino acids in metabolic regulation ...





JMO

[mesocosm]

Greetings All !


Yikes ... I really do get way too excited about this stuff. If it's okay with everyone, let me try this again.

Originally posted by mesocosm
... but rather in terms of PSII shutdown, electron flow sinks, the dynamics of intracellular CO2, and the enzyme regulation of oxidative stress. ...

Please disregard this part for the moment ... it just muddles things up.

Originally posted by mesocosm
... do you think that what folks are reporting is a "chemical toxicity" phenomena, or, a "bleaching" phenomena? I come down on the "bleaching" side of the fence ... hence "photoacclimation". ... I view the ease of remediation as a compelling demonstration against "toxicity".

If we're going to get into this, we need to start here. If folks are viewing this "issue" from a "chemical toxicity" perspective, then nothing I have to suggest will make any sense ... indeed, it will probably come across as irritating techno-babble jibberish.

Folks who have experienced "issues" report that once their alkalinity is restored to the 6.5-8.0 dKH range ... the "issues" disappear. I view this as more than compelling. I consider this to be definitive.

"Photoacclimation" strikes me as a fairly reasonable vocabulary choice to assign to this dynamic, but I'm open to alternative suggestions. Even so, I concede that there is much room for informed perspectives to disagree about this.

Originally posted by mesocosm
Not until we discuss the role of amino acids in metabolic regulation ...

I really, really need to stop with the winking emoticon thing. Not helpful. This is where I'm going with this ...

The Physiological Mechanisms of Acclimatization in Tropical Reef Corals
RUTH D. GATES and PETER J. EDMUNDS
American Zoologist 1999 39(1):30-43; doi:10.1093/icb/39.1.30

Full Article
http://intl-icb.oxfordjournals.org/cgi/reprint/39/1/30


Some extracts from the article ...

As discussed earlier, protein metabolism plays a key role in coral acclimatization and as in non-symbiotic organisms, amino acids for protein metabolism are taken up directly from the environment, released by the catabolism of food, and recycled following protein breakdown. However, corals also acquire translocated essential amino acids from their symbiotic dinoflagellates (Fitzgerald and Szmant, 1997; Swanson and Hoegh-Guldberg, 1999). These amino acids are cyclically available and appear to be rapidly incorporated into host proteins (Gates and Muscatine, unpublished data), although it is unknown whether they are incorporated randomly, or are used to synthesize specific proteins in the host.

Although there are strong anecdotal observations that corals with high growth rates have the tendency to undergo rapid bleaching (Suharsono and Brown, 1990; Jokiel and Coles, 1990; Glynn, 1993; Hoegh-Guldberg and Salvat, 1995), there has been no direct experimental evaluation of the relationship between growth rate and metabolic rate in reef corals. Nevertheless, a non-exhaustive survey of the literature provides some support for the inverse relationship between growth rates and metabolism (Fig. 4). This relationship, although tentative, suggests that corals with low growth rates and high metabolic rates (e.g., Siderastrea siderea; D on Fig. 4) exhibit high rates of protein turnover and an ability to acclimatize readily. In contrast, those with high growth rates and low metabolic rates {e.g., Acropora cervicornis; A on Fig. 4), exhibit lower rates of protein turnover and a reduced capacity to acclimatize. The proposed relationship between growth rates, metabolic rates and acclimatization capacities is also supported by intra-specific differences in the propensity of corals to bleach, assuming that coral bleaching is at one extreme of the range of acclimatization responses.

This supply of amino acids will be changed by environmental conditions that elicit shifts in nutrient uptake, photosynthetic and respiratory pathways. As such, the extent to which the host is dependent on these amino acids for the synthesis of proteins required for acclimatization will dictate the ramifications of the environmental disturbance on the intact association.

In addition to their role in protein metabolism, free amino acids have been implicated as regulatory molecules in some tropical symbioses, controlling the synthesis and translocation of photosynthetically derived metabolites, specifically glycerol, from the dinoflagellates to the host (Gates et al, 1995; Gates et al, 1999).

A heterogeneous pool of free amino acids, identified as a "host factor" in Pocillopora damicornis (Gates et al., 1995), and several other reef corals (Gates, unpublished), sustains the metabolic competency of isolated symbiotic dinoflagellates in vitro, and induces the translocation of metabolites from these dinoflagellates to the surrounding medium (Gates et al, 1995; Gates et al, 1999). Thus proteins and their constituent amino acids occupy highly diverse functional roles in reef corals, a scenario which, by default, implicates protein turnover in the maintenance of these metabolic processes.

"... there are strong anecdotal observations that corals with high growth rates have the tendency to undergo rapid bleaching (Suharsono and Brown, 1990; Jokiel and Coles, 1990; Glynn, 1993; Hoegh-Guldberg and Salvat, 1995), ..."

Sounds a lot like what folks are reporting when they mismanage their alkalinity outside the 6.5-8.0 dKH range ... doesn't it?



JMO

[Redfish]

But Why?

(Those of you with, or experienced with, kids will completely understand the context, meaning and inherent humor of those two words and will currently be rolling on the floor laughing. There is nothing like that split second of thinking you have explained life to your child only to have those two words flung back at you. To mesocosm, my apologies for the humor. It is purely a reflection of my ignorance and, well, maybe the headache you just inflicted upon me.)

[MarkPo]

Originally posted by mesocosm
I would ask your patience and forebearance ... from Chris and others as well ... there is much contention with this stuff, and I choose to move slowly. It is not my intention to be coy, or to play trail-of-breadcrumbs games ...

I don't know about the smart people reading this thread, but I just have enough time to read the smart posts, look up the referenced articles, read them, and look up all the big words I don't know before you guys post again.

Thank you.

[mesocosm]

Greetings All !

Originally posted by Redfish
... There is nothing like that split second of thinking you have explained life to your child only to have those two words flung back at you.

ROTFL ! Trust me when I say I got it immediately. I used to work in summer science camps for kids ages 8-14. Talk about a tough crowd ... cyber-reefkeepers are nothing by comparison.

Originally posted by Redfish
But Why?

Try it from this angle ... what causes decoupling of photosynthesis from calcification within a scleractinian coral's tissues, and what happens to zooxanthellae if the decoupling persists?

From another ... are there any intracellular metabolic pathways in the zooxanthellae-host relationship which might be disrupted by HCO3, pCO2, microbial leakage, and/or nutrient uptake shifts (both + and -) ... or ... by changes in either electrochemical gradients, and/or osmoregulation (in general)?

My answer to the last question is yes ... hence photoacclimation. For the record, I sit ready to concede to a better explanation. I have no personal investment or entanglement with this topic (... other than the absurd willingness to address it in the first place ...), nor have I asserted any claim of superiority of my perspective over another (... nor will I. Speculations about what's going on with the metabolism of corals are indeed contentious, as was previously pointed out). Everyone should feel free to dismiss my opinion at their leisure.

Last bit ... we're not suggesting that what's being reported is a straight-up, single variable bicarbonate water chemistry event, are we?




JMO ... your mileage will vary.

[MCsaxmaster]

My-oh-my this whole thing is getting a bit thick isn't it....

On the whole McConnaughey hypothesis of calcification enhancing photosynthesis in corals (either by producing protons and increasing availability of CO2/HCO3- or increasing nutrient uptake), I just don't buy it. The experiments that have been done really don't seem to support the hypotheses. Ted McConnaughey is a great scientist and these hypotheses (first proposed some 10 years ago now) are good, solid and testable hypotheses and reasonable based on knowledge at the time, but in the last decade I just have not seen support that these factors are really very important. Sure, I can believe that protons produced by calcification (which assumes corals are using HCO3- or CO2 as the source of C) could aide photosynthesis, but to such a small degree that it probably doesn't matter. But again, if the zoox. are saturated with C at NSW levels (and reasonable water flow) then it really doesn't matter. The physiological data is inconsistent, the stoichiometry data is inconsistent and direct tests of the hypothesis appear inconsistent. It is/was a good idea, but I just don't see support for it.

While this hypothesis seems more believable for algae and plants, I still have reservations about it. Terrestrial plants may well calcify accidentally in an effort to get nutrients. Aquatic plants *might* to the same, but it almost seems just a consequence of their physiology, nothing "intended" or mediated. When we start looking at calcifying marine algae I become less convinced that they are calcifying to affect CO2/HCO3- or nutrient availability and think that other reasons to calcify are more likely (e.g., physical defense).

We need to talk ... the effects of osmoregulation and chemoelectric gradients is one of the components of where I'm going. Not in terms of the contrast with mass transfer ... your point with regards to nutrients is entirely well taken ... but rather in terms of PSII shutdown, electron flow sinks, the dynamics of intracellular CO2, and the enzyme regulation of oxidative stress.

Hmmm, please explain further as I'm not sure I follow. Higher alkalinity (assuming constant pH) means more DIC of all species which should reduce problems of photoinhibition, for instance. Also, since most of the C is in the form HCO3- and CO3-- it isn't going to enter the cells passively w/o a channel (can easily flood into a zoox. cell this way). Zoox. almost certainly are using some sort of carbon concentrating mechanism though, so they're probably pumping in HCO3- at pretty good rates. Higher DIC makes this easier...

Here's one for you ... do you think that what folks are reporting is a "chemical toxicity" phenomena, or, a "bleaching" phenomena? I come down on the "bleaching" side of the fence ... hence "photoacclimation".

From a different angle ... am I reading you wrong when I infer that you think it's a "toxicity" thing ("... it is an indirect and unfortunate side effect using whatever it is those folks are using in their systems")? If so, we have something else to discuss. I view the ease of remediation as a compelling demonstration against "toxicity".

See, I guess that's my question too, what they heck is happening to the corals? From what I've heard, if the alkalinity much higher than in NSW some corals will die at the tips but that this problem goes away if the alkalinity is lowered. I haven't heard anything about bleaching but rather actual tissue death, but I really haven't been paying attention either. If the tissue is dying off at higher alkalinity, I wouldn't (and don't) have a clue what is going on, but problems with photoadaptation don't occur to me... If anything, photoadaptation should be easier with higher DIC, right? I suppose that, whatever the problem is, it just strikes me as a defect with the methodology, whatever that methodology is. Corals don't die off at the tips like that if you bump alkalinity in NSW. They don't do that with other sorts of reefkeeping methodologies either, so what is the problem here? To me personally, I'm not sure I really care. Other methods not using all sorts of new-fangled, fancy concoctions and whatever else work great and don't give me those problems, so what do I care why another methodology doesn't work if I already have one that does, know what I mean? Anyway, that's just me...

Let me take a closer look at the Gates and Edmunds paper...

As for Tom Goreau Jr.'s comments: I would take them with a grain of salt--a large grain, actually

Chris

[mesocosm]

Originally posted by MCsaxmaster
My-oh-my this whole thing is getting a bit thick isn't it....

Don't think for a moment that the lack of parsimony in what I'm posting is lost on me. Looking forward to what you think of Gates & Edmunds.




Canarygirl ... PMs are waiting for you.



BTW, for anyone who was wondering ...

Parsimony: In science, parsimony is to prefer least complicated explanation for an observation. This is generally regarded as good when judging hypotheses. Ockham's Razor also states this idea; More logical to accept a hypothesis that depends on a small number of processes rather than based on a large number of independant processes.

[mesocosm]

Greetings All !


Not to physically assault a dying equine, but I wanted to make one last comment. There are many competing models for what's going on, and if you want to see one of the better summaries of the competing topics and rersearch data ... read the discussion section of the following article.


Imbalanced coral growth between organic tissue and carbonate skeleton caused by nutrient enrichment
Tanaka, Miyajima, Koike, Hayashibara & Ogawa
Limnol. Oceanogr., 52(3), 2007, 1139–1146

Full Article
http://www.aslo.org/lo/toc/vol_52/issue_3/1139.pdf



A few extracts ...

In corals that reside in relatively high-nutrient environments, the NO3 uptake system should be repressed due to readily available reduced N, such as NH4 and amino acids. Considering that coral colonies used in the present study actively took up NO3 in their tissue, they might have been originally in a nutrient-limited environment. Translocation of organic N from zooxanthellae to the host may also depend on the host nutrient condition.

In those previous studies, however, nutrient effects were disregarded. Nutrient incorporation generally enhances algal photosynthetic activity, and, accordingly, gross and net primary production (Dubinsky et al. 1990; Marubini and Davies 1996; Ferrier-Page`s et al. 2000a) as also found in the present study. Here, attention was paid to how calcification was affected by the increased photosynthetic DIC uptake due to nutrient incorporation. As a result, the relationship between net photosynthesis and calcification showed statistically significant correlation (p 5 0.01; Fig. 2), but the slope of 0.16 suggests that the calcification was not considerably stimulated by the enhanced photosynthetic activity. In other words, the light-enhanced calcification was almost ata maximum level, and other factors such as organic matrix synthesis (see below) limit the calcification.

Allemand et al. (1998) demonstrated that inhibition of proteinsynthesis reduced Ca deposition rate simultaneously, suggesting that organic matrix biosynthesis, rather than calcium deposition, may be a limiting factor controlling the coral skeletogenesis. In the present study, the nutrient enrichment could have increased amino acid synthesis by the zooxanthellae. This higher amount of amino acids would havebeen translocated to the host and would have increased host biomass (Table 1). Although the C:N ratio of the host did not significantly change, a protein pool for synthesis of theorganic matrix might have been enlarged with the nutrientpretreatment. Several authors have shown that photosyntheticproducts of zooxanthellae may be used as precursors for the organic matrix (e.g., Young et al. 1971).

Third possibility is that the increased supply of metabolic CO2 in the calicoblastic cell enhanced thecalcification rate. Furla et al. (2000) showed that metabolic CO2 would be the main source (70–75%) of total C for calcification. It has also been shown that respiration rates can be increased by higher nutrient conditions and subsequent coral biomass increases (Marubini andDavies 1996; Ferrier-Page`s et al. 2000a), as observed in the present study (Table 1). The nutrient input in this study might have stimulated calcification through increased tissue biomass and supply of metabolic CO2 (Furla et al. 2000).

In the present study, the reduction of translocation during measurement of photosynthesis and calcification could have not occurred because nutrients were depleted during the period. Therefore, calcification rates might decrease by nutrient enrichment according to the processes of not only DIC competition between photosynthesis and calcification but also reduced translocation of photosynthetic products to the host.

JMO ... HTH ... out.

[Redfish]

At the end of the day, or in this case the thread, it seems we really have a good handle on the biology and chemistry. I would like to see a similar thread on debating practical application of what we have discussed. Or maybe, and this would be another novel first for this forum, a thread where a collective practical model is built. It would be interesting to see how political that would get. I have a feeling it would not be as open as this thread was.