Daytime pH as an indicator of coral growth (photosynthesis)

[cobra2326]

Discuss. I found a paper that said alkalinity was a much better indicator. I realize that things like algae and other photosynthetic organisms could skew the numbers. However, in a tank with minimal algae in the display, is this useful at all?

In my tank, I've noticed some days spike a little higher than others, and there seems to be a slight upward trend as things are getting healthier.

 

[Randy Holmes-Farley]

pH can be some indication of photosynthesis. Alkalinity is an indication of calcification. I’m not really sure how tightly they are related even for an SPS coral, but there will be some significant connection.

 

[Dennis Cartier]

I can't find the post right now, but earlier today I was reading a thread where Jonas, the inventor of the Alkatronic alkalinity measuring unit showed a graph where he had put some GFO online and the alkalinity started decreasing. His belief was that the lower phosphate level had increased calcification and was visible in the graph output of his unit. I am not sure if GFO can deplete alk, but assuming not, it was rather interesting to see the cause and effect this way. Almost made me want to run out and buy one. Funny that.

Dennis

 

[cobra2326]

I can't find the post right now, but earlier today I was reading a thread where Jonas, the inventor of the Alkatronic alkalinity measuring unit showed a graph where he had put some GFO online and the alkalinity started decreasing. His belief was that the lower phosphate level had increased calcification and was visible in the graph output of his unit. I am not sure if GFO can deplete alk, but assuming not, it was rather interesting to see the cause and effect this way. Almost made me want to run out and buy one. Funny that.

Dennis

It can: http://www.reefkeeping.com/issues/2004-11/rhf/index.php. That’s one of the neat things you get from continuous monitoring of parameters like that.

There are a lot of variables, but until I get a cheap, reliable way to continuously monitor alk, it’s an interesting thing to watch.

 

[Randy Holmes-Farley]

I can't find the post right now, but earlier today I was reading a thread where Jonas, the inventor of the Alkatronic alkalinity measuring unit showed a graph where he had put some GFO online and the alkalinity started decreasing. His belief was that the lower phosphate level had increased calcification and was visible in the graph output of his unit. I am not sure if GFO can deplete alk, but assuming not, it was rather interesting to see the cause and effect this way. Almost made me want to run out and buy one. Funny that.

Dennis

That isn't the only possible explanation. Two others also may play a role in that observation, besides increased coral growth and a direct effect of GFO on pH.

Released iron can increase abiotic precipitation by nucleating calcium carbonate precipitation (shown in the scientific literature), and decreased phosphate and organics increases abiotic precipitation since phosphate and many organics gets onto growing calcium carbonate surfaces and poisons it for more precipitation. Less phosphate and less organic matter means less of that effect. Both phosphate and organic effects are shown in the scientific literature on precipitation of calcium carbonate.

One or all of these seem likely to be happening since GFO particles and parts of tanks just downstream of GFO reactors often get coated in precipitated calcium carbonate.

 

[Dennis Cartier]

That isn't the only possible explanation. Two others also may play a role in that observation, besides increased coral growth and a direct effect of GFO on pH.

Released iron can increase abiotic precipitation by nucleating calcium carbonate precipitation (shown in the scientific literature), and decreased phosphate and organics increases abiotic precipitation since phosphate and many organics gets onto growing calcium carbonate surfaces and poisons it for more precipitation. Less phosphate and less organic matter means less of that effect. Both phosphate and organic effects are shown in the scientific literature on precipitation of calcium carbonate.

One or all of these seem likely to be happening since GFO particles and parts of tanks just downstream of GFO reactors often get coated in precipitated calcium carbonate.

So let me see if I absorbed what you just said ...

Lowering phosphate using GFO may allow more abiotic precipitation (due to the lower phosphate level) and therefore lower the alkalinity in the process? So is this why lower phosphate levels are also credited with faster growth?

Dennis

 

[Randy Holmes-Farley]

So let me see if I absorbed what you just said ...

Lowering phosphate using GFO may allow more abiotic precipitation (due to the lower phosphate level) and therefore lower the alkalinity in the process? So is this why lower phosphate levels are also credited with faster growth?

Dennis

The first sentence is part of what I suggested, yes.

I would not be surprised if some people might mistake the effect for faster coral growth, but faster growth has also been measured in other ways. Tjhe data supporting it are mixed:


Effects of elevated nitrogen and phosphorus on coral reef growth. Kinsey, Donald W.; Davies, Peter J. Limnol. Oceanogr. (1979), 24(5), 935-40.
"Long term phosphate (2 µM) and nitrogen (20 µM urea + ammonium) enrichment of a patch reef at One Tree Island, Great Barrier Reef, caused >50% suppression of reef calcification. This is attributed primarily to the phosphate. It is suggested that this effect is involved, together with algal competition and the more usually accepted depression of temperature, in reducing the growth rate of reefs adjacent to upwellings."

Effects of phosphate on growth and skeletal density in the scleractinian coral Acropora muricata: A controlled experimental approach
Author links open overlay panelJeremy G.Dunnabc1Paul W.SammarcoacGaryLaFleurJr.a

http://www.sciencedirect.com/science/article/pii/S0022098111004588

►Effects of elevated phosphate on coral growth and density, Acropora formosa.
►Exptl. phosphate levels — 0.09, 0.20, and 0.50 mg/L, > four months lab exposure.
►Growth rates and weight gain highest at 0.50 mg phosphate/L, but skeletal density lowest there.
►Phosphate increases growth but lowers density; coral growth is a poor reef health indicator.
►Results support the Janus effect concept on coral reefs.

 

[JonasRoman]

double post se below

 

[JonasRoman]

@Randy Holmes-Farley , I have you article in mind since long time back, and that was the cause that I think that maybe my lowering of Phosphate was giving increased CaCO3 formation in corals and also other structures, specially as I lowered from very high, 0.2 ppm to 0.1ppm.

BUT, I have one question: I follow your theory that when GFO take up phosphate it releases OH-ions, and in that way causes local higher ph, leading to increased precipitation of CaCo3=, leading to consumption of alk. BUT, that effect will not be acute as far as I understand and maybe not always occur as GFO in reasonable circulation will not be clogged.
So I tested just now to measure alk and pH immediately after marine water is in contact with some GFO and find a very fast and quite big drop in alkalinity! What is the mechanism ? That fast response can not be due to precipitation of Ca CO3 I guess, as this happened after only a few minutes!

It seems like GFO consumes alkalinity not only in a indirect way through increased CaCO3 formation, but also in a direct way. Can it be in this way that it does not only release OH ions, but the O- ion are so tight bounded in the complex ironoxid/hydroxide, so it it releasing H ions?? That could explain the instant drop of alk when marin water is in contact with GFO.

any comments?

Regards
Jonas

 

[JonasRoman]

I can't find the post right now, but earlier today I was reading a thread where Jonas, the inventor of the Alkatronic alkalinity measuring unit showed a graph where he had put some GFO online and the alkalinity started decreasing. His belief was that the lower phosphate level had increased calcification and was visible in the graph output of his unit. I am not sure if GFO can deplete alk, but assuming not, it was rather interesting to see the cause and effect this way. Almost made me want to run out and buy one. Funny that.

Dennis

And independently of the mechanism, Alkatronic detected the alkalinity drop.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley , I have you article in mind since long time back, and that was the cause that I think that maybe my lowering of Phosphate was giving increased CaCO3 formation in corals and also other structures, specially as I lowered from very high, 0.2 ppm to 0.1ppm.

BUT, I have one question: I follow your theory that when GFO take up phosphate it releases OH-ions, and in that way causes local higher ph, leading to increased precipitation of CaCo3=, leading to consumption of alk. BUT, that effect will not be acute as far as I understand and maybe not always occur as GFO in reasonable circulation will not be clogged.
So I tested just now to measure alk and pH immediately after marine water is in contact with some GFO and find a very fast and quite big drop in alkalinity! What is the mechanism ? That fast response can not be due to precipitation of Ca CO3 I guess, as this happened after only a few minutes!

It seems like GFO consumes alkalinity not only in a indirect way through increased CaCO3 formation, but also in a direct way. Can it be in this way that it does not only release OH ions, but the O- ion are so tight bounded in the complex ironoxid/hydroxide, so it it releasing H ions?? That could explain the instant drop of alk when marin water is in contact with GFO.

any comments?

Regards
Jonas

How much of a drop are you seeing and why couldn't it be precipitation? Just because of the speed?

 

[Randy Holmes-Farley]

Do you have some unused GFO of this brand to put in RO/DI to record the pH?

Maybe it was acidified for some reason by the manufacturer, leaving some binding sites as Fe-Cl or other ion besides OH.

 

[JonasRoman]

How much of a drop are you seeing and why couldn't it be precipitation? Just because of the speed?

The drop was instant, after one minute. Used Rowaphos, brand new. KH dropped from 7.7 to 7.2 in one minute. pH from 8.15 to 8.07. No clogging of media, and I think, if the mechanism should be because OH caused pH rise, ph should rise, but it was more following the decreased KH. And I should in that case also see some precipitation in water I guess with cloudiness, but nohting like that. I suspect there must be something else more direct effect on alkalinity..?

 

[JonasRoman]

Do you have some unused GFO of this brand to put in RO/DI to record the pH?

Maybe it was acidified for some reason by the manufacturer, leaving some binding sites as Fe-Cl or other ion besides OH.

yes maybe...i can test with RO water also...but isn't it very instable to measure pH in RO? will that record be reliable?

 

[JonasRoman]

@Randy Holmes-Farley, could in that case the Fe, in the Fe-Cl, take up OH ions from water as a cause of rapid Alk depletion?
Thus that Fe-cl takes both phosphate and OH..?

 

[Randy Holmes-Farley]

yes maybe...i can test with RO water also...but isn't it very instable to measure pH in RO? will that record be reliable?

It is complicated, but if you put the meter in the RO water and dump in some GFO and look for an immediate trend, that could be instructive.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley, could in that case the Fe, in the Fe-Cl, take up OH ions from water as a cause of rapid Alk depletion?
Thus that Fe-cl takes both phosphate and OH..?

Ferric or ferrous chloride will rapidly drop alk as it takes up OH- and releases Cl-.

 

[JonasRoman]

Ferric or ferrous chloride will rapidly drop alk as it takes up OH- and releases Cl-.

that explains. So now we should investigate different brands and see if we get similar effects? I used Rowaphos.