Global Warming, CO2, and Coral

[juvenissun]

Juvenissun, stop shifting the goalposts. Are you so dense as to not realize what chemical equilibrium is? Are you so dense that you think an acid can't dissolve in a basic solution? The pH of the ocean has lowered. I have already told you reactions that would decrease ocean pH. I have given a source for the carbon dioxide. Do you have another explanation? Or do you think that the pH didn't change?

I guess you have nothing better to say.

For example, the pH of ocean water decreased from 7.8 to 7.7. How would this ocean water "dissolve" any coral?

 

[thaumaturgy]

I guess you have nothing better to say.

For example, the pH of ocean water decreased from 7.8 to 7.7. How would this ocean water "dissolve" any coral?

Keep in mind that carbonate can still dissolve in seawater. A couple things to keep in mind:

1. Solubility of calcite does not just "stop" at pH 7 or above. It is greatly lower, but not completely absent.

The molar solubility of calcite at pH 4 is 1.7 while at pH 8 is 0.0011. Very much lower, but not completely absent. Of course, chemically, it is far more likely that any carbonate at this pH will salt out with Ca2+ around.

BUT, the oceans are not simple beakers of water:

2. Solubilty of calcite is also a function of depth, which is why there is something called the carbonate compensation depth in the ocean.

Since calcite is effectively insoluble in surface sea water it will remain insoluble until a specific depth is reached where it becomes soluble which is a point determined not only by pH but also by temperature and pressure (SOURCE)

The reason there are some places on the ocean floor where carbonate sediments are found is, in part, because those areas are above the CCD. Below this none will remain because it is now soluble.

So when you consider that solubility is not simply a matter of "is the pH < or >7" but also the complex chemistry of the ocean itself.

It is dangerous to attempt to "swamp" a buffer system like the ocean. It, like all buffer systems, is robust but not "bullet-proof". And we are, in the words of Revelle (discoverer of the Revelle Buffer Factor) when working on understanding the ocean's buffering system with regards to human impact on CO2:

"Human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future."
(SOURCE)

And this is all the more amazing when you realize Revelle was not some alarmist on this topic. When he spoke these words no one even knew there was the possibility that in 40 or 50 years we'd be facing these very real issues.

 

[juvenissun]

Keep in mind that carbonate can still dissolve in seawater. A couple things to keep in mind:

1. Solubility of calcite does not just "stop" at pH 7 or above. It is greatly lower, but not completely absent.

The molar solubility of calcite at pH 4 is 1.7 while at pH 8 is 0.0011. Very much lower, but not completely absent. Of course, chemically, it is far more likely that any carbonate at this pH will salt out with Ca2+ around.

BUT, the oceans are not simple beakers of water:

2. Solubilty of calcite is also a function of depth, which is why there is something called the carbonate compensation depth in the ocean.

Since calcite is effectively insoluble in surface sea water it will remain insoluble until a specific depth is reached where it becomes soluble which is a point determined not only by pH but also by temperature and pressure (SOURCE)

The reason there are some places on the ocean floor where carbonate sediments are found is, in part, because those areas are above the CCD. Below this none will remain because it is now soluble.

So when you consider that solubility is not simply a matter of "is the pH < or >7" but also the complex chemistry of the ocean itself.

It is dangerous to attempt to "swamp" a buffer system like the ocean. It, like all buffer systems, is robust but not "bullet-proof". And we are, in the words of Revelle (discoverer of the Revelle Buffer Factor) when working on understanding the ocean's buffering system with regards to human impact on CO2:

Both of your points are not likely to be applied in the environment of tropical coral reef.

However, I do believe "some" coral reefs are under erosion. However, the cause of erosion is NOT as simple as CO2 and global warming. And the point is that the OP is a false alarm due to the lack of understanding in geochemistry and hydrogeology.

 

[atomweaver]

Both of your points are not likely to be applied in the environment of tropical coral reef.

Elaborate, please.

 

[juvenissun]

Elaborate, please.

If you do not understand the post by thaumaturgy, then there is no use to elaborate anything else. If you do understand, then there is no need to elaborate.

If you will, you may ask a more specific question.

 

[Vene]

Juv, if CO[sub]2[/sub] isn't the cause of the erosion, than what is the cause?

 

[thaumaturgy]

Both of your points are not likely to be applied in the environment of tropical coral reef.

However, I do believe "some" coral reefs are under erosion. However, the cause of erosion is NOT as simple as CO2 and global warming. And the point is that the OP is a false alarm due to the lack of understanding in geochemistry and hydrogeology.

Well, again, the point being that system is itself far more complex that simply pointing to pH and saying carbonates don't dissolve.

Remember, it's also important to be able to make more calcium carbonate. Here's some points to remember:

Increasing the amount of CO2 dissolved in the ocean lowers the pH, and decreases the availability

of carbonate (CO2&#8722; 3 ) ions and lowers the saturation state of the major shell-forming carbonate minerals (SOURCE)​

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Further:​

Tripling the pre-industrial atmospheric CO2 concentration will cause a reduction in surface ocean
pH that is almost three times greater than that experienced during transitions from glacial to interglacial periods. This is often termed &#8220;ocean acidification&#8221; because it describes the process of decreasing pH. Current projections of ocean acidification suggest that the pH of surface ocean waters will continue to decline. However, the term can also lead to confusion when it is wrongly assumed that the oceans will become acidic, when in reality, ocean pH is never expected

to fall below 7.0; i.e., the oceans are becoming less basic, but not acidic.(ibid)​

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And here's a very importat bit from this same report:​

Calcifying organisms of both neritic and pelagic environments are sensitive to changes in saturation

state; calcification rates of several major groups of marine calcifiers decrease as the carbonate ion concentration decreases (​

Figure 1&#8211;4; Table 1.1). There is also evidence that dissolution rates of carbonates will increase in response to CO2 forcing. Even small changes in CO2 concentrations in surface waters may have large negative impacts on marine calcifiers and ​

natural biogeochemical cycles of the ocean (Gattuso et al. , 1998; Wolf-Gladrow et al., 1999; Langdon et al., 2000; Riebesell et al., 2000; Marubini et al., 2001; Zondervan et al., 2001; Reynaud et al., 2003). For example, decreased carbonate ion concentration significantly reduces the ability of corals to produce their calcium carbonate skeletons. This affects individual corals and the ability of the reef to maintain a positive balance between reef building and reef erosion(Kleypas et al., 2001).​

(Emphasis added)​

So while it appears that the coral reefs are simply going to bubble away, the key is that reefs are dynamic systems fighting not only physical erosion, but marshalling the relative [CO3[sup]2-[/sup]] which is effect by the acidification of the oceans (the process, not the final pH).​

This looks like a really good resource to read through. I just found it and with time I will hopefully get a chance to read through the entire report. It is called:​

Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers, NSF/NOAA/USGS Workshop, June 2006. (LINKY)​

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[juvenissun]

Well, again, the point being that system is itself far more complex that simply pointing to pH and saying carbonates don't dissolve.

Remember, it's also important to be able to make more calcium carbonate. Here's some points to remember:

[/LEFT]
[/LEFT]

Further:​

[/LEFT]

And here's a very importat bit from this same report:​

(Emphasis added)[/LEFT]

So while it appears that the coral reefs are simply going to bubble away, the key is that reefs are dynamic systems fighting not only physical erosion, but marshalling the relative [CO3[sup]2-[/sup]] which is effect by the acidification of the oceans (the process, not the final pH).​

This looks like a really good resource to read through. I just found it and with time I will hopefully get a chance to read through the entire report. It is called:​

Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers, NSF/NOAA/USGS Workshop, June 2006. (LINKY)​

[/LEFT]

Now we start to see something about the real problem.

I believe that said problem is LOCAL and TEMPORARY (this does not mean "geographically limited" or "not repeatable"). And it involves more than just inorganic chemistry of seawater. The biochemistry of coral has to be considered (I don't believe the HCO3 in seawater has to be saturated in order for the coral to grow). Also, the chemistry of surface water which discharged into the coastal region has to be considered.

To address such a complicate problem just by a single factor of CO2 is childish.

 

[Vene]

Juv, tell me what changed the pH and what is responsible for the erosion. And if this is so "childish" you should be able to point out where the chemistry is flawed instead of just saying the system is complex. Especially when this is not a new development, analytical tests show that the ocean's pH in the 1700s was 8.179 and in 1994 it was 8.104 (link). Yes, this is a small number, but for such a change to happen in a buffered system as large as the world's oceans, that is significant. Can you explain why the pH has lowered?

 

[thaumaturgy]

I believe that said problem is LOCAL and TEMPORARY (this does not mean "geographically limited" or "not repeatable"). And it involves more than just inorganic chemistry of seawater. The biochemistry of coral has to be considered (I don't believe the HCO3 in seawater has to be saturated in order for the coral to grow). Also, the chemistry of surface water which discharged into the coastal region has to be considered.

To address such a complicate problem just by a single factor of CO2 is childish.

Huh? In order to keep the rate of production of the corals at level with or greater than the rate of erosion there must be sufficient CO[sub]3[/sub][sup]-2[/sup]. While it may not require saturation with respect to carbonate ions, when you pump more CO2 into the ocean this is what happens:

CO2 + H2O --> HCO3[sup]-1[/sup] + H[sup]+1[/sup]
HCO3[sup]-1[/sup] --> CO[sub]3[/sub][sup]-2[/sup]

Now when you pump more CO2 into the buffer system you run this reaction:

CO2 + H2O + CO[sub]3[/sub][sup]-2[/sup] --> 2HCO3[sup]-1[/sup]



HERE's the relative abundance of species of carbonate and bicarbonate ions with respect to pH dissolved in water. Note how as you drop pH to about 7 the relative amount of CO3[sup]-[/sup] falls off. THIS is the important factor. I know you want to go on about biochemistry of corals in hopes no one will be able to pin you down to something, but do keep in mind this is a very important inorganic reaction we are dealing with here.

Remember what the earlier report pointed out:

Increasing the amount of CO2 dissolved in the ocean lowers the pH, and decreases the availability of carbonate (CO2&#8722; 3 ) ions and lowers the saturation state of the major shell-forming carbonate minerals(SOURCE)​

So we seem to have a pretty clear model. Pump CO2 into the ocean, decrease the amount of available CO3[sup]-2[/sup] and thereby reduce the availability of a shell- or reef-forming species. (This is not to say that calcium cannot form carbonate with bicarbonate around, it apparently can in a reversible reaction:

Ca + 2HCO3[sup]-1[/sup] <--> CaCO3 + CO2 + H2O

But from what I see on pg 8 of the report, the marine calcification process does seem to be dominated by access to CO[sub]3[/sub][sup]-2[/sup]

Am I missing something? If you wish to bring in some biochemistry to the discussion, please do so, don't just declare it "complicate" and then assume you're point is correct.​

Please provide some actual information rather than decreeing something is "childish". ​

(This post is an example of information. Try to provide appropriate descriptions and data. Thanks)​

​

 

[juvenissun]

Huh? In order to keep the rate of production of the corals at level with or greater than the rate of erosion there must be sufficient CO[sub]3[/sub][sup]-2[/sup]. While it may not require saturation with respect to carbonate ions, when you pump more CO2 into the ocean this is what happens:

CO2 + H2O --> HCO3[sup]-1[/sup] + H[sup]+1[/sup]
HCO3[sup]-1[/sup] --> CO[sub]3[/sub][sup]-2[/sup]

Now when you pump more CO2 into the buffer system you run this reaction:

CO2 + H2O + CO[sub]3[/sub][sup]-2[/sup] --> 2HCO3[sup]-1[/sup]



HERE's the relative abundance of species of carbonate and bicarbonate ions with respect to pH dissolved in water. Note how as you drop pH to about 7 the relative amount of CO3[sup]-[/sup] falls off. THIS is the important factor. I know you want to go on about biochemistry of corals in hopes no one will be able to pin you down to something, but do keep in mind this is a very important inorganic reaction we are dealing with here.

Remember what the earlier report pointed out:

So we seem to have a pretty clear model. Pump CO2 into the ocean, decrease the amount of available CO3[sup]-2[/sup] and thereby reduce the availability of a shell- or reef-forming species. (This is not to say that calcium cannot form carbonate with bicarbonate around, it apparently can in a reversible reaction:

Ca + 2HCO3[sup]-1[/sup] <--> CaCO3 + CO2 + H2O

But from what I see on pg 8 of the report, the marine calcification process does seem to be dominated by access to CO[sub]3[/sub][sup]-2[/sup]

Am I missing something? If you wish to bring in some biochemistry to the discussion, please do so, don't just declare it "complicate" and then assume you're point is correct.​

Please provide some actual information rather than decreeing something is "childish". ​

(This post is an example of information. Try to provide appropriate descriptions and data. Thanks)​

​

Your data is good. It shows that the ocean water has enough CO3 for coral to build the reef even under a runoff global warming condition (HCO3 will change to CO3). Why would coral stop extracting CO3 from the water is what I do not understand. It should not be the CO2 problem. If it indeed happened, it is more likely to be a biological problem of coral. Do you know how much change on pH in water could be tolerated by coral? Locally, particularly on surface, and nearshore, the natural temporal variation of pH in seawater could be much larger than 0.1

 

[juvenissun]

Juv, tell me what changed the pH and what is responsible for the erosion. And if this is so "childish" you should be able to point out where the chemistry is flawed instead of just saying the system is complex. Especially when this is not a new development, analytical tests show that the ocean's pH in the 1700s was 8.179 and in 1994 it was 8.104 (link). Yes, this is a small number, but for such a change to happen in a buffered system as large as the world's oceans, that is significant. Can you explain why the pH has lowered?

How about ice melting.
It might be a common feature in all previous interglaciation periods.

 

[thaumaturgy]

Your data is good. It shows that the ocean water has enough CO3 for coral to build the reef even under a runoff global warming condition (HCO3 will change to CO3). Why would coral stop extracting CO3 from the water is what I do not understand. It should not be the CO2 problem. If it indeed happened, it is more likely to be a biological problem of coral. Do you know how much change on pH in water could be tolerated by coral? Locally, particularly on surface, and nearshore, the natural temporal variation of pH in seawater could be much larger than 0.1

I'm not entirely sure you actually read my post. Perhaps you should read through some of the report linked to as well.

I'd like to know how much HCO[sub]3[/sub][sup]-1[/sup] will turn into CO[sub]3[/sub][sup]-2[/sup] under decreasing pH conditions:

HCO[sub]3[/sub][sup]-1[/sup] --> CO[sub]3[/sub][sup]-2[/sup] + H[sup]+[/sup]

Now I'm sure you recall LeChatelier's principal. Can you explain what will happen to the equilibrium as I pump more H+ into the solution?

Just curious.

The report I linked to lays out the problems with ocean acidification. But let me repeat the key points:

Increasing the amount of CO2 dissolved in the ocean lowers the pH, and decreases the availability of carbonate (CO[sub]2[/sub][sup]&#8722; 3[/sup]) ions and lowers the saturation state of the major shell-forming carbonate minerals(SOURCE)

I've emphasized the important bit. Maybe I should repeat it in another color?

So, instead of just decreeing your point, do me a favor and present some actual chemistry.​

​

 

[Vene]

Your data is good. It shows that the ocean water has enough CO3 for coral to build the reef even under a runoff global warming condition (HCO3 will change to CO3).

What? The graph shows that at neutral to acid conditions the amount of CO[sub]3[/sub][sup]2-[/sup] will drastically decrease. That's because it has been protonated. At that pH the equilibrium favors HCO[sub]3[/sub][sup]-[/sup] more than CO[sub]3[/sub][sup]2-[/sup]. It won't be converted into CO[sub]3[/sub][sup]2-[/sup].

Why would coral stop extracting CO3 from the water is what I do not understand. It should not be the CO2 problem. If it indeed happened, it is more likely to be a biological problem of coral. Do you know how much change on pH in water could be tolerated by coral? Locally, particularly on surface, and nearshore, the natural temporal variation of pH in seawater could be much larger than 0.1

Coral extracts carbon dioxide.

And they manage to do so without effecting the pH (although it is currently unknown how) (link)
The issue is that the decrease in pH has also increased the amount of H[sup]+[/sup] in the water, which will break down the CaCO[sub]3[/sub] already deposited faster than the coral can build.

How about ice melting.
It might be a common feature in all previous interglaciation periods.

Ice melting, okay, now I have something to work with. I guess it is possible for more water to be added into the system, diluting the basic ions, and making the ocean more acidic. But, you just shot yourself in the foot. Ice melting would mean that the average temperature of the planet has risen. It's still global warming. Not to mention there is still all of this carbon dioxide being pumped into the air which will still reaction with the water to form an acid.


By the way, I find it interesting that you offer no sources, just saying that it's complicated, and insisting it doesn't work the way the article says without offering any reason why.

 

[thaumaturgy]

By the way, I find it interesting that you offer no sources, just saying that it's complicated, and insisting it doesn't work the way the article says without offering any reason why.

Vene, thanks for the biochem pathway! Unfortunately we are unlikely to get any detailed information about Juvenissun's points. In earlier discussions around geologic issues he was loathe to provide too much detail other than a sprinkling of technical terms. Finally after much cajoling he did provide a few references.

I am very much looking forward to Juvenissun backing up any of his points. He is, apparently, a teacher of some sort. It would be good to see him flex some "teaching muscle" for a change of pace.

 

[juvenissun]

I'd like to know how much HCO[sub]3[/sub][sup]-1[/sup] will turn into CO[sub]3[/sub][sup]-2[/sup] under decreasing pH conditions:

HCO[sub]3[/sub][sup]-1[/sup] --> CO[sub]3[/sub][sup]-2[/sup] + H[sup]+[/sup]

Now I'm sure you recall LeChatelier's principal. Can you explain what will happen to the equilibrium as I pump more H+ into the solution?

Just curious.

OK, I was careless. But my point is: CO3 will NOT decrease so much so that coral could not find any in the seawater to use. I would say the amount of CO3 decrease is minimum, some like 0.01%?

 

[juvenissun]

Coral extracts carbon dioxide.

And they manage to do so without effecting the pH (although it is currently unknown how) (link)
The issue is that the decrease in pH has also increased the amount of H[sup]+[/sup] in the water, which will break down the CaCO[sub]3[/sub] already deposited faster than the coral can build.

Nice link. But I still do not see why would the change of pH from say, 7.8 to 7.7 affect the reef building. The linked article seems said no to this hunch.

 

[Vene]

It's not reef building that's the issue, it's that the existing reefs are being destroyed.

 

[thaumaturgy]

OK, I was careless. But my point is: CO3 will NOT decrease so much so that coral could not find any in the seawater to use. I would say the amount of CO3 decrease is minimum, some like 0.01%?

Will you please provide some support for these contentions?

The problem is, many of these features rely on a specific concentration, not just a raw number of molecules, but at what rate you can bring those molecules to the appropriate sites. It's not like the whole reef can just run across the ocean to a more "oxygen rich" portion.

So, please, I'm begging you, provide something in the way of support for your point. Don't just post some linky and run away, please explain for us and even do the math. I'd love to see your rationalization.

 

[juvenissun]

Will you please provide some support for these contentions?

The problem is, many of these features rely on a specific concentration, not just a raw number of molecules, but at what rate you can bring those molecules to the appropriate sites. It's not like the whole reef can just run across the ocean to a more "oxygen rich" portion.

So, please, I'm begging you, provide something in the way of support for your point. Don't just post some linky and run away, please explain for us and even do the math. I'd love to see your rationalization.

I told you I am not sure how much CO3 was lowered in seawater. The OP suggested it is serious enough to stop the growth of coral. I doubt it. I give a number based on my hunch. I have no support for it. However that does not mean I could find the data. I can do it just the same as you can do it. The search engine is available to all of us. I said the decrease could be less than 0.01%. If you do not think it is right, it is YOUR BURDEN to prove that it is wrong. Why should I spend time to find data to solve YOUR problem?

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Well, here is one. It took me 3 minutes. It is not good enough. But I think it might be sufficient for this occasion.