Carbon dioxide and ocean acidity

[Icemelt]

IPCC WGII Fourth Assessment Report Climate Change 2007

Climate Change Impacts, Adaptation and Vulnerability

 

Quote:

 

"The progressive acidification of oceans due to increasing atmospheric carbon dioxide is expected to have negative impacts on marine shell forming organisms"

 

It has been reported that the increased acidity of the oceans, caused by the current CO2 levels, is preventing crustacea from properly forming their shells and that this will subsequently prevent CO2 extraction in the form of calcium carbonate precipitate sediment.

 

Whilst the dissolving CO2 in water causes some dissociation and an increase in pH, this would seem to be at odds with geological evidence, which shows that the bulk of the world's chalk deposits were formed 100-200 million YBP when CO2 levels were four times the current 380ppmv level, at 1400 & 1600 ppmv.

[ecoli]

has this affect been seen yet?

[1veedo]

Have you ever read about the Paleocene-Eocene Maximum? This is the period of time that mammals started to out-compete other animals for dominance. We had a sudden, partially unexplained, increase in CO2 and temperature which caused many species to go extinct, globally (including fish living miles under the ocean).

 

The increased CO2 caused an increase in ocean acidity which is what's responsible for the extinction of a lot of fish. This is something that is perfectly normal in geological history so contrary to your concerns, there is really nothing wrong with that passage from the IPCC.

[Icemelt]

Oops !

Just keeping you guys on your toes, I'm surprised you didn't jump on me for this one !

Of course I meant to say "- - - some dissociation and a decrease in pH"

 

Yeah 1Veedo, but what I'm syaing here is that the process of laying down chalk requires millions of years of shells to be formed and discarded

Yet during this exact period the CO2 level remained at at 1400 & 1600 ppmv

Also this wasn't a sudden increase in CO2, we're talking about a sustained level in excess of 1300 ppmv from 250,000,000 to 100,000,000 YBP and it didn't drop below 1300 ppmv once in 150,000,000 years !

 

The question is:

At 4 times the current level of CO2 in the atmosphere, the process of dissolving CO2 in water to form carbonic acid, did not produce sufficient ocean acidity to stifle crustacea growth even over 150 million years. So why should anyone be worried about it now ?

 

I believe the phenomenon to which you refer is CO2 dissolving in water droplets to produce acidic rain which would be corrosive to land based egg shells. This has little to do with crustacea.

[1veedo]

This is really just basic chemistry. CO2 causes water's pH to decrease. I don't think you can look at one time period and talk about animal adaption because, like you said, it was a long sustained period. What we're talking about is just a basic fact that increased CO2 causes the oceans to become more acidic.

 

This doesn't mean the plankton are going to die. What it means is exactly what it sounds like on face value: the oceans are going to (correction, they currently are) becoming more acidic.

 

This isn't a good thing though, and we can already see some of the effects of this. Increase ocean acidity, along with increased ocean temperatures, etc, are causing some mild adverse effects. If you have ever had fish, you know that a change in pH of just a couple tenths or a change in temperature of just a few degrees can cause your fish to die.