[Coral-List] High pCO2 and calcification in the far distant past

John Ware jware at erols.com
Wed Jun 1 11:11:26 EDT 2011

Dear List:

For a long time I have thought, as many of you have, that paleo records 
of times with high pCO2 would be good analogs for the future effects of 
high pCO2 on present coral reefs.  Unfortunately, I have not found a 
good reference that looks at available data and then discusses the 
results in an understandable format.  I had thought that the following 
reference was going to be helpful:

Doney,SC; Fabry,VJ; Feely,RA; Kleypas,JA (2009): Ocean acidification: 
the other CO2 problem. Annu. Rev. Mar. Sci. 1, 69-92.

Unfortunately, this is what I found in that reference:  "Periods of high 
pCO2 (Permian, Cret) exhibit massive shallow-water CaCO3 deposits.  
Initially this appears to be a conundrum.  The short answer is that 
saturation states may have been high during these periods despite high 
pCO2.  The long answer is complicated." 

While the above may not be a fully accurate quote, it carries the 
intent.  My problem is that the long and complicated answer is not 
given.  Can anybody out there provide a reference that explains high 
calcification rates the the far past when (presumably) there were 
periods of high atmospheric pCO2 but also high calcification rates.

 I note that some authors claim that pCO2 in the Cretaceous could have 
been in the 1000s (ppmv), and I also realize that the major calcifiers 
in the late Cretaceous were probably rudists (sort of clams) not corals. 
 But what is out there that I have missed?


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