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

Ray Berkelmans R.Berkelmans at aims.gov.au
Thu Jun 2 18:33:39 EDT 2011

Hi all

Charlie Veron has a nice multidisciplinary review article on reef responses to OA - a good basic read! It's out this week in Diversity http://www.mdpi..com/1424-2818/3/2/262/



-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Lee Kump
Sent: Thursday, 2 June 2011 11:45 PM
To: Sam Kahng
Cc: coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] High pCO2 and calcification in the far distant past

Dear Sam, John, and coral listers,

The PETM (56 million years ago) is a nice demonstration of the  
carbonate system response on various timescales. The event played out  
over about 170,000 years, with several millennia of carbon emission  
followed by a much longer recovery period. The injection apparently  
was slow enough to not cause deleterious surface ocean acidification,  
but of sufficient magnitude to drive the deep ocean undersaturated  
with respect to CaCO3, hence the PETM clay layer in many DSDP/ODP/IODP  
drilling sites.

During the long recovery period (over 10's of thousands of years), as  
Sam describes, the greenhouse warmth stimulated chemical weathering on  
land, which brought carbonate to the ocean, leading not only to a  
restoration of the ocean's carbonate system, but actually  
overcompensation, as witnessed by a "white layer" in deep sea  
sediments of nearly pure biogenic CaCO3 (Kelly et al.,  
Paleoceanography 20: PA4023, doi:10.1029/2005PA001163, 2005). This is  
exactly what we expect to happen based on carbon cycle models; it's  
the natural process whereby the ocean rids itself of excess carbon  
added during the initiation of the PETM.

Our best guess for the duration of carbon emission is about 20,000  
years, at rates that are dwarfed by modern rates of fossil-fuel  
burning. This work is to be published in Nature Geoscience on May 5,  
by Cui et al., entitled "Slow release of fossil carbon during the  
Palaeocene Eocene Thermal Maximum". Please see also the July issue  of  
Scientific American for a more digestible version of the recent work.  
Our basic conclusion is that we shouldn't seek solace in the  
observation that with the exception of deep-sea dwelling, benthic  
protozoans (foraminifera), the biota did not suffer a mass extinction  
during the PETM; the rate of environmental change during the PETM was  
considerably slower than that which is likely to be realized under a  
"business as usual" fossil-fuel burning future.

I should note that there's been relatively little work done on the  
response of coral reef ecosystems to the PETM event. Scheiber and  
Speijer (2008) document a progressive demise of reefs from 59-55  
million years ago that they attribute to gradual warming (eEarth, 3,  
19-26, 2008).


On Jun 1, 2011, at 9:51 PM, Sam Kahng wrote:

> Hi John,
> I just taught a section on this to my bio ocn students. Kump et al.  
> (2009) is a good introductory reference for the casual reader,  
> however a basic understanding of carbonate chemistry is required. On  
> geological time scales (greater than residence time of ocean  
> basins), high atm CO2 is generally associated with high ocean  
> alkalinity (TA) and proliific coral reef accretion. The high atm  
> pCO2 causes accelerated terrestrial rock weathering (basalts and  
> carbonates) which floods the oceans with HCO (raising alkalinity  
> despite high atm pCO2). The disconnect with the modern scenario  
> (short-term imbalance) is that weathering feedback and ocean mixing/ 
> equilibration takes a long time. There are many good references that  
> discuss the Paleocene-Eocene Thermal Maximum (PETM) whiich was the  
> most recent "rapid" ocean acidification/carbonation event. Its  
> initial and long-term effects on marine carbonate deposition are  
> fairly well documented by geochemists.
> Kump LR, Bralower TJ, Ridgwell A (2009) Ocean acidification in deep  
> time. Oceanography 22:94-107
> Aloha, Sam
>> Date: Wed, 1 Jun 2011 11:11:26 -0400
>> From: jware at erols.com
>> To: coral-list at coral.aoml.noaa.gov
>> Subject: [Coral-List] High pCO2 and calcification in the far  
>> distant past
>> 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?
>> John
>> -- 
>> *************************************************************
>> * *
>> * John R. Ware, PhD *
>> * President *
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>> * 19572 Club House Road *
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>> * jware at erols.com *
>> * http://www.seaservices.org *
>> * fax: 301 987-8531 *
>> * *
>> * Member of the Council: *
>> * International Society for Reef Studies *
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>> If you are a coral-reef scientist and you are not a member
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>> shame on you.
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Lee R. Kump
Dept. of Geosciences
Penn State
535 Deike Bldg.
University Park, PA 16802 USA

lkump at psu.edu
+1 814 863-1274
+1 814 863-7823 fax

Lee R. Kump
Dept. of Geosciences
Penn State
535 Deike Bldg.
University Park, PA 16802 USA

lkump at psu.edu
+1 814 863-1274
+1 814 863-7823 fax

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