[Vision2020] Coral Reefs: CO2 Source or Sink? Re: Four Levels of Global Warming: A Climate Change Update

Fri Dec 17 10:25:50 PST 2010

As is sometimes the case with scientific issues, answering a given
question can result in uncovering uncertainty and complexity.  Some
seemingly credible sources indicate quite divergent evidence.  When
surveying all the scientific literature on a given question, if there
is widespread disagreement, it is reasonable for a layperson to
consider the question still under investigation.

On the question of whether coral reefs are atmospheric carbon sinks or
emit carbon into the atmosphere, there has been debate in the
published science.  Finding the most recent scientific publications
regarding this question might reveal a more certain answer to the
question, given the more recent science should correct previous
potential scientific errors or omissions.

Some of the following scientific publications make reference to a
"debate" on this issue, so this indicates that indeed there has been
disagreement in the scientific community on this question.

Maybe at this point in time the debate has been mostly resolved.

I have not surveyed enough of the scientific literature to feel
confident about answering this question, in part because I am not sure
exactly how to frame the question, given the complexities of coral
reef communities.  If I read the literature correctly, calcium
carbonate formation must be considered, along with the organisms that
the reef supports, to analyse the carbon cycle.  Some coral reefs
might be carbon sinks, others not.

Below are some scientific sources I found in a brief search.

This first source contains an argument from Tom Goreau, President,
Global Coral Reef Alliance, quite emphatically arguing that coral
reefs are not carbon sinks for atmospheric CO2:

[Coral-List] Climate change and coral reef sequestration of carbon

http://coral.aoml.noaa.gov/pipermail/coral-list/2007-December/005082.html

My comment:

One way or the other regarding this question, the science indicates
coral reefs impact on the carbon cycle influencing atmospheric CO2
level for the time scale (a couple of centuries) in which the hundreds
of billions of tons of CO2 from human emissions are being dumped into
our atmosphere, is minimal.  One of the sources below claims coral
reef emissions of CO2 into the atmosphere are a mere .4 to 1.4 percent
of anthropogenic CO2 emissions.
---------------------------------

http://www.pnas.org/content/95/11/6566.full?related-urls=yes&legid=pnas;95/11/6566

Anomalies in coral reef community metabolism and their potential
importance in the reef CO2 source-sink debate

John R. M. Chisholm * and David J. Barnes

Overall, reef growth may serve to drive CO2 into the atmosphere but
probably to a lesser extent than has been indicated by Lagrangian
measurements of reef flat metabolism at Moorea (31 mmol per m2 per
day) and Yonge Reef on the GBR (182 mmol per m2 per day) (6).
Comparative studies using a Eulerian approach indicated rates of CO2
efflux that were lower by 1–2 orders of magnitude (1.81 mmol per m2
per day at Moorea and 5.1 mmol per m2 per day at Yonge) (9). If these
latter data are the more representative, then inclusion of high net
organic productivity on the seaward slopes of reefs (30) may indicate
that whole reefs act as sinks for atmospheric CO2. The fact that
carbonate rocks store 3 × 104 more inorganic carbon than the
atmosphere (17) shows that reefs are sinks for CO2 over geological
time.

------------------------------
http://www.pnas.org/content/96/23/13017.full.pdf

Measurement of Community Metabolism and Significance in the Coral Reef
CO2 Source-Sink Debate
------------------------------
http://www.sciencemag.org/content/269/5221/214.abstract

Science 14 July 1995:
Vol. 269 no. 5221 pp. 214-216
DOI: 10.1126/science.269.5221.214

Diurnal Changes in the Partial Pressure of Carbon Dioxide in Coral Reef Water
Hajime Kayanne, Atsushi Suzuki and Hiroshi Saito

Coral reefs are considered to be a source of atmospheric carbon
dioxide because of their high calcium carbonate production and low net
primary production. This was tested by direct measurement of diurnal
changes in the partial pressure of carbon dioxide (Pcoco2) in reef
waters during two 3-day periods, one in March 1993 and one in March
1994, on Shiraho reef of the Ryukyu Islands, Japan. Although the
Pcoco2 values in reef waters exhibited large diurnal changes ranging
from 160 to 520 microatmospheres, they indicate that the reef flat
area is a net sink for atmospheric carbon dioxide. This suggests that
the net organic production rate of the reef community exceeded its
calcium carbonate production rate during the observation periods.
--------------------------------
http://www.springerlink.com/content/g2r13h6u35p76763/

Coral Reefs
Volume 11, Number 3, 127-130, DOI: 10.1007/BF00255465
Coral reefs: sources or sinks of atmospheric CO2?
John R. Ware, Stephen V. Smith and Marjorie L. Reaka-Kudla

Abstract

Because the precipitation of calcium carbonate results in the
sequestering of carbon, it frequently has been thought that coral
reefs functions as sinks of global atmospheric CO2. However, the
precipitation of calcium carbonate is accompanied by a shift of pH
that results in the release of CO2. This release of CO2 is less in
buffered sea water than fresh water systems; nevertheless, coral reefs
are sources, not sinks, of atmospheric carbon. Using estimated rates
of coral reef carbonate production, we compute that coral reefs
release 0.02 to 0.08 Gt C as CO2 annually. This is approximately 0.4%
to 1.4% of the current anthropogenic CO2 production due to fossil fuel
combustion.
------------------------------------------
Vision2020 Post: Ted Moffett

On 12/16/10, nickgier at roadrunner.com <nickgier at roadrunner.com> wrote:
> Good Morning Visionaries,
>
> Sam Scripter was kind enough to point out an error in my column on climate
> change. Contrary to what many people think, coral reefs do not act as carbon
> sinks. On balance they are carbon emitters.
>
> Too late to correct for the Sandpoint Reader (I'll send a letter), but I can
> change it for the Idaho State Journal and Los Cabos Daily News, and of
> course my website.
>
> As I said with regard to creation scientists and climate change deniers:
> "The willingness to correct errors always increases the credibility of those
> whom we want to believe.  Only ideologues believe that finding errors or
> conceding them are fatal weakness."
>
> Thanks, Sam.
>
> Nick
>
> --that corals must take carbon out of the a---- Sam Scripter
> <MoscowSam at charter.net> wrote:
>> Nick . . .
>>
>> Did Ted or anyone else point out the error below to you?
>> Have you already "gone to press"?
>>
>> Sam Scripter
>>
>> You wrote:
>>
>> Warmer and more acidic seas destroy coral reefs,
>> which, under normal conditions,*take tons of
>> calcium  out of CO2.*  About 80 percent of the corals
>> at the eastern end of the Indonesian island of
>> Sumatra are now dead.
>>
>>
>> Here is a paragraph from Wikipedia about "coral":
>>
>> Coral's narrow niche <http://en.wikipedia.org/wiki/Ecological_niche> and
>> the stony corals <http://en.wikipedia.org/wiki/Scleractinia>' reliance
>> on calcium carbonate <http://en.wikipedia.org/wiki/Calcium_carbonate>
>> deposition makes them susceptible to changes in water pH
>> <http://en.wikipedia.org/wiki/PH>. The increase
>> in atmospheric carbon dioxide has caused enough dissolution of carbon
>> dioxide to lower the ocean's pH, in a process known as ocean
>> acidification <http://en.wikipedia.org/wiki/Ocean_acidification>.
>> Lowered pH reduces corals' ability to produce calcium carbonate, and at
>> the
>> extreme, can dissolve their skeletons. Without deep and immediate cuts in
>> anthropogenic CO_2 , many scientists fear that acidification will severely
>> degrade or destroy coral ecosystems.^[28]
>> <http://en.wikipedia.org/wiki/Coral#cite_note-Gattuso-27>
>>
>> http://en.wikipedia.org/wiki/Coral
>>
>> nickgier at roadrunner.com wrote:
>> > Warmer and more acidic seas destroy coral reefs, which, under normal
>> > conditions, take tons of calcium out of CO2. About 80 percent of the
>> > corals at the eastern end of the Indonesian island of Sumatra are now
>> > dead.
>> >
>
>