[Coral-List] Inorganic carbon uptake by corals

[Thomas Goreau]

Dear Isabelle Taubner,

Yes indeed, inorganic carbon must be taken up in large
amounts by corals. Models of carbon isotope balance
that I pubished in 1976 show that a significant
fraction of the carbon used in the skeleton must be derived
from uptake of inorganic bicarbonate from the ocean
as well as from respiratory carbon. This confrms the T.
F. Goreau calcification mechanism and model from the
1950s, in which alkalinity generated by photosynthetic CO2 removal  
drives
coral calcification. As I pointed out in an earlier posting, you
cannot derive coral organic carbon uptake from oxygen
balance becauase most of the carbon translocated by
zoocanthellae is immediately released as mucus, so
coral must get most of their carbon from zooplankton
feeding.

Best wishes,
Tom


Thomas J. Goreau, PhD
President
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
617-864-4226
goreau at bestweb.net
http://www.globalcoral.org

Message: 3
Date: Wed, 19 Jul 2006 10:31:30 -0400
Subject:  determination of calcification rates
From: Isabelle Taubner <Isabelle_Taubner at web.de>
Date: Wed, 19 Jul 2006 14:22:01 +0200
To: coral-list at coral.aoml.noaa.gov

Dear coral-listers,

   During my research on the coral Montipora digitata,
I measured
calcification rates using the validated alkalinity
anomaly technique (AAT).

   Since calcification and photosynthesis are the two
main processes
drawing inorganic carbon (Ci) from the seawater pool,
rates of
calcification could also be established by subtracting
photosynthetically fixed carbon from the total uptake
of Ci (sum of both
processes).
While both techniques cross-calibrate well (1:1) when
applied on a red
coralline alga, calculated calcification rates in the
coral double
compared to results gained via AAT.   The "usual
suspects" (calibration
etc.) have been eliminated.

Technique and a thought:
   Total uptake of inorganic carbon was established via
a FID-GC
following the method of Miyajima et al. (1995), which
involves
acidifying samples with 12N HCl in order to convert
inorganic carbon to
CO2.   Photosynthetic activity was measured by O2
evolution.
Photosynthetic quotient (Qp), evolved O2 vs. fixed
carbon, tends to be =
or > 1 in the light, which would actually have the
opposite effect.

   So the rate of calcification seems to be either
underestimated (AAT)
or overestimated ("total Ci", "Ci fixed by
photosynthesis").

"Can inorganic carbon be taken up by the coral,
neither affecting oxygen
evolution nor seawater alkalinity?"

Any suggestions would be greatly appreciated.  Thank
you very much for
your time and effort.

Best,

Isabelle Taubner

-- 
Isabelle Taubner
School of Biological and Chemical Sciences
University of London, Queen Mary College
Mile End
London E1 4NS

End of Coral-List Digest, Vol 37, Issue 20
******************************************

Thomas J. Goreau, PhD
President
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
617-864-4226
goreau at bestweb.net
http://www.globalcoral.org