[Coral-List] determination of calcification rates
Jim.Hendee at noaa.gov
Wed Jul 19 10:31:30 EDT 2006
I'm forwarding the following for Isabelle, as her message somehow
got strange characters in it and the entire message got removed from the
queue; thus, some characters below may confuse the message. Please do
not respond to me concerning this message, rather to her or the list.
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
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
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.
School of Biological and Chemical Sciences
University of London, Queen Mary College
London E1 4NS
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