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The Effect of Algal Symbionts on the Accuracy of Sr/Ca Paleotemperatures from Coral
Anne L. Cohen,*Kathryn E. Owens,Graham D. Layne,Nobumichi Shimizu
The strontium-to-calcium ratio (Sr/Ca) of reef coral skeleton
is commonly used as a paleothermometer to estimate sea surfacetemperatures (SSTs) at crucial times in Earth's climate history.However, these estimates are disputed, because uptake of Sr intocoral
skeleton is thought to be affected by algal symbionts (zooxanthellae)living in the host tissue. Here, we show that significant distortionof
the Sr/Ca temperature record in coral skeleton occurs in thepresence
of algal symbionts. Seasonally resolved Sr/Ca in coralwithout
symbionts reflects local SSTs with a temperature sensitivityequivalent
to that of laboratory aragonite precipitated at equilibriumand the
nighttime skeletal deposits of symbiotic reef corals.However, up to
65% of the Sr/Ca variability in symbiotic skeletonis related to
symbiont activity and does not reflect water temperature.
Department of Geology and Geophysics, Woods Hole Oceanographic
Institution (WHOI), Woods Hole, MA 02543, USA.
*
To whom correspondence should be addressed. E-mail:
acohen{at}whoi.edu
