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Sr/Ca sensitivity to aragonite saturation state in cultured subsamples from a single colony of coral: Mechanism of biomineralization during ocean acidification

Gagnon, Alexander C. and Adkins, Jess F. and Erez, Jonathan and Eiler, John M. and Guan, Yunbin (2013) Sr/Ca sensitivity to aragonite saturation state in cultured subsamples from a single colony of coral: Mechanism of biomineralization during ocean acidification. Geochimica et Cosmochimica Acta, 105 . pp. 240-254. ISSN 0016-7037. https://resolver.caltech.edu/CaltechAUTHORS:20130327-111017326

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Abstract

Using a new and rapid NanoSIMS-based method, we quantified the sensitivity of skeletal Sr/Ca in coral to the aragonite saturation state of seawater (Ω_(SW)). Skeletal Sr/Ca is a common proxy for temperature while Ω_(SW) is a parameter that varied in the past ocean and is predicted to change with continued ocean acidification. Five adult branches of the surface coral Stylophora pistillata were grown at different Ω_(SW) from 2.7 to 4.9 (pH of 7.9–8.5) but at a constant temperature of 25 °C. Despite a large range of growth parameters and a twofold range in calcification rates, the average skeletal Sr/Ca of coral exposed to each condition are within 1.2% of each other (2σ std. dev. of the 5 means). Furthermore, the average skeletal Sr/Ca measured in this study agrees with the results of two previous coral culture experiments conducted at the same temperature but where Ω_(SW) was not controlled. These results suggest that aragonite saturation has little or no influence on Sr/Ca paleothermometry over the range of Ω_(SW) investigated. Combined with existing data for low Ω_(SW) conditions, our results were used to elucidate the mechanisms controlling calcifying fluid acid–base chemistry during coral biomineralization. Assuming that coral drive precipitation through alkalinity pumping, our data suggest that this pumping occurs until the calcifying fluid reaches a target pH. Below a threshold Ω_(SW) bounded by 1 < Ω_(SW) < 2.4, however, coral do not pump enough alkalinity to reach the target pH and instead pump a maximal but finite amount of alkalinity. In this low Ω_(SW) regime, calcifying fluid pH is expected to decrease with Ω_(SW). The interplay between these two alkalinity pumping regimes and external seawater composition explain the full range of observed Sr/Ca sensitivity to Ω_(SW) and suggest that surface coral may become increasingly sensitive to ocean acidification below a threshold Ω_(SW) bounded by 1 < Ω_(SW) < 2.4.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.gca.2012.11.038DOIArticle
http://www.sciencedirect.com/science/article/pii/S0016703712006977PublisherArticle
ORCID:
AuthorORCID
Adkins, Jess F.0000-0002-3174-5190
Guan, Yunbin0000-0002-7636-3735
Additional Information:© 2012 Elsevier Ltd. Received 15 September 2010; accepted in revised form 26 November 2012; available online 10 December 2012. Associate editor: Alfonso Mucci. NanoSIMS analysis was conducted at the Caltech Center for Microanalysis which is supported in part by the Gordon and Betty Moore Foundation. The confocal laser-scanning microscope is housed and maintained by the Caltech Biological Imaging Center. Will Berelson of USC made his lab available for DIC analysis. Several technicians at Hebrew University, Jerusalem assisted with alkalinity titrations. This manuscript benefited from constructive suggestions by several anonymous reviewers as well as the detailed comments and skillful handing of the editor.
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Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20130327-111017326
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130327-111017326
Official Citation:Alexander C. Gagnon, Jess F. Adkins, Jonathan Erez, John M. Eiler, Yunbin Guan, Sr/Ca sensitivity to aragonite saturation state in cultured subsamples from a single colony of coral: Mechanism of biomineralization during ocean acidification, Geochimica et Cosmochimica Acta, Volume 105, 15 March 2013, Pages 240-254, ISSN 0016-7037, 10.1016/j.gca.2012.11.038. (http://www.sciencedirect.com/science/article/pii/S0016703712006977)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37649
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:27 Mar 2013 19:20
Last Modified:26 Nov 2019 23:19

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