Coral Li/Mg thermometry: Caveats and constraints

Kristan Cuny-Guirriec, Eric Douville, Stéphanie Reynaud, Denis Allemand, Louise Bordier, Marine Canesi, Claudio Mazzoli, Marco Taviani, Simonepietro Canese, Malcolm McCulloch, Julie Trotter, Serguei Damián Rico-Esenaro, Joan Albert Sanchez-Cabeza, Ana Carolina Ruiz-Fernández, Juan P. Carricart-Ganivet, Pete M. Scott, Aleksey Sadekov, Paolo Montagna

Research output: Contribution to journalArticle

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Abstract

The coral Li/Mg temperature proxy is revisited through an in-depth trace element analysis of scleractinians collected live from tropical to polar environments. The dataset consists of Li/Ca, Mg/Ca, Sr/Ca and Li/Mg ratios from 64 coral specimens belonging to 8 different taxa, including both reef-building zooxanthellate and cold-water non-zooxanthellate species, from a wide range of water temperature (−1 to 29.5 °C), salinity (34.71 to 38.61), and depth (3 to 670 m). Our results showed that the reliability of the Li/Mg temperature proxy is strongly limited by the organic matter associated with the coral skeleton, which is most evident within the green bands observed in tropical corals. Organic-rich bands can double the Mg content otherwise present in the skeleton, which may ultimately lead to a temperature overestimation exceeding 15 °C. We found that this bias can be overcome by the treatment of coral skeletons with a specific oxidizing cleaning protocol. We also detected the presence of calcite deposits within the aragonite skeleton of some Antarctic living coral specimens, which strongly affects the robustness of the Li/Mg proxy given its temperature sensitivity of ~1.5 °C/1% calcite. Therefore, to obtain reliable reconstructions a correction needs to be applied when organic matter and/or calcite contamination is present, which requires the scrupulous assessment of the integrity of the aragonite prior to geochemical analyses. Given that some species entrap more organic matter than others, and that some are more prone to calcite contamination, a taxon-related effect is apparent. Here we show that the tropical species Porites spp., Pseudodiploria strigosa and Orbicella annularis, and the cold-water species Madrepora oculata, Caryophyllia antarctica and Flabellum impensum, are all suitable candidates for reconstructing seawater temperatures. The integrated results across a wide temperature range, from extreme cold to tropical shallow waters, yield an overall precision for the Li/Mg-temperature proxy of ±1.0 °C, as quantified by the standard error of estimates. If calculated from the 95% prediction intervals, the uncertainty of the temperature estimates is ±0.9 °C at 1 °C, ±1.5 °C at 12 °C and ± 2.6 °C at 25 °C. However, the uncertainty for the tropical corals (e.g. Porites) can be reduced to ±0.6 °C if a Li/Mg and Sr/Ca multi-regression approach is applied.

Original languageEnglish
Pages (from-to)162-178
Number of pages17
JournalChemical Geology
Volume523
DOIs
Publication statusPublished - 30 Sep 2019

Fingerprint

coral
Calcium Carbonate
skeleton
calcite
temperature
Biological materials
Temperature
aragonite
Water
cold water
organic matter
Contamination
water yield
thermometry
Reefs
Trace Elements
Seawater
reef
shallow water
water temperature

Cite this

Cuny-Guirriec, K., Douville, E., Reynaud, S., Allemand, D., Bordier, L., Canesi, M., ... Montagna, P. (2019). Coral Li/Mg thermometry: Caveats and constraints. Chemical Geology, 523, 162-178. https://doi.org/10.1016/j.chemgeo.2019.03.038
Cuny-Guirriec, Kristan ; Douville, Eric ; Reynaud, Stéphanie ; Allemand, Denis ; Bordier, Louise ; Canesi, Marine ; Mazzoli, Claudio ; Taviani, Marco ; Canese, Simonepietro ; McCulloch, Malcolm ; Trotter, Julie ; Rico-Esenaro, Serguei Damián ; Sanchez-Cabeza, Joan Albert ; Ruiz-Fernández, Ana Carolina ; Carricart-Ganivet, Juan P. ; Scott, Pete M. ; Sadekov, Aleksey ; Montagna, Paolo. / Coral Li/Mg thermometry : Caveats and constraints. In: Chemical Geology. 2019 ; Vol. 523. pp. 162-178.
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Cuny-Guirriec, K, Douville, E, Reynaud, S, Allemand, D, Bordier, L, Canesi, M, Mazzoli, C, Taviani, M, Canese, S, McCulloch, M, Trotter, J, Rico-Esenaro, SD, Sanchez-Cabeza, JA, Ruiz-Fernández, AC, Carricart-Ganivet, JP, Scott, PM, Sadekov, A & Montagna, P 2019, 'Coral Li/Mg thermometry: Caveats and constraints' Chemical Geology, vol. 523, pp. 162-178. https://doi.org/10.1016/j.chemgeo.2019.03.038

Coral Li/Mg thermometry : Caveats and constraints. / Cuny-Guirriec, Kristan; Douville, Eric; Reynaud, Stéphanie; Allemand, Denis; Bordier, Louise; Canesi, Marine; Mazzoli, Claudio; Taviani, Marco; Canese, Simonepietro; McCulloch, Malcolm; Trotter, Julie; Rico-Esenaro, Serguei Damián; Sanchez-Cabeza, Joan Albert; Ruiz-Fernández, Ana Carolina; Carricart-Ganivet, Juan P.; Scott, Pete M.; Sadekov, Aleksey; Montagna, Paolo.

In: Chemical Geology, Vol. 523, 30.09.2019, p. 162-178.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Coral Li/Mg thermometry

T2 - Caveats and constraints

AU - Cuny-Guirriec, Kristan

AU - Douville, Eric

AU - Reynaud, Stéphanie

AU - Allemand, Denis

AU - Bordier, Louise

AU - Canesi, Marine

AU - Mazzoli, Claudio

AU - Taviani, Marco

AU - Canese, Simonepietro

AU - McCulloch, Malcolm

AU - Trotter, Julie

AU - Rico-Esenaro, Serguei Damián

AU - Sanchez-Cabeza, Joan Albert

AU - Ruiz-Fernández, Ana Carolina

AU - Carricart-Ganivet, Juan P.

AU - Scott, Pete M.

AU - Sadekov, Aleksey

AU - Montagna, Paolo

PY - 2019/9/30

Y1 - 2019/9/30

N2 - The coral Li/Mg temperature proxy is revisited through an in-depth trace element analysis of scleractinians collected live from tropical to polar environments. The dataset consists of Li/Ca, Mg/Ca, Sr/Ca and Li/Mg ratios from 64 coral specimens belonging to 8 different taxa, including both reef-building zooxanthellate and cold-water non-zooxanthellate species, from a wide range of water temperature (−1 to 29.5 °C), salinity (34.71 to 38.61), and depth (3 to 670 m). Our results showed that the reliability of the Li/Mg temperature proxy is strongly limited by the organic matter associated with the coral skeleton, which is most evident within the green bands observed in tropical corals. Organic-rich bands can double the Mg content otherwise present in the skeleton, which may ultimately lead to a temperature overestimation exceeding 15 °C. We found that this bias can be overcome by the treatment of coral skeletons with a specific oxidizing cleaning protocol. We also detected the presence of calcite deposits within the aragonite skeleton of some Antarctic living coral specimens, which strongly affects the robustness of the Li/Mg proxy given its temperature sensitivity of ~1.5 °C/1% calcite. Therefore, to obtain reliable reconstructions a correction needs to be applied when organic matter and/or calcite contamination is present, which requires the scrupulous assessment of the integrity of the aragonite prior to geochemical analyses. Given that some species entrap more organic matter than others, and that some are more prone to calcite contamination, a taxon-related effect is apparent. Here we show that the tropical species Porites spp., Pseudodiploria strigosa and Orbicella annularis, and the cold-water species Madrepora oculata, Caryophyllia antarctica and Flabellum impensum, are all suitable candidates for reconstructing seawater temperatures. The integrated results across a wide temperature range, from extreme cold to tropical shallow waters, yield an overall precision for the Li/Mg-temperature proxy of ±1.0 °C, as quantified by the standard error of estimates. If calculated from the 95% prediction intervals, the uncertainty of the temperature estimates is ±0.9 °C at 1 °C, ±1.5 °C at 12 °C and ± 2.6 °C at 25 °C. However, the uncertainty for the tropical corals (e.g. Porites) can be reduced to ±0.6 °C if a Li/Mg and Sr/Ca multi-regression approach is applied.

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Cuny-Guirriec K, Douville E, Reynaud S, Allemand D, Bordier L, Canesi M et al. Coral Li/Mg thermometry: Caveats and constraints. Chemical Geology. 2019 Sep 30;523:162-178. https://doi.org/10.1016/j.chemgeo.2019.03.038