A simple biomineralization model to explain Li, Mg, and Sr incorporation into aragonitic foraminifera and corals

T. M. Marchitto, S. P. Bryan, W. Doss, M. T. McCulloch, P. Montagna

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

In contrast to Li/Ca and Mg/Ca, Li/Mg is strongly anticorrelated with temperature in aragonites precipitated by the benthic foraminifer Hoeglundina elegans and a wide range of scleractinian coral taxa. We propose a simple conceptual model of biomineralization that explains this pattern and is consistent with available abiotic aragonite partition coefficients. Under this model the organism actively modifies seawater within its calcification pool by raising its [Ca2+], using a pump that strongly discriminates against both Li+ and Mg2+. Rayleigh fractionation during calcification effectively reverses this process, removing Ca2+ while leaving most Li+ and Mg2+ behind in the calcifying fluid. The net effect of these two processes is that Li/Mg in the calcifying fluid remains very close to the seawater value, and temperature-dependent abiotic partition coefficients are expressed in the biogenic aragonite Li/Mg ratio. We further show that coral Sr/Ca is consistent with this model if the Ca2+ pump barely discriminates against Sr2+. In H. elegans the covariation of Sr/Ca and Mg/Ca requires either that the pump more strongly discriminates against Sr2+, or that cation incorporation is affected by aragonite precipitation rate via the mechanism of surface entrapment. In either case Li/Mg is minimally affected by such ‘vital effects’ which plague other elemental ratio paleotemperature proxies.

LanguageEnglish
Pages20-29
Number of pages10
JournalEarth and Planetary Science Letters
Volume481
DOIs
Publication statusPublished - 1 Jan 2018

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Biomineralization
aragonite
biomineralization
Calcium Carbonate
foraminifera
calcification
coral
pump
Pumps
pumps
Seawater
partition coefficient
partitions
seawater
Fluids
entrapment
fluid
fluids
paleotemperature
coefficients

Cite this

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title = "A simple biomineralization model to explain Li, Mg, and Sr incorporation into aragonitic foraminifera and corals",
abstract = "In contrast to Li/Ca and Mg/Ca, Li/Mg is strongly anticorrelated with temperature in aragonites precipitated by the benthic foraminifer Hoeglundina elegans and a wide range of scleractinian coral taxa. We propose a simple conceptual model of biomineralization that explains this pattern and is consistent with available abiotic aragonite partition coefficients. Under this model the organism actively modifies seawater within its calcification pool by raising its [Ca2+], using a pump that strongly discriminates against both Li+ and Mg2+. Rayleigh fractionation during calcification effectively reverses this process, removing Ca2+ while leaving most Li+ and Mg2+ behind in the calcifying fluid. The net effect of these two processes is that Li/Mg in the calcifying fluid remains very close to the seawater value, and temperature-dependent abiotic partition coefficients are expressed in the biogenic aragonite Li/Mg ratio. We further show that coral Sr/Ca is consistent with this model if the Ca2+ pump barely discriminates against Sr2+. In H. elegans the covariation of Sr/Ca and Mg/Ca requires either that the pump more strongly discriminates against Sr2+, or that cation incorporation is affected by aragonite precipitation rate via the mechanism of surface entrapment. In either case Li/Mg is minimally affected by such ‘vital effects’ which plague other elemental ratio paleotemperature proxies.",
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A simple biomineralization model to explain Li, Mg, and Sr incorporation into aragonitic foraminifera and corals. / Marchitto, T. M.; Bryan, S. P.; Doss, W.; McCulloch, M. T.; Montagna, P.

In: Earth and Planetary Science Letters, Vol. 481, 01.01.2018, p. 20-29.

Research output: Contribution to journalArticle

TY - JOUR

T1 - A simple biomineralization model to explain Li, Mg, and Sr incorporation into aragonitic foraminifera and corals

AU - Marchitto, T. M.

AU - Bryan, S. P.

AU - Doss, W.

AU - McCulloch, M. T.

AU - Montagna, P.

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AB - In contrast to Li/Ca and Mg/Ca, Li/Mg is strongly anticorrelated with temperature in aragonites precipitated by the benthic foraminifer Hoeglundina elegans and a wide range of scleractinian coral taxa. We propose a simple conceptual model of biomineralization that explains this pattern and is consistent with available abiotic aragonite partition coefficients. Under this model the organism actively modifies seawater within its calcification pool by raising its [Ca2+], using a pump that strongly discriminates against both Li+ and Mg2+. Rayleigh fractionation during calcification effectively reverses this process, removing Ca2+ while leaving most Li+ and Mg2+ behind in the calcifying fluid. The net effect of these two processes is that Li/Mg in the calcifying fluid remains very close to the seawater value, and temperature-dependent abiotic partition coefficients are expressed in the biogenic aragonite Li/Mg ratio. We further show that coral Sr/Ca is consistent with this model if the Ca2+ pump barely discriminates against Sr2+. In H. elegans the covariation of Sr/Ca and Mg/Ca requires either that the pump more strongly discriminates against Sr2+, or that cation incorporation is affected by aragonite precipitation rate via the mechanism of surface entrapment. In either case Li/Mg is minimally affected by such ‘vital effects’ which plague other elemental ratio paleotemperature proxies.

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