Controls on potassium incorporation in foraminifera and other marine calcifying organisms
Controls on potassium incorporation in foraminifera and other marine calcifying organisms
Seawater chemistry exerts an important control on the incorporation of trace elements into the shells of marine calcifying organisms. Variability in the major ion chemistry of seawater is a tracer of past geological processes, and the influence of seawater chemistry on trace element incorporation in calcium carbonate can be harnessed to determine changes in the composition of seawater through time. Here, we investigate whether key oceanographic parameters (temperature, salinity, and the carbonate system) affect the incorporation of potassium (K) into foraminiferal calcite, and explore the utility of K/Ca ratios in foraminifera as an indicator of past variability in the seawater Ca2+ concentration. We analysed both low-Mg and high-Mg modern foraminifera, including planktonic (Globigerinoides ruber) and shallow-dwelling larger benthic (Operculina ammonoides) species, using laser-ablation sector-field inductively-coupled plasma mass spectrometry (LA-SF-ICPMS). Both species show no resolvable influence of temperature, salinity, pH, or [CO32−] on K incorporation across the range that these vary at our samples sites. In order to determine the effect of the seawater Ca concentration ([Ca2+]sw) on K incorporation, we analysed laboratory-cultured O. ammonoides, the close living relative of the abundant Eocene Nummulites, grown at four different [Ca2+]sw. We find a significant relationship between seawater and shell K/Ca, albeit with a shallower slope compared to most other trace elements which we suggest is driven by a crystal growth rate effect on K incorporation, constrained using culture experiments of O. ammonoides grown at different pH. If the K+ concentration has remained relatively constant throughout the Phanerozoic Eon, our data may pave the way forward for the use of K/Ca as a direct proxy for past [Ca2+]sw variability. Alternatively, coupling K/Ca with the similar Na/Ca proxy would allow more accurate reconstruction of [Ca2+]sw or verification of whether [K+]sw and [Na+]sw have indeed remained within narrow bounds.
Culture calibration, K/Ca, LA-ICPMS, Larger Benthic Foraminifera (LBF), Na/Ca, Seawater chemistry
125-138
Nambiar, Romi
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Hauzer, Hagar
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Gray, William
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Henehan, Michael James
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Cotton, Laura J.
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Erez, Jonathan
ed56a557-377e-4b63-8ba8-3d23e506e5c0
Rosenthal, Yair
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Renema, Willem
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Müller, Wolfgang
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Evans, David
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15 June 2023
Nambiar, Romi
6eeaba53-0e44-4e63-b3f9-7efc6747f04b
Hauzer, Hagar
68d86aec-9d2c-4c71-9b63-0fedac4ed501
Gray, William
b6a672d9-2fc9-4ada-b939-377cd98c19a0
Henehan, Michael James
292363cf-b6e0-4d4b-82e6-81483daa7ba5
Cotton, Laura J.
a6784c65-de61-4c24-82a8-ec20b70f0f27
Erez, Jonathan
ed56a557-377e-4b63-8ba8-3d23e506e5c0
Rosenthal, Yair
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Renema, Willem
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Müller, Wolfgang
360a71f7-0b47-4ff3-8c32-1912d70401aa
Evans, David
878c65c7-eab9-4362-896b-166e165eb94b
Nambiar, Romi, Hauzer, Hagar, Gray, William and Evans, David
,
et al.
(2023)
Controls on potassium incorporation in foraminifera and other marine calcifying organisms.
Geochimica et Cosmochimica Acta, 351 (6), .
(doi:10.1016/j.gca.2023.04.020).
Abstract
Seawater chemistry exerts an important control on the incorporation of trace elements into the shells of marine calcifying organisms. Variability in the major ion chemistry of seawater is a tracer of past geological processes, and the influence of seawater chemistry on trace element incorporation in calcium carbonate can be harnessed to determine changes in the composition of seawater through time. Here, we investigate whether key oceanographic parameters (temperature, salinity, and the carbonate system) affect the incorporation of potassium (K) into foraminiferal calcite, and explore the utility of K/Ca ratios in foraminifera as an indicator of past variability in the seawater Ca2+ concentration. We analysed both low-Mg and high-Mg modern foraminifera, including planktonic (Globigerinoides ruber) and shallow-dwelling larger benthic (Operculina ammonoides) species, using laser-ablation sector-field inductively-coupled plasma mass spectrometry (LA-SF-ICPMS). Both species show no resolvable influence of temperature, salinity, pH, or [CO32−] on K incorporation across the range that these vary at our samples sites. In order to determine the effect of the seawater Ca concentration ([Ca2+]sw) on K incorporation, we analysed laboratory-cultured O. ammonoides, the close living relative of the abundant Eocene Nummulites, grown at four different [Ca2+]sw. We find a significant relationship between seawater and shell K/Ca, albeit with a shallower slope compared to most other trace elements which we suggest is driven by a crystal growth rate effect on K incorporation, constrained using culture experiments of O. ammonoides grown at different pH. If the K+ concentration has remained relatively constant throughout the Phanerozoic Eon, our data may pave the way forward for the use of K/Ca as a direct proxy for past [Ca2+]sw variability. Alternatively, coupling K/Ca with the similar Na/Ca proxy would allow more accurate reconstruction of [Ca2+]sw or verification of whether [K+]sw and [Na+]sw have indeed remained within narrow bounds.
Text
K_Ca proxy_manuscript_20 April 23-clean.docx
- Accepted Manuscript
More information
Accepted/In Press date: 24 April 2023
Published date: 15 June 2023
Additional Information:
Funding Information:
This work is part of the VeWA consortium funded by the Hessen State Ministry for Higher Education, Research, and the Arts through the LOEWE program. MJH gratefully acknowledges the provision of sample materials by Michal Kucera and Helen Bostock. The foraminifera culture work of HH and DE was carried out in the laboratory of J.Erez and funded by ISF grant # 1886/20. FIERCE is financially supported by the Wilhelm and Else Heraeus Foundation and by the Deutsche Forschungsgemeinschaft (DFG: INST 161/921-1 FUGG, INST 161/923-1 FUGG and INST 161/1073-1 FUGG), which is gratefully acknowledged. This is FIERCE contribution No. 126. We gratefully thank the associate editor Thomas Marchitto, as well as Sambuddha Misra and an anonymous reviewer for their thoughtful consideration of this work.
Funding Information:
This work is part of the VeWA consortium funded by the Hessen State Ministry for Higher Education, Research, and the Arts through the LOEWE program. MJH gratefully acknowledges the provision of sample materials by Michal Kucera and Helen Bostock. The foraminifera culture work of HH and DE was carried out in the laboratory of J.Erez and funded by ISF grant # 1886/20. FIERCE is financially supported by the Wilhelm and Else Heraeus Foundation and by the Deutsche Forschungsgemeinschaft (DFG: INST 161/921-1 FUGG, INST 161/923-1 FUGG and INST 161/1073-1 FUGG), which is gratefully acknowledged. This is FIERCE contribution No. 126. We gratefully thank the associate editor Thomas Marchitto, as well as Sambuddha Misra and an anonymous reviewer for their thoughtful consideration of this work.
Publisher Copyright:
© 2023 Elsevier Ltd
Keywords:
Culture calibration, K/Ca, LA-ICPMS, Larger Benthic Foraminifera (LBF), Na/Ca, Seawater chemistry
Identifiers
Local EPrints ID: 477781
URI: http://eprints.soton.ac.uk/id/eprint/477781
ISSN: 0016-7037
PURE UUID: 82850d17-6f1d-4300-a055-b7682a8e85f2
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Date deposited: 14 Jun 2023 16:40
Last modified: 28 Apr 2024 04:01
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Contributors
Author:
Romi Nambiar
Author:
Hagar Hauzer
Author:
William Gray
Author:
Michael James Henehan
Author:
Laura J. Cotton
Author:
Jonathan Erez
Author:
Yair Rosenthal
Author:
Willem Renema
Author:
Wolfgang Müller
Author:
David Evans
Corporate Author: et al.
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