Effect of different seawater Mg2+ concentrations on calcification in two benthic foraminifers
Mewes, Antje (Alfred Wegener Institute Foundation for Polar and Marine Research)
Langer, Gerald (Cambridge University. Department of Earth Sciences)
De Nooijer, Lennart Jan (Royal Netherlands Institute for Sea Research)
Bijma, Jelle (Alfred Wegener Institute Foundation for Polar and Marine Research)
Reichart, Gert-Jan (University of Utrecht. Department of Earth Sciences)

Date:	2014
Abstract:	Magnesium, incorporated in foraminiferal calcite (Mg/CaCC), is used intensively to reconstruct past seawater temperatures but, in addition to temperature, the Mg/CaCC of foraminiferal tests also depends on the ratio of Mg and Ca in seawater (Mg/CaSW). The physiological mechanisms responsible for these proxy relationships are still unknown. This culture study investigates the impact of different seawater [Mg2+] on calcification in two benthic foraminiferal species precipitating contrasting Mg/CaCC: Ammonia aomoriensis, producing low-Mg calcite and Amphistegina lessonii, producing intermediate-Mg calcite. Foraminiferal growth and test thickness were determined and, Mg/Ca was analyzed using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Results show that at present-day seawater Mg/CaSW of ~5, both species have highest growth rates, reflecting their adaptation to modern seawater element concentrations. Test thickness is not significantly affected by different Mg/CaSW. The relationship between Mg/CaSW and Mg/CaCC shows a distinct positive y-axis intercept, possibly reflecting at least two processes involved in foraminiferal biomineralization. The associated Mg partition (DMg) changes non-linearly with increasing Mg/CaSW, hence suggesting that the DMg is best described by an exponential function approaching an asymptote.
Grants:	European Commission 211384 European Commission 265103 European Commission 267931
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Biomineralization ; Culture experiment ; LA-ICP-MS ; Mg partitioning ; Mg/Ca ; Proxy
Published in:	Marine Micropaleontology, Vol. 113 (December 2014) , p. 56-64, ISSN 0377-8398

DOI: 10.1016/j.marmicro.2014.09.003
PMID: 26089590

9 p, 1.1 MB

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