Effect of different seawater Mg2Â + concentrations on calcification in two benthic foraminifers

Mewes, Antje and Langer, Gerald and de Nooijer, Lennart Jan and Bijma, Jelle and Reichart, Gert-Jan (2014) Effect of different seawater Mg2Â + concentrations on calcification in two benthic foraminifers. Marine Micropaleontology, 113. pp. 56-64. ISSN 0377-8398

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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 {\textasciitilde} 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.

Item Type:	Article
Uncontrolled Keywords:	2014AREP; IA68;
Subjects:	04 - Palaeobiology
Divisions:	04 - Palaeobiology 07 - Gold Open Access
Journal or Publication Title:	Marine Micropaleontology
Volume:	113
Page Range:	pp. 56-64
Depositing User:	Sarah Humbert
Date Deposited:	06 Feb 2015 18:58
Last Modified:	16 Feb 2015 18:15
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3223

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