Skip to content

Research at St Andrews

Calibration of Na partitioning in the calcitic foraminifer Operculina ammonoides under variable Ca concentration: toward reconstructing past seawater composition

Research output: Contribution to journalArticle


Hagar Hauzer, David Evans, Wolfgang Müller, Yair Rosenthal, Jonathan Erez

School/Research organisations


Reconstructions of past changes in the seawater calcium concentration (Casw) are critical for understanding the long-term changes in ocean chemistry, the carbon cycle and for accurate application of elemental proxies (El/CaCaCO3 ) in foraminifera (e.g., Mg/Ca as proxy of temperature). Here we show that Na/Ca ratios in foraminiferal shells could be used for reconstructing Casw and Mg/Ca in the past oceans. Ca has a short residence time in the ocean (∼1 My), whereas Na in seawater has a residence time of ∼100 My. Hence it may be reasonably assumed that Nasw is invariant over the Cenozoic, enabling variations in oceanic Ca to be deduced from foraminiferal Na/Ca (Na/Cashell) if Na incorporation into foraminiferal shells depends on Na/Ca in seawater. Furthermore, the paleo-concentrations of other major and minor elements may then be calculated relative to the Ca in the shells, provided that other environmental or biological factors do not present a further complication. To evaluate this hypothesis, we cultured the benthic foraminifer Operculina ammonoides, an extant relative of the Eocene Nummulites, under varying Casw and temperature. The foraminifera grew well under the experimental conditions and increased their weight by 40–90%. The newly grown calcite (identified using a 135Ba labeling in the experimental seawater) was analyzed by Laser-Ablation ICP-MS for Li, Na, Mg and Sr to Ca ratios. The relationship between Na/Ca and Mg/Ca in the shell and their ratio in the solution are best described as a power function, where the instantaneous distribution coefficient is the derivative of the power fit to the El/Cashell versus El/Casw. In contrast, DSr and DLi are invariant with El/Casw. The influence of temperature on Li, Na and Sr incorporation was smaller than the uncertainty of our measurements. We conclude that Na/Ca in foraminiferal shells can be used to calculate paleo-calcium concentrations in the oceans and also other elements that may change relative to calcium (e.g., Mg, Sr, Li and others).


Original languageEnglish
Pages (from-to)80-91
Number of pages12
JournalEarth and Planetary Science Letters
Early online date20 Jun 2018
StatePublished - 1 Sep 2018

    Research areas

  • Seawater calcium proxy, Na/Ca calibration, Live-foraminifera, Ocean paleochemistry

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by journal

  1. An early diagenetic deglacial origin for basal Ediacaran “cap dolostones”

    Ahms, A-S., Maloof, A., Macdonald, F., Hoffman, P., Bjerrum, C., Bold, U., Rose, C. V., Strauss, J. & Higgins, J. 19 Nov 2018 In : Earth and Planetary Science Letters. 506, p. 292-307

    Research output: Contribution to journalArticle

  2. Constraining the evolution of Neogene ocean carbonate chemistry using the boron isotope pH proxy

    Sosdian, S. M., Greenop, R., Hain, M. P., Foster, G. L., Pearson, P. N. & Lear, C. H. 15 Sep 2018 In : Earth and Planetary Science Letters. 498, p. 362-376 15 p.

    Research output: Contribution to journalArticle

  3. Cryogenic silicification of microorganisms in hydrothermal fluids

    Fox-Powell, M. G., Channing, A., Applin, D., Cloutis, E., Preston, L. J. & Cousins, C. R. 15 Sep 2018 In : Earth and Planetary Science Letters. 498, p. 1-8 8 p.

    Research output: Contribution to journalArticle

  4. Pervasive aerobic nitrogen cycling in the surface ocean across the Paleoproterozoic Era

    Kipp, M. A., Stüeken, E. E., Yun, M., Bekker, A. & Buick, R. 15 Oct 2018 In : Earth and Planetary Science Letters. 500, p. 117-126 10 p.

    Research output: Contribution to journalArticle

Related by journal

  1. Earth and Planetary Science Letters (Journal)

    Hawkesworth, C. (Member of editorial board)

    Activity: Publication peer-review and editorial workEditor of research journal

ID: 253402418