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Stable oxygen isotope composition is biased by shell calcification intensity in planktonic Foraminifera
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  • Manuel F. G. Weinkauf,
  • Jeroen Groeneveld,
  • Joanna Waniek,
  • Torsten Vennemann,
  • Martini Rossana
Manuel F. G. Weinkauf
University of Geneva

Corresponding Author:[email protected]

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Jeroen Groeneveld
Helmholtz-Center for Polar and Marine Sciences
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Joanna Waniek
Leibniz Institute for Baltic Sea Research Warnemünde
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Torsten Vennemann
University of Lausanne
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Martini Rossana
University of Geneva
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Planktonic Foraminifera are widely used for environmental reconstructions through measurements of their shell’s geochemical characteristics, including its stable oxygen and carbon isotope composition. Using these parameters as unbiased proxies requires a firm knowledge of all potential confounding factors influencing foraminiferal shell geochemistry. One such parameter is the shell calcification intensity (shell weight normalized for shell size) that may influence the shell δ18O value either bioenergetically (by reducing energy available and required for equilibrium isotope fractionation during faster calcification) or kinetically (by influencing calcification depth through the shell’s density contrast with seawater). Specimens from the Globigerinoides ruber/elongatus compound from a sediment trap in the North Atlantic have been used to quantify the influence of shell calcification intensity on shell δ18O values. Shell calcification intensity was found to have a significant effect on the shell stable oxygen isotope composition in all species. Through model fitting, it is suggested that the effect size may be in a range of 1 to 2‰ (depending on species, depth migration, and local oceanographic conditions). We show that the confounding effect of shell calcification intensity on stable oxygen isotope composition can be of importance, depending on the anticipated precision of the derived reconstructions. A framework is provided to quantify this effect in future studies.
Nov 2020Published in Paleoceanography and Paleoclimatology volume 35 issue 11. 10.1029/2020PA003941