A new model for biomineralization and trace-element signatures of Foraminifera tests
Nehrke, Gernot (Alfred Wegener Institute Foundation for Polar and Marine Research)
Keul, N. (Columbia University. Lamont-Doherty Earth Observatory)
Langer, Gerald (University of Cambridge. Department of Earth Sciences)
De Nooijer, L. J. (Royal Netherlands Institute for Sea Research. Department of Marine Geology)
Bijma, Jelle (Alfred Wegener Institute Foundation for Polar and Marine Research)
Meibom, A. (Ecole Polytechnique Fédérale de Lausanne)

Date:	2013
Abstract:	The Mg/Ca ratio of Foraminifera calcium carbonate tests is used as proxy for seawater temperature and widely applied to reconstruct global paleo-climatic changes. However, the mechanisms involved in the carbonate biomineralization process are poorly understood. The current paradigm holds that calcium ions for the test are supplied primarily by endocytosis of seawater. Here, we combine confocal-laser scanning-microscopy observations of a membrane-impermeable fluorescent marker in the extant benthic species Ammonia aomoriensis with dynamic 44Ca-labeling and NanoSIMS isotopic imaging of its test. We infer that Ca for the test in A. aomoriensis is supplied primarily via trans-membrane transport, but that a small component of passively transported (e. g. , by endocytosis) seawater to the site of calcification plays a key role in defining the trace-element composition of the test. Our model accounts for the full range of Mg/Ca and Sr/Ca observed for benthic Foraminifera tests and predicts the effect of changing seawater Mg/Ca ratio. This places foram-based paleoclimatology into a strong conceptual framework.
Grants:	European Commission 211384 European Commission 246749 European Commission 267931 European Commission 265103
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Published in:	Biogeosciences, Vol. 10, Issue 10 (October 2013) , p. 6759-6767, ISSN 1726-4189

DOI: 10.5194/bg-10-6759-2013

9 p, 1.7 MB

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