A new model for biomineralization and trace-element signatures of Foraminifera tests

Nehrke, G. and Keul, N. and Langer, G. and de Nooijer, L. J. and Bijma, J. and Meibom, A. (2013) A new model for biomineralization and trace-element signatures of Foraminifera tests. Biogeosciences, 10 (10). pp. 6759-6767. ISSN 1726-4170, ESSN: 1726-4189 DOI 10.5194/bg-10-6759-2013

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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.

Item Type:	Article
Additional Information:	© Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License.
Uncontrolled Keywords:	2013AREP; IA66;
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title:	Biogeosciences
Volume:	10
Page Range:	pp. 6759-6767
Identification Number:	10.5194/bg-10-6759-2013
Depositing User:	Sarah Humbert
Date Deposited:	24 Nov 2013 18:45
Last Modified:	23 Dec 2013 18:33
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2918

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