Impact of seawater [Ca]2+ on the calcification and calcite Mg / Ca of Amphistegina lessonii


Contact
antje.mewes [ at ] awi.de

Abstract

Abstract. Mg= Ca ratios in foraminiferal tests are routinely used as paleotemperature proxies, but on long timescales, they also hold the potential to reconstruct past seawater Mg= Ca. The impact of both temperature and seawater Mg= Ca on Mg incorporation in Foraminifera has been quantified by a number of studies. The underlying mechanism responsible for Mg incorporation in foraminiferal calcite and its sensitivity to environmental conditions, however, has not been fully identified. A recently published biomineralization model (Nehrke et al., 2013) proposes a combination of transmembrane transport and seawater leakage or vacuolization to link calcite Mg= Ca to seawater Mg= Ca and explains interspecies variability in Mg= Ca ratios. To test the assumptions of this model, we conducted a culture study in which seawater Mg= Ca was manipulated by varying [Ca2C] and keeping [Mg2C] constant. Foraminiferal growth rates, test thickness and calcite Mg= Ca of newly formed chambers were analyzed. Results showed optimum growth rates and test thickness at Mg= Ca closest to that of ambient seawater. Calcite Mg= Ca is positively correlated to seawater Mg= Ca, indicating that it is not absolute seawater [Ca2C] and [Mg2C] but their ratio that controls Mg= Ca in tests. These results demonstrate that the calcification process cannot be based only on seawater vacuolization, supporting the mixing model proposed by Nehrke et al. (2013). Here, however, we suggest transmembrane transport fractionation that is not as strong as suggested by Nehrke et al. (2013).



Item Type
Article
Authors
Divisions
Primary Division
Programs
Primary Topic
Peer revision
ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
37749
DOI 10.5194/bg-12-2153-2015

Cite as
Mewes, A. , Langer, G. , Thoms, S. , Nehrke, G. , Reichart, G. J. , de Nooijer, L. J. and Bijma, J. (2015): Impact of seawater [Ca]2+ on the calcification and calcite Mg / Ca of Amphistegina lessonii , Biogeosciences, 12 , pp. 2153-2162 . doi: 10.5194/bg-12-2153-2015


Download
[img]
Preview
PDF
BG_Antje.pdf

Download (1MB) | Preview
Cite this document as:

Share


Citation

Research Platforms
N/A

Campaigns


Actions
Edit Item Edit Item