Boron incorporation in the foraminifer <i>Amphistegina lessonii</i> under a decoupled carbonate chemistry

Kaczmarek, K. and Langer, G. and Nehrke, G. and Horn, I. and Misra, S. and Janse, M. and Bijma, J. (2015) Boron incorporation in the foraminifer <i>Amphistegina lessonii</i> under a decoupled carbonate chemistry. Biogeosciences, 12 (6). pp. 1753-1763. ISSN 1726-4189 DOI https://doi.org/10.5194/bg-12-1753-2015

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Abstract

A number of studies have shown that the boron isotopic composition (δ11B) and the B / Ca ratio of biogenic carbonates (mostly foraminifers) can serve as proxies for two parameters of the ocean's carbonate chemistry, rendering it possible to calculate the entire carbonate system. However, the B incorporation mechanism into marine carbonates is still not fully understood and analyses of field samples show species-specific and hydrographic effects on the B proxies complicating their application. Identifying the carbonate system parameter influencing boron incorporation is difficult due to the co-variation of pH, CO32- and B(OH)4-. To shed light on the question which parameter of the carbonate system is related to the boron incorporation, we performed culture experiments with the benthic symbiont-bearing foraminifer Amphistegina lessonii using a decoupled pH–CO32- chemistry. The determination of the δ11B and B / Ca ratios was performed simultaneously by means of a new in situ technique combining optical emission spectroscopy and laser ablation MC-ICP-MS. The boron isotopic composition in the tests gets heavier with increasing pH and B / Ca increases with increasing B(OH)4- / HCO3- of the culture media. The latter indicates that boron uptake of A. lessonii features a competition between B(OH)4- and HCO3-. Furthermore, the simultaneous determination of B / Ca and δ11B on single specimens allows for assessing the relative variability of these parameters. Among different treatments the B / Ca shows an increasing variability with increasing boron concentration in the test whereas the variability in the isotope distribution is constant.

Item Type:	Article
Uncontrolled Keywords:	2015AREP; IA69;
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems 04 - Palaeobiology
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems 04 - Palaeobiology 07 - Gold Open Access
Journal or Publication Title:	Biogeosciences
Volume:	12
Page Range:	pp. 1753-1763
Identification Number:	https://doi.org/10.5194/bg-12-1753-2015
Depositing User:	Sarah Humbert
Date Deposited:	05 Jun 2015 16:07
Last Modified:	25 Aug 2015 14:32
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3325

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