1Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, am Handelshafen 12, 27570 Bremerhaven, Germany
2Department of Earth Science, University of Cambridge, Dowing Site, CB2 3EQ Cambridge, UK
3Institute of Mineralogy, Leibniz University, Callin street 3, 30167 Hanover, Germany
4Burgers Zoo, Antoon van Hooffplein 1, 6816 SH Arnhem, the Netherlands
Received: 10 Sep 2014 – Discussion started: 05 Dec 2014
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.
Revised: 24 Feb 2015 – Accepted: 28 Feb 2015 – Published: 18 Mar 2015
Please read the corrigendum first before accessing the article.
Kaczmarek, K., Langer, G., Nehrke, G., Horn, I., Misra, S., Janse, M., and Bijma, J.: Boron incorporation in the foraminifer Amphistegina lessonii under a decoupled carbonate chemistry, Biogeosciences, 12, 1753-1763, doi:10.5194/bg-12-1753-2015, 2015.