Boron incorporation in the foraminifer Amphistegina lessonii under a decoupled carbonate chemistry

authored by

K. Kaczmarek, G. Langer, G. Nehrke, I. Horn, S. Misra, M. Janse, J. Bijma

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.

Organisation(s)

Institute of Mineralogy

External Organisation(s)

Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research
University of Cambridge
Burgers’ Zoo

Type

Article

Journal

BIOGEOSCIENCES

Volume

12

Pages

1753-1763

No. of pages

11

ISSN

1726-4170

Publication date

18.03.2015

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Ecology, Evolution, Behavior and Systematics, Earth-Surface Processes

Sustainable Development Goals

SDG 14 - Life Below Water

Electronic version(s)

https://doi.org/10.5194/bg-12-1753-2015 (Access: Open)
https://doi.org/10.5194/bg-12-2469-2015 (Access: Open)