Simultaneous measurement of boron isotopes and the boron/calcium ratio in biogenic marine carbonates as a tool to reconstruct the marine carbonate system
Final Report Abstract
Eventhough we could not carry out all of the work originally proposed, the project turned out to be a great success. This project will greatly advance our understanding of natural global carbon cycling and the role of the oceans (via carbonate chemistry reconstructions) and the impact of abrupt carbon cycle pertubations that are at the basis of ocean acidification. We have addressed some major unknowns with regard to the boron isotope and the B/Ca proxies and developed a new method that will greatly advance the field. In more detail, we have: 1) Developed a new in situ method for the simultaneous determination of δ11B and B/Ca at the nano gram level. This is an important development because this will allow to analyse single tests of foraminifera from cores with the certainty of being time synchronous. Hence, we are now able to investigate natural variability, “seasonality” or monsoon intensity. 2) Used controlled culture experiments with benthic and planktonic foraminifera, to confirm that δ11B, as expected, is controlled by pH and demonstrated, for the first time, that B/Ca is controlled by the bicarbonate (HCO3-) concentration. This will allow us to fully reconstruct the carbonate chemistry. 3) Demonstrated for the inorganic system that temperature and precipitation rate exert a major influence on δ11B and B/Ca and recommend that this should be investigated in living foraminifera. 4) Shown that the coordination of boron in foraminiferal calcite is trigonal planar and that boron is nor distributed homogeneously but in high and low concentration bands similar to the Mg. The Mg and B band are closely correlated but not associated at the atomic scale. We will definitely continue these successful collaborations.
Publications
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2014. Boron in marine biogenic carbonates as a proxy for the carbonate system. Jacobs University, Bremen. Alfred-Wegener-Inst., 136 S.
Kaczmarek, K.
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Boron incorporation in the foraminifer Amphistegina lessonii under decoupled carbonate chemistry. Biogeosciences, 12 (6). pp. 1753-1763, 2015
Kaczmarek, K., Langer, G., Nehrke, G., Horn, I., Misra, S., Janse, M. and J. Bijma
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Simultaneous determination of δ11B and B/Ca in marine biogenic carbonates at nano gram level. Chemical Geology, Volume 392, 21 January 2015, Pages 32-42
Kaczmarek, K., Horn, I., Nehrke, and Bijma, J.
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Investigating the effects of growth rate and temperature on the B/Ca ratio and δ11B during inorganic calcite formation. Chemical Geology, Volume 421, 10 February 2016, Pages 81-92
Kaczmarek, K., Nehrke, G., Misra, S., Elderfield, H. and J. Bijma
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Decoupled carbonate chemistry controls on the incorporation of boron into Orbulina universa. Biogeosciences, European Geosciences Union, 2017, 14 (2), pp.415-430
Howes, E., Raitzsch, M., Mewes, A., Kaczmarek, K., Bijma, N.N., Horn, I., Misra, S., Gattuso, J.-P. and J. Bijma
