Rekonstruktion des marinen Karbonatsystems während des letzten glazial-interglazialen Überganges aus Bor-Isotopen und -Konzentrationen Foraminiferen.
Mineralogie, Petrologie und Geochemie
Physik, Chemie und Biologie des Meeres
Zusammenfassung der Projektergebnisse
owards a better understanding of CO2 storage during ice ages. To accurately predict the consequences of anthropogenic perturbations of the carbon cycle, it is essential to first understand the fluctuations and variability of the natural sources and sinks of the Earth's carbon cycle. This requires an accurate reconstruction of ocean carbonate chemistry, as changes in deep ocean carbon storage are key to explaining the glacial/interglacial variations in atmospheric CO2 observed in ice cores. The main objective of our project was to analyze two independent carbonate chemistry proxies (boron isotopic and elemental ratios) on benthic and planktonic foraminifera from sediment cores recording the last Glacial-Interglacial transition in order to quantify natural CO2 outgassing and contribute to a better understanding of natural carbon storage and release. We thus sought to optimize methods and analytical tools to reduce sample size because benthic foraminifera are very poorly preserved in sediment cores. Development of a protocol requiring a small amount of material. Benthic foraminifera are often very rare in sedimentary cores. It is therefore necessary to develop or optimize techniques for boron isotope analysis from a small amount of carbonate. We opted for two methods: one being the analysis by in situ techniques (laser and ion microprobe) and the other by the reduction of the sample size for dissolved material due to the separation of boron by microsublimation coupled with the optimization of the introduction system in the mass spectrometer. The in-situ techniques were thus used for the first time on the same material and we showed the good agreement between them. However, these techniques are particularly adapted to the study of biomineralization processes and not to the reconstruction of seawater pH. The optimization of the microsublimation technique and the introduction allowed to reduce the quantity of carbonate necessary for an analysis and could thus be applied to foraminifera measurements covering the last glacialinterglacial period. Development of a boron isotope & B/Ca calibration for benthic foraminifera under in situ temperature and pressure. Using a unique high pressure viewing chamber for the microscope we observed, for the first time, behavior and chamber formation of deep-sea Cibicides-type foraminifera under in situ conditions. However, due to the difficulties to maintain the stability of the carbonate system (pH and DIC), it was, unfortunately, not possible to produce a calibration between pH and δ11B in Cibicides. Major results. One of the major results was the development of boron isotope analysis were on very small quantities of carbonate. This development was made possible by, among other things, extremely low chemistry blanks. This new boron isotope extraction and measurement protocol could be applied to the measurement of foraminifera from a sediment core showing the glacial/interglacial transition and thus measure at very high temporal resolution the pH variations of the seawater during this transition. This bilateral French-German project directly resulted in 4 published papers in international peer-reviewed journals. Several articles are still in preparation. This project resulted in a continued collaboration between the partners with regard to the use of lithium isotopes and the Li/Ca ratio in carbonates and contributed or stimulated several related projects as well as papers.
Projektbezogene Publikationen (Auswahl)
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Insight into deep-sea life – Cibicidoides pachyderma substrate and pH-dependent behaviour following disturbance. Deep Sea Research Part I: Oceanographic Research Papers, 138, 34-45.
Wollenburg, Jutta Erika; Zittier, Zora M.C. & Bijma, Jelle
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Technical note: Single-shell δ 11 B analysis of Cibicidoides wuellerstorfi using femtosecond laser ablation MC-ICPMS and secondary ion mass spectrometry. Biogeosciences, 17(21), 5365-5375.
Raitzsch, Markus; Rollion-Bard, Claire; Horn, Ingo; Steinhoefel, Grit; Benthien, Albert; Richter, Klaus-Uwe; Buisson, Matthieu; Louvat, Pascale & Bijma, Jelle
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High precision MC-ICP-MS measurements of11B/10B ratios from ng amounts of boron in carbonate samples using microsublimation and direct injection (μ-dDIHEN). Journal of Analytical Atomic Spectrometry, 36(10), 2116-2131.
Buisson, Matthieu; Louvat, Pascale; Thaler, Caroline & Rollion-Bard, Claire
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Permanent ectoplasmic structures in deep-sea Cibicides and Cibicidoides taxa – long-term observations at in situ pressure. Biogeosciences, 18(12), 3903-3915.
Wollenburg, Jutta E.; Bijma, Jelle; Cremer, Charlotte; Bickmeyer, Ulf & Zittier, Zora Mila Colomba
