Project

Ba Isotopes; Ca Isotopes; Climate Changes; Sea Level; Geochemistry; Environemental Changes

Lead
Lay summary
The preliminary study on Ca isotopes in corals reveals that ∂44/40Ca is not significantly influenced by temperature. In most coral genera, the same holds true for salinity. The only factor that needs to be further constrained appears the biocalcification, specifically the pathway of Ca2+ from the solution to calcification centers. The extension of the research topic to include Ba isotopes aims at establishing the method successfully set up in a previous project. We plan to provide the first study applying systematically Ba isotope geochemistry to carbonates. This systematic study represents the initial phase of using Ba isotopic ratio as a proxy to constrain barium sources and diagenetic barium transport in the oceanic cycle to be developed in cooperation with Thomas Nägler (Bern). We expect to evaluate - Inter-specific variations versus Ca and Ba fractionation using corals cultivated under monitored conditions, with an important link to research at IfM-GEOMAR in Kiel on fractionation in the calcification centers; we collaborate with colleagues in Kiel (Germany) and Monaco. - Growth rates of coral skeleton versus Ca and Ba fractionation using samples from a modern natural environment, Mahahual in Mexico; Research conducted in collaboration with a colleague from UNAM, Puerto Morelos, Mexico. - Variations of the Ca and Ba isotopes in fossil corals from cores of IODP Expedition 310 (focusing on the interval between 20’000 and 10’000 years). This part of the project is conducted in collaboration with T. Felis (Bremen, Germany) and G. Camoin (Aix-en-Provence, France). The overall main goal of the research is to constrain the relationships between external/environmental factors, specifically temperature and salinity, and Ca- and Ba-isotope fractionation for calibrations as proxy records in corals. This will need, in parallel, a better understanding of internal/biological factors such as inter-specific variability, growth rates and mechanisms of biocalcification in order to extract vital effects prior to proxy-based environmental reconstructions. In particular the Ba isotopic signature (instead of elemental Ba that appears unreliable) in carbonates could be linked with paleoproductivity (continental weathering, upwelling influence the oceanic cycle of Ba), given that Ba reacts like a nutrient in the water column. We anticipate that Ba isotopes may become a fundamental proxy in paleoceanography, given the role Ba plays in the ocean and the finding that the isotope fractionation into barium carbonate is essentially independent from temperature.

Direct link to Lay Summary

Last update: 21.02.2013

Active participation

Communication	Title	Media	Place	Year

Number	Title	Start	Funding scheme

The proposal aims at requesting funding for 12 months (August 2012 - July 2013) in continuation of the SNF grant N° 20MA21-115944 (current funding ends July 2012), including the salary for the fourth year of Chloé Pretet (PhD student). We focus on Ca and, additionally, intend to include Ba isotope geochemistry. Sr isotope analysis is being investigated by the Group of A. Eisenhauer at IfM-GEOMAR in Kiel, partner in the frame of ESF EuroMarc project.The preliminary study on Ca isotopes in corals reveals that delta 44/40Ca is not significantly influenced by temperature. In most coral genera, the same holds true for salinity (Pretet et al., submitted a). The only factor that needs to be further constrained appears the biocalcification, specifically the pathway of Ca2+ from the solution to calcification centers. The extension of the research topic to include Ba isotopes aims at establishing the method successfully set up in a previous project (SNF project #200021-107505; von Allmen et al., 2010). We plan to provide the first study applying systematically Ba isotope geochemistry to carbonates. This systematic study represents the initial phase of using Ba isotopic ratio as a proxy to constrain barium sources and diagenetic barium transport in the oceanic cycle to be developed in a project submitted to SNF by Thomas Nägler (Bern) in the frame of CHARON. We expect to evaluate- Inter-specific variations versus Ca and Ba fractionation using corals cultivated under monitored conditions, with an important link to research at IfM-GEOMAR in Kiel on fractionation in the calcification centers; we collaborate with colleagues in Kiel (Germany) and Monaco.- Growth rates of coral skeleton versus Ca and Ba fractionation using samples from a modern natural environment, Mahahual in Mexico; Research conducted in collaboration with a colleague from UNAM, Puerto Morelos, Mexico.- Variations of the Ca and Ba isotopes in fossil corals from cores of IODP Expedition 310 (focusing on the interval between 20’000 and 10’000 years). This part of the project is conducted in collaboration with T. Felis (Bremen, Germany) and G. Camoin (Aix-en-Provence, France).The overall main goal of the research is to constrain the relationships between external/environmental factors, specifically temperature and salinity, and Ca- and Ba-isotope fractionation for calibrations as proxy records in corals. This will need, in parallel, a better understanding of internal/biological factors such as inter-specific variability, growth rates and mechanisms of biocalcification in order to extract vital effects prior to proxy-based environmental reconstructions.In particular the Ba isotopic signature (instead of elemental Ba that appears unreliable; McManus et al., 1998) in carbonates could be linked with paleoproductivity (continental weathering, upwelling influence the oceanic cycle of Ba), given that Ba reacts like a nutrient in the water column. We anticipate that Ba isotopes may become a fundamental proxy in paleoceanography, given the role Ba plays in the ocean and the finding that the isotope fractionation into barium carbonate is essentially independent from temperature (Boettcher et al., 2011).