Periodic Reporting for period 2 - BASE-LiNE Earth (Brachiopods As SEnsitive tracers of gLobal marINe Environment: Insights from alkaline, alkaline Earth metal, and metalloid trace element ratios and isotope systems)
Reporting period: 2017-01-01 to 2018-12-31
A very distinct threat of coral reefs is the effect of ocean acidification which restricts the coral reefs in their ability to calcify. In order to monitor long- and short term changes in natural ocean water acidity and to distinguish it from recent anthropogenically induced acidity we developed laser and mass-spectrometer based methods to detect this changes in high temporal resolution. Our analytical method is based on the observation that the Boron (B) isotopes ratios of 10B and 11B, respectively are directly related to the ocean water acidity reflected as pH-values. The knowledge gained with BASE-LiNE Earth enables us to improve the ability of reconstructing ocean water acidity for the long and recent past. For this purpose we performed culturing experiments in order to verify the influence of increasing ocean acidity on the ability of corals to form shells in more detail. One further task within BASE-LiNE Earth was to investigate the mineralogical and chemical composition of brachiopod shells. These shells show a hierarchical architecture, where organic molecules and mineral substance form a hybrid composite. Overall the organic substances provide flexibility and tensile strength while the mineral composition provides a high elastic modulus, compressive strength, hardness and resistance to abrasion. The understanding of the construction of such a shell is of wider implication because the construction principles of a brachiopod shell may also be copied for other materials and used in special products and applications for the airplane industry and constructions.
The variations of the alkaline earth elements (e.g. Mg, Ca, Sr) are particularly interesting to earth system and life sciences because these elements are most abundant and vital for the evolution of marine life, especially for the calcifying organisms in the ocean. From empirical data and numerical modeling it is known that the concentrations of Ca, Mg and Sr in seawater have varied considerably during the Phanerozoic. In turn, major changes in the balance between the oceanic hydrothermal and the carbonate/dolomite burial fluxes have sensitively influenced oceanic inventories of alkaline earth elements and their isotope systems. Importantly, shifting equilibria between continental weathering fluxes and hydrothermal and/or sedimentary (carbonate, dolomite) fluxes, modulate the evolution of marine Mg/Ca and Sr/Ca ratios over geological time. Determining the biological, environmental and tectonic processes that are responsible for these changes, will improve our understanding of the factors that control chemical composition of the ocean-atmosphere system, and thus the earth’s climate.