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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - 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)

Teaser

Summary

Coral reefs like the Great Barrier Reef off the east coast of Australia cover an area of 133.000 kmÂ² and host breathtaking species richness. Climate change, pollution, fishing and tourism are serious threats to these unique ecosystems. However, how can we detect and quantify reef healthiness and distinguish healthy reefs from threatened ones? A good way to do is to investigate their respiration, which means the exchange of gases between the coral reef and the atmosphere. This is a similar approach to human health where large volumes are exchanged extensively between the lungs and the atmosphere indicating organism functionality. However, for humans feeling sick their respiration is quantitatively restricted. A similar situation is being observed for coral reefs: the higher the amount of respiration between corals and atmosphere the better is their health. However, how can we determine respiration for such an ecosystem like coral reefs with dimensions of kilometers to several hundreds of kilometers? A good way is to look to the isotope composition of the air above coral reefs. The respiration is changing the isotope composition of oxygen (O) and carbon (C), which we are able to detect quite precisely. Currently in the frame of the BASE LiNE Earth project we are developing analytical instrumentation and methods in order to determine isotope changes above large scale reefs in order to quantify changes in the isotope composition above the reefs and link these isotope changes to the healthiness of the reef.
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 are currently developing 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. With BASE-LiNE Earth we intend to reconstruct ocean water acidity for the long and recent past. For this purpose we perform laboratory and field experiments in order to verify the influence of increasing ocean acidity on the ability of corals to form shells in more detail.
Furthermore, a laser ablation based method for the determination of Boron (Î”11B) isotope variations is developed for the purpose of the reconstruction of pH variations in the past ocean. The laser based application of determining isotope fractionation is a fundamentally new approach, which not only requires highly sophisticated analytical instrumentation but also newly numerical methods in order to crunch big data sets and to perform large scale image processing.
In one further task within BASE-LiNE Earth we 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.

Work performed

Fossil and modern Brachiopod sample material has been distributed among BASE-LiNE Earth consortium members. Culturing experiments have been conducted at GEOMAR facilities. Samples were then collected by BASE LiNE Earth members (Dr. Henkel and Mrs. Hana Jurikova) in collaboration with Spanish scientists on the Canary island of La Palma (Paujaudina atlantica, 18 to 26Â°C) but also from Chile (Magellania venosa, 10 to 15Â°C).
The culturing includes both pH- and CO2-experiments, which request sophisticated technical infrastructure and experience in culturing. Moreover, settings with varying Mg/Ca ratios have been established.
There have been two main network wide events, which were the Kick-off Workshop in Kiel as well as the 2nd Workshop in Prague. These events have been project milestones not only due to the scientific training but also due to the soft skill training that have been offered to the students.
BASE-LiNE Earth is actively communicating project related research to both the scientific audience and the general public (e.g. through the organization of scientific sessions on international conferences, hosting student internships, participation in the researcherâ€™s night). Furthermore, BASE-LiNE Earth is promoting the profile of MSCAs within the scientific community. This is implemented by the organization of sessions and workshops such as happened in 2016 and 2017 in the framework of the EGU Conference in Vienna.

Final results

The BASE-LiNE Earth project focuses on the interaction of the dissolved main (e.g. Mg, Ca) and trace elements (e.g. Li, B, Sr) with marine life. One of the BASE-LiNE Earth work packages focus on the complex interaction of two long term geological processes on earth: (i) by the plate tectonic and the spreading rates of the mid-ocean ridges and (ii) the rate of continental uplift weathering. The understanding of such long-term processes is essential in order to understand the environmental situation today and allows a forecast of the future. In particular, both sources and sinks for all substances are dissolved in the oceans and/or present in the earthâ€™s atmosphere. In particular, the balance between these two processes determines the concentration of the most important greenhouse gas on earth, carbon dioxide (CO2), which in turn controls global temperatures in the ocean-atmosphere system, and thus the earthâ€™s climate. Continental movement due to plate tectonic, changes of biological primary productivity, ocean water carbonate mineralogy, sea-level changes, glacial/interglacial cycles and/or bolide impacts superimpose the major processes causing glacial/interglacial temperature cyclicity, biological mass-extinction events and fundamental changes of the chemical and isotope composition of ocean water.
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 earthâ€™s climate.