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Brachiopods As SEnsitive tracers of gLobal marINe Environment: Insights from alkaline, alkaline Earth metal, and metalloid trace element ratios and isotope systems

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

Coral reefs like the Great Barrier Reef off the east coast of Australia cover an area of 133.000 km² and host breathtaking species richness. Climate change, pollution, fishing and tourism are serious threats to these unique ecosystems. Currently this unique habitat is suffering from a series of record-breaking heatwaves, which caused the death of approximately 50% of the corals. 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 healthier they are. 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. In the frame of the BASE LiNE Earth project we developed analytical instrumentation and methods to determine isotope changes above large scale reefs and to quantify changes in the isotope composition above the reefs and link these isotope changes to the status 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 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.
Fossil and modern Brachiopod sample material has been distributed among BASE-LiNE Earth consortium members. Culturing experiments have been conducted at GEOMAR facilities from January 2016, May 2016 respectively until July 2018. Key species for labor experiments were Pajaudina atlantica Logan, 1988 and Magellania venosa (Dixon, 1789). The culturing included both pH- and CO2-experiments. Moreover, settings with varying Mg/Ca ratios were established. First results have been published with 13 papers in peer reviewed journals. The publication process is still ongoing and currently more than 20 manuscripts related to BASE-LiNE Earth are either submitted or will be submitted soon. There have been two main network wide events: the 3rd BASE-LiNE Earth Annual Meeting in Austria in 2017 and the 4th and Final Meeting hosted at the University Milan, Italy in 2018. Another highlight was the active contribution of BASE-LiNE in the organization and implementation of the 8th International Brachiopod Congress in Milan, Italy from September 11-14, 2018 where BASE-LiNE Earth participated with a total of 23 contributions. BASE-LiNE Earth is actively communicating project related research to both the scientific audience and the general public. Thereby more than 72 contributions to international conferences have been provided by the ESRs. Moreover, BASE-LiNErs presented their scientific work to a wider public such as in the framework of the European Researchers Nights in 2016, 2017 and 2018, the “Kieler Woche” in 2018, and the 8th IBC in 2018. On these occasions the BASE-LiNE Earth touring exhibition was presented to the public. Moreover, BASE-LiNE continued to promote the profile of MSCAs within the scientific community by the organization of sessions and workshops in 2017 and 2018 at the EGU Conference in Vienna.
The BASE-LiNE Earth project focused 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 dealt with 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 earth’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 earth’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 earth’s climate.