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

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

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.

Data: CORDIS, © European Union