Cold-water corals: sensitive receiver of isotope proxy signals and how to read the climatic and environmental information

Marine biogenic carbonates such as coral skeletons, bivalve shells or foraminifera can act as sensitive receivers of isotope proxy signals. In recent years, boron (B), lithium (Li) and magnesium (Mg) isotope ratios in marine biogenic carbonates are increasingly used to decipher paleoclimatic and paleooceanographic conditions. However, vital effects of the organisms can lead to large uncertainties in their application. For their use as paleoenvironmental-proxies it is crucial to understand the impacts of these vital effects on the different isotope systems and element concentrations.

In this project, we analyse B, Li and Mg isotope compositions of modern and fossil Lophelia pertusa and Madrepora Oculata samples. The advantage of using these cold-water corals is that they occur in upper (near coast) and deeper (proximal) environments and therefore, offer the possibility to reconstruct environmental and climatic changes on regional and global scales. To evaluate the potential of cold-water corals as receiver of isotope proxy signals, we conduct experiments to examine sample heterogeneities on mm- to cm-scale and investigate different cleaning techniques. In a second step, we investigate the biological and environmental controls on the different isotope systems. For this purpose, we chose modern L. pertusa and M.oculata samples from several locations within the Mediteranean, Atlantic and North Sea to cover a wide range of ocean pH, temperature and salinity conditions. The coral isotope data will be compared with ambient seawater parameters to identify possible relationships between environmental parameters and the incorporation of B, Li or Mg isotopes into the coral skeleton.

In the final phase of the project, we will investigate Li, B and Mg isotope ratios in fossil cold-water corals and evaluate their use as paleo-oceanographic and climatic proxies.