Séminaire
Scleractinian corals can provide multi-century, sub-annual resolution paleoceanographic records. They can be precisely dated by 230 Th/U technique and they systematically incorporate isotopic and chemical tracers that re!ect the environmental conditions of the ambient seawater.
On the other hand, the chemical and isotopic signals encoded into coral skeletons can be used to investigate the biomineralization processes and model the coral calci'cation rate in the future. In particular, the boron isotopes extracted from the skeleton of zooxanthellate and azooxanthellate corals can e*ectively be used to quantify the internal pH and the response of calci'cation to ocean acidi'cation and rising seawater temperature (McCulloch et al., 2012).
With the recent advances in analytical techniques, non-traditional stable and radiogenic isotopes can now be measured in relatively small coral portions and the results can be combined with established tracers in a unique multi-proxy approach.
I will present geochemical results from shallow- and deep-water corals from the Mediterranean Sea and the Southern Ocean. In particular, I will discuss the use of Li/Mg ratio and boron isotopes as reliable proxies for seawater temperature and pH as well as coupled U/Th and 14 C for water-mass ventilation, with examples based on long-lived specimens and coral fragments from sediment cores.
McCulloch M., Falter J., Trotter J., Montagna P. (2012). Coral resilience to ocean acidification and global warming through pH up-regulation. Nature Climate Change, 2, 623-627.
aline.tribollet@ird.fr