20 Mag. 2014 - Paolo Montagna

Geochemical signal in coral skeletons:
tool to understand the climate

Presenta: Paolo Montagna ( CNR-ISMAR, Bologna )

Scleractinian corals can provide multi-century, sub-annual resolution paleoceanographic records. They can be precisely dated by 230Th/U technique and they systematically incorporate isotopic and chemical tracers that reflect 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 calcification rate in the future. In particular, the boron isotopes extracted from the skeleton of zooxanthellate and azooxanthellate corals can effectively be used to quantify the internal pH and the response of calcification to ocean acidification 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 Atlantic Ocean. In particular I will discuss the use of Li/Mg ratio, boron and neodymium isotopes as reliable proxies for seawater temperature, pH and water-mass circulation, 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.

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