TARA-Pacific, which began on 28 May 2016, ended on Saturday 27 October 2018 after 2 and a half years at sea with TARA’s media return to Lorient. The general motivation behind this expedition, coordinated by Serges Planes (CNRS), Denis Allemand (CSM) and Romain Troublé (TARA), is to study the biodiversity of present and past coral reefs across the entire Pacific Ocean using a “cross-disciplinary” approach involving experts from different scientific backgrounds. In particular, the researchers want to take stock of the current state of health of tropical reefs and assess their capacity for resilience and adaptation in the face of global changes caused by the industrial era. To carry out these impact studies, the Centre Scientifique de Monaco (CSM), in close collaboration with the LSCE, organised the drilling of numerous coral cores on board TARA. The results are now extremely positive, with 35 cores covering the last 2 centuries having been taken from 32 islands or atolls in the Pacific Ocean. As part of a MSC-ECA agreement to be signed in December 2018 for the period 2018-2022, we propose to make the most of these samples and thus to reconstruct, on an annual or even seasonal scale, the historical evolution of the temperature and pH-DIC (carbon cycle) of the Pacific Ocean and to compare the geochemical data obtained with those linked to the growth properties of the Porites and Diploastrea coral colonies sampled.
This work involves both cutting-edge geochemical analyses (d11B and B/Ca for pH, trace elements and Li/Mg and Sr/ca ratios for temperature, certain heavy metals or pollutants that can also affect coral health, and stable isotopes of C and O to take account of bio-mineralisation or the Suess effect. These analyses will logically be carried out on the LSCE’s new-generation mass spectrometers (ICP-QMS, MC-ICPMS and IRMS). This work will be accompanied by a qualitative analysis (DRX/MEB) and a density analysis (Tomography/Radiography-X) allowing the counting of annual bands (tropical coral growth model) and the establishment of growth parameters (density, linear extension, calcification rate).
This work on trace elements (B/Ca, Li/Mg, Sr/Ca, etc.) and B isotopes will enable us to reconstruct the historical evolution of temperature and carbonate chemistry in the Pacific Ocean. And these geochemical data, compared with physiological data, will provide unique information on the resilience of corals in the face of global change.
End of the TARA-Pacific expedition (May 2016 – October 2018), France 2 (Télématin 09.11.18)
Coll. CSM & TARA consortium; LSCE-LOV-MIO-CSM PACIFIC-Impacts project submitted to ANR (French National Research Agency)
