ANR COR-Resilience

COR-Resilience project aims at reconstructing, quantifying and evaluating past, present and future impacts of anthropogenically-driven climate change (ocean acidification & global warming), and local stressors (e.g. heavy metals, nutrients) on the calcification and growth mechanisms of two of the main reef-building coral genera (Porites and Diploastrea) found in the Indo-Pacific region, and their associated microboring flora. To achieve this objective, the project will apply a combined “biogeochemical data – modelling” approach and reconstruct long-term key environmental parameters over the 2-5 last centuries based on coral geochemistry. Decadal to centennial scale records of past seawater temperature, carbonate chemistry and heavy metal concentration will be reconstructed and compared with the temporal variability of the microboring flora and the skeletal growth parameters to improve predictions of coral calcification and growth responses to natural and human-induced environmental changes. Such comparisons are rare given that they require a large effort in collecting multiple information on coral growth parameters, dynamics of skeletal colonization by microborers and geochemical proxies.

The project working hypothesis is that coral growth and skeletal macro- and micro-structures are not directly affected by the ambient seawater parameters, but by the direct influence of abiotic/biotic factors on the chemistry of the calcifying fluid from which aragonite precipitates and potentially on the abundance of microboring flora. The main purpose of COR-Resilience project is to provide:

• i- a full characterization of the present-day and past variability of the carbonate chemistry within the extracellular calcifying fluid of several colonies of Porites and Diploastrea from the Indo-Pacific region. Coral geochemistry will be also used to reconstruct the long-term SST variability and heavy metal contents of the ambient seawater;
• ii- a “data – model” comparison of the seawater carbonate chemistry and SST changes over the last centuries;
• iii- a comprehensive evaluation of the effects of multiple stressors on the growth mechanisms of two of the main reef-building coral genera (Porites and Diploastrea), using both field and cultured specimens.

To achieve COR-Resilience objectives, the project has access to high quality ambient environmental data acquired during recent oceanographic cruises and field campaigns (TARA-Pacific, 2016-2018 and TAAF CLIM-Eparses, 2019), as well as a unique collection of long coral cores. COR-Resilience
is scientifically innovative because it will combine a diverse set of established and emerging geochemical proxies (d18O, d13C, d11B, B/Ca, Sr/Ca, Li/Mg, etc.) with the analysis of coral growth parameters (e.g. density) using advanced X-Ray Computed Tomography (XCT & µCT) at various scales (from core size to micrometer). COR-Resilience results from a joint initiative of experimental researchers and climate and biogeochemical modellers from five world-class laboratories (LSCE, LOV, LOCEAN, EPOC and CSM) with expertise in climate and environmental research in tropical regions and international collaborators. The work proposed is organized into five work packages (WPs):

• i- coordination, management and dissemination;
• ii – modern reef environments and proxy calibration,
• iii- coral-based reconstructions;
• iv – coral cultures & growth parameters;
• v- data-modelling comparison.

COR-Resilience results will have major scientific and societal impact and will be shared widely via publications, meetings, social media, outreach events and school programs.