(M/F) Impact of reconstructed climatic and environmental changes in the tropical Pacific zone, using the geochemistry of marine carbonate archives (corals and foraminifera), on associated microbial communities

Descrizione

(M/F) Impact of reconstructed climatic and environmental changes in the tropical Pacific zone, using the geochemistry of marine carbonate archives (corals and foraminifera), on associated microbial communities Sintesi in italiano (traduzione automatica): L'UMR LOCEAN 7159, un laboratorio di oceanografia e clima, cerca un dottorando per un progetto di ricerca sui cambiamenti climatici e ambientali nel Pacifico tropicale. La sede è in Nuova Caledonia, dove il candidato analizzerà i foraminiferi e i coralli per comprendere l'evoluzione delle comunità microbiche in relazione alle variazioni ambientali. È richiesta una laurea in scienze ambientali o discipline affini. Il dottorando avrà accesso a infrastrutture locali avanzate e beneficerà di una supervisione multidisciplinare. Il progetto mira a sviluppare modelli predittivi sull'evoluzione della biodiversità microbica in risposta ai cambiamenti climatici e alle attività umane, affrontando questioni scientifiche e sociali cruciali per la salute degli ecosistemi delle barriere coralline. UMR LOCEAN 7159 (Laboratory of Oceanography and Climate: Experiments and Numerical Approaches) conducts studies on physical and biogeochemical ocean processes and their role in climate, in interaction with marine ecosystems. Its teams, widely recognized at the international level, address a broad range of time and space scales for a better understanding of ocean dynamics and variations within the climate system, as well as its present, past, and future evolution. Dependent on four head institutions – SU, CNRS, IRD, and MNHN –, the laboratory is a major component of the Fédération de Recherche en sciences de l'environnement (IPSL). Since 2014, research in New Caledonia has been structured around CRESICA (Consortium for Research, Higher Education, and Innovation in New Caledonia). This consortium brings together nine institutions (BRGM, CHT, Cirad, CNRS, IAC, Ifremer, IPNC, IRD, UNC) and its mission is to: foster interdisciplinary research, coordinate actors around strategic projects for the region, train young researchers in connection with the École Doctorale du Pacifique, disseminate results to society, and optimize resources by pooling equipment and means. Thus, the PhD student will have privileged access to essential local infrastructures, notably: (LA) ICPMS, ICP-OES, on the IRD site (UAR IMAGO) LAMA (Laboratory of Mineral and Environmental Analyses), and the Plateforme du vivant (Living Platform for microbiology and genomics). The PhD student (F/M) will thus benefit from multidisciplinary supervision and a rich scientific environment, with state-of-the-art infrastructure and a local, regional, and international network, allowing them to develop varied skills in a tropical and island context, with major scientific and societal stakes. Coral reefs ecosystems in the South Pacific, which are biodiversity hotspots, are heavily threatened by climate warming, extreme events, pollution, and urbanization. Their resilience depends in part on their microbiomes, which are essential to their health. Thus, this research project aims to understand how current and past global and local changes influence the evolution of these microbial communities. By studying the links between past environmental and climatic variations reconstructed at high resolution over the last century from the geochemical signature of marine biogenic carbonates (foraminifera and corals), and the parallel co-evolution of microbial biodiversity, determined from the same samples, the objective is to better assess the resilience of these fragile ecosystems and anticipate their future evolution. The PhD student (F/M) will carry out both the identification of benthic foraminifera species from sediment cores collected from selected sites in New Caledonia (anthropized, mining watersheds, pristine...) and at least one other Pacific island (Palau, Nauru, PNG or Fiji), as well as the preparation and geochemical analyses of the shells. In parallel, coral cores will be collected near the sediment cores, and high-resolution geochemical signatures over time will be determined. The elemental and isotopic signatures such as Mg/Ca, B/Ca, Sr/Ca, Ni/Ca, Cr/Ca, δ11B, δ18O, δ34S will be calibrated using measured environmental data (T°C, pH, salinity, metal concentration), before being applied to reconstruct global and local climatic and environmental disturbances recorded over time within these environments, and their correlations with microbial biodiversity variations reconstructed from the same samples. We anticipate close links between the evolution of microbial communities and environmental changes, whether gradual (global warming) or sudden, such as ENSO effects, cyclones, the intensification of human activities, and associated disturbances (e.g., mining). On this basis, predictive models using artificial intelligence tools will be developed to anticipate future trends in microbial biodiversity based on past and current environmental