Retrospective approach to marine ecosystems

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The study of the structural and geochemical information archived in the carbonated structures of many marine organisms (bivalve shells, fish otoliths, rhodoliths, and hence the coccoliths) has undoubtedly been one of the points of interest for some fifteen years. strong and one of the specificities of LEMAR. This work highlights the considerable potential of these biogenic archives as witnesses to the current and past functioning of marine ecosystems. In recent years, LEMAR has focused on calibrating new proxies, including phytoplankton dynamics through bivalve shells (Li / Ca, Mo / Ca, Ba / Ca) or ocean acidification and climate change. with coccoliths (Li / Mg, B / Ca, δ11B), studies marked by the publication of pioneering articles in this field. It will be necessary to understand the biogeochemical mechanisms controlling the incorporation of certain tracers, and potentially new proxies, in these carbonated archives. This mechanistic approach will necessarily involve the implementation of experiments under controlled conditions (now made possible by the integration of Ifremer’s PFOM unit in 2012 and thanks to our methodological developments that make it possible to experimentally reproduce physicochemical forcings. under conditions that are representative of the natural environment), the establishment of a very high-frequency observatory of environmental conditions in Brest Bay, but also a modeling approach to the incorporation of trace elements and stable isotopes into these carbonated archives (eg DEB type models).