The marine biogeochemical cycles of the major and trace elements play fundamental roles in both the biological and chemical functioning of the ocean but also in terrestrial climatic regulation. Marine ecosystems (phytoplankton, zooplankton, bacteria, fish, predators) occupy a central place within these cycles and contribute by various processes (assimilation-degradation-trophic transfer-sedimentation) to transform, store and redistribute the chemical elements in the column. of ocean water. These transformations favor different levels of coupling between the element cycles and interact directly on the climate by modifying the gas exchanges involved in the radiative balance of the atmosphere (CO2, CH4, N2O, DMS). Despite significant progress made in recent decades, this essential role of marine ecosystems on biogeochemical cycles and ultimately on the climate remains poorly quantified and is still a scientific issue.
This issue is all the more important in the current context in which anthropogenic pressures on the ocean and marine organisms continue to increase and multiply. Climate change and modification of environmental forcings (T, pH, pCO2, currents, extension of sea ice), releases of polluting substances (toxic metals, pesticides, microplastics, etc.), intensive exploitation of biological resources or the degradation of natural habitats are all factors that can profoundly alter the structure, functioning and biodiversity of marine ecosystems. What will be the impacts of these modifications on biogeochemical cycles, ocean productivity, gas exchanges? What will be the climate feedbacks and organizations’ response to these changes? These are all questions that the scientific community must answer if it intends to reduce the uncertainties associated with climate simulations and anticipate the joint evolution of marine ecosystems.
It is around these questions that our research team (CHIBIDO) develops its activities. Our objects of study are the biogeochemical cycles of the major elements (C, N, P, S, Si) and metallic traces (Fe, Mn, Cu, Ni, Zn, Co, Cd, Mo, Pb) and we try, by multidisciplinary approaches involving physicists, biologists, chemists and modelers to contribute to the improvement of knowledge on the interactions between oceanic dynamics, biogeochemical cycles, ecosystems and climate. Our research actions combine a wide spectrum of approaches associating the development of new methods of analysis (multi-elementary, isotopic and speciation), the implementation of tracers / geochemical proxies (Baxs, 234Th, δ30Si, δ11B), in situ observation at different scales (microcosms, mesocosms, basin, global), laboratory experimentation and the use of numerical modeling. These approaches are part of the international (IMBER, GEOTRACES, SOLAS) and national (LEFE-CYBER, EC2CO / DRIL, LABEX Sea) programmatic framework and are structured along three lines of research: