The biological carbon pump (BCP) regulates the Earth’s climate by sequestrating photosynthetically fixed CO2 into the dark ocean. The BCP occurs in the form of organic carbon particles (POC) from planktic origins sinking below the surface. POC flux attenuates with depth through remineralisation by heterotrophic organisms. However, the variability of POC flux attenuation remains unexplained. Recent work showed that prokaryotes (Archaea and Bacteria) converting dissolved CO2 into POC (dark CO2 fixers) exist on sinking particles in the dark ocean. Yet, this potentially important new source of C to the dark ocean is not considered in POC flux attenuation. Combining innovative sampling strategy and measurements techniques, ARMORIC will generate unprecedented data on prokaryotic dark CO2 fixation rates and diversity associated to sinking POC. Accounting for dark CO2 fixation on POC may revolutionise conventional views on the apparent quantity of sinking POC being respired in the dark ocean.

The ANR ASTRID MORHOC'H project focused on the study of the interactions between swell and current vorticity. Indeed, it is not rare to encounter such currents in coastal areas, since the combined effects of wind and bathymetry can profoundly modify their vertical profile. The physical and numerical modeling of such areas is a strategic issue, both in the civil domain (coastal security, marine renewable energy, ...) and in the military domain (landing, rescue, naval applications). The project concluded on the importance to take this new parameter into account, as it could play a major role in swell propagation in such situations. Within the framework of this project, several advances had been obtained in terms of modeling. In particular, two results are of particular interest here. In terms of physical modeling, it was necessary to develop a very robust technique to experimentally control the vertical profile of the current, i.e. the horizontal components of vorticity. As far as analytical and numerical modeling is concerned, a new model had been developed, named CMS, to extend the field of application of phase-resolved wave propagation models in order to take into account configurations involving strong current vorticity. The MORHOC'H 2 project therefore aims to increase the degree of maturity of these two results, in order to bring them closer to use in real conditions. First of all, the current profile control device will be extended to larger configurations, and will become applicable in three-dimensional basins. This will allow the device to be adapted to a commercial hydrodynamic test basin, the BGO FIRST, at La Seyne-sur-Mer. Thus, it will become applicable to a wide range of industrial, civil and military tests. In addition, the CMS propagation model will be coupled with the community coastal hydrodynamic circulation code CROCO, developed by SHOM, IRD, CNRS, IFREMER, and INRIA, in order to make it usable under realistic conditions. Indeed, the existing code requires an important evolution, to be coupled with a tool modeling ocean circulation under realistic environmental conditions. A large increase in model maturity will therefore allow to obtain a demonstrator working in operational conditions. Through this project, the two approaches in coastal modeling, physical and numerical, which are totally complementary, will both progress in degrees of maturity, and will thus become more compatible with realistic situations. The different partners of the project will therefore move towards an operational use of the two models. In addition, this project brings together a consortium involving the company Océanide, the MIO and M2C laboratories, but also SHOM, for the optional work. The project will strengthen the collaboration between these different partners, while illustrating their complementarity.

The IRONWOMAN project aim to validate the hypothesis of the primordial role of marine iron-oxidizing bacteria (FeOB) in promoting the development of iron-rich mats, and impacting the iron biogeochemical cycle and the primary production in the deep oceans, according to the variations of the environmental conditions at play. For this purpose, we propose to carry out 1) in situ sampling of iron-rich mats through either punctual annual sampling or deployments of colonization experiments, and a newly developed nucleic acids and fluids sampler instrument enabling monthly collection; 2) continuous monitoring of physico-chemical environmental conditions at two contrasted deep-ocean environments of EMSO Azores (Atlantic hydrothermal site) and EMSO West Ligure (Mediterranean deep coastal plain), taking advantage of their status of deep-sea observatory (IR EMSO France); and 3) geochemical, isotopic, mineralogical, cultural and microbiological multi-omics analyses. Through these multidisciplinary and long-term approaches and instrumental development, the IRONWOMAN project would have an impact on better knowledge of ocean microbial biodiversity and its response to global environmental changes that could impact dO2 and dFe in deep ocean. To achieve our research objective, the work plan will be carried out by a consortium of complementary research team from four national institutions (MIO Marseille, GET Toulouse, URA-OMP Toulouse and LGE Marne La Vallée). The project is divided into five work packages: WP0-Management, to ensure the coordination between partner and the results dissemination; WP1-Sampling and Instrumentation, to ensure sampling and in situ experiments during the annual cruises but also the development of the FLUICS instrument; WP2-Characterization of environmental conditions to characterize the physico-chemical conditions surrounding iron-rich microbial mats; WP3-Biological characterization of mats, to characterize the microbial composition present in iron-rich mats, the active microbial species and their functioning via OMICS approaches; and WP4-Ex situ enrichment culture of microbial mats, to investigate the influence of dFe and dO2 variations on the functioning of microbial mats and iron acquisition pathways. The IRONWOMAN project will be the first dedicated multidisciplinary and long-term approach (relying on TGIR FOF and IR EMSO-France, the French node of the European infrastructure EMSO which is a legal entity under European law ERIC) conducted on entire microbial mats, leading to a full coverage of the complex interactions between them and their environment. Therefore, a combined strategy between in situ colonization through the development of a new device FLUICS and in vitro cultures, will allow us to improve our knowledge on the formation and evolution of iron-rich microbial mats with regards to environmental forcing. Through this topic, The IRONWOMAN project enters within the ANR research axis 1.2 “Terre Vivante”. Indeed, it addresses part of the objectives of the United Nations Ocean Decade (2021-2030) by developing a better knowledge and understanding of the ocean in order to protect and restore the ecosystem and biodiversity. Furthermore, by developing the FLUICS instrument, disseminating our results and dropping off the physico-chemical and sequencing data at databases, it will contribute to the expansion of the global ocean observing system, another objective of the Decade of the Oceans. This project will provide data to define the role of FeOBs as an actor in the iron cycle for primary production in deep waters, on two deep marine sites with different environmental conditions, and the interaction between iron, carbon and nitrogen cycles inside the mats. From its title (IRONWOMAN) to the organization of its Consortium and Work Plan, the IRONWOMAN project is fully gender-sensitive. A total budget of €552k is requested for 48 months, including 60 months of staff support, divided between the partners.

Mercury (Hg) is a global pollutant, able to be converted into highly neurotoxic monomethylmercury (MMHg), a compound bioaccumulated and bioamplified in food webs. Microorganisms regulate environmental MMHg level, by controlling directly inorganic Hg (IHg) methylation and MMHg degradation or indirectly through redox transformations controlling Hg bioavailability. Understanding the biotransformation processes of Hg in the environment is a key component of risk assessment of Hg in ecosystems and human health. However, there is little knowledge on the cellular processes leading to MMHg production. It is of special interest to develop studies at a cellular level to understand Hg transformations in terms of genetic determinism, cellular pathways and environmental factors regulating them. The MicroMer project aims to characterize the process of Hg methylation and demethylation at cellular level and environmental level. At cellular level, MicroMer aims to determine 1) the speciation of Hg in the cell environment favoring Hg transformations, 2) the mechanisms of Hg recognition by the cell, 3) the intracellular steps of Hg speciation and, 4) the Hg species export from the cell. Our hypothesis is that methylation and demethylation processes are coupled and that they are driven by Hg uptake but also its export. Thus, we intend to decipher the role of Hg cell trafficking and Hg speciation (in the extracellular and intracellular compartments) in Hg transformations. The processes will be investigated in Sulfate Reducing Bacteria models, Pseudodesulfovibrio hydrargyri BerOc1, able to methylate IHg and demethylate MMHg and two other strains able only to demethylate MMHg: Pseudodesulfovibrio piezophilus C1TLV30 and Desulfovibrio alaskensis G20. P. hydrargyri BercOc1 mutants of either Hg methylation, sensing, and export, and their heterologous expression in C1TLV30 and G20 will be performed. By experimental evolution, we will also generate BerOc1 strains with higher methylation and demethylation capacities. The consequences of mutations in 1) Hg methylation and demethylation, 2) Hg speciation and nature of Hg ligands (thiols), and 3) localization will be determined. MicroMer explores an outstanding and original line of work to understand Hg transformation based on our solid previous results. The striking combination of genetics, bacterial physiology and imaging methods (nano X-ray fluorescence, and electron microscopy) coupled with X-ray absorption spectroscopy and hyphenated mass spectrometry techniques is, to our knowledge, unique and innovative, and will forcefully bring new results and perspectives in the understanding of Hg methylation and demethylation. The MicroMer project has also an environmental scope that aims to determine the representativeness of the mechanism described in our model strains. By applying metagenomics and metatranscriptomics in a time-dependent (daily and seasonally) approaches, we will determine the fate of our model strain in its original environment. In parallel, we will determine the diversity and expression of major genetic determinisms in order to gain an overview of the representativeness of the model deciphered in MicroMer project in a natural environment. The MicroMer project proposes extensive and collaborative studies on mercury transformations mediated by bacteria using interdisciplinary approaches (molecular genetics, microbial physiology, analytical chemistry, X-ray absorption spectroscopy, imaging and microbial ecology). The project unites research teams (IPREM, MIO, and BIC) with strong expertise on those approaches in order to shed light on challenging topic. The environmental and health implications of the expected data obtained in this basic research project are of major interest. They will provide key information about the highly toxic MMHg production that is essential for risk evaluation, management, and sustainable development.

The ocean is constantly stirred by currents that swirl and mix seawater creating fronts, filaments and eddies. These dynamic structures are known as ‘fine scales’, and feature spatiotemporal scales of 1-100 km and days-weeks. Fine scales alter biogeochemical gradients affecting phytoplankton productivity and carbon export, but their role in nitrogen cycling is unknown. The greatest source of bioavailable nitrogen in the ocean is nitrogen fixation performed by microbes called ‘diazotrophs’. Understanding the role of fine scales on diazotroph activity and distribution requires dynamic sampling approaches at high-resolution. FIESTA will implement parallel measurements of nitrogen fixation rates, diazotroph abundance and diversity at an unprecedented resolution, >50 times higher than current measurements. This will allow more accurate quantification of nitrogen inputs to the dynamic ocean, which is key to constrain its current and future role in CO2 withdrawal and climate change.