Soil microorganisms globally are thought to be a source of carbon (C) because of their central role in releasing greenhouse gases (carbon dioxide and methane). Certain bacteria, archaea and protists consume inorganic C such as carbon dioxide, carbon monoxide and methane, but they are presumed either to be rare community members or with insignificant C assimilation capacities compared to plants. Yet emerging evidence shows that microbial C uptake can contribute significantly to terrestrial primary productivity. Given that both microbial C uptake and release coexist in soils, an enduring question is to which extent and under which conditions these microbial C processes counterbalance each other. Particularly, any decoupling among these coexisting microbial processes resulting from climate change is likely to have consequences for the whole-soil C balance, with unforeseen consequences for future climate conditions. BALANCE will use integrative microbiome studies to advance our fundamental knowledge of how microbial physiological responses to climate change modulate soil-atmosphere C exchanges in peatland ecosystems— a major soil C pool. Specifically, this project aims to 1) probe the metabolic rates that underpin microbial C balance. 2) Examine the biotic and environmental controls of the microbial C balance across space and time to extrapolate its control over peatland C dynamics at the global peatland scale. 3) Perform observational and experimental studies to reveal how climate change alters microbial C balance and predict the consequences at the global peatland scale using geospatial modelling. To fulfil these aims, this work will utilize a powerful approach that harnesses metagenomic, biogeochemistry and geospatial modelling. Its achievement will mark a step-change in microbial ecology theory and understanding, and address a critical research challenge of the Anthropocene in a key natural ecosystem: how climate change will impact soil C cycling by the soil microbiome.

At high latitudes, permafrost, soil remaining below 0°C for 2 consecutive years, is rapidly evolving in relation to climate change. Permafrost soils store 50% of the global soil organic carbon stock. If this long-term sequestered organic carbon stock is released into the active carbon cycle, it could induce a positive feedback to climate change. Peatlands are disproportionally important ecosystems to study permafrost degradation impact, as they store more than one third of permafrost carbon and show the highest carbon density of the Arctic and Subarctic biomes. The potential feedback or mitigation of permafrost peatlands to climate change is controlled by the evolution of their carbon budgets following permafrost thaw: source or sink of carbon. Permafrost peatlands are diverse in the Arctic. The history of peatland initiation and the way permafrost formed can have implications on post thaw carbon cycling (initial carbon stocks, organic matter composition and lability…). The objective of the Arctic-PEAT project is to investigate the evolution of carbon cycling in peatlands after permafrost degradation in different contexts. It will be carried out in 3 locations of discontinuous permafrost, where permafrost peatland degradation is currently occurring, with a focus on Siberia. It is organized in three tasks, interacting in a synergetic way: -Task 1. Spatial and temporal evolution of carbon stocks and accumulation rates following permafrost peatland thaw -Task 2. Evolution of DOM origin, lability and potential priming effect along thawing permafrost peatland chronosequences -Task 3. Heterogeneity and drivers of carbon cycling in permafrost peatlands after permafrost thaw Permafrost peatland degradation induces ground subsidence and the creation of new ecosystems. This allow to identify landscape features representing different time after thaw. These permafrost peatland degradation features are natural experimental devices to apply space for time strategy and define chronosequences. Along these chronosequences, pre and post thaw carbon stocks and accumulation rates will be determined. A remote sensing methodology will be developed, in order to spatially expand these results. Along the chronosequences, the project will focus on dissolved organic matter (DOM), a very dynamic component of carbon cycle. Using 14C, the origin of DOM, but also CO2, CH4 will be analysed in porewater samples. The lability and potential priming effect on permafrost peatlands organic matter of DOM will be determined during incubation experiments. The pre and post thaw carbon dynamics will be modelled using a carbon module developed for Arctic peatlands. This will be coupled available data to determine the main drivers of carbon cycling in Arctic and subarctic peatlands. The Arctic-PEAT project will constitute a unique opportunity for the PI to develop her own research strategy and objectives. It will reinforce collaborations established with other laboratories, in France, Russia, Canada and the US. The Artic- Peat expertise (carbon cycling in peatlands, DOM characterization using stable, radiogenic isotopic and molecular composition, multi proxies for recent chronologies of peat cores, microbial ecology of Artic environments, remote sensing, and modelling of carbon cycling in terrestrial ecosystem) ensure the project’s success. The Arctic PEAT project is expected to generate an innovative dataset on permafrost peatlands. It will contribute the international community efforts to evaluate the feedback of Arctic ecosystem degradation to climate change. In addition to results sharing with the scientific community suing classical way, the Artic-PEAT projects aims at developing a general public outreach with a series of short informative videos mixing videos on permafrost, peatlands, carbon cycle, and research at high latitudes.

The Arctic is one of the planet’s most rapidly warming regions, which will likely alter the biogeochemical processes involved in the bioavailability and transfer of essential (i.e. nutrients such as Cu, Zn, Se) and non-essential (i.e. contaminants such as Pb, Cd, Hg) trace elements. Simultaneously, human presence in the region is increasing due to an expansion of on- and off-shore exploration/extraction of oils & minerals all with a risk of adverse environmental effects. Yet most knowledge about the chemical and biological processes involved in the transfer of trace elements through Arctic food-chains is based on marine and aquatic systems, whereas the Arctic terrestrial ecosystem in general, and Arctic terrestrial food-chains specifically, are vastly unexplored. A better understanding of the cycling of such elements is thus crucial as it may have wide ranging implications on trophic interactions, terrestrial biodiversity and ecosystem functioning as a whole. The ATCAF-project will fill this knowledge gap by targeting the environment – biota – trace element interaction in a high-Arctic terrestrial landscape, while also taking an original approach by directly linking trace elements concentrations in large wildlife to individual and population health. Specifically, the aim is to quantify the above-ground/below-ground linkages of trace elements in a high-Arctic terrestrial ecosystem (i.e. Zackenberg, East Greenland), estimate the transfer efficiency within local food-chains (i.e. in soil, vegetation, prey- & predator-invertebrate insects, herbivores and carnivores), and assess the potential health effects of these elements within large Arctic wildlife (i.e. muskoxen and Arctic fox). To reach this aim, ATCAF will be organized in four interlinked work tasks: Task 1) Ecogeochemistry & the landscape: Mapping of availability and spatial variation in essential and non-essential elements across the soils and vegetation of an Arctic landscape Task 2) Ecogeochemistry & the food-chains: Transfer efficiency of essential- and non-essential elements through Arctic terrestrial food-chains Task 3) Ecogeochemistry & the individual: Trace element distribution within individuals and the potential link between wildlife hair and population health Task 4) Ecogeochemistry and the isotopes: Isotopic composition in blood samples from large Arctic wildlife as diagnostic tool of health By studying the accumulation of contaminants in Arctic terrestrial food-chains in tandem with the uptake of essential elements, ATCAF will provide much needed information on their combined effects on the health and fitness of local biota. Uniting empirical data and predictive modelling approaches, ATCAF will therefore deliver 1) maps showing spatial variation in the trace element composition of different soil and vegetation types in a high-Arctic terrestrial ecosystem, 2) quantitative values of above-ground/below-ground linkages and transfer efficiency of trace elements between trophic levels in the studied system 3) an extensive assessment of within individual trace element distribution and a novel analytical protocol using wildlife hair as a non-invasive long-term bioindicator of individual- and population health, 4) a novel analytical protocol using isotopic composition of blood as a diagnostic tool for wildlife health (e.g. neoplasia, inflammatory status, body condition, pathogen). Combined, the successful outcome of the ATCAF-project will revolutionize science-based monitoring of wildlife health and population trends in systems under pressure. This, in turn, will promote well-informed conservation strategies, wildlife monitoring and ecosystem management with additional socioeconomic and cultural values as it pertains to local populations depending on this wildlife and the ecosystem for their livelihood.

Microplastics (MP) are an emerging contaminant, with significant MP found in oceans and remote terrestrial locations and direct and indirect effects on ecosystem and human health. The quantity of MP polluting the terrestrial environment is unknown, with knowledge gaps in the global MP mass balance. Based on our recent findings, the ATMO-PLASTIC project hypothesizes an important role for the atmosphere in MP cycling, and aims to illustrate atmospheric MP occurrence and transport on a global scale. We will examine a global bank of marine and terrestrial aerosol filters and peat cores to quantify the spatio-temporal variation of global atmospheric MP pollution. Aerosol and peat MP analysis will illustrate the terrestrial and marine MP emission sources and define the temporal trends in atmospheric MP pollution. We will use langrangian and box models for atmospheric source appointment and global MP mass balance closure, and forecasting of global MP dissimination through Earth surface reservoirs during the 21st century.

Nanotechnologies are the new industrial revolution of this century. The dissemination of engineered nanomaterials (NMs) in the environment is suspected. Agricultural soils can be contaminated via nanopesticides and spreading of sewage sludge. It implies that crop plants (first gate into food chain) may be exposed to NMs at large scale. Within this project, we plan to study the fate of TiO2 NMs in an agricultural ecosystem and their impacts on digestive health. Indeed, TiO2 is a large volume manufactured chemical. With an integrative approach we will investigate the toxicity, transfer and transformation of these NMs from soil to crop plants, primary consumer (snails), and up to humans (epithelial intestinal cells and mice). The originality of our study is to link different multidisciplinary approaches (plant, animal and cell biologies, biophysics and modeling) to study different TiO2 NM transfer through the whole food chain. The main objective is to identify the risk for food safety related with NM dissemination and optimize a "safer by design" synthesis of TiO2 material.