Over geological times, the evolution of carbon isotope compositions of carbonates (δ13Ccarb) in sedimentary record highlights many positive isotopic excursions (CIEs), reflecting significant perturbations of the carbon cycle in Earth surface environments. Although generally interpreted as a consequence of an increase of organic carbon burial in sediments, the lack of high organic carbon content, as well as the strong spatial and temporal variability, observed in many sedimentary successions recording CIEs challenge this postulate. Among other alternative hypothesis involving regional or local control, the potential influence of methanogenesis, i.e. the biological process of anaerobic organic matter degradation producing methane (CH4), has been raised; its ability to generate similar isotopic signatures has been demonstrated in modern analogue. Although the processes behind CIEs are questioned, providing more information about methanogenesis impact is challenging based on traditional isotopic tool like δ13Ccarb, as its isotopic effect on is similar to that of organic carbon burial increase. Recently, stable isotope compositions of metals used as enzymatic cofactors of CH4-related processes were investigated to explore their potential as biomarkers of methanogenesis. During the last decade, significant advances have been made on using Ni isotopes as tracers of methanogenesis but important challenges remain to better constrains both their potential and limit. In order to improve our understanding of CH4 cycle and its impact on Earth’s surface environments through geological times, we will investigate further the potential of Ni isotopes and its potential couplings with traditional stable isotope in various modern settings and past environments to enhance our ability to track and discriminate the influence of CH4-related processes through Earth’s history.

NAUTILOS will fill in existing marine observation and modelling gaps through the development of a new generation of cost-effective sensors and samplers for physical (salinity, temperature), chemical (inorganic carbon, nutrients, oxygen), and biological (phytoplankton, zooplankton, marine mammals) essential ocean variables, in addition to micro-/nano-plastics, to improve our understanding of environmental change and anthropogenic impacts related to aquaculture, fisheries, and marine litter. Newly developed marine technologies will be integrated with different observing platforms and deployed through the use of novel approaches in a broad range of key environmental settings (e.g. from shore to deep-sea deployments) and EU policy-relevant applications: - Fisheries & Aquaculture Observing Systems, - Platforms of Opportunity demonstrations, - Augmented Observing Systems demonstration, - Demonstrations on ARGO Platform, - Animal-borne Instruments. The fundamental aim of the project will be to complement and expand current European observation tools and services, to obtain a collection of data at a much higher spatial resolution and temporal regularity and length than currently available at the European scale, and to further enable and democratise the monitoring of the marine environment to both traditional and non-traditional data users. The principles that underlie the NAUTILOS project will be those of the development, integration, validation and demonstration of new cutting-edge technologies with regards to sensors, interoperability and embedding skills. The development will always be guided by the objectives of scalability, modularity, cost-effectiveness and open-source availability of software and data products produced. NAUTILOS will also provide full and open data feed towards well-established portals and data integrators (EMODnet, CMEMS, JERICO).