Operationalising essential ocean variables through robust and trusted QCV Workflows

Essential Ocean Variables (EOVs) play a central role in global ocean observation frameworks. They support the monitoring of biogeochemical processes, ecosystem dynamics, and long-term environmental change. Among them, nitrate is a key biogeochemical EOV, closely linked to primary production and phytoplankton dynamics. And transforming raw observations into reliable, interoperable, and reusable EOV products remains a major operational challenge.The global Argo programme enables unprecedented global monitoring of ocean biogeochemistry through autonomous profiling floats sampling the ocean from 2000 m depth to the surface; at the same time, the sensitivity of biogeochemical sensors to drift, biofouling, and instrumental issues necessitates expert-driven Qualification, Calibration, and Validation (QCV), which operates within a fragmented ecosystem of tools, data formats, execution environments, and methodological practices.This contribution presents a complete nitrate QCV workflow, illustrating in concrete terms how validated EOV products are obtained from raw Argo observations. The workflow integrates global Argo data access, data harmonisation, preparation for visual inspection, expert-driven qualification using Ocean Data View, tracking of manual decisions, nitrate calibration, and delayed-mode data production. Each step is documented, connected, and explicitly handled to ensure traceability of both automated processing and human interventions.The service implementation relies on the Galaxy platform, which provides an open, web-based, and FAIR-oriented environment to orchestrate independent domain tools together with expert-defined QCV procedures into complete, reusable, and transparent workflows. These workflows are accessible to expert users without advanced programming skills. Rather than replacing existing tools, the approach aims to make them work together in a coherent, unified, traceable, and reproducible way, through fixed processing chains covering the full QCV process.The QCV service will be deployed within the European Open Science Cloud (EOSC), building on thematic infrastructures coordinated by ENVRI, on platform services provided by NFDI, and on operational deployment ensured by Data Terra, in order to guarantee accessibility, interoperability, and long-term reuse.Regardless of the selected presentation format, this contribution will introduce the EOV framework and the challenges associated with biogeochemical Argo data, before providing a concrete illustration of a complete nitrate QCV workflow. It will then detail the service implementation through interoperable workflows on the Galaxy platform and its deployment within the European Open Science Cloud (EOSC).