Boosting interoperability of EMODnet chemistry aggregated datasets with a new point of access

European and global institutions are working hard to collect and share high quality environmental data and  information. This is because it is clear that the ocean knows no borders, and data sharing is necessary to make environmental policies based on knowledge that is informed by extensive data.Fifteen years ago, the European DG MARE launched the EMODnet data infrastructure, which today provides a consolidated framework for open access to marine data, products and services. The institutions behind it work together by scientific thematic area to offer FAIR (Findable, Accessible, Interoperable and Reusable) information.The implementation of the FAIR principles on the data is complex and is constantly being developed and improved.The thematic discipline of EMODnet Chemistry focuses on data and information relevant to eutrophication, pollution by hazardous substances and litter. Each year, regional aggregated datasets on these themes are published, containing validated and unrestricted data.There are already various access points to the aggregated data collections, which can be downloaded directly (https://emodnet.ec.europa.eu/en/chemistry#chemistry-data) or used for visualization and subsetting (https://emodnet-chemistry.webodv.awi.de/). So far, none of them is interoperable, but this is being sorted out by establishing an ERDDAP instance for the EMODnet Chemistry aggregated data collections (https://erddap.emodnet-chemistry.eu/erddap/index.html), starting with the eutrophication datasets.ERDDAP was chosen because it is an open-source, simple and user-friendly tool that allows downloading data in different formats. In addition, the automation of requests is possible and it can be linked to other ERDDAPs.Technical research and development work has been carried out to implement a sustainable workflow that can be reused annually with the release of each new version of the collections. Using a series of Python scripts, the data in the extended SeaDataNet ODV-ASCII format (containing metadata and data) are split into small chunks and converted to NetCDF format for uploading to ERDDAP. Using the newly developed tool “erddapcfg” (https://github.com/PlehanSebastian/erddapcfg) and a SQLite database, the ERDDAP metadata are compiled, ensuring that all metadata and data fields are given appropriate scientific meaning. Complementary, a web service with geoserver  provides  a WMS of the data stations.The various thematic datasets differ in their structure, so each type of collection requires a specific development. In the case of the eutrophication datasets, the biggest challenge was the file size.Once the work on the eutrophication datasets is completed, the next step will be to tackle the work on the microlitter datasets, considering the high relevance of this type of data on  a global scale.