A report of the International Marine Debris Data Harmonization Workshop, 29-31 August 2023, Yokohama, Japan

The International Workshop on Marine Debris Data Harmonization took place at the PACIFICO Yokohama on August 29th to 31st 2023. It gathered marine debris professionals with a wide range of expertise from data management and marine debris monitoring to harmonization of methods and modelling. The workshop was hosted by the Ministry of the Environment Japan (MOEJ) with organizational support from the Integrated Marine Debris Observing System (IMDOS). It was co-sponsored by the MOEJ, the EU H2020 EuroSea project, the EU4OceanObs project implemented by Mercator Ocean International, and the H2020 EUROqCHARM project. The goal of the workshop was to enhance the readiness level of data, including associated metadata, to support global data harmonization for selected key marine debris indicators that will underpin the successful mitigation of plastic pollution. The workshop presented the state of the art when it comes to harmonization of monitoring methods and data synthesis efforts, and included several discussion sessions in plenary and dedicated breakout groups. Through a series of presentations and discussion sessions participants achieved the following outcomes: Initiated a coordinated network (community of practice) of ocean surface microplastic data providers with an agreement to adhere to agreed common sampling protocols, metadata and data requirements. The network is to be further organized under the auspices of GOOS and IMDOS. Obtained a consensus on marine debris metadata and data requirements of ocean surface microplastics as a leading example, between key regional and global marine data integrators including MOEJ, EMODnet and NOAA NCEI with an agreed intention to expand onto and any other potential large data integrators globally Provided recommendations for standardized metadata and data requirements for the UNEP GPML Digital Platform data matrix Agreed on a common vision to develop a roadmap for a federated data management system for ocean surface microplastics and selected global-scale marine debris indicators. This report provides a brief account of the different workshop sessions and how they contributed to addressing the workshop objectives and expected outcomes.