Accumulation of plastic litter in the marine environment is a pressing global concern. To study this issue, we use the Blue2 Modelling Framework (Blue2MF), an integrated modelling tool developed by the Joint Research Centre (JRC) of the European Commission. Our study uses the Lagrangian model LTRANS-Zlev (LTRANS) in the Blue2MF to simulate the trajectories, distribution, and accumulation of macroplastics in five European marine basins: the Baltic Sea, Black Sea, Mediterranean Sea, Atlantic Northwest European Shelf, and Atlantic Southwest European Shelf. By incorporating model-estimated macroplastic inputs from land and estimations of maritime (fishing) sources, we simulate distribution patterns of marine macroplastics between 2016 and 2018. Our study addresses the challenges involved in modelling the spatial distribution and abundances of macroplastics with the LTRANS model and the factors that may condition the estimation of the model accuracy when model results are compared/validated with marine litter observations available. We compare our model results with available observations, achieving a good agreement between predicted and observed macroplastic distributions and abundances and estimating the model accuracy for both beached and floating macroplastics. Our study provides a basis for future forecast runs to evaluate the impact of policy/management options on marine macroplastic pollution in European Seas.

The ecological status of the two nautical mile (2 nm) coastal waters of Bulgaria (BG) and Romania (RO) is evaluated in terms of eutrophication, focusing on various environmental and chemical indicators related to nutrient enrichment and its effects. Applying the Blue2 Modelling Framework (Blue2MF) Black Sea model, we simulate diverse combinations of nitrogen (N) and phosphorus (P) reduction. By integrating atmospheric and marine conditions, hydrology and environmental dynamics, the model provides a comprehensive framework for analysing the impact of external pressures on the marine environment and can be used to set regional sustainability goals. Each scenario is assessed with respect to environmental impact, such as enhanced water quality and potential alterations in phytoplankton communities. Furthermore, we establish integrated nutrient criteria for eutrophication control, concentrating on the management of both N and P inputs while maintaining the current ratio between them. The model results indicate that a 20% reduction in both N and P from European Union (EU) rivers would result in about a 24% decrease in N within the BG and RO 2 nm coastal waters, whilst sustaining the N:P ratio across various spatial scales—from river inputs to coastal and offshore zones. This approach is valuable for assessing the potential impacts of different nutrient reduction strategies, aiding the effective management of marine ecosystems to address eutrophication challenges.