Model based estimate of transboundary litter pollution on Mediterranean coasts.

Plastic litter pollution is one of the major concerns for the health of marine ecosystems worldwide. This pervasive form of pollution affects all oceans and seas and it's interacting with multiple levels of the marine food webs. In the European context, several pieces of legislation try to fight against this pervasive and ubiquitous form of pollution. Recently, EU Member States have agreed to a maximum threshold of litter items per coast length (20 items/100 m coastline). One major concern among stakeholders to reach this consensus was the transboundary litter, as measures need to be implemented in the country of origin. Henceforth, a solid method to estimate the amounts of the transboundary litter to a given Member State's coasts is needed. In this contribution, we use a combination of hydrodynamic and Lagrangian models for the Mediterranean Sea in order to understand the origin of coastal litter. Simulations show that the amount of transboundary litter in Mediterranean countries could be as large as 30% although both regional and seasonal differences could be significant.