Plastics are increasingly present in seas and oceans across the globe. The Mediterranean—being a semi-enclosed marine basin—is one of the seas most affected, accumulating more tonnes of plastic waste from land-based sources each day. This growing pollution is putting marine biodiversity and ecosystems at risk. Now, the Universitat Politècnica de Catalunya - BarcelonaTech (UPC), the University of Barcelona (UB) and the company Plastic at Sea are spearheading a citizen science project to better understand the origin and final destination of plastic pollutants reaching the sea, and to enhance conservation strategies for the marine environment in the north-western Mediterranean.

The project, “Participatory strategies for managing cross-border coastal plastic pollution” (TRAP), is led by professor Anna Sánchez-Vidal from the Marine Geoscience Research Group at the UB’s Faculty of Earth Sciences. The main project partners are professor José Alsina from the UPC’s Maritime Engineering Laboratory (LIM) and Dr Edouard Lavergne, head of the plastic pollution quantification hub at Plastic at Sea. 

With a budget of nearly one million euros, the project will run from 2025 to 2028, co-funded through the INTERREG POCTEFA programme—an EU initiative promoting sustainable development in the cross-border region of Spain, France and Andorra.

In line with the Sustainable Development Goals (SDGs) for preserving the health of oceans and seas, TRAP will address key issues concerning the quantity of litter entering and accumulating in this marine region. The project’s ultimate goal is to provide managers with a system for monitoring and forecasting the distribution of plastics across the cross-border coastal region, supporting the design of policies to mitigate the local and regional impact of marine debris.

From the French coast to the Ebro Delta
Most plastic waste threatening the marine environment originates on land and reaches the sea via rivers, beaches, discharges and other ways. TRAP will help preserve the ecological value of the Mediterranean coastline within the Eastern Coastal Functional Area (AFLE), stretching from the Aude River estuary in France to the Ebro Delta in Tarragona, Spain. According to recent studies, marine plastics in this area are found not only near large urban centres but also far offshore, likely due to dispersion by the northward current flowing south from the Gulf of Lion, which is capable of transporting up to a trillion microplastic particles to southern latitudes.

“Marine pollution knows no borders. Due to their buoyancy and durability, plastics can travel long distances from their point of origin and are a major cause of cross-border marine pollution,” explains Anna Sánchez-Vidal of the UB’s Department of Earth and Ocean Dynamics.

Professor José Alsina, the lead investigator at the UPC, adds: “To study plastic transport along the coast, we are taking an open approach, considering potential cross-border flows of particles.” As part of this project and its predecessor TRACE, LIM researchers have developed numerical modelling tools to simulate the dispersion and accumulation of marine litter in the western Mediterranean, from southern France to the Catalan coast. "We’ve tracked the transport of plastic particles using buoys that move with the currents and report their position in real time. We’ve also explored the relationship between water turbidity and microplastic concentration in an effort to derive plastic concentration data from satellite images. As a result, we’ve created plastic concentration maps of the western Mediterranean by combining sampling carried out by researchers from the UB and Plastic at Sea along the coasts of Catalonia and France,” explains Alsina, who is also a professor at the Barcelona School of Industrial Engineering (ETSEIB).

Citizen science and environmental engagement
Citizen science will play a key role in the project’s plastic sampling methodology. It will make it possible to sample over larger geographical areas and more frequently, reduce project costs and increase environmental awareness.

Collaboration between institutions and the public will help characterise and monitor the arrival of marine litter—particularly from land-based sources—and shed light on the spatial and temporal distribution of waste in relation to human activity and environmental variables such as tourism, weather and ocean conditions.

With this combined approach, TRAP will tackle several scientific and social challenges: understanding the mechanisms that drive plastic transport in the north-western Mediterranean coastal region, developing a tool to support improved waste management at local and regional levels, and informing and educating the public on the issue of plastic pollution.

“TRAP is a chance to rethink environmental policies on both sides of the border. The joint work of project partners, organisations and citizens will provide a comprehensive view of plastic pollution along the coast, beyond administrative boundaries, and ultimately help to improve regional environmental policies to protect the marine environment,” concludes Sánchez-Vidal.