Plastic debris is a ubiquitous pollutant found from the sea surface to the seafloor. Understanding the mechanisms driving its pollution is a difficult task mostly due to the complex oceanic circulation, which affects plastic debris in manifold ways. The Lagrangian approach is hence a natural framework to study this problem. Here, I will show the results of TrackMPD, a Lagrangian model simulating the pathways of plastic debris in the Mediterranean Sea, and validated with the most extensive dataset of plastic measurements in this region to date. The Mediterranean Sea lacks in zones of plastic accumulation despite being one of the most polluted basins worldwide. Here, we adopt a different paradigm, by identifying crossroad regions through which large amounts of plastic debris flow. We find that around 20% of Mediterranean plastic debris passed through 1% of the basin surface. The most important crossroads intercepted plastic debris from multiple sources, which had often traveled long distances. During its travel, plastic debris can be colonised by marine organisms, and eventually sink. We found that the locations where debris leaves the surface are significantly different from those where it reaches the seafloor: debris travels hundreds of kilometers during its sinking. In the water column, plastic debris can potentially be mistaken for zooplankton and be ingested, thus impacting marine biota. To quantify this risk, we estimated the plastic debris to zooplankton ratio over the entire Mediterranean Sea, showing a high risk of contamination for both pelagic fish and whales.

Primary Presenter: Alberto Baudena, Laboratory of Oceanography of Villefranche (alberto.baudena@gmail.com)

Authors:

Enrico Ser-Giacomi,   ()

Isabel Jalón-Rojas,   ()

Salomé Fabri-Ruiz,   ()

François Galgani,   ()

Rainer Kiko,   ()

Fabien Lombard,   ()

Jean Olivier Irisson,   ()

Fabien Moullec,   ()

Maria Luiza Pedrotti,   ()