Since deconfinement, plastics have proliferated off the coast of the Alpes-Maritimes, according to the observations of Maria-Luiza Pedrotti, a CNRS researcher at the Institut de la mer in Villefranche-sur-Mer, a world expert on microplastics at sea.
According to your initial observations off the Villefranche-sur-Mer roadstead, the post-confinement situation is worse than before?
From May 11th we were able to resume sampling at sea. I was amazed to see a lot of plastics, and especially the categories of plastics that are normally found very rarely in the Mediterranean, such as the granules known as “mermaid tears”. These are cylinders of 1 to 10mm of plastic prefabricated to make other plastics. They have no use at sea.
How do these raw materials end up at sea?
Ils peuvent provenir de cargos échoués ou qui les ont perdus. Ou bien, pendant le confinement, les industriels ont peut-être laissé des sacs contenant ces plastiques à l’extérieur, qui se sont détériorés et répandus dans les rivières jusqu’à la mer ?
Nous avons aussi trouvé des morceaux de polystyrène expansé, qui proviennent d’emballages arrivés récemment en mer car il ne sont pas encore colonisés par des organismes. On en trouve habituellement 1% en Méditerranée, et là j’ai un échantillon où il y en a 10% ! On dirait que les gens se sont lâchés pendant le confinement.
Some of it’s going back to the beachess
What happens to plastics at sea?
There is a part that will sink into the sea quickly, like PVC and PET. Others will fragment, be colonized by marine organisms that will weigh them down and eventually sink them. Some will be eaten by marine animals, which is called trophic transfer. And some of it will be washed up on the beaches. It is estimated that only 1% of the plastic that reaches the sea is found on the surface.
The worst are micro-plastics?
Some will sink, some eaten by fish, whales and filter feeders such as mussels. So they’ll enter the food chain and may even reach humans. And another part will continue its degradation process down to the nanometric level and escape from our sampling devices and we don’t really know how to characterize them.