“The Mediterranean Sea has the highest densities of plastics in the world.”

© G.Suaria/Tara Expéditions

27 octobre 2014

Researcher at Ifremer, François Galgani has studied plastics for almost 20 years. This Corsican scientist has dedicated his career to petroleum products. On board the schooner this summer between Sardinia and Albania, he recently embarked again for a few hours. A brief passage that allowed Taranautes to talk with him around the big table in the main cabin. Extracts from this discussion.

You’ve worked on the theme of plastic pollution for a long time. When were the first studies on this topic?

The first work done on the beaches — intermittent studies on the quantities of plastic — is from the early 80s.  Since 1992 with Ifremer, we’ve made a little over 30 campaigns along the whole French coast. And plastic already represented 70 to 80% of the waste collected at sea! We then did deep-diving work in the Baltic, North and Adriatic Seas, and followed up with help from submersibles. In the years after 2000 we published a summary of research on all European coasts. In parallel, other researchers were working on floating objects. Over the years, techniques have improved and the analyses have been refined.

Some scientists had already observed the presence of surface microplastics in the 70s, but only since the 90s have organizations relayed the information, especially relating to the accumulation of these micro-particles in convergence zones or oceanic gyres. In 2004, following an article on the evolution of microplastics, the subject was revived. That paper reported a substantial increase in the quantities in the years 2000.

In 2008, the European Commission decided to launch a directive to monitor the marine environment, to achieve “Good Environmental Status” and by necessity, it included marine litter and therefore plastics as one of the 11 descriptors for environmental quality. That’s how the subject entered into mainstream news. For the first time, it was considered as important as eutrophication, biodiversity or chemical contamination.

What were the notable discoveries following this research?

The first modelisation work appeared at that time, in order to better understand the transport of microplastics. Prior to sinking or disappearing, plastics can be conveyed thousands of kilometers on the surface or at depth. It was then found that organisms visible to the naked eye were attached to these plastics.

The study of attached microorganisms is relatively new–  I would say that we’ve been studying them for a year and a half. At present microbiologists are investigating all of the attached bacteria. We know that some species belong to families that are known to be pathogenic. Tara is justly investigating this subject. These attachments could also promote the dispersal of species.

But haven’t species always dispersed by clinging to pieces of driftwood or hidden in ships’ ballast?

Indeed, for millions of years the transport of species from one area to another took place on dead wood; then navigation developed, and boats became supports for living organisms. With the advent of floating debris, especially plastics, the number of vectors has multiplied, i.e. the number of possibilities for transport. Microplastics advance slowly with the currents and they go everywhere, unlike boats that go from one port to another. This means that many more species can attach themselves to the plastics and sail around the world.

What about the Mediterranean?

The Mediterranean Sea has, on average, the highest densities of plastics in the world: 250 billion micro-plastics.

Since this is a closed sea, if a new organism manages to get in, it may be dispersed throughout the whole basin. We also noted that the transport of certain species such as Foraminifera (unicellular species) can be favored. We’re starting to have specific ideas about the existing mechanisms, but there’s still a lot of work to be done. An expedition like Tara is ideal: it allows us to collect data across the entire Mediterranean basin, especially on the quantities of microplastics and the cortege of associated species.

Interview by Noëlie Pansiot

Ifremer Campaign 1995 – François Galgani: Ifremer video produced by François Galgani in 1995, with help from the submersible Cyana. These images were shot at depths between 350 and 1000 meters in canyons of the Mediterranean, 20 kilometers from the French coast. Today the situation remains unchanged.

© François Galgani


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