First measurements of plastics in the Mediterranean deep sea

For the first time at such depths in the Mediterranean, a team of French, Monegasque and Italian scientists were able to analyze marine waste and microplastics at depths of up to 2,200 meters. The result: the deep sea is an area of significant accumulation of our waste, with a marked impact on wildlife. Scientists recommend increasing prevention efforts, as this pollution is impossible to eliminate in such inaccessible environments

A new study published in the journal Science of the Total Environment has been conducted on plastic pollution right into the deep sea in the Mediterranean. The measurements took place in September 2018 thanks to the Victor 6000 submersible, aboard the Ifremer-operated Oceanographic Fleet vessel Atalante.

"We know that there are areas of waste accumulation offshore, but this is the first time we have conducted such precise measurements at such depths in the Mediterranean, with videos close to the bottom and sampling in the sediments," emphasizes François Galgani, Ifremer researcher specializing in plastics and among the main authors of the recent publication.

The scientists focused on an area straddling France, Monaco and Italy in the Ligurian Sea, including 7 submarine canyons and mounts further offshore in the abyssal plain. The results show a strong accumulation of plastic of urban origin, on the canyons in front of big cities like Saint-Tropez, Nice, Cannes or Monaco. The images show a wide variety of objects such as cups, beach buckets, balloons, bottles...

"This urban waste is dominated by plastics. The canyons play a role of conduit, the waste goes down towards the deep sea under the effect of the marine currents. Further out to sea, on seamounts, the waste is of a different nature, more related to fishing, with lost lines or nets. This is the reason why the waste is more related to fishing, with lost lines or nets", explains Michela Angiolillo, researcher at ISPRA and main author of the publication.

Microplastics everywhere, even in the deep sea

The scientists were also able to carry out microplastic analyses, with sediment samples also taken down to 2200 m. The result: all the samples contain significant levels of microplastics. These first measurements will have to be completed in order to obtain more consistent data sets.

Finally, the study has shown the impact of this waste on the fauna living in these deep Mediterranean waters, especially gorgonians and deep-sea corals. "70% of the waste has an interaction with the fauna living on the bottom: either the species use the waste to fix themselves and increase their habitat area, or they are victims of injuries, strangulation, entanglements. We did not expect to find such a high percentage", underlines Olivia Gérigny, researcher at Ifremer and also among the main authors of the study.

An environment too inaccessible to be cleaned: it is imperative to reduce waste at the source

This study opens the way to a more systematic investigation of the deep sea. "The deep-sea environment deserves to be studied more in terms of the impact of waste, because the waste is numerous and the impacts significant. 95% of marine waste ends up on the seabed, and surface pollution is only the 'tip of the iceberg'," reminds François Galgani. This finding also confirms that the best solution to fight against plastic pollution is prevention: "we must reduce waste at the source, because it is absolutely impossible to collect all this waste at such depths," concludes Michela Angiolillo.

A global assessment published by the journal Nature with Ifremer data

A scientific article published on June 10 by the journal Nature Sustainability offers the most complete global assessment to date of the waste cycle at sea, with the compilation of numerous databases (including that of Ifremer for France) and no less than 12 million analyses on the composition of waste. This report confirms the predominance of food packaging and fishing waste in marine waste. The proportion varies according to the regions of the world, it is more marked by food plastics in developing countries, and by fishing gear in industrialized countries.

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About:
The study on the Mediterranean sea bed was carried out with the means of Ifremer and the support of the French Navy, within the framework of the programs of the RAMOGE agreement, whose main objective is to coordinate the actions of the French, Italian and Monegasque states in the preservation of the waters of the Mediterranean coast.