For the first time at such depths in the Mediterranean, a team of French, Monegasque and Italian scientists was able to analyse marine waste and microplastics at depths of 2,200 metres. The result: the deep seas are areas where our waste accumulates in large quantities, with a marked impact on fauna. Scientists are recommending increased 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 carried out on plastic pollution as far down as the deep sea in the Mediterranean. The measurements took place in September 2018 thanks to the Victor 6000 submersible, on board the Atalante vessel of the Oceanographic Fleet operated by Ifremer.
"We know that there are areas where waste accumulates offshore, but this is the first time that we have carried out such precise measurements at such depths in the Mediterranean, with videos close to the seabed and samples taken from the sediment", emphasises François Galgani, an Ifremer researcher specialising in plastics and one of the main authors of the recent publication.
The scientists focused on an area straddling France, Monaco and Italy in the Ligurian Sea, comprising 7 underwater canyons and mounts further offshore on the abyssal plain. The results show a high accumulation of plastic of urban origin in the canyons opposite major cities such as Saint-Tropez, Nice, Cannes and Monaco. The images show a wide variety of objects, including cups, beach buckets, balloons and bottles.
"This urban waste is dominated by plastics. The canyons act as conduits, with the waste sinking to the depths under the effect of the ocean currents. Further offshore, on seamounts, the waste is of a different nature, more related to fishing, with lost lines or nets", explains Michela Angiolillo, a researcher at ISPRA and lead author of the publication.
Microplastics everywhere, right down to the deep sea
The scientists were also able to carry out analyses of microplastics, taking samples of sediment down to 2200 metres. The result: all the samples contained significant levels of microplastics. These initial measurements will have to be supplemented to obtain more substantial data sets.
Finally, the study showed the impact of this waste on the fauna living in these deep Mediterranean waters, particularly gorgonians and deep-water corals. "70% of the waste has an interaction with the fauna living on the seabed: either the species use the waste to fix themselves and increase their habitat area, or they are victims of injury, strangulation or entanglement. We didn't expect to find such a high percentage," stresses Olivia Gérigny, a researcher at Ifremer who is also one of the main authors of the study.
An environment too inaccessible to clean: it's essential to reduce waste at source
This study paves the way for 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 there is a lot of waste and it has a significant impact. 95% of marine waste ends up on the seabed, so surface pollution is just the 'tip of the iceberg'," points out François Galgani. This finding also confirms that the best solution for combating plastic pollution is prevention: "We need to reduce waste at 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 data from Ifremer
A scientific article published on 10 June by the journal Nature Sustainability offers the most comprehensive global assessment to date of the waste cycle at sea, with the compilation of numerous databases (including that of Ifremer in France) and no fewer than 12 million analyses of the composition of waste. This report confirms the predominance of food packaging and fishing waste in marine waste. The proportion varies from one region of the world to another, with food plastics being more prevalent in developing countries and fishing gear in industrialised countries.
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About :
The study of the Mediterranean seabed was carried out with the resources of Ifremer and the support of the French Navy, as part of the RAMOGE agreement programmes, the main aim of which is to coordinate the actions of the French, Italian and Monegasque States to preserve the waters of the Mediterranean coastline.