Thanks to the microparticle filters installed on a monohull of the last Vendée Globe, the scientists expected a unique picture of plastic pollution in remote areas. It was mainly cotton fibers that they harvested, further evidence of the impact of humans on the oceans.
In the autumn of 2020 skipper Fabrice Amadeo will leave for the famous solo sailing race around the world. In addition to CO2 and water temperature meters, a more original sensor is present on board his Imoca: seawater is pumped up through the keel before passing through three 300, 100 and 30 micron sieves to collect microplastics. Filters that the former journalist must replace every 12 hours and keep until he returns to land.
His race ends earlier than expected with a 33rd day retirement. A “bad memory” for him, he says during a press conference. But “interesting” for scientists, with a world tour transformed into a tour of the Atlantic Ocean. The skipper does not forget his oceanographic mission on the way back to France: 53 samples collected in total.
Armed with tweezers, scientists from several French research centers spent months sorting the particles caught by the largest filter, 300 microns. One working day per sieve.
More than 60% of the samples contain at least one microplastic, mainly PET and polyethylene. Not much of a surprise when you know that these particles from the breakdown of bags, bottles, straws and various packaging have been found in the most isolated ecosystems, even in the Mariana Trench, the deepest known.
On the other hand what? “We were very interested in the fact that on all samples we find almost the same amount of fiber, in a much higher concentration, and we find a high proportion of cotton fiber”probably of textile origin, explains AFP Catherine Dreanno, researcher at Ifremer.
The samples contained twice as many cellulose fibers (the main component of plants) as microplastics, with an average concentration of 5.4 fibres/m3 for 2.1 microplastics/m3.
Toxic to shrimp
Science has already shown that synthetic microfibers from polyester, nylon or acrylic clothing and spat out from our washing machines are a major source of plastic pollution in the oceans.
But this campaign shows that textiles made from natural materials can’t be beat, with an initial analysis of the 100-micron filter showing a “even greater share”notes Catherine Dreanno.
And “Just because these are naturally occurring fibers doesn’t mean they aren’t toxic. They can contain certain toxic substances, such as color pigments, and they absorb pollutants from the environment.”keeps them full.
Synthetic or natural, these fibers can clog the digestive systems of small shrimp or shellfish that ingest them. As if a person swallows a rope. Some studies had already shown the presence of fibers of natural origin at sea, especially in the depths of the Mediterranean.
But this underground presence in the Atlantic Ocean “intrigues us”says Catherine Dreanno, referring to a possible “new pollution indicator” made possible by new sampling and analysis techniques.
“We need to reduce pollution at the source”, emphasizes Jérôme Cachot, from the University of Bordeaux. “We are not going to put all those fibers in filters in washing machines”, but he is already arguing for limiting additives in cotton textiles, such as dyes, nanoplastics and biocides.
Another question that came up, on the microplastic side: a strangeness about their spatial distribution. It is known that the distribution of microplastics in the ocean is not homogeneous, they clump together in certain areas under the effect of giant whirlpools formed by ocean currents (gyre), such as the famous “great peaceful wasteland”†
“Where we would have found very legitimate to have very large concentrations, in the subtropical South Atlantic gyre, it is rather there that we see the minimum number of particles”says Christophe Maes, researcher at the IRD. “We have new data, but above all new questions”† Scientists eagerly await Fabrice Amedeo’s next races.