In the oceans, marine currents form gyres—that is, giant whirlpools. These gyres are located at mid-latitudes and are driven by trade winds [i], variations in water density, and the Coriolis force [ii].
Plastic waste discharged into the oceans by human activity is naturally carried by marine currents and partially accumulates in the five gyres identified to date: two in the Atlantic Ocean, two in the Pacific, and one in the Indian Ocean. In the North Pacific, researchers identified nine different languages on the debris studied, and the oldest dated back to 1977!
Although navigator Charles Moore, who was one of the first to speak about this phenomenon in 1997 [iii], used the term “plastic continent,” these accumulation zones are not mainly composed of large waste forming a floating island. They are mostly made up of microplastics that colonize the water column down to at least 30 m in depth, resembling more of a “plastic soup.”
Plastic waste breaks down into microplastics through photodegradation, mechanical abrasion, and biodegradation [iv]. In this form, it becomes impossible to remove from the environment.
Despite the tens of thousands of nautical miles sailed around the world by the sailors of Ekkopol, none have actually seen these so-called continents of waste at sea: the debris floats between two waters and does not form literal continents. Therefore, it is impossible to simply collect it, and its slow degradation represents a deadly threat to biodiversity.
Indeed, the consequences of microplastics are serious and probably still underestimated. We already know that their ingestion by living organisms leads to the spread of pollutants in their bodies and poses a real danger to the entire food chain. For example, whales are contaminated by phthalates [v], the most abundant photosynthetic organism on Earth—Prochlorococcus bacteria—is hindered in its photosynthetic role [vi], and the polar bear (again) faces reproductive challenges.
https://youtube.com/watch?v=grmMBbHcu_Q%3Ffeature%3Doembed
Moreover, ocean gyres are not the only plastic graveyards. While they concentrate plastic, it also continues its journey elsewhere [vii]. It is thus utopian to think we can simply collect debris naturally gathered in the middle of the oceans. These have become “ultimate waste” [x].
High concentrations are also recorded offshore of industrial and urban regions around the world. The Mediterranean Sea alone holds 7% of all microplastics on the planet [viii]. Emilien Pierron, who sailed across the Java Sea and the Strait of Malacca between Bali and Port Kelang, observed a concentration of waste in the water that deeply marked him—something he saw nowhere else during his round-the-world voyage. In Antarctica, near the Weddell Sea where Geoffroy de Kersauson often sails, Greenpeace found in 2018 that seven out of eight water samples contained microplastics and seven out of nine snow samples contained persistent chemicals known to cause developmental and reproductive disorders in animals [ix].
As useful as ocean gyres have been in raising public awareness, they should not be seen as the only marine areas polluted by plastics. This pollution is global and still too little studied. Its consequences on living organisms—including us—remain poorly understood and likely underestimated.
The oceans cannot be cleaned—so let’s reduce waste at the source and prevent it from going to sea.
[i] Océan plastique, Nelly Pons, 2020, p. 65
[ii] The Ocean Plastic Crisis, Ellen MacArthur Foundation, 2016, p. 15
[iii] Ibid.
[iv] Accumulation of microplastics in the North Pacific Subtropical Gyre, Nature, 2018, p. 508
[v] Une partie d’entre eux sont classés comme « substances toxiques pour la reproduction »
[vi] Plastic leachates impair growth and oxygen production in Prochlorococcus, the ocean’s most abundant photosynthetic bacteria, Sasha G. Tetu, Indrani Sarker, Verena Schrameyer, Russell Pickford, Liam D. H. Elbourne, Lisa R. Moore, Ian T. Paulsen, 2019, p. 371-379
[vii] Océans, le mystère plastique, Vincent Perazio, 2016
[viii] Pollution plastique en Méditerranée, sortons du piège !, rapport du WWF, 2018
[ix] Microplastics and persistent fluorinated chemicals in the Antarctic, rapport de Greenpeace, 2018
[x] article L541-2-1 sur les déchets ultimes
