Shimoda (Japan) (AFP)

After drifting for about fifteen minutes on the surface, the "sock" - a funnel-shaped net - is hoisted to the back of the boat and the new catches, nestled in a mud of plankton, are first inspected at the naked eye.

"Blue is microplastic, and that is polystyrene I think", points out Sylvain Agostini, assistant professor at the University of Tsukuba (northeast of Tokyo) and scientific director of the mission Franco-Japanese Tara-Jambio, who has been practicing these samples all around the Japanese archipelago since April 2020.

With more than 200 samples already collected, both on the surface and in the sediments, this mission is the largest study to date on the concentration of microplastics (particles between 0.3 and 5mm) in Japanese coastal waters.

"We want to see whether or not these bacteria can be dangerous for the food chain," said Jonathan Ramtahal, a student from Trinidad and Tobago participating in the mission.

If the scientific results should be delayed until at least 2024, an immediate observation is clear: "There is not a sample where we did not find plastic", according to Mr. Agostini.

The fault of others?

There is nothing exceptional about this, as microplastic pollution is omnipresent in waters around the world, according to various scientific studies including those of the Tara Ocean Foundation, which surveyed the Mediterranean Sea on this subject in 2014 and then nine major European rivers. in 2019.

Sediment samples collected at sea off the port of Shimoda in Japan on October 14, 2021 Charly TRIBALLEAU AFP

However, Japan considers itself a model for managing its plastic waste, 85% "recycled" according to industry figures, even if it is mainly energy recovery, by incineration, emitting CO2. .

"The streets and waterways in Japan are relatively clean compared to those in other countries," said Keiji Nakajima, director of the marine plastic pollution control office at the Ministry of the Environment.

While being a major user of plastic, Japan has a "solid waste management mechanism", adds the official interviewed by AFP.

Why then are microplastics systematically found around the archipelago?

This is partly the fault of others, according to Tokyo: "Japan is located downstream of a major ocean current that carries plastic waste produced in Southeast Asia and China," recalls Mr. Nakajima.

"There is a part of truth" in these explanations, admits Mr. Agostini.

But when plastic is found at the mouth of a river or in almost closed bays, "it does not come from thousands of kilometers but from land nearby," he objected.

Even if a small percentage of Japanese plastic waste escapes collection, "given the enormous quantities that are used in Japan, that makes enormous quantities which end up in the ocean", argues the researcher.

Lead by example

According to the United Nations, Japan ranks second in the world for the amount of plastic packaging waste per capita, after the United States.

Disposable lunch boxes, individually wrapped fruit and cupcakes, double wrapped: in the land of the king customer, the refusal of a lid on his coffee or a plastic straw still arouses the astonishment of sellers today.

"The culture of packaging is part of the Japanese aesthetic and has helped increase the use of plastic" in the country since the 1970s, Kazuo Inaba, chairman of the national network of Japanese marine stations, reminds AFP Jambio.

A researcher examines samples collected from the sea surface in a laboratory in Shimoda, Japan, October 14, 2021 Charly TRIBALLEAU AFP

Japan has started to react, however.

In 2019, the country set itself the target of recycling 100% of new plastic by 2035, and plastic bags have paid off there since 2020.

"If developed countries do not set an example, nobody will. It's like CO2," said Mr. Agostini, while the COP26, the international conference on the climate, starts on October 31 in Glasgow ( Scotland).

© 2021 AFP