Plastic in every corner of the world

Plastic residue is accumulating in the most remote places in the world, whether in isolated lakes or coral reefs in the middle of the ocean. Two new studies are sounding the alarm, with two Ontario lakes in their sample.

plastic continent

“In some lakes, the concentration of plastic particles is higher than that of the plastic continent in the middle of the Pacific,” observes biologist Chelsea Rochman, of the University of Toronto, who signs a commentary accompanying the two studies, Wednesday in the review Nature. “It’s striking. It confirms that the most important factor for plastic pollution is the proximity of populations. »

Two Canadian lakes

The study of 38 lakes and reservoirs, co-authored by some fifty researchers from around the world, focused in particular on two small Ontario lakes, Dickie and Plastic, located east of Georgian Bay. The concentration of plastic there is among the lowest observed, less than one particle per cubic meter of water. The highest densities, between 6 and 13 particles per cubic meter, are observed in Lake Lugano and Lake Maggiore in Italy as well as Lake Tahoe in Nevada and California. The nets used to detect the plastic had mesh sizes of 0.25 mm and 84% of the particles measured less than 5 mm. “In the isolated lakes, we found mainly textile fibers, long but light, probably transported by the atmosphere,” says Veronica Nava, of the University of Milan-Bicocca, the lead author of the study on the lakes.

Mesophotic reefs

The reef study included for the first time mesophotic reefs, located between 30 and 100 meters deep, therefore relatively far from the coast. “The study of plastic in reefs is poorly systematized because plastics get caught on corals,” says lead study author Hudson Pinheiro of the University of São Paulo in Brazil. “So you have to go there by hand. »

The most striking information about plastic in mesophotic reefs is that it comes mainly from the fishing industry, according to biologist Isabelle Côté, a coral scientist from Simon Fraser University.

“It confirms that you have to target fisheries to really tackle the problem of plastic in coral reefs,” says Ms.^me Côté, who also believes that climate change and the direct impacts of fishing have greater effects on corals located far from the coast. The researchers only counted plastics larger than 5 cm and found them in 77 of the 84 coral reefs studied.

The Treaty

These results make negotiations for a treaty on plastic pollution even more urgent, according to Chelsea Rochman. “The deadline for concluding the treaty is the end of 2024, says the biologist. I hope that results like these will shake up public opinion and decision-makers. » The results published in Nature will be important to better understand which hydrographic features – lake size and depth, currents – influence the transport and accumulation of plastics and microplastics. “Only with this information can we fully understand the effect of plastic on living organisms. »

Waste Management

Do the bans on single-use plastic bags and objects already have observable effects? “It’s too early to see it,” said M.^me Rochman. It expects a decrease to be seen starting next year in the microplastic collection sites it has set up at the Port of Toronto and surrounding lakes. “It is certain that the highest concentrations are probably linked to waste management problems,” said Veronica. Nava. But the efficiency of the removal of garbage and recyclable materials is an understudied variable for plastic pollution. The Milanese biologist also wants to look at the microorganisms that live on plastic, an ecosystem called the “plastisphere”.