Some lakes hold more plastic than the ocean’s large accumulation zones

O plastic and microplastic pollution It had a worldwide impact and even affected remote places where human presence is minimal.

A study published in Nature confirms, for the first time, that the concentrations of plastic found in various fresh water bodies are higher than those of some ocean gyres that accumulate large amounts of debris and are known as plastic islands.

The investigation, led by the University of Milano-Bicocca, has the participation of the National Museum of Natural Sciences (MNCN-CSIC) and the Institute of Environmental Diagnosis and Water Studies (IDAEA-CSIC), both of the Higher Council for Scientific Research ( CSIC). ), as well as researchers from the University of A Coruña, among other Spanish centers.

The Sau reservoir in Catalonia is one of the studied lakes. | Quico Llach

“The lakes are like sentinels of pollution, as they end up accumulating plastic waste that is dispersed through various sources such as reservoirs or the atmosphere. In addition, when reaching their waters, lakes can retain, modify and transport plastic waste through watersheds to the oceans”, contextualizes the researcher from IDAEA-CSIC, Miguel Canedo-Arguelles.

Among the lakes where the highest contamination by plastic waste was identified is the Maggiore (Italy), Lugano (between Switzerland and Italy), Tahoe (USA), Neagh (United Kingdom) or Pantà de Sau, in Cataloniawhich is one of those with comparatively the worst levels of microplastics.

The water bodies studied in Galicia (the Abegondo-Cecebre reservoir, the coastal lagoon of Doniños and the lagoon of Meirama) are in line with what is observed in global trends.

Lakes are like sentinels of pollution. Plastic waste that is dispersed by sources such as reservoirs or the atmosphere ends up accumulating in them.

Miguel Cañedo-Argüelles (IDAEA-CSIC)

These lakes function as main sources of drinking water of the surrounding populations. They are also key areas for their respective economies, as numerous recreational activities take place in their vicinity.

“The relevance of these results lies in the fact that, in addition to negatively impacting the drinking water we need, plastic pollution has harmful effects on aquatic organisms and the functioning of ecosystems”, he explains. Veronica Navascientist at the University of Milano-Bicocca.

The collaboration of almost 80 researchers made it possible to collect surface water samples, with plankton nets, from 38 lakes located in 23 different countries, spread over 6 continents. This diversity made it possible to represent different environmental conditions.

In addition to negatively impacting the fresh water we need, plastic pollution has harmful effects on aquatic organisms and ecosystem functioning.

Veronica Nava (University of Milano-Bicocca)

“Once collected, the different teams sent the samples to the Italian university where, using technologies such as Raman microspectroscopy, an extremely precise analysis was carried out with which we were able to confirm the polymeric composition of the microplastics. Among all that was found, the presence of polyester, polypropylene and polyethylene”, points out the researcher from the MNCN-CSIC miguel matias.

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“In addition, we managed to identify determining factors such as population density, urbanization, size of basins and water retention times, which explain the vulnerability of lakes and reservoirs to contamination by plastics”, continues Matias.

Above left: Large piece of longline at 80 m depth on one of the most remote islands in the world: São Paulo Archipelago, off Brazil / Above right: Fire urchin (Asthenosoma varium) clings to a fishing line while camouflaging with a piece of blue plastic bag at about 130m depth in the Philippines / Bottom left: Plastic bag tangled in a coral in the Philippines at about 10m depth / Bottom right: Tangled fishing lines and breaking Dendrophylliid corals at 70 m depth in Cape Verde. / Photos: Luiz Rocha

The long journey of plastics

“Plastic that accumulates on the surface of aquatic systems can promote the release of methane and other greenhouse gases. These residues can interact with the atmosphere, biosphere and lithosphere, affecting biogeochemical cycles”, explains Nava.

“The circulation between the different elements of the earth, which pass from living matter to inorganic matter through chemical reactions, is still not fully understood, requiring a holistic assessment of plastic pollution in lakes”, he continues.

These results demonstrate the global scale of plastic pollution: no lake can be considered truly untouched.

These results demonstrate the global scale of plastic pollution: no lake, even those farthest from human activity, can be considered truly untouched. “This result should lead us to review the strategies of pollution reduction and waste management processes”, concludes Nava.

The project is part of the international Global Lake Ecological Observatory Network (GLEON), focused on researching the processes and phenomena that are triggered in freshwater environments.

Researchers Veronica Nava and Barbara Leoni during the sampling process. / Veronica Nava


Veronica Nava et al. “Plastic debris in lakes and reservoirs”. Nature (2023)

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