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The study, which involves participation from CSIC, reveals the presence of plastic waste in freshwater ecosystems with minimal human impact
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The research includes samples from 38 lakes across 23 countries worldwide
The Sau Reservoir (Pantà de Sau), in Catalonia, is one of the lakes analysed in the study. | Quico Llach
Plastics and microplastics have invaded lakes and reservoirs on a global scale. Pollution caused by this debris affects even the most remote places, where human impact is minimal. A new study published today in Nature shows, for the first time, that in some cases, concentrations of plastic found in freshwater environments are higher than those found in plastic islands in the ocean, so-called ‘garbage patches’.
The research, led by the University of Milano-Bicocca, includes the participation of the National Museum of Natural Sciences (MNCN-CSIC) and the Institute for Environmental Assessment and Water Research (IDAEA-CSIC), both of the Higher Council for Scientific Research (CSIC).
“Lakes are like sentinels of pollution, since they end up accumulating plastic waste that is dispersed through various sources such as reservoirs or the atmosphere. In addition, once they reach their waters, the lakes can retain, modify and transport plastic waste through the hydrographic basins towards the oceans”, explains the IDAEA-CSIC researcher, Miguel Cañedo-Argüelles, one of the authors of the study.
Among the lakes where the highest levels of plastic waste pollution have been identified are Lake Maggiore (Italy), Lake Lugano (between Switzerland and Italy), Lake Tahoe (USA), Lough Neagh (UK), and Pantà de Sau in Catalonia, which, comparatively, shows some of the worst levels of microplastics. These lakes are key sources of drinking water for the surrounding populations and are also important for local economies due to many recreational activities they support.
“The significance of these findings lies in the fact that, in addition to negatively impacting the drinking water we rely on, plastic pollution has harmful effects on aquatic organisms and ecosystem functioning,” explains Verónica Nava, a scientist at the University of Milano-Bicocca.
The collaboration of nearly 80 researchers has made it possible to collect surface water samples using plankton nets from 38 lakes in 23 different countries across six continents. This diversity has allowed for the representation of various environmental conditions. “Once collected, the different teams sent the samples to the Italian university, where, using technologies such as Raman microspectroscopy, we were able to conduct an extremely precise analysis to confirm the polymeric composition of the microplastics.
“Among all the materials found, polyester, polypropylene, and polyethylene stood out the most,” notes Miguel Matias, a researcher at MNCN-CSIC. “Additionally, we identified key factors such as population density, urbanization, watershed size, and water retention times that explain the vulnerability of lakes and reservoirs to plastic pollution,” Matias adds.
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 waste materials can interact with the atmosphere, biosphere, and lithosphere, affecting biogeochemical cycles,” Nava explains. “The circulation of materials between different components of the Earth, transitioning from living matter to inorganic matter through chemical reactions, is still not fully understood. A holistic assessment of plastic pollution in lakes is necessary,” she continues.
These results demonstrate the global scale of plastic pollution: no lake, not even those most remote from human activity, can be considered truly pristine.
“This finding should prompt us to reassess pollution reduction strategies and waste management processes,” Nava concludes.
The project is part of the Global Lake Ecological Observatory Network (GLEON), an international research network focused on studying processes and phenomena occurring in freshwater environments.
Download the press release (in Spanish)
Veronica Nava et al. (2023) Plastic debris in lakes and reservoirs. Nature. DOI: 10.1038/s41586-023-06168-4
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