By Olivia Cook // Jul 30, 2023 / NewsTarget

The American Institute of Physics reported that a large international team of pollution experts has found concentrations of plastics, including microplastics, in some lakes are higher than in the most contaminated parts of the oceans.

Two types of lakes are particularly vulnerable to plastic contamination. The first type pertains to lakes and reservoirs in densely populated and urbanized areas. The second pertains to large lakes and reservoirs with elevated deposition areas, long-water retention times and high levels of environmental change caused or influenced by people – either directly or indirectly.

In the study published in the journal Nature, the authors led by researchers from the University of Milano-Bicocca in Italy sampled 38 lakes and reservoirs around the world, including in Australia, the U.S., the U.K. and Europe. Plastics and microplastics were found at every site, including very remote locations, in varying concentrations. (Related: Sharks are behaving strangely and plastic pollution could be to blame.)

The researchers placed surface nets in lakes around the world – a practice commonly used for collecting data on marine microplastics – sampling lakes with a range of depths, population densities and watershed sizes.

Researchers noted that in the most polluted, concentrations reached or even exceeded those reported in the subtropical oceanic gyres (large systems of rotating ocean currents) – marine areas collecting large amounts of debris.

The team behind the new study, led by Veronica Nava, recorded plastics concentrations more than three times higher than those sampled using a similar method in the North Atlantic subtropical gyre.

The study filtered for microplastics larger than 250 microns, or the width of about three strands of hair. It joined a growing body of research sounding the alarm on the prevalence of microplastics. The tiny plastic particles, less than the size of a sesame seed, have been found all over – in the ocean, in Arctic snow, in the air we breathe, the food we eat and in our blood. There’s seemingly no escape.

Sudeep Chandra, the director of the Global Water Center at the University of Nevada, Reno, and co-author of the study, said the research highlighted just how pervasive microplastics have been in freshwater ecosystems.

Every lake sampled contained microplastics, even the most remote lakes – including Castle Lake near Mt. Shasta in Northern California.

“We often think about plastics being developed in watersheds and then moving into the ocean and collecting in the ocean. But what this study shows you is that fresh waters, including lakes and reservoirs, are important conduits of plastic,” Chandra said.

These findings highlighted the importance of including lakes and reservoirs when addressing plastic pollution – in the context of pollution management and for the continued provision of lake ecosystem services.

Lake Tahoe contained the third-highest concentration of microplastics

Lake Tahoe contained the third-highest concentration of microplastics, the Los Angeles Times reported.

Researchers first reported microplastics in Lake Tahoe in 2019 – a disappointing discovery about the lake, which spans two states, California and Nevada. Decades of conservation efforts and legal protections have worked to preserve the lake and its 72 miles of shoreline, reported The Times.

Compared with the other 37 lakes, Tahoe had a relatively small watershed size — meaning the area of land that drains water into the lake — and some of the best water quality, Chandra said.

He added that the team was expecting to find Tahoe toward the bottom of the list – not at the top – especially because wastewater has been barred from entering the lake since the 1970s.

But there were a couple of characteristics that made Tahoe “strikingly different” from some of the others – namely, its large surface area paired with the amount of recreation it sees. Researchers noted that Tahoe has more than 15 million visitors each year.

Although the study did not cover the source of microplastics – that’s what the researchers will tackle next. Chandra said he suspected “the large surface area primes the lake to receive more microplastics from the atmosphere.”

He pointed to a study on “plastic rain” in protected national parks and wilderness areas, published in  Science in June 2020. The study, by Janice Brahney, an associate professor at Utah State University‘s watershed sciences department, made the headlines in the same year it was published.

“Nothing really surprises me anymore with microplastics work. It’s just cycling the Earth,” Brahney said.

Oceans have been a repository of plastic pollution for more than a century, accumulating plastics that can take hundreds of years to degrade. “That’s why oceans are a huge source of atmospheric microplastics, which can deposit all over,” she added.

Roads are another major source. Brahney said microplastics kicked up from the friction on highways around Lake Tahoe could get caught up in the atmosphere, then deposited into the lake, despite its small watershed.

There’s “no doubt there’s a significant source of atmospheric deposition to Lake Tahoe,” she said.

Tourism also contributes to microplastics in lakes

Another possible source of Tahoe’s high microplastics concentrations is the pollution that follows its tourism industry.

Jesse Patterson, chief executive officer for the nonprofit League to Save Lake Tahoe, said the findings didn’t shock him. Following the Fourth of July weekend, the nonprofit headed a beach cleanup where volunteers removed more than four tons of trash from the water and the shores of Lake Tahoe.

“It’s a highly protected lake, but it’s protected in a way that allows the balance of humans to come here and use it and enjoy it.  It’s that unique setting that has allowed a beautiful place like this to potentially have really high concentrations of microplastics in the water over time,” he said.

“Its beauty kind of hides the problem. And just because we can’t collectively see it, the science shows there’s an issue and we should respond now before we can see it with our own eyes.”

Starting in 2024, a ban on single-use plastic water bottles in the city of South Lake Tahoe will go into effect.

Last month, 17 regional organizations launched the first Lake Tahoe Destination Stewardship Plan, aiming to prioritize the sustainability of the Tahoe area alongside its recreation and tourism industries.

At Tahoe and beyond, the response to the threat of microplastics must be “dramatic,” Brahney said. In a world that runs on plastics, that won’t be an easy feat, she said, but it’s a necessary one.

“It has to be across all levels of government and has to be uncomfortable for everyone,” she said.

Visit Microplastics.news for more stories about plastic pollution in lakes and other bodies of water.

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