Lake Tahoe, renowned for its crystal-clear waters, has an unexpected problem lurking beneath its pristine surface. A recent paper published in the journal Nature reveals that the alpine lake is brimming with microplastics, despite boasting its clearest waters in 40 years.
Researchers found that Lake Tahoe contains the third-highest concentration of microplastics among 38 freshwater reservoirs and lakes worldwide. The density of plastic particles in its waters, at 5.4 plastic particles per cubic meter, even surpasses concentrations found near some of the vast garbage patches swirling in the world’s oceans.
The study confirms a 2019 investigation that initially detected microplastics in Lake Tahoe. Researchers conducted the recent analysis by navigating boats and dragging fine-mesh nets through the water, just below the surface. The samples were then filtered to identify plastic fragments larger than 250 microns. In total, they discovered 9,425 plastic particles, displaying varying sizes, shapes, colors, and materials.
Microplastics are minuscule bits of plastic found nearly everywhere, from human blood to fresh Antarctic snow. But heir high volume in Lake Tahoe was a big surprise to scientists.
The lake’s unique characteristics might contribute to the microplastic accumulation. Its large surface area, high elevation, and lack of significant outflows allow water molecules to spend around 650 years in the lake. Consequently, microplastics persist longer here compared to other lakes. Lake Tahoe’s extensive shoreline and massive surface area also provide ample space for microplastics to land in the reservoir.
Researchers have not yet fully determined the exact sources of the microplastics, but it’s not hard to figure out. Some particles were identified as blue, likely originating from ropes used to moor boats. Others may have come from synthetic clothing worn by tourists, washed and dried at nearby homes and rentals, or airborne particles emitted through dryer vents.
More likely, increased litter and debris are the main source of the issue. Conservation groups have urged the public to respect the area’s around the lake, but incidents like July 5th where more than 8,000 pounds needed to be cleaned up along the lake contribute to the problem.