Divers Find Plastic Litter Accumulating in Lake Tahoe

Researchers completing the first dive survey of Lake Tahoe have found an accumulation of plastic litter in a small section of the lake.

Lake Tahoe, which lies on the border of California and Nevada, is the 10th deepest lake in the world. Last year, researchers from the Desert Research Institute and University of California Davis Tahoe Environmental Research Center collaborated with Clean Up the Lake, a nonprofit focused on cleaning up Lake Tahoe, to send divers into the lake to survey the lakebed.

The divers covered about 9.3 kilometers (5.78 miles) near Lake Tahoe Nevada State Park and Zephyr Cove. In just this small portion of the lake, divers found an average of 83 littered items per kilometer. Hidden Beach and South Sand Harbor lakebeds had higher amounts of waste, about 140 pieces of litter per kilometer in Hidden Beach and 124 littered items per kilometer in South Sand Harbor.

In total, researchers found 673 plastic items. Most of the waste found included food packaging, plastic bags, bottles less than 2 liters and toys, according to Desert Research Institute. Scientists published their findings in Applied Spectroscopy.

“There’s very little work on submerged plastic litter in lakes,” Monica Arienzo, a lead author of the study and an associate research professor of hydrology at Desert Research Institute, said in a statement. “And I think that’s a real issue, because when we think about how plastics may be moving in freshwater systems, there’s a good chance that they’ll end up in a lake.”

Researchers tested the litter samples for chemical composition and found six common polymers across the samples: polyvinyl chloride, polystyrene/expanded polystyrene, polyethylene terephthalate/polyester, polyethylene, polypropylene and polyamide.

These findings can help researchers better understand where larger litter items in the lake are coming from and if they are contributing to microplastic pollution, a known issue in Lake Tahoe.

“When we study microplastics, we only have the chemical information, or the plastic type,” said study co-author Julia Davidson. “We don’t know where it came from — a plastic bag, toy, or otherwise — because it’s just a tiny piece of plastic. But now we can use this litter data to point to the dominant types of plastics and compare them to microplastic data.”

Clean Up the Lake has previously worked on a project to clean up the circumference of Lake Tahoe, which led to a collection of over 25,281 pounds of smaller trash. The organization identified an additional 500 heavy items around the lake to later be removed. In total, the organization has removed 61,541 pounds of litter from the lake from 2018 to now.

As the new research shows, the work is only just beginning. Waste, including a significant amount of plastic, is building up deeper in the lake. In fact, the study researchers found that no section of lakebed in their survey was free of litter. In addition to the cleanups, plastic reduction will be important in reducing the amount of plastic in the lake moving forward.

“There’s a lot of education we can do, as well as continuing to work on reducing the use of those plastics,” Arienzo said. “Because we have to start thinking about turning that plastic pipe off.”