Looking for plastic pollution in Flathead Lake

Flathead Lake researcher Xiong Xiong peers into a clear glass jar filled with water, plant matter and a thin, 3-inch-long piece of plastic. It looks like a bristle from a broom or maybe a piece of fishing line.

Although Flathead Lake is well-known for its brilliantly clear, cold water, unseen pollutants may lurk in the seemingly pristine surface water.

Chinese postdoctoral researcher Xiong is spending a year at the University of Montana’s Flathead Lake Biological Station, working with Director Jim Elser to find out if tiny pieces of plastic are polluting the waters of Flathead Lake, and, if so, how concentrated they are.

“It looks quite clean, but, if this clean lake is suffering from plastics, I want to check that,” Xiong says.

Pieces of plastic smaller than 5 millimeters in size are known as microplastics, which include a wide variety of shapes – from fragments to fibers. One of these types, microfibers, is everywhere. Microfibers can even be found in a polyester T-shirt or fleece coat and carried into the water system after a normal load of laundry.

Plastic does not easily biodegrade. Natural processes break it into smaller and smaller pieces over the years without actually changing the structure. Broken-down plastic still floats around like suds in a bath tub decades after it went into the water.

In his first water sample from Flathead Lake, Xiong found a thin piece of plastic. Although larger than microplastics, bigger plastics also could become a problem, because they eventually break down into microplastics.

Microplastic is a huge pollution problem in water bodies around the world, especially in the oceans, where large piles of garbage accumulate. The largest ocean garbage patch is four times the size of the entire state of Montana in surface area – mostly composed of plastic that is slowly breaking down.

Most microplastic research is done on the ocean.

“I think people think it’s more serious in the ocean, but we want to find the situation in the freshwater inland because many people live inland, and we need the freshwater,” Xiong says. “It may affect our daily life more directly than the plastic in the ocean.”

Xiong’s most recent work, including the work he did for his Ph.D. at the Institute of Hydrobiology, Chinese Academy of Sciences in Wuhan, China, includes testing highland freshwater lakes in the Tibetan Plateau for microplastics. Although a lot fewer people live on the Tibetan plateau than in the big cities of China, Xiong found the lakes still contain microplastics at concentrations high enough to cause concern. He wants to see if a lake in the sparsely populated Flathead Valley of Montana might carry the same kind of baggage.

Microplastics already have been found close to home in the Gallatin River in Southwest Montana by Adventure Scientists, a nonprofit based in Bozeman. Citizen scientists collected water samples from 70 sites in the Gallatin watershed, revealing plastic pollution.

For his own tests for the presence of microplastics in Flathead Lake, Xiong has gathered water samples from 12 locations around the lake with his windsock-shaped sampling net. He tows the mesh net behind a boat, and it plucks up any particles in the water.

He also has piggy-backed on the long-term data sampling that happens every few weeks in Flathead Lake and its tributaries since the 1970s, known as the Flathead Lake Monitoring Program.

The FMP crew intercepts deposition samples, particles of what falls out of the air before it is deposited in the lake. Xiong has checked some of these samples to see if there are microplastics in them, finding a couple particles that are suspicious under the microscope but nothing definitive. He plans to test both his water and deposition samples in the next couple of months.