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Freshwater Contamination: The Overlooked Source of Ocean Plastic Pollution

Dr. Sherri Mason’s research reveals extensive contamination of freshwater ecosystems with microplastics, highlighting the link between freshwater and ocean plastic pollution.

Written by Erica Cirino Published on Read time Approx. 3 minutes
Plastic bottles and other pollutants floating on the surface, Lake Geneva, France. March 2008.

Sherri “Sam” Mason, a scientist at the State University of New York at Fredonia, is sitting in her lab wearing a white smock, quietly peering down the long lens of a high-powered microscope at dried sediment taken from the bottom of Lake Erie. She shifts the plate around and plays with the magnification for a few minutes, and then uses metal tweezers to pluck out what look like a short, thin blue thread and a few small red circular beads – all made of plastic. She drops them into a clear petri dish.

These bits of plastic – in this case, plastic microfibers and microbeads – are found throughout marine habitats, yet they are rarely discharged directly into the sea. Instead, microbeads found in face scrubs and other cosmetic products wash off our bodies while our clothing sheds plastic microfibers with every wash, all flowing into wastewater systems before being discharged into freshwater. From there the microplastics flow into the ocean.

Dr. Sherri Mason examines lake sediment samples for signs of microplastics. (Erica Cirino)

Mason last year published a study measuring concentrations of plastic in the New York-New Jersey Harbor estuary, where freshwater meets saltwater, and determined that there are more than 165 million pieces of plastic floating on surface waters. In her new research, Mason is trying to determine if similar amounts of plastic are found in freshwater sediments. Her work also highlights the interconnectedness of global aquatic ecosystems: flows to saltwater, along with plastic trash that can kill sea turtles, whales and other marine life and leach toxic chemicals into the ocean.

“We’ve long studied the amounts of plastic on surface waters, but not in the sediments,” said Mason, a professor of chemistry who chairs the university’s department of geology and environmental sciences. “More plastic found in freshwater sediments would mean a greater overall plastic load, and thus a greater effect on aquatic ecosystems – both saltwater and freshwater.”

The United States Geological Survey delivers sediment samples to Mason, who distills plastic from the lakebed mud by sieving it and drying it out through a long laboratory process. She then picks out suspected pieces of plastic under a microscope. Finally, she confirms whether the bits she finds are plastic by analyzing them with an FTIR (Fourier transform infrared spectroscopy) machine, a type of spectrometer that measures wavelengths of light absorbed by a particular material. The machine tells Mason what kind of plastic she’s found, which can help her determine what type is most prevalent in an ecosystem.

“If we know what kinds of plastic are most abundant, we can target legislation to curb the production and use of the products that they’re used to make,” said Mason.

Bans have been imposed in some jurisdictions on plastic bags, Styrofoam and microbeads, and now there’s a movement to stop the use of plastic straws. The impact of plastic microfibers on ocean ecosystems is also a growing concern. Mason’s research has found that a single synthetic garment, such as a pullover fleece, can shed more than 1,900 tiny plastic fibers per wash that can end up in waterways and ultimately in the ocean.

Eighty percent of the plastic pollution in the sea originates on land. Plastic bags, plastic water bottles, plastic-based clothing and other consumer products are dumped into rivers and lakes or blow into the ocean from beaches. The problem is worse in developing countries with less-organized trash management systems.

Mason said her research shows the importance of caring for local watersheds, especially her Great Lakes community.

“What’s most covered in the news media is the inundation of plastic trash being found in the oceans,” said Mason. “Many landlocked or lakeside people may not realize that the ocean pollution they hear about in the news actually starts with them.”

To raise awareness of the importance of protecting freshwater ecosystems from plastic pollution, she has planned swims across Lake Chautauqua and Lake Erie. She swam 15.5 miles (25km) in 10 hours and 37 minutes across Lake Chautauqua earlier this month. She’ll do her second swim, 12.5 miles (20km) across Lake Erie, later this summer.

Mason appears to be accomplishing her mission. On the streets of the small upstate New York communities of Fredonia and Dunkirk, as well as in the large nearby city of Buffalo, Mason said people come up to her to congratulate her about her swim, ask about her training and research, and tell her they recognize her from the local newspaper and television news.

“It’s great getting attention for my swims and scientific work,” said Mason. “I only hope it will help increase our appreciation of local aquatic ecosystems and decrease the amount of plastic people dump into them.”

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