Once numbering in the billions across the Tennessee River watershed, mussel populations have sharply declined over the past century due to pollution, habitat loss and industrial activity, according to Dr. Michael McKinney, professor of earth, environmental and planetary sciences at the University of Tennessee.
“There used to be billions of mussels in the Tennessee watershed,” McKinney said. “So we’ve gone from billions to probably millions.”
Dr. McKinney said freshwater mussels are one of the most endangered group of animals in the southeastern United States, adding their decline is driven by multiple factors, including water contamination and their complex reproductive cycle, which depends on host fish species.
Because mussels are filter feeders, they are particularly vulnerable to polluted water. They absorb heavy metals and toxins through a process known as bioaccumulation. Unlike fish, mussels cannot move to cleaner habitats.
“If the water becomes contaminated, they die off,” McKinney said.
Natural filtration system
Despite their low profile, mussels play a significant role in river ecosystems. A single mussel can filter about a liter of water per hour, removing sediment, bacteria and other pollutants that cloud waterways.
“They’re called ecosystem engineers,” McKinney said, noting that other aquatic species rely on mussel beds for habitat and reproduction.
Mussels may also help address a growing environmental concern: microplastics. Tiny plastic particles have been detected in waterways worldwide and in human organs.
“The most efficient way to remove those — it’s with mussels,” McKinney said. “If you had to remove microplastics with a wastewater treatment plant … it would cost much, much more.”
Tracking restoration efforts
Restoring mussel populations requires reintroducing hatchery-raised juveniles into rivers where water quality has improved. The Pigeon River in East Tennessee is one example. After decades of pollution from a paper mill, the river has seen significant cleanup efforts.
Tracking reintroduced mussels has historically been difficult. Many died, and researchers were unable to locate survivors.
That changed when University of Tennessee doctoral student Dana Mills developed a tracking system using small active transponders attached to juvenile mussels. The transmitters allow researchers to detect and monitor mussels from up to 100 yards away using antenna surveys along the river.
“So for the first time ever, we’re now able to locate these mussels,” McKinney said. “We can measure them to see if they’re growing, to see if they’re happy or if they’re not living.”
Community involvement
Public education and litter prevention are also central to river restoration efforts.
Keep the Tennessee River Beautiful, a nonprofit organization founded in 2019, has removed more than 1 million pounds of trash from the watershed with the help of more than 5,000 volunteers across seven states.
“Knoxville has this gorgeous river,” said Kathleen Gibi, executive director of Keep the Tennessee River Beautiful. “But over the years, people have just kind of shifted away from it.”
The organization oversees the Adopt a River Mile program, in which volunteers commit to cleaning designated sections of river twice a year. About 300 miles of the river are currently adopted. Participants have reported removing more than 300,000 pounds of trash.
Gibi said 80% of litter found in waterways originates on land and often enters rivers through storm drains. Cigarette butts — the most littered item worldwide — are also a major source of plastic pollution because their filters contain microplastic fibers.
Nearly 2,000 cigarette receptacles have been installed across the Tennessee River watershed through partnerships with businesses and state parks. The collected filters are recycled. Plastic recovered from 1 million cigarette butts has been used to manufacture two park benches now located at Dollywood.
Adopt a Mussel
In partnership with university researchers, the nonprofit launched an Adopt a Mussel program to raise awareness and funding for restoration efforts. Participants receive digital certificates and updates estimating how much water their adopted mussel has filtered.
The program also supports the use of protective silos, which provide safer holding environments for juvenile mussels before full release into rivers.
Last summer, the organization hosted its first Mussel Fest at Seven Islands State Birding Park. During a demonstration, attendees observed water becoming clearer over the course of the day as mussels filtered sediment.
The next Mussel Fest is scheduled for June 27.
Environmental and economic impact
Protecting the Tennessee River has environmental and economic implications. Gibi said their cleanup efforts support tourism, the second-largest industry in Tennessee, as the Tennessee River generates about $12 billion annually in recreation revenue.
Major fishing events, including the Bassmaster Classic, have drawn national attention and significant revenue to Knoxville in recent years.
“We’re not just protecting those vital ecosystems,” Gibi said. “We are protecting our community.”
McKinney said he hopes residents see the river as more than a scenic waterway.
“I want people … to realize that it’s not just a flowing body of water,” he said. “It’s actually a living ecosystem.”
For more information about river cleanup efforts, the Adopt a River Mile program or the Adopt a Mussel initiative, visit Keep the Tennessee River Beautiful online at www.keeptnriverbeautiful.org.
