Pollution is one of the biggest threats to aquatic environments and the wildlife that depend on them. Most pollution starts on land and enters the watershed not through large-volume spills but by accumulating from numerous sources and then spilling into the ecosystem through runoff.
Scientists had been working to mitigate the problem of runoff for decades when a new contaminant was found lurking in aquatic ecosystems: 6PPD-quinone.
In 2020, a team of researchers from the University of Washington and Washington State University discovered 6PPDQ, a chemical that is formed when 6PPD — a chemical used to prevent degradation in automobile tires — reacts with ozone in the air. They also found that the toxin is deadly to certain species and causes rapid death, for example, in coho salmon swimming in urban streams.
Because salmon are a “keystone” species that has a disproportionately large effect on its natural environment, this impact can have devastating effects that cascade across entire ecosystems and have the potential to bioaccumulate in marine food webs. Bioaccumulation occurs when a living organism absorbs a substance, such as a chemical or pesticide, faster than it can get rid of it.
Enter Dr. Lizbeth Seebacher, a senior research scientist at UW Bothell, who in her latest research has developed a new media for floating treatment wetlands — artificial platforms that create wetlands where there are none to aid in filtration — to mitigate the impacts of 6PPDQ.
Ideas for a solution
An ecologist, Seebacher consults on wetlands, ecological restoration, stormwater treatment and lake restoration projects. She first became interested in the topic of biomedia for pollution remediation while serving as program manager for aquatic invasive plant and cyanobacteria at Washington state’s Department of Ecology.
She heard about its success rate while at a fisheries conference in 2016 where presenters reported a 100% survival rate in coho salmon spawned in stormwater that had passed through biomedia, or porous materials that filter toxins. And in the untreated water? 100% mortality.
“A lot of us in the room were like, “mouth drop,’” Seebacher said. “It was great, but my next thought was, ‘How are we going to get this biomedia on the side of the road at every mile?’”
She continued to follow the research. All the while, the wheels in her head kept turning on how to effectively introduce the biomedia.
“And then I thought, well, in order to get that biomedia into the water column, what if we tried floating treatment wetlands but with a design that would allow us to place it in the water body at the point of stormwater entry?”
The ‘teabag’ effect
Seebacher realized that it wasn’t going to be feasible to attack the problem at every point of entry — adding biomedia infrastructure the full length of a highway would be expensive and labor intensive. Instead, she decided to focus on the areas where she could make the biggest difference: stormwater ponds.
“Road runoff goes straight down the drain and into whatever the nearest body of water is — whether it be a creek, a wetland or the Puget Sound,” she said. “But often, it pools in stormwater ponds on its way there. I hadn’t realized it before, but there really is no treatment going on in stormwater ponds.
“And that was a big awakening.”
In 2018, she received a King County Waterworks grant and began experimenting with different biomedia and modules for floating treatment wetlands. What made her project different from others, she said, was that rather than relying on water running through the biomedia — which can be difficult to achieve in a field environment — her modules simply sit in the water body to passively filter.
“It’s a teabag effect,” she said, “and I think it works very well, especially if the design is right and there’s enough biomedia in there and the contact time is long enough.”
Student skills in the field
When the news about 6PPDQ came out in 2020, Seebacher’s focus shifted, and she continued experimenting with different biomedia to see what worked for the toxin. Supporting her in this project were several research assistants.
“This project really helped me in gaining real-world experience in environmental work,” said Arun Khou, who graduated from UW Bothell in 2021 with a degree in Earth System Science and a minor in Geographic Information Systems. “I honed my skills of data collection and scientific communication with others.”
Brendan McCrindle was a research assistant alongside Khou and began to take on more work after Khou graduated. In the role, he wore many hats, he said, including filling biomedia bags, constructing the modules, installing them in Lake Sammamish and helping to maintain them. The bulk of his work, however, focused on fish use surveys and data collection.
“I think my UW Bothell classes prepared me well for this work,” said McCrindle, a 2025 alumnus from the Earth System Science program. “Getting experience out in the field and getting my hands dirty really prepared me for the problem-solving nature that comes alongside field work. Our field work classes involved setting up monitoring methods and following our plans, and things go wrong, especially when we’re first learning.
“These kinds of experiences slowly build up the ability and confidence in oneself to be comfortable when things don’t go quite right,” he said “That’s the reason I absolutely loved UW Bothell’s field classes — because there is so much opportunity in them to try things and learn by making mistakes.”
“Getting experience out in the field and getting my hands dirty really prepared me for the problem-solving nature that comes alongside field work.”
Brendan McCrindle, Earth System Science ’25
Save the fish
Through her experiments, Seebacher was able to achieve a 100% survival rate of coho salmon using her modules. But it is not a one-size-fits-all solution, she said.
“It’s never a good thing to have something so toxic entering the environment. We also don’t know what it’s doing to humans, although they’re finding it in our bodies,” she said. “But that shouldn’t be the only reason to do something about it. We know that it’s killing fish and the first thing we should be doing is banning the substance to get rid of the source.
“The second,” she said, “is that we need to find remediation methods that work in different situations.
In the meanwhile, she added, “the state should take this work more seriously and fund these modules so that we can get them out there and treat the stormwater before it kills so many more of these fish.”
