Mussels that cling to rocks along the shores of Puget Sound tell stories about what pollutants are floating in the water, from motor oil to pesticides to fire retardants.
They’re so good at filtering poisonous chemicals out of the water that federal researchers use them to gauge the amount of pollution in water bodies across the country, including in Puget Sound.
Along Snohomish County beaches, mussels have been used to find high levels of hydrocarbons, the type of pollutants given off when oil washes into waterways and when tires break apart from wear and tear on the road, said Stef Frenzl, marine resource steward for the Snohomish County Marine Resource Committee.
Other pollutants found in mussels here include lead, pesticides and fire retardants.
In Snohomish County, local environmental officials have embraced the mussel testing program, recently agreeing to harvest and test them in summer months, a national first.
“Blue mussels give us a quick snapshot of Puget Sound’s water quality and ecosystem health,” Frenzl said. “The mussels feed by filtering large quantities of water. Their tissues metabolize most contaminants within 30 days. When we harvest, we receive a snapshot of what pollutants were in the water column.”
Members of the Marine Resources Committee, made up of volunteers and area environmental officials, recently took samples at seven local sites, including one on Camano Island.
“We harvest 150 mussels at each location,” Frenzl said. “We pack them on ice, ship them overnight to a lab. They’re shelled, processed and analyzed for over 100 contaminants.”
The goal is to find out if pollutant levels in the summer are substantially different from the tests traditionally taken in January or February, said Alan Mearns, senior scientist at Emergency Response Division with National Oceanic and Atmospheric Administration in Seattle.
“We have been wondering if (the pollution found in mussels) is a function of mid-winter runoff,” Mearns said. “Maybe the concentrations are less in the summer when there is less runoff.”
If the program in Snohomish County is successful, it could be expanded nationally, where mussels are sampled and tested at some 200 to 300 sites, Mearns said.
The Marine Resource Committee has also increased the number of sites where mussels are sampled from four to seven, Frenzl said. Those sites include the Port of Everett, sites near the Mukilteo and Edmonds ferry terminals, Kayak Point, Hat Island, north Port Susan and Cavalero County Park in Island County.
Only the Port of Everett site has been tested for long, with samples going back to 1986, Frenzl said. Like all Puget Sound sites, Everett shows high levels of petroleum-based pollutants. It also shows sporadically high levels of lead and zinc.
The local mussels are not typically eaten and it’s not clear whether pollutant levels found in them make them dangerous, Frenzl said.
“This program is not an assessment of shellfish and safety,” he said. “It’s not designed to tell us which shellfish are safe to eat.”