Polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs) – organic contaminants known to cause cancer and other health impacts – were among the top four organic contaminants found in mussel samples collected throughout the state, according to data from the 2017-2018 Mussel Monitoring survey. All seven of the metals measured in this study – aluminum, arsenic, cadmium, copper, lead, mercury, and zinc – were also detected in the mussel samples. The survey, coordinated by the Washington Department of Fish and Wildlife’s (WDFW) Stormwater Action Monitoring (SAM) program, works closely with Puget Soundkeeper and other organizations, including Tribes and agencies, to recruit community volunteers in nearshore mussel monitoring efforts. The 2017-2018 Mussel Monitoring survey represented the second successful deployment of mussels in Puget Sound for the purpose of tracking toxic contaminants in nearshore ecosystems.

Why are mussels used to study pollution? Mussels are prolific filter feeders that can filter anywhere from 20-50 gallons of water each day. Because of this, they perform an important ecosystem service – they clean our water! However, this also means that mussels accumulate the chemicals present in their food and water within their tissues. Mussel digestive systems cannot metabolize contaminants and, instead, accumulate them unchanged in their tissues. This is bad news for mussels, but good news for science. Because these chemicals are not biotransformed, mussels provide a comprehensive look at what pollutants are present in a body of water over a period of time.

For the 2017-2018 survey, WDFW staff, Puget Soundkeeper volunteers, and other partners retrieved mussel cages from 92 of the 94 monitoring sites. Similar to the 2015-2016 survey results, polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs), in addition to PCBs and DDTs, were the most abundant organic contaminants detected in mussels at all sites (SAM, Pierce County, Partner). When compared to the 2015-2016 survey results, PCBs and DDTs from mussel samples along shorelines that run parallel to cities and other developed lands had significantly higher median concentrations, indicating those contaminants should be closely monitored in future surveys to track whether there is an increasing trend.

Click HERE to read the full report. To learn more about Puget Soundkeeper’s Mussel Monitoring program and other volunteer opportunities, fill out our volunteer form HERE or email kristin@pugetsoundkeeper.org.