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Mussel Watch

Science | Completed

Overview

Toxic contaminants enter Puget Sound from a variety of pathways, including non-point sources such as stormwater runoff, groundwater releases, and air deposition, and point sources like marinas and sewage treatment plant outfalls. Stormwater is considered one of the biggest contributors to water pollution and can have serious impacts on the health of Puget Sound, particularly in our urban nearshore areas. Monitoring these pollutants over time is critical for developing best management practices to reduce their impacts on our marine environment.

The Mussel Watch Program

The Mussel Watch Program, coordinated by the Washington State Department of Fish and Wildlife (WDFW), involves using citizen science volunteers, including the MRC, to monitor nearshore contamination in Puget Sound. Cages of mussels are deployed at dozens of monitoring sites across Puget Sound. They stay in place for several months, feeding naturally, before being retrieved for contaminant analysis. The results help identify contamination hot spots and evaluate whether pollution‑reduction efforts are working over time.

 

 

 

Photo: Amy Johnson

Project Background

Why Mussels Are Used for Monitoring

Mussels and other filter‑feeding bivalves have been used to monitor contaminant conditions in nearshore environments since the late 1970s. They are ideal for this purpose because they are native to the region, have limited mobility, and accumulate contaminants through filter feeding. Mussels also lack the ability to metabolize many organic contaminants, allowing them to concentrate substances ranging from heavy metals to pharmaceutical residues. By ingesting and filtering contaminated food, sediment, and water, they reflect exposure from both the water column and the seafloor. Because mussels typically retain contaminants for only two to four months, their tissue concentrations represent recent environmental conditions.

How Snohomish County Participates

The Snohomish County Mussel Watch program uses citizen science volunteers, including the MRC, to help select cage locations and assist with placing and retrieving the caged mussels. The cages, which hold mussels sourced from Penn Cove Shellfish’s Coupeville farm, are deployed at multiple shoreline locations during nighttime low tides in the fall. They are anchored securely to protect them from predators and storm events. After several months, volunteers retrieve the cages, document their condition, and place the mussels into coolers for transport to WDFW for processing.

Study Frequency and Reporting

The Mussel Watch studies are conducted biennially. Reports detailing the results of the testing are available from WDFW. The most recent report, includes data from 2023/24 monitoring.

Data Overview

Data trends from the NOAA and WDFW programs are used to monitor the impact of environmental contaminants and events such as oil spills and the effectiveness of management decisions. 

Monitoring Programs Working Together

In Washington State, the TBiOS Mussel Monitoring program supports other local monitoring and adaptive management programs, such as the Puget Sound Partnership's Toxics in Aquatic Life Vital Sign, WDFW's Stormwater Action Monitoring, and NOAA's national monitoring program (NOAA Mussel Watch). 

Local Trends in Snohomish County

The Snohomish County data show spatial differences between the more rural Port Susan to the north and the more urban developed area to the south of the Snohomish River.  Generally, contaminants are lower to the north and higher to the south, with mercury being the exception.  There are also differences between wet and dry seasons.  These trends are presented in the Mussel Watch Report for a compilation of selected parameters. The report, completed in June 2011, summarizes data through Summer 2009. 

Mussel Watch and Stormwater Action Monitoring

Mussel Watch surveys are also the basis for WDFW's Stormwater Action Monitoring. The first time the Mussel Watch program was incorporated into this program was the winter of 2015-16. Data was collected again in 2017/18, 2019/20, and the most recent report includes data from 2023/24 monitoring. The goal of this work is to establish a Puget Sound status and trends monitoring program, which will help inform local stormwater permitting.

Mussels in a cage ready for deployment.

Mussels in a cage ready for deployment.

MRC members walking with buckets on the beach.

 

Edmonds Ferry National Mussel Watch Site Mid-Intertidal Summertime Photo Series 

View the 2007-2012 Edmonds Ferry photo series. These photos were taken by Alan Mearns of NOAA.

These photos capture changes in mussel recruitment. Over time such photo series can be used to monitor cycles in conspicuous intertidal biota.  Photo series could be used to help better understand the interannual variations in mussel populations that Mussel Watch volunteers have observed at Snohomish County Mussel Watch sites.

Northwest Straits Commission (NWSC) Benchmarks Achieved:
Marine Water Quality, Science, Education & Outreach

Three photos of Edmonds Jetty side by side showing differences in mussel coverage.

Example of photo series linked above.

Related Articles

(Bellingham Herald)

WDFW's 2015-2016 Caged Mussel Watch program deployed mussel cages along 73 sites within the Puget Sound. This study will help collect data on the contaminant levels within Washington's waterways. 

(Komo News)

Results from the 2012-2013 Cage Mussel Study show that 100 percent of sampled sites contain trace levels of toxic PCBs. The study also reveals that remote areas along the Sound contain less contaminants, while mussels in more heavily polluted areas of downtown Seattle did not survive the experiment.

(NOAA)

Dr. Alan Mearns, NOAA Senior Staff Scientist posted to the NOAA Office of Response and Restoration blog about the history of the Washington state Mussel Watch program and the key role of citizen science volunteers in giving the program new life.

(Everett Herald)

The Everett Herald featured a front-page article on the MRC Mussel Watch Program and the 2012 winter sampling at the Edmonds Ferry site on Saturday, February 4, 2012. 

Mussel Watch