If you happened to be walking anywhere along the Washington coast late at night during October, you might have chanced upon an unusual site: a group of bundled-up volunteers from Puget Soundkeeper and other groups trekking out into the water, carrying cages full of native mussels.

Before you ask: no, they weren’t headed to an all-night shuck fest in the middle of the Sound. The teams, which consisted of volunteers coordinated by the Department of Fish and Wildlife (WDFW), were installing a total of 73 cages into the Puget Sound area during low tide. The cages will stay in their respective locations for the next three months.

So why were these teams bringing these cages of mussels out into the water in the middle of the night?

These volunteers were carrying out the first stage of a three-month experiment, after which the mussels will be removed and their tissues analyzed for various pollutants.

This experiment is part of the Regional Stormwater Monitoring Program’s Mussel Monitoring Project, a long-term monitoring project aimed at assessing levels of toxic contaminants in nearshore biota of the greater Puget Sound. The project allows scientists to understand the cumulative impact urban centres have on waterways – hence, mussels have been dispersed across marine environments with high pollutant loads, such as those in urban sites. This project will provide important data on recent changes in water quality in Puget Sound.

Puget Soundkeeper: an Invaluable Part of the Project

Along with having to install and retrieve the cages during cold, dark weather (to ensure mussels were placed in ideal locations), there were a number of challenges this project faced; among them, receiving permissions from various property owners to install the cages and, of course, relying on partners and volunteer groups to carry out the project.

Without the support of Puget Soundkeeper and volunteer groups, the Government might not have been able to go forth with sampling such a large area in such a short period of time.

Why Mussels?

Mussels are filter feeders. They attach themselves to substrates like rocks or boats (a quality that has made invasive species like the Zebra Mussel a major nuisance for boat owners and wildlife officers) and feed on small particles in the water column. They have highly sensitive filtering abilities; blue mussels, for example, can filter particles as small as 2 micrometres!

It isn’t just their sensitivity as a filter feeder that makes them so valuable to water quality monitoring projects: their ability to detect both low-level and complex contaminants make them an invaluable resource as a bio-indicator.

What does this mean?

Mussels can accumulate various contaminants in concentrations that exceed those in ambient seawater by thousands of times. In fact, mussels are more sensitive to contaminants than certain chemical analysis instruments and are able to withstand considerable environmental changes, including those in salinity and temperature.

This has made mussels one of the best indicators for contaminants for aquatic systems, and is the primary reason behind their use in detecting marine and freshwater contamination for the last several decades.  As our coastal urban centres grow and expand, we will continue to rely on these species to provide insight into the changes of pollutant loads in our environment, including sewage, industrial waste, and heavy metals.

Threats to Puget Sound

Puget Soundkeeper’s work is invaluable. As the second largest marine estuary, Puget Sound is highly sensitive to changes in temperature, salinity, and pollutant loads. The Sound sits alongside a densely populated urban centre with roughly 4.4 million people, and complex, diverse pressures weigh on its health.

The number of people living in bordering counties has more than doubled since 1960, and this number continues to climb. Continued development of the shoreline will threaten the integrity of the estuary, and millions of pounds of toxic chemicals from surface runoff, groundwater discharges, and wastewater pipes (among others) enter the waterway each year.

Photo by Wonderlane, Flickr

Though the results from this study won’t be available until 2017, we can already see some interesting trends from the 2012 sampling results. Interestingly, four highly carcinogenic compounds (PAHs, PCBs, PBDEs, and DDTs) were the most abudant contaminants (and were found in all mussels in every location), with pollutant loads highest in the most urbanized areas.

We’re looking forward to the 2017 results – and hope it spells good news for Puget Sound. We commend Puget Soundkeeper’s tireless work to protect their shared coastal habitat.

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