PSRF, in partnership with Washington State Department of Health, coordinates a network of volunteers who help monitor biotoxins in shellfish to help keep this essential resource safe for us all.

At sites all across Puget Sound, our volunteers routinely collect shellfish samples and submit them to Washington State Department of Health (DOH) for testing. If shellfish toxins are present at unsafe levels for human consumption, DOH can close beaches for harvest so that no one becomes ill. Our volunteers’ efforts are a critical component of keeping recreational shellfish harvesting safe for all Puget Sound communities. They enable us all to enjoy feasting on the bounty of clams, oysters, and mussels that our waters provide. Washington has one of the most robust biotoxin monitoring programs of any state, thanks to the time and effort of volunteers.

If you are interested in becoming a volunteer, please reach out to Ally, We are especially looking for volunteers willing to sample at sites shown as glowing orange on our biotoxin site map below! Please note that site locations are approximate.

Shellfish like clams, oysters, and mussels are filter feeders, consuming organic particulate matter from the water column. Their diet includes many types of single-celled planktonic algae, a few of which produce toxins. These microalgae are naturally-occuring in our waters, and sometimes may “bloom” into abundance as a result of nutrients, warm temperatures, and sunlight. When these harmful algal blooms occur, shellfish can ingest enough of these toxin-producing cells to cause illness in humans. There are several types of harmful algae that can cause different illnesses. WA DOH monitors Paralytic Shellfish Poisoning (PSP), Amnesic Shellfish Poisoning (ASP), and Diarrhetic Shellfish Poisoning (DSP).

Read more about shellfish biotoxins and learn how to safely harvest and eat shellfish here. To see if your local beaches are open for shellfish harvesting, visit the DOH’s Shellfish Safety Map.

Toxin-producing microscopic algaes are consumed by filter feeding shellfish, making their tissue unsafe for human consumption. Credit: Gray McKenna

Volunteers collect mussels from suspended cages on a weekly basis, preferably on a Monday or Tuesday, and mail them to a lab where they are tested for biotoxins. Time input will vary by site, as some are monitored seasonally and some are monitored year-round. Sampling takes about 1-2 hours total. When biotoxins are detected, sampling occurs weekly. This is more often the case during May-October, when biotoxins are most abundant. When biotoxins are not detected, sampling is only bi-weekly. This is typical for the colder months, November-April.

Our volunteers are individuals who enjoy getting outdoors, learning about their local shellfish resources, and providing a valuable health service to their community by participating in this long-term monitoring effort. 

First and foremost, monitoring biotoxins helps keep shellfish a safe and accessible food resource for Puget Sound communities. In addition, robust monitoring efforts, led by volunteers, help us understand how biotoxin events are changing over time, as climate, land use, and development alter environmental conditions. 

Worldwide, we’re seeing an increase in harmful algal blooms.¹ There is evidence that in Puget Sound, these blooms (specifically Alexandrium spp. blooms, the microscopic algae that can produce paralytic shellfish toxins and cause paralytic shellfish poisoning), are occurring earlier in the year than in the past.²³. Although it is difficult for researchers to disentangle the effects of climate change on harmful algal blooms from other human-caused changes, like excess nutrient run-off, it is likely that climate change is influencing shifts in harmful algal bloom dynamics.⁴ Ongoing monitoring efforts help scientists build our understanding of these long-term trends and changes in biotoxin levels in shellfish. 

A bucket full of recreationally-harvested Manila clams. Credit: Gray McKenna