Have you gone to your favorite beach and seen this sign? Did you get a recent notification from Island County Public Health about a “Biotoxin Closure”.
Washington Department of Health (WDOH) regularly monitors beaches in Puget Sound to test for biotoxins in shellfish.
The biotoxins are produced by certain phytoplankton and can accumulate in shellfish as they feed on phytoplankton. Human health is at risk when we eat toxin-containing shellfish (mussels, clams and oysters). WDOH closes a beach for shellfish harvesting when the toxin levels in shellfish can be harmful to human health.
The recent biotoxin closure was due to Alexandrium (shown at left), a dinoflagellate (phytoplankton) that produces toxins responsible for paralytic shellfish poisoning. PSP affects the nervous system and can be life-threatening. A large increase in phytoplankton abundance is called a bloom. When a bloom is harmful to humans or other marine life it is referred to as a Harmful Algal Bloom (HAB).
Note that the biotoxins are not destroyed by cooking,
Sound Water Stewards monitor year-round for toxin-producing phytoplankton through Sound Toxins, a Washington Sea Grant program. Using a microscope, we count the potentially harmful phytoplankton present at Camano Island State Park and upload to a regional database. Conditions can change rapidly. We didn’t count any Alexandrium at a monitoring in mid-July but the next week we counted 281 cells/liter. Sound Toxins is an early warning system for a phytoplankton bloom.
Puget Sound’s coastline is about 1332 miles. That’s a lot of beaches for the WDOH to keep safe! Several homeowners in Island County regularly send the WDOH mussels to test for biotoxins.
A beach may reopen for some shellfish but remain closed for others, like butter and varnish clams, that retain the toxins longer. Always check the WDOH Shellfish Safety Map for the status of a beach. Sound Water Stewards of Island County sponsored a lecture by Jerry Bourchert , WDOH, on Digging for Dinner Safely and Understanding Beach Closures for Shellfish Harvesting
–Paulette Brunner, SWS Class of 2010, Sound Toxins team member
