Toxins close Island County clam harvest

Two years after an algae bloom containing paralytic shellfish poison, recent samples revealed high levels of toxins are still present in Island County butter and varnish clams. More than a dozen beaches remain closed to harvest.

When a paralytic shellfish poison bloom occurs, shellfish can suck in the algae and retain the poison. Humans who eat shellfish contaminated with the toxins may experience muscle paralysis, severe illness and death.

West Whidbey Island, Port Susan, Saratoga Passage, Penn Cove, Holmes Harbor, Utsalady Bay and Possession Sound are all closed to butter and varnish clam harvest. The initial bloom occurred in August 2021, and the current closures were put in place that October.

Harvest closure signs are posted at public beaches throughout Island County. Current biotoxin closures are listed on the Washington Shellfish Safety Map.

Commercially harvested shellfish sold in grocery stores and served in restaurants are tested for toxins prior to distribution and are safe to eat, according to the state Department of Health.

The state monitors toxins in shellfish every other week. If toxins are detected, the testing frequency is increased. The Department of Health tested butter clams from around Island County over the last few weeks and those tests continue to show high levels of toxins.

Butter and varnish clams clear toxins from their tissues, but slowly: For paralytic shellfish poison, studies estimate butter clams release the toxin at a rate of less than 1% per day. The time it takes is dependent on the maximum levels of the toxin in the clams during the bloom.

The maximum level of paralytic shellfish poison found in shellfish during the 2021 bloom was 3,723 micrograms for every 100 grams of shellfish tissue.

The federal action level is equal to or greater than 80 micrograms paralytic shellfish toxins per 100 grams shellfish tissue.

Warming marine temperatures as a result of climate change have been found to increase the transmission of disease in marine life. In 2021, a large ridge of high atmospheric pressure trapped hot air over the region and brought unprecedented temperatures to the region. The so-called “heat dome” caused a massive shellfish die-off.  

The state Department of Health does not suspect the heat dome had an influence on the 2021 biotoxin-producing algal blooms. However, it did lead state officials to urge people not to eat locally harvested clams or oysters because of an outbreak of vibrio bacteria. The bacteria can multiply in warm waters.

Symptoms from ingesting paralytic shellfish poison may take minutes or hours to appear, usually starting with tingling lips and tongue and moving into hands and feet. The poison can cause difficulty breathing and death. Anyone experiencing these symptoms should contact a health care provider or call 911. 

There is no antidote. Those who ingest toxic shellfish must wait for the toxins to naturally flush from their body.

The toxins cannot be killed off by cooking or freezing shellfish.