Strait a toxic 'hot spot' for shellfish poison source

A new study has revealed the Strait of Juan de Fuca as an incubator for microscopic algae that produces toxic acid that gets into shellfish.

While the toxins can be dangerous, the algae isn't always producing enough to harm living things, making it difficult for shellfish harvest managers to predict for the health of their crop.

But the recently released National Oceanic and Atmospheric Administration study has shed some light on the dark waters at the mouth of the strait where the algae propagates.

The study's findings may help shellfish harvesters have a better idea of when to harvest and when to hold off.

Attacks nervous system

Pseudo-nitzschia is the algae's scientific name and it produces what's called demoic acid, a toxin that attacks the central nervous system.

Sometimes, the algae experiences conditions that make it grow at an exponential rate. It's called an algal bloom. It can happen with many varieties of marine plant life.

But as a result of this bloom, the release of toxic acid also goes up and often causes closures on shellfish harvesting, such as the 2005 closure in Sequim Bay.

"We had an episode with demoic acid here in Sequim Bay more than three years ago, so tracking something like this and keeping tabs on that research is critical for us," said Scott Chitwood, Jamestown S'Klallam Tribe's natural resource director.

New to Puget Sound

"Plus the fact that its detection is new to the Puget Sound, whereas it's been detected on the ocean's coast for 20 years, really makes this research timely."

NOAA teamed with the National Science Foundation to fund the five-year study that took place about 30 miles off the mouth of the Strait of Juan de Fuca. Tests were performed on water that circulates in an eddy at the mouth of the strait. Researchers found the eddy to be a hotspot for the algae's propagation.

"The strait's eddy is a circulating water mass, analogous to a crock pot, incubating these algal cells, getting them ready for deployment after which they can create blooms all along the coast," said Dr. Vera Trainer, lead author of the study and program manager at NOAA's Northwest Fisheries Science Center.

Dan Aires, with the Washington Department of Fish and Wildlife, said he's been looking forward to the results of this study.

Thousands of harvesters

"This will help give us predictability in a subsistence and economic staple of the coastal regions," he said, indicating there can be 20,000 to 30,000 people harvesting on a given day.

In 1987 scientists first made the connection between demoic acid and nervous system problems when a group of 100 people ate mussels contaminated with the poison. Three died, several lost their short-term memories permanently and most were very sick.

Chitwood said that while the eddy may be the source of the algae's early formation, the blooms occur locally and can be fed through a variety of mechanisms.

Other factors

"We have concerns with things like global warming, higher nutrient loads in the water and salinity changes contributing to more frequent blooms in the confined waters of Sequim Bay," Chitwood said.

"These factors don't just encourage Pseudo-nitzschia, they encourage all sorts of toxic blooms, like paralytic shellfish poisoning, or the red tide."

Trainer said the goal of the study is to bring the science and data into real world applications, such as developing a tracking system for toxic algal blooms or, at the very least, the conditions that facilitate the blooms.

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