Emergency Response Mapping of Alexandrium Cysts in the Surface Sediments of Hood Canal WA

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Conference Proceeding


In September and October 2014, an unprecedented bloom of Alexandrium occurred in Dabob and Quilcene Bays, Hood Canal, WA. This area, and southward through Hood Canal, was historically biotoxin free. At the peak of the event, toxin levels in shellfish reached 12,688 μg STX equiv. per 100 g shellfish tissue, more than 150 times the regulatory limit for human consumption. It is not known what caused the bloom, or if the conditions that gave rise to the event will happen again. Nevertheless, concern remains over the increased risk for future blooms because Alexandrium species produce resting cysts that overwinter on the seafloor and can germinate the following season providing the inoculum for more blooms. In response, we conducted an emergency cyst survey throughout Hood Canal in January 2015 to determine if the area had been “seeded” with Alexandrium cysts. Prior cyst mapping efforts from 2011-2013 found zero or very low (5-10 cysts per cc wet sediment) concentrations of cysts throughout Hood Canal. In January 2015, up to 120 and 180 cysts per cc wet sediment were observed in Quilcene Bay and Dabob Bay, respectively, indicating that a new Alexandrium seed bed formed in the area following the 2014 bloom. In 2015, increased vigilance and monitoring by the Washington State Department of Health and the SoundToxins Program provided early warning of a toxic bloom of Alexandrium in April. This toxic event spread throughout Hood Canal over the summer, resulting in shellfish harvesting closures in this area for the first time. Another cyst survey in January 2016 will determine whether the distribution and abundance of Alexandrium cysts in Hood Canal has increased, and will provide human health officials, marine resource managers and shellfish growers with updated maps of newly established cyst beds. The results of all surveys will be presented here.

Publication Title

Harmful Algal Blooms (HABs) and Marine Pathogens in a Changing World

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