Images of Azadinium by Urban Tillmann Images of Azadinium by Urban Tillmann
Image of Azadinium by B. Krock Image of Azadinium by B. Krock

Phytoplankton of the month — March 2015

Azadinium spinosum

Azadinium spinosum are small dinoflagellates that are 12-16µm long and 7-11µm wide. They have a large posterior nucleus and a single chloroplast. These organisms can be mistaken for Heterocapsa and Scrippsiella. Azadinium produce Azaspiracid (AZA-1) and its derivatives (AZA2-30) causing Azaspiracid Poisoning (AZP) in humans. The first case occurred in the 1990s following an outbreak of human illness associated with ingestion of contaminated shellfish from Ireland. SoundToxins volunteers have been working for many years to find Azadinium in Puget Sound, however this cell can easily pass through a 20 µm-mesh phytoplankton net and must be identified in whole water samples.

Azadinium species, including A. spinosum, A. poporum and A. obesum, were identified at several sites throughout Puget Sound in the summer of 2014 using molecular probes. Low levels of AZA-2 were measured in plankton samples collected from Sequim Bay in the summer of 2012.

For more information see
NOAA’s Azadinium Fact Sheet (

SoundToxins, a diverse partnership of Washington state shellfish and finfish growers, environmental learning centers, Native American tribes, and Puget Sound volunteers, is a monitoring program designed to provide early warning of harmful algal bloom events in order to minimize both human health risks and economic losses to Puget Sound fisheries.

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