PS-AHAB (Puget Sound Alexandrium Harmful Algal Blooms) is a component of the NOAA ECOHAB program, focused on modeling favorable habitat areas for Alexandrium catenella in Puget Sound and evaluating the effects of climate change.

The dinoflagellate Alexandrium catenella produces a suite of potent neurotoxins, collectively known as paralytic shellfish toxins (PSTs), which accumulate in shellfish and cause severe illness or death if contaminated shellfish are consumed by humans. Alexandrium catenella form dormant cysts that overwinter on the seafloor and provide the inoculum for toxic blooms the following summer when conditions become favorable again for growth of the motile cell. A 2005 survey of A. catenella cyst distribution in Puget Sound, Washington, identified “seedbeds” with high cyst abundances that correspond to areas where shellfish frequently attain high levels of toxin. However, even at these sites, interannual variability in the magnitude of toxic events is high. In order to provide advanced warning of A. catenella blooms, managers need to know how much “seed” is available to initiate blooms, where this seed is located, when/where this seed could germinate and grow, and how these factors could be altered by future climate change.