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Modeling Favorable Habitat for Alexandrium catenella in Puget Sound

This project began in January 2010 and was completed in December 2013

In Puget Sound, the toxic alga Alexandrium catenella threatens people who eat shellfish contaminated with the algal toxin. Previous studies identify “seedbeds” of Alexandrium resting stages (cysts) on the bottom near areas where shellfish frequently attain high levels of toxin. We will map the distribution of cysts and evaluate areas favorable for Alexandrium cyst germination and cell growth. Models will predict when and where toxic blooms occur, both now and in response to climate change.

Why We Care
The toxic planktonic dinoflagellate alga Alexandrium catenella produces a variety of potent neurotoxins that accumulate in shellfish and cause severe illness or death if humans consume contaminated shellfish. A. catenella forms dormant cysts that overwinter on the seafloor. When conditions are right the following summer, the cysts, like seeds, germinate; the motile cells swim to the surface and grow, leading to another bloom. 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, and when and where this seed could germinate and grow. Evaluating how favorable habitat areas for cyst germination and vegetative growth are altered by climate change will allow for risk assessments of A. catenella blooms for decades to come.

What We Are Doing
Annual cyst surveys were conducted at about 100 stations throughout Puget Sound and in the Strait of Juan de Fuca to determine inter-annual variations in cyst distributions. Researchers are studying cyst germination and vegetative growth under a range of temperature, salinity, and light conditions, to determine the existence of an internal biological clock. A model is in development to predict the most favorable habitat areas for cyst germination and vegetative growth for providing both seasonal forecasts of toxic blooms and assessment of the longer term influence of climate change.

This project is part of the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) program. The multi-institutional project team is led by Dr. Stephanie Moore from the NOAA Northwest Fisheries Science Center (Seattle, Washington), and include investigators from the Woods Hole Oceanographic Institution (Massachusetts) and the University of Washington (Seattle and Tacoma).

Benefits of Our Work
The expected benefits of this project include the production of maps indicating favorable habitat areas for A. catenella in Puget Sound for present day conditions and the future under a warmer climate. These maps will be used by shellfish farmers and managers to guide harvesting and monitoring practices and location of new shellfish farms. On August 18, 2010, investigators held a day-long workshop to introduce this project to stake holders and seek their input. They suggested additional sampling stations to improve modeling and to provide information in areas where researchers anticipated new mariculture activities.

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