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Ecophysiology and Toxicity of the Toxic Alga Heterosigma akashiwo in Puget Sound: A Living Laboratory Ecosystem Approach

This project began in January 2010 and was completed in December 2014

We are identifying toxins and environmental factors causing fish-killing blooms by the alga Heterosigma akashiwo in Puget Sound. We develop tools to improve monitoring, early warning, and mitigation to prevent or reduce impacts on fish farms using measurements in the field and on samples grown in a mobile “living” laboratory. End user groups, such as fish farmers and fish farming advisors, collaborate closely as an integrated team with Puget Sound and Canadian monitoring programs.

Why We Care
Over one half of the world’s fish production for human consumption currently comes from aquaculture while wild fisheries yields remain stable or decline. The raphidophyte-type alga, Heterosigma akashiwo, has caused recurring, extensive mortality of wild and net-penned fish in Puget Sound, Washington and adjacent Canadian waters. Individual events can result in $2–6 million in losses for mariculture, especially of salmon. Scientists believe these episodes are increasing in scope and magnitude in the Puget Sound region and elsewhere in the world over the past two decades.

Fish farmers suffer from the unpredictable nature of harmful H. akashiwo blooms. Currently, they routinely monitor for Heterosigma cells, but blooms can appear very quickly with little warning. Not all blooms are toxic, but because the toxin has not been identified, it is impossible to monitor for toxicity. Finally, it is difficult to develop appropriate mitigation strategies when so little is known about the toxin. The ability to monitor for toxic blooms and understand the conditions that lead to toxic blooms so that effective and timely mitigation strategies can be implemented will insure a safe and economically sustainable finfish aquaculture industry.

What We Are Doing
The mechanism of H. akashiwo toxicity is unknown although a number of potential mechanisms have been proposed. The problem: it is difficult to study mechanisms of toxicity in the field and laboratory cultures appear to lose their toxicity. Similarly, the environmental conditions that foster the growth and initiate the toxicity of H. akashiwo are not well understood.

The project will identify the toxin and determine the environmental factors that stimulate the growth and toxicity in the H. akashiwo populations in Puget Sound. Because previous studies have used H. akashiwo cultures with little or no toxic activity, this approach uses a “living laboratory” to study bloom ecology and toxicity in natural assemblages. Stationing a mobile lab at field sites where researches normally find H. akashiwo cells prevents the loss of toxicity that occurs when cells are taken out of their natural environment. This project is part of the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) program. The project leader is Dr. Vera Trainer, NOAA Northwest Fisheries Science Center, Seattle, Washington.

The project is led by Dr. Vera Trainer of the NOAA National Marine Fisheries Service Northwest Fisheries Science Center in Seattle, WA. Project partners include William Cochlan of  the Romberg Tiburon Center for Environmental Studies, San Francisco State University; Mark Wells of the University of Maine; Charles Trick of the Western University, Ontario, Canada; Chris O. Miles, National Veterinary Institute, Oslo, Norway; Jack Rensel, Rensel Associates Aquatic Sciences; Kevin Bright, America Gold Seafood, and the Canadian Harmful Algal Monitoring Program.

Benefits of Our Work
We are determining how H. akashiwo kills fish and developing methods of measuring toxicity suitable for use in routine monitoring, characterizing the environmental conditions that influence the growth and toxicity in H. akashiwo, and lastly, designing a strategy for predicting and mitigating the impacts of H. akashiwo blooms in Puget Sound.

During the summer of 2012, we collaborated on a test of an Environmental Sample Processor (ESP) for remote, in water, detection of H. akashiwo as well as other HAB species. At Friday Harbor Laboratories workers deployed the instrument from the dock where they conducted field work for this project; they made daily measurements of cell counts for a month. H. akashiwo was always present at low levels, but they also observed a bloom at fish-killing levels and fish farmers were notified.

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