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  • The Ecophysiology and Toxicity of Heterosigma akashiwo in Puget Sound: A Living Laboratory Ecosystem Approach


Northwest Fisheries Science Center (NWFSC) Environmental and Fisheries Sciences EFS - Marine Microbes and Toxins


The Ecophysiology and Toxicity of Heterosigma akashiwo in Puget Sound: A Living Laboratory Ecosystem Approach
Over one half of the worlds fish production for human consumption currently comes from aquaculture, while wild fisheries yields are either stable or declining. Recurring threats from the raphidophyte, Heterosigma akashiwo Hada (Sournia) have caused extensive damage ($2-6 million per episode) to wild and net-penned fish of Puget Sound, Washington, and are believed to be increasing in scope and magnitude in this region, and elsewhere in the world over the past two decades. The mechanism of H. akashiwo toxicity is not well understood. The toxic activity of H. akashiwo has been attributed to the production of reactive oxygen species, brevetoxin-like compound(s), excessive mucus, or hemolytic activity; however these mechanisms are not confirmed consistently in all fish-killing events or cultured strains. The difficulty of conducting research with active, toxin-producing field populations of H. akashiwo have resulted in conflicting findings from those obtained in lab culture studies, thereby limiting the ability of fish farmers to respond to these episodic blooms. Collaborators in this project are: Vera Trainer (NWFSC), William Cochlan (San Francisco State University), Charles Trick (University of Western Ontario), and Mark Wells (University of Maine). The overall goal of this project is to identify the primary toxic element and the specific environmental factors that stimulate fish-killing H. akashiwo blooms, and thereby provide managers with the fundamental tools needed to help reduce the frequency and toxic magnitude of these harmful algal events. Studies to date have provided incomplete and conflicting observations on the mode of toxicity and the environmental stimulation of toxification. We propose a three-pronged approach to study the environmental controls of H. akashiwo growth and toxin production; laboratory culture experiments, field observations, and bottle and mesocosm manipulation experiments.The project objectives are to: 1. identify the element(s) of toxic activity (inorganic, organic, or synergistic) associated with blooms of H. akashiwo and the various cellular morphologies of this alga, 2. determine the environmental parameters that stimulate the growth success and expression of cell toxicity in the H. akashiwo populations of Puget Sound. Because previous studies have used H. akashiwo cultures with little or no toxic activity, our approach is to use a living laboratory to study H. akashiwo bloom ecology and toxicity using natural assemblages. Using a mobile lab at field sites where H. akashiwo cells are regularly found will enable us to fully characterize the toxic element(s) responsible for fish mortality, and the environmental factors influencing toxicity. Findings from annual field studies in June and two rapid response deployments during major bloom events will be confirmed using laboratory studies with fresh ( 6 mo. old) isolates. The expected results are: 1. determination of the key elements of toxicity of H. akashiwo, 2. characterization of the environmental variables that influence either the induction or depression of elements of toxic activity in H. akashiwo, 3. characterization of environmentally-induced metabolites corresponding to condition of toxin production (metabolomics) and 4. design of a strategy for realistic mitigation of H. akashiwo activities in Puget Sound, Washington. This is a stand-alone project funded for 3 years through the NOAA/NSF ECOHAB program.

Research Themes

Sustainable, safe and secure seafood for healthy populations and vibrant communities
Effective fisheries management provides economic opportunities and ensures the long-term sustainability of fisheries and the habitats on which they depend. The NWFSC seeks to improve the quality and quantity of data used in stock assessments, the methods for assessing stocks and ecosystem sustainability within the context of human modification of the environment. The NWFSC also provides state-of-the-art science and technology to support aquaculture while protecting and maintaining ecosystem health. Further, pathogens, toxins from harmful algal blooms (HABs), chemical contaminants and other stressors of marine ecosystems pose significant risks to health of both seafood resources and to humans. The NWFSC focuses on research to improve understanding of those risks, how to forecast them, and identify means to mitigate their impacts.

Research Foci

Provide scientific support to ensure safe seafood for healthier populations and characterize how human activities and climate affect risks from pathogens, chemical contaminants, and biotoxins
The availability of nutritious and safe seafood from marine ecosystems and aquaculture are essential to maintain and maximize human health. Even though fish are known to have a variety of health benefits, some seafood (wild or farmed) may contain levels of toxic compounds (e.g., chemical contaminants, pathogens, biotoxins) from a variety of human-related and natural sources that can pose health risks to humans, especially for those groups with high rates of seafood consumption. The development of novel methods and technologies to assess seafood safety and biological effects of these toxic compounds remains a priority for commercial, subsistence and recreational consumption of seafood. For example, several species (e.g., zebrafish, sea lions, shellfish) are excellent indicators of environmental stress and potential health threats to marine species and humans. These species can serve as informative animal models for investigations of the mechanisms of toxicity or disease processes. Specific research goals include (1) improve methods for monitoring for the presence of pathogens, toxins and contaminants in seafood products, (2) characterize the environmental and climate conditions that may be favorable for potential biotoxin and pathogen outbreaks, (3) develop technologies to remove chemical contaminants from fish feed and to enhance the nutritional content of aquaculture products, (4) develop a better understanding of the net economic and health benefits of seafood consumption balanced with the risk of exposure to pathogens, toxins and contaminants, and (5) develop new mechanistic animal models for the study of infectious diseases, as well as toxicological, physiological, and biochemical processes relevant to marine animal and human health.
Support collaborative community-based data collection, dissemination, and analysis for fishers, fisheries management, science, marketing, seafood safety, and education
Data are no longer the sole province of the agency. As technologies advance, fishers are collecting and analyzing fleet data in near real time. Data collected by fishers are used by the fishing community to reduce bycatch, allocate fishery impacts, and trace products through the processing and marketing system. Fisher-collected data, in combination with survey and oceanographic data, satellite remote sensing, economic data, and sociocultural data provide improved understanding of fish stocks, fishing, and the near-shore ecosystem. Collaborative efforts increase the quantity and quality of data available to the agency for scientific analysis, modeling, fishery management, and conservation. Through cooperation with the science and management agencies, the fishing community stands to gain more control and flexibility of their fishing operations, including the potential for improved economic efficiency. Increased availability of fisheries data creates opportunities for education and outreach both in the school system and to the general public. Further, well-informed local leaders conversant in the latest fishery issues will help garner local support and fisher buy-in for improved information sharing. The NWFSC will work with industry groups to improve distributed data collection, compilation, and distribution for multiple uses in fisheries, management, science, marketing, and education.


marine toxin
toxins produced by certain species of marine phytoplankton


Determine the environmental factors promoting toxicity in Heterosigma to allow forecasting of blooms
Determine the toxin produced by Heterosigma to allow tracking of blooms threatening fish farms
Research paper in special issue on HABs in Stratified Systems


Species Heterosigma akashiwo


Bich-Thuy Eberhart
Brian Bill
Nicolaus Adams
Vera Trainer
Principal Investigator