Seminar: Dr. Gustaaf Hallegraeff, University of Tasmania

Title: “Global Impacts of HABs and Influences of Climate Change”

Speaker: Dr. Gustaaf Hallegraeff, University of Tasmania

Abstract: Global climate change is adding a new level of uncertainty to many seafood safety and HAB monitoring programs. Increasing temperature, enhanced surface stratification, alteration of ocean currents, intensification or weakening of local nutrient upwelling, stimulation of photosynthesis by elevated CO2, and heavy precipitation and storm events causing changes in land runoff and micronutrient availability may all produce contradictory species- or even strain-specific responses. We can expect: (i) Range expansion of warm-water species at the expense of cold-water species; (ii) Species- specific changes in abundance and seasonal window of growth of HAB taxa; (iii) Increased toxin content of some harmful algal cells; and (iv) Secondary effects for marine food webs, when individual zooplankton and fish grazers are differentially impacted by climate change. Some species (e.g. toxic Alexandrium dinoflagellates benefitting from land runoff and ⁄or water column stratification, tropical benthic Gambierdiscus dinoflagellates responding to increased water temperatures and coral reef disturbance) may become more successful, while others may diminish in areas currently impacted. Carefully designed mesocosm experiments are required with due consideration for the complex multivariate interactive effects on the long-term responses of HABs. Extensive investment in global ocean observation systems, improved ocean sensor capabilities and integrated data management are called for in order to define management options and better forecast risks to human health and seafood safety. The greatest problems for human society will be caused by being unprepared for significant HAB range expansions or the increase of algal biotoxin problems in currently poorly monitored areas.