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Master of Science



Collaborative Specialization

Global Health Systems in Africa


Trick, Charles G.


Harmful Algal Blooms (HABs)—an accumulation of toxic phytoplankton—often result from environmental changes reflecting the increasing global human footprint and climate change. One HAB species drawing attention is Heterosigma akashiwo, a fish-killing flagellate that can cause extensive fish loss or be benign, depending on location or environmental conditions. Here, I investigate if this difference in toxicity is regulated by environmental conditions or differences in cellular physiology. Six strains were examined. Three originate from the Salish Sea, where fish-kills are common, and three from Japan, where blooms of Heterosigma are common but fish-kills are rare. By measuring growth and toxicity of cells grown under two environmental stressors—temperature and salinity—I concluded the low frequency of fish-kills in Japan was due to absence of environmental conditions associated with highest toxic expression. However, reduced temperature conditions, which may occur more frequently with climate change, may stimulate toxicity in Japanese strains.

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