Date of Award


Publication Type


Degree Name



Great Lakes Institute for Environmental Research


Ecotoxicology, Gene expression, Harmful algal blooms, Microcystis aeruginosa, Oncorhynchus mykiss, Cyanobacteria







Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


Current trends in cyanobacterial harmful algal blooms (cHABs) demonstrate increasing risks to human health and the health of aquatic ecosystems around the globe. Expansion of algal blooms, both geographically and temporally, serve to place increasing numbers of freshwater species, including fish, in peril. Microcystis aeruginosa, one of the most common species of bloom-causing cyanobacteria, is capable of producing a vast diversity of biologically active compounds, however Microcystis studies are often dominated by microcystins. How non-microcystin metabolites contribute to Microcystis toxicity, particularly in freshwater fish, has been the subject of a limited, but growing, body of research. To contribute to the bridging of this knowledge gap, my thesis examined the effects of extracellular metabolites produced by M. aeruginosa on in vitro fish cell lines derived from multiple tissues of the freshwater salmonid rainbow trout (Oncorhynchus mykiss), incorporating not only changing metabolite production over the lifespan of a bloom, but also toxicity in the absence of microcystins. I found that non-microcystin-producing strains of M. aeruginosa, commonly referred to as ‘non-toxic,’ were capable of producing and releasing metabolites that significantly reduced the viability of cell lines derived from the brain, gills, and milt of fish. Impairment of reproduction can seriously impact the sustainability of a population. In examining the effects of ‘non-toxic’ extracellular metabolites on gene expression, I found that these cyanobacterial mixtures were able to dysregulate genes associated with reproduction and steroidogenesis in brain and gonadal tissue-derived cell lines. While the correlation between in vitro cytotoxic and sub-lethal effects and in vivo ramifications requires further investigation, overall, this thesis highlights the need to integrate non-microcystin metabolites into risk assessments for freshwater systems and fish species impacted by Microcystis algal blooms.