MS Thesis Defense
M.S. Student, Water Resources Science
November 14, 2018
Understanding the composition, distribution, and primary drivers behind cyanobacterial harmful algal blooms in Minnesota lakes
Algae in lakes are incredibly important, but sometimes proliferate rapidly into visible accumulations (blooms) that can create detrimental ecological, public health, and/or socioeconomic impacts. Several potentially-toxic species of cyanobacteria form the most common and noxious type of harmful algal blooms (cyanoHAB's), There has been a documented increase in cyanoHAB's in lakes with differing characteristics across the globe, which has been broadly attributed to the compounding forces of anthropogenic climate change and cultural eutrophication (nutrient over-enrichment). Despite this, we still know very little about the environmental, physical, chemical, and/or biological drivers that regulate the development, proliferation, and senescence of cyanobacteria across spatial and temporal scales. We sampled six Minnesota lakes representative of lakes within Minnesota's broad ecoregions throughout the summer growing season in 2016 and 2017. We characterized the phytoplankton (unattached algae) communities in each lake and among other physical and temporal groups, and finally quantified the primary drivers behind the observed cyanobacterial dynamics. Cyanobacteria were dominant in all lakes, although their community composition differed greatly between groups. Potentially-harmful cyanoHAB conditions were observed in each study lake at least once, although lakes further south experienced increased incidence and risk. Finally, while the drivers behind cyanobacterial proliferation differed between groups, an overall model was developed to predict toxic cyanoHAB conditions across Minnesota.