Date of Award
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Natural Resources
First Advisor
Ana M. Morales-Williams
Abstract
Cyanobacteria blooms are one of the greatest threats facing lake ecosystems, as their proliferation can cause significant negative ecological, societal and economic impacts. Cyanobacteria blooms are commonly associated with loss of species diversity, provide poor food quality for higher trophic levels, and can cause anoxia leading to unsuitable habitats for aquatic organisms. Cyanobacteria blooms pose a significant human health risk, in part due to the suite of toxic secondary metabolites (cyanotoxins) produced by some species of cyanobacteria. Cyanotoxins are known to be harmful to both humans and animals, frequently cause skin irritations, neurologic disorders, gastrointestinal issues, and in severe cases, death. Given these impacts, it is imperative to further understand the drivers of cyanobacteria blooms, why cyanobacteria produce cyanotoxins, and how climate change will influence cyanobacteria community assembly and phenology.
In this dissertation, I specifically address three questions regarding cyanobacteria blooms and cyanotoxin production: 1) How can ecological stoichiometry explain cyanobacteria bloom phenology and toxin production? 2) Which cyanobacteria have the ability to produce cyanotoxins in Lake Champlain and how does their abundance vary with non-toxic species? And 3) How do extreme climatic events impact cyanobacteria bloom phenology? To address these questions, my research integrates five years of high frequency monitoring with weekly discrete sampling campaigns and metagenomic approaches.
In Chapter 2, my research demonstrates that cyanobacteria biomass and toxin concentrations do not always scale together, and that Lake Champlain blooms remain low in toxin concentration when dominated by Dolichospermum spp. I also examine the drivers of differences in bloom severities between Missisquoi Bay and St. Albans Bay and highlight that microcystin production may be constrained to low carbon:nitrogen ratios. In Chapter 3, shotgun metagenomics revealed that in 2023, Microcystis spp. were the only microcystin producers at Burlington Beach sites, and the only recorded bloom followed a late summer heatwave. In Chapter 4, I identify that cyanobacteria phenology is impacted by extreme heat waves and high flushing events, and is mediated by lake conditions at the time of the event and nutrient concentrations. We suggest that heatwaves and flushing events could further exacerbate cyanobacteria blooms in Missisquoi Bay, but in St. Albans Bay, heatwaves and flushing can cause inhibitory effects on blooms when acting alone. However, compound events (flushing events followed by heatwaves) are likely to trigger cyanobacteria bloom development. These results, when taken together, provide further understanding of cyanobacteria blooms in Lake Champlain, and suggest that climate change will cause increased severity of toxic cyanobacteria blooms.
Language
en
Number of Pages
213 p.
Recommended Citation
Warner, Katelynn Eilene, "Assessing Drivers of Cyanobacteria Blooms, Cyanobacteria Toxin Production and Cyanobacteria Response to Climatic Extremes in Lake Champlain" (2024). Graduate College Dissertations and Theses. 1978.
https://scholarworks.uvm.edu/graddis/1978