Date of Award
Level of Access
Doctor of Philosophy (PhD)
Ecology and Environmental Sciences
Second Committee Member
Third Committee Member
Additional Committee Members
Climate change is affecting lake systems throughout the world, including Lake Superior, the world’s largest lake by surface area. Climate-driven physical changes in Lake Superior are well documented, but there is still substantial uncertainty of how recent biological changes are related to climate change. This research addresses these uncertainties using a variety of approaches to understand the effects of modern climate-driven changes on Lake Superior diatom communities. First, I developed models for environmental variables related to diatom abundance using 10 years of summer monitoring data. Second, I investigated changes in fossilized diatom relative abundances before, during, and after the Medieval Climate Anomaly (MCA, 950-1250 CE), a past period of warming with minimal anthropogenic impact. This is compared with sedimentary diatoms from the past two centuries. Third, I compared changes in fossilized diatom relative abundances before, during, and after the MCA with changes occurring throughout the same period in a smaller regional lake to investigate the relationship of lake size to diatom community resilience in Lake Superior.
Modern abundance patterns of Cyclotella sensu lato species, a dominant group of centric planktonic diatoms in Lake Superior, are complex, associated with multiple environmental variables, and suggest synergistic effects of nutrients and, in some instances, climate-driven physical change. Paleolimnological data from fossilized diatoms suggest that multiple variables including climate change, iv as well as anthropogenic activities that alter nutrient cycling, are leading to novel shifts in modern diatom communities. Diatom shifts the past century have no analogue to past warming during the MCA, with no significant shifts in the diatom community occurring throughout the MCA. Diatom communities did shift during the MCA in a smaller, regional lake, suggesting the importance of lake size in mediating diatom community response to climate-driven change.
The more we understand the effects of climate change on lake ecosystems, the better we can protect and manage our drinking water and aquatic ecosystems. However, climate change is a complex, political, and polarizing topic; therefore, the American public has varying beliefs and values relating to climate change, making management of environmental issues relating to climate change especially difficult. Formal public education may be the best route to create an informed and engaged public. I investigated various aspects of climate change education in Maine middle and high schools via an online teacher survey. The survey assessed frequency and breadth of climate change topics in classes, teacher attitudes towards climate change and climate change education, knowledge level of various climate topics, and barriers to effective teaching.
Maine teachers address climate change across a wide variety of subjects, viewing climate change as a major concern and an interdisciplinary subject that should be taught more frequently and broadly. Teachers from multiple disciplines are interested in professional development around climate change education and identified barriers that could lessen effective teaching such as knowledge gaps, outside pressure, and fear of scaring students. Survey results informed suggestions to enhance climate education, such as targeted professional development, strengthening interdisciplinary links, and providing solutions and adaptation strategies.
Kireta, Amy, "Deciphering Climate-Driven Changes in Planktonic Diatom Communities in Lake Superior" (2018). Electronic Theses and Dissertations. 2833.