Date of Award

Summer 8-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Jasmine Saros

Second Committee Member

Jacquelyn Gill

Third Committee Member

Amanda Klemmer

Abstract

Even with similar external drivers, lakes can respond differently because of key ecosystem features that determine lake sensitivity. Identifying factors that determine lake sensitivity are important for successful lake management. The purpose of this research was to determine patterns of algal community change over the past 400 years in lakes with watersheds that vary in surficial geology, specifically the glacio-marine clay layer in Maine known as the Presumpscot formation. Responses to two external drivers, major land use changes and climate change, were assessed. Four lakes were chosen based on their surficial geology and land use history: Unity Pond, Webber Pond, Highland Lake, and Long Lake. Unity and Webber ponds are located on the marine clay layer, while Highland and Long lakes are not. Due to poor diatom preservation and constrained access to the core in recent months, results for Webber Pond are not included here. Unity Pond had higher relative abundances of nutrient-indicating diatoms prior to land use changes compared to the other two lakes. Unity Pond was more sensitive to land use change than Highland and Long lakes, which could be due to disturbance of nutrient-rich soils releasing more P into the lake. In contrast, Highland and Long lakes had no major changes in the sedimentary diatom or pigment profiles following land use change, but did change in the early 20th century, corresponding to warming climate. The results suggest that the more productive lake was more sensitive to major land use changes, whereas the less productive lakes appeared more sensitive to climate change. This work can be used to gauge sensitivity of lakes to external drivers based on key ecosystem features, to inform management decisions in the future.

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