Date of Award

2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Natural Resources

First Advisor

Ana M. Morales

Abstract

Lakes are excellent early indicators of environmental change on a landscape scale. Due to their connectedness in the landscape, any alteration of land-cover extends beyond a single watershed and can only be amplified by the effects of climate change. These processes can reflect differently across lakes of various characteristics, however, combined, they can leave a lasting impact on biogeochemical processes of a lake, resulting in profound effects on biological communities residing in it. Lake sediments are terrific archives that integrate and preserve this evidence, which then allows us to investigate the extent to which a lake has changed given its current state. Akin to regional patterns, Vermont lakes have been undergoing notable increases in nutrient levels, browning, and surface water warming. Understanding changes that took place in Vermont lakes over the last ~200 years requires a proxy-based approach.We analyzed top and bottom sediment samples from over a hundred Vermont lakes to be able to address the anthropogenic impact more confidently on these lakes. In our transfer-function development, we found that total phosphorus has an important impact on modern diatom communities in Vermont lakes, however, both TP and pH show promise in being used as a part of the Vermont-specific transfer function. A reconstructed pH for Beaver Pond is congruent with the idea that the biological recovery often lags behind chemical recovery. Furthermore, our exploration of the diatom-community differences between past and modern communities revealed that this approach should be used with caution if applied across lakes of various differing depths. We found that a significant difference between the two communities exits only in deep lakes. Indicator species of change in modern lake sediments were associated mainly with climate-related stressors, ice cover and water column stability, while some species indicated nutrient enrichment. In conclusion, our results highlight the importance of understanding the environmental-gradient dependent response of lakes to the interaction of multiple stressors.

Language

en

Number of Pages

84 p.

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