Date of Award

Spring 5-2019

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Jasmine E. Saros

Second Committee Member

Mario F. Teisl

Third Committee Member

Craig E. Williamson

Additional Committee Members

Aria Amirbahman

Kathleen P. Bell

Abstract

In boreal regions, increased precipitation events have been linked to increased concentrations of dissolved organic carbon (DOC), however less is known about the extent and implications of these events on lakes. We assessed the effects of precipitation events on six drinking water lakes in Maine, USA to better understand how DOC concentration and quality change in response to precipitation events. Our results revealed three types of responses: (1) an initial spike in DOC concentrations and quality metrics; (2) a sustained increase in DOC concentrations and quality metrics and; (3) no change during all sampling periods. Lake residence time was a key driver of changes in DOC concentration and quality. For the same set of drinking water lakes, we investigated a link between changes in DOC to a household’s willingness to pay (WTP). Our results revealed that percent change in DOC and SUVA254 correspond to initial Secchi depth values. This relationship was used to determine that WTP from improvement in water quality was highest in lakes with shallower Secchi depths and lowest in lakes with deeper Secchi depths. WTP estimates were also correlated with maximum depth, residence time, and percent of wetland coverage. A set of six lakes in Acadia National Park, Maine were evaluated to assess differences in seasonal storm response. Our results revealed differences in the response of DOC quality metrics to an early summer versus an autumn storm. The response of DOC quality metrics to storms was mediated by differing lake and watershed characteristics as well as seasonal changes in climate such as solar radiation and antecedent weather conditions in the early summer versus autumn. Investigation of the effects of ice-out timing on physical, biological, and biogeochemical lake characteristics in Arctic and boreal regions during an early and late ice-out regime revealed differences in mixing depths and strength and stability of stratification. Key drivers of observed responses included a combination of climate factors, including solar insolation, air temperature, precipitation, and, in the Arctic, permafrost thaw. This research provides important insights that will be useful for management of water resources as temperature and precipitation patterns continue to change.

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