Date of Award

Spring 5-11-2019

Level of Access Assigned by Author

Open-Access Thesis

Language

English

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Jasmine Saros

Second Committee Member

Hamish Greig

Third Committee Member

Michael Kinnison

Additional Committee Members

Christopher Osburn

Jeffery Stone

Abstract

Dissolved organic carbon (DOC) is an important component of lake ecology, as it contributes to light attenuation and carbon cycling. In recent years, DOC declined in a suite of lakes in Greenland. I performed experiments to test potential mechanisms of DOC loss. The tested mechanisms did not reduce DOC concentration, but DOC composition was affected. I also paired water quality data with meteorological observations to evaluate effects of climate drivers on lake variables. The lake variables were temporally coherent and associated with patterns of mean annual precipitation.

In the northeastern U.S., recovery from acidification and climate change have contributed to lake brownification. I used paleolimnological techniques to compare algal responses of a clear lake versus a brown lake to multiple drivers in Acadia National Park. My results suggested that algae in the clear lake were more sensitive to light, while the primary control in the brown lake was loss of nutrient subsidies from allochthonous DOC. Both lakes exhibited signs of recovery toward pre-acidification conditions, although this response appeared dampened in the clear lake.

My dissertation research highlighted complex controls of DOC in Arctic lakes and clarified associations between climate drivers and lake variables important for carbon cycling and light attenuation. I also found key differences in algal dynamics in a clear versus a brown lake in Maine in response to multiple environmental drivers. With abrupt climate change in the Arctic and increasing brownification of boreal lakes, my research introduces timely new insights on the effects of these drivers on carbon cycling and algal ecology in Arctic and boreal lakes.

As part of the Integrative Graduate Education and Research Traineeship (IGERT) Collaborative Immersion Project (CIP), I studied temperate Australian lakes in contrast to my focal work in Arctic and boreal systems. Ongoing drought threatens water resources in southeast Australia, many of which experience harmful algal blooms (HABs) rendering them unusable. I used paleolimnological methods to investigate HAB occurrence in a century-long record in two deep lakes. HAB development was likely driven by drought, so seasonal HABs may become a permanent fixture in the HAB-affected lake, as drought intensifies in coming decades.

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