Date of Award:

12-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Erin Rivers

Committee

Erin Rivers

Committee

Michelle Baker

Committee

Karen Beard

Abstract

Globally, saline lakes are experiencing declining water level as a consequence of climate change, water diversions for human consumption, and management strategies that do not account for changing climate and drought conditions. Great Salt Lake (GSL) is a large saline lake in Utah, USA, and is, as most saline lakes, experiencing decreasing lake levels which may impact local carbon cycling. It is unknown how lakebed drying affects processes that control carbon sequestration and carbon emissions to the atmosphere. The goal of this research was to measure various biological processes that use, create, and transform carbon in GSL to understand the impacts of declining lake levels on carbon in this ecosystem Gross primary production (GPP) and respiration (R) are processes within the lake and lakebed sediments, performed by plants, algae, and microorganisms, that use and create oxygen and carbon for energy. Gross primary production (GPP) uses carbon dioxide to create oxygen and organic carbon, while respiration (R) uses oxygen and organic carbon to create carbon dioxide. To determine how the total consumption and production of carbon within the lake is affected by lake level decreases, GPP and R were measured in GSL in 2020 and 2021, during which time lake levels decreased more than .8 m. Measurements showed that GPP and R were very different across regions of GSL. Results showed that there was more R than GPP in both years, indicating that there was a net creation of carbon dioxide by organisms in the lake. Gross primary production and R decreased from 2020 to 2021 due to the large decrease in lake levels. Carbon dioxide emissions from exposed lakebed sediments were also measured in 2020 and showed that there were high levels of carbon dioxide released from sediments during summer months and lower levels released during winter months. Carbon dioxide emissions from the sediments were controlled by the amount of moisture in the sediments and by temperature, indicating that emissions were low in very dry or very wet sediments and lower during cold weather. This research show that there are important changes in the GSL ecosystem as lake levels decrease. Future research should investigate patterns in how organisms use, create, and transform carbon change around the lake and what this means for future changes in GSL.

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