Date of Award

Spring 2024

Project Type

Dissertation

Program or Major

Earth and Environmental Sciences

Degree Name

Doctor of Philosophy

First Advisor

Ruth Varner

Second Advisor

Virginia Rich

Third Advisor

Lawrence Hamilton

Abstract

Lakes in northern latitudes, especially those formed in peatlands, play a critical role in global carbon cycling. They store a substantial amount of organic carbon (OC) in their sediments but remain a poorly understood component of the carbon cycle. Despite their significance, CH₄ emissions from lakes were once considered negligible in climate models. However, recent studies highlight their substantial contribution, prompting the need for their inclusion in climate models, yet uncertainties persist around the CH₄ contributions from these systems.

This dissertation delves into the microbial controls on CH₄ emissions from arctic lake sediments, focusing on Stordalen Mire in northern Sweden, a unique ecosystem characterized by discontinuous permafrost and a series of post-glacial lakes that span the area. While CH₄ emissions from these lakes have been previously investigated, the microbial controls of CH₄ flux remains poorly quantified, despite a few early studies having identified significant relationships between microbial communities and geochemistry. Through marker gene sequencing, geochemical analysis, and incubation experiments, this research aims to identify key microbial players responsible for mediating carbon transformations in Arctic lake sediments and relevant relationships with geochemistry, thereby helping to improve the accuracy of global carbon models in predicting CH₄ emissions.

Additionally, this research addresses the role of submerged aquatic macrophytes (SAM) in CH₄ emission estimates. SAMs have been shown to significantly influence CH₄ dynamics in freshwater systems. By investigating the relationships between microbial communities associated with SAMs and CH₄ emissions, this research contributes to a deeper understanding of the role of vegetation in the carbon cycle of Arctic lakes.

Furthermore, the dissertation endeavors to bridge the gap between scientific research and Indigenous communities, particularly the Sámi community in the Abisko region. Through a comprehensive survey and data analysis, it uncovers barriers that limit Indigenous Collaborative Research (ICR) by non-Indigenous communities. By actively involving Indigenous communities in the research process, promoting knowledge exchange, and respecting ethical guidelines, this work seeks to empower local communities in the face of climate change and promote climate adaptation solutions in the Arctic.

This research offers a transdisciplinary investigation of the complex interactions between microbial communities, carbon cycling, and CH₄ emissions from northern arctic lakes while highlighting some of the barriers to collaborative and inclusive research practices for the benefit of both science and Indigenous communities working and living in the Arctic, providing some examples of how the microbial analysis may have been improved by using Indigenous Collaborative Research methods.

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