Date of Award

Summer 2022

Project Type

Thesis

Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Jessica Ernakovich

Second Advisor

Serita Frey

Third Advisor

Ruth Varner

Abstract

Arctic systems are experiencing warming at more than twice the rate of the global average, causing permafrost—permanently frozen soil—to thaw. Permafrost thaw exposes previously unavailable soil carbon and nutrients to decomposition—a process mediated by microbes—which releases greenhouse gases such as carbon dioxide and methane into the atmosphere. Permafrost is thawing at an accelerated rate, and while there is evidence that the composition and function of the permafrost microbiome changes with thaw, there is still much unknown about the taxa that increase with thaw, particularly among different types of permafrost. Here, I address how permafrost thaw impacts the microbiome, particularly the taxa that respond positively to thaw by increasing in abundance, and abiotic characteristics via a permafrost microcosm incubation using samples from three different field sites. Post-thaw microbial abundance, measured as gene copy number, was positively correlated with cumulative respiration while pre-thaw abundance was not, suggesting an increase in abundance post-thaw and therefore an increase in microbial activity. Microbial diversity decreased with thaw across all sites, supporting that permafrost thaw creates a stressful environment. Microbial thaw response was assessed in taxa across sites and yielded a number of positive thaw responders (i.e., those that increased in their relative abundance with thaw) including members of Actinobacteria, Firmicutes, and Bacteroidetes. Understanding how permafrost thaw affects the permafrost microbiome and abiotic conditions will allow us to better understand the impacts of climate change on Arctic ecosystem structure and function.

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