Date of Award

Winter 2023

Project Type

Thesis

Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

Wilfred Wollheim

Second Advisor

Jessica Ernakovich

Third Advisor

Andrew Robison

Abstract

Benthic microbes are important drivers of biogeochemical cycling in streams, influencing the storage, transformation, and emission of carbon and nutrients. While the impact of land use and land cover on water quality has been extensively studied, the connection between water quality and microbial community composition and function remains unresolved. In this study, we examined how the water quality changes accompanying watershed development impact the diversity, composition, and functional potential of benthic bacterial/archaeal, and fungal communities. This was explored in headwater streams across an urbanization gradient in the northeastern US. We did not find a link between urbanization and α-diversity of bacterial/archaeal or fungal communities. We did find a weak relationship between bacterial/archaeal α-diversity and DOC, which is influenced by wetlands, not suburban land use. The composition of bacterial/archaeal communities was influenced by chloride concentration, sediment C:N, and sulfate concentration which all increase with watershed development, and by pH which does not. The composition of the fungal community was not predominantly influenced by any specific variable(s). Instead, it was equally affected by the entire range of stream chemistry, some of which showed associations with watershed development. Compositional differences in the bacterial/archaeal communities across our study sites are reflected in the functional potential of the communities. For example, the relative abundance of fermentative bacteria/archaea in communities increased with C:N ratio. Further, the relative abundance of denitrifiers increased with the combined effect of increasing nitrate and reduced dissolved oxygen. Although we gained insight into the functional potential of these communities, the metabolic functions of most taxa in our samples remain undocumented. This underscores the significance of future studies that concentrate on investigating specific functions using ex-situ assays or employing other -omics techniques, such as metagenomics or metatranscriptomics.

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