Natural Resources, School of


First Advisor

Mark A. Pegg

Second Advisor

Samodha C. Fernando

Date of this Version

Summer 7-29-2021


Perisho, Esther. 2021. Spatiotemporal trends in bacterial diversity across three watersheds within the Platte River Basin, Nebraska. Master's thesis. University of Nebraska, Lincoln.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Natural Resource Sciences, Under the Supervision of Mark. A Pegg and Samodha C. Fernando. Lincoln, Nebraska: July, 2021

Copyright © 2021 Esther J. Perisho


River bacteria are understudied despite being critical components of river ecosystems. There are even fewer studies considering bacteria communities at large spatiotemporal scales, which may provide insight into drivers of community assembly. We investigated differences in bacterial diversity across environmental gradients within three sub-basins nested in the Platte River Basin, Nebraska. Surface water samples were collected weekly at 36 sites from May to September by the Nebraska Department of Environment and Energy (NDEE) in 2019. Bacterial communities were sequenced using the Illumina MiSeq platform. Sub-basins had similar counts of unique amplicon sequence variants (ASVs) but different community structures. These structural differences were partially driven by environmental factors influenced by climate, land-use, and geomorphology. Two sub-basins exhibited shifts in community structure between early and late summer, but the third exhibited no clear temporal pattern. Relative abundances of typical and common freshwater genera like Flavobacterium contributed the most to structural differences between sub-basins. The most abundant genera across all sub-basins included copiotrophs, suggesting that our study systems are nutrient-enriched. The trend in bacterial diversity observed in our study demonstrates the ecological relevance of considering bacterial diversity at large spatial and temporal scales.

Advisors: Mark A. Pegg and Samodha C. Fernando