Previous work has shown high-elevation ecosystems are especially susceptible to the effects of climate change, but little work has been done on microbial communities in high-elevation aquatic systems. Therefore, my research aimed to improve our understanding of the composition, stability, and factors controlling microbial communities in high-elevation lakes in the Front Range of the Colorado Rocky Mountains. I studied seasonal and inter-annual variations in bacterial (16S rDNA) and eukaryotic (18S rDNA) microbial communities at multiple locations (inlet, outlet, three depths in the water column) within alpine lakes over four years (2014–2017). Communities significantly differed between lake inlets and the lakes as a whole across sampling dates. The most significant variable controlling 16S and 18S community composition was lake discharge rate, indicating that water residence times play a strong role in structuring communities. Furthermore, bacterioplankton communities were correlated with total dissolved nitrogen, whereas eukaryotic plankton were correlated with total dissolved phosphorus, perhaps indicating different limiting nutrients for these communities. Eukaryotic communities also significantly correlated with water temperatures, highlighting the risk that future increases in temperature could pose to these cold-adapted communities. Higher temperatures and lower discharge rates in 2016 were associated with low community diversity as the community became dominated by a few transiently abundant taxa. These results suggest higher temperatures and longer water residence times resulted in extreme selective pressures within the lake. I used community assembly models (Sloan’s neutral and Stegen’s assembly models) to determine the types of selection acting within the lakes. These models provided further evidence that low diversity communities observed in 2016 assembled under strong selection pressures, which increased with increasing lake residence times. The models showed that selective pressures shifted from more stochastic and dispersal-dominated processes during early season snow-melt, to selection-dominated processes during late season high residence times. Overall, these results show that microbial communities of high-elevation lakes were relatively stable, but showed high sensitivity to changes in water temperature and residence times. These variables are expected to increase under predicted global change scenarios, indicating that microbial communities of high elevation lakes could undergo dramatic changes in the coming decades.
|Advisor:||Krauter, Kenneth S., Schmidt, Steven K.|
|School:||University of Colorado at Boulder|
|Department:||Molecular, Cellular and Developmental Biology|
|School Location:||United States -- Colorado|
|Source:||DAI-B 81/6(E), Dissertation Abstracts International|
|Subjects:||Microbiology, Ecology, Bioinformatics|
|Keywords:||Alpine lake, Community assembly, Dispersal, Diversity, Plankton, Selection|
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