Microbial Community Responses to Natural and Anthropogenic Disturbances in Aquatic Ecosystems

• Main Author: Ward, Christopher Spencer
• Other Authors: Hunt, Dana E
• Published: 2015
• Subjects: Microbiology; Ecology
• Online Access: http://hdl.handle.net/10161/11354

<p>Aquatic ecosystems are highly dynamic environments, suggesting that resident microbial communities to respond and adapt to these environmental changes. However, despite the frequency of disturbances in aquatic ecosystems such as annual cycles in environmental parameters and episodic storm events, few studies have examined the impacts of disturbances on aquatic microbial communities. In this dissertation, I investigate community- and taxon-level responses to natural and anthropogenic disturbances in the coastal ocean and wetland mesocosms using ribosomal RNA gene library sequencing. In my first chapter, I present an overview on disturbances in microbial communities and describe microbial interaction network-based approaches for predicting disturbance effects. In my second chapter, I use three years of weekly coastal ocean samples to identify transitions between distinct summer- and winter-associated taxa that occur across the microbial community over relatively short time intervals. Using the same time series, I find that episodic disturbances involve in rapid turnover of both abundant and conditionally rare taxa depending on environmental conditions and initial community composition. Finally, I investigate the microbial responses to acute and chronic environmental loading of an emerging contaminant in replicated wetland mesocosms. Despite the antimicrobial properties of silver nanoparticles, community changes in both treatments appear to be dominated by indirect effects through aquatic plant die-off, though the timing, duration, and magnitude of responses vary. Together, my dissertation demonstrates that associations between microbial taxa, environmental factors, and other components of the ecosystem all contribute to community response to disturbance. By exploring community responses to disturbance, new insights can be gained into the resistance and resilience of microbial communities in response to environmental drivers of community change.</p> === Dissertation