Recent advances in microbiology have underscored the dominant role of bacteria in regulating ecosystem processes. The research proposed here examines the relationship between bacterial diversity and ecosystem dynamics by determining experimentally how seasonal changes in bacterial communities in high-elevation lakes of the Sierra Nevada (California, USA) associate with changes in the composition and metabolism of dissolved organic matter. This study expands on previous dissertation work demonstrating predictable bacterial community changes in these environments and linking community shifts to snowmelt-driven changes in organic matter composition. Regional climate shifts are predicted to significantly affect snowmelt dynamics, and atmospheric deposition of nutrients in the western U.S. is leading to gradual eutrophication (excess nutrients) of montane lakes, many of which are located in protected areas. In collaboration with the National Park Service, the USDA-Forest Service, and the California Air Resources Board the results of this work will inform regional efforts to manage water quality and the maintenance of natural ecosystem function. Finally, by defining temporal dynamics of bacteria in the context of catchment organic matter supply & composition, seasonal lake transitions, and the character and rate of inflowing microbial communities, we aim to develop the first mechanistic illustration of bacterial changes linked to landscape-scale ecosystem processes.
