McMahon, Katherine D. University of Wisconsin-Madison Proposal Number: 0644949
CAREER: Microbes and phosphorus: integrating engineering principles, ecology, and student learning to study eutrophication of freshwater lakes
Intellectual Merit. It is generally accepted that microbes (primarily algae and bacteria) control P-cycling in lakes, through their actions in both the water column and sediments. However, very little is known about the biochemical mechanisms involved in microbial P-cycling, or about the contribution of different taxonomic groups to specific P transformations. Recent studies of freshwater bacterial community dynamics in eutrophic lakes suggest that community composition varies significantly over time, and that this variation is correlated with changes in nutrient availability. A better understanding of the fundamental mechanisms involved, and how these may vary with community composition, will ultimately lead to an improved ability to predict the effects of lake management practices on water quality. The PI will be building strong connections to scientists at the UW Center for Limnology and at Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences. In turn, I will leverage ongoing efforts to build wireless sensor networks for lakes, and to foster international collaborations, both of which will provide tremendous opportunities for student training. Broader Impacts. Lake water quality is a problem that appeals to a vast majority of Wisconsin residents. UW-Madison and its outstanding existing outreach infrastructure will help me to develop and assess outreach materials designed to promote an awareness of lake water quality and the Environmental Engineering and Science discipline, targeting multiple age groups. Staff in the NSF-Funded Center for the Integration of Research, Teaching, and Learning will work with me and my graduate students to engage middle school students through a one-week inquiry-based instructional unit designed to introduce them to Environmental Engineering and Science. The PI will also have a unique opportunity to reach minority and disadvantaged high school students, through the Pre-College Enrichment Opportunity Program for Learning Excellence. The PI has already demonstrated a strong commitment to teaching as research," in introductory Environmental Engineering course for undergraduates, and will continue to engage in this process in order to promote effective teaching and learning while striving to inspire the next generation of Environmental Engineers.
This CAREER award focused on bacteria in eutrophic (nutrient-rich) freshwater lakes. The primary study site was Lake Mendota in Madison, Wisconsin. This lake has been the subject of intense study over the past 100 years and is a site within the NSF-funded North Temperate Lakes Long Term Ecological Research program. The main goals of the project related to interdisciplinary research problems that cut across engineering and biology. Water quality degradation is a critical problem throughout the world and this project aimed to advance our fundamental understanding of how nutrient cycles mediated by bacteria contribute to poor water quality in lakes polluted with excess nitrogen and phosphorus. Six key project outcomes are: We found that bacterial communities are highly dynamic, with distinct species being present at different times of the year. These distinct species have unique characteristics that influence how nutrients and carbon are cycled through lake ecosystems. This has important implications for water quality managers since management decisions are made without regard to shifting bacterial community characteristics. We defined the range and extent of community change through time and space, finding that the pace of change over one day is equivalent to the amount of change observed over one meter in space. This has critical implications for the design of future studies in freshwater microbial ecology since it determines how frequently we should sample, and how many samples we should collect across large lakes. We studied the speciation of phosphorus and how it changes through time in a eutrophic lake, because phosphorus is the primary driver of eutrophication. We discovered surprising variability in certain chemical forms and this variability could be linked to changes in bacterial communities. However, we also identified a critical role for nitrogen in regulating the succession and toxicity of cyanobacterial communities, which as important implications for both human health and water quality management. We recommend that water quality managers put more attention towards nitrogen cycling in eutrophic lakes in an effort to predict and mitigate toxic cyanobacterial blooms. In a fundamental study of bacterial ecology, we identified archetypal groups that are found in all freshwater lakes and proposed a structured and rigorous naming scheme to simplify how researcher communicate about them. Finally, we developed a range of instructional materials for teaching and learning across multiple educational levels including middle school, high school, and undergraduate. These materials were developed in accordance with state standards for secondary education when appropriate. Learning gains were assessed when the materials were implemented within a teaching-as-research framework. The project provided training for four PhD students, two masters students, and five undergraduates. Two undergraduates were underrepresented minorities. Two of the PhD students obtained special certificates in teaching and learning because of their involvement in education and outreach related to this award. Two students obtained doctorates in Microbiology and two in Environmental Engineering.
