My research investigates how human activities alter water, and ultimately how this influences the health and biogeochemistry of natural ecosystems (nutrient cycling, productivity, gas exchange). Microbes (such as diatoms) often dominate material transfer in natural ecosystems (e.g., productivity, decomposition) and respond swiftly to environmental conditions; this makes them important as early-warning indicators of ecosystem change. To this end, I have worked on diatoms in streams, rivers, lakes, coastal regions, and the North American Great Lakes.