Hydrothermal systems are excellent platforms for understanding the spectrum of microbial phylogenetic and functional diversity, and particularly of the phylogenetically deepest diverging lineages among extant life. Further, the interaction between relatively simple chemosynthetic, thermophilic microbial communities and their geochemical environments provide a strong foundation for understanding the interplay between geology, geochemistry, microbial physiology and ecological interactions within communities. I am interested in the ecology of thermal spring microbial communities as a means to understand how microbial physiology, geochemical context and community interactions ultimately lead to community structure and function. I am also particularly interested in understanding how the dynamics of these various components can provide insight into the evolutionary ecology of lineages that are thought to be the earliest to diverge among extant life. I am currently researching a wide range of questions in hydrothermal systems at the organismal and ecosystem levels, but three central foci include 1) understanding the interactions between sulfur oxidizing thermoacidophiles and their environments over evolutionary time in the formation of hyperacidic springs, 2) the potential for subsurface hydrothermal biospheres in Yellowstone National Park (YNP) and elsewhere, and 3) the role of tectonic setting in constraining hydrothermal ecosystems in YNP and Iceland