The biogeochemical cycling of sulfur is intrinsically tied to a diverse suite of microbial reactions. Freshwater environments rich in sulfur can serve as interesting field sites in which to study biological-geological interactions of microbes and their environment. A recent study by Heidi Aronson (advised by Dr. Jan Amend) and the International Geobiology Course characterized the geology, stream geochemistry, and microbial diversity of a sulfur and hydrocarbon-rich site at Santa Paula Creek (Ventura, CA). Water flow, sunlight, and the presence of numerous electron donors and acceptors created heterogeneous geochemical niches that were occupied by morphologically, physiologically, and phylogenetically diverse microbial biofacies. The dynamic sulfur cycle and primary production at this site were largely driven by phototrophic and chemolithotrophic sulfide-oxidizing taxa, but sulfate reducing and disproportionating taxa were also identified. Santa Paula Creek will serve as an easily accessible and useful site for future studies to investigate and isolate the impact of hydrocarbon and sulfur fluxes on terrestrial communities. The full study can be found in Geobiology.