A characterization of microbial diversity in the Winter Wonderland Ice Cave, Uinta Mountains, Utah, USA

Winter Wonderland is an ice cave in the Uinta Mountains of northern Utah, USA. The cave, which has an entrance at 3140 m a.s.l., extends 245 m into a north facing cliff of Mississippi Madison Limestone. The cave was discovered by the U.S. Forest Service in 2014. Winter Wonderland Ice Cave likely originated in the Late Mississippian to Early Pennsylvanian when joints opened up in the vadose zone. The interior of the cave is perennially below freezing with ice covering sections of the floor to a thickness of at least 2 m. Seasonally, meltwater from the epikarst enters the cave, pools on the surface of the older ice and freezes, creating a layered ice mass containing organic matter dating back several centuries. As this water freezes, cryogenic cave carbonates (CCCs) precipitate and are incorporated in the ice. In this study, ice, water, and mineral precipitates in the cave were investigated for the presence of microorganisms adapted to this extreme environment. Samples were collected to investigate the microbial communities that may be present within the Winter Wonderland ice cave, identify what they are, and investigate whether the composition of the microbial community changes spatially within the cave and between sample types. An intact block of ice (18x10x10 cm), liquid water samples (n=8), and 13 CCC samples were collected in August 2019. The ice block was removed from a vertical exposure of ice at the back of the cave using a hand saw, water was collected from a pool on the ice surface, and the CCCs were sampled from the surface of the ice in multiple sections of the cave. The water samples were analyzed for stable isotope composition to better understand water source and freezing history. Crystallographic study of oriented slides cut from the ice revealed that the ice crystallized vertically with some variation in crystal size. All samples were also investigated with fluorescence microscopy, flow cytometry, and DNA sequencing to reveal the abundance and type of microorganisms. Preliminary fluorescence microscopy and SEM imaging reveals the presence of cocci and bacilli type microorganisms within water samples and ~10um wide eukaryotic organisms within the CCCs, suggesting that the CCCs may provide much needed nutrients for the microbes or that the CCCs themselves are products of biomineralization.