Microbial communities and biogeochemistry of a melting Rocky Mountain glacier

Mountain glaciers are disappearing rapidly, and with their disappearance, we may be losing unstudied biodiversity and genetic resources. A variety of habitats for microorganisms exist on glaciers, especially within pockets of supraglacial sediments (cryoconite) that support high levels of biological activity and diversity. We used biogeochemical approaches, high-throughput DNA sequencing, and microscopy to describe the biogeochemistry and microbial communities of supraglacial sediments on the Dinwoody Glacier in the Wind River Range, Wyoming. Carbon (C) and nitrogen (N) concentrations were high, and C:N ratios were close to the Redfield ratio indicating active nutrient cycling. We found unique microbial communities in sediments at different elevations on the glacier, with greater diversity near the terminus. Bacterial communities were dominated by photosynthetic cyanobacteria and numerous polymer-decomposing members of the Bacteroidetes. Eukaryotic communities were dominated by snow algae and ciliated protists among other predators and decomposers. DNA sequencing also yielded evidence of past eolian inputs of insect and plant materials including DNA from Orthoptera that may be remnants of locust swarms that were entombed in the glacier in the past. Overall, we found a robustly functioning ecosystem on Dinwoody Glacier with distinct supraglacial habitats and organisms that are rapidly disappearing due to human-induced climate change.