Dissertation Defense: Nicole Wagner

Candidate: Nicole Wagner

Major: Biology

Advisor: Sarah Johnson, Ph.D.

Title: A Comprehensive Metagenomic Study of the Antarctic Untersee Oasis as an Astrobiological Analog

Astrobiology is the study of the “living universe,” which includes the study of the origin of life as well as its evolution and distribution on Earth and beyond. Prime candidates for alien life include the icy moons of the outer planets, particularly those with a geological or tidal source for thermal energy as well as Mars, which is widely thought to have had conditions conducive to life billions of years ago with biosignatures, or traces of life, potentially still present. To help the search for life beyond Earth, analog environments, terrestrial environments on Earth with conditions similar to alien worlds, are often used. My thesis focuses on one such analog environment, Untersee Oasis in Queen Maud Land, Antarctica. The site includes the perennially ice-covered Lake Untersee and the adjacent Aurkjosen Cirque. At the bottom of Untersee’s southern basin lies an anoxic, methane-rich pocket of water, an analog for Saturn’s moon, Enceladus. Despite the harsh conditions, I discovered an abundant and well-populated microbial community as well as a plethora of metabolic pathways offering a variety of strategies for harvesting energy. Microbial mats on the benthic surface of the northern basin, alongside mats entrained in the ice-cover and paleomats from the cirque, also present the opportunity for a natural experiment in the preservation of biosignatures. I used community profiling to establish a relationship among the mats by identifying overlapping biosignatures. The well-preserved state of biomass in the ice cover demonstrates the potential for recovery of biosignatures representative of the aquatic habitat below, with relevance for the exploration of icy moons. Meanwhile, paleomats preserved in the cirque illuminate how cold and arid conditions slow the degradation of biological material in paleolacustrine basins on Mars