Restricted Microbial Presence, Activity, and Community Structuring Within Dry Valley Soils of Antarctica

• Main Author: George, Scott Fillerup
• Format: Text
• Language: unknown
• Published: BYU ScholarsArchive 2021
• Subjects: astrobiology; bacteria; deliquescence; desert; dry permafrost; fungi; microbial ecology; water tracks; Life Sciences; Beacon Valley; Bya; Taylor Valley; Antarc*; Antarctica; Ice; permafrost; polar desert
• Online Access: https://scholarsarchive.byu.edu/etd/9771; https://scholarsarchive.byu.edu/context/etd/article/10780/viewcontent/4152135723226220150801_etd.pdf

The McMurdo Dry Valley region is the largest ice-free area of Antarctica. Harsh abiotic conditions of the polar desert ecosystem, including extreme cold, aridity, and limited nutrient availability select for unique taxa. The comparatively simple terrestrial ecosystem is well-suited for investigating edaphic influences on microbial presence, activity, and community structuring. The Dry Valleys are viewed as a useful analog for Mars astrobiology investigations. However, most biotic investigations have been focused on lower elevations, where an understanding of edaphic effects on microbial communities within its generally more favorable conditions has emerged. Transiently wetted Dry Valley water tracks may be analogous to recurring slope lineae on Mars. Dry permafrost is rare on Earth, and unique to high-elevation Antarctica soils, but is ubiquitous on Mars. Identifying if abiotic properties known to structure microbial communities within low elevation soils holds true for water tracks and dry permafrost is not known. My dissertation investigates edaphic effects on microbial communities within water track soils and dry permafrost. First, I review the ecological effects of transient wetting within hyperarid environments of the Atacama Desert of Chile and the Dry Valleys of Antarctica and apply the findings to possible habitability of modern and early (i.e., ~3.5 bya) Mars surface environments. I show that deliquescent hygroscopic salts facilitate biological response where little or no biotic activity would occur otherwise, yet the salts can also inhibit life. Transient wetting alone may also not be enough to support life. Secondly, I examine bacterial community composition, richness, and diversity on and off water track soils in Taylor Valley and show they are significantly different in composition, which likely influence ecosystem functioning. Salinity is shown as the best predictor of composition. Third, I examine a bacterial community from a Beacon Valley water track, which we believe is among the highest, ...