@mastersthesis {5019, title = {Development of a laboratory simulation for freeze-thaw of aeolian sediments in glacial systems}, volume = {M.A.}, year = {2024}, month = {2024}, pages = {261}, school = {University of Colorado Boulder}, type = {masters}, address = {Boulder, CO, USA}, abstract = {

Glacial systems are vital for supplying trace metals, nutrients, and weathering products to downstream ecosystems. While subglacial and proglacial weathering pathways are highly studied, supraglacial weathering processes receive less attention. Aeolian sediments on glaciers can lower albedo, generating meltwater; this water can refreeze around sediment grains during cloudy periods or when the sun is obstructed, resulting in a freeze-thaw process. For solute generation in the most upstream source in glacial-proglacial environments, it\&$\#$39;s unclear whether chemical or physical weathering dominates nutrient release. This study presents a methodology to simulate freeze-thaw processes in a controlled laboratory setting to understand the importance of freeze-thaw in nutrient mobilization. Analysis of sediments from Antarctica\&$\#$39;s McMurdo Dry Valleys showed significant differences in the concentrations of ion, nutrient, and trace metal between initial wetting and subsequent freeze-thaw cycles. For example, phosphorus concentrations consistently increased with each cycle, indicating that freeze-thaw is an important mobilization mechanism for this nutrient. Silicon increased from cycle 1-30 but decreased at cycle 60 and iron concentrations were initially higher but decreased during subsequent cycles. This research highlights the importance of freeze-thaw processes in understanding glacial weathering dynamics and nutrient release for downstream ecosystems.

}, keywords = {LTER-MCM, Antarctica, freeze-thaw, nutrients, Taylor Valley, trace metals}, url = {https://www.proquest.com/docview/3066792202}, author = {Mondragon, Denise}, editor = {Melisa A. Diaz} } @article {4718, title = {Elevational constraints on the composition and genomic attributes of microbial communities in Antarctic soils}, journal = {mSystems}, volume = {7}, year = {2022}, month = {01/2022}, pages = {e01330-21}, abstract = {

The inland soils found on the Antarctic continent represent one of the more challenging environments for microbial life on Earth. Nevertheless, Antarctic soils harbor unique bacterial and archaeal (prokaryotic) communities able to cope with extremely cold and dry conditions. These communities are not homogeneous, and the taxonomic composition and functional capabilities (genomic attributes) of these communities across environmental gradients remain largely undetermined. We analyzed the prokaryotic communities in soil samples collected from across the Shackleton Glacier region of Antarctica by coupling quantitative PCR, marker gene amplicon sequencing, and shotgun metagenomic sequencing. We found that elevation was the dominant factor explaining differences in the structures of the soil prokaryotic communities, with the drier and saltier soils found at higher elevations harboring less diverse communities and unique assemblages of cooccurring taxa. The higher-elevation soil communities also had lower maximum potential growth rates (as inferred from metagenome-based estimates of codon usage bias) and an overrepresentation of genes associated with trace gas metabolism. Together, these results highlight the utility of assessing community shifts across pronounced environmental gradients to improve our understanding of the microbial diversity found in Antarctic soils and the strategies used by soil microbes to persist at the limits of habitability.

}, keywords = {LTER-MCM, Antarctica, microbial ecology, soil microbiology, soils}, doi = {10.1128/msystems.01330-21}, url = {https://journals.asm.org/doi/full/10.1128/msystems.01330-21}, author = {Dragone, Nicholas B. and Henley, Jessica B. and Holland-Moritz, Hannah and Melisa A. Diaz and Hogg, Ian D. and W. Berry Lyons and Diana H. Wall and Byron Adams and Noah Fierer}, editor = {Mackelprang, Rachel} } @article {4636, title = {Exploring the boundaries of microbial habitability in soil}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {126}, year = {2021}, month = {06/2021}, abstract = {

Microbes are widely assumed to be capable of colonizing even the most challenging terrestrial surface environments on Earth given enough time. We would not expect to find surface soils uninhabited by microbes as soils typically harbor diverse microbial communities and viable microbes have been detected in soils exposed to even the most inhospitable conditions. However, if uninhabited soils do exist, we might expect to find them in Antarctica. We analyzed 204 ice-free soils collected from across a remote valley in the Transantarctic Mountains (84\–85\°S, 174\–177\°W) and were able to identify a potential limit of microbial habitability. While most of the soils we tested contained diverse microbial communities, with fungi being particularly ubiquitous, microbes could not be detected in many of the driest, higher elevation soils\—results that were confirmed using cultivation-dependent, cultivation-independent, and metabolic assays. While we cannot confirm that this subset of soils is completely sterile and devoid of microbial life, our results suggest that microbial life is severely restricted in the coldest, driest, and saltiest Antarctic soils. Constant exposure to these conditions for thousands of years has limited microbial communities so that their presence and activity is below detectable limits using a variety of standard methods. Such soils are unlikely to be unique to the studied region with this work supporting previous hypotheses that microbial habitability is constrained by near-continuous exposure to cold, dry, and salty conditions, establishing the environmental conditions that limit microbial life in terrestrial surface soils.

}, keywords = {LTER-MCM, Antarctica, astrobiology, bacteria, extremophiles, fungi, soils}, issn = {2169-8953}, doi = {10.1029/2020JG006052}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JG006052}, author = {Dragone, Nicholas B. and Melisa A. Diaz and Hogg, Ian D. and W. Berry Lyons and W. Andrew Jackson and Diana H. Wall and Adams, Byron J. and Noah Fierer} } @article {4471, title = {Geochemistry of aeolian material from the McMurdo Dry Valleys, Antarctica: Insights into Southern Hemisphere dust sources}, journal = {Earth and Planetary Science Letters}, volume = {547}, year = {2020}, month = {10/2020}, abstract = {

In the Southern Hemisphere, the major sources of dust and other aeolian materials are from Patagonia, South Africa, Australia, and New Zealand. Dust from Patagonia and New Zealand has been identified in ice cores throughout Antarctica, suggesting that during arid and windy periods, such as glacial periods, dust can be entrained and transported onto the continent. However, little information exists on modern Antarctic dust sources, transport, and its role in the Southern Hemisphere dust cycle. We present the first geochemical characterization of aeolian materials collected at five heights (between 5 cm and 100 cm) above the surface in four valleys within the McMurdo Dry Valleys, the largest ice-free area in Antarctica. Our mineralogy data indicate that these materials are primarily derived from local rocks of the McMurdo Volcanics, Ferrar Dolerite, Beacon Sandstone and Granite Harbor Intrusives, with varying contributions of each rock type dependent on the valley location. While major oxide, trace element and rare earth element data show that low elevation and coastal locations (with respect to the Ross Sea) are dominated by local sources, high elevation and inland locations have accumulated both local materials and dust from other distant Southern Hemisphere sources. This far-traveled material may not be accumulating today, but represents a paleo source that is resuspended from the soils. By geochemically \“fingerprinting\” aeolian materials from the MDV, we can better inform future studies on the transport of materials within Antarctica and between Southern Hemisphere land masses.

}, keywords = {LTER-MCM, aeolian material, Antarctica, major oxides, mineralogy, rare earth elements, trace elements}, doi = {10.1016/j.epsl.2020.116460}, url = {https://www.sciencedirect.com/science/article/pii/S0012821X20304040}, author = {Melisa A. Diaz and Welch, Susan A. and Sheets, J. M. and Kathleen A. Welch and Khan, Alia L. and Byron Adams and Diane M. McKnight and Craig S Cary and W. Berry Lyons} }