@article {5024, title = {Microbial mat activity and soil biogeochemistry across variable phosphorus availability in Taylor Valley, Antarctica}, journal = {Antarctic Science}, year = {2025}, month = {05/2025}, abstract = {

Primary production is fundamental to ecosystems, and in many extreme environments production is facilitated by microbial mats. Microbial mats are complex assemblages of photo- and heterotrophic microorganisms colonizing sediment and soil surfaces. These communities are the dominant producers of the McMurdo Dry Valleys, Antarctica, where they occupy lentic and lotic environments as well as intermittently wet soils. While the influence of microbial mats on stream nutrient dynamics and lake organic matter cycling is well documented, the influence of microbial mats on underlying soil is less well understood, particularly the effects of microbial mat nitrogen and carbon fixation. Taylor Valley soils occur across variable levels of inorganic phosphorus availability, with the Ross Sea drift containing four times that of the Taylor drifts, providing opportunities to examine how soil geochemistry influences microbial mats and the ecological functions they regulate. We found that inorganic phosphorus availability is positively correlated with microbial mat biomass, pigment concentration and nitrogen fixation potential. Additionally, our results demonstrate that dense microbial mats influence the ecological functioning of underlying soils by enriching organic carbon and total nitrogen stocks (two times higher). This work contributes to ongoing questions regarding the sources of energy fuelling soil food webs and the regional carbon balance in the McMurdo Dry Valleys.

}, keywords = {LTER-MCM, carbon, cyanobacteria, nitrogen fixation, phosphorus, pigments, soil ecology}, issn = {0954-1020}, doi = {10.1017/S0954102025000094}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/microbial-mat-activity-and-soil-biogeochemistry-across-variable-phosphorus-availability-in-taylor-valley-antarctica/0655E2F09B8D6961618B8F396BA692F2}, author = {Power, Sarah N. and Osburn, Ernest D. and John E. Barrett} } @article {4939, title = {Detectability of surface biosignatures for directly imaged rocky exoplanets}, journal = {Astrobiology}, volume = {24}, year = {2024}, month = {03/2024}, pages = {283 - 299}, abstract = {

Modeling the detection of life has never been more opportune. With next-generation space telescopes, such as the currently developing Habitable Worlds Observatory (HWO) concept, we will begin to characterize rocky exoplanets potentially similar to Earth. However, few realistic planetary spectra containing surface biosignatures have been paired with direct imaging telescope instrument models. Therefore, we use a HWO instrument noise model to assess the detection of surface biosignatures affiliated with oxygenic, anoxygenic, and nonphotosynthetic extremophiles. We pair the HWO telescope model to a one-dimensional radiative transfer model to estimate the required exposure times necessary for detecting each biosignature on planets with global microbial coverage and varying atmospheric water vapor concentrations. For modeled planets with 0\–50\% cloud coverage, we determine pigments and the red edge could be detected within 1000\ hr (100\ hr) at distances within 15 pc (11 pc). However, tighter telescope inner working angles (2.5 λ/D) would allow surface biosignature detection at further distances. Anoxygenic photosynthetic biosignatures could also be more easily detectable than nonphotosynthetic pigments and the photosynthetic red edge when compared against a false positive iron oxide slope. Future life detection missions should evaluate the influence of false positives on the detection of multiple surface biosignatures.

}, keywords = {LTER-MCM, extremophiles, false positive, pigments, red edge, reflectance spectroscopy, telescope}, issn = {1531-1074}, doi = {10.1089/ast.2023.0099}, url = {https://www.liebertpub.com/doi/10.1089/ast.2023.0099}, author = {Borges, Schuyler R. and Jones, Gabrielle G. and Robinson, Tyler D.} } @phdthesis {4999, title = {In situ and remote biosignatures from microbial mats in ephemeral streams of Fryxell Basin, Antarctica}, volume = {Ph.D.}, year = {2024}, month = {08/2024}, pages = {340}, school = {Northern Arizona University}, type = {doctoral}, address = {Flagstaff, AZ}, abstract = {

Transient water-limited environments are understood to have hosted microbial communities early in Earth\’s history, and thus, may have been important ecosystems for life in ancient fluvial systems on Mars and water-limited environments on rocky Earth-like exoplanets. Similar environmental systems exist on Earth today, acting as meaningful analogs to study the preservation and detection of life in these environments. Particularly useful analogs are the McMurdo Dry Valleys of Antarctica, given their cold temperatures, aridity, elevated UV radiation exposure, and predominantly microbial ecosystem. Basins in these valleys contain ephemeral glacial meltwater streams, which contain a diversity of microbial communities that are only active when the streams are flowing ten weeks of the summer. These microbial communities were studied to examine how their in situ and remote biosignatures could inform the detection of similar life on Mars and rocky exoplanets. Specifically, these organisms were found in association with carbonate rock coatings, morphologically resembling modern and ancient stromatolites from rivers, ponds, lakes, and hot springs. Microorganisms from these communities were preserved within and influenced the formation of these coatings, becoming an additional Antarctic analog to ancient stromatolites. The presence of these carbonate coatings in an ephemeral stream suggests that processes in transient fluvial environments on Mars could have also generated coatings, which could have preserved biosignatures. We also identified pigments within these microbial communities and correlated the pigments to community composition. We determined how the reflectance spectra of these communities were influenced by their pigments, demonstrating the capability of distinguishing microbial mat community composition in visible and near-infrared spectroscopy. The results of our study indicate that pigment spectral absorptions can act as remote biosignatures which we then applied to modeling the detection of similar life on the surfaces of cold and rocky Earth-like exoplanets. The detection times of Antarctic microbial mat remote biosignatures were compared with those of anoxygenic photosynthetic and nonphotosynthetic microorganisms, accounting for false positives, to determine which biosignatures were most detectable. The results from this work demonstrate the ability of the future space-based telescope, Habitable Worlds Observatory, to detect surface life on rocky Earth-like exoplanets.

}, keywords = {LTER-MCM, Antarctica, astrobiology, pigments, spectroscopy, stromatolites}, url = {https://www.proquest.com/dissertations-theses/em-situ-remote-biosignatures-microbial-mats/docview/3094642420/se-2}, author = {Borges, Schuyler R.} }