Browsing by Author "Power, Sarah N."

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    The Distribution of Surface Soil Moisture over Space and Time in Eastern Taylor Valley, Antarctica
    Salvatore, Mark R.; Barrett, John E.; Fackrell, Laura E.; Sokol, Eric R.; Levy, Joseph S.; Kuentz, Lily C.; Gooseff, Michael N.; Adams, Byron J.; Power, Sarah N.; Knightly, J. Paul; Matul, Haley M.; Szutu, Brian; Doran, Peter T. (MDPI, 2023-06-18)
    Available soil moisture is thought to be the limiting factor for most ecosystem processes in the cold polar desert of the McMurdo Dry Valleys (MDVs) of Antarctica. Previous studies have shown that microfauna throughout the MDVs are capable of biological activity when sufficient soil moisture is available (~2–10% gravimetric water content), but few studies have attempted to quantify the distribution, abundance, and frequency of soil moisture on scales beyond that of traditional field work or local field investigations. In this study, we present our work to quantify the soil moisture content of soils throughout the Fryxell basin using multispectral satellite remote sensing techniques. Our efforts demonstrate that ecologically relevant abundances of liquid water are common across the landscape throughout the austral summer. On average, the Fryxell basin of Taylor Valley is modeled as containing 1.5 ± 0.5% gravimetric water content (GWC) across its non-fluvial landscape with ~23% of the landscape experiencing an average GWC > 2% throughout the study period, which is the observed limit of soil nematode activity. These results indicate that liquid water in the soils of the MDVs may be more abundant than previously thought, and that the distribution and availability of liquid water is dependent on both soil properties and the distribution of water sources. These results can also help to identify ecological hotspots in the harsh polar Antarctic environment and serve as a baseline for detecting future changes in the soil hydrological regime.
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    Remote characterization of Antarctic microbial mat communities
    Power, Sarah N.; Salvatore, Mark R.; Sokol, Eric R.; Stanish, Lee F.; Barrett, John E. (Virginia Tech, 2021-04-30)
    The McMurdo Dry Valleys, Antarctica are ecosystems where life approaches its environmental limits. Cyanobacteria, however, have adapted to survive in this extreme environment as the most dominant life form and the main drivers of primary productivity (i.e., photosynthesis). Cyanobacterial communities exist on soil surfaces adjacent to glacial meltwater streams layered in mats up to several cm thick. The cryptic nature of these communities and their patchy distribution make assessments of productivity challenging. We used satellite imagery coupled with in situ surveying, imaging, and sampling to systematically estimate microbial mat biomass in selected wetland regions in Taylor Valley, Antarctica. On January 19th, 2018, the WorldView-2 multispectral satellite acquired an image of our study areas, where we surveyed and sampled seven 100 m2 plots of microbial mats for percent ground cover, ash-free dry mass, and pigment content. Multispectral analyses revealed spectral signatures consistent with photosynthetic activity (relatively strong reflection at near-infrared wavelengths and relatively strong absorption at visible wavelengths), with average NDVI values of 0.09 to 0.28. Strong correlations of microbial mat ground cover (R2 = 0.84), biomass (R2 = 0.74), chlorophyll-a content (R2 = 0.65), and scytonemin content (R2 = 0.98) with logit transformed NDVI values demonstrate that satellite imagery can detect both the presence of microbial mats and their key biological properties. Using the NDVI – biomass correlation we developed, we estimate carbon (C) stocks of 21,715 kg (14.7 g C m-2) in the Canada Glacier Antarctic Specially Protected Area. By quantitatively comparing biological surface observations to NDVI, this is the first satellite-derived estimate of microbial mat biomass for this region of Antarctica.
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    Response of a Terrestrial Polar Ecosystem to the March 2022 Antarctic Weather Anomaly
    Barrett, John E.; Adams, Byron J.; Doran, Peter T.; Dugan, Hilary A.; Myers, Krista F.; Salvatore, Mark R.; Power, Sarah N.; Snyder, Meredith D.; Wright, Anna T.; Gooseff, Michael N. (American Geophysical Union, 2024-07-31)
    Record high temperatures were documented in the McMurdo Dry Valleys, Antarctica, on 18 March 2022, exceeding average temperatures for that day by nearly 30°C. Satellite imagery and stream gage measurements indicate that surface wetting coincided with this warming more than 2 months after peak summer thaw and likely exceeded thresholds for rehydration and activation of resident organisms that typically survive the cold and dry conditions of the polar fall in a freeze‐dried state. This weather event is notable in both the timing and magnitude of the warming and wetting when temperatures exceeded 0°C at a time when biological communities and streams have typically entered a persistent frozen state. Such events may be a harbinger of future climate conditions characterized by warmer temperatures and greater thaw in this region of Antarctica, which could influence the distribution, activity, and abundance of sentinel taxa. Here we describe the ecosystem responses to this weather anomaly reporting on meteorological and hydrological measurements across the region and on later biological observations from Canada Stream, one of the most diverse and productive ecosystems within the McMurdo Dry Valleys.