02394nas a2200301 4500008004100000022001400041245012200055210006900177260001200246300001100258490000800269520142600277653001501703653002401718653001901742653001901761653003401780653002301814100002801837700002001865700002501885700002401910700002201934700002101956700001901977700002101996856007502017 2025 eng d a0012-965800aRemote sensing for species distribution models: An illustration from a sentinel taxon of the world's driest ecosystem0 aRemote sensing for species distribution models An illustration f c02/2025 ae700350 v1063 a

In situ observed data are commonly used as species occurrence response variables in species distribution models. However, the use of remotely observed data from high-resolution multispectral remote-sensing images as a source of presence/absence data for species distribution models remains under-developed. Here, we describe an ensemble species distribution model of black microbial mats (Nostoc spp.) using presence/absence points derived from the unmixing of 4-m resolution WorldView-2 and WorldView-3 images in the Lake Fryxell basin region of Taylor Valley, Antarctica. Environmental and topographical characteristics such as soil moisture, snow, elevation, slope, and aspect were used as predictor variables in our models. We demonstrate that we can build and run ensemble species distribution models using both dependent and independent variables derived from remote-sensing data to generate spatially explicit habitat suitability maps. Snow and soil moisture were found to be the most important variables accounting for about 80% of the variation in the distribution of black mats throughout the Fryxell basin. This study highlights the potential contribution of high-resolution remote-sensing to species distribution modeling and informs new studies incorporating remotely derived species occurrences in species distribution models, especially in remote areas where access to in situ data is often limited.

10aAntarctica10aMcMurdo Dry Valleys10amicrobial mats10aremote sensing10aspecies distribution modeling10aspecies occurrence1 aThapa‐Magar, Khum, B.1 aSokol, Eric, R.1 aGooseff, Michael, N.1 aSalvatore, Mark, R.1 aBarrett, John, E.1 aLevy, Joseph, S.1 aKnightly, Paul1 aPower, Sarah, N. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.7003502764nas a2200253 4500008004100000022001400041245011400055210006900169260001200238300001100250490000700261520197300268653001502241653002102256653002702277653002202304653001502326653001302341100002102354700002502375700002402400700002402424856006202448 2024 eng d a0885-608700aThe hydrologic and geochemical contributions from snow to streamflow in the McMurdo Dry Valleys of Antarctica0 ahydrologic and geochemical contributions from snow to streamflow c06/2024 ae151950 v383 a

The glacial meltwater streams in the McMurdo Dry Valleys (MDVs), Antarctica only flow during the austral summer and contain abundant algal mats which grow at the onset of flow. Their relative abundance in stream channels of this polar desert make the streams biogeochemical hot spots. The MDVs receive minimal precipitation as snow, which is redistributed by wind and deposited in distinct locations, some of which become persistent snow patches each year. Previous studies identified that MDV streamflow comes from a combination of glacier ice and snow, although snow was assumed to contribute little to the overall water budget. This study uses a combination of satellite imagery, terrain analysis, and field measurements to determine where snow patches accumulate and persist across MDV watersheds, and to quantify the potential hydrologic and biogeochemical contributions of snow patches to streams. Watersheds near the coast have the highest snow-covered area and longest snow persistence. Many of these snow patches accumulate within the stream channels, which results in the potential to contribute to streamflow. During the summer of 2021–2022, stream channel snow patches had the potential to contribute anywhere between <1% and 90% of the total annual discharge in Lake Fryxell Basin streams, and may increase with different hydrometeorological conditions. On average the potential inputs from snow patches to streamflow was between 12% and 25% of the annual discharge during the 2021–2022 season, as determined by snow area and SWE. Snow patches in the majority of the watersheds had higher nitrogen and phosphorous concentrations than stream water, and six streams contained snow with higher N:P ratios than the average N:P in the stream water. This suggests that if such patches melt early in the summer, these nutrient and water inputs could occur at the right time and stoichiometry to be crucial for early season algal mat growth.

10aAntarctica10aephemeral stream10apolar desert hydrology10arunoff generation10asnow patch10asnowmelt1 aWright, Anna, T.1 aGooseff, Michael, N.1 aBergstrom, Anna, J.1 aWelch, Kathleen, A. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.1519502474nas a2200229 4500008004100000245007500041210006900116260001200185300001800197490000800215520178800223653001502011653001602026653002802042653000802070653002202078653000902100100002502109700002502134700002402159856006102183 2022 eng d00aDissolved organic carbon chemostasis in Antarctic polar desert streams0 aDissolved organic carbon chemostasis in Antarctic polar desert s c07/2022 ae2021JG0066490 v1273 a

Dissolved organic carbon (DOC) is a key variable impacting stream biogeochemical processes. The relationship between DOC concentration (C) and stream discharge (q) can elucidate spatial and temporal DOC source dynamics in watersheds. In the ephemeral glacial meltwater streams of the McMurdo Dry Valleys (MDV), Antarctica, the C-q relationship has been applied to dissolved inorganic nitrogen and weathering solutes including silica, which all exhibit chemostatic C-q behavior; but DOC-q dynamics have not been studied. DOC concentrations here are low compared to temperate streams, in the range of 0.1-2 mg C l-1, and their chemical signal clearly indicates derivation from microbial biomass (benthic mats and hyporheic biofilm). To investigate whether the DOC generation rate from these autochthonous organic matter pools was sufficient to maintain chemostasis for DOC, despite these streams' large diel and interannual fluctuations in discharge, we fit the long-term DOC-q data to a power law and an advection-reaction model. Model outputs and coefficients of variation characterize the DOC-q relationship as chemostatic for several MDV streams. We propose a conceptual model in which hyporheic carbon storage, hyporheic exchange rates, and net DOC generation rates are key interacting components that enable chemostatic DOC-q behavior in MDV streams. This model clarifies the role of autochthonous carbon stores in maintaining DOC chemostasis and may be useful for examining these relationships in temperate systems, which typically have larger sources of bioavailable autochthonous organic carbon than MDV streams but where this autochthonous signal could be masked by a stronger allochthonous contribution.

10aAntarctica10achemostasis10aconcentration-discharge10aDOC10aephemeral streams10aLTER1 aTorrens, Christa, L.1 aGooseff, Michael, N.1 aMcKnight, Diane, M. uhttps://onlinelibrary.wiley.com/doi/10.1029/2021JG00664902835nas a2200217 4500008004100000245010200041210006900143260005400212490000900266520215600275653001502431653001002446653001602456653001502472653001402487653001202501653000902513100002202522700002502544856004802569 2021 eng d00aHydrologic response to foehn winds in the McMurdo Dry Valleys, Southern Victoria Land, Antarctica0 aHydrologic response to foehn winds in the McMurdo Dry Valleys So aBoulder, CObUniversity of Colorado Boulderc20200 vM.S.3 a

In the McMurdo Dry Valleys (MDVs), foehn winds are a principal vector of landscape connectivity that facilitate movement of materials between glaciers, streams, soils, lakes and other parts of the ecosystem. While previous publications show that turbulent, warm and dry foehn winds indirectly relate to an increase in lake level rise via an increase in degree days above freezing (DDAF), the direct quantified impact of foehn winds to streamflow and lake level rise remains unclear. The MDVs are the largest ice-free region of Antarctica, which experience minimal precipitation. Valley bottoms contain permanently ice-covered closed basin lakes filled with meltwater from outlet glaciers via stream channels. In Taylor Valley, several meteorological stations and lake monitoring stations record average measurements of weather conditions and lake conditions on 15 to 20-minute intervals. In this thesis, the meteorological definition of foehn winds is refined and hydrologic response to foehn winds is evaluated. During the austral summer streamflow season (November - February), foehn winds are predicted to increase meltwater generation and closed-basin lake level rise. Past publications have shown that foehn wind events contribute to lake ice sublimation year-round, whereas melt does not typically occur in nonsummer months. Analysis of non-summer lake ice ablation utilizing recent lake stage and ablation data is also explored herein. Although a significant correlation was not found, summer foehn winds appear to promote above average daily lake level rise given sufficient air temperatures. Daily average lake level rise is greater for longer periods (i.e., 4-day average daily rise > 3-day average daily rise, etc.) indicating that there is at least a 4-day post-foehn impact on lake level rise during the summer. Lake ice ablation in non-summer months is shown to have a significant relationship with increasing foehn wind occurrence and wind-run. Because foehn winds are expected to increase with global warming, these hydrologic relationships aid in predicting the future of the McMurdo Dry Valley ecosystem in a warming world.

10aAntarctica10afoehn10afoehn winds10ahydrologic10akatabatic10aMcMurdo10awind1 aBeane, Samuel, J.1 aGooseff, Michael, N. uhttps://www.proquest.com/docview/248812693703417nas a2200193 4500008004100000245006200041210006200103260006200165490000800227520280000235653001503035653001903050653002103069653001203090100002203102700002603124700002503150856004803175 2021 eng d00aStream corridor connectivity controls on nitrogen cycling0 aStream corridor connectivity controls on nitrogen cycling aBoulder, CO, USAbUniversity of Colorado Boulderc05/20210 vPhD3 a

As water flows downstream, it is transported to and from environments that surround the visible stream. Along with surface water, these laterally and vertically connected environments comprise the stream corridor. Stream corridor connectivity influences many ecosystem services, including retention of excess nutrients. The subsurface area where stream water and groundwater mixes—the hyporheic zone—represents one of the most biogeochemically active parts of stream corridors.

The goal of my research is to advance understanding of how connectivity between different parts of a stream corridor controls the availability and retention of nitrogen (N), a nutrient that can limit primary productivity (low-N) and negatively impact water quality (excess N). First, I developed and applied a new machine learning method to objectively characterize the extent and variability of hyporheic exchange in terms of statistically unique functional zones using geophysical data. In applying this method to a benchmark dataset, I found that hyporheic extent does not scale uniformly with streamflow and that changes in the heterogeneity of connectivity differ over small (<10 m) distances. Next, I leveraged the relative simplicity of ephemeral streams of the McMurdo Dry Valleys (MDVs), Antarctica, to isolate stream corridor processes that influence the fate of N. Through intensive field sampling campaigns, I found that the hyporheic zone can be a persistent source of N even in this low nutrient environment. Next, I combined historic sample data and remote sensing analysis to estimate how much N is stored in an MDV stream corridor. My results indicate that up to 103 times more N is stored in this system than is exported each year, with most of this storage in the shallow (< 10 cm) hyporheic zone. Lastly, I examined 25 years of data for 10 streams to assess how stream corridor processes control concentration-discharge relationships. I found that in the absence of hillslope connectivity, stream corridor processes alone can maintain chemostasis – relatively small concentration changes with large fluctuations in streamflow – of both geogenic solutes and primary nutrients. My analysis also revealed that solutes subject to greater control by biological processes exhibit more variability within chemostatic relationships than weathering solutes that are only minimally influenced by biota.

Altogether, this research advances understanding of processes that are difficult to measure or are often overlooked in typical studies of temperate stream corridors. My findings provide insight into the surprising ways in which N is mobilized, transformed, and retained due to stream corridor connectivity in intermittent stream systems with few N inputs.

10aAntarctica10ahyporheic zone10anitrogen cycling10astreams1 aSingley, Joel, G.1 aHinckley, Eve-Lyn, S.1 aGooseff, Michael, N. uhttps://www.proquest.com/docview/257259312702639nas a2200301 4500008004100000245008400041210006900125260001200194520169800206653001501904653002101919653002401940653002701964653001301991100002102004700002602025700001702051700001602068700002502084700002502109700001702134700002202151700002302173700002002196700002402216700002402240856007302264 2019 eng d00aThe hydroecology of an ephemeral wetland in the McMurdo Dry Valleys, Antarctica0 ahydroecology of an ephemeral wetland in the McMurdo Dry Valleys  c11/20193 a

The McMurdo Dry Valleys (MDV) is a polar desert on the coast of East Antarctica where ephemeral wetlands become hydrologically active during warm and sunny summers when sub‐surface flows are generated from melting snowfields. To understand the structure and function of polar wetland ecosystems, we investigated the hydroecology of one such wetland, the Wormherder Creek wetland, during the warm and sunny summer of 2008 – 2009, when the wetland was hydrologically reactivated. Conservative tracer (LiCl) was injected for a 2‐hour period into a stream above the wetland to determine flow path orientations and hydrologic residence times. Tracer results indicated that surface water is rapidly exchanged with wetland groundwater and wetland residence times may exceed two austral summers. Major ion concentrations were uniform in samples from surface water and shallow groundwater throughout the wetland. Microbial mats in the wetland had high autotrophic index values (the ratios of chlorophyll a [Chl‐a]/ash‐free dry mass [AFDM]), ranging from 9‐38 μg Chl‐a/mg AFDM, indicative of actively photosynthesizing mat communities. The diatom communities in the mats were relatively uniform compared to those in mats from regularly flowing MDV streams, with four endemic and one widespread diatom taxa of the genus Luticola accounting for an average of 86% of the community. These results indicate that the hydrologic characteristics of the wetland contribute to uniform geochemical conditions. In turn, uniform geochemical conditions may explain the high autotrophic index values of the microbial mats and relatively low spatial variation of the diatom community.

10aAntarctica10adesert hydrology10adiatom biodiversity10ahyporheic interactions10awetlands1 aWlostowski, Adam1 aSchulte, Nicholas, O.1 aAdams, Byron1 aBall, Becky1 aEsposito, Rhea, M.M.1 aGooseff, Michael, N.1 aLyons, Berry1 aNielsen, Uffe, N.1 aVirginia, Ross, A.1 aWall, Diana, H.1 aWelch, Kathleen, A.1 aMcKnight, Diane, M. uhttps://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JG00515303050nas a2200205 4500008004100000245007900041210006900120260004600189300000700235490000900242520242000251653001502671653001602686653001902702653001102721653001602732100002002748700002502768856005102793 2015 eng d00aThe impacts of thermokarst activity on a stream in the McMurdo Dry Valleys0 aimpacts of thermokarst activity on a stream in the McMurdo Dry V aBoulder, CObUniversity of Coloradoc2015 a700 vM.S.3 a

The McMurdo Dry Valleys (MDV) of Antarctica are a unique ice-free landscape that is host to vibrant ecosystems despite the harsh environment (<10 cm water equivalent/yr, -20°C mean air temperature). Aquatic ecosystems in the MDV are dependent on the ephemeral glacial runoff streams which feed the closed basin perennially ice covered lakes. The upland zones of the Dry Valleys have been shown to have some of the slowest ground surface change rates in the world. However, recent observations in the coastal valley transition zones suggest that this area may be nearing a threshold of rapid landscape change.

One of the recent observations that supports this idea is the discovery of extensive thermokarst degradation (permafrost thaw features) along the banks of Crescent Stream in Taylor Valley. In 2012, a large stretch of the West Branch of Crescent Stream was found to have significant thermokarst bank failures, while the adjacent East Branch was found to be unaffected. The thermokarst impacts within this setting are important to understand because of the disturbances that massive sediment loading can impose on downstream biological communities.

Annually repeated terrestrial LiDAR scans (3) were compared to determine the rates of ground surface change due to thermokarst degradation. It was found that the areal extent of the thermokarst was decreasing, however the average linear rates of retreat remained constant. Field measurements including, pebble counts, fine sediment counts, and sieve samples were analyzed to determine the effects of the thermokarst on the stream bed material. It was found that the West Branch and the reach downstream of the confluence were consistently finer than the unaffected East Branch. This suggests that the finer bed material is due to the thermokarst bank degradation. Stream power was calculated for multiple reaches to be used as a metric for the mobilization of the streambed material. It was found that both branches infrequently experience flows substantial enough to mobilize the bed material. Even the finer bed material of the impacted West Branch reach required flows that had a 5 % chance of exceedance for mobilization of the bed. These findings suggest the West Branch of Crescent Stream and the biota supported by this branch of the stream, continue to adjust to the sediment introduced from the thermokarst bank degradation.

10aAntarctica10aDry valleys10aearth sciences10astream10athermokarst1 aSudman, Zachary1 aGooseff, Michael, N. uhttps://search.proquest.com/docview/171758257303517nas a2200349 4500008004100000245015900041210006900200260003400269490000900303520243200312653001502744653002002759653002402779653001402803653002802817653001702845653001302862653001402875653001402889653001302903653002402916653002002940653001402960653001702974653002102991653002103012653001503033653002003048100002503068700002503093856004903118 2011 eng d00aHydrologic controls of nutrient fluxes in glacial meltwater streams at inter-annual, seasonal, and daily timescales in the McMurdo Dry Valleys, Antarctica0 aHydrologic controls of nutrient fluxes in glacial meltwater stre bPennsylvania State University0 vM.S.3 a

In the McMurdo Dry Valleys of Antarctica, glaciers are hydrologically linked to closed-basin lakes at the valley floor by glacial meltwater streams. Streams flow through porous, well-defined channels with extensive chemically active hyporheic zones. Temporally varying dynamics of meltwater generation and sub-stream thaw depth are thought to control the potential for the hyporheic zone and benthic communities to influence transport of nutrients and dissolved ions downstream. Using the McMurdo LTER database, patterns in stream discharge, electrical conductivity (both with 15-minute sampling intervals), and solute chemistry (weekly sampling intervals) were examined on eight MDV streams from 1990-2008. Discharge and electrical conductivity values were highly variable among streams. Discharge values were highly dependent upon glacial source area, but meteorological and topographical complexities create large variability at all time scales. The longer streams were found to have much higher electrical conductivity values than the shorter streams, suggesting that there are more opportunities for hyporheic weathering reactions along longer stream reaches. Weekly sampled water solutes from each stream's entire record were plotted against the discharge recorded at the time when the sample was taken. Silicate concentrations displayed a decreasing logarithmic relationship, while nutrient concentrations had no apparent relationship. This suggests that with the exception to bioreactive solutes, the majority of hyporheic interactions could possibly be characterized by electrical conductivity and discharge. To attain information on in-stream nutrient dynamics and nutrient fluxes, glacial source water at the upper reach of Green Creek and stream outlet water at the lower reach of Green Creek were sampled hourly for two separate diel periods during the 2008-09 austral summer. Both dates were in late January under two distinct flow conditions (~0.5 L/s and ~10 L/s). Under low flow conditions, nutrient cycling was found to be uptake dominated. High flow conditions showed both uptake and regeneration with much higher nutrient loads, but as in the low flow conditions, no apparent temporal trends were found. Nutrient concentrations could not be predicted using the two parameters of discharge and electrical conductivity with in-stream nutrient dynamics likely too complicated at the sub-daily scale.

10aAntarctica10abiogeochemistry10achemical weathering10adischarge10aelectrical conductivity10aglacial melt10aglaciers10ahydrology10ahyporheic10aMCM LTER10aMcMurdo Dry Valleys10anutrient fluxes10anutrients10apolar desert10asolute chemistry10astream chemistry10astreamflow10awater chemistry1 aWeaver, Mitchell, R.1 aGooseff, Michael, N. uhttps://etda.libraries.psu.edu/catalog/11568