01993nas a2200253 4500008004100000022001400041245010200055210006900157260001200226300001100238490000700249520122000256653001501476653000901491653002401500653002201524653001701546653002301563100002501586700002401611700002101635700002101656856006201677 2022 eng d a0885-608700aLong-term stream hydrology and meteorology of a polar desert, the McMurdo Dry Valleys, Antarctica0 aLongterm stream hydrology and meteorology of a polar desert the  c06/2022 ae146230 v363 a

The McMurdo Dry Valleys (MDVs; 77.50°S, 162.25°E) make up the largest ice-free region of Antarctica at 3500 km2. Their position near the coast of the Ross Sea provides for a milder climate than much of the rest of the continent. Alpine and piedmont glaciers in the MDVs melt during the austral summer providing water to down gradient streams and terminal lakes on valley floors. There are currently 14 meteorological stations and 17 stream gauges operating across the MDVs, some with continuous records that go back to 1969. This relatively high density of monitoring stations reflects the fact that glaciers of different sizes and elevation ranges are the main source of water to streams. Thus, each glacier represents a different watershed. The bulk of these records start in the late 1980s/early 1990s. These data collection activities directly support research endeavors of the McMurdo Dry Valleys Long Term Ecological Research project, as well as a host of other science groups working in the MDVs. As such, both real time data and archived data from these sites is available through the online database interface of the project (https://mcmlter.org).

10aAntarctica10aLTER10aMcMurdo Dry Valleys10ameltwater streams10apolar desert10aresearch catchment1 aGooseff, Michael, N.1 aMcKnight, Diane, M.1 aDoran, Peter, T.1 aFountain, Andrew uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.1462302603nas a2200217 4500008004100000022001400041245012400055210006900179260001200248520186200260653001502122653002702137653001902164653002102183653001502204100002202219700002502241700002402266700002602290856006902316 2021 eng d a2169-895300aThe role of hyporheic connectivity in determining nitrogen availability: Insights from an intermittent Antarctic stream0 arole of hyporheic connectivity in determining nitrogen availabil c04/20223 a

Due to widespread manipulation of nitrogen (N), much research has focused on processes controlling the fate of anthropogenic N in streams. Yet, in a variety of oligotrophic systems, N fixed by periphyton is a significant driver of ecosystem metabolism. Due to difficulties partitioning allochthonous and autochthonous sources, there is limited information regarding how the latter is processed. Autochthonous N may be particularly important in alpine, arid, or polar environments. We test the hypothesis that the availability of remineralized autochthonous N is controlled by connectivity between the hyporheic zone and main channel due to the contrasting biogeochemical functions of benthic autotrophs (including N‐fixing Nostoc) and hyporheic heterotrophs in an intermittent Antarctic stream. There, we collected surface water and hyporheic water concurrently at 4‐6 hour intervals over a 32.5‐hr period during one flow season and opportunistically throughout a second. Hyporheic water had 7 to 30 times greater nitrate‐N concentrations relative to surface water across all flow conditions. In contrast, ammonium concentrations were generally lower, although similar among locations. Additionally, nitrate in hyporheic water was positively correlated with silica, an indicator of hyporheic residence time. A laboratory assay confirmed prior inferences that hyporheic microbial communities possess the functional potential to perform nitrification. Together, these findings suggest that remineralized autochthonous N accumulates in the hyporheic zone even as streamflow varies and likely subsidizes stream N availability—which supports prior inferences from N stable isotope data at this site. These results highlight the importance of hyporheic connectivity in controlling autochthonous N cycling and availability in streams.

10aAntarctica10aautochthonous nitrogen10ahyporheic zone10anitrogen cycling10astreamflow1 aSingley, Joel, G.1 aGooseff, Michael, N.1 aMcKnight, Diane, M.1 aHinckley, Eve-Lyn, S. uhttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JG006309