@article {4856, title = {Differentiating physical and biological storage of nitrogen along an intermittent Antarctic stream corridor}, journal = {Freshwater Science}, volume = {42}, year = {2023}, month = {09/2023}, abstract = {

In many temperate streams, biological uptake of N acts to attenuate the transport of excess N from allochthonous anthropogenic imports. Relatively few studies have determined how this N uptake relates to the magnitude of physical vs. biological N storage in the stream corridor, especially for intermittent systems where allochthonous N imports are often low and N transport may only occur during brief periods of streamflow. Glacial meltwater streams in the McMurdo Dry Valleys of Antarctica provide an excellent setting to quantify autochthonous N cycling and storage processes supported by abundant algal mats and well-connected hyporheic zones. We combined historic point-scale sediment and periphyton sample datasets with remote sensing-based modeling of periphyton coverage to estimate how much N was stored in periphyton biomass and the hyporheic zone of a 5-km long McMurdo Dry Valley stream corridor (\>100,000 m2). We contextualized these N storage calculations by estimating the magnitude of annual N imports to and exports from the stream corridor based on \>2 decades of streamflow and surface water data, source glacier ice cores and meltwater data, and past studies of local aeolian deposition and biological N fixation rates. We found that in this highly oligotrophic system, stream corridor-scale N storage was ~1000x that of total annual N import or export fluxes. More than 90\% of this temporarily stored N was autochthonous organic matter in the shallow (\<10 cm) hyporheic zone, which acts as a reservoir that sustains N availability in the water column. Despite its location in a polar desert devoid of higher-order vegetation, area-normalized N storage (~40 g N/m2) was greater than that reported for streams at lower latitudes (~1\–22 g N/m2). We also demonstrated that NH4+ sorption to stream sediment may be an important physicochemical N storage mechanism that responds to short-term fluctuations in streamflow and governs the mobility of inorganic N. Altogether, this research illustrates the importance of quantifying N storage within stream corridors when evaluating the significance of internal cycling and physical retention processes that modulate N availability.

}, keywords = {LTER-MCM, hyporheic zone, McMurdo LTER, nitrogen cycling, nutrient budget, organic matter, periphyton}, issn = {2161-9549}, doi = {10.1086/725676}, url = {https://www.journals.uchicago.edu/doi/10.1086/725676}, author = {Singley, Joel G. and Salvatore, Mark R. and Michael N. Gooseff and Diane M. McKnight and Eve-Lyn S. Hinckley} } @article {4815, title = {Dissolved organic carbon chemostasis in Antarctic polar desert streams}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {127}, year = {2022}, month = {07/2022}, pages = {e2021JG006649}, abstract = {

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\&$\#$39; 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.

}, keywords = {LTER-MCM, Antarctica, chemostasis, concentration-discharge, DOC, ephemeral streams, LTER}, doi = {10.1029/2021JG006649}, url = {https://onlinelibrary.wiley.com/doi/10.1029/2021JG006649}, author = {Torrens, Christa L. and Michael N. Gooseff and Diane M. McKnight} } @article {4586, title = {Diatoms in hyporheic sediments trace organic matter retention and processing in the McMurdo Dry Valleys, Antarctica}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {126}, year = {2021}, month = {02/2021}, pages = {e2020JG006097}, abstract = {

In low-nutrient streams in cold and arid ecosystems, the spiraling of autochthonous particulate organic matter (POM) may provide important nutrient subsidies downstream. Because of its lability and the spatial heterogeneity of processing in hyporheic sediments, the downstream transport and fate of autochthonous POM can be difficult to trace. In Antarctic McMurdo Dry Valley (MDV) streams, any POM retained in the hyporheic zone is expected to be derived from surface microbial mats that contain diatoms with long-lasting silica frustules. We tested whether diatom frustules can be used to trace the retention of autochthonous POM in the hyporheic zone and whether certain geomorphic locations promote this process. The accumulation of diatom frustules in hyporheic sediments, measured as biogenic silica, was correlated with loss-on-ignition organic matter and sorbed ammonium, suggesting that diatoms can be used to identify locations where POM has been retained and processed over long timescales, regardless of whether the POM remains intact. In addition, by modeling the upstream sources of hyporheic diatom assemblages, we found that POM was predominantly derived from N-fixing microbial mats of the genus Nostoc. In terms of spatial variability, we conclude that the hyporheic sediments adjacent to the stream channel that are regularly inundated by daily flood pulses are where the most POM has been retained over long timescales. Autochthonous POM is retained in hyporheic zones of low-nutrient streams beyond the MDVs, and we suggest that biogenic silica and diatom composition can be used to identify locations where this transfer is most prevalent.

}, keywords = {LTER-MCM, benthic processes, biogenic silica, biogeochemical cycles processes and modeling, carbon cycling, diatoms, groundwater/surface water interactions, hyporheic zone, McMurdo Dry Valleys, nitrogen cycling, particulate organic matter}, doi = {10.1029/2020JG006097}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG006097}, author = {Heindel, Ruth C and Darling, Joshua P. and Singley, Joel G. and Bergstrom, Anna J. and Diane M. McKnight and Lukkari, Braeden M. and Kathleen A. Welch and Michael N. Gooseff} } @article {4022, title = {Decadal ecosystem response to an anomalous melt season in a polar desert in Antarctica}, journal = {Nature Ecology \& Evolution}, volume = {1}, year = {2017}, month = {09/2017}, pages = {1334-1338}, keywords = {LTER-MCM}, doi = {10.1038/s41559-017-0253-0}, url = {https://www.nature.com/articles/s41559-017-0253-0}, author = {Michael N. Gooseff and John E. Barrett and Byron Adams and Peter T. Doran and Andrew G Fountain and W. Berry Lyons and Diane M. McKnight and John C. Priscu and Eric R. Sokol and Cristina D. Takacs-Vesbach and Martijn L. Vandegehuchte and Ross A. Virginia and Diana H. Wall} } @article {1319, title = {Denitrification and hydrologic transient storage in a glacial meltwater stream, McMurdo Dry Valleys, Antarctica}, journal = {Limnology and Oceanography}, volume = {49}, year = {2004}, month = {09/2004}, pages = {1884-1895}, keywords = {LTER-MCM}, doi = {10.4319/lo.2004.49.5.1884}, author = {Michael N. Gooseff and Diane M. McKnight and Robert L. Runkel and John H. Duff} } @article {1361, title = {Determining long time-scale hyporheic zone flow paths in Antarctic streams}, journal = {Hydrological Processes}, volume = {17}, year = {2003}, pages = {1691-1710}, keywords = {LTER-MCM}, author = {Michael N. Gooseff and Diane M. McKnight and Robert L. Runkel and Bruce H. Vaughn} } @article {1378, title = {Direct observation of aluminosilicate weathering in the hyporheic zone of an Antarctic Dry Valley stream}, journal = {Geochimica et Cosmochimica Acta}, volume = {66}, year = {2002}, pages = {1335-1347}, keywords = {LTER-MCM}, author = {Maurice, P and Diane M. McKnight and Leff, L and Fulghun, J and Michael N. Gooseff} }