Differentiating physical and biological storage of N along an intermittent Antarctic stream corridor

Joel G. Singley, Mark R. Salvatore, Michael N. Gooseff, Diane M. McKnight, Eve Lyn S. Hinckley

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

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 pointscale 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 ∼1000˟ 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 NH41 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.

Original languageEnglish (US)
Pages (from-to)229-246
Number of pages18
JournalFreshwater Science
Volume42
Issue number3
DOIs
StatePublished - Sep 2023

Keywords

  • McMurdo LTER
  • hyporheic zone
  • nitrogen cycling
  • nutrient budget
  • organic matter
  • periphyton

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Aquatic Science

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