02474nas 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/10.1029/2021JG006649