Why does variability in chemostatic concentration-discharge relationships differ systematically between solutes in Antarctic streams?
Concentration-discharge (C-Q) relationships have been widely applied to infer integrated hydrologic and biogeochemical processes at the catchment-scale. Apart from event hysteresis or comparisons between catchments, relatively little attention has been given to the 鈥渘oise鈥 within long-term C-Q patterns. We analyze over two decades of historic data from 10 streams in the McMurdo Dry Valleys to assess systematic differences in chemostatic C-Q variability for solutes representing a continuum from weathering solutes to primary nutrients. We propose the hypothesis that variability in chemostasis can emerge from asynchronous variations in stream corridor source and sink processes. We present a theoretical test of this hypothesis using an alternative version of the OTIS model that allows for time-varying reaction kinetics. Our analysis demonstrates that (1) chemostasis of both weathering solutes and nutrients can emerge from stream corridor processes, (2) solutes governed by a larger number of coupled processes exhibit more chemostatic variability, and (3) temporal fluctuations in the net balance of source and sink process rates can explain these differences in variability. Our work ultimately highlights the potential to move beyond ignoring 鈥渘oise鈥 in long-term C-Q observations to better understand how the biogeochemical function of stream corridors varies over time.