; The relationship between dissolved solute concentration (; C; ) and; discharge (; q; ) in streams, i.e., the; C-q; relationship, is a; useful diagnostic tool for understanding biogeochemical processes in; watersheds. In the ephemeral glacial meltwater streams of the McMurdo; Dry Valleys [MDVs], Antarctica, studies show significant chemostatic; relationships for weathering solutes and; NO; 3; -; . Dissolved organic carbon (DOC); concentrations here are low compared to temperate streams, in the range; of 0.1 to 2 mg C L; -1; , and their chemical signal; clearly indicates derivation from microbial biomass. Many MDV streams; support abundant microbial mats, which are also a source of organic; matter to underlying hyporheic sediments. We investigated 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. To evaluate the; DOC-; q; relationship, we fit the long-term DOC-; q; data to two; models: a power law and an advection-reaction model. By using model; outputs and other common metrics to characterize the DOC-; q; relationship, we found that this relationship is chemostatic in 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-; q; chemostasis and may be useful for; examining these relationships in temperate systems, where autochthonous; organic carbon is readily bioavailable but where its signal is masked by; a larger allochthonous signal.;
