IntegratingPerspectivesDOCRemovalWhole-StreamMetabolism_Data

Quantifying organic carbon (OC) removal in streams is needed to integrate the functional role of inland waters into landscape carbon budgets. To illustrate how in-stream OC removal measurements can be used to characterize ecosystem and landscape carbon fluxes, we compared two common methods: (1) bioassays measuring water column dissolved organic carbon (DOC) uptake and (2) daily rates of whole-stream metabolism and OC spiraling calculated from fluorescent dissolved organic matter, oxygen, and discharge measurements. We then assessed how OC removal rates from these two methods, measured in two low-productivity heterotrophic streams, affected estimates of terrestrial OC loading and export using a mass balance model. OC mineralization velocities calculated from whole-stream metabolism (0.06 ±0.03 m d-1 (mean±SD)) were greater than water column bioassay DOC uptake velocities (0.01 ±0.01 m d-1), which resulted in higher in-stream OC removal estimates (0.5-15.2% and 0.02-4.2% removal for whole-stream metabolism and bioassays, respectively). Furthermore, the terrestrial OC inputs needed to sustain in-stream OC concentrations differ among methods, with simulated inputs ranging from 79-1300 or 3-350 g OC d-1 for whole-stream metabolism or bioassays, respectively. We show how in-stream OC removal can be used to quantify terrestrial-aquatic linkages by estimating OC inputs needed to fuel whole-stream metabolism in low-productivity streams, and offer future directions to better link OC removal with whole-ecosystem OC budgets. Without appropriate conversions to whole-stream processes, bioassays systematically underestimate whole-stream carbon cycling. By integrating whole-stream metabolism with OC transport, we can better elucidate the role of running waters in landscape carbon budgets and the global carbon cycle.