Abstract
Aquatic ecosystem metabolism encapsulates the daily fixation (gross primary production, (Formula presented.)) and mineralization (ecosystem respiration, (Formula presented.)) of organic carbon. In fluvial systems, these are commonly estimated by inverse solutions to field observations using a model that describes oxygen concentrations varying in the water column in response to metabolic fluxes and air-water gas exchange controlled by a rate coefficient (Formula presented.). The most common conceptual model is the single-station metabolism (SSM) model. The simplicity and flexibility of this conceptualization make it attractive; however, it implicitly assumes that all the processes that consume oxygen in fluvial systems can be lumped into a bulk estimate of respiration with poorly understood consequences for estimates of (Formula presented.), (Formula presented.), and (Formula presented.). Here, we focus on the implications of using SSM conceptualization when estimating metabolic fluxes from oxygen dynamics in channels where hyporheic exchange occurs. We use a new multiscale numerical model for reactive transport in streams that represents hyporheic exchange and streambed heterotrophic respiration. Nondimensionalization of this model reveals dimensionless groups that collectively control oxygen dynamics. Numerical experiments offer a mechanistic understanding of the impacts of hyporheic exchange on diel oxygen dynamics revealing that potential biases arise from neglecting mass transfer limitations. Specifically, we found that hyporheic exchange significantly affects diel oxygen dynamics, even for nonreactive streambed sediments. Moreover, while the SSM performs well in many situations, we find conditions where significant bias is produced by hyporheic exchange, even when oxygen data are well-fitted. These situations pose a major challenge in the interpretation of metabolism assessment estimates.
| Original language | English |
|---|---|
| Article number | e2025WR040208 |
| Journal | Water Resources Research |
| Volume | 62 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2026 |
Funding
This research was funded by the U.S. Department of Energy, Office of Science, Biological and Environmental Research. This work is a product of the Environmental System Science Program, as part of the Watershed Dynamics and Evolution (WaDE) Science Focus Area at Oak Ridge National Laboratory and the IDEAS Watersheds project. This research used resources of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. This manuscript has been co-authored by staff from UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This research was funded by the U.S. Department of Energy, Office of Science, Biological and Environmental Research. This work is a product of the Environmental System Science Program, as part of the Watershed Dynamics and Evolution (WaDE) Science Focus Area at Oak Ridge National Laboratory and the IDEAS Watersheds project. This research used resources of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE‐AC05‐00OR22725. This manuscript has been co‐authored by staff from UT‐Battelle, LLC, under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid‐up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐public‐access‐plan ).
Keywords
- hyporheic exchange
- modeling
- oxygen dynamics
- parameter estimation
- stream metabolism