4.4 Future research directions
Ground-truthing model outputs by collecting samples or deploying sensors in every reach is logistically impossible even for a small sub-catchment. Our RCM approach already incorporates a model-experiment (Modex) loop (Serbin et al. 2021), where laboratory measurements of sediments collected within the Columbia River Basin were used to parameterize biogeochemical rates in the model. We suggest implementing a subsequent ModEx loop, where our allometry estimates can identify sub-catchments that may function as biogeochemical control points (sensu Bernhardt et al. 2017). For instance, by examining residuals in Figure 2 for each regression line fit, we could iteratively identify which reaches adhered most poorly to scaling relationships (where the largest positive residuals represent respiration hot spots) and target field sampling campaigns to confirm whether outliers are due to high respiration or heterogeneity poorly captured by the model.
Predictions of how hyporheic respiration allometrically scales across watersheds that can generalize between basins will dramatically improve our ability to model and therefore forecast how biogeochemical processes influencing, and influenced by, aquatic metabolism will respond to natural or anthropogenic changes in watershed dynamics. Our findings present an initial attempt to characterize how hyporheic respiration scales allometrically with watershed area across two environmentally distinct basins. We found that, while some commonalities exist in allometric scaling patterns and relationships to watershed characteristics, particularly precipitation and elevation, basin-specific patterns suggest that the factors driving hyporheic respiration scaling require additional study. We suggest future studies incorporate a larger number of study basins to more effectively assess generalizability of patterns and relationships to watershed characteristics. Further, incorporation of key disturbances, including non-perenniality, wildfires, and urbanization, whose downstream impacts increasingly influence, and are influenced by, surface and hyporheic biogeochemical processes (Lawrence et al. 2013; Zhao et al. 2021; Ball et al. 2021; DelVecchia et al. 2022), will improve our ability to model the hyporheic zone and more accurately represent river corridor function in earth system models.
Acknowledgements: The authors thank Francisco Guerrero for contributions in conceptualization and analysis to an earlier draft of this manuscript. This research was supported by the U.S. Department of Energy (DOE), Office of Biological and Environmental Research (BER), Environmental System Science (ESS) Program as part of the River Corridor Science Focus Area (SFA) at the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle Memorial Institute for the DOE under Contract No. DE-AC05-76RL01830. The authors declare no conflict of interest.
Ball, G., P. Regier, R. González-Pinzón, J. Reale, and D. Van Horn. 2021. Wildfires increasingly impact western US fluvial networks. Nat. Commun. 12 : 2484. doi:10.1038/s41467-021-22747-3
Bernhardt, E. S., J. R. Blaszczak, C. D. Ficken, M. L. Fork, K. E. Kaiser, and E. C. Seybold. 2017. Control Points in Ecosystems: Moving Beyond the Hot Spot Hot Moment Concept. Ecosystems 20 : 665–682. doi:10.1007/s10021-016-0103-y
Bertuzzo, E., A. M. Helton, Hall Robert O., and T. J. Battin. 2017. Scaling of dissolved organic carbon removal in river networks. Adv. Water Resour. 110 : 136–146. doi:10.1016/j.advwatres.2017.10.009
Briggs, M. A., L. K. Lautz, D. K. Hare, and R. González-Pinzón. 2013. Relating hyporheic fluxes, residence times, and redox-sensitive biogeochemical processes upstream of beaver dams. Freshw. Sci.32 : 622–641. doi:10.1899/12-110.1
Brown, J. H., J. F. Gillooly, A. P. Allen, V. M. Savage, and G. B. West. 2004. Toward a Metabolic Theory of Ecology. Ecology 85 : 1771–1789. doi:10.1890/03-9000
Buser-Young, J. Z., P. E. Garcia, M. O. Schrenk, and others. 2023. Determining the biogeochemical transformations of organic matter composition in rivers using molecular signatures. Front. Water5 .
Chen, T., and T. He. 2023. xgboost: eXtreme Gradient Boosting.
Chiriboga, G., and A. V. Borges. 2023. Andean headwater and piedmont streams are hot spots of carbon dioxide and methane emissions in the Amazon basin. Commun. Earth Environ. 4 : 1–13. doi:10.1038/s43247-023-00745-1
Coulson, L. E., G. Weigelhofer, S. Gill, T. Hein, C. Griebler, and J. Schelker. 2022. Small rain events during drought alter sediment dissolved organic carbon leaching and respiration in intermittent stream sediments. Biogeochemistry 159 : 159–178. doi:10.1007/s10533-022-00919-7
DelVecchia, A. G., M. Shanafield, M. A. Zimmer, and others. 2022. Reconceptualizing the hyporheic zone for nonperennial rivers and streams. Freshw. Sci. Print 41 : 167–182. doi:10.1086/720071
Fang, Y., X. Chen, J. Gomez Velez, and others. 2020. A multirate mass transfer model to represent the interaction of multicomponent biogeochemical processes between surface water and hyporheic zones (SWAT-MRMT-R 1.0). Geosci. Model Dev. 13 : 3553–3569. doi:10.5194/gmd-13-3553-2020
Fulton, S. G., M. Barnes, M. A. Borton, and others. 2024. Yakima River Basin Water Column Respiration is a Minor Component of River Ecosystem Respiration. EGUsphere 1–27. doi:10.5194/egusphere-2023-3038
Gomez-Velez, J. D., and J. W. Harvey. 2014. A hydrogeomorphic river network model predicts where and why hyporheic exchange is important in large basins. Geophys. Res. Lett. 41 : 6403–6412. doi:10.1002/2014GL061099
Gomez-Velez, J. D., S. Krause, and J. L. Wilson. 2014. Effect of low-permeability layers on spatial patterns of hyporheic exchange and groundwater upwelling. Water Resour. Res. 50 : 5196–5215. doi:10.1002/2013WR015054
Krause, S., B. W. Abbott, V. Baranov, and others. 2022. Organizational Principles of Hyporheic Exchange Flow and Biogeochemical Cycling in River Networks Across Scales. Water Resour. Res. 58 : e2021WR029771. doi:10.1029/2021WR029771
Lawrence, J. E., M. E. Skold, F. A. Hussain, D. R. Silverman, V. H. Resh, D. L. Sedlak, R. G. Luthy, and J. E. McCray. 2013. Hyporheic Zone in Urban Streams: A Review and Opportunities for Enhancing Water Quality and Improving Aquatic Habitat by Active Management. Environ. Eng. Sci.30 : 480–501. doi:10.1089/ees.2012.0235
Lee-Cullin, J. A., J. P. Zarnetske, S. S. Ruhala, and S. Plont. 2018. Toward measuring biogeochemistry within the stream-groundwater interface at the network scale: An initial assessment of two spatial sampling strategies. Limnol. Oceanogr. Methods 16 : 722–733. doi:10.1002/lom3.10277
Leggieri, L., C. Feijoó, A. Giorgi, N. Ferreiro, and V. Acuña. 2013. Seasonal weather effects on hydrology drive the metabolism of non-forest lowland streams. Hydrobiologia 716 : 47–58. doi:10.1007/s10750-013-1543-4
Liu, S., T. Maavara, C. B. Brinkerhoff, and P. A. Raymond. 2022. Global Controls on DOC Reaction Versus Export in Watersheds: A Damköhler Number Analysis. Glob. Biogeochem. Cycles 36 : e2021GB007278. doi:10.1029/2021GB007278
McClain, M. E., E. W. Boyer, C. L. Dent, and others. 2003. Biogeochemical Hot Spots and Hot Moments at the Interface of Terrestrial and Aquatic Ecosystems. Ecosystems 6 : 301–312. doi:10.1007/s10021-003-0161-9
Meyer, P. E. 2022. infotheo: Information-Theoretic Measures.
Naegeli, M. W., and U. Uehlinger. 1997. Contribution of the Hyporheic Zone to Ecosystem Metabolism in a Prealpine Gravel-Bed-River. J. North Am. Benthol. Soc. 16 : 794–804. doi:10.2307/1468172
Newcomer, M. E., S. S. Hubbard, J. H. Fleckenstein, and others. 2018. Influence of Hydrological Perturbations and Riverbed Sediment Characteristics on Hyporheic Zone Respiration of CO 2and N 2. J. Geophys. Res. Biogeosciences 123 : 902–922. doi:10.1002/2017JG004090
Nidzieko, N. J. 2018. Allometric scaling of estuarine ecosystem metabolism. Proc. Natl. Acad. Sci. 115 : 6733–6738. doi:10.1073/pnas.1719963115
R Core Team. 2023. R: A Language and Environment for Statistical Computing.
Raymond, P. A., J. E. Saiers, and W. V. Sobczak. 2016. Hydrological and biogeochemical controls on watershed dissolved organic matter transport: pulse-shunt concept. Ecology 97 : 5–16. doi:10.1890/14-1684.1
Sackett, J. D., C. L. Shope, J. C. Bruckner, J. Wallace, C. A. Cooper, and D. P. Moser. 2019. Microbial Community Structure and Metabolic Potential of the Hyporheic Zone of a Large Mid-Stream Channel Bar. Geomicrobiol. J. 36 : 765–776. doi:10.1080/01490451.2019.1621964
Serbin, S. P., S. E. Giangrande, C. Kuang, N. Urban, and L. Pouchard. 2021. AI to Automate ModEx for Optimal Predictive Improvement and Scientific Discovery. AI4ESP-1119. AI4ESP-1119 Artificial Intelligence for Earth System Predictability (AI4ESP) Collaboration (United States).
Son, K., Y. Fang, J. D. Gomez-Velez, K. Byun, and X. Chen. 2022a. Combined Effects of Stream Hydrology and Land Use on Basin-Scale Hyporheic Zone Denitrification in the Columbia River Basin. Water Resour. Res. 58 : e2021WR031131. doi:10.1029/2021WR031131
Son, K., Y. Fang, J. D. Gomez-Velez, and X. Chen. 2022b. Spatial microbial respiration variations in the hyporheic zones within the Columbia River Basin. J. Geophys. Res. Biogeosciences n/a : e2021JG006654. doi:10.1029/2021JG006654
Stegen, J. C., V. A. Garayburu-Caruso, R. E. Danczak, A. E. Goldman, L. Renteria, J. M. Torgeson, and J. Hager. 2023. Maximum respiration rates in hyporheic zone sediments are primarily constrained by organic carbon concentration and secondarily by organic matter chemistry. Biogeosciences 20 : 2857–2867. doi:10.5194/bg-20-2857-2023
Tureţcaia, A. B., V. A. Garayburu-Caruso, M. H. Kaufman, and others. 2023. Rethinking Aerobic Respiration in the Hyporheic Zone under Variation in Carbon and Nitrogen Stoichiometry. Environ. Sci. Technol.57 : 15499–15510. doi:10.1021/acs.est.3c04765
Wollheim, W. M., T. K. Harms, A. L. Robison, L. E. Koenig, A. M. Helton, C. Song, W. B. Bowden, and J. C. Finlay. 2022. Superlinear scaling of riverine biogeochemical function with watershed size. Nat. Commun.13 : 1230. doi:10.1038/s41467-022-28630-z
Zhao, S., B. Zhang, X. Sun, and L. Yang. 2021. Hot spots and hot moments of nitrogen removal from hyporheic and riparian zones: A review. Sci. Total Environ. 762 : 144168. doi:10.1016/j.scitotenv.2020.144168