Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic Flowpath
Abstract Hyporheic exchange is critical to river corridor biogeochemistry, but decameter‐scale flowpaths (∼10‐m long) are understudied due to logistical challenges (e.g., sampling at depth, multi‐day transit times). Some studies suggest that decameter‐scale flowpaths should have initial hot spots fo...
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Wiley
2025-05-01
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| Series: | Water Resources Research |
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| Online Access: | https://doi.org/10.1029/2024WR038410 |
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| author | S. P. Herzog A. S. Ward S. M. Wondzell S. P. Serchan R. González‐Pinzón J. P. Zarnetske |
| author_facet | S. P. Herzog A. S. Ward S. M. Wondzell S. P. Serchan R. González‐Pinzón J. P. Zarnetske |
| author_sort | S. P. Herzog |
| collection | DOAJ |
| description | Abstract Hyporheic exchange is critical to river corridor biogeochemistry, but decameter‐scale flowpaths (∼10‐m long) are understudied due to logistical challenges (e.g., sampling at depth, multi‐day transit times). Some studies suggest that decameter‐scale flowpaths should have initial hot spots followed by transport‐limited conditions, whereas others suggest steady reaction rates and secondary reactions that could make decameter‐scale flowpaths important and unique. We investigated biogeochemistry along a 12‐m hyporheic mesocosm that allowed for controlled testing of seasonal and spatial water quality changes along a flowpath with fixed geometry and constant flow rate. Water quality profiles of oxygen, carbon, and nitrogen were measured at 1‐m intervals along the mesocosm over multiple seasons. The first 6 m of the mesocosm were always oxic and a net nitrogen source to mobile porewater. In winter, oxic conditions persisted to 12 m, whereas the second half of the flowpath became anoxic and a net nitrogen sink in summer. No reactive hot spots were observed in the first meter of the mesocosm. Instead, most reactions were zeroth‐order over 12 m and 54 hr of transit time. Influent chemistry had less impact on hyporheic biogeochemistry than expected due to large amounts of in situ reactant sources compared to stream‐derived reactant sources. Sorbed or buried carbon likely fueled reactions with rates controlled by temperature and redox conditions. Each reactant showed different hyporheic Damköhler numbers, challenging the characterization of flowpaths being intrinsically reaction‐ or transport‐limited. Future research should explore the prevalence and biogeochemical contributions of decameter‐scale flowpaths in diverse field settings. |
| format | Article |
| id | doaj-art-09615a3deb544a9cb19c57716c27b671 |
| institution | DOAJ |
| issn | 0043-1397 1944-7973 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | Wiley |
| record_format | Article |
| series | Water Resources Research |
| spelling | doaj-art-09615a3deb544a9cb19c57716c27b6712025-08-20T03:22:20ZengWileyWater Resources Research0043-13971944-79732025-05-01615n/an/a10.1029/2024WR038410Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic FlowpathS. P. Herzog0A. S. Ward1S. M. Wondzell2S. P. Serchan3R. González‐Pinzón4J. P. Zarnetske5Natural Resources Program Department of Forest Ecosystems & Society College of Forestry Oregon State University‐Cascades Bend OR USABiological and Ecological Engineering Department Oregon State University Corvallis OR USAPacific Northwest Research Station Forest Service United States Department of Agriculture Corvallis OR USADepartment of Geology and Geosciences University of Vermont Burlington VT USAGerald May Department of Civil Construction & Environmental Engineering University of New Mexico Albuquerque NM USADepartment of Earth and Environmental Science Michigan State University East Lansing MI USAAbstract Hyporheic exchange is critical to river corridor biogeochemistry, but decameter‐scale flowpaths (∼10‐m long) are understudied due to logistical challenges (e.g., sampling at depth, multi‐day transit times). Some studies suggest that decameter‐scale flowpaths should have initial hot spots followed by transport‐limited conditions, whereas others suggest steady reaction rates and secondary reactions that could make decameter‐scale flowpaths important and unique. We investigated biogeochemistry along a 12‐m hyporheic mesocosm that allowed for controlled testing of seasonal and spatial water quality changes along a flowpath with fixed geometry and constant flow rate. Water quality profiles of oxygen, carbon, and nitrogen were measured at 1‐m intervals along the mesocosm over multiple seasons. The first 6 m of the mesocosm were always oxic and a net nitrogen source to mobile porewater. In winter, oxic conditions persisted to 12 m, whereas the second half of the flowpath became anoxic and a net nitrogen sink in summer. No reactive hot spots were observed in the first meter of the mesocosm. Instead, most reactions were zeroth‐order over 12 m and 54 hr of transit time. Influent chemistry had less impact on hyporheic biogeochemistry than expected due to large amounts of in situ reactant sources compared to stream‐derived reactant sources. Sorbed or buried carbon likely fueled reactions with rates controlled by temperature and redox conditions. Each reactant showed different hyporheic Damköhler numbers, challenging the characterization of flowpaths being intrinsically reaction‐ or transport‐limited. Future research should explore the prevalence and biogeochemical contributions of decameter‐scale flowpaths in diverse field settings.https://doi.org/10.1029/2024WR038410hyporheic zonewater qualitynutrient cycling |
| spellingShingle | S. P. Herzog A. S. Ward S. M. Wondzell S. P. Serchan R. González‐Pinzón J. P. Zarnetske Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic Flowpath Water Resources Research hyporheic zone water quality nutrient cycling |
| title | Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic Flowpath |
| title_full | Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic Flowpath |
| title_fullStr | Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic Flowpath |
| title_full_unstemmed | Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic Flowpath |
| title_short | Seasonality Controls Biogeochemical Shifts in Oxygen, Carbon, and Nitrogen Along a 12‐m, 54 hr‐Long Hyporheic Flowpath |
| title_sort | seasonality controls biogeochemical shifts in oxygen carbon and nitrogen along a 12 m 54 hr long hyporheic flowpath |
| topic | hyporheic zone water quality nutrient cycling |
| url | https://doi.org/10.1029/2024WR038410 |
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