Keridwen McLeyne Whitmore
University of North Carolina at Chapel Hill
| Subject Areas: | Hydrology, Water Quality, Wetlands, Rivers, Greenhouse Gases |
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ABSTRACT:
Inland waters emit large amounts of carbon and are key players in the global carbon budget. Particularly high rates of carbon emissions have been reported in streams draining mountains, tropical regions, and peatlands. However, few studies have examined the spatial variability of CO2 concentrations and fluxes occurring within these systems, particularly as a function of watershed morphology. Here we evaluated spatial patterns of CO2 in three tropical, headwater watersheds in relation to the river network and stream geomorphology. We measured dissolved carbon dioxide (pCO2), aquatic CO2 evasion, discharge, and stream depth and width at high spatial resolutions along multiple stream reaches. Confirming previous studies, we found that tropical headwater streams are an important source of CO2 to the atmosphere. More notably, we found marked, predictable spatial organization in aquatic carbon fluxes as a function of landscape position. For example, pCO2 was consistently high (>10,000 ppm) at locations close to groundwater sources and just downstream of hydrologically connected wetlands, but consistently low (<1,000 ppm) in high gradient locations or river segments with large drainage areas. We found catchment area and stream slope to be predictive of pCO2 and gas transfer velocity in our streams. pCO2 decreased with catchment area while gas transfer velocity increased. We suggest that accurate estimation of CO2 emissions requires understanding of dynamics across the entire stream network, from the smallest seeps to larger streams.
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Created: Oct. 25, 2024, 2:18 a.m.
Authors: Whitmore, Kriddie · Riveros-Iregui, Diego · Farquhar, Elizabeth · Amanda G. DelVecchia · Gerard Rocher-Ros · Esteban Suárez
ABSTRACT:
Inland waters emit large amounts of carbon and are key players in the global carbon budget. Particularly high rates of carbon emissions have been reported in streams draining mountains, tropical regions, and peatlands. However, few studies have examined the spatial variability of CO2 concentrations and fluxes occurring within these systems, particularly as a function of watershed morphology. Here we evaluated spatial patterns of CO2 in three tropical, headwater watersheds in relation to the river network and stream geomorphology. We measured dissolved carbon dioxide (pCO2), aquatic CO2 evasion, discharge, and stream depth and width at high spatial resolutions along multiple stream reaches. Confirming previous studies, we found that tropical headwater streams are an important source of CO2 to the atmosphere. More notably, we found marked, predictable spatial organization in aquatic carbon fluxes as a function of landscape position. For example, pCO2 was consistently high (>10,000 ppm) at locations close to groundwater sources and just downstream of hydrologically connected wetlands, but consistently low (<1,000 ppm) in high gradient locations or river segments with large drainage areas. We found catchment area and stream slope to be predictive of pCO2 and gas transfer velocity in our streams. pCO2 decreased with catchment area while gas transfer velocity increased. We suggest that accurate estimation of CO2 emissions requires understanding of dynamics across the entire stream network, from the smallest seeps to larger streams.