Decoupling of carbon dioxide and dissolved organic carbon in boreal headwater streams. Issue 10 (20th October 2016)

• Record Type: Journal Article
• Authors: Winterdahl, Mattias; Wallin, Marcus B.; Karlsen, Reinert Huseby; Laudon, Hjalmar; Öquist, Mats; Lyon, Steve W.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 10(2016:Oct.)
• Page Start: 2630
• Page End: 2651
• Publication Date: 2016-10-20
• Subjects: DOC -- CO2 -- mass balance -- water‐atmosphere exchange -- Riparian flow‐concentration Integration Model; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1002/2016JG003420
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Streams and rivers emit large quantities of carbon dioxide (CO2 ) to the atmosphere. The sources of this CO2 are in‐stream mineralization of organic carbon (OC) and CO2 input via groundwater inflow, but their relative importance is largely unknown. In this study, we quantified the role of in‐stream OC mineralization as a source of CO2 in a number of nested boreal headwater streams. The results showed that mineralization of stream OC contributed 3% of CO2 supersaturation at time scales comparable to the estimated water travel times in the streams (<24 h). Mass balances showed that downstream losses of OC were ≤3% in low‐order streams, whereas up to 16% of the OC was lost in the largest (fourth order) streams. In contrast, 85% of the CO2 was lost along the stream network (longest total stream length = 17 km). Under the assumption that in‐stream OC mineralization was the main source of stream CO2, higher rates of OC mineralization (6% of OC) than those reported across the literature (≤0.7% of OC) would be required to sustain observed CO2 supersaturation. Further, model results indicated that groundwater inflows were sufficient to sustain observed stream CO2 concentrations. We hence conclude that in‐stream OC mineralization was a minor source of CO2 in these boreal headwater systems and that the main source of stream CO2 was inflowing groundwater transporting CO2 originating from soil respiration. Key Points: We observed large losses of CO2 in a network of small boreal streams DOC mineralization was a small source of stream CO2 The main source of CO2 was supersaturated groundwater