Stream metabolism controls diel patterns and evasion of CO 2 in Arctic streams

• Published in: Global Change Biology
• Main Authors: Rocher‐Ros, Gerard, Sponseller, Ryan A., Bergström, Ann‐Kristin, Myrstener, Maria, Giesler, Reiner
• Other Authors: Vetenskapsrådet
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: Arctic; Northern Sweden; Tundra
• Online Access: http://dx.doi.org/10.1111/gcb.14895; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgcb.14895; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.14895; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/gcb.14895

Abstract Streams play an important role in the global carbon (C) cycle, accounting for a large portion of CO 2 evaded from inland waters despite their small areal coverage. However, the relative importance of different terrestrial and aquatic processes driving CO 2 production and evasion from streams remains poorly understood. In this study, we measured O 2 and CO 2 continuously in streams draining tundra‐dominated catchments in northern Sweden, during the summers of 2015 and 2016. From this, we estimated daily metabolic rates and CO 2 evasion simultaneously and thus provide insight into the role of stream metabolism as a driver of C dynamics in Arctic streams. Our results show that aquatic biological processes regulate CO 2 concentrations and evasion at multiple timescales. Photosynthesis caused CO 2 concentrations to decrease by as much as 900 ppm during the day, with the magnitude of this diel variation being strongest at the low‐turbulence streams. Diel patterns in CO 2 concentrations in turn influenced evasion, with up to 45% higher rates at night. Throughout the summer, CO 2 evasion was sustained by aquatic ecosystem respiration, which was one order of magnitude higher than gross primary production. Furthermore, in most cases, the contribution of stream respiration exceeded CO 2 evasion, suggesting that some stream reaches serve as net sources of CO 2 , thus creating longitudinal heterogeneity in C production and loss within this stream network. Overall, our results provide the first link between stream metabolism and CO 2 evasion in the Arctic and demonstrate that stream metabolic processes are key drivers of the transformation and fate of terrestrial organic matter exported from these landscapes.