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Stream metabolism controls diel patterns and evasion of CO2 in Arctic streams
Vise andre og tillknytning
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Abstract [en]

Streams play an important role in the global carbon (C) cycle, accounting for a large portion of CO2 evaded from inland waters despite their small areal coverage. However, the relative importance of different terrestrial and aquatic processes driving CO2 production and evasion from streams remains poorly understood. In this study, we measured O2 and CO2 continuously in tundra-dominated streams in northern Sweden to estimate daily metabolic rates and CO2 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 control CO2 concentrations and evasion at multiple time scales. Photosynthesis caused a marked decrease in CO2 concentrations during the day, with up to a 900-ppm difference between day- and night-time values with the magnitude of this diel variation being strongest at the low-turbulence streams. These diel patterns in CO2 concentrations in turn influenced evasion, with up to 45% higher rates at night. Throughout the summer, CO2 evasion was sustained by ecosystem respiration, which was one order of magnitude higher than gross primary production. Furthermore, in most cases the contribution of stream respiration exceeded CO2 evasion, suggesting that some stream reaches serve as net sources of CO2, creating longitudinal heterogeneity in C production and loss within this stream network. Overall, our results provide the first link between stream metabolism and CO2 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.

HSV kategori
Forskningsprogram
limnologi
Identifikatorer
URN: urn:nbn:se:umu:diva-158880OAI: oai:DiVA.org:umu-158880DiVA, id: diva2:1315359
Tilgjengelig fra: 2019-05-13 Laget: 2019-05-13 Sist oppdatert: 2019-06-13
Inngår i avhandling
1. Biophysical controls on CO2 evasion from Arctic inland waters
Åpne denne publikasjonen i ny fane eller vindu >>Biophysical controls on CO2 evasion from Arctic inland waters
2019 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

CO2 evasion to the atmosphere from inland waters is a major component of the global carbon (C) cycle. Yet spatial patterns of CO2 evasion and the sources of C that fuel evasion remain poorly understood. In this thesis, I use detailed measurements of biological and physical drivers of CO2 evasion to assess how C is transformed and evaded from inland waters in the Arctic (Northern Scandinavia and Alaska). I found that lake size was a master variable controlling lake CO2 evasion in an Arctic catchment and that large lakes play a major role at the landscape scale. In stream networks, I found that catchment topography shapes patterns of CO2 evasion by dictating unique domains with high lateral inputs of C, other domains where biological processes were dominant, and domains where physical forces promoted degassing to the atmosphere. Together, these topographically driven domains created a strong spatial heterogeneity that biases regional and global estimates of CO2 evasion. Further, I found that photosynthetic activity in Arctic streams can produce a large change in CO2 concentrations from night to day, and as a result CO2 evasion is up to 45% higher during night than day. The magnitude of the diel change in CO2 was also affected by the turbulence of the stream and photo-chemical production of CO2. Overall, this thesis offers important insights to better understand landscape patterns of CO2 evasion from inland waters, and suggests that stream metabolic processes largely determine the fate of the C delivered from Arctic soils.

sted, utgiver, år, opplag, sider
Umeå: Umeå Univeristy, 2019. s. 32
Emneord
Inland waters, carbon dioxide, organic carbon, inorganic carbon, arctic, CO2 evasion, DOC, DIC, streams, metabolism, oxygen
HSV kategori
Forskningsprogram
limnologi
Identifikatorer
urn:nbn:se:umu:diva-158882 (URN)978-91-7855-075-3 (ISBN)
Disputas
2019-06-14, Carl Kempe Salen, KBC, Umeå University, Umeå, 09:30 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2019-05-24 Laget: 2019-05-13 Sist oppdatert: 2019-05-23bibliografisk kontrollert

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