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  • 1.
    Gómez-Gener, Lluís
    et al.
    Stream Biofilm and Ecosystem Research Laboratory, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Rocher-Ros, Gerard
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Battin, Tom
    Stream Biofilm and Ecosystem Research Laboratory, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Cohen, Matthew J.
    School of Forest Resources and Conservation, University of Florida, FL, Gainesville, United States.
    Dalmagro, Higo J.
    University of Cuiabá, Cuiabá, Brazil.
    Dinsmore, Kerry J.
    Centre for Ecology and Hydrology, Bush Estate, Penicuik, United Kingdom.
    Drake, Travis W.
    Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland.
    Duvert, Clément
    Research Institute for the Environment and Livelihoods, Charles Darwin University, NT, Darwin, Australia.
    Enrich-Prast, Alex
    Biogas Research Center and Department of Thematic Studies–Environmental Change, Linköping University, Linköping, Sweden; Post-Graduate Program in Geosciences (Environmental Geochemistry), Chemistry Institute, Fluminense Federal University, Niterói, Brazil.
    Horgby, Åsa
    Stream Biofilm and Ecosystem Research Laboratory, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Johnson, Mark S.
    Institute for Resources, Environment and Sustainability, University of British Columbia, BC, Vancouver, Canada; Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, BC, Vancouver, Canada.
    Kirk, Lily
    School of Natural Resources and Environment, University of Florida, FL, Gainesville, United States.
    Machado-Silva, Fausto
    Post-Graduate Program in Geosciences (Environmental Geochemistry), Chemistry Institute, Fluminense Federal University, Niterói, Brazil.
    Marzolf, Nicholas S.
    Department of Forestry and Environmental Resources, North Carolina State University, NC, Raleigh, United States.
    McDowell, Mollie J.
    Institute for Resources, Environment and Sustainability, University of British Columbia, BC, Vancouver, Canada; Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, BC, Vancouver, Canada.
    McDowell, William H.
    Department of Natural Resources and the Environment, University of New Hampshire, NH, Durham, United States.
    Miettinen, Heli
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ojala, Anne K.
    Faculty of Biological and Environmental Sciences, Ecosystems and Environment Research Programme, University of Helsinki, Helsinki, Finland.
    Peter, Hannes
    Stream Biofilm and Ecosystem Research Laboratory, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Pumpanen, Jukka
    Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland.
    Ran, Lishan
    Department of Geography, The University of Hong Kong, Pokfulam, Hong Kong.
    Riveros-Iregui, Diego A.
    Department of Geography, University of North Carolina at Chapel Hill, NC, Chapel Hill, United States.
    Santos, Isaac R.
    Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden.
    Six, Johan
    Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland.
    Stanley, Emily H.
    Center for Limnology, University of Wisconsin-Madison, WI, Madison, United States.
    Wallin, Marcus B.
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    White, Shane A.
    National Marine Science Centre, Southern Cross University, NSW, Coffs Harbour, Australia.
    Sponseller, Ryan A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions2021In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 14, no 5, p. 289-294Article in journal (Refereed)
    Abstract [en]

    Carbon dioxide (CO2) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO2 concentrations. Using a global compilation of high-frequency CO2 measurements, we demonstrate that nocturnal CO2 emissions are on average 27% (0.9 gC m−2 d−1) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO2 by photosynthesis. Because current global estimates of CO2 emissions to the atmosphere from running waters (0.65–1.8 PgC yr−1) rely primarily on discrete measurements of dissolved CO2 obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO2 emissions may elevate global estimates from running waters to the atmosphere by 0.20–0.55 PgC yr−1.

  • 2.
    Myrstener, Maria
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Gómez-Gener, Lluís
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Rocher-Ros, Gerard
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Sponseller, Ryan A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Nutrients influence seasonal metabolic patterns and total productivity of Arctic streams2021In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 66, no S1, p. S182-S196Article in journal (Refereed)
    Abstract [en]

    The seasonality of gross primary production (GPP) in streams is driven by multiple physical and chemical factors, yet incident light is often thought to be most important. In Arctic tundra streams, however, light is available in saturating amounts throughout the summer, but sharp declines in nutrient supply during the terrestrial growing season may constrain aquatic productivity. Given the opposing seasonality of these drivers, we hypothesized that "shoulder seasons"-spring and autumn-represent critical time windows when light and nutrients align to optimize rates of stream productivity in the Arctic. To test this, we measured annual patterns of GPP and biofilm accumulation in eight streams in Arctic Sweden. We found that the aquatic growing season length differed by 4 months across streams and was determined largely by the timing of ice-off in spring. During the growing season, temporal variability in GPP for nitrogen (N) poor streams was correlated with inorganic N concentration, while in more N-rich streams GPP was instead linked to changes in phosphorus and light. Annual GPP varied ninefold among streams and was enhanced by N availability, the length of ice-free period, and low flood frequency. Finally, network scale estimates of GPP highlight the overall significance of the shoulder seasons, which accounted for 48% of annual productivity. We suggest that the timing of ice off and nutrient supply from land interact to regulate the annual metabolic regimes of nutrient poor, Arctic streams, leading to unexpected peaks in productivity that are offset from the terrestrial growing season.

  • 3.
    Olid, Carolina
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Rodellas, Valentí
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain.
    Rocher-Ros, Gerard
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Garcia-Orellana, Jordi
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain; Departament de Física, Universitat Autònoma de Barcelona, Bellaterra, Spain.
    Diego-Feliu, Marc
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain; Departament de Física, Universitat Autònoma de Barcelona, Bellaterra, Spain; Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain; Associated Unit: Hydrogeology Group, UPC-CSIC, Barcelona, Spain.
    Alorda-Kleinglass, Aaron
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain.
    Bastviken, David
    Department of Thematic Studies—Environmental Change, Linköping University, Linköping, Sweden.
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Groundwater discharge as a driver of methane emissions from Arctic lakes2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 3667Article in journal (Refereed)
    Abstract [en]

    Lateral CH4 inputs to Arctic lakes through groundwater discharge could be substantial and constitute an important pathway that links CH4 production in thawing permafrost to atmospheric emissions via lakes. Yet, groundwater CH4 inputs and associated drivers are hitherto poorly constrained because their dynamics and spatial variability are largely unknown. Here, we unravel the important role and drivers of groundwater discharge for CH4 emissions from Arctic lakes. Spatial patterns across lakes suggest groundwater inflows are primarily related to lake depth and wetland cover. Groundwater CH4 inputs to lakes are higher in summer than in autumn and are influenced by hydrological (groundwater recharge) and biological drivers (CH4 production). This information on the spatial and temporal patterns on groundwater discharge at high northern latitudes is critical for predicting lake CH4 emissions in the warming Arctic, as rising temperatures, increasing precipitation, and permafrost thawing may further exacerbate groundwater CH4 inputs to lakes.

  • 4.
    Rocher-Ros, Gerard
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Harms, Tamara K.
    Sponseller, Ryan A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Väisänen, Maria
    Mörth, Carl-Magnus
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Metabolism overrides photo-oxidation in CO2 dynamics of Arctic permafrost streams2021In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 66, no S1, p. S169-S181Article in journal (Refereed)
    Abstract [en]

    Global warming is enhancing the mobilization of organic carbon (C) from Arctic soils into streams, where it can be mineralized to CO2 and released to the atmosphere. Abiotic photo‐oxidation might drive C mineralization, but this process has not been quantitatively integrated with biological processes that also influence CO2 dynamics in aquatic ecosystems. We measured CO2 concentrations and the isotopic composition of dissolved inorganic C (δ13CDIC) at diel resolution in two Arctic streams, and coupled this with whole‐system metabolism estimates to assess the effect of biotic and abiotic processes on stream C dynamics. CO2 concentrations consistently decreased from night to day, a pattern counter to the hypothesis that photo‐oxidation is the dominant source of CO2. Instead, the observed decrease in CO2 during daytime was explained by photosynthetic rates, which were strongly correlated with diurnal changes in δ13CDIC values. However, on days when modeled photosynthetic rates were near zero, there was still a significant diel change in δ13CDIC values, suggesting that metabolic estimates are partly masked by O2 consumption from photo‐oxidation. Our results suggest that 6–12 mmol CO2‐C m−2 d−1 may be generated from photo‐oxidation, a range that corresponds well to previous laboratory measurements. Moreover, ecosystem respiration rates were 10 times greater than published photo‐oxidation rates for these Arctic streams, and accounted for 33–80% of total CO2 evasion. Our results suggest that metabolic activity is the dominant process for CO2 production in Arctic streams. Thus, future aquatic CO2 emissions may depend on how biotic processes respond to the ongoing environmental change.

  • 5.
    Rocher-Ros, Gerard
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Sponseller, Ryan A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Bergström, Ann-Kristin
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Myrstener, Maria
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Stream metabolism controls diel patterns and evasion of CO2 in Arctic streams2020In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 26, no 3, p. 1400-1413Article in journal (Refereed)
    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 O-2 and CO2 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 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 regulate CO2 concentrations and evasion at multiple timescales. Photosynthesis caused CO2 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 CO2 concentrations in turn influenced evasion, with up to 45% higher rates at night. Throughout the summer, CO2 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 CO2 evasion, suggesting that some stream reaches serve as net sources of CO2, thus 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.

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