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  • 1.
    Chmiel, Hannah Elisa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Kokic, Jovana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Denfeld, Blaize Amber
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Einarsdóttir, Karólina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Wallin, Marcus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Köhler, Birgit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Isidorova, Anastasija
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Bastviken, David
    Linköping University.
    Ferland, Marie-Ève
    Université du Québec à Montréal, Québec, Canada.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    The role of sediments in the carbon budget of a small boreal lake2016Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, nr 5, s. 1814-1825Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated the role of lake sediments as carbon (C) source and sink in the annual C budget of a small (0.07 km2), shallow (mean depth 3.4 m), and humic lake (mean DOC concentration 17 mg L-1) in boreal Sweden. Organic carbon (OC) burial and mineralization in sediments were quantified from 210Pb-dated sediment and laboratory sediment incubation experiments, respectively, and upscaled to the entire basin and to one whole year, by using sediment thickness derived sub-bottom profiling, basin morphometry, and water column monitoring data of temperature and oxygen concentration. Furthermore, catchment C import, open water metabolism, photochemical mineralization as well as carbon dioxide (CO2) and methane (CH4) emissions to the atmosphere, were quantified to relate sediment processes to other lake C fluxes. We found that on a whole-basin and annual scale, sediment OC mineralization was three times larger than OC burial, and contributed about 16% to the annual CO2 emission from the lake to the atmosphere. Remaining contributions to the CO2 emission were attributed to water column metabolism (31%), photochemical mineralization (6%), and catchment imports via inlet streams and inflow of shallow groundwater (47%). We conclude that on an annual and whole-basin scale 1) sediment OC mineralization dominated over OC burial, 2) water column OC mineralization contributed more than sediments to lake CO2 emission, and 3) catchment import of C to the lake was greater than lake-internal C cycling. 

  • 2.
    Chmiel, Hannah Elisa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Natchimuthu, Sivakiruthika
    Linköping University.
    Bastviken, David
    Linköping University.
    Decreased efficiency of sediment carbon burial in boreal lakes at warming lake water temperaturesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Organic carbon (OC) burial in lake sediments is a fundamental process for aquatic carbon (C) cycling since it removes C from the active cycling pool. Here, we address the effect of lake warming on the OC burial efficiency (OCBE) of sediments in boreal humic lakes to evaluate the impact of warmer water temperatures and altered water column stratification patterns on the OCBE with respect to future climate change. Present-day water column conditions of temperature and oxygen concentration were monitored in two small (<0.1 km2) boreal lakes in central and southwestern Sweden over an annual cycle. Furthermore, OC burial, sediment OC mineralization, the OCBE, and lake CO2 and CH4 emission to the atmosphere, were quantified on a whole-basin scale and for a whole year. Then, future temperature and stratification patterns were simulated in both lakes by adjusting present-day temperature and oxygen conditions according to projected air temperature warming scenarios, in order to quantify the net effect on the OCBE. Present-day conditions were found to be similar in the two study lakes, with annual OC mineralization (~1 t C yr-1) exceeding annual OC burial (<0.5 t C yr-1) at least by a factor of two, returning whole-basin OC burial efficiencies of 28 and 25%, respectively. Also, annual CO2 and CH4 emission was found to be of similar magnitude in both study lakes (6-7 t C yr-1) surpassing sediment C fluxes by at least 5 times. The different lake warming scenarios (RCP 2.6, 4.5 and 8.5, corresponding to increase in annual mean air temperature of 1.5-4.5 °C) caused moderate decreases in the OCBE of 5-16% and 3-11% for each lake, respectively. The more pronounced decreases in OCBE were obtained for the more shallow lake, related to a higher proportion of sediments being affected by warming in the epilimnion. Our results suggest that warmer surface water temperatures in the future are likely to reduce the efficiency of the lake sediment C sink, thereby affecting the long-term C balance of the boreal forest biome.

  • 3.
    Chmiel, Hannah Elisa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Niggemann, Jutta
    University of Oldenburg, Germany.
    Kokic, Jovana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Ferland, Marie-Ève
    Université du Québec à Montréal, Québec, Canada.
    Dittmar, Thorsten
    University of Oldenburg, Germany.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Uncoupled organic matter burial and quality in boreal lake sediments over the Holocene2015Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 120, nr 9, s. 1751-1763Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Boreal lake sediments are important sites of organic carbon (OC) storage, which have accumulated substantial amounts of OC over the Holocene epoch; the temporal evolution and the strength of this Holocene carbon (C) sink is, however, not well constrained. In this study we investigated the temporal record of carbon mass accumulation rates (CMARs), and assessed qualitative changes of terrestrially derived OC in the sediment profiles of seven Swedish boreal lakes, in order to evaluate the variability of boreal lake sediments as a C sink over time.

    CMARs were resolved on a short-term (centennial) and long-term (i.e. over millennia of the Holocene) time scale, using radioactive lead (210 Pb) and carbon (14C) isotope dating. Sources and degradation state of terrestrially derived OC were identified and characterized by molecular analyses of lignin phenols.

    We found that CMARs varied substantially on both short-term and long-term scales, and that the variability was mostly attributed to sedimentation rates and uncoupled from the OC content in the sediment profiles. The lignin phenol analyses revealed that woody material from gymnosperms was a dominant and constant OC source to the sediments over the Holocene. Furthermore, lignin-based degradation indices, such as acid-to-aldehyde ratios, indicated that post-depositional degradation in the sediments was very limited on longer time scales, implying that terrestrial OC is stabilized in the sediments on a permanent basis.

  • 4.
    Denfeld, Blaize A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Wallin, Marcus B.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Sahlée, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Kokic, Jovana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Chmiel, Hannah E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Temporal and spatial carbon dioxide concentration patterns in a small boreal lake in relation to ice cover dynamics2015Inngår i: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 20, nr 6, s. 679-692Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Global carbon dioxide (CO2) emission estimates from inland waters commonly neglect the ice-cover season. To account for CO2 accumulation below ice and consequent emissions into the atmosphere at ice-melt we combined automatically-monitored and manually- sampled spatially-distributed CO2 concentration measurements from a small boreal ice-covered lake in Sweden. In early winter, CO2 accumulated continuously below ice, whereas, in late winter, CO2 concentrations remained rather constant. At ice-melt, two CO2 concentration peaks were recorded, the first one reflecting lateral CO2 transport within the upper water column, and the second one reflecting vertical CO2 transport from bottom waters. We estimated that 66%–85% of the total CO2 accumulated in the water below ice left the lake at ice-melt, while the remainder was stored in bottom waters. Our results imply that CO2 accumulation under ice and emissions at ice-melt are more dynamic than previously reported, and thus need to be more accurately integrated into annual CO2 emission estimates from inland waters.

  • 5.
    Kokic, Jovana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Wallin, Marcus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Chmiel, Hannah
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Denfeld, Blaize
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Carbon dioxide evasion from headwater systems strongly contributes to the total export of carbon from a small boreal lake catchment2015Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 120, nr 1, s. 13-28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inland waters are hotspots for carbon (C) cycling and therefore important for landscape C budgets. Small streams and lakes are particularly important; however, quantifying C fluxes is difficult and has rarely been done for the entire aquatic continuum, composed of connected streams and lakes within the same catchment. We investigated carbon dioxide (CO2) evasion and fluvial fluxes of dissolved inorganic carbon and dissolved organic carbon (DIC and DOC) in stream and lake systems within the 2.3km(2) catchment of a small boreal lake. Our results show pronounced spatial and temporal variability in C fluxes even at a small spatial scale. C loss from the catchment through CO2 evasion from headwaters for the total open water-sampling period was 9.7g C m(-2) catchment, dominating the total catchment C loss (including CO2 evasion, DIC, and DOC export from the lake, which were 2.7, 0.2, and 5.2g C m(-2) catchment, respectively). Aquatic CO2 evasion was dominated by headwater streams that occupy similar to 0.1% of the catchment but contributed 65% to the total aquatic CO2 evasion from the catchment. The importance of streams was mainly an effect of the higher gas transfer velocities than compared to lakes (median, 67 and 2.2cmh(-1), respectively). Accurately estimating the contribution of C fluxes from headwater streams, particularly the temporal and spatial dynamics in their gas transfer velocity, is key to landscape-scale C budgets. This study demonstrates that CO2 evasion from headwaters can be the major pathway of C loss from boreal catchments, even at a small spatial scale.

  • 6.
    Podgrajsek, Eva
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Sahlée, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Bastviken, David
    Linkoping Univ, Dept Themat Studies Environm Change, Linkoping, Sweden.
    Natchimuthu, Siva
    Linkoping Univ, Dept Themat Studies Environm Change, Linkoping, Sweden.
    Kljun, Natascha
    Swansea Univ, Dept Geog, Singleton Pk, Swansea, W Glam, Wales.
    Chmiel, Hannah
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Klemedtsson, Leif
    Univ Gothenburg, Dept Earth Sci, Gothenburg, Sweden.
    Rutgersson, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Methane fluxes from a small boreal lake measured with the eddy covariance method2016Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, s. S41-S50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fluxes of methane, CH4, were measured with the eddy covariance (EC) method at a small boreal lake in Sweden. The mean CH4 flux during the growing season of 2013 was 20.1 nmol m22 s 21 and the median flux was 16 nmol m22 s 21 (corresponding to 1.7 mmol m22 d21 and 1.4 mmol m22 d21 ). Monthly mean values of CH4 flux measured with the EC method were compared with fluxes measured with floating chambers (FC) and were in average 62% higher over the whole study period. The difference was greatest in April partly because EC, but not FC, accounted for fluxes due to ice melt and a subsequent lake mixing event. A footprint analysis revealed that the EC footprint included primarily the shallow side of the lake with a major inlet. This inlet harbors emergent macrophytes that can mediate high CH4 fluxes. The difference between measured EC and FC fluxes can hence be explained by different footprint areas, where the EC system “sees” the part of the lake presumably releasing higher amounts of CH4. EC also provides more frequent measurements than FC and hence more likely captures ebullition events. This study shows that small lakes have CH4 fluxes that are highly variable in time and space. Based on our findings we suggest to measure CH4 fluxes from lakes as continuously as possible and to aim for covering as much of the lakes surface as possible, independently of the selected measuring technique.

  • 7.
    Strauss, Harald
    et al.
    Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany..
    Chmiel, Hannah
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany..
    Christ, Andreas
    Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany..
    Fugmann, Artur
    Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany..
    Hanselmann, Kurt
    ETHZ, Geomicrobiol Grp, Dept Earth Sci, Zurich, Switzerland..
    Kappler, Andreas
    Univ Tubingen, Ctr Appl Geosci, Geomicrobiol, Tubingen, Germany..
    Koeniger, Paul
    Bundesanstalt Geowissensch & Rohstoffe, Stilleweg 2, Hannover, Germany..
    Lutter, Andreas
    Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany..
    Siedenberg, Katharina
    Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany..
    Teichert, Barbara M. A.
    Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany..
    Multiple sulphur and oxygen isotopes reveal microbial sulphur cycling in spring waters in the Lower Engadin, Switzerland2016Inngår i: Isotopes in environmental and health studies, ISSN 1025-6016, E-ISSN 1477-2639, Vol. 52, nr 1-2, s. 75-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Highly mineralized springs in the Scuol-Tarasp area of the Lower Engadin and in the Albula Valley near Alvaneu, Switzerland, display distinct differences with respect to the source and fate of their dissolved sulphur species. High sulphate concentrations and positive sulphur (delta S-34) and oxygen (delta O-18) isotopic compositions argue for the subsurface dissolution of Mesozoic evaporitic sulphate. In contrast, low sulphate concentrations and less positive or even negative delta S-34 and delta O-18 values indicate a substantial contribution of sulphate sulphur from the oxidation of sulphides in the crystalline basement rocks or the Jurassic sedimentary cover rocks. Furthermore, multiple sulphur (delta S-34, Delta S-33) isotopes support the identification of microbial sulphate reduction and sulphide oxidation in the subsurface, the latter is also evident through the presence of thick aggregates of sulphide-oxidizing Thiothrix bacteria.

  • 8.
    Wallin, Marcus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Weyhenmeyer, Gesa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Bastviken, David
    Chmiel, Hannah E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Peter, Simone
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Klemedtsson, Leif
    Temporal control on concentration, character and export of dissolved organic carbon in two hemiboreal headwater streams draining contrasting catchments2015Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 120, nr 5, s. 832-846Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although lateral carbon (C) export from terrestrial to aquatic systems is known to be an important component in landscape C balances, most existing global studies are lacking empirical data on the soil C export. In this study, the concentration, character, and export of dissolved organic carbon (DOC) were studied during 2 years in two hemiboreal headwater streams draining catchments with different soil characteristics (mineral versus peat soils). The streams exposed surprisingly similar strong air temperature controls on the temporal variability in DOC concentration in spite of draining such different catchments. The temporal variability in DOC character (determined by absorbance metrics, specific ultraviolet absorbance 254 (SUVA254) as a proxy for aromaticity and a254/a365 ratio as a proxy for mean molecular weight) was more complex but related to stream discharge. While the two streams showed similar ranges and patterns in SUVA254, we found a significant difference in median a254/a354, suggesting differences in the DOC character. Both streams responded similarly to hydrological changes with higher a254/a365 at higher discharge, although with rather small differences in a254/a365 between base flow and high flow (<0.3). The DOC exports (9.6–25.2 g C m−2 yr−1) were among the highest reported so far for Scandinavia and displayed large interannual and intraannual variability mainly driven by irregular precipitation/discharge patterns. Our results show that air temperature and discharge affect the temporal variability in DOC quantity and character in different ways. This will have implications for the design of representative sampling programs, which in turn will affect the reliability of future estimates of landscape C budgets.

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