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  • 251. Ingram, Travis
    et al.
    Svanbäck, Richard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Kraft, Nathan
    Kratina, Pavel
    Southcott, Laura
    Schluter, Dolph
    Intraguild predation drives evolutionary niche shift in threespine stickleback2012Inngår i: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 66, nr 6, s. 1819-1832Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Intraguild predation—competition and predation by the same antagonist—is widespread, but its evolutionary consequences are unknown. Intraguild prey may evolve antipredator defenses, superior competitive ability on shared resources, or the ability to use an alternative resource, any of which may alter the structure of the food web. We tested for evolutionary responses by threespine stickleback to a benthic intraguild predator, prickly sculpin. We used a comparative morphometric analysis to show that stickleback sympatric with sculpin are more armored and have more limnetic-like body shapes than allopatric stickleback. To test the ecological implications of this shift, we conducted a mesocosm experiment that varied sculpin presence and stickleback population of origin (from one sympatric and one allopatric lake). Predation by sculpin greatly increased the mortality of allopatric stickleback. In contrast, sculpin presence did not affect the mortality of sympatric stickleback, although they did have lower growth rates suggesting increased nonpredatory effects of sculpin. Consistent with their morphology, sympatric stickleback included more pelagic prey in their diets, leading to depletion of zooplankton in the mesocosms. These findings suggest that intraguild prey evolution has altered food web structure by reducing both predation by the intraguild predator and diet overlap between species

  • 252.
    Isidorova, Anastasija
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Bravo, Andrea G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Riise, Gunnhild
    Norwegian Univ Life Sci, Dept Environm Sci, Akershus, Norway..
    Bouchet, Sylvain
    Umea Univ, Dept Chem, Umea, Sweden..
    Björn, Erik
    Umea Univ, Dept Chem, Umea, Sweden..
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    The effect of lake browning and respiration mode on the burial and fate of carbon and mercury in the sediment of two boreal lakes2016Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, nr 1, s. 233-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In many northern temperate regions, the water color of lakes has increased over the past decades (lake browning), probably caused by an increased export of dissolved organic matter from soils. We investigated if the increase in water color in two lakes in Norway has resulted in increased burial of organic carbon (OC) and mercury (Hg) in the sediments and if the Hg was prone to methylation. Lake Solbergvann experienced a threefold water color increase, and OC burial increased approximately twofold concomitant to the water color increase. This lake had prolonged periods of anoxic bottom water, and anoxic OC mineralization rates were only about half of the oxic OC mineralization rates (7.7 and 17.5g C m(-2)yr(-1), respectively), contributing to an efficient OC burial. In Lake Elvaga, where water color increase was only approximately twofold and bottom water was oxygenated, no recent increase in OC burial could be observed. Hg burial increased strongly in both lakes (threefold and 1.6-fold in Lake Solbergvann and Lake Elvaga, respectively), again concomitant to the recent water color increase. The proportion of methylated Hg (MeHg) in surficial sediment was 1 order of magnitude higher in Lake Elvaga (up to 6% MeHg) than in Lake Solbergvann (0.2-0.6% MeHg), probably related to the different oxygenation regimes. We conclude that lake browning can result in increased OC and Hg burial in lake sediments, but the extent of browning and the dominating mode of sediment respiration (aerobic or anaerobic) strongly affect burial and fate of OC and Hg in sediments.

  • 253.
    Isidorova, Anastasija
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Grasset, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Mendonca, Raquel
    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.
    Methane formation in tropical reservoirs predicted from sediment age and nitrogen2019Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, artikkel-id 11017Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Freshwater reservoirs, in particular tropical ones, are an important source of methane (CH4) to the atmosphere, but current estimates are uncertain. The CH4 emitted from reservoirs is microbially produced in their sediments, but at present, the rate of CH4 formation in reservoir sediments cannot be predicted from sediment characteristics, limiting our understanding of reservoir CH4 emission. Here we show through a long-term incubation experiment that the CH4 formation rate in sediments of widely different tropical reservoirs can be predicted from sediment age and total nitrogen concentration. CH4 formation occurs predominantly in sediment layers younger than 6-12 years and beyond these layers sediment organic carbon may be considered effectively buried. Hence mitigating reservoir CH4 emission via improving nutrient management and thus reducing organic matter supply to sediments is within reach. Our model of sediment CH4 formation represents a first step towards constraining reservoir CH4 emission from sediment characteristics.

  • 254.
    Isidorova, Anastasija
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Mendonca, Raquel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Univ Fed Juiz de Fora, Dept Biol, Lab Aquat Ecol, Juiz De Fora, Brazil.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Reduced Mineralization of Terrestrial OC in Anoxic Sediment Suggests Enhanced Burial Efficiency in Reservoirs Compared to Other Depositional Environments2019Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 124, nr 3, s. 678-688Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Freshwater reservoirs are important sites of organic carbon (OC) burial, but the extent to which reservoir OC burial is a new anthropogenic carbon sink is currently unclear. While burial of aquatic OC (by, e.g., phytoplankton) in reservoirs may count as a new C sink, the burial of terrestrial OC in reservoirs constitutes a new C sink only if the burial is more efficient in reservoirs than in other depositional environments. We carried out incubation experiments that mimicked the environmental conditions of different depositional environments along the land‐sea continuum (oxic and anoxic freshwater, oxic and anoxic seawater, oxic river bedload, and atmosphere‐exposed floodplain) to investigate whether reservoirs bury OC more efficiently compared to other depositional environments. For sediment OC predominantly of terrestrial origin, OC degradation rates were significantly lower, by a factor of 2, at anoxic freshwater and saltwater conditions compared to oxic freshwater and saltwater, river, and floodplain conditions. However, the transformation of predominantly terrestrial OC to methane was one order of magnitude higher in anoxic freshwater than at other conditions. For sediment OC predominantly of aquatic origin, OC degradation rates were uniformly high at all conditions, implying equally low burial efficiency of aquatic OC (76% C loss in 57 days). Since anoxia is more common in reservoirs than in the coastal ocean, these results suggest that reservoirs are a depositional environment in which terrestrial OC is prone to become buried at higher efficiency than in the ocean but where also the terrestrial OC most efficiently is transformed to methane.

  • 255. Jacobsen, Carsten Suhr
    et al.
    Nielsen, Tue Kjærgaard
    Vester, Jan Kjølhede
    Stougaard, Peter
    Nielsen, Jeppe Lund
    Voriskova, Jana
    Winding, Anne
    Baldrian, Petr
    Liu, Binbin
    Frostegård, Åsa
    Pedersen, Dorthe
    Tveit, Alexander Tøsdal
    Svenning, Mette Marianne
    Tebbe, Christoph C.
    Øvreås, Lise
    Jakobsen, Pia Bach
    Blazewicz, Steven J.
    Hubablek, Valerie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Hansen, Lars Hestbjerg
    Cary, S. Craig
    Holben, William E.
    Ekelund, Flemming
    Bælum, Jacob
    Inter-laboratory testing of the effect of DNA blocking reagent G2 on DNA extraction from low-biomass clay samples2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 5711Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we show that a commercial blocking reagent (G2) based on modified eukaryotic DNA significantly improved DNA extraction efficiency. We subjected G2 to an inter-laboratory testing, where DNA was extracted from the same clay subsoil using the same batch of kits. The inter-laboratory extraction campaign revealed large variation among the participating laboratories, but the reagent increased the number of PCR-amplified16S rRNA genes recovered from biomass naturally present in the soils by one log unit. An extensive sequencing approach demonstrated that the blocking reagent was free of contaminating DNA, and may therefore also be used in metagenomics studies that require direct sequencing.

  • 256. Jennings, Eleanor
    et al.
    Jones, Stuart
    Arvola, Lauri
    Staehr, Peter A.
    Gaiser, Evelyn
    Jones, Ian D.
    Weathers, Kathleen C.
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Chiu, Chih-Yu
    De Eyto, Elvira
    Effects of weather-related episodic events in lakes: an analysis based on high-frequency data2012Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, nr 3, s. 589-601Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. Weather-related episodic events are typically unpredictable, and their duration is often short. Abiotic and biological responses are often missed in routine monitoring. These responses are, however, now of particular relevance given projected changes in extreme weather conditions.

    2. We present data from high-frequency monitoring stations from lakes in Europe, North America and Asia that illustrate two classes of abiotic effects of weather events: (i) generally short-lived effects of storms on lake thermal structure and (ii) the more prolonged effects of high rainfall events on dissolved organic matter levels and water clarity. We further relate these abiotic effects to changes in dissolved oxygen or in chlorophyll a levels.

    3. Three differing causes for weather-related decreases in surface dissolved oxygen levels were observed: (i) entrainment of anoxic water from depth, (ii) reduction in primary productivity and (iii) increased mineralisation of organic carbon delivered from the catchment.

    4. The duration of in-lake effects tended to be longer for events driven by weather conditions with a longer return period, that is, conditions that were relatively more severe and less frequent at a site. While the susceptibility of lakes to change was related in part to the severity of the meteorological drivers, the impacts also depended on site-specific factors in some cases.

    5. The availability of high-frequency data at these sites provided insight into the capacity of the lakes to absorb current and future pressures. Several of the changes we observed, including increases in carbon availability, decreases in photosynthetically active radiation and increased disturbance, have the capacity to shift lakes towards an increased degree of heterotrophy. The magnitude and direction of any such change will, however, also depend on the magnitude and direction of climate change for a given location and on lake and catchment characteristics.

  • 257. Jennings, Eleanor
    et al.
    Järvinen, Marko
    Allott, Norman
    Arvola, Lauri
    Moore, Karen
    Naden, Pam
    Aonghusa, Caitriona Nic
    Nõges, Tiina
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    The impact of the changing climate on the flux of dissolved organic carbon from catchments2010Inngår i: The impact of climate change on European lakes / [ed] Glen George, Springer , 2010, s. 199-220Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 258.
    Jeske, Jan Torsten
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Microbial adaptations and controlling mechanisms of surface-associated microhabitat heterogeneity in aquatic systems2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Habitat heterogeneity is a driving factor for speciation and ecosystem functioning and is well studied in macro-ecology. Yet our understanding of microbial adaptations, and governing processes is incomplete. The here presented thesis aims at giving us a better understanding of patterns in micro-heterogeneity, and microbial adaptations to such heterogeneity with particular focus on surface-dominated, aquatic habitats. The most prominent microbial adaptation to surface associated mode of life is biofilm formation. Biofilms rely heavily on type IV pili. These pili systems are well studied in Bacteria, but largely unknown in Archaea. Therefore, the first part of this thesis focuses on resolving genetic and structural feature of the type IV like aap-pilus of the thermo-acidophilic Sulfolobus acidocaldarius. We found the aap-pilus to be indispensible for biofilm formation, and to be unparalleled in variability of its quaternary structure and cross regulation with other filaments. The second part of this thesis investigates particle colonization in the water column, focusing on diatoms as a model system, allowing an in situ assessment of different stages of particle colonization, and potential particle-specificity of the associated bacterial community. Opposing reports from marine systems, we did not observe diatom-specificity in the associated bacterial community. Instead we found bacterial community subsets, one likely originating from sediment resuspension, and the other being controlled by biofilm-forming populations (e.g. Flexibacter), able to attach to newly formed particle surfaces and subsequently facilitate secondary colonization by other bacteria. Finally, the habitat heterogeneity in top-layers of lake sediments were investigated in experimental microcosms. Cell-specific oxygen consumption rates were determined, to assess microbial activity across different scales. Individual activity rates differed strongly across all investigated scales, likely due to spatially heterogeneous distribution of nutrients with differing quality. Vice versa, the influence of microbial activity on micro-habitat-heterogeneity was investigated. We correlated sediment redox-state with bacterial community composition and populations. Our results indicate that habitat heterogeneity is generally beneficial for microorganism, and greater heterogeneity results in greater bacterial diversity. However, this heterogeneity-diversity relationship is limited and microorganisms actively stabilize their immediate redox environment to a preferred, community-specific, stable state, if cell abundances exceed a minimum threshold.

    Delarbeid
    1. Structure and function of the adhesive type IV pilus of Sulfolobus acidocaldarius
    Åpne denne publikasjonen i ny fane eller vindu >>Structure and function of the adhesive type IV pilus of Sulfolobus acidocaldarius
    Vise andre…
    2012 (engelsk)Inngår i: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 14, nr 12, s. 3188-3202Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Archaea display a variety of type IV pili on their surface and employ them in different physiological functions. In the crenarchaeon Sulfolobus acidocaldarius the most abundant surface structure is the aap pilus (archaeal adhesive pilus). The construction of in frame deletions of the aap genes revealed that all the five genes (aapA, aapX, aapE, aapF, aapB) are indispensible for assembly of the pilus and an impact on surface motility and biofilm formation was observed. Our analyses revealed that there exists a regulatory cross-talk between the expression of aap genes and archaella (formerly archaeal flagella) genes during different growth phases. The structure of the aap pilus is entirely different from the known bacterial type IV pili as well as other archaeal type IV pili. An aap pilus displayed 3 stranded helices where there is a rotation per subunit of ∼ 138° and a rise per subunit of ∼ 5.7 Å. The filaments have a diameter of ∼ 110 Å and the resolution was judged to be ∼ 9 Å. We concluded that small changes in sequence might be amplified by large changes in higher-order packing. Our finding of an extraordinary stability of aap pili possibly represents an adaptation to harsh environments that S. acidocaldarius encounters.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-192617 (URN)10.1111/j.1462-2920.2012.02898.x (DOI)
    Tilgjengelig fra: 2013-01-23 Laget: 2013-01-23 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    2. Bacterial communities shaping the redox environment in top-layer sediments of an oligotrophic high latitude lake
    Åpne denne publikasjonen i ny fane eller vindu >>Bacterial communities shaping the redox environment in top-layer sediments of an oligotrophic high latitude lake
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Emneord
    Electromicrobiology, Bacteria, Microsensors, Redox potential, Lake Sediments
    HSV kategori
    Forskningsprogram
    Biologi med inriktning mot limnologi
    Identifikatorer
    urn:nbn:se:uu:diva-263205 (URN)
    Tilgjengelig fra: 2015-09-28 Laget: 2015-09-28 Sist oppdatert: 2017-01-25bibliografisk kontrollert
    3. Population-linkages in freshwater bacterial communities associated with individual diatoms and particles
    Åpne denne publikasjonen i ny fane eller vindu >>Population-linkages in freshwater bacterial communities associated with individual diatoms and particles
    Vise andre…
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Emneord
    Freshwater, Diatom, Bacteria community composition, Colonization, Network, Single particle analysis
    HSV kategori
    Forskningsprogram
    Biologi med inriktning mot limnologi
    Identifikatorer
    urn:nbn:se:uu:diva-263204 (URN)
    Tilgjengelig fra: 2015-09-28 Laget: 2015-09-28 Sist oppdatert: 2017-01-25bibliografisk kontrollert
    4. Microscale decoupling of sediment oxygen consumption and microbial biomass in an oligotrophic lake
    Åpne denne publikasjonen i ny fane eller vindu >>Microscale decoupling of sediment oxygen consumption and microbial biomass in an oligotrophic lake
    2016 (engelsk)Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 61, nr 9, s. 1477-1491Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Sediments of aquatic ecosystems are hotspots for biological activity. Here, we address the question if, within surface sediments, oxygen consumption is linearly related to cell abundance. In addition, we identify habitat-specific factors influencing underlying microbial processes. Sediment microcosms were established from three sites within oligotrophic Lake angstrom nnsjon, Sweden, to use microsensors for measuring oxygen profiles and estimate spatially resolved oxygen consumption rates at the water-sediment interfaces. To evaluate differences between habitats, we measured sediment carbon content and C:N:P as a proxy for diagenetic state and organic matter bioavailability. Epifluorescence microscopy was used to assess the microscale distribution and size of surface-colonising microorganisms. There was no linear correlation between oxygen consumption rates and microbial cell abundances. Cell-specific respiration rates were highest in the profundal compared to the littoral- and inflow-sediment microcosms, whereas vertical variability in all these parameters was highest at the inflow, intermediate in the littoral and least variable in profundal sediments. Illumina sequencing of spatially resolved 16SrRNA genes was used to test for possible influence of bacterial diversity on spatially resolved oxygen consumption rates. Bacterial -diversity decreased over depth at each site, but was also lower in sediments from the most active profundal zones of the lake compared to the inflow. We suggest that bacteria in profundal sediments mainly use highly oxidised organic compounds, resulting in overall low growth yield despite high metabolic activity. In the lake inflow and the littoral, more reduced organic substrates of terrestrial origin are used at lower rates but with higher yield.

    Emneord
    Cell-specific respiration, Sediment microbiology, Macro- and Microenvironment heterogeneity, Environmental Microbiology
    HSV kategori
    Forskningsprogram
    Biologi med inriktning mot limnologi
    Identifikatorer
    urn:nbn:se:uu:diva-261278 (URN)10.1111/fwb.12787 (DOI)000380902400010 ()
    Eksternt samarbeid:
    Forskningsfinansiär
    Swedish Research CouncilSwedish Research Council Formas
    Tilgjengelig fra: 2015-09-28 Laget: 2015-09-01 Sist oppdatert: 2017-12-01bibliografisk kontrollert
  • 259.
    Jeske, Jan Torsten
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Helmholtz Ctr Environm Res, Dept Environm Microbiol, Leipzig, Germany.
    Müller, Roger Andre
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Wendeberg, Annelie
    Helmholtz Ctr Environm Res, Dept Environm Microbiol, Leipzig, Germany.
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Microscale decoupling of sediment oxygen consumption and microbial biomass in an oligotrophic lake2016Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 61, nr 9, s. 1477-1491Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sediments of aquatic ecosystems are hotspots for biological activity. Here, we address the question if, within surface sediments, oxygen consumption is linearly related to cell abundance. In addition, we identify habitat-specific factors influencing underlying microbial processes. Sediment microcosms were established from three sites within oligotrophic Lake angstrom nnsjon, Sweden, to use microsensors for measuring oxygen profiles and estimate spatially resolved oxygen consumption rates at the water-sediment interfaces. To evaluate differences between habitats, we measured sediment carbon content and C:N:P as a proxy for diagenetic state and organic matter bioavailability. Epifluorescence microscopy was used to assess the microscale distribution and size of surface-colonising microorganisms. There was no linear correlation between oxygen consumption rates and microbial cell abundances. Cell-specific respiration rates were highest in the profundal compared to the littoral- and inflow-sediment microcosms, whereas vertical variability in all these parameters was highest at the inflow, intermediate in the littoral and least variable in profundal sediments. Illumina sequencing of spatially resolved 16SrRNA genes was used to test for possible influence of bacterial diversity on spatially resolved oxygen consumption rates. Bacterial -diversity decreased over depth at each site, but was also lower in sediments from the most active profundal zones of the lake compared to the inflow. We suggest that bacteria in profundal sediments mainly use highly oxidised organic compounds, resulting in overall low growth yield despite high metabolic activity. In the lake inflow and the littoral, more reduced organic substrates of terrestrial origin are used at lower rates but with higher yield.

  • 260.
    Jeske, Jan Torsten
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Osman Ahmed, Omneya
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Centler, Florian
    Eiler, Alexander
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Wendeberg, Annelie
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Population-linkages in freshwater bacterial communities associated with individual diatoms and particlesManuskript (preprint) (Annet vitenskapelig)
  • 261.
    Jeske, Jan Torsten
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Wendeberg, Annelie
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Bacterial communities shaping the redox environment in top-layer sediments of an oligotrophic high latitude lakeManuskript (preprint) (Annet vitenskapelig)
  • 262.
    Jingying, Xu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Buck, Moritz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Eklöf, Karin
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007, Uppsala, Sweden.
    Ahmed Osman, Omneya
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Schaefer, Jeffra K.
    Department of Environmental Sciences, Rutgers University, New Brunswick, New Jersey 08901, USA.
    Bishop, Kevin
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Skyllberg, Ulf
    Department of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Björn, Erik
    epartment of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Bravo, Andrea Garcia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Department of Marine Biology and Oceanography, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, Barcelona, Catalunya, Spain.
    Mercury methylating microbial communities of boreal forest soils2019Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, artikkel-id 518Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of the potent neurotoxic methylmercury (MeHg) is a microbially mediated process that has raised much concern because MeHg poses threats to wildlife and human health. Since boreal forest soils can be a source of MeHg in aquatic networks, it is crucial to understand the biogeochemical processes involved in the formation of this pollutant. High-throughput sequencing of 16S rRNA and the mercury methyltransferase, hgcA, combined with geochemical characterisation of soils, were used to determine the microbial populations contributing to MeHg formation in forest soils across Sweden. The hgcA sequences obtained were distributed among diverse clades, including Proteobacteria, Firmicutes, and Methanomicrobia, with Deltaproteobacteria, particularly Geobacteraceae, dominating the libraries across all soils examined. Our results also suggest that MeHg formation is linked to the composition of also non-mercury methylating bacterial communities, likely providing growth substrate (e.g. acetate) for the hgcA-carrying microorganisms responsible for the actual methylation process. While previous research focused on mercury methylating microbial communities of wetlands, this study provides some first insights into the diversity of mercury methylating microorganisms in boreal forest soils.

  • 263.
    Jingying, Xu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Liem-Nguyen, Van
    School of Science and Technology, Örebro University, Örebro, Sweden.
    Buck, Moritz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Björn, Erik
    Faculty of Science and Technology, Department of Chemistry, Umeå University, Sweden.
    Bravo, Andrea Garcia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA), Spanish National Research Council (CSIC), Barcelona, Spain.
    Mercury methylating microbial communities in boreal wetlandsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Understanding the formation of the potent neurotoxic methylmercury (MeHg) is a major concern due to its threats to wildlife and human health. As boreal wetlands play a crucial role for Hg cycling on a global scale, it is crucial to understand the biogeochemical processes involved in MeHg formation in this landscape. A strategy combining high-throughput hgcA amplicon sequencing with molecular barcoding was used to revealed diverse clades of Hg(II) methylators in a wide range of wetland soils. Our results confirms a predominant role of Deltaproteobacteria, and in particular Geobacteraceae, as important Hg(II) methylators in boreal wetland soils. Firmicutes, and in particular Ruminococcaceae, were also abundant members of the Hg(II) methylating microbial communities. Our survey highlight the importance of nutrient status for the shaping of Hg(II) methylating communities across the four wetlands and reveal that water content and prevailing redox states are key factors determining the local variation in Hg(II) methylating community composition within individual wetlands. Also, our study suggests that high nutrient levels linked to low redox potential seemed to favour Hg(II) methylating methanogens within the Methanoregulaceae. Our findings expand the current knowledge on the Hg(II) methylating microbial community composition in wetland soils and the geochemical factors underpinning spatial heterogeity in such communities.  

  • 264.
    Juottonen, Heli
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Univ Helsinki, Dept Biosci Gen Microbiol, Helsinki, Finland.; Nat Resources Inst Finland, Helsinki, Finland.;Univ Jyvaskyla, Dept Biol & Environm Sci, Jyvaskyla, Finland..
    Eiler, Alexander
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Biasi, Christina
    Univ Eastern Finland, Dept Environm & Biol Sci, Kuopio, Finland..
    Tuittila, Eeva-Stiina
    Univ Eastern Finland, Sch Forest Sci, Joensuu, Finland..
    Yrjälä, Kim
    Univ Helsinki, Dept Biosci Gen Microbiol, Helsinki, Finland..
    Fritzec, Hannu
    Nat Resources Inst Finland, Helsinki, Finland..
    Distinct Anaerobic Bacterial Consumers of Cellobiose-Derived Carbon in Boreal Fens with Different CO2/CH4 Production Ratios2017Inngår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 83, nr 4, artikkel-id e02533-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Northern peatlands in general have high methane (CH4) emissions, but individual peatlands show considerable variation as CH4 sources. Particularly in nutrient-poor peatlands, CH4 production can be low and exceeded by carbon dioxide (CO2) production from unresolved anaerobic processes. To clarify the role anaerobic bacterial degraders play in this variation, we compared consumers of cellobiose-derived carbon in two fens differing in nutrient status and the ratio of CO2 to CH4 produced. After [C-13] cellobiose amendment, the mesotrophic fen produced equal amounts of CH4 and CO2. The oligotrophic fen had lower CH4 production but produced 3 to 59 times more CO2 than CH4. RNA stable-isotope probing revealed that in the mesotrophic fen with higher CH4 production, cellobiose-derived carbon was mainly assimilated by various recognized fermenters of Firmicutes and by Proteobacteria. The oligotrophic peat with excess CO2 production revealed a wider variety of cellobiose-C consumers, including Firmicutes and Proteobacteria, but also more unconventional degraders, such as Telmatobacter-related Acidobacteria and subphylum 3 of Verrucomicrobia. Prominent and potentially fermentative Planctomycetes and Chloroflexi did not appear to process cellobiose-C. Our results show that anaerobic degradation resulting in different levels of CH4 production can involve distinct sets of bacterial degraders. By distinguishing cellobiose degraders from the total community, this study contributes to defining anaerobic bacteria that process cellulose-derived carbon in peat. Several of the identified degraders, particularly fermenters and potential Fe(III) or humic substance reducers in the oligotrophic peat, represent promising candidates for resolving the origin of excess CO2 production in peatlands. IMPORTANCE Peatlands are major sources of the greenhouse gas methane (CH4), yet in many peatlands, CO2 production from unresolved anaerobic processes exceeds CH4 production. Anaerobic degradation produces the precursors of CH4 production but also represents competing processes. We show that anaerobic degradation leading to high or low CH4 production involved distinct sets of bacteria. Well-known fermenters dominated in a peatland with high CH4 production, while novel and unconventional degraders could be identified in a site where CO2 production greatly exceeds CH4 production. Our results help identify and assign functions to uncharacterized bacteria that promote or inhibit CH4 production and reveal bacteria potentially producing the excess CO2 in acidic peat. This study contributes to understanding the microbiological basis for different levels of CH4 emission from peatlands.

  • 265.
    K. Björkman, Stina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Spatial Variability in Greenhouse Gas Production in Sediments of a Tropical Reservoir2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The objective was to study the spatial variability of organic matter degradation in the sediments of a tropical reservoir to answer the hypothesis that degradation is significantly higher in river inflow areas than in other parts of the reservoir.

    Sediment cores were collected from twelve sites in the nutrient poor drinking water reservoir Chapéu d’Uvas in Minas Gerais, Brazil. The sediments were analysed for CH4 concentrations in the pore water, degradation rates (in incubation experiments), and for the sediment properties: water content, carbon content and C/N-ratio.

    The sediment properties: water content, carbon content and C/N-ratio were found to show higher values in non-inflow areas compared to inflow areas of the reservoir, and lowest in the main inflow river. This indicates other sources of sedimentary organic matter than the inflow rivers, and such sources could be erosion and/or landslides from the surrounding area. Also the CH4 concentration in the pore water was highest in the non-inflow areas, and lowest in the main inflow area. The oxic degradation rates from the sediment core incubation experiment on the other hand showed the highest mineralization rates in the main inflow area of the reservoir and lowest in the non- inflow bays, this is supporting the hypothesis.

    Altogether the superficial aerobic degradation is highest in the inflow area while the methanogenic degradation in the deeper sediment layers is not highest in the inflow area. This implies that the organic load from the inflows is sufficient to supply the superficial degradation but not the degradation in the deeper layers of the sediment, which is fuelled by loads of organic matter from other sources, such as erosion. Other contributing explanations could be that the inflow pattern varies over time, so that the classification of the sites is not accurate for longer timescales.

  • 266. Kara, Emily L.
    et al.
    Hanson, Paul
    Hamilton, David
    Hipsey, Matthew R.
    McMahon, Katherine D.
    Read, Jordan S.
    Winslow, Luke
    Dedrick, John
    Rose, Kevin
    Carey, Cayelan C.
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Marques, David da Motta
    Beversdorf, Lucas
    Miller, Todd
    Wu, Chin
    Hsieh, Yi-Fang
    Gaiser, Evelyn
    Kratz, Tim
    Time-scale dependence in numerical simulations: Assessment of physical, chemical, and biological predictions in a stratified lake at temporal scales of hours to months2012Inngår i: Environmental Modelling & Software, ISSN 1364-8152, E-ISSN 1873-6726, Vol. 35, s. 104-121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We evaluated the predictive ability of a one-dimensional coupled hydrodynamic-biogeochemical model across multiple temporal scales using wavelet analysis and traditional goodness-of-fit metrics. High-frequency in situ automated sensor data and long-term manual observational data from Lake Mendota, Wisconsin, USA, were used to parameterize, calibrate, and evaluate model predictions. We focused specifically on short-term predictions of temperature, dissolved oxygen, and phytoplankton biomass over one season. Traditional goodness-of-fit metrics indicated more accurate prediction of physics than chemical or biological variables in the time domain. This was confirmed by wavelet analysis in both the time and frequency domains. For temperature, predicted and observed global wavelet spectra were closely related, while observed dissolved oxygen and chlorophyll fluorescence spectral characteristics were not reproduced by the model for key time scales, indicating that processes not modeled may be important drivers of the observed signal. Although the magnitude and timing of physical and biological changes were simulated adequately at the seasonal time scale through calibration, time scale-specific dynamics, for example short-term cycles, were difficult to reproduce, and were relatively insensitive to the effects of varying parameters. The use of wavelet analysis is novel to aquatic ecosystem modeling, is complementary to traditional goodness-of-fit metrics, and allows for assessment of variability at specific temporal scales. In this way, the effect of processes operating at distinct temporal scales can be isolated and better understood, both in situ and in silico. Wavelet transforms are particularly well suited for assessment of temporal and spatial heterogeneity when coupled to high-frequency data from automated in situ or remote sensing platforms.

  • 267.
    Karlsson, Konrad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    The effect of visibility and predators on foraging efficiency in littoral and pelagic perch2012Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
    Abstract [en]

    Phenotypic plasticity in Eurasian perch (Perca fluviatilis) can be driven by a trade-off for ecological specialisation to littoral and pelagic resources. Previous studies on perch have found that this specialisation can have different effects on linkage between the littoral and pelagic food web depending on water transparency. In this study I aimed to answer how foraging efficiency and prey preference of phenotypic divergent perch are affected by high and low water transparency, and the presence of a predator in a series of aquarium experiments. Two different phenotypes of perch were kept in littoral and pelagic environments in the lab. By presenting perch with Daphnia sp. and Ephemeroptera, either separately or combined. I found that in clear water the littoral and pelagic phenotypes were comparatively more efficient on resources that were representative of their habitats (Ephemeroptera and Daphnia, respectively) and that both phenotypes prefer Ephemeroptera over Daphnia. In low visibility the differences in foraging efficiency between phenotypes when feeding on Daphnia disappeared but remained similar to clear water when feeding on Ephemeroptera. When vision was constrained littoral and pelagic perch showed no sign of prey preferences. In the presence of a predator the difference in foraging efficiency between the phenotypes, and also prey preference disappeared. I found that littoral phenotypes interacted more with other group members than did pelagic phenotypes, when foraging on littoral prey. And for perch in general, when foraging for Daphnia the interaction among group members was markedly reduced compared to when foraging for Ephemeroptera. In this study I show that morphological adaptation and prey choice is affected by visibility and predation. I also give suggestions how and argue why this can affect linkage of food webs and the community composition in littoral and pelagic habitats.

  • 268. Karlsson, O. Magnus
    et al.
    Malmaeus, J. Mikael
    Viktori, Tomas
    Andersson, M. Gunnar
    Rydin, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    A revised semi-empirical mass balance model for phosphorus in Baltic coastal areas2014Inngår i: Fundamental and Applied Limnology, ISSN 1863-9135, Vol. 185, nr 3-4, s. 209-221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A decade of research on the phosphorus dynamics in Baltic Sea coastal areas using a combination of mathematical modelling, sediment surveys and time series of water quality data from monitoring programs has led to an improved understanding of processes controlling phosphorus turnover and coastal primary production. This paper presents a revised model for phosphorus turnover in non-tidal enclosed Baltic coastal areas. Using a new dataset from 500 sediment sampling stations it was possible to quantify and develop new simplified algorithms for sedimentary processes i.e. burial and erosion that did not decrease the model's predictive power. Our results indicate that erosion of old clays can be an important primary source to phosphorus water concentrations in enclosed coastal areas. A simple laboratory experiment using Common Duckweed (Lemna minor) supports to some extent that phosphorus originating from old clays is partly bioavailable and hence may influence the trophic state in the studied areas.

  • 269.
    Kasurinen, Ville
    et al.
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland; Norwegian Univ Sci & Technol, Dept Hydraul & Environm Engn, Trondheim, Norway.
    Alfredsen, Knut
    Norwegian Univ Sci & Technol, Dept Hydraul & Environm Engn, Trondheim, Norway.
    Ojala, Anne
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland; Univ Helsinki, Dept Environm Sci, Helsinki, Finland.
    Pumpanen, Jukka
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland.
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Futter, Martyn N.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden.
    Laudon, Hjalmar
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, Uppsala, Sweden.
    Berninger, Frank
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland.
    Modeling nonlinear responses of DOC transport in boreal catchments in Sweden2016Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, nr 7, s. 4970-4989Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stream water dissolved organic carbon (DOC) concentrations display high spatial and temporal variation in boreal catchments. Understanding and predicting these patterns is a challenge with great implications for water quality projections and carbon balance estimates. Although several biogeochemical models have been used to estimate stream water DOC dynamics, model biases common during both rain and snow melt-driven events. The parsimonious DOC-model, K-DOC, with 10 calibrated parameters, uses a nonlinear discharge and catchment water storage relationship including soil temperature dependencies of DOC release and consumption. K-DOC was used to estimate the stream water DOC concentrations over 5 years for eighteen nested boreal catchments having total area of 68 km2 (varying from 0.04 to 67.9 km2). The model successfully simulated DOC concentrations during base flow conditions, as well as, hydrological events in catchments dominated by organic and mineral soils reaching NSEs from 0.46 to 0.76. Our semimechanistic model was parsimonious enough to have all parameters estimated using statistical methods. We did not find any clear differences between forest and mire-dominated catchments that could be explained by soil type or tree species composition. However, parameters controlling slow release and consumption of DOC from soil water behaved differently for small headwater catchments (less than 2 km2) than for those that integrate larger areas of different ecosystem types (10–68 km2). Our results emphasize that it is important to account for nonlinear dependencies of both, soil temperature, and catchment water storage, when simulating DOC dynamics of boreal catchments.

  • 270.
    Kayler, Zachary E.
    et al.
    Univ Idaho, Dept Soil & Water Syst, Moscow, ID 83843 USA.
    Premke, Katrin
    Lebniz Inst Freshwater Ecol & Inland Fisheries, Dept Chem Analyt & Biogeochem, Berlin, Germany.
    Gessler, Arthur
    Swiss Fed Inst Forest Snow & Landscape Res WSL, Birmensdorf, Switzerland.
    Gessner, Mark
    TU Berlin, Dept Ecol, Berlin Inst Technol, Berlin, Germany;Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Expt Limnol, Stechlin, Germany.
    Gribler, Christian
    Univ Vienna, Ctr Funct Ecol, Dept Limnol & Biooceanog, Vienna, Austria.
    Hilt, Sabine
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Ecosyst Res, Berlin, Germany.
    Klemedtsson, Leif
    Gothenburg Univ, Dept Earth Sci, Gothenburg, Sweden.
    Kuzyakov, Yakov
    Georg August Univ Gottingen, Dept Soil Sci Temperate Ecosyst, Gottingen, Germany.
    Reichstein, Markus
    Max Planck Inst Biogeochem, Dept Biogeochem Integrat, Jena, Germany.
    Siemens, Jan
    Justus Liebig Univ Giessen, Inst Soil Sci & Soil Conservat, IFZ Res Ctr Biosyst Land Use & Nutr, Giessen, Germany.
    Totsche, Kai-Uwe
    riedrich Schiller Univ Jena, Inst Geosci, Jena, Germany.
    Tranvik, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Wagner, Annekatrin
    Tech Univ Dresden, Inst Hydrobiol, Dresden, Germany.
    Weitere, Markus
    UFZ Helmholtz Ctr Environm Res, Dept River Ecol, Magdeburg, Germany.
    Grossart, Hans-Peter
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Expt Limnol, Stechlin, Germany;Univ Potsdam, Inst Biochem & Biol, Potsdam, Germany.
    Integrating aquatic and terrestrial perspectives to improve insights into organic matter cycling at the landscape scale2019Inngår i: Frontiers in Earth Science, ISSN 2296-6463, Vol. 7, artikkel-id 127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowledge is crucial for a better understanding of OM cycling in a landscape context, in particular since terrestrial and aquatic compartments may respond differently to the ongoing changes in climate, land use, and other anthropogenic interferences.

  • 271. Keller, Andreas Hardy
    et al.
    Schleinitz, Kathleen M.
    Starke, Robert
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Vogt, Carsten
    Kleinsteuber, Sabine
    Metagenome-based metabolic reconstruction reveals the ecophysiological function of Epsilonproteobacteria in a hydrocarbon-contaminated sulfidic aquifer2015Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 6, artikkel-id 1396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The population genome of an uncultured bacterium assigned to the Campylobacterales (Epsilonproteobacteria) was reconstructed from a metagenome dataset obtained by whole-genome shotgun pyrosequencing. Genomic DNA was extracted from a sulfate-reducing, m-xylene-mineralizing enrichment culture isolated from groundwater of a benzene-contaminated sulfidic aquifer. The identical epsilonproteobacterial phylotype has previously been detected in toluene- or benzene-mineralizing, sulfate-reducing consortia enriched from the same site. Previous stable isotope probing (SIP) experiments with 13C6-labeled benzene suggested that this phylotype assimilates benzene-derived carbon in a syntrophic benzene-mineralizing consortium that uses sulfate as terminal electron acceptor. However, the type of energy metabolism and the ecophysiological function of this epsilonproteobacterium within aromatic hydrocarbon-degrading consortia and in the sulfidic aquifer are poorly understood. Annotation of the epsilonproteobacterial population genome suggests that the bacterium plays a key role in sulfur cycling as indicated by the presence of an sqr gene encoding a sulfide quinone oxidoreductase and psr genes encoding a polysulfide reductase. It may gain energy by using sulfide or hydrogen/formate as electron donors. Polysulfide, fumarate, as well as oxygen are potential electron acceptors. Auto- or mixotrophic carbon metabolism seems plausible since a complete reductive citric acid cycle was detected. Thus the bacterium can thrive in pristine groundwater as well as in hydrocarbon-contaminated aquifers. In hydrocarbon-contaminated sulfidic habitats, the epsilonproteobacterium may generate energy by coupling the oxidation of hydrogen or formate and highly abundant sulfide with the reduction of fumarate and/or polysulfide, accompanied by efficient assimilation of acetate produced during fermentation or incomplete oxidation of hydrocarbons. The highly efficient assimilation of acetate was recently demonstrated by a pulsed 13C2-acetate protein SIP experiment. The capability of nitrogen fixation as indicated by the presence of nif genes may provide a selective advantage in nitrogen-depleted habitats. Based on this metabolic reconstruction, we propose acetate capture and sulfur cycling as key functions of Epsilonproteobacteria within the intermediary ecosystem metabolism of hydrocarbon-rich sulfidic sediments.

  • 272.
    Kellerman, Anne M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Dittmar, Thorsten
    Kothawala, Dolly N.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Chemodiversity of dissolved organic matter in lakes driven by climate and hydrology2014Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, s. 3804-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Despite the small continental coverage of lakes, they are hotspots of carbon cycling, largely due to the processing of terrestrially derived dissolved organic matter (DOM). As DOM is an amalgam of heterogeneous compounds comprising gradients of microbial and physicochemical reactivity, the factors influencing DOM processing at the molecular level and the resulting patterns in DOM composition are not well understood. Here we show, using ultrahigh-resolution mass spectrometry to unambiguously identify 4,032 molecular formulae in 120 lakes across Sweden, that the molecular composition of DOM is shaped by precipitation, water residence time and temperature. Terrestrially derived DOM is selectively lost as residence time increases, with warmer temperatures enhancing the production of nitrogen-containing compounds. Using biodiversity concepts, we show that the molecular diversity of DOM, or chemodiversity, increases with DOM and nutrient concentrations. The observed molecular-level patterns indicate that terrestrially derived DOM will become more prevalent in lakes as climate gets wetter.

  • 273.
    Kellerman, Anne M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Kothawala, Dolly N.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Dittmar, Thorsten
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Do we have a weight problem? The discrepancy between actual and apparent molecular weight of dissolved organic matter in lakesManuskript (preprint) (Annet vitenskapelig)
  • 274.
    Kellerman, Anne M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Kothawala, Dolly N.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Dittmar, Thorsten
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Persistence of dissolved organic matter in lakes related to its molecular characteristics2015Inngår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 8, nr 6, s. 454-457Artikkel i tidsskrift (Fagfellevurdert)
  • 275.
    Kellerman, Anne Marie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Molecular-level dissolved organic matter dynamics in lakes: Constraints on reactivity and persistence2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Dissolved organic matter (DOM) is a central component of the global carbon cycle. Thus, small changes to the amount of DOM imported, processed and produced within lakes can have a large effect on regional carbon budgets. In addition to being a vital energy source at the base of the aquatic food web, DOM is physico-chemically reactive. However, identifying and understanding the controls of DOM processing has remained challenging due to the complex composition of DOM. DOM comprises a mixture of decomposition by-products of terrestrial origin as well as newly synthesized material from in situ production. DOM compounds form gradients of reactivity to biogeochemical processes, such as photodegradation, biodegradation, and flocculation, and they perform a suite of functions in aquatic systems. The overarching goal of this thesis was to investigate controls of DOM processing in Swedish lakes. We do this in two ways: 1) by characterizing the molecular-level composition of DOM in lakes, and 2) by investigating interactions between very labile and relatively recalcitrant DOM. The first three chapters utilize ultrahigh resolution mass spectrometry to show that the detailed chemical composition of DOM varies along a hydrology gradient, and secondarily along a temperature gradient that co-varies with agriculture and nutrients. Next, we illustrate the coherence between molecular-level characteristics and bulk optical characteristics. Together, these studies suggest that protein-like fluorescence, aliphatic compounds, and N-containing compounds are either resistant to degradation or tightly cycled in the system, and thus persist at long water residence times. The most oxidized compounds, such as vascular plant-derived polyphenolic compounds, are abundant in areas with high precipitation and are lost with increasing water residence time. Vascular plant-derived polyphenolic compounds were most strongly related to DOM with high apparent molecular weight, suggesting that hydrophobic interactions drive aggregate formation. Furthermore, the association of high molecular weight DOM with polyphenolic compounds suggests that aggregates are hotspots of reactivity in aquatic systems. Finally, we find no indication that the addition of labile organic matter enhances the biodegradation of less reactive DOM. Thus, we suggest that in freshwaters, intrinsic molecular properties, such as the basic structural features of compounds, dominate over extrinsic factors.

    Delarbeid
    1. Chemodiversity of dissolved organic matter in lakes driven by climate and hydrology
    Åpne denne publikasjonen i ny fane eller vindu >>Chemodiversity of dissolved organic matter in lakes driven by climate and hydrology
    2014 (engelsk)Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, s. 3804-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Despite the small continental coverage of lakes, they are hotspots of carbon cycling, largely due to the processing of terrestrially derived dissolved organic matter (DOM). As DOM is an amalgam of heterogeneous compounds comprising gradients of microbial and physicochemical reactivity, the factors influencing DOM processing at the molecular level and the resulting patterns in DOM composition are not well understood. Here we show, using ultrahigh-resolution mass spectrometry to unambiguously identify 4,032 molecular formulae in 120 lakes across Sweden, that the molecular composition of DOM is shaped by precipitation, water residence time and temperature. Terrestrially derived DOM is selectively lost as residence time increases, with warmer temperatures enhancing the production of nitrogen-containing compounds. Using biodiversity concepts, we show that the molecular diversity of DOM, or chemodiversity, increases with DOM and nutrient concentrations. The observed molecular-level patterns indicate that terrestrially derived DOM will become more prevalent in lakes as climate gets wetter.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-224267 (URN)10.1038/ncomms4804 (DOI)000337372200015 ()
    Tilgjengelig fra: 2014-05-08 Laget: 2014-05-08 Sist oppdatert: 2017-12-05bibliografisk kontrollert
    2. Persistence of dissolved organic matter in lakes related to its molecular characteristics
    Åpne denne publikasjonen i ny fane eller vindu >>Persistence of dissolved organic matter in lakes related to its molecular characteristics
    2015 (engelsk)Inngår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 8, nr 6, s. 454-457Artikkel i tidsskrift, Letter (Fagfellevurdert) Published
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-248670 (URN)10.1038/NGEO2440 (DOI)000355236500017 ()
    Tilgjengelig fra: 2015-04-21 Laget: 2015-04-07 Sist oppdatert: 2017-12-04bibliografisk kontrollert
    3. Do we have a weight problem? The discrepancy between actual and apparent molecular weight of dissolved organic matter in lakes
    Åpne denne publikasjonen i ny fane eller vindu >>Do we have a weight problem? The discrepancy between actual and apparent molecular weight of dissolved organic matter in lakes
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-248668 (URN)
    Tilgjengelig fra: 2015-04-21 Laget: 2015-04-07 Sist oppdatert: 2017-11-30
    4. Absence of a priming effect on dissolved organic carbon degradation in lake water
    Åpne denne publikasjonen i ny fane eller vindu >>Absence of a priming effect on dissolved organic carbon degradation in lake water
    Vise andre…
    2015 (engelsk)Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 60, nr 1, s. 159-168Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The idea that small amounts of labile organic carbon might trigger the degradation of previously unreactive organic matter has attracted increasing scientific interest across multiple disciplines. Although this phenomenon, referred to as priming, has been widely reported in soils, evidence in freshwater systems is scarce and inconclusive. Here, we use a multifactorial microcosm experiment to test the conditions under which priming may be observed in freshwater ecosystems. We assessed the effect of pulse additions of three labile carbon sources (acetate, glucose, and cellobiose) on dissolved organic carbon (DOC) consumption using water from lakes with different trophic states (eutrophic to oligotrophic and clear to brownwater lakes). We further analyzed the effect of nutrient availability and the role of attachment of cells to surfaces. Despite the range of conditions tested, we found no clear evidence of a priming effect on DOC degradation, indicating that priming in freshwater systems may be of limited importance.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-243554 (URN)10.1002/lno.10016 (DOI)000349082600014 ()
    Tilgjengelig fra: 2015-02-10 Laget: 2015-02-10 Sist oppdatert: 2017-12-04bibliografisk kontrollert
  • 276. Khalili, Maria I.
    et al.
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Growing season variability of nitrate along a trophic gradient: contrasting patterns between lakes and streams2009Inngår i: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 71, nr 1, s. 25-33Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied the growing season (May to October) variability of NO3-N across Swedish lakes and streams. We found that NO3-N concentrations showed the highest growing season variability among all water chemical variables tested, both in lakes and in streams. However, the growing season variability of NO3-N increased with increasing trophic status in lakes while it decreased in streams. We attributed the contrasting pattern between lakes and streams to the relative importance of biological uptake and denitrification with increasing trophic status. Our results highlight the relation between growing season NO3-N variability and trophic status, which is positive in lakes but negative in streams. The findings of this study have important ramifications for ecosystem studies as well as water management. We suggest that the assessment of growing season variability of NO3-N in aquatic systems can be improved by considering the effect of trophic status.

  • 277.
    Knoll, Lesley B.
    et al.
    Univ Minnesota Twin Cities, Itasca Biol Stn & Labs, Lake Itasca, MN 56470 USA.
    Sharma, Sapna
    York Univ, Dept Biol, Toronto, ON, Canada.
    Denfeld, Blaize A.
    Umea Univ, Dept Ecol & Environm Sci, Umea, Sweden.
    Flaim, Giovanna
    Fdn Edmund Mach, Res & Innovat Ctr, Dept Sustainable Agroecosyst & Bioresources, San Michele All Adige, Italy.
    Hori, Yukari
    Univ Toronto Scarborough, Dept Phys & Environm Sci, Toronto, ON, Canada.
    Magnuson, John, I
    Univ Wisconsin, Ctr Limnol, Madison, WI 53706 USA.
    Straile, Dietmar
    Univ Konstanz, Limnol Inst, Dept Biol, Constance, Germany.
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Consequences of lake and river ice loss on cultural ecosystem services2019Inngår i: Limnology and Oceanography Letters, ISSN 2378-2242, Vol. 4, nr 5, s. 119-131Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    People extensively use lakes and rivers covered by seasonal ice. Although ice cover duration has been declining over the past 150 years for Northern Hemisphere freshwaters, we know relatively little about how ice loss directly affects humans. Here, we synthesize the cultural ecosystem services (i.e., services that provide intangible or nonmaterial benefits) and associated benefits supported by inland ice. We also provide, for the first time, empirical examples that give quantitative evidence for a winter warming effect on a wide range of ice-related cultural ecosystem services and benefits. We show that in recent decades, warmer air temperatures delayed the opening date of winter ice roads and led to cancellations of spiritual ceremonies, outdoor ice skating races, and ice fishing tournaments. Additionally, our synthesis effort suggests unexploited data sets that allow for the use of integrative approaches to evaluate the interplay between inland ice loss and society.

  • 278.
    Koehler, Birgit
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Barsotti, Francesco
    Minella, Marco
    Landelius, Tomas
    Minero, Claudio
    Tranvik, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Vione, Davide
    Simulation of photoreactive transients and of photochemical transformation of organic pollutants in sunlit boreal lakes across 14 degrees of latitude: A photochemical mapping of Sweden2018Inngår i: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 129, s. 94-104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lake water constituents, such as chromophoric dissolved organic matter (CDOM) and nitrate, absorb sunlight which induces an array of photochemical reactions. Although these reactions are a substantial driver of pollutant degradation in lakes they are insufficiently understood, in particular on large scales. Here, we provide for the first time comprehensive photochemical maps covering a large geographic region. Using photochemical kinetics modeling for 1048 lakes across Sweden we simulated the steady-state concentrations of four photoreactive transient species, which are continuously produced and consumed in sunlit lake waters. We then simulated the transient-induced photochemical transformation of organic pollutants, to gain insight into the relevance of the different photoreaction pathways. We found that boreal lakes were often unfavorable environments for photoreactions mediated by hydroxyl radicals ([rad]OH) and carbonate radical anions (CO3−[rad]), while photoreactions mediated by CDOM triplet states (3CDOM*) and, to a lesser extent, singlet oxygen (1O2) were the most prevalent. These conditions promote the photodegradation of phenols, which are used as plastic, medical drug and herbicide precursors. When CDOM concentrations increase, as is currently commonly the case in boreal areas such as Sweden,3CDOM* will also increase, promoting its importance in photochemical pathways even more.

  • 279.
    Koehler, Birgit
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Broman, Elias
    Linnaeus Univ, Ctr Ecol & Evolut Microbial Model Syst EEMiS, S-39182 Kalmar, Sweden.
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Apparent quantum yield of photochemical dissolved organic carbon mineralization in lakes2016Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, nr 6, s. 2207-2221Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Up to one tenth of the carbon dioxide (CO2) emissions from inland waters worldwide are directly induced by the photochemical mineralization of dissolved organic matter (DOM). The photochemical production of dissolved inorganic carbon (DIC) per photon absorbed by chromophoric DOM (CDOM) decreases exponentially with increasing irradiance wavelength, and is commonly described by an “apparent quantum yield” (AQY) spectrum. Although an essential model parameter to simulate photochemical mineralization the AQY remains poorly constrained. Here, the AQY of photochemical DIC production for 25 lakes located in boreal, polar, temperate, and tropical areas, including four saline lagoons, was measured. The wavelength-integrated AQY (300–500 nm; mol DIC mol CDOM-absorbed photons−1) ranged from 0.05 in an Antarctic lake to 0.61 in a humic boreal lake, averaging 0.24 ± 0.03 SE. AQY was positively linearly correlated with the absorption coefficient at 420 nm (a420) as a proxy for CDOM content (R2 of 0.64 at 300 nm and 0.26 at 400 nm), with specific UV absorption coefficients as a proxy for DOM aromaticity (R2 of 0.56 at 300 nm and 0.38 at 400 nm), and with the humification index (R2 of 0.41 at 300 nm and 0.42 at 400 nm). Hence, a considerable fraction of the AQY variability was explained by water optical properties in inland waters. The correlation of AQY with a420 opens up the possibility to improve large-scale model estimates of sunlight-induced CO2 emissions from inland waters based on water color information derived by satellite remote sensing.

  • 280.
    Koehler, Birgit
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Corre, Marife D
    Steger, Kristin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Well, Reinhard
    Zehe, Erwin
    Sueta, Juvia P.
    Veldkamp, Edzo
    An in-depth look into tropical lowland forest soil: nitrogen-addition effects on the content of N2O, CO2 and CH4 ad N2O isotopic signatures down to 2-m depth2012Inngår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 111, nr 1-3, s. 695-713Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Atmospheric nitrogen (N) deposition is rapidly increasing in tropical regions. We investigated how a decade of experimental N addition (125 kg N ha−1 year−1) to a seasonal lowland forest affected depth distribution and contents of soil nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4), as well as natural abundance isotopic signatures of N2O, nitrate (NO3 ) and ammonium (NH4 +). In the control plots during dry season, we deduced limited N2O production by denitrification in the topsoil (0.05–0.40 m) as indicated by: ambient N2O concentrations and ambient 15N-N2O signatures, low water-filled pore space (35–60%), and similar 15N signatures of N2O and NO3 . In the subsoil (0.40–2.00 m), we detected evidence of N2O reduction to N2 during upward diffusion, indicating denitrification activity. During wet season, we found that N2O at 0.05–2.00 m was mainly produced by denitrification with substantial further reduction to N2, as indicated by: lighter 15N-N2O than 15N-NO3 throughout the profile, and increasing N2O concentrations with simultaneously decreasing 15N-N2O enrichment with depth. These interpretations were supported by an isotopomer map and by a positive correlation between 18O-N2O and 15N-N2O site preferences. Long-term N addition did not affect dry-season soil N2O-N contents, doubled wet-season soil N2O-N contents, did not affect 15N signatures of NO3 , and reduced wet-season 15N signatures of N2O compared to the control plots. These suggest that the increased NO3 concentrations have stimulated N2O production and decreased N2O-to-N2 reduction. Soil CO2-C contents did not differ between treatments, implying that N addition essentially did not influence soil C cycling. The pronounced seasonality in soil respiration was largely attributable to enhanced topsoil respiration as indicated by a wet-season increase in the topsoil CO2-C contents. The N-addition plots showed reduced dry-season soil CH4-C contents and threshold CH4 concentrations were reached at a shallower depth compared to the control plots, revealing an N-induced stimulation of methanotrophic activity. However, the net soil CH4 uptake rates remained similar between treatments possibly because diffusive CH4 supply from the atmosphere largely limited CH4 oxidation.

  • 281.
    Koehler, Birgit
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Landelius, Tomas
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Machida, Nanako
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Sunlight-induced carbon dioxide emissions from inland waters2014Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 28, nr 7, s. 696-711Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The emissions of carbon dioxide (CO2) from inland waters are substantial on a global scale. Yet, the fundamental question remains open which proportion of these CO2 emissions is induced by sunlight via photochemical mineralization of dissolved organic carbon (DOC), rather than by microbial respiration during DOC decomposition. Also, it is unknown on larger spatial and temporal scales how photochemical mineralization compares to other C fluxes in the inland water C cycle. We combined field and laboratory data with atmospheric radiative transfer modeling to parameterize a photochemical rate model for each day of the year 2009, for 1086 lakes situated between latitudes from 55 to 69°N in Sweden. The sunlight-induced production of dissolved inorganic carbon (DIC) averaged 3.8 ± 0.04 g C m-2 yr-1, which is a flux comparable in size to the organic carbon burial in the lake sediments. Countrywide, 151 ± 1 kt C yr-1 was produced by photochemical mineralization, corresponding to about 12% of total annual mean CO2 emissions from Swedish lakes. With a median depth of 3.2 m, the lakes were generally deep enough that incoming, photochemically active photons were absorbed in the water column. This resulted in a linear positive relationship between DIC photoproduction and the incoming photon flux, which correspond to the absorbed photons. Therefore, the slope of the regression line represents the wavelength- and depth-integrated apparent quantum yield of DIC photoproduction. We used this relationship to obtain a first estimate of DIC photoproduction in lakes and reservoirs worldwide. Global DIC photoproduction amounted to 13 and 35 Mt C yr-1 under overcast and clear sky, respectively. Consequently, these directly sunlight-induced CO2 emissions contribute up to about one tenth to the global CO2 emissions from lakes and reservoirs, corroborating that microbial respiration contributes a substantially larger share than formerly thought, and generate annual C fluxes similar in magnitude to the C burial in natural lake sediments worldwide.

  • 282.
    Koehler, Birgit
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Zehe, E.
    Corre, M. D.
    Veldkamp, E.
    An inverse analysis reveals limitations of the soil-CO2 profile method to calculate CO2 production and efflux for well-structured soils2010Inngår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, nr 8, s. 2311-2325Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Soil respiration is the second largest flux in the global carbon cycle, yet the underlying below-ground process, carbon dioxide (CO2) production, is not well understood because it can not be measured in the field. CO2 production has frequently been calculated from the vertical CO2 diffusive flux divergence, known as 'soil-CO2 profile method'. This relatively simple model requires knowledge of soil CO2 concentration profiles and soil diffusive properties. Application of the method for a tropical lowland forest soil in Panama gave inconsistent results when using diffusion coefficients (D) calculated based on relationships with soil porosity and moisture ('physically modeled' D). Our objective was to investigate whether these inconsistencies were related to (1) the applied interpolation and solution methods and/or (2) uncertainties in the physically modeled profile of D. First, we show that the calculated CO2 production strongly depends on the function used to interpolate between measured CO2 concentrations. Secondly, using an inverse analysis of the soil-CO2 profile method, we deduce which D would be required to explain the observed CO2 concentrations, assuming the model perception is valid. In the top soil, this inversely modeled D closely resembled the physically modeled D. In the deep soil, however, the inversely modeled D increased sharply while the physically modeled D did not. When imposing a constraint during the fit parameter optimization, a solution could be found where this deviation between the physically and inversely modeled D disappeared. A radon (Rn) mass balance model, in which diffusion was calculated based on the physically modeled or constrained inversely modeled D, simulated observed Rn profiles reasonably well. However, the CO2 concentrations which corresponded to the constrained inversely modeled D were too small compared to the measurements. We suggest that, in well-structured soils, a missing description of steady state CO2 exchange fluxes across water-filled pores causes the soil-CO2 profile method to fail. These fluxes are driven by the different diffusivities in inter- vs. intra-aggregate pores which create permanent CO2 gradients if separated by a 'diffusive water barrier'. These results corroborate other studies which have shown that the theory to treat gas diffusion as homogeneous process, a precondition for use of the soil-CO2 profile method, is inaccurate for pore networks which exhibit spatial separation between CO2 production and diffusion out of the soil.

  • 283. Kohler, Stephan J.
    et al.
    Kothawala, Dolly
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Futter, Martyn N.
    Liungman, Olof
    Tranvik, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    In-Lake Processes Offset Increased Terrestrial Inputs of Dissolved Organic Carbon and Color to Lakes2013Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, nr 8, s. e70598-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increased color in surface waters, or browning, can alter lake ecological function, lake thermal stratification and pose difficulties for drinking water treatment. Mechanisms suggested to cause browning include increased dissolved organic carbon (DOC) and iron concentrations, as well as a shift to more colored DOC. While browning of surface waters is widespread and well documented, little is known about why some lakes resist it. Here, we present a comprehensive study of Malaren, the third largest lake in Sweden. In Malaren, the vast majority of water and DOC enters a western lake basin, and after approximately 2.8 years, drains from an eastern basin. Despite 40 years of increased terrestrial inputs of colored substances to western lake basins, the eastern basin has resisted browning over this time period. Here we find the half-life of iron was far shorter (0.6 years) than colored organic matter (A(420); 1.7 years) and DOC as a whole (6.1 years). We found changes in filtered iron concentrations relate strongly to the observed loss of color in the western basins. In addition, we observed a substantial shift from colored DOC of terrestrial origin, to less colored autochthonous sources, with a substantial decrease in aromaticity (-17%) across the lake. We suggest that rapid losses of iron and colored DOC caused the limited browning observed in eastern lake basins. Across a wider dataset of 69 Swedish lakes, we observed greatest browning in acidic lakes with shorter retention times (< 1.5 years). These findings suggest that water residence time, along with iron, pH and colored DOC may be of central importance when modeling and projecting changes in brownification on broader spatial scales.

  • 284.
    Kokic, Jovana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Gas Exchange over Aquatic Interfaces and its Importance for Greenhouse Gas Emission2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Aquatic ecosystems play a substantial role in global cycling of carbon (C), despite covering only about 4% of the earth surface. They emit large amounts of greenhouse gases (GHG) to the atmosphere, comparable to the amount of C stored annually in terrestrial ecosystems. In addition, C can be buried in lake sediments. Headwater systems are located at the interface of the terrestrial and aquatic environment, and are first in line to process terrestrial C and throughout its journey through the aquatic continuum. The uncertainties in global estimates of aquatic GHG emissions are largely related to these headwater systems, as they are highly variable in time and space, and underrepresented in global assessments. The overall aim of this thesis was therefore to study GHG exchange between sediment, water and air in headwater systems, from both an ecosystem perspective and at the small scale of physical drivers of gas exchange.

    This thesis demonstrates that carbon dioxide (CO2) emission from headwater systems, especially streams, was the main pathway of C loss from surface waters from a lake catchment. Of the total aquatic CO2-emission of the catchment, 65% originated from stream systems that covered only 0.1% of the total catchment area. The gas transfer velocity (k) was the main driver of stream CO2-emission, but there was a high variability in k on small spatial scales (meters). This variability may have implications for upscaling GHG emissions, especially when using scaled k estimates. Lake sediments only contributed 16% to total lake C emission, but in reality, sediment C emission is probably even lower because experimentally determined sediment C flux returns high estimates that are biased since artificially induced turbulence enhances C flux rates beyond in-situ conditions. When sediment C flux is estimated in-situ, in natural bottom water turbulence conditions, flux rates were lower than those estimated experimentally.

    Conclusively, this thesis shows that GHG emissions from small aquatic ecosystems are dominant over other aquatic C fluxes and that our current knowledge regarding the physical processes controlling gas exchange from different small aquatic systems is limited, implying an inherent uncertainty of GHG emission estimates from small aquatic ecosystems.

    Delarbeid
    1. Carbon dioxide evasion from headwater systems strongly contributes to the total export of carbon from a small boreal lake catchment
    Åpne denne publikasjonen i ny fane eller vindu >>Carbon dioxide evasion from headwater systems strongly contributes to the total export of carbon from a small boreal lake catchment
    Vise andre…
    2015 (engelsk)Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 120, nr 1, s. 13-28Artikkel i tidsskrift (Fagfellevurdert) Published
    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.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-241585 (URN)10.1002/2014JG002706 (DOI)000349899200002 ()
    Tilgjengelig fra: 2015-01-13 Laget: 2015-01-13 Sist oppdatert: 2018-05-21bibliografisk kontrollert
    2. The role of sediments in the carbon budget of a small boreal lake
    Åpne denne publikasjonen i ny fane eller vindu >>The role of sediments in the carbon budget of a small boreal lake
    Vise andre…
    2016 (engelsk)Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, nr 5, s. 1814-1825Artikkel i tidsskrift (Fagfellevurdert) Published
    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. 

    Emneord
    mineralization, burial, carbon dioxide, methane, emission, photomineralization
    HSV kategori
    Forskningsprogram
    Biologi med inriktning mot limnologi
    Identifikatorer
    urn:nbn:se:uu:diva-260666 (URN)10.1002/lno.10336 (DOI)000383621800019 ()
    Forskningsfinansiär
    EU, European Research CouncilSwedish Research Council FormasSwedish Research Council
    Tilgjengelig fra: 2015-09-07 Laget: 2015-08-21 Sist oppdatert: 2018-05-21bibliografisk kontrollert
    3. Low sediment-water gas exchange in a small boreal lake
    Åpne denne publikasjonen i ny fane eller vindu >>Low sediment-water gas exchange in a small boreal lake
    2016 (engelsk)Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, nr 9, s. 2493-2505Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Boreal lake sediments are carbon sources by producing CO2. CO2 flux from sediments is partly controlled by turbulence in the water column, which is not given the same attention as CO2production rates in current estimates of CO2 fluxes from sediments. We quantified the in situ CO2flux across the sediment-water interface in a small (0.07 km2) lake in Sweden by measuring the in situ O2 flux with the Eddy Correlation (EC) method and using the apparent respiratory quotient (CO2 production:O2 consumption) derived from sediment incubations. We demonstrate that median CO2 flux estimated by EC was ~70% smaller than estimated by sediment incubations with artificial water mixing (1.0 × 10−2 and 3.6 × 10−2 µmol C m−2 s−1, respectively). Additionally, we show that inducing artificial mixing of supernatant water in the incubation experiment has a positive effect on observed fluxes, enhancing CO2 flux by ~30% compared to not mixing supernatant water. We suggest that the difference between the methods is due to the strong artificial water mixing in sediment incubations compared to the turbulent mixing in this small lake. Additionally, low O2 supply to sediment aerobic heterotrophic microbes during extended periods of low water currents can inhibit respiration and thus CO2 production. These findings suggest that the sediment contribution to total lake CO2 emission might currently be overestimated for small boreal lakes. Care should be taken when upscaling sediment CO2 flux derived from incubation experiments to entire basins of small lakes, as incubation experiments are unlikely to accurately mimic in situ bottom water currents and gas exchange.

    Emneord
    lake sediment, gas exchange, eddy correlation
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-304299 (URN)10.1002/2016JG003372 (DOI)000385712800012 ()
    Forskningsfinansiär
    Swedish Research CouncilEU, European Research Council, 336642
    Tilgjengelig fra: 2016-10-04 Laget: 2016-10-04 Sist oppdatert: 2018-05-21bibliografisk kontrollert
    4. High spatial variability in stream k600 revealed by turbulence measurements – implications for scaling GHG emissions
    Åpne denne publikasjonen i ny fane eller vindu >>High spatial variability in stream k600 revealed by turbulence measurements – implications for scaling GHG emissions
    Vise andre…
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    HSV kategori
    Forskningsprogram
    Biologi med inriktning mot limnologi
    Identifikatorer
    urn:nbn:se:uu:diva-307785 (URN)
    Tilgjengelig fra: 2016-11-24 Laget: 2016-11-21 Sist oppdatert: 2016-11-24
  • 285.
    Kokic, Jovana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Sahlée, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Brand, Andreas
    Swiss Fed Inst Aquat Sci & Technol, Surface Waters Res & Management, Eawag, Kastanienbaum, Switzerland.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Low sediment-water gas exchange in a small boreal lake2016Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, nr 9, s. 2493-2505Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Boreal lake sediments are carbon sources by producing CO2. CO2 flux from sediments is partly controlled by turbulence in the water column, which is not given the same attention as CO2production rates in current estimates of CO2 fluxes from sediments. We quantified the in situ CO2flux across the sediment-water interface in a small (0.07 km2) lake in Sweden by measuring the in situ O2 flux with the Eddy Correlation (EC) method and using the apparent respiratory quotient (CO2 production:O2 consumption) derived from sediment incubations. We demonstrate that median CO2 flux estimated by EC was ~70% smaller than estimated by sediment incubations with artificial water mixing (1.0 × 10−2 and 3.6 × 10−2 µmol C m−2 s−1, respectively). Additionally, we show that inducing artificial mixing of supernatant water in the incubation experiment has a positive effect on observed fluxes, enhancing CO2 flux by ~30% compared to not mixing supernatant water. We suggest that the difference between the methods is due to the strong artificial water mixing in sediment incubations compared to the turbulent mixing in this small lake. Additionally, low O2 supply to sediment aerobic heterotrophic microbes during extended periods of low water currents can inhibit respiration and thus CO2 production. These findings suggest that the sediment contribution to total lake CO2 emission might currently be overestimated for small boreal lakes. Care should be taken when upscaling sediment CO2 flux derived from incubation experiments to entire basins of small lakes, as incubation experiments are unlikely to accurately mimic in situ bottom water currents and gas exchange.

  • 286.
    Kokic, Jovana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    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.
    Vachon, Dominic
    Umeå Univ, Dept Ecol & Environm Sci, Umeå, Sweden.
    Wallin, Marcus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    High spatial variability of gas transfer velocity in streams revealed by turbulence measurements2018Inngår i: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 8, nr 4, s. 461-473Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Streams are major sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere, but current large-scale estimates are associated with high uncertainties because knowledge concerning the spatiotemporal control on stream emissions is limited. One of the largest uncertainties derives from the choice of gas transfer velocity (k600), which describes the physical efficiency of gas exchange across the water–atmosphere interface. This study therefore explored the variability in k600 and subsequent CO2 and CH4 emission rates within and across streams of different stream order (SO). We conducted, for the first time in streams, direct turbulence measurements using an acoustic Doppler velocimeter (ADV) to determine the spatial variability in k600 across a variety of scales with a consistent methodology. The results show high spatial variability in k600 and corresponding CO2 and CH4 emissions at small spatial scales, both within stream reaches and across SO, especially during high discharge. The k600 was positively related to current velocity and Reynolds number. By contrast, no clear relationship was found between k600 and specific stream characteristics such as width and depth, which are parameters often used in empirical models of k600. Improved understanding of the small-scale variability in the physical properties along streams, especially during high discharge, is therefore an important step to reduce the uncertainty in existing gas transfer models and emissions for stream systems. The ADV method was a useful tool for revealing spatial variability in this work, but it needs further development. We recommend that future studies conduct measurements over shorter time periods (e.g., 10–15 min instead of 40 min) and at more sites across the reach of interest, and thereby derive more reliable mean-reach k600 as well as more information about controls on the spatial variability in k600

  • 287.
    Kokic, Jovana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Sahlée, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Wallin, Marcus B.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Vachon, Dominic
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    High spatial variability in stream k600 revealed by turbulence measurements – implications for scaling GHG emissionsManuskript (preprint) (Annet vitenskapelig)
  • 288.
    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.

  • 289.
    Kosten, Sarian
    et al.
    Radboud Univ Nijmegen, Inst Water & Wetland Res, Dept Aquat Ecol & Environm Biol, Nijmegen, Netherlands.
    van den Berg, Sanne
    Radboud Univ Nijmegen, Inst Water & Wetland Res, Dept Aquat Ecol & Environm Biol, Nijmegen, Netherlands; Wageningen Univ, Dept Aquat Ecol & Water Qual Management, Wageningen, Netherlands.
    Mendonça, Raquel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Univ Fed Juiz de Fora, Biol Dept, Juiz De Fora, Brazil.
    Paranaíba, José R.
    Univ Fed Juiz de Fora, Biol Dept, Juiz De Fora, Brazil.
    Roland, Fabio
    Univ Fed Juiz de Fora, Biol Dept, Juiz De Fora, Brazil.
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Van Den Hoek, Jamon
    Oregon State Univ, Coll Earth Ocean & Atmospher Sci, Geog & Geospatial Sci, Corvallis, OR 97331 USA.
    Barros, Nathan
    Univ Fed Juiz de Fora, Biol Dept, Juiz De Fora, Brazil.
    Extreme drought boosts CO2 and CH4 emissions from reservoir drawdown areas2018Inngår i: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 8, nr 3, s. 329-340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although previous studies suggest that greenhouse gas (GHG) emissions from reservoir sediment exposed to the atmosphere during drought may be substantial, this process has not been rigorously quantified. Here we determined carbon dioxide (CO 2) and methane (CH 4) emissions from sediment cores exposed to a drying and rewetting cycle. We found a strong temporal variation in GHG emissions with peaks when the sediment was drained (C emissions from permanently wet sediment and drained sediments were, respectively, 251 and 1646 mg m −2 d −1 for CO 2 and 0.8 and 547.4 mg m −2 d −1 for CH 4) and then again during rewetting (C emissions from permanently wet sediment and rewetted sediments were, respectively, 456 and 1725mg m −2 d −1 for CO 2 and 1.3 and 3.1 mg m −2 d −1 for CH 4). To gain insight into the importance of these emissions at a regional scale, we used Landsat satellite imagery to upscale our results to all Brazilian reservoirs. We found that during the extreme drought of 2014-2015, an additional 1299 km 2 of sediment was exposed, resulting in an estimated emission of 8.5 × 10 11 g of CO 2-eq during the first 15 d after the overlying water disappeared and in the first 33 d after rewetting, the same order of magnitude as the year-round GHG emissions of large (∼mean surface water area 454 km 2) Brazilian reservoirs, excluding the emissions from the draw-down zone. Our estimate, however, has high uncertainty, with actual emissions likely higher. We therefore argue that the effects of drought on reservoir GHG emissions merits further study, especially because climate models indicate an increase in the frequency of severe droughts in the future. We recommend incorporation of emissions during drying and rewetting into GHG budgets of reservoirs to improve regional GHG emission estimates and to enable comparison between GHG emissions from hydroelectric and other electricity sources. We also emphasize that peak emissions at the onset of drought and the later rewetting should be quantified to obtain reliable emission estimates. ARTICLE HISTORY

  • 290.
    Kothawala, Dolly
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Box 7050, S-70507 Uppsala, Sweden.
    Köhler, Stephan J.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Box 7050, S-70507 Uppsala, Sweden..
    Östlund, Anna
    Sandviken Municipal, Sandviken, Sweden..
    Wiberg, Karin
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Box 7050, S-70507 Uppsala, Sweden..
    Ahrens, Lutz
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Box 7050, S-70507 Uppsala, Sweden..
    Influence of dissolved organic matter concentration and composition on the removal efficiency of perfluoroalkyl substances (PFASs) during drinking water treatment2017Inngår i: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 121, s. 320-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Drinking water treatment plants (DWTPs) are constantly adapting to a host of emerging threats including the removal of micro-pollutants like perfluoroalkyl substances (PFASs), while concurrently considering how background levels of dissolved organic matter (DOM) influences their removal efficiency. Two adsorbents, namely anion exchange (AE) and granulated active carbon (GAC) have shown particular promise for PFAS removal, yet the influence of background levels of DOM remains poorly explored. Here we considered how the removal efficiency of 13 PFASs are influenced by two contrasting types of DOM at four concentrations, using both AE (Purolite A-600 (R)) and GAC (Filtrasorb 400 (R)). We placed emphasis on the pre-equilibrium conditions to gain better mechanistic insight into the dynamics between DOM, PFASs and adsorbents. We found AE to be very effective at removing both PFASs and DOM, while largely remaining resistant to even high levels of background DOM (8 mg carbon L-1) and surprisingly found that smaller PFASs were removed slightly more efficiently than longer chained counterparts, In contrast, PFAS removal efficiency with GAC was highly variable with PFAS chain length, often improving in the presence of DOM, but with variable response based on the type of DOM and PFAS chain length.

  • 291.
    Kothawala, Dolly
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Murphy, Kathleen R.
    Stedmon, Colin A.
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Inner filter correction of dissolved organic matter fluorescence2013Inngår i: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 11, s. 616-630Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fluorescence of dissolved organic matter (DOM) is suppressed by a phenomenon of self-quenching known as the inner filter effect (IFE). Despite widespread use of fluorescence to characterize DOM in surface waters, the advantages and constraints of IFE correction are poorly defined. We assessed the effectiveness of a commonly used absorbance-based approach (ABA), and a recently proposed controlled dilution approach (CDA) to correct for IFE. Linearity between corrected fluorescence and total absorbance (ATotal; the sum of absorbance at excitation and emission wavelengths) across the full excitation-emission matrix (EEM) in dilution series of four samples indicated both ABA and CDA were effective to an absorbance of at least 1.5 in a 1 cm cell, regardless of wavelength positioning. In regions of the EEMs where signal to background noise (S/N) was low, CDA correction resulted in more variability than ABA correction. From the ABA algorithm, the onset of significant IFE (>5%) occurs when absorbance exceeds 0.042. In these cases, IFE correction is required, which was the case for the vast majority (97%) of lakes in a nationwide survey (n= 554). For highly absorbing samples, undesirably large dilution factors would be necessary to reduce absorbance below 0.042. For rare EEMs with ATotal > 1.5 (3.0% of the lakes in the Swedish survey), a 2-fold dilution is recommended followed by ABA or CDA correction. This study shows that for the vast majority of natural DOM samples the most commonly applied ABA algorithm provides adequate correction without prior dilution.

  • 292.
    Kothawala, Dolly N.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    Ji, Xing
    Univ Amsterdam, Dept Aquat Microbiol, Inst Biodivers & Ecosyst Dynam, Amsterdam, Netherlands..
    Laudon, Hjalmar
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, S-90183 Umea, Sweden..
    Agren, Anneli M.
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, S-90183 Umea, Sweden..
    Futter, Martyn N.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    Kohler, Stephan J.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    The relative influence of land cover, hydrology, and in-stream processing on the composition of dissolved organic matter in boreal streams2015Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 120, nr 8, s. 1491-1505Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low-order boreal streams are particularly sensitive interfaces where dissolved organic matter (DOM) is transported from soils to inland waters. Disentangling the relative influence of key environmental factors suspected to influence stream water DOM composition is highly relevant to predicting the reactivity and fate of terrestrial DOM entering inland waters. Here we examined changes to DOM composition using absorbance and fluorescence, from 17 boreal streams ranging from first to fourth orders, over 14 months, including the rarely studied winter season, and two snowmelt periods (n = 836). We also analyzed soil pore water samples from three forest soil lysimeters to a depth of 70 cm (n = 60). Of five identified fluorescing parallel factor analysis components, two (C4 and C5) expressed a clear mire wetland or forest signature, providing distinct molecular markers of dominant land cover. In fact, land cover alone explained 49% of the variability in DOM composition. In contrast, seasonal fluctuations in hydrology only contributed to minor shifts (8%) in the composition of stream water DOM, while in-stream transformations to DOM composition were undetectable. These findings suggest that low-order boreal streams act as a passive pipe, since in-stream processing of DOM is restricted by short water residence times (6 h to 2 days). In addition, we demonstrated the sensitivity of optical approaches to distinguish between key terrestrial sources of DOM in the boreal landscape. By distinguishing the proportional leverage of key environmental controls on headwater stream DOM composition, we are better equipped to predict where and when key DOM transformations occur in the aquatic conduit.

  • 293.
    Kothawala, Dolly N.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Stedmon, Colin A.
    Müller, Roger A.
    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.
    Köhler, Stephan J.
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Controls of dissolved organic matter quality: evidence from a large-scale boreal lake survey2014Inngår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 20, nr 4, s. 1101-1114Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inland waters transport large amounts of dissolved organic matter (DOM) from terrestrial environments to the oceans, but DOM also reacts en route, with substantial water column losses by mineralization and sedimentation. For DOM transformations along the aquatic continuum, lakes play an important role as they retain waters in the landscape allowing for more time to alter DOM. We know DOM losses are significant at the global scale, yet little is known about how the reactivity of DOM varies across landscapes and climates. DOM reactivity is inherently linked to its chemical composition. We used fluorescence spectroscopy to explore DOM quality from 560 lakes distributed across Sweden and encompassed a wide climatic gradient typical of the boreal ecozone. Six fluorescence components were identified using parallel factor analysis (PARAFAC). The intensity and relative abundance of these components were analyzed in relation to lake chemistry, catchment, and climate characteristics. Land cover, particularly the percentage of water in the catchment, was a primary factor explaining variability in PARAFAC components. Likewise, lake water retention time influenced DOM quality. These results suggest that processes occurring in upstream water bodies, in addition to the lake itself, have a dominant influence on DOM quality. PARAFAC components with longer emission wavelengths, or red-shifted components, were most reactive. In contrast, protein-like components were most persistent within lakes. Generalized characteristics of PARAFAC components based on emission wavelength could ease future interpretation of fluorescence spectra. An important secondary influence on DOM quality was mean annual temperature, which ranged between −6.2 and +7.5 °C. These results suggest that DOM reactivity depends more heavily on the duration of time taken to pass through the landscape, rather than temperature. Projected increases in runoff in the boreal region may force lake DOM toward a higher overall amount and proportion of humic-like substances.

  • 294.
    Kothawala, Dolly N.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    von Wachenfeldt, Eddie
    Swedish Species Information Centre, Swedish University of Agricultural Sciences.
    Koehler, Birgit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Selective loss and preservation of lake water dissolved organic matter fluorescenceduring long-term dark incubations2012Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 433, s. 238-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The biogeochemical processing of dissolved organic matter (DOM) in inland waters is inherently related to its molecular structure and ecological function. Controlled bioassays are a valuable tool to analyze these relationships, but are seldom conducted and compared at temporal scales that typically prevail in natural inland waters. Here we incubated water from six boreal lakes in the dark and examined changes to the initial fluorescence and absorbance after 3.5 years. We identified five fluorescence components with parallel factor (PARAFAC) analysis (CC, CM, CA, CX and CT) and found a consistent change in the relative intensity of two dominant PARAFAC components (increase in CA:CC, corresponding to Peak A:Peak C), commonly found in lake water, that represent terrestrially-derived DOM. Surprisingly, we only found minor changes to specific absorbance (SUVA), and did not find any changes to other spectral indexes including the fluorescence index, humification index and freshness index. By incorporating lakes spanning a wide range of initial total organic carbon concentrations (3.7 to 32.5 mg L− 1), water residence times, and spectral characteristics (e.g. SUVA 1.13 to 3.77 L·mg C− 1·m− 1), we found that the relative intensities of two humic-like peaks were the most revealing of changes to DOM structure during dark incubations. We also verified that inner filter effects were adequately corrected within the concentration range of incubated samples. Thus, the processing of DOM under dark conditions, including microbial decomposition and flocculation, may have a greater influence on the humic-like peaks, particularly CC (Peak C), with negligible changes to more commonly used spectral indexes.

     

  • 295. Krause, Sascha
    et al.
    Le Roux, Xavier
    Niklaus, Pascal A.
    Van Bodegom, Peter M.
    Lennon, Jay T.
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Grossart, Hans-Peter
    Philippot, Laurent
    Bodelier, Paul L. E.
    Trait-based approaches for understanding microbial biodiversity and ecosystem functioning2014Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 5, s. 251-Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    In ecology, biodiversity-ecosystem functioning (BEE) research has seen a shift in perspective from taxonomy to function in the last two decades, with successful application of trait-based approaches. This shift offers opportunities for a deeper mechanistic understanding of the role of biodiversity in maintaining multiple ecosystem processes and services. In this paper, we highlight studies that have focused on BEE of microbial communities with an emphasis on integrating trait-based approaches to microbial ecology. In doing so, we explore some of the inherent challenges and opportunities of understanding BEE using microbial systems. For example, microbial biologists characterize communities using gene phylogenies that are often unable to resolve functional traits. Additionally, experimental designs of existing microbial BEE studies are often inadequate to unravel BEE relationships. We argue that combining eco-physiological studies with contemporary molecular tools in a trait-based framework can reinforce our ability to link microbial diversity to ecosystem processes. We conclude that such trait-based approaches are a promising framework to increase the understanding of microbial BEE relationships and thus generating systematic principles in microbial ecology and more generally ecology.

  • 296.
    Krizsan, Sophie J
    et al.
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Mateos-Rivera, Alejandro
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Bertilsson, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Felton, Annika
    Swedish University of Agricultural Sciences, Alnarp, Sweden.
    Anttila, Anne
    Helsinki University, Helsinki, Finland.
    Ramin, Mohammad
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Vaga, Merko
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Gidlund, Helena
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Huhtanen, Pekka
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    An in vitro evaluation of browser and grazer fermentation efficiency and microbiota using European moose spring and summer foods2018Inngår i: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 8, s. 4183-4196Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Evolutionary morphological and physiological differences between browsers and grazers contribute to species- specific digestion efficiency of food resources. Rumen microbial community structure of browsers is supposedly adapted to characteristic nutrient composition of the diet source. If this assumption is correct, domesticated ruminants, or grazers, are poor model animals for assessing the nutritional value of food consumed by browsing game species. In this study, typical spring and summer foods of the European moose (Alces alces) were combined with rumen fluid collected from both dairy cows (Bos taurus) and from moose, with the aim of comparing fer- mentation efficiency and microbial community composition. The nutritional value of the food resources was characterized by chemical analysis and advanced in vitro measurements. The study also addressed whether or not feed evaluation based on in vitro techniques with cattle rumen fluid as inoculum could be a practical alternative when evaluating the nutritional value of plants consumed by wild browsers. Our re- sults suggest that the fermentation characteristics of moose spring and summer food are partly host- specific and related to the contribution of the bacterial phyla Firmicutes and Bacteriodetes to the rumen microbial community. Host- specific adaptations of the ruminal microbial community structure could be explained from the evolutionary adaptations related to feeding habitats and morphophysiological differences be- tween browsers and grazers. However, the observed overall differences in microbial community structure could not be related to ruminal digestion parameters measured in vitro. The in vitro evaluation of digestion efficiency reveals that equal amounts of methane were produced across all feed samples regardless of whether the ruminal fluid was from moose or dairy cow. The results of this study suggested that the nutri- tional value of browsers’ spring and summer food can be predicted using rumen fluid from domesticated grazers as inoculum in in vitro assessments of extent of digestion when excluding samples of the white water lily root, but not of fermentation characteristics as indicated by the proportions of individual fermentation fatty acids to the total of volatile fatty acids.

  • 297.
    Kutser, Tiit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    The possibility of using the Landsat image archive for monitoring long time trends in coloured dissolved organic matter concentration in lake waters2012Inngår i: Remote Sensing of Environment, ISSN 0034-4257, E-ISSN 1879-0704, Vol. 123, s. 334-338Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent studies indicate that lakes are regulators of carbon cycling and climate. Therefore, it is important to know how the lake carbon content has changed over the last decades. In situ long time data series about the amount of dissolved organic carbon (DOC) in lakes are rare. The only potential way to study retrospectively the changes in lake carbon over the last decades is by means of remote sensing data provided there are sensors that can provide data about coloured dissolved organic matter (CDOM) in lakes over long periods. Landsat data archive contains images from 1984 to nowadays and covers the whole Earth. Although the sensors were not designed for remote sensing of aquatic environments it is still tempting to utilise the long data series. Landsat 4, Landsat 5 and Landsat 7 imagery available in free Landsat image archive was compared with time series of CDOM in situ data from 19 sampling stations available in the Swedish University of Natural Sciences lake monitoring database. There was no correlation between the image and in situ data when all the above mentioned data were used. Low radiometric resolution of the sensor, small size of many lakes (= large adjacency effects) and high concentration of CDOM (negligible water leaving radiation) could be the reasons. The results were more promising (R-2 = 0.62) when Lake Malaren stations were analysed separately. The lake is sufficiently large and with variable, but not extremely high. CDOM content. The Lake Malaren in situ data showed very different trends in CDOM concentrations in different basins of the lake over the last 45 years. Although the correlation between the image and in situ data was a bit low for accurate daily estimation of CDOM concentrations from Landsat data it could allow detecting general trends in lake CDOM content. Unfortunately, there is currently a gap in Landsat archive (for our study sites) between 1988 and 1998 which makes calculations of long time trends unreasonable for the time being. (C) 2012 Elsevier Inc. All rights reserved.

  • 298.
    Kutser, Tiit
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Alikas, Krista
    Kothawala, Dolly N.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Kohler, Stephan J.
    Impact of iron associated to organic matter on remote sensing estimates of lake carbon content2015Inngår i: Remote Sensing of Environment, ISSN 0034-4257, E-ISSN 1879-0704, Vol. 156, s. 109-116Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a strong need to develop remote sensing methods for mapping lake carbon content on regional to global scales. The use of in situ methods is impractical for monitoring lake water quality over large geographical areas, which is a fundamental requirement to understand the true role of lakes in the global carbon cycle. The coloured component of dissolved organic carbon (DOC), called CDOM, absorbs light strongly in the blue part of the visible spectrum and can be used as a proxy for mapping lake DOC with remote sensing. However, iron associated to organic matter can cause extra browning of waters. Consequently, the remote sensing signal we interpret as DOC may partially be attributed to the presence of iron associated to organic matter, potentially hampering our ability to estimate carbon concentrations. A thorough analysis of biogeochemical parameters was carried out on Lake Malaren on August 23, 2010, and a MERIS full resolution image was acquired simultaneously. MERIS standard, Case 2 Regional, and Boreal processors were used to calculate remote sensing products, which were compared with different lake water characteristics. The carbon to iron ratio was different from the rest of the lake in one of the basins. MERIS standard and Case 2 Regional processors were sensitive to this difference as the correlation between MERIS CDOM product and DOC was low (R-2 = 0.43) for all sampling stations and increased to 0.92 when the one basin was excluded. The Boreal Lakes processor results were less disturbed by the different carbon-iron ratios found in one basin and produced reasonably good results (R-2 = 0.65). We found MERIS products (e.g. total absorption) that provided good correlation (R-2 = 0.80) with DOC-specific absorbance at 254 nm, called SUVA, which is a metric commonly used to assess drinking water treatability. However, none of the MERIS products were suitable for mapping the total organic carbon in Lake Malaren.MERIS total suspended matter product was a good (R-2 = 0.73) proxy for particulate iron, meaning that the particulate iron content in Malaren can be mapped from space. (C) 2014 Elsevier Inc. All rights reserved.

  • 299.
    Kutser, Tiit
    et al.
    Univ Tartu, Estonian Marine Inst, Maealuse 14, EE-12618 Tallinn, Estonia.;Uppsala Univ, Evolutionary Biol Ctr, Limnol, Norbyvagen 18D, S-75236 Uppsala, Sweden..
    Paavel, Birgot
    Univ Tartu, Estonian Marine Inst, Maealuse 14, EE-12618 Tallinn, Estonia..
    Verpoorter, Charles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi. Univ Lille Nord France, Lab Oceanol & Geosci, ULCO, 32 Ave Foch, F-62930 Wimereux, France..
    Ligi, Martin
    Tartu Observ, EE-61602 Toravere, Toravere, Estonia..
    Soomets, Tuuli
    Univ Tartu, Estonian Marine Inst, Maealuse 14, EE-12618 Tallinn, Estonia..
    Toming, Kaire
    Univ Tartu, Estonian Marine Inst, Maealuse 14, EE-12618 Tallinn, Estonia..
    Casal, Gema
    Univ Tartu, Estonian Marine Inst, Maealuse 14, EE-12618 Tallinn, Estonia..
    Remote Sensing of Black Lakes and Using 810 nm Reflectance Peak for Retrieving Water Quality Parameters of Optically Complex Waters2016Inngår i: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 8, nr 6, artikkel-id 497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many lakes in boreal and arctic regions have high concentrations of CDOM (coloured dissolved organic matter). Remote sensing of such lakes is complicated due to very low water leaving signals. There are extreme (black) lakes where the water reflectance values are negligible in almost entire visible part of spectrum (400-700 nm) due to the absorption by CDOM. In these lakes, the only water-leaving signal detectable by remote sensing sensors occurs as two peaksnear 710 nm and 810 nm. The first peak has been widely used in remote sensing of eutrophic waters for more than two decades. We show on the example of field radiometry data collected in Estonian and Swedish lakes that the height of the 810 nm peak can also be used in retrieving water constituents from remote sensing data. This is important especially in black lakes where the height of the 710 nm peak is still affected by CDOM. We have shown that the 810 nm peak can be used also in remote sensing of a wide variety of lakes. The 810 nm peak is caused by combined effect of slight decrease in absorption by water molecules and backscattering from particulate material in the water. Phytoplankton was the dominant particulate material in most of the studied lakes. Therefore, the height of the 810 peak was in good correlation with all proxies of phytoplankton biomasschlorophyll-a (R-2 = 0.77), total suspended matter (R-2 = 0.70), and suspended particulate organic matter (R-2 = 0.68). There was no correlation between the peak height and the suspended particulate inorganic matter. Satellite sensors with sufficient spatial and radiometric resolution for mapping lake water quality (Landsat 8 OLI and Sentinel-2 MSI) were launched recently. In order to test whether these satellites can capture the 810 nm peak we simulated the spectral performance of these two satellites from field radiometry data. Actual satellite imagery from a black lake was also used to study whether these sensors can detect the peak despite their band configuration. Sentinel 2 MSI has a nearly perfectly positioned band at 705 nm to characterize the 700-720 nm peak. We found that the MSI 783 nm band can be used to detect the 810 nm peak despite the location of this band is not in perfect to capture the peak.

  • 300. Kutser, Tiit
    et al.
    Pierson, Donald C.
    Tranvik, L.J.
    Reinart, Anu
    Sobek, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Kallio, Kari Y.
    Using satellite remote sensing to estimate the colored dissolved organic matter absorption coefficient in lakes2005Inngår i: Ecosystems, Vol. 8, s. 709-720Artikkel i tidsskrift (Fagfellevurdert)
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