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  • 1.
    Aeppli, Christoph
    et al.
    Stockholm University, Sweden .
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Andersson, Per
    Swedish Museum Nat Hist, Sweden .
    Gustafsson, Orjan
    Stockholm University, Sweden .
    Chlorine Isotope Effects and Composition of Naturally Produced Organochlorines from Chloroperoxidases, Flavin-Dependent Halogenases, and in Forest Soil2013Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, nr 13, s. 6864-6871Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of stable chlorine isotopic signatures (delta Cl-37) of organochlorine compounds has been suggested as a tool to determine both their origins and transformations in the environment. Here we investigated the delta Cl-37 fractionation of two important pathways for enzymatic natural halogenation: chlorination by chloroperoxidase (CPO) and flavin-dependent halogenases (FDH). Phenolic products of CPO were highly Cl-37 depleted (delta Cl-37 = -12.6 +/- 0.9 parts per thousand); significantly more depleted than all known industrially produced organochlorine compounds (delta Cl-37 = -7 to +6 parts per thousand). In contrast, four FDH products did not exhibit any observable isotopic shifts (delta Cl-37 = -0.3 +/- 0.6 parts per thousand). We attributed the different isotopic effect to the distinctly different chlorination mechanisms employed by the two enzymes. Furthermore, the delta Cl-37 in bulk organochlorines extracted from boreal forest soils were only slightly depleted in Cl-37 relative to inorganic Cl. In contrast to previous suggestions that CPO plays a key role in production of soil organochlorines, this observation points to the additional involvement of either other chlorination pathways, or that dechlorination of naturally produced organochlorines can neutralize delta Cl-37 shifts caused by CPO chlorination. Overall, this study demonstrates that chlorine isotopic signatures are highly useful to understand sources and cycling of organochlorines in nature. Furthermore, this study presents delta Cl-37 values of FDH products as well of bulk organochlorines extracted from pristine forest soil for the first time.

  • 2.
    Aeppli, Christoph
    et al.
    Stockholm University.
    Holmstrand, Henry
    Stockholm University.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Tysklind, Mats
    Umeå University.
    Gustafsson, Orjan
    Stockholm University.
    Investigating formation and degradation of polychlorinated phenols in the environment using chlorine and carbon stable isotope fractionation in ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, vol 242, issue , pp2011Ingår i: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA , 2011, Vol. 242Konferensbidrag (Refereegranskat)
    Abstract [en]

    n/a

  • 3.
    Andersson, Anna
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Ashiq, Muhammad Jamshaid
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Shoeb, Mohammad
    Department of Chemistry, University of Dhaka, Dhaka, Bangladesh.
    Karlsson, Susanne
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Kylin, Henrik
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. Research Unit: Environmental Sciences and Management, North-West University, Potchefstroom, South Africa.
    Evaluating gas chromatography with a halogen-specific detectorfor the determination of disinfection by-products in drinking water2019Ingår i: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 26, s. 7305-7314Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The occurrence of disinfection by-products (DBPs) in drinking water has become an issue of concern during the past decades. The DBPs pose health risks and are suspected to cause various cancer forms, be genotoxic and have negative developmental effects. The vast chemical diversity of DBPs makes comprehensive monitoring challenging. Only few of the DBPs are regulated and included in analytical protocols. In this study, a method for simultaneous measurement of 20 DBPs from five different structural classes (both regulated and non-regulated) was investigated and further developed for 11 DBPs using solid phase extraction and gas chromatography coupled with a halogen specific detector (XSD). The XSD was highly selective towards halogenated DBPs, providing chromatograms with little noise. The method allowed detection down to 0.05 µg/L and showed promising results for the simultaneous determination of a range of neutral DBP classes. Compounds from two classes of emerging DBPs, more cytotoxic than the “traditional” regulated DBPs, were successfully determined using this method. However, haloacetic acids (HAAs) should be analyzed separately as some HAA methyl esters may degrade giving false positives of trihalomethanes (THMs). The method was tested on real water samples from two municipal waterworks where the target DBP concentrations were found below the regulatory limits of Sweden.

  • 4.
    Andersson, Anna
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Harir, Mourad
    Helmholtz Zentrum München, Germany.
    Gonsior, Michael
    University of Maryland Center for Environmental Science, USA.
    Hertkorn, Norbert
    Helmholtz Zentrum München, Germany.
    Schmitt-Kopplin, Philippe
    Helmholtz Zentrum München, Germany.
    Kylin, Henrik
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Karlsson, Susanne
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Ashiq, Muhammad Jamshaid
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Lavonen, Elin
    Norrvatten, Kvalitet och Utveckling.
    Nilsson, Kerstin
    VA SYD.
    Pettersson, Ämma
    Nodra.
    Stavklint, Helena
    Tekniska verken i Linköping.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Waterworks-specific composition of drinking water disinfection by-products2019Ingår i: Environmental Science: Water Research & Technology, ISSN 2053-1419, nr 5, s. 861-872Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reactions between chemical disinfectants and natural organic matter (NOM) upon drinking water treatment result in formation of potentially harmful disinfection by-products (DBPs). The diversity of DBPs formed is high and a large portion remains unknown. Previous studies have shown that non-volatile DBPs are important, as much of the total toxicity from DBPs has been related to this fraction. To further understand the composition and variation of DBPs associated with this fraction, non-target analysis with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to detect DBPs at four Swedish waterworks using different types of raw water and treatments. Samples were collected five times covering a full year. A common group of DBPs formed at all four waterworks was detected, suggesting a similar pool of DBP precursors in all raw waters that might be related to phenolic moieties. However, the largest proportion (64–92%) of the assigned chlorinated and brominated molecular formulae were unique, i.e. were solely found in one of the four waterworks. In contrast, the compositional variations of NOM in the raw waters and samples collected prior to chemical disinfection were rather limited.This indicated that waterworks-specific DBPs presumably originated from matrix effects at the point of disinfection, primarily explained by differences in bromide levels, disinfectants (chlorine versus chloramine) and different relative abundances of isomers among the NOM compositions studied. The large variation of observed DBPs in the toxicologically relevant non-volatile fraction indicates that non-targeted monitoring strategies might be valuable to ensure relevant DBP monitoring in the future.

  • 5.
    Backstrand, K.
    et al.
    Stockholm University.
    Crill, P. M.
    Stockholm University.
    Mastepanov, M.
    Lund University.
    Christensen, T. R.
    Lund University.
    Bastviken, D.
    Stockholm University.
    Non-methane volatile organic compound flux from a subarctic mire in Northern Sweden2008Ingår i: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 60, nr 2, s. 226-237Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biogenic NMVOCs are mainly formed by plants and microorganisms. They have strong impact on the local atmospheric chemistry when emitted to the atmosphere. The objective of this study was to determine if there are significant emissions of non-methane volatile organic compounds (NMVOCs) from a subarctic mire in northern Sweden. Subarctic peatlands in discontinuous permafrost regions are undergoing substantial environmental changes due to their high sensitivity to climate warming and there is need for including NMVOCs in the overall carbon budget. Automatic and manual chamber measurements were used to estimate NMVOC fluxes from three dominating subhabitats on the mire during three growing seasons. Emission rates varied and were related to plant species distribution and seasonal net ecosystem exchange of carbon dioxide. The highest fluxes were observed from wetter sites dominated by Eriophorum and Sphagnum spp. Total NMVOC emissions from the mire (similar to 17 ha) is estimated to consist of similar to 150 kgC during a growing season with 150 d. NMVOC fluxes can account for similar to 5% of total net carbon exchange (-3177 kgC) at the mire during the same period. NMVOC emissions are therefore a significant component in a local carbon budget for peatlands.

  • 6.
    Backstrand, K.
    et al.
    Stockholm University.
    Crill, P. M.
    Stockholm University.
    Mastepanov, M.
    Lund University.
    Christensen, T. R.
    Lund University.
    Bastviken, D.
    Stockholm University.
    Total hydrocarbon flux dynamics at a subarctic mire in northern Sweden2008Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, nr G3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This is a study of the spatial and temporal variability of total hydrocarbon (THC) emissions from vegetation and soil at a subarctic mire, northern Sweden. THCs include methane (CH4) and nonmethane volatile organic compounds (NMVOCs), both of which are atmospherically important trace gases and constitute a significant proportion of the carbon exchange between biosphere and atmosphere. Reliable characterization of the magnitude and the dynamics of the THC fluxes from high latitude peatlands are important when considering to what extent trace gas emissions from such ecosystems may change and feed back on climate regulation as a result of warmer climate and melting permafrost. High frequency measurements of THC and carbon dioxide (CO2) were conducted during four sequential growing seasons in three localities representing the trophic range of plant communities at the mire. The magnitude of the THC flux followed the moisture gradient with increasing emissions from a dry Palsa site (2.2 +/- 0.1 mgC m(-2) d(-1)), to a wet intermediate melt feature with Sphagnum spp. (28 +/- 0.3 mgC m(-2) d(-1)) and highest emissions from a wet Eriophorum spp. site (122 +/- 1.4 mgC m(-2) d(-1)) (overall mean +/- 1 SE, n = 2254, 2231 and 2137). At the Palsa site, daytime THC flux was most strongly related to air temperature while daytime THC emissions at the Sphagnum site had a stronger relation to ground temperature. THC emissions at both the wet sites were correlated to net ecosystem exchange of CO2. An overall spatial correlation indicated that areas with highly productive vegetation communities also had high THC emission potential.

  • 7.
    Barros, Nathan
    et al.
    University Fed Juiz de Fora.
    J Cole, Jonathan
    Cary Institute for Ecosystem Studies.
    Tranvik, Lars J
    Uppsala University.
    Prairie, Yves T
    University of Quebec.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Huszar, Vera L M
    University Fed Rio de Janeiro.
    del Giorgio, Paul
    University of Quebec.
    Roland, Fabio
    University Fed Juiz de Fora.
    Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude2011Ingår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 4, nr 9, s. 593-596Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydroelectric reservoirs cover an area of 3.4 x 10(5) km(2) and comprise about 20% of all reservoirs. In addition, they contain large stores of formerly terrestrial organic carbon. Significant amounts of greenhouse gases are emitted(2), especially in the early years following reservoir creation, but the global extent of these emissions is poorly known. Previous estimates of emissions from all types of reservoir indicate that these human-made systems emit 321 Tg of carbon per year (ref. 4). Here we assess the emissions of carbon dioxide and methane from hydroelectric reservoirs, on the basis of data from 85 globally distributed hydroelectric reservoirs that account for 20% of the global area of these systems. We relate the emissions to reservoir age, location biome, morphometric features and chemical status. We estimate that hydroelectric reservoirs emit about 48 Tg C as CO(2) and 3 Tg C as CH(4), corresponding to 4% of global carbon emissions from inland waters. Our estimates are smaller than previous estimates on the basis of more limited data. Carbon emissions are correlated to reservoir age and latitude, with the highest emission rates from the tropical Amazon region. We conclude that future emissions will be highly dependent on the geographic location of new hydroelectric reservoirs.

  • 8.
    Bastviken, D.
    et al.
    Stockholm University.
    Cole, J. J.
    Institute of Ecosystem Studies, Millbrook.
    Pace, M. L.
    Institute of Ecosystem Studies, Millbrook.
    Van de Bogert, M. C.
    University of Wisconsin.
    Fates of methane from different lake habitats: Connecting whole-lake budgets and CH4 emissions2008Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, nr G2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methane (CH4) represents a major product of organic matter decomposition in lakes. Once produced in the sediments, CH4 can be either oxidized or emitted as a greenhouse gas to the atmosphere. Lakes represent an important source of atmospheric CH4, but the relative magnitudes of the internal pathways that lead to CH4 emissions are not yet clear. We quantified internal cycling and methane emissions in three lakes during summer stratification. These methane budgets included: sediment release of CH4 at different depths; water column transport patterns and methane oxidation; methane storage in the water column; and methane emissions to the atmosphere by diffusion and ebullition. The contribution of CH4 carbon, via oxidation by methanotrophic bacteria, to pelagic food webs was also estimated. Despite the very low concentration of CH4 in surface waters, shallow, epilimnetic sediments were major contributors of CH4 to the atmosphere. While 51 - 80% of the CH4 produced in deep sediments was oxidized in the water column, most of the CH4 released from shallow sediment escaped oxidation and reached the atmosphere. Epilimnetic sediments accounted for 100% of CH4 emitted during summer stratification, and 14 - 76% considering the release of CH4 stored in deep water layers during lake circulation after the stratification period; diffusive emission accounted for 26 - 48% and ebullition the remainder. These results indicate that it is important to address transport rates of CH4 from the shallow sediment along with the production-consumption processes when trying to understand methane dynamics and the regulation of lake methane emissions.

  • 9.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Anoxic degradation of organic matter in lakes: implications for carbon cycling and aquatic food webs2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Considerable evidence from laboratory studies and marine environments suggests that degradation of organic matter (OM) is restricted under anoxic conditions compared to when molecular oxygen (O2) is present. However, other studies contradict this view since they found similar OM degradation rates and bacterial growth rates under both oxic and anoxic conditions in aquatic environments. Studies from freshwater environments are rare, and have been primarily based on bacterial production estimates. Anoxic degradation of OM in lakes is commonly considered to be slow and of little importance for overall lake food webs compared to oxic degradation. The present thesis and the work it is based on challenge this view. First, the performance of a commonly used method to measure bacterial production was tested in both oxic and anoxic lake water. Then, the oxic and anoxic potentials of bacterial growth and OM mineralization were compared in lake water and sediment. In addition, I assessed the potential of carbon transfer from methane (CH4; i.e. an end-product of anoxic degradation) to pelagic food webs. Three methods for measuring water column methane oxidation were evaluated. Then, the potential transport of methane carbon into the microbial community via methane oxidation, and further -up the food web- into the zooplankton community was estimated. Results indicate 1) that OM degradation and bacterial growth may be similar in oxic and anoxic lake environments, 2) that OM characteristics may be more important for the mineralization than the O2 regime per se in the short term (daysweeks), and 3) that methane can be a significant source of carbon and energy for pelagic food webs. This suggests that the anoxic carbon metabolism may be extensive and potentially important for pelagic organisms in many lakes.

  • 10.
    Bastviken, David
    Stockholm University, Sweden.
    Methane2009Ingår i: Encyclopedia of Inland Waters, Oxford: Elsevier , 2009, 1, s. 783-805Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Inland aquatic habitats occur world-wide at all scales from marshes, swamps and temporary puddles, to ponds, lakes and inland seas; from streams and creeks to rolling rivers. Vital for biological diversity, ecosystem function and as resources for human life, commerce and leisure, inland waters are a vital component of life on Earth. The Encyclopedia of Inland Waters describes and explains all the basic features of the subject, from water chemistry and physics, to the biology of aquatic creatures and the complex function and balance of aquatic ecosystems of varying size and complexity. Used and abused as an essential resource, it is vital that we understand and manage them as much as we appreciate and enjoy them. This extraordinary reference brings together the very best research to provide the basic and advanced information necessary for scientists to understand these ecosystems - and for water resource managers and consultants to manage and protect them for future generations. . Encyclopedic reference to Limnology - a key core subject in ecology taught as a specialist course in universities . Over 240 topic related articles cover the field . Gene Likens is a renowned limnologist and conservationist, Emeritus Director of the Institute of Ecosystems Research, elected member of the American Philosophical Society and recipient of the 2001 National Medal of Science . Subject Section Editors and authors include the very best research workers in the field

  • 11.
    Bastviken, David
    et al.
    Linköpings universitet, Utbildningsvetenskap. Linköpings universitet, Institutionen för samhälls- och välfärdsstudier, Lärande, Estetik, Naturvetenskap (LEN).
    Cole, J
    Pace, M
    Tranvik, L
    Methane emissions from lakes: Dependence of lake characteristics, two regional assessments, and a global estimate2004Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 18, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [ 1] Lake sediments are "hot spots'' of methane production in the landscape. However, regional and global lake methane emissions, contributing to the greenhouse effect, are poorly known. We developed predictions of methane emissions from easily measured lake characteristics based on measurements for 11 North American and 13 Swedish lakes, and literature values from 49 lakes. Results suggest that open water methane emission can be predicted from variables such as lake area, water depth, concentrations of total phosphorus, dissolved organic carbon, and methane, and the anoxic lake volume fraction. Using these relations, we provide regional estimates from lakes in Sweden and the upper midwest of the United States. Considering both open water and plant-mediated fluxes, we estimate global emissions as 8 - 48 Tg CH4 yr(-1) (6 - 16% of total natural methane emissions and greater than oceanic emission), indicating that lakes should be included as a significant source in global methane budgets.

  • 12.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Cole, Jonathan
    Institute of Ecosystem Studies, Millbrook, New York, USA.
    Pace, Michael
    Institute of Ecosystem Studies, Millbrook, New York, USA.
    Tranvik, Lars
    Department of Limnology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
    Methane emissions from lakes: Dependence of lake characteristics, two regional assessments, and a global estimate2004Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 18, nr 4, artikel-id GB4009Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [ 1] Lake sediments are "hot spots'' of methane production in the landscape. However, regional and global lake methane emissions, contributing to the greenhouse effect, are poorly known. We developed predictions of methane emissions from easily measured lake characteristics based on measurements for 11 North American and 13 Swedish lakes, and literature values from 49 lakes. Results suggest that open water methane emission can be predicted from variables such as lake area, water depth, concentrations of total phosphorus, dissolved organic carbon, and methane, and the anoxic lake volume fraction. Using these relations, we provide regional estimates from lakes in Sweden and the upper midwest of the United States. Considering both open water and plant-mediated fluxes, we estimate global emissions as 8 - 48 Tg CH4 yr(-1) (6 - 16% of total natural methane emissions and greater than oceanic emission), indicating that lakes should be included as a significant source in global methane budgets.

  • 13.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Ejlertsson, Jörgen
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Sundh, Ingvar
    Department of Microbiology, Swedish University of Agricultural Sciences.
    Tranvik, Lars
    Department of Limnology, Uppsala University.
    Methane as a source of carbon and energy for lake pelagic food webs2003Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 84, nr 4, s. 969-981Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Water-column methane oxidation can represent a substantial carbon transformation pathway in lakes, and circumstantial evidence indicates that methane may be a potentially important source of carbon for pelagic food webs. We estimated methanotrophic bacterial production (MBP), methanotrophic bacterial growth efficiency (MBGE), heterotrophic bacterial production (HBP), primary production (PP), and the relative contribution of methanotrophic bacteria to overall bacterial biomass in three very different lakes during summer and winter. In addition, we measured stable carbon isotope ratios in particulate organic matter (POM), surface sediments, zooplankton, and methane. MBP corresponded to 0.3-7% of the organic C production by primary producers, and 0.5-17% of HBP during summer. During winter, MBP was 3-120% of HBP. MBP generally dominated the heterotrophic bacterial production at greater depths. Methanotrophic biomass was 3-11% of total bacterial biomass on a depth-integrated basis. Zooplankton were generally more depleted in 13C than POM. If phytoplankton d13C signatures were -35 to -30ë, such as the POM signals, observed zooplankton signatures could be explained by a fraction of 5-15% methanotrophic bacteria in their diet. The results indicate that methanotrophic bacteria can provide a significant food source for zooplankton, and that methane oxidation represents a potentially important benthic-pelagic carbon and energy link in many lakes, particularly during winter.

  • 14.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Ejlertsson, Jörgen
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Tranvik, Lars
    Department of Limnology, Uppsala University, Uppsala, Sweden.
    Measurement of methane oxidation in lakes: A comparison of methods2002Ingår i: Environmental Science & Technology, ISSN 0013-936X, Vol. 36, nr 15, s. 3354-3361Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methane oxidation in lakes constrains the methane emissions to the atmosphere and simultaneously enables the transfer of methane carbon to pelagic food webs, Several different methods have been used to estimate methane oxidation, but these methods have not previously been compared. In this study, we present methane oxidation estimates from three different lakes during summer and winter, using methods based on the transformation of added (CH4)-C-14, the fractionation of natural methane C-13, and the mass balance modeling of concentration gradients, All methods yielded similar results, including similar differences between lakes and seasons. Average methane oxidation rates varied from 0.25 to 81 mg of C m(-2) d(-1) and indicate that the three methods are comparable, although they to some extent take different processes into account. Critical issues as well as drawbacks and advantages with the used methods are thoroughly discussed. We conclude that methods using the stable isotope or mass balance modeling approach represent promising alternatives, particularly for studies focusing on ecosystem-scale carbon metabolism.

  • 15.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Ejlertsson, Jörgen
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Tranvik, Lars
    2Department of Limnology, Uppsala University, Sweden.
    Similar bacterial growth on dissolved organic matter in anoxic and oxic lake water2001Ingår i: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 24, nr 1, s. 41-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anoxic metabolism yields less energy per unit substrate utilized than oxic respiration. In addition, substrate availability is believed to be reduced under anoxic conditions since oxygenases cannot be used. Consequently, it is generally assumed that bacteria grow slower in anoxic environments than in oxic environments. The results of the present study challenge this view. We compared the growth of bacterial assemblages under carbon-limited conditions in lake water under anoxic and oxic conditions. Bioassay experiments were performed with water from 3 lakes differin9 in nutrient concentrations and organic matter content. Amon9 bacteria usin9 the same source of organic matter, median anoxic growth rates were 84 to 110% of oxic growth rates. The total biomass yield durin9 the experiments did not differ between anoxic and oxic treatments. We suggest that anoxic bacterial growth was regulated by substrate availability rather than by metabolic energy yield and that availability of organic matter under anoxic conditions was equal to or even greater than that in oxic treatments. This implies that anoxic decomposition rates may actually have been faster than oxic rates.

  • 16.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Lucia Santoro, Ana
    Univ Fed Rio de Janeiro.
    Marotta, Humberto
    Univ Fed Rio de Janeiro.
    Queiroz Pinho, Luana
    Univ Fed Rio de Janeiro.
    Fernandes Calheiros, Debora
    Ctr Agr Res Pantanal Embrapa Pantanal.
    Crill, Patrick
    Stockholm University.
    Enrich-Prast, Alex
    Univ Fed Rio de Janeiro.
    Methane Emissions from Pantanal, South America, during the Low Water Season: Toward More Comprehensive Sampling2010Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 44, nr 14, s. 5450-5455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Freshwater environments contribute 75% of the natural global methane (CH4) emissions. While there are indications that tropical lakes and reservoirs emit 58-400% more CH4 per unit area than similar environments in boreal and temperate biomes, direct measurements of tropical lake emissions are scarce. We measured CH4 emissions from 16 natural shallow lakes in the Pantanal region of South America, one of the worlds largest tropical wetland areas, during the low water period using floating flux chambers. Measured fluxes ranged from 3.9 to 74.2 mmol m(-2) d(-1) with the average from all studied lakes being 8.8 mmol m(-2) d(-1) (131.8 mg CH4 m(-2) d(-1)), of which ebullition accounted for 91% of the flux (28-98% on individual lakes). Diel cycling of emission rates was observed and therefore 24-h long measurements are recommended rather than short-term measurements not accounting for the full diel cycle. Methane emission variability within a lake may be equal to or more important than between lake variability in floodplain areas as this study identified diverse habitats within lakes having widely different flux rates. Future measurements with static floating chambers should be based on many individual chambers distributed in the various subenvironments of a lake that may differ in emissions in order to account for the within lake variability.

  • 17.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Natchimuthu, Sivakiruthika
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Panneer Selvam, Balathandayuthabani
    Lund University, Sweden.
    Letter: Response: Inland water greenhouse gas emissions: when to model and when to measure? in GLOBAL CHANGE BIOLOGY, vol 21, issue 4, pp 1379-13802015Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, nr 4, s. 1379-1380Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    n/a

  • 18.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Olsson, M
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biologi.
    Tranvik, L
    Department of Limnology, Uppsala University.
    Simultaneous measurements of organic carbon mineralization and bacterial production in oxic and anoxic lake sediments2003Ingår i: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 46, nr 1, s. 73-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on work in marine sediments it can be hypothesized that (i) overall OM mineralization depends on the enzymatic capacity and is largely independent from the energy yield, (ii) similar oxic and anoxic rates are expected for fresh OM, while oxic rates should be faster for old OM that is partially degraded or adsorbed to particles, and (iii) that the thermodynamic energy yield does not regulate mineralization, but primarily determines the energy fraction allocated to bacterial production (BP). We addressed these hypotheses by simultaneous measurements of mineralization rates (MR) and BP in sediments from a eutrophic lake, along with MR measurements in sediments of a dystrophic lake. Anoxic MR were 44 and 78% of oxic MR in the eutrophic and dystrophic lake, respectively, which was always higher than expected given the theoretical energy yields. The BP:MR ratio was 0.94 and 0.24 in the oxic and anoxic treatments, respectively, in accordance with the expected energy yields. Thus, the results support all three hypotheses above. We also critically discuss BP measurements in sediments and suggest that bacterial growth efficiency values from simultaneous MR and BP measurements can be used to evaluate the reliability of BP estimates.

  • 19.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Persson, Linn
    Institute of Applied Environmental Research, Stockholm University, Sweden.
    Odham, Göran
    Institute of Applied Environmental Research, Stockholm University, Sweden.
    Tranvik, Lars
    Department of Limnology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
    Degradation of dissolved organic matter in oxic and anoxic lake water2004Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 49, nr 1, s. 109-116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Decades of conflicting results have fueled a debate about how O-2 affects organic matter (OM) degradation and carbon cycling. In a laboratory study, using both OM taken directly from a humic lake and chemically isolated fulvic acid, we monitored the mineralization of dissolved OM in freshwater under purely oxic and anoxic conditions, under oxic then anoxic conditions, and under anoxic then oxic conditions, for 426 d. Between 5% and 24% of the initial OM was mineralized, with most extensive mineralization occurring under purely oxic and anoxic-oxic conditions. A sequential change in the O-2 regime did not result in greater overall degradation, but initially anoxic conditions favored subsequent oxic mineralization. A substantially greater fraction of the OM was degraded than in previous shorter studies, with as much as 50% of the total OM degradation occurring after 147 d into the experiment. Three fractions of the degradable OM were identified: OM degraded only under oxic conditions (68-78%), OM degraded more rapidly under anoxic conditions than under oxic conditions (16-18%), and OM degraded at equal rates under both oxic and anoxic conditions (6-14%). The degradation patterns of natural dissolved OM from a humic lake and chemically isolated fulvic acid were very similar, which indicates a similar level of bioavailability. The difference between anoxic and oxic degradation was greater in our long-term studies than in previous short-term experiments, which indicates that the oxic and anoxic degradation potentials vary with increasing overall OM recalcitrance and that similar oxic and anoxic degradation rates can be expected in short-term experiments in which <30% of the long-term degradable OM is allowed to decompose.

  • 20.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för samhälls- och välfärdsstudier, Lärande, Estetik, Naturvetenskap (LEN). Linköpings universitet, Utbildningsvetenskap.
    Samuelsson, C.
    Ståhlberg, Carina
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Similar organic matter mineralisation rates under oxic, methanogenic, and sulphate reducing conditions in late winter sediment of a Swedish river2006Artikel i tidskrift (Refereegranskat)
  • 21.
    Bastviken, David
    et al.
    Stockholm University.
    Sandén, Per
    Linköpings universitet, Institutionen för tema, Centrum för klimatpolitisk forskning. Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Svensson, Teresia
    Linköpings universitet, Institutionen för tema, Centrum för klimatpolitisk forskning. Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Ståhlberg, Carina
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Magounakis, Malin
    Linköpings universitet, Institutionen för tema, Centrum för klimatpolitisk forskning. Linköpings universitet, Filosofiska fakulteten.
    Öberg, Gunilla
    Linköpings universitet, Institutionen för tema, Centrum för klimatpolitisk forskning. Linköpings universitet, Filosofiska fakulteten.
    Chloride retention and release in a boreal forest soil: effects of soil water residence time and nitrogen and chloride loads2006Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 40, nr 9, s. 2977-2982Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The common assumption that chloride (Cl-) is conservative in soils and can be used as a groundwater tracer is currently being questioned, and an increasing number of studies indicate that Cl- can be retained in soils. We performed lysimeter experiments with soil from a coniferous forest in southeast Sweden to determine whether pore water residence time and nitrogen and Cl- loads affected Cl- retention. Over the first 42 days there was a net retention of Cl- with retention rates averaging 3.1 mg Cl- m-2 d-1 (68% of the added Cl- retained over 42 days). Thereafter, a net release of Cl- at similar rates was observed for the remaining experimental period (85 d). Longer soil water residence time and higher Cl- load gave higher initial retention and subsequent release rates than shorter residence time and lower Cl- load did. Nitrogen load did not affect Cl transformation rates. This study indicates that simultaneous retention and release of Cl- can occur in soils, and that rates may be considerable relative to the load. The retention of Cl- observed was probably due to chlorination of soil organic matter or ion exchange. The cause of the shift between net retention and net release is unclear, but we hypothesize that the presence of O2 or the presence of microbially available organic matter regulates Cl- retention and release rates.

  • 22.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Sundgren, Ingrid
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Natchimuthu, Sivakiruthika
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Reyier, Henrik
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Gålfalk, Magnus
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Technical Note: Cost-efficient approaches to measure carbon dioxide (CO2) fluxes and concentrations in terrestrial and aquatic environments using mini loggers2015Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 12, nr 12, s. 3849-3859Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fluxes of CO2 are important for our understanding of the global carbon cycle and greenhouse gas balances. Several significant CO2 fluxes in nature may still be unknown as illustrated by recent findings of high CO2 emissions from aquatic environments, previously not recognized in global carbon balances. Therefore, it is important to develop convenient and affordable ways to measure CO2 in many types of environments. At present, direct measurements of CO2 fluxes from soil or water, or CO2 concentrations in surface water, are typically labor intensive or require costly equipment. We here present an approach with measurement units based on small inexpensive CO2 loggers, originally made for indoor air quality monitoring, that were tested and adapted for field use. Measurements of soil-atmosphere and lake-atmosphere fluxes, as well as of spatiotemporal dynamics of water CO2 concentrations (expressed as the equivalent partial pressure, pCO(2aq)) in lakes and a stream network are provided as examples. Results from all these examples indicate that this approach can provide a cost- and labor-efficient alternative for direct measurements and monitoring of CO2 flux and pCO(2aq) in terrestrial and aquatic environments.

  • 23.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Svensson, Teresia
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Karlsson, Susanne
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Sandén, Per
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Öberg, Gunilla
    IRES, UBC, Canada.
    Temperature sensitivity indicates enzyme controlled chlorination of soil organic matter2009Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, nr 10, s. 3569-3573Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Old assumptions that chloride is inert and that most chlorinated organic matter in soils is anthropogenic have been challenged by findings of naturally formed organochlorines. Such natural chlorination has been recognized for several decades, but there are still very few measurements of chlorination rates or estimates of the quantitative importance of terrestrial chlorine transformations. While much is known about the formation of specific compounds, bulk chlorination remains poorly understood in terms of mechanisms and effects of environmental factors. We quantified bulk chlorination rates in coniferous forest soil using 36Cl-chloride in tracer experiments at different temperatures and with and without molecular oxygen (O2). Chlorination was enhanced by the presence of O2 and had a temperature optimum at 20 °C. Minimum rates were found at high temperatures (50 °C) or under anoxic conditions. The results indicate (1) that most of the chlorination between 4 and 40 °C was biotic and driven by O2 dependent enzymes, and (2) that there is also slower background chlorination occurring under anoxic conditions at 20 °C and under oxic conditions at 50 °C. Hence, while oxic and biotic chlorination clearly dominated, chlorination by other processes including possible abiotic reactions was also detected.

  • 24.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Svensson, Teresia
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Sandén, Per
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Kylin, Henrik
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Chlorine cycling and fates of 36Cl in terrestrial environments2013Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Klor-36 (36Cl), en radioisotop med en halveringstid på 301 000 år, förekommer i vissa typer av radioaktivt avfall. För att kunna förutse vad som händer om 36Cl når markytan är det viktigt att veta hur klor kan omvandlas och transporteras i olika ekosystem. Denna rapport syftar till att sammanfatta kunskapsläget om klor i naturmiljöer med fokus på landmiljöer.

    Synen på klor i naturen är under omfattande förändring till följd av de senaste decenniernas forskning. Det står nu helt klart att klorid (Cl) som tidigare betraktats som icke-reaktiv och totalt dominerande, istället är i hög grad reaktiv och inte alltid utgör den dominerande klorformen.

    Utifrån de studier som presenteras i rapporten är det tydligt att:

    • Det sker en omfattande naturlig klorering av organiskt material i många miljöer och inte minst i ytliga marklager.
    • Mängden organiskt bunden klor (Clorg) är i många miljöer betydligt högre än mängden Cl. Därmed dominerar Clorg ofta det totala klorförrådet i exempelvis mark.
    • Detta har stor inverkan på transporten av klor eftersom Clorg till stor del finns i partikulärt organiskt material medan Cl är mycket vattenlösligt. Cl som når ytliga marklager är t ex inte lämpligt som spårämne för markvattenflöden såsom tidigare antagits. Cl kommer till stor del att bindas in till Clorg -förrådet och därmed förlänga uppehållstiden i ekosystemen.
    • Cl dominerar både importen och exporten från terrestra ekosystem medan Clorg kan dominera stationära klorförråd i systemen.
    • Framtida mätningar med syfte att klargöra kloromsättning och klorflöden behöver beakta Cl och Clorg separat.

    Därtill finns ett antal troligen viktiga indikationer som skulle behöva bekräftas av ytterligare studier. Dessa inkluderar att:

    • Det sker ett snabbt och omfattande upptag av Cl av organismer och klor tycks ackumuleras i grön växtbiomassa. En stor andel av den totala klormängden i avrinningsområden (upp till 60% i en studie) har påträffats i den terrester biomassa.
    • Avgång av flyktiga klorerade kolväten kan vara en stor okänd exportväg för klor från ekosystem.
    • En del Clorg verkar vara betydligt mer motståndskraftigt mot nedbrytning än det genomsnittliga organiska materialet. Detta kan leda till att Clorg bevaras selektivt i mark och därmed också mindre tillgängligt för mikroorganismer.
    • Det sker en klorering av organiskt material i levande biomassa och klor kan ansamlas som klorerade fettsyror i organismer.

    Övriga aspekter på klor i naturen är till stora delar okända. Centrala okända aspekter inkluderar:

    • Hur klor-förråden utvecklas över tid. Detta är centralt för att förstå förändringar över tid och reglering i förråden.
    • Reglering av klorerings-, deklorerings- och transportprocesser, samt hur dessa påverkas av olika miljövariabler och miljöförhållanden.
    • Den ekologiska förklaringen till varför så många organismer utför klorering av organiskt material.
    • Omsättning av klor i akvatiska system. Här saknas separata data gällande Cl– och Clorg både i sediment och i vattenfasen.

     

    Rapporten fokuserar framför allt på terrestra aspekter av klorcykeln och innehåller också information om vanliga metoder för mätning av olika klorföreningar.

  • 25.
    Bastviken, David T. E.
    et al.
    Uppsala University, Uppsala, Sweden.
    Caraco, Nina F.
    Institute of Ecosystem Studies, Millbrook, USA.
    Cole, Jonathan J.
    Institute of Ecosystem Studies, Millbrook, USA.
    Experimental measurements of zebra mussel (Dreissena polymorpha) impacts on phytoplankton community composition1998Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 39, nr 2, s. 375-386Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. To investigate direct effects of zebra mussel (Dreissena polymorpha) feeding activities on phytoplankton community composition, short-term microcosm experiments were performed in natural water with complex phytoplankton communities. Both gross effects (without resuspension of mussel excretions) and net effects (with resuspension) were studied. 2. Gross clearance rates were not selective; essentially all taxa were removed at similar rates ranging from 24 to 63 mt mussel(-1) h(-1). Net clearance rates were highly selective; different plankton taxa were removed at very different rates, ranging from 12 to 83% of the gross rates, leading to consistent changes in the phytoplankton community composition. Thus, although zebra mussels can cause most phytoplankton to decline, there is considerable variation among taxa in either pre-digestive selection or post-digestive survival. 3. The direct, short-term effects of zebra mussels on phytoplankton community composition are consistent with some of the major changes observed in the Hudson River since establishment of zebra mussels. 4. We show, with simple calculations, how zebra mussel filtration rate, its selective efficiency on various taxa, and phytoplankton growth rates interact to produce changes in the phytoplankton composition.

  • 26.
    Bastviken, David
    et al.
    Department of geology and geochemistry Stockholm University.
    Thomsen, Frida
    The Tema institute Linköpings universitet.
    Svensson, Teresia
    Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Institutionen för tema.
    Karlsson, Susanne
    Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Institutionen för tema.
    Sandén, Per
    Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Institutionen för tema.
    Shaw, George
    Division of agricultural and environmental sciences University of Nottingham.
    Matucha, Miroslav
    Institute of experimental botany Ac. Sci. Czech Rep.
    Öberg, Gunilla
    Institute for resources, environment and sustainability University of British Colombia.
    Chloride retention in forest soil by microbial uptake and by natural chlorination of organic matter2007Ingår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 71, nr 13, s. 3182-3192Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inorganic chlorine (i.e. chloride, Clin) is generally considered inert in soil and is often used as a tracer of soil and ground water movements. However, recent studies indicate that substantial retention or release of Clin can occur in soil, but the rates and processes responsible under different environmental conditions are largely unknown. We performed 36Cl tracer experiments which indicated that short-term microbial uptake and release of Clin, in combination with more long-term natural formation of chlorinated organic matter (Clorg), caused Clin imbalances in coniferous forest soil. Extensive microbial uptake and release of Clin occurred over short time scales, and were probably associated with changes in environmental conditions. Up to 24% of the initially available Clin within pore water was retained by microbial uptake within a week in our experiments, but most of this Clin was released to the pore water again within a month, probably associated with decreasing microbial populations. The natural formation of Clorg resulted in a net immobilization of 4% of the initial pore water Clin over four months. If this rate is representative for the area where soil was collected, Clorg formation would correspond to a conversion of 25% of the yearly wet deposition of Clin. The study illustrates the potential of two Clin retaining processes in addition to those previously addressed elsewhere (e.g. uptake of chloride by vegetation). Hence, several processes operating at different time scales and with different regulation mechanisms can cause Clin imbalances in soil. Altogether, the results of the present study (1) provide evidence that Clin cannot be assumed to be inert in soil, (2) show that microbial exchange can regulate pore water Clin concentrations and (3) confirm the controversial idea of substantial natural chlorination of soil organic matter. © 2007 Elsevier Ltd. All rights reserved.

  • 27.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Tranvik, Lars
    Department of Limnology, Uppsala University, Sweden.
    The leucine incorporation method estimates bacterial growth equally well in both oxic and anoxic lake waters2001Ingår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 67, nr 7, s. 2916-2921Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bacterial biomass production is often estimated from incorporation of radioactively labeled leucine into protein, in both oxic and anoxic waters and sediments. However, the validity of the method in anoxic environments has so far not been tested. We compared the leucine incorporation of bacterial assemblages growing in oxic and anoxic waters from three lakes differing in nutrient and humic contents, The method was modified to avoid O-2 contamination by performing the incubation in syringes. Isotope saturation levels in oxic and anoxic waters were determined, and leucine incorporation rates were compared to microscopically observed bacterial growth. Finally, we evaluated the effects of O-2 contamination during incubation with leucine, as well as the potential effects of a headspace in the incubation vessel, isotope saturation occurred at a leucine concentration of above about 50 nM in both ode and anoxic waters from all three lakes. Leucine incorporation rates were linearly correlated to observed growth, and there was no significant difference between oxic and anoxic conditions. O-2 contamination of anoxic water during I-h incubations with leucine had no detectable impact on the incorporation rate, while a headspace in the incubation vessel caused leucine incorporation to increase in both anoxic and O-2-contaminated samples. The results indicate that the leucine incorporation method relates equally to bacterial growth rates under oxic and anoxic conditions and that incubation should be performed without a headspace.

  • 28.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Tranvik, Lars J.
    Uppsala universitet.
    Downing, John A.
    Iowa State University.
    Crill, Patrick M.
    Stockholms universitet.
    Enrich-Prast, Alex
    University of Rio de Janeiro.
    Freshwater Methane Emissions Offset the Continental Carbon Sink2011Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 331, nr 6013, s. 50-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.

  • 29.
    Bengtson, P.
    et al.
    Lund University, Sweden.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    de Boer, W.
    Centre for Terrestrial Ecology, Netherlands.
    Öberg, Gunilla
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Possible role of reactive chlorine in microbial antagonism and organic matter chlorination in terrestrial environments2009Ingår i: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 11, nr 6, s. 1330-1339Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several studies have demonstrated that extensive formation of organically bound chlorine occurs both in soil and in decaying plant material. Previous studies suggest that enzymatic formation of reactive chlorine outside cells is a major source. However, the ecological role of microbial-induced extracellular chlorination processes remains unclear. In the present paper, we assess whether or not the literature supports the hypothesis that extracellular chlorination is involved in direct antagonism against competitors for the same resources. Our review shows that it is by no means rare that biotic processes create conditions that render biocidal concentrations of reactive chlorine compounds, which suggest that extracellular production of reactive chlorine may have an important role in antagonistic microbial interactions. To test the validity, we searched the UniprotPK database for microorganisms that are known to produce haloperoxidases. It appeared that many of the identified haloperoxidases from terrestrial environments are originating from organisms that are associated with living plants or decomposing plant material. The results of the in silico screening were supported by various field and laboratory studies on natural chlorination. Hence, the ability to produce reactive chlorine seems to be especially common in environments that are known for antibiotic-mediated competition for resources (interference competition). Yet, the ability to produce haloperoxidases is also recorded, for example, for plant endosymbionts and parasites, and there is little or no empirical evidence that suggests that these organisms are antagonistic.

  • 30.
    Bengtson, Per
    et al.
    Lund University, Sweden .
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Oeberg, Gunilla
    University of British Columbia, Canada .
    Possible roles of reactive chlorine II: assessing biotic chlorination as a way for organisms to handle oxygen stress2013Ingår i: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 15, nr 4, s. 991-1000Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Natural formation of organically bound chlorine is extensive in many environments. The enzymes associated with the formation of chlorinated organic matter are produced by a large variety of organisms. Little is known about the ecological role of the process, the key question being: why do microorganisms promote chlorination of organic matter? In a recent paper we discuss whether organic matter chlorination may be a result of antagonistic interactions among microorganisms. In the present paper we evaluate whether extracellular microbial formation of reactive chlorine may be used as a defence against oxygen stress, and we discuss whether this process is likely to contribute to the formation of chlorinated organic matter. Our analysis suggests that periodic exposure to elevated concentrations of reactive oxygen species is a common denominator among the multitude of organisms that are able to enzymatically catalyse formation of reactive chlorine. There is also some evidence suggesting that the production of such enzymes in algae and bacteria is induced by oxygen stress. The relative contribution from this process to the extensive formation of chlorinated organic matter in natural environments remains to be empirically assessed.

  • 31.
    Björn, Annika
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Svensson, Teresia
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Öberg, Gunilla
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Problem-oriented laboratory work in environmental education: Experiences from a new master´s programme at Linköping Univerity, Sweden1999Ingår i: AuDes 5th Conference on Environmental Education, 1999Konferensbidrag (Övrigt vetenskapligt)
  • 32.
    Bäckstrand, Kristina
    et al.
    Stockholm University.
    Crill, P. M.
    Stockholm University.
    Jackowicz-Korczyñski, M.
    Lund University.
    Mastepanov, M.
    Lund University.
    Christensen, T. R.
    Lund University.
    Bastviken, David
    Department of Geology and Geochemistry, Stockholm University.
    Annual carbon gas budget for a subarctic peatland, northern Sweden2010Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, s. 95-108Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

     Temperatures in the Arctic regions are rising, thawing permafrost and exposing previously stable soil organic carbon (OC) to decomposition. This can result in northern latitude soils, which have accumulated large amounts of OC potentially shifting from atmospheric C sinks to C sources with positive feedback on climate warming. In this paper, we estimate the annual net C gas balance (NCB) of the subarctic mire Stordalen, based on automatic chamber measurements of CO2 and total hydrocarbon (THC; CH4 and NMVOCs) exchange. We studied the dominant vegetation communities with different moisture and permafrost characteristics; a dry Palsa underlain by permafrost, an intermediate thaw site with Sphagnum spp. and a wet site with Eriophorum spp. where the soil thaws completely. Whole year accumulated fluxes of CO2 were estimated to 29.7, −35.3 and −34.9 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum sites (positive flux indicates an addition of C to the atmospheric pool). The corresponding annual THC emissions were 0.5, 6.2 and 31.8 gC m−2 for the same sites. Therefore, the NCB for each of the sites was 30.2, −29.1 and −3.1 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum site. On average, the whole mire was a CO2 sink of 2.6 gC m−2 and a THC source of 6.4 gC m−2 over a year. Consequently, the mire was a net source of C to the atmosphere by 3.9 gC m−2 (based on area weighted estimates for each of the three plant communities). Early and late snow season efflux of CO2 and THC emphasize the importance of winter measurements for complete annual C budgets. Decadal vegetation changes at Stordalen indicate that both the productivity and the THC emissions increased between 1970 and 2000. Considering the GWP100 of CH4, the net radiative forcing on climate increased 21% over the same time. In conclusion, reduced C compounds in these environments have high importance for both the annual C balance and climate.

  • 33.
    Carpenter, Stephen R.
    et al.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA.
    Cole, Jonathan J.
    Institute of Ecosystem Studies, Millbrook, New York, USA.
    Pace, Michael L.
    Institute of Ecosystem Studies, Millbrook, New York, USA.
    Van de Bogert, Matthew
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA; Institute of Ecosystem Studies, Millbrook, New York, USA.
    Bade, Darrren L.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA; Institute of Ecosystem Studies, Millbrook, New York, USA.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Gille, Caitlin M.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA.
    Hodgson, James R.
    Department of Biology, St. Norbert College, De Pere, Wisconsin, USA.
    Kitchell, James F.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA.
    Kritzberg, Emma S.
    Department of Ecology/Limnology, Lund University, Lund, Sweden.
    Ecosystem subsidies: Terrestrial support of aquatic food webs from C-13 addition to contrasting lakes2005Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 86, nr 10, s. 2737-2750Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Whole-lake additions of dissolved inorganic C-13 were used to measure allochthony (the terrestrial contribution of organic carbon to aquatic consumers) in two unproductive lakes (Paul and Peter Lakes in 2001), a nutrient-enriched lake (Peter Lake in 2002), and a dystrophic lake (Tuesday Lake in 2002). Three kinds of dynamic models were used to estimate allochthony: a process-rich, dual-isotope flow model based on mass balances of two carbon isotopes in 12 carbon pools; simple univariate time-series models driven by observed time courses of delta(13)CO(2); and multivariate autoregression models that combined information from time series of delta(13)C in several interacting carbon pools. All three models gave similar estimates of allochthony. In the three experiments without nutrient enrichment, flows of terrestrial carbon to dissolved and particulate organic carbon, zooplankton, Chaoborus, and fishes were substantial. For example, terrestrial sources accounted for more than half the carbon flow to juvenile and adult largemouth bass, pumpkinseed sunfish, golden shiners, brook sticklebacks, and fathead minnows in the unenriched experiments. Allochthony was highest in the dystrophic lake and lowest in the nutrient-enriched lake. Nutrient enrichment of Peter Lake decreased allochthony of zooplankton from 0.34-0.48 to 0-0.12, and of fishes from 0.51-0.80 to 0.25-0.55. These experiments show that lake ecosystem carbon cycles, including carbon flows to consumers, are heavily subsidized by organic carbon from the surrounding landscape.

  • 34.
    Chmiel, Hannah E.
    et al.
    Uppsala University, Sweden.
    Kokic, Jovana
    Uppsala University, Sweden.
    Denfeld, Blaize A.
    Uppsala University, Sweden.
    Einarsdottir, Karolina
    Uppsala University, Sweden.
    Wallin, Marcus B.
    Uppsala University, Sweden.
    Koehler, Birgit
    Uppsala University, Sweden.
    Isidorova, Anastasija
    Uppsala University, Sweden.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Ferland, Marie-Eve
    University of Quebec, Canada.
    Sobek, Sebastian
    Uppsala University, Sweden.
    The role of sediments in the carbon budget of a small boreal lake2016Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, nr 5, s. 1814-1825Artikel i tidskrift (Refereegranskat)
    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 km(2)) and shallow (mean depth, 3.4 m), humic lake in boreal Sweden. Organic carbon (OC) burial and mineralization in the sediments were quantified from Pb-210-dated sediment and laboratory sediment incubation experiments, respectively. Burial and mineralization rates were then upscaled to the entire basin and to one whole year using sediment thickness derived from 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. Other contributions to CO2 emission were water column metabolism (31%), photochemical mineralization (6%), and catchment imports via inlet streams and inflow of shallow groundwater (22%). The remainder (25%) could not be explained by our flux calculations, but was most likely attributed to an underestimation in groundwater inflow. 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 to lake CO2 emission than sediment OC mineralization, and (3) catchment import of C to the lake was greater than lake-internal C cycling.

  • 35.
    Cole, Jonathan J
    et al.
    Cary Institute of Ecosystem Studies, Millbrook, NY.
    Bade, Darren L.
    Kent State University, Kent, OH.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Pace, Michael L.
    University of Virginia, Charlottesville, VA.
    Van de Bogert, Matthew
    Center for Limnology, University of Wisconsin, Madison, WI.
    Multiple approaches to estimating air-water gas exchange in small lakes2010Ingår i: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 8, s. 285-293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rate of gas exchange between air and water is an essential quantity in a number of contexts, from mass balances to the calculation of whole-system metabolism. The exchange of a gas between water and the atmosphere is controlled by differential partial pressures of gases in air and in water (both straightforward to measure) and by the amount of turbulent energy exchange between the air-water interface, the measurement of which is neither simple nor direct. This physical exchange is often expressed as a piston velocity (k). We compared four methods for estimating k in a series of small (0.3 to 45 ha), low-wind (mean wind < 3 m s–1) lakes: 1) floating chambers using ambient CH4; 2) whole-lake SF6 additions; 3) three wind-based models from the literature; and 4) C mass balances constrained by whole-lake 13C additions. All of the methods, with the exception of one windbased model, converged on values for k600 of between 0.35 and 0.74 m d–1 with no biases among methods. The floating chambers, if designed properly, are a cost-effective way of obtaining site-specific values of k for low wind lakes over fairly short time frames (hours).

  • 36.
    de Boer, Wietse
    et al.
    Netherlands Institute of Ecology.
    Folman, Larissa B.
    Netherlands Institute of Ecology.
    Klein Gunnewiek, Paulien J.A.
    Netherlands Institute of Ecology.
    Svensson, Teresia
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Öberg, Gunilla
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    del Rio, José C.
    Instituto de Recursos Naturales y Agrobiología de Sevilla.
    Boddy, Lynne
    Cardiff School of Biosciences.
    Mechanism of antibacterial activity of the white-rot fungus Hypholoma fasciculare colonizing wood2010Ingår i: Canadian journal of microbiology (Print), ISSN 0008-4166, E-ISSN 1480-3275, Vol. 56, nr 5, s. 380-388Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    In a previous study it was shown that the number of wood-inhabiting bacteria was drastically reduced after colonization of beech (Fagus sylvatica) wood blocks by the white-rot fungus Hypholoma fasciculare, or sulfur tuft (Folman et al. 2008). Here we report on the mechanisms of this fungal-induced antibacterial activity. Hypholoma fasciculare was allowed to invade beech and pine (Pinus sylvestris) wood blocks that had been precolonized by microorganisms from forest soil. The changes in the number of bacteria, fungal biomass, and fungal-related wood properties were followed for 23 weeks. Colonization by the fungus resulted in a rapid and large reduction in the number of bacteria (colony-forming units), which was already apparent after 4 weeks of incubation. The reduction in the number of bacteria coincided with fungal-induced acidification in both beech and pine wood blocks. No evidence was found for the involvement of toxic secondary metabolites or reactive oxygen species in the reduction of the number of bacteria. Additional experiments showed that the dominant bacteria present in the wood blocks were not able to grow under the acidic conditions (pH 3.5) created by the fungus. Hence our research pointed at rapid acidification as the major factor causing reduction of wood-inhabiting bacteria upon colonization of wood by H. fasciculare.

  • 37.
    Denfeld, Blaize A.
    et al.
    Uppsala University, Sweden; Umeå University, Sweden.
    Ricao Canelhas, Monica
    Uppsala University, Sweden.
    Weyhenmeyer, Gesa A.
    Uppsala University, Sweden.
    Bertilsson, Stefan
    Uppsala University, Sweden.
    Eiler, Alexander
    Uppsala University, Sweden.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Constraints on methane oxidation in ice-covered boreal lakes2016Ingår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, nr 7, s. 1924-1933Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Boreal lakes can be ice covered for a substantial portion of the year at which time methane (CH4) can accumulate below ice. The amount of CH4 emitted at ice melt is partially determined by the interplay between CH4 production and CH4 oxidation, performed by methane-oxidizing bacteria (MOB). Yet the balance between oxidation and emission and the potential for CH4 oxidation in various lakes during winter is largely unknown. To address this, we performed incubations at 2 degrees C to screen for wintertime CH4 oxidation potential in seven lakes. Results showed that CH4 oxidation was restricted to three lakes, where the phosphate concentrations were highest. Molecular analyses revealed that MOB were initially detected in all lakes, although an increase in type I MOB only occurred in the three lake water incubations where oxidation could be observed. Accordingly, the increase in CO2 was on average 5 times higher in these three lake water incubations. For one lake where no oxidation was measured, we tested if temperature and CH4 availability could trigger CH4 oxidation. However, regardless of incubation temperatures and CH4 concentrations, ranging from 2 to 20 degrees C and 1-500M, respectively, no oxidation was observed. Our study indicates that some lakes with active wintertime CH4 oxidation may have low emissions during ice melt, while other and particularly nutrient poor lakes may accumulate large amounts of CH4 below ice that, in the absence of CH4 oxidation, will be emitted following ice melt. This variability in CH4 oxidation rates between lakes needs to be accounted for in large-scale CH4 emission estimates.

  • 38.
    Ekblad, Alf
    et al.
    School of Science and Technology, Örebro University, Örebro, Sweden.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Deforestation releases old carbon2019Ingår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 12, nr 7, s. 499-500Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract not available.

  • 39.
    Enrich-Prast, Alex
    et al.
    Federal University of Rio de Janeiro, Brazil.
    Bastviken, David
    Stockholm University, Sweden.
    Crill, P.M.
    Stockholm University, Sweden.
    Chemosynthesis2009Ingår i: Encyclopedia of Inland Waters, Oxford: Elsevier , 2009, 1, s. 211-225Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Inland aquatic habitats occur world-wide at all scales from marshes, swamps and temporary puddles, to ponds, lakes and inland seas; from streams and creeks to rolling rivers. Vital for biological diversity, ecosystem function and as resources for human life, commerce and leisure, inland waters are a vital component of life on Earth. "The Encyclopedia of Inland Waters" describes and explains all the basic features of the subject, from water chemistry and physics, to the biology of aquatic creatures and the complex function and balance of aquatic ecosystems of varying size and complexity. Used and abused as an essential resource, it is vital that we understand and manage them as much as we appreciate and enjoy them. This extraordinary reference brings together the very best research to provide the basic and advanced information necessary for scientists to understand these ecosystems - and for water resource managers and consultants to manage and protect them for future generations. Encyclopedic reference to Limnology is a key core subject in ecology taught as a specialist course in universities. Over 240 topic related articles cover the field.Gene Likens is a renowned limnologist and conservationist, Emeritus Director of the Institute of Ecosystems Research, elected member of the American Philosophical Society and recipient of the 2001 National Medal of Science. Subject Section Editors and authors include the very best research workers in the field.

  • 40.
    Erkkila, Kukka-Maaria
    et al.
    Univ Helsinki, Finland.
    Ojala, Anne
    Univ Helsinki, Finland.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Biermann, Tobias
    Lund Univ, Sweden.
    Heiskanen, Jouni J.
    Univ Helsinki, Finland.
    Lindroth, Anders
    Lund Univ, Sweden.
    Peltola, Olli
    Univ Helsinki, Finland.
    Rantakari, Miitta
    Univ Helsinki, Finland; Univ Helsinki, Finland.
    Vesala, Timo
    Univ Helsinki, Finland.
    Mammarella, Ivan
    Univ Helsinki, Finland.
    Methane and carbon dioxide fluxes over a lake: comparison between eddy covariance, floating chambers and boundary layer method2018Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, nr 2, s. 429-445Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2) and methane (CH4) to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, k CC (introduced by Cole and Caraco, 1998), for calculating diffusive flux with the boundary layer method (BLM). We compared CH4 and CO2 fluxes from BLM with k CC and two other gas transfer velocities (k TE and k HE), which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC) and floating chamber (FC) fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajarvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model k TE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajarvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference between CO2 fluxes from shallower and deeper areas. We highlight that while all flux measurement methods have their pros and cons, it is important to carefully think about the chosen method and measurement interval, as well as their effects on the resulting flux.

  • 41.
    Gonsior, M
    et al.
    University of Maryland, MD 20688 USA .
    Schmitt-Kopplin, P
    German Research Centre Environm Heatlh, Germany .
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Depth-dependent molecular composition and photo-reactivity of dissolved organic matter in a boreal lake under winter and summer conditions2013Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 10, nr 11, s. 6945-6956Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transformations of dissolved organic matter (DOM) in boreal lakes lead to large greenhouse gas emissions as well as substantial carbon storage in sediments. Using novel molecular characterization approaches and photochemical degradation experiments we studied how seasonal patterns in water column stratification affected the DOM in a Swedish lake under early spring and summer conditions. Dissolved organic carbon (DOC) concentrations were consistently higher above the sediment when compared to surface waters throughout the sampling periods. Photobleaching alone could not explain this difference in DOC because the lake was covered by 40 cm-thick ice during late winter sampling and still showed the same DOC trend. The differences in the molecular diversity between surface DOM in winter and summer were consistent with ongoing photobleaching/ decarboxylation and a possible bacterial consumption of photo-products. Additional photo-degradation experiments using simulated sunlight showed a production of highly oxidized organic molecules and low molecular weight compounds in all late winter samples and also in the deep water sample in summer. In the surface summer DOM sample, few such molecules were produced during the photo-degradation experiments, confirming that DOM was already photobleached prior to the experiments. This study suggests that photobleaching, and therefore also the ice cover during winter, plays a central role in surface DOM transformation, with important differences in the molecular composition of DOM between surface and deep boreal lake waters. The release of DOC from boreal lake sediments also contribute to this pattern. Photochemical degradation of DOM may be more extensive following ice-out and water column turnover when non-light exposed and thereby photosensitive DOM is photo-mineralized. Hence, the yearly DOM photo-mineralization may be greater than inferred from studies of recently light-exposed DOM.

  • 42.
    Gonsior, Michael
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten. University of Maryland , USA.
    Hertkorn, Norbert
    Helmholtz Zentrum, Munich, Germany.
    Conte, Maureen
    Bermuda Institute of Ocean Sciences, Bermuda, UK.
    Cooper, William
    University of California, Irvine, USA.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Druffel, Ellen
    University of California, Irvine, USA.
    Schimtt-Kopplin, Philippe
    Helmholtz Zentrum, Munich, Germany.
    Photochemical Production of Polyols arising from Significant Photo-transformation of Dissolved Organic Matter in the Oligotrophic Surface Ocean2014Ingår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 163, s. 10-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultrahigh resolution mass spectrometry of marine dissolved organic matter (DOM) has suggested the presence of many common molecular compositions throughout the open ocean. The majority of these supposedly ubiquitous molecules was concluded to represent the refractory marine DOM pool. This study demonstrates that 24 h of exposure of Atlantic and Pacific surface DOM to simulated sunlight causes phototransformation of about half of these supposedly refractory molecular compositions. It is suggested that these transformations are related to indirect photobleaching possibly involving reactive oxygen species (e.g. hydroxyl radicals), because very little change in the fluorescent component of the DOM (FDOM) was observed during the photo-degradation experiments. A significant decline in average mass with distinct decrease of average O/C ratios and concomitant increase of H/C ratios was observed. NMR spectra revealed a decrease in aromatic and olefinic unsaturation and the formation of a limited and near identical suite of oxygenated aliphatic compounds in both Atlantic and Pacific surface DOM. Their NMR characteristics indicated a mixture of about 10 polyols that are plausible products of convergent pathways of photochemical carbohydrate decomposition and oxidation of functionalized, branched aliphatic compounds. These prominent photochemical signature molecules amounted to -2% of total proton NMR integral and are expected to be quickly consumed by various microorganisms in the open ocean. These results may suggest a fast photo-induced large-scale cycling of DOM within the surface ocean dynamic equilibrium of photo- and bio-transformations. (C) 2014 Elsevier B.V. All rights reserved.

  • 43.
    Gonsior, Michael
    et al.
    University of Maryland, MD 20688 USA.
    Schmitt-Kopplin, Philippe
    Helmholtz Zentrum Munchen, Germany; Technical University of Munich, Germany.
    Stavklint, Helena
    Tekniska Verken Linkoping AB, S-58115 Linkoping, Sweden.
    Richardson, Susan D.
    University of S Carolina, SC 29208 USA.
    Hertkorn, Norbert
    Helmholtz Zentrum Munchen, Germany.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Changes in Dissolved Organic Matter during the Treatment Processes of a Drinking Water Plant in Sweden and Formation of Previously Unknown Disinfection Byproducts2014Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, nr 21, s. 12714-12722Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The changes in dissolved organic matter (DOM) throughout the treatment processes in a drinking water treatment plant in Sweden and the formation of disinfection byproducts (DBPs) were evaluated by using ultra-high-resolution mass spectrometry (resolution of similar to 500000 at m/z 400) and nuclear magnetic resonance (NMR). Mass spectrometric results revealed that flocculation induced substantial changes in the DOM and caused quantitative removal of DOM constituents that usually are associated with DBP formation While half of the chromophoric DOM (CDOM) was removed by flocculation, similar to 4-5 mg L-1 total organic carbon remained in the finished water. A conservative approach revealed the formation of similar to 800 mass spectrometry ions with unambiguous molecular formula assignments that contained at least one halogen atom. These molecules likely represented new DBPs, which could not be prevented by the flocculation process. The most abundant m/z peaks, associated with formed DBPs, could be assigned to C5HO3Cl3, C5HO3Cl2Br, C5HO3ClBr2 using isotope simulation patterns. Other halogen-containing formulas suggested the presence of halogenated polyphenolic and aromatic acid-type structures, which was supported by possible structures that matched the lower molecular mass range (maximum of 10 carbon atoms) of these DBPs. H-1 NMR before and after disinfection revealed an similar to 2% change in the overall H-1 NMR signals supporting a significant change in the DOM caused by disinfection. This study underlines the fact that a large and increasing number of people are exposed to a very diverse pool of organohalogens through water by both drinking and uptake through the skin upon contact. Nontarget analytical approaches are indispensable for revealing the magnitude of this exposure and to test alternative ways to reduce it.

  • 44.
    Gonsior, Michael
    et al.
    University of Maryland, MD 20688 USA.
    Valle, Juliana
    University of Federal Rio de Janeiro, Brazil; Helmholtz Zentrum Munchen, Germany.
    Schmitt-Kopplin, Philippe
    Helmholtz Zentrum Munchen, Germany; Technical University of Munich, Germany.
    Hertkorn, Norbert
    Helmholtz Zentrum Munchen, Germany.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Luek, Jenna
    University of Maryland, MD 20688 USA.
    Harir, Mourad
    Helmholtz Zentrum Munchen, Germany.
    Bastos, Wanderley
    University of Federal Rondonia, Brazil.
    Enrich Prast, Alex
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. University of Federal Rio de Janeiro, Brazil.
    Chemodiversity of dissolved organic matter in the Amazon Basin2016Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, nr 14, s. 4279-4290Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapajos River areas to characterize the molecular DOM composition and distribution. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur-and nitrogen-containing molecules in this white water river system. Waters from the Tapajos main stem did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary, even after mixing with the main stem of the Amazon River. Beside ubiquitous DOM at average H / C and O / C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life.

  • 45.
    Grasset, Charlotte
    et al.
    Univ Fed Juiz de Fora, Brazil; Uppsala Univ, Sweden.
    Mendonca, Raquel
    Univ Fed Juiz de Fora, Brazil; Uppsala Univ, Sweden.
    Saucedo, Gabriella Villamor
    Univ Fed Juiz de Fora, Brazil; Uppsala Univ, Sweden.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Roland, Fabio
    Univ Fed Juiz de Fora, Brazil.
    Sobek, Sebastian
    Uppsala Univ, Sweden.
    Large but variable methane production in anoxic freshwater sediment upon addition of allochthonous and autochthonous organic matter2018Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, nr 4, s. 1488-1501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An important question in the context of climate change is to understand how CH4 production is regulated in anoxic sediments of lakes and reservoirs. The type of organic carbon (OC) present in lakes is a key factor controlling CH4 production at anoxic conditions, but the studies investigating the methanogenic potential of the main OC types are fragmented. We incubated different types of allochthonous OC (alloOC; terrestrial plant leaves) and autochthonous OC (autoOC; phytoplankton and two aquatic plants species) in an anoxic sediment during 130 d. We tested if (1) the supply of fresh alloOC and autoOC to an anoxic refractory sediment would fuel CH4 production and if (2) autoOC would decompose faster than alloOC. The addition of fresh OC greatly increased CH4 production and the delta C-13-CH4 partitioning indicated that CH4 originated exclusively from the fresh OC. The large CH4 production in an anoxic sediment fueled by alloOC is a new finding which indicates that all systems with anoxic conditions and high sedimentation rates have the potential to be CH4 emitters. The autoOC decomposed faster than alloOC, but the total CH4 production was not higher for all autoOC types, one aquatic plant species having values as low as the terrestrial leaves, and the other one having values as high as phytoplankton. Our study is the first to report such variability, suggesting that the extent to which C fixed by aquatic plants is emitted as greenhouse gases or buried as OC in sediment could more generally differ between aquatic vegetation types.

  • 46.
    Grinham, Alistair
    et al.
    Univ Queensland, Australia.
    Albert, Simon
    Univ Queensland, Australia.
    Deering, Nathaniel
    Univ Queensland, Australia.
    Dunbabin, Matthew
    Queensland Univ Technol, Australia.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Sherman, Bradford
    CSIRO Land and Water, Australia.
    Lovelock, Catherine E.
    Univ Queensland, Australia.
    Evans, Christopher D.
    Environm Ctr Wales, Wales.
    The importance of small artificial water bodies as sources of methane emissions in Queensland, Australia2018Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, nr 10, s. 5281-5298Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Emissions from flooded land represent a direct source of anthropogenic greenhouse gas (GHG) emissions. Methane emissions from large, artificial water bodies have previously been considered, with numerous studies assessing emission rates and relatively simple procedures available to determine their surface area and generate upscaled emissions estimates. In contrast, the role of small artificial water bodies (ponds) is very poorly quantified, and estimation of emissions is constrained both by a lack of data on their spatial extent and a scarcity of direct flux measurements. In this study, we quantified the total surface area of water bodies amp;lt; 10(5) m(2) across Queensland, Australia, and emission rates from a variety of water body types and size classes. We found that the omission of small ponds from current official land use data has led to an underestimate of total flooded land area by 24 %, of small artificial water body surface area by 57% and of the total number of artificial water bodies by 1 order of magnitude. All studied ponds were significant hotspots of methane production, dominated by ebullition (bubble) emissions. Two scaling approaches were developed with one based on pond primary use (stock watering, irrigation and urban lakes) and the other using size class. Both approaches indicated that ponds in Queensland alone emit over 1.6 Mt CO2 eq.yr(-1), equivalent to 10% of the states entire land use, land use change and forestry sector emissions. With limited data from other regions suggesting similarly large numbers of ponds, high emissions per unit area and under-reporting of spatial extent, we conclude that small artificial water bodies may be a globally important missing source of anthropogenic greenhouse gas emissions.

  • 47. Gudasz, Cristian
    et al.
    Bastviken, David
    Premke, Katrin
    Steger, Kristin
    Tranvik, Lars J.
    Constrained microbial processing of allochthonous organic carbon in boreal lake sediments2012Ingår i: LIMNOLOGY AND OCEANOGRAPHY, ISSN 0024-3590, Vol. 57, nr 1, s. 163-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated sediment bacterial metabolism in eight lakes with different inputs of allochthonous and autochthonous organic carbon in south-central Sweden. Sediment bacterial production, mineralization, and biomass were measured seasonally and along a lake depth gradient in lakes with different water and sediment characteristics. Sediment bacterial metabolism was primarily controlled by temperature but also by the quality and origin of organic carbon. Metabolism was positively correlated to measures of autochthonous influence on the sediment organic carbon, but did not show a similar increase with increasing input of allochthonous organic carbon. Hence, in contrast to what is currently known for the water column, increasing terrestrial organic carbon influence does not result in enhanced sediment bacterial metabolism. The role of allochthonous organic carbon as the main driver of sediment bacterial metabolism suggested so far is contrary to our findings. Meio- and macrobenthic invertebrate biomass were, at most, weakly correlated to bacterial metabolism and biomass, suggesting limited control of sediment bacteria by grazing. Bacterial metabolism in boreal lake sediments is constrained by low temperatures and by the recalcitrant nature of the dominant organic carbon, resulting in sediments being an effective sink of organic carbon.

  • 48.
    Gudasz, Cristian
    et al.
    Uppsala University.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Premke, Katrin
    Uppsala University.
    Steger, Kristin
    Uppsala University.
    Tranvik, Lars J.
    Uppsala University.
    Constrained microbial processing of allochthonous organic carbon in boreal lake sediments2012Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 57, nr 1, s. 163-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated sediment bacterial metabolism in eight lakes with different inputs of allochthonous and autochthonous organic carbon in south-central Sweden. Sediment bacterial production, mineralization, and biomass were measured seasonally and along a lake depth gradient in lakes with different water and sediment characteristics. Sediment bacterial metabolism was primarily controlled by temperature but also by the quality and origin of organic carbon. Metabolism was positively correlated to measures of autochthonous influence on the sediment organic carbon, but did not show a similar increase with increasing input of allochthonous organic carbon. Hence, in contrast to what is currently known for the water column, increasing terrestrial organic carbon influence does not result in enhanced sediment bacterial metabolism. The role of allochthonous organic carbon as the main driver of sediment bacterial metabolism suggested so far is contrary to our findings. Meio- and macrobenthic invertebrate biomass were, at most, weakly correlated to bacterial metabolism and biomass, suggesting limited control of sediment bacteria by grazing. Bacterial metabolism in boreal lake sediments is constrained by low temperatures and by the recalcitrant nature of the dominant organic carbon, resulting in sediments being an effective sink of organic carbon.

  • 49.
    Gudasz, Cristian
    et al.
    Limnology, Department of Ecology and Evolution, Uppsala University.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Steger, Kristin
    Limnology, Department of Ecology and Evolution, Uppsala University.
    Premke, Katrin
    Limnology, Department of Ecology and Evolution, Uppsala University.
    Sobek, Sebastian
    Limnology, Department of Ecology and Evolution, Uppsala University.
    Tranvik, Lars J.
    Limnology, Department of Ecology and Evolution, Uppsala University.
    Temperature-controlled organic carbon mineralization in lake sediments2010Ingår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 466, nr 7305, s. 478-481Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Peatlands, soils and the ocean floor are well-recognized as sites of organic carbon accumulation and represent important global carbon sinks. Although the annual burial of organic carbon in lakes and reservoirs exceeds that of ocean sediments, these inland waters are components of the global carbon cycle that receive only limited attention. Of the organic carbon that is being deposited onto the sediments, a certain proportion will be mineralized and the remainder will be buried over geological timescales. Here we assess the relationship between sediment organic carbon mineralization and temperature in a cross-system survey of boreal lakes in Sweden, and with input from a compilation of published data from a wide range of lakes that differ with respect to climate, productivity and organic carbon source. We find that the mineralization of organic carbon in lake sediments exhibits a strongly positive relationship with temperature, which suggests that warmer water temperatures lead to more mineralization and less organic carbon burial. Assuming that future organic carbon delivery to the lake sediments will be similar to that under present-day conditions, we estimate that temperature increases following the latest scenarios presented by the Intergovernmental Panel on Climate Change could result in a 4-27 per cent (0.9-6.4 Tg C yr(-1)) decrease in annual organic carbon burial in boreal lakes.

  • 50.
    Gudasz, Cristian
    et al.
    Uppsala University, Sweden.
    Sobek, Sebastian
    Uppsala University, Sweden.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Koehler, Birgit
    Uppsala University, Sweden.
    Tranvik, Lars J.
    Uppsala University, Sweden.
    Temperature sensitivity of organic carbon mineralization in contrasting lake sediments2015Ingår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 120, nr 7, s. 1215-1225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Temperature alone explains a great amount of variation in sediment organic carbon (OC) mineralization. Studies on decomposition of soil OC suggest that (1) temperature sensitivity differs between the fast and slowly decomposition OC and (2) over time, decreasing soil respiration is coupled with increase in temperature sensitivity. In lakes, autochthonous and allochthonous OC sources are generally regarded as fast and slowly decomposing OC, respectively. Lake sediments with different contributions of allochthonous and autochthonous components, however, showed similar temperature sensitivity in short-term incubation experiments. Whether the mineralization of OC in lake sediments dominated by allochthonous or autochthonous OC has different temperature sensitivity in the longer term has not been addressed. We incubated sediments from two boreal lakes that had contrasting OC origin (allochthonous versus autochthonous), and OC characteristics (C/N ratios of 21 and 10) at 1, 3, 5, 8, 13, and 21 degrees C for five months. Compared to soil and litter mineralization, sediment OC mineralization rates were low in spite of low apparent activation energy (E-a). The fraction of the total OC pool that was lost during five months varied between 0.4 and 14.8%. We estimate that the sediment OC pool not becoming long-term preserved was degraded with average apparent turnover times between 3 and 32years. While OC mineralization was strongly dependent on temperature as well as on OC composition and origin, temperature sensitivity was similar across lakes and over time. We suggest that the temperature sensitivity of OC mineralization in lake sediments is similar across systems within the relevant seasonal scales of OC supply and degradation.

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