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  • 1.
    Algesten, Grete
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Wikner, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Sobek, Sobek
    Department of Limnology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden .
    Tranvik, Lars T.
    Department of Limnology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden .
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Seasonal variation of CO2 saturation in the Gulf of Bothnia: Indications of marine net heterotrophy2004Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 18, s. 4021-4028Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Seasonal variation of pCO2 and primary and bacterioplankton production were measured in the Gulf of Bothnia during an annual cycle. Surface water was supersaturated with CO2 on an annual basis, indicating net heterotrophy and a source of CO2 to the atmosphere. However, the Gulf of Bothnia oscillated between being a sink and a source of CO2 over the studied period, largely decided by temporal variation in bacterial respiration (BR) and primary production (PP) in the water column above the pycnocline. The calculated annual respiration-production balance (BR-PP) was very similar to the estimated CO2 emission from the Gulf of Bothnia, which indicates that these processes were major determinants of the exchange of CO2 between water and atmosphere. The southern basin (the Bothnian Sea) had a lower net release of CO2 to the atmosphere than the northern Bothnian Bay (7.1 and 9.7 mmol C m−2 d−1, respectively), due to higher primary production, which to a larger extent balanced respiration in this basin.

  • 2.
    Ask, Jenny
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Net ecosystem production in clear-water and brown-water lakes2012Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 26, s. GB1017-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied 15 lakes in northern Sweden with respect to primary production and respiration in benthic and pelagic habitats. The lakes were characterized by different concentrations of colored dissolved organic carbon (DOC) of terrestrial origin, forming a gradient ranging from clear-water to brown-water lakes. Primary production decreased and respiration increased on a whole-lake scale along the gradient of increasing DOC. Thus, the lakes became more net heterotrophic, i.e., had lower net ecosystem production (NEP = gross primary production - community respiration), with increasing terrestrial DOC and this change coincided with increasing partial pressure of carbon dioxide (pCO(2)) in the surface waters. The single most important process for the increasing net heterotrophy along the DOC gradient was pelagic respiration of terrestrial organic carbon. In spite of high metabolic activity in the benthic habitat, benthic primary production and benthic respiration decreased simultaneously with increasing DOC, showing that the benthic habitat was in metabolic balance throughout the gradient. Therefore, the net heterotrophic states of the lakes depended on the terrestrial DOC export to lakes and the concomitant respiration of terrestrial organic carbon in the pelagic habitat.

  • 3.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Laudon, Hjalmar
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Landscape regulation of bacterial growth efficiency in boreal freshwaters2007Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Allochthonous organic carbon in aquatic systems is metabolized by heterotrophic bacteria, with significant consequences for the biostructure and energy pathways of freshwater ecosystems. The degree to which allochthonous substrates support growth of bacteria is largely dependent on bacterial growth efficiency (BGE), i.e., bacterial production (BP) per unit of assimilated carbon. Here we show how the spatial variability of BGE in the boreal region can be mediated by the distribution of the two dominating landscape elements forest and mires. Using an 11 days bioassay approach, the production and respiration of bacteria were measured in water samples from nine small Swedish streams (64°N 19°E), representing a gradient ranging from organic carbon supplied mainly from peat mires to carbon supplied mainly from coniferous forests. BP was positively correlated to forest coverage (%) of the catchment, while bacterial respiration was similar in all streams. Consequently, BGE showed a strong positive correlation with forest coverage. Partial least square regression showed that BGE was chiefly regulated by qualitative properties of the organic material, indicated by the absorbance ratio a254/a365 plus C/N and C/P ratios. The data suggest that a share of the organic carbon pool, drained mainly from forest soils, had a potential of being incorporated into bacterial biomass with great efficiency. Its potential for supporting growth was probably nutrient regulated as indicated by inorganic nutrient enrichment experiments.

  • 4. Burdett, Heidi L.
    et al.
    Hatton, Angela D.
    Kamenos, Nicholas A.
    School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK.
    Coralline algae as a globally significant pool of marine dimethylated sulfur2015Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 29, nr 10, s. 1845-1853Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Marine algae are key sources of the biogenic sulfur compound dimethylsulphoniopropionate (DMSP), a vital component of the marine sulfur cycle. Autotrophic ecosystem engineers such as red coralline algae support highly diverse and biogeochemically active ecosystems and are known to be high DMSP producers, but their importance in the global marine sulfur cycle has not yet been appreciated. Using a global sampling approach, we show that red coralline algae are a globally significant pool of DMSP in the oceans, estimated to be similar to 110x10(12) moles worldwide during the summer months. Latitude was a major driver of observed regional-scale variations, with peaks in polar and tropical climate regimes, reflecting the varied cellular functions for DMSP (e.g., as a cryoprotectant and antioxidant). A temperate coralline algal bed was investigated in more detail to also identify local-scale temporal variations. Here, water column DMSP was driven by water temperature, and to a lesser extent, cloud cover; two factors which are also vital in controlling coralline algal growth. This study demonstrates that coralline algae harbor a large pool of dimethylated sulfur, thereby playing a significant role in both the sulfur and carbon marine biogeochemical cycles. However, coralline algal habitats are severely threatened by projected climate change; a loss of this habitat may thus detrimentally impact oceanic sulfur and carbon biogeochemical cycling.

    Fulltekst (pdf)
    fulltext
  • 5. Catalán, N.
    et al.
    Casas-Ruiz, J. P.
    Arce, M. I.
    Abril, M.
    Bravo, A. G.
    del Campo, R.
    Estévez, E.
    Freixa, A.
    Giménez-Grau, P.
    González-Ferreras, A. M.
    Gómez-Gener, Luís
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lupon, A.
    Martinez, A.
    Palacin-Lizarbe, C.
    Poblador, S.
    Rasines-Ladero, R.
    Reyes, M.
    Rodriguez-Castillo, T.
    Rodriguez-Lozano, P.
    Sanpera-Calbet, I.
    Tornero, I.
    Pastor, A.
    Behind the Scenes: mechanisms Regulating Climatic Patterns of Dissolved Organic Carbon Uptake in Headwater Streams2018Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 32, nr 10, s. 1528-1541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large variability in dissolved organic carbon (DOC) uptake rates has been reported for headwater streams, but the causes of this variability are still not well understood. Here we assessed acetate uptake rates across 11 European streams comprising different ecoregions by using whole-reach pulse acetate additions. We evaluated the main climatic and biogeochemical drivers of acetate uptake during two seasonal periods. Our results show a minor influence of sampling periods but a strong effect of climate and dissolved organic matter (DOM) composition on acetate uptake. In particular, mean annual precipitation explained half of the variability of the acetate uptake velocities (Vf(Acetate)) across streams. Temperate streams presented the lowest Vf(Acetate), together with humic-like DOM and the highest stream respiration rates. In contrast, higher Vf(Acetate) were found in semiarid streams, with protein-like DOM, indicating a dominance of reactive, labile compounds. This, together with lower stream respiration rates and molar ratios of DOC to nitrate, suggests a strong C limitation in semiarid streams, likely due to reduced inputs from the catchment. Overall, this study highlights the interplay of climate and DOM composition and its relevance to understand the biogeochemical mechanisms controlling DOC uptake in streams. Plain Language Summary Headwater streams receive and degrade organic carbon and nutrients from the surrounding catchments. That degradation can be assessed by measuring the uptake of simple compounds of carbon or nitrogen such as acetate or nitrate. Here we determine the variability in acetate and nitrate uptake rates across headwater streams and elucidate the mechanisms behind that variability. The balance between nutrients, the composition of the organic materials present in the streams, and the climatic background is at interplay.

  • 6.
    Costello, David M.
    et al.
    Department of Biological Sciences, Kent State University, OH, Kent, United States; Environmental Science and Design Research Institute, Kent State University, OH, Kent, United States.
    Tiegs, Scott D.
    Department of Biological Sciences, Oakland University, MI, Rochester, United States.
    Boyero, Luz
    Department of Plant Biology and Ecology, University of the Basque Country, Bilbao, Spain; Ikerbasque, Bilbao, Spain.
    Canhoto, Cristina
    Department of Life Sciences, Centre for Functional Ecology, University of Coimbra, Coimbra, Portugal.
    Capps, Krista A.
    Odum School of Ecology, University of Georgia, GA, Athens, United States; Savannah River Ecology Laboratory, University of Georgia, GA, Athens, United States.
    Danger, Michael
    LIEC-CNRS, University of Lorraine, Metz, France.
    Frost, Paul C.
    Department of Biology, Trent University, ON, Peterborough, Canada.
    Gessner, Mark O.
    Department of Experimental Limnology, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Stechlin, Germany; Department of Ecology, Berlin Institute of Technology (TU Berlin), Berlin, Germany.
    Griffiths, Natalie A.
    Climate Change Science Institute and Environmental Sciences Division, Oak Ridge National Laboratory, TN, Oak Ridge, United States.
    Halvorson, Halvor M.
    Department of Biology, University of Central Arkansas, AR, Conway, United States.
    Kuehn, Kevin A.
    School of Biological, Environmental and Earth Sciences, University of Southern Mississippi, MS, Hattiesburg, United States.
    Marcarelli, Amy M.
    Department of Biological Sciences, Michigan Technological University, MI, Houghton, United States.
    Royer, Todd V.
    O'Neill School of Public and Environmental Affairs, Indiana University, IN, Bloomington, United States.
    Mathie, Devan M.
    Department of Biological Sciences, Kent State University, OH, Kent, United States.
    Albariño, Ricardo J.
    INIBIOMA, Universidad Nacional Comahue (CONICET), San Carlos de Bariloche, Argentina.
    Arango, Clay P.
    Department of Biological Sciences, Central Washington University, WA, Ellensburg, United States.
    Aroviita, Jukka
    Freshwater Centre, Finnish Environment Institute (SYKE), Helsinki, Finland.
    Baxter, Colden V.
    Department of Biological Sciences, Stream Ecology Center, Idaho State University, ID, Pocatello, United States.
    Bellinger, Brent J.
    Watershed Protection Department, City of Austin, TX, Austin, United States.
    Bruder, Andreas
    Institute of Microbiology, University of Applied Sciences and Arts of Southern Switzerland, Canobbio, Switzerland.
    Burdon, Francis J.
    Department of Aquatic Ecology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
    Callisto, Marcos
    Genetics, Ecology and Evolution Department of Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
    Camacho, Antonio
    Cavanilles Institute for Biodiversity and Evolutionary Biology, University of Valencia, Paterna, Spain.
    Colas, Fanny
    ENTPE, Université Claude Bernard Lyon 1, Lyon, France.
    Cornut, Julien
    Institute of Earth Sciences, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland.
    Crespo-Pérez, Verónica
    Limnology Laboratory, Zoology Museum QCAZ-I, Quito, Ecuador; School of Biological Sciences, Pontifical Catholic University of Ecuador, Quito, Ecuador.
    Cross, Wyatt F.
    Department of Ecology, Montana State University, MT, Bozeman, United States.
    Derry, Alison M.
    Department of Biological Sciences, Université Du Québec à Montréal, QC, Montreal, Canada.
    Douglas, Michael M.
    School of Biological Sciences, University of Western Australia, WA, Perth, Australia.
    Elosegi, Arturo
    Department of Plant Biology and Ecology, University of the Basque Country, Bilbao, Spain.
    de Eyto, Elvira
    Marine Institute, Galway, Ireland.
    Ferreira, Verónica
    Department of Life Sciences, Marine and Environmental Sciences Centre (MARE), University of Coimbra, Coimbra, Portugal.
    Ferriol, Carmen
    Department of Microbiology and Ecology, University of Valencia, Valencia, Spain.
    Fleituch, Tadeusz
    Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland.
    Follstad Shah, Jennifer J.
    Department of Geography, University of Utah, UT, Salt Lake City, United States.
    Frainer, André
    Department of Arctic and Marine Biology, UiT the Arctic University of Norway, Tromsø, Norway; Norwegian Institute for Nature Research (NINA), University of Tromsø, Tromsø, Norway.
    Garcia, Erica A.
    Research Institute for the Environment and Livelihoods, Charles Darwin University, NT, Casuarina, Australia.
    García, Liliana
    Department of Ecology and Animal Biology, University of Vigo, Vigo, Spain.
    García, Pavel E.
    Escuela de Biología, Universidad de San Carlos de Guatemala, Guatamala City, Guatemala; Ecology and Evolution Program, University of Montana, MT, Missoula, United States.
    Giling, Darren P.
    Department of Experimental Limnology, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Stechlin, Germany; Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, ACT, Canberra, Australia; CSIRO Land and Water, ACT, Canberra, Australia.
    Gonzales-Pomar, R. Karina
    Instituto de Ecología, Univerdiad Mayor de San Andrés, La Paz, Bolivia.
    Graça, Manuel A. S.
    Department of Life Sciences, Marine and Environmental Sciences Centre (MARE), University of Coimbra, Coimbra, Portugal.
    Grossart, Hans-Peter
    Department of Experimental Limnology, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Stechlin, Germany; Institute for Biochemistry and Biology, Potsdam University, Potsdam, Germany.
    Guérold, François
    LIEC-CNRS, University of Lorraine, Metz, France.
    Hepp, Luiz U.
    Universidade Federal de Mato Grosso do Sul, Campus Três Lagoas, Campo Grande, Brazil.
    Higgins, Scott N.
    International Institute for Sustainable Development, MB, Winnipeg, Canada.
    Hishi, Takuo
    Shiiba Research Forest, Kyushu University, Kyushu, Japan.
    Iñiguez-Armijos, Carlos
    Departamento de Ciencias Biológicas, Universidad Técnica Particular de Loja, Loja, Ecuador.
    Iwata, Tomoya
    Department of Environmental Sciences, University of Yamanashi, Kofu, Japan.
    Kirkwood, Andrea E.
    Faculty of Science, Ontario Tech University, ON, Oshawa, Canada.
    Koning, Aaron A.
    Global Water Center, University of Nevada, NV, Reno, United States.
    Kosten, Sarian
    Department of Aquatic Ecology and Environmental Biology, Radboud University, Nijmegen, Netherlands; Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands.
    Laudon, Hjalmar
    Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Leavitt, Peter R.
    Department of Biology, University of Regina, SK, Regina, Canada.
    Lemes da Silva, Aurea L.
    Department of Ecology and Zoology, Federal University of Santa Catarina, Santa Catarina, Brazil.
    Leroux, Shawn J.
    Department of Biology, Memorial University of Newfoundland, NL, St. Johns, Canada.
    LeRoy, Carri J.
    Environmental Studies Program, The Evergreen State College, WA, Olympia, United States.
    Lisi, Peter J.
    Center for Limnology, University of Wisconsin, WI, Madison, United States.
    Masese, Frank O.
    Department of Fisheries & Aquatic Science, University of Eldoret, Eldoret, Kenya.
    McIntyre, Peter B.
    Department of Natural Resources and the Environment, Cornell University, NY, Ithaca, United States.
    McKie, Brendan G.
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Medeiros, Adriana O.
    Institute of Biology, Federal University of Bahia (UFBA), Salvador, Brazil.
    Miliša, Marko
    Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia.
    Miyake, Yo
    Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan.
    Mooney, Robert J.
    Center for Limnology, University of Wisconsin, WI, Madison, United States.
    Muotka, Timo
    Department of Ecology & Genetics, University of Oulu, Oulu, Finland.
    Nimptsch, Jorge
    Instituto de Ciencias Marinas y Limnologicas, Universidad Austral de Chile, Valdivia, Chile.
    Paavola, Riku
    Oulanka Research Station, University of Oulu, Oulu, Finland.
    Pardo, Isabel
    Department of Ecology and Animal Biology, University of Vigo, Vigo, Spain.
    Parnikoza, Ivan Y.
    National Antarctic Scientific Center of Ukraine, Kiev, Ukraine; Institute of Molecular Biology and Genetics, National Institute of Science of Ukraine, Kiev, Ukraine.
    Patrick, Christopher J.
    Department of Biological Science, Virginia Institute of Marine Science, College of William and Mary, VA, Gloucester Point, United States.
    Peeters, Edwin T. H. M.
    Aquatic Ecology and Water Quality Management Group, Wageningen University, Wageningen, Netherlands.
    Pozo, Jesus
    Department of Plant Biology and Ecology, University of the Basque Country, Bilbao, Spain.
    Reid, Brian
    Research Center on Ecosystems of Patagonia, Centro de Investigacion en Ecosistemas de La Patagonia, Valdivia, Chile.
    Richardson, John S.
    Department of Forest & Conservation Sciences, University of British Columbia, BC, Vancouver, Canada.
    Rincón, José
    Departamento de Biología, Universidad Del Zulia, Maracaibo, Venezuela.
    Risnoveanu, Geta
    Department of Systems Ecology and Sustainability, University of Bucharest, Bucharest, Romania.
    Robinson, Christopher T.
    Department of Aquatic Ecology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
    Santamans, Anna C.
    Cavanilles Institute for Biodiversity and Evolutionary Biology, University of Valencia, Paterna, Spain.
    Simiyu, Gelas M.
    School of Environmental Studies, University of Eldoret, Eldoret, Kenya.
    Skuja, Agnija
    Institute of Biology, University of Latvia, Riga, Latvia.
    Smykla, Jerzy
    Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland.
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Teixeira-de Mello, Franco
    Department de Ecología y Gestión Ambiental, Universidad de La República (CURE), Maldonado, Uruguay.
    Vilbaste, Sirje
    Institute of Agricultural and Environmental Science, Estonian University of Life Sciences, Tartu, Estonia.
    Villanueva, Verónica D.
    INIBIOMA, Universidad Nacional Comahue (CONICET), San Carlos de Bariloche, Argentina.
    Webster, Jackson R.
    Department of Biological Sciences, Virginia Tech, VA, Blacksburg, United States.
    Woelfl, Stefan
    Instituto de Ciencias Marinas y Limnologicas, Universidad Austral de Chile, Valdivia, Chile.
    Xenopoulos, Marguerite A.
    Department of Biology, Trent University, ON, Peterborough, Canada.
    Yates, Adam G.
    Department of Biology, University of Waterloo, ON, Waterloo, Canada; Canadian Rivers Institute, NB, Saint John, Canada.
    Yule, Catherine M.
    School of Science, Technology and Engineering, University of the Sunshine Coast, QLD, Maroochydore, Australia.
    Zhang, Yixin
    Department of Landscape Architecture, Soochow University, Suzhou, China; Zhejiang Institute of Research and Innovation, The University of Hong Kong, Kowloon, Hong Kong.
    Zwart, Jacob A.
    U.S. Geological Survey Integrated Information Dissemination Division, VA, Reston, United States.
    Global patterns and controls of nutrient immobilization on decomposing cellulose in riverine ecosystems2022Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 36, nr 3, artikkel-id e2021GB007163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.

  • 7.
    Eckdahl, Johan A.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
    Rodriguez, Pere Casal
    Department of Geology, Lund University, Lund, Sweden.
    Kristensen, Jeppe A.
    Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
    Metcalfe, Daniel B.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ljung, Karl
    Department of Geology, Lund University, Lund, Sweden.
    Mineral soils are an important intermediate storage pool of black carbon in fennoscandian boreal forests2022Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 36, nr 11, artikkel-id e2022GB007489Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Approximately 40% of earth's carbon (C) stored in land vegetation and soil is within the boreal region. This large C pool is subjected to substantial removals and transformations during periodic wildfire. Fire-altered C, commonly known as pyrogenic carbon (PyC), plays a significant role in forest ecosystem functioning and composes a considerable fraction of C transport to limnic and oceanic sediments. While PyC stores are beginning to be quantified globally, knowledge is lacking regarding the drivers of their production and transport across ecosystems. This study used the chemo-thermal oxidation at 375°C (CTO-375) method to isolate a particularly refractory subset of PyC compounds, here called black carbon (BC), finding an average increase of 11.6 g BC m−2 at 1 year postfire in 50 separate wildfires occurring in Sweden during 2018. These increases could not be linked to proposed drivers, however BC storage in 50 additional nearby unburnt soils related strongly to soil mass while its proportion of the larger C pool related negatively to soil C:N. Fire approximately doubled BC stocks in the mineral layer but had no significant effect on BC in the organic layer where it was likely produced. Suppressed decomposition rates and low heating during fire in mineral subsoil relative to upper layers suggests potential removals of the doubled mineral layer BC are more likely transported out of the soil system than degraded in situ. Therefore, mineral soils are suggested to be an important storage pool for BC that can buffer short-term (production in fire) and long-term (cross-ecosystem transport) BC cycling.

    Fulltekst (pdf)
    fulltext
  • 8.
    Giesler, Reiner
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Morth, Carl-Magnus
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundin, Erik J.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lyon, Steve W.
    Humborg, Christoph
    Spatiotemporal variations of pCO(2) and delta C-13-DIC in subarctic streams in northern Sweden2013Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 27, nr 1, s. 176-186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Current predictions of climate-related changes in high-latitude environments suggest major effects on the C export in streams and rivers. To what extent this will also affect the stream water CO2 concentrations is poorly understood. In this study we examined the spatiotemporal variation in partial pressure of CO2 (pCO(2)) and in stable isotopic composition of dissolved inorganic carbon (delta C-13-DIC) in subarctic streams in northern Sweden. The selected watersheds are characterized by large variations in high-latitude boreal forest and tundra and differences in bedrock. We found that all streams generally were supersaturated in pCO(2) with an average concentration of 850 mu atm. The variability in pCO(2) across streams was poorly related to vegetation cover, and carbonaceous bedrock influence was manifested in high DIC concentrations but not reflected in either stream pCO(2) or delta C-13-DIC. Stream water pCO(2) values were highest during winter base flow when we also observed the lowest delta C-13-DIC values, and this pattern is interpreted as a high contribution from CO2 from soil respiration. Summer base flow delta C-13-DIC values probably are more affected by in situ stream processes such as aquatic production/respiration and degassing. A challenge for further studies will be to disentangle the origin of stream water CO2 and quantify their relative importance.

  • 9.
    Isles, Peter D. F.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Creed, Irena F.
    Bergström, Ann-Kristin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Recent Synchronous Declines in DIN:TP in Swedish Lakes2018Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 32, nr 2, s. 208-225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Declining atmospheric nitrogen (N) deposition in northern Europe and parts of North America, coupled with ongoing changes in climate, has the potential to alter the nutrient limitation status of freshwater ecosystems. In this study we compared time series data of atmospheric N deposition, air temperature, and precipitation with corresponding estimates of dissolved inorganic nitrogen (DIN), total phosphorus (TP), DIN: TP, and total organic carbon from 78 headwater streams and 95 nutrient-poor lakes in Sweden from 1998 to 2013 to assess trends in, and potential drivers of, lake N:P ratios. We found that trends in nutrients were variable at the scale of individual lakes but were highly synchronous at the regional scale, suggesting underlying control by broad-scale environmental drivers mediated by site-specific characteristics. Widespread declines in lake DIN throughout Sweden were correlated with declines in atmospheric N deposition, particularly in northern areas. TP did not have strong directional trends, but interannual variability was synchronous at regional scales, implying that broad-scale climate drivers were affecting these trends. Overall, we observed a significant decline in DIN:TP throughout Sweden over the monitoring period. At the beginning of the study period, 32% of lakes were N limited and 45% colimited by N and P. Proportions increased to 63% of lakes N limited and 20% colimited by N and P at the end of the study period. These results suggest that N limitation is likely to become more widespread in subarctic and boreal areas of Europe in the future if recent trends continue. Plain Language Summary This article examines the way in which changes in the amount of nitrogen from the atmosphere being delivered to lakes (as a result of fossil fuel combustion) are interacting with global climate change to affect nutrient availability in Swedish lakes. Nitrogen can act as fertilizer in lakes, supporting increased growth of algae and aquatic plants. The amount of nitrogen relative to other important elements such as phosphorus can help to determine which groups of plants and algae dominate lake ecosystems, as well as how much living biomass lakes can sustain. We find that declines in atmospheric deposition of nitrogen, which have resulted from the adoption of policies controlling emissions from fossil fuel combustion, have caused declines in nitrogen concentrations in lakes throughout Sweden. This has changed the balance of nitrogen and phosphorus, which may result in changes to the structure of lake biological communities. At the same time, variability in climate also has subtle but widespread affects on lake nutrient concentrations, suggesting that the availability of nutrients in lakes at northern latitudes is likely to change in the future as the climate warms.

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  • 10.
    Klaus, Marcus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Seekell, David A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lidberg, William
    Department of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Evaluations of Climate and Land Management Effects on Lake Carbon Cycling Need to Account Temporal Variability in CO2 Concentration2019Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 33, nr 3, s. 243-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon dioxide (CO2) concentrations in lakes vary strongly over time. This variability is rarely captured by environmental monitoring but is crucial for accurately assessing the magnitude of lake CO2 emissions. However, it is unknown to what extent temporal variability needs to be captured to understand important drivers of lake carbon cycling such as climate and land management. We used environmental monitoring data of Swedish forest lakes collected in autumn (n = 439) and throughout the whole open water season (n = 22) from a wet and a dry year to assess temporal variability in effects of climate and forestry on CO2 concentrations across lakes. Effects differed depending on the season and year sampled. According to cross-lake comparisons based on autumn data, CO2 concentrations increased with annual mean air temperature (dry year) or catchment forest productivity (wet year) but were not related to colored dissolved organic matter concentrations. In contrast, open water-season averaged CO2 concentrations were similar across temperature and productivity gradients but increased with colored dissolved organic matter. These contradictions resulted from scale mismatches in input data, lead to weak explanatory power (R-2 = 9-32%), and were consistent across published data from 79 temperate, boreal, and arctic lakes. In a global survey of 144 published studies, we identified a trade-off between temporal and spatial coverage of CO2 sampling. This trade-off clearly determines which conclusions are drawn from landscape-scale CO(2 )assessments. Accurate evaluations of the effects of climate and land management require spatially and temporally representative data that can be provided by emerging sensor technologies and forms of collaborative sampling.

  • 11. Kronberg, Rose-Marie
    et al.
    Drott, Andreas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jiskra, Martin
    Wiederhold, Jan G.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skyllberg, Ulf
    Forest harvest contribution to Boreal freshwater methyl mercury load2016Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 30, nr 6, s. 825-843Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Effects of Boreal forest harvest on mercury (Hg) and methyl mercury (MeHg) soil pools and export by stream runoff were quantified by comparing 10 reference watersheds (REFs) covered by >80year old Norway spruce (Picea abies Karst.) forests with 10 similar watersheds subjected to clear-cutting (CCs). While total Hg soil storage did not change, MeHg pools increased seven times (p=0.006) in the organic topsoil 2 years after clear-cutting. In undulating terrain, situated above the postglacial marine limit (ML) of the ancient Baltic Sea, the mass ratio between flux-weighted MeHg and dissolved organic carbon (MeHg/DOC) in stream runoff increased 1.8 times (p<0.004) as a consequence of forest harvest. When recalculated to 100% clear-cutting of the watershed, the annual MeHg stream export increased 3.8 times (p=0.047). Below the ML, where the terrain was flatter, neither the MeHg/DOC ratio nor the annual export of MeHg differed between REFs and CCs, likely because of the larger contribution of MeHg exported from peaty soils and small wetlands. The most robust measure, MeHg/DOC, was used to calculate MeHg loadings to Boreal headwaters. If the forest harvest effect lasts 10years, clear-cutting increases MeHg runoff by 12-20% in Sweden and 2% in the Boreal zone as a whole. In Sweden, having intensely managed forests, 37% and 56% of MeHg are exported from peatlands and forest soils, respectively, and forest clear-cutting is adding another 6.6%. In the Boreal zone as a whole peatlands and forests soils contribute with 53% and 46%, respectively, and clear-cutting is estimated to add another 1.0%. An expected rapid increase in Boreal forest harvest and disturbance urge for inclusion of land use effects in mercury biogeochemical cycling models at different scales.

  • 12. Serrano, O.
    et al.
    Martinez-Cortizas, A.
    Mateo, M. A.
    Biester, H.
    Bindler, Richard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Millennial scale impact on the marine biogeochemical cycle of mercury from early mining on the Iberian Peninsula2013Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 27, nr 1, s. 21-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The high-resolution mercury record of a Posidonia oceanica mat in the northwest Mediterranean provides an unprecedented testimony of changes in environmental mercury (Hg) loading to the coastal marine environment over the past 4315 yr BP. The period reconstructed made it possible to establish tentative preanthropogenic background Hg levels for the area (6.8 +/- 1.5 ng g(-1) in bulk sediments). A small, but significant, anthropogenic Hg increase was identifiable by similar to 2500 yr BP, in agreement with the beginning of intense mining in Spain. Changes in the record suggest four major periods of anthropogenic Hg pollution inputs to the Mediterranean: first, during the Roman Empire (2100-1800 yr BP); second, in the Late Middle Ages (970-650 yr BP); third, in the modern historical era (530-380 yr BP); and fourth, in the industrial period (last 250 years), with Hg concentrations two-, four-, five-, and tenfold higher than background concentrations, respectively. Hg from anthropogenic sources has dominated during the last millennium (increase from similar to 12 to similar to 100 ng g(-1)), which can be related to the widespread historical exploitation of ore resources on the Iberian Peninsula. The chronology of Hg concentrations in the mat archive, together with other Hg pollution records from the Iberian Peninsula, suggests regional-scale Hg transport and deposition and shows earlier marine Hg pollution than elsewhere in Europe. Moreover, the mat also records a higher number of historic contamination phases, in comparison with other natural archives, probably due to the fact that the bioaccumulating capacity of P. oceanica magnify environmental changes in Hg concentrations. In this study, we demonstrate the uniqueness of P. oceanica meadows as a long-term archive recording trends in Hg abundance in the marine coastal environment, as well as its potential role in the Mediterranean as a long-term Hg sink.

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  • 13.
    Siewert, Matthias B.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lantuit, H.
    Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany; Institute for Geosciences, University of Potsdam, Potsdam, Germany.
    Richter, A.
    Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
    Hugelius, G.
    Department of Physical Geography, Stockholm University, Stockholm, Sweden; Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden.
    Permafrost Causes Unique Fine-Scale Spatial Variability Across Tundra Soils2021Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 35, nr 3, artikkel-id e2020GB006659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spatial analysis in earth sciences is often based on the concept of spatial autocorrelation, expressed by W. Tobler as the first law of geography: “everything is related to everything else, but near things are more related than distant things." Here, we show that subsurface soil properties in permafrost tundra terrain exhibit tremendous spatial variability. We describe the subsurface variability of soil organic carbon (SOC) and ground ice content from the centimeter to the landscape scale in three typical tundra terrain types common across the Arctic region. At the soil pedon scale, that is, from centimeters to 1–2 m, variability is caused by cryoturbation and affected by tussocks, hummocks and nonsorted circles. At the terrain scale, from meters to tens of meters, variability is caused by different generations of ice-wedges. Variability at the landscape scale, that is, ranging hundreds of meters, is associated with geomorphic disturbances and catenary shifts. The co-occurrence and overlap of different processes and landforms creates a spatial structure unique to permafrost environments. The coefficient of variation of SOC at the pedon scale (21%–73%) exceeds that found at terrain (17%–66%) and even landscape scale (24%–67%). Such high values for spatial variation are otherwise found at regional to continental scale. Clearly, permafrost soils do not conform to Tobler's law, but are among the most variable soils on Earth. This needs to be accounted for in mapping and predictions of the permafrost carbon feedbacks through various ecosystem processes. We conclude that scale deserves special attention in permafrost regions.

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  • 14. Soerensen, A. L.
    et al.
    Schartup, A. T.
    Skrobonja, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bouchet, S.
    Amouroux, D.
    Liem-Nguyen, Van
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. School of Science and Technology, Örebro University, Örebro, Sweden.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Deciphering the Role of Water Column Redoxclines on Methylmercury Cycling Using Speciation Modeling and Observations From the Baltic Sea2018Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 32, nr 10, s. 1498-1513Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxygen-depleted areas are spreading in coastal and offshore waters worldwide, but the implication for production and bioaccumulation of neurotoxic methylmercury (MeHg) is uncertain. We combined observations from six cruises in the Baltic Sea with speciation modeling and incubation experiments to gain insights into mercury (Hg) dynamics in oxygen depleted systems. We then developed a conceptual model describing the main drivers of Hg speciation, fluxes, and transformations in water columns with steep redox gradients. MeHg concentrations were 2-6 and 30-55 times higher in hypoxic and anoxic than in normoxic water, respectively, while only 1-3 and 1-2 times higher for total Hg (THg). We systematically detected divalent inorganic Hg (Hg-II) methylation in anoxic water but rarely in other waters. In anoxic water, high concentrations of dissolved sulfide cause formation of dissolved species of Hg-II: HgS2H(aq)- and Hg (SH)(2)(0)((aq)). This prolongs the lifetime and increases the reservoir of Hg-II readily available for methylation, driving the high MeHg concentrations in anoxic zones. In the hypoxic zone and at the hypoxic-anoxic interface, Hg concentrations, partitioning, and speciation are all highly dynamic due to processes linked to the iron and sulfur cycles. This causes a large variability in bioavailability of Hg, and thereby MeHg concentrations, in these zones. We find that zooplankton in the summertime are exposed to 2-6 times higher MeHg concentrations in hypoxic than in normoxic water. The current spread of hypoxic zones in coastal systems worldwide could thus cause an increase in the MeHg exposure of food webs.

  • 15. Teutschbein, C.
    et al.
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Grabs, T.
    Blackburn, M.
    Boyer, E. W.
    Hytteborn, J. K.
    Bishop, K.
    Future Riverine Inorganic Nitrogen Load to the Baltic Sea From Sweden: An Ensemble Approach to Assessing Climate Change Effects2017Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 31, nr 11, s. 1674-1701Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dramatic increase of bioreactive nitrogen entering the Earth's ecosystems continues to attract growing attention. Increasingly large quantities of inorganic nitrogen are flushed from land to water, accelerating freshwater, and marine eutrophication. Multiple, interacting, and potentially countervailing drivers control the future hydrologic export of inorganic nitrogen. In this paper, we attempt to resolve these land-water interactions across boreal/hemiboreal Sweden in the face of a changing climate with help of a versatile modeling framework to maximize the information value of existing measurement time series. We combined 6,962 spatially distributed water chemistry observations spread over 31years with daily streamflow and air temperature records. An ensemble of climate model projections, hydrological simulations, and several parameter parsimonious regression models was employed to project future riverine inorganic nitrogen dynamics across Sweden. The median predicted increase in total inorganic nitrogen export from Sweden (2061-2090) due to climate change was 14% (interquartile range 0-29%), based on the ensemble of 7,500 different predictions for each study site. The overall export as well as the seasonal pattern of inorganic nitrogen loads in a future climate are mostly influenced by longer growing seasons and more winter flow, which offset the expected decline in spring flood. The predicted increase in inorganic nitrogen loading due to climate change means that the political efforts for reducing anthropogenic nitrogen inputs need to be increased if ambitions for reducing the eutrophication of the Baltic Sea are to be achieved.

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  • 16.
    Vachon, Dominic
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rosvall, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Controls on terrestrial carbon fluxes in simulated networks of connected streams and lakes2023Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 37, nr 3, artikkel-id e2022GB007597Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inland waters play a critical role in the carbon cycle by emitting significant amounts of land-exported carbon to the atmosphere. While carbon gas emissions from individual aquatic systems have been extensively studied, how networks of connected streams and lakes regulate integrated fluxes of organic and inorganic forms remain poorly understood. Here, we develop a process-based model to simulate the fate of terrestrial dissolved organic carbon (DOC) and carbon dioxide (CO2) in artificial inland water networks with variable topology, hydrology, and DOC reactivity. While the role of lakes is highly dependent on DOC reactivity, we find that the mineralization of terrestrial DOC is more efficient in lake-rich networks. Regardless of typology and hydrology, terrestrial CO2 is emitted almost entirely within the network boundary. Consequently, the proportion of exported terrestrial carbon emitted from inland water networks increases with the CO2 versus DOC export ratio. Overall, our results suggest that CO2 emissions from inland waters are governed by interactions between the relative amount and reactivity of terrestrial DOC and CO2 inputs and the network configuration of recipient lakes and streams.

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  • 17. von Schiller, D.
    et al.
    Datry, T.
    Corti, R.
    Foulquier, A.
    Tockner, K.
    Marce, R.
    Garcia-Baquero, G.
    Odriozola, I
    Obrador, B.
    Elosegi, A.
    Mendoza-Lera, C.
    Gessner, M. O.
    Stubbington, R.
    Albarino, R.
    Allen, D. C.
    Altermatt, F.
    Arce, M. , I
    Arnon, S.
    Banas, D.
    Banegas-Medina, A.
    Beller, E.
    Blanchette, M. L.
    Blanco-Libreros, J. F.
    Blessing, J.
    Boechat, I. G.
    Boersma, K. S.
    Bogan, M. T.
    Bonada, N.
    Bond, N. R.
    Brintrup, K.
    Bruder, A.
    Burrows, R. M.
    Cancellario, T.
    Carlson, S. M.
    Cauvy-Fraunie, S.
    Cid, N.
    Danger, M.
    de Freitas Terra, B.
    Dehedin, A.
    De Girolamo, A. M.
    del Campo, R.
    Diaz-Villanueva, V.
    Duerdoth, C. P.
    Dyer, F.
    Faye, E.
    Febria, C.
    Figueroa, R.
    Four, B.
    Gafny, S.
    Gomez, R.
    Gómez-Gener, Lluís
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Graca, M. A. S.
    Guareschi, S.
    Gucker, B.
    Hoppeler, F.
    Hwan, J. L.
    Kubheka, S.
    Laini, A.
    Langhans, S. D.
    Leigh, C.
    Little, C. J.
    Lorenz, S.
    Marshall, J.
    Martin, E. J.
    McIntosh, A.
    Meyer, E. , I
    Milisa, M.
    Mlambo, M. C.
    Moleon, M.
    Morais, M.
    Negus, P.
    Niyogi, D.
    Papatheodoulou, A.
    Pardo, I
    Paril, P.
    Pesic, V
    Piscart, C.
    Polasek, M.
    Rodriguez-Lozano, P.
    Rolls, R. J.
    Sanchez-Montoya, M. M.
    Savic, A.
    Shumilova, O.
    Steward, A.
    Taleb, A.
    Uzan, A.
    Vander Vorste, R.
    Waltham, N.
    Woelfle-Erskine, C.
    Zak, D.
    Zarfl, C.
    Zoppini, A.
    Sediment Respiration Pulses in Intermittent Rivers and Ephemeral Streams2019Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 33, nr 10, s. 1251-1263Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32-fold to 66-fold upon sediment rewetting. Structural equation modeling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use, and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2-0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting-drying cycles on respiration and CO2 emissions in stream networks.

  • 18.
    Škerlep, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Biology Department, Faculty of Science, Lund University, Lund, Sweden.
    Nehzati, S.
    Biology Department, Faculty of Science, Lund University, Lund, Sweden; MAX IV Laboratory, Lund University, Lund, Sweden.
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, P.
    Centre for Environmental and Climate Science, Faculty of Science, Lund University, Lund, Sweden.
    Laudon, H.
    Department of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Kritzberg, E.S.
    Biology Department, Faculty of Science, Lund University, Lund, Sweden.
    Differential trends in iron concentrations of boreal streams linked to catchment characteristics2023Inngår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 37, nr 3, artikkel-id e2022GB007484Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increasing iron (Fe) concentrations have been reported for freshwaters across northern Europe over the last decades. This increase, together with elevated concentrations of dissolved organic carbon (DOC), leads to browning of freshwaters, which affects aquatic organisms, ecosystem functioning, biogeochemical cycles, and brings challenges to drinking water production. However, how such increasing trends in stream Fe concentrations reflect the contribution of different catchment sources remains poorly resolved. Here, we explored how catchment characteristics, that is, mires and coniferous soils, regulate spatial and temporal patterns of Fe in a boreal stream network. For this, we determined Fe speciation in riparian and mire soils, and studied temporal Fe dynamics in soil-water and stream-water over a span of 18 years. Positive Fe trends were found in the solution of the riparian soil, while no long-term trend was observed in the mire. These differences were reflected in stream-water, where three headwater streams dominated by coniferous cover also displayed positive Fe trends, whereas the mire dominated stream showed no trend. Surprisingly, the majority of higher order streams showed declining Fe trends, despite long-term increases in DOC. In addition, we found that an extreme drought event led to a prolonged release of Fe and DOC from the riparian soils, that could have long-term effects on stream Fe concentrations. Our results show that riparian forest soils can be major contributors to ongoing increases in freshwater Fe concentrations and that drought can further promote the release of Fe from organic soils.

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