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  • 1.
    Barrientos, Natalia
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Arctic Ocean benthic foraminifera preservation and Mg/Ca ratios: Implications for bottom water palaeothermometry2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reconstructions of Arctic Ocean palaeotemperatures are needed to disentangle natural variability from anthropogenic changes and understand the role of ocean heat transport in forcing or providing feedbacks on Arctic climate change. Despite known complications with calcareous microfossil preservation in Arctic Ocean sediments, calcareous benthic foraminifera can be common in interglacial sequences. However, thus far they have been underutilized in palaeoceanographic studies. This thesis explores the application of the Mg/Ca palaeothermometry proxy for reconstructing bottom water temperatures (BWT) in the Arctic Ocean during the late Quaternary. This method, which is supported by previous empirical studies demonstrating a strong temperature control on trace Mg inclusion into foraminiferal shell calcite, has been applied in many ocean regions and time intervals. Until now its application in the Arctic Ocean has been sparingly explored.

    The results of this doctoral thesis are based on benthic foraminifera retrieved from marine sediment cores covering a wide geographical Arctic Ocean area including both the shallow and vast continental shelves and slopes to the intermediate-to-deep waters of the Lomonosov Ridge and Morris Jesup Rise. These provide the first benthic foraminifera Mg/Ca ratios from the central Arctic Ocean region. In the first study, mechanisms that could affect Mg incorporation in Arctic benthic foraminifera are investigated using oceanographic field data and six 'live' modern Arctic species (Elphidium clavatum, Nonionella labradorica, Cassidulina neoteretis, Oridorsalis tener, Cibicidoides wuellerstorfi and Quinqueloculina arctica). The result is new species-specific Mg/Ca–BWT field calibrations that provide important constraints at the cold end of the BWT spectrum (-2 to 1°C) (Paper I). Using the new Mg/Ca–BWT equation for E. clavatum, a palaeotemperature record was generated for the late Holocene (past ca. 4100 yr) from the western Chukchi Sea. The data showed BWT fluctuations from -2 to 1°C that are interpreted as showing pulses of warmer Pacific water inflow at 500–1000 yr periods, thus revealing multi-centennial variability in heat transport into the Arctic Ocean driven by low latitude forcings (Paper II). Complications with foraminiferal calcite preservation that limit Mg/Ca palaeothermometry in the Arctic were discovered and these are tackled in two additional papers. Anomalously high Mg content in benthic foraminifera from the central Arctic Ocean is linked to diagenetic contamination as a result of the unique oceanographic, sedimentary and geochemical environment (Paper III). Lastly, the dramatic post-recovery dissolution of foraminifera from a Chukchi Shelf sediment core during core storage is investigated and attributed to acidification driven by sulphide oxidation in this organic rich and calcite poor shelf setting (Paper IV).

    The findings of this thesis demonstrate that benthic foraminiferal Mg/Ca-palaeothermometry can be applied in the Arctic Ocean and capture small BWT change (on the order of -2 to 2°C) even at low temperatures. In practice, preservational complexities can be limiting and require special sample handling or analysis due to the high potential for diagenetic contamination in the central Arctic Ocean and rapid post coring calcite dissolution in the seasonally productive shelf seas. This Ph.D. project is a component of the multidisciplinary SWERUS-C3 (Swedish-Russian-US Arctic Ocean Climate-Cryosphere- Carbon Interactions) project that included an expedition with Swedish icebreaker Oden to the East Siberian Arctic Ocean.

  • 2. Chiappelli, Francesco
    et al.
    Penhaskashi, Jaden
    Permafrost Immunity2022In: Bioinformation, ISSN 0973-8894, E-ISSN 0973-2063, Vol. 18, no 9, p. 734-738Article in journal (Refereed)
    Abstract [en]

    Thawing permafrost is a serious and worrisome threat to the environment, because it releases trapped heavy metals and greenhousegasses. Thawing permafrost is also a health threat because, in addition to releasing these noxious gasses, thawing permafrost may freenovel and undiscovered antibiotic-resistant bacteria, viruses, fungi and parasites among a plethora of dormant pathogens. Our immunesystem is ill-prepared to counter these challenges, and will require significant adaptation, or allostasis, which can be subsumed under thegeneric term of permafrost immunity. Since most of the most gravely threatening pathogens released by thawing permafrost are likely topenetrate the organism through the oral cavity, permafrost immunity may first be identified in the oral mucosa. 

  • 3.
    Cornelissen, Johannes H C
    et al.
    Vrije Universiteit.
    Van Bodegom, Peter M
    Vrije Universiteit.
    Aerts, Rien
    Vrije Universiteit.
    Callaghan, Terry V
    University of Sheffield.
    Van Logtestijn, Richard S.P.
    Vrije Universiteit.
    Alatalo, Juha
    VINNOVA.
    Chapin, Stuart F.
    University of Alaska.
    Gerdol, Renato G
    Università degli Studi di Ferrara Dipartimento delle Risorse Naturali e Cultural.
    Gudmundsson, Jon
    Agricultural University of Iceland.
    Gwynn-Jones, Dylan
    University of Wales.
    Hartley, Anne E
    Florida International University.
    Hik, David S
    University of Alberta.
    Hofgaard, Annika
    Norwegian Institute for Nature Research.
    Jónsdóttir, Ingibjörg S.
    Agricultural University of Iceland.
    Karlsson, Staffan
    Vetenskapsrådet.
    Klein, Julia A
    Colorado State University.
    Laundre, Jim
    Marine Biological Labratory.
    Magnusson, Borgthor
    Icelandic Institute of Natural History.
    Michelsen, Anders
    University of Copenhagen.
    Molau, Ulf
    Göteborgs Universitet.
    Onipchenko, Vladimir G.
    Moscow State University.
    Quested, Helen M.
    Stockholms Universitet.
    Sandvik, Sylvi M
    Agder University College.
    Schmidt, Inger K.
    Royal Veterinary and Agricultural University Denmark.
    Shaver, Gus R.
    Marine Biological Labratory.
    Solheim, Bjørn S
    University of Tromsø.
    Soudzilovskaia, Nadejda A
    Vrije Universiteit, Moscow State University.
    Stenström, Anna
    Länsstyrelsen Västra Götaland.
    Tolvanen, Anne
    Finnish Forest Research Institute.
    Totland, Ørjan T
    Norwegian University of Life Sciences.
    Wada, Naoya W
    University of Toyama.
    Welker, Jeffrey M
    University of Alaska Anchorage.
    Zhao, Xinquan
    Chinese Academy of Sciences.
    Brancaleoni, Lisa
    Brancaleoni, Laura
    De Beus, Miranda A.H
    Cooper, Elisabeth J.
    Dalen, Linda
    Harte, John
    Hobbie, Sarah E
    Hoefsloot, Gerlof
    Jägerbrand, Annika K
    Göteborg University.
    Jonasson, Sven
    Lee, John A
    Lindblad, Karin
    Melillo, Jerry M
    Neill, Christopher
    Press, Malcolm C
    Rozema, Jelte
    Zielke, Matthias
    Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes2007In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 10, no 7, p. 619-627Article in journal (Refereed)
    Abstract [en]

    Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.

    Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

  • 4.
    Danielsson, Sara
    et al.
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Odsjö, Tjelvar
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Bignert, Anders
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Remberger, Mikael
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Organic Contaminants in Moose (Alces alces) and Reindeer (Rangifer tarandus) in Sweden from the past twenty years: Comments Concerning the National Swedish Contaminant Monitoring Programme in Terrestrial Biota2008Report (Other academic)
    Abstract [sv]

    Föreliggande rapport är resultatet av ett uppdrag från Naturvårdsverket (Överenskommelse 221 0730) som syftar till att ta fram en aktuell bild av förekomsten av ett antal pesticider eller ofullständigt kända föroreningar i svensk terrestrisk natur där alltså osäkerhet om ämnenas spridning och ackumulation i landlevande organismvärlden råder. Som matris i detta fall har vävnader och organ av älg och ren från mellersta respektive norra Sverige valts. Matriserna finns tillgängliga i Miljöprovbanken vid Naturhistoriska riksmuseet Valet av ämnen har vägletts av tidigare resultat från övervakningen av föroreningar i svensk natur samt av resultat från screeningundersökningar av ofullständigt kända ämnen som tagits fram i Naturvårdsvekets regi. Listan över analyserade ämnen innehåller enskilda substanser samt närbesläktade substanser tillhörande bl. a. följande grupper: klorbensen, HCBD, oktaklorstyren, PCB, DDT, klordan, HCH, PBDE, dioxiner, furaner, endosulfan, heptaklor, pentaklorfenol och PAH. Från Grimsö i Västmanland har vävnadsprover av årskalvar av älg insamlats till Miljöprovbanken och använts för analys av innehåll av miljögifter i denna studie. Med några få undantag är de provtagna individerna av hankön. Skillnader i halter av kadmium mellan könen har i tidigare studier visat sig icke existera. De utvalda proven av älg representerar perioden 1986-2005. Ett homogenat av muskel har beretts per år under perioden baserat på 10 g av tio individer per år. På samma sätt har prover av ren från sommarbetet S Abisko årligen insamlats i Rensjön NV Kiruna i samband med första höstslakten i mitten av september. Vävnadsprover har tagits av handjur av en ålder mellan 2 och 4 år, mestadels av 3-åriga djur. 1998 uppsköts den ordinarie slakten från första halvan av september till första halvan av november, vilket bör uppmärksammas vid tolkningen av analysresultaten. På samma sätt sköts slakten 2004 fram till mitten av december. Det förhållandet att renen förflyttas avsevärda sträckor under höstvandringen, från sommarbetet i de västra delarna av fjällkedjan till det mellansvenska skogslandet under vintern medför en ändring av föda, vilket kan inverka på exponering och bioackumulation av de studerade substanserna. Ju längre avvikelse från normal slakttid desto längre exponering via lavar som är stapelföda i skogslandet under vintern och som innehåller högre koncentrationer av många ackumulerade ämnen. För den aktuella studien valdes hanrenar av tre års ålder härrörande från Gabna, Lævas and Girjas samebyar vilka bildar ett sammanhängande område i norra Lappland. Provserien omfattar perioden 1987-2006. Ett homogenat per år bereddes baserat på 12 g muskel från tio individer per år. Många av de analyserade ämnena förekommer i koncentrationer under detektionsnivån (LOD) under alla eller de flesta av de undersökta åren (Tabell 2). Halterna funna i älg och ren är i många fall lägre än de nivåer som observerats i fisk från såväl limniska som marina områden. Som exempel har PBDE och HBCD inte ens detekterats i vare sig älg eller ren men finns närvarande i både insjöfisk och havsfisk (Bignert et al 2008). Penta- och hexaklorbensen, oktaklorstyren, polyklorerade bifenyler, - och -hexaklor-cyklohexan och polycykliska aromatiska kolväten förekommer samtliga i halter över LOD under samtliga eller större delen av åren under den undersökta perioden. Koncentrationerna av dessa ämnen har sjunkit med undantag för PAH där koncentrationerna är ungefär desamma under hela perioden. Den genomsnittliga årliga nedgången ligger mellan 3% och 10% med undantag för -HCH som visar den mest uttalade minskningen med 22% i älg och 17% i ren. Dessa resultat är samstämmiga med vad som observerats i biota från insjöar och marina områden i Sverige (Bignert et al. 2008, Bignert 2001). De sjunkande halterna i landanknuten biota under de gångna 20 åren är sannolikt orsakade av regleringar och ansträngningar för att minimera utsläpp av kända persistenta, bioackumulerande och toxiska ämnen till miljön. Ämnen hörande till PAHerna är huvudsakligen oavsiktligt spridda genom ofullständig förbränning av organiska ämnen. Källorna är många och varierande och till följd därav svåra att åtgärda med förbättringar. Detta är troligtvis förklaringen till avsaknaden av nedgående tendens för PAHer. Koncentrationerna av PFCs i både älg och ren var i allmänhet låga. Samtliga analyserade prover hade koncentrationer under LOQ. Närvaro av PFOSA, PFOS och PFOA kunde emellertid detekteras vissa år men inte i nivåer tillräckligt höga för att kvantifieras

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  • 5.
    Hein, Catherine L.
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Öhlund, Gunnar
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Englund, Göran
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Fish introductions reveal the temperature dependence of species interactions2014In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 281, no 1775, p. 20132641-Article in journal (Refereed)
    Abstract [en]

    A major area of current research is to understand how climate change will impact species interactions and ultimately biodiversity. A variety of environmental conditions are rapidly changing owing to climate warming, and these conditions often affect both the strength and outcome of species interactions. We used fish distributions and replicated fish introductions to investigate environmental conditions influencing the coexistence of two fishes in Swedish lakes: brown trout (Salmo trutta) and pike (Esox lucius). A logistic regression model of brown trout and pike coexistence showed that these species coexist in large lakes (more than 4.5 km(2)), but not in small, warm lakes (annual air temperature more than 0.9-1.5 degrees C). We then explored how climate change will alter coexistence by substituting climate scenarios for 2091-2100 into our model. The model predicts that brown trout will be extirpated from approximately half of the lakes where they presently coexist with pike and from nearly all 9100 lakes where pike are predicted to invade. Context dependency was critical for understanding pike-brown trout interactions, and, given the widespread occurrence of context-dependent species interactions, this aspect will probably be critical for accurately predicting climate impacts on biodiversity.

  • 6.
    Horstkotte, Tim
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Contested Landscapes: social-ecological interactions between forestry and reindeer husbandry2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Throughout northern Fennoscandia, reindeer husbandry is a central part in the cultural heritage of the Sámi people. In its history, Sámi culture and reindeer husbandry have undergone significant adaptations to environmental, social and political challenges. Landscape changes on the winter grazing grounds were mainly driven by resource exploitation, especially by industrialized forestry. Important grazing resources were lost, i.e. terrestrial and arboreal lichens that constitute essential key elements in the herding year.

    In my thesis, I explore the consequences of these transformations in Swedish boreal forests for reindeer husbandry. The multi-disciplinary approach integrates interview studies, ecological fieldwork and theoretical modeling of forest development.

    I emphasize the understanding of landscapes as multi-dimensional concepts with ecological, social and economic components. They interact in determining the amount of landscape fragmentation in physical or administrative ways, or in enabling reindeer herders to move between different landscape elements. These elements, e.g. forest stands of different ages, can react differently to winter weather. Thus, they enable reindeer herders to adjust their grazing grounds according to the availability of forage, mediated by snow conditions. However, forestry practices have reduced the abundance of old-growth forests, and therewith the functionality of the landscape. By comparing snow conditions in different forest types, I show that multi-layered canopies can offer a more diverse pattern of snow hardness. However, the interaction between forest characteristics with snow is strongly dependent on weather conditions, e.g. the timing and intensity of warm spells. The prevalence of single-layered forest stands therefore can lead to a reduction in snow variability and potentially restricts the availability of suitable grazing grounds for reindeer. If snow conditions hinder reindeer in foraging on terrestrial lichens, old forests formerly supplied reindeer with arboreal lichens. I show how industrial forestry has reduced the availability of this emergency forage by the reduction of old forests and increased landscape fragmentation and analyze the consequences of different management strategies on future habitat availability for arboreal lichens. By integrating these results into a model of forest management, I offer insights into consequences arising from different priorities that either favor timber production or the development of lichen-rich grazing grounds.

    In conclusion, I emphasize the importance of landscape diversity, as well as the ability to make use of this diversity, as a source of adaptability of reindeer husbandry to changes in grazing conditions by e.g. winter weather dynamics. A shared future of reindeer husbandry and forestry could be fostered by encouraging the social-ecological co-evolution of multiple use landscapes and the enhancement of the cultural and biological significance of the Swedish boreal forests.

     

  • 7.
    Jansen, Joachim
    et al.
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Thornton, Brett F.
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Cortés, Alicia
    Snöälv, Jo
    Wik, Martin
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    MacIntyre, Sally
    Crill, Patrick M.
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Drivers of diffusive lake CH4 emissions on daily to multi-year time scales2020In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 17, no 7, p. 1911-1932Article in journal (Refereed)
    Abstract [en]

    Lakes and reservoirs are important emitters of climate forcing trace gases. Various environmental drivers of the flux, such as temperature and wind speed, have been identified, but their relative importance remains poorly understood. Here we use an extensive field dataset to disentangle physical and biogeochemical controls on the turbulence-driven diffusive flux of methane (CH4) on daily to multi-year timescales. We compare 8 years of floating chamber fluxes from three small, shallow subarctic lakes (2010–2017, n = 1306) with fluxes computed using 9 years of surface water concentration measurements (2009–2017, n = 606) and a small-eddy surface renewal model informed by in situ meteorological observations. Chamber fluxes averaged 6.9 ± 0.3 mg m−2 d−1 and gas transfer velocities (k600) from the chamber-calibrated surface renewal model averaged 4.0 ± 0.1 cm h−1. We find robust (R2 ≥ 0.93, p < 0.01) Arrhenius-type temperature functions of the CH4 flux (Ea' = 0.90 ± 0.14 eV) and of the surface CH4 concentration (Ea' = 0.88 ± 0.09 eV). Chamber derived gas transfer velocities tracked the power-law wind speed relation of the model (k ∝ u3/4). While the flux increased with wind speed, during storm events (U10 ≥ 6.5 m s−1) emissions were reduced by rapid water column degassing. Spectral analysis revealed that on timescales shorter than a month emissions were driven by wind shear, but on longer timescales variations in water temperature governed the flux, suggesting emissions were strongly coupled to production. Our findings suggest that accurate short- and long term projections of lake CH4 emissions can be based on distinct weather- and climate controlled drivers of the flux.

  • 8.
    Jantunen, Liisa
    et al.
    Environment Canada, Canada.
    Wong, Fiona
    Stockholm University.
    Gawor, Anya
    Environment Canada.
    Kylin, Henrik
    Linköpings universitet, Tema Miljöförändring.
    Helm, Paul
    Ontario Ministry of the Environment, Canada.
    Stern, Gary
    University of Manitoba, Canada.
    Strachan, William
    Environment Canada, Canada.
    Burniston, Deborah
    Environment Canada, Canada.
    Bidleman, Terry
    Umeå University.
    20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean2015In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 23, p. 13844-13852Article in journal (Refereed)
    Abstract [en]

    The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air−water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water−air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR < 1.0) for ΣCHBs. Net deposition was shown for ENDO-I on all expeditions, while the net exchange direction of other CUPs varied. Understanding the processes and current state of air−surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals.

  • 9.
    Jonsson, Sofi
    et al.
    Stockholms universitet, Institutionen för miljövetenskap.
    Mastromonaco, Michelle N.
    Wang, Feiyue
    Bravo, Andrea G.
    Cairns, Warren R. L.
    Chételat, John
    Douglas, Thomas A.
    Lescord, Gretchen
    Ukonmaanaho, Liisa
    Heimbürger-Boavida, Lars-Eric
    Arctic methylmercury cycling2022In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 850, article id 157445Article in journal (Refereed)
    Abstract [en]

    Anthropogenic mercury (Hg) undergoes long-range transport to the Arctic where some of it is transformed into methylmercury (MeHg), potentially leading to high exposure in some Arctic inhabitants and wildlife. The environmental exposure of Hg is determined not just by the amount of Hg entering the Arctic, but also by biogeochemical and ecological processes occurring in the Arctic. These processes affect MeHg uptake in biota by regulating the bioavailability, methylation and demethylation, bioaccumulation and biomagnification of MeHg in Arctic ecosystems. Here, we present a new budget for pools and fluxes of MeHg in the Arctic and review the scientific advances made in the last decade on processes leading to environmental exposure to Hg. Methylation and demethylation are key processes controlling the pool of MeHg available for bioaccumulation. Methylation of Hg occurs in diverse Arctic environments including permafrost, sediments and the ocean water column, and is primarily a process carried out by microorganisms. While microorganisms carrying the hgcAB gene pair (responsible for Hg methylation) have been identified in Arctic soils and thawing permafrost, the formation pathway of MeHg in oxic marine waters remains less clear. Hotspots for methylation of Hg in terrestrial environments include thermokarst wetlands, ponds and lakes. The shallow sub-surface enrichment of MeHg in the Arctic Ocean, in comparison to other marine systems, is a possible explanation for high MeHg concentrations in some Arctic biota. Bioconcentration of aqueous MeHg in bacteria and algae is a critical step in the transfer of Hg to top predators, which may be dampened or enhanced by the presence of organic matter. Variable trophic position has an important influence on MeHg concentrations among populations of top predator species such as ringed seal and polar bears distributed across the circumpolar Arctic. These scientific advances highlight key processes that affect the fate of anthropogenic Hg deposited to Arctic environments.

  • 10.
    Karlsson, Per Erik
    et al.
    IVL Svenska Miljöinstitutet.
    Pleijel, Håkan
    Andersson, Camilla
    Bergström, Robert
    Engardt, Magnuz
    Eriksen, Aud
    Falk, Stefanie
    Klingberg, Jenny
    Langner, Joakim
    Manninen, Sirkku
    Stordal, Frode
    Tømmervik, Hans
    Vollsnes, Ane
    The vulnerability of northern European vegetation to ozone damage in a changing climate2021Report (Other academic)
    Abstract [en]

    The potential vulnerability of vegetation at northern latitudes to ozone damage was assessed based on current knowledge with regard to air ozone concentrations and leaf ozone uptake as well as to plant traits affecting ozone tolerance. The focus was on the northern European arctic, alpine and northern boreal vegetation zones, with a special focus on high-altitude vegetation. In particular, we analysed if there are increasing risks for ozone impacts on northern vegetation due to high spring ozone concentrations in relation to climate change induced shifts such as e.g. an earlier start of the growing season.

    The current state of knowledge implies that ecosystems in the far north are not more susceptible to ozone than vegetation in other parts of Europe. Hence, we cannot advocate for a stronger reduction of ozone precursors emissions based exclusively on the ozone sensitivity of vegetation in the far north. Thus, policies designed to reduce emissions of ozone precursors to protect vegetation in other parts of Europe as well as in the entire northern hemisphere are likely to suffice to protect vegetation in northern Fennoscandia.

  • 11.
    Kassel, Marlene
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Effects of climate change on freezing damage in three subarctic bryophyte species2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Climate change is expected to have a strong impact on subarctic ecosystems. Increased temperatures as well as altered precipitation and snow cover patterns are predicted to change species distribution and affect biogeochemical processes in the subarctic tundra. Bryophytes are an essential vegetational component in northern ecosystems, due to their high abundance and importance in many ecological processes. In this study the effects of elevation and altered snow cover on the temporal dynamics of freezing damage in three subarctic bryophyte species (Hylocomium splendens, Ptilidium ciliare, and Sphagnum fuscum) were studied in a snow manipulation field experiment in Abisko, during early spring. Soil temperature and field moisture of moss shoots were collected. A freeze-thaw incubation experiment was conducted to investigate the freeze-thaw cycle resistance of H. splendens and P. ciliare originating from habitats with two differing snow-cover thicknesses. Freezing damage differed significantly between the bryophytes species with P. ciliare experiencing the least and S. fuscum the highest damage. Damage was higher at the low elevation, possibly attributable to acclimation effects. Snow removal led to higher damage in moss shoots, but no interactions of the different snow cover treatments with elevation, species or time were found. Freezing damage increased over time and no recovery occurred, likely due to temporal patterns in soil freeze-thaw cycles during early spring. Soil freeze-thaw cycles were the main factor influencing damage in bryophytes after snow melt. Measured environmental parameters could not explain the entire variation in damage. Damage might additionally be attributable to increased UV radiation or disturbances by herbivores.

  • 12.
    Klaus, Marcus
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Verheijen, Hendricus A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Seekell, David A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Depth and basin shape constrain ecosystem metabolism in lakes dominated by benthic primary producers2022In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 67, no 12, p. 2763-2778Article in journal (Refereed)
    Abstract [en]

    Metabolism is one of the most fundamental ecosystem processes, but the drivers of variation in metabolic rates among lakes dominated by benthic primary producers remain poorly constrained. Here, we report the magnitudes and potential drivers of whole-lake metabolism across 43 Swedish arctic–alpine lakes, based on the free-water diel oxygen technique with sondes deployed during the open-water season near the surface and bottom of the lakes. Gross primary production (GPP) and ecosystem respiration (R) were strongly coupled and ranged from 0.06 to 0.45 mg and 0.05 to 0.43 mg L−1 d−1 among lakes. On average, GPP and R decreased eightfold from relatively shallow to deep lakes (mean depth 0.5–10.9 m) and twofold from concave to convex lakes (mean depth: maximum depth 0.2–0.5). We attribute this to light limitation and shape-specific sensitivity of benthic GPP to disturbance by lake ice. Net ecosystem production (GPP-R) ranged from −0.09 to 0.14 mg L−1 d−1 and switched, on average, from positive to negative towards deeper lakes and lakes richer in dissolved organic carbon (DOC; 0.5–7.4 mg DOC L−1). Uncertainties in metabolism estimates were high (around one and three times mean R and GPP), especially in deep lakes with low insulation and diurnally variable wind speed. Our results confirm the role of DOC in stimulating net heterotrophy and highlight novel effects of lake shape on productivity in benthic-dominated lake ecosystems and its response to changes in lake ice cover.

  • 13.
    Kluge, Mariana
    et al.
    Swedish Univ Agr Sci, Dept Forest Mycol & Plant Pathol, Sci Life Lab, Uppsala, Sweden..
    Wurzbacher, Christian
    Tech Univ Munich, Dept Civil Geo & Environm Engn, Munich, Germany..
    Wauthy, Maxime
    Univ Quebec Chicoutimi, Dept Sci Fondamentales, Saguenay, PQ, Canada.;Univ Laval, Ctr Northern Studies CEN, Quebec City, PQ, Canada..
    Clemmensen, Karina Engelbrecht
    Swedish Univ Agr Sci, Dept Forest Mycol & Plant Pathol, Sci Life Lab, Uppsala, Sweden..
    Hawkes, Jeffrey A.
    Uppsala universitet, Institutionen för kemi - BMC.
    Einarsdóttir, Karólina
    Uppsala universitet, Limnologi.
    Stenlid, Jan
    Swedish Univ Agr Sci, Dept Forest Mycol & Plant Pathol, Sci Life Lab, Uppsala, Sweden..
    Peura, Sari
    Swedish Univ Agr Sci, Dept Forest Mycol & Plant Pathol, Sci Life Lab, Uppsala, Sweden..
    Community composition of aquatic fungi across the thawing Arctic2021In: Scientific Data, E-ISSN 2052-4463, Vol. 8, no 1, article id 221Article in journal (Refereed)
    Abstract [en]

    Thermokarst activity at permafrost sites releases considerable amounts of ancient carbon to the atmosphere. A large part of this carbon is released via thermokarst ponds, and fungi could be an important organismal group enabling its recycling. However, our knowledge about aquatic fungi in thermokarstic systems is extremely limited. In this study, we collected samples from five permafrost sites distributed across circumpolar Arctic and representing different stages of permafrost integrity. Surface water samples were taken from the ponds and, additionally, for most of the ponds also the detritus and sediment samples were taken. All the samples were extracted for total DNA, which was then amplified for the fungal ITS2 region of the ribosomal genes. These amplicons were sequenced using PacBio technology. Water samples were also collected to analyze the chemical conditions in the ponds, including nutrient status and the quality and quantity of dissolved organic carbon. This dataset gives a unique overview of the impact of the thawing permafrost on fungal communities and their potential role on carbon recycling.

  • 14.
    Kuhn, McKenzie
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Lundin, Erik J
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Johansson, Margareta
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Emissions from thaw ponds largely offset the carbon sink of northern permafrost wetlands2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, article id 9535Article in journal (Refereed)
    Abstract [en]

    Northern regions have received considerable attention not only because the effects of climate change are amplified at high latitudes but also because this region holds vast amounts of carbon (C) stored in permafrost. These carbon stocks are vulnerable to warming temperatures and increased permafrost thaw and the breakdown and release of soil C in the form of carbon dioxide (CO2) and methane (CH4). The majority of research has focused on quantifying and upscaling the effects of thaw on CO2 and CH4 emissions from terrestrial systems. However, small ponds formed in permafrost wetlands following thawing have been recognized as hotspots for C emissions. Here, we examined the importance of small ponds for C fluxes in two permafrost wetland ecosystems in northern Sweden. Detailed flux estimates of thaw ponds during the growing season show that ponds emit, on average (±SD), 279 ± 415 and 7 ± 11 mmol C m−2 d−1 of CO2 and CH4, respectively. Importantly, addition of pond emissions to the total C budget of the wetland decreases the C sink by ~39%. Our results emphasize the need for integrated research linking C cycling on land and in water in order to make correct assessments of contemporary C balances.

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  • 15.
    Kylin, Henrik
    Linköpings universitet, Tema Miljöförändring.
    Marine debris on two Arctic beaches in the Russian Far East2020In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 39, article id 3381Article in journal (Refereed)
    Abstract [en]

    In August 2005, marine debris was counted on two Arctic beaches in the RussianFar East. On the north coast of the Chukchi Peninsula east of Kolyuchin Bay, a beach stretch of ca. 2.4 km held a total of 736 items, 0.024 items m‑2, while no more than 0.0011 items m‑2, 12 items in total, were found on a beach stretch of ca. 1.2 km on southern Wrangel Island. The likely explanation for this difference is that the area around the mainland beach is ice-free for a longer period each year, but a contributing factor may be that late spring ice movement removed plastic from the beach on Wrangel Island. The language on the few items with identifiable labels was for the most part Russian or English, making the Chukchi Sea a possible source region. Beaches at the same latitude in the Atlantic may hold more debris on account of the higher human population density, more shipping and transport of floating debris unhindered by a narrow strait that is ice-covered much of the year. Fishing gear blown across the tundra is suggested as a potential threat to reindeer and other terrestrial wildlife.

  • 16. Mansor, Muammar
    et al.
    Drabesch, Sören
    Bayer, Timm
    Van Le, Anh
    Chauhan, Ankita
    Schmidtmann, Johanna
    Peiffer, Stefan
    Kappler, Andreas
    Application of Single-Particle ICP-MS to Determine the Mass Distribution and Number Concentrations of Environmental Nanoparticles and Colloids2021In: Environmental Science & Technology Letters, Vol. 8, no 7, p. 589-595Article in journal (Refereed)
    Abstract [en]

    Analyzing the elemental compositions and size distributions of nanoparticles, colloids, and their aggregates in environmental samples represents a key task in understanding contaminant, substrate, and nutrient cycling. Single-particle ICP-MS (spICP-MS) is a high-throughput method that is capable of providing the elemental mass of thousands of particles within minutes. The challenge, however, lies in data analysis and interpretation, especially for complex environmental samples. Here we present successful applications of spICP-MS for environmental samples. We first analyzed the homoaggregation behavior of synthetic microplastic and magnetite (abiogenic and biogenic) nanoparticles. The measured distribution of aggregate mass was described as a function of the number of primary particles/aggregate (Npp). In tandem with dynamic light scattering data, differences in aggregates’ compactness (primary particles per nanometer) between samples can be determined. Second, we showed how sequential elemental analysis allows evaluation of the mobility of a toxic arsenic metalloid and its inferred association with colloidal Fe(III) (oxyhydr)oxides. Finally, we investigated the composition of heterogeneous iron–carbon-rich colloidal flocs, highlighting distinct colloidal Fe and C distributions and C/Fe ratios between samples from different permafrost thawing stages. On the basis of our results, we provide guidelines for successful sample preparation and promising future spICP-MS opportunities and applications with environmental samples.

  • 17.
    Mashayekhy Rad, Farshid
    Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi.
    Analytical methods for biomolecules involved in atmospheric aerosol formation in the Arctic2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the Arctic, increasing ice-free conditions and nutrients freed from the melting ice must strongly influence the marine life. Aerosol emissions from microbiological marine processes may affect the low clouds and fogs over the summer Arctic, which in turn have effects on the melting of sea ice. The radiative properties of the high Arctic low clouds are strongly dependent on the number concentration of airborne water-soluble particles, known as cloud condensation nuclei (CCN). If the effects of CCN on cloud optical properties is to be fully understood it is important to be able to specify the source and concentrations of the Arctic aerosol particles.

    Previous studies in the Arctic have indicated that organic material formed in the uppermost ocean surface is transferred to the atmosphere and plays a potentially very important role in the aerosol-fog/cloud cycle. However, many aspects of this process remain unverified and chemical characterisation of targeted groups of biomolecules is still notably fragmentary or non-existing. Investigation of biomolecules, particularly amino acids, peptides and proteins together with mono- and polysac­charides and fatty acids in the airborne aerosol, and their relative contributions to fog/cloud water, requires development of an array of “cutting edge” analytical techniques and methods.

    In this thesis, electrospray ionization mass spectrometry was used for all applications and target biomolecules. The measurements in the Arctic turned out to be challenging due to the highly complex, salty matrices, combined with very low concentration and high diversity of the target biomolecules, and each step of the analytical chain needed careful consideration. To increase the detectability of the very low levels of polysaccharides and proteins in aerosols, these compounds were hydrolyzed to their subunits, monosaccharides and amino acids. Monosaccharides were separated using hydrophilic interaction chromatography, which was beneficial for their detection in electrospray ionization mass spectrometry. Amino acids were derivatized, yielding improvement in reversed-phase chromatographic separation, ionization efficiency as well as selectivity. For fatty acids in a sea surface sample, a novel fast screening method was developed, utilizing travelling-wave ion mobility separation as an orthogonal technique connected to mass spectrometry. In addition, a method for the detection of wood burning as an anthropogenic source of aerosols was developed, utilizing anhydrous monosaccharides as markers. This method can be used in the upcoming expeditions for source apportionment studies.

    The results from the analyses of the aerosol and fog water samples, collected over the summer pack ice north of 80 °N, show that both total polysaccharides and total proteinaceous compounds (sum of proteins, peptides and amino acids) occurred at the pmol m-3 to nmol m-3 level. Interestingly, the levels were found higher between different years, suggested to be coupled to less ice coverage and thus to a higher biological activity in the ocean surface. The highest concentrations of polysaccharides, as an indication of marine polymer gels, were found during the summer over the pack ice area. In addition, a pilot source apportionment study was carried out combining the measurement of different molecular tracers, used as source markers. This study indicates the seasonality and abundance of marine polymer gels as an important feature of the Arctic Ocean connected to the melting and freezing of sea ice. It should be further studied how the abundance of these gels, which have a high potential for cloud droplet activation, affect the melting and freezing of the perennial sea ice.

    Given the successful development of analytical methods for targeted groups of biomolecules, this thesis has supported the importance of biomolecules as CCN and for cloud formation in the Arctic. Less ice coverage may further increase the number of biomolecular CCN which could change the radiative balance, by the formation of more low-level clouds. Overall, more studies are required to further unravel the complex relationship of biogenic sources, atmospheric chemistry and meteorology to assess the impact of climate change on the Arctic.

  • 18. Mastromonaco, Michelle G. Nerentorp
    et al.
    Gardfeldt, Katarina
    Assmann, Karen M.
    Langer, Sarka
    Delali, Tulasi
    Shlyapnikov, Yaroslav M.
    Zivkovic, Igor
    Horvat, Milena
    Speciation of mercury in the waters of the Weddell, Amundsen and Ross Seas (Southern Ocean)2017In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 193, p. 20-33Article in journal (Refereed)
    Abstract [en]

    Despite the distance from large anthropogenic emission sources, toxic mercury is transported via the atmosphere and oceans to the Southern Ocean. Seawater samples were collected at selected stations and were analysed for total mercury (HgT) (8 stations), dissolved gaseous mercury (DGM) (62 stations) and methylmercury (12 stations) during winter (Weddell Sea), spring (Weddell Sea) and summer (Amundsen and Ross Seas) in the Southern Ocean. The HgT distribution in water columns was found to not vary significantly with depth. In the Weddell Sea the average column concentration was higher in spring (2.6 +/- 1.3 pM, 2 stations) than in winter (2.0 +/- 1.0 pM, 6 stations). We hypothesize that the seasonal HgT increase is due to atmospheric deposition of particulate Hg(II) formed during atmospheric mercury depletion events (AMDEs), as well as the addition of inorganic mercury species from melting sea ice and snow. Furthermore, HgT concentrations found in this study were significantly higher than previously measured in the Southern Ocean (Cossa et al., 2011), which was hypothesized to be due to seasonal variations in atmospheric deposition. The average water column DGM concentration in the Weddell Sea was 454 +/- 254 fM in winter and 384 +/- 239 fM in spring. The lowest average DGM concentration was found in summer in the Amundsen and Ross Seas (299 +/- 137 fM). The highest observed concentration in winter was hypothesized to be caused by the larger sea ice coverage, which is known to reduce the evasion of Hg(0) from the sea surface. The average monomethylmercury (MMHg) concentration in the Weddell Sea was 60 +/- 30 fM in winter (6 stations) and 95 +/- 85 fM in spring (2 stations), showing no significant seasonal difference. In the Amundsen and Ross Seas the summer average concentration of MeHg (MMHg and dimethylmercury; DMHg) was 135 +/- 189 fM (4 stations). The highest MeHg concentration was found in modified circumpolar deep water, which is known to have high primary production. 2017 Elsevier B.V. All rights reserved.

  • 19. Mastromonaco, Michelle G. Nerentorp
    et al.
    Gardfeldt, Katarina
    Langer, Sarka
    Mercury flux over West Antarctic Seas during winter, spring and summer2017In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 193, p. 44-54Article in journal (Refereed)
    Abstract [en]

    For the first time elemental mercury in air and surface seawater was measured continuously in the remote seas of western Antarctica. A major contributor to atmospheric emissions of the toxic and globally dispersed pollutant mercury is the re-evasion from water surfaces, due to a supersaturation of dissolved gaseous mercury (DGM) in surface water. In this study the degree of saturation and mercury flux at the air-sea surface interface have been estimated from continuous measurements of gaseous elemental mercury (GEM) or total gaseous mercury (TGM) in air, DGM in surface water and meteorological parameters. The measurements were performed during winter and spring (2013) in the Weddell Sea and during summer (2010/2011) in the Bellingshausen, Amundsen and Ross Seas, and show spatial and seasonal variations. The average DGM concentration in surface water in open sea was highest during spring (12 +/- 7pg L-1) and lowest during summer (7 +/- 6.8 pg L-1), resulting in a net evasion of mercury during spring (1.1 +/- 1.6 ng m(-2)h(-1)) and a net deposition during summer (-0.2 +/- 1.3 ng m(-2)h(-1)). In open sea, higher average concentrations of GEM (or TGM) and DGM were found close to the Drake Passage compared to in the Bellingshausen and Weddell Seas. Emission sources from the South American continent, identified with back trajectories, were suggested to explain the observed variations. The yearly mercury evasion from open sea surfaces in the Southern Ocean was estimated to 30 ( -450-1700) tons, using the average (and min and max) flux rates obtained in this study. Higher DGM was measured under sea ice (19-62 pg L-1 compared to in open sea due to a capsuling effect, resulting in a theoretical prevented evasion of 520 (0-3400) tons per year. Diminishing sea ice and higher water temperatures in polar regions could result in increased mercury evasion to the atmosphere. However, the contribution of the Southern Ocean to the global modeled annual emissions of mercury from sea surfaces would probably only be a few percent. (C) 2016 Elsevier B.V. All rights reserved.

  • 20.
    Monteux, Sylvain
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    A song of ice and mud: Interactions of microbes with roots, fauna and carbon in warming permafrost-affected soils2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Permafrost-affected soils store a large quantity of soil organic matter (SOM) – ca. half of worldwide soil carbon – and currently undergo rapid and severe warming due to climate change. Increased SOM decomposition by microorganisms and soil fauna due to climate change, poses the risk of a positive climate feedback through the release of greenhouse gases. Direct effects of climate change on SOM decomposition, through such mechanisms as deepening of the seasonally-thawing active layer and increasing soil temperatures, have gathered considerable scientific attention in the last two decades. Yet, indirect effects mediated by changes in plant, microbial, and fauna communities, remain poorly understood. Microbial communities, which may be affected by climate change-induced changes in vegetation composition or rooting patterns, and may in turn affect SOM decomposition, are the primary focus of the work described in this thesis.

    We used (I) a field-scale permafrost thaw experiment in a palsa peatland, (II) a laboratory incubation of Yedoma permafrost with inoculation by exotic microorganisms, (III) a microcosm experiment with five plant species grown either in Sphagnum peat or in newly-thawed permafrost peat, and (IV) a field-scale cold season warming experiment in cryoturbated tundra to address the indirect effects of climate change on microbial drivers of SOM decomposition. Community composition data for bacteria and fungi were obtained by amplicon sequencing and phospholipid fatty acid extraction, and for collembola by Tullgren extraction, alongside measurements of soil chemistry, CO2 emissions and root density.

    We showed that in situ thawing of a palsa peatland caused colonization of permafrost soil by overlying soil microbes. Further, we observed that functional limitations of permafrost microbial communities can hamper microbial metabolism in vitro. Relieving these functional limitations in vitro increased cumulative CO2 emissions by 32% over 161 days and introduced nitrification. In addition, we found that different plant species did not harbour different rhizosphere bacterial communities in Sphagnum peat topsoil, but did when grown in newly-thawed permafrost peat. Plant species may thus differ in how they affect functional limitations in thawing permafrost soil. Therefore, climate change-induced changes in vegetation composition might alter functioning in the newly-thawed, subsoil permafrost layer of northern peatlands, but less likely so in the topsoil. Finally, we observed that vegetation encroachment in barren cryoturbated soil, due to reduced cryogenic activity with higher temperatures, change both bacterial and collembola community composition, which may in turn affect soil functioning.

    This thesis shows that microbial community dynamics and plant-decomposer interactions play an important role in the functioning of warming permafrost-affected soils. More specifically, it demonstrates that the effects of climate change on plants can trickle down on microbial communities, in turn affecting SOM decomposition in thawing permafrost.

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  • 21.
    Newton, Seth
    Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi.
    Occurrence and fate of emerging and legacy flame retardants: from indoor environments to remote areas2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Persistent organic pollutants (POPs) are toxic chemicals that can be found in various matrices in all corners of the planet, including remote areas such as the Arctic.  Several POPs are known and monitored but given the abundance of new chemicals in commerce about which little is known, chemicals that may be new POPs are constantly being screened for. The use of flame retardants, particularly brominated flame retardants (BFRs), has been increasing for decades. PBDEs and HBCDDs are two types of BFRs that have historically been used in large volumes but recently faced legislative restrictions. However, in order to meet fire safety standards, these BFRs have been replaced by a variety of emerging flame retardants (EFRs) about which little is known especially concerning their toxicity, production volumes, and environmental behavior. The main purpose of this thesis was to investigate the occurrence and fate in indoor and outdoor environments of several EFRs and compare them with PBDEs, HBCDDs, and legacy POPs.

    Several indoor environments in the city of Stockholm, Sweden were sampled for dust, indoor air, and ventilation system air (Paper II).  Results from these samples revealed a number of EFRs that humans are exposed to and that are emitted from buildings through ventilation systems. These included DDC-CO, DBE-DBCH, PBT, HBB, EHTBB, and BEH-TEBP. PBDE levels seem to be declining compared to previous studies in Stockholm.  Outdoor air and soil were sampled across transects of Stockholm (Paper II) and Birmingham, United Kingdom (Paper III).  Results from these samples showed the presence of many of the same EFRs in the outdoor environment that were found in indoor environments.  Urban pulses in air were discovered for PBDEs in both cities and for some EFRs in Stockholm, indicating that the cities are sources of EFRs to the outdoor environment.  Atmospheric deposition samples were taken at two sites in northern Sweden (Paper I).  Three EFRs (DDC-CO, DBE-DBCH, and BTBPE) and two current-use pesticides (trifluralin and chlorothalonil) were identified, indicating these compounds’ potential for long range transport and global contamination.  Other legacy POPs such as HCH, PCBs, and PBDEs were measured in the deposition samples as well.  The bulk of deposition was comprised of HCH and PCBs with only minor contributions from PBDEs, chlordanes, and emerging compounds.  Finally, passive and active air sampling methods were compared for BFRs in offices in Beijing, China.  Some EFRs were identified in indoor air from China; however, BDE-209 was the most predominant compound found (Paper IV).  Air samples collected with passive samplers generally had measured FR concentrations within a factor of 2-3 of those collected with active samplers. The use of a GFF in the passive samplers resulted in concentrations of particle-bound contaminants such as BDE-209 that were more comparable to those in active samples. The positioning of the PUF in the passive samplers affected the sampling rates for gaseous compounds and particle retention on PUFs was shown to be a large source of uncertainty in passive sampling.

  • 22. Olid, C.
    et al.
    Zannella, A.
    Lau, D. C. P.
    The Role of Methane Transport From the Active Layer in Sustaining Methane Emissions and Food Chains in Subarctic Ponds2021In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 126, no 3, article id e2020JG005810Article in journal (Refereed)
    Abstract [en]

    Groundwater discharge from the seasonally thawed active layer is increasingly recognized as an important pathway for delivering methane (CH4) into Arctic lakes and streams, but its contribution to CH4 emissions from thaw ponds and its influence on the trophic support and nutritional quality of pond food chains remains unexplored. We quantified the transport of CH4 from the active layer through groundwater discharge into thaw ponds in a subarctic catchment in northern Sweden, using radon (222Rn) as groundwater tracer. We analyzed stable isotopes and fatty acids of pond macroinvertebrates to evaluate the potential effects of groundwater-mediated CH4 inputs on the aquatic food chains. Our results indicate that active layer groundwater discharge flows are nontrivial (range 6%–46% of pond volume per day) and the associated CH4 fluxes (median 339 mg C m−2day−1, interquartile range [IQR]: 179–419 mg C m−2 day−1) can sustain the diffusive CH4 emissions from most of the ponds (155 mg C m−2 day−1, IQR: 55–234 mg C m−2 day−1). Consumers in ponds receiving greater CH4 inputs from the active layer had lower stable carbon (C) isotope signatures that indicates a greater trophic reliance on methane oxidizing bacteria (MOB), and they had lower nutritional quality as indicated by their lower tissue concentrations of polyunsaturated fatty acids. Overall, this work links physical (CH4 transport from the active layer), biogeochemical (CH4 emission), and ecological (MOB-consumer interaction) processes to provide direct evidence for the role of active layer groundwater discharge in CH4 cycling of subarctic thaw ponds.

  • 23.
    Olid, Carolina
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Rodellas, Valentí
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain.
    Rocher-Ros, Gerard
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Garcia-Orellana, Jordi
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain; Departament de Física, Universitat Autònoma de Barcelona, Bellaterra, Spain.
    Diego-Feliu, Marc
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain; Departament de Física, Universitat Autònoma de Barcelona, Bellaterra, Spain; Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain; Associated Unit: Hydrogeology Group, UPC-CSIC, Barcelona, Spain.
    Alorda-Kleinglass, Aaron
    Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain.
    Bastviken, David
    Department of Thematic Studies—Environmental Change, Linköping University, Linköping, Sweden.
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Groundwater discharge as a driver of methane emissions from Arctic lakes2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 3667Article in journal (Refereed)
    Abstract [en]

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

  • 24.
    Pihl Karlsson, Gunilla
    et al.
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Blomgren, Håkan
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Petersson, Kjell
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Svensson, Annika
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Sjöberg, Karin
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Nationell miljöövervakning av luft och nederbördskemi 20022003Report (Other academic)
  • 25. Pokrovsky, Oleg S.
    et al.
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Freeze-thaw cycles of Arctic thaw ponds remove colloidal metals and generate low-molecular-weight organic matter2018In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 137, no 3, p. 321-336Article in journal (Refereed)
    Abstract [en]

    High-latitude boreal and arctic surface/inland waters contain sizeable reservoirs of dissolved organic matter (DOM) and trace elements (TE), which are subject to seasonal freezing. Specifically, shallow ponds and lakes in the permafrost zone often freeze solid, which can lead to transformations in the colloidal and dissolved fractions of DOM and TE. Here, we present results from experimental freeze-thaw cycles using iron (Fe)- and DOM-rich water from thaw ponds situated in Stordalen and Storflaket palsa mires in northern Sweden. After ten cycles of freezing, 85% of Fe and 25% of dissolved organic carbon (DOC) were removed from solution in circumneutral fen water (pH 6.9) but a much smaller removal of Fe and DOC (< 7%) was found in acidic bog water (pH 3.6). This removal pattern was consistent with initial supersaturation of fen water with respect to Fe hydroxide and a lack of supersaturation with any secondary mineral phase in the bog water. There was a nearly two- to threefold increase in the low-molecular-weight (LMW) fraction of organic carbon (OC) and several TEs caused by the repeated freeze-thaw cycles. Future increases in the freeze-thaw frequency of surface waters with climate warming may remove up to 25% of DOC in circumneutral organic-rich waters. Furthermore, an increase of LMW OC may result in enhanced carbon dioxide losses from aquatic ecosystems since this fraction is potentially more susceptible to biodegradation.

  • 26. Poppeliers, Sanne W M
    et al.
    Hefting, Mariet
    Dorrepaal, Ellen
    Weedon, James T
    Functional microbial ecology in arctic soils: the need for a year-round perspective2022In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 98, no 12Article in journal (Refereed)
    Abstract [en]

    The microbial ecology of arctic and sub-arctic soils is an important aspect of the global carbon cycle, due to the sensitivity of the large soil carbon stocks to ongoing climate warming. These regions are characterized by strong climatic seasonality, but the emphasis of most studies on the short vegetation growing season could potentially limit our ability to predict year-round ecosystem functions. We compiled a database of studies from arctic, subarctic, and boreal environments that include sampling of microbial community and functions outside the growing season. We found that for studies comparing across seasons, in most environments, microbial biomass and community composition vary intra-annually, with the spring thaw period often identified by researchers as the most dynamic time of year. This seasonality of microbial communities will have consequences for predictions of ecosystem function under climate change if it results in: seasonality in process kinetics of microbe-mediated functions; intra-annual variation in the importance of different (a)biotic drivers; and/or potential temporal asynchrony between climate change-related perturbations and their corresponding effects. Future research should focus on (i) sampling throughout the entire year; (ii) linking these multi-season measures of microbial community composition with corresponding functional or physiological measurements to elucidate the temporal dynamics of the links between them; and (iii) identifying dominant biotic and abiotic drivers of intra-annual variation in different ecological contexts.

  • 27.
    Rocher-Ros, Gerard
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Harms, Tamara K.
    Sponseller, Ryan A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Väisänen, Maria
    Mörth, Carl-Magnus
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Metabolism overrides photo-oxidation in CO2 dynamics of Arctic permafrost streams2021In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 66, no S1, p. S169-S181Article in journal (Refereed)
    Abstract [en]

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

  • 28. Rodriguez, Patricia
    et al.
    Ask, Jenny
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Hein, Catherine L.
    Jansson, Mats
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Benthic organic carbon release stimulates bacterioplankton production in a clear-water subarctic lake2013In: Freshwater Science, ISSN 2161-9549, E-ISSN 2161-9565, Vol. 32, no 1, p. 176-182Article in journal (Refereed)
    Abstract [en]

    We carried out a set of experiments in a small clear-water lake in northern Sweden during summer 2010 to assess the effect of organic C (OC) released from epipelic algae on pelagic bacterial production (BP). The release rate of OC (dissolved and particulate) from epipelic algae was similar to 45.4 ng C m(-2) h(-1) Bacterioplankton uptake of dissolved OC was P-limited, and pelagic primary production (PP) was colimited by N and P. Pelagic BP (3.2 +/- 6 mu g C L-1 h(-1)) exceeded pelagic PP (0.012 +/- 0.008 mu g C L-1 h(-1)). Pelagic BP was higher in lake water in contact with sediments and the epipelic algae growing on their surface than in water separated from the sediments. Epipelic algae release OC to lake water and potentially stimulate pelagic BP. However, exploitation of benthic OC probably is suboptimal because of nutrient limitation (primarily by inorganic P) of BP.

  • 29. Rousk, Kathrin
    et al.
    Sorensen, Pernille L.
    Lett, Signe
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Michelsen, Anders
    Across-Habitat Comparison of Diazotroph Activity in the Subarctic2015In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 69, no 4, p. 778-787Article in journal (Refereed)
    Abstract [en]

    Nitrogen (N) fixation by N-2-fixing bacteria (diazotrophs) is the primary N input to pristine ecosystems like boreal forests and subarctic and arctic tundra. However, the contribution by the various diazotrophs to habitat N-2 fixation remains unclear. We present results from in situ assessments of N-2 fixation of five diazotroph associations (with a legume, lichen, feather moss, Sphagnum moss and free-living) incorporating the ground cover of the associations in five typical habitats in the subarctic (wet and dry heath, polygon-heath, birch forest, mire). Further, we assessed the importance of soil and air temperature, as well as moisture conditions for N-2 fixation. Across the growing season, the legume had the highest total as well as the highest fraction of N-2 fixation rates at habitat level in the heaths (> 85 % of habitat N-2 fixation), whereas the free-living diazotrophs had the highest N-2 fixation rates in the polygon heath (56 %), the lichen in the birch forest (87 %) and Sphagnum in the mire (100 %). The feather moss did not contribute more than 15 % to habitat N-2 fixation in any of the habitats despite its high ground cover. Moisture content seemed to be a major driver of N-2 fixation in the lichen, feather moss and free-living diazotrophs. Our results show that the range of N-2 fixers found in pristine habitats contribute differently to habitat N-2 fixation and that ground cover of the associates does not necessarily mirror contribution.

  • 30.
    Seekell, David A.
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Cael, B.
    National Oceanography Centre, Southampton, United Kingdom.
    Norman, Sven
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Patterns and Variation of Littoral Habitat Size Among Lakes2021In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 48, no 20, article id e2021GL095046Article in journal (Refereed)
    Abstract [en]

    The littoral zone varies in size among lakes from ∼3% to 100% of lake surface area. In this paper, we derive a simple theoretical scaling relationship that explains this variation, and test this theory using bathymetric data across the size spectra of freshwater lakes (surface area = 0.01–82,103 km2, maximum depth = 2–1,741 m). Littoral area primarily reflects the ratio of the maximum depth of photosynthesis to maximum lake depth. However, lakes that are similar in these characteristics can have different relative littoral areas because of variation in basin shape. Hypsometric (area-elevation) models that describe these patterns for individual lakes can be generalized among lakes to accurately predict the relative size of littoral habitat when there is incomplete bathymetric information. Collectively, our results provide simple rules for understanding patterns of littoral habitat size at the regional and global scales.

  • 31.
    Selberg, Cecilia
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Konsumenters köpvilja och inställning till ekologiska livsmedel: En jämförelse av konsumtionsmönster i storstad och landsbygd2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Sales of organic food is 6 procent of total food sales in Sweden. This study investigates if consumption patterns and attitudes towards organic food differs depending on if the consumer lives in urban or rural areas. In total 1 200 questionnaires were distributed in Stockholm, Gnesta, Älvdalen and Abisko of which 246 responses were received.

    The respondents were positive to organic food and didn´t mind buying these, although they might as well buy nonorganic especially if the taste and quality was good and if it was produced in Sweden. Organic food was mainly bought for health reasons, not containing toxins and heavy metals, animals and workers´conditions and environmental reasons. Main reasons contributing not buying organic food were a too high price, old purchase habits and difficulties getting organic alternatives.

    The study resulted in some differences between urban and rural areas. Respondents in rural areas gave more thought to environment and health and bought organic thereof. They also found it more important to buy organic, locally and Swedish produced food and bought organic more frequent. Contributing demographic reasons to the higher purchase frequency in the countryside can be that more women and more families with children responded from rural areas.

  • 32.
    Sjöberg, Karin
    et al.
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Svensson, Annika
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Pihl Karlsson, Gunilla
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Blomgren, Håkan
    Utförare miljöövervakning, IVL Svenska Miljöinstitutet AB.
    Nationell miljöövervakning inom EMEP och Luft och Nederbördskemiska nätet 2004 & 20052006Report (Other academic)
  • 33.
    Svensson, Sören
    Utförare miljöövervakning, Lunds universitet, biologiska institutionen.
    Bevakning av häckningsframgången hos staren. Årsrapport för 20092010Report (Other academic)
    Abstract [sv]

    (1) Antal starar som skrider till häckning i bevakningsområdena och som således ligger till grund för analys av häckningens förlopp och produktionen av ungar samt möjliggör provtagning för miljögiftsanalyser är efter uppsättning av kompletteringsholkar i vissa av områdena nu helt tillfredsställande i Grimsö, Kvismaren, Tiveden, Svartedalen, Fleringe, Ottenby och Revinge. I Berg har antal häckningar minskat och om trenden inte vänder kan en kompletterande holkgrupp komma att behövas. För Tyresta behövs ett kompletterings- eller ersättningsområde. (2) Den genomsnittliga äggkullstorleken var hög 2009, men andelen flygga ungar var däremot låg i förhållande till vad som gällt under senare delen av 1990-talet och 2000-talet. Den var dock högre än många år under 1980-talet och första delen av 1990-talet. Långsiktigt över hela bevakningsperioden sedan början av 1980-talet finns inga övergripande negativa trender. (3) Äggläggningen startade 2009 tidigare än någonsin i flera av områdena och nytt tidighetsrekord slogs i en holk i Fleringe där första ägget lades 16 april. Starens häckningsstart och häckningsframgång är känsliga för vårens väder och därför indikatorer på effekter av klimatförändringar.

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  • 34. Svensson, Sören
    Fågelinventeringar i Norrbottens län 1981-1996 inom Naturvårdsverketsmiljökvalitetsprogram (PMK)2011Report (Other academic)
    Abstract [sv]

    Inom ramen för naturvårdsverkets program för miljökvalitetsövervakning (PMK) genomfördes fågelinventeringar i Norrbottens län åren 1981–1996. Tre s.k. referensområden låg helt inom (Abisko, Muddus och Reivo) och ett fjärde (Sorsele) berörde delvis länet.

    Inventeringarna bedrevs dels med punkt- och linjetaxeringar (s.k. milrutter) över större områden, dels med revirkartering i mindre provytor. Antalet milrutter var femton i Abisko, nitton i Muddus, åtta i Reivo och sexton i Sorsele. Milrutter inventerades i Abisko 1981–1995, i Muddus 1983–1984 och 1994–1995, i Reivo 1987–1994 och i Sorsele 1982–1984. Det sammanlagda antalet inventerade mil var 129 i Abisko, 55 i Muddus, 54 i Reivo och 45 i Sorsele. Antalet provytor var tre i Abisko, två i Muddus samt en vardera i Reivo och Sorsele.

    De inventerades ungefär samma år som milrutterna. Materialet från Abisko, som omfattar björkskog, kalfjäll och myrmark, är stort och av hög kvalitet och utgör en utmärkt bas för jämförelse vid en eventuell återinventering. Materialen från Muddus, Reivo och Sorsele, områden som domineras av barrskog och myrmark, är mindre bra eftersom antalet rutter och år med inventeringar är färre. Tillsammans representerar emellertid dessa tre områden ett stort stickprov om 43 olika rutter, en period om fjorton år och totalt 154 inventerade mil. Såväl tätheter som artsammansättning var inbördes lika i de tre områdena i skogslandet och de kan tillsammans betraktas som ett homogent stickprov i Norrlands inre skogsland. Vid en återinventering bör därför de tre områdena tillsammans utgöra jämförelsematerialet.

    Förändringar i fågelfaunan kunde med tillförsikt endast analyseras med det mångåriga materialet från Abisko. Där skedde en svag men signifikant nedgång av både artantal och antalet fåglar. I Muddus och Reivo var också negativa förändringar fler än positiva.

    Totalbilden för länet verkar således ha varit negativ under perioden, vilket innebär att fågelfaunans utveckling Norrland liknade den i södra Sverige under samma period.

    I Muddus gjordes en jämförelse mellan ruttsträckor som löpte innanför och utanför nationalparkens gräns. Den totala fågeltätheten var densamma innanför och utanför och de

    skillnader som fanns på artnivå var inte entydiga.

    En jämförelse mellan milrutterna och angränsande standardrutter, inventerade på 2000-talet, gjordes. De skillnader i fågeltätheter som observerades kan ge vissa antydningar om förändringar i fågelfaunan, men tolkningen är mycket osäker eftersom mil- och standardrutter inte är identiska utan har olika biotopsammansättning.

    Rekommendationen inför återinventering är att i första hand välja milrutterna i Abisko och i andra hand milrutterna i de tre barrskogsomårdena. Provytorna har lägre prioritet. Abisko ges prioritet både för att materialet är så gediget och för att fågelarterna i björk- och lågfjällszonerna länge varit betydligt sämre övervakade än arterna i skogslandet.

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  • 35.
    Thompson, Megan Shera
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Klaminder, Jonatan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Size and characteristics of the DOC pool in near-surface subarctic mire permafrost as a potential source for nearby freshwaters2015In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 47, no 1, p. 49-58Article in journal (Refereed)
    Abstract [en]

    Subarctic peatlands are rich sources of organic carbon for freshwater ecosystems. Where those peatlands are underlain by permafrost, permafrost thaw may cause an initial release of bioavailable dissolved organic carbon (DOC) to surrounding freshwaters. In this study, we measured icebound and potentially leachable (extracted) DOC quantities and indices of DOC quality in active layer and permafrost layers from two subarctic peat mires, Stord-alen and Storflaket. Most of the permafrost layers did not contain more organic matter or exportable DOC (as g kg(-1) dry soil) than the overlying active layer, and there was no difference in aromaticity, molecular weight, or the ratio between labile and recalcitrant DOC extracted from the permafrost and active layer. However, DOC held in segregated ice of the near-surface permafrost had relatively low aromaticity compared to extracted DOC from the same depth. Total icebound and potentially leachable DOC in the Stordalen mire permafrost that is predicted to experience active layer deepening during each of the next 50 years corresponded to about 0.1% of the current annual aquatic export of DOC from the mire. We conclude that the pool of potentially leachable DOC currently stored in permafrost layers is small. We also highlight differences in permafrost organic material between the two studied mire systems, which has an effect on the pool and properties of leachable DOC that is potentially available for export during thaw. Moreover, the geomorphological form of permafrost thaw will influence future hydrological connectedness and DOC production, in turn determining future DOC export from the mires.

  • 36.
    Törnqvist, Viveka
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Fexofenadins påverkan på löslighet av organiskt budnet kol och kväve i humus2021Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Antihistamines are a group of pharmaceuticals that enter the environment and may affect microorganisms that regulate decomposing of organic matter and the release of carbon and nitrogen from soils. In this study I investigated if the antihistamine fexofenadine decreases the concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) from humus. I used humus from two vegetation types (heath and meadow), and used a batch experiment approach, where humus was mixed with fexofenadine solutions (2000 ng/L and 20 000 ng/L). After ten days in room temperature, the samples with fexofenadine were compared with batches containing pure water solutions (control). I found differences in the concentration of DOC, DON and pH that were dependent on the studied vegetation types. There were higher concentrations of DOC and DON in heath (35.9 mg/L and 2.0 mg/L) than in the more nutrient rich meadow (9.2 mg/L and 0.5 mg/L). The latter vegetation type did also have a higher pH. In contrast to my hypothesis, the concentration of DOC and DON was not significantly affected by the fexofenadine. However, if considering a 90%-level of significance, there were a significant interaction effect where concentration of DOC decreased in meadow and increased it in heath. A possible vegetation specific effect of fexofenadin seems plausible as microbial biomass and activity in the vegetation types are known to differ. My findings cannot exclude that fexofenadine stimulates degradation of DOC in the more microbial active meadow humus, but not in the humus of heath where activities are lower. 

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  • 37. Veen, G. F. (Ciska)
    et al.
    Sundqvist, Maja K.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Metcalfe, Daniel
    Wilson, Scott D.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Above-ground and below-ground plant responses to fertilization in two subarctic ecosystems2015In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 47, no 4, p. 693-702Article in journal (Refereed)
    Abstract [en]

    Soil nutrient supply is likely to change in the Arctic due to altered process rates associated with climate change. Here, we compare the responses of herbaceous tundra and birch forest understory to fertilization, considering both above-and below-ground responses. We added nitrogen and phosphorus to plots in both vegetation types for three years near Abisko, northern Sweden, and measured the effect on above-and below-ground plant community properties and soil characteristics. Fertilization increased ground-layer shoot mass, the cover of grasses, and tended to enhance total root length below-ground, while it reduced the cover of low statured deciduous dwarf-shrubs. The only statistically significant interaction between vegetation type and fertilization was for grass cover, which increased twofold in forest understory but sixfold in tundra following fertilization. The lack of interactions for other variables suggests that the ground layers in these contrasting vegetation types have similar responses to fertilization. The nutrient-driven increase in grass cover and species-specific differences in productivity and root characters may alter ecosystem dynamics and C cycling in the long-term, but our study indicates that the response of birch forest understory and tundra vegetation may be consistent.

  • 38.
    Wik, Martin
    et al.
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Crill, Patrick M.
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Varner, Ruth K.
    Bastviken, David
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Multiyear measurements of ebullitive methane flux from three subarctic lakes2013In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 118, no 3, p. 1307-1321Article in journal (Refereed)
    Abstract [en]

    Ebullition (bubbling) from small lakes and ponds at high latitudes is an important yet unconstrained source of atmospheric methane (CH4). Small water bodies are most abundant in permanently frozen peatlands, and it is speculated that their emissions will increase as the permafrost thaws. We made 6806 measurements of CH4 ebullition during four consecutive summers using a total of 40 bubble traps that were systematically distributed across the depth zones of three lakes in a sporadic permafrost landscape in northernmost Sweden. We identified significant spatial and temporal variations in ebullition and observed a large spread in the bubbles' CH4 concentration, ranging from 0.04% to 98.6%. Ebullition followed lake temperatures, and releases were significantly larger during periods with decreasing atmospheric pressure. Although shallow zone ebullition dominated the seasonal bubble CH4 flux, we found a shift in the depth dependency towards higher fluxes from intermediate and deep zones in early fall. The average daily flux of 13.4mg CH4 m(-2) was lower than those measured in most other high-latitude lakes. Locally, however, our study lakes are a substantial CH4 source; we estimate that 350kg of CH4 is released via ebullition during summer (June-September), which is approximately 40% of total whole year emissions from the nearby peatland. In order to capture the large variability and to accurately scale lake CH4 ebullition temporally and spatially, frequent measurements over long time periods are critical.

  • 39. Zhang, Hui
    et al.
    Väliranta, Minna
    Swindles, Graeme T.
    Aquino-López, Marco A.
    Mullan, Donal
    Tan, Ning
    Amesbury, Matthew
    Babeshko, Kirill V.
    Bao, Kunshan
    Bobrov, Anatoly
    Chernyshov, Viktor
    Davies, Marissa A.
    Diaconu, Andrei-Cosmin
    Feurdean, Angelica
    Finkelstein, Sarah A.
    Garneau, Michelle
    Guo, Zhengtang
    Jones, Miriam C.
    Kay, Martin
    Klein, Eric S.
    Lamentowicz, Mariusz
    Magnan, Gabriel
    Marcisz, Katarzyna
    Mazei, Natalia
    Mazei, Yuri
    Payne, Richard
    Pelletier, Nicolas
    Piilo, Sanna R.
    Pratte, Steve
    Roland, Thomas
    Saldaev, Damir
    Shotyk, William
    Sim, Thomas G.
    Sloan, Thomas J.
    Słowiński, Michał
    Talbot, Julie
    Taylor, Liam
    Tsyganov, Andrey N.
    Wetterich, Sebastian
    Xing, Wei
    Zhao, Yan
    Recent climate change has driven divergent hydrological shifts in high-latitude peatlands2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1Article in journal (Refereed)
    Abstract [en]

    High-latitude peatlands are changing rapidly in response to climate change, including permafrost thaw. Here, we reconstruct hydrological conditions since the seventeenth century using testate amoeba data from 103 high-latitude peat archives. We show that 54% of the peatlands have been drying and 32% have been wetting over this period, illustrating the complex ecohydrological dynamics of high latitude peatlands and their highly uncertain responses to a warming climate.

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