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  • 51.
    Beier, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Uncoupling of chitinase activity and uptake of hydrolyses products in freshwater bacterioplankton2011In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 56, no 4, p. 1179-1188Article in journal (Refereed)
    Abstract [en]

    We investigated to what extent chitinolytic bacteria subsidize bacterial populations that do not produce chitinolytic enzymes but still use the products of chitin hydrolysis. Applying single-cell techniques to untreated and chitin-enriched lake water, we show that the number of planktonic cells taking up chitin hydrolysis products by far exceeds the number of cells expressing chitinases. Flavobacteria, Actinobacteria, and specifically members of the abundant and ubiquitous freshwater Ac1 cluster of the Actinobacteria, increased in abundance and were enriched in response to the chitin amendment. Flavobacteria were frequently observed in dense clusters on chitin particles, suggesting that they are actively involved in the hydrolysis and solubilization of chitin. In contrast, Actinobacteria were exclusively planktonic. We propose that planktonic Actinobacteria contain commensals specialized in the uptake of small hydrolysis products without expressing or possibly even possessing the machinery for chitin hydrolysis. More research is needed to assess the importance of such "cheater'' substrate acquisition strategies in the turnover and degradation of polymeric organic matter in aquatic ecosystems.

  • 52.
    Beier, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Jones, Christopher M.
    Mohit, Vani
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Hallin, Sara
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Global Phylogeography of Chitinase Genes in Aquatic Metagenomes2011In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 77, no 3, p. 1101-1106Article in journal (Refereed)
    Abstract [en]

    Phylogeny-based analysis of chitinase and 16S rRNA genes from metagenomic data suggests that salinity is a major driver for the distribution of both chitinolytic and total bacterial communities in aquatic systems. Additionally, more acidic chitinase proteins were observed with increasing salinity. Congruent habitat separation was further observed for both genes according to latitude and proximity to the coastline. However, comparison of chitinase and 16S rRNA genes extracted from different geographic locations showed little congruence in distribution. There was no indication that dispersal limited the global distribution of either gene.

  • 53.
    Beier, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Kim, Ok-Sun
    Junier, Pilar
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Witzel, Karl-Paul
    Betaproteobacterial ammonia oxidizers in root zones of aquatic macrophytes2010In: Fundamental and Applied Limnology, ISSN 1863-9135, Vol. 177, no 4, p. 241-255Article in journal (Refereed)
    Abstract [en]

    Enhanced nitrification and coupled denitrification in macrophyte root zones may contribute to the depletion of nitrogen from the rhizosphere and are both critical processes for agriculture and rhizoremediation. We examined one factor likely to affect these processes: the ammonia oxidizing betaproteobacterial community composition, and whether or not it is influenced by plant species (Eleocharis acicularis, Eleocharis palustris, Typha angustifolia) or sediment characteristics. Genes coding for ammonia monooxygenase (amoA) and 16S rRNA of betaproteobacterial ammonia oxidizers were targeted. The betaproteobacterial ammonia oxidizing community in root surface biofilms was distinct from the surrounding rhizosphere sediment. In contrast, communities in rhizosphere and bulk sediment samples were very similar. Our results showed the occurrence of Nitrosomonas europaea-like bacteria nearly exclusively in the rhizoplane biofilms, while sequences affiliated with the Nitrosomonas oligotropha, Nitrosomonas communis and Nitrosospira-lineages were more frequently detected in the surrounding sediment. Our results further suggest that the presence of N. europaea on macrophyte roots depends on the sampling site rather than on the studied macrophyte species. We propose that the rhizoplane of aquatic macrophytes is a natural habitat for N. europaea.

  • 54.
    Beier, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Mohit, Vani
    Département de Biologie, Québec-Océan and Institut de biologie integrative et des systèmes, Université Laval.
    Ettema, Thijs J. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Östman, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Pronounced seasonal dynamics of freshwater chitinase genes and chitin processing2012In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 14, no 9, p. 2467-2479Article in journal (Refereed)
    Abstract [en]

    Seasonal variation in activity of enzymes involved in polymer degradation, including chitinases, has been observed previously in freshwater environments. However, it is not known whether the seasonal dynamics are due to shifts in the activity of bacteria already present, or shifts in community structure towards emergence or disappearance of chitinolytic organisms. We traced seasonal shifts in the chitinase gene assemblage in a temperate lake and linked these communities to variation in chitinase activity. Chitinase genes from 20 samples collected over a full yearly cycle were characterized by pyrosequencing. Pronounced temporal shifts in composition of the chitinase gene pool (beta diversity) occurred along with distinct shifts in richness (alpha diversity) as well as chitin processing. Changes in the chitinase gene pool correlated mainly with temperature, abundance of crustacean zooplankton and phytoplankton blooms. Also changes in the physical structure of the lake, e.g. stratification and mixing were associated with changes in the chitinolytic community, while differences were minor between surface and suboxic hypolimnetic water. The lake characteristics influencing the chitinolytic community are all linked to changes in organic particles and we suggest that seasonal changes in particle quality and availability foster microbial communities adapted to efficiently degrade them.

  • 55. Beisner, Beatrix E.
    et al.
    Peres-Neto, Pedro R.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Barnett, Alain
    Longhi, Maria Lorena
    The role of environmental and spatial processes in structuring lake communities from bacteria to fish2006In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 87, no 12, p. 2985-2991Article in journal (Refereed)
    Abstract [en]

    We assessed the relative roles of local environmental conditions and dispersal on community structure in a landscape of lakes for the major trophic groups. We use taxonomic presence–absence and abundance data for bacteria, phytoplankton, zooplankton, and fish from 18 lakes in southern Quebec, Canada. The question of interest was whether communities composed of organisms with more limited dispersal abilities, because of size and life history (zooplankton and fish) would show a different effect of lake distribution than communities composed of good dispersers (bacteria and phytoplankton). We examine the variation in structure attributable to local environmental (i.e., lake chemical and physical variables) vs. dispersal predictors (i.e., overland and watercourse distances between lakes) using variation partitioning techniques. Overall, we show that less motile species (crustacean zooplankton and fish) are better predicted by spatial factors than by local environmental ones. Furthermore, we show that for zooplankton abundances, both overland and watercourse dispersal pathways are equally strong, though they may select for different components of the community, while for fish, only watercourses are relevant dispersal pathways. These results suggest that crustacean zooplankton and fish are more constrained by dispersal and therefore more likely to operate as a metacommunity than are bacteria and phytoplankton within this studied landscape.

  • 56. Bendall, Matthew L
    et al.
    Stevens, Sarah LR
    Chan, Leong-Keat
    Malfatti, Stephanie
    Schwientek, Patrick
    Tremblay, Julien
    Schackwitz, Wendy
    Martin, Joel
    Pati, Amrita
    Bushnell, Brian
    Froula, Jeff
    Kang, Dongwan
    Tringe, Susannah G
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Moran, Mary A
    Shade, Ashley
    Newton, Ryan J
    McMahon, Katherine D
    Malmstrom, Rex R
    Genome-wide selective sweeps and gene-specific sweeps in natural bacterial populations2016In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 7, p. 1589-1601Article in journal (Refereed)
    Abstract [en]

    Multiple models describe the formation and evolution of distinct microbial phylogenetic groups. These evolutionary models make different predictions regarding how adaptive alleles spread through populations and how genetic diversity is maintained. Processes predicted by competing evolutionary models, for example, genome-wide selective sweeps vs gene-specific sweeps, could be captured in natural populations using time-series metagenomics if the approach were applied over a sufficiently long time frame. Direct observations of either process would help resolve how distinct microbial groups evolve. Here, from a 9-year metagenomic study of a freshwater lake (2005-2013), we explore changes in single-nucleotide polymorphism (SNP) frequencies and patterns of gene gain and loss in 30 bacterial populations. SNP analyses revealed substantial genetic heterogeneity within these populations, although the degree of heterogeneity varied by >1000-fold among populations. SNP allele frequencies also changed dramatically over time within some populations. Interestingly, nearly all SNP variants were slowly purged over several years from one population of green sulfur bacteria, while at the same time multiple genes either swept through or were lost from this population. These patterns were consistent with a genome-wide selective sweep in progress, a process predicted by the /`ecotype model/' of speciation but not previously observed in nature. In contrast, other populations contained large, SNP-free genomic regions that appear to have swept independently through the populations prior to the study without purging diversity elsewhere in the genome. Evidence for both genome-wide and gene-specific sweeps suggests that different models of bacterial speciation may apply to different populations coexisting in the same environment.

  • 57.
    Bengtsson, Mia M.
    et al.
    Ernst Moritz Arndt Univ Greifswald, Inst Microbiol, Felix Hausdorff Str 8, D-17489 Greifswald, Germany.
    Attermeyer, Katrin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. WasserCluster Lunz, Dr Carl Kupelwieser Promenade 5, A-3293 Lunz Am See, Austria.
    Catalan, Nuria
    Catalan Inst Water Res ICRA, Emili Grahit 101, Girona 17003, Spain.
    Interactive effects on organic matter processing from soils to the ocean: are priming effects relevant in aquatic ecosystems?2018In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 822, no 1, p. 1-17Article, review/survey (Refereed)
    Abstract [en]

    Organic matter (OM) is degraded during transport from soils to oceans. However, there are spatial and temporal variabilities along the aquatic continuum, which hamper the development of carbon cycling models. One concept that has been applied in this context is the priming effect (PE), describing non-additive effects on OM degradation after mixing sources of contrasting bioavailability. Studies on the aquatic PE report divergent results from positive (increased OM degradation rates) to neutral, to negative (decreased OM degradation rates) effects upon mixing. Here, we aim to condense the outcomes of these studies on aquatic PE. Based on a literature review, we discuss differences in the reported PEs across freshwater and marine ecosystems, identifying system-specific features that could favour non-additive effects on OM degradation. Using a quantitative meta-analysis approach, we evaluated the occurrence, direction (positive vs. negative) and magnitude of aquatic PE. The meta-analysis revealed a mean PE of 12.6%, which was not significantly different from zero across studies. Hence, mixing of contrasting OM sources in aquatic ecosystems does not necessarily result in a change in OM degradation rates. Therefore, we suggest to focus on molecular and microbial diversity and function, which could provide a better mechanistic understanding of processes driving OM interactions.

  • 58.
    Bennke, Christin M.
    et al.
    Max Planck Inst Marine Microbiol, Dept Mol Ecol, Bremen, Germany..
    Reintjes, Greta
    Max Planck Inst Marine Microbiol, Dept Mol Ecol, Bremen, Germany..
    Schattenhofer, Martha
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Max Planck Inst Marine Microbiol, Dept Mol Ecol, Bremen, Germany..
    Ellrott, Andreas
    Max Planck Inst Marine Microbiol, Dept Mol Ecol, Bremen, Germany..
    Wulf, Jörg
    Max Planck Inst Marine Microbiol, Dept Mol Ecol, Bremen, Germany..
    Zeder, Michael
    Max Planck Inst Marine Microbiol, Dept Mol Ecol, Bremen, Germany.;Technobiol GmbH, Buchrain, Switzerland..
    Fuchs, Bernhard M.
    Max Planck Inst Marine Microbiol, Dept Mol Ecol, Bremen, Germany..
    Modification of a High-Throughput Automatic Microbial Cell Enumeration System for Shipboard Analyses2016In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 82, no 11, p. 3289-3296Article in journal (Refereed)
    Abstract [en]

    In the age of ever-increasing "-omics" studies, the accurate and statistically robust determination of microbial cell numbers within often-complex samples remains a key task in microbial ecology. Microscopic quantification is still the only method to enumerate specific subgroups of microbial clades within complex communities by, for example, fluorescence in situ hybridization (FISH). In this study, we improved an existing automatic image acquisition and cell enumeration system and adapted it for usage at high seas on board an oceanographic research ship. The system was evaluated by testing settings such as minimal pixel area and image exposure times ashore under stable laboratory conditions before being brought on board and tested under various wind and wave conditions. The system was robust enough to produce high-quality images even with ship heaves of up to 3m and pitch and roll angles of up to 6.3 degrees. On board the research ship, on average, 25% of the images acquired from plankton samples on filter membranes could be used for cell enumeration. Automated enumeration was highly correlated with manual counts (r(2)>0.9). Even the smallest of microbial cells in the open ocean, members of the alphaproteobacterial SAR11 clade, could be confidently detected and enumerated. The automated image acquisition and cell enumeration system developed here enables an accurate and reproducible determination of microbial cell counts in planktonic samples and allows insight into the abundance and distribution of specific microorganisms already on board within a few hours.

    IMPORTANCE In this research article, we report on a new system and software pipeline, which allows for an easy and quick image acquisition and the subsequent enumeration of cells in the acquired images. We put this pipeline through vigorous testing and compared it to manual microscopy counts of microbial cells on membrane filters. Furthermore, we tested this system at sea on board a marine research vessel and counted bacteria on board within a few hours after the retrieval of water samples. The imaging and counting system described here has been successfully applied to a number of laboratory-based studies and allowed the quantification of thousands of samples and FISH preparations (see, e.g., H. Teeling, B. M. Fuchs, D. Becher, C. Klockow, A. Gardebrecht, C. M. Bennke, M. Kassabgy, S. Huang, A. J. Mann, J. Waldmann, M. Weber, A. Klindworth, A. Otto, J. Lange, J. Bernhardt, C. Reinsch, M. Hecker, J. Peplies, F. D. Bockelmann, U. Callies, G. Gerdts, A. Wichels, K. H. Wiltshire, F. O. Glockner, T. Schweder, and R. Amann, Science 336:608-611, 2012, http://dx.doi.org/10.1126/science.1218344). We adjusted the standard image acquisition software to withstand ship movements. This system will allow for more targeted sampling of the microbial community, leading to a better understanding of the role of microorganisms in the global oceans.

  • 59. Benson, Barbara J.
    et al.
    Magnuson, John J.
    Jensen, Olaf P.
    Card, Virginia M.
    Hodgkins, Glenn
    Korhonen, Johanna
    Livingstone, David M.
    Stewart, Kenton M.
    Weyhenmeyer, Gesa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Granin, Nick G.
    Extreme events, trends, and variability in Northern Hemisphere lake-ice phenology (1855-2005)2012In: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 112, no 2, p. 299-323Article in journal (Refereed)
    Abstract [en]

    Often extreme events, more than changes in mean conditions, have the greatest impact on the environment and human well-being. Here we examine changes in the occurrence of extremes in the timing of the annual formation and disappearance of lake ice in the Northern Hemisphere. Both changes in the mean condition and in variability around the mean condition can alter the probability of extreme events. Using long-term ice phenology data covering two periods 1855-6 to 2004-5 and 1905-6 to 2004-5 for a total of 75 lakes, we examined patterns in long-term trends and variability in the context of understanding the occurrence of extreme events. We also examined patterns in trends for a 30-year subset (1975-6 to 2004-5) of the 100-year data set. Trends for ice variables in the recent 30-year period were steeper than those in the 100- and 150-year periods, and trends in the 150-year period were steeper than in the 100-year period. Ranges of rates of change (days per decade) among time periods based on linear regression were 0.3-1.6 later for freeze, 0.5-1.9 earlier for breakup, and 0.7-4.3 shorter for duration. Mostly, standard deviation did not change, or it decreased in the 150-year and 100-year periods. During the recent 50-year period, standard deviation calculated in 10-year windows increased for all ice measures. For the 150-year and 100-year periods changes in the mean ice dates rather than changes in variability most strongly influenced the significant increases in the frequency of extreme lake ice events associated with warmer conditions and decreases in the frequency of extreme events associated with cooler conditions.

  • 60.
    Berga, Mercè
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Yinghua, Zha
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Székely, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Testing responses of bacterial communities to environmental change using whole ecosystem manipulation experimentsManuscript (preprint) (Other academic)
  • 61.
    Berga, Mercè
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Biological Oceanography, Leibniz Institute for Baltic Sea Research Warnemünde, Germany.
    Zha, Yinghua
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Székely, Anna J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Functional and Compositional Stability of Bacterial Metacommunities in Response to Salinity Changes2017In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 8, article id 948Article in journal (Refereed)
    Abstract [en]

    Disturbances and environmental change are important factors determining the diversity,composition, and functioning of communities. However, knowledge about how naturalbacterial communities are affected by such perturbations is still sparse. We performeda whole ecosystem manipulation experiment with freshwater rock pools where weapplied salinity disturbances of different intensities. The aim was to test how thecompositional and functional resistance and resilience of bacterial communities,alpha- and beta-diversity and the relative importance of stochastic and deterministiccommunity assembly processes changed along a disturbance intensity gradient.We found that bacterial communities were functionally resistant to all salinity levels (3, 6, and 12 psu) and compositionally resistant to a salinity increase to 3 psu andresilient to increases of 6 and 12 psu. Increasing salinities had no effect on local richnessand evenness, beta-diversity and the proportion of deterministically vs. stochasticallyassembled communities. Our results show a high functional and compositional stabilityof bacterial communities to salinity changes of different intensities both at localand regional scales, which possibly reflects long-term adaptation to environmentalconditions in the study system.

  • 62.
    Berga, Mercè
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Lindström, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Effects of predation and dispersal on the diversity an functioning of bacterial metacommunitiesManuscript (preprint) (Other academic)
  • 63.
    Berga, Mercè
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Combined effects of zooplankton grazing and dispersal on the diversity and assembly mechanisms of bacterial metacommunities2015In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 17, no 7, p. 2275-2287Article in journal (Refereed)
    Abstract [en]

    Effects of dispersal and the presence of predators on diversity, assembly and functioning of bacterial communities are well studied in isolation. In reality, however, dispersal and trophic interactions act simultaneously and can therefore have combined effects, which are poorly investigated. We performed an experiment with aquatic metacommunities consisting of three environmentally different patches and manipulated dispersal rates among them as well as the presence or absence of the keystone species Daphnia magnaDaphnia magnareduced both local and regional diversity, whereas dispersal increased local diversity but decreased beta-diversity having no net effect on regional diversity. Dispersal modified the assembly mechanisms of bacterial communities by increasing the degree of determinism. Additionally, the combination of the D. magna and dispersal increased the importance of deterministic processes, presumably because predator-tolerant taxa were spread in the metacommunity via dispersal. Moreover, the presence of D. magna affected community composition, increased community respiration rates but did not affect bacterial production or abundance, whereas dispersal slightly increased bacterial production. In conclusion, our study suggests that predation by a keystone species such as D. magna and dispersal additively influence bacterial diversity, assembly processes and ecosystem functioning.

  • 64.
    Berga, Mercé
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Székely, Anna J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Effects of Disturbance Intensity and Frequency on Bacterial Community Composition and Function2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 5, p. e36959-Article in journal (Refereed)
    Abstract [en]

    Disturbances influence community structure and ecosystem functioning. Bacteria are key players in ecosystems and it is therefore crucial to understand the effect of disturbances on bacterial communities and how they respond to them, both compositionally and functionally. The main aim of this study was to test the effect of differences in disturbance strength on bacterial communities. For this, we implemented two independent short-term experiments with dialysis bags containing natural bacterial communities, which were transplanted between ambient and 'disturbed' incubation tanks, manipulating either the intensity or the frequency of a salinity disturbance. We followed changes in community composition by terminal restriction fragment analysis (T-RFLP) and measured various community functions (bacterial production, carbon substrate utilization profiles and rates) directly after and after a short period of recovery under ambient conditions. Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions. In the disturbance intensity experiment, the sensitivity to the disturbance and the ability of recovery differed between different functions. In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed. Moreover, in case of the intensity experiment, there was also a time lag in the responses of community composition and functions, with functional responses being faster than compositional ones. To summarize, our study shows that disturbance strength has the potential to change the functional performance and composition of bacterial communities. It further highlights that the overall effects, rates of recovery and the degree of congruence in the response patterns of community composition and functioning along disturbance gradients depend on the type of function and the character of the disturbance.

  • 65.
    Berga Quintana, Mercè
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Assembly Mechanisms in Aquatic Bacterial Communities: The Role of Disturbances, Dispersal and History2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Environmental conditions, biotic interactions, dispersal and history have been suggested to be important processes influencing the spatial distribution of organisms and thus to affect community assembly. Understanding how these processes influence community assembly is important, particularly because community diversity and composition are suggested to be relevant for ecosystem functioning. Moreover, bacteria are strongly contributing to nutrient and carbon cycle. Bacteria are highly abundant and ubiquitous, and thus it is relevant to study how they are assembled. This thesis aims to gain insight on the role of these processes on aquatic bacterial community assembly, diversity and functioning. The studies included in this thesis involve transplant and microcosm experiments performed in the lab as well as manipulation experiments and field surveys in a natural rock pool systems. Bacterial community composition was addressed by analysis of 16S rRNA gene and community functioning by measuring bacterial production, community respiration and the ability to use different carbon substrates. This thesis highlights that species sorting is a very important assembly mechanism for bacterial communities, but also finds that other processes such as dispersal and history contribute to the patterns observed. Dispersal caused rescuing effects compensating for losses of diversity; at the same time it increased the similarity between communities. Moreover, bacteria have shown a high level of functional plasticity when colonizing a new locality. Interestingly, past environmental conditions explained the structure of bacterial communities better than present-day environmental conditions. Disturbances and biotic interactions are also important in the assembly of communities. Disturbance caused temporary shifts in bacterial function and changes in composition, the magnitude of which depended on the intensity and the frequency of the disturbance. However, natural aquatic bacterial communities showed quite high resilience capacities. Competition can shift the proportion of generalists and specialists species whereas predation or trophic interactions have been found to decrease diversity and to modify the importance of stochasticity. Both caused alterations of community functioning. Finally, this thesis shows that the diversity-functioning relationship is context dependent. Further research should be directed to understanding the intensity and direction of changes in composition and how this affects the functionality of bacterial communities

    List of papers
    1. Effects of Disturbance Intensity and Frequency on Bacterial Community Composition and Function
    Open this publication in new window or tab >>Effects of Disturbance Intensity and Frequency on Bacterial Community Composition and Function
    2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 5, p. e36959-Article in journal (Refereed) Published
    Abstract [en]

    Disturbances influence community structure and ecosystem functioning. Bacteria are key players in ecosystems and it is therefore crucial to understand the effect of disturbances on bacterial communities and how they respond to them, both compositionally and functionally. The main aim of this study was to test the effect of differences in disturbance strength on bacterial communities. For this, we implemented two independent short-term experiments with dialysis bags containing natural bacterial communities, which were transplanted between ambient and 'disturbed' incubation tanks, manipulating either the intensity or the frequency of a salinity disturbance. We followed changes in community composition by terminal restriction fragment analysis (T-RFLP) and measured various community functions (bacterial production, carbon substrate utilization profiles and rates) directly after and after a short period of recovery under ambient conditions. Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions. In the disturbance intensity experiment, the sensitivity to the disturbance and the ability of recovery differed between different functions. In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed. Moreover, in case of the intensity experiment, there was also a time lag in the responses of community composition and functions, with functional responses being faster than compositional ones. To summarize, our study shows that disturbance strength has the potential to change the functional performance and composition of bacterial communities. It further highlights that the overall effects, rates of recovery and the degree of congruence in the response patterns of community composition and functioning along disturbance gradients depend on the type of function and the character of the disturbance.

    National Category
    Biological Sciences
    Identifiers
    urn:nbn:se:uu:diva-177625 (URN)10.1371/journal.pone.0036959 (DOI)000305339400046 ()
    Available from: 2012-07-18 Created: 2012-07-17 Last updated: 2017-12-07Bibliographically approved
    2. Testing responses of bacterial communities to environmental change using whole ecosystem manipulation experiments
    Open this publication in new window or tab >>Testing responses of bacterial communities to environmental change using whole ecosystem manipulation experiments
    (English)Manuscript (preprint) (Other academic)
    National Category
    Ecology Microbiology
    Identifiers
    urn:nbn:se:uu:diva-207179 (URN)
    Available from: 2013-09-10 Created: 2013-09-10 Last updated: 2014-05-08
    3. Mechanisms determining the fate of dispersed bacterial communities in new environments
    Open this publication in new window or tab >>Mechanisms determining the fate of dispersed bacterial communities in new environments
    2013 (English)In: ISME Journal, ISSN 1751-7362, Vol. 7, no 1, p. 61-71Article in journal (Refereed) Published
    Abstract [en]

    Recent work has shown that dispersal has an important role in shaping microbial communities. However, little is known about how dispersed bacteria cope with new environmental conditions and how they compete with local resident communities. To test this, we implemented two full-factorial transplant experiments with bacterial communities originating from two sources (freshwater or saline water), which were incubated, separately or in mixes, under both environmental conditions. Thus, we were able to separately test for the effects of the new environment with and without interactions with local communities. We determined community composition using 454-pyrosequencing of bacterial 16S rRNA to specifically target the active fraction of the communities, and measured several functional parameters. In absence of a local resident community, the net functional response was mainly affected by the environmental conditions, suggesting successful functional adaptation to the new environmental conditions. Community composition was influenced both by the source and the incubation environment, suggesting simultaneous effects of species sorting and functional plasticity. In presence of a local resident community, functional parameters were higher compared with those expected from proportional mixes of the unmixed communities in three out of four cases. This was accompanied by an increase in the relative abundance of generalists, suggesting that competitive interactions among local and immigrant taxa could explain the observed functional overachievement. In summary, our results suggest that environmental filtering, functional plasticity and competition are all important mechanisms influencing the fate of dispersed communities.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-192014 (URN)10.1038/ismej.2012.80 (DOI)000313236000006 ()
    Available from: 2013-01-24 Created: 2013-01-15 Last updated: 2014-01-23Bibliographically approved
    4. The spatial structure of bacterial communities is influenced by historical environmental conditions
    Open this publication in new window or tab >>The spatial structure of bacterial communities is influenced by historical environmental conditions
    2014 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 5, p. 1134-1140Article in journal (Refereed) Published
    Abstract [en]

    The spatial structure of ecological communities, including that of bacteria, is often influenced by species sorting by contemporary environmental conditions. Moreover, historical processes, i.e., ecological and evolutionary events that have occurred at some point in the past, such as dispersal limitation, drift, priority effects, or selection by past environmental conditions, can be important, but are generally investigated much less. Here, we conducted a field study using 16 rock pools, where we specifically compared the importance of past vs. contemporary environmental conditions for bacterial community structure by correlating present differences in bacterial community composition among pools to environmental conditions measured on the same day, as well as to those measured 2, 4, 6, and 8 d earlier. The results prove that selection by past environmental conditions exists, since we were able to show that bacterial communities are, to a greater extent, an imprint of past compared to contemporary environmental conditions. We suggest that this is the result of a combination of different mechanisms, including priority effects that cause rapid adaptation to new environmental conditions of taxa that have been initially selected by past environmental conditions, and slower rates of turnover in community composition compared to environmental conditions.

    National Category
    Ecology Microbiology
    Identifiers
    urn:nbn:se:uu:diva-207181 (URN)10.1890/13-1300.1 (DOI)000336740500003 ()
    Available from: 2013-09-10 Created: 2013-09-10 Last updated: 2017-12-06Bibliographically approved
    5. Effects of predation and dispersal on the diversity an functioning of bacterial metacommunities
    Open this publication in new window or tab >>Effects of predation and dispersal on the diversity an functioning of bacterial metacommunities
    (English)Manuscript (preprint) (Other academic)
    National Category
    Ecology Microbiology
    Identifiers
    urn:nbn:se:uu:diva-207177 (URN)
    Available from: 2013-09-10 Created: 2013-09-10 Last updated: 2014-01-23
  • 66.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    How to see more: double hybridization to reveal ecological differentiation among close bacterial relatives2017In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 19, no 6, p. 2110-2111Article in journal (Other academic)
  • 67.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Sjöns mikroskopiska liv: en myllrande mångfald2016In: Biodiverse, ISSN 1401-5064, no 4, p. 10-10Article in journal (Other (popular science, discussion, etc.))
  • 68.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Strategies to Map the Microbiome of Freshwater Lakes: Sampling and Context2017In: Hydrocarbon and lipid microbiology protocols, Springer Berlin/Heidelberg, 2017, p. 199-217Chapter in book (Refereed)
    Abstract [en]

    Freshwater lakes are indispensible resources for humankind and as such also exposed to significant pressure from anthropogenic activities and environmental change. Organic matter holds a central role in these ecosystems, both in providing energy for the food web and in modifying water quality. The transformation, degradation, and internal production of organic matter is largely mediated by microorganisms and there is hence great interest in learning more about the ecology and function of these microscopic but abundant key players in lake ecosystems. The focus of this chapter is thus on strategies to study the spatial and temporal organization of the freshwater lake microbiome, with special attention to representative and rational sampling of freshwater lakes for subsequent analyses of microbial process or community features. Within-system heterogeneity across spatial and temporal scales will be presented and linkages between the physical structure, chemical gradients, and microbial distribution patterns will be discussed. Useful practical considerations to sample water for experiments or cells for biomolecular analyses will be presented along with recommendations regarding how to collect and compile basic but critically important contextual information. It is evident that the long-standing myth of freshwater lakes as homogenous systems delimited by defined shoreline boundaries is incorrect and that heterogeneity should be considered already in designing sampling strategies.

  • 69.
    Bertilsson, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Burgin, A.
    Carey, C.C.
    Fey, S.B.
    Grossart, H.P.
    Grubisic, L.M.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Jones, I.D.
    Kirillin, G.
    Lennon, J.T.
    Shade, A.
    Smith, R.L.
    The under-ice microbiome of seasonally frozen lakes2013In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 58, no 6, p. 1998-2012Article, review/survey (Refereed)
    Abstract [en]

    Compared to the well-studied open water of the ‘‘growing’’ season, under-ice conditions in lakes are characterized by low and rather constant temperature, slow water movements, limited light availability, and reduced exchange with the surrounding landscape. These conditions interact with ice-cover duration to shape microbial processes in temperate lakes and ultimately influence the phenology of community and ecosystem processes. We review the current knowledge on microorganisms in seasonally frozen lakes. Specifically, we highlight how under-ice conditions alter lake physics and the ways that this can affect the distribution and metabolism of auto- and heterotrophic microorganisms. We identify functional traits that we hypothesize are important for understanding under-ice dynamics and discuss how these traits influence species interactions. As ice coverage duration has already been seen to reduce as air temperatures have warmed, the dynamics of the under- ice microbiome are important for understanding and predicting the dynamics and functioning of seasonally frozen lakes in the near future.

  • 70. Besemer, Katharina
    et al.
    Peter, Hannes
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Logue, Jürg B.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Battin, Tom J.
    Unraveling assembly of stream biofilm communities2012In: The ISME Journal: multidisciplinary journal of microbial ecology, ISSN 1751-7362, Vol. 6, no 8, p. 1459-1468Article in journal (Refereed)
    Abstract [en]

    Microbial biofilms assemble from cells that attach to a surface, where they develop into matrix-enclosed communities. Mechanistic insights into community assembly are crucial to better understand the functioning of natural biofilms, which drive key ecosystem processes in numerous aquatic habitats. We studied the role of the suspended microbial community as the source of the biofilm community in three streams using terminal-restriction fragment length polymorphism and 454 pyrosequencing of the 16S ribosomal RNA (rRNA) and the 16S rRNA gene (as a measure for the active and the bulk community, respectively). Diversity was consistently lower in the biofilm communities than in the suspended stream water communities. We propose that the higher diversity in the suspended communities is supported by continuous inflow from various sources within the catchment. Community composition clearly differed between biofilms and suspended communities, whereas biofilm communities were similar in all three streams. This suggests that biofilm assembly did not simply reflect differences in the source communities, but that certain microbial groups from the source community proliferate in the biofilm. We compared the biofilm communities with random samples of the respective community suspended in the stream water. This analysis confirmed that stochastic dispersal from the source community was unlikely to shape the observed community composition of the biofilms, in support of species sorting as a major biofilm assembly mechanism. Bulk and active populations generated comparable patterns of community composition in the biofilms and the suspended communities, which suggests similar assembly controls on these populations.

  • 71.
    Bier, Raven L.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Field and chemistry data from 2016 Fluctuations Project2016Data set
  • 72.
    Björnerås, C.
    et al.
    Lund University, Lund, Sweden.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Evans, C. D.
    Environm Ctr Wales, Bangor, Wales.
    Gessner, M. O.
    Leibniz Inst Freshwater Ecol & Inland Fisheries I, Stechlin, Germany; TU Berlin, Berlin, Germany.
    Grossart, H. P.
    Potsdam Univ, Potsdam, Germany.
    Kangur, K.
    Estonian Univ Life Sci, Rannu, Estonia.
    Kokorite, I.
    Univ Latvia, Riga, Latvia.
    Kortelainen, P.
    Finnish Environm Inst, Helsinki, Finland.
    Laudon, H.
    Swedish Univ Agr Sci, Umeå, Sweden.
    Lehtoranta, J.
    Finnish Environm Inst, Helsinki, Finland.
    Lottig, N.
    Univ Wisconsin, Madison, USA.
    Monteith, D. T.
    Lancaster Environm Ctr, Lancaster, England.
    Nõges, P.
    Estonian Univ Life Sci, Tartu, Estonia.
    Nõges, T.
    Estonian Univ Life Sci, Tartu, Estonia.
    Oulehle, F.
    Czech Geol Survey, Prague, Czech Republic.
    Riise, G.
    Norwegian Univ Life Sci NMBU, As, Norway.
    Rusak, J. A.
    Ontario Minist Environm & Climate Change, Dorset, Canada.
    Räike, A.
    Finnish Environm Inst, Helsinki, Finland.
    Sire, J.
    Latvian Environm Geol & Meteorol Ctr, Riga, Latvia.
    Sterling, S.
    Dalhousie Univ, Halifax, Canada.
    Kritzberg, E. S.
    Lund University, Lund, Sweden.
    Widespread Increases in Iron Concentration in European and North American Freshwaters2017In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 31, no 10, p. 1488-1500Article in journal (Refereed)
    Abstract [en]

    Recent reports of increasing iron (Fe) concentrations in freshwaters are of concern, given the fundamental role of Fe in biogeochemical processes. Still, little is known about the frequency and geographical distribution of Fe trends or about the underlying drivers. We analyzed temporal trends of Fe concentrations across 340 water bodies distributed over 10 countries in northern Europe and North America in order to gain a clearer understanding of where, to what extent, and why Fe concentrations are on the rise. We found that Fe concentrations have significantly increased in 28% of sites, and decreased in 4%, with most positive trends located in northern Europe. Regions with rising Fe concentrations tend to coincide with those with organic carbon (OC) increases. Fe and OC increases may not be directly mechanistically linked, but may nevertheless be responding to common regional-scale drivers such as declining sulfur deposition or hydrological changes. A role of hydrological factors was supported by covarying trends in Fe and dissolved silica, as these elements tend to stem from similar soil depths. A positive relationship between Fe increases and conifer cover suggests that changing land use and expanded forestry could have contributed to enhanced Fe export, although increases were also observed in nonforested areas. We conclude that the phenomenon of increasing Fe concentrations is widespread, especially in northern Europe, with potentially significant implications for wider ecosystem biogeochemistry, and for the current browning of freshwaters.

  • 73.
    Blake, Chelsea A.
    et al.
    Lewis & Clark Community Coll, Natl Great Rivers Res & Educ Ctr, 1 Confluence Way, East Alton, IL 62024 USA;Lund Univ, Dept Biol, Aquat Ecol Unit, Ecol Bldg, SE-22362 Lund, Sweden.
    Andersson, Matilda L.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Lund Univ, Dept Biol, Aquat Ecol Unit, Ecol Bldg, SE-22362 Lund, Sweden.
    Hulthen, Kaj
    North Carolina State Univ, Dept Biol Sci, Box 7617, Raleigh, NC USA;North Carolina State Univ, WM Keck Ctr Behav Biol, Box 7617, Raleigh, NC USA;Lund Univ, Dept Biol, Aquat Ecol Unit, Ecol Bldg, SE-22362 Lund, Sweden.
    Nilsson, P. Anders
    Karlstad Univ, Dept Environm & Life Sci, S-65188 Karlstad, Sweden;Lund Univ, Dept Biol, Aquat Ecol Unit, Ecol Bldg, SE-22362 Lund, Sweden.
    Bronmark, Christer
    Lund Univ, Dept Biol, Aquat Ecol Unit, Ecol Bldg, SE-22362 Lund, Sweden.
    Conspecific boldness and predator species determine predation-risk consequences of prey personality2018In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 72, no 8, article id 133Article in journal (Refereed)
    Abstract [en]

    Individual variation in the behavior of prey can influence predation risk in complex ways. We ran individual roach (Rutilus rutilus), a common freshwater fish, through a standard refuge emergence protocol to characterize their boldness, a key animal personality trait. We then paired a bold and a shy roach and exposed the pair to one of two predator species that have contrasting hunting modes to ascertain how personality traits shaped their survival during predator encounters. When a paired bold and shy prey fish interacted with a perch predator (active foraging mode), bold and shy prey were consumed in almost equal numbers. However, pike predators (ambush foraging mode) selectively consumed more shy prey, and prey body size and boldness score both contributed significantly to which prey fish was eaten. Our findings support the idea that multiple predators with different foraging modes, and hence differential selection on prey personality, could contribute to maintaining variation in personality in prey populations. Furthermore, for social species, including shoaling fish, the ultimate consequences of an individual's personality may depend upon the personality of its nearby conspecifics. Animals of the same species often look similar, but individuals show differences in their behavior that can have important consequences, for instance when these individuals interact with predators. The common roach is a freshwater fish that shows inter-individual variation in its propensity to take risks, a key personality trait often termed boldness. Variation in boldness may affect the outcome when roach interact with predators, i.e., if they get eaten or survive. However, we found the impact of roachs' personality type depends on what species of predatory fish they face. When we put a shy and a bold roach together with predatory perch, the roachs' personality did not significantly affect which individual was eaten. But when the predator was a pike, the predators selectively ate more shy roach, and the likelihood an individual would be eaten depended on their body size.

  • 74.
    Blenckner, Thorsten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Adrian, Rita
    Arvola, Lauri
    Järvinen, Marko
    Nõges, Peeter
    Nõges, Tiina
    Pettersson, Kurt
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The impact of climate change on lakes in northern Europe2010In: The impact of climate change on European lakes / [ed] D.G. George, Springer , 2010, p. 339-358Chapter in book (Other academic)
  • 75. Bloch, Ina
    et al.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Long-term changes in physical and chemical conditions of nutrient-poor lakes along a latitudinal gradient: is there a coherent phytoplankton community response?2012In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 74, no 1, p. 77-85Article in journal (Refereed)
    Abstract [en]

    To evaluate climate and atmospheric deposition induced physical and water chemical changes and their effects on phytoplankton communities, we used complete time series (14 years, monthly measurements during the growing season) of 18 physical and chemical variables and phytoplankton data from 13 nutrient-poor Swedish reference lakes along a latitudinal gradient. We found numerous strong significant changes over time that were most coherent among lakes for sulfate concentrations, conductivity, calcium, magnesium, chloride, potassium, water color, surface water temperature and the intensity of thermal stratification. Despite these pronounced coherent physical and water chemical changes over Sweden, the phytoplankton biomass and species richness of six phytoplankton groups, measured at the same time as the water chemical variables, showed only few and weak significant changes over time. The only coherent significant change over Sweden, occurring in seven lakes, was observed in the species richness of chlorophytes. The number of chlorophyte taxa significantly declined over Sweden. Using a partial least square model for each lake, we attributed the decline primarily to an increase in water temperatures and water color, which were among the most important variables for the model performance of each lake. All other taxonomic groups were driven primarily by non-coherent changes in nutrient concentrations, pH and probably also non-coherent grazing pressure. We concluded that coherent phytoplankton responses can only be achieved for taxonomic groups that are driven primarily by coherent physical/chemical changes. According to our study, chlorophytes belong to such a group, making them possible global change indicators. Our findings give new insights into global change effects on different phytoplankton taxonomic groups in nutrient-poor lakes.

  • 76.
    Block, Benjamin D.
    et al.
    Univ Vermont, Rubenstein Ecosyst Sci Lab, Burlington, VT 05405 USA.
    Denfeld, Blaize A.
    Umea Univ, Dept Ecol & Environm Sci, Umea, Sweden.
    Stockwell, Jason D.
    Univ Vermont, Rubenstein Ecosyst Sci Lab, Burlington, VT 05405 USA.
    Flaim, Giovanna
    FEM, Res & Innovat Ctr, Dept Sustainable Agroecosyst & Bioresources, San Michele All Adige, Italy.
    Grossart, Hans-Peter F.
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Expt Limnol, Stechlin, Germany;Potsdam Univ, Inst Biochem & Biol, Potsdam, Germany.
    Knoll, Lesley B.
    Univ Minnesota Twin Cities, Itasca Biol Stn & Labs, Lake Itasca, MN USA.
    Maier, Dominique B.
    Umea Univ, Dept Ecol & Environm Sci, Umea, Sweden.
    North, Rebecca L.
    Univ Missouri, Sch Nat Resources, Columbia, MO USA.
    Rautio, Milla
    Univ Quebec Chicoutimi, Dept Sci Fondamentales, Chicoutimi, PQ, Canada;Univ Laval, Ctr Northern Studies CEN, Quebec City, PQ, Canada;Univ Montreal, Grp Interuniv Res Limnol & Aquat Environm GRIL, Montreal, PQ, Canada.
    Rusak, James A.
    Ontario Minist Environm & Climate Change, Dorset Environm Sci Ctr, Dorset, ON, Canada;Queens Univ, Dept Biol, Kingston, ON, Canada.
    Sadro, Steve
    Univ Calif Davis, Tahoe Environm Res Ctr, Dept Environm Sci & Policy, Davis, CA 95616 USA.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bramburger, Andrew J.
    Univ Minnesota, Nat Resources Res Inst, Duluth, MN 55811 USA.
    Branstrator, Donn K.
    Univ Minnesota, Dept Biol, Duluth, MN 55812 USA.
    Salonen, Kalevi
    Univ Helsinki, Lammi Biol Stn, Helsinki, Finland.
    Hampton, Stephanie E.
    Washington State Univ, Ctr Environm Res Educ & Outreach, Pullman, WA 99164 USA.
    The unique methodological challenges of winter limnology2019In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 17, no 1, p. 42-57Article, review/survey (Refereed)
    Abstract [en]

    Winter is an important season for many limnological processes, which can range from biogeochemical transformations to ecological interactions. Interest in the structure and function of lake ecosystems under ice is on the rise. Although limnologists working at polar latitudes have a long history of winter work, the required knowledge to successfully sample under winter conditions is not widely available and relatively few limnologists receive formal training. In particular, the deployment and operation of equipment in below 0 degrees C temperatures pose considerable logistical and methodological challenges, as do the safety risks of sampling during the ice-covered period. Here, we consolidate information on winter lake sampling and describe effective methods to measure physical, chemical, and biological variables in and under ice. We describe variation in snow and ice conditions and discuss implications for sampling logistics and safety. We outline commonly encountered methodological challenges and make recommendations for best practices to maximize safety and efficiency when sampling through ice or deploying instruments in ice-covered lakes. Application of such practices over a broad range of ice-covered lakes will contribute to a better understanding of the factors that regulate lakes during winter and how winter conditions affect the subsequent ice-free period.

  • 77. Bolnick, D.I.
    et al.
    Snowberg, Lisa K.
    Hirsch, Philippe E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lauber, Christian L.
    Org, Elin
    Parks, Brian
    Lusis, Aldons J.
    Knight, Rob
    Caporaso, J. Gregory
    Svanbäck, Richard
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Individual diet has sex-dependent
effects on vertebrate gut microbiota2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 4500-Article in journal (Refereed)
  • 78. Bolnick, D.I.
    et al.
    Snowberg, L.K.
    Hirsch, P.E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lauber, C.L.
    Knight, R.
    Caporaso, J.G.
    Svanbäck, Richard
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Individuals’ diet diversity influences gut microbial diversity in two freshwater fish (threespine stickleback and Eurasian perch)2014In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 17, no 8, p. 979-987Article in journal (Refereed)
    Abstract [en]

    Vertebrates' diets profoundly influence the composition of symbiotic gut microbial communities. Studies documenting diet-microbiota associations typically focus on univariate or categorical diet variables. However, in nature individuals often consume diverse combinations of foods. If diet components act independently, each providing distinct microbial colonists or nutrients, we expect a positive relationship between diet diversity and microbial diversity. We tested this prediction within each of two fish species (stickleback and perch), in which individuals vary in their propensity to eat littoral or pelagic invertebrates or mixtures of both prey. Unexpectedly, in most cases individuals with more generalised diets had less diverse microbiota than dietary specialists, in both natural and laboratory populations. This negative association between diet diversity and microbial diversity was small but significant, and most apparent after accounting for complex interactions between sex, size and diet. Our results suggest that multiple diet components can interact non-additively to influence gut microbial diversity.

  • 79.
    Boy, Michael
    et al.
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Thomson, Erik S.
    Univ Gothenburg, Dept Chem & Mol Biol Atmospher Sci, S-41296 Gothenburg, Sweden.
    Acosta Navarro, Juan-C.
    BSC, Earth Sci Dept, Barcelona, Spain.
    Arnalds, Olafur
    Agr Univ Iceland, Fac Agr & Environm Sci, Hvanneyri, Iceland.
    Batchvarova, Ekaterina
    Tech Univ Denmark, DTU Wind Energy, Riso Campus, Roskilde, Denmark;Bulgarian Acad Sci, Natl Inst Meteorol & Hydrol, Sofia, Bulgaria.
    Bäck, Jaana
    Univ Helsinki, Inst Atmospher & Earth Syst Res Forest, POB 27, FIN-00014 Helsinki, Finland.
    Berninger, Frank
    Univ Helsinki, Inst Atmospher & Earth Syst Res Forest, POB 27, FIN-00014 Helsinki, Finland.
    Bilde, Merete
    Aarhus Univ, Dept Chem, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
    Brasseur, Zoe
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Dagsson-Waldhauserova, Pavla
    Agr Univ Iceland, Fac Agr & Environm Sci, Hvanneyri, Iceland;Univ Iceland, Dept Phys Sci, Reykjavik, Iceland;Czech Univ Life Sci, Fac Environm Sci, Prague, Czech Republic.
    Castarede, Dimitri
    Univ Gothenburg, Dept Chem & Mol Biol Atmospher Sci, S-41296 Gothenburg, Sweden.
    Dalirian, Maryam
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    de Leeuw, Gerrit
    Finnish Meteorol Inst, Climate Res Programme, Helsinki, Finland.
    Dragosics, Monika
    Univ Iceland, Inst Earth Sci, Reykjavik, Iceland.
    Duplissy, Ella-Maria
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Duplissy, Jonathan
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Ekman, Annica M. L.
    Stockholm Univ, Dept Meteorol, Stockholm, Sweden;Stockholm Univ, Bolin Ctr Climate Res, Stockholm, Sweden.
    Fang, Keyan
    Fujian Normal Univ, Inst Geog, Key Lab Humid Subtrop Ecogeog Proc, Fuzhou, Fujian, Peoples R China.
    Gallet, Jean-Charles
    Norwegian Polar Res Inst, FRAM High North Res Ctr Climate & Environm, N-9296 Tromso, Norway.
    Glasius, Marianne
    Aarhus Univ, Dept Chem, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
    Gryning, Sven-Erik
    Tech Univ Denmark, DTU Wind Energy, Riso Campus, Roskilde, Denmark.
    Grythe, Henrik
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden;NILU Norwegian Inst Air Res, Kjeller, Norway.
    Hansson, Hans-Christen
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Hansson, Margareta
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden.
    Isaksson, Elisabeth
    Norwegian Polar Res Inst, FRAM High North Res Ctr Climate & Environm, N-9296 Tromso, Norway.
    Iversen, Trond
    Norwegian Meteorol Inst, Oslo, Norway.
    Jonsdottir, Ingibjorg
    Univ Iceland, Inst Earth Sci, Reykjavik, Iceland.
    Kasurinen, Ville
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland;Univ Helsinki, Inst Atmospher & Earth Syst Res Forest, POB 27, FIN-00014 Helsinki, Finland.
    Kirkevåg, Alf
    Norwegian Meteorol Inst, Oslo, Norway.
    Korhola, Atte
    Univ Helsinki, Fac Biol & Environm Sci, Ecosyst & Environm Res Programme, ECRU, POB 65, FIN-00014 Helsinki, Finland.
    Krejci, Radovan
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Kristjansson, Jon Egill
    Univ Oslo, Dept Geosci, Oslo, Norway.
    Lappalainen, Hanna K.
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland;Finnish Meteorol Inst, Climate Res Programme, Helsinki, Finland;Tyumen State Univ, Dept Cryosphere, Tyumen 625003, Russia.
    Lauri, Antti
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Leppäranta, Matti
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Lihavainen, Heikki
    Finnish Meteorol Inst, Climate Res Programme, Helsinki, Finland.
    Makkonen, Risto
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Massling, Andreas
    Aarhus Univ, Arct Res Ctr, Dept Environm Sci, Climate, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
    Meinander, Outi
    Finnish Meteorol Inst, Climate Res Programme, Helsinki, Finland.
    Nilsson, E. Douglas
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Olafsson, Haraldur
    Univ Iceland, Dept Phys Sci, Reykjavik, Iceland;Icelandic Meteorol Off, Reykjavik, Iceland.
    Pettersson, Jan B. C.
    Univ Gothenburg, Dept Chem & Mol Biol Atmospher Sci, S-41296 Gothenburg, Sweden.
    Prisle, Nonne L.
    Univ Oulu, Nano & Mol Syst Res Unit, POB 3000, Oulu 90014, Finland.
    Riipinen, Ilona
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Roldin, Pontus
    Lund Univ, Dept Phys, Div Nucl Phys, POB 118, S-22100 Lund, Sweden.
    Ruppel, Meri
    Univ Helsinki, Fac Biol & Environm Sci, Ecosyst & Environm Res Programme, ECRU, POB 65, FIN-00014 Helsinki, Finland.
    Salter, Matthew
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Sand, Maria
    CICERO, Oslo, Norway.
    Seland, Öyvind
    Norwegian Meteorol Inst, Oslo, Norway.
    Seppä, Heikki
    Univ Helsinki, Dept Geosci & Geog, Helsinki, Finland.
    Skov, Henrik
    Aarhus Univ, Arct Res Ctr, Dept Environm Sci, Climate, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
    Soares, Joana
    Finnish Meteorol Inst, Climate Res Programme, Helsinki, Finland;Air Qual Res Div Environm & Climate Change Canada, Toronto, ON M3H5T4, Canada.
    Stohl, Andreas
    NILU Norwegian Inst Air Res, Kjeller, Norway.
    Ström, Johan
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Svensson, Jonas
    Finnish Meteorol Inst, Climate Res Programme, Helsinki, Finland.
    Swietlicki, Erik
    Lund Univ, Dept Phys, Div Nucl Phys, POB 118, S-22100 Lund, Sweden.
    Tabakova, Ksenia
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Thorsteinsson, Throstur
    Univ Iceland, Inst Earth Sci, Reykjavik, Iceland;Univ Iceland, Environm & Nat Resources, Reykjavik, Iceland.
    Virkkula, Aki
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland;Finnish Meteorol Inst, Climate Res Programme, Helsinki, Finland.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wu, Yusheng
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Zieger, Paul
    Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Kulmala, Markku
    Univ Helsinki, Inst Atmospher & Earth Syst Res Phys, POB 64, FIN-00014 Helsinki, Finland.
    Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes2019In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 19, no 3, p. 2015-2061Article in journal (Refereed)
    Abstract [en]

    The Nordic Centre of Excellence CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change-cryosphere interactions that affect Arctic amplification.

  • 80. Bragee, Petra
    et al.
    Choudhary, Preetam
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Routh, Joyanto
    Boyle, John F.
    Hammarlund, Dan
    Lake ecosystem responses to catchment disturbance and airborne pollution: an 800-year perspective in southern Sweden2013In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 50, no 4, p. 545-560Article in journal (Refereed)
    Abstract [en]

    Sediment sequences spanning the last 800 years from two small lakes in the south Swedish uplands were explored for assessment of effects of changing human population, local land-use practices and airborne pollution on lake-ecosystem functioning and resilience. Variations in nutrient cycling and deposition of lithogenic elements were studied, using a multi-proxy stratigraphic approach. Carbon and nitrogen elemental and isotopic analyses were applied in combination with records of hydrocarbons (n-alkanes) to investigate the sources and depositional conditions of sediment organic matter. Changes in fluvial and airborne delivery of inorganic matter were based on X-ray fluorescence measurements. The results reveal that population growth and related increases in land-use pressure had a major impact on catchment erosion and input of terrestrial organic matter to the lakes from the 1500s to the end of the 1800s. Evidence also exists of a brief period of catchment disturbance at ca. 1200-1300, followed by recovery, likely connected to the Black Death pandemic. At ca. 1900 synchronous shifts in most of the proxy records suggest a marked change in external forcing common to the two lakes related to a major decrease in population density and the introduction of modern forestry following the industrial revolution. Interestingly, the two sediment records exhibit generally coherent trends in C/N ratio, organic C content and delta C-13, both before and after 1900, indicating broadly similar sensitivities of the lake ecosystems to human impact. In contrast, deviating trends in total N content, delta N-15 and lithogenic element concentrations (K, Ti, Rb and Zr) reflect site-specific responses to local disturbances during the last century due to different nutrient conditions and catchment properties. Our companion sediment records highlight the importance of understanding long-term human impact on watersheds and demonstrate how regional versus local forcing of lake ecosystems, as well as site-specific responses related to catchment characteristics can be reconstructed.

  • 81.
    Bravo, Andrea G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Bouchet, Sylvain
    Umea Univ, Dept Chem, SE-90187 Umea, Sweden..
    Tolu, Julie
    Umea Univ, Dept Ecol & Environm Sci, SE-90187 Umea, Sweden..
    Bjorn, Erik
    Umea Univ, Dept Chem, SE-90187 Umea, Sweden..
    Mateos-Rivera, Alejandro
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Molecular composition of organic matter controls methylmercury formation in boreal lakes2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, article id 14255Article in journal (Refereed)
    Abstract [en]

    A detailed understanding of the formation of the potent neurotoxic methylmercury is needed to explain the large observed variability in methylmercury levels in aquatic systems. While it is known that organic matter interacts strongly with mercury, the role of organic matter composition in the formation of methylmercury in aquatic systems remains poorly understood. Here we show that phytoplankton-derived organic compounds enhance mercury methylation rates in boreal lake sediments through an overall increase of bacterial activity. Accordingly, in situ mercury methylation defines methylmercury levels in lake sediments strongly influenced by planktonic blooms. In contrast, sediments dominated by terrigenous organic matter inputs have far lower methylation rates but higher concentrations of methylmercury, suggesting that methylmercury was formed in the catchment and imported into lakes. Our findings demonstrate that the origin and molecular composition of organic matter are critical parameters to understand and predict methylmercury formation and accumulation in boreal lake sediments.

  • 82. Bravo, Andrea G.
    et al.
    Kothawala, Dolly
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Attermeyer, Katrin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tessier, Emmanuel
    Bodmer, Pascal
    Ledesma, José L.J.
    Audet, Joachim
    Casas-Ruiz, Joan Pere
    Catalán, Núria
    Cauvy-Fraunié, Sophie
    Colls, Miriam
    Deininger, Anne
    Evtimova, Vesela V.
    Fonvielle, Jérémy A.
    Fuß, Thomas
    Gilbert, Peter
    Herrero Ortega, Sonia
    Liu, Liu
    Mendoza-Lera, Clara
    Monteiro, Juliana
    Mor, Jordi-René
    Nagler, Magdalena
    Niedrist, Georg H.
    Nydahl, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Pastor, Ada
    Pegg, Josephine
    Gutmann Roberts, Catherine
    Pilotto, Francesca
    Portela, Ana Paula
    González-Quijano, Clara Romero
    Romero, Ferran
    Rulík, Martin
    Amouroux, David
    The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems: A latitudinal study across Europe2018In: Water Research, ISSN 0043-1354, Vol. 144, p. 172-182Article in journal (Refereed)
    Abstract [en]

    Large-scale studies are needed to identify the drivers of total mercury (THg) and monomethyl-mercury (MeHg) concentrations in aquatic ecosystems. Studies attempting to link dissolved organic matter (DOM) to levels of THg or MeHg are few and geographically constrained. Additionally, stream and river systems have been understudied as compared to lakes. Hence, the aim of this study was to examine the influence of DOM concentration and composition, morphological descriptors, land uses and water chemistry on THg and MeHg concentrations and the percentage of THg as MeHg (%MeHg) in 29 streams across Europe spanning from 41°N to 64 °N. THg concentrations (0.06–2.78 ng L−1) were highest in streams characterized by DOM with a high terrestrial soil signature and low nutrient content. MeHg concentrations (7.8–159 pg L−1) varied non-systematically across systems. Relationships between DOM bulk characteristics and THg and MeHg suggest that while soil derived DOM inputs control THg concentrations, autochthonous DOM (aquatically produced) and the availability of electron acceptors for Hg methylating microorganisms (e.g. sulfate) drive %MeHg and potentially MeHg concentration. Overall, these results highlight the large spatial variability in THg and MeHg concentrations at the European scale, and underscore the importance of DOM composition on mercury cycling in fluvial systems.

  • 83.
    Bravo, Andrea G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Loizeau, Jean-Luc
    Univ Geneva, Inst FA Forel, Earth & Environm Sci, 10 Route Suisse, CH-1290 Versoix, Switzerland..
    Dranguet, Perrine
    Univ Geneva, Inst FA Forel, Earth & Environm Sci, 10 Route Suisse, CH-1290 Versoix, Switzerland..
    Makri, Stamatina
    Univ Geneva, Inst FA Forel, Earth & Environm Sci, 10 Route Suisse, CH-1290 Versoix, Switzerland..
    Bjorn, Erik
    Umea Univ, Dept Chem, SE-90187 Umea, Sweden..
    Ungureanu, Viorel Gh.
    Univ Bucharest, Fac Geol & Geophys, Bucharest, Romania.;GeoEcoMar, Natl Res & Dev Inst Marine Geol & Geoecol, Bucharest, Romania..
    Slaveykova, Vera I.
    Univ Geneva, Inst FA Forel, Earth & Environm Sci, 10 Route Suisse, CH-1290 Versoix, Switzerland..
    Cosio, Claudia
    Univ Geneva, Inst FA Forel, Earth & Environm Sci, 10 Route Suisse, CH-1290 Versoix, Switzerland..
    Persistent Hg contamination and occurrence of Hg-methylating transcript (hgcA) downstream of a chlor-alkali plant in the Olt River (Romania)2016In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 23, no 11, p. 10529-10541Article in journal (Refereed)
    Abstract [en]

    Chlor-alkali plants using mercury (Hg) cell technology are acute point sources of Hg pollution in the aquatic environment. While there have been recent efforts to reduce the use of Hg cells, some of the emitted Hg can be transformed to neurotoxic methylmercury (MeHg). Here, we aimed (i) to study the dispersion of Hg in four reservoirs located downstream of a chlor-alkali plant along the Olt River (Romania) and (ii) to track the activity of bacterial functional genes involved in Hg methylation. Total Hg (THg) concentrations in water and sediments decreased successively from the initial reservoir to downstream reservoirs. Suspended fine size particles and seston appeared to be responsible for the transport of THg into downstream reservoirs, while macrophytes reflected the local bioavailability of Hg. The concentration and proportion of MeHg were correlated with THg, but were not correlated with bacterial activity in sediments, while the abundance of hgcA transcript correlated with organic matter and Cl- concentration, indicating the importance of Hg bioavailability in sediments for Hg methylation. Our data clearly highlights the importance of considering Hg contamination as a legacy pollutant since there is a high risk of continued Hg accumulation in food webs long after Hg-cell phase out.

  • 84. Bravo, Andrea Garcia
    et al.
    Kothawala, Dolly
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Attermeyer, Katrin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tessier, Emmanuel
    Bodmer, Pascal
    Amouroux, David
    Cleaning and sampling protocol for analysis of mercury and dissolved organic matter in freshwater systems2018In: MethodsX, ISSN 1258-780X, E-ISSN 2215-0161, Vol. 5, p. 1017-1026Article in journal (Refereed)
    Abstract [en]

    Mercury (Hg), and in particular its methylated form (methylmercury, MeHg), is a hazardous substance with the potential to produce significant adverse neurological and other health effects. Enhanced anthropogenic emissions and long-range transport of atmospheric Hg have increased Hg concentrations above background levels in aquatic systems. In this context, the Minamata Convention, a global legally binding agreement that seeks to prevent human exposure to Hg, was signed and enforced by 128 countries, and today more than 90 Parties have ratified it. All these Parties have committed to develop Hg monitoring programs to report the effectiveness of the convention. For this purpose, we provide a standardized cleaning and water sampling protocol for the determination of total-Hg and MeHg in freshwaters at ambient levels. As Hg and organic matter are tightly bound, the protocol also describes sample collection for dissolved organic carbon (DOC) concentration and characterization of dissolved organic matter (DOM) composition by fluorescence spectroscopy. This protocol is highly useful to non-experts without a prior background in Hg sampling and analysis, and can serve as a useful basis for national monitoring programs. Furthermore, this protocol should help increase quantitative inventories of DOC, inorganic-Hg (IHg) and MeHg concentrations and DOM composition in freshwater, which are severely lacking at a global scale. • Provides a standardized method to collect water samples for IHg, MeHg, DOC and DOM composition from freshwater ecosystems.

  • 85.
    Bravo, Andrea Garcia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab. Department of Marine Biology and Oceanography, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, Barcelona, Catalonia, Spain.
    Peura, Sari
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Buck, Moritz
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Osman, Omneya
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Mateos-Rivera, Alejandro
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Herrero Ortega, Sonia
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Schaefer, Jeffra K.
    Bouchet, Sylvain
    Tolu, Julie
    Björn, Erik
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Methanogens and Iron-Reducing Bacteria: the Overlooked Members of Mercury-Methylating Microbial Communities in Boreal Lakes2018In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 84, no 23, article id e01774-18Article in journal (Refereed)
    Abstract [en]

    Methylmercury is a potent human neurotoxin which biomagnifies in aquatic food webs. Although anaerobic microorganisms containing the hgcA gene potentially mediate the formation of methylmercury in natural environments, the di- versity of these mercury-methylating microbial communities remains largely unex- plored. Previous studies have implicated sulfate-reducing bacteria as the main mer- cury methylators in aquatic ecosystems. In the present study, we characterized the diversity of mercury-methylating microbial communities of boreal lake sediments us- ing high-throughput sequencing of 16S rRNA and hgcA genes. Our results show that in the lake sediments, Methanomicrobiales and Geobacteraceae also represent abun- dant members of the mercury-methylating communities. In fact, incubation experi- ments with a mercury isotopic tracer and molybdate revealed that only between 38% and 45% of mercury methylation was attributed to sulfate reduction. These re- sults suggest that methanogens and iron-reducing bacteria may contribute to more than half of the mercury methylation in boreal lakes.

  • 86.
    Bravo, Andrea Garcia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Zopfi, J
    Buck, Moritz
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Xu, J
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Schaefer, J. K.
    Poté, J.
    Cosio, C.
    Geobacteraceae are important members of mercury-methylating microbial communities of sediments impacted by wastewater releasesIn: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370Article in journal (Refereed)
  • 87.
    Bravo, Andrea Garcia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Zopfi, Jakob
    Aquatic and Stable Isotope Biogeochemistry, University of Basel, Basel CH-4056, Switzerland.
    Buck, Moritz
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Jingying, Xu
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Schaefer, Jeffra K.
    Environmental Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
    Poté, John
    Environmental Biogeochemistry and Ecotoxicology, University of Geneva, Geneva CH-1205, Switzerland.
    Cosio, Claudia
    Environmental Biogeochemistry and Ecotoxicology, University of Geneva, Geneva CH-1205, Switzerland.;Unité Stress Environnementaux et BIOSurveillance des Milieux Aquatiques UMR-I 02 (SEBIO), Université de Reims Champagne Ardenne, Reims F-51687, France.
    Geobacteraceae are important members of mercury-methylating microbial communities of sediments impacted by waste water releases2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, p. 802-812Article in journal (Refereed)
    Abstract [en]

    Microbial mercury (Hg) methylation in sediments can result in bioaccumulation of the neurotoxin methylmercury (MMHg) in aquatic food webs. Recently, the discovery of the gene hgcA, required for Hg methylation, revealed that the diversity of Hg methylators is much broader than previously thought. However, little is known about the identity of Hg-methylating microbial organisms and the environmental factors controlling their activity and distribution in lakes. Here, we combined high-throughput sequencing of 16S rRNA and hgcA genes with the chemical characterization of sediments impacted by a waste water treatment plant that releases significant amounts of organic matter and iron. Our results highlight that the ferruginous geochemical conditions prevailing at 1–2 cm depth are conducive to MMHg formation and that the Hgmethylating guild is composed of iron and sulfur-transforming bacteria, syntrophs, and methanogens. Deltaproteobacteria, notably Geobacteraceae, dominated the hgcA carrying communities, while sulfate reducers constituted only a minor component, despite being considered the main Hg methylators in many anoxic aquatic environments. Because iron is widely applied in waste water treatment, the importance of Geobacteraceae for Hg methylation and the complexity of Hgmethylating communities reported here are likely to occur worldwide in sediments impacted by waste water treatment plant discharges and in iron-rich sediments in general.

  • 88.
    Breed, Martin F.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ottewell, K. M.
    Gardner, M. G.
    Marklund, Maria H. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Dormontt, E. E.
    Lowe, A. J.
    Mating patterns and pollinator mobility are critical traits in forest fragmentation genetics2015In: Heredity, ISSN 0018-067X, E-ISSN 1365-2540, Vol. 115, no 2, p. 108-114Article in journal (Refereed)
    Abstract [en]

    Most woody plants are animal-pollinated, but the global problem of habitat fragmentation is changing the pollination dynamics. Consequently, the genetic diversity and fitness of the progeny of animal-pollinated woody plants sired in fragmented landscapes tend to decline due to shifts in plant-mating patterns (for example, reduced outcrossing rate, pollen diversity). However, the magnitude of this mating-pattern shift should theoretically be a function of pollinator mobility. We first test this hypothesis by exploring the mating patterns of three ecologically divergent eucalypts sampled across a habitat fragmentation gradient in southern Australia. We demonstrate increased selfing and decreased pollen diversity with increased fragmentation for two small-insect-pollinated eucalypts, but no such relationship for the mobile-bird-pollinated eucalypt. In a meta-analysis, we then show that fragmentation generally does increase selfing rates and decrease pollen diversity, and that more mobile pollinators tended to dampen these mating-pattern shifts. Together, our findings support the premise that variation in pollinator form contributes to the diversity of mating-pattern responses to habitat fragmentation.

  • 89.
    Breed, Martin F.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ottewell, K. M.
    Gardner, M. G.
    Marklund, Maria H. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Stead, M. G.
    Harris, J. B. C.
    Lowe, A. J.
    Mating system and early viability resistance to habitat fragmentation in a bird-pollinated eucalypt2015In: Heredity, ISSN 0018-067X, E-ISSN 1365-2540, Vol. 115, no 2, p. 100-107Article in journal (Refereed)
    Abstract [en]

    Habitat fragmentation has been shown to disrupt ecosystem processes such as plant-pollinator mutualisms. Consequently, mating patterns in remnant tree populations are expected to shift towards increased inbreeding and reduced pollen diversity, with fitness consequences for future generations. However, mating patterns and phenotypic assessments of open-pollinated progeny have rarely been combined in a single study. Here, we collected seeds from 37 Eucalyptus incrassata trees from contrasting stand densities following recent clearance in a single South Australian population (intact woodland = 12.6 trees ha(-1); isolated pasture = 1.7 trees ha(-1); population area = 10 km(2)). 649 progeny from these trees were genotyped at eight microsatellite loci. We estimated genetic diversity, spatial genetic structure, indirect contemporary pollen flow and mating patterns for adults older than the clearance events and open-pollinated progeny sired post-clearance. A proxy of early stage progeny viability was assessed in a common garden experiment. Density had no impact on mating patterns, adult and progeny genetic diversity or progeny growth, but was associated with increased mean pollen dispersal. Weak spatial genetic structure among adults suggests high historical gene flow. We observed preliminary evidence for inbreeding depression related to stress caused by fungal infection, but which was not associated with density. Higher observed heterozygosities in adults compared with progeny may relate to weak selection on progeny and lifetime-accumulated mortality of inbred adults. E. incrassata appears to be resistant to the negative mating pattern and fitness changes expected within fragmented landscapes. This pattern is likely explained by strong outcrossing and regular long-distance pollen flow.

  • 90.
    Breed, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Marklund, Maria H. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Ottewell, Kym M.
    Gardner, Michael G.
    Harris, J. Berton C.
    Lowe, Andrew J.
    Pollen diversity matters: revealing the neglected effect of pollen diversity on fitness in fragmented landscapes2012In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 21, no 24, p. 5955-5968Article in journal (Refereed)
    Abstract [en]

    Few studies have documented the impacts of habitat fragmentation on plant mating patterns together with fitness. Yet, these processes require urgent attention to better understand the impact of contemporary landscape change on biodiversity and for guiding native plant genetic resource management. We examined these relationships using the predominantly insect-pollinated Eucalyptus socialis. Progeny were collected from trees located in three increasingly disturbed landscapes in southern Australia and were planted out in common garden experiments. We show that individual mating patterns were increasingly impacted by lower conspecific density caused by habitat fragmentation. We determined that reduced pollen diversity probably has effects over and above those of inbreeding on progeny fitness. This provides an alternative mechanistic explanation for the indirect density dependence often inferred between conspecific density and offspring fitness.

  • 91.
    Brentrup, Jennifer A.
    et al.
    Miami Univ, Dept Biol, Oxford, OH 45056 USA..
    Williamson, Craig E.
    Miami Univ, Dept Biol, Oxford, OH 45056 USA..
    Colom-Montero, William
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Eckert, Werner
    Yigal Allon Kinneret Limnol Lab, Israel Oceanog & Limnol Res, Migdal, Israel..
    de Eyto, Elvira
    Inst Marine, Newport, Mayo, Ireland..
    Grossart, Hans-Peter
    Leibniz Inst Freshwater Ecol & Inland Fisheries I, Dept Expt Limnol, Stechlin, Germany.;Univ Potsdam, Inst Biochem & Biol, Potsdam, Germany..
    Huot, Yannick
    Univ Sherbrooke, Dept Geomat Appl, Sherbrooke, PQ, Canada..
    Isles, Peter D. F.
    Univ Vermont, Rubenstein Sch Environm & Nat Resources, Burlington, VT USA..
    Knoll, Lesley B.
    Univ Minnesota, Itasca Biol Stn, Lake Itasca, MN USA..
    Leach, Taylor H.
    Miami Univ, Dept Biol, Oxford, OH 45056 USA..
    McBride, Chris G.
    Univ Waikato, Environm Res Inst, Waikato, New Zealand..
    Pierson, Don
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Pomati, Francesco
    Swiss Fed Inst Aquat Sci & Technol, Dept Aquat Ecol, Dubendorf, Switzerland..
    Read, Jordan S.
    US Geol Survey, Ctr Integrated Data Analyt, Middleton, WI USA..
    Rose, Kevin C.
    Rensselaer Polytech Inst, Dept Biol Sci, Troy, NY USA..
    Samal, Nihar R.
    Univ New Hampshire, Earth Syst Res Ctr, Durham, NH 03824 USA..
    Staehr, Peter A.
    Aarhus Univ, Dept Biosci, Roskilde, Denmark..
    Winslow, Luke A.
    US Geol Survey, Ctr Integrated Data Analyt, Middleton, WI USA..
    The potential of high-frequency profiling to assess vertical and seasonal patterns of phytoplankton dynamics in lakes: an extension of the Plankton Ecology Group (PEG) model2016In: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 6, no 4, p. 565-580Article in journal (Refereed)
    Abstract [en]

    The use of high-frequency sensors on profiling buoys to investigate physical, chemical, and biological processes in lakes is increasing rapidly. Profiling buoys with automated winches and sensors that collect high-frequency chlorophyll fluorescence (ChlF) profiles in 11 lakes in the Global Lake Ecological Observatory Network (GLEON) allowed the study of the vertical and temporal distribution of ChlF, including the formation of subsurface chlorophyll maxima (SSCM). The effectiveness of 3 methods for sampling phytoplankton distributions in lakes, including (1) manual profiles, (2) single-depth buoys, and (3) profiling buoys were assessed. High-frequency ChlF surface data and profiles were compared to predictions from the Plankton Ecology Group (PEG) model. The depth-integrated ChlF dynamics measured by the profiling buoy data revealed a greater complexity that neither conventional sampling nor the generalized PEG model captured. Conventional sampling techniques would have missed SSCM in 7 of 11 study lakes. Although surface-only ChlF data underestimated average water column ChlF, at times by nearly 2-fold in 4 of the lakes, overall there was a remarkable similarity between surface and mean water column data. Contrary to the PEG model's proposed negligible role for physical control of phytoplankton during the growing season, thermal structure and light availability were closely associated with ChlF seasonal depth distribution. Thus, an extension of the PEG model is proposed, with a new conceptual framework that explicitly includes physical metrics to better predict SSCM formation in lakes and highlight when profiling buoys are especially informative.

  • 92. Bruce, Louise C
    et al.
    Frassl, Marieke A
    Arhonditsis, George B
    Gal, Gideon
    Hamilton, David P
    Hanson, Paul C
    Hetherington, Amy L
    Melack, John M
    Read, Jordan S
    Rinke, Karsten
    Rigosi, Anna
    Trolle, Dennis
    Winslow, Luke
    Adrian, Rita
    Ayala, Ana I
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bocaniov, Serghei A
    Boehrer, Bertram
    Boon, Casper
    Brookes, Justin D
    Bueche, Thomas
    Busch, Brendan D
    Copetti, Diego
    Cortés, Alicia
    de Eyto, Elvira
    Elliott, J Alex
    Gallina, Nicole
    Gilboa, Yael
    Guyennon, Nicolas
    Huang, Lei
    Kerimoglu, Onur
    Lenters, John D
    MacIntyre, Sally
    Makler-Pick, Vardit
    McBride, Chris G
    Moreira, Santiago
    Özkundakci, Deniz
    Pilotti, Marco
    Rueda, Francisco J
    Rusak, James A
    Samal, Nihar R
    Schmid, Martin
    Shatwell, Tom
    Snorthheim, Craig
    Soulignac, Frédéric
    Valerio, Giulia
    van der Linden, Leon
    Vetter, Mark
    Vinçon-Leite, Brigitte
    Wang, Junbo
    Weber, Michael
    Wickramaratne, Chaturangi
    Woolway, R Iestyn
    Yao, Huaxia
    Hipsey, Matthew R
    A multi-lake comparative analysis of the General Lake Model (GLM): Stress-testing across a global observatory network2018In: Environmental Modelling & Software, ISSN 1364-8152, E-ISSN 1873-6726, Vol. 102, p. 274-291Article in journal (Refereed)
    Abstract [en]

    The modelling community has identified challenges for the integration and assessment of lake models due to the diversity of modelling approaches and lakes. In this study, we develop and assess a one-dimensional lake model and apply it to 32 lakes from a global observatory network. The data set included lakes over broad ranges in latitude, climatic zones, size, residence time, mixing regime and trophic level. Model performance was evaluated using several error assessment metrics, and a sensitivity analysis was conducted for nine parameters that governed the surface heat exchange and mixing efficiency. There was low correlation between input data uncertainty and model performance and predictions of temperature were less sensitive to model parameters than prediction of thermocline depth and Schmidt stability. The study provides guidance to where the general model approach and associated assumptions work, and cases where adjustments to model parameterisations and/or structure are required.

  • 93. Bråte, Jon
    et al.
    Logares, Ramiro
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berney, Cedric
    Ree, Dan Kristofer
    Klaveness, Dag
    Jakobsen, Kjetill S.
    Shalchian-Tabrizi, Kamran
    Freshwater Perkinsea and marine-freshwater colonizations revealed by pyrosequencing and phylogeny of environmental rDNA2010In: ISME Journal, ISSN 1751-7362, Vol. 4, no 9, p. 1144-1153Article in journal (Refereed)
    Abstract [en]

    Protist parasites are ecologically important, as they can have great impact on host population dynamics and functioning of entire ecosystems. Nevertheless, little is known about their prevalence in aquatic habitats. Here, we investigate the diversity and distributional patterns of the protist parasites Perkinsus and Parvilucifera (Perkinsea). Our approach included 454 pyrosequencing of the 18S rDNA gene obtained from a high-altitude lake (Lake Finsevatn, Norway) and phylogenetic analyses of all publicly available sequences related to Perkinsea. The applied PCR primers target a 450 bp region that encompass the variable V4 region of the 18S rDNA gene and have been optimized for the Titanium upgrade of the 454 technology. Nearly 5000 sequences longer than 150 bp were recovered from nearly all eukaryotic supergroups, and of those, 13 unique sequences were affiliated to Perkinsea. Thus, our new strategy for 454 amplicon sequencing was able to recover a large diversity of distantly related eukaryotes and previously unknown species of Perkinsea. In addition, we identified 40 Perkinsea sequences in GenBank generated by other recent diversity surveys. Importantly, phylogenetic analyses of these sequences identified 17 habitat-specific marine and freshwater clades (PERK 1-17). Hence, only a few successful transitions between these habitats have taken place over the entire history of Perkinsea, suggesting that the boundary between marine and fresh waters may constitute a barrier to cross-colonizations for intracellular parasites.

  • 94.
    Buck, Moritz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Nilsson, Louise K. J.
    Swedish Univ Agr Sci SLU, Dept Ecol, S-75007 Uppsala, Sweden..
    Brunius, Carl
    Swedish Univ Agr Sci SLU, Dept Food Sci, S-75007 Uppsala, Sweden..
    Dabire, Roch K.
    Inst Rech Sci Sante, Ctr Muraz, O1 BP 390, Bobo Dioulasso 01, Burkina Faso..
    Hopkins, Richard
    Swedish Univ Agr Sci SLU, Dept Ecol, S-75007 Uppsala, Sweden.;Univ Greenwich, Nat Resources Inst, Cent Ave, Chatham ME4 4TB, Kent, England..
    Terenius, Olle
    Swedish Univ Agr Sci SLU, Dept Ecol, S-75007 Uppsala, Sweden..
    Bacterial associations reveal spatial population dynamics in Anopheles gambiae mosquitoes2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 22806Article in journal (Refereed)
    Abstract [en]

    The intolerable burden of malaria has for too long plagued humanity and the prospect of eradicating malaria is an optimistic, but reachable, target in the 21st century. However, extensive knowledge is needed about the spatial structure of mosquito populations in order to develop effective interventions against malaria transmission. We hypothesized that the microbiota associated with a mosquito reflects acquisition of bacteria in different environments. By analyzing the whole-body bacterial flora of An. gambiae mosquitoes from Burkina Faso by 16 S amplicon sequencing, we found that the different environments gave each mosquito a specific bacterial profile. In addition, the bacterial profiles provided precise and predicting information on the spatial dynamics of the mosquito population as a whole and showed that the mosquitoes formed clear local populations within a meta-population network. We believe that using microbiotas as proxies for population structures will greatly aid improving the performance of vector interventions around the world.

  • 95.
    Buck, Moritz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Nilsson, Louise K. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Microbiology. Swedish Univ Agr Sci SLU, Dept Ecol, S-75007 Uppsala, Sweden..
    Brunius, Carl
    Swedish Univ Agr Sci SLU, Dept Food Sci, S-75007 Uppsala, Sweden..
    Dabire, Roch K.
    Inst Rech Sci Sante, Ctr Muraz, O1 BP 390, Bobo Dioulasso 01, Burkina Faso..
    Hopkins, Richard
    Swedish Univ Agr Sci SLU, Dept Ecol, S-75007 Uppsala, Sweden.;Univ Greenwich, Nat Resources Inst, Cent Ave, Chatham ME4 4TB, Kent, England..
    Terenius, Olle
    Swedish Univ Agr Sci SLU, Dept Ecol, S-75007 Uppsala, Sweden..
    Bacterial associations reveal spatial population dynamics in Anopheles gambiae mosquitoes2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 22806Article in journal (Refereed)
    Abstract [en]

    The intolerable burden of malaria has for too long plagued humanity and the prospect of eradicating malaria is an optimistic, but reachable, target in the 21st century. However, extensive knowledge is needed about the spatial structure of mosquito populations in order to develop effective interventions against malaria transmission. We hypothesized that the microbiota associated with a mosquito reflects acquisition of bacteria in different environments. By analyzing the whole-body bacterial flora of An. gambiae mosquitoes from Burkina Faso by 16 S amplicon sequencing, we found that the different environments gave each mosquito a specific bacterial profile. In addition, the bacterial profiles provided precise and predicting information on the spatial dynamics of the mosquito population as a whole and showed that the mosquitoes formed clear local populations within a meta-population network. We believe that using microbiotas as proxies for population structures will greatly aid improving the performance of vector interventions around the world.

  • 96.
    Burgmer, Tanja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Reiss, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wickham, Stephen A.
    Hillebrand, Helmut
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Effects of snail grazers and light on the benthic microbial food web in periphyton communities2010In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 61, no 2, p. 163-178Article in journal (Refereed)
    Abstract [en]

    Periphyton harbours a complex microbial food web with different trophic levels, but little is known about trophic interactions within this food web and its response to factors that potentially control the entire community. We used natural periphyton communities from Lake Erken (Sweden) in 2 experiments manipulating grazer presence. In addition to an ungrazed control, we included natural densities of either of 2 snail species (Theodoxus fluviatilis and Bithynia tentaculata) in order to test how generalist consumers affect different components of the periphyton. In the second experiment, we additionally manipulated light supply to alter the heterotroph-autotroph ratio in the periphyton and thus potentially the trophic interactions. In both experiments, grazer presence decreased algal biomass immediately and shifted the community composition from dominance of large filamentous forms to dominance of prostrate and motile unicellular species. Biomass of bacteria, heterotrophic nanoflagellates, ciliates and meiofauna also decreased with grazing, but with differentiated temporal dynamics and effect strength. In the ungrazed control, first heterotrophic protists and later meiofaunal biomass increased, indicating strong bottom-up and top-down propagation of trophic interactions in the microbial food web. High light increased the biomass of mixotrophic ciliates and nanoautotrophs but not total algal biomass. Grazer presence decreased algal richness in the second experiment, but increased evenness of the algal community under high light conditions. We conclude that grazer presence puts different pressure on the components of the periphyton, which are further linked by direct or indirect internal trophic processes.

  • 97. Camino-Serrano, Marta
    et al.
    Guenet, Bertrand
    Luyssaert, Sebastiaan
    Ciais, Philippe
    Bastrikov, Vladislav
    De Vos, Bruno
    Gielen, Bert
    Gleixner, Gerd
    Jornet-Puig, Albert
    Kaiser, Klaus
    Kothawala, Dolly
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lauerwald, Ronny
    Peñuelas, Josep
    Schrumpf, Marion
    Vicca, Sara
    Vuichard, Nicolas
    Walmsley, David
    Janssens, Ivan A.
    ORCHIDEE-SOM: Modeling soil organic carbon (SOC) and dissolved organic carbon (DOC) dynamics along vertical soil profiles in Europe2018In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 11, no 3, p. 937-957Article in journal (Refereed)
    Abstract [en]

    Current Land Surface Models (LSMs) typically represent soils in a very simplistic way, assuming soil organic carbon (SOC) as a bulk, thus impeding a correct representation of deep soil carbon dynamics. Moreover, LSMs generally neglect the production and export of dissolved organic carbon (DOC) from soils to rivers, leading to overestimations of the potential carbon sequestration on land. These common oversimplified processing of SOC in LSMs is partly responsible for the large uncertainty in the predictions of the soil carbon response to climate change. In this study, we present a new soil carbon module called ORCHIDEE-SOM, embedded within the land surface model ORCHIDEE, which is able to reproduce the DOC and SOC dynamics in a vertically discretized soil to two meters. The model includes processes of biological production and consumption of SOC and DOC, DOC adsorption on- and desorption from soil minerals, diffusion of SOC and DOC and DOC transport with water through and out of the soils to rivers. We evaluated ORCHIDEE-SOM against observations of DOC concentrations and SOC stocks from four European sites with different vegetation covers: a coniferous forest, a deciduous forest, a grassland and a cropland. The model was able to reproduce the SOC stocks along their vertical profiles at the four sites and the DOC concentrations within the range of measurements, with the exception of the DOC concentrations in the upper soil horizon at the coniferous forest. However, the model was not able to fully capture the temporal dynamics of DOC concentrations. Further model improvements should focus on a plant- and depth- dependent parameterization of the new input model parameters, such as the decomposition times of DOC and the microbial carbon use efficiency. We suggest that this new soil module, when parameterized for global simulations, will improve the representation of the global carbon cycle in LSMs, thus helping to constrain the predictions of the future SOC response to global warming.

  • 98.
    Cardoso, Simone J.
    et al.
    Laboratory of Aquatic Ecology, Federal University of Juiz de Fora, Juiz de Fora, Brazil.
    Vidal, Luciana O.
    Laboratory of Aquatic Ecology, Federal University of Juiz de Fora, Juiz de Fora, Brazil.
    Mendonça, Raquel F.
    Laboratory of Aquatic Ecology, Federal University of Juiz de Fora, Juiz de Fora, Brazil.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Fábio, Roland
    Laboratory of Aquatic Ecology, Federal University of Juiz de Fora, Juiz de Fora, Brazil.
    Spatial variation of sediment mineralization supports differential CO2 emissions from a tropical hydroelectric reservoir2013In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 4, p. 101-Article in journal (Refereed)
    Abstract [en]

    Substantial amounts of organic matter (OM) from terrestrial ecosystems are buried as sediments in inland waters. It is still unclear to what extent this OM constitutes a sink of carbon, and how much of it is returned to the atmosphere upon mineralization to carbon dioxide (CO2). The construction of reservoirs affects the carbon cycle by increasing OM sedimentation at the regional scale. In this study we determine the OM mineralization in the sediment of three zones (river, transition, and dam) of a tropical hydroelectric reservoir in Brazil as well as identify the composition of the carbon pool available for mineralization. We measured sediment organic carbon mineralization rates and related them to the composition of the OM, bacterial abundance and pCO2 of the surface water of the reservoir. Terrestrial OM was an important substrate for the mineralization. In the river and transition zones most of the OM was allochthonous (56 and 48%, respectively) while the dam zone had the lowest allochthonous contribution (7%). The highest mineralization rates were found in the transition zone (154.80 ± 33.50 mg C m-2 d-1) and the lowest in the dam (51.60 ± 26.80 mg C m-2 d-1). Moreover, mineralization rates were significantly related to bacterial abundance (r2= 0.50, p < 0.001) and pCO2 in the surface water of the reservoir (r2 = 0.73, p < 0.001). The results indicate that allochthonous OM has different contributions to sediment mineralization in the three zones of the reservoir. Further, the sediment mineralization, mediated by heterotrophic bacteria metabolism, significantly contributes to CO2supersaturation in the water column, resulting in higher pCO2 in the river and transition zones in comparison with the dam zone, affecting greenhouse gas emission estimations from hydroelectric reservoirs.

  • 99. Casas-Ruiz, Joan P.
    et al.
    Catalan, Nuria
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Gomez-Gener, Lluis
    von Schiller, Daniel
    Obrador, Biel
    Kothawala, Dolly
    Swedish University of Agricultural Sciences.
    Lopez, Pilar
    Sabater, Sergi
    Marce, Rafael
    A tale of pipes and reactors: Controls on the in-stream dynamics of dissolved organic matter in rivers2017In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 62, p. S85-S94Article in journal (Refereed)
    Abstract [en]

    The potential for rivers to alter the flux of dissolved organic matter (DOM) from land to ocean is widely accepted. Yet anticipating when and where rivers behave as active reactors vs. passive pipes of DOM stands as a major knowledge gap in river biogeochemistry, resulting in uncertainties for global carbon models. Here, we investigate the controls on in-stream DOM dynamics by evaluating changes in DOM concentration and composition along several reaches of a medium-sized river network over one full hydrological year. Roughly half of the observations over time and space showed active reactor conditions and, among these, similar pro-portion of gains and losses was measured. High water residence times promoted the active over passive behavior of the reaches, while DOM properties and nitrate availability determined whether they supplied or removed DOM from the river. Among different DOM fractions, protein-like DOM both of terrestrial and aquatic origin seemed to drive bulk DOM patterns. Our study emphasizes the role of water residence time as a physical constraint for in-stream processes, and provides new insights into the key factors governing the net balance between in-stream gains and losses of DOM in rivers.

  • 100.
    Casas-Ruiz, Joan P.
    et al.
    Catalan Inst Water Res ICRA, Emili Grahit 101, Girona 17003, Spain..
    Tittel, Joerg
    UFZ Helmholtz Ctr Environm Res, Dept Lake Res, Bruckstr 3a, D-39114 Magdeburg, Germany..
    von Schiller, Daniel
    Univ Basque Country, Fac Sci & Technol, Dept Plant Biol & Ecol, Apdo 644, Bilbao 48080, Spain..
    Catalan, Nuria
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Obrador, Biel
    Univ Barcelona, Dept Ecol, Av Diagonal 643, E-08028 Barcelona, Spain..
    Gomez-Gener, Lluis
    Univ Barcelona, Dept Ecol, Av Diagonal 643, E-08028 Barcelona, Spain..
    Zwirnmann, Elke
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Muggelseedamm 301, D-12587 Berlin, Germany..
    Sabater, Sergi
    Catalan Inst Water Res ICRA, Emili Grahit 101, Girona 17003, Spain.;Univ Girona, Inst Aquat Ecol, Girona 17071, Spain..
    Marce, Rafael
    Catalan Inst Water Res ICRA, Emili Grahit 101, Girona 17003, Spain..
    Drought-induced discontinuities in the source and degradation of dissolved organic matter in a Mediterranean river2016In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 127, no 1, p. 125-139Article in journal (Refereed)
    Abstract [en]

    The composition of dissolved organic matter (DOM) in rivers results from the different sources and in-stream transformations along the land to ocean aquatic continuum. Riverine DOM sources are highly dependent on the hydrological connection between the river channel and the surrounding terrestrial ecosystems, but how the lack of this connectivity (e.g., during drought episodes) affects the sources and biodegradation of DOM in rivers remains unclear. Here we identified the DOM sources as well as the different DOM pools that are respired along a Mediterranean river during drought by combining absorbance-fluorescence spectroscopy, size-exclusion chromatography, biodegradation assays, and stable and radiocarbon isotopes. DOM composition was highly heterogeneous along the river in response to different sources and in-stream processes in each distinct aquatic environment (i.e., isolated water pools, running waters, and impounded waters in weirs). The reduced hydrological connectivity with terrestrial ecosystems promoted the influence of autochthonous DOM sources. Still, tree leaves from overhanging canopies stood out as an important terrestrial DOM source, especially in sites where water residence time was high such as isolated pools and weirs. Degradation of leaf leachates was a relevant process in these sites, whereas autochthonous DOM and groundwater millennial DOM (> 1300 year B.P.) seemed to be degraded in running waters. Overall, our results highlight that the drought-induced hydrological disconnection entails a great spatial heterogeneity in the sources of DOM, which at the same time determines the different DOM pools that are respired in each environment along the river.

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