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  • 1. Bergfur, J.
    et al.
    Johnson, J.K
    Sandin, L.
    Goedkoop, W.
    Nygren, kristiina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Effects of nutrient enrichment on boreal streams: Invertebrates, fungi and leaf-litter breakdown2007In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 52, no 8, p. 1618-1633Article in journal (Refereed)
    Abstract [en]

    Summary 1. The effect of nutrient enrichment on structural (invertebrate indices) and functional (leaf-litter breakdown rates) characteristics of stream integrity was studied in nine boreal streams.2. The results showed predicted changes in biotic indices and leaf-litter breakdown along a complex (principal component) nutrient gradient. Biotic indices were better correlated with nutrient effects than leaf-litter breakdown.3. Fungal biomass and invertebrate densities in the litter bags were positively correlated with leaf-litter breakdown, and both were also positively related to the nutrient gradient.4. Invertebrate community composition influenced breakdown rate. High breakdown rates at one site were associated with the high abundance of the detritivore Asellus aquaticus. 5. This study lends support to the importance of invertebrate and fungi as mediators of leaf-litter decomposition. However, our study also shows that study design (length of incubation) can confound the interpretation of nutrient-induced effects on decomposition.

  • 2. Bergström, Ann-Kristin
    et al.
    Bigler, Christian
    Stensdotter, Ulrika
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Composition and dispersal of riverine and lake phytoplankton communities in connected systems with different hydraulic retention times2008In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 53, no 12, p. 2520-2529Article in journal (Refereed)
    Abstract [en]

    1. Lake phytoplankton community structure may be influenced by both internal factors (predation, competition, resource constraints) and external ones, such as dispersal of materials and cells between connected habitats. However, little is known about the importance of cell dispersal for phytoplankton community structure in lakes.

    2. We investigated the abundance and dispersal of phytoplankton cells between connected rivers and lakes, and analysed whether similarities in phytoplankton community composition between rivers and lakes were primarily related to cell import rates or to characteristics of the local habitat. We focused on lakes along a gradient of theoretical water retention times (TWRT). Two data sets from Swedish lakes were used; a seasonal study of two connected boreal forest lakes, differing in TWRT, and a multi-lake study of 13 lakes with a continuous range of TWRTs.

    3. Phytoplankton cells were transported and dispersed in all investigated rivers. In the seasonal study, cell import rates and similarities in phytoplankton community composition between the lake and its inlet(s) were much higher in the lake with a shorter TWRT. Phytoplankton community structure in different habitats was associated with total organic carbon (TOC). This indicates that local habitat characteristics may be important in determining lake phytoplankton community composition, even in the presence of substantial cell import.

    4. The multi-lake study also showed a negative relationship between TWRT and similarities in phytoplankton community composition between inlets and lakes. Moreover, similarity in community structure was related to both cell import rates from inlet to lake and differences in habitat characteristics between inlet and lake. However, the variable most strongly correlated with community structure was TOC, indicating that species sorting rather than a mass effect was the most important mechanism underlying the correlation between community structure and retention time.

    5. Overall, our data suggest that local habitat characteristics may play a key role in determining community similarity in this set of lakes covering a large range of habitat connectedness. Due to the strong co-variations between cell dispersal and TOC, it was hard to unequivocally disentangle the different mechanisms; hence, there is a need for further studies of the role of dispersal for phytoplankton community structures

  • 3.
    Beven, Keith J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Alcock, Ruth E.
    Modelling everything everywhere: a new approach to decision-making for water management under uncertainty2012In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, p. 124-132Article in journal (Refereed)
    Abstract [en]

    1. There are increasing demands to predict ecohydrological responses to future changes in catchments but such predictions will be inevitably uncertain because of natural variability and different sources of knowledge (epistemic) uncertainty. 2. Policy setting and decision-making should therefore reflect these inherent uncertainties in both model predictions and potential consequences. 3. This is the focus of a U.K. Natural Environment Research Council knowledge exchange project called the Catchment Change Network (CCN). The aim is to bring academics and practitioners together to define Guidelines for Good Practice in incorporating risk and uncertainty into assessments of the impacts of change. 4. Here, we assess the development of such Guidelines in the context of having catchment models of everywhere.

  • 4.
    Brunberg, Anna-Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Nilsson, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Blomqvist, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Characteristics of oligotrophic hardwater lakes in a postglacial land-rise area in mid-Sweden2002In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 47, no 8, p. 1451-1462Article in journal (Refereed)
    Abstract [en]

    1. We describe some remarkable ephemeral, oligotrophic hardwater lakes formed becauseof land rise in the coastal areas of the Baltic Sea, that are unique in Sweden and probablyalso worldwide. Two younger, coastal lakes were studied by regular sampling for 1 yearand compared with an older (i.e. greater altitude) lake, that passed through theoligotrophic hardwater stage some 3–4000 years ago.

    2. Despite some differences in composition of the catchment, the two younger lakes weresimilar with regard to water chemistry and plankton community composition. Theconcentration of phosphorus was low while nitrogen was high, resulting in very high N/Pquotients (101 and 131). Although water colour was moderate, the concentration of organiccarbon was extremely high (average values of ‡ 20 lg TOC L–1), consisting mainly ofdissolved compounds (DOC).

    3. While the plankton was poorly developed, sediments in both lakes were covered by alayer of photosynthesising micro-organisms. This substantial 'microbial mat', which hasnot been described in detail before, was up to 15 cm thick and dominated by cyanobacteriaand purple sulphur bacteria. The concentration of sediment phosphorus was extremelylow (352 lg g–1 dw) in one of the lakes and dominated by organic-bound (residual)phosphorus.

    4. Deep sediments in the older lake, representing its oligotrophic hardwater period,differed in phosphorus composition from the currently oligotrophic hardwater lakes byhaving a strong dominance of HCl-extractable (Ca-bound) phosphorus. This indicates thatphosphorus, initially organic-bound within the microbial mat, is subsequently bound tocalcium. We hypothesise that this is promoted by the environmental conditions created bythe benthic photosynthetic activity, in combination with the prevailing hardwaterconditions.

    5. The rich and flourishing microbial community on the sediments may also explain thehigh concentration of DOC in the lake.

  • 5.
    de Melo, Michaela L
    et al.
    Departamento de Hidrobiologia, Universidade Federal de São Carlos, São Carlos, Brazil.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Amaral, João Henrique F
    Coordenação de Dinâmica Ambiental, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil.
    Barbosa, Pedro M
    Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
    Forsberg, Bruce R
    Coordenação de Dinâmica Ambiental, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil.
    Sarmento, Hugo
    Departamento de Hidrobiologia, Universidade Federal de São Carlos, São Carlos, Brazil.
    Flood pulse regulation of bacterioplankton community composition in an Amazonian floodplain lake2019In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 64, no 1, p. 108-120Article in journal (Refereed)
    Abstract [en]

    Understanding spatial and temporal dynamics of microbial communities is a central challenge in microbial ecology since microorganisms play a key role in ecosystem functioning and biogeochemical cycles. Amazonian aquatic systems comprise a dynamic mosaic of heterogeneous habits but are understudied and there is limited information about the mechanisms that shape bacterial community composition (BCC). There is a consensus that environmental selection (species sorting) and dispersal processes (source?sink dynamics) act in concert to shape the composition of these communities, but the relative importance of each mechanism may vary dramatically through time and between systems. Applying 16S rRNA gene amplicon high-throughput sequencing, we studied factors and processes that modulate BCC in an Amazonian floodplain lake and used source-tracking models to trace the main dispersal sources of microorganisms in the whole floodplain system during a full hydrological cycle. Our source-tracking models indicated that dispersal processes were predominant, explaining most of the BCC variability throughout the study period. We observed more sources contributing to the sink community during the falling water than rising water period, when contributions from the Solim?es River dominated. There was a clear seasonal pattern in BCC, closely related to environmental variables, suggesting that the successful establishment of dispersing bacteria also depends on environmental filtering that is linked to water flow. In summary, source?sink dynamics and species sorting were strongly affected by water exchange and connectivity with the main river that varied throughout the flood pulse cycle. Our results demonstrated the influence of lateral transport and temporal dynamics on BCC in Amazonian floodplain lakes that could ultimately impact regional carbon budgets and biogeochemical cycles.

  • 6.
    Drakare, Stina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Liess, Antonia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Local factors control the community composition of cyanobacteria in lakes while heterotrophic bacteria follow a neutral model2010In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 55, no 12, p. 2447-2457Article in journal (Refereed)
    Abstract [en]

    1. Neutral community models are derived from the proposition that basic probabilities of species loss (extinction, emigration) and gain (immigration, speciation) explain biological community structure, such that species with many individuals are very likely to be widespread. Niche models on the other hand assume that interactions between species and differential resource use mediate species coexistence, thus invoking environmental factors to explain community patterns. 2. In this study, we compared neutral and niche models to test how much of the spatial variability of assemblages of heterotrophic bacteria and phytoplankton in 13 lakes they could explain. Analysis of phytoplankton was restricted to cyanobacteria, so that they could be studied with the same molecular fingerprinting method, automated ribosomal intergenic spaces analysis (ARISA), as heterotrophic bacteria. We determined local biotic and abiotic lake variables as well as lake age, glacial history and distance between sites. 3. The neutral community model had a good fit to the community composition of heterotrophic bacteria (R-2 = 0.69), whereas it could not produce a significant model for the community composition of cyanobacteria. 4. The community composition of cyanobacteria was instead correlated to environmental variables. The best model, a combination of total organic carbon, biomass of eukaryotic phytoplankton, pH and conductivity, could explain 8% of the variation. In contrast, variation in the community composition of heterotrophic bacteria was not predicted by any of the environmental variables. Historical and spatial variables were not correlated to the community composition of either group. 5. The pattern found for heterotrophic bacteria suggests that stochastic processes are important. The correlation of cyanobacteria with local environmental variables alone is consistent with the niche model. We suggest that cyanobacteria, a group of organisms containing bloom-forming species, may be less likely to fit a neutral community model, since these blooms are usually triggered by a particular combination of environmental conditions.

  • 7.
    Fischer, Helmut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bergfur, Jenny
    Goedkoop, Willem
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Microbial leaf degraders in boreal streams: bringing together stochastic and deterministic regulators of community composition2009In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 54, no 11, p. 2276-2289Article in journal (Refereed)
    Abstract [en]

    Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream. 2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within-streams, although communities differed more strongly between streams. 3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition. 4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in-stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.

  • 8.
    Flenner, Ida
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
    Richter, Otto
    Suhling, Frank
    Rising temperature and development in dragonfly populations at different latitudes2010In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 55, no 2, p. 397-410Article in journal (Refereed)
    Abstract [en]

    1. For modelling the future ecological responses to climate change, data on individual species and on variation within and between populations from different latitudes are required. 2. We examined life cycle regulation and growth responses to temperature in Mediterranean and temperate populations of a widespread European odonate, Orthetrum cancellatum. In an experiment, offspring from individual females from different parts of the range were kept separately to elucidate differences between families. 3. The experiment was run outdoors at 52 degrees N at a natural photoperiod for almost a year. We used four temperature regimes, ambient (i.e. following local air temperature) and ambient temperature increased by 2, 4 and 6 degrees C, to mimic future temperature rise. A mathematical model was used to categorise the type of seasonal regulation and estimate parameters of the temperature response curve. 4. Growth rate varied significantly with temperature sum, survival and geographic origin, as well as with family. Offspring of all females from the temperate part of the range had a life cycle with a 12 h day-length threshold necessary to induce diapause (i.e. diapause was induced once day length fell below 12 h). By contrast, Mediterranean families had a 10 h threshold or had an unregulated life cycle allowing winter growth. The temperature response did not significantly differ between populations, but varied between families with a greater variation in the optimum temperature for growth in the Mediterranean population. 5. The variation in seasonal regulation leads to a diversity in voltinism patterns within species, ranging from bivoltine to semivoltine along a latitudinal gradient. Given that the type of seasonal regulation is genetically fixed, rising temperatures will not allow faster than univoltine development in temperate populations. We discuss the consequences of our results in the light of rising temperature in central Europe.

  • 9.
    Grasset, Charlotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Abril, Gwenaël
    Guillard, Ludovic
    Delolme, Cécile
    Bornette, Gudrun
    Carbon emission along a eutrophication gradient in temperate riverine wetlands: effect of primary productivity and plant community composition2016In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 61, p. 1405-1420Article in journal (Refereed)
    Abstract [en]

    Eutrophication increases primary productivity and favours the predominance of floating vegetation in wetlands. Carbon (C) fluxes in wetlands are strongly driven by primary productivity and can differ by vegetation type. However, to the best of our knowledge, the role of eutrophication in C fluxes has rarely been assessed. Consequently, we aimed to measure the seasonal variation in carbon dioxide (CO2) and methane (CH4) fluxes at six aquatic sites in four temperate wetlands, ranging along a gradient of sediment total phosphorus content, and determine whether C fluxes correlate with above-ground net primary productivity (ANPP) and plant community composition along this eutrophication gradient. Daytime CO2 emissions were significantly and negatively correlated with wetland net primary productivity as a result of the greater C fixation by photosynthesis during the peak of production. Conversely, CH4 emissions were significantly and positively correlated with wetland ANPP, possibly due to higher litter production and anaerobic decomposition. The highest CH4 emissions were observed above floating vegetation, which favoured hypoxic conditions in the water column. CH4 emissions including ebullition were higher above macroalgal belts than above vascular plants with floating leaves. CH4 emissions without ebullition (i.e. resulting from plant transport and diffusion) better correlated with the abundance of macroalgae than with the abundance of vascular plants with floating leaves. Our results suggest that eutrophication may greatly modify CO2 and CH4 emissions from wetlands through changes in vegetation type and productivity.

  • 10.
    Grubisic, Lorena M.
    et al.
    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.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Heinrich, Friederike
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Brutemark, Andreas
    Tvarminne Zool Stn, Hango, Finland.;Novia Univ Appl Sci, ARONIA Coastal Zone Res Team, Ekenas, Finland.;Abo Akad Univ, Ekenas, Finland..
    Alonso-Sáez, Laura
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Andersson, Anders F.
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. KTH Royal Inst Technol & Sci Life Lab, Sch Biotechnol, Stockholm, Sweden.
    Gantner, Stephan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab. Leibniz Inst Sci & Math Educ, Dept Educ Sci Biol, Kiel, Germany..
    Riemann, Lasse
    Univ Copenhagen, Dept Biol, Marine Biol Sect, Helsingor, Denmark..
    Beier, Sara
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Leibniz Inst Balt Sea Res Warnemunde IOW, Rostock, Germany..
    Lake bacterioplankton dynamics over diurnal timescales2017In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 62, no 1, p. 191-204Article in journal (Refereed)
    Abstract [en]

    1. Planktonic bacterial community dynamics over short timescales can be of great importance for food webs and ecosystem functioning but are rarely described when microbial community and composition are assessed. To study the significance of such dynamics we sampled the surface water at the deepest point of a mesotrophic lake (Lake Erken, Sweden) every third hour over two days. 2. By combining 454 pyrosequencing of 16S rRNA genes with bromodeoxyuridine immunocapturing of DNA, replicating populations were identified and compared to the community retrieved from total DNA samples. This comparison revealed a significant difference between the actively replicating and total community. 3. The high-frequency diurnal sampling was compared to a year-long survey conducted in the same lake in order to compare the diurnal and seasonal variation in bacterioplankton community composition. At the diurnal-scale, the variation was significantly higher in the replicating than in the total community. However, variation in both active and total diurnal community was significantly lower than the variation in the seasonal total community. 4. Our analysis revealed pronounced short-term dynamics of individual bacterial populations uncoupled from the diurnal light cycle. For example, the proliferating fraction of the most abundant bacterial tribe (LD12) followed a cyclic pattern that covaried with viral abundance. This implies that environmental factors other than light may act as important drivers of microbial community composition, at least in mesotrophic Lake Erken.

  • 11. Jennings, Eleanor
    et al.
    Jones, Stuart
    Arvola, Lauri
    Staehr, Peter A.
    Gaiser, Evelyn
    Jones, Ian D.
    Weathers, Kathleen C.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Chiu, Chih-Yu
    De Eyto, Elvira
    Effects of weather-related episodic events in lakes: an analysis based on high-frequency data2012In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, no 3, p. 589-601Article in journal (Refereed)
    Abstract [en]

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

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

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

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

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

  • 12.
    Jeske, Jan Torsten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Helmholtz Ctr Environm Res, Dept Environm Microbiol, Leipzig, Germany.
    Müller, Roger Andre
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wendeberg, Annelie
    Helmholtz Ctr Environm Res, Dept Environm Microbiol, Leipzig, Germany.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Microscale decoupling of sediment oxygen consumption and microbial biomass in an oligotrophic lake2016In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 61, no 9, p. 1477-1491Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Karlsson-Elfgren, Irene
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Rengefors, Karin
    Gustafsson, Susanne
    Factors regulating recruitment from the sediment to the water column in the bloom-forming cyanobacterium Gloeotrichia echinulata2004In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 49, no 3, p. 265-273Article in journal (Refereed)
    Abstract [en]

    Summary

    1. The influence of light, temperature, sediment mixing and sediment origin (water depth) on the recruitment of the cyanobacterium Gloeotrichia echinulata was examined in the laboratory.

    2. Light and temperature were the most important factors initiating germination in G. echinulata.

    3. The extent of germination (recruited biovolume) was mainly regulated by temperature and sediment mixing. Furthermore, sediment mixing significantly enhanced the frequency of observed heterocysts and colonies.

    4. Despite the fact that the deep and shallow sediments contained a similar number of akinete colonies, the highest recruitment occurred from shallow sediments, indicating that akinetes from shallow sediments have a higher viability than those from deeper parts of the lake.

    5. Our results support the hypothesis that shallow sediments are more important than profundal sediments for the recruitment of G. echinulata to the pelagic zone.

  • 14.
    Liess, Antonia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Drakare, Stina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Kahlert, M.
    Atmospheric nitrogen-deposition may intensify phosphorus limitation of shallow epilithic periphyton in unproductive lakes2009In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 54, no 8, p. 1759-1773Article in journal (Refereed)
    Abstract [en]

    1. We tested whether increasing atmospheric nitrogen (N) deposition along a north-south gradient intensifies epilithic phosphorus (P) limitation in oligotrophic Swedish lakes from the north to the south. We examined the epilithic community at a shallow depth from seven northern and six southern Swedish lakes, and also compared the results with a lake located geographically between the two groups. We determined lake nutrient state, epilithic nutrient ratios and epilithic algal composition, as well as grazer N : P ratios, grazer-epilithon N : P imbalance, and N : P cycling ratios. 2. Epilithic communities appear to be generally more N-limited in the northern lakes and more P-limited in the southern lakes. Lake water total N (Tot-N) and epilithic N : P ratios were lower in northern than in southern lakes and the proportion of N2-fixing cyanobacteria was higher in northern than in southern lakes. 3. Gastropod grazers had lower N : P imbalances and cycled less N relative to P in northern than in southern lakes. 4. Atmospheric N-deposition showed a strong positive correlation with lake water Tot-N and a much weaker positive correlation with epilithon N : P ratios. Atmospheric N-deposition also correlated negatively with the proportion of N2- fixing cyanobacteria. 5. There are indications that increased atmospheric N-deposition towards the south might intensify P-limitation of epilithic algae and invertebrate grazers, although more studies are needed to show the strength and generality of our findings.

  • 15.
    Liess, Antonia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Haglund, Ann-Louise
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Periphyton responds differentially to nutrients recycled in dissolved or faecal pellet form by the snail grazer Theodoxus fluviatilis2007In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 52, no 10, p. 1997-2008Article in journal (Refereed)
    Abstract [en]

    1. We aimed to separate the effects of grazers on periphyton via grazing from that of nutrient recycling from their faecal pellets.2. We set up three different experimental treatments (snails/no snails/faecal pellets) and sampled over 16 days. The `snail' treatment contained a low density (snail biomass c. 14 g−2) of the gastropod grazer Theodoxus fluviatilis and the `faecal pellet' treatment received the same amount of faecal pellets as were produced in the `snail' treatment. Whereas the `faecal pellet' treatment provided extra nutrients to periphyton from the faeces, the `snail' treatment provided nutrients in the form of both faeces and in excreta. There was also direct grazing on periphyton in the `snail' treatment. The `no snail' was not grazed and received no nutrients in faeces or excreta. 3. We measured periphyton C, N and P content, chlorophyll-a (chl-a), primary production, bacterial biomass, bacterial production and bacterial respiratory activity. In the water column we measured dissolved inorganic N and soluble reactive P. 4. Snails increased the amount of dissolved inorganic N in the water. On day 16, the periphyton N : P ratio in the `faecal pellet' treatment was lower, and periphyton P content was higher, than in the other two treatments. N : P ratios decreased over time in the `faecal pellet' treatment. Primary and bacterial production were positively correlated in all treatments.5. Algal chl-a and primary production of periphyton per unit area and periphyton chl-a : C ratios increased over the 16 day in the `snail' treatment, and thus excretion of dissolved N by snails had a stronger positive effect on the periphyton community than N and P in faecal pellets. 6. Our data show that excretion and egestion can have different effects on periphyton, probably because of the higher proportion of dissolved N in excreta and the higher proportion of P recycled in faecal pellets. The relative effect of nutrients recycled in egesta or in excretions, probably depends on the form of nutrient limitation of the periphyton. Further, the different components of the periphyton matrix could react differently to the different forms of nutrient recycling.7. We conclude that direct grazing effects are less important than nutrient effects when nutrients are limiting and grazing pressure is low. Further, the spatial separation of different grazing effects can lead to differences in periphyton production and nutrient stoichiometry. This might be an explanation for the patchiness of periphyton in nature.

  • 16. Lischke, Betty
    et al.
    Mehner, Thomas
    Hilt, Sabine
    Attermeyer, Katrin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Leibniz Inst Freshwater Ecol & Inland Fisheries, Stechlin, Germany.
    Brauns, Mario
    Brothers, Soren
    Grossart, Hans Peter
    Köhler, Jan
    Scharnweber, Kristin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Leibniz Inst Freshwater Ecol & Inland Fisheries, Berlin, Germany.
    Gaedke, Ursula
    Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes2017In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 62, no 10, p. 1693-1706Article in journal (Refereed)
    Abstract [en]

    1. The sum of benthic autotrophic and bacterial production often exceeds the sum of pelagic autotrophic and bacterial production, and hence may contribute sub- stantially to whole-lake carbon fluxes, especially in shallow lakes. Furthermore, both benthic and pelagic autotrophic and bacterial production are highly edible and of sufficient nutritional quality for animal consumers. We thus hypothesised that pelagic and benthic transfer efficiencies (ratios of production at adjacent trophic levels) in shallow lakes should be similar. 2. We performed whole ecosystem studies in two shallow lakes (3.5 ha, mean depth 2 m), one with and one without submerged macrophytes, and quantified pelagic and benthic biomass, production and transfer efficiencies for bacteria, phytoplank- ton, epipelon, epiphyton, macrophytes, zooplankton, macrozoobenthos and fish. We expected higher transfer efficiencies in the lake with macrophytes, because these provide shelter and food for macrozoobenthos and may thus enable a more efficient conversion of basal production to consumer production. 3. In both lakes, the majority of the whole-lake autotrophic and bacterial produc- tion was provided by benthic organisms, but whole-lake primary consumer pro- duction mostly relied on pelagic autotrophic and bacterial production. Consequently, transfer efficiency of benthic autotrophic and bacterial production to macrozoobenthos production was an order of magnitude lower than the transfer efficiency of pelagic autotrophic and bacterial production to rotifer and crustacean production. Between-lake differences in transfer efficiencies were minor. 4. We discuss several aspects potentially causing the unexpectedly low benthic transfer efficiencies, such as the food quality of producers, pelagic–benthic links, oxygen concentrations in the deeper lake areas and additional unaccounted con- sumer production by pelagic and benthic protozoa and meiobenthos at interme- diate or top trophic levels. None of these processes convincingly explain the large differences between benthic and pelagic transfer efficiencies. 5. Our data indicate that shallow eutrophic lakes, even with a major share of auto- trophic and bacterial production in the benthic zone, can function as pelagic sys- tems with respect to primary consumer production. We suggest that the benthic autotrophic production was mostly transferred to benthic bacterial production, which remained in the sediments, potentially cycling internally in a similar way to what has previously been described for the microbial loop in pelagic habitats. Understanding the energetics of whole-lake food webs, including the fate of the substantial benthic bacterial production, which is either mineralised at the sedi- ment surface or permanently buried, has important implications for regional and global carbon cycling

  • 17.
    Lymer, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Changing phosphorus concentration and subsequent prophage induction alter composition of a freshwater viral assemblage2010In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 55, no 9, p. 1984-1996Article in journal (Refereed)
    Abstract [en]

    P>1. The effects of nutrients on the temporal variation in viral assemblage composition, and in particular the occurrence of temperate phages, were assessed in mesotrophic Lake Erken over 5 months of the ice-free period. The percentage of the bacterial community that contained inducible prophages (lysogenic bacteria, LB) changed over the season, being lowest in late spring and highest in early autumn. The most important variables for predicting LB were concentrations of total nitrogen (TN), total phosphorus (TP) and temperature. 2. The viral assemblage composition, as determined by pulsed-field gel electrophoresis (PFGE), also changed over the season. Prophages were induced by incubations with mitomycin C and we show, for the first time for natural communities, that the resulting temperate phages could be detected using PFGE. 3. A substantial fraction (19%) of the number of detected operational taxonomic units (OTUs: defined as unique genome sizes) appeared unique to temperate phages and 41% of OTUs increased in relative abundance after treatment with mitomycin C. 4. Different viral OTUs were induced at different times during the season. The most important environmental factor covarying with viral assemblage composition over the period of study, as determined by multivariate analysis, was concentration of TP. In re-growth cultures with natural bacteria and lowered viral abundance (VA) (decreased virus to bacteria ratio), addition of PO4-P induced prophages and resulted in subsequent production of temperate phages, as indicated by a decreased percentage of LB and increased VA. Incubations of natural bacterial communities with mitomycin C (field data) or PO4-P (experiment) changed the viral assemblage composition at a similar rate as the observed monthly changes in the lake.

  • 18.
    Lymer, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Vrede, Katarina
    Variable importance of viral-induced bacterial mortality along gradients of trophic status and humic content in lakes2008In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 53, no 6, p. 1101-1113Article in journal (Refereed)
    Abstract [en]

    1. The goals of this study were to assess which environmental gradients can be important in predicting viral abundance (VA), the frequency of virus-infected cells (FVIC) and burst size (BS), and to assess which lake characters favour viral-induced bacterial mortality (VBM) as opposed to potential grazer-induced bacterial mortality (PGBM). 2. The epilimnion and hypolimnion of 21 lakes differing in trophic status and humic content were investigated. Samples were obtained for viral and bacterial abundance, the FVIC and burst size, flagellate and ciliate abundances and water chemistry. The potential importance of VBM in relation to PGBM was calculated based on data on FVIC and flagellate and ciliate abundance. 3. Partial least squares regression (PLS) analysis showed that VA as well as the ratio between viral and bacterial abundance were positively related to inorganic nutrient concentrations, dissolved organic carbon concentration, chlorophyll-a concentration and bacterial production. 4. The PLS model also revealed that FVIC decreased with increasing trophic status whereas BS increased. Furthermore, potential grazing was positively related to increasing trophic status and decreasing humic content. PGBM appeared to be dominating over VBM in the majority of lakes sampled, especially in the epilimnion. 5. Thus, the relative importance of viruses for bacterial mortality was potentially highest in humic lakes of medium trophic status and it was also greater in the hypolimnion than in the epilimnion.

  • 19.
    Lymer, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Logue, Jürg Brendan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Brussaard, Corina P. D.
    Baudoux, Anne-Claire
    Vrede, Katarina
    Lindström, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Temporal variation in freshwater viral and bacterial community composition2008In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 53, no 6, p. 1163-1175Article in journal (Refereed)
    Abstract [en]

    1. The goal of this study conducted in three lakes differing in nutrient content and size was to assess the temporal variation in viral community composition and possible co-variation with compositional changes in bacterial communities.   

    2. The viral community composition differed among lakes and changed over the season. Changes could also be detected on short-time scales, i.e. over a few days. These changes were comparable in magnitude to the changes detected between months or seasons.   

    3. The most important environmental factors co-varying with viral community composition, as determined by multivariate analysis, differed over the year and among lakes. Temperature and concentrations of dissolved organic carbon (DOC), total phosphorus and soluble reactive phosphorus were the most important factors.

    4. Bacterial community composition also varied over the season and among lakes. The most important factors co-varying with bacterial community composition, as determined by multivariate analysis, were also temperature and DOC concentration.

    5. Correlation between viral and bacterial community composition was weak and appeared to be a result of an indirect connection rather than a direct relationship between bacteria and viruses.

  • 20.
    Naddafi, Rahmat
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Pettersson, Kurt
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Eklöv, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    The effect of seasonal variation in selective feeding by zebra mussels (Dreissena polymorpha) on phytoplankton community composition2007In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 52, no 5, p. 823-842Article in journal (Refereed)
    Abstract [en]

    To investigate the impact of zebra mussels (Dreissena polymorpha) on phytoplankton community composition, temporal variability in selective feeding by the mussels was determined from April to November 2005 in a natural lake using Delayed Fluorescence (DF) excitation spectroscopy. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics; mussels showed a consistent preference for cryptophytes and avoidance of chlorophytes and cyanobacteria. Diatoms, chrysophytes and dinoflagellates responded differentially to zebra mussel grazing depending on their size. Analysis of excreted products of the zebra mussels revealed that in addition to chlorophytes and cyanobacteria, phytoplankton >50 μm and very small phytoplankton (≤7 μm) were largely expelled in pseudofaeces. The zebra mussel is a selective filter-feeder that alters its feeding behaviour in relation to phytoplankton composition to capture and ingest high quality phytoplankton, especially when phytoplankton occur in preferred size ranges. Flexibility of zebra mussel feeding behaviour and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences.

  • 21.
    Persson, Irina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Jones, Ian D.
    The effect of water colour on lake hydrodynamics: a modelling study2008In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 53, no 12, p. 2345-2355Article in journal (Refereed)
    Abstract [en]

    1. The one-dimensional equation solver, PROgram for Boundary layers in the Environment, was used to simulate the temperature structure of Lake Erken, a medium-sized Swedish lake, assuming differing extinction coefficients for a series of modelled years driven by observed meteorological data and by a set of idealized meteorological data. Results suggested that, as expected, larger extinction coefficients initially led to surface waters becoming warmer. The reverse was true late in the summer, however, as the warming induced by greater absorption of solar radiation was outweighed by the cooling effects of entrained colder hypolimnetic water. 3. There was between a two- and fourfold inter-annual variation in the effects on key physical lake parameters, induced by changing extinction coefficient, such as maximum heat flux, heat content and Schmidt stability. 4. The change in surface heat flux induced by a change in extinction coefficient was up to almost 50 W m(-2). In the summer, changes in extinction coefficient from 0.5 to 0.2 m(-1) led to a dramatic shift in the duration of the stratified period as well as to enormous changes in Schmidt stability and hypolimnetic temperature. 6. Future changes to extinction coefficients of small and medium-sized lakes are likely to have wide-ranging effects on lake thermal structure and ecology.

  • 22.
    Sniegula, Szymon
    et al.
    Polish Acad Sci, Dept Ecosyst Conservat, Inst Nat Conservat, Krakow, Poland.
    Nsanzimana, Jean d'Amour
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Johansson, Frank
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Predation risk affects egg mortality and carry over effects in the larval stages in damselflies2019In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 64, no 4, p. 778-786Article in journal (Refereed)
    Abstract [en]

    The non-consumptive predator effect may incur physiological costs that affect growth and development and ultimately survival. While studies have shown that the effect can affect development and growth in organisms with complex life cycles, we have limited knowledge on the effect in the egg and early larval stage. Here, we used a laboratory experiment to examine how the presence of chemical cues, a non-consumptive predator effect, from an aquatic predator, perch, affected hatching success of larvae in three species of damselfly, Ischnura elegans, Coenagrion pulchellum, and Enallagma cyathigerum. In addition, we examined how exposure to predation risk in the early larval stages affected growth in the late larval stages of I. elegans. We found that the presence of chemical predator cues (1) increased egg mortality in all three species, (2) caused earlier hatching of eggs in one species, no change in a second species and a delay in egg hatching in a third species. We also found that predator cues have the potential to cause a carryover effect from early larval stages to late larval stages in terms of larval growth rate. The addition of non-consumptive predator cues in the form of fish water caused higher algal growth than in the control experimental containers, and we suggest that this algal growth has the potential to confound predator stress cues. Our results show that the non-consumptive predator effects affect survival and growth, and hence they have the potential to affect predator-prey dynamics in natural systems. Future studies on such effects in aquatic systems should consider confounding stressors, such as algae, fungi, oxygen, and nutrients levels, that might come with the addition of predation cues in water and thus add additional stress.

  • 23.
    Szabó, Katalin É.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Makk, Judit
    Kiss, Keve Tihamér
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ács, Éva
    Tóth, Bence
    Kiss, Áron Keve
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Sequential colonization of river periphyton analysed by microscopy and molecular fingerprinting2008In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 53, no 7, p. 1359-1371Article in journal (Refereed)
    Abstract [en]

    1. An artificial glass substratum was incubated in the River Danube for a period of 28 days in order to detect the sequential colonization of microorganisms.

    2. Light and fluorescent microscopy showed that microalgae and the picoalgal fraction on the slides increased rapidly over the first 2 weeks of colonization. Diatoms were numerically the most abundant component of the periphyton and their species richness and diversity increased rapidly in the early phase of colonization whereas diversity subsequently increased moderately.

    3. Evenness of the diatom community was initially high, lower in the intermediate phase and again higher later on. Succession involving early, intermediate and late colonizer species was observed. Community composition during the first 5 days of colonization was very different from later stages whereas there were only minor changes subsequently.

    4. Molecular community analysis by means of terminal restriction fragment length polymorphism analysis of PCR amplified 16S rRNA and 18S rRNA genes pointed to even larger differences between the composition of samples obtained early and late in the period.

    5. The number of 18S rRNA and 16S rRNA terminal restriction fragments (T-RF-s) was variable over the colonization period and the fragment patterns of both the bacterial and eukaryotic portion of the microbial community were variable, with most T-RF-s unique to a single sample, suggesting a wide diversity and dynamic properties of periphytic organisms.

  • 24. Tobler, Michael
    et al.
    Scharnweber, Kristin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Greenway, Ryan
    Passow, Courtney N.
    Arias-Rodriquez, Lenin
    García-De-León, Francisco J.
    Convergent changes in the trophic ecology of extremophile fish occurring along replicated environmental gradients2015In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 60, no 4, p. 768-780Article in journal (Refereed)
    Abstract [en]

    Divergent selection along environmental gradients connecting locally restricted extreme habitats and adjacent benign habitats can shape convergent evolution of traits involved in coping with physiochemical stressors and can drive speciation. At the same time, the presence of such stressors alters aspects of the biotic environment, including resource availability and competitive regimes. However, it remains unclear whether and how the ecology of populations occurring in both extreme and benign environments varies in a predictable fashion. We investigated the trophic ecology of live-bearing fishes of the genus Poecilia that have independently colonised multiple springs containing toxic hydrogen sulphide in southern Mexico. Sulphide spring fish are adapted to the unique environmental conditions and are reproductively isolated from ancestral populations in adjacent non-sulphidic habitats. We used gut content analyses to test whether colonisation of extreme habitats was accompanied by shifts of trophic resource use and expansions of trophic niche width. Furthermore, we tested whether dietary shifts were reflected in trophic morphology by comparing intestinal tract lengths among populations using both wild-caught and common garden-raised individuals. Gut content analyses revealed that fish inhabiting toxic springs expanded their trophic niche width and changed their dietary resource use from detritus and algae to sulphide bacteria and invertebrates. This dietary shift was paralleled by changes in intestinal tract morphology, whereby sulphide spring fish had shorter intestines than fish from adjacent non-sulphidic habitats. Analysis of common garden-raised fish indicated that morphological differences between sulphidic and non-sulphidic populations are at least in part due to genetic differentiation. Both patterns of trophic resource use and differentiation in trophic morphology were consistent across replicated pairs of sulphidic and non-sulphidic populations, although the magnitude of differentiation varied among river drainages. Our results suggest that colonisation of and adaptation to sulphide springs in southern Mexico was paralleled by convergent changes in trophic ecology. This highlights the complexity of environmental gradients and the necessity of considering multiple sources of selection when studying the evolution of complex phenotypes.

  • 25.
    Urrutia Cordero, Pablo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Lund Univ, Dept Biol Aquat Ecol, Lund, Sweden.
    Ekvall, Mattias K.
    Lund Univ, Dept Biol Aquat Ecol, Lund, Sweden..
    Ratcovich, Jens
    Lund Univ, Dept Biol Aquat Ecol, Lund, Sweden.;Lansstyrelsen Kalmar Ian, Vattenenheten, Tillvaxt & Miljo, Kalmar, Sweden..
    Soares, Margarida
    Lund Univ, Dept Biol Aquat Ecol, Lund, Sweden.;Lund Univ, Dept Biol Microbial Ecol, Lund, Sweden..
    Wilken, Susanne
    Lund Univ, Dept Biol Aquat Ecol, Lund, Sweden.;Netherlands Inst Ecol NIOO KNAW, Dept Aquat Ecol, Wageningen, Netherlands.;Monterey Bay Aquarium Res Inst, Moss Landing, CA USA..
    Zhang, Huan
    Lund Univ, Dept Biol Aquat Ecol, Lund, Sweden..
    Hansson, Lars-Anders
    Lund Univ, Dept Biol Aquat Ecol, Lund, Sweden..
    Phytoplankton diversity loss along a gradient of future warming and brownification in freshwater mesocosms2017In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 62, no 11, p. 1869-1878Article in journal (Refereed)
    Abstract [en]

    1. Globally, freshwater ecosystems are warming at unprecedented rates and northern temperate lakes are simultaneously experiencing increased runoff of humic substances (brownification), with little known consequences for future conservation of biodiversity and ecosystem functioning.

    2. We employed an outdoor mesocosm experiment during spring and summer to investigate the combined effects of gradually increasing warming and brownification perturbations on the phytoplankton community structure (biodiversity and composition) and functioning (biomass).

    3. While we did not observe overall significant treatment effects on total phytoplankton biomasses, we show that predicted increases in warming and brownification can reduce biodiversity considerably, occasionally up to 90% of Shannon diversity estimates. Our results demonstrate that the loss of biodiversity is driven by the dominance of mixotrophic algae (Dinobryon and Cryptomonas), whereas several other phytoplankton taxa may be temporarily displaced from the community, including Cyclotella, Desmodesmus, Monoraphidium, Tetraedron, Nitzschia and Golenkinia.

    4. The observed loss of biodiversity coincided with an increase in bacterial production providing resources for potential mixotrophs along the gradient of warming and brownification. This coupling between bacterial production and mixotrophs was likely a major cause behind the competitive displacement of obligate phototrophs and supports evidence for the importance of consumer-prey dynamics in shaping environmental impacts on phytoplankton communities.

    5. We conclude that warming and brownification are likely to cause a profound loss of biodiversity by indirectly affecting competitive interactions among phytoplankton taxa. Importantly, our results did not show an abrupt loss of biodiversity; instead the reduction in taxa richness levelled off after exceeding a threshold of warming and brownification. These results exemplify the complex nonlinear responses of biodiversity to environmental perturbations and provide further insights for predicting biodiversity patterns to the future warming and brownification of freshwaters.

  • 26.
    Vrede, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ballantyne, Ashley P.
    Mille-Lindblom, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Algesten, Grete
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Gudasz, Cristian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lindahl, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Brunberg, Anna-Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Effects of N:P loading ratios on phytoplankton community composition, primary production, and N fixation in a eutrophic lake2009In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 54, no 2, p. 331-344Article in journal (Refereed)
    Abstract [en]

    1. The aim of this study was to assess the effects of different nitrogen (N) to  phosphorus (P) loading ratios on phytoplankton community composition and primary production in a naturally eutrophic lake. Furthermore, the sources of N fuelling primary production were estimated using 15N stable isotope tracers.

    2. A mesocosm experiment was performed with the same amount of P added to all mesocosms (similar to internal loading rates) but with a range of N additions (0–86 μm N), resulting in a gradient of N : P supply ratios.

    3. Low N : P supply ratios resulted in a significant shift in the phytoplankton assemblage to a community dominated by N-fixing cyanobacteria and a supply of atmospheric N2 estimated to be up to 60% of total supply.

    4. The N : P loading ratio had no significant effect on primary production, total nitrogen (TN) concentration or particulate N concentration.

    5. Our results imply that a reduced N : P ratio of the nutrient load does not necessarily result in a lower TN concentration and downstream N export due to compensation by N-fixing cyanobacteria.

     

     

  • 27.
    Weyhenmeyer, Gesa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Peter, Hannes
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Willen, Eva
    Shifts in phytoplankton species richness and biomass along a latitudinal gradient: consequences for relationships between biodiversity and ecosystem functioning2013In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 58, no 3 (SI), p. 612-623Article in journal (Refereed)
    Abstract [en]

    1. Analysing phytoplankton community data from 205 small, mainly oligotrophic Swedish lakes along a 13 degrees latitudinal gradient, we found that the duration of the open-water season (DT>0) was best related to phytoplankton speciesrichness and biomass, probably because DT>0 can be used as a proxy for nutrient concentrations, as well as for light and temperature conditions in lakes. 2. The relationships between DT>0 and phytoplankton species richness and biomass were not linear but showed significant shifts, that is, richness suddenly doubled at DT>0=170days and phytoplankton biomass began to strongly increase at DT>0 around 220days. 3. The doubling in species richness corresponded to a change in the seasonal plankton succession from one to two peaks per year, and the shift in biomass corresponded to ashift in nutrient concentrations. 4. The geographical differences in richness and biomassshifts resulted in an exponential biodiversityecosystem functioning relationship along aDT>0 gradient. 5. We conclude that phytoplankton species richness and biomass are driven by different environmental factors, resulting in a nonlinear biodiversityecosystem functioning relationship. The shape of the diversityfunctioning relationship varies alongwith variations in environmental drivers, which is of highest importance for ongoing discussions about impacts of global change on biodiversity and ecosystem functioning.

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