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  • 1.
    Al Jawaheri, Raad
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Sahlén, Göran
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS).
    Negative impact of lake liming programmes on the species richness of dragonflies (Odonata): a study from southern Sweden2017Ingår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 788, nr 1, s. 99-113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Liming programmes aiming to restore fish populations are being implemented in many acidified aquatic systems in northern Europe. We studied Odonata communities in 47 forest lakes in SW Sweden, 13 that are currently being limed, and 8 that have previously been limed. Thirty-one species were recorded, with the highest mean number in untreated lakes, followed by previously treated lakes and currently treated lakes. Species communities differed between untreated and limed lakes, but only few rare species found in the untreated lakes were absent in the treated lakes. Likewise, species known to thrive in acid environments were either rare or showed no preferences. Comparing the number of records of odonate species within a large regional area to the proportion of lakes inhabited in our study, we found that seven of the most commonly observed species occurred less frequently in limed lakes than in the untreated ones, including two of the three most common taxa. Reduced species numbers in limed lakes might be due to conditions on other trophic levels, including fish predation. We argue that Odonata should be considered when developing new biological indices of water quality, although the causes of the observed occurrence patterns need to be studied further. © 2016 Springer International Publishing Switzerland

  • 2.
    Brönmark, Christer
    et al.
    Limnology, Department of Ecology, Lund University, Lund, Sweden.
    Weisner, Stefan E. B.
    Limnology, Department of Ecology, Lund University, Lund, Sweden.
    Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes: an alternative mechanism1992Ingår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 243/244, nr 1, s. 293-301Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The loss of submerged macrophytes during eutrophication of shallow takes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment. © 1992 Kluwer Academic Publishers.

  • 3.
    Johannesson, Karin M.
    et al.
    IFM Biology, Section Ecology, Linköping University, Linköping, Sweden.
    Andersson, Jonas L.
    WRS Uppsala AB, Uppsala, Sweden.
    Tonderski, Karin S.
    IFM Biology, Section Ecology, Linköping University, Linköping, Sweden.
    Efficiency of a constructed wetland for retention of sediment-associated phosphorus2011Ingår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 674, nr 1, s. 179-190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A constructed wetland (2.1 ha; 2% of catchment area) in southeast Sweden, in a catchment with 35% arable land on clay soils, was investigated with respect to phosphorus (P) retention, focusing on particulate P (PP) and sediment accretion. The aims were to (i) estimate P retention and identify the dominating retention processes; (ii) investigate how well estimates of P retention based on inflow-outflow measurements compared with the amount of P accumulated in the sediment. In- and outflow of P was measured during 4 years with continuous flow measurements and flow-proportional weekly composite samples. P in the accumulated sediment was estimated based on core samples and analyzed using sequential fractionation. Total P load during 4 years was 65 kg ha-1 and intensive sampling events detected 69% as PP. Based on inflow-outflow estimates the mean P retention was 2.8 kg ha-1 year-1, or 17%, but the amount of P accumulated in the inlet zone equated 78% of the TP load. This discrepancy showed the need to add studies of sediment accumulation to inflow-outflow estimates for an improved understanding of the P retention. The dominating P forms in the sediment were organic P (38%) and P associated with iron or aluminum (39%), i.e., potentially mobile forms. In areas colonized by Typha latifolia, the amount of P in the upper sediment layer (390 kg) was more than double the total P load of 136 kg. Cycling and release in those areas is a potential source of P that deserves further attention. © 2011 Springer Science+Business Media B.V.

  • 4.
    Schmidt Dalzochio, Marina
    et al.
    Ecology and Evolution, University of Vale do Taquari, UNIVATES, Lajeado, Brazil.
    Périco, Eduardo
    Ecology and Evolution, University of Vale do Taquari, UNIVATES, Lajeado, Brazil.
    Renner, Samuel
    Ecology and Evolution, University of Vale do Taquari, UNIVATES, Lajeado, Brazil.
    Sahlén, Göran
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS).
    Effect of tree plantations on the functional composition of Odonata species in the highlands of southern Brazil2018Ingår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 808, nr 1, s. 283-300Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Changes in biodiversity have mainly been assessed using taxonomical diversity indices. Although these approaches contribute to the scientific understanding of species richness and composition patterns, trait-based metrics may be more useful for detecting responses to land use change. We used odonates as a model system to compare traits composition in mixed ombrophilous forest (MOF) and tree plantations: exotic species (Pinus sp.) and native species (Araucaria angustifolia). Our goal was to understand and compare how each vegetation type affects the selection of species traits, and which factors are responsible for the presence of the species in the environment. We recorded 36 Odonata species distributed across 14 functional groups. The functional composition varied between MOF and exotic tree plantations and was similar between these two habitats and native tree plantations. Native forest favoured specialist traits. Our results suggest that the conversion of MOF to tree plantations, especially exotic ones, results in a shift to less specialized Odonata communities with altered functional group composition. This result highlights the negative impact associated with the conversion of native forests into exotic plantations. Our results show that odonates with specialist traits are limited to natural forest sites, which makes the conservation of such areas crucial. © 2017 Springer International Publishing AG, part of Springer Nature

  • 5.
    Strand, John A.
    et al.
    Limnology, Lund University, Lund, Sweden.
    Weisner, Stefan
    Limnology, Lund University, Lund, Sweden.
    Wave exposure related growth of epiphyton: Implications for the distribution of submerged macrophytes in eutrophic lakes1996Ingår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 325, nr 2, s. 113-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The distribution of submerged macrophytes in eutrophic lakes has been found to be skewed towards sites with intermediate exposure to waves. Low submerged macrophyte biomass at exposed sites has been explained by, for instance, physical damage from waves. The aim of this study was to investigate if lower biomass at sheltered sites compared to sites with intermediate exposure to waves can be caused by competition from epiphyton. Investigations were performed in eutrophic lakes in southern Sweden. Samples of submerged macrophytes and epiphytic algae on the macrophytes were taken along a wave exposure gradient. The amount of epiphyton (AFDW) per macrophyte biomass decreased with increased exposure. Biomass of submerged macrophytes, on the other hand, increased with increased exposure until a relatively abrupt disappearance of submerged vegetation occurred at high exposures. Production of epiphytic algae was monitored on artificial substrates from June to September at a sheltered and an exposed site in three lakes. It was higher at sheltered sites compared with exposed sites. We suggest that epiphytic algae may be an important factor in limiting the distribution of submerged macrophytes at sheltered sites in eutrophic lakes.

  • 6.
    Weisner, Stefan E.B.
    Limnology, Lund University, Lund, Sweden .
    Effects of an organic sediment on performance of young Phragmites australis clones at different water depth treatments1996Ingår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 330, nr 3, s. 189-194Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Performance of young Phragmites australis plants was examined after 7 weeks on an artificial nutrient-enriched inorganic substrate and on the same substrate to which an organic sediment from a eutrophic lake was added, at three different water depth treatments. Growth decreased, and proportional allocation of biomass to roots increased, with the addition of sediment. These differences were significant in shallow and deep water, but not at a medium depth. Concentrations of phosphorus and nitrogen in plant biomass decreased, and concentration of iron increased, with addition of sediment. The effects of sediment addition may have resulted from a decreased availability of nutrients in the substrate or from an impaired root functioning. Nutrient exhaustion in the substrate, due to a fast plant growth, can explain the relatively strong effects in shallow water. Deep water, on the other hand, probably restricted oxygen transport to the roots, resulting in an impaired root functioning in the low-redox sediment environment. The results show that, especially in relatively deep water, growth of undisturbed plants of P. australis may be inhibited by eutrophication of sediments, probably because of an impaired root functioning in sediments containing reduced toxic compounds (e.g. ferrous iron).

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