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  • 1.
    Ekström, Sara M.
    et al.
    Lund University.
    Sandahl, Margareta
    Lund University.
    Nilsson, Per Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. Lund University.
    Kleja, Dan B.
    Swedish University of Agricultural Sciences.
    Kritzberg, Emma S.
    Lund University.
    Reactivity of dissolved organic matter in response to acid deposition2016In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 78, no 3, p. 463-475Article in journal (Refereed)
    Abstract [en]

    Fluvial export of organic matter from the terrestrial catchment to the aquatic system is a large and increasing carbon flux. The successful reduction in sulfuric acid deposition since the 1980s has been shown to enhance the mobility of organic matter in the soil, with more terrestrially derived dissolved organic matter (DOM) reaching aquatic systems. Changes in soil acidity also affect the quality of the DOM. In this study we explore the consequences this may have on the reactivity and turnover of the terrestrially derived DOM as it reaches the aquatic system. DOM of different quality (estimated by absorbance, fluorescence and size exclusion chromatography) was produced through extraction of boreal forest O-horizon soils from podzol at two sulfuric acid concentrations corresponding to natural throughfall in spruce forest in Southern Sweden around 1980 and today. Extraction was done using two different methods, i.e. field leaching and laboratory extraction. The DOM extracts were used to assess if differences in acidity generate DOM of different reactivity. Three reactivity experiments were performed: photodegradation by UV exposure, biodegradation by bacteria, and biodegradation after UV exposure. Reactivity was assessed by measuring loss of dissolved organic carbon and absorbance, change in fluorescence and molecular weight, and bacterial production. DOM extracted at lower sulfuric acid concentration was more susceptible to photooxidation, and less susceptible to bacterial degradation, than DOM extracted at a higher sulfuric acid concentration. Thus the relative importance of these two turnover processes may be altered with changes in acid deposition.

  • 2.
    Vezza, Paolo
    et al.
    Institut d’Investigació per a la Gestió Integrada de Zones Costaneres, Universitat Politècnica de València, Spain.
    Parasiewicz, P.
    Rushing Rivers Institute, Amherst, MA, USA .
    Calles, Olle
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Spairani, M.
    FLUME s.r.l, Aosta, Italy .
    Comoglio, Claudio
    Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, Turin, Italy .
    Modelling habitat requirements of bullhead (Cottus gobio)in Alpine streams2014In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 76, no 1, p. 1-15Article in journal (Refereed)
    Abstract [en]

    In the context of water resources planning andmanagement, the prediction of fish distribution related tohabitat characteristics is fundamental for the definition ofenvironmental flows and habitat restoration measures. Inparticular, threatened and endemic fish species should bethe targets of biodiversity safeguard and wildlife conservationactions. The recently developed meso-scale habitatmodel (MesoHABSIM) can provide solutions in this senseby using multivariate statistical techniques to predict fishspecies distribution and to define habitat suitability criteria.In this research, Random Forests (RF) and LogisticRegressions (LR) models were used to predict the distributionof bullhead (Cottus gobio) as a function of habitatconditions. In ten reference streams of the Alps (NW Italy),95 mesohabitats were sampled for hydro-morphologic andbiological parameters, and RF and LR were used todistinguish between absence/presence and presence/abundanceof fish. The obtained models were compared on thebasis of their performances (model accuracy, sensitivity,specificity, Cohen’s kappa and area under ROC curve).Results indicate that RF outperformed LR, for bothabsence/presence (RF: 84 % accuracy, k = 0.58 andAUC = 0.88; LR: 78 % accuracy, k = 0.54 and AUC =0.85) and presence/abundance models (RF: 79 % accuracy,k = 0.57 and AUC = 0.87; LR: 69 % accuracy, k = 0.43and AUC = 0.81). The most important variables, selectedin each model, are discussed and compared to the availableliterature. Lastly, results from models’ application in regulatedsites are presented to show the possible use of RF inpredicting habitat availability for fish in Alpine streams.

  • 3.
    Österling, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Timing, growth and proportion of spawners of the threatened unionoid mussel Margaritifera margaritifera: Influence of water temperature, turbidity and mussel density2015In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 77, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Anthropogenic disturbances often cause decline and extinction of threatened species. The present study investigated how gravid freshwater mussels, Margaritifera margaritifera, were affected by turbidity and water temperature, and by mussel density. At an early date of mussel spawning, there were lower proportions of gravid mussels in streams with evidence of mussel recruitment than in streams without mussel recruitment. At a late spawning date, this pattern was reversed. Higher water temperature in streams without recruitment was probably responsible for this difference. The combination of high water temperature and turbidity may be one reason for reduced growth of gravid mussels in streams without recruitment. There was a positive relationship between adult mussel density and the proportions of gravid mussels. Early gravidity may lead to early release of larvae, early infestation on the host fish and an earlier start of the benthic phase, which may reduce survival rates. Clear-cutting of forests and global warming are factors that are likely to cause increased turbidity/sedimentation and water temperatures in streams. One restoration measure that reduces sediment input and water temperatures is maintaining or restoring riparian zones, but these are long-term measures that require many years before they have an effect in streams.

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