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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.
    Greenberg, Larry
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Calles, Olle
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Andersson, Jonas
    Länsstyrelsen i Värmland.
    Engqvist, Therese
    Länsstyrelsen i Kalmar.
    Effect of trash diverters ad overhead cover on downstream migrating brown trout smolts2012In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 48, no November, p. 25-29Article in journal (Refereed)
    Abstract [en]

    Power plant dams constitute barriers for downstream migration by smolts. The purpose of this study was to measure guidance efficiency of existing trash diverters and the use of overhead cover in combination with trash diverters to guide brown trout (

    Salmo trutta L.) smolts away from turbine intakes into trash spillway gates at two power plants in the Emån River, southern Sweden. A total of 44 trout smolts were caught, radio-tagged, released at the two power plants and tracked daily for six weeks. The trash diverter at the lower power plant had a significant guiding effect, as the proportion of smolt that entered the spillway gate was significantly greater than the relative proportion of water that flowed through the gate (52% vs 17%). In contrast, there was no evidence of a guidance effect at upper Finsjö, where the proportion of smolts that entered the spillway gate did not differ significantly from the relative proportion of water that flowed through the gate (0% vs 10%). The lack of a guidance effect at upper Finsjö could not be explained. The effect of overhead cover was tested at the upper power plant as illumination from outdoor, overhead lamps at the power station was believed to attract smolts to the turbine intake. This was accomplishing by setting up and removing a tarpaulin placed between the trash deflector and the turbine intake approximately every 2–5 days for about one month, so that 52.6% of the time the tarpaulin was in place and 47.4% of the time it was not. The presence of the tarpaulin reduced turbine passage, as 31% of the smolts swam through the trash spillway gate instead of the turbines when the tarpaulin was in place, whereas all smolts entered the turbines when no tarpaulin was used. For fish that passed through the turbines, mortality was higher at the upper power plant, equipped with two twin-Francis turbines, than at the lower one, equipped with a single Kaplan turbine.

  • 3. Guenard, G.
    et al.
    Boisclair, Daniel
    Ugedal, Ola
    Forseth, Torbjörn
    Fleming, Ian A.
    Jonsson, Bror
    The bioenergetics ofdensity-dependent growth in Arctic char (Salvelinus alpinus L.)2012In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 69, p. 1651-1662Article in journal (Refereed)
  • 4.
    Gustafsson, Stina
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Calles, Olle
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Skurdal, Jostein
    Österling, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Invertebrate colonization of a nature-like fishway in Eldforsen, Sweden; the effect of habitat design2012Conference paper (Refereed)
  • 5. Jonsson, Bror
    et al.
    Finstad, Anders G.
    Jonsson, Nina
    Winter temperature and food quality affect age and size at maturity in ectotherms: an experimentaltest with Atlantic salmon2012In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 69, no 11, p. 1817-1826Article in journal (Refereed)
    Abstract [en]

    Field studies have revealed that many ectotherms mature younger and smaller in warmer environments although they grow faster. This has puzzled ecologists because the direct effect of factors that accelerate growth is expected to be larger, not smaller size. We tested this experimentally for Atlantic salmon (Salmo salar) at two winter temperatures and diets. Logistic regression revealed that the probability of maturation during the second year in sea water, relative to the probability of older maturation, increased with temperature and growth rate during the first winter. Also, large size and high condition factor 1 year prior to maturation stimulated maturation. In females, a high lipid diet increased the probability of maturation as one-sea-winter fish, and there were significant interactions between winter temperature and food quality and between body size and condition factor the first autumn in sea water. Thus, if the direct effect of temperature on growth rate is the main effect of warming, salmon are likely to attain maturity younger and smaller. Also, richer food decreased age at maturation in females. This finding has consequences for interpretations of climate change impacts on age at maturity in Atlantic salmon and may also hold for many other ectotherm species.

    Salmo salar) at two winter temperatures and

    diets. Logistic regression revealed that the probability of maturation during the second year in sea water, relative to the

    probability of older maturation, increased with temperature and growth rate during the first winter. Also, large size and

    high condition factor 1 year prior to maturation stimulated maturation. In females, a high lipid diet increased the probability of

    maturation as one-sea-winter fish, and there were significant interactions between winter temperature and food quality and

    between body size and condition factor the first autumn in sea water. Thus, if the direct effect of temperature on growth rate is

    the main effect of warming, salmon are likely to attain maturity younger and smaller. Also, richer food decreased age at

    maturation in females. This finding has consequences for interpretations of climate change impacts on age at maturity in Atlantic salmon and may also hold for many other ectotherm species.

  • 6.
    Lans, Linnea
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Behaviour and metabolic rates of brown trout and Atlantic salmon: Influence of food, environment and social interactions2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    For Atlantic salmon (Salmo salar) and brown trout (Salmo trutta), the decision to migrate or when to migrate is believed to be influenced by the individual’s metabolic rate (MR) relative its food intake. As MR was expected to be related to behaviour, the potential links between behaviour and metabolic costs was studied. For both salmon and trout the dominant individual had a higher standard metabolic rate (SMR) than its subordinate counterpart. Also, successful migrants of brown trout had a higher SMR than unsuccessful migrants, whereas no such difference was found for obligate migratory Atlantic salmon. Measures of variation in MR and boldness indicated that Atlantic salmon was more sensitive to stress than brown trout and became passive when stressed. When two trout were interacting, an increase in ventilation rate (VR) was positively correlated to fighting intensity. The first day after an interaction, VR did not differ between small dominant and subordinate trout (mean size 3.7g), whereas for large trout (26.0g) subordinates had higher VR than dominants. However, a combination of low temperature (10°C) and high water velocity (22cm/s) eliminated this difference. This probably reflects the high swimming activity of small dominants and the low motivation for dominants to defend a large territory when temperatures were low and the cost of moving was high. These results show that the relationship between MR and behaviour may differ depending on species, fish size and environmental factors.

  • 7.
    Piccolo, John
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    The role of ecology in the salmonid conservation: ecology in practice and didactics2012Conference paper (Refereed)
  • 8.
    Piccolo, John
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Time for an update of the Lake Vänern food web model2012Conference paper (Refereed)
  • 9.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Test and application of a non-destructive photo-method investigating the parasitic stage of the threatened mussel Margaritifera margaritifera on its host fish (Salmo trutta)2012Conference paper (Refereed)
  • 10.
    Österling, Martin E
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, Björn L
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Greenberg, Larry A
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Habitat degradation and the decline of the threatened mussel Margaritifera maragaritifera: influence of turbidity and sedimentation on mussel an its host2010In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 47, no 4, p. 759-768Article in journal (Refereed)
    Abstract [en]

    1. Habitat degradation is a major reason for species extinctions. For parasite–host interactions, the decline of a parasite may not only be related to the parasite’s tolerance to habitat degradation but also indirectly through the host’s tolerance to the same disturbance.

    2. Our objective was to explore the cause of population declines of the freshwater pearl mussel Margaritifera margaritifera by relating the age distribution, density and growth of the mussels with turbidity, sedimentation rates and density of the mussel’s host, trout Salmo trutta, in 26 Swedish streams.

    3. An analysis of the age structure of nine mussel populations showed that maximum age differed by 60 years, with five populations having low proportions of juvenile mussels. Adult mussel density was higher at sites where juvenile mussels occurred than at sites lacking juvenile mussels.

    4. Growth of adult mussels during the past 10 years was lower in the five streams lacking recent recruitment than in the four streams with recent recruitment, indicating that some environmental factor may be negatively impacting these populations.

    5. A comparison among 24 populations indicated that turbidity and sedimentation may be responsible for recruitment failure in 58% of the populations. The age of the youngest mussel was positively related to turbidity and sedimentation, and juvenile mussel density was negatively related to turbidity and sedimentation. In contrast, trout density was not related to recruitment of mussels or sedimentation, but was positively related to turbidity in all streams, both with and without recent mussel recruitment.

    6.Synthesis and applications. Recruitment failure of M. margaritifera appears to be related to its own vulnerability to turbidity and sedimentation rather than to its host’s response to this type of habitat degradation. The results from our study suggest that managers might be able to evaluate the potential viability of mussel populations by measuring stream turbidity. Restoration activities to improve the mussels’ environment should focus on reducing fine material transport into streams.

  • 11.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Söderberg, Håkan
    Anthropogenic changes of brown trout Salmo trutta and the impact on its parasitic mussel Margaritifera margaritifera.2012Conference paper (Refereed)
1 - 11 of 11
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