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  • 22301.
    Östberg, Linda
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Some Aspects on Pulp Pre-treatment Prior to Viscose Preparation2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Large amounts of carbon disulphide are consumed in the conventional production of viscose. Until a novel, eco-friendly, wood-based process for the production of cellulose textile fibres has been developed and implemented, it is important to try to find ways to improve the conventional viscose process, e.g. in terms of reducing the carbon disulphide requirement of the process. The aim of this thesis was to reduce the amount of carbon disulphide consumed in the preparation of high-viscosity viscose by pre-treating pulps with enzymes. It also aimed at investigating and linking the different measurements of reactivity, i.e. gamma number, Fock reactivity and Kw, and determining the sensitivity of the gamma number to the hemicellulose content of pulp. Reactivity was measured as Fock reactivity and gamma number. The gamma number of viscose solutions remained unchanged when an enzyme stage was used prior to the viscose process. The gamma number analysis was found to be selective not only to cellulose but also to the hemicellulosic material. It was verified that both cellulose and hemicellulose molecules in the pulp material were substituted in the viscose preparation stages, showing that the gamma number of the pulp is due to both substituted cellulose and substituted hemicelluloses. The mechanisms responsible for the Fock reactivity, or the filter-clogging value (Kw) on the one hand and the gamma number on the other, are probably not the same. It was speculated that the analysis method employed in Fock´s test and the filter-clogging value measure the results on a fibre level, whereas the gamma number measures changes mainly on a molecular level. This could explain the difference in the levels of reactivity found in this study.

  • 22302.
    Östberg, Linda
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Some Aspects of the Reactivity of Pulp Intended for High-Viscosity Viscose: Influence on the Reactivity and the Gamma Number2011Conference paper (Other (popular science, discussion, etc.))
  • 22303.
    Östberg, Linda
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Some aspects on the activation of dissolving pulps and the influence on the reactivity in a following viscose stage2013In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 47, no 3-4, p. 165-169Article in journal (Refereed)
    Abstract [en]

    It was found that, for a dissolving pulp, an enzymatic pre-treatment with an endoglucanase prior to viscose preparation did not change the correlation between the gamma number of the viscose dope and the carbon disulphide charge. Thus, the pulp stoichiometry, or reactivity, was not changed by an endoglucanase pre-treatment. It has nevertheless previously been found that the pulp reactivity, measured either by Fock's test or as the filter clogging value (Kw), increased for the same type of enzyme pre-treatment. Thus, the pulp reactivity seems to be influenced by the analysis method employed.

  • 22304.
    Östberg, Linda
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Some Aspects on the Reactivity of a Dissolving Pulp when used for Viscose PreparationIn: O papelArticle in journal (Refereed)
  • 22305.
    Östberg, Linda
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Håkansson, Helena
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science.
    Some aspects of the reactivity of pulp intended for high-viscosity viscose2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 1, p. 743-755Article in journal (Refereed)
    Abstract [en]

    The original objective of this study was to reduce the consumption of carbon disulphide in the preparation of high-viscosity viscose by pre-treating two softwood pulps with enzymes prior to the viscose stages. Reactivity can, however, be measured in different ways and the methods used in this study are Fock´s test of the pulp and the gamma number of the viscose solution prior to regeneration. It was found that whilst the reactivity of a pulp that had been subjected to enzyme pretreatment increased according to Fock´s test, it did not increase when the gamma number obtained in a standardized viscose preparation process was used. This unexpected difference that was discovered between the two reactivity tests made it difficult to analyze the impact of the enzyme stage on reactivity; the underlying reasons for the different reactivity results obtained were therefore investigated first. The conclusion that may be drawn from this investigation is that Fock´s test measures the extent to which carbon disulphide reacts with a pulp sample during a standardized test whereas the gamma number measures the resulting degree of xanthate substitution on the cellulose backbone. These two reactivity tests are thus not totally correlated. It was concluded that the gamma number was the more relevant of the two tests since it reflects the dissolution ability of a pulp in the viscose preparation, which is a very basic property of viscose. A higher gamma number also means that the coagulation time in the spinning process is prolonged; this is beneficial as it can be used to increase the tenacity of the viscose fibres. Measuring the reactivity according to Fock´s test, on the contrary, provides more dubious results as the test has no undisputed correlation to the viscose preparation process.

  • 22306.
    Östberg, Linda
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Kvarnlöf, Niklas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    The hemicellulose content in two chemical pulps and its influence on Fock´s test and the gamma number of the resulting viscose dope2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, no 3, p. 4p. 377-380Article in journal (Refereed)
  • 22307.
    Östberg, Linda
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Kvarnlöf, Niklas
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    The Influence of the Hemicellulose Content in Dissolving Pulps on the Gamma Number of Viscose DopesIn: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Article in journal (Refereed)
  • 22308.
    Österberg, Johan
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Social and Psychological Studies (from 2013).
    We want you as our new recruit: Prerequisites for recruitment to and retention in the Swedish Armed Forces2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The purpose of this thesis was to study the prerequisites for the Swedish Armed Forces (SAF) in order to recruit sufficient numbers of suitable individuals to the organization, and to retain those within the organization.

    The thesis comprises three studies (Study 1-3) where Study One comprises data gathered, with a longitudinal design, when Sweden relied on conscription for the manning of the Armed Forces. Results show that those wanting to do international military service assessed themselves higher for required qualities than those individuals not volunteering for international military service. Study Two shows that job satisfaction, according to Hackman and Oldham´s Job satisfaction model, is higher when job characteristics are good, and they in turn affect the Critical Psychological States, as proposed by Hackman and Oldham. Study Three indicates that there is a relation between performance orientation, job characteristics, job satisfaction and retention. In sum, this thesis suggests that there are different incentives for recruiting and retaining personnel to a conscripted force, and an all-volunteer force. Furthermore, the thesis indicates that an all-volunteer force concept is not the best way of manning the armed forces, for Sweden and countries with similar society, size and likewise a critical geopolitical position.

  • 22309.
    Österberg, Johan
    et al.
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Social and Psychological Studies (from 2013). Försvarshögskolan.
    Rydstedt, L W
    Inland Norway University of Applied Sciences, Department of Social Sciences, Lillehammer, Norway.
    Kleiven, J
    Inland Norway University of Applied Sciences, Department of Social Sciences, Lillehammer, Norway.
    Fors Brandebo, M
    Swedish Defence University (SEDU), Karlstad, Sweden.
    The Path to Job Satisfaction: Applying the Theory of Purposeful Behavior to Military Conditions2017In: Journal of Defense Resources Management, ISSN 2068-9403, E-ISSN 2247-6466, Vol. 8, no 1, p. 27-42Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to examine the relationships between, on one hand,personality and performance orientation and, on the other, job satisfaction andturnover intentions, using Barrick’s et al. theory of purposeful behavior. Using aquestionnaire, data about job satisfaction, performance orientation and turnover intentions were collected from 300 newly recruited Swedish soldiers. A path analysis gave partial, but not full support to the assumptions behind the theory of purposeful behavior model. No relationships were found between the personality traits of emotional stability and conscientiousness, nor to either performance orientation or directly to job satisfaction. On the other hand, performance orientation showed a consistent relationship to perceived levels of the job characteristics, which mediated the path between the person-related variables and the outcome variables.Performance orientation also showed a strong direct relationship to general job satisfaction, which, in turn, was strongly related to turnover intentions.

  • 22310.
    Österberg, Johan
    et al.
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Social and Psychological Studies (from 2013).
    Rydstedt, Leif
    Inland Norway University of Applied Sciences, Lillehammer, Norway.
    Job satisfaction among Swedish soldiers: Applying the Job Characteristics Model to newly recruited military personnel2018In: Military Psychology, ISSN 0899-5605, E-ISSN 1532-7876, Vol. 30, no 4, p. 302-310Article in journal (Refereed)
    Abstract [en]

    A professional military organization was introduced in Sweden in 2010. This means that the Swedish Armed Forces (SAF) need to attract and employ soldiers, and to retain them within the organization. This scenario creates new types of challenges in manning the organization. The transition to an all-volunteer force puts job satisfaction in focus in order to retain personnel. This cross-sectional study of the relations between working conditions and job involvement among 300 recently employed soldiers showed that the dimensions of the Job Characteristics Model related significantly to job satisfaction and work motivation and (negatively) to turnover intentions from the SAF. The results further showed that all the critical psychological states contributed independently to the variance in the outcome variables.

  • 22311.
    Östergaard, Edvin
    et al.
    Norwegian University of Life Sciences, Norway.
    Hugo, Aksel
    Rudolf Stein College of Education, Norway.
    Dahlin, Bo
    Karlstad University, Faculty of Arts and Education, Department of Education.
    From phenomenon to concept: designing phenomenological science education2007In: Proceedings of the 6th IOSTE Symposium for Central and Eastern Europe / [ed] V. Lamanauskas & G. Vaidogas, 2007, p. 123-129Conference paper (Refereed)
  • 22312.
    Österholm, Magnus
    et al.
    Umeå universitet, Umeå forskningscentrum för matematikdidaktik (UFM).
    Bergqvist, Tomas
    Umeå universitet, Institutionen för tillämpad utbildningsvetenskap.
    Liljekvist, Yvonne
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). Uppsala universitet.
    van Bommel, Jorryt
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Utvärdering av Matematiklyftets resultat: slutrapport2016Report (Other (popular science, discussion, etc.))
    Abstract [sv]

    Matematiklyftet är en fortbildning för alla lärare i Sverige som undervisar i matematik. Den genomfördes 2012-2016. Kärnan i fortbildningen var det kollegiala lärandet. Lärare arbetade tillsammans med olika moduler som var och en bestod av didaktiskt material att använda vid planering, diskuss-ioner och genomförande av matematikundervisning, samt vid kollegiala reflektioner och diskussioner. Genom modulerna belystes primärt fyra olika didaktiska perspektiv: (1) att undervisa matematik utifrån förmågorna, (2) bedömning för lärande och undervisning i matematik, dvs. formativ bedömning, (3) rutiner/interaktioner i klassrummet och (4) klassrumsnormer/sociomatematiska normer.

    Denna rapport presenterar en utvärdering av Matematiklyftets resultat där det undersökts i vilken utsträckning Matematiklyftet har bidragit till att utveckla en bestående undervisningskultur och en bestående fortbildningskultur. Utvärderingen syftar också till att identifiera faktorer som gynnar eller missgynnar Matematiklyftets resultat och ska även fungera både formativt och summativt. Det innebär att både slutsatser om hur Matematiklyftet har uppnått målen att utveckla undervisnings- och fortbildningskulturen och slutsatser om hur stöd till planeringar och genomförande av liknande fort-bildningssatsningar formuleras. Urvalet i utvärderingen består av 35 grund-och gymnasieskolor. På varje skola har tre lärare slumpmässigt valts ut att ingå i utvärderingen, dvs. totalt 105 lärare. I utvärderingen ingår också varje skolas rektor och representant för skolhuvudman. Skolorna har besökts vid två tillfällen för att kunna undersöka förändring i undervisnings- och fortbildningskultur. Datamaterialet består av observationer av matematiklektioner och av kollegiala samtal, intervjuer och enkäter med lärare och rektorer, samt intervjuer med representanter för skolhuvudmän. I datamaterialet ingår även insamlade dokument (t.ex. fortbildningsplaner och kopior av undervisningsmaterial) och bakgrundsinformation om de besökta skolorna (från externa databaser). Denna rapport utgör slutrapporten för utvärderingen av Matematiklyftets resultat. Nedan redovisas utvärderingens huvudsakliga resultat tillsammans med rekommendationer inför framtida fortbildningssatsningar av samma typ som Matematiklyftet.

  • 22313.
    Österholm, Magnus
    et al.
    Umeå universitet.
    Bergqvist, Tomas
    Umeå universitet.
    van Bommel, Jorryt
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Liljekvist, Yvonne
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Utvärdering av matematiklyftets resultat: delrapport 12014Report (Other academic)
    Abstract [sv]

    Denna rapport är en första delrapport inom utvärderingen av Matematiklyftets resultat. I detta skede har utvärderingen pågått i cirka sex månader. Arbetet har under denna period till största delen bestått av planeringsarbete inför kommande insamling och analyser av data. 

  • 22314.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Anthropogenic impact on recruitment, growth and host-fish of Margaritifera margaritifera.2010Conference paper (Other academic)
  • 22315.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Anthropogenic impact on recruitment, growth and host-fish of Margaritifera margaritifera.2011Conference paper (Refereed)
  • 22316.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Bevarandebiologi flodpärlmusslan – Status, habitatförsämring och åtgärder.2008Conference paper (Other academic)
  • 22317.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Bevarandebiologi flodpärlmusslan – Status, habitatförsämring och åtgärder.2010Conference paper (Other (popular science, discussion, etc.))
  • 22318.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Bevarandebiologi flodpärlmusslan Status, habitatförsämring och åtgärder2008Conference paper (Refereed)
  • 22319.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Biotiska och abiotiska faktorers betydelse för flodpärlmusslans fortplantning och överlevnad i Ljungans biflöden2010Report (Other academic)
    Abstract [sv]

    Stormusslorna är en av de organismgrupper i sötvatten som är allra mest hotad. En av Sveriges stormusslor är flodpärlmusslan, vilken minskar i antal inom hela sitt utbredningsområde och som sedan maj 2010 är klassad som starkt hotad i den Internationella naturvårdsunionens rödlista. Målet med föreliggande projekt var att undersöka vad som begränsar flodpärlmusslans reproduktion och överlevnad. I anslutning till undersökningarna gjordes dessutom en film som berättar om projektet. Projektet är ett samarbete mellan Karlstads universitet och Fortums nordiska miljöfond och utfördes under åren 2007 och 2008 i 26 biflöden till Ljungan i Västernorrland.

    Flodpärlmusslan reproducerar sig på sommaren, då musslan släpper sina glochidielarver i vattnet. Larverna måste träffa på öring eller lax, där larverna kapslas in på fiskens gälar för att sedan leva där som parasit under 10-12 månader. När de små musslorna släppt från värdfiskens gälar lever de nedgrävda i sedimentet under några år. Från 10-20 års ålder räknas musslan som vuxen och kan delta i reproduktionen.

    I många musselvattendrag saknas juvenila musslor. Eftersom musslan har en så komplicerad livscykel är det flera livscykelstadier som bör undersökas för att ta reda på när rekryteringen av juvenila musslor begränsas. I detta projekt undersöktes följande livscykelstadier i 26 vattendrag i Ljungans avrinningsområde: gravida musslor, glochidieinfektion på öring och juvenila musslor. För att mäta  glochidielarvernas infektion på öringen utan att avliva öringen utvecklades en ny metod att uppskatta infektionsgraden m.h.a. fotografering av larverna på öringens gälar. Dessutom undersöktes öringtätheter och förändring i musseltäthet mellan 1990-1991 och 2005-2006. Slutligen undersöktes hur abiotiska faktorer såsom turbiditet, sedimentation, sedimentvattenkemi och vattentemperaturer påverkade musslans livscykelstadier.

    Resultaten visade att musseltätheten ökade generellt i vattendrag med rekrytering av juvenila musslor, men minskade i vattendrag utan rekrytering från 1990-1991 till 2005-2006. En minskning i musseltäthet sker alltså idag i vattendrag utan rekrytering och har troligtvis också skett under längre tid, vilket sannolikt resulterat i den lägre musseltäthet som finns idag i vattendrag utan rekrytering i Ljungans biflöden. Därmed är situationen allvarlig, där glesare populationer kan resultera i lägre reproduktion och förändra musslornas viktiga funktioner som filtrerare och paraplyart i vattendragen. På sikt är risken stor att arten försvinner helt från dessa vattendrag om man inte finner problemen och åtgärdar dem.

    Gravida musslor verkar inte vara det livscykelstadium som begränsar rekryteringen, eftersom ungefär hälften av musslorna var gravida, både i vattendrag med och utan rekrytering. Däremot var musslorna gravida tidigare i vattendrag utan rekrytering än i vattendrag med rekrytering. Gravida musslor var också kortare än musslor som inte var gravida i vattendrag utan rekrytering men inte i vattendrag med rekrytering. Proportionen gravida musslor ökade också som en funktion av musseltätheten. Sammantaget visar detta att larvproduktionen kanske inte fungerar helt optimalt i vattendrag utan rekrytering.

    Den nya metoden att mäta larver på öringens gälar genom att fotografera gälarna som utvecklades inom projektet fungerade bra. Ett akvarieexperiment visade att tillväxt eller överlevnad hos öring inte försämrades på grund av fotometoden. Detta visar alltså på att man kan undersöka infektionen av mussellarver på öring utan att öringen tar skada.

    Med hjälp av fotometoden kunde infektionsstadiet av mussellarver på öring av olika ålder mätas. Infektionen av mussellarver var högre i vattendrag med rekrytering än i vattendrag utan rekrytering på årsungar och på äldre öring. För infektionen på årsungarna berodde detta främst på en högre täthet av årsungar i vattendrag med rekrytering än i vattendrag utan rekrytering. Detta tyder på att årsungarnas täthet är negativt påverkad av någon faktor, vilket i sin tur leder till färre antal larver hos årsungarna i vattendrag utan rekrytering. Skillnaden i infektionen på äldre öring var orsakad av en högre musseltäthet i vattendrag med rekrytering än i vattendrag utan rekrytering. Den minskande musseltätheten i vattendrag utan rekrytering resulterar troligtvis i sin tur i en minskad produktion av glochidielarver. Sammantaget verkar det alltså som att en lägre täthet av öringens årsungar och en låg musseltäthet bidrar till lägre antal glochidielarver i vattendrag utan rekrytering, vilket sannolikt resulterar i en lägre rekrytering av juvenila musslor.

    Nästa tidiga livscykelstadium, juvenila musslor, var även det påverkat av musseltäthet och årsungarnas täthet. Detta tyder på att både infektionsstadium och juvenila musslor är negativt påverkade. Tätheten av juvenila musslor var negativt relaterad till turbiditet. Hög turbiditet hänger ofta ihop med hög sedimentation, vilket kan begränsa juvenila musslors överlevnad genom låga syrehalter och höga ammoniumhalter i sedimentet. Den sämre vattenomsättningen som uppmättes i vattendrag utan rekrytering kan vara ett resultat av en hög sedimentation och därmed resultera i dåliga förhållanden i sedimenten med en låg överlevnad av juvenila musslor som följd. Dessutom kan högre vattentemperaturer, vilket uppmättes på sommaren i vattendrag utan rekrytering, försämra tillväxt och överlevnad hos juvenila musslor.

    Turbiditet visade sig ha högst förklaringsgrad för frånvaron av juvenila musslor, följt av vattentemperaturen, medan täthet av årsungar av öring, musseltäthet och täthet av äldre öring, i nämnd ordning, var viktiga för rekryteringen av juvenila musslor. Detta pekar på att en minskning av sedimenttillförsel till vattendragen skulle kunna vända trenden med avsaknad av musselrekrytering. Minskad sedimentation skulle också kunna förbättra öringens reproduktion och därmed även förbättra rekryteringen av musslan, om en högre sedimenttransport också påverkar öringäggens utveckling negativt.

    Brukande av marken bredvid vattendrag kan vara en viktig orsak till hög turbiditet och sedimentation och kan också orsaka höga vattentemperaturer på grund av ökad solinstrålning. För överlevnaden av juvenila flodpärlmusslor är det också viktigt att naturliga flödestoppar inte förhindras, utan tillåts byta ut vattnet i sedimentet. En kombination av lågt vattenflöde och avsaknad av en beväxt kantzon på sommaren kan troligtvis bidra till dåliga förhållanden i bottenvattnet och för höga vattentemperaturer, vilket kan påverka både musslor och öring negativt.

    För att uppnå bättre förhållanden för flodpärlmusslan bör brukandet av marken utföras så att silt och sand inte släpps ut i vattendragen. Genom att inte störa marken närmast vattendragen genom dikning och skogsavverkning kan en ökad sedimentation förhindras. Om man lämnar intakta kantzoner närmast vattendragen kan dessa även stabilisera vattendragen mot erosion. Dessutom kan ökad beskuggning av vegetationen i en intakt kantzon förhindra alltför höga vattentemperaturer sommartid. Samtidigt bör regleringen av dammar uppströms musselpopulationer vara sådan att högflödestoppar, vilka bidrar till att vatten spolas genom sedimenten, inte begränsas. Om marken bredvid bäckarna och vattenregleringen sköts på rätt sätt  kan det bidra till att rekryteringen av flodpärlmusslor återupptas. Detta bör dock ske inom en snar framtid eftersom effekter av restaurering av vattendrag ofta tar lång tid och det också tar lång tid för flodpärlmusslan att återkolonisera när tätheterna har reducerats mycket.

  • 22320.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Biotiska och abiotiska faktorers betydelse för flodpärlmusslans reproduktion och överlevnad i Ljungans biflöden2010Book (Other academic)
  • 22321.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Ecology of freshwater mussels in disturbed environments2007Conference paper (Other (popular science, discussion, etc.))
  • 22322.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences.
    Ecology of freshwater mussels in disturbed environments2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The number of species extinctions is increasing at an alarming rate. Long-lived freshwater mussels of the order Unionoida, which include a parasitic stage on a host fish, are highly threatened. Habitat degradation by turbidity and sedimentation is thought to be one major reason for their decline. The objective of this thesis was to examine recruitment patterns and identify the causes of the lack of recruitment in the threatened unionoid freshwater pearl mussel (Margaritifera margaritifera). In addition, I investigated the effects of turbidity on non-endangered dreissenid mussels, where turbidity was manipulated through use of bioturbating mayflies.

    In a survey of 107 Swedish streams, mussel population size and trout density were both positively correlated to recruitment probability of M. margaritifera. A more in-depth study of the age-structure of nine populations revealed that four of these populations showed no signs of recruitment over the last ten years. Within-stream variation in recruitment was high as both mussels and trout had patchy distribution, and may be important for population regulation. Moreover, examination of different life stages revealed no differences in the gravid mussel stage or the stage when mussels infect salmonid fish. Instead, differences were observed for the juvenile, benthic stage, presumably related to differences in turbidity and sedimentation. High turbidity may affect filter-feeding efficiency of mussels and high sedimentation may reduce survival by clogging sediments, thereby altering, for example, oxygen and food conditions. In the study of the effects of turbidity, bioturbating mayflies increased turbidity and filter-feeding dreissenid mussels reduced turbidity. Mussel growth both decreased and increased with increasing turbidity, depending on sediment type.

    Turbidity and sedimentation often impact entire stream systems, and a holistic, catchment-based management strategy may be needed to reduce the effects of sedimentation on freshwater pearl mussels. The effects of restoration take a long time and must start soon if recruitment of mussels is to be re-established. Restoration may also be more urgent in some streams than in others, as the maximum age of M. margaritifera populations in my study differed by as much as 60 years. As mussel and trout densities seem to be important for recruitment success, one conservation method may be to concentrate mussels into sites where trout density is high.

  • 22323.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Ecology of the freshwater pearl mussel2003Conference paper (Other (popular science, discussion, etc.))
  • 22324.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Effects of filamentous green algal mats on benthic macrofaunal functional feeding groups2001In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 263, p. 159-183Article in journal (Refereed)
  • 22325.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Flodpärlmussla – En indikator för gränsöverskridande biologisk mångfald. Conservation.2008Conference paper (Other academic)
  • 22326.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Flodpärlmusslan Status, hot och populationsreglering2006Conference paper (Other (popular science, discussion, etc.))
  • 22327.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Flodpärlmusslan i Ljungans avrinningsområde.2008Conference paper (Other (popular science, discussion, etc.))
  • 22328.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Habitat degradation and early life stages of M. margaritifera – Ljungans Catchment Area, Västernorrland.2008Conference paper (Other academic)
  • 22329.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Habitat degradation and early life stages of M. margaritifera – threats and conservation.2008Conference paper (Other (popular science, discussion, etc.))
  • 22330.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Hot mot flodpärlmusslans tidiga livscykelstadier i södra och mellersta Sverige.2009Conference paper (Other academic)
  • 22331.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Hot mot flodpärlmusslans tidiga livscykelstadier i södra och mellersta Sverige2009Other (Other (popular science, discussion, etc.))
  • 22332.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of habitat degradation on recruitment of the freshwater pearl mussel M. margaritifera.2011Conference paper (Refereed)
  • 22333.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of sedimentation on freshwater mussels.2009In: Increased sedimentation, a widespread problem leading to degradation of freshwater communities and habitats”. 26-28 November 2009.: Conference in Clervaux, Luxembourg. / [ed] Frankie Thielen, Projet LIFE‐Nature « Restauration des , 2009, p. 1-59Conference paper (Refereed)
  • 22334.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of turbidity and sedimentation in Swedish M. margaritifera populations2008Report (Refereed)
  • 22335.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of turbidity and sedimentation on recruitment, growth and host fish of M. margaritfera.2009In: International Symposium of the Freshwater Mollusc Conservation Society Baltimore, Maryland April 19-24, 2009., 2009Conference paper (Refereed)
  • 22336.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Indirect environmental interactions between filter feeding mussels and bioturbatingmayflies2009Conference paper (Refereed)
  • 22337.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Influence of host fish age on a mussel parasite differs among rivers: Implications for conservation2015In: Limnologica, ISSN 0075-9511, E-ISSN 1873-5851, Vol. 50, p. 75-79Article in journal (Refereed)
    Abstract [en]

    Unionoid mussels are obligate parasites on one or more fish species. The objective was to compare growth and survival of encysted mussel larvae of the freshwater pearl mussel (Margaritifera margaritifera) on young-of-the-year (YOY) versus one-year old brown trout (Salmo trutta). YOY and one-year old trout from the Brattefors and Lade Rivers, Sweden, were infested with mussel larvae from their home river. The mass-normalized encystment abundance was higher on YOY trout than on one-year old trout. The proportional decrease in mass-normalized encystment abundance was larger on YOY brown trout from the Brattefors River than on YOY brown trout from the Lark River. Encystment per individual fish was higher on YOY trout than on one-year old trout from the Brattefors River, whereas this relationship was reversed for trout from the Larje River. Larval growth was higher on YOY trout than on one-year old trout. There was a larger difference in larval growth between YOY trout and one-year old trout from the Brattefors River than on the brown trout from the Lade River. The ability to use both YOY and older fish, such as in the Ude River, may increase the reproduction potential of mussel populations, compared to a reduced ability to use more than one year class, such as in the Brattefors River. This may also affect the dispersal of mussels, as older brown trout often move and migrate to a higher degree within and between rivers. The dispersal potential of mussels may therefore be relatively high in the Lade River, but low in the Brattefors River. In rivers where the mussels have to rely on YOY brown trout, it could be worth facilitating passage through migration obstacles for YOY brown trout. Infested YOY brown trout could be artificially re-distributed within rivers, to places with former mussel distributions. It could also be worth testing the suitability of brown trout of different age classes when starting breeding programs.

  • 22338.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Interactions between trout and parasitic larvae of freshwater mussels2005Conference paper (Refereed)
  • 22339.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 12007Report (Other academic)
  • 22340.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 22007Report (Other academic)
  • 22341.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 32008Report (Other academic)
  • 22342.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 42008Report (Other academic)
  • 22343.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 52008Report (Other academic)
  • 22344.
    Österling, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Sedimentation affects emergence rate of host fish fry in unionoid mussel streams2019In: Animal Conservation, ISSN 1367-9430, E-ISSN 1469-1795, Vol. 22, no 5, p. 444-451Article in journal (Refereed)
    Abstract [en]

    Free-living, sympatric sedentary life stages of hosts and parasites are often adapted to similar environmental conditions. When the environment where these life stages occur is disturbed, both species can decline, causing strong negative effects on the parasitic species. For the highly threatened unionoid mussels with their larval parasitic life stage on fish, habitat degradation may simultaneously affect the conditions for the sedentary host fish eggs and the juvenile mussels in the sediment. This study provides novel information on the effect of sedimentation on the emergence rate of yolk sac fry, and its relation to mussel recruitment in two drainage basins, and is exemplified by the brown trout Salmo trutta, host fish for the threatened freshwater pearl mussel Margaritifera margaritifera. The results imply that turbidity and sedimentation can reduce the survival of trout eggs and yolk sac fry emergence rate regardless of trout strain and drainage basin. The results further suggest that low yolk sac fry emergence rates reduce the potential for mussel infestation and recruitment. The results indicate a year round negative effect of sedimentation, having strong and combined direct and indirect effects on juvenile mussel recruitment. Conservation measures that reduce anthropogenic sediment transportation into streams are a key factor for the conservation of mussels and their host fish. 

  • 22345.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Spawning and glochidiosis in the freshwater pearl mussel2006Conference paper (Refereed)
  • 22346.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Substrate, turbidity and sedimentation in Swedish Margaritifera margaritifera populations2006Report (Refereed)
  • 22347.
    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 E. Salmo trutta2011In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 144, no 12, p. 2984-2990Article in journal (Refereed)
    Abstract [en]

    The objective was to test the application of a novel, non-destructive photo-method estimating the larval encystment of one of the highly threatened unionid mussels, the freshwater pearl mussel (Margaritifera margaritifera) on the gills of its host fish, brown trout (Salmo trutta). There were significant correlations between the encystment intensity based on microscope counts and using the new photo-method for both young-of-the-year and older brown trout just after the encystment in October 2007 and just before larval release from the host fish in June 2008. The mean encystment intensity based on the two methods did not differ from each other for the two age classes of trout when based on comparisons including all individuals. An aquaria experiment showed that there were no differences in survival or growth between fish subjected to the treatments: photo-method and individual marking, photo-method and a control. When applied to encystment in single streams, there were significant correlations between the mean encystment intensity in each stream based on the methods for both trout age classes. Therefore, it may be possible to get reliable estimation of the encystment rates without injuring the mussel or the host fish, which may also be used in restoration and cultivation work. Furthermore, the larvae of M. margaritifera are among the smallest of all the worldwide-distributed, threatened unionid mussel species. The photomethod may therefore also be used for other mussel species with larger larvae, as they are more easily recognized on photos. Therefore, it may now be possible to investigate every life stage of unionid species without using harmful methods at all.

  • 22348.
    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)
  • 22349.
    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).2010Conference paper (Refereed)
  • 22350.
    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)
444445446447448 22301 - 22350 of 22400
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