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<p>Syftet med denna uppsats är att undersöka huruvida fiskvägar förbi vattenkraftverket vid Finsjö i Emån fungerar eller inte. För att finna svar på den frågan har två olika metoder använts, dels telemetrisändare för att se om fiskar hittar fram till fiskvägarna (attraktionseffektivitet) och dels PIT-tags för att mäta om fiskarna lyckas passera genom fiskvägarna (passageeffektivitet). Undersökningen fann att det var en högre passageeffektivitet, 89 % vid nedre Finsjö och 100 % vid övre Finsjö, i Emån jämfört med andra liknande studier. Attraktionseffektiviteten var 75 % vid nedre Finsjö och 59 % vid övre Finsjö, vilket tyder på att det finns något som stör fisken innan de når fram till fiskvägen, särskilt vid övre Finsjö.</p> / <p>The purpose of this paper is to determine the extent to which trout used fishways to swim past two power plants at Finsjö in River Emån. Two different methods of  collecting data were used, radiotelemetry to determine if fish find the fishways (attraction efficiency) and PIT-tags to measure the number of fish that passed through the fishways (passage efficiency). The study showed that passageefficiency, being 89 % at lower Finsjö and 100 % at upper Finsjö, was high compared to other similar studies. Attraction efficiency was 75 % at lower Finsjö and 59 % at upper Finsjö, which indicates that the fish have difficulty finding the fishway entrances, particularly at upper Finsjö.</p>

Syftet med denna uppsats är att undersöka huruvida fiskvägar förbi vattenkraftverket vid Finsjö i Emån fungerar eller inte. För att finna svar på den frågan har två olika metoder använts, dels telemetrisändare för att se om fiskar hittar fram till fiskvägarna (attraktionseffektivitet) och dels PIT-tags för att mäta om fiskarna lyckas passera genom fiskvägarna (passageeffektivitet). Undersökningen fann att det var en högre passageeffektivitet, 89 % vid nedre Finsjö och 100 % vid övre Finsjö, i Emån jämfört med andra liknande studier. Attraktionseffektiviteten var 75 % vid nedre Finsjö och 59 % vid övre Finsjö, vilket tyder på att det finns något som stör fisken innan de når fram till fiskvägen, särskilt vid övre Finsjö. / The purpose of this paper is to determine the extent to which trout used fishways to swim past two power plants at Finsjö in River Emån. Two different methods of  collecting data were used, radiotelemetry to determine if fish find the fishways (attraction efficiency) and PIT-tags to measure the number of fish that passed through the fishways (passage efficiency). The study showed that passageefficiency, being 89 % at lower Finsjö and 100 % at upper Finsjö, was high compared to other similar studies. Attraction efficiency was 75 % at lower Finsjö and 59 % at upper Finsjö, which indicates that the fish have difficulty finding the fishway entrances, particularly at upper Finsjö.

Viruses has a relatively recently been discovered in high abundances in aquatic systems. Their possible importance has therefore been largely overlooked. In aquatic food webs there should be large differences in carbon and nutrient fluxes depending on whether the main cause of bacterial mortality is viral infection or grazing, where lysis following viral infection should result in a release of organic carbon and nutrients from the lysed bacteria and hence not reach higher trophic levels. Recent research on aquatic viruses has mainly focused on marine environments and the number of studies on freshwater viral ecology is limited. Hence, there is a need for more studies on the importance and functioning of viruses in freshwater systems. The aims of this thesis were to explore the functioning and diversity of viruses that infects bacteria (phages) in freshwater systems. To effectively address this I conducted two experiments and three field studies in 23 lakes in different parts of Sweden. The results show that viral infection and subsequent lysis of the host cell can partly explain the formation of non-nucleoid-containing bacteria and further that viruses can respond to increases in phosphorus concentrations without any net increase in bacterial abundance. Generally, a larger part of bacterial production in lakes were grazed by flagellates than lysed by viruses, but a larger fraction of the total bacterial mortality can be attributed to viruses in hypolimnion compared to in epilimnion. Further, the largest impact of phages on bacterial production may be in humic lakes, which have a relatively high frequency of visibly infected bacterial cells, but low flagellate abundance. Community composition of bacteria and viruses were only weakly coupled in the studied systems. The most important factors for predicting viral community composition were temperature and concentrations of dissolved organic carbon, total phosphorus and soluble reactive phosphorus. The viral community composition changed over the season and temperate phages could be detected by incubations with mitomycin C showing that a large fraction of the viruses detected appeared to be temperate phages. The most important environmental factor co-varying with viral community composition was again concentrations of total phosphorus. To summarize, bacteriophages, as a bacterial mortality factor, are important in freshwater microbial food webs and phosphorus supply has a potential central function in the regulation of the importance of bacteriophages and additionally for viral diversity.

Copper toxicity was investigated using the green alga, Selenastrum capricornutum. Two major areas were investigated: the forms of copper which are toxic to growth of the alga and factors that can change the concentration of free copper, Cu2+ (aq), in the growth medium during the logarithmic growth of the organism. This research has shown that S. capricornutum is sensitive to the free Copper ion, Cu 2+ (aq), irrespective of the total copper concentration.

Detailed analysis of the physical, chemical, pollen and diatom stratigraphy of sediment cores from Bull Run Lake, Oregon reveals that the lake has been subject to repeated episodes of disruption by volcanic ash fall, fire and other disturbance over the past 4300 years. With the exception of fire, these disruptions have not resulted in long term changes in the watershed or in the characteristics of Bull Run Lake. A major fire in the watershed about 750 years ago altered the vegetation. Since that time the forest has been returning to its former condition.

Modelling of stream macroinvertebrate communities has been widely accepted as an interesting and powerful tool to support water quality assessment and management. Stream Decision Support Framework (SDSF) offers an alternative approach to the current statistical models as Australian River Assessment Scheme (AusRivAs) for the derivation of scientific basis to support management applications regarding fresh water systems. Implementation of Artificial Neural Networks (ANNs) offers a possibility to overcome constraints of the statistical methods in dealing with high nonlinearity of stream data. This thesis includes several case studies illustrating application of Self Organising Map (SOM) and Multilayer Perceptron (MLP) neural networks to various tasks involving analysis, assessment and prediction of stream macroinvertebrates in three Australian states. The data for this study have been provided by the Queensland Department of Natural Resources (NR&M), EPA Victoria and the Department of Land and Water Conservation, New South Wales (NSW). SDSF approach utilises predictive models for both 'referential' and 'dirty-water' approaches. Applicability and high accuracy of ANN models for the purpose of prediction both occurrence of individual taxa and taxonomic richness of stream macroinvertebrates have been demonstrated using data from Victoria and NSW. A comprehensive analysis of salinity sensitivity of stream macroinvertebrate has been demonstrated using both types of ANNs plus statistical methods, and pressure specific Salinity Index was suggested as a measurement of changes within macroinvertebrate communities in response to the secondary salinisation. Scenario analysis of the combined effect of increasing salinity and nutrient load demonstrated predictability and ecological meaningfulness of the Salinity Index. Application of SOM has been demonstrated using the data from Queensland and Victoria in order to analyse natural variability of macroinvertebrate communities between reference sites. SOM component planes provided a valuable insight into the relationships between abiotic variables (as water quality and geoclimatic factors) and distribution of taxa and trophic structure of macroinvertebrate communities. Potential of SOM as data exploration tool has been also demonstrated for the analysis of the output of scenario simulation in order to understand the difference in response to salinisation in different sites. Flexibility and potential of SDSF have been illustrated by using the combination of SOM and MLP, and combination of ANNs with statistical methods. Application of both SOM and Canonical Correspondence Analysis allowed the extraction of additional information and provided convenient visualisation of the relationships between water quality factors and the structure of macroinvertebrate communities. In general, SDSF provides convenient, flexible and accurate approach for the analysis, assessment and prediction of stream biota. In addition to the freedom from the limitations inherent to the traditional statistical methods it allows many more options than currently used modelling frameworks, namely: highly accurate predictions using both 'referential' and 'dirty-water' approaches, sensitivity analysis, scenario analysis and pattern exploration using SOM. / Thesis (Ph.D.)--School of Earth & Environmental Sciences, 2005.

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<p>In the spring of 2007 the Kuba Dam in Nätra Stream was removed for restoration purposes, mainly to give free passage to migrating fish. This action gave an opportunity to study the effects of dam removal on organisms both on land and in water, a type of study which is in demand for planning purposes of future dam removals. This study focuses on the effects upon the vegetation along the stream where the former reservoir was situated. Willow cuttings and sunflower seeds were used as phytometers to assess the growth conditions one year after removal at three different elevation levels at four different sites along the Nätra Stream. The reaches studied were the former reservoir of Kuba Dam (Site A), the area just downstream of this former dam (Site B), further upstream in the reservoir of the existing Nyfors Dam (Site C), and even further upstream at Myreforsen, a reference area not affected by dams (Site D). Willow cuttings and sunflower seeds were planted at three different riparian levels at the sites in June and left to grow until August when growth results were collected. Many of the cuttings had died but statistically significant differences between sites could still be detected. They showed that the former reservoir shorelines in Kuba (Site A) had a plant growth significantly higher than the other regulated site. In other words, it was no longer equal to an existing reservoir but not yet similar to a free-flowing reach. The western side of the stream at this site had a higher growth than the eastern side and also higher than all the other sites. As for the three levels, the results showed a higher growth at the lowest elevation level at site A than all at the other levels and sites. This suggests that a combination of good access to sunlight and nutrients and fine-grade moist substrate results in a good growing conditions nearer the water in this former reservoir. The results for the sunflower seeds showed that the reference reach had a higher colonization success than the other sites.</p> / <p>Utrivningen av Kubadammen i Nätraån våren 2007 gav möjlighet att studera och följa upp hur en sådan förändring påverkar organismer på land och i vatten både uppströms och nedströms den tidigare dammen. Denna typ av undersökningar efterfrågas allt mer i och med att fler och fler dammar rivs av olika anledningar. I Kubadammens fall hade dammen förlorat sin ursprungliga roll och de fördelar som magasinet förde med sig för bland annat rekreation vägde inte längre upp dämningens negativa effekter på vattendragets ekosystem, till exempel som vandringshinder för fiskar. I denna studie har fokus lagts på vad som sker med vegetationen på stränderna längs det forna vattenmagasinet efter rivning. Med hjälp av videkvistar och solrosfrön som fytometrar undersöktes tillväxten ett år efter rivning på tre olika strandnivåer på fyra olika lokaler längs Nätraån. Dessa lokaler var Kubadammens gamla magasin (Lokal A), området direkt nedströms den före detta dammen (Lokal B), den nuvarande Nyforsdammens magasin (Lokal C) uppströms den före detta dammen, samt en referenssträcka vid Myreforsen (Lokal D) uppströms alla Nätraåns dammar och därmed ej påverkad av dämningseffekter. Videkvistarna och solrosorna planterades på tre nivåer på de olika lokalerna i juni och tilläts växa till augusti då tillväxtresultaten samlades in. Många kvistar hade dött under tiden men tillräckligt många överlevde för att det skulle gå att läsa ut statistiskt signifikanta skillnader i tillväxt. Resultaten visade att det före detta magasinet vid Kuba (Lokal A) hade en signifikant högre tillväxt än de andra lokalerna, vilket visar på att tillväxtförhållandena för vide varken liknar dem i ett befintligt magasin eller på en orörd sträcka eller nedströmssträckan, utan var betydligt mer gynnsamma. På denna lokal växte fytometrarna dessutom signifikant bättre på den västra sidan än på den östra sidan. När man ser till de tre nivåerna så växte videkvistarna i nivån närmast vattnet i det före detta magasinet vid Kuba bättre än på de övriga nivåerna på samma lokal och på de övriga lokalerna. Troligtvis beror detta på en kombination av öppenhet som ger bra tillgång till solljus, bra näringstillgång, substratets finkornighet och förmåga att hålla kvar fukt närmare vattnet. Resultaten av solrosfrönas etablering visade på att referenssträckan hade en högre etablering än övriga lokaler.</p>