Abstract Water level regulation for purposes of hydropower production has caused notable changes in the littoral zones of regulated lakes in northern Finland. Marked geomorphological changes have taken place in the lakes with a raised water level. Lowering of the ice cover during the winter has also caused rapid changes in the littoral. Changes in the environmental conditions and aquatic macrophyte communities were studied largely by comparing the regulated Lake Ontojärvi and the unregulated Lake Lentua in the Kainuu area. The general aims of the study were to analyse environmental effects, to produce information of ecological relationships for remedial measures on the littoral and to apply the restoration methods in the management of regulated lakes. The most obvious effect of regulation was the expanded area of extending ice, which caused an almost complete disappearance of large ice-sensitive isoetids (Isoetes lacustris L., Lobelia dortmanna L.). These species were largely replaced by small erosion resistant isoetids (Ranunculus reptans L., Eleocharis acicularis (L.) Roem. & Schult.). Another significant change was the decreased frequency of large helophytes due to increased erosion. A model based on environmental factors was able to predict roughly the main vegetation types. Permanent plot studies showed no significant differences in the stability of the vegetation between the research lakes, which means that the species pool had adapted to the harsh environment. Restoration techniques based on mechanical protection of shorelines and revegetation were applied to Lake Ontojärvi. The hostile environmental conditions caused a rapid decline of the planted species, but tall Salix phylicifolia L. seedlings and Carex rostrata Stokes were able to survive, although in low abundance. More significant remedial measures were provided by the Ecologically-based Regulation Practices (ERP), which have been applied to several lakes under hydropower production. This procedure, which was largely based on the results of the Kainuu studies, offers a simple way to illustrate the differences between various regulation practices. Two case studies showed that an exceptional year with extremely high or low water levels can largely abolish the positive succession achieved by ERP. The huge financial losses caused by ERP for hydropower production have also promoted the use of other conventional restoration measures.

The aim of this thesis is to evaluate developement of selected lakes in area Základna in upper Lužnice basin. The area of interest is located in nature reservation Horní Lužnice, which extends from state border with Austria to Suchdol nad Lužnicí. This part of the river is very preserved almost without any anthropogenic influence. Eventhough it is the middle part of the river, it has developed floodplain with meandering belt, which is typical for lower parts of rivers. Because of its conditions, this area is very convenient for observing natural spills and studying fluvial lakes, which occure here in huge amount. First part of this work describes characteristic of the study area, fluvial lakes and natural spills and floods in the area. The main second part focuses on research of selected lakes and their developement. During several field researches the lakes were mapped and measured and soil samples were taken from the lake beds. Furthermore flow in floodplain during river spill was measured and data from automatic surface level sensors were evaluated, which show mutual connections of fluctuations of the lakes and the river. In conclusion the results of measurement were compared with previous theses regarding this area. Main results are that common spills cause clogging of lakes but intense floods...

<p>High density sampling (n=50) was conducted in Cootes Paradise, a shallow wetland on the western shoreline of Lake Ontario near the city of Hamilton. Cootes Paradise is an urban wetland that has been affected by pollutants and nutrients and invasive carp. Thecamoebian analyses paired with site specific environmental measurements (depth, sp. conductivity, temperature, DO and pH) and substrate characteristics (textural and organic content -LOI) show relationships (R² = 0.6) with depth (0-1m) and corresponding sp. conductivity (0.5 to 0.65 mS/cm) and temperature (26.5 to 30.5 °C). Q-mode cluster analysis recognized two biofacies. Biofacies 1 samples (n= 26) are found in the deeper areas (0.70 ± 0.27 m) and dominated by <em>C. tricuspis</em> 36 ± 8% (1 std), <em>L. vas</em> 18 ± 13% and <em>D. protaeiformis “claviformis”</em> 14 ± 6%. Mean water temperature is 28.0 ± 0.6 °C and conductivity at 0.56 ± 0.04 mS/cm. This assemblage has low species diversity (SDI=1.9 ± 0.3) which indicates a transitional environment. Biofacies 2 contains samples (n= 24) which are found in shallower areas (0.38 ± 0.15 m) and the assemblage is characterized by <em>C. constricta “aerophila”</em> 25 ± 8%, <em>C. tricuspis</em> 18 ± 5%, <em>Cyclopyxis sp.</em> 9 ± 6 % and <em>L. vas</em> 9 ± 4 %. The SDI for Biofacies 2 is 2.2 ± 0.2 and like Biofacies 1 shows a transitional environment. The average temperature is and 29.0 ± 1.0 °C with mean sp. conductivity also slightly higher than Biofacies 1 at 0.6 ± 0.04 mS/cm.</p> / Master of Science (MSc)

The scope of this thesis was to identify, describe and quantify important life-history traits for the pseudoannual aquatic plant Ranunculus lingua in different ecological settings, by comparing populations from geographically marginal vs. central habitats. Results from a four-year field study showed that abiotic factors (water-level fluctuations and associated processes) tended to have a greater influence in marginal populations, whereas biotic factors (competition, insect grazing and fungal infections) dominated in central populations. This was reflected in different depth distribution of ramet numbers and ramet sizes between the areas, and In different dynamic patterns, with a higher flux of ramets in marginal populations. In a reciprocal transplant experiment, marginal ramets produced more but smaller rhizomes, whereas central ramets produced Individually larger but fewer rhizomes, irrespective of transplant site. A possible selection for genotypes producing large rhizomes in the central habitat was supported by the fact that initially smaller ramets were more likely to be diseased by the fungal pathogen Peronospora gigantea and damaged by insect grazing. In the marginal population, where density-independent mortality factors tend to dominate, a high reproductive output, expressed in production of high numbers of rhizomes, was suggested to be a favoured life-history trait. In a glasshouse experiment, ramets from marginal and central populations were grown in low and high densities and under three contrasting nutrient levels. The allocation to sexual structures was generally very low, and did not incur any costs in terms of reduced rhizome production. Rhizome production showed strong positive allometrical relationships to mother ramet size. Increasing mother ramet size resulted in a larger increase in rhizome numbers for the marginal than for the central population, whereas the increase in mean rhizome mass was more pronounced for the centred population. Both populations showed similar reductions in rhizome production in response to increased density and lowered nutrient levels, which could not be explained by size-dependent effects adone. The dispersal, dynamics and distribution of R. lingua were studied in a marginal river population in northern Sweden, where the only means of dispersal is by vegetative diaspores, i.e. floating rhizome fragments. Stranding occurred mainly in river curves and at obstacles, and the distribution of established stands was also highly correlated with these features. Relative changes in ramet numbers were correlated with water-level fluctuations during the present and previous growing seasons, with winter low-water, and with duration of spring-flood. The predictability of change was high within but low between stands. It was concluded that the patterns and mechanisms of dispersal are fundamental for local distribution patterns as well as variation in regional abundance in R. lingua / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 4 uppsatser</p> / digitalisering@umu