The aim of this report was to quantify the accumulation of carbon dioxide (CO2) and methane (CH4) in ice-covered lakes in winter (October-March) during three consecutive years, and to assess whether the concentrations of DIC and CH4, as well as the ratio DIC:CH4 differs between years and between lakes affected by clearcutting and untreated reference lakes. Water- and gas samples were collected from four boreal lakes (two affected by clearcutting and two untreated reference lakes) located in Västerbottens inland in spring. The lakes were found to accumulate on average 91, 55, and 84 mgCm-2d-1 during winters 2012-2013, 2013-2014, and 2014-2015, mostly originating from CO2. The concentrations of DIC (autumn and spring) were higher in the affected clear-cut lakes compared to reference lakes for all years, including the reference year (2012-2013) before clear-cutting. No such difference was found for CH4 or the ratio DIC:CH4.

Forestry is an important industry in Sweden, with clear-cut as the most commonly used method for harvesting. Here the long-term impact of clear-cut on lake water quality (dissolved organic carbon (DOC), nitrogen, phosphorus and pH) has been investigated, based on 23 lakes sampled during autumn. Data for additional 15 lakes sampled for the Swedish monitoring program were also used. Lakes were classified as 5, 25, 40 and 60 year based on data of the forest age in the catchment, gathered from the Swedish national forest inventory. Clear-cut lakes were classified as 5 years (>20% of the catchment clear-cut during the last 10 years).

This work investigates the breeding success of the Black-throated Diver, Gavia arctica, related to the water quality in three lakes located in the Vallentuna area, north of Stockholm, Sweden.For more than 30 years, I have studied the bird life around these three and other nearby lakes, and noticed that the Black-throated Diver breeds in some lakes, but not in others.The results confirm that the deep and clear lakes Tärnan and Stora Harsjön have good water quality regarding pH, alkalinity, aluminium and Secchi disk values. As expected, the Black-throated Diver shows breeding success in those two lakes, but does not breed in the shallow and eutrophic lake Mysslingen. .

Konflikterna i Great Lakes-regionen har präglats av både flyktingströmmar och etniska dimensioner. Vi har genomfört en fallstudie på detta område för att undersöka vilken betydelse flyktingar har för konflikterna i regionen.Vi visar hur flyktingströmmarnas karaktär och flyktingskapets utsatthet leder till skärpta etniska spänningar och bidrar till försvagandet av stater. Flyktingarnas osäkra livssituation och kollektiva minnen innebär ett särskilt starkt identitetsbehov, vilket kan leda till ökad etnisk polarisering och gör att de blir lätta att mobilisera politiskt.Flyktingströmmar orsakar ett allvarligt försvagande av stater, eftersom de på ett fundamentalt sätt underminerar statens legitimitet, genom exempelvis deras förlorade förtroende för staten och dess institutioner samt deras inblandning i väpnade attacker mot hemlandet.Generellt uppmärksammas flyktingströmmar oftast bara som en allvarlig konsekvens av konflikter, men vi visar hur de också kan förstås som en starkt bidragande orsak till inomstatlig och regional instabilitet..

Freshwater ecosystems have long been neglected as an important part of the global carbon cycle. However, research shows that most of the world?s lakes are net-heterotrophic and consequently emitters of greenhouse gases to the atmosphere. In many boreal and north-temperate lakes, most of the yearly emissions usually occur in spring, shortly after ice-thaw. The aim of this study was to quantify the flux of carbon dioxide (CO2) and methane (CH4) in three boreal lakes, during this annual event.

To investigate effects of nitrogen on in-lake CO2 and CH4 production during winter, three pair of lakes was subject for a fertilizing experiment in which one lake in each pair was fertilized with nitric acid (HNO3) directly into the water column in the summer of 2012. The lakes in each pair are assumed to be morphologically, hydrologically and biologically similar, that is, the non-fertilized lakes are considered references. The pairs do differ in one major way by being progressively less humic, going from around 25 mg/l to 10 mg/l DOC. Sampling and analysis was carried out at the end of the frozen period in 2013. Results show a significantly higher concentration of both CO2 (p<0,001) and CH4 (?=0,1, p=0,053) between impact and reference sites in the two less humic pairs.

According to the Water Framework Directive of the European Union, macrophytes should be used as indicators in the ecological and environmental monitoring of lakes. In the member state Sweden the Environmental Protection Agency has elaborated assessment criteria for determining lake status based on macrophytes. The main focus of this thesis is to evaluate the efficiency of the assessment criteria for macrophytes. In addition the concordance between the ecological status classes of the four quality factors included was analysed.The assessment criteria for macrophytes are based on the total phosphorus preference of the respective species. The focus is thus mainly on the nutrient level of the investigated lakes and the environmental problem monitored is eutrophication.

Lake lowering in sulphide-rich areas is currently a major environmental impact for surface water. This study focuses on whether there is a relationship between a gradient of lake lowering and surface water impacts in areas of sulphide-rich sediments, in order to better understand their contribution of heavy metals and sulfuric acid. Also, is it a reasonable method to use the reduced lake area in order to quantify the gradient? The survey was conducted by collecting water samples from reference lakes and lowered lakes from south to north in coastal areas within the county of Västerbotten. Water samples were then analyzed for TOC, pH, conductivity, anions, base cations, alkalinity, acidity, sulfate, Al, Cd, Fe, Mn, Cu, Zn and Pb.

In this study the practical work with the EU Water Framework starts on the island of Gotland. 33 lakes and 32 streams have been characterized and classified regarding to their ecological status. The aim with the characterisation is to create a uniform discription of all waterbodies and a comparable estimation for the future. The aim with the classification is both to study the waterbodies ecological status and to gain knowledge of where the resources should be concentrated so that the ecological status in all waterbodies will be good in 2015.The characterisation has been done according to the EU Water Framework Directive, and the factors that have been applied are the mean depth and area of the lake. The length and size on the catchment area are the factors that have been used on streams.

Stage-discharge equations for lakes without disharge measurementsSimon AnderssonIn 2015 all lakes, rivers, coastal water and groundwater should be of good ecological statusaccording to the water framework directive from the European Union. In the process ofimproving the quality of Swedish water bodies, knowledge of where problems occur isneeded in order to utilize the resources optimally. The ability of lakes to store water is animportant factor since it controls the flow of water through the country. A stage-dischargeequation is a mathematical relation between discharge from a lake and its water level. Bybetter understanding of stage-discharge equations for lakes, their storage capacity can bedescribed better in hydrological models.This master thesis aims to evaluate methods for determining stage-discharge equations forlakes where a variable amount of field measurements is available.

The main purposes of this study were to 1) quantify bacterial production in winter during ice conditions, and 2) to compare these production measures with values measured from summer and open water conditions in three humic lakes situated in northern Sweden. Another purpose of this study was to 3) examine whether clear-cutting significantly affected bacterial production or water chemistry in two lakes situated in catchments were a large part of the forest had been removed through logging compared to an undisturbed reference lake. In winter (March/April 2014), the bacterial production ranged from 0, 7 - 2, 2 µgC/L/day and in the summer of 2013 the production values was 4 ? 10 times higher. The main reason for lower bacterial production in winter was ascribed to lower water temperatures as well as to older and more recalcitrant DOC, as there were no significant differences in total dissolved nitrogen or DOC concentration or -quality, that could explain a lower production compared to summer.

This is a study of the insect community associated to the wood-decaying fungus Inonotus radiatus found on Alnus glutinosa trees growing in riparian forests at the northern and southern shores of boreal lakes in the province Uppland. Little is known about this particular bracket fungus and its inhabitants. Insects were reared out at the laboratory from samples of fruiting bodies of the fungus taken at five lakes. During the fieldwork in 2009, data about several environmental variables was also taken. After the rearing period, these variables and their effects over the insects were analyzed.

Development of morphs within European whitefish (Coregonus lavaretus), might be considered as a beginning of a sympatric speciation process. Unpublished data suggests that presence of the keystone piscivore northern pike (Esox lucius) is the main driver of sympatric divergence in European whitefish (Coregonus lavaretus). Using introduced whitefish populations as controlled experiments, it is possible to determine when different characters diverge in the speciation process. In this study, I analysed age and growth within European whitefish populations of different age to assess if these characters change over time in absence of pike. With using otoliths from whitefish populations of different age, I was possible to determine individual age, and by measuring the length of the fish, growth was calculated.

The Earths climate is changing at a higher rate, i.e between 1861 and 1994 the annual mean temperature in Scandinavia increased with 0,68º C and according to recent climate models the annual mean temperature is likely to rise with another 3º C during this century.A warmer climate in many ways is associated with changing conditions for lake ecosystems. An expected higher water temperature and a stronger summer stratification of the water column increases the risk of anoxic conditions at the lake bottom. Thus anoxic conditions are likely to cause a phosphate leakage from the sediment, i.e. a higher internal loading of phosphate.In this project, the extremely warm summer of 2002 has been used as an example for a possible scenario for a future climate. By comparing levels of phosphorus in the summer of 2002 with a ten-year median value, a phosphorus related sensitivity to climate change has been analyzed for 55 Swedish lakes.

A distributed hydrological rainfall-runoff model has been developed using a GIS integrated with a dynamic programming module (PCRaster). The model has been developed within the framework of the EU-project TWINBAS at IVL Swedish Environmental Research Institute, and is intended for use in WATSHMAN ? a tool for watershed management developed at IVL. The model simulates runoff from a catchment based on daily mean values of temperature and precipitation. The GIS input data consist of maps with soil type, land-use, lakes, rivers and a digital elevation model.