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Since 1750, human emissions of greenhouse gases have created a temperature increase, affecting the whole world. Diatoms, single-celled microscopic algae that lives in waters all over the world, have different environmental preferences such as the water depth at which the thrive, salinity, nutrients, pH-values and more. Diatoms also responds quickly to changing circumstances, which makes the suitable as environmental indicators. The purpose of the study is to investigate how the abundance and composition of diatoms has changed during the last 200 years in lake Ensjön, located just south of Norrköping, and to relate those changes both to climate change and known events and environmental factors in the area. The survey is conducted by subsampling sediment cores from which each diatom sample was prepared in accordance with the scheme of Battarbee (1984). The diatoms in the samples were counted under a microscope and the results were analyzed and related to the Cyclotella-Aulacoseira-Fragilaria-theory (CAF) and documented historical events in the local environment. The result of the analysis shows that the composition and abundance of diatoms has changed during the last 200 years, and that this change is due to both climate change (temperature and precipitation increase) and the land-use history of Ensjön. The cahnges in composition of Aulacoseira spp. and Cyclotella spp., where Aulacoseira spp. is expected to decrease, and Cyclotella spp. is expected to increase with a rising temperature, match the CAF-theory for the most part. The change in composition also coincides with several documented environmental factors in the area, especially the change in use of fertilizers and herbicides in agriculture., Människans utsläpp av växthusgaser har sedan år 1750 skapat en temperaturökning som går allt snabbare, och påverkar hela världen. Kiselalger, encelliga mikroskopiska alger som lever i vatten över hela världen, har olika miljöpreferenser såsom bland annat på vilket vattendjup de trivs, optimal halt av salt, näringsvärden, pH-värden, samt reagerar snabbt på förändrade omständigheter, vilket gör dem lämpliga som miljöindikatorer. Syftet med studien är att studera förändringar i kiselalgernas sammansättning under de senaste 200 åren i den lilla sjön Ensjön belägen något söder om Norrköping och att relatera dessa förändringar till dokumenterade händelser och miljöfaktorer i sjöns avrinningsområde samt till de pågående klimatförändringarna. Undersökningen är utförd genom provtagning av sedimentkärnor från vilka prover preparerades enligt Battarbees (1984) flödesschema. Proverna av kiselalger räknades under mikroskop och sammansättningen analyserades utifrån teorin Cyclotella-Aulacoseira-Fragilaria (CAF) och kända historiska händelser i närmiljön. Analysresultatet visade att kiselalgssammansättningen har förändrats under de senaste 200 åren, och att denna förändring sannolikt kan kopplas både till klimatförändringar (en ökad temperatur) och Ensjöns markanvändningshistoria. Förändringen hos Aulacoseira spp. och Cyclotella spp. följer till stor del CAF-teorin om att det första släktet skulle minska och det andra skulle öka vid en temperaturökning. Vid flera tillfällen sammanfaller förändringar i kiselalgssammansättningen med kända miljöfaktorer i närmiljön, främst i samband med utvecklingen i användningen av mineralgödsel och växtskyddsmedel.

An overview of the diatom flora of the last interglacial (Eemian) lacustrine gyttja deposit at Sokli, northeastern Finland is presented together with descriptions including photomicrographs of resting spores similar to the Aulacoseira islandica-skvortzowii group, not found in recent material from Europe. Comparisons are made with literature data on similar taxa. The morphology of the resting spores (e.g., the number of striae and areolae in 10 mu m) links them to the A. islandica-skvortzowii group, but the lack of vegetative cells in the Sokli record makes the determination of true synonymy difficult. The presence of spores similar/related to the A. islandica-skvortzowii group in the Sokli Eemian palaeolake may reflect a more widespread distribution of this group in the past.

N/A, In the last few decades, Nyanza Gulf, which is one of the largest, shallow and semi-enclosed gulfs (1400 km2, mean depth, 5m) of Lake Victoria, has become eutrophic as revealed by the regular occurrence of harmful algal blooms formed by cyanobacteria of the genus Microcystis. Nyanza Gulf is connected to the main lake basin through the wide Rusinga Channel. In May 2017, a section of the Mbita Channel, which is another natural water exchange route, was reopened. The reconnection has been expected to enhance water exchange with the main basin, eventually increasing dilution of the Gulf. The aims of this thesis were (i) to investigate the main basin influence on water chemistry and phytoplankton in Nyanza Gulf using specific conductivity as a tracer (chapter 1), (ii) examine the response of planktonic diatom composition to eutrophication in Nyanza Gulf (chapter 2), (iii) quantify microcystins (MC) concentrations and other cyanotoxins (chapter 3), (iv) quantify MCs concentrations in plankton and in small sized fish in the period before the reopening of the Mbita channel. Three sampling stations West Gulf (located near the main basin), Mid Gulf (located at the central part of the gulf) and East Gulf (located close to Kisumu City) were sampled monthly from July 2017 to July 2018. In order to monitor the water exchange with the main basin specific conductivity and water level were recorded daily from the shore located close to sampling points. During a follow-up study from September 2019 to August 2020, daily measurements for specific conductivity and surface flow through the Mbita-Rusinga Bridge were performed in parallel to recording water level and specific conductivity at the East Gulf shore. Phytoplankton were enumerated using an inverted microscope, and light microscopy (LM) and scanning electron microscopy (SEM) were used to investigate diatom taxonomy (SEM). The total phosphorus (TP) determination was performed using the Ammonium Molybdate Method after water samples, by Bernard Mucholwa Simiyu, Kumulative Dissertation aus fünf Artikeln, Dissertation University of Innsbruck 2021

N/A, In the last few decades, Nyanza Gulf, which is one of the largest, shallow and semi-enclosed gulfs (1400 km2, mean depth, 5m) of Lake Victoria, has become eutrophic as revealed by the regular occurrence of harmful algal blooms formed by cyanobacteria of the genus Microcystis. Nyanza Gulf is connected to the main lake basin through the wide Rusinga Channel. In May 2017, a section of the Mbita Channel, which is another natural water exchange route, was reopened. The reconnection has been expected to enhance water exchange with the main basin, eventually increasing dilution of the Gulf. The aims of this thesis were (i) to investigate the main basin influence on water chemistry and phytoplankton in Nyanza Gulf using specific conductivity as a tracer (chapter 1), (ii) examine the response of planktonic diatom composition to eutrophication in Nyanza Gulf (chapter 2), (iii) quantify microcystins (MC) concentrations and other cyanotoxins (chapter 3), (iv) quantify MCs concentrations in plankton and in small sized fish in the period before the reopening of the Mbita channel. Three sampling stations West Gulf (located near the main basin), Mid Gulf (located at the central part of the gulf) and East Gulf (located close to Kisumu City) were sampled monthly from July 2017 to July 2018. In order to monitor the water exchange with the main basin specific conductivity and water level were recorded daily from the shore located close to sampling points. During a follow-up study from September 2019 to August 2020, daily measurements for specific conductivity and surface flow through the Mbita-Rusinga Bridge were performed in parallel to recording water level and specific conductivity at the East Gulf shore. Phytoplankton were enumerated using an inverted microscope, and light microscopy (LM) and scanning electron microscopy (SEM) were used to investigate diatom taxonomy (SEM). The total phosphorus (TP) determination was performed using the Ammonium Molybdate Method after water samples, by Bernard Mucholwa Simiyu, Kumulative Dissertation aus fünf Artikeln, Dissertation University of Innsbruck 2021

Since 1750, human emissions of greenhouse gases have created a temperature increase, affecting the whole world. Diatoms, single-celled microscopic algae that lives in waters all over the world, have different environmental preferences such as the water depth at which the thrive, salinity, nutrients, pH-values and more. Diatoms also responds quickly to changing circumstances, which makes the suitable as environmental indicators. The purpose of the study is to investigate how the abundance and composition of diatoms has changed during the last 200 years in lake Ensjön, located just south of Norrköping, and to relate those changes both to climate change and known events and environmental factors in the area. The survey is conducted by subsampling sediment cores from which each diatom sample was prepared in accordance with the scheme of Battarbee (1984). The diatoms in the samples were counted under a microscope and the results were analyzed and related to the Cyclotella-Aulacoseira-Fragilaria-theory (CAF) and documented historical events in the local environment. The result of the analysis shows that the composition and abundance of diatoms has changed during the last 200 years, and that this change is due to both climate change (temperature and precipitation increase) and the land-use history of Ensjön. The cahnges in composition of Aulacoseira spp. and Cyclotella spp., where Aulacoseira spp. is expected to decrease, and Cyclotella spp. is expected to increase with a rising temperature, match the CAF-theory for the most part. The change in composition also coincides with several documented environmental factors in the area, especially the change in use of fertilizers and herbicides in agriculture., Människans utsläpp av växthusgaser har sedan år 1750 skapat en temperaturökning som går allt snabbare, och påverkar hela världen. Kiselalger, encelliga mikroskopiska alger som lever i vatten över hela världen, har olika miljöpreferenser såsom bland annat på vilket vattendjup de trivs, optimal halt av salt, näringsvärden, pH-värden, samt reagerar snabbt på förändrade omständigheter, vilket gör dem lämpliga som miljöindikatorer. Syftet med studien är att studera förändringar i kiselalgernas sammansättning under de senaste 200 åren i den lilla sjön Ensjön belägen något söder om Norrköping och att relatera dessa förändringar till dokumenterade händelser och miljöfaktorer i sjöns avrinningsområde samt till de pågående klimatförändringarna. Undersökningen är utförd genom provtagning av sedimentkärnor från vilka prover preparerades enligt Battarbees (1984) flödesschema. Proverna av kiselalger räknades under mikroskop och sammansättningen analyserades utifrån teorin Cyclotella-Aulacoseira-Fragilaria (CAF) och kända historiska händelser i närmiljön. Analysresultatet visade att kiselalgssammansättningen har förändrats under de senaste 200 åren, och att denna förändring sannolikt kan kopplas både till klimatförändringar (en ökad temperatur) och Ensjöns markanvändningshistoria. Förändringen hos Aulacoseira spp. och Cyclotella spp. följer till stor del CAF-teorin om att det första släktet skulle minska och det andra skulle öka vid en temperaturökning. Vid flera tillfällen sammanfaller förändringar i kiselalgssammansättningen med kända miljöfaktorer i närmiljön, främst i samband med utvecklingen i användningen av mineralgödsel och växtskyddsmedel.

Aulacoseira subarctica f. subborealis differs from A. subarctica var. subarctica by a number of morphological features (smaller linking spines without areolae on their base, shorter spine grooves, discus always areolated, shallower mantle and different 'Formwechsel', considerably finer structure, rimoportula on the inner side of the pseudoseptum), as well as its ecological preferences. It is therefore considered to represent a separate species: A. subborealis stat. nov. Characteristics that differ from those of the similar species, A. alpigena, include the non-spathulate linking spines, each one originating from two pervalvar ribs, more numerous areolae on the disci, smaller dimensions, finer areolation of the mantle and, in the LM, absence of more marked mantle areolae next to the collum. In the LM, confusion may further arise with A. laevissima, A. distans or A. nygaardii, which also show some resemblance to A. subborealis. Aulacoseira subborealis is widely distributed in rivers and lakes in W-Europe and Australia, and presumably occurs in New Zealand and North America as well, but has been reported only rarely because of confusion with other taxa. It appears to develop especially well in more alkaline and rather eutrophic, highly turbid fresh water. Yet, this planktonic species is unable to withstand extremely severe eutrophication or pollution.

An overview of the diatom flora of the last interglacial (Eemian) lacustrine gyttja deposit at Sokli, northeastern Finland is presented together with detailed descriptions including photomicrographs of resting spores similar to the Aulacoseira islandica-skvortzowii group, not found in recent material from Europe. Comparisons are made with literature data on similar taxa. The morphology of the resting spores (e.g. the number of striae and areolae in 10 µm) attributes them to the A. islandica-skvortzowii group but the lack of vegetative cells in the Sokli record makes declaration of true synonymy difficult. The presence of spores similar/related to the A. islandica-skvortzowii group in the Sokli Eemian palaeolake may reflect a more widespread distribution of this group in the past.