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Microdomains in freshwater sediment as a driving factor in the biogeochemical processes
Duchoslav, Vojtěch ; Falteisek, Lukáš (advisor) ; Beranová, Jana (referee)
A natural arsenic anomaly at Mokrsko is a site of biogenic precipitation of realgar (As4S4) in stream sediment. The extent of the phenomenon in Mokrsko is globally unique. A previous study showed the ability of microorganisms to solubilize arsenic from its secondary minerals and to produce realgar precursors, i.e. sulfides and arsenites, by anaerobic respiration. The study also raised questions about the mechanism of realgar precipitation since physicochemical conditions favoring this reaction were never detected despite significant sampling efforts. We chemically and microbiologically analyzed sedimentary profiles to the depth of ca. 120 cm in order to understand the functioning of the biogeochemical system. The profiles comprised both the unsaturated and the saturated zone. We distinguished six different domains representing environments from the surface soil to anoxic sedimnent containing realgar-encrusted wood. An analysis of phylogenetic dissimilarity revealed that microbial communities from the various domains form distinct clusters. This suggests that different conditions prevail in the various domains, and that different biogeochemical processes take place there. Incubation (microcosm) experiments showed that bioprecipitation of realgar can be conducted in vitro. It requires a suppression...
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Methods of study habitats and microhabitats preferences of freshwater fishes of Central Europe
Žák, Jakub ; Švátora, Miroslav (advisor) ; Drozd, Bořek (referee)
Small streams are a common habitat in Central Europe with unstable, rapidly-changing conditions. We can examine habitats on three different scales: microhabitat, mesohabitat and macrohabitat. Habitat preferences were among the fields of interest of Antonín Frič as he tried to describe the changing gradient of fish assemblages from source to the river's mouth on the macrohabitat scale. Habitat preferences are examined from a spatial point of view (substrate, depth, shelter), temporal point of view (season, day/night), biotic point of view (interspecies and intraspecies competition) and abiotic point of view (dissolved chemicals, velocity). For obtaining data of good quality, it is necessary to choose the right location and select the opti- mal strategy of examining fish assemblages (e.g. electrofishing, radiotelemetry, cameras). All variables which can affect habitat preferences in fish are measured. Multivariate statistical methods (e.g. PCA, RDA, CCA, CA) are used for evaluation of obtained datasets. Currently, we live in a fast developing period of this scientific area because of the need of evaluation of the human impact on freshwater biotope. The aim of this bachelor thesis is to introduce variables which influence habitat pref- erences of fish, to propose a modern review of methods commonly...
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Microdomains in freshwater sediment as a driving factor in the biogeochemical processes
Duchoslav, Vojtěch ; Falteisek, Lukáš (advisor) ; Beranová, Jana (referee)
A natural arsenic anomaly at Mokrsko is a site of biogenic precipitation of realgar (As4S4) in stream sediment. The extent of the phenomenon in Mokrsko is globally unique. A previous study showed the ability of microorganisms to solubilize arsenic from its secondary minerals and to produce realgar precursors, i.e. sulfides and arsenites, by anaerobic respiration. The study also raised questions about the mechanism of realgar precipitation since physicochemical conditions favoring this reaction were never detected despite significant sampling efforts. We chemically and microbiologically analyzed sedimentary profiles to the depth of ca. 120 cm in order to understand the functioning of the biogeochemical system. The profiles comprised both the unsaturated and the saturated zone. We distinguished six different domains representing environments from the surface soil to anoxic sedimnent containing realgar-encrusted wood. An analysis of phylogenetic dissimilarity revealed that microbial communities from the various domains form distinct clusters. This suggests that different conditions prevail in the various domains, and that different biogeochemical processes take place there. Incubation (microcosm) experiments showed that bioprecipitation of realgar can be conducted in vitro. It requires a suppression...
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Methods of study habitats and microhabitats preferences of freshwater fishes of Central Europe
Žák, Jakub ; Švátora, Miroslav (advisor) ; Drozd, Bořek (referee)
Small streams are a common habitat in Central Europe with unstable, rapidly-changing conditions. We can examine habitats on three different scales: microhabitat, mesohabitat and macrohabitat. Habitat preferences were among the fields of interest of Antonín Frič as he tried to describe the changing gradient of fish assemblages from source to the river's mouth on the macrohabitat scale. Habitat preferences are examined from a spatial point of view (substrate, depth, shelter), temporal point of view (season, day/night), biotic point of view (interspecies and intraspecies competition) and abiotic point of view (dissolved chemicals, velocity). For obtaining data of good quality, it is necessary to choose the right location and select the opti- mal strategy of examining fish assemblages (e.g. electrofishing, radiotelemetry, cameras). All variables which can affect habitat preferences in fish are measured. Multivariate statistical methods (e.g. PCA, RDA, CCA, CA) are used for evaluation of obtained datasets. Currently, we live in a fast developing period of this scientific area because of the need of evaluation of the human impact on freshwater biotope. The aim of this bachelor thesis is to introduce variables which influence habitat pref- erences of fish, to propose a modern review of methods commonly...
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