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Microbial assemblages associated with methane release from the Greenland ice sheet
Znamínko, Matěj ; Stibal, Marek (advisor) ; Cameron, Karen (referee)
Subglacial environments provide conditions suitable for the microbial production of methane, an important greenhouse gas, which can be released from beneath the ice as a result of glacial melting. High gaseous methane emissions have recently been discovered at Russell Glacier, an outlet of the southwestern margin of the Greenland Ice Sheet, acting not only as a potential climate amplifier but also as a substrate for methane-consuming microorganisms. Here, we describe the composition of the microbial assemblage exported in meltwater from the methane release hotspot at Russell Glacier and its changes over the melt season and as it travels downstream. We found that a substantial part (27.1 %) of the exported assemblage was made up of methylotrophs and that the relative abundance of methylotrophs increased as the melt season progressed, likely due to the seasonal development of the glacial drainage system. The methylotrophs were dominated by representatives of Type I methanotrophs from the Gammaproteobacteria; however, their relative abundance decreased with increasing distance from the ice margin at the expense of methylotrophs from the Betaproteobacteria and Type II methanotrophs (Alphaproteobacteria). These changes could be attributed to the different physiological demands of these groups. Our...
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Kinetics of selected herbicides and their biodegradation in soil and water environments
Šabršulová, Anna ; Matoušková, Milada (advisor) ; Stibal, Marek (referee)
The three most commonly used herbicides in the Czech Republic (chloracetanilides, triazines and glyphosate) are also the herbicidal compounds found in the highest concentration in surface water. After agricultural application, they interact with soil and water due to their chemical properties and environmental factors affecting them. Adsorption coefficient, solubility in water environment, precipitation and drift have high impacts on the kinetics of these herbicides and degradates emerging from them. While moving through soil, parent compounds of mentioned herbicides are actively biodegraded by microorganisms, the most effective decomposers in nature. Biodegradation in soil and water environments is accelerated or slowed by temperature, moisture, quantity of microbial communities and many other environmental factors. Even if the microbial degradation is effective in a water or soil environment, there are many other new, arising compounds whose persistence in the environment is significantly higher than that of the parent compound. Degradates can end up in surface water by run off or wash out from agricultural fields and can remain there for decades depending on their chemical properties and natural conditions. Key words: surface water, herbicides, herbicides degradation products, rainfall-runoff...
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Mobilisation of subglacial microbes during deglaciation and their export to downstream ecosystems
Znamínko, Matěj ; Stibal, Marek (advisor) ; Řeháková, Klára (referee)
Subglacial environments harbor active microbial communities. The composition of these communities is influenced by a number of factors, with glacial hydrology being one of the most important ones. This affects not only formation of subglacial communities but also the mobilisation of microorganisms and their subsequent release to downstream ecosystems. The seasonally evolving drainage system connects supraglacial and subglacial environments, and thus microorganisms from supraglacial environments are exported to proglacial streams along with subglacial microorganisms. The contribution of these two microbial communities to proglacial assemblage is not uniform and may be influenced by the size or geographical location of the glacier or by the phase of the glacier drainage system. Microorganisms from proglacial assemblages can form biofilms in proglacial streams or contribute to the community composition in downstream ecosystems. This work summarizes current knowledge of mobilisation and subsequent export of microorganisms from subglacial environments.
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Genetic potential for methane metabolism in the Greenland subglacial ecosystem
Rybár, Marek ; Stibal, Marek (advisor) ; Šabacká, Marie (referee)
Subglacial environments, located at the interface of glacier ice and bedrock, represent one of the major ecosystems associated with glaciers and ice sheets. This environment contains liquid water and underlying sediment with large amounts of organic matter overridden during periods of ice advance. Large areas of subglacial sediment are exposed annually by glacier melting and retreat, which affects the subglacial carbon stores and may significantly impact regional carbon fluxes. Due to the widespread anoxia at glacier beds, subglacial environments are potential producers and reservoirs of methane that can be released into the atmosphere as a consequence of glacial retreat. While the presence of methanogens and methane oxidisers has been shown based on 16S rRNA gene data, no data on the functional genetic potential for methane metabolism currently exist. In this study, the first subglacial metagenomes obtained from subglacial sediment exported from beneath the Greenland ice sheet by a meltwater river were used to characterize the metabolic potential for methane metabolism by the identification and quantification of genes involved in methane production and consumption. Functional genes of potential syntrophic pathways were also investigated. Functional genes of methanogenesis/anaerobic oxidation of methane and...
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Kinetics of selected herbicides and their biodegradation in soil and water environments
Šabršulová, Anna ; Matoušková, Milada (advisor) ; Stibal, Marek (referee)
The three most commonly used herbicides in the Czech Republic (chloracetanilides, triazines and glyphosate) are also the herbicidal compounds found in the highest concentration in surface water. After agricultural application, they interact with soil and water due to their chemical properties and environmental factors affecting them. Adsorption coefficient, solubility in water environment, precipitation and drift have high impacts on the kinetics of these herbicides and degradates emerging from them. While moving through soil, parent compounds of mentioned herbicides are actively biodegraded by microorganisms, the most effective decomposers in nature. Biodegradation in soil and water environments is accelerated or slowed by temperature, moisture, quantity of microbial communities and many other environmental factors. Even if the microbial degradation is effective in a water or soil environment, there are many other new, arising compounds whose persistence in the environment is significantly higher than that of the parent compound. Degradates can end up in surface water by run off or wash out from agricultural fields and can remain there for decades depending on their chemical properties and natural conditions. Key words: surface water, herbicides, herbicides degradation products, rainfall-runoff...
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Microbial communities and carbon cycling in subglacial ecosystems and their analogues
Rybár, Marek ; Stibal, Marek (advisor) ; Řeháková, Klára (referee)
Subglacial environments are located at the interface of glacier ice and bedrock. They represent one of the major ecosystems associated with glaciers and ice sheets. They contain liquid water and fine material including organic matter, accumulated during periods of glacier advance. It is well established that there are active microbial communities residing in these environments, which are adapted to living in extreme conditions. Subglacial ecosystems are mostly isolated from the atmosphere and thus their oxygen content is usually very low. Therefore, the organisms residing in these environments often employ anaerobic/anoxic strategies to ensure their survival. However, knowledge of these communities is limited due to practical constrains associated with subglacial ecology and biogeochemistry research. The activity of microorganisms beneath glaciers significantly influences carbon cycling. In recent years, this ecosystem is dynamically changing and may have important impact on regional and global carbon cycle. Therefore, it is important to better understand this ecosystem. This thesis summarizes recent knowledge of microbial communities and carbon cycling in this ecosystem and discusses suitable analogues, which could help us understand the fascinating subglacial ecosystem and formulate future research...
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Photoautotrophic microorganisms in the glacial ecosystem of Svalbard, high Arctic
STIBAL, Marek
Photoautotrophic microorganisms, i.e. cyanobacteria and microalgae, are ubiquitous in the glacial ecosystem of the high Arctic archipelago of Svalbard. Their communities play significant roles in the ecosystem, including organic carbon production on the glacier surface and its supply to downstream environments, initiating microbial colonisation after glacier retreat and preparing proglacial substrata for further succession.
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