1,721,022 research outputs found
Mobilisation of subglacial microbes during deglaciation and their export to downstream ecosystems
Full text linkSubglacial 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
Microbial communities and carbon cycling in subglacial ecosystems and their analogues
Full text linkSubglacial 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..
Mikrobiální skrumáže metanových vývěrů z Grónského ledovce
Full text linkSubglaciální prostředí poskytuje podmínky vhodné k mikrobiální produkci metanu, který se může z ledovců uvolňovat během jejich tání. Vysoké emise metanu byly naměřeny v místě subglaciálního portálu ledovce Russell, který se nachází na jihozápadě Grónského ledovcového příkrovu. Exportovaný metan nejen pozitivně ovlivňuje globální oteplování, ale může sloužit i jako vhodný substrát pro metanotrofní mikroorganismy. Tato diplomová práce se zabývá změnami ve složení exportované mikrobiální skrumáže během sezóny tání a také popisuje její změny v proglaciálním toku. Bylo zjištěno, že významná část exportované skrumáže (27.1 %) je tvořena metylotrofními mikroorganismy a jejich relativní zastoupení se zvyšovalo během sezóny tání, pravděpodobně kvůli změnám ledovcového odvodňovacího systému. Převážná část exportovaných metylotrofů byla z kmene Gammaproteobacteria, nicméně jejich relativní zastoupení ve skrumáži klesalo se vzdáleností od ledovcového portálu. A naopak relativní zastoupení metylotrofů z kmene Alphaproteobacteria rostlo. Jako pravděpodobné vysvětlení se jeví odlišné fyziologické nároky těchto dvou skupin. Data prezentovaná v této práci ukazují, že místa s vysokými emisemi subglaciálního metanu, mohou být hojně osídlena metylotrofními mikroorganismy, jejichž metabolická činnost může potenciálně...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...Katedra ekologieDepartment of EcologyPřírodovědecká fakultaFaculty of Scienc
Genetic potential for methane metabolism in the Greenland subglacial ecosystem
No full textSubglacial 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..
Microbial assemblages associated with methane release from the Greenland ice sheet
No full textSubglacial 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..
Genetický potenciál pro metabolismus metanu v grónském subglaciálním ekosystému
Full text linkSubglacial 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...Subglaciální prostředí se nachází na rozhraní ledovců a jejich podloží. Představuje jeden z hlavních ekosystémů spojených s ledovci a ledovcovými pokrývkami. Zahrnuje tekutou vodu i jemný materiál rozdrcený pohybem ledovců obsahující organický materiál. Velké oblasti subglaciálního sedimentu jsou každoročně obnaženy kvůli tání a ústupu ledovců, což ovlivňuje subglaciální zásoby uhlíku a může mít významný dopad na regionální toky uhlíku. Vzhledem k rozšířené anoxii v ledovcových podloží jsou subglaciální prostředí potenciálními producenty a zásobárnami metanu, který může být uvolněn do atmosféry v důsledku ústupu ledovců. Zatímco přítomnost metanogenů a organizmů oxidujících metan v subglaciálním prostředí byla ukázána na základě 16S rRNA genových dat, v současné době neexistují žádná data o funkčním genetickém potenciálu metabolismu metanu. V této studii byly poprvé využity metagenomy, získané ze subglaciálního sedimentu exportovaného řekou zpod Grónského ledovce, k charakterizaci metabolického potenciálu metabolismu metanu a identifikaci a kvantifikaci genů zapojených do produkce a spotřeby metanu. Byly také zkoumány funkční geny potenciálních syntrofních drah. Funkční geny metanogeneze/anaerobní oxidace metanu a metanotrofie byly zaznamenány ve všech čtyřech metagenomech. Výsledky analýz poskytují...Katedra ekologieDepartment of EcologyFaculty of SciencePřírodovědecká fakult
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Particulate organic carbon (POC) concentration in meltwater runoff of Leverett Glacier, Russell Glacier, and Isunnguata Sermia, southwest Greenland (2009-2018)
No full textThis dataset describes particulate organic carbon (POC) and particulate carbon (PC) concentrations of suspended sediments in the proglacial rivers of 3 land-terminating glaciers in the Kangerlussuaq area, Southwest Greenland: Leverett Glacier (LG), Leverett River; Russell Glacier (RG), Akuliarusiarsuup Kuua; and Isunnguata Sermia (IS), Isortoq River. Both the Leverett River and Akuliarusiarsuup Kuua are tributaries of the Qinnguata Kuussua (also known as Watson River). The data have already been part of 3 different publications (Lawson et al. 2014, Kohler et al. 2017, and Vrbická et al. 2022) but are archived here for the first time.
POC data was collected for LG during the 2009 and 2010 melt seasons (Lawson et al. 2014) as well as 2015 (Kohler et al. 2017). For the 2018 melt season, only total carbon concentrations of suspended sediments (PC) is archived as opposed to POC (see Vrbická et al. 2022).Additional funding from:
NERC CASE studentship (NERC DTG/GEOG SN1316.6525)
Czech Science Foundation Junior grant (GACR 15-17346Y)
Charles University grant (GAUK 279715)
Leverhulme Trust Research Grant (RPG-2016-439)
Royal Society Wolfson Merit Award to J.L.W.
Czech Science Foundation grants (GACR; 15-17346Y and 18-12630S)
Charles University Research Centre program no. 20406
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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