National Repository of Grey Literature 13 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Abrupt cooling events in the Late Glacial and the Early Holocene
Švanda, Petr ; Vondrák, Daniel (advisor) ; Tichá, Anna (referee)
This bachelor thesis is prepared in the form of a literature review focused on abrupt cooling events in the Late Glacial Interstadial and the Early Holocene (14 700 to 8 200 cal. BP). The aim was to summarize the scientific knowledge on six such climate fluctuations and their causes and consequences. All of these events (GI-1d, GI-1c2, GI-1b, 11 400 event, 9 300 evenet, 8 200 event) lasted more than 50 years and are followed by cooling of more than 1 řC. Literature sources on this topic are based on interdisciplinary studies of various natural archives and the interpretation of so-called proxy data. For each climatic event, an assessment of its effects on ecosystems and human societies at the time was also made. The above findings are finally discussed in the context of the current climate change issues and the possible future of weakening the Atlantic Meridional Overturnig Circulation.
Interpretation of carbon stable isotope data from lake sediment archives
Lánová, Zuzana ; Tátosová, Jolana (advisor) ; Jandová, Kateřina (referee)
Lake sediments consist of terrestric plant matter, lacustrine plancton primary production and microbial lake biomass. All of these organism groups discriminate during C-substate fixation and/or its further assimilation heavier and more stable 13 C carbon at a certain ratio, which is reflected by 13 C concentration in their biomass and consequently in sediments. The reason of discrimination at these enzymatically controlled biochemical reactions lies at kinetic fractionation controlled by binding energies of chemical substances. Isotopic signature contained in organic matter of lake sediments can be influenced by photosyntesis intensity, formation of anoxic zone allowing methanogenic a methanotrophic bacteries activity, lake trophic state or hydrologic isolation (long periods of drought). Keywords: Paleolimnology, carbon isotopes, discrimination processes, lake sediments
The Quaternary Paleoecological Analysis of the Soos National Nature Reserve
Rajdlová, Hana ; Holcová, Katarína (advisor) ; Novák, Jan (referee)
The Quaternary Paleoecological Analysis of the Soos National Nature Reserve The aim of this proposed diploma thesis is to describe the structure of diatom communities in the diatomite deposits of the Soos National Nature Reserve and compare the finding of this thesis with those of older publications. Another aim was to reconstruct the history of the basin trough with the outputs of diatom analysis accomplished in the 3,4 m long sediment profile. The similarity of diatom communites in individual diatomite types was also tested. Key words: subfossil diatoms, Soos National Nature Reserve, paleolimnology, Late Glacial, Holocene
A comparison between paleo and recent freshwater diatom communities from Vega Island, Antarctica.
Bulínová, Marie ; Kopalová, Kateřina (advisor) ; Spaulding, Sarah (referee)
In Antarctica, diatoms inhabit multiple limno-terrestrial habitat types, which may each individually offer unique ecological information for use in biomonitoring, paleoecology, and biogeography. However, we are still at the initial exploration stage of documenting the diversity among habitat types from different Antarctic regions, which is necessary to serve as baseline data for the aforementioned scientific disciplines, and ultimately inform conservation decisions. To gain insight into the spatial and habitat controls on Antarctic diatom communities, the importance of habitat type and island aspect was investigated by studying diatoms living in ponds, mosses, streams, and seepage areas on two opposite sides Vega Island, Antarctic Peninsula. A diverse flora of 136 taxa belonging to 31 genera was revealed, which was dominated by the genus Nitzschia, and suggests that the flora of Vega Island is biogeographically influenced by both continental and Maritime Antarctic bioregions. Habitat type was found to be a crucial factor for diatom community composition, and was stronger than the influence of island aspect. In ordination analyses, moss samples were separated primarily by their abundances of the diatom Chamaepinnularia krookiformis, while pond samples were separated by Nitzschia paleacea and stream...
Historical record of the fairyshrimp Branchinecta gaini in the James Ross archipelago, and its phylogeography
Pokorný, Matěj ; Sacherová, Veronika (advisor) ; Janko, Karel (referee)
The Fairy shrimp Branchinecta gaini Daday, 1910 is the largest freshwater invertebrate in Antarctica and the top-level consumer of local freshwater food webs. Ecological demands of B. gaini that are accompanied by 'ruderal' life strategy together with its spatial distribution that exceeds to Patagonia indicate that it had survived last glacial period in South America and expanded to Antarctica shortly after this epoch endeed. On James Ross Island that is the most extreme environment where B. gaini occurs today was this fairy shrimp considered extinct until year 2008. Its disappearance was based on paleolimnological analysis of several lake sediment cores according to which it inhabited this island between years 4200 to approximately 1500 before present when it died out because of changes in lake catchments caused by harsh neoglacial conditions. Paleolimnological analysis of Monolith Lake presented in this study has shown that this assumption was wrong and B. gaini has lived on James Ross Island throughout neoglacial period up to recent time. Phylogeographic analysis of 16S rDNA of specimens from Patagonia, South Orkneys, South Shetlands and James Ross Island revealed that its high morphological diversity is not supported by this gene and that all examined populations of B. gaini is one species with very few...
Identification and synchronization of YD period from Eruopaen lake sediments
Skurčáková, Anežka ; Tátosová, Jolana (advisor) ; Sacherová, Veronika (referee)
The bachelor thesis is the rewiew based on paleolimnological determining of Younger Dryas (YD), the final cold episode of the Last Glacial, and its diferent progress in European regions. It contains a describsion and an evaluation of methods of the YD identification (oxygen izotopes 18 O, varve chronology, radiocarbon dating, analysis of diatoms, pollen, chironomids, insect and geochemical and sedimentological analysis). The summary of results of studies from different parts of Europe showed that the first half of the YD in Western Europe was cooler and wetter than the second one. The climate during the YD period had similar temperature profile in Eastern Europe, but humidity had a different trend (the first half was colder and drier while the second one was warmer and wetter. According to the study of lake Švarcenberk in the Czech Republic, the YD had similar phases like in Western Europe. The YD period was synchronous in the most of Europe, its duration was approximately 1,200 years (12 726 - 11 564 years BP). Keywords: Younger Dryas, paleolimnology, oxygen izotopes, radiocarbon dating, varve chronology, climate in Europe
Historical development of zooplankton of the Starolesnianske lake (the High Tatra Mountains, Slovakia) in the context of global changes
Blechová, Magdalena ; Hořická, Zuzana (advisor) ; Sacherová, Veronika (referee)
The aims of the thesis were to document the history of the Cladocera (Crustacea) community structure in the Starolesnianske Lake (the High Tatra Mountains, Slovakia) with regards to environmental changes (e. g., Medieval Warm Period, Little Ice Age, anthropogenic acidification, recovery from acidification), and to analyze in detail the development of zooplankton (Cladocera, Copepoda, Rotifera) during the peaking acidification and recovery from acidification (1978 - 2015). Based on results of both the approaches, the appropriateness of using historical data on zooplankton in Tatra lakes between 1909 - 1913 (Minkiewicz, 1914) as a reference condition for the evaluating biological recovery from acidification should have been assessed. The methods used were paleolimnological analyses of lake sediment (namely subfossil Cladocera), analysis of recent zooplankton, and analyses of lake water chemistry. It was found that in the historical record, relative abundances of Cladocera species significantly changed cca 150 years ago (at the end of the Little Ice Age and, in the main, in the period of anthropogenic acidification). The lake, though, has had a very stable species composition of Cladocera during the last cca 2,000 years, represented by four species: Alona quadrangularis, Alonella excisa, Ceriodaphnia...
Palaeoecological reconstruction of Komořany Lake in Late Glacial based on diatom analysis
Poštulková, Anna ; Nedbalová, Linda (advisor) ; Tátosová, Jolana (referee)
Diatom analysis of basal part of profile PK-1-L contributes to multi-proxy research of former Lake Komořany. At this part of profile radiocarbon dating (dates sediments into Late Glacial and Early Holocene) and LOI (loss on ignition) had been conducted before, of which results have been utilized to more accurate interpretation of diatom analysis conclusions. Apart from diatom valves, presence of stomatocysts of Chrysophyceae has been observed. Having separated diatom valves from 32 sediment samples in intervals 0,4-0,6 cm, permanent preparates have been created. Concentration of valves in a gramme of dry sediment and relative abundance of diatom taxons in each sample have been investigated using light microscopy. In a half of samples subdominants and rare taxons have been observed separately to eliminate the interference from dominant taxons. Cluster analysis based on relative abundances of diatom taxons have been calculated and on its results have been subsequently determined three diatom accumulation zones (DAZ). Moreover trophic and saprobic indices have been calculated and levels of pH, conductivity and concentration of total phosphorus (TP) have been estimated by transfer functions. Even before beginning of Holocene the major shift in composition of diatom communities have happened, to the...

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