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Recovery of zooplankton community from the acidification in mountain lakes
Bartošíková, Martina ; Sacherová, Veronika (advisor) ; Šorf, Michal (referee)
Mountain Lakes in Bohemian forest are currently undergoing a process of acidification. In spite of the rapid improvement of chemistry, the biological recovery is considerably delayed. This state may be due to a number of factors, such as persistent periodic pH fluctuations and hence increased aluminum leaching, phosphorus limitation, resistance of acid-tolerant communities, or limited opportunities for spreading from surrounding sites or damage to the egg bank. With the delay in improving the chemical composition of water gradually comes the improvement of the biological state, which manifests in the first phase by increasing the abundance of the existing species, in the second by increasing the number of species. In addition to the fish, it seems that the largest filtering dwarfs of the genus Daphnia are returned. In spite of their efforts to accelerate their return in the natural experiment by repatriating the species Cyclops abyssorum and Daphnia longispina to Plešné Lake in 2004, the wildebeests did not enjoy the new locality. Still, after almost ten years, individual individuals of this kind were found in lake litoral. This diploma thesis builds on the research of the Bohemian forest lakes, which is going on for almost 150 years. The zooplankton's response to changes in chemistry was studied...
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Feeding ecology of freshwater Heteroptera (Nepomorpha)
Šretrová, Martina ; Sacherová, Veronika (advisor) ; Kment, Petr (referee)
This bachelor thesis focuses on the aquatic Nepomorpha living in freshwater, especially on the most common representatives from families, which we can find in the Czech Republic. The main theme of this work is the mapping of the feeding ecology of water-bugs. Various feeding strategies can be observed, such as phytophagy, carnivory and omnivory. The most important strategy used by most water-bugs is predation. This behavior is related to morphological adaptations, such as modifications of the mouthparts and forelegs. Ways of obtaining and processing prey are described in detail and the influence of predators on their prey is discussed. A special chapter is dedicated to the Corixidae family, which differs morphologically and ecologically from other families.
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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...
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Spatial orientation in Odonata
Hupková, Lenka ; Černý, Martin (advisor) ; Sacherová, Veronika (referee)
The aim of this review is to evaluate and sum up an existing knowledge about spatial orientation of dragonflies, particularly at small and medium spatial scales. I deal mostly with orientation by horizontally polarized light, which belongs among the most explored field of orientation of Odonata; beside that I explore an orientation of dragonflies during the habitat selection and within their home ranges / territories. Regarding the latter, I pay an attention namely to the function of spatial landmarks, which has not been yet fully explored and offers a lot of opportunities for further research (like many other orientation topics of Odonata). I also briefly discuss an orientation of dragonflies during migrations. Besides the visual orientation I mention the orientation by olfactory sense, tough Odonata was concerned anosmic for a long time. Key words: spatial orientation, visual orientation, dragonflies, Odonata, landmarks
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Diversity of freshwater epigean amphipods
Rutová, Tereza ; Petrusek, Adam (advisor) ; Sacherová, Veronika (referee)
Gammarids, the most diverse group of Amphipoda are present in marine, brackish and fresh waters. In freshwater there are forms inhabiting the surface (epigean) and underground (hypogean) habitats and this thesis will be focused on epigean freshwater groups. Freshwater gammarids inhabit the continental waters of all continents, but the highest species diversity is evident in the Palearctic region. However they cannot be found in the surface waters of the tropical regions. These amphipods are characterized by the absence of any resistant or larval stages. Thus the present diversity and distribution reflects historical events like the fluctuation in sea levels, orogeny or period of glaciation from the Paleocene to the present. The goal of this thesis will be to summarize which processes and in which period the diversity of freshwater epigean amphipods were affected. One part of this thesis is dedicated to the families occurring in Australia (Chiltonidae), New Zealand (eg. Phreathogammaridae) and the North and the South America (Hyalellidae). The main focus is on family Gammaridae in which according to recent studies should include lineages occurring in the entire Palearctis including endemic groups in the Lake Baikal and across the Ponto-Caspian area. In the history of the development of gammarids...
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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
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