Diatom-rich sediment formation in lakes

Unicellular photosynthetic golden algae called diatoms are one of the most abundant silicifying organisms. Diatoms take up silicon and build their frustules, in the form of biogenic silica (BSi), which have high preservation potential, and thus are found in sediments. Around 27 % of the annual dissolved silicon (DSi) delivery from the land to the ocean is retained in lakes and reservoirs in the form of BSi. Therefore, diatom production in lakes creates silicon sinks and influences the Si cycle. However, the processes driving and regulating lacustrine diatom-rich sedimentation are poorly constrained.This dissertation investigates two lakes in very different settings to evaluate the major factors governing diatomrichsediment accumulation. The first study site is a small subarctic, high-latitude lake, Lake 850 in Northern Sweden, and the other study site is in the hydrothermally active and DSi-rich Yellowstone Lake in Yellowstone National Park, Wyoming, U.S.A.The study of the recent Si cycle in Lake 850 revealed the importance of groundwater input to the lake’s Si budget. Groundwaterbrings 3 times more DSi compared to the stream inlet and thus is the main source of DSi for diatom production. Low sedimentation rates in the last 150 years are responsible for BSi accumulation as high as 20 dry weight%. The Holocene sedimentary record shows that the lake had low detrital input throughout the last 7400 years, likely due to low-reliefgeomorphology and a stable environment in the lake’s watershed. The stable Si isotopes of fossil diatoms suggest a stable DSi supply for the lake, where only the relative proportion of stream influx and groundwater influx of DSi are driving isotopic changes. The BSi accumulation in the sediment of Lake 850, as high as 46 dry weight% throughout the Holocene, is driven by a combination of sufficient DSi supply from groundwater and the stream inlet, low detrital input and good preservation of diatoms in the sediment.In Yellowstone Lake the importance of hydrothermal vents bringing DSi into the lake was shown. The impact of hydrothermalDSi supply is observed in the sedimentary record over the last 9800 years as elevated Ge/Si ratios (up to 37 μmol/mol). Holocene hydrothermal input is responsible for a long-term stable lake DSi concentration and its Si isotopic signature, reflected in the fossil diatoms. The high sustained input of DSi masks the effects of the sublacustrine Elliott’s Crater hydrothermal explosion ~8500 years ago. The relative proportion of the DSi sources from hydrothermal fluids and stream inlets, diatom production and dissolution are concurrent processes responsible for the variation of the Si isotopic signal. The BSi accumulation is accounted for by low accumulation rates with limited amounts of detrital input and high diatom preservation, which results in BSi concentrations in the sediment of up to 52 dry weight%.On Holocene timescales, neither lake was DSi limited, which resulted from presence of the additional sources of DSi –groundwater or hydrothermal fluids. The unlimited DSi is partly responsible for BSi accumulation. Additionally, low sediment accumulation rates due to low detrital input, often driven by changes in climate and hydrology, are factors contributing to high BSi concentration. Finally, a fine balance between diatom production and dissolution may influence BSi accumulation. These studies suggest that diatom-rich sediments are likely to accumulate in lakes situated on silicon-rich bedrock and regions influenced by volcanic and hydrothermal activity if accompanied by low clastic sediment inputs. Highlatitude lakes, which may have high groundwater input also are candidates for high BSi accumulation. Lakes with low-relief watershed morphology and with limited stream input bringing only finegrained clastic input have the potential to accumulate BSi

Izotopy uhlíku jako nástroj ke studiu paleoklimatu

Ústav geologie a paleontologieInstitute of Geology and PaleontologyPřírodovědecká fakultaFaculty of Scienc

Studium autekologie vybraných taxonů křídových rostlin pomocí izotopů uhlíku

1 Abstrakt Tato práce se zabývá analýzou fosilních rostlin z cenomanských Perucko-korycanských souvrství České křídové pánve a Bückebergským souvrstvím z Dolnosaské pánve v Německu. Na základě dřívějších studií je známo, že obě lokality poskytují fluviální sedimenty, které byly utvářeny v oblastech ovlivněných příliv-odlivovými cykly. Mezi fosilními vzorky jsou za- stoupeny listy skupiny Ginkgoales - Eretmophyllum, Tritaenia, větve jehličnanu Frenelopsis a také listy lauroidních angiosperm - Eucalyptolaurus. Za halofytní rostliny jsou považovány Frenelopsis, Eretmophyllum a Tritaenia, zatímco lauroidní angiospermy jsou považovány za sladkomilnější druhy. Hlavní použitá metodika byla kutikulární analýza, analýza stabilních izotopů z Bulk (celkového uhlíku) a analýza stabilních izotopů listových vosků. Vzorky byly pozorovány makroskopicky a mikroskopicky pod světelným mikroskopem a skenovacím elektronovým mikroskopem. Stejnými metodami byly zkoumány jak fosilní, tak recentní vzorky. Pro nalezení podmínek prostředí byly navzorkovány a následně využity recentní rostliny pocházející ze slaných marší ve Velké Británii. Interpretace podporují hypotézu modelu založeného na sedimentologických datech, tedy prostředí slaných marší. Frenelopsis je interpretován jako slanomilná rostlina, rostl v prostředích s nízkou...1 Abstract This thesis presents an analysis of fossil plants from the Cenomanian Peruc-Korycany Formation of the Bohemian Cretaceous Basin and from the Bückeberg Formation of the Lower Saxony Basin in Germany. Based on earlier studies, both areas provide sediments that are considered to have developed in tidally influenced fluvial systems. Studied fossil plants are represented by ginkgoalean plant leaves (Ertemophyllum, Tritaenia), branches of conifers (Frenelopsis) and lauroid angiosperms (Eucalyptolaurus). Frenelopsis, Eretmophyllum and Tritaenia are considered to be halophytic plants, while Lauroid angiosperms were considered to grow in fresh water conditions. The fossil plants were studied using cuticle analysis and two methods of stable carbon isotope analysis: Bulk carbon isotope analysis and Compound Specific Isotope analysis. For cuticle analysis samples were observed and documented macroscopically and microscopically. To specify the environmental conditions, recent samples from three salt marshes in Great Britain were studied and analysed using the same methods as the fossil samples. The data from all observations and measurements were processed and their interpretation supported the modelled environment based on the sedimentological data. Frenelopsis were growing in a haline environment with low...Ústav geologie a paleontologieInstitute of Geology and PaleontologyPřírodovědecká fakultaFaculty of Scienc

Multi-proxy record of Holocene paleoenvironmental conditions from Yellowstone Lake, Wyoming, USA

A composite 11.82 m-long (9876e-67 cal yr BP) sediment record from Yellowstone Lake, Wyoming was analyzed using a robust set of biological and geochemical proxies to investigate the paleoenvironmental evolution of the lake and its catchment in response to long-term climate forcing. Oxygen isotopes from diatom frustules were analyzed to reconstruct Holocene climate changes, and pollen, charcoal, diatom assemblages, and biogenic silica provided information on terrestrial and limnological responses. The long-term trends recorded in the terrestrial and limnic ecosystems over the last 9800 years reflect the influence of changes in the amplification of the seasonal cycle of insolation on regional climate. The early Holocene (9880e6700 cal yr BP) summer insolation maximum and strengthening of the northeastern Pacific subtropical high-pressure system created warm dry conditions and decreasing summer insolation in the middle (6700e3000 cal yr BP) and late (3000e-67 cal yr BP) Holocene resulted in progressively cooler, wetter conditions. Submillenial climate variation is also apparent, with a wetter/cooler interval between 7000 and 6800 cal yr BP and warmer and/or drier conditions from 4500 to 3000 cal yr BP and at ca. 1100 cal yr BP. These data show that the Yellowstone Lake basin had a climate history typical of a summer-dry region, which helps to better define the spatial variability of Holocene climate in the Greater Yellowstone Ecosystem

Financial Balance of Households

The aim of this thesis is to evaluate the financial balance of the households and to find the factors which affect them. The theoretical part is focused on two main issues, incomes and expenditures of the family budget. In the practical part are used data from the Public Database of the Czech Statistical Office and then time series are processed, which capture development of net money income and consumption expenditure for some types of households. The practical part also contains the research project, which is realized through a questionnaire survey. The results show which factors affect the financial balance or how people manage their finances. Part of the thesis is also the identification of households threatened with insolvency.Cílem této bakalářské práce je posouzení finanční bilance domácností a vyhledávání faktorů, které ji ovlivňují. Teoretická část je věnována především dvěma hlavním tématům, a to příjmům a výdajům rodinného rozpočtu. V praktické části jsou nejprve použita data z Veřejné databáze Českého statistického úřadu a následně zpracovávány časové řady, které zachycují vývoj čistých peněžních příjmů a spotřebního vydání u některých typů domácností. Praktická část také obsahuje vlastní výzkumný projekt, který je realizován formou dotazníkového šetření. Výsledky ukazují, které faktory ovlivňují finanční bilanci, nebo jak lidé hospodaří s peněžními prostředky. Součástí práce je i vytipování domácností ohrožených platební neschopností

Autecological study of selected Cretaceous plants using stable Carbon isotopes

1 Abstract This thesis presents an analysis of fossil plants from the Cenomanian Peruc-Korycany Formation of the Bohemian Cretaceous Basin and from the Bückeberg Formation of the Lower Saxony Basin in Germany. Based on earlier studies, both areas provide sediments that are considered to have developed in tidally influenced fluvial systems. Studied fossil plants are represented by ginkgoalean plant leaves (Ertemophyllum, Tritaenia), branches of conifers (Frenelopsis) and lauroid angiosperms (Eucalyptolaurus). Frenelopsis, Eretmophyllum and Tritaenia are considered to be halophytic plants, while Lauroid angiosperms were considered to grow in fresh water conditions. The fossil plants were studied using cuticle analysis and two methods of stable carbon isotope analysis: Bulk carbon isotope analysis and Compound Specific Isotope analysis. For cuticle analysis samples were observed and documented macroscopically and microscopically. To specify the environmental conditions, recent samples from three salt marshes in Great Britain were studied and analysed using the same methods as the fossil samples. The data from all observations and measurements were processed and their interpretation supported the modelled environment based on the sedimentological data. Frenelopsis were growing in a haline environment with low..

Autecological study of selected Cretaceous plants using stable Carbon isotopes

1 Abstract This thesis presents an analysis of fossil plants from the Cenomanian Peruc-Korycany Formation of the Bohemian Cretaceous Basin and from the Bückeberg Formation of the Lower Saxony Basin in Germany. Based on earlier studies, both areas provide sediments that are considered to have developed in tidally influenced fluvial systems. Studied fossil plants are represented by ginkgoalean plant leaves (Ertemophyllum, Tritaenia), branches of conifers (Frenelopsis) and lauroid angiosperms (Eucalyptolaurus). Frenelopsis, Eretmophyllum and Tritaenia are considered to be halophytic plants, while Lauroid angiosperms were considered to grow in fresh water conditions. The fossil plants were studied using cuticle analysis and two methods of stable carbon isotope analysis: Bulk carbon isotope analysis and Compound Specific Isotope analysis. For cuticle analysis samples were observed and documented macroscopically and microscopically. To specify the environmental conditions, recent samples from three salt marshes in Great Britain were studied and analysed using the same methods as the fossil samples. The data from all observations and measurements were processed and their interpretation supported the modelled environment based on the sedimentological data. Frenelopsis were growing in a haline environment with low..