Download or read book Sources and Temporal Variability of Lipid Biomarkers in Lake Chala East Africa with Implications for Their Sedimentary Record written by Louise Gerarda Johanna van Bree and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The East African Great Lakes Limnology Palaeolimnology and Biodiversity written by Eric O. Odada and published by Springer Science & Business Media. This book was released on 2006-03-09 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Second International Symposium on the East African Lakes was held from 10-15 January 2000 at Club Makokola on the southern shore of Lake Malawi. The symposium was organized by the International Decade for the East African Lakes (IDEAL), a research consortium of African, European and North American scientists interested in promoting the investigations of African Great Lakes as archives of environmental and climatic dynamics. Over one hundred African, European and North American scientists with special expertise in the tropical lakes participated in the symposium which featured compelling presentations on the limnology, climatology, palaeoclimatology and biodiversity of the East African Lakes. It is their papers that comprise this book. The large lakes of East Africa are important natural resources that are heavily utilized by their bordering countries for transportation, water supply, fisheries, waste disposal, recreation and tourism. The lakes are unique in many ways: they are sensitive to climatic change and their circulation dynamics, water-column chemistry and biological complexity differ significantly from large lakes at higher latitudes; they have long, continuous, high resolution records of past climatic change; and they have rich and diverse populations of endemic organisms. These unique properties and the significance of the palaeolimnological records demand and attract research interest from around the world.

Download or read book A Lipid Biomarker Investigation of Organic Matter Sources and Methane Cycling in Alaskan Thaw Lake Sediments written by Mark Richard Williams and published by . This book was released on 2012 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Barrow Peninsula is located on the North Slope of Alaska with much of it consisting of high latitude wetlands. Thaw lakes, an important feature of these wetlands, have been shown to be significant sources of methane to the atmosphere; however the origins of the methane remain poorly constrained. We have used lipid biomarkers to better understand biogenic methane production in lake sediments by characterizing microbial communities that may be involved in methane cycling as well as the organic matter that is available as substrates for methanogens.

Download or read book Lipid Biomarker Composition of Particulate Organic Matter in the Lower Chesapeake Bay written by Elizabeth A. Canuel and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this report we present results from a sampling program designed to characterize the abundance, sources, and composition of particulate organic matter (POM) in the lower Chesapeake Bay. To meet these objectives, we used measurements of bulk parameters (total suspended solids, chlorophylls, particulate carbon and nitrogen concentrations) combined with information on the concentration of two classes of lipid biomarker compounds (fatty acids and sterols). In addition to providing baseline information on the sources and composition of POM important to the lower Bay, the study addressed spatial and temporal variations in organic matter quality. This was accomplished using an experimental design which incorporated seasonal samplings to investigate temporal variability. Spatial variability was examined by comparison of sites located at the mouths of two tributaries (York and Rappahannock Rivers) to two sites located in the Bay mainstem. A further goal of the research project was to improve our understanding of the role of biological and physical processes in controlling the distribution and quality of organic matter. This information can then be used to understand how POM composition changes spatially and temporally in this region of the CB and to provide important insights regarding the nutritional value of the POM to consumer organisms.

Download or read book Mountain Lake Sedimentary Biomarker Records as Indicators of Holocene Climate Variability written by Julie Anne Scott and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Composition and Distribution of Lipid Biomarkers in Altamaha Estuarine Sediments written by Wei Shi and published by . This book was released on 1998 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Environmental Change and Response in East African Lakes written by J.T. Lehman and published by Springer. This book was released on 2013-01-18 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The idea for this book was born at the June 1996 meeting of the IDEAL Steering Committee in Milwaukee, Wisconsin. We had just completed a successful and stimulating special symposium during the annual meeting of the American Society for Limnology and Oceanography, and enthusiasm was running high for the production of a volume that could assemble in one place the scientific findings that were starting to emerge from East Africa. IDEAL, an International Decade for the East African Lakes, had ended one round of field investigations, many of which had been centered on Lake Victoria. As the climatologists, geologists, paleolimnologists, and biologists displayed their results and debated interpretations, it appeared that some paradigms were shifting, and that new explanations of climate history and modem processes were taking shape. The Steering Committee endorsed the production of a volume that would draw together the different research results that were emerging and which would be representative of the scope of science issues that exist within IDEAL. This book follows in the spirit of The Limnology, Climatology, and Paleoclimatology of the East African Lakes, published in 1996, but has a somewhat different purpose. The previous publication also included original science results, but it was conceived to review the state of knowledge, identify critical problems, and point to new paths of inquiry. It accompanied the development of our first Science and Implementation Plan for the East African Lakes.

Download or read book Molecular Studies of the Sources and Significance of Archaeal Lipids in the Oceans written by Sara Ann Lincoln Lincoln (Ph. D.) and published by . This book was released on 2013 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: Marine archaea are ubiquitous and abundant in the modem oceans and have a geologic record extending >100 million years. However, factors influencing the populations of the major clades - chemolithoautotrophic Marine Group I Thaumarchaeota (MG-I) and heterotrophic Marine Group II Euryarchaeota (MG-II) - and their membrane lipid signatures are not well understood. Here, I paired techniques of organic geochemistry and molecular biology to explore the sources and significance of archaeal tetraether lipids in the marine water column. Using metagenomics, 16S rDNA pyrosequencing, QPCR and mass spectrometric analyses, I found that uncultivated MG-IL Euryarchaeota synthesize glycerol dialkyl glycerol tetraether (GDGT) lipids - including crenarchaeol, previously thought limited to autotrophic Thaumarchaeota. This finding has important implications for paleoenvironmental proxies reliant upon GDGTs. To investigate the effects of organic matter and bicarbonate + ammonia amendments on archaeal tetraether lipids and microbial community composition, I conducted large scale microcosm experiments. Experimental conditions did not promote the overall growth of archaea, but several changes in tetraether lipid abundance and relative ring distribution suggest that future incubation labeling studies using whole seawater may be valuable in probing the metabolism of individual archaeal clades in mixed populations. A rapid decrease in GDGT concentrations was observed within the first 44 h of the experiment, suggesting that the residence time of these compounds in the open ocean may be short. Changes in functional gene representation and microbial community composition over the course of the experiment provide potential insight into mechanisms of copiotrophy and the identity of bacteria that may degrade GDGTs. Finally, I present the results of a study of the sources and patterns of bacterial and archaeal GDGTs detected in the Lost City Hydrothermal Vent Field. Branched GDGTs, generally considered markers of terrestrial input to marine sediments, were detected in carbonate chimneys of this alkaline site near the mid-Atlantic Ridge. A relatively uncommon H-shaped GDGT was also present, and appears to be a marker of hydrothermal archaeal input rather than a mesophilic euryarchaeotal signal. Taken together, the work presented in this thesis emphasizes the necessity of understanding the biological underpinnings of archaeal lipids in the environment, increasingly used as biomarkers in microbial ecology and paleoenvironmental reconstruction.

Download or read book Biological Markers in the Sedimentary Record written by R. B. Johns and published by . This book was released on 1986 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lake Sediment Studies in East Africa written by Daniel A. Livingstone and published by . This book was released on 1964 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Paleolimnological Evidence of the Effects of Recent Cultural Eutrophication and Climatic Variability During the Last 300 Years in Lake Malawi East Africa electronic Resource written by Megan K. Puchniak and published by University of Waterloo. This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Lake Malawi is the second largest lake in Africa, supporting diverse populations of endemic cichlids and supplying essential water resources to Malawi, Mozambique and Tanzania. However, population growth, rapid deforestation and intensive agriculture, especially in the southern catchments, have accelerated soil erosion during the last half century. These anthropogenically-disturbed catchments have caused rivers to transport greater sediment loads into Lake Malawi than rivers within forested catchments. Lake Malawi's immense size and oligotrophic nature may retard detection of inputs of external contaminants. Reversing the effects of increased nutrient loading to Lake Malawi once observed would likely take generations, as the residence time of water is over 140 years. Therefore, sensitive metrics are required to assess the effects of land use change and climate variability in Lake Malawi in advance of deleterious effects. In this study, paleolimnological analyses of four sediment cores collected in 1997 and 1998 along a longitudinal transect of Lake Malawi, dated with ℗l°Pb analyses and analyzed for biogenic silica and sedimentary diatom assemblages, were used to create a long-term water quality dataset. These four sites span gradients of land use and latitude in order to reconstruct limnological conditions over the whole lake during the last 300 years. Paleoecological results indicate that patterns of diatom assemblage change are not uniform lake wide. Southern cores contain evidence of nutrient enrichment starting as early as ca. 1940, indicated by increased silica, carbon and nitrogen burial. By ca. 1970, increased rates of sedimentation, diatom influx and changes in diatom community composition, characterized by increased percent abundance of eutrophic diatom taxa, are attributable to accelerated enrichment by terrestrial soil erosion. The succession of diatoms in southern Lake Malawi begins with high percent abundance of Aulacoseira nyassensis and Fragilaria africana, which thrive in nutrient-rich waters, followed by a shift towards diatom taxa with reduced silica requirements by ca. 1980 (e.g. Stephanodiscus nyassae, S. minutulus, S. muelleri, Cyclostephanos and small Nitzschia species.), a pattern comparable to the eutrophication-induced decline in silica to phosphorus ratios in Lake Victoria. In Lake Malawi, evidence of eutrophication extends to the mid lake as indicated by similar diatom assemblage changes in the sediment core from the central region. Diatom stratigraphies from the north end of the lake indicate no observable impacts of land use change on the northern basin of Lake Malawi during the past 350 years. However, a nine-meter rise in water level ca. 1860 AD appears to have resulted in elevated diatom influxes at that time comparable to the recent eutrophication-induced diatom influxes of the southern cores. The effects of this rise in water level was recorded in all three measured sites, southern, central and northern Lake Malawi, indicating lake-wide increased productivity, yet changes to the diatom community composition were imperceptible. This study shows evidence of recent cultural eutrophication altering limnological conditions with impacts to the biogeochemical cycling of silica, the available silica to phosphorus ratios and the biotic communities of a large portion of Lake Malawi. Thus, providing an early warning that proper stewardship of Lake Malawi requires effective management of land-use practices within the catchment to reduce soil erosion and avoid widespread water quality deterioration of this great lake.

Download or read book Biomarkers in Lake Albano and Lake Constance Sediment Records written by Sabine Hanisch and published by . This book was released on 2004 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biomarker and Sedimentological Investigations of Mis 8 Through Mis 12 from Lake El gygytgyn NE Arctic Russia written by Jeremy H. Wei and published by . This book was released on 2013 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiple proxy analysis of lake sediment records are crucial for understanding changes in environmental and climate conditions over historical and geological time. Most recently, the use of biomarker proxies coupled with sedimentological investigations provides a new approach for gaining insight into the lake processes that capture information about past climate change. This approach is applied here to better understand the paleoclimate record from Lake El'gygytgyn in Western Beringia. Multiple organic geochemical compound concentrations were measure as proxies for both aquatic and terrestrial biological productivity. Measurements of n-alkane (plant leaf waxes) as well as concentrations of the compounds arborinol (marker for trees), dinosterol (dinoflagellates), and long chain (C28 to C32) 1,15 n-alkyl diols (eustigmatophyte algae) demonstrate warming conditions around Lake El'gygytgyn during MIS 9 and MIS 11, especially when compared to diatom production and palynological investigations from Melles et al. (2012). These time periods illustrate the presence of extensive forest cover as well as elevated concentrations of all aquatic biomarkers analyzed, corroborating their super interglacial designation. Analysis of branched glycerol dialkyl glycerol tetraethers, a relatively new proxy used to estimate mean annual temperatures and soil pH, was applied also suggesting warming conditions during MIS 9 and MIS 11, although further calibration techniques are needed to accurately estimate temperature changes. Sedimentological results include the analysis of bulk mineralogy, clay mineralogy, iron oxide, and color measurements for the same MIS 8 through MIS 12 interval. The hue color parameter, measured from high resolution core scans, suggests a link to global climate records, with green sediments reflective of cold intervals and red sediments indicative of warmer climate conditions. Validation of the color record was done in part by analyzing the clay mineralogy and the abundances of clay minerals. These data show that clay deposition dominates interglacial periods. Moreover the clay polytypes can be linked to bedrock weathering. Bulk mineralogy measurements allow for the reconstruction of synthetic color spectra which link mineralogy to sediment color. Overprinted on the mineralogical color signal is red color staining from iron oxide minerals, formed within the catchment during wet intervals when increasing amounts of eroded Fe - bearing silicate minerals are available for oxidation. If true, interpretation of the hue record then suggests hue is a proxy for wet/dry conditions within the lake, and when paired with the biomarker analysis shows significant warmer and wetter conditions during MIS 9 and 11. However, the hue record also demonstrates notable variability outside of these two interglacial periods, not recognized by other proxies, are not currently well understood. Overall, the multi-proxy results from this work can be further applied to the longer temporal scale of the Lake El'gygytgyn sediment core, and potentially elucidate climate changes deeper into the Pleistocene, and even into the Pliocene portions of the sediment record.

Download or read book Lipid Biomarker Records of Environmental Conditions and Habitation During the Mid Neolithic Dalmatia Coast Croatia written by Emma Hartke and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Records of environmental change during the mid-Neolithic/Early Holocene show both pronounced global deglaciation climate trends and significant impacts from human activity. Included among these was the encroachment of human groups into Europe as they shifted from nomadic, pastoral lifestyles to more stationary, agro-pastoral lifestyles. The relationship between anthropogenic impacts and both on-going postglacial changes and punctuated climate events, however, is less clear. Separation of climate and anthropogenic signals in the paleorecord to resolve questions of timing is aided by a continuous sedimentary record that can be evaluated with a suite of geochemical tools. This study uses new abundance and distribution patterns of lipid biomarkers, including n-alkanes (plant wax compounds) and polycyclic aromatic hydrocarbons (PAHS; fire indicator compounds), and previously collected data including bulk organic carbon and bulk carbonate carbon and oxygen isotope records, charcoal data, pollen records, and archaeological findings to reconstruct the presence and pace of human and environmental changes during this period. These were applied to a continuous sediment core sampled from a paleolake near a mid-Neolithic human habitation site Krivače, located along the Dalmatia Coast (Croatia). N-alkane and PAH concentrations increased dramatically between 8000 and 6000 yrs BP, possibly due to changing climate, human activity, or a combination of both. High proportions of atypical short even-chain n-alkanes detected across this same interval were potentially sourced from autochthonous lake bacteria or derived from soil inputs. While PAHs increased in abundance during this interval, plant biomarker-normalized patterns did not increase, which suggests fire activity did not increase out of proportion to increased fuel loads. These patterns possibly indicate increased input of soil-derived contributions. Results from this project inform the timing and appearance of human-environmental events. Specifically, biomarker distributions of plant-derived n-alkanes tracked climate trends (temperature and hydroclimate), suggesting biomass increased with regionally under wetter conditions and decreased under drier conditions. PAH abundances, which tracked plant wax n-alkane inputs, indicated no large change in flammability was associated with habitation. The anomalous distributions between 8000 and 6000 yrs BP suggest significant inputs from human activity by soil disturbance, but also coincide with hydroclimate extremes (wetter conditions marked by flooding events) which could have also enhanced mobilization of soil-derived materials from the lake catchment. Further geochemical tools, such as fecal sterols and compound-specific isotope data, can help resolve these. The results of this study suggest human habitation during this period may have started earlier and extended beyond the timeframe currently documented by archaeological evidence. Additional studies can help us improve the timeline of early human history and reckon with human-environmental changes in a rapidly warming climate.

Download or read book Sedimentary Lipid Biomarkers and Trace Metals as Indicators for Past Hypoxia and Eutrophication written by Sebastian Näher and published by . This book was released on 2012 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Deciphering the Relationships Between Reactivity and Sources of Organic Matter in Marine Sediments written by Felipe Sales de Freitas and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lipid Biomarkers in Spanish Saline Lake Sediments written by Emma Jane Pearson and published by . This book was released on 2003 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: