Global ETD Search

591	Ancient environmental DNA as a means of understanding ecological restructuring during the Pleistocene-Holocene transition in Yukon, Canada Murchie, Tyler James January 2021 (has links) Humans evolved in a world of giant creatures. Current evidence suggests that most ice age megafauna went extinct around the transition to our current Holocene epoch. The ecological reverberations associated with the loss of over 65% of Earth’s largest terrestrial animals transformed ecosystems and human lifeways forever thereafter. However, there is still substantial debate as to the cause of this mass extinction. Evidence variously supports climate change and anthropogenic factors as primary drivers in the restructuring of the terrestrial biosphere. Much of the ongoing debate is driven by the insufficient resolution accessible via macro-remains. To help fill in the gaps in our understandings of the Pleistocene-Holocene transition, I utilized the growing power of sedimentary ancient DNA (sedaDNA) to reconstruct shifting signals of plants and animals in central Yukon. To date, sedaDNA has typically been analyzed by amplifying small, taxonomically informative regions. However, this approach is not ideally suited to the degraded characteristics of sedaDNA and ignores most of the potential data. Means of isolating sedaDNA have also suffered from the use of overly aggressive purification techniques resulting in substantial loss. To address these limitations, I first experimentally developed a novel means of releasing and isolating sedaDNA. Secondly, I developed a novel environmental bait-set designed to simultaneously capture DNA informative of macro-scale ecosystems. When combined, we identify a substantial improvement in the quantity and breadth of biomolecules recovered. These optimizations facilitated the unexpected discovery of horse and mammoth surviving thousands of years after their supposed extirpation. I followed up these results by extracting DNA from multiple permafrost cores where we confirm the late survival signal and identify a far more complex and high-resolution dataset beyond those identifiable by complementary methods. I was also able to reconstruct mitochondrial genomes from multiple megafauna simultaneously solely from sediment, demonstrating the information potential of sedaDNA. / Dissertation / Doctor of Philosophy (PhD) / A new addition to the rapidly growing field of palaeogenetics is environmental DNA (eDNA) with its immense wealth of biomolecules preserved over millennia outside of biological tissues. Organisms are constantly shedding cells, and while most of this DNA is metabolized or otherwise degraded, some small fraction is preserved through sedimentary mineral-binding. I experimentally developed new ancient eDNA methods for recovery, isolation, and analysis to maximize our access to these biomolecules and demonstrate that this novel approach outperforms alternative protocols. Thereafter, I used these methods to extract DNA from ice age permafrost samples dating between 30,000–6,000 years before present. These data demonstrate the power of ancient eDNA for reconstructing ecosystem change through time, as well as identifying evidence for the Holocene survival of caballine horse and woolly mammoth in continental North America. This late persistence of Pleistocene fauna has implications for understanding the human ecological and climatological factors involved in the Late Pleistocene mass extinction event. This effort is paralleled with megafaunal mitogenomic assembly and phylogenetics solely from sediment. This thesis demonstrates that environmental DNA can significantly augment macro-scale buried records in palaeoecology. Ancient DNA Environmental DNA Late Quaternary Extinctions Pleistocene/Holocene Transition Megafauna Beringia Archaeology Palaeontology Palaeoecology Metagenomics Palaeogenetics Mitogenome Environmental turnover Human ecology Anthropocene Yukon Woolly mammoth Steppe bison Yukon wild horse Palaeoamerica Palaeochip Arctic-1.0 Targeted capture enrichment DNA extraction Permafrost
592	Diatoms from the late Holocene of the western Chukchi Sea, Arctic Ocean: environmental signals and palaeoceanography / Diatoméer från sen holocen i västra Tjukjerhavet, Arktiska oceanen: miljösignaler och paleoceanografi Browaldh, Erik January 2022 (has links) The sediment Core SWERUS-L2-2-PC1 (2PC) retrieved from the Chukchi Sea, Arctic Ocean sits in an oceanographically dynamic location at the Arctic-Pacific Ocean gateway. The 8.3 m-long core was retrieved in Herald Canyon at the marginal ice zone at 57 m depth. Core 2PC is well-positioned to record variability in inflow of Bering Sea Water (BSW) and Pacific Water (PW) in Herald Canyon. With the 2PC high sedimentation rate (200 cm/kyr), two independent age models (radiocarbon and palaeomagnetism) based on tephra age markers, and a richness in well-preserved siliceous sediment, validate 2PC as an outstanding sequence for applying diatom assemblage analysis as a proxy for ocean-climate change back to 4250 years BP, including the past few hundred years where global warming and sea ice decline is recorded by instrumental records. These characteristics make Core-2PC a useful record for investigating the role of PW on sea ice variability in the Chukchi Sea, both in the past and predicting the future. To investigate the impact of PW on ocean and sea ice conditions in the Chukchi Sea, diatom assemblage analysis was performed on 49 samples through the Late Holocene. The over-arching goal was to test the hypothesis, suggested by existing research on 2PC using benthic foraminifera Mg/Ca palaeothermometry, that the strength of PW inflow into the Chukchi Sea via Herald Canyon has varied on a time scales of ~500-1000 years in the past 4000 years. PW is slightly warmer than resident Arctic surface waters and is known to be an important control on Arctic sea-ice. The diatom assemblage approach assumes that there are recognizable differences between end-member diatom assemblages that are characteristic of PW versus Arctic Ocean type environments associated with extensive sea-ice conditions. The mapping of species in the Herald Canyon was used to test the idea of variability of sea-ice extent and the role of the Pacific Ocean forcings into the western Chukchi Sea. The results reveal diverse diatom assemblages throughout the past 4000 years in Herald Canyon, showing this core to be very useful for diatom palaeoclimate reconstructions. A total of 126 species with abundance >1% are recognized. Several generalist species typically dominate assemblages especially Chaetoceros, ice-algae, marine-neritic and near ice or cold-water planktic centric diatoms. Distinct changes in stratigraphy are illustrated by changes in identified diatom assemblage zones. The 2PC diatom assemblages were contrasted with records from Chukchi-, Laptev-, East Siberian- and Bering Sea and North Pacific Ocean. At 2PC, sympagic (sea-ice related), planktic and neritic species abundance varies on time scales of ~500-1000 years. Importantly, there is a clear similarity between the timing of diatom assemblage changes and the 2PC benthic foraminifera Mg/Ca bottom water temperature (BWT) reconstruction. In particular, abundance changes in the warm water species Thalassionema nitzschioides, Shionodiscus oestrupii and Thalassionema simonsenii, tychoplanktic Paralia sulcata, Ice algae- and sympagic assemblages and cold-water indicators correspond best to BWT fluctuations shown by the Mg/Ca reconstruction. These oscillations are suggestive of changes in warmer PW inflow. Other aspects of the diatom data appear to correlate with colder and warmer climate events and suggest that changes in PW inflow amplified the effects of these events in the Chukchi Sea region through the Late Holocene in the Northern Hemisphere. It can thus, be concluded that diatoms from 2PC, support the palaeoceanographic reconstruction suggested by the benthic foraminifera Mg/Ca palaeothermometry and that variations in PW inflow through Herald Canyon is an important driver of sea ice variability on thousand-year time scales. diatoms late holocene SWERUS-L2-2-PC1 Herald Canyon Chukchi Sea ice-algae sympagic cryophilic warm water diatom Bering Sea Water species bottom water temperature BWT benthic foraminifera palaeothermometry ice dynamics Fragilariopsis Fossula arctica Paralia sulcata Shionodiscus oestrupii Thalassiosira simonsenii Chaetoceros Chaetoceros sp. 7 Geology Geologi
593	A History of Place: Using Phytolith Analysis to Discern Holocene Vegetation Change on Sanak Island, Western Gulf of Alaska Wilbur, Cricket C. January 2013 (has links) No description available. Archaeology Botany Climate Change Conservation Earth Ecology Environmental Science Freshwater Ecology Geology Limnology Native Americans Natural Resource Management Paleobotany Paleoclimate Science Paleoecology Plant Biology Pollen Paleolimnology Phytoliths Phytolith Analysis Aleutian Islands Sanak Island Western Gulf of Alaska Stomata Maritime tundra Grasses Dicotyldons Arctic ecosystems Climate change Paleoenvironmental reconstruction Holocene Lake sediment
594	Stable isotope investigations on speleothems from different cave systems in Germany. / Stabile Isotopen-Untersuchungen an Speläothemen aus verschiedenen Höhlensystemen in Deutschland. Nordhoff, Peter 13 June 2005 (has links) No description available. 550 Geowissenschaften VAO 200 VDI 200 VDI 210 VDI 220 VEB 127 VEB 147 VJJ 100 Mathematics and Natural Science Speläotheme Stalagmiten Stalaktiten Tropfwasser Deutschland Schwäbische Alb Fränkische Alb Harz Paläoklima δ18O/δ13C stabile Isotope 234U/230Th TIMS Zaininger Höhle Hintere Kohlhaldenhöhle Baumannshöhle Herrmannshöhle Mühlbachquellhöhle Höhlenruine Hunas thermodynamische Equilibrium kinetische Fraktionierung OIS2 Jüngere Dryas Bölling/Alleröd T1 Pleistozän Holozän 8.2ka Holozänes Optimum speleothem stalagmites stalactites dripwater Germany Swabian Alb Franconian Alb Harz Mountains paleoclimate δ18O/δ13C stable isotopes 234U/230Th TIMS Zaininger Cave Hintere Kohlhalden Cave Baumanns-Cave Herrmanns-Cave Mühlbach-Cave Paleocave Hunas hendy test equilibrium conditions kinetic fractionation OIS2 Younger Dryas Bölling/Alleröd T1 Pleistocene Holocene 8.2 kyr. Holocene Climatic Optimum 38.03 38.82 38.17 38.19 38.32
595	Der glazifluviale Formenschatz im Gletschervorfeld des Himalaya und der Versuch einer relativ-zeitlichen Einordnung / Glaciofluvial sequence of forms in the glacier foreland of the Himalayas and their chronological classification Tombrink, Gerrit 23 November 2017 (has links) No description available. 910 550 Himalaya Khumbu Himal Pangong Tso Nepal Indien Hochasien Glaziale Serie Glazifluviale Serie Gletscherschwankungen Fluvialgeomorphologie Hochgebirgsgeomorphologie Glaziologie Vergletscherung Historische Vergletscherungsstadien Rezente Gletscherschmelze Quartärforschung Holozän Klimawandel Flussformen Proglaziale Formen Gletschervorfeld Sander Himalaya Khumbu Himal Pangong Tso Nepal India High Asia Fluvial Geomorphology Glacial Geomorphology Glaciology Glaciation Glacier Historical Glacier Fluctuations Recent Glacier Melting Climate Change Quaternary Science Holocene River River forms Proglacial forms Glacier foreland Sandur Geographie (PPN621264008)
596	Palynological studies and Holocene ecosystem dynamics in north western Khyber Pakhtunkhwa Province of Pakistan in the Hindu Kush Himalayan region / Trends of pollen grain size variation in C3 and C4 Poaceae species using pollen morphology for future assessment of grassland ecosystem dynamics / Vegetation and pollen along a 200 km transect in Khyber Pakhtunkhwa Province, north western Pakistan / Vegetation and climate dynamics in Khyber Pakhtunkhwa, north-western Pakistan, inferred from the Kabal Swat pollen record during the last 3300 years Farooq, Jan 30 April 2015 (has links) Khyber Pakhtunkhwa (31 ° 49'N, 70 ° 55'E bis 35 ° 50'N, 71 ° 47'E) liegt im Nordwesten Pakistans im Süden Asiens. Das Hindukusch-Gebirge in Afghanistan liegt im Westen, dem indischen Himalaya im Nordosten und die Karakorum Berge südlich vom tibetischen Hochland auf der Nordseite. Diese Arbeit besteht überwiegend aus drei separaten Studien entlang eines 200 km langen Transekts mit einem Höhengradienten ausgehend von den Sedimentbecken im Peshawar Tal (275 m ü.M.) bis hinauf zu den Malam Jabba Hills im Swat-Tal (2600 m ü.M.). Die erste Studie, die auf einer Datengrundlage von 160 Poaceae Arten beruht, zeigt Trends, dass polyploide C3- und C4-Poaceae-Arten größere Pollenkkörner als die jeweiligen diploiden Arten haben. In diesem Datensatz haben alle C4-Arten größere Pollenkörner als die C3-Arten. Ob Grassländer von C3 oder C4 Arten dominiert werden kann in verschiedenen Regionen und Lebensräumen durch die Untersuchung der Muster des Trends von zu- oder abnehmenden Pollenkorngrößen ermittelt werden. In unserem Datensatz ist Polyploidie bei C4-Gräsern häufiger als bei den C3 Arten. Die verwendete Methode kann auf Poaceae-Pollenkörner in Umweltarchiven angewendet werden, um das Klima der Vergangenheit zu rekonstruieren und die Dynamik der früheren Graslandökosysteme zu bewerten. Dieser Ansatz wird nicht nur bei laufenden paläoökologischen Studien helfen aufzuklären, wie die Änderungen der Vegetations-zusammensetzung und die Veränderungen in Biomen vergangener Graslandökosysteme zu entschlüsseln sind, sondern auch nützliche Erkenntnisse für die Vorhersage zukünftiger Entwicklungen ermöglichen. Die zweite Studie befasst sich mit modernen Pollenspektren aus Oberflächenproben und ihre Beziehung zu der umgebenden Vegetation, die nützliche Daten für die Interpretation von holozänen Pollenprofilen bietet. Dabei konnten entlang eines 200 km langen Höhengradienten vier verschiedene Höhenstufen unterschieden werden, wo die dominierenden Pflanzenfamilien, Poaceae, Asteraceae, Cyperaceae, Verbenaceae, Acanthaceae und Euphorbiaceae eine signifikante Korrelation mit dem gefunden Pollenniederschlag hatten, während sich bei anderen Familien, den Boraginaceae, Saxifragaceae, Apiaceae, Balsaminaceae und Rubiaceae große Unterschiede zu der zugehörigen Vegetationszusammensetzung ergaben. Für die Kalibrierung und Interpretation fossiler Pollendaten sollte also immer auch die aktuellen Beziehungen von Pollenniederschlag und Vegetationsdaten zumindest auf der Familienebene berücksichtigt werden. Die dritte Studie befasst sich mit einem Pollenprofil aus der Kabal Swat-Region, welches eine detaillierte Geschichte der Vegetation und des Klimas des Hindukuschs der letzten 3300 Jahre, also dem späten Holozäns enthält. Von 3300 bis 2400 cal BP, war eine subtropische semiaride krautige Vegetation hauptsächlich durch Cyperaceae- und Poaceae-Arten vertreten. Sie wurde ersetzt von gemischten Nadelwäldern mit Taxus, Pinus, sowie Juglans, Poaceae und Cyperaceae während der Zeit von 2400 bis 900 cal BP, was auf eine vergleichsweise moderate Klimaschwankung während des späten Holozäns weist. Der Rückgang der Poaceae von 2400 bis1500 cal BP und eine erneute Zunahme von 1500 bis 1200 cal BP Jahre zeigen, dass das Kabal Swat nass-kühlere und trocken-wärmere Phasen durchmachte. Nadelbäume in den gemischten Nadelwäldern treten heute bei größeren Höhe im alpinen Bereich auf. Weitere hochauflösende holozäne Pollenprofile des Hindukusch sind notwendig, um einen ausführlicheren Vergleich zu anderen süd- und zentralasiatischen Paläo-Archiven zu ermöglichen, die auch ein detaillierteres und anwendbares Wissen für Management und Naturschutzfragen ergeben. 570 Table of contents Summary Zusammenfassung CHAPTER 1 Introduction CHAPTER 5 Synthesis References Appendix tables Declaration statement Holocene climate dynamics pollen record Kabal Swat Khyber Pakhtunkhwa Pakistan Hindu Kush Western Himalaya Indian monsoon elevational gradient lowlands to montane vegetation pollen rain relationship secondary vegetation pollen grain size C3 and C4 Poaceae ploidy Afghanistan Europe Africa South America Biologie (PPN619462639)
597	Postglazialer Anstieg des Meeresspiegels, Paläoklima und Hydrographie, aufgezeichnet in Sedimenten der Bermuda inshore waters / Postglacial rise of sea level, palaeoclimate and hydrography, recorded in sediments of the Bermuda inshore waters Vollbrecht, Rüdiger Dr. 13 January 1997 (has links) No description available. 550 Geowissenschaften Mathematics and Computer Science Postglazial Meeresspiegel Paläoklima Hydrography Bermuda Sedimente Pleistozän Holozän Quartär Seen Küste Laminite Solarzyklen Sonnenzyklen marin lakustrin Geologie Karbonate Böden Karst Torf Isotopen-Geochemie Altersbestimmung Fazies Paläökologie postglacial sea level palaeoclimate paleoclimate hydrography Bermuda sediments Pleistocene Holocene Quaternary inshore waters lakes laminites solar cycles lacustrine marine geology carbonates soil karst peat isotope geochemistry radiocarbon dating facies palaeoecology paleoecology 38.48 Marine Geologie 38.41 Sedimentation 38.82 Klimatologie 38.19 Historische Geologie: Sonstiges 38.32 Geochemie 38.88 Regionale Hydrologie 38.47 Moore 38.90 Ozeanologie Ozeanographie VAT 250 Litorale Sedimente VCA 520 Quartärgeologie VDI 210 Pleistozän VDI 220 Holozän VEW 200 Karibischer Raum VEZ 130 Inselgruppen TWC 600 Paläoklimatologie VKB 380 Sedimente bestimmter Regionen VKB 378 Rhytmite VKB 376 Organogene Sedimentgesteine VKB 340 Fazieskunde VKB 333 Sonstige Sedimentationsprozesse VKB 332 Sedimentationsbedingungen UHA 700 Marine Geologie (Küsten Watt Inselbildung etc.) UHA 440 Schwankungen

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