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1
Yung, Cheuk-man, and 容卓敏. "Molecular ecology of chasmoendolithic environments in Miers Valley, McMurdo Dry Valleys, Antarctica." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B4784999X.
Full textAbstract:
The McMurdo Dry Valleys comprise some 4,800km2 of ice-free terrain in east
Antarctica and this constitutes the coldest and most arid desert on Earth. The
ecosystem of the Dry Valleys is characterized by microbial processes since
environmental extremes severely limit higher plant and animal life. A major
international collaborative research effort co-ordinated by the International Center
for Terrestrial Antarctic Research (ICTAR), identified long-term study sites
representative of maritime and inland Dry Valleys environments. The maritime site,
Miers Valley, has been the subject of intensive multi-disciplinary study in recent
years, of which the work in this thesis is a part. Previous studies have identified
soil microbial communities and their putative functional roles, but lithic communities
have not been previously appreciated. This thesis reports aspects on the
biodiversity and ecology of lithic microbial communities in Miers Valley.
A survey of terrain revealed extensive weathered granite, but no porous
sandstone or limestone rocks more commonly associated with cryptoendolithic
communities (those colonizing pore spaces within rock substrates). Granite was
extensively colonized (30-100% of available substrate) by chasmoendolithic
microorganisms (colonizing cracks and fissures in weathered rock). Visual
examination of colonized rocks revealed a distinct zone of biomass 2-5mm below the
rock surface, and this was overlain by a weathered and friable matrix of rock.
Microscopy revealed a community dominated by diverse cyanobacterial
morphotypes, plus other unidentifiable microbes of varied morphology.
A quantitative approach to broad-scale community fingerprinting was adopted,
utilizing terminal restriction fragment length polymorphism (TRFLP) and sequence
based identifications of restriction fragments. The multi-domain approach
encompassed Archaea, Bacteria and Eukarya. The results revealed relatively low
species richness (0.6-1.8) for each domain with community richness estimates also
relatively low (<3). Nonetheless very clear and statistically supported patterns in
the occurrence of phylotypes within chasmolithic communities were related to aspect
(which strongly affects temperature and moisture availability in Dry Valleys
locations). The bacterial assemblages formed two groups (cold-dry south facing
slopes and valley floor moraine). The eukaryal assemblages also formed two
groups although here the moraine samples grouped with the warmer wetter north
facing slope and the cold-dry south facing slope assemblages formed a separate
group. The archaeal assemblages displayed no difference within different valley
terrain.
Extensive sequence based interrogation of community structure using clone
libraries revealed a community dominated by cyanobacteria, Actinobacteria,
Deinococci and putative lichens. These phyla are all known for their extreme
tolerance to desiccation and occurrence in arid landscapes. Phylogenetic analysis
revealed that these abundant taxa shared close affiliation with those from other
Antarctic refuge niches such as hypoliths and cryptoendoliths. The cyanobacteria
were mainly Oscillatoriales, but other genera such as Chroococcidiopsis and Nostoc
commonly recovered in hot desert lithic communities were generally absent. The
eukaryal community was dominated by chlorophyte algae, whilst the archaeal
phylotypes were a diverse collection spanning both euryachaeal and crenarchaeal
lineages.
Overall the data revealed the chasmoendolithic community in Miers Valley
was widespread and with relatively restricted diversity. The selection pressures
related to topology of the valley have resulted in different community structure
within the valley.published_or_final_version
Biological Sciences
Master
Master of Philosophy
2
Deuerling, Kelly M. "Aeolian Sediments of the McMurdo Dry Valleys, Antarctica." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1290524862.
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3
Lapalme, Caitlin. "Near-Surface Ground Ice Conditions In University Valley, McMurdo Dry Valleys of Antarctica." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33412.
Full textAbstract:
This study aims to quantify ground ice content and describe the cryostructures and sediment in 15 ice-bearing permafrost cores collected from nine sand-wedge polygons in University Valley. The objectives were reached through laboratory measurements and computed tomodensitometric (CT) scanned image analysis of the permafrost cores. The soils in the valley were predominantly medium-sand. Four types of cryostructures were present in the cores: structureless, suspended, crustal and porphyritic. Excess ice content ranged from 0 to 93%, gravimetric water content ranged from 13 to 1881% and volumetric ice content varied from 28 to 93%. Median excess ice, volumetric ice and gravimetric water contents significantly increased in the top 20 cm of the cores taken from the polygon shoulders with increasing distance from University Glacier. Ground ice was preferentially stored in the centre of the investigated polygons where the ground surface remains cryotic throughout the year. Conversely, higher ground ice contents were measured in the shoulders of the investigated polygon where the ground surface is seasonally non-cryotic. CT-scanned images were shown to reasonably assess the distribution and presence of excess ice in permafrost cores taken from a cold and hyper-arid environment. The results of this thesis provide the first cryostratigraphic study in the McMurdo Dry Valleys of Antarctica.
4
Hoffman, Matthew James. "Spatial and Temporal Variability of Glacier Melt in the McMurdo Dry Valleys, Antarctica." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/744.
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In the McMurdo Dry Valleys, Victoria Land, East Antarctica, melting of glacial ice is the primary source of water to streams, lakes, and associated ecosystems. To better understand meltwater production, three hypotheses are tested: 1) that small changes in the surface energy balance on these glaciers will result in large changes in melt, 2) that subsurface melt does not contribute significantly to runoff, and 3) that melt from 25-m high terminal cliffs is the dominant source of baseflow during cold periods. These hypotheses were investigated using a surface energy balance model applied to the glaciers of Taylor Valley using 14 years of meteorological data and calibrated to ablation measurements. Inclusion of transmission of solar radiation into the ice through a source term in a one-dimensional heat transfer equation was necessary to accurately model summer ablation and ice temperatures. Results showed good correspondence between calculated and measured ablation and ice temperatures over the 14 years using both daily and hourly time steps, but an hourly time step allowed resolution of short duration melt events and melt within the upper 15 cm of the ice. Resolution of short duration melt events was not important for properly resolving seasonal ablation totals. Across the smooth surfaces of the glaciers, ablation was dominated by sublimation and melting was rare. Above freezing air temperatures did not necessarily result in melt, and low wind speed was important for melt initiation. According to the model, subsurface melt between 5 and 15 cm depth was extensive and lasted for up to six weeks in some summers. The model was better able to predict ablation if some subsurface melt was assumed to drain, lowering ice density, consistent with observations of a low density weathering crust that forms over the course of the summer on Dry Valley glaciers. In extreme summers, drainage of subsurface melt may have contributed up to half of the observed surface lowering through reduction of ice density and possibly through collapse of highly weathered ice. When applied spatially, the model successfully predicted proglacial streamflow at seasonal and daily time scales. This was despite omitting a routing scheme, and instead assuming that all melt generated exits the glacier on the same day, suggesting refreezing is not substantial. Including subsurface melt as runoff improved predictions of runoff volume and timing, particularly for the recession of large flood peaks. Because overland flow was rarely observed over much of these glaciers, these model results suggest that runoff may be predominantly transported beneath the surface in a partially melted permeable layer of weathered ice. According to the model, topographic basins, particularly the low albedo basin floors, played a prominent role in runoff production. Smooth glacier surfaces exhibited low melt rates, but were important during high melt conditions due to their large surface area. Estimated runoff contributions from cliffs and cryoconite holes was somewhat smaller than suggested in previous studies. Spatial and temporal variability in albedo due to snow and debris played a dominant role in flow variations between streams and seasons. In general, the model supported the existing assumption that snowmelt is insignificant, but in extreme melt years snowmelt in the accumulation area may contribute significantly to runoff in some locations.
5
Sabacka, Marie. "Wind as an ecological factor in the McMurdo Dry Valleys, Antarctica." Diss., Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/sabacka/SabackaM0512.pdf.
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The aim of this work was to investigate the role of wind on the ecology of the McMurdo Dry Valleys in Antarctica (MDV), one of the coldest and driest deserts on Earth. The MDV landscape consists of a mosaic of permanently ice-covered lakes, ephemeral streams, exposed soils, and glaciers, all of which contain habitats dominated by microorganisms. Data on wind-driven flux of sediments and associated organic matter were collected using passive aeolian traps and dynamic mass erosion particle counters to investigate the timing, direction and magnitude of aeolian sediment transport. Combination of genomic techniques and phenotypical fingerprinting (pigment analysis) was used to examine microbial diversity over a wide variety of wind-eroded habitats across the MDV landscape to elucidate the role of wind dispersal on the contemporary distribution of microorganisms across the MDVs. Sediment entrainment occurs predominantly within 20 cm of the ground surface and has character of saltation bursts that occupy <3% of the total time within a year. The high-energy winter fo��hn winds uplift sediments in the upper parts of the MDVs and transport them down-valley where they are deposited onto the surface of perennially ice-covered lakes and surrounding soils. The sediment that enters the water column of the lakes does not provide a significant source of organic carbon for bacterioplankton communities compared to the in situ production by phytoplankton but can be a source of new microbial propagules. The aeolian material is low in organic matter (<1% dw) but is composed of a relatively large numbers of cyanobacterial taxa (~20 OTUs) that can be found in all other MDV habitats. In conclusion, wind distributes microorganisms across the MDV landscape but local environment selects for specific taxa. Predicted climate warming will increase the importance of wind transport, which will affect nutrient cycling and connectivity among MDV ecosystem components. 'Co-authored by John C. Priscu, Hassan J. Basagic, Andrew G. Fountain, Diana H. Wall, Ross A. Virginia and Mark C. Greenwood, J. E. Barrett, Diane McKnight and Alexander B. Michaud.'
6
Power, Sarah Nicole. "Microbial Mat Abundance and Activity in the McMurdo Dry Valleys, Antarctica." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/101078.
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Primary productivity is a fundamental ecological process and an important measure of ecosystem response to environmental change. Currently, there is a considerable lapse in our understanding of primary productivity in hot and cold deserts, due to the difficulty of measuring production in cryptogam vegetation. However, remote sensing can provide long-term, spatially-extensive estimates of primary production and are particularly well suited to remote environments, such as in the McMurdo Dry Valleys (MDV) of Antarctica, where cyanobacterial communities are the main drivers of primary production. These microbial communities form multi-layered sheets (i.e., microbial mats) on top of desert pavement. The cryptic nature of these communities, their often patchy spatial distribution, and their ability to survive desiccation make assessments of productivity challenging. I used field-based surveys of microbial mat biomass and pigment chemistry in conjunction with analyses of multispectral satellite data to examine the distribution and activity of microbial mats. This is the first satellite-derived estimate of microbial mat biomass for Antarctic microbial mat communities. I show strong correlations between multispectral satellite data (i.e., NDVI) and ground based measurements of microbial mats, including ground cover, biomass, and pigment chemistry. Elemental (C, N) and isotopic composition (15N, 13C) of microbial mats show that they have significant effects on biogeochemical cycling in the soil and sediment of this region where they occur. Using these relationships, I developed a statistical model that estimates biomass (kg of C) in selected wetlands in the Lake Fryxell Basin, Antarctica. Overall, this research demonstrates the importance of terrestrial microbial mats on C and N cycling in the McMurdo Dry Valleys, Antarctica.Master of Science
7
Ramsey, Meridith Ann. "OSL Dating of High-Elevation Alluvial Sediments: McMurdo Dry Valleys, Antarctica." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27578.
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High-elevation alluvial fans in the McMurdo Dry Valleys are a record of short-term, occasional melting events along the margins of the East Antarctic Ice Sheet. Sediment samples were dated from five fans using Optically Stimulated Luminescence (OSL) dating. OSL dates the time since quartz grains were last exposed to sunlight; all sample preparation takes place in a dark room. Thirteen samples were dated for this thesis, the ages were stratigraphically consistent and ranged from 1.1 ka to 105.9 ka. Clusters of fan activity occurred between 1.1 and 3.1 ka and 8.1 and 11.1 ka. The melting events appear to be linked to insolation, with periods of fan activity occurring usually at times of increased mean annual insolation. The alluvial fans show promise as a possible archive for climate proxies in this region of Antarctica.
8
Steinhoff, Daniel Frederick. "Dynamics and Variability of Foehn Winds in the McMurdo Dry Valleys Antarctica." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306437539.
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Barbier, Beatrice A. "Investigating the Biodiversity of Microbial Communities in the McMurdo Dry Valleys, Antarctica: An Inter-Valley Comparison Study." The University of Waikato, 2009. http://hdl.handle.net/10289/2775.
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Extreme environments provide a unique source of often highly adapted and tolerant organisms. Research on organisms in these habitats has led to the discovery of novel and useful compounds and may assist in understanding the impact of global change on biodiversity. The Dry Valleys of Eastern Antarctica are vast, ice-free regions believed to be the coldest, driest desert on Earth. Despite these harsh conditions, there is an increasing amount of evidence demonstrating that the soil ecosystems of the Dry Valleys sustain a wide diversity of microorganisms. The research presented is an inter-valley comparison study which aims to scrutinize microbial communities and environmental factors driving their distribution in the Dry Valleys. Automated ribosomal intergenic spacer analysis (ARISA) was used to provide a snapshot of bacterial and cyanobacterial communities living in the mineral sands in Miers Valley, Beacon Valley, Upper Wright Valley and at Battleship Promontory. Rigorous analysis of physico-chemical differences between the soils of these four valleys was undertaken in hope to understand the environmental parameters driving the distribution and biodiversity of microbial communities present. Multivariate statistical analysis and ordination of ARISA and physico-chemical data revealed that bacterial communities from each valley form distinctive clusters. Conversely, cyanobacterial communities showed less diversity and a more even distribution between valleys.
10
Zamora, Felix Jacob. "Measuring and Modeling Evolution of Cryoconite Holes in the McMurdo Dry Valleys, Antarctica." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4706.
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Cryoconite holes are vertical columns of meltwater within the shallow subsurface of glaciers. In the McMurdo Dry Valleys (MDV) of Antarctica cryoconite holes are a source of meltwater and harbor microbial communities in an otherwise arid environment with low biologic activity. The holes form as sediments on the ice surface, which are darker than the surrounding ice, are preferentially heated by solar radiation. The warm sediments melt the underlying ice and migrate downwards. An ice lid forms, isolating them from the below-freezing atmosphere enabling them to remain thawed. In this study, field observations, laboratory experiments, and numerical modeling are used to characterize the fundamental variables controlling cryoconite hole development.
Field and laboratory results show that solar radiation drives cryoconite hole melting by controlling the energy available to the cryoconite and to warm the surrounding ice. Holes deepen further in warmer ice. Laboratory results show that at temperatures of -10º C at least 405 (W m-2) are needed to warm the cryoconite sufficiently to melt surrounding ice. Numerical modeling shows that increased radiation flux into the subsurface and warmer air temperatures cause cryoconite to descend deeper and the meltwater-filled holes to enlarge, while increased surface ablation decreases their average depth. Cryoconite holes thaw sooner and refreeze later when the optical properties of the ice facilitate greater radiation transmission. Cryoconite warms the ice significantly more than ice without cryoconite. Within the melt-filled hole, the heat capacity of the water keeps the surrounding ice warm for several weeks after the cryoconite-free ice has cooled. The cryoconite itself is last to completely freeze.
11
Clocksin, Kate M. "Isolation and characterization of heterotrophic bacteria from Lake Hoare, McMurdo Dry Valleys, Antarctica /." Available to subscribers only, 2005. http://proquest.umi.com/pqdweb?did=1079660831&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (M.S.)--Southern Illinois University Carbondale, 2005."Department of Molecular Biology, Microbiology and Biochemisty." Includes bibliographical references (leaves 48-54). Also available online.
12
Zamora, Felix Jacob. "Measuring and Modeling Evolution of Cryoconite Holes in the McMurdo Dry Valleys, Antarctica." Thesis, Portland State University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10935931.
Full textAbstract:
Cryoconite holes are vertical columns of meltwater within the shallow subsurface of glaciers. In the McMurdo Dry Valleys (MDV) of Antarctica cryoconite holes are a source of meltwater and harbor microbial communities in an otherwise arid environment with low biologic activity. The holes form as sediments on the ice surface, which are darker than the surrounding ice, are preferentially heated by solar radiation. The warm sediments melt the underlying ice and migrate downwards. An ice lid forms, isolating them from the below-freezing atmosphere enabling them to remain thawed. In this study, field observations, laboratory experiments, and numerical modeling are used to characterize the fundamental variables controlling cryoconite hole development.
Field and laboratory results show that solar radiation drives cryoconite hole melting by controlling the energy available to the cryoconite and to warm the surrounding ice. Holes deepen further in warmer ice. Laboratory results show that at temperatures of –10 °C at least 405 (W m–2 ) are needed to warm the cryoconite sufficiently to melt surrounding ice. Numerical modeling shows that increased radiation flux into the subsurface and warmer air temperatures cause cryoconite to descend deeper and the meltwater-filled holes to enlarge, while increased surface ablation decreases their average depth. Cryoconite holes thaw sooner and refreeze later when the optical properties of the ice facilitate greater radiation transmission. Cryoconite warms the ice significantly more than ice without cryoconite. Within the melt-filled hole, the heat capacity of the water keeps the surrounding ice warm for several weeks after the cryoconite-free ice has cooled. The cryoconite itself is last to completely freeze.
13
Mager, Sarah M., and n/a. "A compositional approach to understanding the formation of basal ice in the Antartic glaciers." University of Otago. Department of Geography, 2006. http://adt.otago.ac.nz./public/adt-NZDU20061129.150045.
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The composition of ice from four case studies based on the facies, solute, stable isotope, and debris content reveals compositional differences reflective of different modes of ice formation. In Southern McMurdo Sound, there is a distinctive geochemical signature that differentiates between meteoric-origin and marine-origin ice. Analysis of the basal ice of three glaciers from the McMurdo Dry Valleys shows that liquid water does contribute to its formation. The basal ice sequences are structurally and compositionally different and are reflective of different modes of formation or entrainment active at the glacier margins. In the cases of the Rhone and Wright Lower glaciers marginal sediments and liquid water are key to understanding the accretion of debris-rich ice and both have basal facies consistent with refreezing in subzero conditions. The liquid water is formed by ephemeral melt during the summer. In the Rhone Glacier, melt water refreezes on the apron and is entrained into the advancing glacier. By contrast, by the Wright Lower Glacier adjacent streams or ponds saturate unconsolidated sediments which are entrained during ice advance. In the Taylor Glacier, the basal ice is comprised of a thick sequence of intercalated layers of clean clear ice and fine-grained debris layers. These laminated facies have a solute composition consistent with evaporites formed from a relict seawater intrusion. The combination of entrained debris, high solutes and laminations is consistent with interaction at the glacier bed and regelation. Interpreting empirically derived co-isotopic slopes is problematic, as highlighted in the case study of the Taylor Glacier where laminated facies have all the hallmarks of refrozen ice, yet plot on a co-isotopic slope that is typically interpreted as meteoric. Similarly, ice from the McMurdo Ice Shelf shows a clear difference in absolute isotope values which is interpreted as being refrozen from seawater, yet its co-isotopic plot is statistically indistinguishable from the meteoric water line. The ice compositional approach has highlighted several shortcomings. Firstly, solutes deposited in inland areas have limited solute pathways and do not distinguish between different types of ice but are useful in distinguishing between marine and continental salts. Secondly, co-isotopic analysis to reconstruct freezing history is dependent on statistically-derived interpretations which do not explain slopes that lie between physically-based models of meteoric and freezing slopes. In empirical studies, slopes between 5 and 8 are common, and are probably cosmopolitan samples. Finally, ice composition is inconsistent between similar ice types in the McMurdo Dry Valleys, as similar facies have different ice compositions, and origins. This underlines the problem with the premise that structurally similar ice facies are formed by the same process.
14
Drake, Alexandra. "Mapping of Massive Ground Ice Using Ground Penetrating Radar Data in Taylor Valley, McMurdo Dry Valleys of Antarctica." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-260357.
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The distribution of massive ground ice in the ground in Taylor Valley of the McMurdo Dry Valleys, Antarctica, is quite unknown, and could provide answers to questions such as where the ice comes from, if it has been affected and removed by proglacial lakes and how landscapes underlain by massive ground ice responds to climate change. It could also be a source for atmospheric information in the past and hence a key in climate research. The main goal with this project was therefore to map the distribution of massive ground ice mainly in Taylor Valley, but also in the adjacent Salmon Valley and Wright Valley, using ground penetrating radar to see how the distribution varied and if there was any spatial patterns. The technical computing programme MATLAB was used for editing of the raw radar data, merging of GPR profiles and digitalization of reflectors for possible massive ground ice and several compilations of different files. The data obtained from MATLAB was imported and interpreted using the geographic information system ArcGIS. A series of histograms showing the distribution of massive ground ice depending on the parameters elevation, slope and aspect were made by using the spreadsheet application Microsoft Excel. The results showed that the distribution of massive ground ice was more common at elevations up to 200 m, at the mouth of the valleys and also more frequent in Taylor Valley than in Wright Valley. There was a slightly higher amount of massive ground ice at northeast-east aspects, probably due to different incoming solar radiation. The lack of, or not that prominent, differences for slope and aspect can be due to lack of data, a not enough detailed digital elevation model or that it have existed for a too short period of time to display big differences caused by effects from these parameters. The higher frequency of massive ground ice in Taylor Valley can be due to a thicker sediment cover when compared with the situation in Wright Valley. The distribution of massive ground ice at different slopes seems to follow the distribution of radar measurements, whereas the origin of the massive ground ice and sediment cover can be responsible for the distribution across different elevations. The reason why massive ground ice still occurs despite the existence of Glacial Lake Washburn that previously occupied Taylor Valley could be that the glacial lake did not remain for a sufficiently long time to melt all the massive ice. Massive ground ice is very common in a zone that is believed to be very susceptible for future warming, which means that changes that already have been observed in areas rich in massive ground ice can continue to happen and changes in other areas with massive ice can be enabled. The ice can thus play a major role in the development of the landscape in the McMurdo Dry Valleys depending on the amount of warming.Markis kan hittas i mark som har temperaturer under 0°C under åtminstone 2 år i följd och därav klassas som permafrost, skillnaden mellan markis och permafrost är däremot att permafrost inte behöver vara just is utan kan enbart vara kall mark. För att markis ska klassas som massiv is så ska andelen is i marken vara minst 250 % jämfört med vikten på torr jord. Utbredningen av sådan massiv is i Taylor Valley i McMurdos torrdalar på Antarktis är inte helt känd, och kunskapen om att veta vart den finns (om den finns) skulle kunna ge svar på frågor som vart den kommer ifrån, om den har påverkats och smält bort av isuppdämda sjöar och hur landskap som är grundade av massiv markis påverkas av klimatförändringar. Isen skulle även kunna vara en informationskälla för tidigare atmosfäriska förhållanden. Huvudsyftet med detta arbete var därför att kartlägga utbredningen av massiv is främst i Taylor Valley, men även i de närliggande dalarna Salmon Valley och Wright Valley, och undersöka hur utbredningen varierar beroende på olika landskapsegenskaper som påverkar dess förekomst. Datorprogrammet och programspråket MATLAB användes för att editera rådatat från radar-mätningarna i området, samt för att sammanföra och digitalisera horisonter för möjlig massiv markis i radarfigurerna och för ett antal sammanställningar av olika filer. Data erhållet från MATLAB importerades till det geografiska informationssystemet ArcGIS där det kunde visualiseras i kartor och tolkas. Ett antal histogram skapades i kalkylprogrammet Microsoft Excel för att visa frekvensen av massiv markis vid olika höjder, sluttningsvinklar och olika väderstrecksriktningar. Resultaten visade att det var mer vanligt med massiv is höjder upp till 200 m, vid mynningarna av dalarna samt i Taylor Valley jämfört med Wright Valley. Det var en aning mer vanligt med massiv markis vid nordöst-östliga sluttningsriktningar, vilket antagligen beror på olika mängder inkommande solstrålning till de olika riktningarna. Avsaknaden av, eller inte så märkbara, skillnader för olika sluttningsvinklar och riktningar kan bero på att mängden data var för liten, att höjdkartan inte var tillräckligt detaljerad eller att isen inte har funnits tillräckligt länge för att bli påverkad av dessa parametrar. Anledningen till att det finns mer massiv markis i Taylor Valley än i Wright Valley kan vara att det skyddande sedimenttäcket är tunnare i Wright Valley än i Taylor Valley. Frekvensen av massiv markis vid olika sluttningsvinklar verkar bero på det totala antalet mätningar gjorda, fler mätningar leder till en högre frekvens av markis, medan dess ursprung samt det antagna tunnare sedimenttäcket på högre höjder kan vara anledningen till de olika frekvenserna av massiv markis vid olika höjder. Anledningen till varför det fortfarande finns massiv markis trots existensen av den isuppdämda sjön Washburn som tidigare fanns i Taylor Valley, och att isen således inte helt har smält bort på grund av sjön, kan vara att den fanns under en för kort tid så att de långsamma termodynamiska processerna som skulle orsaka smältningen inte hann agera tillräckligt länge för att smälta all is. Den massiva markisen är vanlig i en zon som tros vara väldigt mottaglig för framtida uppvärmning, vilket betyder att landskapsförändringar som redan har observerats i områden med mycket massiv markis kan fortsätta att ske samtidigt som andra områden med massiv markis kan börja förändras. Isen kan därför spela en stor roll i landskapsutvecklingen i McMurdos torrdalar beroende på hur mycket varmare det blir i området.
15
Tregoning, George Seibert. "Isolation and Characterization of Halophilic Heterotrophic Bacteria from Lake Vanda, McMurdo Dry Valleys, Antarctica." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/395.
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Lake Vanda is a meromictic, permanently ice-covered lake in the McMurdo Dry Valleys. The McMurdo Dry Valleys are a polar desert in Southern Victorialand Antarctica. This area experiences very little rainfall and very cold average temperatures, around –20°C. Lake Vanda has an unusual limnological profile, with a sharp physical and chemical gradient at about 60 m where the water transitions from cold, oxic, and fresh, to warm, hypersaline, and sulfidic; CaCl2 rather than NaCl is the dominant salt. Aerobic enrichment techniques were used to isolate what turned out to be several strains of a species of Chromohalobacter, a genus of the Gammaproteobacteria, from Lake Vanda deep waters, while targeted enrichments for anaerobic and spore-forming bacteria were negative. The isolates were characterized for their temperature and pH optima, carbon and nitrogen nutrition, and salt tolerance and requirements. The results showed the organisms to be obligately aerobic with a broad pH range (optima pH 7). The isolates used some sugars and organic acids but not alcohols or fatty acids for energy and cell carbon, and showed a moderate requirement for NaCl but no requirement for CaCl2, even though CaCl2 is the predominant salt in their environment.
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Tang, Chao. "Microbial diversity studies in sediments of perennially ice-covered lakes, McMurdo Dry Valleys, Antarctica." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957340921&SrchMode=2&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1269022997&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 20, 2010). Includes bibliographical references. Also issued in print.
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Diaz, Melisa A. "Spatial and Temporal Geochemical Characterization of Aeolian Material from the McMurdo Dry Valleys, Antarctica." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500468216147725.
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Sherwell, Shasten S. "Response of Microbial Communities to Climatic Disturbances in Lake Bonney, McMurdo Dry Valleys, Antarctica." Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami1595958688364877.
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Mikucki, Jill Ann. "Microbial Ecology of an Antarctic Subglacial Environment." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/mikucki/MikuckiJ1205.pdf.
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The research presented in this dissertation focused on the microbial ecology of the subglacial discharge from the Taylor Glacier in the McMurdo Dry Valleys, Antarctica. The major objectives of my research were to 1) define the biogeochemistry of the subglacial outflow 2) describe the microbial diversity of the subglacial outflow and 3) examine the impact of subglacial outflow on the geochemistry and biology of the west lobe of Lake Bonney, a lake that abuts the glacier. The subglacial outflow from the Taylor Glacier is known as Blood Falls owing to a visible accumulation of iron-oxides at the point where it flows from the snout of the glacier. The subglacial reservoir is thought to originate from the Pliocene Epoch (~5 Mya) when the dry valleys were fjordlands. The episodic release of subglacial water at Blood Falls provides a sample of what is believed to be ancient seawater trapped in the upper Taylor Valley and eventually covered by the Taylor Glacier as it advanced. Biogeochemical measurements, culture-based techniques, and molecular analysis (based on 16S rDNA sequences), were used to characterize microbes and chemistry associated with the subglacial outflow. Culture and molecular-based techniques, along with geochemical data, indicate the presence of a diverse chemoautotrophic and heterotrophic bacterial assemblage that utilizes iron and sulfur minerals for growth. 16S rDNA clone library phylotypes and cultured isolates were related to organisms that inhabit permanently cold environments. The biological and geochemical component of the ancient outflow changes as it travels from the subglacial environment to the moat of the west lobe of Lake Bonney and eventually into the saline deep water in the lake proper. The bottom water of the west lobe of Lake Bonney is geochemically similar to ancient subglacial outflow, but the microbial diversity in the two systems is distinct, and ancient subglacial brine does not appear to provide the microbial seed for the deep water of Lake Bonney. Collectively, my data indicate that the habitat beneath the Taylor Glacier harbors a functional microbial ecosystem that utilizes chemosynthetic and heterotrophicactivity to obtain carbon and energy in the absence of light.
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Fair, Alexandria C. "Elemental Cycling in a Flow-Through Lake in the McMurdo Dry Valleys, Antarctica: Lake Miers." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1413291502.
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Godfrey, Myfanwy Jane. "2D and 3D Geophysical Imaging of Polygonal Patterned Ground in the McMurdo Dry Valleys, Antarctica." Thesis, University of Canterbury. Geological Sciences, 2008. http://hdl.handle.net/10092/2255.
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The PPG found in the Dry Valleys is some of the oldest on the planet with ages of up to 8 million years assigned to them. The activity of some of these Antarctic PPG areas has come into question with the proposal that they may be the result of sublimation processes rather than actively re-working freeze and thaw processes. Near surface geophysical methods of ground penetrating radar (GPR), resistivity tomography and electromagnetism have been applied to four Antarctic Dry Valleys polygonal patterned ground (PPG) areas; two in Victoria Valley and two in Beacon Valley. The aim was to resolve subsurface structure and activity of the PPG without disturbing the delicate permafrost soils. Multiple techniques were used so that there could be greater reliability on the interpretations of this data without the need for damaging subsurface geological calibration of the geophysics by obtaining direct subsurface data through methods such as trenching or drilling. Subsurface structure of the PPG was resolved; active layer depth, deformation of permafrost in the vicinity of contraction cracks and zones of attenuation were identified. Significant deformation in the subsurface horizons of the permafrost and associated with thermal contraction crack wedge growth was identified over PPG suggested to be formed only by sublimation in Beacon Valley, thus calling into question this interpretation of the PPG activity. The most reliable identification of subsurface features occurred with correlation between GPR and resistivity tomography results.
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Antibus, Doug E. "Molecular and Cultivation-based Characterization of Ancient Algal Mats from the McMurdo Dry Valleys, Antarctica." Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1258702723.
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Williamson, Bruce R. "Sources and Deposition Processes Linking Atmospheric Chemistry and Firn Records from Four Glacier Accumulation Zones in the McMurdo Dry Valleys, Antarctica." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/WilliamsonBR2006.pdf.
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Mondino, Lindsay Jean. "Isolation and characterization of cold-active heterotrophic bacteria from lakes Bonney and Vida, McMurdo Dry Valleys, Antarctica /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1650504141&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (M.S.)--Southern Illinois University Carbondale, 2008."Department of Molecular Biology, Microbiology and Biochemisty." Includes bibliographical references (p. 48-51). Also available online.
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Faucher, Benoit. "Distribution, Source and Cycling of Organic Carbon and Nitrogen in the Icy Soils of University Valley (McMurdo Dry Valleys of Antarctica)." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35741.
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Between 2009 and 2013, 16 ice-bearing permafrost cores were collected from 10 polygons along the floor of University Valley (McMurdo Dry Valleys of Antarctica) and were subsequently analysed in order to assess the geochemical properties of the valley’s icy soils and ground ice. Elemental analysis showed that icy soils located in the seasonally non-cryotic zone (NCZ) of the valley contained (on average) twice as much organic carbon (1.19 mg/g) as the ice cemented permafrost soils sampled in its perennially cryotic zone (PCZ). It also showed that nitrogen accumulation in the icy soils was a result of atmospheric fallout and chemical weathering of mineral soils. Isotopic analysis showed that the organic matter contained in the valley’s icy soils are mostly derived from the deposition and burial of cryptoendolithic communities living in the adjacent sandstone valley walls. Dissolved organic carbon (DOC) concentration measures indicated that soils containing the highest amounts of DOC were enriched in 13CDOC relatively to soils with low DOC concentrations. This indicated that microbial activity in soils was the highest during past super interglacial periods. A soil habitability index calculation from Stoker et al. (2010) was used to establish that soils located in the NCZ were more habitable than soils sampled in the PCZ and also presumably more habitable than soils at many Mars landing sites.
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Geyer, Kevin M. "Environmental Controls Over the Distribution and Function of Antarctic Soil Microbial Communities." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64417.
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Microbial community composition plays a vital role in soil biogeochemical cycling. Information that explains the biogeography of microorganisms is consequently necessary for predicting the timing and magnitude of important ecosystem services mediated by soil biota, such as decomposition and nutrient cycling. Theory developed to explain patterns in plant and animal distributions such as the prevalent relationship between ecosystem productivity and diversity may be successfully extended to microbial systems and accelerate an emerging ecological understanding of the "unseen majority." These considerations suggest a need to define the important mechanisms which affect microbial biogeography as well as the sensitivity of community structure/function to changing climatic or environmental conditions. To this end, my dissertation covers three data chapters in which I have 1) examined patterns in bacterial biogeography using gradients of environmental severity and productivity to identify changes in community diversity (e.g. taxonomic richness) and structure (e.g. similarity); 2) detected potential bacterial ecotypes associated with distinct soil habitats such as those of high alkalinity or electrical conductivity and; 3) measured environmental controls over the function (e.g. primary production, exoenzyme activity) of soil organisms in an environment of severe environmental limitations. Sampling was performed in the polar desert of Antarctica's McMurdo Dry Valleys, a model ecosystem which hosts microbially-dominated soil foodwebs and displays heterogeneously distributed soil properties across the landscape. Results for Chapter 2 indicate differential effects of resource availability and geochemical severity on bacterial communities, with a significant productivity-diversity relationship that plateaus near the highest observed concentrations of the limiting resource organic carbon (0.30mg C/g soil). Geochemical severity (e.g. pH, electrical conductivity) primarily affected bacterial community similarity and successfully explained the divergent structure of a subset of samples. 16S rRNA amplicon pyrosequencing further revealed in Chapter 3 the identity of specific phyla that preferentially exist within certain habitats (i.e. Acidobacteria in alkaline soils, Nitrospira in mesic soils) suggesting the presence of niche specialists and spatial heterogeneity of taxa-specific functions (i.e. nitrite oxidation). Additionally, environmental parameters had different explanatory power towards predicting bacterial richness at varying taxonomic scales, from 57% of phylum-level richness with pH to 91% of order- and genus-level richness with moisture. Finally, Chapter 4 details a simultaneous sampling of soil communities and their associated ecosystem functions (primary productivity, enzymatic decomposition) and indicates that the overall organic substrate diversity may be greater in mesic soils where bacterial diversity is also highest, thus a potentially unforeseen driver of community dynamics. I also quantified annual rates of soil production which range between 0.7 - 18.1g C/m2/yr from the more arid to productive soils, respectively. In conclusion, the extension of biogeographical theory for macroorganisms has proven successful and both environmental severity and resource availability have obvious (although different) effects on the diversity and composition of soil microbial communities.Ph. D.
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Foo, Wilson L. "Comparative analysis of microbial community composition throughout three perennially ice-covered lake systems in the McMurdo Dry Valleys, Antarctica and its relationship with lake geochemistry." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957301371&SrchMode=2&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268759757&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 16, 2010). Includes bibliographical references. Also issued in print.
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Zamora, Felix. "Alluvial Fans in the McMurdo Dry Valleys: A Proxy for Melting Along Terrestrial Margins of the East Antarctic Ice Sheet." Thesis, North Dakota State University, 2013. https://hdl.handle.net/10365/26872.
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Surface melting along Antarctic ice sheet margins is the most poorly understood input in models of future sea level rise. Alluvial fans in the McMurdo Dry Valleys originate from meltwater produced from high-elevation glaciers and snowbanks along these margins but many show no evidence for recent melting. These fans could serve as a record of past melting along terrestrial ice sheet margins, which would help quantify inputs to sea-level rise.To describe how melting has taken place in the past, five representative fans were examined. Fans are composed of thin, planar-bedded gravelly sands deposited by sheetflooding. Geospatial analsysis suggests the distance of the meltwater source from the Ross Sea is the predominant control on fan activity, and that aggradation results when regional climatic gradients shift inland. Geomorphic observations suggest centuries to millennia pass between periods of aggradation. OSL dating indicates that fans are no older than Holocene in age.
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Altrichter, Adam E. "Landscape history and contemporary environmental drivers of microbial community structure and function." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31883.
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Recent work in microbial ecology has focused on elucidating controls over biogeographic patterns and connecting microbial community composition to ecosystem function. My objective was to investigate the relative influences of landscape legacies and contemporary environmental factors on the distribution of soil microbial communities and their contribution to ecosystem processes across a glacial till sequence in Taylor Valley, Antarctica. Within each till unit, I sampled from dry areas and areas with visible evidence of recent surface water movement generated by seasonal melting of ephemeral snow packs and hillslope ground ice. Using T-RFLP 16S rRNA gene profiles of microbial communities, I analyzed the contribution of till and environmental factors to community similarity, and assessed the functional potential of the microbial community using extracellular enzyme activity assays. Microbial communities were influenced by geochemical differences among both tills and local environments, but especially organized by variables associated with water availability as the first axis of an NMDS ordination was strongly related to shifts in soil moisture content. CCA revealed that tills explained only 3.4% of the variability in community similarity among sites, while geochemical variables explained 18.5%. Extracellular enzyme activity was correlated with relevant geochemical variables reflecting the influence of nutrient limitation on microbial activity. In addition, enzyme activity was related to changes in community similarity, particularly in wet environments with a partial Mantel correlation of 0.32. These results demonstrate how landscape history and environmental conditions can shape the functional potential of a microbial community mediated through shifts in microbial community composition.Master of Science
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Thompson, Andrew Robert. "Heterotrophic Protists as Useful Models for Studying Microbial Food Webs in a Model Soil Ecosystem and the Universality of Complex Unicellular Life." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8575.
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Heterotrophic protists, consisting largely of the Cercozoa, Amoebozoa, Ciliophora, Discoba and some Stramenopiles, are a poorly characterized component of life on Earth. They play an important ecological role in soil communities and provide key insights into the nature of one of life’s most enigmatic evolutionary transitions: the development of the complex unicell. Soil ecosystems are crucial to the functioning of global biogeochemical cycles (e.g. carbon and nitrogen) but are at risk of drastic change from anthropogenic climate change. Heterotrophic protists are the primary regulators of bacterial diversity in soils and as such play integral roles in biogeochemical cycling, nutrient mobilization, and trophic cascades in food webs under stress. Understanding the nature of these changes requires examining the rates, diversity, and resiliency of interactions that occur between soil organisms. However, soils are the most taxonomically diverse ecosystems on Earth and disentangling the complexities of dynamic and varied biotic interactions in them requires a unique model system. The McMurdo Dry Valleys of Antarctica, one of the harshest terrestrial environments on Earth, serve as a model soil ecosystem owing to their highly reduced biological diversity. Exploring the functioning of heterotrophic protists in these valleys provides a way to test the applicability of this model system to other soil food webs. However, very little is known about their taxonomic diversity, which is a strong predictor of function. Therefore, I reviewed the Antarctic literature to compile a checklist of all known terrestrial heterotrophic protists in Antarctica. I found significant geographical, methodological, and taxonomic biases and outlined how to address these in future research programs. I also conducted a molecular survey of whole soil communities using 18 shotgun metagenomes representing major landscape features of the McMurdo Dry Valleys. The results revealed the dominance of Cercozoa and point to an Antarctic heterotrophic protist soil community that is taxonomically diverse and reflects the structure and composition of communities at lower latitudes. To investigate whether biotic interactions or abiotic factors were a larger driver for Antarctic heterotrophic protists, I conducted variation partitioning using environmental data (e.g. moisture, pH and electrical conductivity). Biotic variables were more significant and accounted for more of the variation than environmental variables. Taken together, it is clear that heterotrophic protists play key ecological roles in this ecosystem. Deeper insights into the ecology of these organisms in the McMurdo Dry Valleys also have implications for the search for complex unicellular life in our universe. I discuss the theoretical underpinnings of searching for these forms of life outside of Earth, conclude that they are likely to occur, and postulate how future missions could practically search for complex unicells.
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Cariani, Zev. "Impact of simulated polar night on Antarctic mixotrophic and strict photoautotrophic phytoplankton." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1547204599969081.
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Leslie, Deborah L. "The Application of Stable Isotopes, δ11B, δ18O, and δD, in Geochemical and Hydrological Investigations." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386000037.
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Teufel, Amber Grace. "Influence of abiotic drivers (light and nutrients) on photobiology and diversity of Antarctic lake phytoplankton communities." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1468411564.
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Witherow, Rebecca A. "Minor Alkaline Earth Element and Alkali Metal Behavior in Closed-Basin Lakes." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250628213.
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Roberts, Emily. "Protozoan participation in planktonic carbon cycling in the McMurdo Dry Valley lakes, Antarctica." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310978.
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Adhikari, Bishwo. "Genomic Analysis of Nematode-Environment Interaction." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2578.
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The natural environments of organisms present a multitude of biotic and abiotic challenges that require both short-term ecological and long-term evolutionary responses. Though most environmental response studies have focused on effects at the ecosystem, community and organismal levels, the ultimate controls of these responses are located in the genome of the organism. Soil nematodes are highly responsive to, and display a wide variety of responses to changing environmental conditions, making them ideal models for the study of organismal interactions with their environment. In an attempt to examine responses to environmental stress (desiccation and freezing), genomic level analyses of gene expression during anhydrobiosis of the Antarctic nematode Plectus murrayi was undertaken. An EST library representative of the desiccation induced transcripts was established and the transcripts differentially expressed during desiccation stress were identified. The expressed genome of P. murrayi showed that desiccation survival in nematodes involves differential expression of a suite of genes from diverse functional areas, and constitutive expression of a number of stress related genes. My study also revealed that exposure to slow desiccation and freezing plays an important role in the transcription of stress related genes, improves desiccation and freezing survival of nematodes. Deterioration of traits essential for biological control has been recognized in diverse biological control agents including insect pathogenic nematodes. I studied the genetic mechanisms behind such deterioration using expression profiling. My results showed that trait deterioration of insect pathogenic nematode induces substantial overall changes in the nematode transcriptome and exhibits a general pattern of metabolic shift causing massive changes in metabolic and other processes. Finally, through field observations and molecular laboratory experiments the validity of the growth rate hypothesis in natural populations of Antarctic nematodes was tested. My results indicated that elemental stoichiometry influences evolutionary adaptations in gene expression and genome evolution. My study, in addition to providing immediate insight into the mechanisms by which multicellular animals respond to their environment, is transformative in its potential to inform other fundamental ecological and evolutionary questions, such as the evolution of life-history patterns and the relationship between community structure and ecological function in ecosystems.
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Hage, Melissa Margaret. "Biomarker and stable isotope characterization of coastal pond organic matter, McMurdo Dry Valleys, Antarctica." 2006. http://etd.utk.edu/2006/HageMelissa.pdf.
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Raga, González Raül. "Landsat 8 satellite data-based estimation of soil moisture in McMurdo Dry Valleys, Antarctica." Master's thesis, 2021. http://hdl.handle.net/10362/113892.
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Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Geospatial TechnologiesSoil moisture is the total amount of water present in the upper 10 cm of soil and it represents the water in land surface which resides in the pores of the soil which is not in river, lakes or groundwater and which depends of the weather conditions, soil type and associated vegetation, among others. Soil moisture assessments are important to understand the hydrological cycles and biophysical processes caused by global climate changes (Finn et al., 2011). Usually, soil moisture has been mapped with airborne microwave radiometers (Klemas et al., 2014) to measure the water retained in the spaces between soil particles. Its importance is due to the microorganism metabolic activity, regulation of the soil temperature and carriage of nutrients, among others. Soil moisture typically takes the form of small ice crystals, vapour, or small parts of liquid water in cold desert soils (Campbell & Claridge, 1982). Antarctic soils are composed by basically no organic and very low moisture content (Campbell and Claridge, 1987). Antarctica is a sensitive area to balance the global climate and its changes and its soil ecosystems are strongly regulated by variables of the abiotic environment and due to this, a research measures the incidence and spatial occurrence of the layer freezing to know how regional climate change could affect the energy exchange of this layer and its invertebrate communities (Wlostowski et al., 2017). Also, knowing how the dynamic of the surface varies in polar regions is transcendent to predict the impact of climate change in global sea-level rise in the future (Quincey & Luckman, 2009).
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Lamp, Jennifer Lynn. "Rock weathering, erosion, and sublimation rates of ancient buried ice in the McMurdo Dry Valleys, Antarctica." Thesis, 2016. https://hdl.handle.net/2144/17058.
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The inland region of the McMurdo Dry Valleys (MDV) of Antarctica represents a subzero, hyper-arid endmember for physical weathering, and is Earth’s closest terrestrial analog to the Martian surface. In order to document the style and rate of rock breakdown in this region, I conducted field-based, experimental, and numerical modeling studies of supraglacial debris (Mullins till) on Mullins Glacier. These investigations were designed to (1) quantify the rate and processes of physical breakdown of surface rocks on Mullins till, particularly of Ferrar Dolerite, (2) determine the efficacy of thermal stress weathering as an agent in rock erosion, and (3) examine the role of physical weathering in altering the sublimation of buried glacial ice.
Results from morphometric field surveys characterizing changes in rock shape, strength, and small-scale surface features, coupled with an iterative cosmogenic nuclide-based age model for Mullins Glacier, show that total erosion rates for clasts of Ferrar Dolerite on Mullins till range from 1.1 to 15 cm Myr-1. In situ field measurements of rock surface temperatures and local ambient conditions recorded at 15-second intervals, combined with a numerical finite element model elucidating changes in internal rock temperatures and associated strain, show that thermal stress weathering is sufficient to induce spalling by propagating existing microcracks of ≥1.1 cm that typically occur at the base of thin, mm-scale alteration rinds. The implication is that thermal stress weathering, previously undocumented in this region, may account for >80% of the total estimated erosion of Ferrar Dolerite. Furthermore, the spalled fragments (up to 5% of Mullins till) provide a negative feedback that slows the rate of subsurface ice sublimation and internal vapor diffusion. Experimental analyses in a controlled environmental chamber set with Mullins till and driven by local meteorological conditions measured in the field yields an average effective diffusivity of 4.5 x 10-6 m2 s-1 for Mullins till and annual rates of buried ice loss of <0.068 mm (assuming Fickian diffusion); these values are consistent with theoretical estimates, demonstrate the importance of physical weathering in modifying supraglacial deposits, and support arguments for persistent cold-desert conditions in the MDV for the last several million years.
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Howard, Meg Elizabeth. "Geochemical characterization of coastal pond and adjacent soil organic matter in two distinct field areas of the McMurdo Dry Valleys, Antarctica." 2006. http://etd.utk.edu/2006/HowardMeg.pdf.
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