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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1980. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 111-115. / by Frances Luellen Stephenson Hotchkiss. / M.S.

Historical climate disturbances such as glacial cycling and fluctuating stream, lake, and sea levels strongly influence the distribution and evolutionary trajectories of Antarctic terrestrial species. Antarctic invertebrates, with limited long-range mobility, including the ubiquitous sentinel nematode species Scottnema lindsayae, are especially sensitive to climate disturbances. We tested hypotheses associated with the historical geographic and population genetic structure of this species as it occurs across the McMurdo Dry Valleys (MDVs) of Antarctica. In order to reconstruct the influence of climate disturbance and ecological conditions on this species, partial mitochondrial COI gene sequences were sequenced and analyzed from individual S. lindsayae collected from sites across the MDVs reflecting a opposing gradients of climate disturbance during the Last Glacial Maximum (LGM). We found that populations were strongly geomorphic barriers with distinct haplotypes associated with valleys except among valleys that experienced glacial advance and retreat during the LGM. One monophyletic clade corresponds with valley systems that were undisturbed during the LGM indicating putative refugia areas. A second monophyletic clade corresponds to recent dispersal and expansion of evolutionarily younger populations into valleys that were strongly reworked by glacial activity during the LGM. Our work shows that contemporary populations of these animals are strongly structured by prior climate history. Such findings can be useful for interpreting long-term monitoring of demographic shifts of soil organisms in response to changing climate trends in the McMurdo Dry Valleys.

<p> The Paleozoic bedrock surface of southern Ontario is dissected by an interconnected system of buried bedrock valleys that are infilled with thick successions of glacial, interglacial and fluvial sediments. These valleys can be several kilometers wide, reach depths of up to 250m and the coarse-grained units are known to host significant local and regional groundwater aquifers.</p> <p> Two buried bedrock valleys located near the Niagara Escarpment in the Region of Halton were under investigation in the fall of 1999 for their potential to host additional municipal groundwater aquifers to supply drinking water to the towns of Milton and Georgetown. Detailed logging of sediment recovered from eleven continuously-cored boreholes, drilled within the Georgetown and Milton bedrock valleys, forms the basis for this study. Four distinct facies types were identified within the borehole cores including sand, gravel, fine-grained sediment and diamict (sand-rich, mud-rich and clast-rich). These four facies types were used to subdivide the cores into six stratigraphic units based on textural characteristics and stratigraphic position. These six units form a stacked succession of aquifers and aquitards within the valley infill with two stratigraphic units being identified as potential municipal aquifers.</p> <p> The Georgetown buried bedrock valley contains narrow bedrock channel interpreted to have been fluvially incised, lying within a broader flat-bottom valley likely formed by glacial scouring of the bedrock. It is feasible that regional bedrock jointing created a zone of weakness that was later exploited by a drainage network. The valley infill sediments record the approach of the Laurentide Ice Sheet into southern Ontario during the Early to Mid-Wisconsin, and the subsequent overriding of the area during the Late Wisconsin period.</p> / Thesis / Master of Science (MSc)

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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

The Seven Valleys is an interactive 3D installation based artwork inspired by mystical writings of the Bahá'í Faith. Created as a modification of the firstperson shooter Unreal Tournament 2003 (Epic, 2003) it subverts the original paradigm of the game to create an experience of the numinous, which in spirit, is diametrically opposed to the original intent of the gameplay design. This artwork presents an exploration of, and allusion to, the often subtle and illusive concepts found in the sacred treatise The Seven Valleys (Bahá'u'lláh, 1991) in which the user engages in an experiential journey through the work. The user is faced with conditions and situations that provide motivation to question, explore and attempt to fathom the abstract sense of the numinous. Each of The Seven Valleys contains its own individual mysteries while at the same time contributing its part to the telling of a collective story. / Master of Arts