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Item Geochemical characterization of shallow sediments from the grounding zone of the Whillans Ice Stream(Montana State University - Bozeman, College of Agriculture, 2019) Roush, Kimberly Anne; Chairperson, Graduate Committee: John C. Priscu and John Dore (co-chair); John Priscu, Mark Skidmore, Alex Michaud and the WISSARD Science Team were co-authors of the article, 'Signatures of subglacial water in shallow sediments of the Whillans grounding zone and overlying water column' which is contained within this thesis.; John Priscu, John Dore, Wei Li, Tristy Vick-Majors and the WISSARD Science Team were co-authors of the article, 'Sediment porewater organic matter content' which is contained within this thesis.The research presented in this thesis focused on subglacial flow beneath the West Antarctic Ice Sheet (WAIS) and its potential influence near the grounding zone. Antarctic grounding zones are of specific scientific interest because they can impact the stability of the continental ice sheet and its breakup, potentially resulting in significant sea level rise. My major objective was to determine whether there was influence of subglacial water at the Whillans Grounding Zone (WGZ) on the Siple Coast of the WAIS. A gravity corer was used to collect a 70 cm sediment core through 780 m of ice borehole drilled using a hot water clean access drilling system. The core was collected in a marine embayment adjacent to the WGZ beneath a 10 m water column. I used a combination of geochemical, isotopic and organic matter analyses to characterize the benthic sediments, porewater and water column. The geochemical and isotopic data showed the influence of subglacial freshwater on sediment porewater at specific depths in the 70 cm core. Vertical gradients of chloride and sulfate between surficial sediment and the overlying water column indicated ion diffusion from porewater to the column water. Dissolved organic matter concentration of sediment porewater and the overlying water column also indicated upward diffusion occurs from porewater to the overlying seawater. Sediment particulate carbon and nitrogen data showed that benthic sediments were more depleted in nitrogen than the overlying seawater. Sediment particulate carbon and nitrogen data showed that benthic sediments were more depleted in nitrogen than the overlying seawater. Geochemical, isotopic and organic matter data supports the influence of subglacial freshwater at the WGZ.Item Ecosystem engineering at the streambed: how net-spinning caddisflies influence substrate flow dynamics(Montana State University - Bozeman, College of Letters & Science, 2020) MacDonald, Michael Joseph; Chairperson, Graduate Committee: Lindsey Albertson; Lindsey K. Albertson and Geoffrey C. Poole were co-authors of the article, 'Ecosystem engineering at the streambed: how net-spinning caddisflies influence substrate flow dynamics' submitted to the journal 'Ecohydrology' which is contained within this thesis.The streambed is an ecotone between surface waters and underlying hyporheic systems. Identifying the controls on advective flow through this ecotone is critical to understanding the movement of energy and matter in streams. Hydropsychids (net-spinning caddisflies) are aquatic macroinvertebrate ecosystem engineers that influence streambed cohesion, yet evidence of direct influence on hydrologic processes is lacking. Utilizing a novel downward flow permeameter, we demonstrate how net-spinning caddisfly colonization of the streambed interstitia at moderate but common densities (2,000 m^-2) can reduce the vertical hydraulic conductivity (KV) by up to 55% in coarse sand and gravels (median diameter = 12.91 mm). Sediment columns incubated in artificial stream water occupied by caddisflies showed greater reductions in KV relative to those without caddisflies. Additionally, organic matter content within sediment columns showed that occupation by caddisflies resulted in nearly two-fold increases in organic matter AFDM. Our research shows that the ubiquitous and numerous net-spinning caddisflies are likely to modulate the exchange of channel and hyporheic water by constructing nets in open pore spaces, increasing flow resistance, and decreasing flow velocities, as well as stimulating organic matter deposition with potential consequences for biofilm growth. These results suggest that caddisfly induced reductions to flow may influence transfer processes occurring at the streambed ecotone, altering biogeochemical processes in streams.Item Sedimentary tectonics of the Mesoproterozoic Lahood Formation, southwest Montana(Montana State University - Bozeman, College of Letters & Science, 2017) Fox, Nicholas Reid; Chairperson, Graduate Committee: David W. MogkThe LaHood Formation plays a critical role in constraining the sources and tectonic setting during the initial stages of formation of the Mesoproterozoic Belt Basin, particularly in the Helena Embayment. In the Bridger Range the LaHood Formation is composed of coarse conglomerates, lithic arkoses, calcareous shales and siliceous shales. Twelve measured stratigraphic sections show a general fining to the northeast with calcareous shales exposed only in the northern half of the Range. Lithology provides the basis for the LaHood Formation to be divided into three Members: A) conglomerate; B) lithic arkose and sandy micaceous shale; C) interbedded Member B with calcareous and siliceous shales that are interpreted as correlative rocks of the upper Newland Formation. U-Pb ages of detrital zircons (LA-ICP-MS) from four sandstones show: 1) The basal conglomerate and coarse arkosic facies in the lower and southern two sections have a primary age distribution at ~3.2 Ga with a minor ~3.5 Ga component that corresponds to the major TTG crust-forming event in the northern Wyoming Province; 2) zircons from an arkosic sandstone inter-fingered with calcareous shales have a dominant ~3.2 Ga signal, but includes a significant secondary concentration at 2.8 Ga, which corresponds to the age of the Beartooth-Bighorn Magmatic Zone; 3) the northernmost section exhibits a concentration near 3.2 Ga, a more significant ~2.8 Ga signal, and the first occurrence of ~1.8 Ga grains, indicative of the Great Falls Tectonic Zone. These detrital zircon ages confirm the results of Guerrero et al. (2015) in the Bridger Range and from LaHood exposures in the Horseshoe Hills to the west, but differ significantly from the dominant 3.4-3.5 Ga signal from LaHood exposures in Jefferson Canyon and north of Cardwell, MT (Ross and Villeneuve, 2003; Mueller et al., 2016). Collectively, the detrital zircon ages demonstrate a) occurrences of the LaHood Formation across the Belt Basin received sediment from temporally distinct sources that do not necessarily include proximal Archean basement, and b) the stratigraphic succession reflects contributions from progressively younger source areas. The significant variety of ages and abrupt facies changes in the LaHood Formation support a series of compartmentalized sub basins.Item Thermal insulation versus capacitance: a comparison of shading and hyporheic exchange on daily and annual stream temperature patterns(Montana State University - Bozeman, College of Agriculture, 2017) Fogg, Sarah Kathleen; Chairperson, Graduate Committee: Geoffrey Poole; Geoffrey C. Poole, AnnMarie Reinhold and Scott J. O'Daniel were co-authors of the article, 'Thermal insulation versus capacitance: a comparison of shade and hyporheic exchange on daily and annual stream temperature cycles' submitted to the journal 'Water resources research' which is contained within this thesis.Channel shading and hyporheic exchange both effect daily and annual stream temperature cycles. In streams with thermal regimes that are too warm to support native biota, increasing shading or hyporheic exchange have largely been thought of as interchangeable management strategies because they influence summertime stream channel temperatures in similar ways. But, shading and hyporheic exchange operate via different mechanisms and influence stream temperature differently at differently times of the year. To understand daily and seasonal differences of shading and hyporheic exchange on stream channel temperature we used a process-based heat-budget model of channel temperature. Our model incorporates stream channel-atmospheric energy exchanges and a novel channel-subsurface heat exchange model that more appropriately represents the effects of hyporheic residence time distributions. We used our model to conduct an in silico experiment where we vary shading and hyporheic exchange on the same stream reach. In summer, the cooling and damping of channel temperatures associated with an expansive, coarse-grained hyporheic zone were similar to shading effects. However, the differences between shading and hyporheic exchange effects were most pronounced in the winter when channel warming associated with hyporheic exchange was substantially greater than warming associated with shade. By interpreting the changes in heat fluxes between shading a stream and adding hyporheic exchange, we find that shading acts as a thermal insulator and hyporheic exchange acts as a thermal capacitor. Our results show that shading and hyporheic exchange can have similar and differently effects on stream channel temperatures depending on what part of the year the effects are investigated, which has important management and modeling implications. Geography and geomorphic context of a stream are important considerations when choosing shading or hyporheic exchange for thermal restoration. In bedrock-confined streams that historically had closed canopies, shading has the greatest potential to reduce summer temperatures while restoration of hyporheic restoration is impractical in these systems. In contrast, in large, coarse-grained alluvial stream reaches, where riparian vegetation is historically sparse, restoring hyporheic influences has the greatest potential for reducing summer temperatures while increasing streamside shading is likely unattainable.Item Sedimentology, provenance, and paleotectonic significance of the cretaceous Newark Canyon Formation, Cortez Mountains, Nevada(Montana State University - Bozeman, College of Letters & Science, 1988) Suydam, James DavidItem Effects of fine sediment accumulation on egg-to-fry survival of cutthroat trout inhabiting a highly sedimented headwater stream(Montana State University - Bozeman, College of Letters & Science, 1998) Bowersox, Andrew LeeItem Time of grazing effects on stream channel stability instream sediment loads(Montana State University - Bozeman, College of Agriculture, 1985) Pogacnik, Thomas MartinItem The effects of snow compaction on water release & sediment yield(Montana State University - Bozeman, College of Letters & Science, 1982) Grady, Thomas R.Item Influences of chemical speciation and solid phase partitioning on microbial toxicity : single organism to in situ community response(Montana State University - Bozeman, College of Engineering, 2010) Moberly, James Gill; Chairperson, Graduate Committee: Brent M. PeytonThe waters and sediments of Lake Coeur d'Alene (LCDA) in northern Idaho have been contaminated by heavy metals because of decades of mining operations. Metal speciation is critical in assessing toxicity because it may vary considerably with pH and is dependent on other aqueous constituents. There has been little research on integrated investigations of the effects of heavy metal speciation on indigenous microbes from LCDA, especially large scale community analysis. The focus of this research in the LCDA system was to determine the effect of heavy metal speciation on toxicity, first in a defined single organism system, followed by in situ studies. Combined results of thermodynamic modeling, statistical analysis, and batch culture studies using Arthrobacter sp. JM018 suggest that the toxic species is not solely limited to the free ion, but also includes ZnHPO 4 0(aq). Cellular uptake of ZnHPO 4 0(aq) through the inorganic phosphate transporter (pit family), which requires a neutral metal phosphate complex for phosphate transport, may explain the observed toxicity. These findings show the important role of "minor" Zn species in organism toxicity and have wider implications since the pit inorganic phosphate transport system is widely distributed in bacteria, archaea, and eukaryotes. Using a multivariate statistical approach, correlations between the microbial community (via 16S rDNA microarray) in sediment cores and operationally defined heavy metal phases (via continuous sequential extractions) were explored. Candidate phyla NC10, OP8 and LD1PA were only present in metal contaminated cores and diversity doubled among Natronoanaerobium in metal contaminated cores which may suggest some increased fitness of these phyla in contaminated sediments. Correlations show decreases in diversity from presumed sulfate reducing lineages within most taxa from Desulfovibrionales and Bdellovibrionales and from metal reducing bacterial lineages Shewanellaceae, Geobacteraceae, and Rhodocyclaceae with increases in the ratio of more bioavailable Pb exchangeable/carbonate to less bioavailable Pb oxyhydroxide. This is the first time these techniques have been used in combination to describe a contaminated system.