Scholarworks
ScholarWorks is an open access repository for the capture of the intellectual work of Montana State University (MSU) in support of its teaching, research and service missions. MSU ScholarWorks is a central point of discovery for accessing, collecting, sharing, preserving, and distributing knowledge to the Montana State University community and the world.
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The effect of net-spinning caddisflies on nitrate uptake in stream mesocosms
(Montana State University - Bozeman, College of Agriculture, 2023) Mohr, Elizabeth Jane; Chairperson, Graduate Committee: Tim Covino
Streambeds are thought to play an important role in reducing downstream nitrate export since they provide habitat for microorganisms that use nitrate to build biomass and generate energy. Hydropsychid (net-spinning caddisfly) larvae inhabit the streambed, where they construct silk net and retreat structures. Previous work suggests that the ecosystem engineering activity of net-spinning caddisfly larvae can support higher levels of streambed sediment biomass and create habitat for denitrifying microorganisms, yet it remains unclear whether these effects lead to changes in whole-stream nitrate uptake. We hypothesized that net-spinning caddisflies increase the capacity of the streambed microbial community to take up nitrate. To test this hypothesis, we constructed 15 stream mesocosms and added caddisflies to each according to one of five density treatments ranging from 0 to 2,500 larvae m -2. We measured whole- mesocosm nitrate uptake and characterized hydrologic exchange three weeks after releasing the caddisflies by adding potassium nitrate and sodium chloride to each mesocosm and measuring nitrate + nitrite concentrations over the next 10 hours. To characterize rates of nitrate uptake in the mesocosm streambed, a proxy for the capacity of the streambed microbial community, we used a model that accounts for hydrologic differences among the mesocosms using specific conductance measurements. We found some evidence that higher net-spinning caddisfly densities resulted in higher rates of whole-mesocosm nitrate uptake, or greater nitrate removal. However, we found little evidence that net spinning caddisflies had a substantial effect on nitrate uptake rates in the streambed. We outline several limitations of our study and provide recommendations for improving the experimental set-up and modeling approach in future work. Overall, this research demonstrates some potential for net-spinning caddisflies to serve as ecosystem engineers by altering nitrate removal in streams, though research is needed to lend additional evidence to our findings and to better understand the mechanism by which caddisflies impact nitrate uptake.
Reconstructing physical and hydrologic processes beneath the Mercer Ice Stream, Antarctica using subglacial sediments
(Montana State University - Bozeman, College of Letters & Science, 2023) Campbell, Timothy David; Chairperson, Graduate Committee: Mark L. Skidmore; This is a manuscript style paper that includes co-authored chapters.
The West Antarctic Ice Sheet's (WAIS) response to warming ocean and atmospheric temperatures is of scientific interest because of its potential contributions to global sea level rise. Beneath the ice sheet is a dynamic hydrologic network of channels, lakes, and groundwater reservoirs that in part lubricate the base, supporting fast ice flow, and have a profound effect on ice sheet dynamics. Expanding our records of the temporal and spatial variability of subglacial hydrology and basal conditions will improve our understanding to the future behavior of the ice sheet. I employed a suite of sedimentological, geochemical, and image processing analyses to reconstruct past basal conditions and meltwater activity at Mercer Subglacial Lake (SLM), West Antarctica. A composite 2.06 m sediment record comprised massive-to-stratified diamicts, massive muds, and laminated muds with drop stones. I interpret the lithostratigraphic variability to reflect the emplacement of glacial tills interbedded with meltwater drainage deposits and capped by rhythmically laminated subglacial lake sediments. The meltwater sediments were deposited by suspension settling in a slowly flowing or ponded setting. The rhymically laminated lake sediments were produced by changes in the sedimentation rate and sorting of suspended sediment transported into the lake and fallout of material from melting basal ice. Borehole camera imagery revealed a ~5 m thick accreted basal ice sequence directly above the ice-lake water interface. Image analysis of the borehole wall imagery demonstrated that the basal ice layer was composed of two main ice sequences and were differentiated by sediment debris content. The lower sequence contained up to 25 times more sediment than the upper unit. The observed stratigraphic variability in basal ice sequence represents contrasting periods of meltwater availability that range from meltwater abundant to restrictive. Meltwater availability also determines the style and volume of sediment incorporation into basal ice, forming two ice types. Collectively, the two geologic records presented here provide a complex archive of subglacial hydrologic conditions and thermal histories that are linked to past ice stream variability within the late Holocene.
Investigating the role of the central metabolism in the gut-brain axis of familial dysautonomia
(Montana State University - Bozeman, College of Letters & Science, 2023) Costello, Stephanann Marin; Chairperson, Graduate Committee: Valerie Copie; This is a manuscript style paper that includes co-authored chapters.
Familial dysautonomia (FD) is a rare, highly debilitating, developmental, and progressive neurodegenerative disease, with recessive heritability, and primary penetrance among Eastern European Jewish populations. The disease affects both the central and peripheral nervous systems, with primary deficits in the autonomic and sensory divisions. Patients thus present with numerous complex neurological phenotypes, and those of primary interest include severe gastrointestinal dyscoordination, cardiovascular instability, baroreceptor imbalances that promote autonomic "crises" marked by uncontrollable retching, and progressive visual decline leading to blindness. There is no cure for FD, and patients are still subject to a poor quality of life despite current advances in understanding the cellular mechanisms mediating the disease. The nervous system, gut-microbial ecosystem, and central metabolism are individually complex, but ever more intricate due to the crosstalk between these systems. Thus, dysregulation or damage in one system could facilitate disruption in another, thus creating a negative feedback loop between the gut-brain-metabolism axis and ultimately perpetuating neurodegeneration, gut dysbiosis, and a dysfunctional metabolism. Understanding how each individual system is affected by the FD founder mutation could lead to methods for restoring healthy function to one of the branches of the gut-brain-metabolism axis, thus arresting the negative feedback loop and disease perpetuation. In this work, nuclear magnetic resonance-based metabolomics was employed along with targeted mass spectrometry techniques to characterize the metabolic changes of FD patients, and subsequently to interrogate the retinal metabolome of a retina specific FD mouse model (Pax6). Insights into the critical changes in FD patients' fecal metabolites were found and associated with neuronal networks and the gut-microbiome. Further avenues exploring these results and the role of metabolic dysfunction in FD led to the interrogation of the retinal metabolome of the Pax6 mouse model, and identification of altered metabolites associated with energy circuits of the eye, mitochondrial function, and retinal ganglion cell health. These data demonstrate metabolic dysfunction in FD patients, and the Pax6 model, with disruptions being analogous to clinical phenotypes, gut-dysbiosis, and the cellular degeneration of FD patients, thus providing foundational information for the generation of novel therapeutic options targeting the cellular metabolic pathways of the gut-brain-metabolism axis.
Developing a monitoring program for dusky grouse in Montana
(Montana State University - Bozeman, College of Agriculture, 2023) Leipold, Elizabeth Ashley; Chairperson, Graduate Committee: Lance McNew; This is a manuscript style paper that includes co-authored chapters.
Rigorous monitoring programs for Dusky Grouse (Dendragapus obscurus), a game species, are lacking. Difficult-to-reach habitat and low probability of detection makes monitoring Dusky Grouse difficult. Our objectives were to 1) evaluate Dusky Grouse habitat associations and generate a state-wide map predicting Dusky Grouse habitat, 2) evaluate sampling methods and survey conditions for maximizing Dusky Grouse detection, and 3) evaluate protocols (i.e., number of sites and visits) and analytical methods for producing annual unbiased and precise indices of abundance. We created our habitat model using resource selection functions, random forest, and an ensemble approach. We compared spring v. summer sampling, use of electronic playback to increase detection, effect of route type (off-trail, trail, road) on point counts, and the effect of weather, background noise, day, and time on probability of detection. We evaluated and compared four analytical methods using simulations: time-to-detection model with hierarchical distance sampling, N-mixture model, raw count (naive) and hierarchical distance sampling model. Multiple habitat characteristics affected relative probability of Dusky Grouse use including tree height and conifer forest vegetation types. Both habitat modeling methods were highly predictive and therefore we used an ensemble (frequency histogram) approach to create a state-wide map of Dusky Grouse habitat that was used to identify appropriate sampling sites for population monitoring. Spring point-count surveys conducted with electronic playback were most effective. Surveys located along roads/trails best balanced the trade-offs between sampling effort and survey design requirements, despite limiting inferences to Dusky Grouse populations located in prime habitat along roads/trails. Detection of Dusky Grouse was highest on clear days, with little wind and background noise, with surveys occurring 9-162 minutes post-sunrise during 3-23 May. Simulation results indicated that N-mixture models where 80 sites visited four times resulted in unbiased estimates of population size with the highest precision. Transect-based distance sampling survey protocols during the spring also produced unbiased and acceptably precise (< or = 15% CV) estimates of grouse density when > or = 35 transects of > or = 2.6-km length were surveyed per area of inference (e.g., administrative region). Our results provide baseline information necessary for the development of a state-wide monitoring program for Montana.
Exploring extrusion technology in developing value-added products from Montana lentils
(Montana State University - Bozeman, The Graduate School, 2023) Allan, Edwin Yenbono; Chairperson, Graduate Committee: Wan-Yuan Kuo; This is a manuscript style paper that includes co-authored chapters.
This study seeks to demonstrate that lentil flour and its fractionates are viable ingredients for use in the development of lentil puffs, lentil couscous and lentil texturized vegetable protein with a twin-screw pilot-scale extruder (Buhler-30 mm). Regarding the development of lentil puffs, an experimental design with three formulation factors of lentil flour (x1), lentil starch concentrate (x2) and lentil protein concentrate (x3) was created. The overall acceptance and texture liking score of lentil puff formulations was found to be dependent on all three formulation factors. An optimum lentil puff formulation was therefore predicted at a 50% ratio of lentil starch concentrate to 25% ratios of both lentil flour and lentil protein concentrate to be produced at an extrusion feed .rate of 20 kg/h, a moisture rate of 10% and a screw speed of 350 rpm. For the development of lentil couscous, an experimental design with factors of the ratio of lentil protein concentrate to lentil flour (x1) and the extruder screw speed (x2) was created. Increasing the ratio of lentil protein concentrate to lentil flour decreased the water absorption index, cohesiveness, chewiness, and resilience texture of lentil couscous formulations. Higher sensory acceptance, appearance, flavor and texture scores for lentil couscous samples were observed for formulations with lentil protein concentrate levels at 20% and a screw speed of 250 rpm. Clustering sensory results revealed that participants who issued higher sensory score were willing to buy the presented lentil couscous at $3.37 for 10 oz of lentil couscous with lentil protein concentrate levels at 20% and produced at a screw speed of 250 rpm. The development of a lentil TVP with lentil protein concentrate revealed that the techno functional properties of lentil TVPs were dependent on the total protein content, extrusion conditions and pH. Adding pea protein isolate to lentil protein concentrate in formulations increased the protein content to levels ideal for texturization. Increasing the extrusion dry feed rate and screw speed also increased the degree of texturization of ingredient mixes. Despite exploring the addition of gums, salts, transglutaminase as well as cross-linking agents, a change in pH, with additives of citric acid and calcium hydroxide, was the only strategy observed to influence the techno functional properties of lentil TVP samples. In comparison to the reference soy TVP produced from soy protein concentrate, lentil TVP samples produced from trials with higher contents of pea protein isolate (> or = 30%, w/w, d.b. in the dry feed) presented higher instrumental springiness, cohesiveness, and chewiness texture.