Environmental & Conservation Sciences Doctoral Work

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Three-dimensional Structures of Flows in a River Bend: Open Surface and Ice-covered Condition
(North Dakota State University, 2024) Koyuncu, Berkay
The existence of river ice has a significant role in flow characteristics during the winter and spring seasons. From the onset of freeze-up until the ice cover melts, river ice alters the flow structures, resulting in severe consequences such as ice jams, ice dams, and flash floods in spring. Nonetheless, the hydraulic and hydrologic mechanisms of river ice remain largely unknown due to difficulties of the field scale studies in severe winter seasons. In this work, the impacts of the ice cover on the vertical and cross-sectional velocity profile, secondary flow patterns, and shear velocity are investigated using analytical methods and fieldwork observations as well as the state-of-the-art computational fluid dynamics (large-eddy simulation) model. Results show the presence of river ice alters the secondary flow patterns and may induce double circulation in the thalweg area of natural cross-sections or near vertical channel walls of artificial channels/flumes. Results also indicate that the lateral distribution of the shear velocity is differentiated from the open surface condition as the high shear velocity can be observed near the inner and outer banks in ice-covered conditions. In this work, a numerical method is also developed to estimate the depth-averaged velocity profile based on the cross-section geometry. Model results demonstrate that the numerical method can accurately capture the velocity profile in irregular cross-sections based on fieldwork observations. This method helps to minimize the fieldwork efforts during the winter seasons. The future work will focus on the combined impact of the ice cover and the channel curvature (river bend) on the three-dimensional flow structures under different scenarios including the transitional stage. This work provides insights into the transient dynamics of flows during the freeze-up and breakup periods.
Anthropogenic stressors on freshwater wetlands: a microbial perspective
(North Dakota State University, 2024) Cornish, Christine
Benthic microbial communities play fundamental roles in wetland ecosystems including nutrient and energy cycling, and the degradation and assimilation of pollutants. Because of these crucial roles, along with their short-life cycles and high diversity, microorganisms can also play an important role as indicators of environmental change, which is particularly relevant in the current climate of increasing anthropogenic stressors, including factors such as emerging pollutants and climate change. Consequently, understanding the responses of microbes to environmental change is critical. To assess the effects of anthropogenic stressors on microbial communities in wetland ecosystems, I examined the response of sediment microorganisms from North Dakota wetlands in both microcosm and field-scale studies. First, I used 16S rRNA gene sequencing to analyze wetland microbial community responses to glyphosate treatments using an experimental microcosm approach. I found no significant differences in microbial communities among concentrations or treatments compared to controls, suggesting microorganisms in this region may have evolved glyphosate tolerance. Second, also taking an experimental approach, I measured methane, carbon dioxide, and nitrous oxide flux and porewater concentrations in microcosms to analyze net microbial production and consumption of greenhouse gases following glyphosate and/or 2,4-D treatment. I found high glyphosate concentrations significantly increased carbon dioxide emissions potentially due to increased microbial activity from the use of glyphosate as a substrate, or due to increased respiration as a stress response. Lastly, I used 16S rRNA gene sequencing to compare microbial communities in natural and restored wetlands across the North Dakota Prairie Pothole Region to assess the effects of a physical stressor, hydrologic restoration. I found no significant differences in microbial communities across wetlands, which may be due to the lack of direct sediment disturbance from restoration, or due to the ability of microorganisms to rapidly recover, thus showing no assemblage differences 25 years after restoration. Overall, I demonstrated that integrating microbial ecology with ecotoxicology and restoration ecology can be a beneficial and applicable research approach to understanding the impact of anthropogenic-induced environmental change on wetlands and show that the use of microbial metrics and mechanisms can provide valuable insight on pertinent issues of global concern.
Freshwater Cyanotoxin Mixtures in Recurring Cyanobacterial Blooms in Voyageurs National Park
(North Dakota State University, 2021) Christensen, Victoria
Algal and cyanobacterial blooms can foul water systems, inhibit recreation, and produce cyanotoxins, which can be toxic to humans, domestic animals, and wildlife. Blooms that recur yearly present a special challenge, in that chronic effects of most cyanotoxins are unknown. To better understand cyanotoxin timing, possible environmental triggers, and inter-relations among taxa and toxins in bloom communities, recurring cyanobacterial blooms were investigated at three recreational sites in Kabetogama Lake in Voyageurs National Park from 2016-2019. Results indicated that peak neurotoxin concentrations occurred before peak microcystin concentrations and that toxin-forming cyanobacteria were present before visible blooms, which is a serious human health concern. Two cyanotoxin mixture models (MIX) and two microcystin (MC) models were developed using near-real-time environmental variables and additional comprehensive variables based on laboratory analyses. Comprehensive models explained more variability than the environmental models and neither MIX model was a better fit than the MC models. However, the MIX models produced no false negatives, indicating that all observations above human-health regulatory guidelines were simulated by the MIX models. The results show that a model based on a cyanotoxin mixture is more protective of human health than a model based on microcystin alone. In 2019, 7 of 19 toxins were detected in various mixtures. The potential toxin producing cyanobacteria, Microcystis, was significantly correlated with microcystin-YR, while Pseudanabaena sp. and Synechococcus sp. were negatively correlated to several toxins. Jaccard and Sorenson indices indicated strong same-day similarities among the three bloom communities. Nitrogen-fixing cyanobacteria were present at every site, and when combined with internal loading of phosphorus, might explain similarities among sites, and why seasonal differences, even in samples from the same site, were stronger. Information from this dissertation adds to the body of work on recurring blooms and under-studied toxins and toxin mixtures, providing a better understanding of future research options for freshwater cyanotoxins in and outside of Voyageurs National Park.
Investigation of Organic Nitrogen Activity in Biological Processes of Water Resource Recovery Facilities
(North Dakota State University, 2021) Bhardwaj, Ruchi Joshi
The decrease in effluent inorganic nitrogen concentration in water resource recovery facilities (WRRFs) has been effectively achieved by including or finetuning the biological nutrient removal process. However, soluble organic nitrogen (sON) remains relatively unchanged, resulting in no reduction in the proportion of sON in effluent nitrogen. Therefore, for some WRRFs subjected to stringent nitrogen discharge limits, the removal of sON is crucial. Furthermore, the interest in sON is growing due to its impact on eutrophication, close relationship with the membrane fouling in wastewater treatment and the formation of nitrogenous disinfection byproducts in drinking water treatment. The overall aim of this research work was to determine the limits and capabilities pertaining to the removal and production of organic N in two different biological wastewater treatment processes, activated sludge process and moving bed biofilm reactors (MBBRs). Three research tasks were performed. In the first task, the effect of sludge retention time (SRT) on the production of organic nitrogen fractions (particulate, colloidal and soluble) and the biodegradability of produced sON in an activated sludge process was investigated. SRT influenced each fraction (particulate, colloidal and soluble) of organic nitrogen along with the biodegradability of effluent sON. The second task investigated sON activity in batch reactors mimicking nitrifying MBBRs. Although net production of sON was observed, both production and ammonification coexisted in the reactors which regulated the sON concentration. Organic carbon bioavailability and/or ammonia concentration were found to influence the production and ammonification of sON. The task also identified the variation in the bacterial activity in the biofilm during nitrification when exposed to different C/N ratios in the influent. The third task examined sON activity under heterotrophic and nitrifying sludge to identify how one sludge type is better than the other in removing sON under a simple aerobic reactor. Higher degradation of sON was identified in the presence of heterotrophic sludge than nitrifying sludge. Results from this dissertation research provide a better understanding of sON activity for two different biological wastewater treatment processes, which is critical for optimizing the removal of sON in WRRFs.
An Agent-Based Model for the Water Allocation and Management of Hydraulic Fracturing
(North Dakota State University, 2022) Lin, Tong
An agent-based model (ABM) is developed to simulate the impacts on streamflow and groundwater levels by the dramatic increase of hydraulic fracturing (HF) water use. To develop the agent-based model, institution theory is used to model the regulation policies, while evolutionary programming allows agents to select appropriate strategies when applying for potential water use permits. Cognitive maps endow agents’ ability and willingness to compete for more water sales. All agents have their influence boundaries that restrict their competitive behavior toward their neighbors but not to non-neighboring agents. The decision-making process is constructed and parameterized with both quantitative and qualitative information. By linking institution theory, evolutionary programming, and cognitive maps, our approach is a new exploration of modeling the dynamics of coupled human-natural systems (CHNS) to address the high complexity of the decision-making process involved in the CHNS. The ABM is calibrated with HF water-use data, and the calibration results show that it is reliable in simulating water depot number, depot locations, and depot water uses. The SWAT (Soil and Water Assessment Tool) model of the Little Muddy River basin and the MODFLOW of the Fox Hill-Hell Creek regional aquifer are coupled with the ABM to simulate the changes in streamflow and groundwater level, respectively, under different scenarios such as HF water demand, climate, and regulatory policies. The integrated modeling framework of ABM, SWAT, and MODFLOW can be used to support making scientifically sound policies in water allocation and management for hydraulic fracturing.
Evolutionary and Ecological Processes in Conservation and Preservation of Plant Adaptive Potential
(North Dakota State University, 2022) Di Santo, Lionel Nicolas
Anthropogenetic disturbances, such as habitat loss and fragmentation, overexploitation, and climate change have diminished population sizes of many species, increasing risks of population extirpation or species extinction. Consequently, conservation of genetic variability, to preserve and maintain rare species’ evolutionary potential and avoid within-population inbreeding, is a major goal of conservation biology. For plants, various approaches and guidelines have been developed to preserve species’ genetic diversity ex situ (“off-site”). However, effective methods to guide conservation and management decisions without relying on the availability of genetic data or knowledge about population size and population genetic structure are lacking. With the first two chapters of my dissertation, I aimed to complement existing ex situ strategies by investigating surrogates for estimating genetic variation to optimize conservation of rare species’ evolutionary potential when access to genetic data is limited. My results demonstrated that guiding population sampling using environmental and geographic distances, as opposed to randomly selecting source populations, can increase genetic diversity and differentiation captured in simulated ex situ collections. Likewise, my research showed that for species with largely heritable seed traits, morphological variation estimated from contemporary seed collections can be used as a proxy for standing genetic variation and help inform sampling efforts aiming to optimize genetic diversity preserved ex situ. Although strategies targeted to conserve rare species’ evolutionary potential where genetic data may be lacking are needed, the increasing affordability of next-generation sequencing technologies is increasing access to genomic data for rare species. With my third chapter, I investigated whether inferring rare species’ evolutionary history from genomic data may help inform conservation practices. My results demonstrated that teasing apart spatial and temporal effects of stochastic and deterministic processes on population genetic structure may be used to estimate past and contemporary changes in populations’ evolutionary potential, as well as to evaluate risks and benefits of genetic rescue as a management strategy. Overall, my PhD research establishes tools and approaches to preserve genetic variation for rare species using different types of data. As world’s biodiversity continue to decline, tool development to accommodate species-specific data availability for preservation of genetic variation is crucial.
Graphene Oxide Supported Metal Oxide Nanohybrids for Aqueous Arsenic Removal
(North Dakota State University, 2021) Das, Tonoy Kumar
Arsenic contamination of drinking water is a major public health concern affecting more than 200 million people globally. Iron(Fe)-based adsorbents though promoted for aqueous arsenic removal because of their low cost and easy availability, their field application is limited due to their low efficiency and slow adsorption kinetics. In this work, two graphene oxide (GO)-Fe nanohybrids, namely GO-supported nano magnetite (GM) and GO-supported nanoscale zero-valent iron (GFeN), were compared for arsenic removal. Controls were run with bare (i.e., no GO) nanoscale zero-valent iron (FeNP) and nano magnetite (M). GFeN worked more efficiently (>90%) over a wide pH range (3-9) for both the inorganic arsenic species, As(III) and As(V). GM worked well at pH 3 (>90% efficient) for As(V), and pH 9 (80%) for As(III). GFeN exhibited better aqueous dispersibility with a zeta potential of -21.02 mV. In GFeN and FeNP, surface complexation was dominant in the adsorption of both As(III) and As(V), and electrostatic attraction played a limited role. In GM and M, As(V) removal was controlled by electrostatic attraction while As(III) adsorption was ligand exchange and surface complexation. The arsenic removal data based on normalized iron content in the adsorbents indicated that the nanohybrids (GFeN and GM) removed arsenic more efficiently compared to the bare nanoparticles (FeNP and M) with GFeN performing the best. Arsenic adsorption capacities of GFeN were found to be 306 mg/g for As(III) and 431 mg/g for As(V). The GO-sheets in GFeN acted as reservoirs for the electrons released during surface corrosion of the FeNPs. The stored electrons were transferred back to the FeNPs to reduce the oxidized iron surface, and the rejuvenated surface helped in additional arsenic removal. The arsenic desorption pattern from two As(V)-sorbed nanohybrids (GFeN and graphene oxide-supported ceria (GO-CeO2)) was studied. GFeN released ~5.73% and GO-CeO2 released ~0.94% of sorbed arsenic over a period of two years. While sorbed arsenic remained as As(V) on the GFeN surface, some As(V) in GO-CeO2 got reduced to As(III). The surface oxide composition in GFeN (FeOOH and Fe2O3) and GO-CeO2 (Ce3+/Ce4+ ratio) underwent changes over time and that played a role in arsenic desorption.
Taphonomic, Taxonomic, and Behavioral Diversity of Wormworld Fossil Assemblages from Ediacaran Units of the Western United States
(North Dakota State University, 2020) O'Neil, Gretchen Rose
The western United States Deep Spring and Wood Canyon formations contain a variety of late Ediacaran fossils, representing the enigmatic Ediacara biota and a metazoan worm-like fauna. The latter, dubbed “Wormworld”, is comprised of a number of tube-dwelling organisms whose tubes were preserved through pervasive pyritization and carbonaceous compressions, as well as abundant horizontal burrows and grazing traces. One particular site, within Ancient Bristlecone Pine Forest presents a challenge that is not faced at the other localities, as it contains abundant tube-shaped fossils that are lacking in morphological characteristics due to poor preservation. Through investigations into what remains of the fossils and the potential preservational pathways that could produce such fossils, it is possible to use the findings to identify additional tube worm assemblages that may have been overlooked due to the assumed restriction on exceptional preservation based on sedimentology. Alternatively, trace fossils in the area appear to be more readily preserved and abundant, allowing for investigations into trends in frequency and faunal occurrences leading into the Cambrian Explosion. These traces and the trace maker activities are of a particular interest, as they represent the first communities of established bioturbators, which helped oxygenate the seafloor and mix the previously stratified microbial mat-rich substrate. The trace fossils on the surface of the beds represented ichnotaxa that are well-known in Cambrian deposits. However, petrographic thin sectioning revealed an unexpected fossil, Lamonte trevallis, previously only reported from South China. The presence of Lamonte trevallis is evidence for more advanced, complex Cambrian-like feeding behaviors occurring prior to the Precambrian–Cambrian boundary. The diversity of the Ediacaran fossils from the western United States places it among the established Ediacaran exceptional preservation localities and justifies the designation of the Deep Spring/Wood Canyon assemblage as an Ediacaran Lagerstätte.
Holocene Postglacial Fluvial Processes and Landforms in Low Relief Landscapes
(North Dakota State University, 2020) Phillips, Zachary Rockford
Postglacial rivers are part of the relatively young low-relief landscape system left behind by glaciers. Over time, postglacial rivers are susceptible to both minor and major channel planform changes as the Earth and its newly exposed rivers adjust to new isostatic and geomorphic equilibriums. Those planform changes result in topographic features that are well preserved among the largely unaltered landscape and offer opportunities to learn about the processes that create them. This work focuses on those minor and major planform changes and the resulting landforms, with a focus on processes effecting the glaciolacustrine Red River Valley. Here, three studies were conducted, two regarding minor planform changes and one focusing on major planform changes. Studies included in this work regard 1) the spatial distribution of meander cutoffs and meander cutoff relief on the Red River, 2), avulsion timing and length resulting from isostatic tilting and 3) mobile river ice and bank interaction frequency, locations, and erosion in meandering rivers. Results show that rivers develop meander cutoffs that faster in areas where geologic materials are more easily eroded and their relief shows a positive relationship with the rate of river incision. Major channel path changes (avulsions) in the presence of isostatic tilting were found to be most frequent soon after river establishment while rates of isostatic rebound are high enough to outpace channel incision. River ice was found to most frequently interact with the outer banks of channels with long, tight bends and high sinuosity, potentially contributing to the meandering process. From these results it can be interpreted that postglacial rivers were highly dynamic early in their history and have stabilized over time, with most of the changes occurring in areas with more erodible alluvium. Presently, rivers undergo most of their changes during the spring thaw when mobile river ice is impacting the banks, with sinuous river reaches impacted most frequently by mobile river ice.
Nitrogen Mineralization Dynamics of Post Harvest Crop Residue in No-Till Systems
(North Dakota State University, 2020) Alghamdi, Rashad Saeed
In North Dakota, adoption of conservation tillage practices has resulted in an accumulation of crop residue remaining on the soil surface. North Dakota producers receive a nitrogen credit for long-term no-till but due to previous crop residue this credit may not be realistic for providing partial nutrient needs to subsequent crops in a cool environment with a short growing season. Our objectives were to evaluate the N mineralization potential of common crop residues to determine whether crop residue accumulation in no-till systems can provide sufficient nitrogen quantities needed for subsequent crops. Three lab incubation studies were conducted to provide N mineralization insights for individual crop residues, crop residues over several simulated growing seasons, and crop residue in diversified cropping systems. Differences in soil texture, surface application versus incorporation of residue, freeze and thaw cycles and combinations of residues were all factors examined. Results indicated that crop residue decomposition and N release from the residue treatments generally immobilized N but were not significantly different from the bare soil for nearly all studies. The only exception observed was for the forage radish cover crop which showed the potential to improve soil N mineralization in select three-year rotations. Findings of these studies show that most wide C:N ratio crop residues will immobilize soil N in a no-till system under ideal conditions (i.e. moisture, temperature, and residue particle size). These findings suggestion that a fertilizer N credits may require reevaluation and take into consideration soil moisture with validated data to support the fertilizer N credit.
Aquatic Macroinvertebrate Response to Shifts in Hydroclimatic Variability and Ecohydrological Conditions in Prairie-Pothole Wetlands: Implications for Biodiversity Conservation
(North Dakota State University, 2020) McLean, Kyle Ian
Ecosystem degradation and subsequent biodiversity loss has plagued freshwater environments globally. Wetland ecosystems, such as the depressional wetlands found in the Prairie Pothole Region of North America, have been heavily impacted by historical land-use change and continue to be vulnerable to continued landscape modifications and climate change. Using existing literature, I summarized how recent shifts in climate coupled with historic and contemporary landscape modifications have driven a shift in wetland ecohydrological variability. However, clear trends in biodiversity were often limited by the spatial and temporal resolution of published research. I used 24 years (1992–2015) of hydrologic and aquatic-macroinvertebrate data from a complex of 16 prairie-pothole wetlands located in North Dakota to relate wetland ecohydrological variability to biodiversity. I used structural equation modeling techniques to test a set of causal hypotheses linking a wetland’s hydrogeologic setting and local climate conditions (i.e., the Wetland Continuum) to changes in hydrology, water chemistry, and biology, with an emphasis on aquatic-macroinvertebrate community response. I then examined the temporal synchrony of aquatic-macroinvertebrate populations to examine the relative importance of landscape-scale controls (e.g., climate, metacommunity dynamics) and wetland-specific controls on community assembly. Using this information, I then quantified among-wetland and amongyear changes in aquatic-macroinvertebrate beta diversity to investigate patterns of biotic homogenization. I found that spatial and temporal variability in aquatic-macroinvertebrate composition was strongly influenced by ponded-water dynamics. In addition to hydrologic controls, the high levels of temporal coherence of aquatic-macroinvertebrate compositional turnover supported the hypothesis that wetland biodiversity is also dependent on metacommunity dynamics. Analyses of spatio-temporal patterns in beta diversity did not reveal climate driven homogenization of aquatic-macroinvertebrate taxa among wetlands. However, shifts towards more permanently ponded water regimes corresponded with lasting shifts in aquatic-macroinvertebrate community composition. The communities of temporarily ponded wetlands maintained high levels of both temporal and spatial beta diversity. My collective findings indicate that the conservation of aquatic-macroinvertebrate diversity is dependent on the conservation of heterogenous, wellconnected, wetland complexes.
Chironomids Then and Now: Climate Change Effects on a Tundra Food Web in the Alaskan Arctic
(North Dakota State University, 2019) Lackmann, Alec Ray
Although climate change is a global phenomenon, the Arctic is warming faster than any other region on earth. These climatic changes have driven rapid regional changes over the past half-century in both the physical landscape and the ecosystems therein. One such ecological interaction is between migratory shorebird survival and local insect emergence. Annually, tens of millions of migratory shorebirds travel to the Arctic to rear their young in the relative absence of predators, but in a relative abundance of food (insects). Over evolutionary time, these trophic levels have coupled: shorebird chicks tend to hatch during the period of highest terrestrial insect availability. However, climate change is currently uncoupling this food-web synchrony, creating potential for trophic mismatch. In the High Arctic near Utqiaġvik (formerly Barrow), Alaska, trophic mismatch between nesting shorebirds and their insect food base is already detectable. In this ecosystem, flies in the Family Chironomidae (non-biting midges) dominate the prey trophic level in the avian food web. We have found that the pre-emergence development of one particular midge, Trichotanypus alaskensis, defies conventional wisdom of the Family, as this species molts to an additional fifth larval instar prior to pupation and emergence (all other chironomids are known to have four larval instars). We discovered an Utqiaġvik midge that reproduces asexually, a species that was not documented in the 1970s. Utilizing controlled temperature rearings of Utqiaġvik midge larvae, we discovered that as temperatures rise, emerging chironomid adults are generally smaller in size. We have found that chironomid pre-emergence developmental rates follow a positive exponential relationship as temperatures increase, can vary by taxon, yet are consistent across field and lab settings for a given taxon. At Utqiaġvik in the 2010s, chironomid emergence occurs 8-12 days earlier than it did in the 1970s. These findings shape our understanding of trophic mismatch in this arctic food web.
The Effect of Zinc Oxide Nanoparticles on Plants, and on Host-Pathogen Interactions
(North Dakota State University, 2019) Deka, Priyanka
Zinc oxide nanoparticles (ZnO NPs) are a type of engineered nanomaterial that is currently being explored for use in different aspects of agriculture. So far, research on this area is limited to evaluating the phenotypical responses of plants to a high concentration of the NPs which is realistically not feasible in the actual environment. This research aims to investigate the molecular-level interactions between ZnO NPs and plants, together with another significant component of the environment, a fungal plant pathogen. Prior to studying these molecular-level interactions, the uptake of ZnO NPs in planta was validated using a fluorescent zinc ion sensor, Zinpyr-1 and a zinc ion chelator, TPEN in confocal laser scanning microscopy (CLSM) and Transmission Electron Microscopy (TEM). Phenotypical effects were studied in soybean plants exposed to environmentally relevant concentrations of ZnO NPs and bioaccumulation of zinc was studied in seeds of soybean and other soy products. The next phase of this research focused on investigating the physiological responses of plants exposed to ZnO NPs. This was achieved by elucidating the complete transcriptome of the plants using a Next Generation sequencing (NGS) platform, RNA seq. A significant part of this research emphasized on exploring the effects of ZnO NPs on host-pathogen interactions. The model monocot plant, barley was used in this study, together with a necrotrophic pathogen, Pyrenophora teres f. teres (Ptt). The barley line which was used, CI5791 is resistant to the disease Net Form Net Blotch (NFNB), caused by Ptt. Rapid responses of plants to ZnO NPs were observed that subsided at the later time-points, whereas the heightened responses to the pathogen alone (P) and combined application (ZnO NP + P) persisted. Exposure to ZnO NPs also induced transcriptional reprogramming in the Ptt inoculated plant that resulted in compromised immunity in the otherwise resistant barley, due to the persistence of salicylic acid (SA)-related genes. In ZnO NP-exposed Arabidopsis thaliana, the effects were contradictory. From the barley and Arabidopsis expression data, it could be concluded that both species react differently to ZnO NPs, giving a glimpse of the differential responses that ZnO NPs may elicit in different plant species.
Multi-Element Composition of Triglochin Maritima L. from Contrasting Habitats including Hot Springs and Metal Enriched Areas
(North Dakota State University, 2011) Sunwar, Sharmila
The aim of this PhD research was to study multi-element composition in wetland plants from contrasting habitats, including hot springs, temporary wetlands, and metal-rich areas. Triglochin maritima L. (seaside arrowgrass) was chosen for the study because this species is common in alkaline/saline soils and is adapted to diverse habitats. Eleocharis rostellata, Juncus balticus, Salix exigua, S. boothii, and S. wolfii were also included in the study. Field studies and greenhouse experiments were conducted to study the multi-element composition in plants. In the greenhouse experiment the effects of temperature and soil biota on multielement uptake in T. maritima were studied. Root-zone soils and plant samples were analyzed for 32 - 50 elements using inductively coupled plasma OES/MS spectrometry. The expected outcomes from this research were: 1) the development of multi-element fingerprints for T. maritima and other plant species from contrasting habitats, and 2) a better understanding of the effects of temperature and soil biota on multi-element uptake in T. maritima. Habitat specific element concentration patterns in T. maritima were observed; concentrations of Mn, Li, and B were high in plants from hot spring influenced wetlands, whereas Ca, P, Mg, Fe, Sr, Ba, Ti, and Cu were higher in the plants of temporary wetlands. J. balticus and Salix species from mine impacted and uncontaminated sites revealed distinct differences in multi-element fingerprints. J. balticus showed high concentrations of S, K, Mn, Fe, Cu, Al, As, and Cd at contaminated sites compared to un-contaminated sites. Multi-element fingerprints of Salix species showed that S. boothii had higher concentrations of Mn, Fe, Al, and Ti compared to S. exigua and S. wolfii. To our knowledge for the first time the association of mycorrhizal fungus in T. maritima was confirmed, and significant effects of temperature on element concentrations, contents, and their translocation in plants were observed. Generally, the distribution of the total contents of P, Na, Mn, B, Cu, Mo, Li, Sr, Ti, and Cs in both roots and leaves were lower at 40 °C compared to 20 and 30 °C, but their distribution and translocation from root to leaves were higher at 40°C. Even though the biological and physiological functions of Li, Sr, Ba, Rb, and Ti in plants are not fully understood, these elements were substantially taken up by T. maritima, and significant positive correlations of these elements were found with elements that have known biological functions. Overall, concentrations of Ca, P, Mg, Mn, B, Sr, and Ba in T. maritima showed variation due to differences in habitats, temperature, and experimental growing conditions (greenhouse and field condition). Concentration patterns of Na, K, and Zn were species specific and affected by temperature. Li concentrations varied due to habitat differences, growth conditions, and species differences. Future research directions could include: 1) identification of the fungal species associated with T. maritima and studies to elucidate their possible role in survival of T. maritima in the elevated temperature of hot springs, 2) the effects of soil factors, such as salinity and 3) seasonal variation in uptake and translocation, particularly for the less studied elements with yet unrecognized but potential biological functions in plants.
Multi-Element Fingerprinting of River Sediments to Identify Diffuse Pollution Sources
(North Dakota State University, 2011) Wijeyaratne, Dimuthu Nilmini
This study was carried out in the Souris and Turtle Rivers in North Dakota. The aim of this study was to develop multi-element fingerprints of the Souris River and Turtle River sediments and to evaluate the suitability of these fingerprints to assess the geographic origin of potential pollutants of the two rivers. Preliminary analysis of Souris River sediment samples confirmed that the multi-element fingerprinting can be used to assess the sediment and contaminant loading patterns. Laboratory experiments were performed to assess the validity of linear mixing assumption in multi-element fingerprinting studies. The results of these experiments verified the assumptions and showed that there is a statistically significant spatial and temporal variation in the element concentrations depending on their mobility and re-deposition. Field studies were conducted in the Souris River and Turtle River to assess the variation of element concentrations in the top riverbed samples along the main rivers and their tributaries. The sediment contribution from the tributaries and the phosphorus concentrations in the main channel were used to calculate the phosphorus contributions from the tributary sediments to the Souris River. The differences in phosphorus contributions from tributaries were related to land use, underlying geology, and the size of the watersheds of the tributaries in the Souris River watershed. Similar analysis was used in the Turtle River to calculate Arsenic, Cadmium and Selenium contribution from the tributaries to the Turtle River. The differences in the contribution of these elements were related to the underlying geology and the size of the watersheds. This study provides a detailed analysis of element concentrations and relative sediments and element loading rates from the tributaries to the main rivers along the Souris and Turtle Rivers in North Dakota. The multi-element fingerprinting technique can be successfully used as a tool to identify the relative contribution of sediments and assessing and tracing pollution sources in rivers. Multi-element fingerprinting provides a relatively low cost, rapid tool for sediment tracking, without the need for addition of exotic chemicals such radio-tracers or dyes to natural ecosystems.
Examination of the Period of Preparation for Breeding in Male and Female Songbirds
(North Dakota State University, 2017) Needham, Katie Beth
In virtually all species, reproduction must be precisely timed to coordinate breeding and rearing of offspring with favorable conditions. It is imperative for individuals to time the highest energetic cost to themselves or highest needs by offspring with greatest food availability in either abundance or nutrient make-up. To accomplish this, individuals must integrate signals conveying both internal and external status and accordingly alter the activity of the reproductive axis. To date most efforts to identify variation in control mechanisms for reproduction in seasonally breeding animals have focused on the brain as the initiator for reproduction. However, recent studies have re-directed attention to two other potential tissues, the pituitary and ovary, where variation in brake sensitivity may be important. To this end, a series of experiments were performed in two songbird species to elucidate the hormonal role in timing of breeding and the interaction of an energetic trade-off on the decision to breed in both males and females. I used two species, the wild dark-eyed junco (Junco hyemalis) and the wild-caught captive house sparrow (Passer domesticus) as model systems to address the following questions: 1) What physiological mechanisms explain individual variation in onset of gametogenesis? And 2) How are mechanisms of energy integrated with the reproductive axis’ control of reproduction and timing of breeding to regulate energetic trade-offs? Specifically, we focused the role of testosterone in males (Chapter 2), and mechanisms downstream of the hypothalamus in females (Chapter 3). Next, in Chapter 4, the question of whether an energetic demand would reduce sperm quality was addressed. Lastly, in Chapter 5, we asked if an energetically costly immune challenge would result in the delay of clutch initiation. The results of these studies demonstrate the significant differences between sexes in the signals conveying an individual’s internal and external status in order to alter activity of the reproductive axis, and therefore timing of breeding. Collectively, these findings provide further evidence that females are ‘in the driver’s seat’ for onset of breeding and should be the focus of future research.
Understanding the Relationships between Plant Communities, Fish Communities, and Sediment Chemistry in Pristine Shallow Lake Wetlands, Red Lake, MN
(North Dakota State University, 2016) Hummel, Stephanie Elizabeth
Over 90% wetland loss in many areas of the United States has triggered extreme concern for declining biodiversity and loss of ecosystem services. Studies assessing ecological characteristics of unaltered wetlands are critical to interpreting potential responses to anthropogenic changes and how ecosystem characteristics and services might respond to future climate dynamics. Previous research shows fish and plant communities play an important role in shallow lake ecology by creating stability within the clear state. Understanding these mechanisms in a pristine setting is important for successful conservation and restoration. Our objectives, part of a long term monitoring study (2009-2015), were 1) Evaluate patterns in multi-element concentrations of pore water along a gradient from upland areas through emergent vegetation to the open water of shallow lake wetlands 2) Assess seasonal changes of multi-element concentrations of pore water during the growing season of shallow lake wetlands 3) Measure the influence of fish communities species composition on plant communities species composition 4) Evaluate how sediment chemistry impacts plant communities. We evaluated pore water chemistry on two lakes using dialysis vials from June-October 2014. We selected 24 shallow lakes located within Red Lake Nation Indian Reservation, MN, USA to conduct the remaining objectives. At each lake we assessed fish community structure and abundance using fyke nets and experimental gill nets for a 24-hr period during July. Aquatic and emergent vegetation was assessed simultaneously by rake throws and Daubenmire frame, and sediment samples were collected by taking a surface grab sample. Sediment samples were taken in the open water and emergent vegetation zones. Pore water did not change across a gradient from upland to open water, but did change over the season from June to October. We found fish community composition did not change significantly from 2009 to 2015, but fish biomass significantly decreased from 2009 to 2015. No species-specific relationships between vegetation and fish existed, but species specific relationships existed between vegetation and sediment characteristics in both the open water and emergent vegetation zones. Results will be used as reference points for restoration and conservation, and serve for a better understanding of shallow lake state stability.
Determining Greenhouse Gas Emissions and Nitrogen Dynamics of Solid Beef Manure Applied to Fargo-Clay Soil of the Red River Valley
(North Dakota State University, 2018) Niraula, Suresh
Land application of solid beef manure may prompt greenhouse gases (GHGs) - nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions. Nitrogen (N) in manure can also be lost through ammonia volatilization (NH3), leaching (NO3-), denitrification, and erosion. The objectives of this research were to assess the effects of (i) land application of solid beef manure (SM) on emission of GHGs, NH3 volatilization, and corn (Zea mays L.) yield, (ii) soil moisture [(30, 60, and 90% water-holding capacity (WHC)] on GHGs and NH3 emissions from urea and manure application, and (iii) soil temperature (5, 10, 15, and 25°C) on GHGs and NH3 emissions from urea and manure amended Fargo-Ryan silty clay soil of the RRV. The two-year growing season cumulative N2O emission (cN2O) ranged from 0.3 (non-fertilized, NF) to 1.2 (urea only, UO) kg N ha-1. The UO reduced cumulative carbon dioxide (cCO2) by 42% compared to manure N sources. The cumulative CH4 (cCH4) emission ranged from -0.03 to 0.23 kg CH4-C ha-1 CH4-C ha-1, with the highest emission from manure with straw bedding (BM). Manure reduced cNH3 by ~11% compared to UO. Cumulative soil N in 2017 were significantly greater by 11%, respectively, compared to 2016. Nitrogen source did not show any difference in grain yield and grain N uptake in field study. In the laboratory, across WHC levels, 1.01% of the total applied N was lost as N2O at 60% WHC from urea treated soil. Soil CO2 from manure was up to two times the emission from CF treated soils. The cumulative NH3 volatilization loss from soil ranged from 29.4 to 1250.5 µg NH3-N kg−1 soil, with the highest loss from CF amended soils at 30% WHC. In addition, laboratory study showed cumulative GHGs and NH3 emission generally increased with increase in temperature, with the highest emission observed at 25 °C. The results highlight the challenge of meeting crop nutrients demand while reducing GHG emissions by selection of an N source.
Sperm Telomere Dynamics: Natural Variation and Sensitivity to Environmental Influences in House Sparrows (Passer domesticus)
(North Dakota State University, 2018) Kucera, Aurelia
Understanding the mechanisms that contribute to variation in lifespan is of central importance to diverse fields including life history theory. Although the causes of aging are not fully understood, telomere dynamics (length and loss rate) is a potentially critical mechanism underlying longevity. Telomeres are highly conserved, non-coding regions of DNA at the ends of eukaryotic chromosomes. Telomere loss occurs throughout life due to accumulating oxidative damage and normal cell replication. When telomeres reach a critically short length, they stop dividing and functioning normally.While early life telomere length is predictive of lifespan in birds, the mechanism of inheritance of telomere length is unknown. One hypothesized mechanism is by direct transfer from gamete telomeres. However, very little is known about telomere dynamics in gametes. Stress exposure has been shown to accelerate telomere loss and reduce longevity, particularly when stress is experienced early in life. Exposure to elevated glucocorticoid hormones during activation of the stress response is thought to lead to increased oxidative damage, and thereby accelerate telomere loss. Sperm are particularly sensitive to oxidative damage. Therefore, exposure to stress may accelerate aging within individuals, but also may accelerate sperm telomere loss and thereby impact the telomere dynamics of their offspring. To test this hypothesis, I measured natural variation in sperm telomere length and offspring early life telomeres, sperm telomere length in response to acute and chronic stress exposure, and the relationship between stress sensitivity and telomere length. In free-living sparrows, I found no relationship between paternal sperm telomere length and offspring early life telomere dynamics. Across studies, there was a consistent positive correlation between blood and sperm telomere length, suggesting that sperm telomeres may decline with age in birds. I also found variation in sperm telomere length across the breeding season, and no relationship between stress sensitivity and sperm telomere length. Finally, I found that while sperm telomere length in free-living birds exceeded blood telomere length, in captivity sperm telomeres were equal length or shorter than blood telomeres, potentially related to the duration of captivity. These findings suggest that sperm telomeres are sensitive to environmental factors including stress exposure.
Impact of Carbon Nanotubes on Bacterial Viability: Indicators, Mitigation, and Role of Phage Shock Proteins
(North Dakota State University, 2014) Le, Tu Thi Anh
The toxicity of single walled carbon nanotubes (SWCNTs) to a model bacterium, Escherichia coli ATCC 8739 was investigated. Estimates of E. coli viability following treatment with SWCNTs were similar using four viability methods: plate count, galactosidase enzyme assay, LIVE/DEAD® Baclight™ assay, and RNA quantificatio. Pristine SWCNTs, carboxylic functionalized SWCNTs (SWCNT-COOHs) and hydroxyl functionalized SWCNTs (SWCNTOHs) were used to assess toxicity. Regardless of the length of SWCNTs, the toxicity was in the following order: SWCNT-OHs < SWCNTs < SWCNT-COOHs. While there was no difference in the impact of short and long SWCNT-OHs, the long pristine SWCNTs and SWCNT-COOHs were more toxic than the corresponding short SWCNTs. The viability of cells exposed to all three types of SWCNTs was greater with increasing cell density. Alterations of cell morphology ware observed after the cells were exposed to SWCNTs. Entrapment of cells in alginate and polyvinyl alcohol (PVA) as a means to limit the antibacterial effect of SWCNTs was examined. The results showed that cell entrapment could reduce the bactericidal effects of SWCNTs. Calcium alginate and PVA provided equivalent cell protection against SWCNTs. The toxicity of SWCNTs for entrapped cells depended on the length and concentrations of SWCNTs, the presence of functional groups, and the initial cell density. Transcriptomic and proteomic analyses were used to study the molecular mechanisms by which SWCNTs induce bactericidal activity. Expression levels of genes and proteins, particularly phage shock proteins (Psp) that are known to react under membrane stress such as iv pspA, pspB, and pspC, changed following cell exposure to SWCNTs. Expression of the Psp operon was affected by the length, concentration, and functionalization of SWCNTs. Overall, this study provided multiple methods that can be used to quantify the toxicity of SWCNTs for bacterial cells. A way to mitigate the bactericidal effects of SWCNTs was identified and verified. Gene and protein expression, particularly expression of the Psp operon, were reported in cells stressed by exposure to SWCNTs.

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