Theses/Dissertations - Ecological, Earth, and Environmental Sciences

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    Regulation of phycobilin pigments and nutrient metabolism traits drive cyanobacteria bloom stoichiometry.
    (2022-04-21) Wang, Jingyu, 1990-; Scott, J. Thad (Jefferson Thad)
    Cyanobacteria blooms may substantially impact the nutrient cycling in freshwater systems, as they consume dissolved nitrogen (N) and phosphorus (P) at different rates under different conditions, resulting in various elemental ratios within the cell. The adaptations of cyanobacteria to respond to diverse growing conditions are largely unknown despite decades of research. Phycobilin pigments (PBPs) are N-rich macromolecules which have the potential to support growth as N-storage site and may play a major role in the variability of cyanobacteria N stoichiometry. However, the regulation of phycobilin pigments for N-fixing and non N-fixing cyanobacteria remains unclear. This project investigates how cyanobacteria regulate the PBP and elemental stoichiometry under varied nutrient and light conditions and characterizes the flexibility in nutrient metabolism traits using a numerical model for Microcystis aeruginosa and Dolichospermum flos-aquae. Our results revealed both HAB forming species responded similarly to light intensity, with decreasing light causing an increased production of PBP, although at different rates. However, we observed dissimilar PBP responses to varied N availability. We found that M. aeruginosa stored as much as 30% of cellular N in PBP under high N conditions, while D. flos-aquae only allocated 5% of the cellular N in PBP. Furthermore, we found that during bloom formation, M. aeruginosa regulate PBP synthesis according to ambient N and P concentrations. While the PBP cell quota was more constant and independent to ambient nutrient in D. flos-aquae blooms. Differing regulation on PBP may explain the constrained C: N stoichiometry in D. flos-aquae blooms. A numerical model study quantified the flexibility in half-saturation concentrations for the classic Monod model and suggest improvement regarding cyanobacteria growth representation in current model applications.
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    Cross-scale interaction effects of socio-ecological conditions on forest bird abundance in the eastern United States.
    (2021-07-12) Chaudhary, Anand, 1975-; Gutzwiller, Kevin J.
    Hierarchy theory explains that processes act at multiple spatial scales, and that broad-scale processes can influence fine-scale patterns. Many of these hierarchical processes are human-driven, and as anthropogenic pressure increases on natural systems, there is increasing urgency to assess such influences on biodiversity. I investigated the cross-scale interaction (CSI) effects of broad-scale climate and landscape-scale socioeconomic and ecological variables on forest bird abundance in the eastern United States. There were three distinct projects: Project I investigated effects of CSIs and within-scale interactions (WSIs) involving climate (regional and landscape breeding-season temperature) and landscape socioeconomics (percent female, percent college-educated, median age, and median income) on eight species’ abundances; Project II investigated effects of CSIs involving sub-regional climate (breeding- and pre-breeding season temperature and precipitation) and landscape forest patch size and percent exurban cover on eight species’ abundances; and Project III investigated effects of CSIs involving sub-regional climate (breeding-season temperature and precipitation) and landscape agriculture cover and clumpiness on five species’ abundances. For each project, I used Akaike’s Information Criterion to identify the best-supported model in a set of a priori competing negative binomial regression models. There were informative CSIs or WSIs in 10 of the 32 models in Project I, and informative CSIs in 9 of the 16 models in Project II and 4 of the 5 models in Project III. In some, but not in most models, CSIs were more influential than were the additive influence (main effects) of the interacting variables, similar WSIs, and other environmental variables considered. I did not find clear differences in CSI or WSI effects between forest-interior and forest-edge species, or between Neotropical-wintering and Nearctic-wintering species. In all projects, I found species-specific responses to CSIs. Responses of forest birds to CSIs were different from what would be expected from additive influences of the interacting variables, and therefore ignoring CSI influences may be misleading. These findings underscore the need to incorporate CSIs into analyses designed to inform conservation. Understanding how CSIs modify the effects of variables at different spatial scales may be crucial for the effective management of biodiversity in the face of limited conservation resources.
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    Evaluating the cellular uptake and translocation of silver nanoparticles using in vitro models.
    (2016-07-31) Zhang, Fan, 1987-; Bruce, Erica Dawn.
    Nanoparticles (NPs) are used in a wide range of applications for various characteristics associated with their size and shape. This research evaluated silver nanoparticles (AgNPs) as a model NP system to evaluate uptake, translocation, and associated toxicity. This study investigated the influence of capping agents for AgNPs on the cellular uptake in two epithelial cell lines at realistic exposure levels. In addition, it also investigated the interaction between soluble proteins and modeled cell membraneusing giant unilamellar vesicles (GUVs) and supported lipid bilayers, at physiologically relevant protein concentrations. Further, we developed a three-dimensional (3D) organotypic lung model resembling in vivo conditions, and tracked the translocation of AgNPs across the modeled lung barrier. Results show that particular capping agent on a AgNP modulates the extent of cellular uptake into different cell lines. Among the three investigated capping agents, tannic-acid coating was most efficient in delivering AgNPs into cells. Although the amount of internalized silver varied, none of the tested AgNPs resulted in cytotoxicity. Additionally, soluble proteins such as bovine serum albumin, hemoglobin, lysozyme and fetal bovine serum could induce structural changes in GUVs due to non-specific protein adsorption onto lipid membranes. The minimum concentration of proteins required for the onset of adsorption, and the relative affinities of adsorption, were dependent on the vesicle charge and the dipolar characteristics of a protein. Furthermore, by engaging human bronchial epithelial cells, microvascular endothelial cells and macrophage-like cells into a tri-culture, 3D system the overall structure exhibited similar properties to the alveolar-capillary barrier. Tannic acid-AgNPs were tested as model NPs, and translocated through multiple cell layers at both 4°C and 37°C. Cytotoxicity of AgNPs in tri-culture was more potent than that monoculture or biculture. The active response from tri-culture was most physiological relevant due to secretion of pro-inflammatory markers by macrophage like cells. The overall study highlighted the important role of the physiochemical properties of AgNPs in their biological fate. The intrinsic proteins aid the cellular internalization of AgNPs by altering lipid membrane stability and permeability. Physiologically relevant in vitro models can be a reliable tool in the evaluation of transport and toxicity of NPs.
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    High-throughput analytical methods for persistent organic pollutants in high-lipid matrices.
    (2014-09-05) Robinson, Eleanor Marian.; Usenko, Sascha.; Ecological, Earth, and Environmental Sciences.; Trumble, Stephen John.; Noren, Shawn R.; Davis, Jay.; Kanatous, Shane B.; Jia, Mo, 1984-; Subedi, Bikram.; Sanders, Rebel L.; Berman-Kowalewski, Michelle.; Potter, Charles W.; Baylor University. Institute of Ecological, Earth and Environmental Sciences.
    Persistent organic pollutant (POP) trends and profiles reconstructed from environmental matrices, such as mammal tissues, have provided a wealth of information regarding contaminant behavior and environmental fate. These POP trends and profiles are unique and often irreplaceable due to difficulties in obtaining marine mammal samples. Historically, sample preparation methods for lipid-rich marine mammal matrices require an extraction followed by multiple cleanup and concentration steps. Due to the volatility of select POPs, during sample preparation steps (traditional packed column and GPC cleanup steps followed by a concentration step via nitrogen) there are possibilities for analyte loss and contamination. The goal of sample preparation methods for POPs should seek to reduce the overall number of steps. Selective pressurized liquid extractions (SPLE; an analytical technique that combines PLE with sorbent cleanup) has reduced and/or eliminated the number of cleanup steps associated with organic pollutants extraction and cleanup. SPLE methods for lipid-rich matrices were developed and improved for the trace analysis of multiple classes of organic pollutants (organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers). Analytical methods for lipid-rich matrices, such as marine mammal blubber (Weddell seal Leptonychotes weddelli and bowhead whale blubber Balaena mysticetus) and whale earwax (blue whale Balaenoptera musculus), were developed and emphasized improvements on sample preparation for the analysis of organic pollutants. Marine mammal blubber methods utilizing SPLE followed by GPC were developed (Chapter II; Weddell seal blubber tissue), and improved to eliminate all post-extraction (i.e. GPC) cleanup steps (Chapter III; bowhead whale blubber tissue). An SPLE method for whale earwax with no post-extraction cleanup was also developed (Chapter IV). These methods were applied to environmental samples and utilized to generate irreplaceable data including the first identification of PBDEs in Antarctica’s Weddell seals (Chapter II) as well as in Arctic bowhead whales (Chapter III), and the first identification (Chapter IV) and reconstruction (Chapter V) of contaminant profiles in whale earplugs.
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    Development and application of high-throughput sample preparation methods for solid matrices.
    (2014-09-05) Aguilar Lázaro, Lissette.; Usenko, Sascha.; Ecological, Earth, and Environmental Sciences.; Brooks, Bryan W.; Oziolor, Elias M., 1990-; Matson, Cole W.; Robinson, Eleanor Marian.; Trumble, Stephen John.; Williams, E. Spencer.; Subedi, Bikram.; Bigorgne, Emilie.; Horstmann-Dehn, Lara.; Baylor University. Institute of Ecological, Earth and Environmental Sciences.
    This research presents the development and application of high-throughput sample preparation methods for the analysis of organic and inorganic contaminants from solid samples. The approach presented evaluates conventional methods to identify potential areas of improvement. In this sense, conventional methods serve as a framework for the development of high-throughput sample preparation methods. In general, improvements include expansion of target analyte list thereby increase the environmental applicability, reduction of sample preparation steps, and as a result, reduction of sample preparation time. The analytical bottleneck is often associated with sample preparation, especially in the analysis of organic contaminants from environmental samples. Many environmental analytical chemistry methods can be broken down into one or more sample preparation steps followed by one or more chemical analysis steps. Improvement of historical methods has focused on the development of advance instrumentation (i.e. focusing on the chemical analysis). However, recent efforts have focused on the overall reduction of time and/or steps associated with sample preparation. For example, post-extraction cleanup adsorbents can be incorporated into the pressurized liquid extraction step to perform a selective pressurized liquid extraction (SPLE). SPLE methods significantly reduced sample preparation time, solvent requirements, and waste production. Specific examples presented in this dissertation include: 1) the development and application of SPLE methods for the analysis of organic contaminants from sediments and biological tissues; 2) the development and application of a simplified acid digestion method for the analysis of mercury and selenium in rare samples of Pacific walrus (Odobenus rosmarus divergens) muscle (L. dorsi). These examples illustrate the approach for the development of high-throughput sample preparation methods that have successfully combined techniques into a single method, and/or eliminated post-extraction cleanup steps. The availability of these methods increases laboratory’s capacity and preparedness to analyze rapidly large volumes of samples. These methods could find use in routine analysis and monitoring studies of environmental samples, food and pharmaceutical industries, agriculture, toxicology studies, and forensic sciences among others. Lastly, this dissertation discusses a few opportunities that lay ahead for improvement and development in sample preparation.
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    Towards an understanding of pharmaceutical exposure and bioaccumulation in effluent-dependent systems.
    (2014-09-05) Du, Bowen.; Brooks, Bryan W.; Chambliss, C. Kevin.; Ecological, Earth, and Environmental Sciences.; German Environmental Specimen Bank; TCEQ; Snyderville Basin Water Reclamation District; Carollo Engineers; City of Waco; CRASR at Baylor; Baylor Stable Isotope Lab; U.S. EPA; SETAC NA; USDA; Baylor University. Institute of Ecological, Earth and Environmental Sciences.
    Environmental risks of pharmaceuticals and other contaminants of emerging concern (CECs) are not well understood due to relatively limited information on fate, transport, exposure, bioaccumulation and effects. The objective of this research was to improve understanding of the relationships among CEC accumulation in aquatic organisms through developing robust analytical methods and studying exposure and bioaccumulation. In chapter 2, an isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was successfully developed and applied to identify 15 pharmaceuticals and 2 pharmaceutically-active metabolites in fish tissues. The method was successfully applied to trout samples collected from different river locations in Utah, USA. In chapter 3, occurrence, removal and discharge of selected CECs were compared between municipal and on-site treatment systems receiving a common wastewater influent. Such a unique study design was conducted at the Baylor Wastewater Research Program site at the Waco Municipal Area Sewerage System, Waco, Texas, USA. This novel comparative examination of centralized and decentralized effluent quality also employed a fish plasma model approach to estimate the therapeutic hazards of pharmaceuticals in each effluent discharge. Within investigated treatment systems, the septic system consistently possessed the lowest water quality and therapeutic hazards. Coupling a constructed subsurface wetland may lower ecological risks associated with effluent discharge from septic systems. Occurrence and bioaccumulation of pharmaceuticals and other CECs were then examined in a common snail (Planorbid sp.) grazer and periphyton from the North Bosque River in central Texas, USA, during a historic drought when stream flow was effluent-dependent. Limited observations of pharmaceuticals in periphyton compared to water and snail samples suggested that water exposure represented the primary route of pharmaceutical exposure to Planorbid sp. in the North Bosque River. In chapter 5, a fish plasma model, initially developed from laboratory studies and applied in chapter 3 to assess effluent quality, was tested to examine observed versus predicted internal doses of select pharmaceuticals in the North Bosque River. In addition, characterization of trophic transfer for select pharmaceuticals suggested that uptake of ionizable pharmaceuticals by aquatic organisms in this effluent-dependent wadeable stream more likely resulted from inhalation than dietary exposure.
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    Qualitative and quantitative assessment of UCM in PM2.5 of Bakersfield, CA.
    (2014-01-28) Nallathamby, Punith Dev.; Sheesley, Rebecca Jacobs.; Environmental Science.; Baylor University. Dept. of Environmental Science.
    Fine particulate matter (PM ₂.₅ ) was collected in Bakersfield, CA during the CalNex 2010 field experiment and was analyzed for primary organics using a gas chromatograph – mass spectrometer (GC-MS). Substantial presence of unresolved complex mixture (UCM) was observed in the collected PM ₂.₅ . To quantify the overlapping UCM peaks, a method was developed for the deconvolution (peak separation) of the UCM. This enabled unique quantification of each UCM peak. The developed method was tested on several runs of a standard reference material for urban dust, which yielded consistent values with a standard deviation of ~16%. The UCMs in the Bakersfield sample were quantified separately and qualitatively assessed for possible emission sources. The average spectrum from the UCM suggested the presence of alkanes, alkenes, and alkynes in the low-molecular weight UCM; and the presence of linear, branched, and cyclic alkanes in the high-molecular weight UCM. The method developed in the current study has the potential for application to a variety of environmental media.
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    Fire disturbance effects on regional carbon cycling in a sub-humid woodland.
    (2013-05-15) Yao, Jian, 1984-; White, Joseph Daniel.; Ecological, Earth, and Environmental Sciences.; Baylor University. Institute of Ecological, Earth and Environmental Sciences.
    Fire disturbance affects many ecosystem processes, especially carbon (C) cycling. In addition, fire is routinely used as a management tool in wildland ecosystems. In this study, I measured the fire-affected C storage, vegetation composition, habitat suitability for an endangered bird species (golden-cheeked warble), and charcoal content in juniperoak woodlands with documented past surface fires within Balcones Canyonlands National Wildlife Refuge. Using this information, I modified a process-based model of ecosystem biogeochemical cycling (Biome-BGC) to simulate the effects of different fire types, the production and loss of fire-derived charcoal, and the charcoal effects on soil water availability. From my field measurements, I found significantly different total aboveground biomass C with average values of 5.25, 6.86, and 9.18 kg m-2 for 60 plots with known fire histories that categorized into the recent (<40 year), old (>=40 year), and no fire group, respectively. These data also showed that higher oak recruitment was associated with fires that occurred in years with low summer precipitation. I concluded that fire may have a dual effect on habitat suitability with catastrophic wildfire damaging potential habitat and significantly reducing regional C storage, and moderate intensity fires in dense young juniper stands promoting tree species diversity. From the laboratory analysis of soils derived from these same plots, I estimated that the regional average soil charcoal concentration to be 1.40 g C kg-1 soil (20.8 g C kg-1 SOC) based on the methods of 13C nuclear magnetic resonance and mid-infrared spectroscopy, with fire-affected sites having significantly higher soil charcoal concentrations than the non-fire sites. I calculated the regional annual soil charcoal loss rate to be 4.7%, potentially due to soilerosion on steep slopes. Finally, the modified Biome-BGC model was able to reasonably simulate fire-affected C and charcoal storage changes. The model also indicated that the effects of fire on the ecosystem properties (vegetation C, leaf area index, and net ecosystem exchange) were closely associated with the severity of fire. The fire-derived charcoal did not appear to have significant effects on the simulated ecosystem properties. My results provided detailed ecological information regarding fire-affected processes in these woodland ecosystems.
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    Influence of pH and total dissolve solids on harmful algal blooms of Prymnesium parvum.
    (2013-05-15) Prosser, Krista Noel.; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.
    Harmful blooms of Prymnesium parvum in inland waters continue to expand, in part, due to anthropogenic influences and climate change. This thesis examines influences of pH and total dissolved solids (TDS) on P. parvum blooms, growth, and toxicity to aquatic life. Chapter 1 evaluated pH effects on P. parvum bloom development and toxicity by manipulating in situ limnocorrals during 21 d pre-bloom and bloom development experiments. Though neutral pH levels preempted P. parvum bloom development, higher pH resulted in bloom formation and ambient toxicity. Chapter 2 examined whether TDS with major ionic composition associated with hydraulic fracturing influenced P. parvum growth and toxicity across nutrient conditions. Though no growth was observed at 130 mg/L, higher treatment levels of TDS stimulated P. parvum growth and increased acute toxicity to fish. Such novel observations provide pH and TDS thresholds for potentially supporting management of P. parvum growth and acute toxicity in inland waters.
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    Using multiple parameters to compare effluent quality of eight wastewater treatment systems.
    (2013-05-15) Price, Amy E.; Yelderman, Joe C.; Baylor University. Dept. of Environmental Science.; Texas Onsite Wastewater Treatment Research Council.; C. Gus Glasscock, Jr. Endowed Fund for Excellence in Environmental Sciences.; Baylor University. Dept. of Environmental Science.
    Wastewater effluent qualities from two study sites in central Texas were compared using whole effluent toxicity (WET) tests and chemical indicator parameters. Three of the effluents were collected from the City of Whitney Wastewater Treatment Facility in Whitney, TX; the remaining five effluents were collected at the Waco Metropolitan Area Regional Sewerage System (WMARSS) and the Baylor Wastewater Research Program site near Waco, TX. The first hypothesis examined at the City of Whitney Wastewater Treatment Facility was that effluent water quality improves through a pond and wetland treatment system. The second hypothesis examined was that there is no difference of effluent water qualities between two seasons. The first hypothesis examined for the Waco effluents was that effluent qualities of the four on-site systems are comparable to a centralized municipal wastewater treatment effluent: WMARSS. The second hypothesis examined was that there is no difference of effluent water qualities between two seasons.
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    Advancing an understanding of ecological risk assessment approaches for ionizable contaminants in aquatic systems.
    (2010) Valenti, Theodore Walter.; Brooks, Bryan W.; Ecological, Earth, and Environmental Sciences.; Baylor University. Institute of Ecological, Earth and Environmental Sciences.
    Freshwater is increasingly becoming a finite resource in many regions of the world. Gaps between estimated water supply and demand continue to narrow and the prospects of acquiring additional sources of freshwater remain limited. Furthermore, economically efficient water resource management practices are perplexed by increasing urbanization and changing land-use in semi-arid regions. Although repeated use of water is a practical and effective means for easing strain on water supplies, there is concern that unnecessary contamination may diminish future value of this important resource. Some surface waters in semi-arid regions of the U.S. are effluent-dominated as flow is comprised of >90% treated wastewater. Ionizable compounds are chemicals often associated with urban development and examples include pharmaceuticals, agrochemicals, natural toxins, and other common contaminants (e.g. ammonia). Because continued population growth and urbanization are likely to increase contaminant release and alter dilution capacity of receiving systems, it is important that best management approaches are developed at the watershed scale to limit water quality degradation associated with ionizable compounds. Current methods for prospective and retrospective ecological risk assessments of ionizable compounds seldom consider site-specific conditions during the analysis of effects of phase. Ionization state is largely controlled by the acid/base dissociation constant (pKa) and pH of the solution where a compound resides. Stream water quality can therefore influence ionization state, which is important because the unionized forms a more lipophilic and have a greater propensity to cross cellular membranes. Consequently, the unionized forms are hypothetically more toxic. I completed toxicity tests in the laboratory using various contaminants as model ionizable compounds over a gradient of environmentally-relevant surface water pH and then related measured toxicological endpoints to observed pH of surface waters using both discrete and probabilistic ecological risk assessment approaches. The result of my studies clearly demonstrated that site-specific pH may influence the toxicity of ionizable contaminants. Potential modifications to conceptual frameworks of ecological risk assessment for ionizable contaminants are suggested so that uncertainty can be reduced.