Latest content added for UNT Digital Library Partner: UNT Librarieshttps://digital.library.unt.edu/explore/partners/UNT/browse/?fq=dc_rights_access:public&display=grid&fq=str_degree_discipline:Environmental+Science2024-01-27T21:16:33-06:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Partner: UNT LibrariesAvian Community Response to Riverby Ranch Restoration Reconstruction2024-01-27T21:16:33-06:00https://digital.library.unt.edu/ark:/67531/metadc2257146/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc2257146/"><img alt="Avian Community Response to Riverby Ranch Restoration Reconstruction" title="Avian Community Response to Riverby Ranch Restoration Reconstruction" src="https://digital.library.unt.edu/ark:/67531/metadc2257146/small/"/></a></p><p>Anthropogenic activities have caused many wildlife spices to decline in populations worldwide. The grassland bird communities are especially being impacted by these land use changes. Breeding success is closely tied to functional habitats for most grassland bird species in North Texas. Restoring these degraded habitats is an important component to aid in conserving wildlife biodiversity. We surveyed the bird population at Riverby Ranch Mitigation site by conducting point count sampling. This site consists of recently restored grassland, wetland, and forested habitat. This research was focused on conducting post restoration monitoring of the bird community in the early succession of the restored habitats. We set out to use the bird community as biomonitors to help assess if the restoration practices could be considered successful. We found that density estimates were more than double at the restored site when comparing to three different references sites under different management practices. This included an unrestored working ranch, a wildlife management area, and a conservation managed prairie site. We found that biodiversity metrics were as high or higher than the reference sites. In addition, we also found that there were more observations of species of high conservation concern present at the restored stie. This research supports that the reconstructive restoration that took place at Riverby Ranch was highly effective at restoring a diverse and abundant grassland and wetland bird community.</p>Investigating the Spatial Relationship between Suicide and Race/Ethnicity: The Case for Alternate Rate Adjustment Techniques in Medical Geography2023-02-09T17:41:13-06:00https://digital.library.unt.edu/ark:/67531/metadc2048689/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc2048689/"><img alt="Investigating the Spatial Relationship between Suicide and Race/Ethnicity: The Case for Alternate Rate Adjustment Techniques in Medical Geography" title="Investigating the Spatial Relationship between Suicide and Race/Ethnicity: The Case for Alternate Rate Adjustment Techniques in Medical Geography" src="https://digital.library.unt.edu/ark:/67531/metadc2048689/small/"/></a></p><p>This work explores potential distortions created by race and ethnicity on the visualization, interpretation, and understanding of the spatial distribution of suicide in the United States. Due to radically different suicide rates among racial/ethnic groups, traditional crude or age-adjusted rates may introduce statistical confounding in both linear and spatial models. Using correlation, choropleth mapping, hot spot analysis, and location-allocation modeling, this work shows how traditional methods of health system planning may unintentionally overlook elevated risk in minority-dominated areas like inner cities, the Texas/Mexico border region, and the Deep South. The final chapter introduces a simulation protocol for examining potential distortions in datasets to identify spatial and non-spatial distortions created by the underlying population composition. Methodologically, this dissertation contributes to the discourse on place context versus population composition. More generally, this research points to potential hazards to creating a more inclusive and equitable healthcare system.</p>Space Use, Microhabitat and Macrohabitat Use of the Three-Toed Box Turtle (Terrapene carolina) in North Texas2023-02-09T17:03:12-06:00https://digital.library.unt.edu/ark:/67531/metadc2048629/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc2048629/"><img alt="Space Use, Microhabitat and Macrohabitat Use of the Three-Toed Box Turtle (Terrapene carolina) in North Texas" title="Space Use, Microhabitat and Macrohabitat Use of the Three-Toed Box Turtle (Terrapene carolina) in North Texas" src="https://digital.library.unt.edu/ark:/67531/metadc2048629/small/"/></a></p><p>Box turtle (Terrapene carolina) populations are steadily declining due their unique natural history, effects of climate change, and anthropogenic land use change. There is a need for updated information on box turtle space and micro and macro-habitat use to inform conservation efforts. This study used VHF radiotelemetry and GPS data loggers to examine box turtle space and habitat use in North Texas. Box turtle home range sizes averaged 6.6ha (range = 0.79 - 18.08, n = 23), and males (n = 9) had larger home ranges than females (n = 14; W = 31.5, P = 0.05). Home range size was best explained by a combination of variables including sex and body size, but overall, home ranges that consisted of higher percentages of suitable box turtle habitat were smaller. Box turtles used deciduous forest more than expected and wetlands less than expected by chance (Fisher's exact test, P < 0.0001). The most informative variable for box turtle macrohabitat selection was NDVI. Box turtles selected microhabitats with a higher percent litter (t = -2.16, P < 0.05) and understory cover (t = -5.03, P < 0.05). The results of CART analysis showed the nested importance of macro- and microhabitat and identified NDVI as the most important variable for predicting suitable box turtle habitat. Given these results, we postulate that NDVI can be used to identify suitable box turtle habitat at landscape scales to aid in management and conservation efforts. We found that three-toed box turtles are using habitat differently than what has been reported in eastern box turtles, providing support for the theory that three-toed box turtles should be classified as a separate species.</p>Acute Toxicity of Crude Oil Exposures to Early Life Stage Teleosts: Contribution of Impaired Renal Function and Select Environmental Factors2022-09-03T10:29:01-05:00https://digital.library.unt.edu/ark:/67531/metadc1985773/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1985773/"><img alt="Acute Toxicity of Crude Oil Exposures to Early Life Stage Teleosts: Contribution of Impaired Renal Function and Select Environmental Factors" title="Acute Toxicity of Crude Oil Exposures to Early Life Stage Teleosts: Contribution of Impaired Renal Function and Select Environmental Factors" src="https://digital.library.unt.edu/ark:/67531/metadc1985773/small/"/></a></p><p>Oil spills are well-known adverse anthropogenic events, as they can induce severe impacts on the environment and negative economic consequences. Still, much remains to be learned regarding the effects of crude oil exposure to aquatic organisms. The objectives of this dissertation were to fill some of those knowledge gaps by examining the effects of Deepwater Horizon (DWH) crude oil exposure on teleost kidney development and function. To this end, I analyzed how these effects translate into potential osmoregulatory impairments and investigated the interactive effects of ubiquitous natural factors, such as dissolved organic carbon (DOC) and ultraviolet (UV) light, on acute crude oil toxicity. Results demonstrated that acute early life stage (ELS) crude oil exposure induces developmental defects to the primordial kidney in teleost fish (i.e., the pronephros) as evident by alterations in: (1) transcriptional responses of key genes involved in pronephros development and function and (2) alterations in pronephros morphology. Crude oil-exposed zebrafish (Danio rerio) larvae presented defective pronephric function characterized by reduced renal clearance capacity and altered filtration selectivity, factors that likely contributed to the formation of edema. Latent osmoregulatory implications of crude oil exposure during ELS were observed in red drum (Sciaenops ocellatus) larvae, which manifested reduced survival in hypoosmotic waters, likely due to defective pronephros development and function. Finally, DOC-UV co-exposure slightly reduced acute crude oil photo-enhanced toxicity in red drum larvae. This dissertation provided novel information regarding crude oil toxicity that can be incorporated into environmental risk assessment and management for future oil spills.</p>Metacommunity Dynamics of Medium- and Large-Bodied Mammals in the LBJ National Grasslands2022-06-16T10:59:05-05:00https://digital.library.unt.edu/ark:/67531/metadc1944350/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1944350/"><img alt="Metacommunity Dynamics of Medium- and Large-Bodied Mammals in the LBJ National Grasslands" title="Metacommunity Dynamics of Medium- and Large-Bodied Mammals in the LBJ National Grasslands" src="https://digital.library.unt.edu/ark:/67531/metadc1944350/small/"/></a></p><p>Using metacommunity theory, I investigated the mechanisms of meta-assemblage structure and assembly among medium- to large-bodied mammals in North Texas. Mammals were surveyed with camera-traps in thirty property units of the LBJ National Grasslands (LBJNG). In Chapter II the dispersal and environmental-control based processes in community assembly were quantified within a metacommunity context and the best-fit metacommunity structure identified. A hypothesis-driven modelling approach was used in Chapter III to determine if the patterns of species composition and site use could be explained by island biogeography theory (IBT) or the habitat amount hypothesis (HAH). Islands were defined as the LBJNG property unit or the forest patch bounded by the property unit. Forest cover was selected as the focal habitat for the HAH. Seasonal dynamics were explored in both chapters. Metacommunity structure changed with each season, resulting in quasi-nested and both quasi and idealized Gleasonian and Clementsian structures. Results indicated that the anthropogenic development is, overall, not disadvantageous for this assemblage, that community assembly receives equal contributions from spatial and environmental factors, and that the metacommunity appears to operate under the mass effects paradigm. The patterns of species composition and site use were not explained by either IBT or HAH. Likely because this assemblage of generalist, dispersal-capable mammals are utilizing multiple habitat types both in the protected land and in the private land. This research highlights the versatility of these species and the potential value of rural countryside landscapes for wildlife conservation.</p>Ecosystem Services and Sustainability: A Framework for Improving Decision-Making in Urban Areas2022-06-16T10:55:53-05:00https://digital.library.unt.edu/ark:/67531/metadc1944341/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1944341/"><img alt="Ecosystem Services and Sustainability: A Framework for Improving Decision-Making in Urban Areas" title="Ecosystem Services and Sustainability: A Framework for Improving Decision-Making in Urban Areas" src="https://digital.library.unt.edu/ark:/67531/metadc1944341/small/"/></a></p><p>Ecosystem services are the varied goods and benefits provided by ecosystems that make human life possible. This concept has fostered scientific explorations of the services that nature provides to people with the goal of sustaining those services for future generations. As the world becomes increasingly urban, ecosystems are reshaped, and services are degraded. Provisioning and regulating ecosystem services, landscape planning, decision making, and agricultural systems and technologies play a distinctive role in feeding and sustaining the expanding urban population. Hence, the integrated assessment of these coupled components is necessary to understand food security and sustainable development. Nevertheless, frameworks that incorporate ecosystem services, urbanization, and human wellbeing are still scarce due to several conceptual and methodological gaps that challenge this assessment. As a consequence, these frameworks are not operationalized, and ecosystem services rarely receive proper attention in decision making. This dissertation seeks to improve our understanding of the role of ecosystem services at the landscape level and provides an approach for operationalizing decisions that affect sustainable practices and human wellbeing.</p>Correlation of Watershed NDVI Values to Benthic Macroinvertebrate Biodiversity in Eight North American Wadeable Streams2022-06-16T09:46:05-05:00https://digital.library.unt.edu/ark:/67531/metadc1944222/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1944222/"><img alt="Correlation of Watershed NDVI Values to Benthic Macroinvertebrate Biodiversity in Eight North American Wadeable Streams" title="Correlation of Watershed NDVI Values to Benthic Macroinvertebrate Biodiversity in Eight North American Wadeable Streams" src="https://digital.library.unt.edu/ark:/67531/metadc1944222/small/"/></a></p><p>Water quality of a stream or river is influenced by the surrounding landscape and vegetation. The Normalized Difference Vegetation Index (NDVI) is commonly used to characterize landcover and vegetation density. Benthic macroinvertebrates are ubiquitous in freshwater streams and are excellent indicators of the quality of freshwater habitats. Data from one NDVI remote sensing flight and one macroinvertebrate sampling event for eight wadeable stream study sites in the National Ecological Observatory Network (NEON) were acquired. Proportions of high, moderate, and sparse vegetation were calculated for each stream watershed using ArcGIS. Functional feeding groups and tolerance values were assigned to macroinvertebrate taxa. The Fourth-corner and RLQ methods of analysis, available in the ade4 package for R software, were used to evaluate the relationships of macroinvertebrate traits with environmental variables. Hypothesis testing using Model 6 in the ade4 package resulted in p-values of 0.066 and 0.057 for global (overall) significance. Mean NDVI values of moderately vegetated areas and proportion of sparse vegetation were found to be significant to percent shredders at alpha ≤ 0.05. Results of these methods of analysis, when combined with traditional macroinvertebrate sampling metrics, show that NDVI can be a useful, additional tool to characterize a watershed and its effects on macroinvertebrate community composition and structure.</p>Ecological Responses to Severe Flooding in Coastal Ecosystems: Determining the Vegetation Response to Hurricane Harvey within a Texas Coast Salt Marsh2021-08-26T20:33:20-05:00https://digital.library.unt.edu/ark:/67531/metadc1833477/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1833477/"><img alt="Ecological Responses to Severe Flooding in Coastal Ecosystems: Determining the Vegetation Response to Hurricane Harvey within a Texas Coast Salt Marsh" title="Ecological Responses to Severe Flooding in Coastal Ecosystems: Determining the Vegetation Response to Hurricane Harvey within a Texas Coast Salt Marsh" src="https://digital.library.unt.edu/ark:/67531/metadc1833477/small/"/></a></p><p>Vegetative health was measured both before and after Hurricane Harvey using remotely sensed vegetation indices on the coastal marshland surrounding Galveston Island's West Bay. Data were recorded on a monthly basis following the hurricane from September of 2005 until September of 2019 in order to document the vegetation response to this significant disturbance event. Both initial impact and recovery were found to be dependent on a variety of factors, including elevation zone, spatial proximity to the bay, the season during which recovery took place, as well as the amount of time since the hurricane. Slope was also tested as a potential variable using a LiDAR-derived slope raster, and while unable to significantly explain variations in vegetative health immediately following the hurricane, it was able to explain some degree of variability among spatially close data points. Among environmental factors, elevation zone appeared to be the most key in determining the degree of vegetation impact, suggesting that the different plant assemblages that make up different portions of the marsh react differently to the severe flooding that took place during Harvey.</p>Ozone Pollution Monitoring and Population Vulnerability in Dallas-Ft. Worth: A Decision Support Approach2021-08-26T20:07:23-05:00https://digital.library.unt.edu/ark:/67531/metadc1833430/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1833430/"><img alt="Ozone Pollution Monitoring and Population Vulnerability in Dallas-Ft. Worth: A Decision Support Approach" title="Ozone Pollution Monitoring and Population Vulnerability in Dallas-Ft. Worth: A Decision Support Approach" src="https://digital.library.unt.edu/ark:/67531/metadc1833430/small/"/></a></p><p>In urban environments, ozone air pollution, poses significant risks to respiratory health. Fixed site monitoring is the primary method of measuring ozone concentrations for health advisories and pollutant reduction, but the spatial scale may not reflect the current population distribution or its future growth. Moreover, formal methods for the placement of ozone monitoring sites within populations potentially omit important spatial criteria, producing monitoring locations that could unintentionally underestimate the exposure burden. Although air pollution affects all people, the combination of underlying health, socioeconomic and demographic factors exacerbate the impact for socially vulnerable population groups. A need exists for assessing the spatial representativeness and data gaps of existing pollution sensor networks and to evaluate future placement strategies of additional sensors. This research also seeks to understand how air pollution monitor placement strategies may neglect social vulnerabilities and therefore, potentially underestimate exposure burdens in vulnerable populations.</p>Biomonitoring at Dallas-Fort Worth International Airport: Relating Watershed Land Use with Aquatic Life Use2021-08-26T20:06:29-05:00https://digital.library.unt.edu/ark:/67531/metadc1833427/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1833427/"><img alt="Biomonitoring at Dallas-Fort Worth International Airport: Relating Watershed Land Use with Aquatic Life Use" title="Biomonitoring at Dallas-Fort Worth International Airport: Relating Watershed Land Use with Aquatic Life Use" src="https://digital.library.unt.edu/ark:/67531/metadc1833427/small/"/></a></p><p>The Dallas-Fort Worth International (DFW) Airport is located in a densely urbanized area with one of the fastest-growing populations in the U.S.A. The airport property includes a large tract of "protected" riparian forest that is unique to the urban surroundings. This dissertation explores variables that influence the benthic macroinvertebrate community structure found in urbanized prairie streams that were initially assessed by the University of North Texas (UNT) Benthic Ecology Lab during four, non-consecutive biomonitoring studies (2004, 2005, 2008, and 2014) funded by the DFW Airport. Additionally, land use analysis was performed using 5-meter resolution satellite imagery and eCognition to characterize the imperviousness of the study area watersheds at multiple scales. Overall, flow conditions and imperviousness at the watershed scale explained the most variability in the benthic stream community. Chironomidae taxa made up 20-50% of stream communities and outperformed all other taxa groups in discriminating between sites of similar flows and urban impairments. This finding highlights the need for genus level identifications of the chironomid family, especially as the dominant taxa in urban prairie streams. Over the course of these biomonitoring survey events, normal flow conditions and flows associated with supra-seasonal drought were experienced. Prevailing drought conditions of 2014 did not negatively influence stream communities, allowing this study to capture the long-term natural (temporal) variability of urban prairie stream communities. Such long-term studies are imperative for discerning between stream impairment versus natural variation, especially as droughts become more frequent and severe.</p>Conducting Tick-Borne Disease Research in Texas with a Focus on Rickettsia spp.2020-06-15T19:38:58-05:00https://digital.library.unt.edu/ark:/67531/metadc1703370/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1703370/"><img alt="Conducting Tick-Borne Disease Research in Texas with a Focus on Rickettsia spp." title="Conducting Tick-Borne Disease Research in Texas with a Focus on Rickettsia spp." src="https://digital.library.unt.edu/ark:/67531/metadc1703370/small/"/></a></p><p>The field of vector-borne disease research uses multidisciplinary approaches to help understand complicated interactions. This dissertation, covers three different aspects of tick-borne disease research which all focus on exploring tick-borne diseases in the non-endemic areas of Denton, County Texas and the state of Texas with a focus on Rickettsia spp. These aspects include tick sampling, testing ticks for the presence of Rickettsia spp., and creating species distribution maps of the Rickettsia spp. Rickettsia amblyommatis and tick species Amblyomma americanum.</p>The Effects of Leadership Development on Student Retention in STEM2020-06-15T19:38:58-05:00https://digital.library.unt.edu/ark:/67531/metadc1703378/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1703378/"><img alt="The Effects of Leadership Development on Student Retention in STEM" title="The Effects of Leadership Development on Student Retention in STEM" src="https://digital.library.unt.edu/ark:/67531/metadc1703378/small/"/></a></p><p>The Science Teaching and Research (STAR) Leadership Program at Austin College was designed to intentionally include leadership development into the science curriculum and provides an opportunity to determine the effects of student leadership development on the retention of students in science, technology, engineering, and mathematics (STEM). This dissertation used a quasi-experimental design to determine: 1) if STEM retention can be explained though the inclusion of leadership development into the curriculum; 2) if there is a difference between Austin College students who choose a STEM major compared to students who do not; and 3) if there is a difference between Austin College students who complete a STEM degree compared to students who do not. Census data were collected on 2,137 students who enrolled in STEM courses beginning in the fall of 2008 through the spring of 2017, and factors affecting retention were compared across three 3-year time periods that spanned before the program was initiated through wider implementation. A logistic regression showed that there was no significant positive association between leadership development and STEM retention when taking into account other pre-college and demographic factors that have been linked to retention in the literature. However, a one-way ANOVA showed that the academic factors significantly decreased as the STAR program progressed. Further studies are required to understand student benefits associated with the current program.</p>Irrigation Methods and Their Effects on Irrigation Water Efficiency in High Tunnels2020-01-24T06:07:59-06:00https://digital.library.unt.edu/ark:/67531/metadc1609101/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1609101/"><img alt="Irrigation Methods and Their Effects on Irrigation Water Efficiency in High Tunnels" title="Irrigation Methods and Their Effects on Irrigation Water Efficiency in High Tunnels" src="https://digital.library.unt.edu/ark:/67531/metadc1609101/small/"/></a></p><p>Improving water efficiency is and will continue to be a top concern to meet the world food production demands for a growing population. By having a clear understanding of water efficiencies, communities will be able to address these concerns from an economic standpoint and use more productive methods to grow food and limit water consumption. This study examines the water efficiencies of three irrigation methods over a single growing season in southeastern Oklahoma. Two crops, tomatoes and cucumbers, were grown using drip irrigation, a self-wicking container, and a non-circulating hydroponics barrel. Results at the end of the season showed the drip irrigation method had the highest water efficiency in terms of yield of product over water applied for both crops. The drip irrigation method also had the lowest associated set up costs and second lowest time requirements after the hydroponics method. These results were found to be consistent with other studies that compared drip irrigation to other irrigation methods and showed drip to have the highest water efficiencies.</p>Exploration of Explanatory Variables in the Creation of Linear Regression Models and Logistic Regression Models to Predict the Performance of Preservice Teachers on the Science Portion of the EC-6 TExES Certification Examination2020-01-24T06:07:59-06:00https://digital.library.unt.edu/ark:/67531/metadc1609094/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1609094/"><img alt="Exploration of Explanatory Variables in the Creation of Linear Regression Models and Logistic Regression Models to Predict the Performance of Preservice Teachers on the Science Portion of the EC-6 TExES Certification Examination" title="Exploration of Explanatory Variables in the Creation of Linear Regression Models and Logistic Regression Models to Predict the Performance of Preservice Teachers on the Science Portion of the EC-6 TExES Certification Examination" src="https://digital.library.unt.edu/ark:/67531/metadc1609094/small/"/></a></p><p>The purpose of this study was to analyze the current and pre-service conditions that can affect student teachers' preparedness to pass the science portion of the EC-6 Texas Examinations for Educator Standards (TExES), one of the mandatory certification exam to become a teacher in Texas. Two types of prediction models were employed in this study: binomial logistic regression and multiple linear regression. The independent variables used in this study were: final grade in BIOL 1082, classification of students, transfer status, taken college biology, taken college chemistry, taken college physics, taken college environmental science, taken college earth science, attending college part-time, number of credits taken during the semester, first-generation college student, relatives with degree in education, and current GPA. The dependent variable of this study was the posttest score on science portion of the EC-6 TExES practice exam. A total of 170 preservice teachers participated this study. This study used students enrolled in BIOL 1082, who volunteered to take a Biology for Educators QualtricsTM survey and the EC-6 TExES practice exam in a pretest (start of semester) and posttest (end of semester) form. The findings of this study revealed that the single best predictor of preservice teachers' performance on the science portion of EC-6 TExES practice certification examination was the Grade in BIOL 1082.</p>Spatial Variations and Cultural Explanations to Obesity in Ghana2019-08-29T10:25:12-05:00https://digital.library.unt.edu/ark:/67531/metadc1538645/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1538645/"><img alt="Spatial Variations and Cultural Explanations to Obesity in Ghana" title="Spatial Variations and Cultural Explanations to Obesity in Ghana" src="https://digital.library.unt.edu/ark:/67531/metadc1538645/small/"/></a></p><p>While obesity is now recognized as a major health concern in Ghana, the major drivers, causal factors, and their spatial variation remain unclear. Nutritional changes and lack of physical activity are frequently blamed but the underlying factors, particularly cultural values and practices, remain understudied. Using hot spot analysis and spatial autocorrelation, this research investigates the spatial patterns of obesity in Ghana and the explanatory factors. We also use focus group discussions to examine the primary cultural factors underlying these patterns. The results show that wealth, high education, and urban residence are the best positive predictors of obesity, while poverty, low education, and rural residence are the best (negative) predictors of obesity. Consequently, improving the socioeconomic status, for example, through higher levels of education and urbanization may increase obesity rates. Furthermore, the cultural preference for fat body as the ideal body size drives individual aspiration for weight gain which can lead to obesity. Thus, reducing obesity rates in Ghana is impossible without addressing the underlying cultural values.</p>American Lawn Addictions: Effects of Environmental Education on Student Preferences for Xeriscaping as an Alternative in North Central Texas, USA2019-06-09T21:09:49-05:00https://digital.library.unt.edu/ark:/67531/metadc1505240/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1505240/"><img alt="American Lawn Addictions: Effects of Environmental Education on Student Preferences for Xeriscaping as an Alternative in North Central Texas, USA" title="American Lawn Addictions: Effects of Environmental Education on Student Preferences for Xeriscaping as an Alternative in North Central Texas, USA" src="https://digital.library.unt.edu/ark:/67531/metadc1505240/small/"/></a></p><p>Urban land use and land cover has changed in the USA, giving rise to the American lawn – manicured, resource-intensive, and non-native. Green infrastructure design has been suggested in the literature as a potential alternative to the American lawn when managed as native xeriscapes, which require little to no irrigation after establishment. Given the influence of public preference on landscaping decisions, what is the relationship between the perceived value and ecological benefits of the American lawn compared to such alternatives? Few studies have explored this question in addition to the effects of college courses on influencing student preferences, as future stakeholders, towards native xeriscapes as alternatives to the American lawn. This research measured the effects of an introductory environmental education (EE) course on measurably influencing undergraduate student preferences for four xeriscapes as alternatives to the American lawn. To measure these effects, this study utilized the perceptions of 488 students enrolled in an indirect introductory EE course and 131 students enrolled in an introductory non-EE course. Three key results emerged from this research. Students preferred the American lawn more than xeriscape alternatives, irrespective to course enrolled. Introductory non-EE did not have an effect on student preferences, whereas indirect introductory EE did show some effects on student preferences. Lastly, student preferences were negatively associated with NPP per photosynthetically active square meter. The data from this study suggests that indirect introductory EE does not shift aesthetic landscape preferences towards pro-environmental alternatives. These results show promise for shifting such preferences via more direct EE approaches.</p>Long-Term Citizen Science Water Monitoring Data: An Exploration of Accuracy over Space and Time2019-01-19T21:34:31-06:00https://digital.library.unt.edu/ark:/67531/metadc1404518/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1404518/"><img alt="Long-Term Citizen Science Water Monitoring Data: An Exploration of Accuracy over Space and Time" title="Long-Term Citizen Science Water Monitoring Data: An Exploration of Accuracy over Space and Time" src="https://digital.library.unt.edu/ark:/67531/metadc1404518/small/"/></a></p><p>The Texas Stream Team (TST) is one of an increasing number of citizen science water monitoring programs throughout the US which have been continuously collecting surface water quality data under quality assurance protocols for decades. Volunteer monitoring efforts have generated monitoring datasets that are long-term, continuous, and cover a large geographic area - characteristics shown to be valuable for scientists and professional agencies. However, citizen science data has been of limited use to researchers due to concerns about the accuracy of data collected by volunteers, and the decades of water quality monitoring data collected by TST volunteers is not widely used, if at all. A growing body of studies have attempted to address accuracy concerns by comparing volunteer data to professional data, but this has rarely been done with large-scale, existing datasets like those collected by TST. This study assesses the accuracy of the volunteer water quality data collected across the state of Texas by the TST citizen science program between 1992-2017 by comparing it to professional data from corresponding stations during the same time period, as well as comparing existing and experimental data from a local TST partner agency. The results indicate that even large-scale, existing volunteer and professional data with unpaired samples that may have been taken months apart can show statewide agreement of 80% for all parameters (DO = 77%, pH = 79%, conductivity = 85%) over the 38 years of sampling included in the analyses, across all locations. The local case study using paired datasets for which a greater number of factors were controlled for show an even higher agreement between volunteers and professionals (DO = 91%, pH = 87%, conductivity = 100%) and show no significant difference between experimental and existing sampling data. The results from this study indicate that TST has been collecting water sampling data for decades that is comparable to professional data and provides compelling evidence for researchers and managers to better utilize TST's and other large-scale monitoring datasets already in existence from similar citizen science water monitoring programs across the country.</p>Mass Spectrometry-Based Identification of Ceramic-Bound Archaeological Protein Residues: Method Validation, Residue Taphonomy, and Prospects2019-01-19T21:34:31-06:00https://digital.library.unt.edu/ark:/67531/metadc1404522/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1404522/"><img alt="Mass Spectrometry-Based Identification of Ceramic-Bound Archaeological Protein Residues: Method Validation, Residue Taphonomy, and Prospects" title="Mass Spectrometry-Based Identification of Ceramic-Bound Archaeological Protein Residues: Method Validation, Residue Taphonomy, and Prospects" src="https://digital.library.unt.edu/ark:/67531/metadc1404522/small/"/></a></p><p>Despite the variety of successful reports of the preservation, recovery, and identification of archaeological proteins in general, there are few positive reports regarding mass spectrometry-based identification of ceramic-bound proteins. In large part, this shortage is due to the lack of consideration for the unique taphonomic histories of such residues and, in general, methods development. Further, because negative results are rarely published, there is no baseline to which results can be compared. This paper attempts to address these challenges via a multi-pronged approach that uses mass spectrometry and complementary approaches to evaluate ceramic-bound protein preservation in both controlled, actualistic experiments, and in archaeological artifacts. By comparing the results obtained from protein-spiked, experimentally-aged ceramic to those obtained from both faunal and ceramic archaeological materials, an enhanced perspective on protein preservation and subsequent recovery and identification is revealed. This perspective, focusing on taphonomy, reveals why negative results may be the norm for ceramic artifacts when non-targeted methods are employed, and provides insight into how further method development may improve the likelihood of obtaining positive results.</p>Producing a Film on Oil Spill Research for the Public2019-01-19T21:34:31-06:00https://digital.library.unt.edu/ark:/67531/metadc1404585/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1404585/"><img alt="Producing a Film on Oil Spill Research for the Public" title="Producing a Film on Oil Spill Research for the Public" src="https://digital.library.unt.edu/ark:/67531/metadc1404585/small/"/></a></p><p>The Deepwater Horizon oil drilling rig exploded on April 20, 2010, off the coast of Louisiana in the Gulf of Mexico. Following the spill, British Petroleum, leaser of the rig, set up a funding institution known as the Gulf of Mexico Research Initiative (GoMRI) to support research and understanding of the spill on the environments and peoples of the gulf. This outreach project was created alongside research of the RECOVER consortium, funded by GoMRI, to communicate what is happening within research labs around the country to understand the effect that the spill had on fish in pelagic and coastal regions of the gulf. The outreach project is composed of a short film (Deepwaters: The Science of a Spill, 18 min) and related outreach materials posted to Instagram (@FishandOilSpills).</p>Corbicula fluminea Invasion as a Secondary Effect of Hydrilla verticillata Management via Triploid Grass Carp (Ctenopharyngodon idella)2018-01-27T07:36:46-06:00https://digital.library.unt.edu/ark:/67531/metadc1062823/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1062823/"><img alt="Corbicula fluminea Invasion as a Secondary Effect of Hydrilla verticillata Management via Triploid Grass Carp (Ctenopharyngodon idella)" title="Corbicula fluminea Invasion as a Secondary Effect of Hydrilla verticillata Management via Triploid Grass Carp (Ctenopharyngodon idella)" src="https://digital.library.unt.edu/ark:/67531/metadc1062823/small/"/></a></p><p>A study of Asian clam (Corbicula fluminea Müller) colonization in relation to changes in aquatic vegetation community as a result of management of Hydrilla verticillata (L. f.) Royle with grass carp was conducted at the Lewisville Aquatic Ecosystem Research Facility (LAERF), Lewisville, TX, from April 2015 through October 2016. Percent vegetation cover, C. fluminea abundance and water quality metrics (pH, turbidity, conductivity, DO, calcium, chlorophyll a) from 16 experimental subjects were analyzed. Treatments included four replicated grass carp stocking densities; 1-control with no fish stocked (n = 4), 2-low density of 40-43 fish per vegetated ha (n = 4), 3-medium density of 72-81 fish per vegetated ha (n = 4) and 4-high density of 110-129 fish per vegetated ha (n = 4). Data analysis showed statistical significance in the relation of C. fluminea abundance to percent vegetation cover (multiple linear regression, r2 = 0.820), grass carp stocking densities (two-way analysis of variance, p = <0.001) and chlorophyll a (multiple linear regression, r2 = 0.339). Findings of this research indicate the possibility that management of hydrilla had enabled establishment of secondary invasive species.</p>The Influence of Disease Mapping Methods on Spatial Patterns and Neighborhood Characteristics for Health Risk2018-01-27T07:36:46-06:00https://digital.library.unt.edu/ark:/67531/metadc1062838/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1062838/"><img alt="The Influence of Disease Mapping Methods on Spatial Patterns and Neighborhood Characteristics for Health Risk" title="The Influence of Disease Mapping Methods on Spatial Patterns and Neighborhood Characteristics for Health Risk" src="https://digital.library.unt.edu/ark:/67531/metadc1062838/small/"/></a></p><p>This thesis addresses three interrelated challenges of disease mapping and contributes a new approach for improving visualization of disease burdens to enhance disease surveillance systems. First, it determines an appropriate threshold choice (smoothing parameter) for the adaptive kernel density estimation (KDE) in disease mapping. The results show that the appropriate threshold value depends on the characteristics of data, and bandwidth selector algorithms can be used to guide such decisions about mapping parameters. Similar approaches are recommended for map-makers who are faced with decisions about choosing threshold values for their own data. This can facilitate threshold selection. Second, the study evaluates the relative performance of the adaptive KDE and spatial empirical Bayes for disease mapping. The results reveal that while the estimated rates at the state level computed from both methods are identical, those at the zip code level are slightly different. These findings indicate that using either the adaptive KDE or spatial empirical Bayes method to map disease in urban areas may provide identical rate estimates, but caution is necessary when mapping diseases in non-urban (sparsely populated) areas. This study contributes insights on the relative performance in terms of accuracy of visual representation and associated limitations. Lastly, the study contributes a new approach for delimiting spatial units of disease risk using straightforward statistical and spatial methods and social determinants of health. The results show that the neighborhood risk map not only helps in geographically targeting where but also in tailoring interventions in those areas to those high risk populations. Moreover, when health data is limited, the neighborhood risk map alone is adequate for identifying where and which populations are at risk. These findings will benefit public health tasks of planning and targeting appropriate intervention even in areas with limited and poor-quality health data. This study not only fills the identified gaps of knowledge in disease mapping but also has a wide range of broader impacts. The findings of this study improve and enhance the use of the adaptive KDE method in health research, provide better awareness and understanding of disease mapping methods, and offer an alternative method to identify populations at risk in areas with limited health data. Overall, these findings will benefit public health practitioners and health researchers as well as enhance disease surveillance systems.</p>The Effects of Air Pollution on the Intestinal Microbiota: A Novel Approach to Assess How Gut Microbe Interactions with the Environment Affect Human Health2017-07-12T03:17:08-05:00https://digital.library.unt.edu/ark:/67531/metadc984173/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc984173/"><img alt="The Effects of Air Pollution on the Intestinal Microbiota: A Novel Approach to Assess How Gut Microbe Interactions with the Environment Affect Human Health" title="The Effects of Air Pollution on the Intestinal Microbiota: A Novel Approach to Assess How Gut Microbe Interactions with the Environment Affect Human Health" src="https://digital.library.unt.edu/ark:/67531/metadc984173/small/"/></a></p><p>This thesis investigates how air pollution, both natural and anthropogenic, affects changes in the proximal small intestine and ileum microbiota profile, as well as intestinal barrier integrity, histological changes, and inflammation. APO-E KO mice on a high fat diet were randomly selected to be exposed by whole body inhalation to either wood smoke (WS) or mixed vehicular exhaust (MVE), with filtered air (FA) acting as the control. Intestinal integrity and histology were assessed by observing expression of well- known structural components tight junction proteins (TJPs), matrix metallopeptidase-9 (MMP-9), and gel-forming mucin (MUC2), as well known inflammatory related factors: TNF-α, IL-1β, and toll-like receptor (TLR)-4. Bacterial profiling was done using DNA analysis of microbiota within the ileum, utilizing 16S metagenomics sequencing (Illumina miSeq) technique. Overall results of this experiment suggest that air pollution, both anthropogenic and natural, cause a breach in the intestinal barrier with an increase in inflammatory factors and a decrease in beneficial bacteria. This evidence suggests the possibility of air pollution being a potential causative agent of intestinal disease as well as a possible contributing mechanism for induction of systemic inflammation.</p>Adrenergic and Cholinergic Regulation of Cardiovascular Function in Embryonic Neotropic Cormorants (Phalacrocorax basilianus)2017-07-12T03:17:08-05:00https://digital.library.unt.edu/ark:/67531/metadc984219/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc984219/"><img alt="Adrenergic and Cholinergic Regulation of Cardiovascular Function in Embryonic Neotropic Cormorants (Phalacrocorax basilianus)" title="Adrenergic and Cholinergic Regulation of Cardiovascular Function in Embryonic Neotropic Cormorants (Phalacrocorax basilianus)" src="https://digital.library.unt.edu/ark:/67531/metadc984219/small/"/></a></p><p>Investigations of cholinergic and adrenergic tone on heart rate (fH) and mean arterial pressure (Pm) during embryonic development have been conducted on numerous avian species. While these investigations have documented that adrenergic tone, a continuous stimulation, on fH and Pm is vital to embryonic development in the birds studied to date, development of cholinergic tone on fH has been shown to vary even within species. Further, past studies have been bias to focus primarily on precocial species while altricial species remain poorly understood in this context. The goal of this investigation was to investigate the role of cholinergic and adrenergic tone on fH and Pm of an altricial species, the neotropic cormorant (P. brasilianus) to address this bias. The embryonic neotropic cormorant possesses B-and-a adrenergic tone on fH and Pm at 70% and 90% incubation while cholinergic tone on fH occurs at 90% incubation. This pattern of control is similar to that previously reported for several species of precocial birds suggesting the development of tonic cardiovascular regulation may be conserved across avian taxa.</p>Analysis of Students' Knowledge, Perceptions, and Interest in Engineering Post Teacher Participation in a National Science Foundation (NSF) Research Experience for Teachers (RET) Professional Development2017-02-19T19:42:09-06:00https://digital.library.unt.edu/ark:/67531/metadc955105/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc955105/"><img alt="Analysis of Students' Knowledge, Perceptions, and Interest in Engineering Post Teacher Participation in a National Science Foundation (NSF) Research Experience for Teachers (RET) Professional Development" title="Analysis of Students' Knowledge, Perceptions, and Interest in Engineering Post Teacher Participation in a National Science Foundation (NSF) Research Experience for Teachers (RET) Professional Development" src="https://digital.library.unt.edu/ark:/67531/metadc955105/small/"/></a></p><p>This study examined the impact of the National Science Foundation's Research Experience for Teachers (RET) in engineering at University of North Texas on students after their teachers' participation in the program. Students were evaluated in terms of self-efficacy, knowledge of engineering, perceptions of engineering, and interest in engineering. A 22-item Likert pre/post survey was used for analysis, and participants included 589 students from six high schools, one middle school, and one magnet school. Paired surveys were analyzed to determine if there was a statistically significant difference in attitudes and knowledge after teachers implemented lessons from their time at the RET. Surveys were also analyzed to determine if there was a statistically significant difference in student response based on gender or student school type. Results showed no statistically significant difference in the self-efficacy of students, however there was a statistically significant difference in knowledge, perceptions, and interest in engineering. In addition, there was a statistically significant difference between genders on an isolated question, and seven out of the 22 Likert questions showed a statistically significant difference between student school types.</p>Monitoring Watershed Health in the Upper Trinity River Basin, North Central Texas2016-11-15T10:54:02-06:00https://digital.library.unt.edu/ark:/67531/metadc935823/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc935823/"><img alt="Monitoring Watershed Health in the Upper Trinity River Basin, North Central Texas" title="Monitoring Watershed Health in the Upper Trinity River Basin, North Central Texas" src="https://digital.library.unt.edu/ark:/67531/metadc935823/small/"/></a></p><p>This study conducts watershed analysis using biological and geo-spatial techniques. Incorporating landscape features with biological attributes has been shown to be an effective method of monitoring environmental quality within watersheds. In situ biomonitoring using the Asiatic Clam, Corbicula fluminea, habitat suitability, and water quality data were evaluated for their potential to describe ecological conditions in agricultural and urban areas within the Upper Trinity River watershed. These data were analyzed with GIS to identify effects of land use on ecological conditions. C. fluminea downstream of point source effluents was effective detecting in-stream toxicity. Ambient toxicity appears to have improved in the Trinity, although urban influences limit aspects of aquatic life. No association between habitat quality and land use was identified.</p>Assessment of Radio-Tagged Grass Carp (Ctenopharnygodon idella) Dispersion, Vegetation, and Temperature Preferences in North Lake Reservoir2016-11-15T10:54:02-06:00https://digital.library.unt.edu/ark:/67531/metadc935626/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc935626/"><img alt="Assessment of Radio-Tagged Grass Carp (Ctenopharnygodon idella) Dispersion, Vegetation, and Temperature Preferences in North Lake Reservoir" title="Assessment of Radio-Tagged Grass Carp (Ctenopharnygodon idella) Dispersion, Vegetation, and Temperature Preferences in North Lake Reservoir" src="https://digital.library.unt.edu/ark:/67531/metadc935626/small/"/></a></p><p>Twenty-nine (Group One, June 8,1995) grass carp (Ctenopharyngodon idella) and five (Group Two, April 18, 1996) grass carp were radio-tagged to monitor movement patterns and habitat preferences on North Lake, a 335 hectare multi-use reservoir located in Irving, Texas. Overall fish mean Average Daily Movement (ADM) rates were 49.2 meters/day (during Half One, 6/8/95-11/30/95) and 5.3 meters/day (during Half Two, 12/14/95-6/6/96). Aquatic macrophtye distribution data were obtained. Radio-tagged grass carp were located in Hydrilla verticillata infested areas increasingly throughout the study, however, percent frequency of Hydrilla along 15 transects did not decrease. Radio-transmitters were equipped with temperature-sensors (10-35 Celsius range). Results indicated that radio-tagged grass carp showed no avoidance of areas of North Lake with elevated water temperatures. Radio-tagged grass carp dispersed quickly from stocking point, then moved into littoral areas infested with Hydrilla. After an initial movement period, most fish remained in a localized area.</p>Residential Grid-Connected Photovoltaics Adoption in North Central Texas: Lessons from the Solarize Plano Project2016-08-31T22:41:47-05:00https://digital.library.unt.edu/ark:/67531/metadc862819/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc862819/"><img alt="Residential Grid-Connected Photovoltaics Adoption in North Central Texas: Lessons from the Solarize Plano Project" title="Residential Grid-Connected Photovoltaics Adoption in North Central Texas: Lessons from the Solarize Plano Project" src="https://digital.library.unt.edu/ark:/67531/metadc862819/small/"/></a></p><p>Residential Grid-Connected Photovoltaics (GPV) systems hold remarkable promise in their potential to reduce energy use, air pollution, greenhouse gas emissions, and energy costs to consumers, while also providing grid efficiency and demand-side management benefits to utilities. Broader adoption of customer-sited GPV also has the potential to transform the traditional model of electricity generation and delivery. Interest and activity has grown in recent years to promote GPV in north central Texas. This study employs a mixed methods design to better understand the status of residential GPV adoption in the DFW area, and those factors influencing a homeowner's decision of whether or not to install a system. Basic metrics are summarized, including installation numbers, distribution and socio-demographic information for the case study city of Plano, the DFW region, Texas, and the United States. Qualitative interview methods are used to gain an in-depth understanding of the factors influencing adoption for the Solarize Plano case study participants; to evaluate the effectiveness of the Solarize Plano program; and to identify concepts that may be regionally relevant. Recommendations are presented for additional research that may advance GPV adoption in north central Texas.</p>The Influence of Urban Green Spaces on Declining Bumble Bees (Hymenoptera: Apidae)2016-06-28T16:28:55-05:00https://digital.library.unt.edu/ark:/67531/metadc849737/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc849737/"><img alt="The Influence of Urban Green Spaces on Declining Bumble Bees (Hymenoptera: Apidae)" title="The Influence of Urban Green Spaces on Declining Bumble Bees (Hymenoptera: Apidae)" src="https://digital.library.unt.edu/ark:/67531/metadc849737/small/"/></a></p><p>Bumble bees (Bombus spp.) are adept pollinators of countless cultivated and wild flowering plants, but many species have experienced declines in recent decades. Though urban sprawl has been implicated as a driving force of such losses, urban green spaces hold the potential to serve as habitat islands for bumble bees. As human populations continue to grow and metropolitan areas become larger, the survival of many bumble bee species will hinge on the identification and implementation of appropriate conservation measures at regional and finer scales. North Texas is home to some the fastest-growing urban areas in the country, including Denton County, as well as at least two declining bumble bee species (B. pensylvanicus and B. fraternus). Using a combination of field , molevular DNA and GIS methods I evaluated the persistence of historic bumble bee species in Denton County, and investigated the genetic structure and connectivity of the populations in these spaces. Field sampling resulted in the discovery of both B. pensylvanicus and B. fraternus in Denton County's urban green spaces. While the relative abundance of B. fraternus in these spaces was significantly lower than historic levels gleaned from museum recors, that of B. pensylvanicus was significantly higher. Statistical analyses found that both bare ground and tree cover surrounding sample sites were negatively associated with numbers of bumble bee individuals and hives detected in these green spaces. Additionally, limited genetic structuring of bumble bee populations was detected, leading to the conclusion that extensive gene flow is occurring across populations in Denton County.</p>Biodiversity and Genetic Structure of Benthic Macroinvertebrates Along an Altitudinal Gradient: A Comparison of the Windhond and Róbalo River Communities on Navarino Island, Chile2016-06-28T16:28:55-05:00https://digital.library.unt.edu/ark:/67531/metadc849782/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc849782/"><img alt="Biodiversity and Genetic Structure of Benthic Macroinvertebrates Along an Altitudinal Gradient: A Comparison of the Windhond and Róbalo River Communities on Navarino Island, Chile" title="Biodiversity and Genetic Structure of Benthic Macroinvertebrates Along an Altitudinal Gradient: A Comparison of the Windhond and Róbalo River Communities on Navarino Island, Chile" src="https://digital.library.unt.edu/ark:/67531/metadc849782/small/"/></a></p><p>Altitudinal gradients in Sub-Antarctic freshwater systems present unique opportunities to study the effect of distinct environmental gradients on benthic macroinvertebrate community composition and dispersal. This study investigates patterns in biodiversity, dispersal and population genetic structure of benthic macroinvertebrate fauna across an altitudinal gradient between two watersheds on Navarino Island in southern Chile. Patterns in diversity, density, evenness and functional feeding groups were not significantly different across the altitudinal gradient in both the Windhond and Róbalo Rivers. Taxa richness in both rivers generally increased from the headwaters of the river to the mouth, and functional feeding group patterns were consistent with the predictions of the River Continuum Concept.
Population genetic structure and gene flow was investigated by sampling the mitochondrial cytochrome oxidase I gene in two invertebrate species with different dispersal strategies. Hyalella simplex (Amphipoda) is an obligate aquatic species, and Meridialaris chiloeense (Ephemeroptera) is an aquatic larvae and a terrestrial winged adult. Contrasting patterns of population genetic structure were observed. Results for Hyalella simplex indicate significant differentiation in genetic structure in the Amphipod populations between watersheds and lower genetic diversity in the Róbalo River samples, which may be a result of instream dispersal barriers. Meridialaris chiloeense exhibited weak population structure but higher genetic diversity, which suggests this species is able to disperse widely as a winged adult.</p>Informing Conservation Management Using Genetic Approaches: Greater Sage-Grouse and Galápagos Short-Eared Owls as Case Studies2016-06-28T16:28:55-05:00https://digital.library.unt.edu/ark:/67531/metadc849663/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc849663/"><img alt="Informing Conservation Management Using Genetic Approaches: Greater Sage-Grouse and Galápagos Short-Eared Owls as Case Studies" title="Informing Conservation Management Using Genetic Approaches: Greater Sage-Grouse and Galápagos Short-Eared Owls as Case Studies" src="https://digital.library.unt.edu/ark:/67531/metadc849663/small/"/></a></p><p>Small isolated populations are of particular conservation interest due to their increased extinction risk. This dissertation investigates two small wild bird populations using genetic approaches to inform their conservation. Specifically, one case study investigated a Greater Sage-grouse (Centrocercus urophasianus) population located in northwest Wyoming near Jackson Hole and Grand Teton National Park. Microsatellite data showed that the Jackson sage-grouse population possessed significantly reduced levels of neutral genetic diversity and was isolated from other Wyoming populations. Analysis with single nucleotide polymorphisms (SNPs) and microsatellite data provided further evidence that the population's timing of isolation was relatively recent and most likely due to recent anthropogenic habitat changes. Conservation recommendations include maintaining or increasing the population's current size and reestablishing gene flow with the nearest large population. The second case study investigated the genetic distinctiveness of the Floreana island population of the Galápagos Short-eared Owl (Asio flammeus galapagoensis). Mitochondrial DNA sequence data did not detect differences across nine island populations, yet microsatellite and morphometric data indicated that limited gene flow existed with the population and surrounding island populations, which appeared asymmetric in direction from Floreana to Santa Cruz with no indication of gene flow into Floreana. These results have important conservation implications and recommend that the Floreana Short-eared Owl population be held in captivity during the rodenticide application planned for an ecosystem restoration project in 2018. The population is less likely to receive immigrants from surrounding island populations if negatively effected by feeding on poisoned rodents.</p>The Effects of Neonicotinoid Exposure on Embryonic Development and Organ Mass in Northern Bobwhite Quail2016-06-28T16:28:55-05:00https://digital.library.unt.edu/ark:/67531/metadc849707/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc849707/"><img alt="The Effects of Neonicotinoid Exposure on Embryonic Development and Organ Mass in Northern Bobwhite Quail" title="The Effects of Neonicotinoid Exposure on Embryonic Development and Organ Mass in Northern Bobwhite Quail" src="https://digital.library.unt.edu/ark:/67531/metadc849707/small/"/></a></p><p>Since their emergence in the early 1990s, neonicotinoid use has increased exponentially to make them the world's most prevalent insecticides. Although there is considerable research concerning the lethality of neonicotinoids, their sub-lethal and developmental effects are still being explored, especially with regards to non-mammalian species. The goal of this research was to investigate the effects of the neonicotinoid imidacloprid on the morphological and physiological development of northern bobwhite quail (Colinus virginianus). Bobwhite eggs (n = 650) were injected with imidacloprid concentrations of 0 (sham), 10, 50, 100 and 150 grams per kilogram of egg mass, which was administered at day 0 (pre-incubation), 3, 6, 9, or 12 of growth. Embryos were dissected on day 19 when they were weighed, staged, and examined for any overt structural deformities. Embryonic heart, liver, lungs and kidneys were also weighed and preserved for future use. Treated embryos exhibited increased frequency of severely deformed beaks and legs, as well as larger hearts and smaller lungs at the higher dosing concentrations. Some impacts are more pronounced in specific dosing periods, implying that there may be critical windows of development when embryos are highly susceptible to neonicotinoid exposure. This investigation suggests that imidacloprid could play a significant role in chick survival and declining quail populations in treated regions of the country.</p>Spatially Explicit Modeling of West Nile Virus Risk Using Environmental Data2016-03-20T10:34:12-05:00https://digital.library.unt.edu/ark:/67531/metadc822841/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc822841/"><img alt="Spatially Explicit Modeling of West Nile Virus Risk Using Environmental Data" title="Spatially Explicit Modeling of West Nile Virus Risk Using Environmental Data" src="https://digital.library.unt.edu/ark:/67531/metadc822841/small/"/></a></p><p>West Nile virus (WNV) is an emerging infectious disease that has widespread implications for public health practitioners across the world. Within a few years of its arrival in the United States the virus had spread across the North American continent. This research focuses on the development of a spatially explicit GIS-based predictive epidemiological model based on suitable environmental factors. We examined eleven commonly mapped environmental factors using both ordinary least squares regression (OLS) and geographically weighted regression (GWR). The GWR model was utilized to ascertain the impact of environmental factors on WNV risk patterns without the confounding effects of spatial non-stationarity that exist between place and health. It identifies the important underlying environmental factors related to suitable mosquito habitat conditions to make meaningful and spatially explicit predictions. Our model represents a multi-criteria decision analysis approach to create disease risk maps under data sparse situations. The best fitting model with an adjusted R2 of 0.71 revealed a strong association between WNV infection risk and a subset of environmental risk factors including road density, stream density, and land surface temperature. This research also postulates that understanding the underlying place characteristics and population composition for the occurrence of WNV infection is important for mitigating future outbreaks. While many spatial and aspatial models have attempted to predict the risk of WNV transmission, efforts to link these factors within a GIS framework are limited. One of the major challenges for such integration is the high dimensionality and large volumes typically associated with such models and data. This research uses a spatially explicit, multivariate geovisualization framework to integrate an environmental model of mosquito habitat with human risk factors derived from socio-economic and demographic variables. Our results show that such an integrated approach facilitates the exploratory analysis of complex data and supports reasoning about the underlying spatial processes that result in differential risks for WNV. This research provides different tools and techniques for predicting the WNV epidemic and provides more insights into targeting specific areas for controlling WNV outbreaks.</p>Photoinduced Toxicity in Early Lifestage Fiddler Crab (Uca longisignalis) Following Exposure to Deepwater Horizon Spill Oil2016-03-20T10:34:12-05:00https://digital.library.unt.edu/ark:/67531/metadc822799/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc822799/"><img alt="Photoinduced Toxicity in Early Lifestage Fiddler Crab (Uca longisignalis) Following Exposure to Deepwater Horizon Spill Oil" title="Photoinduced Toxicity in Early Lifestage Fiddler Crab (Uca longisignalis) Following Exposure to Deepwater Horizon Spill Oil" src="https://digital.library.unt.edu/ark:/67531/metadc822799/small/"/></a></p><p>The 2010 Deepwater Horizon (DWH) oil spill resulted in a large release of polycyclic aromatic hydrocarbons (PAH) into the Gulf of Mexico. PAH can interact with ultraviolet radiation (UV) resulting in increased toxicity, particularly to early lifestage organisms. The goal of this research was to determine the sensitivity of fiddler crab larvae (Uca longisignalis) to photo-induced toxicity following exposure to Deepwater Horizon spill oil in support of the DWH Natural Resource Damage Assessment. Five replicate dishes each containing 20 larvae, were exposed to one of three UV treatments (10%, 50%, and 100% ambient natural sunlight) and one of five dilutions of water accommodated fractions of two naturally weathered source oils. A dose dependent effect of PAH and UV on larval mortality was observed. Mortality was markedly higher in PAH treatments that included co-exposure to more intense UV light. PAH treatments under low intensity sunlight had relatively high survival. These data demonstrate the importance of considering combined effects of non-chemical (i.e. UV exposure) and chemical stressors and the potential for photo-induced effects after exposure to PAH following the Deepwater Horizon spill.</p>Photo-induced Toxicity of Deepwater Horizon Spill Oil to Four Native Gulf of Mexico Species2016-03-20T10:34:12-05:00https://digital.library.unt.edu/ark:/67531/metadc822778/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc822778/"><img alt="Photo-induced Toxicity of Deepwater Horizon Spill Oil to Four Native Gulf of Mexico Species" title="Photo-induced Toxicity of Deepwater Horizon Spill Oil to Four Native Gulf of Mexico Species" src="https://digital.library.unt.edu/ark:/67531/metadc822778/small/"/></a></p><p>The 2010 Deepwater Horizon oil spill resulted in the accidental release of millions of barrels of crude oil into the Gulf of Mexico (GoM). Photo-induced toxicity following co-exposure to ultraviolet (UV) radiation is one mechanism by which polycyclic aromatic hydrocarbons (PAHs) from oil spills may exert toxicity. Blue crab (Callinectes sapidus) are an important commercial and ecological resource in the Gulf of Mexico and their largely transparent larvae may make them sensitive to PAH photo-induced toxicity. Mahi-mahi (Coryphaena hippurus), an important fishery resource, have positively buoyant, transparent eggs. These characteristics may result in mahi-mahi embryos being at particular risk from photo-induced toxicity. Red drum (Sciaenops ocellatus) and speckled seatrout (Cynoscion nebulosus) are both important fishery resources in the GoM. They spawn near-shore and produce positively buoyant embryos that hatch into larvae in about 24 h. The goal of this body of work was to determine whether exposure to UV as natural sunlight enhances the toxicity of crude oil to early lifestage GoM species. Larval and embryonic organisms were exposed to several dilutions of water accommodated fractions (WAF) from several different oils collected in the field under chain of custody during the 2010 spill and two to three gradations of natural sunlight in a factorial design. Here, we report that co-exposure to natural sunlight and oil significantly reduced larval survival and embryo hatch compared to exposure to oil alone.</p>Effects of Macrophyte Functional Diversity on Taxonomic and Functional Diversity and Stability of Tropical Floodplain Fish Assemblages2016-03-04T16:14:01-06:00https://digital.library.unt.edu/ark:/67531/metadc804900/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc804900/"><img alt="Effects of Macrophyte Functional Diversity on Taxonomic and Functional Diversity and Stability of Tropical Floodplain Fish Assemblages" title="Effects of Macrophyte Functional Diversity on Taxonomic and Functional Diversity and Stability of Tropical Floodplain Fish Assemblages" src="https://digital.library.unt.edu/ark:/67531/metadc804900/small/"/></a></p><p>Multiple dimensions of biodiversity within and across producer and consumer guilds in the food web affect an ecosystem’s functionality and stability. Tropical and subtropical aquatic ecosystems, which are extremely diverse, have received much less attention than terrestrial ecosystems in regards to the effects of biodiversity on ecosystem functioning. We conducted a field experiment that tested for effects of macrophyte functional diversity on diversity and stability of associated fish assemblages in floodplain lakes of the Upper Paraná River floodplain, Brazil. Three levels of macrophyte functional diversity were maintained through time in five floodplain lakes and response variables included various components of fish taxonomic and functional diversity and stability. Components of functional diversity of fish assemblages were quantified using a suite of ecomorphological traits that relate to foraging and habitat use. Response variables primarily distinguished macrophyte treatments from the control. Macrophyte treatments had, on average, double the number of species and total abundance than the control treatment, but only limited effects on stability. The high diversity treatment was essentially nested within the low diversity for assemblage structure and had similar or even slightly lower levels of species richness and abundance in most cases. Gymnotiformes and young-of-year were diverse and relatively abundant in macrophyte treatments contributing to the large differences in diversity between macrophyte and control treatments. Higher fish diversity in structured habitats compared to more homogenous habitats is likely associated with increased ecomorphological diversity to exploit heterogeneous microhabitats and resources provided by the macrophytes.</p>Dynamics of Stream Fish Metacommunities in Response to Drought and Re-connectivity2016-03-04T16:14:01-06:00https://digital.library.unt.edu/ark:/67531/metadc804923/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc804923/"><img alt="Dynamics of Stream Fish Metacommunities in Response to Drought and Re-connectivity" title="Dynamics of Stream Fish Metacommunities in Response to Drought and Re-connectivity" src="https://digital.library.unt.edu/ark:/67531/metadc804923/small/"/></a></p><p>This dissertation investigates the spatio-temporal dynamics of intermittent stream fish metacommunities in response drought-induced fragmentation and re-connectivity using both field and experimental approaches. A detailed field study was conducted in two streams and included pre-drought, drought, and post-drought hydrological periods. Fish assemblages and metacommunity structure responded strongly to changes in hydrological conditions with dramatic declines in species richness and abundance during prolonged drought. Return of stream flows resulted in a trend toward recovery but ultimately assemblages failed to fully recover. Differential mortality, dispersal, recruitment among species indicates species specific responses to hydrologic fragmentation, connectivity, and habitat refugia. Two manipulative experiments tested the effects of drought conditions on realistic fish assemblages. Fishes responded strongly to drought conditions in which deeper pools acted as refugia, harboring greater numbers of fish. Variability in assemblage structure and movement patterns among stream pools indicated species specific habitat preferences in response predation, resource competition, and desiccation. Connecting stream flows mediated the impacts of drought conditions and metacommunity dynamics in both experiments. Results from field and experimental studies indicate that stream fish metacommunities are influenced by changes in hydrological conditions and that the timing, duration, and magnitude of drought-induced fragmentation and reconnecting stream flows have important consequences metacommunity dynamics.</p>Developing a Forest Gap Model to Be Applied to a Watershed-scaled Landscape in the Cross Timbers Ecoregion Using a Topographic Wetness Index2015-08-21T05:42:39-05:00https://digital.library.unt.edu/ark:/67531/metadc700050/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc700050/"><img alt="Developing a Forest Gap Model to Be Applied to a Watershed-scaled Landscape in the Cross Timbers Ecoregion Using a Topographic Wetness Index" title="Developing a Forest Gap Model to Be Applied to a Watershed-scaled Landscape in the Cross Timbers Ecoregion Using a Topographic Wetness Index" src="https://digital.library.unt.edu/ark:/67531/metadc700050/small/"/></a></p><p>A method was developed for extending a fine-scaled forest gap model to a watershed-scaled landscape, using the Eastern Cross Timbers ecoregion as a case study for the method. A topographic wetness index calculated from digital elevation data was used as a measure of hydrologic across the modeled landscape, and the gap model modified to have with a topographically-based hydrologic input parameter. The model was parameterized by terrain type units that were defined using combinations of USDA soil series and classes of the topographic wetness index. A number of issues regarding the sources, grid resolutions, and processing methods of the digital elevation data are addressed in this application of the topographic wetness index. Three different grid sizes, 5, 10, and 29 meter, from both LiDAR-derived and contour-derived elevation grids were used, and the grids were processed using both single-directional flow algorithm and bi-directional flow algorithm. The result of these different grids were compared and analyzed in context of their application in defining terrain types for the forest gap model. Refinements were made in the timescale of gap model’s weather model, converting it into a daily weather generator, in order to incorporate the effects of the new topographic/hydrologic input parameter. The precipitation model was converted to use a Markov model to initiate a sequence of wet and dry days for each month, and then daily precipitation amounts were determined using a gamma distribution. The output of the new precipitation model was analyzed and compared with a 100-year history of daily weather records at daily, monthly, and annual timescales. Model assumptions and requirements for biological parameters were thoroughly investigated and questioned. Often these biological parameters are based on little more than assumptions and intuition. An effort to base as many of the model’s biological parameters on measured data was made, including a new technique for estimating optimal volumetric growth rate by measuring tree rings. The gap model was set up to simulate various terrain types within the landscape.</p>The Role of Rainfed Farm Ponds in Sustaining Agriculture and Soil Conservation in the Dry High Valley Region of Cochabamba, Bolivia: Design Considerations and Post Impoundment Analysis2015-03-09T08:15:06-05:00https://digital.library.unt.edu/ark:/67531/metadc501015/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc501015/"><img alt="The Role of Rainfed Farm Ponds in Sustaining Agriculture and Soil Conservation in the Dry High Valley Region of Cochabamba, Bolivia: Design Considerations and Post Impoundment Analysis" title="The Role of Rainfed Farm Ponds in Sustaining Agriculture and Soil Conservation in the Dry High Valley Region of Cochabamba, Bolivia: Design Considerations and Post Impoundment Analysis" src="https://digital.library.unt.edu/ark:/67531/metadc501015/small/"/></a></p><p>Lack of sufficient water for irrigation is a major problem in and around the valleys surrounding the town of Aiquile, Cochabamba Bolivia. In addition, much of the region is undergoing desertification compounded by drought, deforestation, bad traditional agricultural practices, over grazing and a "torrential" rainfall pattern leading to severe soil erosion and low agricultural production. Between 1992 and 1994, the author constructed a network of 24 small, mostly rainfed farm ponds to increase agricultural production and alleviate soil erosion and land-use problems by improving cover conditions. A 5-year post-impoundment analysis was carried out in 1998. The analysis examined current pond conditions, design criteria, irrigation water / crop production increases and the alleviation of land-use problems. Current pond conditions fell into four distinct categories with only 25 percent of the ponds being deemed as "functioning well." The project increased irrigation in the region and improved cover conditions in 66 percent of the pond sites.</p>Estimated Extent and Fate of Chlorinated Solvent Contamination in the Soil of the Naval Air Station, Dallas, Texas2015-03-09T08:15:06-05:00https://digital.library.unt.edu/ark:/67531/metadc500858/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc500858/"><img alt="Estimated Extent and Fate of Chlorinated Solvent Contamination in the Soil of the Naval Air Station, Dallas, Texas" title="Estimated Extent and Fate of Chlorinated Solvent Contamination in the Soil of the Naval Air Station, Dallas, Texas" src="https://digital.library.unt.edu/ark:/67531/metadc500858/small/"/></a></p><p>This thesis estimates the spatial extent of chlorinated solvent contamination of the soil at the Naval Air Station, Dallas, then estimates the fate and transport of these contaminants, over time, using the Soil Transport and Fate database and the Vadose-Zone Interactive Processes (VIP) modeling software. Geostatistical analysis identifies two areas with serious chlorinated solvent contamination. Fate and transport modeling estimates that this contamination will degrade and disperse from the soil phase to below regulatory limits within one year, although there is a risk of groundwater contamination. Contaminants are estimated to persist in the water and air phases of the soil. Further sampling is recommended to confirm the results of this study.</p>Tissue-specific Bioconcentration Factor of the Synthetic Steroid Hormone Medroxyprogesterone Acetate (Mpa) in the Common Carp, Cyprinus Carpia2015-03-08T17:44:37-05:00https://digital.library.unt.edu/ark:/67531/metadc500141/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc500141/"><img alt="Tissue-specific Bioconcentration Factor of the Synthetic Steroid Hormone Medroxyprogesterone Acetate (Mpa) in the Common Carp, Cyprinus Carpia" title="Tissue-specific Bioconcentration Factor of the Synthetic Steroid Hormone Medroxyprogesterone Acetate (Mpa) in the Common Carp, Cyprinus Carpia" src="https://digital.library.unt.edu/ark:/67531/metadc500141/small/"/></a></p><p>Due to the wide spread occurrence of medroxyprogesterone acetate (MPA), a pharmaceutical compound, in wastewater effluent and surface waters, the objectives of this work were to determine the tissue specific uptake and bioconcentration factor (BCF) for MPA in common carp. BCFs were experimentally determined for MPA in fish using a 14-day laboratory test whereby carp where exposed to 100 μg/L of MPA for a 7-day period followed by a depuration phase in which fish were maintained in dechlorinated tap water for an additional 7 days. MPA concentrations in muscle, brain, liver and plasma were determined by liquid chromatography/mass spectrometry (LC/MS). The results from the experiment indicate that MPA can accumulate in fish, however, MPA is not considered to be bioaccumulative based on regulatory standards (BCF ≥ 1000). Although MPA has a low BCF value in common carp, this compound may cause reproductive effects in fish at environmentally relevant concentrations.</p>The Effect of Natural Gas Well Setback Distance on Drillable Land in the City of Denton, Texas2015-03-08T17:44:37-05:00https://digital.library.unt.edu/ark:/67531/metadc499998/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc499998/"><img alt="The Effect of Natural Gas Well Setback Distance on Drillable Land in the City of Denton, Texas" title="The Effect of Natural Gas Well Setback Distance on Drillable Land in the City of Denton, Texas" src="https://digital.library.unt.edu/ark:/67531/metadc499998/small/"/></a></p><p>Municipalities protect human health and environmental resources from impacts of urban natural gas drilling through setback distances; the regulation of distances between well sites and residences, freshwater wells, and other protected uses. Setback distances have increased over time, having the potential to alter the amount and geographical distribution of drillable land within a municipality, thereby having implications for future land use planning and increasing the potential for future incompatible land uses. This study geographically applies a range of setback distances to protected uses and freshwater wells in the city limits of Denton, Texas to investigate the effect on the amount of land remaining for future gas well development and production. Denton lies on the edge of a productive region of the Barnett Shale geological formation, coinciding with a large concentration of drillable land in the southwestern region of the study area. This region will have the greatest potential for impacts to future municipal development and land use planning as a result of future gas well development and higher setback standards. Given the relatively high acreage of drillable land in industrially zoned subcategory IC-G and the concern regarding gas well drilling in more populated areas, future drilling in IC-G, specifically in IC-G land cover classes mowed/grazed/agriculture and herbaceous, would have the least impact on residential uses and tree cover, as well as decreasing the potential for future incompatible land uses.</p>Macroinvertebrate Colonization and Assemblages Associated with Aquatic Macrophytes in a Newly Created Urban Floodway Ecosystem, Dallas, Tx2015-03-08T17:44:37-05:00https://digital.library.unt.edu/ark:/67531/metadc500077/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc500077/"><img alt="Macroinvertebrate Colonization and Assemblages Associated with Aquatic Macrophytes in a Newly Created Urban Floodway Ecosystem, Dallas, Tx" title="Macroinvertebrate Colonization and Assemblages Associated with Aquatic Macrophytes in a Newly Created Urban Floodway Ecosystem, Dallas, Tx" src="https://digital.library.unt.edu/ark:/67531/metadc500077/small/"/></a></p><p>A study of macroinvertebrate colonization and assemblages, including secondary productivity of the familiar bluet damselfly or Enallagma civile Hagen (Odonata: Coenagrionidae), associated with the aquatic macrophytes Heteranthera dubia (Jacq.) MacMill. (water stargrass) and Potamogeton nodosus Poir. (American pondweed) was conducted at the Dallas Floodway Extension Trinity River Project (DFE) Lower Chain of Wetlands (LCOW), Dallas, TX, from September 2010 through November 2011. Macroinvertebrate abundance, taxa richness, Simpson's index of diversity, and Simpson's evenness from the two macrophytes and from three different wetland cells of varying construction completion dates, water sources, and native aquatic vegetation establishment were analyzed along with basic water quality metrics (temperature °C, pH, dissolved oxygen mg/L, and conductivity µs/cm). E. civile nymphs were separated into five developmental classes for secondary productivity estimations between macrophytes and wetland cell types. Mean annual secondary productivity in the DFE LCOW among two macrophytes of E. civile was 1392.90 ash-free dry weight mg/m²/yr, standing stock biomass was 136.77 AFDW mg/m2/yr, cohort production / biomass (P/B) ratio was calculated to be 4.30 / yr and the annual production / biomass (P/B) ratio was 10.18 /yr.</p>Population Dynamics of Zebra Mussels (Dreissena Polymorpha) in a North Texas Reservoir: Implications for Invasions in the Southern United States2014-11-08T11:56:31-06:00https://digital.library.unt.edu/ark:/67531/metadc407755/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc407755/"><img alt="Population Dynamics of Zebra Mussels (Dreissena Polymorpha) in a North Texas Reservoir: Implications for Invasions in the Southern United States" title="Population Dynamics of Zebra Mussels (Dreissena Polymorpha) in a North Texas Reservoir: Implications for Invasions in the Southern United States" src="https://digital.library.unt.edu/ark:/67531/metadc407755/small/"/></a></p><p>This dissertation has two main objectives: first, quantify the effects of environmental conditions on spatio-temporal spawning and larval dynamics of zebra mussels (Dreissena polymorpha [Pallas 1771]) in Lake Texoma, and second, quantify the effects of environmental conditions on survival, growth, and reproduction of young of the year (YOY) juvenile zebra mussels. These biological responses directly influence population establishment success and invasive spread dynamics. Reproductive output of the zebra mussel population in Lake Texoma was significantly related to water temperature and lake elevation. Annual maximum larval (veliger) density decreased significantly indicating a population crash, which was likely caused by thermal stress and variability of lake elevation. In 2011, temperatures peaked at 34.3°C and lake elevation decreased to the lowest level recorded during the previous 18 years, which desiccated a substantial number of settled mussels in littoral zones. Estimated mean date of first spawn in Lake Texoma was observed approximately 1.5 months earlier than in Lake Erie, and peak veliger densities were observed two months earlier. Veligers were observed in the deepest oxygenated water after lake stratification. During a 69-day in situ experiment during summer in Lake Texoma, age-specific mortality of zebra mussels was generally high until temperatures decreased to approximately 28°C, which was observed after lake turnover in late summer. No study organism died after temperatures decreased to less than 26°C, which indicates individuals that survive high summer temperatures are likely to persist into autumn/winter. Shell length growth and soft tissue growth rates were related to temperature and chlorophyll-a concentration, respectively. Growth rates of study organisms were among the highest ever reported for D. polymorpha. Water temperature and body size influenced reproduction of YOY zebra mussels in Lake Texoma. Fecundity of females were positively related to temperature; however, sperm production was negatively related to temperature, which indicates males could be more sensitive to physiologically-stressful conditions than females and could perform better in cooler waters. YOY mussels spawned up to approximately 40,000 eggs and 3.47E+08 sperm after a single-summer growing season. Reproductive effort and reproductive mass were independent of sex. YOY individuals from each study site (n = 5) were able to spawn viable gametes capable of sperm binding and egg cleavage, which provides the first evidence that YOY zebra mussels can successfully reproduce. Individual mortality of zebra mussels will likely be high in warm waters and intermittent, extreme droughts, which are observed more frequently at lower latitudes, can significantly reduce population sizes. However, rapid growth and single-season maturation can decrease generation times and could facilitate establishment and spread of zebra mussels in warm-water environments in the southern United States.</p>Modeling the Effects of Chronic Toxicity of Pharmaceutical Chemicals on the Life History Strategies of Ceriodaphnia Dubia: a Multigenerational Study2014-11-08T11:56:31-06:00https://digital.library.unt.edu/ark:/67531/metadc407771/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc407771/"><img alt="Modeling the Effects of Chronic Toxicity of Pharmaceutical Chemicals on the Life History Strategies of Ceriodaphnia Dubia: a Multigenerational Study" title="Modeling the Effects of Chronic Toxicity of Pharmaceutical Chemicals on the Life History Strategies of Ceriodaphnia Dubia: a Multigenerational Study" src="https://digital.library.unt.edu/ark:/67531/metadc407771/small/"/></a></p><p>Trace quantities of pharmaceuticals (including carbamazepine and sertraline) are continuously discharged into the environment, which causes concern among scientists and regulators regarding their potential long-term impacts on aquatic ecosystems. These compounds and their metabolites are continuously interacting with the orgranisms in various life stages, and may differentially influence development of embryo, larvae, juvenile, and adult stages. To fully understand the potential ecological risks of two candidate pharmaceutical chemicals (carbamazepine (CBZ) and sertraline (SERT)) exposure on survival, growth and reproduction of Ceriodaphnia dubia in three sucessive generations under static renewal toxicity test, a multigenerational approach was taken. Results indicate that SERT exposure showed higher sensitivity to chronic exposure to C. dubia growth and reproduction than CBZ exposure. The lowest concentration to affect fecundity and growth was at 50 µg L-1 SERT in the first two generations. These parameters become more sensitive during the third generation where the LOEC was 4.8 µg L-1. The effective concentrations (EC50) for the number of offspring per female, offspring body size, and dry weight were 17.2, 21.2, and 26.2 µg SERT L-1, respectively. Endpoints measured in this study demonstrate that chronic exposure of C. dubia to SERT leads to effects that occur at concentrations an order of magnitude higher than predicted environmental concentrations indicating potential transgenerationals effects. Additionally, a process-based dynamic energy budget (DEB) model is implemented to predict the simulated effects of chronic toxicity of SERT and CBZ to C. dubia individual behavior at laboratory condition. The model‘s output indicates the ecotoxicological mode of action of SERT exposure, which acts on feeding or assimilation with an effect that rapidly saturates at higher concentrations. Offspring size decreases with the toxic effects on feeding, and offspring number is thus less affected than total investment in reproduction. Consequently, CBZ affects direclty in reproduction which are captured by DEBtox model as increased embryonic hazard and reproduction cost as well as growth and maintenance costs. Furthermore, stress factor linearly increased not only with increasing chemical concentrations but also with exposure time. The DEBtox model establishes a cumulative life history consequence of multigenerational exposure to CBZ and SERT. This approach provides a tool to which to understand the effect of chemical to the individual organism and predict the population level effects in ecological risk assessment of the emerging contaminants.</p>Assessing Regional Gully Erosion Risk: A Remote Sensing and Geographic Information Systems Approach2014-08-27T07:42:59-05:00https://digital.library.unt.edu/ark:/67531/metadc332453/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332453/"><img alt="Assessing Regional Gully Erosion Risk: A Remote Sensing and Geographic Information Systems Approach" title="Assessing Regional Gully Erosion Risk: A Remote Sensing and Geographic Information Systems Approach" src="https://digital.library.unt.edu/ark:/67531/metadc332453/small/"/></a></p><p>Gully erosion has been established as a major source of sediment pollution in the upper Trinity River watershed in north-central Texas. This fact, along with a lack of models appropriate for a large-area gully erosion analysis established a need for a gully erosion study in the upper Trinity basin. This thesis project attempted to address this need by deriving an index indicative of gully erosion risk using remote sensing and geographic information systems (GIS) methodology. In context of previous field studies, the coarse spatial resolution of the input GIS data layers presented a challenge to prediction of gully prone areas. However, the remote sensing/GIS approach was found to provide useful reconnaissance information on gully risk over large areas.</p>The Tarrant County Atlas for Planning: A Geographic Information System for Open Space Design2014-08-27T07:42:59-05:00https://digital.library.unt.edu/ark:/67531/metadc332537/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332537/"><img alt="The Tarrant County Atlas for Planning: A Geographic Information System for Open Space Design" title="The Tarrant County Atlas for Planning: A Geographic Information System for Open Space Design" src="https://digital.library.unt.edu/ark:/67531/metadc332537/small/"/></a></p><p>This project demonstrates the construction of a land planning geographic information system (GIS) for Tarrant County, and explores how the technology could be used to select sites for a county wide open space preservation plan. As Texas' Tarrant County continues to undergo rapid change due to growth and expansion, the need for proactive, resourceful community planning is greater than ever. One crucial issue facing the region is how to preserve open areas that serve the county's citizens' ecological, recreational, cultural and economic needs. In order to assess how much open space is needed and which sites should be considered for special attention, large amounts of varied spatial information must be analyzed. The answer to effectively dealing with such data sets is a geographic information system (GIS) that stores all pertinent data digitally and allows for its manipulation through use of a computer software package. This project demonstrates the construction of a land planning GIS for Tarrant County, and explores how the technology could be used to select sites for a county wide open space preservation plan.</p>Comparative Phyto-uptake Across Distribution Coefficients of Pharmaceutical Compounds and Aquatic Macrophytes: Carbamazepine and Amiodarone Uptake in Lemna Spp2014-04-23T20:20:45-05:00https://digital.library.unt.edu/ark:/67531/metadc283798/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc283798/"><img alt="Comparative Phyto-uptake Across Distribution Coefficients of Pharmaceutical Compounds and Aquatic Macrophytes: Carbamazepine and Amiodarone Uptake in Lemna Spp" title="Comparative Phyto-uptake Across Distribution Coefficients of Pharmaceutical Compounds and Aquatic Macrophytes: Carbamazepine and Amiodarone Uptake in Lemna Spp" src="https://digital.library.unt.edu/ark:/67531/metadc283798/small/"/></a></p><p>Few studies have been conducted on the effectiveness of phytoremediation of pharmaceutical compounds, although the persistent and non-acutely toxic nature of many of these compounds in today's water bodies may yield an ideal application for this practice. To quantify the potential effectiveness of plant uptake, kinetic and proportional bioconcentration factors (BCFk, and BCFp, respectively) in nanograms (ng) carbamazepine and amiodarone per gram (g) wet weight plant tissue for Lemna spp. were determined utilizing a 14-day continuous flow-through study. Samples were analyzed using isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) running in positive ion mode. Kinetic BCF was estimated at 0.538, while proportional BCF was estimated at 0.485. Kinetic BCF for the amiodarone study was estimated at 23.033, whereas proportional BCF was estimated at 41.340. Possible contamination of the C18 column and peristaltic pump failure may have impacted uptake results. In light of variability and current lack of research in the field, this work should be considered exploratory rather than conclusive.</p>Quantifying Forest Vertical Structure to Determine Bird Habitat Quality in the Greenbelt Corridor, Denton, Tx2014-04-23T20:20:45-05:00https://digital.library.unt.edu/ark:/67531/metadc283803/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc283803/"><img alt="Quantifying Forest Vertical Structure to Determine Bird Habitat Quality in the Greenbelt Corridor, Denton, Tx" title="Quantifying Forest Vertical Structure to Determine Bird Habitat Quality in the Greenbelt Corridor, Denton, Tx" src="https://digital.library.unt.edu/ark:/67531/metadc283803/small/"/></a></p><p>This study presents the integration of light detection and range (LiDAR) and hyperspectral remote sensing to create a three-dimensional bird habitat map in the Greenbelt Corridor of the Elm Fork of the Trinity River. This map permits to examine the relationship between forest stand structure, landscape heterogeneity, and bird community composition. A biannual bird census was conducted at this site during the breeding seasons of 2009 and 2010. Census data combined with the three-dimensional map suggest that local breeding bird abundance, community structure, and spatial distribution patterns are highly influenced by vertical heterogeneity of vegetation surface. For local breeding birds, vertical heterogeneity of canopy surface within stands, connectivity to adjacent forest patches, largest forest patch index, and habitat (vegetation) types proved to be the most influential factors to determine bird community assemblages. Results also highlight the critical role of secondary forests to increase functional connectivity of forest patches. Overall, three-dimensional habitat descriptions derived from integrated LiDAR and hyperspectral data serve as a powerful bird conservation tool that shows how the distribution of bird species relates to forest composition and structure at various scales.</p>Simulating Thermal and Chemical Spills in Coupled Cooling Reservoirs2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279271/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279271/"><img alt="Simulating Thermal and Chemical Spills in Coupled Cooling Reservoirs" title="Simulating Thermal and Chemical Spills in Coupled Cooling Reservoirs" src="https://digital.library.unt.edu/ark:/67531/metadc279271/small/"/></a></p><p>Hot water discharges and potential chemical spills are factors that threaten water
quality in cooling reservoirs of chemical and power plants. In this thesis, three models are used to analyze the impact of these factors in a particular case study.</p>A Laboratory Study of the Asiatic Clam (Corbicula fluminea Müller) as Influenced by Substrate, Food Source and Water Type2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279067/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279067/"><img alt="A Laboratory Study of the Asiatic Clam (Corbicula fluminea Müller) as Influenced by Substrate, Food Source and Water Type" title="A Laboratory Study of the Asiatic Clam (Corbicula fluminea Müller) as Influenced by Substrate, Food Source and Water Type" src="https://digital.library.unt.edu/ark:/67531/metadc279067/small/"/></a></p><p>Growth of Corbicula fluminea was monitored in the laboratory. Three experiments were conducted. Experiment I utilized three substrates and one food type. Experiment II utilized three substrates and two food types. Experiments I and II were conducted to determine if substrate type or food type effected growth. Experiment III used no substrates, one food type and was conducted to determine growth response to different types of water. Clams were maintained in three substrates: sand, gravel and clay. Clams were also maintained without substrate. Growth was monitored by measuring shell length (mm) and recording the weight (mg) of clams over a period of thirty days. At the end of the test period data were evaluated for normality and homogeneity.</p>