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open access

Adaptive Advantages of Carotenoid Pigments in Alpine and Subalpine Copepod Responses to Polycyclic Aromatic Hydrocarbon Induced Phototoxicity

Description: Alpine zooplankton are exposed to a variety of stressors in their natural environment including ultraviolet radiation. Physiological coping mechanisms such as the accumulation of photoprotective compounds provide these zooplankton protection from many of these stressors. Elevated levels of carotenoid compounds such as astaxanthin have been shown to help zooplankton survive longer when exposed to ultraviolet radiation presumably due to the strong antioxidant properties of carotenoid compounds. T… more
Date: May 2010
Creator: Kovach, Matthew James
Item Type: Refine your search to only Thesis or Dissertation
open access

Effects of Suspended Multi-Walled Carbon Nanotubes on Daphnid Growth and Reproduction

Description: Multi-walled carbon nanotube aggregates can be suspended in the aqueous phase by natural organic matter. These aggregates are ingested by filter feeding zooplankton. Ingested aggregates result in decreased growth and decreased reproduction. These effects may be caused by reduction in energy input from normal feeding behavior. pH alters natural organic matter structure through changes in electrostatic repulsion. Altered natural organic matter structure changes multi-walled carbon nanotube aggreg… more
Date: May 2010
Creator: Alloy, Matthew Michael
Item Type: Refine your search to only Thesis or Dissertation
open access

Role of N-Acylethanolamines in Plant Defense Responses: Modulation by Pathogens and Commercial Antimicrobial Stressors

Description: N-acyl ethanolamines (NAEs) are a class of lipids recently recognized as signaling molecules which are controlled, in part, by their degradation by fatty acid amide hydrolase (FAAH). On the basis of previous studies indicating increased NAE levels in a tobacco cell suspension-xylanase elicitor exposure system and the availability of FAAH mutants, overexpressor and knockout (OE and KO) genotypes in Arabidopsis thaliana, further roles of NAEs in A. thaliana plant defense was investigated. The com… more
Date: August 2010
Creator: Vadapalli, Vatsala
Item Type: Refine your search to only Thesis or Dissertation
open access

Wind Energy-related Wildlife Impacts: Analysis and Potential Implications for Rare, Threatened and Endangered Species of Birds and Bats in Texas

Description: Texas currently maintains the highest installed nameplate capacity and does not require publicly available post-construction monitoring studies that examine the impacts of wind energy production on surrounding fauna. This thesis examines potential wind energy impacts on avian and bat species in Texas through a three-part objective. The first two objectives synthesize literature on variables attractive to species within wind development areas and estimate impacted ranges outside of Texas, based … more
Date: August 2010
Creator: Graham, Tara L.
Item Type: Refine your search to only Thesis or Dissertation
open access

Hepatotoxicity of Mercury to Fish

Description: Tissue samples from spotted gar (Lepisosteus oculatus) and largemouth bass (Micropterus salmoides) were collected from Caddo Lake. Gar and bass livers were subjected to histological investigation and color analysis. Liver color (as abs at 400 nm) was significantly correlated with total mercury in the liver (r2 = 0.57, p = 0.02) and muscle (r2 = 0.58, p = 0.01) of gar. Evidence of liver damage as lipofuscin and discoloration was found in both species but only correlated with liver mercury con… more
Date: August 2010
Creator: Barst, Benjamin Daniel
Item Type: Refine your search to only Thesis or Dissertation
open access

Evaluation of the Developmental Effects and Bioaccumulation Potential of Triclosan and Triclocarban Using the South African Clawed Frog, Xenopus Laevis

Description: Triclosan (TCS) and triclocarban (TCC) are antimicrobials found in U.S. surface waters. This dissertation assessed the effects of TCS and TCC on early development and investigated their potential to bioaccumulate using Xenopus laevis as a model. The effects of TCS on metamorphosis were also investigated. For 0-week tadpoles, LC50 values for TCS and TCC were 0.87 mg/L and 4.22 mg/L, respectively, and both compounds caused a significant stunting of growth. For 4-week tadpoles, the LC50 values… more
Date: December 2010
Creator: King, Marie Kumsher
Item Type: Refine your search to only Thesis or Dissertation
open access

Habitat Fragmentation by Land-Use Change: One-Horned Rhinoceros in Nepal and Red-Cockaded Woodpecker in Texas

Description: This research focuses on the spatial analysis of the habitat of two vulnerable species, the one-horn rhinoceros in the grasslands of southern Nepal, and the red-cockaded woodpecker in the Piney woods of southeast Texas, in the USA. A study sites relevant for biodiversity conservation was selected in each country: Chitwan National Park in Nepal, and areas near the Big Thicket National Preserve in Texas. Land-use differs in the two study areas: the first is still undergoing agrarian development w… more
Date: December 2010
Creator: Thapa, Vivek
Item Type: Refine your search to only Thesis or Dissertation
open access

Reproductive and Growth Responses of the Fathead Minnow (Pimephales Promelas) and Japanese Medaka (Oryzias Latipes) to the Synthetic Progestin, Norethindrone

Description: A commonly prescribed contraceptive, the synthetic progestin norethindrone (NET) inhibits ovulation in humans. However, ecotoxicological data are lacking. Preliminary tests produced an LC50 for NET of > 1.0 mg/L (96-hour, fathead minnow (FHM) and medaka) and a NOEC of 242.0 µg/L, a LOEC of 485.0 µg/L (7-day, growth for FHM and medaka). Reproductive testing revealed a LOEC for fecundity of 24.1 ng/L (21 days, medaka). Further testing confirmed the LOEC of 24.1 ng/L while defining a NOEC of 4.7 n… more
Date: May 2011
Creator: Paulos, Peter M.
Item Type: Refine your search to only Thesis or Dissertation
open access

Characterization of Triclocarban, Methyl- Triclosan, and Triclosan in Water, Sediment, and Corbicula Fluminea (Müller, 1774) Using Laboratory, in Situ, and Field Assessments

Description: In the last decade emerging contaminants research has intensified in a bid to answer questions about fate, transport, and effects as these chemicals as they get released into the environment. The chemicals of interest were the antimicrobials; triclocarban (TCC) and triclosan (TCS), and a metabolite of triclosan, methyl triclosan (MTCS). This research was designed to answer the question: what is the fate of these chemicals once they are released from the waste water treatment plant into receivin… more
Date: May 2011
Creator: Edziyie, Regina E.
Item Type: Refine your search to only Thesis or Dissertation
open access

Soil and Forest Variation by Topography and Succession Stages in the Greenbelt Corridor, Floodplain of the Elm Fork of the Trinity River, North Texas.

Description: The Greenbelt Corridor (GBC), located in a floodplain of the Elm Fork of the Trinity River, contains patches of bottomland forest and serves as part of Lake Lewisville’s flood control backwaters. This study examines forest structure and composition in relation to topographic position and forest stage in the GBC. Thirty two plots were surveyed within various stage classes, topographic positions, and USDA soil types. Trees were identified and measured for height and DBH. Density, basal area, and … more
Date: August 2011
Creator: Rijal, Rajan
Item Type: Refine your search to only Thesis or Dissertation
open access

Bioconcentration of Triclosan, Methyl-Triclosan, and Triclocarban in the Plants and Sediments of a Constructed Wetland

Description: Triclosan and triclocarban are antimicrobial compounds added to a variety of consumer products that are commonly detected in waste water effluent. The focus of this study was to determine whether the bioconcentration of these compounds in wetland plants and sediments exhibited species specific and site specific differences by collecting field samples from a constructed wetland in Denton, Texas. The study showed that species-specific differences in bioconcentration exist for triclosan and triclo… more
Date: August 2011
Creator: Zarate, Frederick M., Jr.
Item Type: Refine your search to only Thesis or Dissertation
open access

Integrating Selective Herbicide and Native Plant Restoration to Control Alternanthera philoxeroides (Alligator Weed)

Description: Exotic invasive aquatic weeds such as alligator weed (Alternanthera philoxeroides) threaten native ecosystems by interfering with native plant communities, disrupting hydrology, and diminishing water quality. Development of new tools to combat invaders is important for the well being of these sensitive areas. Integrated pest management offers managers an approach that combines multiple control methods for better control than any one method used exclusively. In a greenhouse and field study, we t… more
Date: December 2011
Creator: Adams, Justin
Item Type: Refine your search to only Thesis or Dissertation
open access

A Characterization Of Jackson Blue Spring, Jackson County, Florida

Description: Jackson Blue is a first magnitude spring in the karst terrane of northeast Florida. Previous studies have identified inorganic fertilizer as the source of high nitrate levels in the spring. Agricultural land use and karst vulnerability make Jackson Blue a good model for conservation concerns. This work offers an aggregation of studies relating to the springshed, providing a valuable tool for planning and conservation efforts in the region. An analysis of nitrate levels and other water quality p… more
Date: December 2011
Creator: Reiser, Cora
Item Type: Refine your search to only Thesis or Dissertation
open access

Ultraviolet Radiation Tolerance in High Elevation Copepods from the Rocky Mountains of Colorado, USA

Description: Copepods in high elevation lakes and ponds in Colorado are exposed to significant levels of ultraviolet radiation (UV), necessitating development of UV avoidance behavior and photoprotective physiological adaptations. The copepods are brightly pigmented due to accumulation of astaxanthin, a carotenoid which has photoprotective and antioxidant properties. Astaxanthin interacts with a crustacyanin-like protein, shifting its absorbance from 473 nm (hydrophobic free form, appears red) to 632 nm (pr… more
Date: December 2011
Creator: Hudelson, Karista
Item Type: Refine your search to only Thesis or Dissertation
open access

Measuring Atmospheric Ozone and Nitrogen Dioxide Concentration by Differential Optical Absorption Spectroscopy

Description: The main objective was to develop a procedure based on differential optical absorption spectroscopy (DOAS) to measure atmospheric total column of ozone, using the automated instrument developed at the University of North Texas (UNT) by Nebgen in 2006. This project also explored the ability of this instrument to provide measurements of atmospheric total column nitrogen dioxide. The instrument is located on top of UNT’s Environmental Education, Science and Technology Building. It employs a low co… more
Date: December 2011
Creator: Jerez, Carlos J.
Item Type: Refine your search to only Thesis or Dissertation
open access

Effect of Rancher’s Management Philosophy, Grazing Practices, and Personal Characteristics on Sustainability Indices for North Central Texas Rangeland

Description: To assess sustainability of privately owned rangeland, a questionnaire was used to gathered data from ranches in Cooke, Montague, Clay, Wise, Parker, and Jack counties in North Central Texas. Information evaluated included: management philosophy, economics, grazing practices, environmental condition, quality of life, and demographics. Sustainability indices were created based on economic and land health indicator variables meeting a minimum Cronbach‘s alpha coefficient (α = 0.7). Hierarchic… more
Date: December 2011
Creator: Becker, Wayne
Item Type: Refine your search to only Thesis or Dissertation
open access

A Comparison of Mercury Localization, Speciation, and Histology in Multiple Fish Species From Caddo Lake, a Fresh Water Wetland

Description: This work explores the metabolism of mercury in liver and spleen tissue of fish from a methylmercury contaminated wetland. Wild-caught bass, catfish, bowfin and gar were collected. Macrophage centers, which are both reactive and primary germinal centers in various fish tissues, were hypothesized to be the cause of demethylation of methylmercury in fish tissue. Macrophage centers are differentially expressed in fish tissue based on phylogenetic lineage, and are found primarily in the livers of p… more
Date: May 2012
Creator: Smith, James Durward
Item Type: Refine your search to only Thesis or Dissertation
open access

Ecological Significance and Underlying Mechanisms of Body Size Differentiation in White-tailed Deer

Description: Body size varies according to nutritional availability, which is of ecological and evolutionary relevance. The purpose of this study is to test the hypothesis that differences in adult body size are realized by increasing juvenile growth rate for white-tailed deer (Odocoileus virginianus). Harvest records are used to construct growth rate estimates by empirical nonlinear curve fitting. Results are compared to those of previous models that include additional parameters. The rate of growth increa… more
Date: May 2012
Creator: Barr, Brannon
Item Type: Refine your search to only Thesis or Dissertation
open access

Effects of Layer Double Hydroxide Nanoclays on the Toxicity of Copper to Daphnia Magna

Description: Nanoparticles may affect secondary pollutants such as copper. Layer Double Hydroxides (LDH) are synthetically produced nanoparticles that adsorb copper via cation exchange. Pretreatment of copper test solutions with LDH nanoparticles followed by filtration removal of LDH nanoparticles demonstrated the smallest LDH aggregates removed the most copper toxicity. This was due to increased surface area for cation exchange relative to larger particle aggregates. Co-exposure tests of copper chlorid… more
Date: May 2012
Creator: Blake, Deanne Renee
Item Type: Refine your search to only Thesis or Dissertation
open access

Optimizing Scientific and Social Attributes of Pharmaceutical Take Back Programs to Improve Public and Environmental Health

Description: Research continues to show that pharmaceutical environmental contamination has caused adverse environmental effects, with one of the most studied effects being feminization of fish exposed to pharmaceutical endocrine disruptors. Additionally, there are also public health risks associated with pharmaceuticals because in-home reserves of medications provide opportunities for accidental poisoning and intentional medication abuse. Pharmaceutical take back programs have been seen as a remedy to th… more
Date: August 2012
Creator: Stoddard, Kati Ireland
Item Type: Refine your search to only Thesis or Dissertation
open access

Modeling the Relationship Between Golden Algae Blooms in Lake Texoma, Usa, Versus Nearby Land Use and Other Physical Variables

Description: Pyrmnesium parvum, commonly known as golden algae, is an algal species that under certain circumstances releases toxins which can lead to fish kills and the death of other economically and ecologically important organisms. One of the major objectives of the study was to investigate whether a relationship exists between land use and Prymnesium parvum abundance in littoral sites of Lake Texoma, USA. Another objective was to investigate whether a relationship exists between other physical variable… more
Date: August 2012
Creator: Ware, Trudy M.
Item Type: Refine your search to only Thesis or Dissertation
open access

Comparative Phyto-uptake Across Distribution Coefficients of Pharmaceutical Compounds and Aquatic Macrophytes: Carbamazepine and Amiodarone Uptake in Lemna Spp

Description: 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 d… more
Date: August 2013
Creator: Woodard, Jennifer Kristin
Item Type: Refine your search to only Thesis or Dissertation
open access

Quantifying Forest Vertical Structure to Determine Bird Habitat Quality in the Greenbelt Corridor, Denton, Tx

Description: 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 … more
Date: August 2013
Creator: Matsubayashi, Shiho
Item Type: Refine your search to only Thesis or Dissertation
open access

Population Dynamics of Zebra Mussels (Dreissena Polymorpha) in a North Texas Reservoir: Implications for Invasions in the Southern United States

Description: 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 … more
Date: December 2013
Creator: Churchill, Christopher J.
Item Type: Refine your search to only Thesis or Dissertation
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