Theses/Dissertations - Environmental Science
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Browsing Theses/Dissertations - Environmental Science by Author "Bratton, Susan."
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Item Microplastic ingestion by freshwater and marine fish from the Brazos River basin and Texas nearshore marine waters.(2018-07-16) Peters, Colleen Ann, 1990-; Bratton, Susan.This dissertation serves as one of the first comprehensive system investigations of microplastic ingestion by freshwater and marine fish from the Brazos River basin and Texas nearshore marine waters. In total, 436 freshwater sunfish were sampled and 45% contained ingested anthropogenic materials, consisting of -macro (4%) and -micro (96%) sized contaminants. Microplastic ingestion was greater within fish collected from urban areas, in comparison to upstream and downstream sites, suggesting that human development (i.e. paved roadways) and local urbanization are two possible factors impacting microplastic ingestion by sunfish. The marine portion of this research (Chapter Four) examined a total of 1,381 fish, inclusive of six species of a shared ecological guild, and 42.2% of stomachs contained microplastic fibers (86.4%), beads (12.9%) and fragments (<1%). Despite a substantial overlap in diet, ordination of ingested prey items clustered samples into distinctive species groupings, reflective of the foraging gradient among species. Grunt displayed the lowest overall frequency of microplastic ingestion and the most distinctive ordination grouping, indicating their selective invertebrate foraging preferences. While all six species had ingested microplastic, the results suggest that grunt, as selective invertebrate foragers, are less likely to ingest microplastic than species which exhibit generalist foraging preferences and methods of prey capture. When comparing microplastic ingestion between freshwater sunfish and marine pinfish, species which serve as ecological analogs between the systems, there was no significant difference in the overall frequency or mean number of microplastics ingested. However, the pinfish stomach content contained microplastic fiber, bead, and fragment morphologies, while the sunfish stomach content only contained microplastic fibers. Pyr-GC/MS analysis classified forty-three of the marine microplastic samples as polyvinyl chloride (34.8%), polyethylene terephthalate (9.3%), nylon (9.3%), silicone (2.3%), and epoxy resin (2.3%). Approximately 42% of samples could not be classified into a specific polymer class, due to a limited formation of pyrolytic products, low product abundance, or a lack of comparative standards. Overall, this dissertation demonstrates that microplastic ingestion is ubiquitous throughout Texas aquatic environments, influenced by species diet and foraging methods, and reflective of local land use patterns and major sources of pollution.Item Microplastic pollution in surface waters of urban watersheds in Central Texas, USA : a comparison above and below treated wastewater effluents.(2018-11-20) Stovall, Jasmine K., 1992-; Bratton, Susan.Microplastics are polymer-based particles ranging in size from 50 µm to 5 mm. The behavior of microplastics within freshwater systems remains understudied. The purposes of this study are to assess microplastic levels in spring-fed and runoff-fed freshwater systems in small, urban watersheds above and below local point-source wastewater effluents, to investigate patterns in microplastic spatial distribution and to evaluate the influence that seasonality and land use may have on microplastic frequency and form. A total of 779 surface water samples of 800-mL were collected across five study locales and analyzed via visual inspection. In total, 1,198 microplastics were found, inclusive of fibers (95.0%) and fragments (5.0%). Approximately 57% of all samples were contaminated with microplastics, on average, ranging from 33.3%-80% per study locale. Overall, significant differences between sample site and sampling interval suggest that seasonality and land use influence microplastic frequency within a system, while spatial locale influences particle color and form.Item The oaks of Independence : a landscape history of the original site of Baylor University and the potential surrounding historic district.(2011-05-12T15:23:51Z) Crumpton, Thomas William.; Bratton, Susan.; Environmental Science.; Baylor University. Dept. of Environmental Science.The landscape in and around the village of Independence in northeastern Washington County, Texas, is characterized by dense old growth riparian zones, released old fields, open pastures, and regenerated woodlots. The results of this project signify shifts in the appearance and use of the local landscape, including an increase in general woody vegetation since the late nineteenth century, and conversion from row crop and plantation agriculture to livestock production and leisure use. Live Oak Groves of the town and surrounding properties remain a constant within the changing landscape, and many trees pre-date Anglo settlement in the area. A regression for DBH/Age relationship was created from local tree measurements, which allowed identification of thirty-four trees older than the Republic of Texas, and ninety-three trees dating to the period of Baylor University’s residence in Independence. Intensive surveys of seventeen sites helped to identify historic landscape and vegetation features within a cultural context.Item The sublime and the synthetic: riparian art and industrialization.(2009-01-07T22:25:12Z) Turner, Bradley T.; Bratton, Susan.; Environmental Science.; Baylor University. Dept. of Environmental Science.This study proposes that traditional, American riparian artistry provided the greatest retaliation against the harsh environmental changes imposed by industry during the Gilded Age. Common environmental ethics and widespread social identification with nature established popular criteria that the American public used to determine the merits of industrialism. An eclectic mixture of local and national riparian artwork demonstrates the full influence of riparian aesthetics during the Gilded Age. Waco, Texas serves as the example of local artwork because of the city’s central riparian location and Waco’s cultural identification with the Brazos River. This thesis evaluates the extent of the natural, American sublime in direct contrast with the human synthetic to evaluate the connection between the natural and the material.Item Support host selection of Lonicera japonica and its interaction with different environmental and biotic factors in Cameron Park, Waco, Texas.(2008-06-05T14:41:08Z) Gao, Song, 1981-; Bratton, Susan.; Environmental Science.; Baylor University. Dept. of Environmental Science.Japanese honeysuckle (Lonicera japonica), an exotic woody vine, has naturalized in riparian forests in central Texas. The objective of this study was to quantify its existence pattern associated with different environmental and biotic factors in Cameron Park, Waco, Texas. Eighty-eight 8 × 4 meter plots were established along twelve trails in the area and treatment experiments were taken during May to August 2007. Through cumulative ordinal regression analysis, I found that cover of L. japonica was only significantly related to native vine cover and only the treatment of clearing both native and exotic vines showed a significant effect. As for the support host, its height class is strongly correlated with the climbing behavior of L. japonica. These results suggested that biotic factors play a more important role in its invasion and support hosts with low to medium height contribute to its spread from understory to canopy layer of the forest, whereas high tree hosts carry more stems to a longer distance in the canopy.