Environmental Science & Technology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2748
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Item SMALL MAMMAL POPULATIONS, TICKS, AND TICK-BORNE DISEASES IN URBAN PARKS(2024) Coriell, Carson; Mullinax, Jennifer; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As urban environments expand, the distribution of wildlife, particularly white-footed mice, influences public health through zoonotic pathogen transmission, such as Lyme disease. This study examined pathogen risk in urban green spaces, focusing on interactions among small mammal communities, black-legged ticks, and the bacterium Borreliella (Borrelia) burgdorferi. Over two years, small mammal trapping was conducted across six urban park sites in Maryland to 1) quantify small mammal densities in six unique urban sites and 2) identify correlations between small mammal community and habitat structure related to pathogen prevalence. Findings revealed significant differences in pathogen risk between parks, driven by elevation and landscape features, with open shrub-scrub, and upland habitats, such as powerline corridors, linked to increased transmission risk. These results underscore the importance of habitat-level management strategies for urban green spaces to mitigate pathogen risk, rather than focusing solely on white-footed mice.Item Managing Cover Crops for Better N Efficiency and Soil Health(2024) Stefun, Melissa; Weil, Ray; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Winter cover cropping is a major tool that agriculture can use to protect soil and water quality and mitigate climate change. Unlike farmland in the world at large, most Maryland cropland has seen little tillage disturbance and some level of cover cropping for decades. With that background, field experiments on two soils with contrasting textures at the Beltsville Facility of Central Maryland Research and Education Center tested the effects of cover crop management enhancements on nitrogen (N) leaching, soil health indicators, and cover crop N uptake over three years. Two cover crops (sole rye and a mixture of forage radish, crimson clover, and rye) were compared to a control where cover cropping was ceased. The cash crops were corn and soybean grown in rotation. With best nutrient management practices applied, suction lysimeter sampling at 90 cm depth from October through April showed low levels of N leaching in general, but NO3-N concentrations were significantly lower under cover crops. Overall mean concentrations of NO3-N were 2.20 mg N/L in the control but 0.43 mg N/L under cover crops. Additionally, soil water samples were digested to determine dissolved organic N (DON) which was found to make up between 44-60% of the total dissolved N in the leaching water. In additional experiments, a small fertilizer N application was made to cover crops to stimulate rapid deep rooting with the goal of accessing soluble N deep in the profile to increase N capture by more than the amount of N applied. The response to fall N fertilization failed to accomplish this goal and was not related to the surface soil NO3-N concentration as expected. In spring, cover crops were terminated on three dates from mid-April to mid-May and rye biomass doubled with each extra two weeks it was allowed to grow whether it was in the mix or alone. The effect of cover crops on soil health indicators was evident with increased soil permanganate oxidizable carbon, total soil carbon, lower bulk density, and greater aggregation. These experiments demonstrated that cover crops with enhanced management can have marked effects on an agricultural system already using sustainable practices.Item ANTHROPOGENIC INFLUENCES ON BOTTOM-UP AND TOP-DOWN REGULATION OF ANIMAL DISTRIBUTIONS, POPULATIONS, AND BEHAVIORS IN URBAN ENVIRONMENTS(2024) Herrera, Daniel Joseph; Gallo, Travis; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Animal populations are simultaneously governed by both bottom-up (e.g., habitat availability) and top-down (e.g., predation) regulation. While ecologists historically sought to differentiate the roles of bottom-up and top-down regulation on ecosystems, the two are not so easily defined in urban ecosystems due to the immense influence humans have on ecological processes in cities. In Chapter One, I present this argument from a philosophical perspective and comment on how this philosophy has shaped my worldview. In Chapter Two, I examine the legacy of historical park planning on urban bird assemblages using archived municipal maps and historical bird data. My analysis found a positive correlation between percent park area and both species richness and functional richness of birds. Additionally, I found the effect size of park area was larger than the effect of certain life history traits thought to facilitate urban exploitation. These results indicate that landscape features and life history traits are equally responsible for the success of synurbic species. Chapter Three explores the effect of urbanization on animal behavior by analyzing anti-predator behavior of white-tailed deer (Odocoileus virginianus) in relation to ambient light, noise, and human activity. Despite negligible predation risk in my study area, deer expressed higher vigilance behavior in dark and noisy conditions, and increased their foraging group size during noisy conditions. These results suggest that anti-predator behaviors are a response to the perception of predation risk rather than a response to the actual presence of predators. Although predation of deer is rare in urban ecosystems, predation of smaller wildlife species by mesopredators, such as non-native domestic cats (Felis catus) is common. Chapter Four examines the potential for predation and zoonotic disease transmission between cats and eight native mammals by estimating the spatial and temporal overlap between species. I found that cat distribution was largely driven by anthropogenic features, whereas native wildlife was generally deterred by anthropogenic features and instead occupied forested areas. I also found that cats, as a species, were active on the landscape during the full 24-hour cycle. As a result, while spatial overlap between cats and wildlife varied across the study area, temporal overlap was possible anywhere cats and wildlife co-occurred. Chapter Five expands on Chapter Four and investigates predation directly by using observations of cats carrying prey documented by motion-activated cameras. I found that predation by cats was higher in areas where supplemental cat food was prevalent, but declined near forested areas. Additionally, my results indicate that cats within 250 meters of a forest edge predominantly preyed on native wildlife, whereas cats generally preyed on non-native rats (Rattus norvegicus) when greater than 250 meters from a forest edge. Each chapter provides applied recommendations to the management and conservation of urban wildlife, but together, my work demonstrates the entanglement of bottom-up, top-down, and anthropogenic forces in urban ecosystems. In light of these findings, I advocate for a more nuanced understanding of ecosystem regulation through a socio-ecological lens.Item MOSQUITOES AND VEGETATION ACROSS SOCIOECONOMIC GRADIENTS(2024) Rothman, Sarah; Leisnham, Paul T; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The biomass and composition of local vegetation is a key resource for juvenile mosquitoes, affecting a suite of life history traits including survival, development rate, and body size. In cities across the United States, both plant and mosquito communities vary with socioeconomics. Vegetation is typically more abundant and biodiverse in high-income neighborhoods, whereas mosquitoes are often more numerous and more likely to vector diseases in low-income neighborhoods. While prior work has examined the effects of plant resources on mosquitoes, my dissertation evaluates how these communities interact across a socioeconomically diverse urban landscape. Chapter 1 is a scoping review of current knowledge of the individual relationships between mosquitoes, plants, and socioeconomics in cities. In Chapter 2, I describe fine-scale vegetation surveys on socioeconomically diverse residential properties in Baltimore, MD and Washington, D.C. that revealed less canopy cover, more vines, and more non-native plant species on lower-income blocks. In Chapter 3, I used leaves from the most frequently observed canopy species on low- and high-income blocks, and species common to both, as detrital resource bases in competition trials between two dominant urban mosquitoes, Aedes albopictus and Culex pipiens. Population performance for both species was greater when reared with characteristically low-income than characteristically high-income detritus, suggesting that socioeconomically diverse plant communities are an important factor in shaping urban mosquito communities. Overall, population performances were greatest when mosquitoes were reared in the regionally representative detritus, and I used this detritus base in Chapter 4 to evaluate the effects of varying temperatures. Aedes albopictus population performance was optimized at higher mean temperatures characteristic of low-income blocks, while C. pipiens performance was best at lower mean temperatures characteristic of high-income blocks. Population performance was often lower, however, when temperatures fluctuated around a high or low mean than when the temperature was stable, suggesting that laboratory studies may need to mimic field conditions to obtain applicable results. My research provides a deeper understanding of the mechanisms behind previously observed relationships, and may help guide management and policy strategies to address environmental injustices and public health threats.Item MODELING GROUNDWATER FLUCTUATIONS IN THE COASTAL PLAIN OF MARYLAND: AN ANN POWERED STRATEGY(2024) Steeple, Jennifer Lynne; Negahban-Azar, Masoud; Shirmohammadi, Adel; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Groundwater management in the face of climate change presents a critical challenge with far-reaching implications for water resource sustainability. This study evaluates the effectiveness of Artificial Neural Networks (ANNs) as predictive tools for estimating current groundwater levels and forecasting future groundwater levels in the Aquia aquifer in the Coastal Plain ofMaryland. The groundwater levels of the Aquia aquifer have declined under the pressures of land use change, increases in agricultural irrigation, and population growth. We tested, trained, and employed eight county-level artificial neural network (ANNs) models to predict and project Aquia aquifer groundwater levels for the near (2030-2050) and far (2050-2100) future under two socio-economic pathways (SSP245 and SSP585). The models exhibited significant predictive performance during testing (R²= 0.82-0.99). Minimum temperature and population were the most influential variables across all county-based models. When used to forecast groundwater level under two climate scenarios, the models predicted declining groundwater levels over time in Calvert, Caroline, Queen Anne’s, and Kent counties, aligning with regional trends in the Aquia aquifer. Conversely, Anne Arundel, Charles, St. Mary’s, and Talbot counties exhibited projected increases in groundwater levels, likely influenced by correlations with the variable irrigated farm acreage, underscoring the importance of considering nonlinear relationships and interactions among variables in groundwater modeling. The study highlights the ability of ANNs to accurately predict county-scale groundwater levels, even with limited data, indicating their potential utility for informing decision-making processes regarding water resource management and climate change adaptation strategies. This study also assessed the usability of multiple methods to fill in the missing data and concluded that using the repeated groundwater level data still resulted in powerful ANN models capable of both predicting and forecasting ground water levels in the Coastal Plain of Maryland.Item Sperm Quality Characterization of Male Mummichog (Fundulus heteroclitus) in Response to Legacy Contaminants(2024) Malik, Sabine; Yonkos, Lance; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Historically contaminated rivers persist as hazards to ecosystem and human health despite remediation attempts, impacting the species found in these ecosystems. These rivers contain complex mixtures of legacy contaminants, including dioxins, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons, many of which are classified as endocrine disrupting compounds. Due to this level of contamination, few fish species are pervasive in these systems, an exception being the mummichog (Fundulus heteroclitus), known for its acquired tolerance of contaminated environmental conditions. While female and offspring reproductive success have been well-documented in the literature, few studies have investigated the use of sperm quality as a tool for assessing reproductive harm from contaminant exposure. Therefore, this study aims to demonstrate the usefulness of sperm quality characterization through the use of three assays: computer-assisted sperm analysis (CASA), a bioluminescent adenosine triphosphate (ATP) assay, and a modified Comet assay. This novel method was developed through field-collection of F. heteroclitus in three historically-contaminated tidal rivers in the United States: the Passaic River, NJ, the Christina River, DE, and the Anacostia River, MD. The results of this study not only present a novel method for investigating fish health in contaminated aquatic environments, but also a comparison of differential outcomes that can occur in rivers with varied contaminants and histories of pollution.Item GENERATING BIOENERGY AND HIGH-VALUE PRODUCTS FROM HIGH SALINITY FOOD WASTE(2024) McCoy, Emily Lim; Lansing, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioenergy generation and volatile fatty acids (VFAs) production from household food waste and high salinity food processing waste were explored using anaerobic digestion and dark fermentation processes, respectively. This study tested adding value to three organic waste streams: household food waste, high salinity food processing waste (composed of glycerin sludge from biodiesel production), and residual solids from VFAs separation after dark fermentation of food waste. The investigations were conducted using batch and semi-continuous systems in mesophilic conditions (35°C). Methane (CH4) potential tests were conducted to determine the bioenergy production of food waste and residual solids, including the addition of dark fermentation gas at four ratios of hydrogen (H2) to carbon dioxide (CO2) (1:1, 1:2, 1:3, 1:5) into the liquid portion of the reactor to enhance CH4 production and three inoculum to substrate ratios (1.5:1, 2:1, 4:1). Additionally, a semi-continuous dark fermentation study was used to determine the VFA production from household food waste and high salinity food processing waste combinations over 62 days. The anaerobic digestion of residual solids from VFAs separation had similar bioenergy potential as household food waste when normalized by volatile solids (VS) added (492 ± 11 mL CH4/g VS and 470 ± 11 mL CH4/g VS, respectively). Dark fermentation gas added into the liquid portion of the reactor during anaerobic digestion decreased CH4 yields, especially at low H2:CO2 ratios, suggesting that only dark fermentation reactors that produce high H2:CO2 ratios should have the gas sparged into anaerobic digestion systems. When the residual solids from dark fermentation were fermented at three inoculum to substrate ratios (1.5:1, 2:1, 4:1), the lowest inoculum to substrate ratio (1.5:1) had the highest VFAs concentration (28.05 ± 0.89 g/L) after nine days of fermentation, which showed that residual solids can be fermented with low inoculum levels, allowing more room for substrate fermentation. Additionally, the mono- and co-fermentation of household food waste and high salinity food processing waste showed that the high salinity waste improved VFA production due to the high pH (9 – 10) and high organic loading (6.3 – 17.8 g VS/L-day), even with high salinity levels (21.4 – 85.6 g/L Na) in this waste. There was significantly higher VFA production in high salinity food processing waste (36.04 ± 0.54 g/L) compared to household food waste (9.29 ± 1.01 g/L). The maximum VFA concentration (36.04 ± 0.54 g/L) was achieved after 51 days of high salinity food processing waste semi-continuous fermentation. The findings in this study can be used to improve operations of anaerobic digestion and dark fermentation systems by using residual solids for bioenergy generation or VFA production. The testing of mono- and co-fermentation of household food waste and high salinity food processing waste showed high VFA production in fermenting high salinity food processing waste. This work showed the valorization of three organic waste streams through bioconversion to both bioenergy and high-value products (VFAs), which redirected these waste products from municipal solids landfills and into resources, thereby reducing CH4 released into the atmosphere from landfills and reducing global warming potential.Item THE EFFECTS OF HISTORICAL AND CURRENT LAND USE ON THE HABITAT USE AND COMMUNITIES OF URBAN WILDLIFE IN THE WASHINGTON, D.C. METROPOLITAN AREA(2024) Collins, Merri Kathleen; Gallo, Travis; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Understanding past legacies of urban land use is important to identify ecological processes and inform best management practices for wildlife-friendly cities in the future. My first dissertation chapter is an overview of my personal research philosophy and how it relates to this dissertation. The second chapter is a systematic literature review that addresses the state of global urban wildlife research. Urban wildlife research is predominantly conducted in North America, Europe, and Australia by academic researchers, and less so in the Global South. The third chapter explores how a gregarious species, the Eastern wild turkey (Meleagris gallopavo silvestris) once extant from the Washinton, D.C. landscape, is making a comeback. Wild turkey had a higher probability of occupying sites further from roads and at lower elevations. The fourth and concluding chapter looks at historic neighborhood valuation in Washington, D.C. to identify any legacy effects of racist and discriminatory urban planning on mammal communities. While I did not find any relationship, I did find similar mammal communities across the city regardless of neighborhood categorization and I derive management implications from this information.Item INVASIVE LIANA HEDERA HELIX (ENGLISH IVY) IMPACTS ON ECOLOGICAL CHARACTERISTICS AND NUTRIENT CYCLING IN BALTIMORE FOREST PATCHES(2023) Shdaimah, Elad; Pavao-Zuckerman, Mitchell A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The effects of invasive plants on forest ecology and nutrient cycling are highly variable and poorly understood. Many studies have found that species and location make each plant invasion unique. Thus, studying invasive plants on the species and local level is necessary to understand how they impact ecosystems and how to manage them. Ninety-four percent of forest patches in Baltimore contain invasive plants. Hedera helix is one of the most prominent. My study explores how different characteristics and intensities of H. helix invasion impact ecology and nutrient cycling in Baltimore forest patches. I analyzed canopy structure, litter properties, soil properties, and steps of C and N cycling in forest patch plots. I compared findings across the invasion characteristics: presence, canopy invasion intensity, and ground cover presence. My study revealed that invasion characteristics and location strongly influence the impact of H. helix on Baltimore forest patch plots. The presence of ground cover appeared to be dictated by soil hydrology, which varied by location. Invaded plots with ground cover had significantly altered soil properties, increased soil respiration rates (2.86 times greater than control plots, p = 0.047), and may have increased decomposition rates. These differences in C cycling metrics appear to be driven by altered soil temperature, structure, and chemistry (i.e., 1.62 times more TN than control plots, p = 0.022). Canopy invasions may have caused tree loss and altered canopy structure, which indicate potentially negative consequences for forest patch ecology in the future. pH may have been higher in the presence of H. helix (1.17 times higher pH than control plots, p = 0.090). Several ecological characteristics and nutrient cycling variables may have also been more variable in the presence of H. helix. No significant differences were detected in N cycling due to invasion. These findings can help Baltimore forest patch managers to assess problematic H. helix invasions and allocate resources to control it when necessary. They also lay out further groundwork for plant invasion research, demonstrating the necessity of species-specific, location-specific studies.Item INDIGENOUS INVOLVEMENT IN ECOLOGICAL RESTORATION: AN ANALYSIS OF VIRGINIA’S SOVEREIGN NATIONS INVOLVEMENT IN THE CHESAPEAKE BAY PROGRAM(2023) Brooks, Nicole L; Shaffer, L. J.; Rose, Kenneth A.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Indigenous involvement in conservation and restoration practices, specifically those funded by government entities (e.g., EPA, USGS, NOAA), is not well documented in the Mid-Atlantic region of the United States. Increased Indigenous involvement in conservation and restoration projects globally, raises questions regarding this apparent environmental practice gap in the Eastern United States (McAlvay, 2021; Poto, 2021; Turner, 2010). Currently, government-led restoration projects in the Chesapeake Bay, led by the Chesapeake Bay Program, lack a strong Indigenous presence or contribution despite 7 federally-recognized Sovereign Nations in the surrounding watershed. To understand this gap, a literature review was first conducted to provide an initial context for viewing the contemporary Indigenous involvement in Chesapeake Bay restoration. The review was the basis for a detailed analysis of Virginia’s Sovereign Nation involvement in the Chesapeake Bay Program that used a series of interviews, participant observations, and a social network analysis. Interview participants were classified into one of three representative categories: Sovereign Nation, government organization, and non-government organization. Questions about working relationships between organizations were assessed to understand the political-ecological dynamics driving the interactions in the Chesapeake Bay restoration social network, specifically among the representative categories. Results showed a lack of a consistent and intentional relationship between the Sovereign Nations of Virginia and the Chesapeake Bay Program. According to the federal trust relationship, this infers that the lack of a strong Sovereign Nation involvement in the Chesapeake Bay Program may be contributing to a continued state of Environmental Injustice. To begin to address this low-level of involvement, the Chesapeake Bay Program should devote significant effort to building intentional relationships with the Sovereign Nations, including a more formal and official representation within the Chesapeake Bay Program.