UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
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Item Insights into benthic macroinvertebrate ecology in the northern Bering and southern Chukchi Seas from stable isotope analysis(2022) Green, Emma Mackenzie; Cooper, Lee W; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the Pacific Arctic Region, the northern Bering Sea and southern Chukchi Sea support large and diverse communities of benthic macroinvertebrates that provide an important link to the pelagic communities and marine mammals that rely on the benthic populations for food. While the abundance and biomass of these benthic macroinvertebrates are well documented, little is known about how benthic macroinvertebrates interact with each other and how these interactions are affected by climate change. I measured the stable isotope composition (bulk δ15N and δ13C values) of similar species collected in 2014, 2016, 2017, and 2021 in the northern Bering and southern Chukchi Seas. Although there was little change over time in either δ15N or δ13C values, both stable isotope ratios were significantly different between stations with differing production phenologies. The southern Chukchi Sea (a productive set of sites with high chlorophyll concentrations throughout the summer) had lower δ15N values and higher δ13C values, while the northern Bering Sea site with production mostly associated with the period of sea ice breakup had higher δ15N values and lower δ13C values. This pattern was observed across similar species and feeding types. The higher δ15N values in the northern Bering Sea could be due to an extra step in the food chain from bacterial reworking. The contrast between these two regions in δ13C might indicate higher primary production in the southern Chukchi Sea compared to the northern Bering Sea. The differing food web dynamics between these two sites highlight the benthic diversity across small scales and similar organisms in Pacific Arctic food webs.Item EVALUATING RELATIONSHIPS BETWEEN BATS AND LANDSCAPE CHARACTERISTICS IN A WHITE-NOSE SYNDROME POSITIVE REGION: DOES URBANIZATION PLAY AN IMPORTANT ROLE?(2021) Browne, Shannon P.; Mullinax, Jennifer M.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)White-nose Syndrome (WNS) is a cascading disease process, initiated by a skin fungus, killing most cave bat populations across North America. WNS severity differs with the ecology of both the pathogen and the bat species host. This study aimed to identify the habitat features most related to cave bat species by surveying cave bats and habitat features across the urban-rural gradient in Maryland. Our understanding of cave bat ecology in Maryland has changed recently due to technological advancements, though prominent gaps still exist in the urbanized Piedmont and Coastal Plain provinces. As such, a novel urban definition was created to allow research sites to well represent each level of the gradient, and sites were surveyed in random order during four seasons from 2015 to 2017. We found unique results when analyzing predator-prey correlations at weekly scales as well as nightly generalized linear mixed models (GLMM) of habitat usage. At both temporal scales, big brown (Eptesicus fuscus) and tri-colored bat (Perimyotis subflavus) activity were higher at urban than suburban sites. While analyzing predatory-prey correlations at the weekly level, big brown bat activity was highly related to their preferred prey counts at urban sites, while tri-colored bat activity correlated to their preferred prey counts at rural sites. Tri-colored bat activity also occurred at sites during seasons that supported less activity by big brown bats. When analyzing habitat features at the nightly level using GLMMs, in suburbia, big brown bat activity appeared most related to their preferred prey and taller trees. Meanwhile, tri-colored bat activity still held a strong relationship with prey at rural sites across multiple seasons. Big brown bats may select suburbia for roosting and foraging while tri-colored bats may select rural settings for foraging. Interestingly, prey were most abundant at rural sites, indicating rural settings may support higher habitat quality along the gradient. Possible reasons for the seemingly spatial and temporal partitioning by these two species included differing resource availability and some form of niche partitioning. Repeated acoustic surveys and telemetry studies across spatial and temporal scales are recommended to aid bats in greatest need during WNS.Item An evaluation of methods for measuring phytoplankton and ecosystem status in the Chukchi Sea(2020) Neeley, Aimee Renee; Harris, Lora A; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation represents a three-pronged approach for evaluating ecosystem-level changes in the Chukchi Sea: 1) evaluation of uncertainties in field measurements of absorption 2) direct measurements of phytoplankton taxonomy and the community’s interaction with the environment and 3) apply existing and new remote sensing tools to measure ecosystem-level changes over large spatio-temporal scales. The first and final chapters provide context for the dissertation and conclusions. The second chapter quantifies the magnitude of uncertainty within multiple methods for measuring particle absorption. The light field exiting the surface ocean is measured by satellite instruments as ocean color and is impacted by water column absorption. Biogeochemically-relevant products, such as phytoplankton and particle absorption are derived from the light field using algorithms. Therefore, accurate measurements of absorption are critical to algorithm development and validation. I employed a multi-method approach to estimate the precision of measuring optical density of particles on a filter pad using two common spectrophotometric methods, and assessed the uncertainty of the computational techniques for estimating ap. The uncertainty ranged from 7.48%-119%. Values of ap at 555 nm and 670 nm exhibited the highest values of uncertainty. Poor performance of modeled ap compared to measured ap suggests the uncertainties are propagated into bio-optical algorithms. The third chapter investigates the consequences of earlier seasonal sea ice retreat and a longer sea-ice-free season on phytoplankton community composition. The timing of sea ice retreat, light availability and sea surface stratification largely control the phytoplankton community composition in the Chukchi Sea. This region is experiencing a significant warming trend, decrease in sea ice cover, and a documented decline in annual sea ice persistence and thickness over the past several decades. I applied multivariate statistical techniques to elucidate the mechanisms that relate environmental variables to phytoplankton community composition in the Chukchi Sea using data collected during a single field campaign in the summer of 2011. Three phytoplankton groups emerged that were correlated with sea ice, sea surface temperature, nutrients, salinity and light. The fourth chapter evaluates a new remote sensing tool for its utility to trace trends in ocean color over the summer months, 2003-2018, in the Chukchi Sea. The apparent visible wavelength reduces an ocean color spectrum to one number that represents the apparent color of the water. Median trend analysis of apparent visible wavelength and Chlorophyll a indicated that an ecosystem-level change in phytoplankton and nonalgal particles has occurred, correlated with the loss of sea ice.Item An American River: Discourses of Ecocatastrophe, Sustainability, and Belonging in the Potomac River Basin and Beyond(2019) Kier, Bailey; Sies, Mary; American Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An American River: Discourses of Ecocatastrophe, Sustainability, and Belonging in the Potomac River and Beyond is a queer ecological intervention in American, Queer, Trans(Gender), and Popular Culture Studies. It critiques the primary reliance on the category of culture to analyze the ways media, science, public policy, and the state make knowledge assumptions about sex, gender, and reproduction to construct stories about environmental catastrophe, species, and kind. Transdisciplinary methods are used to uncover the ecologies, relations, adaptations, and resiliencies that might not otherwise be possibly investigated and known, and challenge conventional popular discourses of environmentalism and conservation in an effort to create the intellectual equivalent of biodiversity. Three distinct but interrelated cases are considered. First, an examination of the Theodore Roosevelt Memorial Island interrogates how sex, gender and reproduction were intimately tied to discourses of wilderness, nature and nation, and the ways in which those concepts have been sanitized for consistency with modern sensibilities about an appropriate memorial for an “environmental” president. Next, a consideration of the popular discourse around the emergence of “transgender fish” in the Potomac River leads to an analysis of how trans-related language and concepts can be used to enrich human understanding of transformations and interactions across ecologies, species, and populations. I offer “interdependent ecological transsex” as a term broadly defined through a hormonal, metabolistic, and adaptive prism to imagine other bodies—not just transsexual human bodies, but fish, bodies of water, and any other kind of body that experiences change in relation to a larger ecology. Third, I examine the possibilities for queering agriculture, or envisaging alternatives to mainstream rhetorics of agriculture, food security, and farming. An American River concludes arguing human knowledge about nature, environmentalism, race, reproduction, and transsexuality is laden in antroheterocentric assumptions about progress, degeneracy, and evolution that is problematic for ethically and equitably addressing social and environmental problems. A queer eco ethic is presented to offer ways humans might begin to imagine nature and the environment differently.Item THE INFLUENCE OF THE RIVER OTTER ON AQUATIC CONSERVATION IN THE GREATER YELLOWSTONE ECOSYSTEM: A SOCIO-ECOLOGICAL APPROACH TO EVALUATING CONSERVATION FLAGSHIPS(2019) Pearce, Kelly J; Stylinski, Cathlyn; Serfass, Thomas L; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Large scale habitat loss, unprecedented rates of species extinction, and other biodiversity issues have prompted wildlife conservationists to increasingly apply the “flagship” species concept to guide conservation decision making. Flagships are designated based on their ability to serve a socio-economic role, attracting public attention and financial support to conservation initiatives. Critical to flagships success is selecting an appropriate flagship—one that will be widely supported and will not invoke ill-will among any stakeholders. Thus, determining if the species meets certain pre-established criteria that are known to influence social-psychological processes is a critical step in flagship selection. The river otter (Lontra canadensis) is a widely distributed apex predator and possesses various other socio-ecological traits that make it suitable for a flagship species. However, empirical evidence supporting the use of the river otter as a flagship is lacking. In this dissertation, I study the ability of the river otter to serve as a flagship species in the Greater Yellowstone Ecosystem, one of the largest intact temperate-zone ecosystems in the world. I examine visitor attitudes and perceived resource conflicts with river otters and anglers, assess visitor willingness to engage in pro-conservation behaviors to help river otter conservation, and estimate probability of viewing the river otter using camera-traps along the Snake River. In addition to fulfilling certain recommended criteria of a flagship species, such as having a large body size, being charismatic, encompassing a wide-spread geographic range, and being uncommon across the landscape, my results suggest that visitors and anglers have positive attitudes towards the river otter, and that exposure to the river otter increases people’s willingness to engage in pro-conservation behaviors to help conserve the river otter and its aquatic habitat. However, pre-existing negative media portrayals as well as low visibility of the species, are potential liabilities of the river otter as a conservation flagship. The studies in this dissertation deepen the understanding of river otter socio-ecology as well as develop and apply elements of a socio-ecological framework that refine the approach of effectively selecting a successful conservation flagship.Item Tightness-Looseness in the United States: Ecological Predictors and State Level Outcomes(2014) Harrington, Jesse Ryan; Gelfand, Michele J; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research demonstrates wide variation in tightness-looseness (strength of punishment and degree of permissiveness) at the state level in the United States, and its association with various ecological and historical factors, psychological characteristics, and state-level outcomes. Consistent with theory and past research, ecological and man-made threats--more natural disasters, greater disease prevalence, fewer natural resources, and greater external threat--predict increased tightness at the state level. Tightness is also associated with higher trait conscientiousness and lower trait openness. Compared with loose states, tight states have more social stability, indicated by lowered drug and alcohol use, lower rates of homelessness, and lower social disorganization. However, tight states also have relatively higher incarceration rates, greater discrimination and inequality, lower creativity, and lower happiness. In all, tightness-looseness provides a parsimonious explanation of the wide variation seen across the 50 states of the United States of America.Item VALUING FOREST ECOSYSTEM SERVICES IN MARYLAND AND SUGGESTING FAIR PAYMENT USING THE PRINCIPLES OF SYSTEMS ECOLOGY(2012) Campbell, Elliott Thomas; Tilley, David R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Forests provide a multitude of vital benefits to the ecosystems, economies and people of Maryland. Forests regulate atmospheric gas exchange, ameliorate micro-climates, stabilize coastlines and riverbanks, provide wildlife habitat, generate and maintain soils, improve water quality, dampen storm flows, abate air pollution, and provide food, fiber, fuel and shelter. While markets exist to set the price for an economic good like timber, many of the ecosystem services listed above are poorly valued, if at all. This research provides a connection between biophysical and economic methods for evaluating the environment. The hydrology, soil, carbon, air pollution, pollination and biodiversity of a forest are measured from a biophysical standpoint with emergy and converted to dollars using new emergy-to-dollar ratios; termed eco-prices. The functioning of the forest is compared to the most likely alternative land-use (suburbia) and biophysical value is assigned based on this difference. The novel method for assigning value to ecosystem services and the ability to link biophysical evaluation and economic valuation has the potential to be influential in how ecosystem services are incorporated into the economy and used to guide decision making in the future. This research seeks to value ecosystem services provided by forests in Maryland and proposes that an Ecological Investment Corporation (EIC) could be an additional tool for society to direct payments from consumers to land stewards to encourage the production of ecosystem services. To ensure that Maryland forests continue to produce ecosystem services at the current rate, land stewards should receive compensation between $178 and $744 million. On a per capita basis, a resident of Maryland enjoys $850 worth of ecosystem services from the forest as public value. On an area basis, the typical acre of forest in Maryland generates over $2000 of ecosystem services as public value. Based on our compensation estimates for ecosystem services, a land steward should receive a fair payment price of $71 to $298 per year per a typical acre of forest. This research is a step forward for emergy science, providing novel methods for quantifying ecosystem services, calculating ecological debt, and converting renewable emergy flows to dollars.Item The effects of low dissolved oxygen on predation interactions between Mnemiopsis leidyi ctenophores and larval fish in the Chesapeake Bay ecosystem(2006-11-27) Kolesar, Sarah Elizabeth; Breitburg, Denise L; Boynton, Walter R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Differences in predator and prey tolerances to low dissolved oxygen (DO) concentrations are important to planktonic food webs in seasonally hypoxic environments like Chesapeake Bay. Hypoxia alters field distributions, encounter rates, and predator-prey interactions between hypoxia-tolerant ctenophores, Mnemiopsis leidyi, and less tolerant ichthyoplankton and zooplankton prey. To examine the effect of hypoxia on estuarine food web species' interactions, I conducted medium and small-scale experiments, field sampling, and collaborated on individual-based model development, focusing on ctenophore-larval fish dynamics. Laboratory estimates of clearance rates for ctenophores on bay anchovy (Anchoa mitchilli) eggs and yolk sac larvae, and naked goby (Gobiosoma bosc) feeding larvae were the same at low and high DO. Field sampling for M. leidyi, ichthyoplankton, mesozooplankton, and scyphomedusae (Chrysaora quinquecirrha) during day and night at two sites in the Patuxent River indicated increased abundance of most species in the bottom layer with increasing bottom DO. Vertical overlap between predator and prey pairs also increased with higher bottom DO, increasing potential encounters and predation. Larval fish swimming speeds did not differ significantly with DO, but ctenophores swam significantly faster at intermediate DO (2.5 mg L-1) than at either low or high DO. DO did not significantly affect ingestion. Greater ingestion of fish larvae by ctenophores followed multiple encounters (56%) than initial encounters (10%) at all DO concentrations, highlighting the potential importance of repeated predator-prey interactions. DO did not significantly affect encounter model estimates of ingestion rates. Ingestions averaged 0.4 fish larvae d-1 m-3 for first encounters and 2 fish larvae d-1 m-3 for multiple encounters. Results from laboratory and field studies parameterized a spatially-explicit individual based model of a ctenophore-ichthyoplankton-copepod intraguild predation food web. Ctenophore predation had a bigger effect on survival of modeled ichthyoplankton than did competition between ctenophores and fish larvae for shared zooplankton prey, but competition more strongly affected larval fish growth rates. DO did not alter the relative importance of ctenophore predation and competition, but low DO did decrease larval fish survival and increase growth rates. Results suggest that effects of DO on vertical distribution and species overlap are more important to predation than direct DO effects.Item INTERACTIONS OF VIBRIO CHOLERAE SEROGROUPS O1 AND O139 AND COPEPODS(2005-05-26) Rawlings, Tonya Kafi; Colwell, Rita R; Ruiz, Greg M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vibrio cholerae O1 El Tor and O139 Bengal have caused cholera epidemics throughout Bangladesh and elsewhere in the world with a seasonal regularity. This has raised questions about whether clinical presentations of cholera caused by these two epidemic serogroups of V. cholerae reflect similar responses to their aquatic habitat. The association of V. cholerae with plankton has been suggested to be an important factor in transmission of the disease. In this study, differences in resource utilization of copepods and chitin by V. cholerae O1 and O139 were analyzed using laboratory microcosm experiments. When occurring separately, V. cholerae O1 and O139 were able to colonize copepods, including Acartia tonsa and Eurytemora affinis. However, V. cholerae O1 had a higher affinity for colonizing adults of both copepod species, as well as the multiple life stages of E. affinis, than V. cholerae O139. In sympatry, colonization of copepods by V. cholerae O1 and O139 did not result in specific exclusion of one serogroup by the other. Results of this study indicate that cells that are already established may facilitate attachment through new biofilm formation, notably by V. cholerae O139. Soluble chitin, employed as a nutrient source, supported growth of V. cholerae O1 and O139. Growth of both serogroups with the addition of chitin was significantly greater than in river water alone. In competition assays, V. cholerae O139 had a deleterious effect on V. cholerae O1 growth, but not vice versa. Together, these data indicate that V. cholerae O1 and O139 respond differently to copepods as habitat, as well as nutrient resources. Such differences may play a role in cholera epidemics. The spatiotemporal dynamics of V. cholerae in the environment is complex, and understanding what drives cholera outbreaks requires explicit consideration of population responses and interactions of multiple serogroups.