Theses and Dissertations from UMD
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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 give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Impact of Plant-Derived Allelochemicals on Harmful Algal Blooms(2023) Armstrong, Christen Taylor; Place, Allen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Harmful algal blooms (HABs) are a global concern in both freshwater and coastal systems; creating dire consequences for public health, water resources, and local economies. Thus, there is a focus among scientists and environmental managers on HAB prediction, prevention, and mitigation. Current chemical mitigation methods include algicides such as copper sulphate, chlorination, and hydrogen peroxide, which can have high financial costs and secondary pollution associated with them. The use of natural allelochemicals produced by plants and bacteria has received considerable attention as an alternative to synthetic algicides, as they can have negligible toxins, be highly selective, and easily degraded in the environment. This dissertation is a coalition of research looking into new sources of plant allelochemicals and whether natural levels of allelochemicals in the water column, can impact phytoplankton communities and the presence of toxin-producing algal species. The first objective focused on the use of the waste product: brewer’s spent grain (BSG), as a new control mechanism to inhibit the growth of toxic algae. BSG extract of doses higher than 250mg/L inhibited the growth of freshwater and marine toxin-producing cyanobacteria and dinoflagellate species (Microcystis aeruginosa and Karenia brevis), while not impacting the diatom and chlorophyte tested (Scenedesmus obliquus and Prorocentrum tricornutum). This same dosage of BSG caused cyanobacteria abundance in lake water to decline by 90% within 4 days and chlorophytes to dominate the community by day 6 during a microcosm study. However, an experiment controlling bacteria levels demonstrated that the decline of K. brevis growth was likely due to the increase in abundance or presence of certain types of bacteria growing with exposure to BSG extract rather than due to chemicals released from the BSG. The second and third objectives shifted focus to the New Jersey Pinelands and whether the chemicals released into the water from terrestrial and marine plants in these waters, like phenolic compounds, impact the phytoplankton community and toxin-producing species. The second objective focused on the spatial and temporal distribution of phycotoxins along two New Jersey estuaries using passive samplers and whether the utility of passive samplers was impacted by the excess phenolic compounds in the water. By utilizing passive samplers in New Jersey, phycotoxins not previously reported in the area were described, such as azaspiracids, goniodomin-A and yessotoxins. However, this objective also showed some of the caveats of passive samplers, especially at sites with high phenolic compounds. The third objective focused on identifying the primary environmental drivers of chlorophyll a concentration and phytoplankton community along the freshwater – marine continuum of two New Jersey Estuaries with varying levels of disturbance. This dissertation explored BSG as a novel control method of HABs, and provided new information for monitoring, managing, and modeling HABs based on phenolic content measured in the water.Item Optical Properties of Marine and Picocyanobacteria-derived Dissolved Organic Matter in the Atlantic, Pacific and during Long-term Incubation Experiments(2022) Lahm, Madeline Amelia; Gonsior, Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Marine dissolved organic matter (DOM) is a large, dynamic, and complex pool of carbon, comparable in size to the carbon dioxide pool in the atmosphere, yet it is arguably the least understood component of the global carbon cycle. DOM deriving from picocyanobacterial cells via situationally unique mechanisms, such as viral lysis and metazoan grazing, complicate the picture as the resident pool present reflects sequestration processes that occur at time scales ranging from days to hundreds of thousands of years. Recently virus induced cell lysis released from the globally distributed picocyanobacteria, such as Synechococcus and Prochlorococcus, have been shown to release optically active DOM known as Chromophoric DOM (CDOM) that closely matches the “humic-like” appearance of marine CDOM raising questions about our understanding of this carbon pool given the reliance on spectral measures to assess its composition. Hence, this thesis is seeking to understand CDOM released by lysed picocyanobacteria and to investigate the molecular chemical composition of picocyanobacteria-derived DOM in general. A special focus will be to confirm the refractory nature of chromophores released by lysed picocyanobacteria (Synechococcus) given the reliance on optical properties of recalcitrant DOM being used in the investigation of timescales of carbon storage and biological processing of carbon. As we consider the outcomes of the current global carbon inventory with a sizable error in flux, linking products of microbial processes to chromophore structures and spectrometry is a capstone in understanding the global carbon cycle for decades of research. This study offers a direct comparison of fluorescence signatures from the Bermuda Atlantic Time-Series (BATS) and the Hawai'i Ocean Time-series (HOT), observes optical and nutrient profiles tracking long-term incubation experiments of oligotrophic microbial communities amended with Synechococcus-derived DOM, and explores new techniques in DOM solid-phase extraction (SPE). This work is part of a National Science Foundation project - The Fate of Lysis Products of Picocyanobacteria Contributes to Marine Humic-like Chromophoric Dissolved Organic Matter – linking the accumulating evidence of picocyanobacterial-derived DOM to our understanding of marine organic carbon. Furthermore, we seek to understand how picocyanobacteria-derived DOM is degraded and what role changing heterotrophic microbial communities plays. This research is important to the concept of a microbial carbon pump that supplies a constrained and constant source of DOM which has important implications for the marine carbon cycle and its role in global climate.Item Effects of seawater Sr/Ca on coral paleothermometry in the Florida Keys and Virgin Islands revealed by multi-year continuous monitoring(2020) Hughes, Hunter Passman; Kilbourne, Kelly H; Schijf, Johan; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Coral skeletal Sr/Ca is a widely applied proxy indicator for tropical sea surface temperature (SST) because the elemental ratio in coral aragonite is influenced by both SST and seawater Sr/Ca. Application of the methodology assumes that seawater Sr/Ca is a constant in coral reef environments, and the ratio can be used to solve for paleotemperatures based upon an established coral Sr/Ca – SST relationship. This study tests that assumption by documenting seawater Sr/Ca variability in the Florida Keys and in the U.S. and British Virgin Islands using continuous osmotic pumps. Samples are analyzed for Sr/Ca using a novel method via Inductively Coupled Plasma – Atomic Emission Spectrometry. While mean seawater Sr/Ca did not vary significantly between sites, all sites exhibited significant annual variability (~0.5 – 0.1 mmol/mol), with the greatest variability observed in locations most impacted by freshwater discharge. These findings correspond to large temperature offsets (>2 degrees Celsius) in standard coral Sr/Ca-based SST reconstructions.Item YEAR-ROUND DETERMINATION OF METHANE (CH4) SOURCES AND SINKS IN ARCTIC LAKES USING CONTINUOUS AND AUTONOMOUS SAMPLING(2020) McIntosh Marcek, Hadley; Lapham, Laura L; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Methane (CH4) is a potent greenhouse gas and its concentration has been increasing in the atmosphere. While natural emissions from inland water bodies are known to be important, there is large uncertainty in the amount of methane released from lakes to the atmosphere, especially from Northern latitudes. Part of this is due to limited sampling in these systems during dynamic periods, such as ice-over and ice-melt. To better understand these temporal dynamics, I used autonomous, continuous samplers (OsmoSamplers) to collect lake water year-round over two years (2015-2017). Lake water was collected at a fine temporal resolution to provide time-integrated (~1 week) samples from multiple Arctic lakes within the Mackenzie Delta. The Mackenzie Delta is a lake-rich, productive environment that is expected to be a significant source of methane to the atmosphere. Lakes spanning the central delta and outer delta were sampled for methane concentration and stable carbon isotope ratio (δ13C-CH4) changes, ion concentrations, and water column characteristics were measured with continuous sensor data (temperature, water pressure, conductivity, light, and dissolved oxygen). These unique time-series datasets show lakes exhibit a close coupling of dissolved oxygen, and other electron acceptors, with the timing of methane increasing during ice-cover. The increase in methane concentrations is primarily from diffusion out of sediments and possibly water-column methanogenesis. One lake in the outer delta exhibited thermogenic gas bubble dissolution that contributed to under-ice methane concentration increases. Following ice-melt, lake depth appears to impact methane release to the atmosphere. Shallower lakes exhibit rapid fluxes followed by significant microbial methanotrophy. Deeper lakes in the central delta are connected to groundwater, though it does not appear groundwater transports methane. This is the first study of dissolved methane and gas bubble 14C-age in the Mackenzie Delta and shows that dissolved methane is produced primarily from modern carbon sources, such as macrophyte biomass and terrestrial material, but some methane transported in gas bubbles is significantly older, with seeps in the outer delta rapidly releasing radiocarbon-dead, thermogenic methane. This study demonstrates the importance of multi-lake studies particularly with fine scale temporal sampling to understand methane processes in seasonally ice-covered lakes.Item POTENTIAL IMPACT OF VARIATION IN THE SEAWATER STRONTIUM TO CALCIUM RATIO ON CORAL PALEOTHERMOMETRY IN THE FLORIDA KEYS, USA(2018) Khare, Agraj; Kilbourne, Kelly H; Schijf, Johan; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Standard methods of reconstructing past sea surface temperatures with coral skeletal Sr/Ca ratios assume that the seawater Sr/Ca ratio is constant. However, data to support this assumption are sparse in coral reef environments, in part because analytical techniques capable of determining seawater Sr/Ca with sufficient accuracy and precision are time-consuming and not widely available. This work presents a new method to measure seawater Sr/Ca based on inductively coupled plasma atomic emission spectrometry that can be easily adopted by many coral paleothermometry laboratories. The work also presents a spatially gridded study of summer and winter seawater Sr/Ca from the middle Florida Keys Reef Tract. The results indicate that seawater Sr/Ca in nearshore waters influenced by the Florida Bay varies by ~0.1 mmol/mol. The observed variation could lead to errors of ~2°C in temperature reconstructions and suggests that corals growing in waters influenced by Florida Bay are less suited for paleoclimate studies.Item Sampling Errors Arising from Entrainment and Insufficient Flushing of Oceanographic Sampling Bottles(2017) Paver, Christopher Raymond; Codispoti, Louis A; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Collection of representative water samples is important for accurately determining biological and chemical constituents. Modern carousel packages can permit bottle “soak times” to approach zero while increasing the impacts of entrainment due to their large size. In addition, some modern sampling bottles have relatively small openings relative to their volumes, a factor that inhibits flushing. Examination of qualitative evidence from various expeditions suggested that insufficient “soak times” can produce unrepresentative water samples. In this study, historical data are presented, but the emphasis is on field experiment data that better quantifies the errors that can arise from insufficient bottle flushing. The experiments suggest that under some conditions, soak times of more than 2 minutes may be required to collect representative water samples. The experiments also suggest the occurrence of stratification within bottles. The impact of insufficient soak times on some chemical gradients is discussed and improved sampling protocols are suggested.Item Systems Engineering-Based Model Development: Application to Predictive Simulation of a Net-zero Home(2017) Uy, Alan; Adomaitis, Raymond A.; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Building design has grown increasingly sophisticated throughout the decades. In recent years, assessments of building performance and sustainability has grown in popularity as the U.S. Green Building Council published LEED certifications for new and existing constructs. The LEED rating system utilizes standards made by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) for areas in thermal comfort, air quality, energy building performance, and heat, ventilation, and air conditioning (HVAC) operation. Energy building performance has a more overarching role in this rating as the other three standards play into the overall loads associated with any building. Submittal of energy performance building reports for construction design and green building rating systems is becoming more common as building performance assessment software becomes more widely available. The University of Maryland currently is a participant in the Solar Decathlon intercollegiate competition sponsored by the Department of Energy. The University of Maryland's reACT team is working to construct a net-zero solar powered house for judging in Denver, CO in October 2017. Concurrently with the housing design, a substantial effort was put into assessing the projected building performance to aid in the design process and to set the stage for model-based home automation. While software such as OpenStudio and BEOPT are available and were used for year-averaged performance reports, a physically based model of the house was built from scratch to serve as a real-time simulation of virtual versions of reACT located in College Park, MD and Denver, CO and is described in detail as the Virtual House. The overall system design of the Virtual House can be described as a general set of inputs, dynamic simulation, and output of overall profiles. Inputs for the system include geometric design of the house, specified materials, schedules, daily weather data, and solar irradiance. Dynamic simulation refers to a simultaneous integration of both independent and dependent fluctuating loads upon the time of day regarding both heat and power balances. Finally, outputs showcase heat and power profiles throughout a day. The bulk of analysis of inputs and simulation has been rooted in fundamental calculations. In terms of future work, outputs coming from the Virtual House are currently being stored and are now looking towards validation with measured sensor data. As of now reACT is not in construction phase and measured data is unavailable. In order to validate the Virtual House, there are current plans to outfit the previous Solar Decathlon 2007 entry LEAFhouse with sensors. With this, measured and simulated data can be assessed after modifying the current Virtual House model for LEAFhouse specific inputs. Ultimately, work will be transitioned back to reACT as it is built with Solar Decathlon 2017 in mind.Item An investigation of the physio-chemical characteristics of a river estuary(1952) Provenza, D. Vincent; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item A Proteomics Approach to the Examination of Proteins in Marine Systems(2014) Faux, Jessica Felicia; Harvey, Henry R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The response of global carbon and nitrogen cycles to future climate change is uncertain. In order to understand the impacts that future changes to climate will have on these cycles, a more detailed understanding of them is essential. This dissertation utilizes a combined approach of molecular biomarkers and proteomic investigations to elucidate historic source material contributions and microbial protein production to contribute to a more thorough understanding of the marine carbon and nitrogen cycles. The examination of molecular organic biomarkers throughout an Arctic sediment core showed the dominant input in the area was from marine sources with lower but steady contributions from terrestrial sources during the Holocene. Attempts to recover proteins from deeper sediments to correlate with lipid biomarkers were unsuccessful but led to the optimization of an extraction protocol for an added protein standard, bovine serum albumin, from sediments. An investigation into the expressed proteome of the heterotrophic marine bacterium, Ruegeria pomeroyi, under environmentally realistic carbon supply conditions during exponential and stationary growth phases identified over 2000 proteins. The most abundant proteins identified were responsible for porins, transport, binding, translation, and protein refolding and could represent potential biomarkers of bacterial processes and/or activity. A parallel study of R. pomeroyi, in which 13C-labeled leucine was added to the culture during exponential growth phase, showed labeled incorporation ranging from 16 to 21% of the total proteins produced depending on growth phase. The widespread distribution of the label among the growth phases indicates active recycling by the bacteria. This study demonstrates a method through which bacterial protein synthesis can be tracked. A study of the marine diatom Thalassiosira pseudonana acclimated to iron replete or iron-limited conditions showed iron-limited organisms increased proteins involved in pathways associated with intracellular protein recycling, the pentose phosphate pathway, lower photosynthetic energy production, enhancement of photorespiration, and increased polysaccharide production. This application of proteomics to the examination of proteins in marine sediments, a marine diatom, and a heterotrophic marine bacterium shows the potential for these techniques to help elucidate the fate of proteins in marine environments and could be used in conjunction with well-established molecular organic marker studies.Item MODELING THE PH DEPENDENT OPTICAL PROPERTIES OF AQUATIC, TERRESTRIAL AND MICROBIAL HUMIC SUBSTANCES(2013) Heighton, Lynne Page; Mignerey, Alice C; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Humic substances (HS) and chromophoric dissolved organic matter (CDOM) are ubiquitous, widely impacting environmental processes, yet despite decades of study the link between structure and the unique optical properties evident in HS/CDOM remains elusive. Model compounds derived from a solely microbial source, as well as terrestrial sources from both aquatic environments and soil systems, exhibit many of the same optical properties despite their disparate methods of generation and sources. All show a pH dependent absorbance, exhibit increasing absorbance as wavelength decreases and a loss of absorbance upon borohydride reduction. The link between colored humic substances is their ability to form electronic interactions that extend long wavelength absorbance. The underlying processes by which charge transfer bands or electronic interactions in HS/CDOM are generated are investigated by optical and potentiometic titrations of untreated and borohydride reduced material. Borohydride reduction targets carbonyl functional groups such as aromatic ketones and quinones. The reduction of these groups affects the optical properties by reducing long wavelength absorbance and causing a blue shift in the fluorescence emission spectra. A direct comparison of divergent sources of fulvic and humic acids including an aquatic fulvic acid, Suwannee River Fulvic Acid (SRFA) and a microbial source of fulvic acid, Pony Lake Fulvic Acid (PLFA), the soil derived humic acids, Elliott (EHA) and Leonardite Humic Acids (LHA), an aquatic humic acid Suwannee River Humic Acid (SRHA) as well as Lignin Alkali Carboxylate (LAC) highlights differences between sources of humic material as exemplified by borohydride induced optical changes such as absorbance intensity in the UV and visible range, difference (DA), fractional difference, spectral slope (S), fluorescence excitation-emission matrix spectra (EEMS), and differential emission spectra (DF) as well as quantum yield. Traditional Raman spectroscopy, although capable of providing relevant chemical functional group information, cannot be applied to untreated CDOM because of high fluorescence background. Surface enhanced Raman scattering (SERS) provides the capability of overcoming the florescence background, thus providing useful Raman spectral data. SERS spectra of model compounds and CDOM were collected using roughened silver electrodes. Functional groups were identified from selected borohydride reduced CDOM SERS spectra.