Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
8 results
Search Results
Item The Role of Urban Agriculture in Baltimore Food Systems(2024) Mathews, Meghna Anjali; Zhang, Xin; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The United States is one of the most agriculturally productive countries; and yet, food insecurityremains a significant issue. Urban agriculture in Baltimore, Maryland should be studied further because of its potential to address food insecurity while overcoming systemic barriers created and embedded within food systems. While numerous previous studies have explored food insecurity, knowledge gaps still exist regarding how urban agriculture has influenced food accessibility, and how availability, cultural values of foods, etc. can be improved through increased production and distribution practices of fresher fruits and vegetables in Healthy Food Priority Areas. To address these knowledge gaps, we queried food insecure community members and urban farmers in Baltimore, Maryland to better understand the underlying factors that influence low fruit and vegetable consumption and how they can be mitigated through the establishment of urban agriculture. Urban farmers were interviewed in detail about their production and distribution patterns, and factors influencing the low consumption of fresh fruits and vegetables by community members in Baltimore. Food insecure individuals were asked about their food consumption habits and the accessibility of fruit and vegetables, their food purchasing behavior and related challenges, and community needs. Results indicate that while accessibility and availability are two main factors in fresh produce consumption, there are other important factors that might have received limited attention in existing literature. Our interviews revealed that income, cultural value, and a lack of knowledge in food preparation are key factors in low consumption and purchase of fresh fruits and vegetables. To address the underlying factors and improve the accessibility and availability of fresh produce to low-income communities, it is important to assess community needs and provide policy recommendations that can potentially enhance their nutrition. Ensuring access to individuals with limited resources is a critical component of advancing social justice.Item QUANTIFYING NITROUS OXIDE AND METHANE FLUXES USING THE TOWER-BASED GRADIENT METHOD ON A DRAINAGE WATER MANAGED FARM ON THE EASTERN SHORE OF MARYLAND(2022) Zhu, Qiurui; Davidson, Eric A.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Excess nitrogen resulting from agricultural fertilizer and manure applications on the Eastern Shore degrades the Chesapeake Bay's water quality and causes environmental issues such as algal blooms and "dead zones". Drainage water management (DWM) is an effective best management practice (BMP) to reduce hydrological nitrate export from croplands to surface and ground water by controlling the timing and the amount of ditch discharge and retaining water within ditches and adjacent fields using drainage control structures (DCS). While promoted denitrification in the subsurface and reduction in nitrate leaching are intended consequences of maintaining higher water table level, an unintended environmental consequence is possible production of nitrous oxide (N2O) from denitrification and methane (CH4) from methanogenesis, which are both potent greenhouse gases (GHGs). Whether the application of DWM leads to a "pollution swapping" concern (i.e., trading reduction of nitrate concentrations in ditch water for increases in emissions of N2O and CH4 to the atmosphere) is a question that must be addressed before more widespread implementation of DWM can be endorsed. In this dissertation, I employed a micrometeorological method called the flux gradient (FG) method to a corn-soybean rotation agricultural system with DCS in eastern Maryland on the Delmarva Peninsula to answer this question. This method was chosen because it allows near-continuous measurements of soil trace gas exchanges at multiple locations with a single laser spectrometer at a fine temporal resolution without disturbing the microclimate between soils and the atmosphere. Soil N2O and CH4 fluxes were quantified using the FG method on this drainage water managed farm for three consecutive years when no fertilizer, synthetic fertilizer, and biosolids were applied in 2018 (soybean), 2019 (corn), and 2020 (corn), respectively. Statistical tests indicated that there were no consistent treatment effects of DWM on soil GHG emissions between DWM and non-DWM conditions, suggesting that DWM did not trade the intended consequence of reduced nitrate leaching for the unintended consequence of increased soil GHG emissions. The biosolid addition in 2020 led to the largest N2O emissions among the three years, while the lowest N2O emissions in the growing season were found in the unfertilized soybean year of 2018. In contrast, different fertilization regimes did not yield distinct differences between the three years for CH4 fluxes. In addition, some potential methodological concerns associated with this tower-based micrometeorological approach were addressed and resolved, conferring confidence that the FG method can be applied simultaneously to multiple plots for N2O and CH4 measurements. This research adds to the existing understanding of the impacts of DWM on soil GHG emissions and suggests that this BMP could be applicable in other regions of the Chesapeake Bay as well as other watersheds. This work also contributes to the efforts of studying the impacts of soil organic amendments on soil GHG emissions and deriving improved estimates of emission factors (EFs) for organic amendments.Item Optimizing desiccation as a biofouling control strategy for water-column cultured oysters, Crassostrea virginica, in the Chesapeake Bay(2022) Hood, Shannon Marie; Plough, Louis V; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Oyster aquaculture is flourishing in the US and internationally, delivering wide-ranging benefits to coastal communities, economies, and ecosystems. While the oyster aquaculture industry has grown substantially, a number of ongoing challenges limit industry growth. The issue of biofouling is paramount among these impediments to industry growth and farmers employ a range of techniques for biofouling control, including chemical immersion, physical methods, paints or coatings, and biological control methods. Desiccation, or the periodic aerial exposure of oysters and cages, is a popular biofouling control strategy and previous research has demonstrated the effectiveness of 24 consecutive hours of desiccation at a weekly frequency (compared to 24 hours bi-weekly, monthly, or seasonally), but this treatment has yielded a growth penalty in addition to biofouling control. The optimal interval (duration) of desiccation has not been thoroughly investigated and shorter intervals applied at a weekly frequency may yield different results. Therefore, this dissertation set out to investigate the effects of multiple weekly desiccation intervals (0-, 4-, 8-, and 24-hours) on eastern oyster (Crassostrea virginica) production and biofouling control. In Chapter 2, I examined responses of the biofouling community and oysters to three weekly desiccation intervals (0-, 8-, and 24-hours) at three commercial oyster farms in the Chesapeake Bay over 4 months. In Chapter 3, I conducted longer term (7 month) monitoring of the response of the biofouling community and oysters to four weekly desiccation intervals (0-, 4-, 8-, and 24-hours) at a single site in the Choptank River. In Chapter 4, I examined molecular (heat shock protein expression) and physiological (filtering rate, gametogenic stage, glycogen content) responses of oysters to four weekly desiccation intervals (0-, 4-, 8-, and 24-hours) in the Choptank River over 3 months. Results indicate broad-scale effectiveness of all desiccation treatments in reducing total biofouling coverage, although species- and site-specific responses were observed. Oyster growth was inconsistently affected by desiccation treatment, but reduced growth was observed in the 8- and 24-hour treatments in two of the three years of field investigations, perhaps influenced by reduced time spent in the water feeding and a delay in the onset of filtering post-desiccation. However, the timing of the greatest reduction in growth rates with desiccation suggests that concomitant stress of desiccation plus gametogenesis may have elevated the oysters’ stress response (reduced growth). Indeed, gametogenic stage and glycogen content were influenced by desiccation interval and oysters in the 24-hour treatment were the most likely to spawn. A high-level stress response via the upregulation of heat shock proteins (HSPs) was absent in oysters from the 8- and 24-hour treatments, indicating depressed HSP expression (and cellular protection) among the most stressed oysters. Future research into the importance of environmental factors during desiccation (air temperature, wind, humidity, etc.) could yield useful information to allow oyster farmers to target desiccation during optimal conditions, potentially limiting oyster exposure time in order to minimize oyster stress. Fouling reduction was significant in all treatments (4-, 8-, and 24-hour) and most consistent in the longer (8- and 24-hour) treatments. Therefore, a tradeoff is present between biofouling control and yield. Farmers prioritizing minimal biofouling may opt to desiccate for 8 or 24 hours weekly, while farmers seeking to maximize growth rates and minimize oyster stress may opt to desiccate for 4 hours weekly. Individual farmers must consider their own preferences regarding suitability of this husbandry technique, but results suggest that desiccation is an effective approach to biofouling control and can be applied with minimal stress to the oysters.Item EXAMINATION OF SOIL GREENHOUSE GAS FLUXES AND DENITRIFICATION TO ASSESS POLLUTION SWAPPING IN AGRICULTURAL DRAINAGE WATER MANAGEMENT(2022) Hagedorn, Jacob; Davidson, Eric A; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increases in agricultural nitrogen (N) inputs driven by synthetic N fertilizer application over the past century have led to higher crop yields but have also intensified riverine nitrate (NO3-) loading, contributing to environmental degradation. Drainage water management (DWM) is a best management practice (BMP) implemented on agricultural ditches to reduce downstream NO3- loading by slowing ditch discharge with drainage control structures that raise the in-field water table, creating anaerobic conditions. More anaerobic conditions stimulate denitrification and possibly methanogenesis. Denitrification consumes NO3-, thereby reducing the downstream N loading, but also increases production of N gases nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2). This research examined the potential consequence of greenhouse gas (GHG) emissions, specifically methane (CH4) and N2O, as a result of DWM-induced low oxygen conditions in a replicated experimental design. Using multiple methods such as soil gas flux measurements, N isotope analyses, gases dissolved in groundwater, and N budgets, this project examined the potential pollution trade-offs between dissolved NO3- and soil GHG fluxes. In chapter 2, I quantified soil N2O and CH4 fluxes using static chambers over three years in a corn/soybean rotation system. I also measured soil environmental variables to assess controls on gas production. Results indicated that the DWM treatment raised the groundwater level near the ditch edge but did not increase the surface soil moisture, which likely led to the observation that DWM did not significantly increase soil N2O and CH4 emissions. Variation in N2O fluxes were heavily influenced by N fertilizer application events. A N budget indicated that this farm site had a lower than average N use efficiency in the U.S. and higher than average soil N2O emissions. In chapter 3, I qualitatively and quantitatively examined the role of denitrification in this DWM system by using natural abundance NO3- isotopes measured across a leaching continuum (topsoil to deep soil to groundwater to ditch water). Results demonstrated that isotopic values of δ15N and δ18O increased in residual NO3- along the leaching continuum, providing evidence of denitrification. However, the net effects of nitrification and denitrification resulted in NO3- less enriched in 15N than expected by denitrification alone. These isotopic values were then applied to a mass balance of total N and δ15N to quantitively calculate the magnitude of total gaseous N export and to constrain that estimate using a net N isotopic discrimination factor. The calculated gaseous N export and denitrification rates fell within but toward the high end of previously reported literature ranges. The N budget indicated lower hydrologic N export in the DWM treatment, suggesting increased denitrification, but uncertainty of the corresponding estimates of increased gaseous N export was greater than the difference between treatments, rendering inconclusive the hypothesis that DWM treatment causes more total gaseous N production and denitrification. Inclusion of isotopes in the N mass balance established a lower bound of total gaseous N export, which was still large relative to other budget terms. In chapter 4, I synthesized results from the previous two chapters to explore the components of total gaseous N export. I also estimated annual export via dissolved N2O and N2 in groundwater entering the drainage ditches. Soil N2 emissions were estimated by subtracting annual estimates of soil N2O and groundwater dissolved N2 and N2O from the total gaseous N export. Results showed that soil N2 emissions dominated the gaseous N export. The N2O/(N2 + N2O) ratios of soil emissions were within but on the lower side of the literature range. This study demonstrated that, at least for this farm, the decrease in hydrologic N loading due to implementation of DWM outweighed the small and statistically non-significant observed increase in GHG production. This result lends support for policies to further incentivize adoption of DWM in ditched agricultural settings. This study also provides a novel, multi-methodological approach for quantitatively assessing and constraining denitrification rates and N2 emissions. It also is the first study to incorporate measurement of multiple fractions of total gaseous N export on the farm scale as part of annualized agricultural N budget.Item APPLIED STASIS THEORY AND Q-SORTING FOR ORGANIZING ENVIRONMENTAL SCIENCE COLLABORATION FOR POLICY DELIBERATION: A CASE OF POULTRY HOUSE EMISSIONS—AMMONIA AND PARTICULATE MATTER—ON THE DELMARVA PENINSULA/EASTERN SHORE(2022) Shea, Mary E; Tjaden, Robert; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)CONTEXT: Poultry farmers respond to national and global demand for low cost, packaged chicken. Raising poultry for market results in ammonia and poultry litter (manure and dust). However, for the Delmarva part of the Chesapeake Bay Watershed and Airsheds, ammonia and poultry litter mean nitrogen pollution, which effects water quality and human health. Therefore, this inquiry looks closely at the values and benefits that shape poultry farmer decisions about managing ammonia from their poultry houses using two technologies: Vegetated Emissions Buffers (VEBs) and Poultry Litter Treatments (PLTs). QUESTION: How can we better understand the values and benefits embodied in ammonia management choices by poultry farmers? METHODS: This dissertation uses three methods to engage with poultry farmers (2012-19) to better understand a range of values—economic and non-economic—about voluntary ammonia management strategies. 1. Stasis theory (Chapter Two), 2. Scaling of conceptual diagrams to three inch by four-inch cards, for designing visual Q-cards (Chapter Three), 3. Q-sorting of cards and findings (Chapter Four). FINDINGS: The Q-sorting events in this November 2019 study (25 value/benefits statements, sorted with 13 poultry producers) did not meet respondent number thresholds for formal Q-method factor analysis. However, results were studied using exploratory data analysis and chi-square testing of Q-sorting data. One important finding is that these eight cards appeared as important in two analysis categories: first, six cards likely MOST IMPORTANT (Photo 1); and second, the next two cards (Photo 2) as perhaps SOMEWHAT IMPORTANT. These pictured two sets of cards are ranked overall as having greater importance to poultry farmers, compared to aggregate card rankings of the other 17 cards in the 25-member card set. Photo 1: In the aggregate, these six cards were sorted most often into the MOST IMPORTANT category. Photo 2: In the aggregate, these two cards were sorted most often into the IMPORTANT category. The six cards in Photo 1 (MOST IMPORTANT) can be understood in several ways. First, these three cards (position noted in bold) represent economic benefits to poultry farmers, important for farm fiscal stability. The three cards on the left all represent health gains for chickens, meaning a better payout when healthy, unblemished, full-weight birds are sold to the poultry company:• Top-left card: This card symbolizes healthy chickens as “happy”—a visual shorthand for healthy—commanding more per pound at payout. • Middle-left card: This card shows reduced in-house ammonia, which means that chicken flesh is less likely to be burned or marred by ammonia, commanding more per pound at payout; generally, lowered in-house ammonia also means healthier birds, which is a specific value noted in just above in the top-left card description. • Bottom-left card: This card shows unblemished chicken “paws” which can command an extra premium for Asian specialty food markets. This portion of the bird represents a newer market for poultry producers. Within this group, two of these cards in Photo 1 (top- and middle-left) also show the value to farmers of using an enhanced schedule of PLTs to reduce ammonia inside the poultry house. The right-hand cards in Photo 1 can be understood thusly as relying on VEB use:• Top-right card: This card shows energy savings from using VEBs to shade poultry houses and provide winter wind cover, thereby reducing energy costs annually, supporting farm fiscal status. • Middle-right card: This card symbolizes reduced ammonia odor by VEB capture, which can help avoid neighbor and nuisance complaints. • Bottom-right card: This card shows the value of VEBs as helping the farmer meet existing nutrient management planning, a state-administered requirement for many poultry farmers. nitrogen and phosphorus are two nutrients associated with poultry production, poultry litter storage/composting, and poultry litter application as field fertilizer. These three VEB-focused cards in Photo 1 share the common context of concerning ammonia management strategies outside the poultry house, relying on the pollution remediation strategies of VEBs, a type of designed hedgerow plant structure._____ The two cards in Photo 2, noted as IMPORTANT but not as MOST IMPORTANT as the six cards in Photo 1 just described, relate to farmer concerns about human health. • Top card: This card show that poultry farmers can use VEBs outside poultry houses to capture ammonia and particle pollution, thereby improving local air quality, especially for farm families who live close to their poultry houses. • Bottom card: This card show that poultry farmers can use enhanced PLTs to reduce in-house ammonia, thereby improving worker conditions inside the poultry house. CONCLUSION: This case study demonstrates the value of Q-sorting used with Delmarva poultry farmers and attitudes about ammonia management. These findings can be also understood as ground-truthing evidence, in that the visual card-sorting data confirm as important the eight cards discussed above. These values/benefits depicted on these cards fit the poultry context of the Chesapeake Bay ecosystem. Additional Q-sorting activities with these cards or revised card sets to meet research needs are worthy undertakings. This dissertation case study also shows the value of humanities within environmental policy deliberation. Stasis theory, from rhetorical studies, helped organize the complexity of this project, as well as made a clear role for valuing activities (including Q-sorting). A second field of humanities inquiry is science visualization studies. This field, closely allied with rhetoric, helped with design values to build clear and environmentally-situated picture cards for Q-sorting the ranked importance of these cards to poultry farmers. Finally, the last chapter reflects on ways that a human dimensions approach supports a re-imagined Delmarva poultry production. One central design criterion about poultry production futures centers the role of poultry farmers, especially young farmers, in planning for resiliency. Among the pressures on poultry production is the well-documented wetter and warmer Delmarva, to climate change. The COVID-19 pandemic due to the 2019 emergence of the SARS-CoV-2 virus, also posed risks to Delmarva poultry resiliency. Scenario analysis and design options are better with humanist and social science knowledge, combined with environmental science.Item The effect of salinity on species survival and carbon storage on the Lower Eastern Shore of Maryland due to saltwater intrusion(2019) de la Reguera, Elizabeth; Tully, Kate; Palmer, Margaret; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As sea levels continue to rise, coastal ecosystems are vulnerable to saltwater intrusion (SWI), the landward movement of sea salts. Specifically, in coastal farmlands, we expect SWI to drive changes in plant species composition and carbon (C) storage. As soils salinize, standard crops (i.e. corn, soybean, and wheat) can no longer survive and farmers must consider alternatives. Further, transitioning agricultural fields may become C sinks as SWI advances inland and farmlands begin to resemble tidal wetlands. My objectives were to determine: (1) the effect of SWI on the germination of standard and alternative crop species, and (2) the C storage potential of salt-intruded farmlands. Most standard and alternative crops were intolerant to high levels of osmotic and ionic stress at the germination stage. However, sorghum and salt-tolerant soybean showed promise in field experiments. I show that agricultural fields exposed to SWI have a high potential to store C in soils.Item Taurine: An Indispensable Ingredient in the Development of Sustainable Aquafeeds(2013) Watson, Aaron Mackenzie; Place, Allen R.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Aquaculture as a global industry is at a crossroad; increased production cannot rely on the unsustainable harvest of forage fish for feed production. The use of fishmeal and fish oil as components in feeds for aquaculture, most notably for high value marine carnivores must be reduced or eliminated. The most promising and sustainable sources of replacement feed must be plant derived, such as soybean meal, wheat flour, and corn gluten along with dozens of other plant derived sources. Likewise for fish oil the most promising sources are plant oils such as soybean and canola oil supplemented with necessary omega-3 fatty acids. This work was undertaken to examine the effects of switching marine carnivores from fishmeal-based feeds to fishmeal-free, plant-based diets. The majority of this research has been conducted with cobia, Rachycentron canadum, a promising species for intensive aquaculture due to its rapid growth rates, high disease resistance, and lack of a major commercial fishery as competition. A variety of plant proteins, plant protein blends and alternative lipid sources were examined for digestibility and efficacy as fishmeal replacement sources in regards to their effects on growth rates, feed conversion, and a range of physiological characteristics. This work has explored the hypothesis that marine carnivores have lost the ability to synthesize taurine, a non-protein amino acid, in sufficient quantities and must therefore be supplied through the diet, and should be considered essential for all marine carnivores. By measurement of gene expression of the genes in taurine biosynthesis, this work shows that cobia do not possess the ability to regulate taurine biosynthesis confirming taurine must be supplied through the diet. Overall, this work has developed multiple plant protein-based feeds that perform equivalently or better than commercial and commercial-like diets. Taurine has been shown to be an essential ingredient when seeking to reduce or preferably, eliminate fishmeal and thereby making aquaculture sustainable in providing protein to meet the world's growing population.Item Identifying Molecular Functions of Heliotropic Motor Tissue Through Proteomic Analysis of Soybean Pulvini(2013) Lee, Hakme; Sullivan, Joseph; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Heliotropic and nyctinastic leaf movement are mediated in soybean through turgor changes in the motor cells of the pulvinus, located at the base of the leaves. While some elements of the signaling pathways have been studied, a broad-scale protein identification has not yet been reported. In my research pulvini proteins were extracted in light- and dark-harvested soybean using the TCA/acetone method and identified by LC-MS/MS. Gene ontology analysis revealed proteins involved in proton transport were enriched in the soybean pulvinus proteome compared to a background soybean proteome. Proteins more highly expressed in the light were mostly stress response proteins, while under-expressed proteins were categorized as energy proteins. Further investigations using more sensitive extraction protocols and a multitude of sample times will build on these initial results to provide a thorough examination of heliotropic mechanisms at the molecular level.