Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
8 results
Search Results
Item Climate Change and Vibrio species: Investigation of Environmental Parameters Associated with Occurrence and Transmission(2023) Brumfield, Kyle David; Colwell, Rita R.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Climate change, associated with shifts in the geographical range of biological species, has become increasingly important in emergence and re-emergence of disease. Vibrio spp., native to aquatic ecosystems, are commonly associated with aquatic invertebrates, notably crustaceans and zooplankton. Some species of the genus Vibrio cause infection in humans, of which Vibrio cholerae, the etiological agent of pandemic cholera, is the most documented. Pathogenic non-cholera Vibrio spp., namely Vibrio parahaemolyticus and Vibrio vulnificus, cause gastroenteritis and also septicemia and extra-intestinal infections. They are responsible for a large number of public health emergencies in developed countries, including the United States. As sea temperatures rise and salinity profiles are altered, a pattern of poleward spreading of non-cholera Vibrio spp. has been observed globally, demonstrating significant geographic expansion of these bacterial populations, corroborated by an associated increase in the number of reported vibriosis cases. Since Vibrio spp., including pathogenic vibrios, play an important role in the degradation of polymeric substances, such as chitin, and in biogeochemical processes, they cannot be eradicated. Hence, routine monitoring and an early warning system are needed for public health preparedness. Since the 1960’s, ongoing research has focused on environmental factors linked with occurrence and distribution of clinically relevant Vibrio spp. and their role in disease transmission. We have reported that lack of, or damage to, water, sanitation, and hygiene (WASH) infrastructure, coupled with elevated air temperatures, and followed by above average rainfall promotes exposure of a population to contaminated water, hence increases the risk of an outbreak of cholera. Global predictive intelligence models applicable to diseases caused by non-cholera Vibrio spp. are in development. The research reported here describes results of intensive sampling to detect and characterize Vibrio spp. in the Chesapeake Bay, Maryland, and the Florida Gulf Coast, the latter an area significantly impacted by Hurricane Ian, September 2022, with a spike in confirmed vibriosis cases and deaths during weeks following the storm. Results of this study provide confirmation of environmental predictors for Vibrio spp. and document long-term increase and extended seasonality of Vibrio populations in the Chesapeake Bay. Using satellite remote sensing data, we demonstrate the impact of extreme heat, precipitation, and other key environmental and geophysical factors (e.g., temperature, salinity, and chlorophyll) on prevalence of pathogenic Vibrio spp. in aquatic systems. This study lays the groundwork for a predictive intelligence system for Vibrio spp. and other pathogens under varying climatic scenarios.Item Building Flood Resilience in Social-Ecological Systems(2023) Snider, Natalie L.; Dennison, William C.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Historic driving forces of economic development, continually growing population and expanding inequities, are already challenging the resilience of the social-ecological system (SES) on multiple fronts, including socially, economically and environmentally. Existing and increasing threats from climate change will exacerbate the challenges in managing for resilience. The dynamic nature, involvement of multiscale feedback mechanisms between the natural and social sub-systems, possible existence of multiple states of the social-ecological system and inability to ever gain full control or understanding make it a challenge for institutions and actors to define and manage the system boundaries, its components and feedbacks. This complexity requires a transdisciplinary approach that integrates those most impacted into building knowledge and solutions across the environmental, economic and social fields. Similarly, institutions managing these systems will need to develop new approaches and strategies to integrate social, ecological, economic and political aspects of the SES and expand the participation of individual actors in the system, including a redistribution of power to successfully achieve resilience outcomes. The Social-Ecological Resilience Framework, proposed here, seeks to build resilience in the SES through purposeful interventions to maintain or change the forms, functions or both. This framework relates the key terms of sustainability, adaptation, transition and transformation, under the overall umbrella term of resilience. Within this framework, resilience is defined as the ability of the system to sustain, adapt, transition or transform in the face of acute or systemic change. Each subsequent term is then defined by the level of change in forms and functions: (1) sustainable maintains the same forms and functions, (2) adaptation changes the forms while maintain the functions, (3) transition changes the functions while maintaining the forms and (4) transformation changes both forms and functions. The framework can be used to manage the changes that society is experiencing in these systems. Adaptive management and social learning are two examples of approaches for managing the SES under the overarching construct of the Social-Ecological Resilience Framework. Adaptive management, an iterative decision-making process to address uncertainties and adapt to future conditions, should be combined with social learning, a participatory process where knowledge, skills and values are gained or modified through social interactions and collective learning. This dissertation demonstrates the framework and these approaches through five case studies focused on building resilience to flood impacts. Flooding is the costliest natural disaster in the world. However, the calculation of disasters costs typically only includes the cost of flood damages to infrastructure. But flooding is also putting a toll on society’s ability to provide social services, maintain important social factors, such as community cohesion, impacting both physical and mental health, exacerbating inequities and deteriorating the environment and ecosystem services, all with significant costs. In China’s Sponge Cities Program, the key takeaway is that defining the SES, both geographically and in terms of important forms and functions relevant to achieving the resilience goals, should be identified early to be able to address any barriers to success. The key takeaway of the Coastal Structures case study is that roles and responsibilities need to be clearly defined for institutions and actors, by which they can collectively achieve both institutional goals of reducing the societal impacts of flooding and the actors’ goals of reducing their own impacts to well-being. In the Honduras case study, the key takeaway is that building institutional support requires a redistribution of power dynamics to facilitate bottom-up approaches that can increase the utility of resilience actions to solving more than one social, ecological or economic problem within the SES. In Indonesia’s case study, by identifying the key forms and functions for each resilience goal, the range of possible vulnerabilities can be better defined, and timelines of potential changes and strategies to safeguard that positive outcomes are achieved can be developed. And finally, in Louisiana, the key takeaway is that institutions should not be defining the future of the SES without all the key actors engaged or represented. Institutions should support building a common vision of a resilient future through an integrated adaptive management and social learning program. The dissertation discusses a proposed Social-Ecological Resilience Framework (Chapter 1) to define key terms that integrates the notion of resilience, sustainability, adaptation, transition and transformation in relationship to each other and in relationship to the form and function of the SES. Several case studies from around the world demonstrate various aspects of operationalizing the framework. Technical aspects of adaptive management are developed and applied to a case study in Louisiana (Chapter 2). Lastly, social learning is then integrated into adaptive management using the same case study (Chapter 3). Both of these two chapters discuss actions to build resilience in the SES at a localized scale. Managing a social-ecological system (SES) can be an arduous task, and many institutions, such as governmental, non-profit, and research entities, may feel overwhelmed by the complexity and scope of this challenge. It's tempting to concentrate on a particular aspect of the system that seems more manageable or familiar. Nevertheless, without adopting a systems-thinking approach and examining the interactions within and beyond the SES, there is a risk of unintended and cascading consequences and missed opportunities to tackle multiple vulnerabilities collectively. Although this dissertation focuses on flood-related risks, the underlying themes and methodologies are relevant to any disaster, whether caused by nature or humans. Ultimately, our shared efforts to shape a more equitable, resilient, and sustainable world for present and future generations can benefit from these approaches.Item UNDERSTANDING MANAGED RETREAT THROUGH A MULTI-STAKEHOLDER LENS: A CASE STUDY ON THE LOWER EASTERN SHORE OF MARYLAND(2021) Miralles, Andrea Maria; Paolisso, Michael J.; Alcañiz, Isabella; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Due to concerns about increasing sea levels and climate displacement, there has been a growing interest in the adaptation option of managed retreat. In managed retreat, shorelines move inland acting as a natural buffer to coastal climate impacts, while coastal communities move to higher ground through voluntary home buyouts. Managed retreat is also highly controversial, as it is poorly understood and presents significant challenges to equity. In order to address these issues, this thesis research provides a multi-stakeholder analysis on the Lower Eastern Shore of Maryland focused on understandings and trust in managed retreat processes. Key findings from this research are that communities, government and non-governmental organizations have different understandings of managed retreat, that retreat discussions need to occur at official levels now, that equity must be a central component of planning, that trust is necessary for successful retreat and that any future retreat must emphasize community agency and collaboration.Item Integrating genetic information with macroscale models of species' distributions and phenology: a case study with balsam poplar (Populus balsamifera L.)(2019) Gougherty, Andrew Vincent; Fitzpatrick, Matthew; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To keep pace with future climate change, forest tree species are often predicted to need to shift their geographic ranges and phenology to minimize exposure to climates they have not experienced in the recent past. While many approaches have been developed to predict range shifts and shifting phenology, most large-scale, spatial techniques do not explicitly account for intraspecific genetic variation. This can be problematic when populations are locally adapted to climate, a common characteristic of plant species, as species-level responses to climate may not be representative of populations. In this dissertation, I use balsam poplar (Populus balsamifera L.), a northern North American deciduous tree species, to test a variety of techniques of integrating genetic information with spatial models of balsam poplar’s distribution and phenology. First, I tested multiple hypotheses, identified in the literature, for their ability to predict genetic diversity in balsam poplar. Results show that diversity in balsam poplar was highest in the center of the range and lowest near the range edge – consistent with the ‘central-periphery hypothesis.’ Second, I tested whether genetically-informed distribution models are more transferable through time, than standard distribution models. Using pollen and fossil records to validate models, I show that standard and genetically-informed distribution models perform similarly through time, but genetically-informed models offer additional insights into where populations may have originated on the landscape during the last glacial maximum. Third, I developed a new approach to predict population’s exposure to future climate change. Using spatial models of adaptive genetic differentiation, I show that populations in the eastern portion of balsam poplar’s range have the greatest predicted exposure to climate change as they would need to migrate the furthest and will see the greatest disruption in their gene-climate association. Fourth, I assessed whether a genomic prediction of common garden observations of phenology can inform phenology measured on the landscape with remote sensing. I show that the genomic prediction was the most important variable explaining the date of spring onset on the landscape, but was relatively unimportant in predicting the heat sum accumulated at the date of spring onset. I also show that model error was correlated with multiple meteorological variables, including winter temperatures – illustrating the challenges of predicting phenology in changing climates.Item THE ORGANISMAL AND POPULATION EFFECTS OF CLIMATE CHANGE ON JUVENILE BLUE CRAB (CALLINECTES SAPIDUS) IN THE PATUXENT RIVER, CHESAPEAKE BAY(2017) Glandon, Hillary Lane; Miller, Thomas J; Paynter, Kennedy T; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Future climate scenarios predict an increase in temperature and dissolved carbon dioxide (pCO2) of the marine environment in the next century. Calcifying marine invertebrates are thought to be especially vulnerable to increases in pCO2 and although the effect of increasing temperature in many of these taxa is understood, less is known about the interactive effects of these stressors on the physiology of calcifying invertebrates. In the present study, juvenile blue crab (Callinectes sapidus) were exposed predicted future levels of temperature and pCO2 in a 2x2 factorial design for two complete molts (approximately 30 days). Increased temperature caused a significant increase in crab growth rate and food consumption, but at a cost to carapace thickness and chemistry. The carapaces of individuals exposed to increased temperature were significantly thinner and had significantly lower percent high-magnesium calcite (HMC), the mineral from which the carapace derives its strength. Although there was a significant increase in percent HMC in response to increased pCO2, this was paired with an increase in the concentration of magnesium, complicating the overall effect of increased pCO2 on the carapace. The temperature range tested in this study was not large enough to elicit a significant difference in mean oxygen consumption rate. Crabs were resilient to exposure to extremely high levels of pCO2; there was no significant effect of increased pCO2 on crab growth rate, food consumption, or oxygen consumption rate. Individual physiological response data were utilized in concert with historical and predicted water temperatures to determine effects of future predicted increases in water temperature on blue crab overwintering behavior in the Chesapeake Bay. Model data indicated a significant shortening of the overwintering period from approximately 3.5 months currently to between 1.5 and 3 months, depending on the climate model utilized for the predictions. Increases to growing season length, combined with predicted increases in crab growth rate and food consumption, indicate that in the future blue crab will mature faster and may possibly grow year-round, similar to individuals that live in the southern extent of the species’ range.Item SPONGE MUTUALISM IN THE FACE OF CLIMATE CHANGE(2016) Vicente, Jan; Hill, Russell T; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Three epizoic symbioses between new sponge species of the genera Plakortis, Haliclona, and Xestospongia deweerdtae are reported here. Barcoding of the cytochrome oxidase subunit 1, 28S rRNA and 18S rRNA genes allowed me to formally describe the Plakortis spp. as P. deweerdtaephila and P. symbiotica. Both Plakortis spp. are obligate hosts of the sponge X. deweerdtae. Unlike Plakortis spp., X. deweerdtae can have a free-living lifestyle. This discovery motivated me to: 1) Use next-generation sequencing to ask whether microbial symbionts are playing a role in shaping these sponge associations; 2) Evaluate how top-down factors influence these associations by analyzing crude extracts of each species by LCMS and determine their palatability to fish to test if chemical defenses from Plakortis spp. translocate into the Xestospongia tissue, and protect it from predation, and 3) Test whether the X. deweerdtae and P. deweerdtaephila sponge pairs in Panama are more resilient than free-living X. deweerdtae in the face of climate change. My results on bacterial and sponge cell counts revealed that Plakortis spp. are high microbial abundance sponges and that X. deweerdtae and H. plakophila are low microbial abundance sponges. Diversity indices showed no differences in microbial richness but a higher Simpson’s index (D) for Plakortis spp. than both epibionts. Microbial community shifts in X. deweerdtae epibionts not observed in the free-living lifestyle were a consequence of the presence of microbial phyla found in the Plakortis spp. basibiont, suggesting the possibility of horizontal transfer of symbionts from the basibiont to the epibiont. Crude extracts from tissues of both free-living and associated lifestyles of X. deweerdtae confer chemical defense. These results suggest that top-down predation pressures from reef fish do not influence the associated life-style of X. deweerdtae. Exposure to high pCO2 and warmer temperature revealed that acidification had an ameliorating effect against necrosis caused by high temperatures in free-living and associated individuals of X. deweerdtae as well as their P. deweerdtaephila basibiont. The X. deweerdtae epibiont was more resistant to temperature increments than P. deweerdtaephila. I performed a similar experiment on an invasive Hawaiian sponge Mycale grandis and discovered that neither acidification nor temperature affect skeleton synthesis. Taken together these findings suggest that these symbioses are mutualistic in nature and that sponges are likely to survive the predicted temperature and pCO2 conditions for the end of the century.Item EXPOSURE TO EXTREME HEAT EVENTS AND CHRONIC RESPIRATORY DISEASES AMONG A NATIONALLY REPRESENTATIVE SAMPLE OF THE UNITED STATES POPULATION(2016) Romeo, Crystal Eloma; Sapkota, Amir; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Previous studies have shown that extreme weather events are on the rise in response to our changing climate. Such events are projected to become more frequent, more intense, and longer lasting. A consistent exposure metric for measuring these extreme events as well as information regarding how these events lead to ill health are needed to inform meaningful adaptation strategies that are specific to the needs of local communities. Using federal meteorological data corresponding to 17 years (1997-2013) of the National Health Interview Survey, this research: 1) developed a location-specific exposure metric that captures individuals’ “exposure” at a spatial scale that is consistent with publicly available county-level health outcome data; 2) characterized the United States’ population in counties that have experienced higher numbers of extreme heat events and thus identified population groups likely to experience future events; and 3) developed an empirical model describing the association between exposure to extreme heat events and hay fever. This research confirmed that the natural modes of forcing (e.g., El Niño-Southern Oscillation), seasonality, urban-rural classification, and division of country have an impact on the number extreme heat events recorded. Also, many of the areas affected by extreme heat events are shown to have a variety of vulnerable populations including women of childbearing age, people who are poor, and older adults. Lastly, this research showed that adults in the highest quartile of exposure to extreme heat events had a 7% increased odds of hay fever compared to those in the lowest quartile, suggesting that exposure to extreme heat events increases risk of hay fever among US adults.Item The Effects of CO2 and Temperature on the Soil Microbial Carbon and Nitrogen of Urban and Rural Forests(2015) Kulka, Elizabeth; McIntosh, Marla S; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study investigated and compared the effects of elevated temperature and elevated CO2 on the microbial biomass carbon (MBC) and nitrogen (MBN) of urban and rural forest soils. Soils analyzed from Baltimore Long-Term Ecological Research forests in June and October, 2014 had greater MBC and MBN quantities in rural than urban forests. A controlled environmental chamber study was conducted where June-collected soils were planted with hybrid poplars and exposed to ambient and elevated temperature and CO2 levels. After exposure for 49 days, MBC and MBN quantities were again greater in rural than urban soils. Soil MBC was greater under elevated than ambient CO2, while soil MBN was greater under elevated than ambient CO2 and temperature. Results suggest that if temperature and CO2 levels increase in the Baltimore area as predicted, microbial C and N pools in the studied forests will increase, and will remain greater in rural than urban soils.