MEES Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/19655

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End date: 2019Subject: search.filters.subject.Ecology

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    EFFECTS OF SEA LEVEL RISE ON TIDAL FRESHWATER, OLIGOHALINE, AND BRACKISH MARSHES: ACCRETION, NUTRIENT BURIAL, AND BIOGEOCHEMICAL PROCESSES
    (2019) Allen, Jenny; Baldwin, Andrew H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Tidal wetlands provide critically important ecosystem services such as storm surge and flood attenuation, pollution retention and transformation, and carbon sequestration. The ability of tidal wetlands to maintain surface elevation under accelerated sea level rise is critical for their persistence. Saltwater intrusion can further threaten tidal freshwater marshes by decreasing primary production and organic matter accumulation as well as cause shifts in microbial pathways, leading to increases in organic matter decomposition and an overall decrease in marsh elevation. The objectives of this research were to examine accretion dynamics across the estuarine gradient of the Nanticoke River, a major tributary of the Chesapeake Bay, and determine the relative contribution of organic and inorganic matter to accretion in the marshes; determine the accumulation rates of C, N, and P across the estuarine gradient; and examine the effects of sulfate intrusion on biogeochemical transformations and marsh surface elevation in tidal freshwater marsh soil. Results of the collective studies suggest that the mechanisms controlling accretion dynamics and nutrient accumulation are complex and are likely driven by site-specific factors rather than estuary-wide factors. Accretion rates and nutrient accumulation rates were highly variable across the estuarine gradient, but were largely dependent on both organic matter accumulation and inorganic sedimentation. Only 8 out of the 15 subsites had accretion rates higher than relative sea level rise for the area, with the lowest rates of accretion found in the oligohaline marshes. Organic matter accumulation is especially important in marshes with low mineral sediment supply, particularly mid-estuarine oligohaline marshes, but may not be enough to help keep these marshes above relative sea level. The tidal marshes along the Nanticoke River removed approximately 15% and 9% of the total N and P load entering the system, but their ability to continue to remove nutrients may be compromised due to rising sea levels. Shifts in microbial pathways and increases in organic matter decomposition due to saltwater intrusion further threaten the ability of these marshes to keep pace with sea level rise, potentially resulting in the loss of an extremely valuable ecosystem.
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    Seasonal Migrations of Atlantic Sturgeon and Striped Bass Through the Maryland Wind Energy Area
    (2019) Rothermel, Ella Rick; Secor, David; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Baseline information is needed on migrations through US Mid-Atlantic Bight shelf waters in advance of offshore wind development. Acoustically-tagged Atlantic sturgeon and striped bass were detected from 2016-2019 in an array of 20 acoustic telemetry receivers centered on the Maryland Wind Energy Area and extending 10-50 km offshore. Both species were transient (mean residency < 3 days), but migration patterns differed seasonally and were related to depth and temperature. Generalized additive models showed that Atlantic sturgeon occur at inshore sites during spring while striped bass shifted toward the outer shelf as inshore waters cooled in winter. The movement of hundreds of tagged striped bass and sturgeon, originating from shelf waters from Maine to South Carolina suggests that the Wind Energy Area is part of a multi-species Atlantic coastal flyway, particularly during spring, fall, and winter periods. Thus, summer presents a potential window for wind tower construction.
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    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.
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    EFFECTS OF THE INVASIVE PHRAGMITES AUSTRALIS ON THE PREDATION OF MOSQUITOES THROUGH CHANGES IN HABITAT COMPLEXITY
    (2019) Weeks, Virginia Lynn; Leisnham, Paul; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Ephemeral stormwater ponds in the eastern United States are often invaded by non-native Phragmites australis which has been associated with numerous negative impacts on resident systems, including changes in hydrology, displacement of native macrophytes, and degradation of wildlife habitat. Few studies have documented the impacts of invasive P.australis on macroinvertebrate communities. Vegetated edges of stormwater retention facilities are often important developmental habitat for medically significant mosquitoes and the invertebrate predators that regulate their abundances. The displacement of resident macrophytes by P.australis could alter the physical structure of pond vegetation and disrupt the interactions between mosquitoes and their visual predators. The overall goal of my thesis was to evaluate differences in habitat complexity between native macrophytes, T.latifolia and J.effuses, and P.australis, and explore how those differences may impact predation of mosquitoes. I addressed this goal by conducting a controlled laboratory predation experiment and field surveys of four stormwater ponds.
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    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.
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    Patterns of oyster natural mortality in Chesapeake Bay, Maryland during 1991-2017 and its relationships with environmental factors and disease
    (2019) Doering, Kathryn Leah; Wilberg, Michael J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A common method of estimating natural mortality in bivalves includes several assumptions that are likely violated for oysters Crassostrea virginica in Chesapeake Bay, Maryland. In addition, while oyster disease dynamics are well studied spatially and temporally in the mid-Atlantic region, changes in disease-related relationships have not been investigated in Maryland. We developed a Bayesian estimator for natural mortality and applied it to oysters in Maryland. We then used the model output along with environmental factors and disease data to explore changes in the disease system over time. We found the largest differences in natural mortality estimates between the box count method and Bayesian model 1-3 years after a high mortality event. Some relationships changed over time in the disease system, most notably those associated with MSX, suggesting resistance to MSX has potentially developed. This work improves our estimates of natural mortality and understanding of oyster disease dynamics in Maryland.
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    Turion size advantage in the restoration of Vallisneria americana: the importance of genetic identity and diversity
    (2019) Carew, Anne; Engelhardt, Katia; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The restoration and rehabilitation of damaged ecosystems has become a worldwide endeavor utilizing vast resources and ecological knowledge to build functioning and resilient ecosystems. Biodiversity restoration increases the likelihood that present species are well-adapted to the environment or can complement each other in resource use. Genetic diversity in populations may increase establishment rate, resistance to invasion, and resilience in a changing world. In parallel field and greenhouse experiments, I established colonies of the submersed aquatic macrophyte Vallisneria americana. Colony survival and performance was affected by environmental conditions in the field and genotypic diversity in the greenhouse. In the presence of nonnative Hydrilla verticillata, V. americana height was reduced; however, biomass increased, suggesting resource partitioning in response to competition. These results suggest that genotypic identity and diversity are important in early establishment of plant populations and calls attention to designing restorations that incorporate genetic information about source populations.
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    ELUCIDATING RECRUITMENT STRESSORS FOR THE MARYLAND STATE ENDANGERED COMMON TERN (Sterna hirundo) THROUGH USE OF A MINIMALLY INVASIVE SURVEILLANCE SYSTEM
    (2018) Marban, Paul Ramon; Murrow, Jennifer L; Prosser, Diann J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In this thesis, I monitored two breeding colonies of the Maryland state endangered common tern (Sterna hirundo) using a surveillance system composed of video cameras and temperature loggers. This system was coupled with an in-depth image analysis of Landsat scenes to quantify island loss in the Chesapeake Bay and coastal bays of Maryland and Virginia from 1986 to 2016. Incubation duration was determined through analysis of both in-nest temperature and video footage. Incubation trends varied between colonies but an overall trend of nighttime desertion was observed on Skimmer Island as a result of predator presence. Island loss was documented in the region since 1986. Area of beach habitat, key for breeding populations of this species, increased in 1996 and 2011 as a result of sand accretion on coastal islands and the construction of Poplar Island. All other habitat types declined. This thesis is the first to document island loss in the Chesapeake Bay beyond 2011 and the first to quantify the impact of Poplar Island’s construction on the region. To promote future breeding of common terns in Maryland, resources must be allocated to create new habitat islands removed from the mainland and free of nesting predators. Existing islands must also be supplemented yearly with substrate to mitigate erosion from sea level rise.
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    TROPHIC ECOLOGY AND PHYSIOLOGICAL CONDITION OF BLACK SEA BASS CENTROPRISTIS STRIATA IN THE MIDDLE ATLANTIC BIGHT
    (2018) La Rosa, Ginni Alice; Woodland, Ryan J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Black sea bass Centropristis striata (Linnaeus, 1758) is a valuable Middle Atlantic Bight fisheries species, but spatial patterns in condition and diet during summer residence at inshore reefs remain largely unknown. I examined a suite of potential drivers of physiological condition and trophic niche of C. striata using morphometric, stomach contents, and stable isotope indicators. Regional differences in liver tissue lipid content and standard condition indices covaried with additional biotic and abiotic factors. I show that liver tissue must be corrected for lipid content prior to interpreting liver carbon stable isotope data and I provide a correction equation for this species. Both spatial and biological factors explained observed patterns in diet and trophic niche metrics. An understanding of the factors that underlie spatial and temporal patterns in condition and trophic ecology provides insights necessary to help inform ecologically-focused management decisions.
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    SPATIAL AND TEMPORAL DYNAMICS OF THE CHESAPEAKE BAY SEA NETTLE
    (2018) Shahrestani, Suzan; Bi, Hongsheng; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The jellyfish Chrysaora chesapeakei forms large summer blooms in Chesapeake Bay, and has substantial ecological and economic impacts on local ecosystems. Limited information on this species is mostly due to difficulties collecting spatial information on jellyfish in dynamic coastal ecosystems. Spatial gaps of C. chesapeakei were addressed by applying a multi-scale approach across life stages and within a source-sink context, reflected by the ecology and habitat utilization of C. chesapeakei. An Adaptive Resolution Imaging System (ARIS, SoundMetrics, Inc.) was used to collect high-resolution data on medusae in 2016 and 2017, within a Patuxent River waterscape. Polyp settlement plates were deployed at eight sites to understand the distributional range of the sessile benthic stage in Chesapeake Bay, but polyps successfully overwintered at only one of the sites, indicating that settlement alone was insufficient to explain C. chesapeakei dispersal to new habitat. Using high-resolution sonar data, a multi-scale spatial analysis was conducted to understand medusae dispersion and abundance. Medusae were three times more abundant in 2017 than in 2016. However, differences in water-column concentration were not apparent at the fine-scale (<5m) where medusae were randomly dispersed in both years. At the mesoscale (10km), spatial dependency was observed in both years, with more transport of jellyfish to dispersal habitat in the high-abundance year (2017). Overall, polyp settlement and overwintering survival in potential habitat seem to control the spatial distribution of C. chesapeakei at the Bay-wide scale while medusae appear responsible for mesoscale dispersal to new habitat, demonstrating high dispersal to sink habitat in a high-density year and low dispersal in a low-density year.