Physical Sciences and Mathematics Commons^™

Importance Of Muddy Bed Aggregate Processes In Cohesive Sediment Dynamics Associated With Sediment Management Projects, David Perkey

Dissertations, Theses, and Masters Projects

The erosion and transport processes of fine sediment is largely impacted by the aggregation state. Understanding fine sediment transport processes is a key component to managing the nation’s navigation channels, ports, and reservoirs. To improve its ability to apply management strategies related to fine sediments, the USACE has undertaken research that focusses on the aggregation state of fine sediment. Of particular interest is the ability to expand the use of fine-grained sediment in projects that seek to beneficially use dredge material. In this study, a newly developed camera system was used to evaluate the aggregation state of eroded sediment from …

Feedbacks Among Benthic Metabolism, Nitrogen Cycling, And Intense Phytoplankton Blooms In The York River Estuary, Michelle H. Woods

Dissertations, Theses, and Masters Projects

Benthic-pelagic coupling is defined as the deposition of organic matter from the water column to the sediments, and the subsequent remineralization of this organic matter and release of inorganic nutrients back to the water column. This process plays an important role in determining the magnitude of benthic net community production (NCP), a metric that reflects the balance between gross primary production and respiration. Environmental factors, such as the presence or absence of intense phytoplankton blooms can influence the direction and magnitude of benthic-pelagic coupling and determine if benthic NCP is net autotrophic or heterotrophic. The objective this thesis was to …

Ecosystem Enriching And Efficient Solar Energy: Exploring The Effects Of Pollinator-Friendly Solar Facilities On Ecosystem Function And Solar Panel Efficiency, Jordan Martin

Dissertations, Theses, and Masters Projects

As the solar energy industry grows, many hundreds of thousands of acres of land will be transformed into solar panel facilities. With this large change in land use, there is the opportunity to promote biodiversity and support pollinators by using pollinator-friendly management practices at the solar facilities. This paper explores the ecological and economic effects of a pollinator-friendly solar facility compared to a turfgrass solar facility.

I hypothesized that a pollinator-friendly solar facility would be functionally equivalent in pollinator support and overall insect diversity to a pollinator-friendly non-solar field and that both sites would have far greater pollinator support and …

Barrier-Island Dynamics: Transgression, Regression, And State Changes, Justin Lee Shawler

Dissertations, Theses, and Masters Projects

Barrier islands provide critical habitat for shorebirds and buffer backbarrier and inland coastal habitats and communities from the direct effects of storms and wave energy. Yet, barrier systems are under threat from these very same processes. In particular, whereas long-term barrier behavior and landward migration rate is directly related to the rate of sea-level rise, decadal to centennial barrier-island dynamics are more complicated, and often highly localized. Barrier-island dynamics—including state changes between seaward growth and landward migration—are driven by a complex interplay of forcings and interactions, including changes in longshore and cross-shore sediment fluxes, underlying geology and slope, barrier-marsh and …

Differential Nitrogen Uptake By Aquatic Communities In A Chesapeake Bay Tributary And In The Coastal Alaskan Arctic, Brianna Stanley

Dissertations, Theses, and Masters Projects

Nitrogen (N) is one of the essential building blocks for all life and is available in the form of dissolved N in aquatic ecosystems. It is important to understand how this N can support primary and secondary production mediated by phytoplankton and bacteria, respectively, as it can affect both microbial loop biogeochemistry and the higher trophic levels of food webs. Nitrogen studies have traditionally focused on dissolved inorganic N (DIN) as a labile N source. Dissolved organic N (DON), while still often considered refractory, has been increasingly recognized as an important N source supporting primary and secondary production. However, the …

Water Clarity And Suspended Particle Dynamics In The Chesapeake Bay: Local Effects Of Oyster Aquaculture, Regional Effects Of Reduced Shoreline Erosion, And Long-Term Trends In Remotely Sensed Reflectance, Jessica Turner

Dissertations, Theses, and Masters Projects

Water clarity is a key indicator of the ecosystem health in the Chesapeake Bay. Estuarine water clarity fluctuates due to external inputs from the watershed as well as processes occurring within the estuary itself, such as sediment resuspension and organic matter production. Therefore, water clarity requires study at multiple spatial and temporal scales and with multiple metrics. One local-scale process potentially influencing water clarity is shellfish aquaculture. One part of this dissertation examined how water quality and hydrodynamics varied among oyster farms as well as inside versus outside the extent of caged areas located in southern Chesapeake Bay. Current speed …

Controls On Estuarine Sediment Bed Erodibility: Insights From The York River Estuary, Cristin Lee Wright

Dissertations, Theses, and Masters Projects

The erodibility of estuarine sediment beds has a number of ecological and societal implications, including alteration of benthic habitats, light-limitation of primary production, and reintroduction of pollutants to the water column, as well as impacts on dredging operations and on the fate of potentially dangerous objects on the seafloor. The objectives of this study are to better understand controls on bed erodibility in estuarine environments, including the roles of sediment grain size, water content, percent organics, and bed fabric, as well as effects of tides, storms, salinity distribution, river discharge, and location within the estuary. An extensive set of erosion …

Sediment And Terrestrial Organic Carbon Budgets For The Offshore Ayeyarwady Delta: Establishing A Baseline For Future Change, Evan Rose Flynn

Dissertations, Theses, and Masters Projects

Large river deltas serve as globally important archives of terrestrial and shallow marine biogeochemical signatures because of rapid sediment burial, and have the potential to impact global biogeochemical cycling on modern and geologic timescales. This study investigates modern sediment and terrestrial organic carbon (TerrOC) accumulation within the offshore Ayeyarwady Delta in order to determine sediment and TerrOC budgets for this largely understudied mega-delta. The Ayeyarwady is the world’s third largest delta in terms of sediment supply, and remains one of the last long free-flowing rivers in Asia. However, recent increases in regional anthropogenic impacts risk severe alterations to sediment and …

The Role Of Suspended Sediment In Assessing Coastal Wetland Vulnerability, Daniel J. Coleman

Dissertations, Theses, and Masters Projects

Coastal wetlands sequester carbon, attenuate waves and storm surge, filter out nutrients and pollutants, and act as nursery habitat for important fisheries. The value of these ecosystems is underscored by their vulnerability to climate change, especially sea level rise. To persist under the threat of rising sea level, coastal wetlands must build elevation vertically. Delivery of sediment to the marsh during tidal flooding is a key component in the ecogeomorphic feedbacks that lead to elevation gain. Despite the importance of suspended sediment to assessing coastal wetland vulnerability, many questions remain unanswered. This dissertation addresses the impact of suspended sediment concentration …

Filling In The Gaps: Applications Of Deep Learning, Satellite Imagery, And High Performance Computing For The Estimation And Distribution Of Geospatial Data, Seth Goodman

Dissertations, Theses, and Masters Projects

Many regions around the world suffer from a lack of authoritatively-collected data on factors critical to understanding human well-being. This challenges our ability to understand the progress society is making towards reducing poverty, improving lifespans, or otherwise improving livelihoods. A growing body of research is exploring how deep learning algorithms can be used to produce novel estimates of sparse development data, and how access to such data can impact development efforts. This dissertation contributes to this literature in three parts. First, using Landsat 8 satellite imagery and data from the Armed Conflict Location & Event Data Project, convolutional neural networks …

Impacts Of Fertilization On Salt Marsh Resilience: Altered By Location-Specific Drivers, Kenneth Michael Czapla

Dissertations, Theses, and Masters Projects

Salt marshes provide valuable ecosystem services to human society, but are currently under threat from accelerating sea level rise and nutrient enrichment. Carbon (C) and mineral accumulation allow salt marshes to maintain elevation above sea level and survive. Anthropogenic nitrogen (N) loading is increasing in many salt marshes, causing negative impacts on marsh resilience such as increased decomposition and decreased below-ground production. However, increasing N may also have simultaneous positive effects such as increased primary production and above-ground biomass, surface sediment accretion, and denitrification rates, which remove excess N from coastal waters. Many studies have been conducted to determine the …

Beach-Ridge Sedimentology As An Archive Of Terrestrial Climate Change: Insights From Geochemical And Stratigraphic Study Of The Tijucas Strandplain, Southern Brazil, Julie Lauren Krask

Dissertations, Theses, and Masters Projects

Millennial-scale variations in climate forcing are recognized to drive changes in terrestrial processes, and, by extension, impart controls on fluvial sediment loads (e.g., weathering and erosion). However, the impact of decadal- to centennial- scale climate fluctuations on downstream coastal sedimentation patterns and landscape evolution remains unclear. Specifically, the connection between long-term (decades or more) precipitation intensity/seasonality and sediment export from river systems has not been established. This study examines the manner in which sub-millennial-scale fluctuations in precipitation within a river catchment in southern Brazil are recorded in a coastal sedimentary archive. The 5-km wide Tijucas Strandplain formed over the last …

Assessment Of The High-Resolution Sediment Gravity Flow Record In Prince William Sound, Alaska, Elisabeth Rose Clyne

Dissertations, Theses, and Masters Projects

South-Central Alaska is one of the most seismically active and climatologically sensitive places in the world. Within this region, Prince William Sound (PWS) receives abundant sediment from multiple sources, potentially housing a high-resolution environmental record spanning the past 4,000 years. Inputs to PWS are derived from local rivers and glaciers, and may include earthquake- and glacial-outburst-triggered sediment gravity flows. Therefore, this is an ideal location to investigate the long-term record of seismic, glacial, and riverine activity. This study examines the elemental, grain size, and stable isotope signatures in PWS to identify gravity flow deposits and the potential paleoseismic and paleoclimate …

The Role Of Seabed Resuspension On Oxygen And Nutrient Dynamics In Coastal Systems: A Numerical Modeling Study, Julia Miege Moriarty

Dissertations, Theses, and Masters Projects

Seabed resuspension can impact organic matter fate and water column biogeochemistry in coastal environments. Cycles of erosion and deposition can, for example, affect remineralization rates, seabed-water column fluxes of dissolved oxygen and nutrients, and light attenuation. Yet, models that incorporate both sediment transport and biogeochemical processes are rare, and nearly all neglect the effect of resuspension on oxygen and nutrient dynamics. Development of a novel tool, i.e. a coupled hydrodynamic-sediment transport-biogeochemical model, allowed for an investigation of the role of resuspension on oxygen and nitrogen dynamics within three distinct coastal environments. Called HydroBioSed, the coupled model was built within the …

Reconstructing Coastal Forest Retreat And Marsh Migration Response To Historical Sea Level Rise, Nathalie Schieder

Dissertations, Theses, and Masters Projects

Climate change assessments predict that rates of relative sea level rise will increase in the future, leading to enhanced inundation of low-lying coastal regions and a 20 – 50 % decline in salt marsh area by 2100. Global sea level rise began accelerating in the late 19th to early 20th century, and local rates along the U.S. mid-Atlantic coast are twice as fast as global estimates. Frequent flooding and salt stress associated with sea level rise lead to coastal transgression, and the survival of ecosystems depends on their ability to migrate inland faster than they erode and submerge. Here, I …

Using High-Resolution Glider Data And Biogeochemical Modeling To Investigate Phytoplankton Variability In The Ross Sea, Daniel Edward Kaufman

Dissertations, Theses, and Masters Projects

As Earth’s climate changes, polar environments experience a disproportionate share of extreme shifts. Because the Ross Sea shelf has the highest annual productivity of any Antarctic continental shelf, this region is of particular interest when striving to characterize current and future changes in Antarctic systems. However, understanding of mesoscale variability of biogeochemical patterns in the Ross Sea and how this variability affects assemblage dynamics is incomplete. Furthermore, it is unknown how the Ross Sea may respond to projected warming, reduced summer sea ice concentrations, and shallower mixed layers during the next century. to investigate these dynamics and explore their consequences …

Impact Of Climate Change Variables On Nutrient Cycling By Marine Microorganisms In The Southern California Bight And Ross Sea, Antarctica, Jenna Lee Spackeen

Dissertations, Theses, and Masters Projects

Ocean environments are being impacted by climate warming, elevated carbon dioxide (CO2) levels, and shifting nutrient sources and sinks. It is essential to quantify the sensitivity of microorganisms to these effects of global change because they form the base of the marine food web and are an integral component of nutrient cycling on the planet. their role in photosynthesis, nutrient uptake, and transfer of organic matter into higher trophic levels or to the deep ocean via the biological pump render microorganisms key in ecosystem structure and function and in regulating the global climate. The goal of this dissertation research was …

Biogeochemistry Of Redox-Sensitive Elements In The Subterranean Estuary, Alison E. O'Connor

Dissertations, Theses, and Masters Projects

Submarine groundwater discharge (SGD) is any flow of water along the continental margins from the seabed into the coastal ocean, and it represents an important source of nutrients and trace metals to the coastal ocean. The chemical composition of SGD is strongly influenced by biogeochemical reactions that take place within the subterranean estuary (STE), the subsurface mixing zone of fresh and saline waters. Understanding the reactions that take place within the shallow STE is critical to evaluating the composition of SGD, and therefore SGD-driven chemical fluxes. In this dissertation, I seek to determine the biogeochemical processes controlling the behavior of …

Signature Of Recent Sediment Accumulating In Prince William Sound, Alaska: A Record Of Storms, Earthquakes, And Seasonal Inputs, Nicole R. Marshall

Dissertations, Theses, and Masters Projects

This study focuses on the development o f provenance signatures for sediments accumulating in Prince William Sound, with an emphasis on interpreting mechanisms of sediment deposition using historical earthquake, wave, river discharge, and glacial outburst flood records. A highresolution sedimentary sequence in Prince William Sound, Alaska contains sediments sourced from local watersheds as a result of seasonal and event-driven sedimentation. This study contributes to the development of paleo-proxies for sediment provenance, earthquakes, shelf sediment resuspension, and Copper River discharge. Geochemical studies of sediment cores and end-member samples using X-ray fluorescence and inductively coupled plasma mass spectrometry allows for the development …

Storm Event Impact On Organic Matter Flux, Composition And Reactivity In Taskinas Creek, Va, Sarah Schillawski Cammer

Dissertations, Theses, and Masters Projects

Carbon export from the land to the ocean are an important part of the global carbon cycle, linking terrestrial watersheds and the global carbon cycle. Burial of terrestrial organic carbon represents a long term sink for atmospheric CO2. Approximately 0.4 Pg Cy-1 is delivered to the global ocean from rivers, equally divided between POC and DOC. However, the amount of carbon entering the ocean is a small portion of the total amount entering rivers from the terrestrial environment, suggesting a large amount of processing in inland waters and estuaries. Most monitoring efforts have focused the processing of organic matter on …

Sediment Deposition And Reworking: A Modeling Study Using Isotopically Tagged Sediment Classes, Justin J. Birchler

Dissertations, Theses, and Masters Projects

A sediment transport model within the Regional Ocean Modeling System (ROMS) was used to examine how repeated cycles of deposition, erosion, and bioturbation influence flood and storm event bed character offshore of a significant fluvial source. Short-lived radioisotopes Beryllium-7 (7Be) and Thorium-234 (234Th) can be used as tracers of deposition and reworking on the continental shelf, and modeled profiles of these radioisotopes, along with simulated profiles of sediment bed grain size distributions, were analyzed for various model runs.The presence of an atmospherically derived radionuclide,7Be, in seafloor sedimentindicates terrestrial (riverine derived) sediment deposition offshore of a fluvial source.In contrast,234Th naturally occurs …

A Biogeochemical Data Assimilative Modeling Study In The Mid-Atlantic Bight, Yongjin Xiao

Dissertations, Theses, and Masters Projects

Continental shelves are generally believed to play a critical role in ocean biogeochemical cycling, however this has raised the question as to the relative importance of various nitrogen flux terms such as denitrification, burial, net community production and advective fluxes. Quantifying these fluxes on an annual area-integrated basis using traditional observational means is often difficult, due to the fact that these fluxes rapidly change on relatively small spatial scales, making inadequate data resolution a significant problem. Satellite remote sensing data and numerical modeling provide alternative ways to fill the data gaps, and hence have the potential to generate quantitative estimates …

Sediment And Organic Carbon Burial In Englebright Lake, Ca Over The Last Century, Christina Rose Pondell

Dissertations, Theses, and Masters Projects

The proliferation of dams has impacted over 67% of the world's largest rivers, degrading ecosystems, severing river-watershed connectivity, and reducing water, sediment, and carbon supply from rivers to the coastal ocean by 20 to 100%. Many studies have focused on the downstream impacts of dams, but few have quantified the amounts and quality of organic matter stored within impoundments. This study examined organic carbon (OC) sources and accumulation in a reservoir in northern California to characterize the organic matter retained in terrestrial systems by these man-made structures and relate the amounts and quality of OC to mining, damming and flood …

Development Of A Large-Scale Storm Surge And High-Resolution Sub-Grid Inundation Model For Coastal Flooding Applications: A Case Study During Hurricane Sandy, Jon Derek Loftis

Dissertations, Theses, and Masters Projects

Coastal inundation initiated via storm surge by hurricanes and nor'easters along the U.S. East Coast is a substantial threat to residential properties, community infrastructure, and human life. During and after the storm, compounding with heavy precipitation and upland drainage, inundation can be caused by the combination of storm surge and river-induced inland flooding in various locations throughout the coastal plain. Thus, coastal inundation can be expanded from the open coast upstream into the tributaries of the New York Bay including the Hudson and East River systems. Given the cross-disciplinary nature of the dynamics (encompassing hydraulics, oceanography, and hydrology), and the …

High-Resolution Sediment Records Of Seismicity And Seasonal Sedimentation From Prince William Sound, Alaska, Using Xrf Core Scanning, Eric J. Miller

Dissertations, Theses, and Masters Projects

The southern coast of Alaska is a climatically sensitive and tectonically active region, however due to its remoteness and harsh climate there are limited long-term historical records of environmental conditions such as storm frequency, river discharge, and earthquakes. In order to determine the potential for Prince William Sound sediments to contain high-resolution paleorecords of these conditions, a suite of 11 gravity cores was collected within the Sound in order to determine the modern day sediment depositional trends and to develop elemental proxies for earthquakes and seasonal sedimentation. 210Pb/137Cs-derived sedimentation rates and grain size trends indicate that there are two distinct …

Submarine Groundwater Discharge To The York River Estuary: Quantifying Groundwater Flux And Potential For Biogeochemical Cycling, Jenna Lynn Luek

Dissertations, Theses, and Masters Projects

No abstract provided.

Seasonal Nitrogen Uptake And Regeneration In The Water Column And Sea-Ice Of The Western Coastal Arctic, Steven E. Baer

Dissertations, Theses, and Masters Projects

The logistical difficulties of research in extremely low temperatures and lack of access to the Arctic have meant that there is a historic dearth of knowledge of coastal Arctic biogeochemistry, especially during winter when sea ice is present. Recent observations, however, indicate that the Arctic is changing rapidly. Changes include increased temperatures, decreased extent and volume of sea ice, and increased freshwater inputs. How these changes influence biogeochemical cycles is an open question, especially in the highly productive coastal regions of the Chukchi Sea. Here I present nitrogen (N) uptake and regeneration rates for phytoplankton and bacteria measured in the …

Application Of Acoustics And Optics For The Characterization Of Suspended Particulate Matter Within An Estuarine Observing System, Grace M. Cartwright

Dissertations, Theses, and Masters Projects

As part of this dissertation work, a long term observing station at Clay Bank on the York River in Virginia has been established and maintained since 2006, and was used to gain a better understanding of sediment processes in a muddy estuary and in muddy coastal environments in general. While data from this NSF-funded Multi-Disciplinary Benthic Exchange Dynamic (MUDBED) observing system has and will be used by other students for this general purpose, this dissertation focuses specifically on better understanding and interpretation of the data collected by key instrumentation regularly deployed at the observing station, especially the acoustic Doppler velocimeter …

Acoustic And Sedimentological Investigations Of Seabed Conditions And Related Bio-Geological Parameters In A Tidally Energetic, Fine-Grained Environment: York River Estuary, Virginia, Lindsey M. Kraatz

Dissertations, Theses, and Masters Projects

The transport and fate of fine-grained sediments is a critical factor affecting the physical, chemical, and biological health of estuaries, coastal embayments, riverine, lacustrine, and continental shelf environments. A geophysical and sedimentological study of the York River as a part of the NSF Multi-disciplinary Benthic Exchange Dynamics (MUDBED) project was conducted to determine: 1) the primary drivers of sediment erodibility within a fine-grained system, 2) if these drivers can be accurately measured through sedimentological and acoustic information, and 3) the spatial and seasonal variability of erosion within the estuary. Previous studies indicate that increased erodibility within the York River Estuary …

Composition, Sources, And Age Of Dissolved And Particulate Organic Matter In The Delaware River And Estuary, Hadley Allaben Mcintosh

Dissertations, Theses, and Masters Projects

Estuaries are important sites of organic matter (OM) transformation, exchange, and burial but remain one of the least understood regions in the global carbon cycle. The carbon cycle within these regions is complex due to strong gradients in biological and physical processes, and increasing anthropogenic impacts. This is further complicated by the many sources of particulate and dissolved organic matter (OM) in estuaries, including materials derived from terrestrial and anthropogenic sources as well as aquatic and marine primary production. This study combined lipid biomarker analyses with stable and radiocarbon signatures of lipids and source-specific biomarkers to better understand the sources …