Physical Sciences and Mathematics Commons^™

Honey As A Biomonitor For Air Pollutant Deposition In The Eastern United States Using Ion Chromatography And Scanning Electron Microscopy, Cole Cochran

Undergraduate Honors Theses

Anthropogenic activities generate metal, acid, and particulate air pollutants which negatively impact human and ecological health. In the United States, power plant, industrial, and vehicle emissions are leading causes of air pollution, however, the measurement of air pollution at high-resolution spatial regimes remains a challenge. Honey has emerged as a powerful biomonitoring tool to effectively quantify contaminants without the need for a large array of monitoring instruments. I hypothesized that honey could be used to effectively measure and map modern air pollutant spatiotemporal relationships over the Eastern U.S. Using ion chromatography with sulfate as an indicator for air pollution and …

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 …

Drivers And Seasonal Variability Of Redox-Sensitive Metal Chemistry In A Shallow Subterranean Estuary, Alison E. O'Connor, Elizabeth A. Canuel, Aaron J. Beck

VIMS Articles

The subterranean estuary (STE) has been historically defined in terms of the mixing of saline and fresh water, in an analogy to surface estuaries. However, redox gradients are also a defining characteristic of the STE and influence its role as a source or sink for metals in the environment. Approaching the STE from a redox-focused biogeochemical perspective (e.g., considering the role of microbial respiration and availability of organic matter) provides the ability to quantify drivers of metal transport across spatial and temporal scales. This study measured the groundwater composition of a shallow STE over 2 years and used multiple linear …

Nutrient Function Over Form: Organic And Inorganic Nitrogen Additions Have Similar Effects On Lake Phytoplankton Nutrient Limitation, Sabrina N. Volponi, Heather L. Wander, (...), Brian S. Kim, Et Al

VIMS Articles

The concentration of dissolved organic nitrogen (DON) is increasing in many northern hemisphere lakes, yet its use by phytoplankton and fate in the environment seldom have been quantified. We conducted 1 week, insitu, microcosm incubations across 25 lakes in northeastern North America to understand how DON, dissolved norganic nitrogen (DIN), and dissolved inorganic phosphorus (P) affected phytoplankton biomass. In addition,we tested whether lakes were limited by single macronutrients (N or P) or colimited by both. Phytoplankton biomass in 80% of lakes responded similarly to DON and DIN additions. Of the lakes where N form produced differential responses, the majority of …

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 …

Three Centuries Of Vegetation Change In The William & Mary College Woods Reconstructed Using Phytoliths, Timothy Terlizzi

Undergraduate Honors Theses

The College Woods, west of William & Mary’s campus, consists of ~900 acres of protected southern mixed hardwood forest. The woods surround Lake Matoaka, a former millpond established in ~1700. Despite the rich history of the area, little is known about how the dominant vegetative landcover has shifted over the last 300 years. This study set out to quantify the modern vegetation within the College Woods via the phytolith assemblages within the soil and identify shifts in the assemblages since the creation of Lake Matoaka and whether these changes are distinct from the vegetation that existed in the area before …

Riverine Carbon Cycling Over The Past Century In The Mid-Atlantic Region Of The United States, Yuanzi Yao, Hanqin Tian, Shufen Pan, Raymond G. Najjar, Marjorie A.M. Friedrichs, Et Al

VIMS Articles

Rivers are an important component of the terrestrial-aquatic ocean continuum as they serve as a conduit for transporting carbon from the land to the coastal ocean. It is essential to track the fate of this carbon, including how much carbon is buried in the riverbed, outgassed to the atmosphere, and exported to the ocean. However, it is often difficult to quantify these carbon transport processes on the watershed scale because observational data obtained by field surveys can only be used to estimate the magnitude of these processes at distinct points. In this study, we used a coupled terrestrial-aquatic ecosystem model …

Estuaries As Filters For Riverine Microplastics: Simulations In A Large, Coastal-Plain Estuary, Alexander G. Lopez, Raymond G. Najjar, Marjorie A.M. Friedrichs, Michael A. Hickner, Denice H. Wardrop

VIMS Articles

Public awareness of microplastics and their widespread presence throughout most bodies of water are increasingly documented. The accumulation of microplastics in the ocean, however, appears to be far less than their riverine inputs, suggesting that there is a “missing sink” of plastics in the ocean. Estuaries have long been recognized as filters for riverine material in marine biogeochemical budgets. Here we use a model of estuarine microplastic transport to test the hypothesis that the Chesapeake Bay, a large coastal-plain estuary in eastern North America, is a potentially large filter, or “sink,” of riverine microplastics. The 1-year composite simulation, which tracks …

Relative Impacts Of Global Changes And Regional Watershed Changes On The Inorganic Carbon Balance Of The Chesapeake Bay, Pierre St-Laurent, Marjorie A.M. Friedrichs, Raymond G. Najjar, Elizabeth Shadwick, Hanquin Tian, Yuanzhi Yao

VIMS Articles

The Chesapeake Bay is a large coastal-plain estuary that has experienced considerable anthropogenic changeover the past century. At the regional scale, land-use change has doubled the nutrient input from rivers and led to an increase in riverine carbon and alkalinity. The bay has also experienced global changes, including the rise of atmospheric temperature and CO2. Here we seek to understand the relative impact of these changes on the inorganic carbon balance of the bay between the early 1900s and the early 2000s. We use a linked land–estuarine–ocean modeling system that includes both inorganic and organic carbon and nitrogen cycling. Sensitivity …

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 …

Seasonal And Spatial Variation In The Location And Reactivity Of A Nitrate‐Contaminated Groundwater Discharge Zone In A Lakebed, Rl Smith, Da Repert, Dl Stoliker, Db Kent, Bk Song, Et Al

VIMS Articles

Groundwater discharge delivering anthropogenic N from surrounding watersheds can impact lake nutrient budgets. However, upgradient groundwater processes and changing dynamics in N biogeochemistry at the groundwater‐lake interface are complex. In this study, seasonal water‐level variations in a groundwater flow‐through lake altered discharge patterns of a wastewater‐derived groundwater contaminant plume, thereby affecting biogeochemical processes controlling N transport. Pore water collected 15 cm under the lakebed along transects perpendicular to shore varied from oxic to anoxic with increasing nitrate concentrations (10–75 μM) and corresponding gradients in nitrite and nitrous oxide. Pore water depth profiles of nitrate concentrations and stable isotopic compositions largely …

Advancing Marine Biogeochemical And Ecosystem Reanalyses And Forecasts As Tools For Monitoring And Managing Ecosystem Health, K Fennel, M Gehlen, P Brasseur, Cw Brown, C Ciavatta, G Cossarini, A Crise, Ca Edwards, D Ford, Marjorie A.M. Friedrichs, Et Al

VIMS Articles

Ocean ecosystems are subject to a multitude of stressors, including changes in ocean physics and biogeochemistry, and direct anthropogenic influences. Implementation of protective and adaptive measures for ocean ecosystems requires a combination of ocean observations with analysis and prediction tools. These can guide assessments of the current state of ocean ecosystems, elucidate ongoing trends and shifts, and anticipate impacts of climate change and management policies. Analysis and prediction tools are defined here as ocean circulation models that are coupled to biogeochemical or ecological models. The range of potential applications for these systems is broad, ranging from reanalyses for the assessment …

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 …

Soed Open Course: Seamless Modeling From Creek To Ocean On Unstructured Grids, Y. Joseph Zhang

Miscellaneous

This course explains the basic formulations used in the cross-scale SCHISM model, including the recent new developments. Hands-on tutorials will be conducted to familiarize the trainees with the basic tools useful for the modeling system. Although no formal pre-requisites are expected, trainees with prior UG model experience may find it easier to learn. Upon completion the trainees will have acquired basic knowledge on workflow in typical SCHISM simulations and be able to conduct simulations for cross-scale baroclinic processes as found in geophysical fluid dynamics (GFD)

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A Model Archive For A Coupled Hydrodynamic-Sediment Transport-Biogeochemistry Model For The Rhône River Sub-Aqueous Delta, France, Julia Moriarty, Courtney K. Harris, Katja Fennel, Kehui Xu, Christophe Rabouille, Marjorie A.M. Friedrichs

Data

This dataset includes model input, code, and output used in the publication Moriarty et al. (2017, Biogeosciences), which used a coupled hydrodynamic-sediment transport-biogeochemical model to investigate the roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics on the Rhône River sub-aqueous delta, France. Model development for this project focused on coupling the sediment transport and water-column biogeochemistry modules in the Regional Ocean Modeling System (ROMS) by incorporating a seabed biogeochemistry module into the ROMS framework. As described in Moriarty et al. (2017, Biogeosciences), the coupled model can account for diffusion of nutrients across the seabed-water-column interface; storage …

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 …

Ocean Acidification Compromises A Planktic Calcifier With Implications For Global Carbon Cycling, Cv Davis, Emily B. Rivest, Et Al

VIMS Articles

Anthropogenically-forced changes in ocean chemistry at both the global and regional scale have the potential to negatively impact calcifying plankton, which play a key role in ecosystem functioning and marine carbon cycling. We cultured a globally important calcifying marine plankter (the foraminifer, Globigerina bulloides) under an ecologically relevant range of seawater pH (7.5 to 8.3 total scale). Multiple metrics of calcification and physiological performance varied with pH. At pH > 8.0, increased calcification occurred without a concomitant rise in respiration rates. However, as pH declined from 8.0 to 7.5, calcification and oxygen consumption both decreased, suggesting a reduced ability to precipitate …

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 …

Primary Production In The Delta: Then And Now, James E. Cloern, April Robinson, (...), Elizabeth A. Canuel, Et Al

VIMS Articles

To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical …

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 …

Efficacy Of Sediment Remediation Efforts On Pah Contaminant Flux Via Porewater Advection At The Sediment-Surface Water Interface, Julie L. Krask, Michael A. Unger, George G. Vadas, Michele A. Cochran, Aaron J. Beck

Presentations

Groundwater advection at the sediment-surface water interface is an important biogeochemical mechanism controlling the transport and bioavailability of contaminants in estuaries. At sites along the Elizabeth River (VA, USA) where the subterranean environment is heavily contaminated with polycyclic aromatic hydrocarbon (PAH)-rich dense non-aqueous phase liquid (DNAPL), consideration of groundwater-surface water dynamics and associated chemical exchange is critical for effective remediation. Preliminary data suggest that porewater advection in permeable sediments at this location is controlled by a host of physical forcing mechanisms that correspond with total flow estimates of up to 15,000 centimeters/year. Here, the efficacy of sediment remediation strategies, including …

Effects Of Commercial Clam Aquaculture On Biogeochemical Cycling In Shallow Coastal Ecosystems, Annie E. Murphy, Iris C. Anderson, Mark W. Luckenbach

Presentations

The bivalve aquaculture industry is expanding worldwide; sustainability requires improved understanding of its interactions with the environment. As suspension feeders, bivalves, such as clams, reduce primary production through feeding, and thus dampen eutrophication. Additionally, enhanced rates of denitrification, the microbial removal of reactive nitrogen, have been reported in bivalve sediments due to increased organic matter supply through biodeposition; another potential, yet indirect, control on eutrophication. Simultaneously, bivalves can influence local ‘bottom-up’ effects on production by enhancing nutrient regeneration through excretion and microbial mineralization of biodeposits. At clam aquaculture sediments, respiration and nutrient regeneration rates were significantly higher compared to uncultivated …

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 …

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 …

Regression Modeling Of The North East Atlantic Spring Bloom Suggests Previously Unrecognized Biological Roles For V And Mo, Nj Klein, Aj Beck, Da Hutchins, Sa Sanudo-Wilhelmy

VIMS Articles

In order to identify the biogeochemical parameters controlling pCO(2), total chlorophyll a, and dimethyl sulfide (DMS) concentrations during the North East Atlantic Spring Bloom (NASB), we used previously unpublished particulate and dissolved elemental concentrations to construct several linear regression models; first by hypothesis testing, and then with exhaustive stepwise linear regression followed by leave-one-out cross-validation. The field data was obtained along a latitudinal transect from the Azores Islands to the North Atlantic, and best-fit models (determined by lowest predictive error) of up to three variables are presented. Total chlorophyll a is predicted best by biomass (POC, PON) parameters and by …

Impact Of Diatom-Diazotroph Associations On Carbon Export In The Amazon River Plume, Ly Yeung, Wm Berelsen, Et Al, Deborah K. Steinberg, Et Al

VIMS Articles

Offshore tropical river plumes are associated with areas of high N-2 fixation (diazotrophy) and biological carbon drawdown. Episodic blooms of the diatom Hemiaulus hauckii and its diazotrophic cyanobacterial symbiont Richelia intracellularis are believed to dominate that carbon drawdown, but the mechanism is not well understood. We report primary productivity associated with blooms of these diatom-diazotroph assemblages (DDAs) in the offshore plume of the Amazon River using simultaneous measurements of O-2/Ar ratios and the triple-isotope composition of dissolved O-2. In these blooms, we observe peaks in net community productivity, but relatively small changes in gross primary productivity, suggesting that DDA blooms …

The Role Of Copepods And Heterotrophic Dinoflagellates In The Production Of Dissolved Organic Matter And Inorganic Nutrients, Grace Kathleen Saba

Dissertations, Theses, and Masters Projects

Zooplankton play a key role in the cycling of dissolved organic matter (DOM) and inorganic nutrients. The factors that affect these processes, however, are not fully understood. I measured the effects of various diets on DOM and inorganic nutrient production by the copepod Acartia tonsa and the heterotrophic dinoflagellate Oxyrrhis marina, and explored the mechanisms of nutrient release from copepods. Copepods feeding on a mixed diet, the preferred diet of most copepods, had significantly lower dissolved organic carbon (DOC), ammonium (NH4+), and total dissolved nitrogen (TDN) release rates compared to feeding on a carnivorous or herbivorous diet. Thus, copepod feeding …

Salt Marsh Ecosystem Biogeochemical Responses To Nutrient Enrichment: A Paired N-15 Tracer Study, Dc Drake, Bj Peterson, Et Al, Le Lemay, Et Al

VIMS Articles

We compared processing and fate of dissolved NO3- in two New England salt marsh ecosystems, one receiving natural flood tide concentrations of similar to 1-4 mu mol NO3-/L and the other receiving experimentally fertilized flood tides containing similar to 70-100 mu mol NO3-/L. We conducted simultaneous (NO3-)-N-15 (isotope) tracer additions from 23 to 28 July 2005 in the reference (8.4 ha) and fertilized (12.4 ha) systems to compare N dynamics and fate. Two full tidal cycles were intensively studied during the paired tracer additions. Resulting mass balances showed that essentially 100% (0.48-0.61 mol NO3-N.ha(-1).h(-1)) of incoming NO3- was assimilated, dissimilated, …