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Environmental Controls On Carbon And Nitrogen Cycling In Alaskan Arctic Coastal Lagoons
Get PDFAt the intersection of land, sea, and atmosphere, coastal lagoons act as bioreactors, processing both terrestrial and autochthonous organic matter production before export to the coastal ocean. Approximately half of the Beaufort Sea coast is outlined by barrier island chains that enclose shallow lagoons and sounds. These lagoons are subject to extreme seasonal variations in ice cover, temperature, and salinity, yet are home to a diverse and productive food web. Bound between the arctic tundra and Beaufort Sea, these shallow systems receive and process resources from both sea and particularly land in the form of coastal erosion and riverine export. While we know these terrestrial inputs are driving increasing rates of primary production in the Arctic Ocean, the role of nearshore coastal retention and processing of this material before export remains underexplored. To that end, the overarching goal of this dissertation was to assess seasonal and spatial dynamics of carbon and nutrient cycling in coastal Arctic lagoons as part of the Beaufort Lagoon Ecosystems Long-Term Ecological Research (BLE-LTER) program from 2018-2022. Water column and sediment samples were collected at five lagoons (Elson Lagoon, Simpson Lagoon, Stefansson Sound, Kaktovik Lagoon, Jago Lagoon) during Ice Cover (April), Break Up (June), and Open Water (August) in alignment with the major hydrological phases. In Chapter 2, Abiotic and biotic controls on nutrient cycling in coastal Arctic lagoons, I present seasonally collected water column nutrient data and estimated physical vs. biological controls on their concentrations. During Ice Cover, inorganic nutrient concentrations likely increased in response to brine exclusion and biotic remineralization. In contrast nutrient concentrations rapidly decreased during Break Up and Open Water through freshwater input dilution and autotrophic uptake during Break Up. In Chapter 3, Physical drivers of sediment distribution and organic matter oxidation in coastal Arctic lagoons, I focused on sediment characteristics and the physical conditions that drive organic matter distribution and microbial aerobic oxidation. Sediment grain size, organic matter content, and isotopic composition consistently differed between lagoons and water depths, reflecting the variability in sediment organic matter retention, source, and processing. In Chapter 4, Seasonal cycles of benthic productivity and N cycling in Beaufort Sea lagoons I present results from seasonal batch sediment incubations to quantify benthic metabolism and nitrogen cycling. In general, lagoon sediments shifted from net heterotrophy in Ice Cover, exhibiting net inorganic nutrient production and net denitrification before transitioning into net autotrophy during Break Up and Open Water with increased sediment nutrient consumption and nitrogen fixation. As the coastal Arctic undergoes rapid changes in temperature, duration of sea ice, river discharge, and coastal erosion, our understanding of seasonal nearshore coastal metabolism will help to better constrain future projections of coastal Arctic ecosystem productivity.Virginia Institute of Marine ScienceDoctor of Philosophy (Ph.D.
Virginia Game Fish Tagging Program: 2023 Annual Report
No full textThrough 2023, the Virginia Game Fish Tagging Program (VGFTP) has maintained a 28-year database of records for tagged and recaptured fish. The program is a cooperative project of the Virginia Saltwater Fishing Tournament (VSFT) under the Virginia Marine Resources Commission-(VMRC) and the Virginia Insitute of Marine Science (VIMS) of William & Mary (under the VIMS Marine Advisory Program). The main goal of the program is to train and maintain an experienced group of anglers who volunteer their time to properly tag and release fishes. Data on tagged and recaptured fish are summarized in annual re- ports and are accessible on VIMS website: http://www.vims.edu/vgftp/. Time series data are organized and provided when requested by anglers, angling groups, researchers, and fishery managers.Virginia Institute of Marine Scienc
Mid-21St Century Chesapeake Bay Hypoxia: The Role Of Climate Change At The Atmospheric, Terrestrial, And Oceanic Boundaries
No full textClimate change is already increasing the volume and duration of coastal hypoxia and threatening living resources, particularly in eutrophic ecosystems. Atmospheric warming exacerbates deoxygenation by decreasing gas solubility and enhancing respiration and remineralization. Changes in terrestrial runoff and sea level influence hypoxia via nutrient availability and altered water temperature, respectively. However, the impacts of other future climate changes, including winds, shortwave and longwave radiation, non-runoff precipitation, and ocean water conditions, are still unknown. In this study, the impacts of such future climate changes on hypoxia in Chesapeake Bay were examined using a 3-D coupled estuarine hydrodynamic–biogeochemical model linked to a regulatory watershed model. A control run simulated 1991-1995; while mid-21st century projections assuming no change in management actions were generated by applying downscaled outputs of three Earth System Models (ESMs), run under a “business as usual” emissions scenario. Mid-21st century hypoxic volume (O2 < 3 mg L-1) integrated over all days of a given year, also called annual hypoxic volume (AHV), is projected to increase by a minimum of 13% up to a maximum of 35%, when using the centroid ESM, with higher freshwater discharge years resulting in smaller percent increases. The use of future climate projections from the other two ESMs resulted in five-year average percent increases in AHV of 5% (relatively cool and dry ESM), 21% (centroid ESM) and 35% (relatively hot and wet ESM). Future changes to hypoxia are projected to vary seasonally, with hypoxic conditions projected to start earlier, but no change or decreased hypoxia in mid-summer. Finally, model runs with subsets of modified climate forcings revealed that air temperature accounted for the majority (72 ± 18%, five-year mean ± standard deviation) of the increase in AHV. Next most impactful to AHV were climate changes to watershed inputs (21 ± 31%) and sea level (-1 ± 24%), with both impacts being highly dependent on freshwater discharge. Finally, changes to winds, radiation, non-runoff precipitation, and ocean water conditions cumulatively accounted for only small future percent increases in AHV (5 ± 3%). To reach regulatory water quality goals despite these competing impacts of climate change, future nutrient management actions will likely need to be more aggressive.Virginia Institute of Marine ScienceMaster of Science (M.Sc.
Investigation Of The Pqse:rhlr Complex As A Target For Quorum Sensing Inhibition In Pseudomonas Aeruginosa
No full textPseudomonas aeruginosa is responsible for tens of thousands of infections and thousands of deaths each year. While primarily infecting immunocompromised individuals and people with cystic fibrosis, the ability of P. aeruginosa to evade treatment with antibiotics makes it a significant clinical burden. The imminence of antibiotic resistance and stagnation of new antibiotic development spurs researchers to investigate new strategies for combatting P. aeruginosa infection. It is known that P. aeruginosa relies on quorum sensing, the chemical cell-cell communication process, to carry out pathogenic behaviors. Further, the interaction between two proteins, PqsE and RhlR, has been identified for its indispensable role in translating chemical signals into infection. By using an Escherichia coli reporter, small molecule libraries were screened to discover inhibitors of the PqsE:RhlR protein-protein interaction. Hit molecules were then confirmed using both in vitro and in vivo experiments. Fluorescence polarization and esterase assays measured the affinity of small molecule inhibitors for the active site of PqsE and the ability of these inhibitors to block enzyme activity. Cell-based assays in P. aeruginosa included measuring the effect hit molecules have on virulence factor production. Furthermore, E. coli and P. aeruginosa reporters were constructed to understand how PqsE influences RhlR transcription factor activity in a gene-specific manner. These experiments link gene expression in the newly built E. coli reporters with analogous virulence factor production in P. aeruginosa. Finding and characterizing quorum sensing inhibitors, as well as understanding the link between quorum sensing and virulence, opens the door to new ways of treating P. aeruginosa infections, not by killing the bacteria, rather by keeping them from coordinating pathogenic behaviors.ChemistryMaster of Science (M.Sc.
Optimizing Single-Molecule Blink-Based Multiplexing
No full textMulticolor super-resolved imaging is a powerful technique for visualizing biological structures with unprecedented levels of detail. However, in order to differentiate various fluorophores, they must exhibit distinct emission spectra, thus limiting the set of available probes and adding to experimental demands. To overcome these issues, the Wustholz lab has developed blinking-based multiplexing (BBM), a novel method for differentiating spectrally-overlapped emitters such as rhodamine 6G (R6G) and CdSe/ZnS quantum dots (QD) based solely on their characteristic blinking behavior. Blinking is defined as the fluctuations in emission intensity that occur in individual fluorophores while undergoing continuous photoexcitation via a laser. BBM was previously demonstrated to be effective on a glass substrate at ~1 µW excitation power using emitter concentrations of ~1 nM, but the impact of imaging conditions on classification accuracy are unknown. Here, the impact of excitation power and labeling density on BBM performance for QD and R6G emitters is investigated using a confocal microscope. We demonstrate that excitation power can be tuned to optimize classification accuracy from ~83% at 0.8 µW to ~93% at 1.2 µW. To mimic typical imaging conditions, BBM is evaluated at increased labeling densities. Although classification accuracies of ~93% are maintained, differentiation may be artificially enhanced by aggregation of QD at high concentrations. We then transition to widefield microscopy, using an electron-multiplying charge-coupled device (EMCCD) camera to optimize localization precision for the purposes of creating super-resolved images with BBM.ChemistryBachelors of Science (BS
The Costumes are Always the Best Part: An Intersectional Analysis of William & Mary's Theatre History
No full textThis thesis was displayed as a series of informational boards in the lobby of Phi Beta Kappa Memorial Hall. In addition to a digital version of those boards, there are included photos and notes from the archival research done for this thesis.Theatre, Speech & DanceBachelors of Arts (BA
Exploring Transient Execution Vulnerabilities, Side-Channel Attacks, And Defenses
No full textModern microprocessors utilize branch prediction and speculative execution to enhance instruction throughput. Instead of stalling the pipeline and waiting for branch targets to be computed, the CPU consults branch predictors for a possible destination and performs speculative execution. These microarchitectural techniques improve the efficiency of instruction pipelining and out-of-order execution, enabling higher performance and better resource utilization. Despite their widespread adoption, the potential security implications of branch misprediction and transient execution have not drawn much attention until recently. Around early 2018, the discovery of Spectre attacks exposed critical vulnerabilities in CPUs, undermining both software and hardware isolation and confidentiality. These attacks exploit the side effects of speculative execution stemming from branch predictions. By manipulating branch predictors to generate incorrect predictions, an attacker can trigger speculative execution to bypass bound checks or operate on arbitrary memory space. Consequently, such exploits can access sensitive data during speculative execution and then exfiltrate the information through various microarchitectural side channels. Spectre and its variants pose a significant security threat that is challenging to mitigate, and existing defenses often come with substantial performance overheads. This dissertation tackles the threat from two perspectives. We first enhance the understanding of exploitable hardware primitives by introducing new transient trojan attacks. Second, we propose secure microarchitecture designs without compromising performance. We first challenge the perception that the triggers and effects of transient execution attacks are fully understood and that the existing protections leave no room for any attack to occur. We present transient trojans, software modules that conceal malicious activity within transient execution mode. These trojans appear entirely benign, pass static and dynamic analysis checks, but reveal sensitive data when triggered. To construct these trojans, we conducted a comprehensive analysis of the current attack surface in light of recommended mitigation techniques. We uncovered new exploitation techniques through reverse-engineering branch predictors in a selection of recent x86_64 processors. Leveraging these findings, we design three types of transient trojans, showcasing their ability to evade detection and their effectiveness. Second, we present the secret token branch predictor unit (STBPU), a secure BPU design to defend against collision-based speculative execution attacks and BPU side channels with minimal performance impact. Securing branch predictors is challenging, as techniques like partitioning or flushing the BPU only partially mitigate collision-based exploits. Moreover, such mitigations compromise branch prediction accuracy, leading to overall CPU performance degradation. STBPU resolves these challenges by customizing BPU data representations for each software entity that requires isolation. Furthermore, STBPU monitors related hardware events and preemptively adjusts BPU data representations.Computer ScienceDoctor of Philosophy (Ph.D.
Training Grammaticality: Can people be taught to perceive the singular ‘they’ as grammatical?
No full textAs the usage of personal pronouns other than he and she becomes more mainstream, debates about their usage have become more and more common. Many of the reasons discouraging their use are rooted in negative attitudes toward people who prefer to be referred to as such (Patev, et al 2019). However, prior research has also found that perceptions of singular gender-neutral pronouns like they/them as being grammatically confusing can be an obstacle toward their use, even by people who otherwise hold positive opinions towards transgender and gender non-conforming (TGNC) individuals (Patev, et al 2019). Given the role that language use plays in gender inclusion, this study aims to see if individuals can be trained to perceive “they," “them," “their," and other pronouns in the set, as more grammatically acceptable. In particular, I examine whether people view the singular “they’” as more grammatical after being given explicit instruction about the rules of their use by comparing grammaticality judgments of sentences using these pronouns before and after receiving training explaining grammar rules. I compare these judgments to those of people who receive diversity-focused trainings, as is the norm for many organizational trainings. While participants in both groups demonstrated an increase in their acceptability ratings of these sentences two weeks after completing the training, the groups improved to a similar degree, indicating that it is the act of thinking about pronoun usage, rather than any particular justification for its acceptability, that affects grammaticality perception. Furthermore, this indicates that this perception of grammatical confusingness is likely an overt justification for covert sociolinguistic attitudes against the use of such pronouns, rather than a true reflection of the mental grammar.LinguisticsBachelors of Arts (BA
“When making a left turn, you must downshift while going forward:” Reading, Analyzing & Staging of Paula Vogel’s How I Learned to Drive as a Senior Directorial
No full textThis paper contains a complete look at research and dramaturgical analysis of Paula Vogel's 1997 How I Learned to Drive in preparation for my senior directorial. How I Learned to Drive is a memory play following a woman, Li'l Bit, as she looks back at the relationship she had with her Uncle Peck, who groomed her. Common themes that thread throughout Vogel's work include the sexualization of children, the distortion of truth through the use of memory and fantasy, and the use of humor as a tool to tell difficult and taboo stories. These themes, as well as Vogel's life and career are investigated in this paper. A major influence and inspiration in Vogel's writing is Vladimir Nabokov's novel Lolita, which I analyze and compare to How I Learned to Drive along with Kate Elizabeth Russell's 2020 novel My Dark Vanessa, which also follows a woman's journey as she looks back at a relationship she had with a man who groomed her. This paper also examines How I Learned to Drive's influence as a survivor play and its continued relevance over 20 years after its first production. Finally, this paper documents the process of staging How I Learned to Drive as a senior directorial at William & Mary.Theatre, Speech & DanceBachelors of Science (BS
“Due to the Tender and Close Relationship”: The Italian Inquisition’s Investigations of Jews and Christians in the Sixteenth Century
No full textThis thesis looks at the Italian Inquisition’s treatment of Jews and those suspected of being Jews and thus sits at the intersection of two different historical subfields: Jewish studies and Inquisition studies. Each subfield is broad but overlaps with the other. I analyze six Inquisition cases—four from Venice and two from Florence—and recount the original accusations, before delving into the likely circumstances of the people involved, based on witness testimony. By looking at these cases, I show how blurred religious identity could be, as people adopted the guise of one faith and then another, depending on the time and place. Because of this confusion, some of these Inquisition cases involve the body trying to determine whether someone was a Christian or a Jew. Other cases demonstrate the sociability of members of the Christian and Jewish communities, much to the Inquisition’s disapproval. By examining these cases, I show the gap between law and reality that existed concerning religious boundaries in early-modern Italy.HistoryBachelors of Arts (BA