School of Environmental Studies
Meet Our Current PhD Students
Meet our current students and read about their research below.
Abigail G. Blake-Bradshaw- Biology
Abby’s research is titled: "Mallard (Anas platyrhynchos) wintering ecology and the effects of sanctuary and disturbance." Abby is studying wintering waterfowl ecology and is interested in assessing impacts of anthropogenic disturbance on wintering mallards. In particular, she is determining factors that influence sanctuary use in west Tennessee, a current and historically important region for waterfowl hunting. She aims to provide information to better understand and manage sanctuaries to meet wintering waterfowl needs.
Peter Blum- Biology
Peter's research is titled: "Transfer of PCBs from Emergent Insects to Terrestrial Consumers in Historically Contaminated Streams and Reservoir." His dissertation focuses on how stream insects that develop in polychlorinated biphenyls (PCBs) contaminated sediments can transfer PCBs to terrestrial consumers when they emerge as winged adults. Gray bats (Myotis grisescens) utilize emergent aquatic insects in their diet, which provides a route for PCB exposure and a potential concern for their conservation. Because PCBs are resistant to decomposition, historical contamination of PCBs at Wood’s Reservoir and several streams near Arnold Air Force Base may be sources of PCB exposure to local gray bat colonies. His research investigates how much insect biomass is emerging from these streams and reservoirs sites as a potential food source for bats, the PCB flux from these emergent aquatic insects, and how nutrient stoichiometry (the ratios of major nutrients in insects) affects PCB biomagnification.
Martine Patiance Bowombe-Toko- Agriculture
Martine is originally from Mbanga (Littoral region, Cameroon) and her research study focuses on preventing or controlling periodical cicada oviposition damage associated with nursery tree crops. Her dissertation is titled, "Determining control strategies for periodical cicadas in commercial ornamental nursery plants in Tennessee." To accomplish this goal, two major priorities will be addressed: 1) evaluation of new or current insecticide treatments to manage periodical cicada adults using cage studies in shadehouse settings and 2) assessment of nursery tree damage by periodical cicada adults (Brood X, 2021) in cooperating East Tennessee field nurseries. However, with limited nurseries located so far, they will include the insurance assessment reports from the 2011 emergence, to return in 2024, and from the 2008 emergence to return in 2025.
Robert Brown- Biology
Dissertation title: "Linking Nutrient Removal Pathways with Riverine Nutrient Subsidies in Restored Floodplain Wetlands."
Abstract: Intact soil core incubations with nutrient rich water provide valuable estimates of potential nitrogen (N) and phosphorus (P) cycling rates at the interface of aquatic and terrestrial ecosystems. These data facilitate understanding of management practices that enable soils to remove N and P from floodwater and reduce impacts of agricultural runoff on downstream ecosystems. My research focuses on: 1) scaling-up N and P removal rates from soil core incubations across representative management areas enrolled in the USDA Wetlands Reserve Program; 2) identifying tradeoffs between desirable N removal (N2 gas production) and greenhouse gas emissions (N2O gas production); and 3) placing N and P removal rates measured in the laboratory within context of natural floodwater by measuring nutrient concentration patterns across a reconnected floodplain forest and six tributaries of the Mississippi River.
Sabrina Buer- Integrated Research
Sabrina's research is titled, "Experimental and Modeling Approaches for Using Platinum-Doped Thin Film Photocatalysis for Simultaneous Contaminant Degradation and Hydrogen Production in Wastewater Treatment Systems." As the amount of human and industrial waste in the environment increases, the need for more effective and efficient water treatment methods is higher than ever. Current wastewater treatment processes have been found to be ineffective against a growing number of contaminants, including pharmaceutical compounds. Sabrina’s work focuses on the need for a safe and environmentally-friendly method of removing pharmaceutical compounds from surface and drinking water sources, and will address this issue from two perspectives: 1) The photocatalytic degradation of acetaminophen via UV-C radiation and a titanium dioxide photocatalyst, and 2) The development of a mathematical model to provide essential information regarding reactor volume, the amount of photocatalyst (titanium dioxide) needed for degradation, and the time it would take to achieve complete contaminant degradation.
Bryant Davis- Integrated Research
Bryant's project is titled "Geochemical Fingerprinting of Natural Waters in Middle Tennessee." Geochemical fingerprinting is an analysis of the chemical species, present within natural waters, to determine both the source and alteration of these systems. These chemical fingerprints are defined as specific patterns of analytes unique to each body of water. This research examines the presence of metals in surface waters that are located on two distinct physiographic regions of Tennessee: the Highland Rim and the Cumberland Plateau. Water bodies from these regions were chosen due to differences in local geology and land use patterns that each respective system are subjected to. Grab samples were obtained from various locations in order to obtain an identity of each respective system. Linear regression was then utilized to determine ratios of analytes so that a comparative analysis could then be performed. The obtained correlation coefficients should indicate how local geology and land use patterns affect the chemical identity of natural waters within Middle Tennessee.
Brooke Grubb- Biology
Dissertation title: "An interdisciplinary approach to understanding ecology and genetics of a narrow endemic
crayfish species, Faxonius wrighti."
Brooke is studying the taxonomic validity, habitat needs, conservation genetics, and movement of Faxonius wrighti (Hardin Crayfish). Her work will involve aspects of landscape ecology and genomics to understand how the environment influences crayfish movement, genetic structure, and generate predictive models under different climate change scenarios to highlight populations at increased risk of extirpation. Her research will aid in the generation of a species status assessment (SSA) used to make federal listing and management decisions.
Rachel Kaiser- Geoscience
Rachel's dissertation is titled, "An Interdisciplinary Approach Towards Understanding Antibiotic Resistance in Urban karst Groundwater Systems." Rachel's research is studying the prevalence of antibiotic resistance in groundwater resources, particularly urban karst areas, in correlation with environmental determinants, including water quality and spatio-temporal trends, to understand the resistome in urban karst environments. This understanding, along with a global and national antimicrobial resistance policy and program analysis, will also contribute to the development of an integrated framework of antimicrobial resistance stewardship for water resources utilizing the four pillars of surveillance, innovation, mitigation, and prevention.
Erik Koehler - Agriculture
Erik's dissertation title is "Insect Resistance and Horticultural Trait Evaluation of Acylsugar Tomato Breeding Lines." His research entails evaluating insect resistant tomato lines for their horticultural and resistance traits for protection against silverleaf whitefly (Bemsia tabaci) and brown marmorated stink bug (Halyomorpha halys). These two invasive insects are responsible for billions of dollars in crop losses each year across the globe. The studied tomato lines were bred to exude acylsugars; a sticky, all-purpose plant defense compound. The stickiness and chemistry of the acylsugars act as insect deterrents. Chemically, acylsugars are glucose or sucrose molecules with esterified fatty acid chains ranging in size from two to sixteen carbons in length. Acylsugars are naturally derived and do not pose acute human health issues. This research hopes to reduce grower reliance on synthetic pesticides which are harmful to the applicator and agricultural environment.
Nicholas Masto- Biology
Nick's dissertation is titled, "Annual cycle ecology of mallards from the Mississippi Alluvial Valley." Nick is studying movements, habitat selection, and other behaviors of mallards (Anas platyrhynchos) across their annual life cycle (i.e., migration, wintering, breeding) using state-of-the-art GPS-GSM telemetry units.
Catherine "Kitty" Phillips - Integrated Research
The title of Kitty's dissertation is "Ethnobotany Among Cherokee and Chocktaw Women: Medical and Spiritual Uses." The basic premise of her research is to explore the plants and methods used by the Cherokee and Choctaw women to cure ills, to prevent illness, to heal wounds, and for overall health. She will explore which methods worked and why. In addition, she is researching the spiritual or ritualistic uses of plants in their culture. She also want to determine the overlap between the uses.
Kenny Pierce- Agriculture
Kenny's research is titled: "Development of rapid-screening protocols for predicting allelopathic interactions among cover crops, weeds, and market crops." Allelopathy is broadly defined as the biochemical interactions between all types of plants, including microorganisms. Because allelopathic effects include both inhibitory and stimulatory responses and may be species and cultivar specific, a method for rapidly screening crops and weeds for allelopathic interactions is needed. The objective of this research is to establish growth chamber and greenhouse protocols for rapidly screening plant species and cultivars for allelopathic interactions that are consistent with allelopathic interactions observed in field production situations.
Richard Pirkle- Biology
Canada geese in the Upper Cumberland region of Tennessee have been intensively banded over the past two decades. Richard's research involves the analysis of this long-term dataset for patterns that explain Canada goose dispersal, reproduction, and molt site fidelity. In particular, he is interested in how stress may impact nesting physiology and influence social structure amongst unrelated Canada geese. He is also interested in the impact of increased hunting mortality due to banding.
Phillip Roberson- Geology
Phillip's research focuses on understanding ancient reef-like structures known as Waulsortian mounds. He will be examining the paleoecology, stratigraphy, and geochemistry of these mounds to better understand how and why they formed.
Christopher Waters- Biology
Chris's research is titled, "Metabarcoding environmental DNA to examine pollinator communities across the range of Physaria globosa (Brassicaceae).” and is part of the recovery and conservation efforts for a federally endangered mustard species called Short’s bladderpod (Physaria globosa(Desv.) O'Kane and Al-Shehbaz). The primary goal of Chirs's research is to investigate and monitor pollinator communities across the range of Short’s bladderpod via metabarcoding environmental DNA (eDNA) on flowers. As insects visit flowers they can leave behind small fragments of DNA in saliva or shed hairs that can be extracted from the flowers and identified to species or taxonomic group. This method allows us to identify and monitor the pollinator community composition across the range of Short’s bladderpod more efficiently compared to traditional sampling techniques.
Spencer Womble- Biology
The title of Spencer's dissertation is "Factors Influencing Nutrient Flux Rates in Restored Agricultural Floodplain Wetlands in western Tennessee and Kentucky, USA." His research focuses on how wetland hydrology influences nutrient retention in restored agricultural floodplain wetlands in the upper Mississippi Alluvial Valley. Soil cores are collected from various restored wetland habitats across western Kentucky and Tennessee and incubated with high nutrient water to estimate maximum nutrient flux rates for each habitat. Environmental data from each sampling location are also collected to see which factors correlate with nutrient flux rates. Further, Spencer is using remotely sensed data to examining how cycles of wetting and drying in areas where soil cores are collected affect nutrient flux rates.