Graduate Theses

The Center for Environmental Studies offers a thesis-based Masters of Science (MS) in Environmental Studies.  Here are the most recent theses from this program.


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- Over 40 faculty and students participated in an online Zoom symposium the afternoon of May 12.  The Mountain Creeks to Metro Canals symposium was created to support students that planned to share their research at the River Management Training Symposium originally scheduled for May 2020 and postponed to the following year due to COVID-19. Eight students presented at the event, hosted by VCU Center for Environmental Studies (CES) in collaboration with Northern Arizona University (NAU) and the River Management Society (RMS). Katie Schmidt, (M.S.’20/CES) was the moderator and a presenter. Presentations included: Jack Ryan (VCU) Assessing the feasibility of freshwater mussel restoration in urban and non-urban streams of Central Virginia Rachel Henderson  (VCU) - Microbial Source Tracking of Fecal Contamination in the James River Ryland Stunkle (VCU) - Flood modeling of riverine rock pools using an unmanned aerial vehicle Richie Dang (VCU) Identifying drivers of ecosystem production and respiration in riverine rock pools Andrew Davidson (VCU) Predicting warming’s impacts on mosquito control by larval predators Riley Swanson (NAU) Assessing Groundwater Resources in the Colorado River Basin: Quantifying Base Flow in the Greater Grand Canyon Region James Major (NAU) Utilizing Extant Conservation Policy to Fill Identified Gaps in Riverine Protected Areas Katie Schmidt (VCU) Let it Flow: Restoring Dry River Reaches in the Southeast Questions were posed after each presentation, and a panel discussion ensued at the conclusion. The full YouTube playlist of presentations can be found here. Five of the students – Stunkle, Dang, Schmidt from VCU and Swanson and Major from NAU – completed their Rivers Studies Leadership Certificate requirements with this presentation A surprise addition to the agenda came from Risa Shimoda, executive director of RMS, with the presentation of the Outstanding Contribution to River Management Society award to James Vonesh, Ph.D., associate professor and assistant director of… Read More
2019 RMS Symposium Student Poster Session, Vancouver, WA [View Image]
Student River Research Symposium - While the 2020 River Management Training Symposium has been rescheduled for May 2021, to support the students that planned to share their research at this event we have created the Mountain Creeks to Metro Canals  - Online Student Research Symposium. This will take place as a ZOOM webinar Tuesday, 12 May,  1:00 - 3:00 PM EDT. Join from PC, Mac, Linux, iOS or Android: https://vcu.zoom.us/j/92284877483 We have a diverse line up of presentations that range from freshwater mussel restoration, flood modeling, and predator-prey ecology, to groundwater issues and conservation policy. We hope you can join us! Time Student University Presentation 1:00 Katie Schmidt Welcome 1:10 Jack Ryan Virginia Commonwealth University Assessing the feasibility of freshwater mussel restoration in urban and non-urban streams of Central Virginia 1:20 Rachel Henderson Virginia Commonwealth University Microbial Source Tracking of Fecal Contamination in the James River 1:30 Ryland Stunkle Virginia Commonwealth University Flood modelling of riverine rock pools using an unmanned aerial vehicle 1:40 Richie Dang Virginia Commonwealth University Identifying drivers of ecosystem production and respiration in riverine rock pools. 1:50 Andrew Davidson Virginia Commonwealth University Predicting warming’s impacts on mosquito control by larval predators 2:00 Riley Swanson Northern Arizona University Assessing Groundwater Resources in the Colorado River Basin: Quantifying Base Flow in the Greater Grand Canyon Region 2:10 James Major Northern Arizona University Utilizing Extant Conservation Policy to Fill Identified Gaps in Riverine Protected Areas 2:20 Katie Schmidt Virginia Commonwealth University Let it Flow: Restoring Dry River Reaches in the Southeast 2:30 Risa Shimoda River Management Society River Studies & Leadership Certificate Awards 2:40 Katie Schmidt Closing Read More
Photo shows a freshwater mussel in hand [View Image]
Graduate Position – Endangered Freshwater Mussel Conservation Research - A freshwater mussel apocalypse is underway. Want to be part of the solution? Graduate Position - Endangered Freshwater Mussel Conservation Research The Environmental Studies Program at Virginia Commonwealth University (https://ces.vcu.edu/) in collaboration with the United States Fish and Wildlife Service (USFWS; https://www.fws.gov/harrisonlake/) invites applications from prospective graduate students for Fall 2020 to collaborate on our USFWS funded project on in vitro propagation of imperiled freshwater mussels. Freshwater mussels are one of the most imperiled groups of animals in the country, 72% of them are extinct, endangered, threatened, or state/federally listed. Over 900 species exist in the world and 300 reside in North America; many of them in Virginia, the 6th most diverse state in the country. Since the mid-90's some wildlife resource agencies have been using propagation and culture of mussels to release juveniles back into the wild to augment and recover declining populations. Freshwater mussels require the use of a host fish to complete their life-cycle to reproduce successfully; however, for some mussel species the host is unknown, not abundant, or it does not produce enough juveniles to adequately augment or restore wild populations. In these cases, in vitro propagation is being used to produce juveniles without the host fish. This research focuses on improving our current techniques for in vitro mussel propagation and performs fundamental experiments to begin our understanding of any life history or population-level effects that in vitro mussels could have on wild populations. Work will mainly occur at the VCU Rice Rivers Center in the USFWS in vitro lab, as well as occasional fieldwork to collect brooding female mussels. Working with some of the most endangered animals in the world as well as working with VCU and the USFWS represents an excellent opportunity for interested students. There is also a great opportunity to work on the… Read More
Climate Change and Mountaintop Removal Mining: A MaxEnt Assessment of the Potential Dual Threat to West Virginia Fishes - Hendrick, Lindsey R.F.  MS Thesis. Accounts of species’ range shifts in response to climate change, most often as latitudinal shifts towards the poles or upslope shifts to higher elevations, are rapidly accumulating. These range shifts are often attributed to species ‘tracking’ their thermal niches as temperatures in their native ranges increase. Our objective was to estimate the degree to which climate change-driven shifts in water temperature may increase the exposure of West Virginia’s native freshwater fishes to mountaintop removal surface coal mining. Mid-century shifts in habitat suitability for nine non-game West Virginia fishes were projected via Maximum Entropy species distribution modeling, using a combination of physical habitat, historical climate conditions, and future climate data. Modeling projections for a high-emissions scenario (Representative Concentration Pathway 8.5) predict that habitat suitability will increase in high elevation streams for eight of nine species, with marginal increases in habitat suitability ranging from 46-418%. We conclude that many West Virginia fishes will be at risk of increased exposure to mountaintop removal surface coal mining if climate change continues at a rapid pace. Read More
Forest Structural Complexity and Net Primary Production Resilience Across a Gradient of Disturbance in a Great Lakes Ecosystem - Haber, Lisa T.  MS Thesis. Forests are an important component of the global carbon (C) cycle and contribute to climate change mitigation through atmospheric C uptake and storage in biomass and soils. However, the forest C sink is susceptible to disturbance, which modifies physical and biological structure and limits spatial extent of forests. Unlike severe, stand-replacing disturbances that reset forest successional trajectories and may simplify ecosystem structure, moderate severity disturbances may instead introduce complexity in ways that sustain net primary production (NPP), leading to the phenomenon of “NPP resilience.” In this study, we examined the linkage between disturbance severity and ecosystem biological and physical structural change, and implications for NPP within an experimentally disturbed forest in northern Michigan, USA. We computed spatially resolved and spatially agnostic metrics of forest biological and physical structure before and 10 years after disturbance across a continuum of severity. We found that while biological structure did not change in response to disturbance, three of four physical structural measures increased or were unimodally related to disturbance severity. Physical structural shifts mediated by disturbance were not found to directly influence processes coupled with NPP. However, decadal changes in the spatial aggregation index of Clark and Evans, though not a function of disturbance severity, were found to predict canopy light uptake, leaf physiological variability, and relative NPP within plots. We conclude that ecosystem structural shifts across disturbance severity continua are variable and differ in their relationship to NPP resilience. Read More
Migratory patterns and population genetic structure in a declining wetland-dependent songbird - DeSaix, Matthew G.  MS Thesis. Understanding migratory connectivity is essential for assessing the drivers behind population dynamics and for implementing effective management in migratory species. Genetic markers provide a means to describe migratory connectivity, as well as incorporate population genetic analyses, however genetic markers can be uninformative for species with weak genetic structure. In this study, we evaluate range-wide population genetic structure and migratory connectivity in the prothonotary warbler, Protonotaria citrea, a wetland-dependent neotropical migratory songbird, using high-resolution genetic markers. We reveal regional genetic structure between sampling sites in the Mississippi River Valley and the Atlantic Seaboard with overall weak genetic differentiation among populations (FST = 0.0051). By ranking loci by FST and using subsets of the most differentiated genetic markers (200 – 3000), we identify a maximum assignment accuracy (89.7% to site, 94.3% to region) using 600 single nucleotide polymorphisms. We assign samples from unknown origin nonbreeding sites to a breeding region, illustrating weak migratory connectivity between prothonotary warbler breeding and nonbreeding grounds. Our results highlight the importance of using high-resolution markers in studies of migratory connectivity with species exhibiting weak genetic structure. Using similar techniques, studies may begin to describe population genetic structure that was previously undocumented, allowing us to infer the migratory patterns of an increasing number of species. Read More
DETERMINING TIDAL CHARACTERISTICS IN A RESTORED TIDAL WETLAND USING UNMANNED AERIAL VEHICLES AND DERIVED DATA - Thornton, Victor. MS Thesis Species’ distributions are influenced by abiotic and biotic factors but direct comparison of their relative importance is difficult, particularly when working with complex, multi-species datasets. Here, we present a flexible method to compare abiotic and biotic influences at common scales. First, data representing abiotic and biotic factors are collected using a combination of geographic information system, remotely sensed, and species’ functional trait data. Next, the relative influences of each predictor variable on the occurrence of a focal species are compared. Specifically, ‘sample’ data from sites of known occurrence are compared with ‘background’ data (i.e. pseudo-absence data collected at sites where occurrence is unknown, combined with sample data). Predictor variables that may have the strongest influence on the focal species are identified as those where sample data are clearly distinct from the corresponding background distribution. To demonstrate the method, effects of hydrology, physical habitat, and co-occurring fish functional traits are assessed relative to the contemporary (1950 – 1990) distribution of the American Eel (Anguilla rostrata) in six Mid-Atlantic (USA) rivers. We find that Eel distribution has likely been influenced by the functional characteristics of co-occurring fishes and by local dam density, but not by other physical habitat or hydrologic factors. Read More
ASSESSING THE RELATIVE INFLUENCES OF ABIOTIC AND BIOTIC FACTORS ON A SPECIES’ DISTRIBUTION USING PSEUDO-ABSENCE AND FUNCTIONAL TRAIT DATA: A CASE STUDY WITH THE AMERICAN EEL (Anguilla rostrata) - Woods, Taylor E.   MS Thesis Species’ distributions are influenced by abiotic and biotic factors but direct comparison of their relative importance is difficult, particularly when working with complex, multi-species datasets. Here, we present a flexible method to compare abiotic and biotic influences at common scales. First, data representing abiotic and biotic factors are collected using a combination of geographic information system, remotely sensed, and species’ functional trait data. Next, the relative influences of each predictor variable on the occurrence of a focal species are compared. Specifically, ‘sample’ data from sites of known occurrence are compared with ‘background’ data (i.e. pseudo-absence data collected at sites where occurrence is unknown, combined with sample data). Predictor variables that may have the strongest influence on the focal species are identified as those where sample data are clearly distinct from the corresponding background distribution. To demonstrate the method, effects of hydrology, physical habitat, and co-occurring fish functional traits are assessed relative to the contemporary (1950 – 1990) distribution of the American Eel (Anguilla rostrata) in six Mid-Atlantic (USA) rivers. We find that Eel distribution has likely been influenced by the functional characteristics of co-occurring fishes and by local dam density, but not by other physical habitat or hydrologic factors. Read More
IMPROVING THE CONSERVATION OF A CRYPTIC ENDANGERED FRESHWATER MUSSEL (PARVASPINA COLLINA) THROUGH THE USE OF ENVIRONMENTAL DNA AND SPECIES DISTRIBUTION MODELING - Roderique, Bonnie A., MS Thesis Conservation efforts that involve habitat protection, population augmentation, and species reintroductions require knowledge of the habitat requirements, distribution, and abundance of a species—information that can be challenging to acquire, especially for rare organisms with patchy distributions. In this thesis, I develop a protocol for the use of environmental DNA (eDNA) and create a Species Distribution Model for the endangered James spinymussel, Parvaspina collina (Unionidae). The results of this work show that eDNA is a robust tool for identifying species presence but not for estimating the relative abundance of populations. This study found that P. collina’s distribution is influenced by abiotic habitat characteristics related to sedimentation and runoff rather than by the distribution of its host fishes. The predicted habitat suitability was used to identify locations of priority conservation concern and these results can be used to direct future sampling efforts, identify potential dispersal routes, and inform conservation decisions. Read More
PELAGIC FISH DIVERSITY AND DENSITY ON AND OFF RESTORED OYSTER REEF HABITAT - McCulloch, Danielle.  MS Thesis The heterogeneity provided by structured habitats is important in supporting diverse and dense fish communities. The biogenic reefs created by the native Eastern Oyster, Crassostrea virginica, were once the dominant structural habitat in Chesapeake Bay, and have since declined to less than 1% of historic estimates. Conflicting results on the effects of oyster reef restoration on pelagic fish assemblages make further investigation necessary. Incorporating multiple sampling strategies may help elucidate oyster reef habitat influence on fish assemblages. This study used multi-panel gillnets, hydroacoustic technology, and day-night sampling to describe pelagic fish assemblages on and off oyster reef habitat in the lower Piankatank River, VA. Data from oyster reef habitat, adjacent sandy-mud bottom habitat, and unstructured sandy habitat outside of a reef restoration area compared fish diversity, species composition, and density among habitat types. A multivariate analysis using day of the year, day or night, and habitat type as model terms found temporal factors explained variation in fish distribution more than habitat. Fish diversity varied significantly with day or night and habitat type. Diversity and density were significantly higher at night, demonstrating the necessity of nocturnal sampling in fish assemblage research. Results from this study conclude that fish assemblages were not significantly more diverse or denser on reef than non-reef habitat. We suggest that future work should concentrate on studying areas where oyster reef habitat comprises a larger proportion of the study area. Read More
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