Terrestrial and Aquatic Ecology Commons^™

Spatial And Hydrologic Effects Of Climate Change And Urbanization On Freshwater Fish Communities In North Georgia Watersheds, Mayuko Mizutani

Master's Theses

Urbanization and climate change are altering streamflow and land cover across the southeastern United States, threatening freshwater biodiversity in rivers already burdened by impoundments and habitat loss. I investigated how changes in streamflow and land cover might affect fish community biodiversity in the Etowah River watershed of North Georgia. By combining a dataset of fish collections from 1999 through 2019 with contemporaneous land use and daily streamflow, I was able to model fish community responses to urbanization and climate-driven hydrologic changes and then forecast fish community structure under multiple CMIP6 global climate models and greenhouse gas emissions scenarios (SSP2-4.5 and …

Impacts Of Halophila Stipulacea Invasion On Organic Matter Dynamics In Thalassia Testudinum Dominated Seagrass Meadows, Puerto Rico, Jonathan D. Herald

Master's Theses

Halophila stipulacea (Forsskål & Niebuhr) is a tropical seagrass native to the Red Sea, Persian Gulf, and Indian Ocean. In 2002, invasive populations of H. stipulacea were identified in the Caribbean Sea where it now forms large meadows, displaces native seagrasses, alters invertebrate and fish communities, and potentially affects organic matter dynamics in invaded meadows. This study investigated differences in organic matter dynamics between meadows of H. stipulacea and native Thalassia testudinum within the Jobos Bay National Estuarine Research Reserve (JBNERR) on the southern coast of Puerto Rico. From March 2023-March 2024, sampling was conducted across four sites to investigate …

Exploring Fisheries Species Distribution Shifts In Response To Freshwater Inflow Through The Bonnet Carré Spillway Using Species Distribution Models, David T. May

Master's Theses

The Bonnet Carre Spillway (BCS) is a flood control structure on the Mississippi River (MR) ~52 km upstream of New Orleans. The BCS protects downstream communities from MR flooding by diverting floodwaters into Lake Pontchartrain when the MR exceeds 5.18m flood stage. Diverted waters flow east into the Mississippi Sound (MSS), introducing turbid, nutrient rich freshwater to the estuary before draining into the Gulf of Mexico. BCS openings have become much more frequent in the last decade, though little work has been done to explore the impact of the BCS on nektonic fisheries species. Here, a series of seasonal Maximum …

When Trees Disappear: Understory Successional Implications Of Sudden Oak Death And High-Severity Wildfire In Big Sur, California, Sam J. Balthazard

Master's Theses

The rapidly emerging disease sudden oak death, caused by the non-native pathogen Phytophthora ramorum, is transforming coastal California forests by driving extensive mortality of tanoak (Notholithocarpus densiflorus) and increasing fire severity. As a novel disturbance, sudden oak death and its interaction with wildfire may catalyze unexpected shifts in successional trajectories and reconfigure forest understory communities. Furthermore, how tanoak influences the forest understory and how its decline might reshape understory dynamics remain poorly understood. We hypothesize that disease alone and the compounding disturbances of disease and wildfire alter successional dynamics, and that the potential functional extinction of N. …

Population Estimates, Demography, And Habitat Assessment Of The Pearl River Map Turtle (Graptemys Pearlensis) In The Pearl River Drainage Of Mississippi, Noah Devros

Master's Theses

The Pearl River map turtle (Graptemys pearlensis) is a highly riverine Emydid endemic to the Pearl River drainage of central and southern Mississippi and southern Louisiana. First described in 2010, G. pearlensis was listed as federally Threatened in 2024. . Due to its relative novelty as a species, no rigorous site-specific population estimates of G. pearlensis in Mississippi have been conducted. The primary goal of this study was to implement a replicable method of assessing the population of G. pearlensis throughout the Pearl River drainage system of Mississippi. A secondary goal was to describe habitat associated with G. …

Investigating Nekton Response To Changing Salinities In The Mississippi Sound: An Experimental And Statistical Approach, Adam Murray

Master's Theses

The Mississippi Sound provides nursery habitats for many coastal species and is recognized for its commercial fisheries. Previous freshening events linked to the Bonnet Carré Spillway, a Mississippi River flood diversion structure, proved catastrophic for oyster populations in the Mississippi Sound, but effects on mobile fish and shellfish species are not well-defined. The planned Mid-Breton Sediment Diversion (MBSD), an initiative to combat wetland loss, is also forecasted to lower salinities in the region, increasing the need to better understand responses of commercially and ecologically important species to freshening events. The objective of this study was to characterize effects of salinity …

Of Geese And Grass: Investigating Impacts Of Brant Grazing On Eeelgrass, Dakota L. Osborne

Master's Theses

Grazing pressure is important in structuring plant communities, particularly in aquatic environments. Eelgrass (Zostera marina), a keystone species in estuaries across North America, is experiencing widespread population declines. As a keystone species, eelgrass provides numerous important functions, including: 1) water filtration, 2) sediment stabilization, 3) providing refuge and nursery habitat for numerous species, and 4) carbon sequestration. Benefits which could be lost if eelgrass beds continue to diminish. California has experienced some of the greatest eelgrass declines, and Morro Bay, CA experienced a 96% decrease in eelgrass from 2007 to 2017. Most studies to date have examined bottom-up …

Identifying New Potential Breeding Pond Sites For The Dusky Gopher Frog In Southern Mississippi, Shelbie Kellum

Master's Theses

The main objective of this thesis was to identify potential new pond sites across southern Mississippi for the critically endangered dusky gopher frog (DGF). Ephemeral ponds are the preferred breeding habitat for the species, but they are quite rare in the region due to the diminishment of the longleaf pine ecosystem. This research addresses gaps in the current literature by providing a broad overview of dusky gopher frog breeding habitat identification. LiDAR derived datasets as well as tools within ArcGIS Pro were utilized in order to perform spatial analysis on sites of interest in south Mississippi. By using this methodology …

Spatial And Abiotic Effects Of Urbanization On Small Mammal Communities, Bri Casement

Master's Theses

Urbanization, the phenomenon of increasing human population density and artificial structures, is known to decrease the richness, abundance, and diversity of native wildlife populations, fragment natural areas, and increase human and human-commensal animal interactions with wildlife. Dynamics of species persistence in habitat fragments is often understood in the framework of island biogeography theory (IBT), with habitat fragments being analogous to oceanic islands. Despite the conceptual similarities between oceanic islands in IBT and urbanized habitat fragments (fragment size, fragment age, and distance to immigration sources), there are important differences. In urban fragments, the matrix is not completely impassible, habitats within fragments …

Lichens Of Ultramafic Rocks: A Multidisciplinary Approach To Understanding The Ecology Of An Understudied Organism In A Well-Studied System, Michael Mulroy

Master's Theses

Lichens are among the most prominent and successful life forms of metal-rich habitats, including ultramafic rocks and soils; however, research on lichens of ultramafic habitats is limited, especially on the North American continent. A review of the published literature on lichens of ultramafic substrates in North America yielded a total of 437 lichen species reported from ultramafic rocks and soils. Lichen assemblages of ultramafic substrates vary in composition and are dominated by acidophytic (low pH preferring) taxa with a minor, but consistent, basiphytic (high pH preferring) component. Species lists from ultramafic habitats in different geographic regions varied widely, suggesting that …

Hide And Seek: An Exploration Of Antipredator And Predator Avoidance Mechanisms In Orthopodomyia Signifera In Response To Predation From Toxorhynchites Rutilus, Nathaniel Dahlberg

Master's Theses

There have been many observations of larval Orthopodomyia signifera coexisting with the predator Toxorhynchites rutilus. There are three hypotheses that could explain how Or. signifera resists predation from Tx. rutilus. The first hypothesis states that larvae adapt behavioral changes that limit predation. The second hypothesis states thoracic setae serve as a physical defense that prevents Tx. rutilus from grasping Or. signifera. The third hypothesis states Or. signifera possess a chemical defense indicated by aposematic coloration. To test the first hypothesis larval Or. signifera were exposed to conspecific and heterospecific predation cues and their behavior was observed. Both cues …

Investigation Of Dead Ocean Quahogs (Arctica Islandica) Shells On The Mid-Atlantic Bight Continental Shelf, Alyssa Leclaire

Master's Theses

Ocean quahogs, Arctica islandica, are a long-lived, widely dispersed, biomass dominate in the Mid-Atlantic; therefore, quahog shells are valuable resources for studying climate change over time. Recently, dead ocean quahog shells were discovered south and inshore of the present biogeographic range of this animal. The presence of ocean quahog shells outside the current range is presumably a consequence of past regressions and transgressions of the Cold Pool, the bottom-trapped, cool body of water that allows boreal animals to live at lower latitudes. Dead ocean quahog shells were collected offshore of the DelMarVa Peninsula then radiocarbon-dated, evaluated for taphonomic condition, …

Disturbance Ecology Of The Sonadora River Rock Pool Insect Assemblage At Luquillo Experimental Forest, Puerto Rico, Patrick Gilkey

Master's Theses

Freshwater rock pools can serve as habitat for aquatic insects. Flash-flooding can have profound effects on insect communities in streams and rivers, but these effects have not been studied on freshwater rock pools. The goal of this thesis was to describe ecological patterns of the Sonadora River rock pool insect community at the Luquillo Experiment Forrest, Puerto Rico, specifically in response to intense flash-flooding, and then perform experiments to elucidate possible processes to explain those patterns. The rock pools contained primarily three taxa of Dipteran (true-fly) larvae, in order of decreasing abundance, 1) a newly discovered species of ceratopogonid (biting …

Distribution And Ecological Function Of Pacific Lamprey In The San Luis Obispo Creek Watershed, Parker Kalan

Master's Theses

Pacific lamprey (Entosphenus tridentatus) is an endemic species to coastal watersheds along the Pacific Rim in North America and Asia. The species' geographic distribution is retracting and has not been mapped precisely, and the ability for the species to provide ecosystem services, such as water filtration, for supporting watershed management has not been tested. The San Luis Obispo Creek watershed, California, USA is at the southern end of Pacific lamprey’s retracting distribution, and the San Luis Obispo watershed is impacted by degraded water quality, making investigation of Pacific lamprey in the San Luis Obispo Creek watershed of direct …

Investigation Of Dna Variability And Phylogenetic Relationships Of Perlesta (Plecoptera: Perlidae) In Mississippi, James C. Valentine, Mac H. Alford

Master's Theses

The genus Perlesta Banks, 1906 (Plecoptera: Perlidae) consists of 35 species, 33 native to the United States and Canada and two native to China. For over a century these small, brown stonefly adults and freckled yellow nymphs have gone by the name of the type species of the genus, Perlesta placida, but taxonomic work in the genus since 1989 has resulted in the recognition of additional species. These species were mostly recognized and described using morphological characteristics, but two areas that are lacking include (1) linking nymphs to adults and (2) phylogenetic analysis of all species occurring in Mississippi …

An Assessment Of The Diverse Freshwater Turtle Fauna Of Mississippi, Lucas Haralson

Master's Theses

Nestled within the Southeastern United States Turtle Priority Area, Mississippi boasts impressive freshwater turtle diversity and is home to 8.6% of extant turtle species. Despite this impressive richness, few studies have assessed freshwater turtle assemblages in this hotspot of aquatic diversity. This research aimed to elucidate the distributions and abundances of freshwater turtle species through a statewide investigation of all major river drainages of the state. Using baited hoop nets (90 cm and 120 cm diameter), turtles were collected, identified to species and sex, and measured, before being released. Turtle assemblages were assessed in both lotic and lentic environments from …

Analysis Of The Slo Bay Microbiome From A Network Perspective, Lien Viet Nguyen

Master's Theses

Microorganisms are key players in the ecosystem functioning. In this thesis, we developed a framework to preprocess raw microbiome data, build a correlation network, and analyze co-occurrence patterns between microbes. We then applied this framework to a marine microbiome dataset. The dataset used in this study comes from a year-long time-series to characterize the microbial communities in our coastal waters off the Cal Poly Pier. In analyzing this dataset, we were able to observe and confirm previously discovered patterns of interactions and generate hypotheses about new patterns. The analysis of co-occurrences between prokaryotic and eukaryotic taxa is relatively novel and …

Anthropogenic Litter In Illinois Streams: Monitoring, Distribution, And Relationship To Biological Indicators Of Stream Health, Lauren Wisbrock

Master's Theses

Anthropogenic litter (i.e., trash; AL) is increasing in aquatic ecosystems worldwide. AL shows a patchy, uneven distribution in lotic ecosystems due to heterogeneity in its sources, how it moves, and mechanisms of retention. In addition, the diversity of material types, size, and mobility makes developing techniques to measure AL assemblage in rivers a challenge. In rivers, watershed land-use and riparian features likely impact AL abundance and composition, but this impact is not fully understood. Measuring AL can be time consuming and labor intensive, so rapid assessments are needed for ecosystem managers to quantify the level of AL impairment in a …

Effects Of Infection Of The Protist Parasite, Dermomycoides Sp., In Dusky Gopher Frog Tadpoles, Jaime Smith

Master's Theses

Infections of the protist parasite, Dermomycoides sp. are thought to have caused several years of low recruitment in the dusky gopher frog (Rana sevosa) populations. I evaluated the effects of density of the infective zoospores, host developmental stage, and tadpoles' ability to acquire resistance to Dermomycoides sp. on dusky gopher frog tadpoles. Tadpoles were exposed to zoospore densities of 0, 250, 500, and 750 zoospores/µL at Gosner stage 25, and we found no significant differences among treatments in tadpole mortality. In evaluating susceptibility by development stage, I exposed R. sevosa to 50 zoospores/µL as eggs, embryos, hatchlings, and …

Do Mosquito Pesticides Harm Their Natural Enemies? Ecological Impacts And Non-Target Effects Of Larvicides On Mosquito Predators, Joseph Nelsen

Master's Theses

Larvicides are chemicals used to kill juvenile mosquitoes. When applied to an area, other aquatic organisms are exposed to these chemicals. The removal or impairment of top insect predators could be beneficial to mosquito populations once harmful pesticide levels dissipate. Two common larvicides were examined: growth regulators (IGRs) and surface films (SFs). The goal of this project was to determine if larvicides harm mosquito predators common to southern Mississippi. I surveyed aquatic sites before and after IGR and SF treatments, and then compared changes in insect community structure. Community evenness was lower in SF treated habitats. When analyzing prey taxa …

The Effect Of Plastic On Leaf Litter Breakdown In Urban Streams, Lisa Haneul Kim

Master's Theses

The plastic component of anthropogenic litter (AL) is an emerging ecological concern and has been a focus of research, as it is long-lived, mobile, interacts with physical and chemical components of aquatic ecosystems, and breaks down into smaller pieces (i.e., microplastic, <5mm particles). Rivers are considered a major source of plastic to oceans, but little is known about plastic's abundance, distribution, and effects on ecological processes in urban streams. Previous studies report plastic is abundant in freshwater systems, especially in naturally occurring debris dam structures and overhanging vegetation which accumulate high quantities of AL, especially plastic items (i.e. bags, wrappers, packaging material), along with leaf litter and other coarse particulate organic matter. in temperate, forested streams, leaf litter is a critical food source and plays an essential role in the stream food web. the rate at which leaves break down is affected by many variables such as hydrology, water chemistry, and macroinvertebrate and microbial communities. We predicted that plastic accumulation along with leaf litter can slow leaf breakdown by reducing diversity and abundance of microbial decomposers, as well as macroinvertebrate consumers. We measured leaf breakdown, and characterized macroinvertebrate and microbial (i.e., bacterial, fungal, algal) communities in 3 litter bag treatments: leaves alone, plastic alone, and leaves mixed with plastic. Although plastic did not reduce leaf breakdown rates or have a significant effect on macroinvertebrate consumer communities, it showed distinct microbial communities compared to leaf substrates. Results will provide a new understanding of how plastic and microbial communities interact, and set the framework for future studies to look at microbial succession and macroinvertebrate diversity on other synthetic substrates in freshwater systems.

Influence Of Varying Inorganic Nutrients Supply On Ergosterol And Glucosamine Concentrations And Biomass Nutrient Stoichiometry In Ectomycorrhizal Fungi, Stephanie S. Koury

Master's Theses

Ectomycorrhizal (ECM) fungi are critical for the health of forest ecosystems where they can sequester large amounts of carbon in the form of soil organic matter, a matter of growing interest due to anthropogenic climate change. A clear understanding of their growth dynamics and responses to environmental changes is imperative for future work in forest management and the possible mitigation of increased atmospheric CO₂. Six ECM fungal species were grown in liquid culture under varying nitrogen and phosphorus concentrations and ratios to assess how exogenous nutrient supplies affect fungal biomass stoichiometry and the degree of elemental homeostasis. Additional …

Effects Of Light And Macroinvertebrate Consumers On Detrital Microbial Biofilms In Streams, Cheyenne M. Brady

Master's Theses

In lotic freshwater systems, aquatic macroinvertebrates are key processors of biofilms that grow upon organic matter. Although macroinvertebrate effects on biofilms may depend on light availability, the combined effects of consumers and light remain unexplored. Here, I conducted experiments to test effects of presence/absence of the omnivorous shrimp Macrobrachium ohione and the shredding caddisfly Pycnopsyche sp. on Liriodendron tulipifera litter biofilms in experimental streams under light or darkness. I measured litter-associated algal, fungal and bacterial biomasses and production rates, as well as litter decomposition, over 49 days. Both experiments exhibited significant positive effects of light on algal productivity and interactions …

Play Behavior And The Development Of Boldness And Caution In Juvenile Belding’S Ground Squirrels (Urocitellus Beldingi), Madelene Shehan

Master's Theses

The ubiquity of play among juvenile mammals suggests it provides adaptive benefits, potentially through influences on the development of temperament in young animals. Juvenile Belding’s ground squirrels (Urocitellus beldingi) must balance competing demands for boldness and caution imposed by the fundamental trade-off between their short active season and their vulnerability to predation. In this study, I evaluated whether play helps to facilitate the development of an appropriate balance between boldness and caution in juvenile U. beldingi.I observed the play behavior of juvenile U. beldingiand conducted flight-initiation distance tests to measure boldness-caution at the beginning and toward …

Comparative Thermal Ecology Of Coastal And Inland Pacific Rattlesnakes (Crotalus Oreganus), Hayley Layne Crowell

Master's Theses

Global biodiversity is declining as a direct result of anthropogenic climate change. Ectothermic species have become focal organisms for studying the ecological effects of altered climates due to the clear relationship between environmental temperatures and ectotherms’ basic physiological functions. Historically, examinations of these effects have focused heavily on heliothermic lizards, and most others have tended to focus on single populations or sympatric species within a single community. Addressing the longterm energetic implications of environmental temperature variation will provide valuable insight into the cascading physiological effects that certain populations or species may experience as a result of altered climates.

In this …

Microplastic In Aquatic Food Webs: Museum Specimens And Ingestion Experiments Reveal Controls On Microplastic Ingestion By Freshwater Fish, Loren Hou

Master's Theses

Plastic is pervasive in modern economies and ecosystems. Early research suggests freshwater fish commonly ingest microplastic (particles < 5 mm), which may influence fish digestive tissues, but no studies have examined historical patterns in microplastic consumption or rates of microplastic retention in fish. We measured microplastic in digestive tissue of specimens collected and preserved over the last century (Field Museum, Chicago). We selected Micropterus salmoides (largemouth bass), Notropis stramineus (sand shiner), Ictalurus punctatus (channel catfish), and Neogobius melanostomus (round goby) because each was well represented in the museum collection, with specimens from urban rivers. Specimens from 1900-2018 showed increases in microplastic concentration from the 1950's to present. in a second project, we collected round gobies from Lake Michigan in Chicago to conduct feeding experiments to measure microplastic ingestion and retention rates. the majority of microplastic was excreted within 72 hours of ingestion. Results will aid in understanding ecological interactions of microplastic and freshwater fish, informing further work on the movement of microplastic in aquatic food webs.

Coastal Wetland Dynamics Under Sea-Level Rise And Wetland Restoration In The Northern Gulf Of Mexico Using Bayesian Multilevel Models And A Web Tool, Tyler Hardy

Master's Theses

There is currently a lack of modeling framework to predict how relative sea-level rise (SLR), combined with restoration activities, affects landscapes of coastal wetlands with uncertainties accounted for at the entire northern Gulf of Mexico (NGOM). I developed such a modeling framework – Bayesian multi-level models to study the spatial pattern of wetland loss in the NGOM, driven by relative RSLR, vegetation productivity, tidal range, coastal slope, and wave height – all interacting with river-borne sediment availability, indicated by hydrological regimes. These interactions have not been comprehensively investigated before. I further modified this model to assess the efficacy of restoration …

Crossing Corridors: Wildlife Use Of Jumpouts And Undercrossings Along A Highway With Wildlife Exclusion Fencing, Alex J. Jensen

Master's Theses

Roads pose two central problems for wildlife: wildlife-vehicle collisions (WVCs) and habitat fragmentation. Wildlife exclusion fencing can reduce WVCs but can exacerbate fragmentation. In Chapter 1, I summarize the relevant studies addressing these two problems, with a focus on large mammals in North America. Chapters 2 and 3 summarize field assessments of technologies to reduce WVCs and maintain connectivity, specifically jumpout ramps and underpasses, along Highway 101 near San Luis Obispo, CA. In a fenced highway, some animals inevitably breach the fence and become trapped, which increases the risk of a wildlife-vehicle collision. Earthen escape ramps, or “jumpouts”, can allow …

The Role And Contribution Of Saprotrophic Fungi During Standing Litter Decomposition Of Two Perennial Grass Species, Schizachyrium Scoparium And Schizachyrium Tenerum, Matthew Lodato

Master's Theses

In terrestrial ecosystems, most of the plant biomass produced enters the detrital pool, where microbial decomposers colonize, enzymatically degrade, and assimilate plant litter carbon and nutrients in amounts sufficient to bring about the decomposition of plant litter. Here, I estimated the biomass and production of fungi and microbial respiration associated with decaying Schizachyrium scoparium and Schizachyrium tenerum leaf litter, and constructed a partial organic matter budget estimating C flow into and through fungal decomposers. Significant losses in S. scoparium (57%) and S. tenerum (68%) leaf mass was observed during litter decomposition along with concomitant increases in fungal biomass, which reached …

Linkages Between Marsh Fragmentation, Prey Availability, And Blue Crab (Callinectes Sapidus) Abundance And Mortality, Lennah Shakeri

Master's Theses

Coastal marshes are important nursery habitats for many commercially important invertebrate species, yet these marshes are being lost worldwide at an unprecedented rate due to subsidence, erosion, climate change, and human activity. As marsh is lost, it creates the opportunity for submerged aquatic vegetation (SAV) colonization and establishment in newly created open water areas. Blue crabs, Callinectes sapidus, use both marsh edge and SAV habitat during the juvenile stages and support one of the largest fisheries in the Gulf of Mexico, worth over $70 million in 2015. This thesis studied the linkages between habitat type, SAV cover, benthic prey …