Biogeochemistry Commons^™

Temperature And Hydrologic Context Influence Methane Variability In A Low-Salinity Marsh, Zoie Brauser

Dissertations and Theses

Coastal wetlands are biogeochemical hotspots that capture and transform carbon and nutrients. Wetland restoration is increasingly used as a climate mitigation strategy because of wetlands' capacity to sequester large amounts of carbon. However, low-salinity tidal marshes exhibit high variability in methane (CH₄) emissions, which could partially offset carbon sequestration under certain conditions. Understanding the drivers of CH₄ variability is crucial for restoration and conservation work. This project uses an observational research approach to assess the relationships between environmental factors and carbon dioxide (CO₂) and CH₄ soil gas fluxes in a restored low-salinity tidal marsh …

Mechanics And Physical Attributes Of Nature-Based Alterations: Rock Reinforcement And Urban Heat Island Assessment, Mary Chikondi Ngoma

Dissertations

Ground improvement is critical to geotechnical and geo-engineering systems, where modification of the properties of geomaterials (rocks and soils) is required to maintain stability and prevent failure of infrastructure installed within and around them. This need has become increasingly important with rapid urbanization and population growth, which intensify demands on surface and subsurface systems and further challenge the performance of supporting geomaterials. As a result, there is growing interest in nature-based solutions, particularly biologically mediated processes such as biocementation, which can enhance the physical, hydraulic, and mechanical properties of geomaterials while offering environmentally sustainable alternatives to conventional ground improvement techniques. …

Evaluating Soil Health And Crop Yield In Louisiana Agricultural Systems: Impacts Of Best Management Practices And Prediction Models, Hector J. Mendoza Lagos

LSU Doctoral Dissertations

The adoption of conservation management practices is critical for improving soil health, enhancing nutrient use efficiency, and sustaining crop productivity in row crop systems in Louisiana. This study evaluated the role of conservation agronomic practices, soil biochemical indicators, and machine learning predictive models to improve soil nutrient dynamics, soil health indicators, microbial communities (MC), and crop productivity on a corn (Zea mays L.) research plot scale and in a commercial forty-hectare cotton (Gassypium hirsutum L.)-corn-soybean (Glycine max L.) rotation system in northeast Louisiana. The objectives of the study were to evaluate soil nutrient dynamics and MCs under …

Quantifying Co2 And Ch4 Fluxes In A Semi-Arid Floodplain: Assessing Spatial And Temporal Drivers, Miles E. Kelsey

Earth and Planetary Sciences ETDs

Rivers transport sediment and carbon across Earth’s surface, and their floodplains can store carbon over decades to millennia, making them important to terrestrial carbon management. While soil carbon can persist long term, it may be released as greenhouse gases through processes like methanogenesis and heterotrophic respiration. Environmental controls on these fluxes remain poorly constrained across floodplains in different climate and geomorphic setting, but especially in semi-arid systems where measurements are limited. To address this gap, we quantified CO₂ and CH₄ fluxes along the Middle Rio Grande (New Mexico, USA) using 227 chamber measurements collected May to November 2025 at three …

Biogeochemical Controls On Phosphorus Transport And Legacy Storage Across A Coastal Watershed, Lee Potter

LSU Doctoral Dissertations

Excess phosphorus (P) loading is a key driver of eutrophication and harmful algal blooms (HABs) in aquatic systems worldwide. This relationship is of increasing concern in coastal Louisiana, where climate variability, altered hydrology, and land-use change converge, resulting in increased hydrologic and nutrient loading into coastal systems. This dissertation examines controls on P cycling in the Lake Pontchartrain Basin through a multi-scale framework linking estuarine processes, watershed loading, climate and weather patterns, and sediment dynamics. The dissertation begins with an overview of the study region, P dynamics, and changes in hydrology and nutrient loading patterns. Chapter 2 presents a spatial …

Use Of Stable Isotope Geochemistry To Determine The Paleoenvironment Of The Pond Creek Coal Bed, Pike County, Eastern Kentucky, Vivian A. Edwards

Theses and Dissertations--Earth and Environmental Sciences

Wetlands are both critical habitats and bellwethers of the health of the environment. Coal, being the remains of wetlands, offers the possibility of understanding the evolution of wetlands over large climatic shifts. The paleoenvironment of coals can be determined from palynology, petrology, and geochemistry. Stable isotope ratios within coal, including carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S), are established tools for paleoenvironmental reconstructions. These ratios can be correlated to flora, geochemistry, macerals, and bacterial activity. However, carbon, nitrogen, and sulfur have given conflicting results in some studies and their correlation to known variables is …

High Algal Biomass Is Decoupled From Metabolism In The Gallatin River, Cora Mae Steinbach

Graduate Student Theses, Dissertations, & Professional Papers

Assessing eutrophication in rivers is difficult compared to lakes and coastal waters, because most algal biomass occurs on the riverbed and flows interact and co-vary with production (Biggs and Close, 1989; Bernhardt et al., 2018). Riverine eutrophication is typically assessed using algal biomass and water column nutrients (U.S. Environmental Protection Agency, 2000), but biomass is highly variable and labor-intensive to measure, while nutrient concentrations often underestimate enrichment due to rapid biological uptake (Dodds and Smith, 2016). Reach-scale river metabolism can help evaluate long-term functional change in rivers recovering from nutrient enrichment (Arroita et al., 2019; Jankowski et al., 2021; Diamond …

Overview And Methods Of Molecular Paleontology: A Review, Shelby Touchstone

Williams Honors College, Honors Research Projects

Molecular paleontology—the study of ancient biomolecules preserved in fossils and sediments, including ancient DNA, lipids, and proteins—has motivated researchers since the 1950s, inspiring both scientific inquiry and broader cultural imagination. Think Jurassic Park. This honors thesis presents a comprehensive review of the history, current state, and methods of the field of molecular paleontology. Drawing on peer-reviewed literature and scholarly resources accessed through databases such as EBSCO and Bierce library, this review examines key techniques such as Next Generation Sequencing and amino acid racemization and will go over limitations and controversies in the field. It will also explore potential new …

Assessing Dissolved Organic Matter Sources And Dynamics In Urban Stormwater: Implications For Greenhouse Gases, Harper W. Schmalz

Theses and Dissertations (Comprehensive)

Stormwater management ponds (SWMPs) are important aspects of land-use planning and increasingly recognized as active sites of biogeochemical processing that influence carbon cycling; however, little research has investigated the controls on dissolved organic and dissolved inorganic carbon (DOC and DIC) within these systems. This thesis examined the processing and transformations of dissolved carbon between three compartments to support the development of a greenhouse gas (GHG) box-model for urban stormwater ponds, including SWMP sediment, surface water, and vegetation. The objective of this thesis was to assess the biogeochemical processes that govern the rate and transformation of DOC and DIC between these …

Impacts Of Burn Severity On The Hydro-Physical, Chemical And Thermal Properties Of Sub-Arctic Peat, Joshua B. Meyer Mr

Theses and Dissertations (Comprehensive)

Under current climate change, summer season in the boreal regions of Canada is becoming increasingly warmer and drier. This shift is driving increases in the frequency and intensity of naturally occurring wildfires and allowing access to areas not normally susceptible to fire such as wetlands. In peatland areas, these increasingly large fires can create complex burn scars, which contain a wide variety of different burn severities across different landcover types. This variety calls for a greater understanding of how varying fire intensity affects the hydro physical, chemical, and thermal characteristics of boreal peat. This study aims to deepen that understanding …

Aluminum As A Tracer Of Dust Deposition To The Ocean: A Case Study From The Bermuda Region, Tara Elizabeth Williams

OES Theses and Dissertations

Aluminum (Al), a major component of mineral aerosol (dust), partially dissolves in seawater and is widely used as a tracer for estimating time‐averaged dust fluxes to the ocean. Such estimates rely on dissolved Al (DAl) inventories in the surface mixed layer (SML), an assumed SML residence time of DAl (_TDAl), the fractional solubility of Al in dust (Al_S), and the mass fraction of Al in dust. In this study, dust flux estimated from seasonal, water-column DAl data from the Bermuda Atlantic Time-series Study (BATS) region are compared with direct dust flux estimated from contemporaneous measurements of …

Tracing The Journey Of Dissolved Organic Matter: From Leaf Litter Photodegradation To Microbial Processing In Tropical Streams, Samantha Nicole Sullivan

Chemistry & Biochemistry Theses & Dissertations

Dissolved organic matter (DOM) is a major reservoir of organic carbon in aquatic ecosystems and plays a central role in global carbon cycling through its transformation and remineralization to carbon dioxide (CO₂). As DOM moves from terrestrial environments into streams and rivers, its chemical composition is altered by a combination of microbial and photochemical oxidation processes that regulate both its reactivity and its persistence during transport. However, the molecular mechanisms governing these oxidative transitions, particularly in tropical ecosystems characterized by strong hydrologic seasonality and substantial inputs of plant-derived material, remain insufficiently resolved. This dissertation integrates ultrahigh-resolution mass spectrometry, optical characterization, …

Modeling Aerosol Transport During High Particulate Matter Episodes In El Paso-Juarez Region And Mitigating Mining-Related Emissions Of Rare Earth Elements (Rees) To The Air, Suzan Aranda Luna

Open Access Theses & Dissertations

This dissertation examines the use of the HYSPLIT model to develop a methodology for the transport and dispersion of air masses affecting particulate matter (PM) concentrations in the El Paso Region, and bioleaching experiments as an alternative to mitigating rare-earth concentrations in the air. Chapter 2 describes the study methodology, 3 and 4 cover the modeling methodology using two-representative high PM2.5 episodes, occurring on February 28, 2024, and June 19, 2024, respectively. These sections encompass the analysis of backward trajectories using four different meteorological datasets to build trajectory frequency maps, the exploratory model analysis of modeled outputs from lower to …

What Limits Dryland Ecosystems? Patterns Of Soil Fertility And Resource Limitation In The Chihuahuan Desert, Dylan Stover

Open Access Theses & Dissertations

Human activities are substantially altering global resource cycles with widespread implications for biogeochemistry and ecosystem functioning globally. Drylands, regions where precipitation is outweighed by water losses, are especially sensitive to these large shifts in resource cycles due to their inherently low and variable resource availability. In these regions, resource availability and biological activity are often concentrated around plants – or fertile islands – and predominantly driven by pulses of water. However, our knowledge of the processes influencing biological productivity in drylands – patterns of soil fertility and resource limitation – remains lacking, and their unique biogeochemical and biological processes create …

Direct And Satellite-Based Quantification Of Greenhouse Gas Fluxes In Small Ponds., Mark Christopher Tierney

Electronic Theses and Dissertations

As evidenced by their historic losses due to anthropogenic activities, wetlands are undervalued ecosystems that provide numerous ecosystem services, from recreational opportunities to carbon (C) storage. However, these wetlands are also the largest natural source of atmospheric methane (CH₄). Additionally, small water bodies (< 10,000 m²) are disproportionately large emitters relative to larger lakes and reservoirs. As construction and restoration efforts proceed, it is crucial to identify wetlands that need restoration and to understand the factors driving both greenhouse gas (GHG) fluxes and the C balance of these systems. This dissertation investigates the drivers of greenhouse gas fluxes …

Mcl1 And Hexokinase 2 Form A Glucose Metabolic Regulatory Axis, Robert Lee

All ETDs from UAB

Hexokinase 2 (HK2) initiates glucose metabolism by catalyzing the conversion of glucose to glucose-6-phosphate providing the starting substrate for a vast array of metabolic pathways such as glycolysis, pentose phosphate pathway (PPP), amino acid biosynthesis and others. While HK2’s metabolic role in normal physiologic function (such as in cardiomyocytes) and cancers (through driving the Warburg Effect) are well established, there is emerging evidence that supports HK2 is also a critical mediator of protein-protein interactions that regulate cell survival. Through comprehensive review, we explore how HK2 contributes to cell survival through metabolic and protein scaffolding roles. We also investigate a novel …

Compound-Specific Isotope Records Of Dust Provenance And Hydroclimate In The North Pacific And Marginal Seas Of East Asia: Integrating N-Alkane Δ13c And Δd With Standardized Analytical Frameworks, Julian W. Traphagan

LSU Doctoral Dissertations

This dissertation presents advancements in compound-specific isotope analysis (CSIA) through methodological innovation and paleoclimate reconstruction in Central and East Asia. Utilizing plant wax n-alkanes from International Ocean Discovery Program (IODP) and Ocean Drilling Program (ODP) sediment cores, this research reconstructs atmospheric circulation shifts responding to tectonic evolution and climate transitions since the Late Miocene.

Chapter 1 investigates hydrogen isotope compositions (δD_wax) from IODP U1430 (Sea of Japan), ODP 886, and ODP 1208 (North Pacific) to trace dust provenance and hydroclimate changes since ~13 Ma. Results reveal persistently segmented source-to-sink systems: the Sea of Japan dominated by westerly …

Effect Of Seasonal Variability In Methane Emissions And Iron Redox Chemistry At Terrestrial-Aquatic Interfaces, Hermes C. Ruiz

Master's Theses

Methane (CH₄) emissions at terrestrial–aquatic interfaces (TAIs) are significant contributors to the global carbon budget, yet the mechanisms driving methanogenesis remain poorly understood. Limited data exist on how seasonal variations and redox processes influence CH₄ fluxes in these dynamic ecosystems. This study addressed two questions: (1) How are CH₄ fluxes in riverine floodplains and adjacent hillslopes impacted by seasonal variations? (2) What roles do metal redox processes (e.g., iron (Fe)) play in regulating methanogenesis?

In-situ CH₄ flux and solid-phase Fe speciation were quantified in East River, CO, under flooded and drained conditions. Groundwater chemistry, gas flux, and soil physical properties …

Assessing Greenhouse Gas Emissions From Michigan’S Drowned River Mouths Using In Situ And Remote Sensing Methods, Jillian A. Greene

Masters Theses

Freshwater estuaries are natural contributors to the carbon cycle including production and emission of methane (CH4) and carbon dioxide (CO2), potent greenhouse gases (GHGs); however, estimates of their contribution to regional and global GHG emissions is largely unconstrained. Few studies have examined the quantification and drivers of lake CH4 and CO2 production in the Great Lakes region and how it may differ in response to anthropogenic development. In this study, CH4 and CO2 emissions were measured from three drowned river mouth estuaries (DRMs) along the eastern shore of Lake Michigan in 2024. The DRMs exist along a latitudinal gradient ranging …

Comparison Of Nutrient Concentrations And Primary Production Indicators Across Plume Fronts, Taylor Dishon

Electronic Theses and Dissertations

Coastal buoyant plumes carry low-salinity waters containing particulate and dissolved terrestrial materials with an abundance of nutrients into the coastal ocean, including inorganic nitrogen and phosphorous. Plume fronts act as transport barriers created from the convergence of a fresher plume with an older, saltier plume or with ambient waters, leading to potential accumulation of phytoplankton and nutrients. This accumulation creates an optimal environment for primary production. The primary goals of this study were: to investigate the distribution of and potential relationships between nutrient concentrations and chlorophyll a across plume fronts of the Winyah Bay River Plume, and examine potential relationships …

Using Triple Oxygen Isotopes To Investigate Water Usage In Desert Ecosystems, Cloe V. Knutson

Earth and Planetary Sciences ETDs

In arid environments, maintaining water balance can be more critical for survival than obtaining food. As droughts intensify, understanding how animals manage body water is essential. Triple oxygen isotope analysis provides a novel way to trace water sources in animals, distinguishing contributions from free water, food-derived oxygen, and atmospheric O₂. We developed an equilibration method using CO₂–H₂O oxygen exchange and measured δ^’18O and Δ^’17O values via tunable infrared laser direct spectroscopy (TILDAS). Validated against traditional fluorination methods, this technique enables streamlined analysis of whole blood and plant samples. Applied to …

Phosphorus: From The Origins Of Life To The Origin Of An Industry, Joshua Abbatiello

USF Tampa Graduate Theses and Dissertations

The element phosphorus is a key biogenic element that is often the limiting reagent for life. Phosphorus is quickly bound by metal divalent cations making it virtually insoluble and inert in water (forming the phosphate mineral apatite). Due to this, it becomes imperative to understand alternative pathways to increase biogenically available phosphorus in environments. To that end, this dissertation involved examining olivine as an alternative source of phosphorus to apatite, analyzing a novel grain of iron silicide found via lightning reduction in a fulgurite, and finally sought to understand the impact of phosphate mining through phosphogypsum stacks. Olivine is a …

Unveiling The Vital Role Of Blue Carbon In Mangroves: Understanding Environmental Influences, Jahnelle Howe

Dissertations, Theses, and Capstone Projects

Mangrove ecosystems provide essential ecological services, including carbon sequestration, coastal protection, and heavy metal retention. However, their resilience and functionality are increasingly influenced by hurricanes, climate variability, and anthropogenic contamination. This dissertation integrates three research efforts examining mangrove canopy dynamics, carbon storage, and heavy metal contamination in two Puerto Rican mangrove systems: La Parguera and Laguna Grande.

Using remote sensing techniques (LiDAR and NDVI analysis), we assessed the impact of Hurricane Maria (Category 4, 2017) on mangrove canopy structure and vegetation health. Results revealed significant canopy height loss, with greater damage at Laguna Grande, where pre-storm canopy height and human …

Investigating Potential Sugar-Related Uncertainties In A Proxy For Ancient Co2, Liam Cooper

Student Theses and Dissertations

The ε_p proxy for ancient pCO₂ can potentially estimate ancient pCO₂ as from the evolution of rubisco-based photosynthesis, using the difference in stable carbon isotope ratios (δ¹³C) between fixed and inorganic carbon, assuming this difference is proportional to pCO₂. This study aims to address uncertainty with the use of photosynthetic microbes in proxies for ancient pCO₂. While previous studies address uncertainties related to the δ¹³C of initial fixed photosynthate (e.g., growth rate), we aim to address the effects of downstream carbon allocation. Specifically, if a significant fraction of fixed …

Diel Patterns Of Biogeochemical Indicators In Tidally-Dominated Creeks, Juliana Calderone

Honors Theses

Marshes and swashes are vital environments as a controlling barrier between land affected by various pollutants and the ocean. Eutrophication and the effects of this process can be detrimental for the areas experiencing it. I am interested in ways areas that have little contact with human interactions compare to areas that are heavily urbanized, and whether either of these locations is at a higher risk for eutrophication. Using spectrophotometry and fluorometry, I analyzed samples collected from the relatively undeveloped and restricted-access locations of Waities Island Beach and Dunn Sound monthly for dissolved nutrients, and chlorophyll. At the time of sampling, …

From Land To Lagoon: The Spatiotemporal Biogeochemical Dynamics Of Arctic Coastal Erosion In Elson Lagoon, Alaska, Sasha Victoria Peterson

Open Access Theses & Dissertations

TThe Arctic is warming rapidly, driving widespread environmental change across coastal landscapes, including permafrost thaw, shoreline erosion, and shifts in sediment and carbon dynamics, pose growing challenges for predicting carbon cycling and climate feedbacks. This dissertation investigates the spatiotemporal variability of erosion, decomposition, and nearshore turbidity in Elson Lagoon, Alaska (1955–2023), to better understand how carbon, nitrogen, and sediment are mobilized, transformed, and potentially emitted as greenhouse gases in Arctic coastal systems. Chapter 2 presents a high-resolution analysis of shoreline change and erosion-driven material fluxes spanning nearly seven decades. Drawing on 795 soil data points, airborne LiDAR, and five shoreline …

The Effect Of Hiv-1 Infection Associated Bacterial Lipopolysaccharide (Lps) On Human Oral Keratinocytes: Implications For Promoting Chronic Inflammation, Md Shafayat Jamil

Theses and Dissertations

Human immunodeficiency virus type 1 (HIV-1) remains a major global health concern, affecting approximately 39 million people worldwide, with 500,000 new infections reported in 2022. While combined antiretroviral therapy (cART) has significantly reduced viral replication, HIV-1 infection is linked to various comorbidities, including oral dysbiosis and accelerated aging. Immune dysregulation in HIV-1–infected individuals promotes the proliferation of pathogenic gram-negative bacteria like Porphyromonas gingivalis, a key contributor to periodontal disease. P. gingivalis secretes lipopolysaccharide (LPS), which adversely affects human oral keratinocytes (HOK), the first line of defense against microbial threats in the oral cavity. HOK recognize LPS as a threat, …

Spatio-Temporal Pattern Of Nutrient Dynamics In The South Texas Coastal Watershed, Mohammad Sadman Alam

Theses and Dissertations

Eutrophication threatens aquatic ecosystems by altering productivity through excessive nutrient inputs. In some systems, primary productivity is limited by nitrogen (N), phosphorus (P), or both, based on the N:P ratio defined by the "Redfield" ratio. South Texas, facing rapid urban growth and industrialization, is at risk of higher nutrient loads, but research on nutrient dynamics in this region is limited. This study investigates nutrient variations in the freshwater (FW) abandoned distributaries of the Rio Grande and hypersaline saltwater (SW) systems. Results showed a significant decrease in dissolved inorganic nitrogen (DIN) and an increase in dissolved inorganic phosphorus (DIP), shifting the …

Tracing The Sources Of Nitrogen In Submarine Groundwater Discharge And Primary Producers In The Great South Bay Estuary, Nia H. Rene

Dissertations, Theses, and Capstone Projects

The primary aim of this research was to elucidate the impact of submarine groundwater discharge (SGD) and septic effluent on coastal primary producers in the Great South Bay (GSB). The study focused on three main objectives: assessing the impact of precipitation patterns on SGD, tracing nitrogen sources into the GSB, and determining the impact of these nitrogen sources on coastal primary producers. The research revealed that current precipitation patterns significantly influence SGD across different seasons, highlighting the seasonal variability in groundwater discharge and its implications for nutrient loading in coastal waters. A suite of tracers was employed to identify and …

Evaluation Of Practical Methods To Determine If A Karst Creek Is Gaining Or Losing: Case Study Of Leith Creek, Elizabeth Jones

Graduate Theses/Dissertations

Karst landscapes are abundant in Missouri, with features such as caves, springs, and sinkholes that form through the dissolution of limestone. Leith Creek is a small stream in Polk County, Missouri fed by two springs and the shallow unconfined Springfield Plateau aquifer, a highly karstified aquifer which is made up of limestone and minor interbedded shale-mudstone units. To determine if Leith Creek is gaining or losing, stream flow, water chemistry and temperature sensors were monitored. Stream flow results required multiple visits to take measurements while temperature sensors required two visits, one to install the dataloggers and another to remove the …