Biogeochemistry Commons^™

Indolic Glucosinolate Pathway Provides Resistance To Mycorrhizal Fungal Colonization In A Non-Host Brassicaceae, Mark A. Anthony, J. L. Celenza, A. Armstrong, Serita D. Frey

Faculty Publications

Most terrestrial plants form mycorrhizas, but a number of agricultural plants, including the Brassicaceae, are non-mycorrhizal. Brassicaceae can still be colonized by arbuscular mycorrhizal fungi (AMF), but species like Arabidopsis thaliana experience growth reductions following AMF colonization at similar magnitude to that of fungal pathogen infections and lack key genes necessary for nutrient exchange. Arabidopsis also produces specific secondary compounds via the modification of tryptophan, including indolic glucosinolates (IGs), which have anti-fungal properties and may therefore be involved in reducing AMF colonization. This study therefore addressed whether the ability to produce IGs facilitates resistance to AMF colonization and growth suppression. …

Ramped Thermal Analysis For Isolating Biologically Meaningful Soil Organic Matter Fractions With Distinct Residence Times, Jonathan Sanderman, A. Stuart Grandy

Faculty Publications

In this work, we assess whether or not ramped thermal oxidation coupled with determination of the radiocarbon content of the evolved CO2 can be used to isolate distinct thermal fractions of soil organic matter (SOM) along with direct information on the turnover rate of each thermal fraction. Using a 30-year time series of soil samples from a well-characterized agronomic trial, we found that the incorporation of the bomb spike in atmospheric 14CO2 into thermal fractions of increasing resistance to thermal decomposition could be successfully modeled. With increasing temperature, which is proportional to activation energy, the mean residence time of the …

Correcting Tree-Ring Δ13c Time Series For Tree-Size Effects In Eight Temperate Tree Species, Matthew A. Vadeboncoeur, Katie A. Jennings, Andrew P. Ouimette, Heidi Asbjornsen

All Materials

Stable carbon isotope ratios (δ¹³C) in tree rings have been widely used to study changes in intrinsic water-use efficiency (iWUE), sometimes with limited consideration of how C-isotope discrimination is affected by tree height and canopy position. Our goals were to quantify the relationships between tree size or tree microenvironment and wood δ¹³C for eight functionally diverse temperate tree species in northern New England, and to better understand the physical and physiological mechanisms underlying these differences. We collected short increment cores in closed-canopy stands and analyzed δ¹³C in the most recent 5 years of growth. …

Diatom Community Composition Shifts Driven By Coherent Cyclonic Mesoscale Eddies In The California Current System, Zuzanna Maria Abdala

OES Theses and Dissertations

The California Current System (CCS) is characterized by an equatorward flowing eastern boundary current, as well as seasonal wind-driven coastal upwelling which supplies nutrient-rich waters to the surface and drives high coastal productivity. Cyclonic mesoscale eddies form off the coast in the CCS where they trap the highly productive upwelled coastal waters, along with their resident planktonic communities, and transport them offshore into the more oligotrophic California Current waters. The interaction between waters within and outside of the eddies is limited, and so the eddies act as natural mesocosms, where the resident phytoplankton population undergo ecological succession as the eddy …

Long-Term Evidence Shows That Crop-Rotation Diversification Increases Agricultural Resilience To Adverse Growing Conditions In North America, Timothy M. Bowles, Maria Mooshammer, Yvonne Socolar, Francisco Calderon, Michel A. Cavigelli, Steve W. Culman, William Deen, Craig F. Drury, Axel Garcia Y Garcia, Amelie C. M. Gaudin, W. Scott Harkcom, R. Michael Lehman, Shannon L. Osborne, G. Philip Robertson, Jonathan Salerno, Marty R. Schmer, Jeffrey Strock, A. Stuart Grandy

Faculty Publications

A grand challenge facing humanity is how to produce food for a growing population in the face of a changing climate and environmental degradation. Although empirical evidence remains sparse, management strategies that increase environmental sustainability, such as increasing agroecosystem diversity through crop rotations, may also increase resilience to weather extremes without sacrificing yields. We used multilevel regression analyses of long-term crop yield datasets across a continental precipitation gradient to assess how temporal crop diversification affects maize yields in intensively managed grain systems. More diverse rotations increased maize yields over time and across all growing conditions (28.1% on average), including in …

Mechanisms Of Carbon Movement And Stabilization In Mangrove Wetlands, Carey Schafer

USF Tampa Graduate Theses and Dissertations

Mangrove forests have higher rates of carbon storage per unit area than any other coastal or terrestrial habitat, largely due to their significant soil stocks. More effort has been placed on quantifying mangrove soil carbon stock, the amount of carbon stored in the upper meter of mangrove soils, than identifying the processes governing in situ soil organic carbon (SOC) cycling and stabilization. An understanding of the mechanisms related to carbon transport and stability is necessary to constrain current wetland carbon stocks and to determine how sea level rise will impact future carbon stores. This study uses a variety of radiometric …

Assessment Of Soil Protein And Refractory Soil Organic Matter Across Two Chronosequences Of Newly Developing Marshes In Coastal Louisiana, Usa, Stuart Alexander Mcclellan

LSU Doctoral Dissertations

The impacts of sea-level rise and hydrologic manipulation are threatening the stability of coastal marshes throughout the world, thereby increasing the potential for re-mineralization of soil organic matter (SOM) in these systems. Such threats have prompted marsh restoration efforts, particularly in coastal Louisiana, yet it is unclear how the slowly decomposing (refractory) and quickly decomposing (labile) fractions of SOM may be differentially affected by different approaches to marsh restoration. Additionally, otherwise labile compounds may accumulate in the soil via a range of protective mechanisms, including rapid burial and association with organic compounds that are thought to enhance soil aggregation, such …

Organic Sulfur: A Spatially Variable And Understudied Component Of Marine Organic Matter, Krista Longnecker, Lisa Oswald, Melissa C. Kido Soule, Gregory A. Cutter, Elizabeth B. Kujawinski

OES Faculty Publications

Sulfur (S) is a major heteroatom in organic matter. This project evaluated spatial variability in the concentration and molecular-level composition of organic sulfur along gradients of depth and latitude. We measured the concentration of total organic sulfur (TOS) directly from whole seawater. Our data reveal high variability in organic sulfur, relative to established variability in total organic carbon or nitrogen. The deep ocean contained significant amounts of organic sulfur, and the concentration of TOS in North Atlantic Deep Water (NADW) decreased with increasing age while total organic carbon remained stable. Analysis of dissolved organic matter extracts by ultrahigh resolution mass …

Carbon Use Efficiency And Its Temperature Sensitivity Covary In Soil Bacteria, Grace Pold, Luiz A. Domeignoz-Horta, Eric W. Morrison, Serita D. Frey, Seeta A. Sistla, Kristen M. Deangelis

Faculty Publications

The strategy that microbial decomposers take with respect to using substrate for growth versus maintenance is one essential biological determinant of the propensity of carbon to remain in soil. To quantify the environmental sensitivity of this key physiological trade-off, we characterized the carbon use efficiency (CUE) of 23 soil bacterial isolates across seven phyla at three temperatures and with up to four substrates. Temperature altered CUE in both an isolate-specific manner and a substrate-specific manner. We searched for genes correlated with the temperature sensitivity of CUE on glucose and deemed those functional genes which were similarly correlated with CUE on …

Microdialysis: A Method For Quantifying In Situ Nitrogen Fluxes In Soil Microsites, Srusti Maddala, Mary C. Savin, Julie A. Stenken, Lisa S. Wood

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Microdialysis, a diffusion-based sampling technique commonly used in biomedical research, has recently been recognized as a candidate for monitoring chemical changes in the rhizosphere. The information it provides about nutrient diffusion may improve nitrogen use efficiency, leading to enhanced management and success of restoration projects. The objective of this study was to determine the efficacy of microdialysis sampling to quantify the relative recoveries (RR%) of nitrate-N and ammonium-N, the two inorganic nitrogen compounds typically found in soil. The effects of microdialysis flow rate, sample medium concentration, and the presence of both analytes in solution on the relative recoveries obtained from …

Ecosystem Health In Guánica Bay And La Parguera, Puerto Rico: Remote Sensing Of Ocean Color And Metal Analysis Of Coral Tissue And Surficial Sediments, Jahnelle Howe

Dissertations and Theses

Guánica Bay is an estuary located in southwest Puerto Rico, with a coral reef ecosystem at its periphery. This ecosystem is affected by sediments, nutrients, and contaminants from the watershed through the Bay and into the offshore water. This project evaluates Guánica Bay and La Parguera coastal areas through remote sensing and chemical analysis to assess coastal ecosystem health. The concentration of metals in two coral species and their associated surface sediments was were analyzed by X-ray fluorescence (XRF) and Direct Mercury Analyzer (DMA- 80). Ocean color remote sensing was used to estimate nutrient inputs and phytoplankton biomass through chlorophyll- …

Using Satellite Observations Of Soil Moisture To Improve Modeling Of Terrestrial Water Cycles, Colin W. Brust

Graduate Student Theses, Dissertations, & Professional Papers

Terrestrial evapotranspiration (ET) describes the flux of water from the Earth’s surface to the atmosphere, calculated as the sum of evaporation from soil and leaf surfaces, and transpiration through plant stomata. ET is the largest terrestrial water flux, returning over half of the precipitation that falls on land back to the atmosphere, annually. Additionally, ET plays a key role in Earth’s carbon, water, and energy cycles, linking them together via the movement of water and CO₂ through plant stomata. Because of its important role in these Earth system processes, it is essential that existing methods of measuring and modeling …

Comparison Of Fe(Iii) Reduction Rates By Iron-Reducing Bacteria Within Sub Muros Samples From Quadrilátero Ferrífero Iron-Ore Caves, Brazil, Summer Ellis

Williams Honors College, Honors Research Projects

Previous research investigating the speleogenesis of iron-ore caves (IOC) in the Quadrilátero Ferrífero, or “Iron Quadrangle,” of Brazil suggests that microbial iron reduction and subsequent dissolution of the surrounding Fe(III) rich rocks is responsible for cave formation. A soft intra-wall substance (sub muros) containing iron-reducing bacteria (FeRB) was discovered underneath the durable crusts of cave walls. The goal of the study was to determine if reduction rates were comparable between sub muros samples, while additionally observing how different electron donors affect microbial iron reduction. To do this, I compared Fe(III) reduction rates between sub muros samples collected from …

Microbial Degradability Of Terrigenous, Marsh-Exported, And Estuarine Colored Dissolved Organic Matter In Long Island Sound, John R. Supino

Dissertations and Theses

The Long Island Sound is one of the world's most urbanized estuaries, polluted from excess nutrients which impact the quality of water through increased biological productivity. Dissolved organic matter (DOM) is a sensitive indicator of anthropogenic pollution and nutrient enrichment in coastal waters as well as an important part of the carbon cycle and serves as a primary food source for aquatic food webs. Additionally, the colored portion of DOM (CDOM) impacts coastal optical properties, ocean color, and light attenuation. High levels of CDOM have been shown to inhibit the growth of phytoplankton and limit photosynthesis, damaging the food chain …

Dissolved Organic Matter Movement Across Lake Superior’S Terrestrial-Stream-Coastal Interface, Karl M. Meingast

Dissertations, Master's Theses and Master's Reports

Dissolved organic matter (DOM) represents a carbon pool that can be easily translocated between ecosystems with the movement of water. This study examines the controls on DOM quantity and character delivered to Lake Superior primarily during the snowmelt period. We employed long-term stream dissolved organic carbon (DOC) data to determine quantity as well as absorption and fluorescence spectroscopy to analyze DOM structure. Our results indicate that an increasing trend in DOC concentrations, likely driven by decreases in acidity of precipitation, combined with slightly less annual runoff have resulted in relatively constant fluxes of DOM to Lake Superior. Additionally, our study …

Age-Specific And Species-Specific Tree Response To Seasonal Drought In Tropical Dry Forests, Emily A. Santos

Cal Poly Humboldt theses and projects

Millions of people live in or depend on ecoregions dominated by Tropical Dry Forests (TDFs), but due to their high accessibility, convenient topography and mild climate conditions their distribution is fragmented with less than 10% of their original extent remaining in many countries. Despite the vast ecosystem services provided by TDFs, including vital water resources in water limited environments, ecohydrological research in this biome has been limited to a small number of short-term investigations. Similar to worldwide trends, the TDF surrounding Bahía de Caráquez (Bahía), Ecuador, has been severely deforested over the past 400 years. The land use history in …

Understanding And Measuring Net Positive Business Strategies, Luke Ruffner Robinson

Graduate Student Theses, Dissertations, & Professional Papers

Despite their attempts to mitigate ecological impacts through sustainability initiatives, businesses are a major cause of the world's ecological problems. Some progressive businesses are attempting to move beyond “net zero” in terms of achieving neutral environmental impacts and instead are now pursuing a goal of net positive. Net positive refers to the idea that business activities could contribute value-added benefits to earth’s ecological systems, for example, by using technologies that sequester and store carbon. However, except for a handful of high-profile corporate case studies, little is known about how companies are developing their strategies to become net positive and …

Reconstructing Hydrologic Conditions And Metals Supplied By The Peace River To The Peace-Athabasca Delta, Jelle André Faber

Theses and Dissertations (Comprehensive)

The Peace-Athabasca Delta (PAD) in northern Alberta, Canada, is recognized internationally for its ecological, historical, and cultural significance. The delta is mostly within Wood Buffalo National Park, a UNESCO World Heritage Site, and is a Ramsar Wetland of International Importance. The construction of the WAC Bennett Dam (1967) and the Site C Dam (ongoing, 2024) on the Peace River, and expansion of the Alberta Oil Sands industry along the Athabasca River have raised concerns over water quantity and quality in the delta. When industry operations began, effective monitoring had not been implemented. Consequently, pre-industrial reference conditions are unknown and can …

Investigating Diel, Seasonal, And Interannual Variability Of Dissolved And Particulate Stable Carbon Isotope Values In A Eutrophic Boreal Lake, Rachel Henderson

Theses and Dissertations (Comprehensive)

Lakes are globally significant sources, sinks, and conduits of carbon. Cultural eutrophication of freshwater promotes the growth of phytoplankton blooms, which can transform, respire, and sequester large amounts of carbon. Analysis of stable carbon isotopes is a common tool to study the movement of carbon through the aquatic carbon cycle. The causes of temporal variability in δ¹³C values at different timescales are not well understood, and differ between lakes. In this study, I investigated diel, seasonal, and interannual variability in δ¹³C values of dissolved inorganic carbon (DIC) and particulate organic carbon (POC) in Lake 227, an …

Estimating Carbon Flux From Optically Recording Total Particle Volume At Depths Below The Primary Pycnocline, Alexander B. Bochdansky, Robert B. Dunbar, Dennis A. Hansell, Gerhard J. Herndl

OES Faculty Publications

Optical instruments can rapidly determine numbers and characteristics of water column particles with high sensitivity. Here we show the usefulness of optically assessed total particle volume below the main pycnocline to estimate carbon export in two systems: the open subarctic North Atlantic and the Ross Sea, Antarctica. Both regions exhibit seasonally high phytoplankton production and efficient export (i.e., a strong biological pump). Total particle volumes in the mesopelagic (200-300 m) were significantly correlated with those in the overlying surface mixed layer (50-60 m), indicating that most particles at depth reflect export from the surface. This connectivity, however, is modulated by …

Pesticide Seed Treatments Containing Neonicotinoids Have Limited Effect On Soil Microbial Community Structure Under Different Tillage Regimes, Jessica E. Mackay, Richard G. Smith, Jessica G. Ernakovich, Lukas T. Bernhardt

Faculty Publications

Pesticide seed treatments (PST) which contain fungicides and insecticides are commonly used in agriculture; however, little is known about their effect on soil microbial communities and soil health. Neonicotinoids – controversial insecticides which are common in PST – have received criticism due to potential non-target effects. While fungal pathogens need to be moderated, PST have the potential to disturb broader fungal communities which could lead to reduced nutrient cycling and poor soil health. Given the broad use of PST, their effect on soil fungi needs to be studied within the context of other agricultural management practices. For example, tillage regimes …

Reconstructing Energy Flow Through Modern And Historical Marine Communities: Insights From Amino Acid Isotope Analysis, Emma A. Elliott Smith

Biology ETDs

The fundamental currency of life is energy. Organisms need energy to grow, to survive and to reproduce. Understanding the acquisition of energy by consumers is thus a foundational aspect of biological research. This is especially important in the modern era, as impacts of ongoing anthropogenic effects will be mediated or amplified through food webs. Here, I explore how isotopic analysis of individual amino acids – a technique new to ecological studies – can be used to trace energy flow through animal communities in modern and ancient time periods. In particular, I focus on kelp forest food webs, which are nearshore …

Employing Earth Observations And Artificial Intelligence To Address Key Global Environmental Challenges In Service Of The Sdgs, Wenzhao Li

Computational and Data Sciences (PhD) Dissertations

Earth Observation (EO) data provides the capability to integrate data from multiple sources and helps to produce more relevant, frequent, and accurate information about complex processes. EO, empowered by methodologies from Artificial Intelligence (AI), supports various aspects of the UN’s Sustainable Development Goals (SDGs). This dissertation presents author’s major studies using EO to fill in knowledge gaps and develop methodologies and cloud-based applications in selected SDGs, including SDG 6 (Clean Water and Sanitation), SDG 11 (Sustainable Cities and Communities), SDG 14 (Life below Water) and SDG 15 (Life on Land). For SDG 6, the study focuses on spatiotemporal water recharge …

Growth Phase Proteomics Of The Heterotrophic Marine Bacterium Ruegeria Pomeroyi, Dasha Krayushkina, Emma Timmins-Schiffman, Jessica Faux, Damon H. May, Michael Riffle, H. Rodger Harvey, Brook L. Nunn

OES Faculty Publications

The heterotrophic marine bacterium, Ruegeria pomeroyi, was experimentally cultured under environmentally realistic carbon conditions and with a tracer-level addition of ¹³C-labeled leucine to track bacterial protein biosynthesis through growth phases. A combination of methods allowed observation of real-time bacterial protein production to understand metabolic priorities through the different growth phases. Over 2000 proteins were identified in each experimental culture from exponential and stationary growth phases. Within two hours of the ¹³C-labeled leucine addition, R. pomeroyi significantly assimilated the newly encountered substrate into new proteins. This dataset provides a fundamental baseline for understanding growth phase differences in molecular …

An Investigation Of Metal Sulfides As The Source Of The Low Emissivity Anomaly On The Highlands Of Venus, Sara Taeko Port

Graduate Theses and Dissertations

Since its detection in the 1960s the source of the unusual radar emissivity signal seen on several highlands on Venus has long eluded researchers. Researchers have determined that a mineral with a high dielectric constant could explain the signal. Using a Venus simulation chamber, we experimentally investigated this enigma to build upon the candidate mineral list that has been compiled over the last several decades. We tested the stability of 8 different minerals and elements at two to three different temperature/pressure regimes in three different gas mixtures meant to simulate the conditions found on Venus for a period of no …

Reconstructing Geographic And Trophic Histories Of Fish Using Bulk And Compound-Specific Stable Isotopes From Eye Lenses, Amy A. Wallace

USF Tampa Graduate Theses and Dissertations

The present research examined the viability and utility of eye lenses as a source of lifetime stable-isotope records in fish. It is presented in three sections. The first section compared bulk isotopic variation (bulk analysis) within fish eye-lenses at two temporal resolutions and compared patterns obtained from left and right eyes. The first temporal resolution was lower in an attempt to expose broad-scale isotopic changes during life while reducing effort and cost. This approach did reveal lifetime patterns, but tended to miss certain life events, particularly during early life. The second resolution was higher and provided detail that was missed …

Closing The Oxygen Mass Balance In Shallow Coastal Ecosystems, Matthew H. Long, Jennie E. Rheuban, Daniel C. Mccorkle, David J. Burdige, Richard C. Zimmerman

OES Faculty Publications

The oxygen concentration in marine ecosystems is influenced by production and consumption in the water column and fluxes across both the atmosphere-water and benthic-water boundaries. Each of these fluxes has the potential to be significant in shallow ecosystems due to high fluxes and low water volumes. This study evaluated the contributions of these three fluxes to the oxygen budget in two contrasting ecosystems, a Zostera marina (eelgrass) meadow in Virginia, U.S.A., and a coral reef in Bermuda. Benthic oxygen fluxes were evaluated by eddy covariance. Water column oxygen production and consumption were measured using an automated water incubation system. Atmosphere-water …

Magnetite Magnetosome Biomineralization In Magnetospirillum Magneticum Strain Amb-1: A Time Course Study, Lucas Le Nagard, Xiaohui Zhu, Hao Yuan, Karim Benzerara, Dennis A. Bazylinski, Cécile Fradin, Adrien Besson, Sufal Swaraj, Stefan Stanescu, Rachid Belkhou, Adam P. Hitchcock

Life Sciences Faculty Research

Magnetotactic bacteria are a highly studied group of diverse prokaryotes that biomineralize chains of magnetosomes, single domain, single crystal magnetic nanoparticles of magnetite or greigite, enclosed by a lipid bilayer membrane whose synthesis is under strict genetic control.

A Numerical Investigation Of Sediment Dynamics In The Northern Gulf Of Mexico In Connection With Hurricanes, Fluid Mud, Climate Change, And Biogeochemical Cycling, Zhengchen Zang

LSU Doctoral Dissertations

Sediment transport and deposition in marginal seas is jointly controlled by many factors including hydrodynamics, fluvial inputs, and the characteristics of sediment particles. This dissertation study employs the coupled ocean-atmosphere-wave-and-sediment transport modeling system (COAWST) to investigate the mechanism of sediment transport in the northern Gulf of Mexico (nGoM) on different temporal scales, as well as its interaction with biogeochemical processes.

First of all, a three-way coupled (atmosphere-wave-ocean) hurricane model reproduced the hydro- and sediment dynamics during hurricane Gustav (2008). Intensive alongshore and offshore currents were simulated on the eastern/western sectors of hurricane track, respectively. High suspended sediment concentration (SSC) was …

Short Term Effects Of Hurricane Irma And Cyanobacterial Blooms On Ammonium Cycling Along A Freshwater-Estuarine Continuum In South Florida, Justyna J. Hampel, Mark J. Mccarthy, Megan H. Reed, Silvia E. Newell

Faculty Publications

Lacustrine and coastal systems are vulnerable to the increasing number and intensity of tropical storms driven by climate change. Strong winds associated with tropical storms can mobilize nutrients in sediments and alter nitrogen and phosphorus cycling, leading to amplification of preexisting conditions, such as eutrophication and cyanobacterial blooms (cyanoHABs). In 2016, Florida declared a State of Emergency within and downstream of Lake Okeechobee (LO) due to toxic cyanobacterial blooms (primarily Microcystis). The blooms originated in LO, but flood control measures released water from LO to the brackish St. Lucie Estuary (SLE). In September 2017, Hurricane Irma traversed the Florida …