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Articles 241 - 270 of 831

Full-Text Articles in Biogeochemistry

Defining The Environmental Niche Of The Two Main Clades Of Trichodesmium: A Study On The West Florida Shelf, Kristina Confesor, Corday Selden, Kimberly Powell, Angela Knapp, Kristen Buck, Laura Donahue, Dreux Chappell Apr 2021

Defining The Environmental Niche Of The Two Main Clades Of Trichodesmium: A Study On The West Florida Shelf, Kristina Confesor, Corday Selden, Kimberly Powell, Angela Knapp, Kristen Buck, Laura Donahue, Dreux Chappell

College of Sciences Posters

Dinitrogen (N2) fixation is the process of taking widely abundant but mostly biologically inaccessible N2 gas and converting it into more biologically accessible forms of the essential macronutrient nitrogen. Only a small fraction of organisms known as diazotrophs can perform biological N2 fixation. Trichodesmium is one such genus of N2-fixing marine cyanobacteria that is commonly observed in waters along the West Florida Shelf (WFS). We hypothesize that the two main Trichodesmium clades (T. erythraeum and T. thiebautii) occupy distinct environmental niches, one being more coastal and one being more oceanic. To test …

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A Foray Into Laboratory Scale Soil Incubations With Corn Stover And High Lignin Fermentation Byproduct, Michelle Wang Apr 2021

A Foray Into Laboratory Scale Soil Incubations With Corn Stover And High Lignin Fermentation Byproduct, Michelle Wang

ENGS 88 Honors Thesis (AB Students)

As the production of biofuels increases to meet the demands of a growing low carbon economy, questions of sustainability surrounding its feedstock and waste streams have become increasingly relevant. In the biofuel production process, crop residues like corn stover are harvested from the field and converted to biofuels leaving generating a residue called high lignin fermentation byproduct (HLFB). From extensive process modelling in the literature, it is suggested that HLFB should be either combusted to fuel auxiliary conversion processes or returned to the soil in place of the crop residues that were harvested. Currently, there is little literature testing the …

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Effects Of Marsh Management In Coastal Marsh Impoundments On Marsh Vertical Accretion In The Face Of Sea Level Rise., Scott P. Graham Mar 2021

Effects Of Marsh Management In Coastal Marsh Impoundments On Marsh Vertical Accretion In The Face Of Sea Level Rise., Scott P. Graham

LSU Master's Theses

Many coastal marshes are managed for wildlife through the use of levees and water control structures. Management techniques such as water manipulation, herbicide application, and controlled burns are used to set back succession and facilitate recruitment of annual plant species, which are highly sought after by many wildlife. These marsh impoundments alter or prevent natural tidal exchange, which might alter or prevent sediment and nutrient inputs to the marsh. Although these management techniques are effective in managing for wildlife, there are few studies comparing vertical accretion between managed and unmanaged marshes. Vertical accretion is important because it allows coastal wetlands …

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Retaining Eucalyptus Harvest Residues Promotes Different Pathways For Particulate And Mineral-Associated Organic Matter, Gabriel W. D. Ferreira, Fernanda C. C. Oliveira, Emanuelle M. B. Soares, Jorg Schnecker, Ivo R. Silva, A. Stuart Grandy Mar 2021

Retaining Eucalyptus Harvest Residues Promotes Different Pathways For Particulate And Mineral-Associated Organic Matter, Gabriel W. D. Ferreira, Fernanda C. C. Oliveira, Emanuelle M. B. Soares, Jorg Schnecker, Ivo R. Silva, A. Stuart Grandy

Faculty Publications

Eucalyptus plantations have replaced other (agro)ecosystems over 5.6 Mha in Brazil. While these plantations rapidly accumulate carbon (C) in their biomass, the C storage in living forest biomass is transient, and thus, longer-term sustainability relies on sustaining soil organic matter (SOM) stocks. A significant amount of harvest residues (HR) is generated every rotation and can yield SOM if retained in the field. Yet, there is little information on how managing eucalyptus HR changes SOM dynamics. We used isotopic and molecular approaches in a 3-yr field decomposition experiment where a native grassland has been replaced by eucalyptus plantations to assess how …

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On The Genesis Of Aluminum-Rich Speleothems In A Granite Cave Of Nw Spain, Jorge Sanjurjo-Sanchez, Carlos Arce Chamorro, Juan Ramón Vidal Romaní, Marcos Vaqueiro-Rodríguez, Victor Barrientos, Joeri Kaal Feb 2021

On The Genesis Of Aluminum-Rich Speleothems In A Granite Cave Of Nw Spain, Jorge Sanjurjo-Sanchez, Carlos Arce Chamorro, Juan Ramón Vidal Romaní, Marcos Vaqueiro-Rodríguez, Victor Barrientos, Joeri Kaal

International Journal of Speleology

Granite massifs often contain caves, with dimensions ranging from a few meters up to 1,000 m, also referred to as pseudokarst. The speleothems in such caves are mostly composed of either Si-rich (commonly opal-A) or Al-rich authigenic mineraloids. Whereas the formation and geochemical composition of opal-A biospeleothems have been studied and are fairly well understood, knowledge on the Al-rich analogues is scarce. This work reports for the first time a study on the composition, accretion process, age and growth rate of an Al-rich speleothem type flowstone from the A Trapa Cave System (Galicia, NW Spain), developed in a granite cave. …

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Synergies Among Environmental Science Research And Monitoring Networks: A Research Agenda, J. A. Jones, P. M. Groffman, J. Blair, F. W. Davis, H. Dugan, E. E. Euskirchen, Serita D. Frey, T. K. Harms, E. Hinckley, M. Kosmala, S. Loberg, S. Malone, K. Novick, S. Malone, K. Novick, S. Record, A. V. Rocha, B. L. Ruddell, E. H. Stanley, C. Sturtevant, A. Thorpe, T. White, W. R. Wieder, L. Zhai, K. Zhu Feb 2021

Synergies Among Environmental Science Research And Monitoring Networks: A Research Agenda, J. A. Jones, P. M. Groffman, J. Blair, F. W. Davis, H. Dugan, E. E. Euskirchen, Serita D. Frey, T. K. Harms, E. Hinckley, M. Kosmala, S. Loberg, S. Malone, K. Novick, S. Malone, K. Novick, S. Record, A. V. Rocha, B. L. Ruddell, E. H. Stanley, C. Sturtevant, A. Thorpe, T. White, W. R. Wieder, L. Zhai, K. Zhu

Faculty Publications

Many research and monitoring networks in recent decades have provided publicly available data documenting environmental and ecological change, but little is known about the status of efforts to synthesize this information across networks. We convened a working group to assess ongoing and potential cross-network synthesis research and outline opportunities and challenges for the future, focusing on the US-based research network (the US Long-Term Ecological Research network, LTER) and monitoring network (the National Ecological Observatory Network, NEON). LTER-NEON cross-network research synergies arise from the potentials for LTER measurements, experiments, models, and observational studies to provide context and mechanisms for interpreting NEON …

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Carbon Fluxes And Microbial Activities From Boreal Peatlands Experiencing Permafrost Thaw, M. P. Waldrop, J. W. Mcfarland, K. L. Manies, M. C. Leewis, S. J. Blazewicz, M. C. Jones, R. B. Neumann, Jason K. Keller, L. Cohen, E. S. Euskirchen, C. Edgar, M. R. Turetsky, W. L. Cable Feb 2021

Carbon Fluxes And Microbial Activities From Boreal Peatlands Experiencing Permafrost Thaw, M. P. Waldrop, J. W. Mcfarland, K. L. Manies, M. C. Leewis, S. J. Blazewicz, M. C. Jones, R. B. Neumann, Jason K. Keller, L. Cohen, E. S. Euskirchen, C. Edgar, M. R. Turetsky, W. L. Cable

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Permafrost thaw in northern ecosystems may cause large quantities of carbon (C) to move from soil to atmospheric pools. Because soil microbial communities play a critical role in regulating C fluxes from soils, we examined microbial activity and greenhouse gas production soon after permafrost thaw and ground collapse (into collapse‐scar bogs), relative to the permafrost plateau or older thaw features. Using multiple field and laboratory‐based assays at a field site in interior Alaska, we show that the youngest collapse‐scar bog had the highest CH4 production potential from soil incubations, and, based upon temporal changes in porewater concentrations and 13 …

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Insect Reproductive Behaviors Are Important Mediators Of Carrion Nutrient Release Into Soil, Brooke K. Woelber-Kastner, Serita D. Frey, Daniel R. Howard, Carrie L. Hall Feb 2021

Insect Reproductive Behaviors Are Important Mediators Of Carrion Nutrient Release Into Soil, Brooke K. Woelber-Kastner, Serita D. Frey, Daniel R. Howard, Carrie L. Hall

Faculty Publications

Current declines in terrestrial insect biomass and abundance have raised global concern for the fate of insects and the ecosystem services they provide. However, the ecological and economic contributions of many insects have yet to be quantified. Carrion-specializing invertebrates are important mediators of carrion decomposition; however, the role of their reproductive activities in facilitating this nutrient pulse into ecosystems is poorly understood. Here, we investigate whether insects that sequester carrion belowground for reproduction alter soil biotic and abiotic properties in North American temperate forests. We conducted a field experiment that measured soil conditions in control, surface carrion alone, and beetle-utilized …

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Multi-Source Eo For Dynamic Wetland Mapping And Monitoring In The Great Lakes Basin, Michael Battaglia, Sarah Banks, Amir Behnamian, Laura Bourgeau-Chavez Feb 2021

Multi-Source Eo For Dynamic Wetland Mapping And Monitoring In The Great Lakes Basin, Michael Battaglia, Sarah Banks, Amir Behnamian, Laura Bourgeau-Chavez

Michigan Tech Publications, Part 1

Wetland managers, citizens and government leaders are observing rapid changes in coastal wetlands and associated habitats around the Great Lakes Basin due to human activity and climate variability. SAR and optical satellite sensors offer cost effective management tools that can be used to monitor wetlands over time, covering large areas like the Great Lakes and providing information to those making management and policy decisions. In this paper we describe ongoing efforts to monitor dynamic changes in wetland vegetation, surface water extent, and water level change. Included are assessments of simulated Radarsat Constellation Mission data to determine feasibility of continued monitoring …

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Linking Genes To Traits In Fungi, A. L. Romero-Olivares, Eric W. Morrison, A. Pringle, Serita D. Frey Jan 2021

Linking Genes To Traits In Fungi, A. L. Romero-Olivares, Eric W. Morrison, A. Pringle, Serita D. Frey

Faculty Publications

Fungi are mediators of the nitrogen and carbon cycles in terrestrial ecosystems. Examining how nitrogen uptake and organic matter decomposition potential differs in fungi can provide insight into the underlying mechanisms driving fungal ecological processes and ecosystem functioning. In this study, we assessed the frequency of genes encoding for specific enzymes that facilitate nitrogen uptake and organic matter decomposition in 879 fungal genomes with fungal taxa grouped into trait-based categories. Our linked gene-trait data approach revealed that gene frequencies vary across and within trait-based groups and that trait-based categories differ in trait space. We present two examples of how this …

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Increased Carbon Capture By A Silicate-Treated Forested Watershed Affected By Acid Deposition, Lyla L. Taylor, Charles T. Driscoll, Peter M. Groffman, Greg H. Rau, Joel D. Blum, David J. Beerling J. Beerling Jan 2021

Increased Carbon Capture By A Silicate-Treated Forested Watershed Affected By Acid Deposition, Lyla L. Taylor, Charles T. Driscoll, Peter M. Groffman, Greg H. Rau, Joel D. Blum, David J. Beerling J. Beerling

Advanced Science Research Center

Meeting internationally agreed-upon climate targets requires carbon dioxide removal (CDR) strategies coupled with an urgent phase-down of fossil fuel emissions. However, the efficacy and wider impacts of CDR are poorly understood. Enhanced rock weathering (ERW) is a land-based CDR strategy requiring large-scale field trials. Here we show that a low 3.44 t ha−1 wollastonite treatment in an 11.8 ha acid-rain-impacted forested watershed in New Hampshire, USA, led to cumulative carbon capture by carbonic acid weathering of 0.025–0.13 t CO2 ha−1 over 15 years. Despite a 0.8–2.4 t CO2 ha−1 logistical carbon penalty from mining, grinding, transportation, and spreading, by 2015 …

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Trimethylornithine Membrane Lipids: Discovered In Planctomycetes And Identified In Diverse Environments, Eli K. Moore Jan 2021

Trimethylornithine Membrane Lipids: Discovered In Planctomycetes And Identified In Diverse Environments, Eli K. Moore

School of Earth & Environment Departmental Research

Intact polar membrane lipids (IPLs) are the building blocks of all cell membranes. There is a wide range of phosphorus-free IPL structures, including amino acid containing IPLs, that can be taxonomically specific. Trimethylornithine membrane lipids (TMOs) were discovered in northern wetland Planctomycete species that were isolated and described in the last decade. The trimethylated terminal nitrogen moiety of the ornithine amino acid in the TMO structure gives the lipid a charged polar head group, similar to certain phospholipids. Since their discovery, TMOs have been identified in various other recently described northern latitude Planctomycete species, and in diverse environments including tundra …

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Antibiotic Resistant Gene Concentrations In Bacteria In Groundwater From Agricultural Waste, Koji Barnaby Jan 2021

Antibiotic Resistant Gene Concentrations In Bacteria In Groundwater From Agricultural Waste, Koji Barnaby

Mahurin Honors College Capstone Experience/Thesis Projects

The overuse of antibiotics has led to an increase in antibiotic resistant bacteria since some antibiotics are sent into the wastewater system by waste produced by both humans and agriculture, making exposure to these bacteria more likely. The evolution of these bacteria in groundwater is of particular concern, as groundwater is used as a source of drinking water, and infections by these bacteria would be more difficult to treat. There are no policies in place to monitor or regulate antibiotic resistance bacteria in groundwater, leaving the threat to public health unknown. The study area of Crumps Cave in Smiths Grove, …

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High Frequency Concurrent Measurements In Watershed And Impaired Estuary Reveal Coupled Doc And Decoupled Nitrate Dynamics, Gopal K. Mulukutla, Wilfred Wollheim, Joseph Salisbury, Richard O. Carey, Thomas Gregory, William H. Mcdowell Jan 2021

High Frequency Concurrent Measurements In Watershed And Impaired Estuary Reveal Coupled Doc And Decoupled Nitrate Dynamics, Gopal K. Mulukutla, Wilfred Wollheim, Joseph Salisbury, Richard O. Carey, Thomas Gregory, William H. Mcdowell

All Materials

Rapid changes in land use, pollution inputs, and climate are altering the quantity, timing and form of materials delivered from watersheds to estuaries. To better characterize these alterations simultaneous measurements of biogeochemical conditions in watersheds and estuaries over a range of times scales are needed. We examined the strength of watershed-estuarine biogeochemical coupling using data of in situ measurements of nitrate, terrestrial dissolved organic carbon (DOC) and chloride collected over a seven-month period in a nitrogen impaired estuary in the northeastern US. The watershed was observed exerting strong control over concentrations of terrestrially derived DOC in the estuary, attributable to …

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Preclassic Cultural Eutrophication Of Lake Petén Itzá, Lowland Guatemala, By The Early Maya Of Nixtun-Ch'ich', Brooke A. Birkett Jan 2021

Preclassic Cultural Eutrophication Of Lake Petén Itzá, Lowland Guatemala, By The Early Maya Of Nixtun-Ch'ich', Brooke A. Birkett

Masters Theses

"Paleolimnological evidence indicates the ancient Maya transformed lowland terrestrial ecosystems by felling forest vegetation to construct large civic-ceremonial centers and expand agriculture. The effects of prehistoric Maya land alterations on lake trophic status, however, remain poorly understood. We analyzed a 515-cm-long sediment core from Lake Petén Itzá, lowland Guatemala, to infer paleoenvironmental changes resulting from Maya occupation of the riparian archaeological site of Nixtun-Ch'ich'. Substantial increases in charcoal and fecal stanol concentrations indicate Maya occupation of the Candelaria Peninsula by the late Early Preclassic period beginning ca. 1400 cal yr Before the Common Era (hereafter BCE), despite scant archaeological evidence …

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The Quantitative Assessment Of Pond Scum: An Examination Of The Biogeochemistry Of Phosphorus Cycling In The Belgrade Lakes, Abbey M. Sykes Jan 2021

The Quantitative Assessment Of Pond Scum: An Examination Of The Biogeochemistry Of Phosphorus Cycling In The Belgrade Lakes, Abbey M. Sykes

Honors Theses

The internal recycling phosphorus in freshwater lake bottom sediments represents a significant source of hypolimnetic phosphorus (P) release for many of Maine’s lakes. In summer months, Maine lakes often thermally stratify and the lake hypolimnion develops anoxia, leading to a reduction in redox potential at the sediment-water interface. These reducing conditions facilitate the reductive dissolution of ferric iron, and, since phosphorus is often present in freshwater lake sediments as solid FeOOH-PO4 complexes, results in release of soluble phosphorus into the water column. Our current study presents field and laboratory data from sediment fractionation extractions designed to quantify concentrations of …

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Bioactive Trace Metals And Their Isotopes As Paleoproductivity Proxies: An Assessment Using Geotraces-Era Data, T. J. Horner, S. H. Little, T. W. Conway, J. R. Farmer, Jennifer E. Hertzberg, D. J. Janssen, A.J.M. Lough, J.L. Mckay, A. Tessin, S.J.G. Galer, S. L. Jaccard, F. Lacan, A. Paytan, K. Wuttig, Geotraces-Pages Biological Productivity Working Group Members Jan 2021

Bioactive Trace Metals And Their Isotopes As Paleoproductivity Proxies: An Assessment Using Geotraces-Era Data, T. J. Horner, S. H. Little, T. W. Conway, J. R. Farmer, Jennifer E. Hertzberg, D. J. Janssen, A.J.M. Lough, J.L. Mckay, A. Tessin, S.J.G. Galer, S. L. Jaccard, F. Lacan, A. Paytan, K. Wuttig, Geotraces-Pages Biological Productivity Working Group Members

OES Faculty Publications

Phytoplankton productivity and export sequester climatically significant quantities of atmospheric carbon dioxide as particulate organic carbon through a suite of processes termed the biological pump. Constraining how the biological pump operated in the past is important for understanding past atmospheric carbon dioxide concentrations and Earth's climate history. However, reconstructing the history of the biological pump requires proxies. Due to their intimate association with biological processes, several bioactive trace metals and their isotopes are potential proxies for past phytoplankton productivity, including iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver. Here, we review the oceanic distributions, driving processes, and depositional …

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Neodymium Isotope Geochemistry Of A Subterranean Estuary, Darren A. Chevis, T. Jade Mohajerin, Ningfang Yang, Jaye E. Cable, E. Troy Rasbury, Sidney R. Hemming, David J. Burdige, Jonathan B. Martin, Christopher D. White, Karen H. Johannesson Jan 2021

Neodymium Isotope Geochemistry Of A Subterranean Estuary, Darren A. Chevis, T. Jade Mohajerin, Ningfang Yang, Jaye E. Cable, E. Troy Rasbury, Sidney R. Hemming, David J. Burdige, Jonathan B. Martin, Christopher D. White, Karen H. Johannesson

OES Faculty Publications

Rare earth elements (REE) and Nd isotope compositions of surface and groundwaters from the Indian River Lagoon in Florida were measured to investigate the influence of submarine groundwater discharge (SGD) on these parameters in coastal waters. The Nd flux of the terrestrial component of SGD is around 0.7 ± 0.03 μmol Nd/day per m of shoreline across the nearshore seepage face of the subterranean estuary. This translates to a terrestrial SGD Nd flux of 4 ± 0.2 mmol/day for the entire 5,880 m long shoreline of the studied portion of the lagoon. The Nd flux from bioirrigation across the nearshore …

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Taxonomic And Nutrient Controls On Phytoplankton Iron Quotas In The Ocean, Benjamin S. Twining, Olga Antipova, P. Dreux Chappell, Natalie R. Cohen, Jeremy E. Jacquot, Elizabeth L. Mann, Adrian Marchetti, Daniel C. Ohnemus, Sara Rauschenberg, Alessandro Tagliabue Jan 2021

Taxonomic And Nutrient Controls On Phytoplankton Iron Quotas In The Ocean, Benjamin S. Twining, Olga Antipova, P. Dreux Chappell, Natalie R. Cohen, Jeremy E. Jacquot, Elizabeth L. Mann, Adrian Marchetti, Daniel C. Ohnemus, Sara Rauschenberg, Alessandro Tagliabue

OES Faculty Publications

Phytoplankton iron contents (i.e., quotas) directly link biogeochemical cycles of iron and carbon and drive patterns of nutrient limitation, recycling, and export. Ocean biogeochemical models typically assume that iron quotas are either static or controlled by dissolved iron availability. We measured iron quotas in phytoplankton communities across nutrient gradients in the Pacific Ocean and found that quotas diverged significantly in taxon‐specific ways from laboratory‐derived predictions. Iron quotas varied 40‐fold across nutrient gradients, and nitrogen‐limitation allowed diatoms to accumulate fivefold more iron than co‐occurring flagellates even under low iron availability. Modeling indicates such “luxury” uptake is common in large regions of …

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Nitrogen Dynamics And Transport Along Flowpaths In A Rural Wetland-Stream Complex, Colton Kyro Jan 2021

Nitrogen Dynamics And Transport Along Flowpaths In A Rural Wetland-Stream Complex, Colton Kyro

Graduate Student Theses, Dissertations, & Professional Papers

Human activities have doubled the rate of nitrogen inputs onto the landscape resulting in elevated nitrogen concentrations in our streams. Anthropogenically applied nitrogen is largely transported to stream networks via groundwater movement. Groundwater discharge occurs in distinct points along a stream but whose influences can often persist far beyond that area due to insufficient biogeochemical removal of imported nitrogen potentially causing alterations in community structure and precipitating large algae blooms. To understand the factors governing nitrogen abundance in a historical polluted stream, I used a mass-balance approach to quantify groundwater-surface water interaction and the magnitude of groundwater nitrogen input and …

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Spatial Variability Of Sediment Amorphous Silica And Its Reactivity In A Northern Gulf Of Mexico Estuary And Coastal Zone, Elliot J. Kemp, Ryan R. Roseburrough, Emily A. Elliott, Jeffrey W. Krause Jan 2021

Spatial Variability Of Sediment Amorphous Silica And Its Reactivity In A Northern Gulf Of Mexico Estuary And Coastal Zone, Elliot J. Kemp, Ryan R. Roseburrough, Emily A. Elliott, Jeffrey W. Krause

Gulf and Caribbean Research

No abstract provided.

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Modeling Stromatolite Formation With Diffusion-Limited Aggregation, Laura E. Stevens Jan 2021

Modeling Stromatolite Formation With Diffusion-Limited Aggregation, Laura E. Stevens

Graduate Student Theses, Dissertations, & Professional Papers

Stromatolites, microbialites, and other microbially induced sedimentary structures exist in the rock record as far back as 3.6 billion years ago and continue to form in the present day. Better characterizing these structures and better understanding how they form is crucial in distinguishing these biosignatures from similar, abiotic structures, which can help us to understand the conditions of early Earth and early Mars. To that end, I have modified DLA 3D EXT, an open-source stromatolite modeling program, to more closely reflect the process of microbial trapping-and-binding by filamentous microbes in a calcite-precipitating hot spring system. This modified program includes a …

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Comparing Capabilities Of Shewanella Oneidensis Mr-1 And The Microbial Community Of Iron Caves To Reduce Fe(Iii), Aaron Douglas Pham Jan 2021

Comparing Capabilities Of Shewanella Oneidensis Mr-1 And The Microbial Community Of Iron Caves To Reduce Fe(Iii), Aaron Douglas Pham

Williams Honors College, Honors Research Projects

Caves are generally formed by the erosion and/or dissolution of rock and its subsequent removal by water. Iron ore caves (IOCs) form despite being hosted by relatively insoluble and weathering-resistant rock. Due to the discovery of a microbial community behind the walls of these caves, it was hypothesized that these bacteria could be responsible for speleogenesis. Iron ore exists in an oxidized (Fe(III)) state, but reduced (Fe(II)) form is soluble. It was further reasoned that the bacteria might be able to reduce Fe(III) through direct metabolic activity, which uses iron as an electron acceptor. Here we show that cave microorganisms …

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Understanding The Effects Of Complex Topography On Cover Crop Dynamics And Maize Production In Kentucky Agroecosystems, Samuel John Leuthold Jan 2021

Understanding The Effects Of Complex Topography On Cover Crop Dynamics And Maize Production In Kentucky Agroecosystems, Samuel John Leuthold

Theses and Dissertations--Plant and Soil Sciences

In Central Kentucky, rolling hill cropland presents a number of challenges related to soil sustainability. Increased topographic complexity can lead to increased erosion, inefficient crop nutrient use and increased nutrient loss. Further, grain crop yields can be variable across both space and time in rolling hill fields and are less resilient to changes in weather conditions than flatter, more homogeneous areas. More than 30% of cropland in Kentucky has a slope greater than 3⁰, which means a large swath of the row crop production land in the state is at increased risk of contribution to soil and water resource degradation. …

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Long Term Nutrient And Chlorophyll A Dynamics Across Long Island Sound And Impacts On Dissolved Oxygen Conditions Within The Western Sound (1991-2019), Sherry Perreira Jan 2021

Long Term Nutrient And Chlorophyll A Dynamics Across Long Island Sound And Impacts On Dissolved Oxygen Conditions Within The Western Sound (1991-2019), Sherry Perreira

Dissertations and Theses

Nitrogen overload, eutrophication, and hypoxia have been challenging and persistent water quality problems in Long Island Sound (LIS) over the past decades with major impacts on commercial industries, ecology, and recreational activities in the region. Recognizing these problems, the EPA enforced three phases of the Clean Water Act (CWA) to reduce nitrogen loads in an effort to improve this important estuary. This study examines how nitrogen (NH3, NOx & TDN), chlorophyll a (CHLA), and dissolved oxygen (DO) concentrations changed in LIS over the past 30 years, in response to water quality regulations as well as changes in …

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The Role Of Symbiotic Algae In The Acclimatization Of Oculina Arbuscula To Ocean Acidification, Erin M. Arneson Jan 2021

The Role Of Symbiotic Algae In The Acclimatization Of Oculina Arbuscula To Ocean Acidification, Erin M. Arneson

College of Graduate Studies: Theses & Dissertations

Ocean acidification (OA) caused by CO2 emissions is projected to decrease seawater pH to 7.6 by 2100. Scleractinian corals are at risk because excess H+ in seawater binds to carbonate (CO32-), reducing its availability for CaCO3 skeletons. The energy demand for skeletal growth increases as pH decreases because corals must actively purge excess H+ from their seawater sourced calcifying fluid to maintain high calcification rates. In scleractinian corals it is hypothesized that photosynthesis by symbiotic algae is critical to meet this increased energy demand. To test this hypothesis, I conducted laboratory and field …

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Effects Of Tidal Flooding On Estuarine Biogeochemistry: Quantifying Flood-Driven Nitrogen Inputs In An Urban, Lower Chesapeake Bay Sub-Tributary, Alfonso Macías-Tapia, Margaret R. Mulholland, Corday R. Selden, J. Derek Loftis, Peter W. Bernhardt Jan 2021

Effects Of Tidal Flooding On Estuarine Biogeochemistry: Quantifying Flood-Driven Nitrogen Inputs In An Urban, Lower Chesapeake Bay Sub-Tributary, Alfonso Macías-Tapia, Margaret R. Mulholland, Corday R. Selden, J. Derek Loftis, Peter W. Bernhardt

OES Faculty Publications

Sea level rise has increased the frequency of tidal flooding even without accompanying precipitation in many coastal areas worldwide. As the tide rises, inundates the landscape, and then recedes, it can transport organic and inorganic matter between terrestrial systems and adjacent aquatic environments. However, the chemical and biological effects of tidal flooding on urban estuarine systems remain poorly constrained. Here, we provide the first extensive quantification of floodwater nutrient concentrations during a tidal flooding event and estimate the nitrogen (N) loading to the Lafayette River, an urban tidal sub-tributary of the lower Chesapeake Bay (USA). To enable the scale of …

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Characterizing Reactive Iron Mineral Coatings And Their Roles In Natural Attenuation At A Site With Historical Contamination, Han Hua Dec 2020

Characterizing Reactive Iron Mineral Coatings And Their Roles In Natural Attenuation At A Site With Historical Contamination, Han Hua

Dissertations

Reactive iron mineral coatings in redox transition zones play an important role in contaminant attenuation. These mineral coatings include poorly crystalline to crystalline iron sulfides, carbonates, and oxyhydroxides, and are a signature of the biogeochemical processes occurring. To better understand these processes, reactive iron mineral coatings are characterized in an 18-m Anaerobic Core collected from a contaminated industrial site. This study targets redox transition zones uncovered in the core. A suite of complementary analyses is applied to distinguish the surface coating mineralogy using X-ray Diffraction, X-ray fluorescence, and field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray analyzer (EDX). In …

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In The Margins: Reconsidering The Range And Contribution Of Diazotrophs In Nearshore Environments, Corday R. Selden Dec 2020

In The Margins: Reconsidering The Range And Contribution Of Diazotrophs In Nearshore Environments, Corday R. Selden

OES Theses and Dissertations

Dinitrogen (N2) fixation enables primary production and, consequently, carbon dioxide drawdown in nitrogen (N) limited marine systems, exerting a powerful influence over the coupled carbon and N cycles. Our understanding of the environmental factors regulating its distribution and magnitude are largely based on the range and sensitivity of one genus, Trichodesmium. However, recent work suggests that the niche preferences of distinct diazotrophic (N2 fixing) clades differ due to their metabolic and ecological diversity, hampering efforts to close the N budget and model N2 fixation accurately. Here, I explore the range of N2 fixation …

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Advances In The Understanding Of Sourcing And Fate Of Pyrogenic Organic Matter In The Environment, Aleksandar Ivaylov Goranov Dec 2020

Advances In The Understanding Of Sourcing And Fate Of Pyrogenic Organic Matter In The Environment, Aleksandar Ivaylov Goranov

Chemistry & Biochemistry Theses & Dissertations

With higher occurrences of forest fires worldwide, there has been an increase in scientific interest surrounding the chemistry of pyrogenic organic matter (pyOM). The main structural components of pyOM, the condensed aromatic compounds (ConAC), exhibit intriguing physico-chemical properties and have been one of the main focuses of biogeochemical research. The overwhelmingly large number of scientific articles regarding pyOM and ConAC are guided by the assumption that ConAC in the environment are exclusively of pyrogenic origin, even though some recent studies have suggested that some of these ConAC could also be derived from non-pyrogenic radical-driven processes. To evaluate this controversial proposition, …

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