Earth Sciences Commons^™

Enhancing Our Understanding Of Ancient Oceans Through The Investigation Of Molybdenum Behavior Under Sulfidic Conditions, Rachel Faye Phillips

Open Access Theses & Dissertations

The most abundant trace metal in the ocean today, molybdenum (Mo), exhibits distinct behavior in oxygenated water, where it remains predominantly dissolved, compared to euxinic (i.e., oxygen-free and sulfidic) water, in which it is sequestered into the sediment. This dissimilar behavior allows us to use Mo concentrations and isotopic compositions in sediment to reconstruct marine oxygenation conditions throughout geologic history. However, Mo sequestration mechanisms under euxinic conditions remain unresolved, which limits the accuracy and precision of reconstructions made using Mo signatures in the rock record. For my doctoral research, I experimentally investigated abiotic and biotic Mo sequestration mechanisms under various …

The Ecological Effects Of Nitrogen Enrichment In Aridlands, Jennifer Holguin

Open Access Theses & Dissertations

Anthropogenic nitrogen (N) deposition is one of the most prominent factors driving global change. Across the globe, N deposition has driven major changes in terrestrial ecosystems, such as declines in plant biodiversity, enhanced exotic plant growth, and changes to biogeochemical processes involved in carbon and nutrient cycling. While noteworthy effort has been put forth to investigate the effects of N deposition on terrestrial ecosystems, a disproportionate number of N addition studies have been conducted in temperate mesic systems. Thus, we lack a holistic and mechanistic understanding of how N deposition impact aridland ecosystems. Additionally, our predictions of the effects of …

Linking Decomposition Reactions In Arctic Soils To Microbial Enzyme Production, Jane Karen Martinez

Open Access Theses & Dissertations

Microbial processes such as soil enzyme production are a major driver of decomposition and a current topic of interest in arctic soils due to the effects of climate warming. Despite the advances in understanding soil enzymes, there are still knowledge gaps regarding the role of enzymes in decomposition. In this dissertation, I addressed three of those gaps in the following chapters: (Ch.2) to explore the location of enzymes within the soil matrix, (Ch.3) to identify peptides matched to soil enzymes produced by microorganisms for organic matter decomposition, and (Ch.4) understand the longevity of enzymes in the soil after microbial production. …

Geological Problems With Microbiological Solutions: Deciphering The Authigenesis Of Calcite, Dolomite, And Native Sulfur In Salty Environments, Amanda L. Labrado

Open Access Theses & Dissertations

Microbial activity is known to impact the formation and alteration of many different rock types. For carbonate caprock (CCR), a lithology found on salt diapirs, it is generally accepted that microbial activity drives the precipitation of carbonate minerals, forming limestone and/or dolomite and native (elemental) sulfur. It appears that there are two types of CCR: 1) limestone associated with native sulfur (S0) and 2) limestone associated with dolomite. The mechanics of CCR formation are poorly understood. For example, it is unclear why native sulfur and dolomite are rarely found in the same CCR assemblage, and why either are formed at …

Fishers' Ecological Knowledge And Stable Isotope Analysis: A Social-Ecological Systems Approach To Endangered Species Conservation, Kathryn Rose Wedemeyer-Strombel

Open Access Theses & Dissertations

Identifying developmental habitat is essential for understanding population structure and species resiliency, especially for critically endangered species. In long-lived, oceanic, migratory animals such as sea turtles, elucidating developmental grounds is particularly difficult. When data are deficient or challenging to acquire, scientists often lean towards traditional quantitative methods when a social-ecological systems approach could better provide crucial baseline data and guiding information. Fishers’ ecological knowledge (FEK), the combination of experiential and culturally transmitted knowledge, is expert knowledge and should be treated as such. In 2008, FEK led to the “rediscovery” of the critically endangered eastern Pacific (EP) population of hawksbill sea …

Geostatistical And Geospatial Distribution Of Multiple Metallic Elements In Agricultural Regions Of The Mid-Continental Usa, Najwah Alssaeidi Ahmed Almesleh

Open Access Theses & Dissertations

Regional geochemical mapping constitute the chemistry of the surface of the earth in a large scale and relatively low sample density. It is widely accepted scientific activity and man uses some cases to identify contamination. In the present study, data present in national geochemical survey database was used to investigate the chemical loading loading of the agricultural soil. In the mid-continent region of the United States. Several traditional parameters were used mainly the enrichment factor (EF), and geoaccumulation index (I geo). Total chemical influence (TCI) maps were used to guide sampling. In addition, regional trace element chemistry of bedrock was …

Effects Of Increasing Deciduous Shrub Litter On Ecosystem Functioning In Alpine Tundra, Alejandro Emmanuel Benhumea

Open Access Theses & Dissertations

Rising temperatures due to global warming have resulted in rapid environmental changes in northern environments, resulting in an increase in deciduous shrub growth which has the potential to alter soil ecosystem properties and processes. In order to address some potential mechanisms by which shrubs alter ecosystem properties and processes, we designed an experiment which separated the effects of physical shrub presence and the effects of litter quantity in a fully factorial experiment on a north facing alpine plateau in the southwest Yukon, Canada. Specifically, we asked the following questions: What are effects of shrub litter, independent of shrub presence, on …

Trace Metal And Metalloid Behavior In The Submicron Scale Components Of Coal Fly Ashes: Insights From Combined Microscopic And Microbiological Studies, Matthew Costa

Open Access Theses & Dissertations

For over a century, coal has been used worldwide to meet ever-growing energy demands. Coal combustion accounts for over 30% of electricity generation in the United States. In the U.S., coal combustion produces annually over 100 million tons of coal combustion products (CCPs) of which only 30% are used in beneficial and economic ways. One of the primary CCPs from coal-burning power plants is fly ash, typically fine-sized and enriched in many trace elements (e.g., arsenic, chromium, lead, and vanadium). When disposed in the environment, fly ash may release significant concentrations of trace elements into surrounding ecosystems and induce toxicity …

Biologically Available Phosphorus In Biocrust-Dominated Soils Of The Chihuahuan Desert, Grace Margaret Crain

Open Access Theses & Dissertations

In desert soils, phosphorus (P) is an important limiting nutrient and its cycling characteristics are less understood compared to nitrogen and carbon. Phosphorus cycling is controlled by both geochemical and biological factors. Traditionally, P availability has been characterized via sequential extraction analyses such as Hedley fractionation, but newly developed extraction methods allow for the examination of more biologically relevant P fractions, providing insight on mechanisms of P acquisition by plants and microbes. We examined these P cycling features in the context of biological soil crusts (biocrusts), which have been found to be important drivers of nutrient cycling and have the …

Carbon Emissions From Soil Respiration In The Northern Chihuahuan Desert Shrubland, Anna Cristina Ortiz

Open Access Theses & Dissertations

The United States Department of Agriculture's Jornada Experimental Range (JER), is located in the northern Chihuahuan Desert in southern New Mexico and historically functioned as an experimental rangeland for cattle grazing. Historical grazing in the US Southwest has been identified as a leading, but not the sole, factor that has led to the conversion of pristine grasslands to shrublands, such has been the case on the JER. The estimated increased variability in precipitation intensity and frequency that is predicted to occur with climate warming will likely affect ecosystem responses from ecological processes including primary productivity, microbial decomposition, and thus respiration. …

The Impact Of Decadal Land Cover Change On The Global Warming Potential Of Beringian Arctic Tundra, David Hwei-Len Lin

Open Access Theses & Dissertations

Arctic terrestrial ecosystems play an important role in the global carbon cycle. If arctic warming continues to rise as projected, large amounts of soil carbon stored in these ecosystems could be released to the atmosphere as carbon dioxide or methane and positively enhance greenhouse warming. Thus, improving understanding of the likely future state and fate of arctic soil carbon, and the carbon uptake potential of arctic terrestrial ecosystems are well recognized research priorities.

At the pan-arctic scale, decadal increases in NDVI (Normalized Difference Vegetation Index), an index of vegetation productivity, have been observed from satellite imagery, indicating a general greening …

Implications Of Decade Time Scale Arctic Plant Community Change On Ecosystem Function, Mark Jason Lara

Open Access Theses & Dissertations

Almost half the global soil organic carbon pool is found in northern high latitudes. The majority of this soil carbon is stored in a greenhouse inert state within permafrost. As pronounced warming of high northern latitudes ensues, there is a strong likelihood that this substantial soil organic carbon pool will be mobilized to the atmosphere where it is likely to positively enhance greenhouse warming. Modeling studies suggest this positive feedback could alter future climate states of the Arctic and the globe, and affect how humans may need to adapt to climate change. Accordingly, understanding the patterns and controls and the …

Copper Isotope Fractionation During Surface Adsorption And Intracellular Incorporation By Bacteria, Jesica Urbina Navarrete

Open Access Theses & Dissertations

Copper isotopes may prove to be a useful tool for investigating bacteria-metal interactions recorded in natural waters, soils, and rocks. However, experimental data that constrain Cu isotope fractionation in biologic systems are limited and unclear. In this study we utilized Cu isotopes (65Cu) as a tool to investigate Cu-bacteria interactions, including surface adsorption and intracellular incorporation. Experiments were conducted with individual Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacterial species as well as with bacterial consortia from several natural environments. Adsorption experiments were conducted with live or dead cells over the pH range 2.5 to 6. Surface adsorption of Cu …

Pdi, Reactive Oxygen Species Stress And Polyphenolic Phytochemicals: Implications For Neurodegenerative Diseases, Rituraj Pal

Open Access Theses & Dissertations

PDI, protein disulfide isomerase, is one of the most versatile proteins and highly expressed in mammalian cells because there is a vast number of proteins that must undergo processing before secretion to their final destinations. PDI has several functions: oxidation of nascent proteins and isomerization of existing disulfide bonds. It also possesses chaperone activity and participates in protein degradation. Because of its structure, PDI can exist in a reduced or oxidized form. In mammalian cells it is mostly reduced due to the high demand of disulfide bond shuffling of secreted proteins within the ER, PDI a, a', and b' posses …