Dissolved Organic Carbon Fluxes From A New England Salt Marsh, 2016 University of Massachusetts Boston
Dissolved Organic Carbon Fluxes From A New England Salt Marsh, Hayley Nicole Schiebel
Graduate Doctoral Dissertations
Blue carbon systems (mangroves, salt marshes, and seagrass beds) sequester large amounts of carbon via primary productivity and sedimentation. Sequestered carbon can be respired back to the atmosphere, buried for long time periods, or exported (“outwelled”) to adjacent ecosystems. This study estimates the total outwelling of dissolved organic carbon (DOC) from the Neponset Salt Marsh (Boston, Massachusetts) as well as the major plant and sediment processes contributing to the overall flux. The total export was quantified via high-resolution in situ chromophoric dissolved organic matter (CDOM) measurements as a proxy for DOC using 12 years of transect data. Seasonal trends, alternate ...
Cone In Cone Concretions Of The Stanley Group In Southeastern Oklahoma, 2016 Stephen F Austin State University
Cone In Cone Concretions Of The Stanley Group In Southeastern Oklahoma, Kyle B. Ayres
Electronic Theses and Dissertations
Cone in cone concretions found in the Stanley Group of Southeastern Oklahoma have a variety of external and internal attributes which allow diagenetic and theoretical models of formation to be hypothesized. Stanley Group carbonate cone in cone concretions are initially formed in sulfur reducing horizons at shallow burial depths in a poorly circulated possibly deep trough containing siliceous sediments and organic matter. Collected concretions near the town of Smithville, Oklahoma displayed four different external morphologies and four variations of mineral constituents. All concretions contained microscopic cones which initiated diffusion and/or fluid patterns and is an early cementation process that ...
Statistical Modeling To Predict N2O Production Within The Hyporheic Zone By Coupling Denitrifying Microbial Community Abundance To Geochemical And Hydrological Parameters, Tiffany Brooke Farrell
Boise State University Theses and Dissertations
The hyporheic zone (HZ) of streams can be a significant source of nitrous oxide (N2O). However, the biogeochemical processes controlling N2O emissions remain poorly constrained due to difficulties in obtaining high-resolution chemical, physical, and biological data from streams. We performed a large-scale flume experiment to unravel the complexities of a natural system by constraining streambed morphology, flow rate, organic carbon loading, grain size distribution, and exogenous nitrate loading while enabling regular monitoring of dissolved oxygen, pH, alkalinity, and concentrations of NO3-, NO2-, NH4+, and N2O in the HZ. We employed real-time ...
Gone With The Wind: Soil Moisture Effects On Gaseous Nitrogen Removal From Wastewater, 2016 University of Rhode Island
Gone With The Wind: Soil Moisture Effects On Gaseous Nitrogen Removal From Wastewater, Faith L. Anderson
Senior Honors Projects
Onsite wastewater treatment systems (OWTS), or septic systems, release nitrogen (N), which can be detrimental to aquatic ecosystems. The final step in the treatment of wastewater is dispersal onto a drainfield, where it percolates through the soil. Part of the N is removed from wastewater and released into the atmosphere as N2 and N2O by denitrification, which requires anoxic conditions. Previous studies looking at the effect of soil water-filled pore space (WFPS) on denitrification using clean water with a high level of dissolved O2 (DO) have identified a minimum of 60% WFPS for denitrification to take ...
Photocatalytic Reduction Of Fumarate To Succinate On Zns Mineral Surfaces, 2016 University of Kentucky
Photocatalytic Reduction Of Fumarate To Succinate On Zns Mineral Surfaces, Ruixin Zhou, Marcelo I. Guzman
Chemistry Faculty Publications
The reductive tricarboxylic acid (rTCA) cycle is an important central biosynthetic pathway that fixes CO2 into carboxylic acids. Among the five reductive steps in the rTCA cycle, the two-electron reduction of fumarate to succinate proceeds nonenzymatically on the surface of photoexcited sphalerite (ZnS) colloids suspended in water. This model reaction is chosen to systematically study the surface photoprocess occurring on ZnS in the presence of [Na2S] (1–10 mM) hole scavenger at 15 °C. Experiments at variable pH (5–10) indicate that monodissociated fumaric acid is the primary electron acceptor forming the monoprotic form of succinic acid ...
Iron Concretions In The Cretaceous Dakota Formation, 2016 University of Nebraska-Lincoln
Iron Concretions In The Cretaceous Dakota Formation, Anthony Kohtz, Richard Kettler, David Loope
UCARE Research Products
The Cretaceous Dakota Formation contains abundant iron oxide concretions. The precursors to the iron concretions are siderite (FeCO3) nodules that formed in a reducing floodplain environment. A variety of concretion morphologies formed when the precursor siderite nodules were dissolved by oxidizing groundwater in a paleoaquifer. Iron-oxidizing bacteria are able to oxidize aqueous Fe(II) to Fe(III) oxy-hydroxide at microaerophilic and neutrophilic conditions. This study investigated these concretions to determine if there was a microbial element in their formation and to characterize the concretion morphologies present in the Dakota. This is important for complete paleoenvironment interpretations and astrobiology pursuits.
Testing For Ecosystem Regime Change Inferred From The Autotrophic Pigment Signals In Lake Erie Sediments, 2016 Kent State University - Kent Campus
Testing For Ecosystem Regime Change Inferred From The Autotrophic Pigment Signals In Lake Erie Sediments, Xiangming Zhao, Joseph D. Ortiz, Beverley Z. Saylor
Undergraduate Research Symposium
Human activities (agricultural nutrient runoff, point source pollution and invasive species) coupled with local impacts of climate change have contributed to profound changes in aquatic ecosystem function in Lake Erie. Yuan et al., (2014) argued that evidence of these changes were preserved as an increasing trend in trace metal content in a core raised from the Sandusky subbasin of the central basin of Lake Erie, which signaled a shift in algal dominance toward Harmful Algae Bloom (HAB) forming cyanophytes. These algal changes have been bringing serious problems to local citizen life as well as economy, such as the HAB ...
Effects Of Epichloë Coenophiala−Tall Fescue Symbiosis On Plant-Microbe-Soil Interactions In A Temperate Pasture, 2016 University of Kentucky
Effects Of Epichloë Coenophiala−Tall Fescue Symbiosis On Plant-Microbe-Soil Interactions In A Temperate Pasture, Lindsey C. Slaughter
Theses and Dissertations--Plant and Soil Sciences
Plants interact in myriad ways with microorganisms to influence ecosystem processes such as nutrient cycling, which can regulate ecosystem response to global change. One important plant-microbe symbiosis occurs between cool-season grasses and asexual fungal Epichloë endophytes, such as tall fescue (Schedonorus arundinaceus) and Epichloë coenophiala. Because the common toxic strain of the endophyte (CTE) harms grazing livestock, non-livestock toxic endophyte (NTE) strains have been developed and are increasingly deployed in pastures. Little is known about how these symbioses impact other plant-microbe interactions and microbe-mediated soil processes in grassland ecosystems. I conducted three studies to determine how E. coenophiala presence (+) or ...
The Role Of Amino Acids In The Nitrogen Cycle Of Peatlands, 2016 Michigan Technological University
The Role Of Amino Acids In The Nitrogen Cycle Of Peatlands, Tia Scarpelli
Dissertations, Master's Theses and Master's Reports
Future release of carbon from peatlands in response to climate change may be impacted by nitrogen limitation. The current study considers the role of amino acids as a nitrogen source in peatlands. The total free amino acid (TFAA) concentration for peats ranged from 0-2.3 µM, and leucine was the primary contributor. The dominance of sedge or ericaceous shrub plant types did not significantly impact the TFAA pool. Ammonium concentrations were much greater than TFAA and nitrate concentrations. TFAA concentrations were greatest in spring and least in fall. The springtime maxima and summer decrease in concentrations were simulated in a ...
A Shift In Louisiana Salt Marsh Microbial Communities Reflecting Changes In Salinity And Biogeochemical Parameters, 2016 University of Colorado, Boulder
A Shift In Louisiana Salt Marsh Microbial Communities Reflecting Changes In Salinity And Biogeochemical Parameters, Haley Holladay
Undergraduate Honors Theses
The relationship between microbial communities, salinity, soil depth, and time was evaluated using phospholipid fatty acids (PLFA) collected from coastal wetlands in Louisiana post hurricanes Katrina and Rita. The three marsh types studied included freshwater and intermediate marshes from the Jean Lafitte Preserve as well as two brackish marsh sites from the Caernarvon Basin. The Caernarvon Basin was heavily impacted from the hurricanes leaving the lower sites sampled remnant marsh. The goal of this study was to examine microbial community changes along a salinity gradient to further understand the impact of salinity on the wetland ecosystem. This was done using ...
Surface Chlorophyll Variability In The Drake Passage Region Of The Southern Ocean, 2016 University of Colorado, Boulder
Surface Chlorophyll Variability In The Drake Passage Region Of The Southern Ocean, Joseph C. Gradone
Undergraduate Honors Theses
The Southern Ocean, the ocean surrounding the Antarctic continent, supports a diverse array of biological species and unique food webs. Given the important role of phytoplankton in Southern Ocean food webs and their influence on the global carbon reservoir, it is of interest to know whether their abundance has changed over time. Chlorophyll is a pigment present in all photosynthesizing phytoplankton that can be used to estimate the biomass and productivity of phytoplankton at a given time and location. This study analyzes surface chlorophyll variability in the Drake Passage region of the Southern Ocean using underway fluorometer derived chlorophyll from ...
Testing Of The Late-Ordovician Pre-Gice Warm Water Carbonate Hypothesis In Alabama, 2016 James Madison University
Testing Of The Late-Ordovician Pre-Gice Warm Water Carbonate Hypothesis In Alabama, Brandon Euker, Stacey Law
Senior Honors Projects
The Guttenberg Carbon Isotope Excursion (GICE) (uppermost Sandbian-lower Katian, Late Ordovician) has been suggested to represent the transition from a Cambrian-Ordovician greenhouse world to Late Ordovician icehouse world. This transition is thought to coincide with a proposed shift from deposition of warm water carbonate rocks to cool water carbonate rocks in the North American midcontinent. We used oxygen isotopes (d18O) of conodonts to test the idea that the rocks below the GICE interval represent a consistently warm environment. Conodonts were isolated from samples of the Chickamauga Group collected at the Tidwell Hollow section in Blount County, AL, from ...
Compost Land Management And Soil Carbon Sequestration, 2016 James Madison University
Compost Land Management And Soil Carbon Sequestration, Kylene A. Hohman
Senior Honors Projects
Extensive fossil fuel burning has released carbon dioxide into the atmosphere. Under proper ecological conditions plants convert atmospheric carbon dioxide into stable soil organic matter, a natural and efficient means of mitigating climate change. In the symbiotic relationship between mycorrhizae and plants, mycorrhizae provide plants with essential nutrients in exchange for carbon sugars leaked from the plants. Mycorrhizae convert carbon sugars to an exudate called glomalin, a protein that assists in developing soil aggregates composed of sand, silt, and clay. These aggregates, called humus, store carbon for hundreds of years under healthy ecological conditions. Compost prompts soil microbes to aerobically ...
Perchlorate Variations Over 300 Years: Influence Of Human Activities, Volcanic Eruptions And Bolide Events, 2016 South Dakota State University
Perchlorate Variations Over 300 Years: Influence Of Human Activities, Volcanic Eruptions And Bolide Events, Kari Peterson
Theses and Dissertations
Perchlorate, which derives from both anthropogenic and natural sources in the current environment, constitutes a significant health risk to humans because it competitively inhibits iodine uptake by the thyroid gland. Thus, there has been considerable interest in reducing the human exposure to environmental perchlorate by limiting the release of perchlorate from anthropogenic sources. However, a lack of understanding of the relative contributions from anthropogenic and natural sources has prevented widespread regulation. A 300-year ice core perchlorate record from Summit Station, Greenland (1700-2007 C.E.) that extends beyond the onset of the Industrial Revolution (1850 C.E.) is used to assess ...
Evaluating The Biogeochemical Functioning Of A Constructed Fen On The Post-Mining Landscape Of Athabasca Oil Sands Region, Fort Mcmurray, Alberta, Canada, Felix C. Nwaishi
Theses and Dissertations (Comprehensive)
Peatlands have a unique biogeochemical function, characterized by an imbalance between the rates of biomass accumulation and decomposition. These characteristics facilitate the ability of peatlands to support the sequestration of nutrients and carbon. In disturbed peatlands, these functions are compromised. Thus, reclamation targets amongst other key functions, the recovery of biogeochemical functioning. These functions could serve as a measure of recovery to conditions that are present in natural analogues. This thesis examines the recovery of microbially-mediated nutrient transformation processes in a fen peatland that was constructed on a post-mining landscape in the Athabasca oil sands region, Fort McMurray, Alberta. The ...
Gaseous Carbon Emissions (Methane And Carbon Dioxide) From Wetland Soils In A Re-Created Everglades Landscape, 2015 Florida International University
Gaseous Carbon Emissions (Methane And Carbon Dioxide) From Wetland Soils In A Re-Created Everglades Landscape, Bradley R. Schonhoff
FIU Electronic Theses and Dissertations
Reducing the rates of greenhouse gas (GHG) emissions is critical in combatting global climate change. Carbon dioxide (CO2) and methane (CH4) are the two most important carbon-based GHGs, for their atmospheric warming potential. Wetlands such as the Florida Everglades play major roles in the global carbon cycle, as varying hydrologic conditions lead to differential production rates of these two GHGs. This study measured CO2 and CH4 emissions in a re-created Everglades ridge-and-slough wetland, where water levels were controlled to reflect natural flood patterns. As expected, lower elevations were flooded longer and produced more CH4, while ...
In Situ Studies Of Limestone Dissolution In A Coastal Submarine Spring, 2015 University of South Florida
In Situ Studies Of Limestone Dissolution In A Coastal Submarine Spring, Rachel Marie Schweers
Graduate Theses and Dissertations
Limestone dissolution in karst environments is likely due to geochemistry of the water, the actions of microbial communities, and the effect of water flow. We explored the rate of
limestone dissolution and will examine here the microbial communities associated with the limestone. A conduit within the brackish cave, Double Keyhole Spring, on the coast of central west Florida was the site of the experiment. PVC pipes (5cm x 16cm) were filled with crushed limestone that was screened to a 1.9cm – 2.54cm size range. There were three treatments (5 replicates each): Control - sealed autoclaved controls with limestone and conduit ...
Source-Specific Molecular Signatures For Light-Absorbing Organic Aerosols, 2015 Old Dominion University
Source-Specific Molecular Signatures For Light-Absorbing Organic Aerosols, Amanda Susan Willoughby
Chemistry & Biochemistry Theses & Dissertations
Organic aerosols (OA) are universally regarded as an important component of the atmosphere based on quantitative significance as well as the far-reaching impact they have on global climate forcing and human health. Despite the acknowledged importance, OA amounts and impacts remain the largest uncertainties regarding radiative forcing estimates. Incomplete chemical characterization of aerosol organic matter (OM) and a lack of concrete source apportionment is a major source of this uncertainty. The primary focus of this study is to provide much needed molecular details regarding ambient OA from key emission sources, and establish links between molecular and optical properties.
Complete chemical ...
Disentangling Climatic And Anthropogenic Controls On Global Terrestrial Evapotranspiration Trends, 2015 Oak Ridge National Laboratory
Disentangling Climatic And Anthropogenic Controls On Global Terrestrial Evapotranspiration Trends, Jiafu Mao, Wenting Fu, Xiaoying Shi, Daniel Ricciuto, Joshua Fisher, Robert Dickinson, Yaxing Wei, Willis Shem, Shilong Piao, Kaicun Wang, Christopher Schwalm, Hanqin Tian, Mingquan Mu, Altaf Arain, Philippe Ciais, Robert Cook, Yongdiu Dai, Daniel Hayes, Forrest Hoffman, Maoyi Huang, Suo Huang, Deborah Huntzinger, Akihiko Ito, Atul Jain, Anthony King, Huimin Lei, Chaoqun Lu, Huimin Lei, Anna Michalak, Changhui Peng, Shushi Peng, Benjamin Poulter, Kevin Schaefer, Elshin Jafarov, Peter Thornton, Weile Wang, Ning Zeng, Zhenzhong Zeng, Fang Zhao, Qiuan Zhu, Zaichun Zhu
Chaoqun (Crystal) Lu
We examined natural and anthropogenic controls on terrestrial evapotranspiration (ET) changes from 1982 to 2010 using multiple estimates from remote sensing-based datasets and process-oriented land surface models.A significant increasing trend of ET in each hemisphere was consistently revealed by observationally-constrained data and multi-model ensembles that considered historic natural and anthropogenic drivers. The climate impacts were simulated to determine the spatiotemporal variations in ET. Globally, risingCO2 ranked second in these models after the predominant climatic influences, and yielded decreasing trends in canopy transpiration and ET, especially for tropical forests and high-latitude shrub land. Increasing nitrogen deposition slightly amplified global ET ...
Environmental Forcing Does Not Induce Diel Or Synoptic Variation In The Carbon Isotope Content Of Forest Soil Respiration, Steven Hall, D. R. Bowling, J. E. Egan
Steven J. Hall
Recent studies have examined temporal fluctuations in the amount and carbon isotope content (δ13C) of CO2 produced by the respiration of roots and soil organisms. These changes have been correlated with diel cycles of environmental forcing (e.g., sunlight and soil temperature) and with synoptic-scale atmospheric motion (e.g., rain events and pressure-induced ventilation). We used an extensive suite of measurements to examine soil respiration over 2 months in a subalpine forest in Colorado, USA (the Niwot Ridge AmeriFlux forest). Observations included automated measurements of CO2 and δ13C of CO2 in the soil efflux, the soil gas profile, and forest ...