Physical Sciences and Mathematics Commons^™

Benthic Nitrogen Dynamics In Response To Deltaic Succession, Anthropogenic Fertilization And Hurricane Events In An Emerging Coastal Deltaic Floodplain Within The Mississippi River Delta Plain, Song Li

LSU Doctoral Dissertations

Increasing concentrations of nitrogenous fertilizer (NO₃^-) in rivers have potentially altered benthic nitrogen (N) cycling in coastal deltaic floodplains at the continental margins of major rivers. Here I evaluated the N removal capacity of a newly emergent coastal deltaic floodplain [Wax Lake Delta (WLD)] within the Mississippi River Delta Plain using continuous flow-through incubations. I investigated the response of benthic N dynamics in WLD to deltaic succession, anthropogenic fertilization and hurricane events. The estimated annual NO₃^- removal of 896 Mg N yr^-1 in WLD accounts for 10 to 27% of total NO₃^{- …}

Determining Sources Of Nitrate In The Semi-Arid Rio Grande Using Nitrogen And Oxygen Isotopes, Diego Alberto Sanchez Hernandez

Masters Theses

The Rio Grande, a semi-arid river in the American Southwest, is a major source of surface water for agriculture and drinking supplies in New Mexico and Texas. In addition to increasing salinity, considerable increases of NO₃^- [nitrate] have been observed in the semi-arid portion of the Rio Grande. It is possible that elevated water salinity inhibits denitrification on irrigated fields and, thus, fails to mediate excess nutrient load from anthropogenic activities. Therefore, two major goals of this project were to 1) characterize and quantify major NO₃^- sources, and 2) assess whether elevated water salinity affects microbial …

Multiple Metabolisms Constrain The Anaerobic Nitrite Budget In The Eastern Tropical South Pacific, Andrew R. Babbin, Brian D. Peters, Calvin W. Mordy, Brittany Widner, Karen L. Casciotti, Bess B. Ward

OES Faculty Publications

The Eastern Tropical South Pacific is one of the three major oxygen deficient zones (ODZs) in the global ocean and is responsible for approximately one third of marine water column nitrogen loss. It is the best studied of the ODZs and, like the others, features a broad nitrite maximum across the low oxygen layer. How the microbial processes that produce and consume nitrite in anoxic waters interact to sustain this feature is unknown. Here we used ¹⁵N-tracer experiments to disentangle five of the biologically mediated processes that control the nitrite pool, including a high-resolution profile of nitrogen loss rates. …

Impact Of Glacial/Interglacial Sea Level Change On The Ocean Nitrogen Cycle, Haojia Ren, Daniel M. Sigman, Alfredo Martínez-García, Robert F. Anderson, Chen Min-Te, Ana Christina Ravelo, Marietta Straub, George T. F. Wong, Gerald H. Haug

OES Faculty Publications

The continental shelves are the most biologically dynamic regions of the ocean, and they are extensive worldwide, especially in the western North Pacific. Their area has varied dramatically over the glacial/interglacial cycles of the last million years, but the effects of this variation on ocean biological and chemical processes remain poorly understood. Conversion of nitrate to N2 by denitrification in sediments accounts for half or more of the removal of biologically available nitrogen ("fixed N") from the ocean. The emergence of continental shelves during ice ages and their flooding during interglacials have been hypothesized to drive changes in sedimentary denitrification. …

Differential Responses Of Soil Greenhouse Gas Production And Denitrification To Salinity Alterations Along A Wetland Salinity Gradient, Natalie Ceresnak

LSU Master's Theses

Coastal wetlands provide several valuable services, such as carbon (C) storage and nitrogen (N) removal. Although wetlands serve as net C sinks, wetland soils release greenhouse gases (GHGs) including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Wetlands can buffer the influx of nitrate (NO3-) by transforming it into gaseous N (N2O, N2) through denitrification microbial pathway. Salinity is a regulator of soil biogeochemistry and long- (e.g. saltwater intrusion) and short-term (e.g. storm surges, river diversions) exposures may affect soil GHG production and denitrification. In this study, soil GHG production and denitrification enzyme activity (DEA) rates were examined over …

Dissolved Nutrient Distributions In The Gulf Of Mexico Following The Deepwater Horizon Oil Spill, Ashley Ann Parks

USF Tampa Graduate Theses and Dissertations

The Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GoM) in the spring of 2010 introduced 4.4 million of barrels of oil to the ecosystem. Some biodegradation of the oil occurs when microorganisms, particularly bacteria, metabolize the oil as a carbon source. During this process, the microbes also require nutrients for energy. An introduction of oil at this magnitude has the ability to induce large blooms of microbes, which in turn can affect nutrient concentrations. Microbial petroleum degradation decreases nutrient concentrations, whereas the microbial assimilation and decay of organic matter increase nutrient concentrations. This study assessed whether any …

Effect Of The Bp Deepwater Horizon Oil Spill On Critical Marsh Soil Microbial Functions, Jason Paul Pietroski

LSU Master's Theses

On April 20, 2010, the BP Deepwater Horizon (DWH) offshore oil platform exploded releasing ~ 795 million L of southern Louisiana (LA) light sweet crude oil into the Gulf of Mexico. Approximately 7.9 million liters of dispersant, Corexit EC9500A, were applied for remediation. The effect of BP DWH crude oil and Corexit EC9500A on two marsh soil microbial processes, (mineralizable nitrogen and denitrification), were examined in the laboratory. Surface soil samples were collected from an unimpacted salt marsh site proximal to areas that suffered light to heavily oiling in Barataria Bay, LA. Additions of oil were at a ratio of …

The Effects Of Carbon On Nitrogen Transformations In Restored Wetland And Wastewater Soils, Jared M. Theriot

LSU Master's Theses

Since the industrialization of the Haber-Bosch process in the 1940’s, anthropogenic activity has nearly doubled the Earth’s nitrogen fixation. Furthermore, nitrate has become the number one groundwater contaminant in the United States and has harmful effects such as eutrophication, algal blooms, and pollution of drinking water. Soils from two sites influenced by high nitrate loading were examined to determine their biogeochemical integrity. First, the Loosahatchie Bar, located northwest of Memphis, Tennessee, is influenced by excess surface water nitrate loading by the Mississippi River. The Loosahatchie Bar is a newly restored wetland that now has similar hydrologic influence to an upstream …

Nitrous Oxide Emission From Denitrification In Stream And River Networks, Jake J. Beaulieu, Clay P. Arango

All Faculty Scholarship for the College of the Sciences

Nitrous oxide (N₂O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N₂O via microbial denitrification that converts N to N₂O and dinitrogen (N₂). The fraction of denitrified N that escapes as N₂O rather than N₂ (i.e., the N₂O yield) is an important determinant of how much N₂O is produced by river networks, but little is known about the N₂O yield in flowing waters. Here, …

Fate Of Mississippi River Diverted Nitrate On Vegetated And Non-Vegetated Coastal Marshes Of Breton Sound Estuary, Christine M. Vanzomeren

LSU Master's Theses

The Caernarvon Diversion meters Mississippi River water into coastal marshes of Breton Sound. Elevated levels of nitrogen in river water have sparked concerns that nutrient loading may affect marsh resilience and belowground biomass, as evidence from several marsh fertilization studies. These concerns resulted from observation that fresh and brackish Breton Sound marshes suffered extensive damage from Hurricane Katrina. The goal of this study is to determine the fate of nitrate (the dominant inorganic nitrogen form in the Mississippi River) in Breton Sound Estuary marshes. We hypothesized that most nitrate would be removed by denitrification and that nitrate loading would not …

The Effects Of Salinity On Nitrogen Cycling In Wetland Soils And Sediments Of The Breton Sound Estuary, La, Brett Whitfield Marks

LSU Master's Theses

Wetlands in the coastal zone are slowly becoming more saline under rising sea level over the long-term. However, there are a number of events in the coastal environment which lead to quick and temporary changes in the salinity of coastal marshes. Seawater driven inland from storm surge can significantly increase salinity in oligohaline wetlands over the short-term (weeks). Recent large-scale efforts to restore coastal wetlands in Louisiana have utilized Mississippi River surface water diversions to re-introduce freshwater into coastal marshes, decreasing the salinity of coastal marshes. We examined the effect of salinity changes on two important nitrogen cycling processes, potential …

Applying The Isotope Pairing Technique To Evaluate How Water Temperature And Habitat Type Influence Denitrification Estimates In Breton Sound, Louisiana, Peter L. Lenaker

LSU Master's Theses

The upper Breton Sound estuary was hydrologically reconnected to the Mississippi River via the Caernarvon freshwater diversion structure in 1991. The Caernarvon structure can provide controlled freshwater pulses to the upper Breton Sound estuarine ecosystem, replicating historic freshwater pulsed events, although the original authorization was to control salinity isohalines at specific locations in the estuary. However, unlike historic freshwater pulsed events prior to the construction of levees, the current freshwater pulse contains an unprecedented amount of inorganic nitrogen, predominately as nitrate (annual average 71.4 µM NO3-). Denitrification is a microbial process, which can potentially remove excess nitrate entering coastal Louisiana …

Cbod₅ Treatment And Nitrogen Transformations Of The Marshland Upwelling System In Intermediate And Saltwater Marshes, Lorna Anne Putnam

LSU Doctoral Dissertations

The marshland upwelling system (MUS) was designed to treat domestic wastewater from coastal dwellings where conventional methods are inadequate due to high water tables, poor hydraulic soil conditions, anaerobic soils, and saline groundwater. Currently there is no adequate treatment system available and coastal dwellings are contributing to water quality problems. This study focused on determining the treatment effectiveness of the MUS for organic matter and understanding the specific processes involved in nitrogen treatment.

The treatment of organic matter, measured as five-day carbonaceous biological oxygen demand (CBOD₅), was effective in field tests for both saltwater and intermediate marshes. Global …

Land Use Influences The Spatiotemporal Controls On Nitrification And Denitrification In Headwater Streams, Clay P. Arango, J. L. Tank

All Faculty Scholarship for the College of the Sciences

N and C cycles in headwater streams are coupled, and land use can modify these cycles by increasing N availability and removing riparian vegetation. To increase our understanding of how land use modifies the controls on N cycling, we quantified rates of 2 microbial N transformations in a total of 18 agricultural and urban streams (with and without riparian buffers) for 3 y to examine how riparian vegetation and land use influence sediment nitrification and denitrification. Nitrification rates were highest in agricultural streams in late spring. Nitrification was not related to streamwater NH₄⁺ concentrations but was positively related …

Pelagic Functional Group Modeling: Progress, Challenges And Prospects, Raleigh R. Hood, Edward A. Laws, Robert A. Armstrong, Nicholas R. Bates, Christopher W. Brown, Craig A. Carlson, Fei Chai, Scott C. Doney, Paul G. Falkowski, Richard A. Feely, Marjorie A. M. Friedrichs

CCPO Publications

In this paper, we review the state of the art and major challenges in current efforts to incorporate biogeochemical functional groups into models that can be applied on basin-wide and global scales, with an emphasis on models that might ultimately be used to predict how biogeochemical cycles in the ocean will respond to global warming. We define the term "biogeochemical functional group" to refer to groups of organisms that mediate specific chemical reactions in the ocean. Thus, according to this definition, "functional groups" have no phylogenetic meaning-these are composed of many different species with common biogeochemical functions.

Substantial progress has …

Denitrification And Greenhouse Gas Emissions From Cultivated And Wetland Alluvial Soils, Sami Ullah

LSU Doctoral Dissertations

Agricultural development in the Mississippi River Basin has contributed to an 3-fold increase in NO3 loading of the river. Increased NO3 loading is a primary cause of eutrophication in the northern Gulf of Mexico. Identification of best management practices (BMPs) to reduce NO3 loss and wetlands restoration to remove NO3 through denitrification are critically needed. The objectives of this research were to determine factors controlling denitrification potential of different landscape units in an agricultural watershed and quantify the effects of BMPs and organic C amendments on denitrification rates of cultivated lands and restored forested wetlands. N2O, CH4 and CO2 emissions …

Nitrate Reduction And Methane Formation As Influenced By Iron-Centered Intermediate Redox Processes In Rice Soils, Bin Huang

LSU Doctoral Dissertations

Rice fields are a major source of the greenhouse gases methane (CH₄) and nitrous oxide (N₂O) and contribute to nitrate (NO₃^-) pollution in waters. Ferric iron (Fe³⁺) and manganic manganese (Mn⁴⁺) are two intermediate alternative electron acceptors (AEAs) capable of regeneration in freshwater soils. In this investigation, the influences of iron-centered intermediate redox processes on NO₃^- reduction and CH₄ formation in rice soils were studied using soil slurries, soil columns, and potted rice. Reduction of Fe³⁺-centered intermediate AEAs was mainly mediated by obligate anaerobes …

A Comparison Of No And N20 Production By The Autophic Nitrifier Nitrosomonas Europaea And The Heterotrophic Nitrifier Alcaligenes Faecalis, Iris C. Anderson, Mark Poth, Julie Homstead, David J. Burdige

OES Faculty Publications

Soil microorganisms are important sources of the nitrogen trace gases NO and N₂O for the atmosphere. Present evidence suggests that autotrophic nitrifiers such as Nitrosomonas europaea are the primary producers of NO and N₂O in aerobic soils, whereas denitrifiers such as Pseudomonas spp. or Alcaligenes spp. are responsible for most of the NO and N₂O emissions from anaerobic soils. It has been shown that Alcaligenes faecalis, a bacterium common in both soil and water, is capable of concomitant heterotrophic nitrification and denitrification. This study was undertaken to determine whether heterotrophic nitrification might be …

Simulation Of The Fate Of Nitrogen From The Disposal Of Poultry Litter, H. D. Scott

Technical Reports

A PC/AT computer model was developed to simulate the transport of water, nitrate and ammonia in the soil profile after an application of poultry litter to pasture. The model was written using FORTRAN 77 compiler and can be used on any IBM type compatible computer with a math coprocessor. Poultry litter has been shown to be a potential source of plant nutrients, but mismanagement can result in nitrate pollution of the surface and groundwater. The model is composed of a main program, 11 subroutines and three subprograms. An example was shown of the flexibility and dynamic nature of the computer …