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Articles 1 - 16 of 16
Full-Text Articles in Physical Sciences and Mathematics
The Effects Of Carbon On Nitrogen Transformations In Restored Wetland And Wastewater Soils, Jared M. Theriot
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 …
An Evaluation Of Alternative Approaches For Simulating Animal Movement In Spatially-Explicit Individual-Based Models, Katherine Shepard Watkins
An Evaluation Of Alternative Approaches For Simulating Animal Movement In Spatially-Explicit Individual-Based Models, Katherine Shepard Watkins
LSU Doctoral Dissertations
Simulating animal movement in spatially-explicit individual-based models (IBMs) is both challenging and critically important to accurately estimating population dynamics. I compared four distinct movement approaches or sub-models (restricted-area search, kinesis, event-based, and run and tumble) in a series of simulation experiments. I used an IBM loosely based on a small pelagic fish that simulated growth, mortality, and movement of a cohort on a 2-dimensional grid. First, I tested the sub-models calibrated (i.e., trained) with a genetic algorithm in one set of environmental conditions in three other novel environments. The sub-models performed well, except restricted-area search and event-based that needed to …
Greenhouse Gas Emissions And Nutrients Dynamics In Restored Wetlands Of The Mississippi River Basin, Christopher Lundberg
Greenhouse Gas Emissions And Nutrients Dynamics In Restored Wetlands Of The Mississippi River Basin, Christopher Lundberg
LSU Doctoral Dissertations
Greenhouse gases were sampled during spring and summer months in 2010 and 2011 at two sites in the Mississippi River Basin: a riparian forested wetland under restored flood pulsing near Memphis, TN and a coastal estuarine marsh complex impacted by a river diversion at Caernarvon, LA. Mean methane fluxes at Caernarvon (-0.09 g CH4-C m-2 d-1) were lower than those at Memphis (0.53 g CH4-C m-2 d-1), and did not differ between seasons. Nitrous oxide fluxes were generally below detection limits. Fluxes were uncorrelated with water depth, soil temperature, and ambient air temperature, though sampling occurred over a narrow range …
Identification And Incorporation Of Quantitative Indicators Of Ecosystem Function Into Single-Species Fishery Stock Assessment Models And The Associated Biological Reference Points, Melissa Hedges Monk
Identification And Incorporation Of Quantitative Indicators Of Ecosystem Function Into Single-Species Fishery Stock Assessment Models And The Associated Biological Reference Points, Melissa Hedges Monk
LSU Doctoral Dissertations
The move towards an ecosystem approach to fisheries management requires baseline information on the biotic communities and an understanding of the interactions among species. The two objectives of this study were to describe the demersal fish community (DFC) associated with the northwestern Gulf shrimp trawl fishery, and to utilize a multispecies Lotka-Volterra model to examine possible community level effects of fishing. Community level effects include predator-prey interactions and the responses of fish in the same community to fishing pressure. The summer and fall Southeast Area Monitoring and Assessment Program (SEAMAP) bottomfish trawl surveys were used to identify spatial and temporal …
Nitrogen Biogeochemistry In A Restored Mississippi River Delta: A Modeling Approach, Benjamin Lee Branoff
Nitrogen Biogeochemistry In A Restored Mississippi River Delta: A Modeling Approach, Benjamin Lee Branoff
LSU Master's Theses
There is evidence that significant reductions (about 50%) in surface water nitrate concentrations within coastal deltaic wetlands receiving diverted Mississippi River water can be contributed to denitrification. Yet there is also contrasting evidence that other processes could be responsible for this nitrate reduction. As Louisiana plans the implementation of major Mississippi River sediment diversions, a thorough understanding of nitrogen dynamics is necessary to reduce risks of coastal eutrophication and offshore hypoxia. A mechanistic numerical computer model has been developed to simulate nitrogen biogeochemistry within the wetlands of the prograding Wax Lake Delta. This model is calibrated to observed fluxes within …
Factors Affecting Short-Term Oxygen Variability In The Northern Gulf Of Mexico Hypoxic Zone, Brenda Leroux Babin
Factors Affecting Short-Term Oxygen Variability In The Northern Gulf Of Mexico Hypoxic Zone, Brenda Leroux Babin
LSU Doctoral Dissertations
Open-water continuous monitoring of DO concentrations at a single station (C6) in the Gulf of Mexico from 1989 to 2008 afforded an excellent opportunity to characterize short-term oxygen variability and to estimate the relative importance of key physical and biological factors controlling the development, persistence, and dissipation of hypoxia. I investigated temporal trends in three aspects of short-term DO variability: respiration rates (i.e., how quickly bottom waters become hypoxic), persistence of hypoxia, and the dissipation of hypoxia (i.e., re-aeration events). I identified the range of respiration rates present at the study site, and showed how these rates vary throughout the …
Developing A Geospatial Protocol For Coral Epizootiology, Jennifer Anne Lentz
Developing A Geospatial Protocol For Coral Epizootiology, Jennifer Anne Lentz
LSU Doctoral Dissertations
This dissertation explores how geographic information systems (GIS) and spatial statistics, specifically the techniques used to map, detect, and spatially analyze disease epidemics, could be used to advance our understanding of coral reef health. Given that different types of spatial analysis, as well as different parameter settings within each analysis, can produce noticeably different results, poor selection or improper use of a given technique would likely lead to inaccurate representations of the spatial distribution and false interpretations of the disease. For this reason, I performed a comprehensive review of the following types of exploratory spatial data analysis (ESDA): mapping and …
What Does The ¹⁴C Method For Estimating Photosynthetic Rates In The Ocean Really Measure?, Shaofeng Pei
What Does The ¹⁴C Method For Estimating Photosynthetic Rates In The Ocean Really Measure?, Shaofeng Pei
LSU Doctoral Dissertations
The 14C method has been used extensively by both limnologists and oceanographers to measure photosynthetic rates in aquatic systems, and the large database of 14C measurements that now exists is the ground truth with which satellite algorithms for estimating marine photosynthetic rates on a basin and global scale have been calibrated. However, disconcerting uncertainties still remain with respect to whether and under what circumstances the 14C method provides an estimate of net or gross photosynthesis, or something in between. My study combined batch and continuous culture studies to clarify this ambiguous issue. The batch culture work with …
Skill Assessment And Optimization Of The Third Generation Wave Models For Applications In Gulf Of Mexico, Seyed Mostafa Siadatmousavi
Skill Assessment And Optimization Of The Third Generation Wave Models For Applications In Gulf Of Mexico, Seyed Mostafa Siadatmousavi
LSU Doctoral Dissertations
Numerical phase-averaged wave models are the best option to obtain the spatial and temporal distribution of the wave energy over a large domain, such as the Gulf of Mexico. Parallel implementation of unstructured SWAN and WAVEWATCH-III were engaged in this research to evaluate the performance of third generation wave models for different conditions. Met-ocean data from a network of NDBC buoys and WAVCIS stations were used to assess the predictive skills of the wave models. Deep water wave energy dissipation formulations were carefully analyzed and modified to improve the accuracy of the bulk wave parameters. Moreover, the importance of the …
Biomass And Mass Balance Isotope Content Of Mussel Seep Populations, Philip Martin Riekenberg
Biomass And Mass Balance Isotope Content Of Mussel Seep Populations, Philip Martin Riekenberg
LSU Master's Theses
Cold seep mussels, Bathymodiolus childressi, are common cold seep constituents that form large populations at upper continental slope (500-1000 m) cold seep sites in the Northern Gulf of Mexico. These mussels utilize methane present through symbiotic relationships with methanotrophic bacteria. This study uses a coupled isotope technique to determine the relative incorporation of respiratory carbon in the shell as a measure of the availability of methane between different seep sites. This method indicates a higher abundance of methane at the Brine Pool site than at the Bush Hill site which appears significantly more resource limited and that changes in methane …
Effects Of Mimic Artificial Oyster Reefs On The Ecology Of Juvenile Fishes In Marsh Ponds: A Before-After-Control-Impact Analysis, Steven B. Garner
Effects Of Mimic Artificial Oyster Reefs On The Ecology Of Juvenile Fishes In Marsh Ponds: A Before-After-Control-Impact Analysis, Steven B. Garner
LSU Master's Theses
I sought to assess the enhancement potential of mimic artificial oyster reefs (MAORs) on trophic dynamics of juvenile estuarine fishes in marsh ponds. Tropic dynamics were investigated by determining the impacts of MAOR addition on meiofauna and macrofauna and then comparing these results to the gut contents and condition of four abundant estuarine fishes: Atlantic croaker (Micropogonias undulatus), bay whiff (Citharichthys spilopterus), sand seatrout (Cynoscion arenarius), and pinfish (Lagodon rhomboides). Samples were collected every other month for two years (March 2009 – 11) employing a Before-After-Control-Impact (BACI) design. Halfway through the experiment (March 2010), two mud sites in two marsh …
Linking Nitrogen Biogeochemistry To Different Stages Of Wetland Soil Development In The Mississippi River Delta, Louisiana, Kelly Marie Henry
Linking Nitrogen Biogeochemistry To Different Stages Of Wetland Soil Development In The Mississippi River Delta, Louisiana, Kelly Marie Henry
LSU Doctoral Dissertations
Extensive wetland loss and nutrient-enhanced eutrophication occur across the Mississippi River delta and include newly emergent landscapes, in the early stages of ecological succession, and older landscape formations, with fully developed ecological communities. Here I tested how the anthropogenic effects of a climate-induced vegetation shift, an oil spill, and nitrate-enrichment regulate the principal environmental factors controlling nutrient biogeochemistry in wetland soils at different stages of development throughout the Mississippi River delta. In the older, transgressing Barataria basin, there was no clear effect of the climate-induced species shift from Spartina alterniflora Loisel to Avicennia germinans L. on soil nutrient chemistry. Observed …
Function And Diversity Of The Ship, Trinity, And Tiger Shoal Complex, With Emphasis On Macrofauna And Spawning Blue Crabs (Callinectes Sapidus), Carey George Gelpi Jr.
Function And Diversity Of The Ship, Trinity, And Tiger Shoal Complex, With Emphasis On Macrofauna And Spawning Blue Crabs (Callinectes Sapidus), Carey George Gelpi Jr.
LSU Doctoral Dissertations
The ecological and economic value of sandy shoals off the Louisiana coast is not well understood. During three years of comprehensive benthic sampling and environmental measurements I studied the Ship, Trinity, Tiger Shoal Complex (STTSC), which comprises changing and discrete benthic habitats including high relief sandy shoals, and muddier, mostly deeper off-shoal areas, prone to hypoxia. Benthic macrofaunal assemblages of shoals included endemic species, and shoal communities were significantly different from each other and the muddier offshoal habitat, contributing to northern Gulf of Mexico (GoM) regional biodiversity. Sand percentage was the most influential environmental parameter shaping macrofaunal community composition across …
Effect Of Hurricane Forward Speed And Approach Angle On Coastal Storm Surge, Chenguang Zhang
Effect Of Hurricane Forward Speed And Approach Angle On Coastal Storm Surge, Chenguang Zhang
LSU Master's Theses
Hurricane induced storm surges can be destructive and can pose great threats to coastal communities. There are many factors affecting storm surges, including the hurricane’s intensity and movement, the bathymetry and coastline of affected area, rainfall, tide, and river stage. This thesis focuses on the effects of hurricane approach angle (θ) and forward speed (U), which together describe the hurricane’s motion. The problem is approached through several numerical experiments with increasing complexity. First are some process studies of long wave propagations near the coast, followed by examination of the generation of long waves by a traveling wind field. The central …
Investigation Of Colored Dissolved Organic Matter And Dissolved Organic Carbon Using Combination Of Ocean Color Data And Numerical Model In The Northern Gulf Of Mexico, Nazanin Chaichitehrani
Investigation Of Colored Dissolved Organic Matter And Dissolved Organic Carbon Using Combination Of Ocean Color Data And Numerical Model In The Northern Gulf Of Mexico, Nazanin Chaichitehrani
LSU Master's Theses
The first part of this thesis includes evaluating and developing empirical band ratio algorithms for the estimation of colored dissolved organic matter (CDOM) and dissolved organic carbon (DOC) for SeaWiFS, MODIS and MERIS ocean color sensors for the northern Gulf of Mexico. For CDOM, matchup comparison between SeaWiFS-derived CDOM absorption coefficients and in situ absorption measurements at 412 nm (aCDOM(412)) were examined using the D’Sa et al. (2006) and the Mannino et al. (2008) algorithms. These reflectance band ratio algorithms were also assessed to retrieve aCDOM(412) from MODIS and MERIS data using the Rrs(488)/Rrs(555) and Rrs(510)/Rrs(560) band ratios, respectively. Since …
Habitat- And Region-Specific Reproductive Biology Of Female Red Snapper (Lutjanus Campechanus) In The Gulf Of Mexico, Dannielle Helen Kulaw
Habitat- And Region-Specific Reproductive Biology Of Female Red Snapper (Lutjanus Campechanus) In The Gulf Of Mexico, Dannielle Helen Kulaw
LSU Master's Theses
This study compares reproductive biology estimates of female red snapper among three habitat types (natural shelf-edge banks, standing petroleum platforms and toppled petroleum platforms) and among six regions in the Gulf of Mexico (central Florida, northwest Florida, Alabama, Louisiana, north Texas and south Texas). In both studies, batch fecundity and spawning frequency increased with length, weight and age, and batch fecundity was best correlated with maternal length. Gulf-wide, 75% maturity was achieved by age-3 and 100% maturity was reached by age-8. Sizes- and ages-at-maturity differed among habitat types and regions. Females from natural habitat reached 50% maturity the slowest (age-5, …