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Articles 271 - 300 of 377
Full-Text Articles in Oceanography and Atmospheric Sciences and Meteorology
Assessment Of Oxygen Sources And Sinks In The Northern Gulf Of Mexico Using Stable Oxygen Isotopes, Zoraida Jazmin Quinones-Rivera
Assessment Of Oxygen Sources And Sinks In The Northern Gulf Of Mexico Using Stable Oxygen Isotopes, Zoraida Jazmin Quinones-Rivera
LSU Doctoral Dissertations
Coastal hypoxia (< 2 mg O2L-1) represents a global problem that continues to worsen as nutrient fluxes to these areas increase. The second largest zone of human-induced hypoxia is located on the Louisiana continental shelf where hypoxic bottom waters commonly occur during summertime. This region is strongly impacted by the large flux of freshwater and nutrients from the Mississippi River, which influences both biological and physical processes that control oxygen dynamics. Yet, based on oxygen concentration measurements alone, it is difficult to separate the effects of biological factors from physical factors. To address this problem, I used a dual budget approach to assess the importance of oxygen sources and sinks on the Louisiana continental shelf. The dual budget was based on using stable oxygen isotopes (ä18O) in combination with conventional oxygen concentration measurements. To analyze temporal trends, surface and bottom water samples were collected monthly between July 2001 and July 2003 along an onshore-offshore transect. For better spatial resolution, shelfwide sampling was conducted extending from the Mississippi River Delta to the Louisiana-Texas border in the month of July of 2001, 2002, and 2003. Oxygen saturations values ranged between 180% at the surface and almost 0% close to the bottom with a corresponding range of ä18O values from 15‰ to 50‰. Biological parameters were important during all seasons for surface oxygen dynamics. The effects of physical factors were less apparent, except during severe physical disturbances. Bottom water oxygen dynamics showed clear seasonal signals of high oxygen depletion and larger contributions of benthic respiration during the summer, which corresponded to the strong stratification of the water column. In bottom waters, summer oxygen depletion was predominantly due to benthic respiration, accounting for about 73%, 80% and 60% of the total oxygen loss for 2001, 2002 and 2003 respectively. Model estimates of production/respiration (P/R) ratio during the July shelfwide cruises indicated that surface waters were productive with an average calculated P/R above 1. Depth stratified sampling (5 m intervals), which started in July 2002, showed that productivity in the mixed layer (5 to 10 m) was not homogeneous. Calculated P/R exceeded 1 only in the surface layer, while at 5 m P/R was approximately 1 and at a depth of 10 m, P/R was less than 1. Additionally, hypoxic conditions were only detected within 5 m of the bottom sediments. The dual budget approach yielded new estimates of productivity dynamics in surface waters and of sediment oxygen demand in bottom waters. For the first time, this study provided routine insight into productivity and respiration dynamics over large temporal and spatial scales. This could not have been accomplished using traditional methods because they commonly rely on time-consuming incubations. The study has shown that respiration dynamics in bottom waters vary seasonally with higher contribution of benthic respiration during stratified summer conditions and prevalent water column respiration during fall and winter. In contrast, seasonality in surface waters was less pronounced as productivity was more dependent on (salinity-inferred) nutrient supply than climatic forcing.
A Century Of Land Use And Water Quality In Watersheds Of The Continental U.S., Whitney P. Broussard Iii
A Century Of Land Use And Water Quality In Watersheds Of The Continental U.S., Whitney P. Broussard Iii
LSU Doctoral Dissertations
Human endeavors, particularly the agricultural and industrial activities of the last half century, now produce more biologically available nitrogen (N) than all other natural sources combined. The increased N availability can have consequences for the health of aquatic biota on the local, regional, and global scales. One manifestation of this problem is the formation of coastal hypoxic zones where terrestrial N loading creates eutrophic conditions in coastal waters. This dissertation examines a century of changes in land use and water quality to quantify the relationships between agricultural land use practices and riverine N yields in the Mississippi River Basin and …
Elucidating Marine Pore Water Exchange And Fresh Aquifer Sources In Estimates Of Submarine Groundwater Discharge To A Coastal Lagoon, Christopher Gerald Smith
Elucidating Marine Pore Water Exchange And Fresh Aquifer Sources In Estimates Of Submarine Groundwater Discharge To A Coastal Lagoon, Christopher Gerald Smith
LSU Doctoral Dissertations
Dynamic balances between fresh groundwater, saline groundwater, and surface water control the physics and chemistry of subterranean estuaries. Investigations were performed in a subterranean estuary on physical processes contributing to fresh groundwater and saline water mixing, vertical and lateral positioning of this mixing zone, and how this mixing affects spatial and temporal distributions of 234,238U, 226Ra, and 222Rn. The subterranean estuary is located in an unconfined aquifer beneath Indian River Lagoon, Florida, USA, where I could examine redox responses to altered flow regimes. Continuous groundwater and surface water level measurements suggest a strong hydrologic connection between this …
Swamp Ecology In A Dynamic Coastal Landscape: An Investigation Through Field Study And Simulation Modeling, Susanne Sigrid Hoeppner
Swamp Ecology In A Dynamic Coastal Landscape: An Investigation Through Field Study And Simulation Modeling, Susanne Sigrid Hoeppner
LSU Doctoral Dissertations
Increased flooding, nutrient and sediment deprivation, and saltwater intrusion have been implicated as probable causes of coastal swamp deterioration in the Mississippi Delta. An understanding of the interactive effects of these factors is required to enable successful planning of wetland restoration activities. I used field data collected from 2000 till 2005 at forty study sites to characterize the baseline conditions of the Maurepas swamp. I used a cluster analysis to identify four swamp habitat clusters, and characterized the clusters on the basis of soil properties, salinity, basal area, stem density, and other tree-related variables. ANOVA and related statistical techniques showed …
Effect Of Hydrology On The Structure And Function Of Mangrove Ecosystems In The Can Gio Mangrove Biosphere Reserve, Vietnam, Loi Tan Le
LSU Doctoral Dissertations
The influence of hydrology on the mangrove forests of Vietnam has received little scientific attention, even though hydrology is recognized as the primary forcing function in mangrove ecosystems worldwide. The purpose of this dissertation research was to determine the effects of hydrology on specific structural attributes and functional processes within the mangrove forests of Can Gio, a province in southeastern Vietnam. Khe Vinh (KV) and Mui O (MO), two locations within compartment 17 of the Can Gio Mangrove Biosphere Reserve, were chosen as study sites. This research addressed two questions: (1) What are the characteristics of the hydrological regime at …
Hypoxia In The Northern Gulf Of Mexico: Does The Science Support The Plan To Reduce, Mitigate, And Control Hypoxia?, Nancy N. Rabalais, R. Eugene Turner, B.K. Sen Gupta, D. F. Boesch, P. Chapman, M. C. Murrell
Hypoxia In The Northern Gulf Of Mexico: Does The Science Support The Plan To Reduce, Mitigate, And Control Hypoxia?, Nancy N. Rabalais, R. Eugene Turner, B.K. Sen Gupta, D. F. Boesch, P. Chapman, M. C. Murrell
Faculty Publications
We update and reevaluate the scientific information on the distribution, history, and causes of continental shelf hypoxia that supports the 2001 Action Plan for Reducing, Mitigating, and Controlling Hypoxia in the Northern Gulf of Mexico (Mississippi River/Gulf of Mexico Watershed Nutrient Task Force 2001), incorporating data, publications, and research results produced since the 1999 integrated assessment. The metric of mid-summer hypoxic area on the Louisiana-Texas shelf is an adequate and suitable measure for continued efforts to reduce nutrients loads from the Mississippi River and hypoxia in the northern Gulf of Mexico as outlined in the Action Plan. More frequent measurements …
A Comparison Of Channel Morphology, Marsh Elevation, And Biological Processes In Natural And Dredged Tidal Salt Marshes In Louisiana, Jennifer S. Spicer
A Comparison Of Channel Morphology, Marsh Elevation, And Biological Processes In Natural And Dredged Tidal Salt Marshes In Louisiana, Jennifer S. Spicer
LSU Doctoral Dissertations
Channel networks in tidal marshes serve as conduits for the exchange of water between the estuary and the marsh surface and form the spatial structure that regulates the flow of organisms, materials, and energy throughout the marsh system. Canal dredging creates channels with distinct linear shapes, and the artificial levee created from the dredged material creates ‘spoil banks’ along either side of the channel edge. Differences in morphology and adjacent marsh surface elevation between natural and dredged channel systems have not been well quantified, but may have important implications for the functioning of tidal channels as habitat for marsh-dependent species. …
Rna:Dna As An Indicator Of Nutritional Condition And Growth In Larval Naked Goby, Gobiosoma Bosc, Michelle C. Satterwhite
Rna:Dna As An Indicator Of Nutritional Condition And Growth In Larval Naked Goby, Gobiosoma Bosc, Michelle C. Satterwhite
LSU Master's Theses
Developing organism-based metrics for assessing habitat quality is an important tool in conservation and restoration of aquatic habitats. The use of the RNA:DNA ratio as an early indicator of habitat effects on growth of nekton species has been suggested, but requires species-specific laboratory assessment prior to field application. We used food availability in laboratory treatments to simulate differences in habitat quality. Wild Gobiosoma bosc eggs were collected using nest-traps constructed of PVC pipe. Eggs from several different nests collected in the field were hatched in the lab, yielding larvae that were randomly assigned to three feeding treatments in two replicate …
Disturbance Effects On Nekton Communities Of Seagrasses And Bare Substrates In Biloxi Marsh, Louisiana, Jamie Lynn Maiaro
Disturbance Effects On Nekton Communities Of Seagrasses And Bare Substrates In Biloxi Marsh, Louisiana, Jamie Lynn Maiaro
LSU Master's Theses
With marshes deteriorating rapidly across the Louisiana coast, the role of seagrasses in sustaining fisheries has come into question. Seagrasses are known to shelter small fish from larger predators. Seagrasses also act as a foraging ground for commercially important species, including spotted seatrout. Thirty samples, fifteen from seagrass habitats and fifteen from bare substrate habitats, were collected inside Biloxi Marsh using a drop sampler in May 2005. After the passage of Hurricanes Cindy and Katrina on July 6, 2005 and August 29, 2005, respectively, the seagrasses in Biloxi Marsh were either uprooted, buried, or both. The May 2005 sites were …
The Anatomy Of A Coastal Bay/Lake System, Michelle Greene
The Anatomy Of A Coastal Bay/Lake System, Michelle Greene
LSU Master's Theses
A comprehensive and integrated approach involving sedimentology, shallow surface geophysics and radio-chemistry was used to understand lakebed sediment dynamics in Little Lake. This methodology attempted to (1) define the morphology and origin of the lake, (2) understand the variability in lake-bottom sediments, (3) assess short-term and long-term sediment accumulation rates, and (4) image lakebed features. Subbottom chirp, single beam echo sounder, and side scan sonar data were collected to define hydrographic depths, lateral variability in seabed sediment type, lakebed features, and shallow subsurface structure. Sediment samples were taken at representative locations throughout the lake and particle size distributions were determined. …
Sediment Flux And Fate In The Mississippi River Diversion At West Bay: Observation Study, Thomas Mitchell Andrus
Sediment Flux And Fate In The Mississippi River Diversion At West Bay: Observation Study, Thomas Mitchell Andrus
LSU Master's Theses
Land-building sediment diversions, such as the Mississippi River Diversion at West Bay, can be used as important building blocks in the conservation and restoration of Mississippi Delta wetlands. Sediment deposition and retention patterns were studied in the West Bay diversion outfall area through analyses of sediment cores, hydrodynamics, and bathymetry. Cores and x-ray samples were collected at twenty stations in March 2004, August 2004, November 2005, and April 2006. Cores were analyzed for grain-size distributions and 7Be activities, in order to examine patterns of recent sediment deposition. In comparing ratios of total 7Be inventory to atmospheric 7Be …
Ecosystem Effects Of Expanding Populations Of Avicennia Germinans In A Southeastern Louisiana Spartina Alterniflora Saltmarsh, Carey Lynn Perry
Ecosystem Effects Of Expanding Populations Of Avicennia Germinans In A Southeastern Louisiana Spartina Alterniflora Saltmarsh, Carey Lynn Perry
LSU Master's Theses
Although the Earth may be in the early stages of the projected trends of global warming, several ecological responses to recent warming are already evident. The timing of seasonal activities of plants and animals has begun to shift, and the advancement of species poleward is occurring in several regions of the world. One unique distributional shift is the movement of Avicennia germinans (black mangrove) northward into temperate salt marshes dominated by the marsh grass, Spartina alterniflora. In Louisiana, black mangroves were historically restricted to the southernmost barrier islands and beaches; however, in recent years a noticeable expansion of Avicennia northward …
The Effects Of Trawling And Habitat Use On Red Snapper And The Associated Community, Robert Joseph David Wells
The Effects Of Trawling And Habitat Use On Red Snapper And The Associated Community, Robert Joseph David Wells
LSU Doctoral Dissertations
The primary impediment to the recovery of Gulf of Mexico (GOM) red snapper is believed to be high levels of bycatch of age 0 and age 1 individuals in shrimp trawls. Thus, conservation of GOM red snapper involves evaluating both habitat-specific function and effects of shrimp trawls on red snapper and the associated benthic ecosystem. The two goals of this study were to evaluate the effects commercial shrimp trawls have on juvenile red snapper life history parameters, on associated fish and invertebrate communities and their habitat, and to identify essential fish habitat (EFH) for red snapper by applying all four …
A Comparison Of Individual-Based And Matrix Projection Models To Applied To Fish Population And Community Dynamics, Shaye Ellen Sable
A Comparison Of Individual-Based And Matrix Projection Models To Applied To Fish Population And Community Dynamics, Shaye Ellen Sable
LSU Doctoral Dissertations
Matrix projection models and individual-based models (IBM) are commonly used for the analysis and management of fish populations. Matrix models break down the population into age or stage classes, while IBMs track individuals. I perform a series of quantitative comparisons between the predictions of the two modeling approaches using the IBM as the standard of comparison to demonstrate when individual variation, species interactions, and spatial heterogeneity adversely affect matrix model performance. I first evaluate the matrix approach for predicting yellow perch population responses when perch are involved in size-specific predator-prey interactions with walleye. I created density-dependent and stochastic age-structured and …
Early Flotant Establishment And Growth Dynamics In A Nutrient Amended Wetland In The Lower Mississippi River Delta, Caleb W. Izdepski
Early Flotant Establishment And Growth Dynamics In A Nutrient Amended Wetland In The Lower Mississippi River Delta, Caleb W. Izdepski
LSU Master's Theses
Nutrient dynamics and seasonal marsh growth were examined in a newly formed Panicum virgatum floating marsh at Thibodaux LA. The floating marsh formed in a cleared area of forested wetland receiving secondarily treated effluent. Net Areal Primary Productivity (NAPP), total belowground biomass, NO3, and δ15N ratios varied significantly (P <0.05) along a 75m marsh transect while mean δ13C varied between plant species. The upland end of the transect had the highest NAPP (3876 g m-2y-1), total belowground biomass (4079.0 ± 298.5 g m-2), and mean NO3 (5.4 ± 2.9 mg l-1). The mean floating-marsh …
Assessment And Analysis Of Quikscat And Coamps Model Vector Wind Products For The Gulf Of Mexico: A Long-Term And Hurricane Perspective, Neha Sharma
LSU Master's Theses
Global weather changes have become a matter of grave concern in hurricane prone areas as intensities of hurricanes are observed to be increasing every year, necessitating improved monitoring capabilities. NASA’s QuikSCAT satellite sensor has provided significant support in analyzing and forecasting winds for the past 8 years. In this study, the performance of QuikSCAT products, including JPL’s latest L2B 12.5km swath winds, was evaluated against buoy-measured winds in the Gulf of Mexico. The long-term study period was 1/2005 – 2/2007. The Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS) was also assessed. The regression analyses showed very good results for QuikSCAT products, …
Predicting Water Quality Effects On Bay Anchovy (Anchoa Mitchilli) Growth And Production In Chesapeake Bay: Linking Water Quality And Individual-Based Fish Models, Aaron Thomas Adamack
Predicting Water Quality Effects On Bay Anchovy (Anchoa Mitchilli) Growth And Production In Chesapeake Bay: Linking Water Quality And Individual-Based Fish Models, Aaron Thomas Adamack
LSU Doctoral Dissertations
Water quality in the Chesapeake Bay and the Patuxent River has decreased since the 1950s due to an increase in nutrient loadings. Increased nutrient loads have caused an increase in the extent and duration of hypoxic conditions. Restoration via large-scale reductions in nutrient loadings is now underway. How reducing nutrient loadings will affect water quality is well predicted; however the effect on fish is generally unknown as most water quality models do not include trophic levels higher than zooplankton. I combined two water quality models with bay anchovy models (Anchoa mitchilli) to examine the effects of changes in nutrient loadings …
Will Lowering Estuarine Salinity Increase Gulf Of Mexico Oyster Landings?, R. Eugene Turner
Will Lowering Estuarine Salinity Increase Gulf Of Mexico Oyster Landings?, R. Eugene Turner
Faculty Publications
Previous studies provide conflicting opinions on whether lower than average salinities in Gulf of Mexico (GOM) estuaries are likely to increase or decrease oyster harvests (Crassostrea virginica), which represented 69% and 54% of the United States oyster landings by weight, and dockside value, respectively, in 2003. The present study examined a 54-yr record (1950–2003) of oyster harvests and river discharge in five major estuaries in GOM states (Florida, Alabama, Mississippi, Louisiana, and Texas). Oyster landings were inversely related to freshwater inflow. Peaks in landings, 21 of 23 in West Florida, Alabama, Mississippi, and Texas combined, were coincidental with …
Oxygen Depletion In The Gulf Of Mexico Adjacent To The Mississippi River, Nancy N. Rabalais, R. Eugene Turner
Oxygen Depletion In The Gulf Of Mexico Adjacent To The Mississippi River, Nancy N. Rabalais, R. Eugene Turner
Faculty Publications
The seasonal formation of a bottom water layer severely depleted in dissolved oxygen has become a perennial occurrence on the Louisiana continental shelf adjacent to the Mississippi River system. Dramatic changes have occurred in this coastal ecosystem in the last half of the 20th century as the loads of dissolved inorganic nitrogen tripled. There are increases in primary production, shifts in phytoplankton community composition, changes in trophic interactions, and worsening severity of hypoxia. The hypoxic conditions (dissolved oxygen less than 2 mg l-1) cover up to 22,000 km2 of the seabed in mid-summer. Dissolved oxygen concentrations seldom decrease to anoxia, …
Quantifying Changes In Fish Habitat Use In Coastal Waters Of Louisiana, Usa: A Hydroacoustic Approach, Kevin Mershon Boswell
Quantifying Changes In Fish Habitat Use In Coastal Waters Of Louisiana, Usa: A Hydroacoustic Approach, Kevin Mershon Boswell
LSU Doctoral Dissertations
The development of reliable tools for identifying essential fish habitat (EFH) has proven problematic. Knowledge of the distribution and biomass of fishes over discrete habitat types is a prerequisite for effective use of EFH in the management of important commercial and recreational fish species. Resolution of the influence of habitat type and environmental factors on the distribution of fishes is confounded by limitations of traditional sampling gears. To date, hydroacoustic technology has been widely accepted as a tool for surveying fishery resources; however few studies have implemented acoustics in ultra shallow (<2 m) coastal waters. Efforts should be made to utilize hydroacoustics for quantifying changes in fish distributions within estuarine environments given the benefits provided through acoustic technology (e.g. ease of deployment, reduced sampling effort, and non-invasive sampling attributes). A technique was developed for acoustically sensing fishes in the shallow, turbid waters of Barataria Bay, Louisiana. A robust and lightweight remotely-controlled transducer platform was designed for deploying acoustic gear. Sources of scattering within the bay were identified through a series of exclosure net experiments designed to quantify potential effects of plankton and suspended solids on acoustic scattering. Analysis filters were developed to reduce the effects of bubble-induced noise, often observed during periods when wind speeds were greater than 4.5 m s-1. Side-aspect acoustic target strength-length and target …
Belowground Biomass Of Spartina Alterniflora: Seasonal Variability And Response To Nutrients, Faith Armand Darby
Belowground Biomass Of Spartina Alterniflora: Seasonal Variability And Response To Nutrients, Faith Armand Darby
LSU Doctoral Dissertations
Spartina alterniflora is a salt marsh macrophyte found from Canada to the Gulf of Mexico which often provides the dominant plant cover. Although S. alterniflora is well known for its high aboveground productivity, fifty to ninety percent of the total plant production occurs belowground. No previous studies address the seasonal variation of belowground biomass or the response of above-and belowground biomass to nutrients at the southern limits of its U. S. range. The objectives of this study were to: 1) document the seasonal variability of its above- and belowground biomass and test for responses to various combinations of N, P, …
Effects Of Diesel-Fuel And Copper Contaminants On Benthic Microalgae, Soraya Silva
Effects Of Diesel-Fuel And Copper Contaminants On Benthic Microalgae, Soraya Silva
LSU Doctoral Dissertations
Salt marshes are dynamic, highly productive habitats and serve as nursery grounds for many commercially and economically important species. Benthic microalgae (BMA) are considered an important food source for benthos and provide the principal source of nutrition that fuels secondary production. Estuarine sediments around the world are a repository for many contaminants from anthropogenic sources. In particular, hydrocarbons and metals are ubiquitous contaminants in coastal systems. The primary goal of this study was to study the effects of diesel fuel and copper, alone and in combination, on the BMA assemblage from a coastal salt marsh. To achieve this objective, salt …
Habitat Use By Nekton In A Saltmarsh Estuary Along A Stream-Order Gradient In Northeastern Barataria Bay, Louisiana, Pablo Granados-Dieseldorff
Habitat Use By Nekton In A Saltmarsh Estuary Along A Stream-Order Gradient In Northeastern Barataria Bay, Louisiana, Pablo Granados-Dieseldorff
LSU Master's Theses
Mesohaline estuarine regions in Louisiana play an important role in coastal ecosystems. To begin to understand how nektonic species and communities respond to environmental variables before habitat modification, I examined patterns of habitat use by fishes and decapod crustaceans in a seemingly pristine mesohaline system that drains into Bay Batiste, southeastern Louisiana. The study area was focused on a relatively unaltered core saltmarsh complex drained by intertidal and subtidal streams and it was representative of a larger surrounding system in terms of nekton community structure and associated environmental variables. Stratified monthly sampling (February – November 2004) along a stream-order gradient …
Petrological And Geochemical Investigations Of Deep Sea Turbidite Sands In The Pandora And Moresby Troughs: Source To Sink Papua New Guinea Focus Area, Luke Jeremiah Patterson
Petrological And Geochemical Investigations Of Deep Sea Turbidite Sands In The Pandora And Moresby Troughs: Source To Sink Papua New Guinea Focus Area, Luke Jeremiah Patterson
LSU Master's Theses
The Moresby and Pandora Troughs of the northern Coral Sea are components of the deep-sea depositional system that is the ultimate sink for the Source to Sink Papua New Guinea (PNG) Focus Area. Cores collected from the R/V Melville during March-April 2004 reveal marine volcaniclastic and terrigenous turbidites deposited in these troughs during the Quaternary. Constraining the spatial, temporal, and provenance characteristics for these terrigenous sands through mineralogical, chemical, and textural analysis is the primary focus of this study. All cores contain thinly-bedded sandy turbidite packages interlayered with hemipelagic marls and typical centimeter-to-meter-thick turbidite sequences. The Moresby Trough core JPC22 …
Laboratory And Field Measurements Of Bioturbation By Macrofauna In A Coastal Setting, Skyler Neylon
Laboratory And Field Measurements Of Bioturbation By Macrofauna In A Coastal Setting, Skyler Neylon
LSU Master's Theses
Two ophiuroid species, Hemipholis elongata and Ophiophragmus spp. were studied in laboratory microcosms to elucidate patterns of sediment mixing for key bioturbators in the Mississippi Sound, Mississippi. The effects of bioturbation on artificially stratified sediments in microcosms were traced via time-series digital x-radiography. Preliminary results indicate that for three population densities of the brittle stars (comparable to field densities), a steady state volumetric bioturbation rate of 1-2 cm3/d is reached within two months of introduction to a fresh system. The preservation quotient, q, a fractional measure of preserved primary fabric, reached a minimum of 0.5 during the 16-week experiment. Maximum …
Salt Marsh Restoration With Sediment-Slurry Amendments Following A Drought-Induced, Large-Scale Disturbance, Angela Marie Schrift
Salt Marsh Restoration With Sediment-Slurry Amendments Following A Drought-Induced, Large-Scale Disturbance, Angela Marie Schrift
LSU Master's Theses
A large-scale, drought-induced disturbance occurred in Louisiana during the spring and summer of 2000. Approximately 100,000 acres of Spartina dominated marshes died-back and turned brown. This die-off caused considerable concern because in the absence of recovery dieback marshes can transform to mudflats, which can subside leading to open ponds. The state of Louisiana is attempting to restore some of the dieback marshes through the addition of sediment-slurries. The sediment-slurry generated significantly different marsh elevations: high elevation (mean and 95 % confidence interval: 29, 26 to 32 cm above ambient marsh), medium elevation (21, 19 to 24 cm), low elevation (14, …
Application Of Short-Term Sediment Dynamics And Particle-Bound Phosphorus Fractionation Methods (Sedex) To Estimate The Benthic Nutrient Loading Potential In Upper Newport Estuary, California, Hilary Amanda Collis
Application Of Short-Term Sediment Dynamics And Particle-Bound Phosphorus Fractionation Methods (Sedex) To Estimate The Benthic Nutrient Loading Potential In Upper Newport Estuary, California, Hilary Amanda Collis
LSU Master's Theses
Estuaries act as sources, sinks, and biogeochemical transformation sites for natural and anthropogenically-derived nutrients. Sediment loading from watersheds provides an important source of particulate nutrients to estuaries often neglected when constructing nutrient budgets. Deposition and resuspension of these sediments are known to impact biogeochemical cycles in estuarine environments. Phosphorus (P) exists in many forms in aquatic environments, and increased P loading to coastal environments increases primary productivity potentially leading to eutrophication. Magnitude and variability of sediment deposition, resuspension, and sediment-bound P concentrations were evaluated in Upper Newport Bay (UNB), California. During 2004, seven push cores were collected from the intertidal …
Nutrient Constraints On Plant Community Production And Organic Matter Accumulation Of Subtropical Floating Marshes, Guerry O., Jr. Holm Jr.
Nutrient Constraints On Plant Community Production And Organic Matter Accumulation Of Subtropical Floating Marshes, Guerry O., Jr. Holm Jr.
LSU Doctoral Dissertations
In the cycle of delta growth and decay, peat-forming wetlands span a time and space continuum. Later in the delta cycle, freshwater floating marshes become increasingly removed from external sediment subsidy and internal nutrient cycling controls plant productivity and organic matter accumulation. An interesting question is whether increased external nutrient loading can affect the basic processes that lead to peat formation—plant production and organic matter decomposition. I conducted several field studies to understand whether belowground organic matter accumulation and decomposition were affected with increased nutrient exposure; in addition, the plant community was monitored over three years. A laboratory soil respiration …
Modeling The Effects Of Endocrine Disrupting Chemicals On Atlantic Croaker: Understanding Biomarkers And Predicting Population Responses, Cheryl Anne Murphy
Modeling The Effects Of Endocrine Disrupting Chemicals On Atlantic Croaker: Understanding Biomarkers And Predicting Population Responses, Cheryl Anne Murphy
LSU Doctoral Dissertations
A number of environmental stressors have been shown to interfere with reproductive and behavioral processes of fish by interfering with endocrine function. Most biomarkers of endocrine disturbance tend to be static measurements from dynamic systems making them difficult to evaluate within the context of an individual, or subtle effects that do not relate well to endpoints of ecological significance. I present an approach that uses a series of models, based on Atlantic croaker, to extrapolate laboratory results to indicators of individual and population health. First, I created a physiologically based model that simulates vitellogenesis in a female fish. The model …
Using Life-History, Surplus Production, And Individual-Based Population Models For Stock Assessment Of Data-Poor Stocks: An Application To Small Pelagic Fisheries Of The Lingayen Gulf, Philippines, Ronald B. Lachica
LSU Master's Theses
Stock assessment methods that quantify the status of fishery resources are critical to effective fisheries management. There is a need for stock assessment methods applicable for management of tropical species based on limited, un-aged catch data. I applied four stock assessment approaches to situation with limited life-history information and with short-term, un-aged catch data. The four approaches are: life-history invariants, length-based catch analysis, individual-based modeling, and surplus production modeling. All four approaches were applied to catch data from Lingayen Gulf, Philippines. The life-history invariant, length-based catch analysis, and individual-based modeling were applied to monthly length-frequency data of commercial catch for …