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Articles 1 - 14 of 14
Full-Text Articles in Physical Sciences and Mathematics
Global Patterns Of Dissolved N, P And Si In Large Rivers, R. Eugene Turner, Nancy N. Rabalais, D. Justic', Q. Dortch
Global Patterns Of Dissolved N, P And Si In Large Rivers, R. Eugene Turner, Nancy N. Rabalais, D. Justic', Q. Dortch
Faculty Publications
The concentration of dissolved inorganic nitrogen (DIN), dissolved nitrate-N, Total-N (TN), dissolved inorganic phosphate (DIP), total phosphorus (TP), dissolved silicate-Si (DSi) and their ratios in the world's largest rivers are examined using a global data base that includes 37% of the earth's watershed area and half its population. These data were compared to water quality in 42 subbasins of the relatively well-monitored Mississippi River basin (MRB) and of 82 small watersheds of the United States. The average total nitrogen concentration varies over three orders of magnitude among both world river watersheds and the MRB, and is primarily dependent on variations …
Valuation Of Continuous And Intermittent Phragmites Control, R. Eugene Turner, R. S. Warren
Valuation Of Continuous And Intermittent Phragmites Control, R. Eugene Turner, R. S. Warren
Faculty Publications
Quantifying the relative value of Phragmites australis and Spartina alterniflora habitat is important to evaluate the benefits and risks of different attempts to address Phragmites expansion on the U.S. eastern seaboard. Two contrasting approaches commonly used to restore tidal marsh habitats invaded by Phragmites communities involve spraying Phragmites with herbicide only when its coverage of a particular marsh area is near or close to 100%. Alternatively, after the first application, herbicide is annually applied on any surviving patches of Phragmites present in a mosaic of other marsh vegetation. A model is introduced to evaluate the relative habitat value of these …
Climatic Influences On Riverine Nitrate Flux: Implications For Coastal Marine Eutrophication And Hypoxia, Dubravko Justic, R. Eugene Turner, Nancy N. Rabalais
Climatic Influences On Riverine Nitrate Flux: Implications For Coastal Marine Eutrophication And Hypoxia, Dubravko Justic, R. Eugene Turner, Nancy N. Rabalais
Faculty Publications
The average nitrate flux of the lower Mississippi River increased 3.3-fold between 1954–1967 and 1983–2000. During the same time period, the average nitrate concentration increased 2.3-fold while the average discharge increased 40%. Partitioning of the observed trend in nitrate flux among the two flux components, nitrate concentration and discharge, revealed that about 80% of the observed increase in flux could be explained by the increase in nitrate concentration. This indicates that a historical increase in the anthropogenic nutrient inputs has had a far greater impact on the lower Mississippi River nitrate flux than a change in climate. The influence of …
Abundance Trends And Environmental Habitat Usage Patterns Of Bottlenose Dolphins (Tursiops Truncatus) In Lower Barataria And Caminada Bays, Louisiana, Cara Edina Miller
Abundance Trends And Environmental Habitat Usage Patterns Of Bottlenose Dolphins (Tursiops Truncatus) In Lower Barataria And Caminada Bays, Louisiana, Cara Edina Miller
LSU Doctoral Dissertations
The paucity of research into the environmental requirements, stock membership, abundance and residency patterns of bottlenose dolphins (Tursiops truncatus) in coastal Louisiana creates difficulty in understanding how local ecosystems and threats (such as fishery interactions, habitat degradation and pollution) affect populations. This study combined fine-scale environmental measurements and photo-identification techniques to describe patterns of habitat usage and abundance of bottlenose dolphins in lower Barataria Basin from June 1999 to May 2002. In addition I investigated the validity and limitations of using mark-recapture models to estimate abundance from cetacean photo-identification data. Bottlenose dolphins were present year-round in a wide range of …
Black Willow (Salix Nigra) Use In Phytoremediation Techniques To Remove The Herbicide Bentazon From Shallow Groundwater, Robert Mark Conger
Black Willow (Salix Nigra) Use In Phytoremediation Techniques To Remove The Herbicide Bentazon From Shallow Groundwater, Robert Mark Conger
LSU Doctoral Dissertations
Wetland environments have been impacted by the activities of man over the past several hundred years in North America. Industrialization into wetland areas has brought with it anthropogenic compounds that have been released into soils and groundwater. The use of phytoremediation to detoxify soil and groundwater began in the mid 1990's and has become a popular remediation technology. In 1994, a feasibility study for using phytoremediation in such an industrialized wetland area was conducted at a petrochemical facility at BASF Corporation, located about 20 kilometers south of Baton Rouge, Louisiana in Ascension Parish. The test site consisted of low level …
A Comparison Of Life Histories And Ecological Aspects Among Snappers (Pisces: Lutjanidae), Fernando Martinez-Andrade
A Comparison Of Life Histories And Ecological Aspects Among Snappers (Pisces: Lutjanidae), Fernando Martinez-Andrade
LSU Doctoral Dissertations
An extensive search for data on life-history and ecological variables was conducted for a representative number of the species within the family Lutjanidae. After creating different databases and standardizing all data, these variables were examined in statistical, correlation and graphic analyses. Additionally, a series of Principal Component Analyses were used to examine patterns among variables. Life-history variables included age at length zero, asymptotic length, maximum length, longevity, asymptotic weight, length at maturity, age at maturity, reproductive life span, growth rate and mortality rate. Ecological variables included latitudinal and vertical distribution, habitat selection (represented by substrate type), and spawning seasons. The …
A Comparison Of Finfish Assemblages On Subtidal Oyster Shell (Cultched Oyster Lease) And Mud Bottom In Barataria Bay, Louisiana, John Plunket
LSU Master's Theses
Recent research suggests that oyster reefs provide unique three-dimensional hard bottom habitat for many fish species. Along the northern shore of the Gulf of Mexico, oyster shell bottoms are predominantly flat, subtidal and cultched, lacking the vertical relief and spatial heterogeneity provided by natural reefs. This study compared finfish assemblages, gut contents, and macroinvertebrate assemblages at subtidal oyster shell (cultched oyster lease) and mud bottoms in Barataria Bay, Louisiana. Three mud and three shell sites were sampled on seven dates from October 2001 to October 2002, using gill nets and substrate trays. Data from the gill nets were used to …
Swimming Performance Of Juvenile Florida Pompano (Trachinotus Carolinus) And Atlantic Spadefish (Chaetodipterus Faber) Exposed To Sublethal Concentrations Of Ethylene Glycol And Methanol: Individual And Synergistic Effects, Mark Alan Stead
LSU Master's Theses
Recently, new technology has pushed petrochemical exploration into increasingly deeper water (>305 m) at increased risks to marine fauna. One risk is from chemical additives used to enhance deepwater production such as ethylene glycol and methanol which are used during the production and treatment to prevent the formation of gas hydrates in deepwater wells and pipelines. Juvenile Florida pompano (Trachinotus carolinus) were used in controlled experiments to test the effects of 3.0 % ethylene glycol (EG), 1.07 % methanol (MeOH) and a combination of the two chemicals(EG + MeOH) on swimming performance of individual fish. Swimming performance was evaluated …
The Effects Of Sediment Grain Size And Oil Exploration On Microbial Atp Biomass, Eric Tyson Guilbeau
The Effects Of Sediment Grain Size And Oil Exploration On Microbial Atp Biomass, Eric Tyson Guilbeau
LSU Master's Theses
Adenosine triphosphate (ATP) is a unique biochemical indicator of active microbial biomass and its relationship to environmental conditions. Its assay in sediments is complicated, however, by adsorptive loss to the sediment matrix and subsequent interferences in the luciferin-luciferase assay by compounds released during the extraction process. Corrections must be applied to correct for these losses and we describe a novel approach using radioactive ATP to correct for ATP adsorption. The sediment matrix also plays a significant role in determining both the magnitude of the ATP pool and the extent of the ATP adsorptive loss. Coarser sediments were found to have …
The Ecology Of Two Estuarine-Dependent Tonguefishes, The Blackcheek Tonguefish (Symphurus Plagiusa) And The Offshore Tonguefish (S. Civitatium), In Coastal Louisiana, Theodore Scott Switzer
The Ecology Of Two Estuarine-Dependent Tonguefishes, The Blackcheek Tonguefish (Symphurus Plagiusa) And The Offshore Tonguefish (S. Civitatium), In Coastal Louisiana, Theodore Scott Switzer
LSU Doctoral Dissertations
The pattern and process of wetland loss in coastal Louisiana has the potential to influence the distribution and abundance of fishes and macroinvertebrates that utilize inshore estuarine habitat as nurseries during their early life histories. Current management plans designed to stabilize marsh elevations, such as freshwater diversions, may also influence the distribution and abundance of estuarine-dependent nekton. Given the importance of nursery function of inshore estuaries in coastal Louisiana, it is of interest to explore the response of estuarine-dependent organisms to environmental gradients. To this end I examined the ecology of two sympatric tonguefishes, the blackcheek tonguefish (Symphurus plagiusa) and …
The Effect On Water Quality Of Riverine Input Into Coastal Wetlands, Robert Raymond Lane
The Effect On Water Quality Of Riverine Input Into Coastal Wetlands, Robert Raymond Lane
LSU Doctoral Dissertations
This dissertation focuses on impact on water quality of two freshwater diversions, the Bonnet Carre Spillway and the Caernarvon freshwater diversion, as well as the Atchafalaya River Estuarine Complex. As water passed through the Bonnet Carre Spillway, there were reductions in total suspended sediment concentrations of 82-83%, in nitrite+nitrate of 28-42%, in total nitrogen (TN) of 26-30%, and in total phosphorus (TP) of 50-59%. The Si:N ratio generally increased and the N:P ratio decreased from the river to the plume edge in Lake Pontchartrain. At the Caernarvon diversion, there were reductions in concentrations of dissolved inorganic Si, N, and P …
Quantifying Habitat Quality Of Larval Bay Anchovy (Anchoa Mitchilli) In Chesapeake Bay By Linking An Individual-Based Model With Spatially-Detailed Field Data, Aaron Thomas Adamack
Quantifying Habitat Quality Of Larval Bay Anchovy (Anchoa Mitchilli) In Chesapeake Bay By Linking An Individual-Based Model With Spatially-Detailed Field Data, Aaron Thomas Adamack
LSU Master's Theses
Larval bay anchovy (Anchoa mitchilli) habitat quality in Chesapeake Bay was predicted using an individual-based model applied to spatially-detailed field data from Rilling and Houde (1999). Habitat quality was predicted using the ratio of instantaneous mortality rate to instantaneous growth rate. Model predictions of habitat quality were compared to field estimates of habitat quality derived from the spatially-detailed field data. Three sets of one-day simulations were performed to estimate larval growth and mortality rates throughout Chesapeake Bay during June and during July 1993. Field-based simulations used field data to estimate the model inputs of water temperature, zooplankton densities, and the …
An Ecopath/Ecosim Analysis Of An Estuarine Food Web: Seasonal Energy Flow And Response To River-Flow Related Perturbations, Laura Lynette Althauser
An Ecopath/Ecosim Analysis Of An Estuarine Food Web: Seasonal Energy Flow And Response To River-Flow Related Perturbations, Laura Lynette Althauser
LSU Master's Theses
Estuaries are often the receiving basins for major river systems which makes them vulnerable to anthropogenic influences. I used Ecopath and Ecosim to investigate the structure of the Weeks Bay, Alabama, USA food web, and the responses of the food web to bottom-up perturbations. Four season-specific steady-state Ecopath models were developed and used to compare the production, biomass, consumption, biomass flows, and higher order indices of ecosystem functioning of the Weeks Bay food web under winter, spring, summer, and fall conditions. The season-specific Ecopath snapshots indicated that the structure of the Weeks Bay food web was resilient. Winter had the …
Pulsed River Flooding Effects On Sediment Deposition In Breton Sound Estuary, Louisiana, Katherine Wheelock
Pulsed River Flooding Effects On Sediment Deposition In Breton Sound Estuary, Louisiana, Katherine Wheelock
LSU Master's Theses
Louisiana's deltaic coast is a dynamic sedimentary environment made vulnerable by Mississippi River channelization, which restricts freshwater, sediment, and nutrient inputs to adjacent estuaries. Freshwater diversions now reconnect some estuaries with historic fluvial sources, like Breton Sound basin, which receives Mississippi River suspended loads through the Caernarvon freshwater diversion. The project objectives were to quantify short-term sediment accumulation using sediment traps, evaluate sediment trap effectiveness, and compare long-term deposition using feldspar horizon markers and 210Pb dating to the annual sediment trap deposition. Magnitude and variations of sediment deposition at 14 sites were compared during an 18-month study in the upper …