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Articles 9901 - 9930 of 14028

Full-Text Articles in Oceanography and Atmospheric Sciences and Meteorology

The Colonial Zoanthid Palythoa Caribaeorum: Population Dynamics On Southeast Florida Reefs, Joanna C. Walczak Jan 2008

The Colonial Zoanthid Palythoa Caribaeorum: Population Dynamics On Southeast Florida Reefs, Joanna C. Walczak

HCNSO Student Theses and Dissertations

The colonial zoanthid Palythoa caribaeorum (Cnidaria, Zoanthidea) (Duchassaing and Michelotti 1861) is a major benthic component of most Caribbean reefs and is an extremely aggressive spatial competitor (Suchanek and Green 1981). This study looks at annual visits to 16 permanent monitoring sites over 3 reef designations (Inshore Ridge Complex, Middle Reef, and Outer Reef) in Broward County, Florida from 2002-2006. The data obtained in this study fills an informational void regarding the role of zoanthids in the southeast Florida reef benthic community. The study was conducted in two parts. Part One used digital imagery analysis to quantify the spatial cover …

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U.S. Law Of The Sea Cruise To Map The Western Insular Margin And 2500-M Isobath Of Guam And The Northern Mariana Islands. Cruise Report, James V. Gardner Jan 2008

U.S. Law Of The Sea Cruise To Map The Western Insular Margin And 2500-M Isobath Of Guam And The Northern Mariana Islands. Cruise Report, James V. Gardner

Center for Coastal and Ocean Mapping

U.S. Law of the Sea cruise to map the western insular margin and 2500-m isobath of Guam and the Northern Mariana Islands. CRUISE BD07-1 November 16, to December 17, 2007 Garapan, Saipan, to Garapan, Saipan, Commonwealth of the Northern Mariana Islands

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Evaluation Of 1,3,5 Trimethylbenzene Degradation In The Detailed Tropospheric Chemistry Mechanism, Mcmv3.1, Using Environmental Chamber Data, A. Metzger, J. Dommen, J. Duplissy, A. S.H. Prevot, J. Kleffmann, Yasin F. Elshorbany, A. Wisthaler, U. Baltensperger Jan 2008

Evaluation Of 1,3,5 Trimethylbenzene Degradation In The Detailed Tropospheric Chemistry Mechanism, Mcmv3.1, Using Environmental Chamber Data, A. Metzger, J. Dommen, J. Duplissy, A. S.H. Prevot, J. Kleffmann, Yasin F. Elshorbany, A. Wisthaler, U. Baltensperger

USF St. Petersburg Campus Faculty Publications

The degradation mechanism of 1,3,5-trimethyl-benzene (TMB) as implemented in the Master Chemical Mechanism version 3.1 (MCM) was evaluated using data from the environmental chamber at the Paul Scherrer Institute. The results show that the MCM provides a consistent description of the photo-oxidation of TMB/NO(x) mixtures for a range of conditions. In all cases the agreement between the measurement and the simulation decreases with decreasing VOC-NO(x) ratio and in addition with increasing precursor concentration. A significant underestimation of the decay rate of TMB and thus underestimation of reactivity in the system, consistent with results from previous appraisals of the MCM, was …

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Naturally Present Fatty Acids As Internal Calibrants For Fourier Transform Mass Spectra Of Dissolved Organic Matter, Rachel L. Sleighter, Georgina A. Mckee, Zhanfei Liu, Patrick G. Hatcher Jan 2008

Naturally Present Fatty Acids As Internal Calibrants For Fourier Transform Mass Spectra Of Dissolved Organic Matter, Rachel L. Sleighter, Georgina A. Mckee, Zhanfei Liu, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

The analysis of dissolved organic matter ( DOM) by Fourier transform ion cyclotron resonance mass spectrometry ( FTICR- MS) has gained wide interest recently, driven primarily by its ultrahigh resolving power and mass accuracy. Accurate calibration of mass spectra is a key step to successfully decipher the DOM components. We propose a simple and accurate method to internally calibrate the peaks in the complex spectra without the need to add a calibrant. Mass spectra of DOM samples from the Dismal Swamp, Virginia, and the lower Chesapeake Bay display the presence of naturally occurring fatty acids which can be readily recognized …

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Determination Of Photochemically Produced Carbon Dioxide In Seawater, Emily M. White, David J. Kieber, Kenneth Mopper Jan 2008

Determination Of Photochemically Produced Carbon Dioxide In Seawater, Emily M. White, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

An analytical system was developed to determine photochemically produced carbon dioxide in marine waters. Our system was designed to measure low levels of carbon dioxide by maintaining a closed system to prevent atmospheric contamination during sample preparation, irradiation, and analysis. To detect low levels of photoproduced carbon dioxide in seawater, background dissolved inorganic carbon (DIC) was removed before irradiation. To strip out DIC, samples were acidified to pH 3.0 (converting DIC to carbon dioxide) and bubbled with low carbon dioxide air. The pH was then readjusted back to the original value, and the resulting low-DIC seawater samples were transferred pneumatically …

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Characterization And Analysis Of Hailstorms In The Northern Great Plains, Thomas Sando Jan 2008

Characterization And Analysis Of Hailstorms In The Northern Great Plains, Thomas Sando

The Journal of Undergraduate Research

Hail is a meteorological occurrence that appears frequently during spring and summer across the Northern Great Plains. This paper first characterizes patterns associated with reported hail events occurring within a five-state region (North Dakota, Minnesota, South Dakota, Iowa, and Nebraska) from 2000-2006 using records taken from the National Climatic Data Center (NCDC) Severe Storms database. Patterns of interest include the seasonality of hail activity for each state and across the region, observational bias in the reporting of hailstone size, and temporal trends in the number of hail reports across the region and in each state. This paper then explores a …

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Behavior Of An Escolar Lepidocybium Flavobrunneum In The Windward Passage As Determined By Popup Satellite Archival Tagging, David Kerstetter, P. H. Rice, Derke Snodgrass, Eric Prince Jan 2008

Behavior Of An Escolar Lepidocybium Flavobrunneum In The Windward Passage As Determined By Popup Satellite Archival Tagging, David Kerstetter, P. H. Rice, Derke Snodgrass, Eric Prince

Marine & Environmental Sciences Faculty Articles

In June 2003, fisheries research was conducted in the Windward Passage using a chartered commercial pelagic longline vessel (Rice and Snodgrass 2003). This paper describes the habitat use by an escolar in this location tagged with a pop-up satellite archival tag (PSAT) that remained attached to the fish for 14 d. Data recovered from the PSAT were used to directly document diel vertical migration and ambient temperature range for the first time in a mesopelagic teleost.

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Salt Marshes As A Source Of Chromophoric Dissolved Organic Matter (Cdom) To Southern California Coastal Waters, Catherine D. Clark, Liannea P. Litz, Stanley B. Grant Jan 2008

Salt Marshes As A Source Of Chromophoric Dissolved Organic Matter (Cdom) To Southern California Coastal Waters, Catherine D. Clark, Liannea P. Litz, Stanley B. Grant

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

To determine chromophoric dissolved organic matter (CDOM) sources in Southern California coastal waters, optical properties of a river outlet and adjacent tidally flushed salt marshes were monitored (dry season; June July 2001). Average absorption coefficients doubled at ebb vs. flood tides (4.8 +/- 1.5 vs. 2.1 +/- 0.9 m(-1); 300 nm), suggesting significant salt marsh CDOM inputs into coastal waters. Average spectral slopes were not statistically different for any sites or tides (0.010 +/- 0.002 nm(-1)), consistent with salt marsh CDOM dominating coastal waters. Three-dimensional fluorescence excitation-emission matrices (EEMs) at ebb tide showed contributions from terrestrial, protein, and marine humic-like …

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Time Evolution Of Terrestrial Gamma Ray Flashes, Brian W. Grefenstette, David M. Smith, Joseph R. Dwyer, Gerald Jerry Fishman Jan 2008

Time Evolution Of Terrestrial Gamma Ray Flashes, Brian W. Grefenstette, David M. Smith, Joseph R. Dwyer, Gerald Jerry Fishman

Aerospace, Physics, and Space Science Faculty Publications

We present a study of the time evolution of TGFs observed by both RHESSI and BATSE and compare the data with Monte Carlo simulations of relativistic runaway electron avalanches that record the time of flight for individual photons. Our analysis of the RHESSI data shows that the average delay between the main, hard peak and the secondary, soft tail in the RHESSI data is 28 ± 3 μs. We show that this is consistent with Compton downscattering of hard photons in the atmosphere in our simulations when the source region is located at or below 21 km, which is consistent …

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High-Energy Electron Beams Launched Into Space By Thunderstorms, Joseph R. Dwyer, Brian W. Grefenstette, David M. Smith Jan 2008

High-Energy Electron Beams Launched Into Space By Thunderstorms, Joseph R. Dwyer, Brian W. Grefenstette, David M. Smith

Aerospace, Physics, and Space Science Faculty Publications

Using CGRO/BATSE data, a possible new source of high-energy electrons and positrons in the earth's inner magnetosphere is presented. These particles are generated within the upper atmosphere by Compton scattering and pair-production of gamma-rays originating from near the tropopause as Terrestrial Gamma-ray Flashes (TGFs). Once created, these energetic electrons and positrons follow the geomagnetic field into the inner magnetosphere where they can be detected in low-earth orbit, either near the TGF magnetic foot point or at the conjugate point several thousand kilometers away. Approximately 17% of CGRO/BATSE events previously identified as terrestrial gamma-ray flashes are, in fact, such electrons and …

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Co-Location Of Lightning Leader X-Ray And Electric Field Change Sources, John J. Howard, Martin A. Uman, Joseph R. Dwyer, Dustin Hill, Christopher J. Biagi, Ziad H. Saleh, Jason E. Jerauld, Hamid K. Rassoul Jan 2008

Co-Location Of Lightning Leader X-Ray And Electric Field Change Sources, John J. Howard, Martin A. Uman, Joseph R. Dwyer, Dustin Hill, Christopher J. Biagi, Ziad H. Saleh, Jason E. Jerauld, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Using an eight-station time of arrival (TOA) network composed of NaI(Tl) scintillation detectors and wideband electric field derivative (dE/dt) antennas covering approximately 1 km² on the ground, we have located both the sources of X-ray emissions and electric field changes produced during the leader phase of both downward negative natural and rocket-triggered lightning strokes. We show that the sources of X rays and leader step electric field changes are co-located in space within 50 m and that the located X rays are emitted 0.1 to 1.3 μs after the origin of the leader step electric field changes.

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Apparent Tolerance Of Turkey Vultures (Cathartes Aura) To The Non-Steroidal Anti-Inflammatory Drug Diclofenac, Barnett A. Rattner, Maria A. Whitehead, Grace Gasper, Carol U. Meteyer, William A. Link, Mark A. Taggart, Andrew A. Meharg, Oliver H. Pattee, Deborah J. Pain Jan 2008

Apparent Tolerance Of Turkey Vultures (Cathartes Aura) To The Non-Steroidal Anti-Inflammatory Drug Diclofenac, Barnett A. Rattner, Maria A. Whitehead, Grace Gasper, Carol U. Meteyer, William A. Link, Mark A. Taggart, Andrew A. Meharg, Oliver H. Pattee, Deborah J. Pain

United States Geological Survey: Staff Publications

The nonsteroidal anti-inflammatory drug diclofenac is extremely toxic to Old World Gyps vultures (median lethal dose ~0.1–0.2 mg/kg), evoking visceral gout, renal necrosis, and mortality within a few days of exposure. Unintentional secondary poisoning of vultures that fed upon carcasses of diclofenac-treated livestock decimated populations in the Indian subcontinent. Because of the widespread use of diclofenac and other cyclooxygenase-2 inhibiting drugs, a toxicological study was undertaken in turkey vultures (Cathartes aura) as an initial step in examining sensitivity of New World scavenging birds. Two trials were conducted entailing oral gavage of diclofenac at doses ranging from 0.08 to …

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Shading Facilitates Sessile Invertebrate Dominance In The Rocky Subtidal Gulf Of Maine, Ron J. Etter, Robert J. Miller Jan 2008

Shading Facilitates Sessile Invertebrate Dominance In The Rocky Subtidal Gulf Of Maine, Ron J. Etter, Robert J. Miller

Biology Faculty Publication Series

Dramatic shifts in community composition occur between vertical and horizontal rocky surfaces in subtidal environments worldwide, yet the forces mediating this transition are poorly understood. Vertical rock walls are often covered by lush, diverse communities of sessile suspension-feeding invertebrates, while adjacent horizontal substrates are dominated by algae, or corals in the tropics. Multiple factors, including light, sedimentation, water flow, and predation have been proposed to explain this pattern, but experimental tests of these hypotheses are lacking. We manipulated light level and predation to test whether variation in these mechanisms could be responsible for the shift in composition of sessile communities …

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Dms Air/Sea Flux And Gas Transfer Coefficients From The North Atlantic Summertime Coccolithophore Bloom, Christa Marandino, Warren J. De Bruyn, Scott Miller, Eric S. Saltzman Jan 2008

Dms Air/Sea Flux And Gas Transfer Coefficients From The North Atlantic Summertime Coccolithophore Bloom, Christa Marandino, Warren J. De Bruyn, Scott Miller, Eric S. Saltzman

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Dimethylsulfide (DMS) atmospheric and oceanic concentrations and eddy covariance air/sea fluxes were measured over the N. Atlantic Ocean during July 2007 from Iceland to Woods Hole, MA, USA. Seawater DMS levels north of 55 degrees N ranged from 3 to 17 nM, with variability related to the satellite-derived distributions of coccoliths and to a lesser extent, chlorophyll. For the most intense bloom region southwest of Iceland, DMS air/sea fluxes were as high as 300 mu mol m(-2) d(-1), larger than current model estimates. The observations imply that gas exchange coefficients in this region are significantly greater than those estimated using …

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Otolith Chemistry Indicates Population Structuring By The Antarctic Circumpolar Current, Julian R. Ashford, Cynthia M. Jones, Eileen E. Hofmann, Inigo Everson, Carlos A. Moreno, Guy Duhamel, Richard Williams Jan 2008

Otolith Chemistry Indicates Population Structuring By The Antarctic Circumpolar Current, Julian R. Ashford, Cynthia M. Jones, Eileen E. Hofmann, Inigo Everson, Carlos A. Moreno, Guy Duhamel, Richard Williams

CCPO Publications

Large-scale transport of seawater in ocean currents may generate spatially complex population structure through the advection of life stages of marine fish species. To test this, we compared the chemistry of otolith nuclei from Patagonian toothfish (Dissostichus eleginoides), presently managed as spatially discrete Populations corresponding to fishing management areas along the Antarctic Circumpolar Current (ACC), which transports water eastward around the Southern Ocean. The chemistry of otolith nuclei, laid down during early life, differed significantly between fishing areas Off South America and the Antarctic and between some Antarctic areas. However, we found significant discrepancies from expectation for a …

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Impacts Of Chromophoric Dissolved Organic Material On Surface Ocean Heating In The Chukchi Sea, Victoria J. Hill Jan 2008

Impacts Of Chromophoric Dissolved Organic Material On Surface Ocean Heating In The Chukchi Sea, Victoria J. Hill

OES Faculty Publications

Recent observations show visible light attenuation in the Arctic Ocean to be greater than previously assumed. High attenuation observed during the period prior to ice melt and increased phytoplankton production, was attributed primarily to the high levels of absorption by chromophoric dissolved organic material ( CDOM) present in these waters. Preliminary evidence suggests this material is produced by ice algae in the early spring. Optical data from the Chukchi shelf system collected in the spring and summer of 2002, were used to model energy absorption in the mixed layer by both dissolved and particulate material. In the spring, absorption by …

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A Modelling Study Of Developmental Stage And Environmental Variability Effects On Copepod Foraging, Jerry D. Wiggert, Eileen E. Hofmann, Gustav-Adolf Paffenhöfer Jan 2008

A Modelling Study Of Developmental Stage And Environmental Variability Effects On Copepod Foraging, Jerry D. Wiggert, Eileen E. Hofmann, Gustav-Adolf Paffenhöfer

CCPO Publications

We used a stochastic Lagrangian model to study how behaviour contributes to copepod grazing success. The model simulates distinct foraging behaviours of Clausocalanus furcatus, Paracalanus aculeatus, and Oithona plumifera. Three sets of simulations were performed to investigate the effects of (a) prey-size preference; (b) variation in prey-size spectra; and (c) turbulence intensity on these species’ grazing rates. The size preference simulations demonstrate that, compared with copepodites, mature females have cell ingestion rates that are an order of magnitude lower, while carbon uptake is reduced by 35%. A prey spectrum that is skewed towards cells ,<6 >μm promotes copepodite …

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Transverse Structure Of Wind-Driven Flow At The Entrance To An Estuary: Nansemond River, Diego A. Narváez, Arnoldo Valle-Levinson Jan 2008

Transverse Structure Of Wind-Driven Flow At The Entrance To An Estuary: Nansemond River, Diego A. Narváez, Arnoldo Valle-Levinson

CCPO Publications

Observations of current velocity profiles were combined with an analytical solution to study the transverse partition of the wind-driven flow in an estuary, the Nansemond River, which is a tributary of the James River in the Chesapeake Bay. Observations spanned two periods of nearly 3 months in autumn-winter of 2003-2004 and spring-summer 2004. The wind-driven circulation consisted of downwind flow over the shoal and upwind flow in the channel at the entrance to the estuary. This pattern developed mainly with landward winds and provided observational evidence that sustains analytical and numerical model results. The transverse structure of the flow showed …

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Absorption Spectral Slopes And Slope Ratios As Indicators Of Molecular Weight, Source, And Photobleaching Of Chromophoric Dissolved Organic Matter, John R. Helms, Aron Stubbins, Jason D. Ritchie, Elizabeth C. Minor, David J. Kieber, Kenneth Mopper Jan 2008

Absorption Spectral Slopes And Slope Ratios As Indicators Of Molecular Weight, Source, And Photobleaching Of Chromophoric Dissolved Organic Matter, John R. Helms, Aron Stubbins, Jason D. Ritchie, Elizabeth C. Minor, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

A new approach for parameterizing dissolved organic matter ( DOM) ultraviolet-visible absorption spectra is presented. Two distinct spectral slope regions ( 275-295 nm and 350-400 nm) within log-transformed absorption spectra were used to compare DOM from contrasting water types, ranging from wetlands (Great Dismal Swamp and Suwannee River) to photobleached oceanic water ( Atlantic Ocean). On the basis of DOM size-fractionation studies ( ultrafiltration and gel filtration chromatography), the slope of the 275-295- nm region and the ratio of these slopes (SR; 275-295- nm slope : 350-400- nm slope) were related to DOM molecular weight ( MW) and …

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Technical Note: Molecular Characterization Of Aerosol-Derived Water Soluble Organic Carbon Using Ultrahigh Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, A. S. Wozniak, J. E. Bauer, R. L. Sleighter, R. M. Dickhut, Patrick Hatcher Jan 2008

Technical Note: Molecular Characterization Of Aerosol-Derived Water Soluble Organic Carbon Using Ultrahigh Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, A. S. Wozniak, J. E. Bauer, R. L. Sleighter, R. M. Dickhut, Patrick Hatcher

Chemistry & Biochemistry Faculty Publications

Despite the acknowledged relevance of aerosol-derived water-soluble organic carbon (WSOC) to climate and biogeochemical cycling, characterization of aerosol WSOC has been limited. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was utilized in this study to provide detailed molecular level characterization of the hi(,h molecular weight (HMW; m/z>223) component of aerosol-derived WSOC collected from rural sites in Virginia and New York, USA. More than 3000 peaks were detected by ESI FT-ICR MS within a m/z range of 223-600 for each sample. Approximately 86% (Virginia) and 78% (New York) of these peaks were assigned molecular formulas …

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Contrasting The 2007 And 2005 Hurricane Seasons: Evidence Of Possible Impacts Of Saharan Dry Air And Dust On Tropical Cyclone Activity In The Atlantic Basin, D. Sun, K. M. Lau, Menas Kafatos Jan 2008

Contrasting The 2007 And 2005 Hurricane Seasons: Evidence Of Possible Impacts Of Saharan Dry Air And Dust On Tropical Cyclone Activity In The Atlantic Basin, D. Sun, K. M. Lau, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this study, we provide preliminary evidence of possible modulation by Saharan dust of hurricane genesis and intensification, by contrasting the 2007 and 2005 hurricane seasons. It is found that dust aerosol loadings over the Atlantic Ocean are much higher in 2007 than in 2005. The temperature difference between 2007 and 2005 shows warming in the low-middle troposphere (900–700 hPa) in the dusty region in the eastern North Atlantic, and cooling in the Main Development Region (MDR). The humidity (wind) differences between 2007 and 2005 indicate significant drying (subsidence) in the Western North Atlantic (WNA) in 2007. The drier air …

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A Study Of Land Surface Processes Using Land Surface Models Over The Little River Experimental Watershed, A. K. Sahoo, P. A. Dirmeyer, P. R. Houser, Menas Kafatos Jan 2008

A Study Of Land Surface Processes Using Land Surface Models Over The Little River Experimental Watershed, A. K. Sahoo, P. A. Dirmeyer, P. R. Houser, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Three different land surface models (Hydrological improvements to the Simplified version of the Simple Biosphere model (HySSiB), Noah model, and Community Land Model (CLM)) were simulated on the NASA Goddard Space Flight Center’s Land Information System platform at 1-km resolution over the Little River Experimental Watershed, Georgia, and the simulated results were analyzed to address the local-scale land-atmosphere processes. All the three models simulated the soil moisture in space and time realistically. The Noah model produced higher soil moisture whereas the CLM got lower soil moisture with many dry down phases. CLM and HySSiB models were oversensitive to the atmospheric …

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Using Combined Prediction Models To Quantify And Visualize Stormwater Runoff In An Urban Watershed, Keshia Koehn, Cristina Scarlat, Kristofor Brye Jan 2008

Using Combined Prediction Models To Quantify And Visualize Stormwater Runoff In An Urban Watershed, Keshia Koehn, Cristina Scarlat, Kristofor Brye

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Stormwater runoff can transport nutrients, sediments, chemicals, and pathogens to surface waterbodies. Managing runoff is crucial to preserving water quality in rapidly developing urban watersheds like those in Northwest Arkansas. A watershed containing the majority of the University of Arkansas campus was designated as the study area because stormwater from it drains into the West Fork of the White River, designated as an impaired waterbody due to siltation. The project objective was to develop methodology to test existing stormwater drainage infrastructure, identify potential areas of improvement, and estimate potentially contaminated runoff by combining two widely used prediction models. The U.S. …

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Mesoamerican Reef Spawning Aggregations Help Maintain Fish Population: A Review Of Connectivity Research And Priorities For Science Management, W. Heyman, W. B. Kjerfve, T. Ezer Jan 2008

Mesoamerican Reef Spawning Aggregations Help Maintain Fish Population: A Review Of Connectivity Research And Priorities For Science Management, W. Heyman, W. B. Kjerfve, T. Ezer

CCPO Publications

The life history of most marine organisms includes an obligate period of pelagic larval dispersal. Migration to spawning areas and pelagic dispersal is often well beyond the home range of these organisms. Designing marine protected areas to include a broad range of taxa and their various dispersal patterns is an important and daunting challenge. This paper addresses the issue of connectivity for one set of species in a limited geographic area. We focus on transient spawning reef fish within the Mesoamerican Reef and their connectivity. We divide our scientific review into four sections as follows: (1) ecological characterization of transient …

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Quantifying Vertical Mixing In Estuaries, W. Rockwell Geyer, Malcolm E. Scully, David K. Ralston Jan 2008

Quantifying Vertical Mixing In Estuaries, W. Rockwell Geyer, Malcolm E. Scully, David K. Ralston

CCPO Publications

Estuarine turbulence is notable in that both the dissipation rate and the buoyancy frequency extend to much higher values than in other natural environments. The high dissipation rates lead to a distinct inertial subrange in the velocity and scalar spectra, which can be exploited for quantifying the turbulence quantities. However, high buoyancy frequencies lead to small Ozmidov scales, which require high sampling rates and small spatial aperture to resolve the turbulent fluxes. A set of observations in a highly stratified estuary demonstrate the effectiveness of a vessel-mounted turbulence array for resolving turbulent processes, and for relating the turbulence to the …

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Denitrification Enzyme Activity As An Indicator Of Nitrate Loading In A Wetland Receiving Diverted Mississippi River Water, Lisa Michelle Gardner Jan 2008

Denitrification Enzyme Activity As An Indicator Of Nitrate Loading In A Wetland Receiving Diverted Mississippi River Water, Lisa Michelle Gardner

LSU Master's Theses

The Davis Pond freshwater diversion discharges nutrient-rich Mississippi River water to a 3,760 ha receiving marsh in upper Barataria Basin, LA. Excess nitrate in the Mississippi River has been linked to algal blooms and hypoxia in the Gulf of Mexico with potential to negatively impact Barataria Basin. We hypothesized that 1) soil denitrification enzyme activity (DEA) will increase with higher surface water nitrate concentrations, and 2) the spatial distribution of DEA in Davis Pond marsh will provide information about the extent nitrate loading at a specific discharge rate. Intact soil cores collected from the marsh received a continuous flow of …

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Survival Of Eastern Oysters Crassostrea Virginica From Three Lines Following Experimental Challenge With Bacterial Pathogens, Javier Gomez-Leon, Luisa Villamil, Scott A. Salger, Rachel Sallum, Antonio Remacha-Trivino, Dale F. Leavitt, Marta Gomez-Chiarri Jan 2008

Survival Of Eastern Oysters Crassostrea Virginica From Three Lines Following Experimental Challenge With Bacterial Pathogens, Javier Gomez-Leon, Luisa Villamil, Scott A. Salger, Rachel Sallum, Antonio Remacha-Trivino, Dale F. Leavitt, Marta Gomez-Chiarri

Fisheries, Animal and Veterinary Sciences Faculty Publications

Shellfish production is often affected by bacterial pathogens that cause high losses in hatcheries and nurseries. We evaluated the relative survival of larvae and juveniles of 3 Crassostrea virginica oyster lines: (1) GHP, a Rhode Island line; (2) NEHY, a line resistant to dermo and multinucleated sphere X diseases; and (3) FLOWERS, a line resistant to Roseovarius oyster disease, experimental challenge with Vibrio spp. isolates RE22 and RE101, causative agents of bacillary necrosis in Pacific oyster larvae, and the type strain of Roseovarius crassostreae, causative agent of Roseovarius oyster disease. All of the isolates were able to induce significant …

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Swamp Ecology In A Dynamic Coastal Landscape: An Investigation Through Field Study And Simulation Modeling, Susanne Sigrid Hoeppner Jan 2008

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 …

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A Century Of Land Use And Water Quality In Watersheds Of The Continental U.S., Whitney P. Broussard Iii Jan 2008

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 …

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Elucidating Marine Pore Water Exchange And Fresh Aquifer Sources In Estimates Of Submarine Groundwater Discharge To A Coastal Lagoon, Christopher Gerald Smith Jan 2008

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 …

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