Digital Commons Network^™

Understanding The Flow Dynamics Of The Pearl River, Ms, Through Hydrodynamic Modeling, Nahruma Mehzabeen Pieu

Master's Theses

The Pearl River brings fresh water and nutrients into Lake Borgne regulating conditions for oyster growth in estuarine waters. However, there are no flow measurement stations installed on East Pearl or West Pearl either at the river outlets or after the upstream bifurcation of the Pearl. This study aims to model the Lower Pearl River to understand the flow dynamics in the major branches, and to determine the final outflow distribution into the Mississippi Sound, aiming to improve river forcing for ocean models studying estuarine dynamics of the Mississippi Sound.

Synthetic meandering bathymetry with updated banks is developed and applied …

Understanding The Impacts Of Topobathymetric Data On Storm Surge Model Predictions, Sydni Crain

Master's Theses

The topobathymetric characteristics of a region are regularly altered by natural and anthropogenic causes. This directly impacts the resulting storm surge during a hurricane. The primary goal of this research was to gain a better understanding of the impact that topography and bathymetry have on storm surge models, particularly the Advanced Circulation (ADCIRC) Model. Hurricane Zeta (2020) and Hurricane Ida (2021) were chosen as case studies; therefore, the Gulf of Mexico (GOM) was chosen as the study site. This research was completed by comparing ADCIRC storm surge results which were based on older, lower-resolution data with results derived from more …

Determining The Refractive Index Of Phytoplankton Via Direct Measurement Of Cellular Structures, Michael Kamowski

Master's Theses

The refractive index of phytoplankton has never been directly measured before despite its importance towards studying the optical characteristics of marine particles. Previous attempts to measure it have been done through indirect methods. While these methods have proven useful, they contain assumptions about the particles morphology and composition that cause for uncertainty with the measurements. Through the use of the 3D Cell Explorer, a high precision holotomographic microscope, the RI of phytoplankton can be directly measured for the first time. With volume measurements, the phytoplankton were found to not display a single bulk RI, instead the bulk RI was different …

Benthic Habitat Mapping Of Mountain Top Bank Within The Northern Gulf Of Mexico Through Integrated Geophysical And Visual Data Analysis, Bethany Pertain

Master's Theses

Mesophotic coral ecosystems (MCEs) are among the seafloor ecosystems that have been poorly studied throughout the world’s oceans, but they are a vital and diverse ecosystem that should be prioritized for future mapping and ecological studies. Priority should be given to them because they possess natural, social, and economic values, and face a variety of threats, all of which, if not better understood will result in the loss of this unique ecosystem. Insights into these ecosystems, among other deep-sea environments, are lacking due to difficulty accessing them, inherent lag between data collection by an autonomous system and observation by a …

Investigation Of Dead Ocean Quahogs (Arctica Islandica) Shells On The Mid-Atlantic Bight Continental Shelf, Alyssa Leclaire

Master's Theses

Ocean quahogs, Arctica islandica, are a long-lived, widely dispersed, biomass dominate in the Mid-Atlantic; therefore, quahog shells are valuable resources for studying climate change over time. Recently, dead ocean quahog shells were discovered south and inshore of the present biogeographic range of this animal. The presence of ocean quahog shells outside the current range is presumably a consequence of past regressions and transgressions of the Cold Pool, the bottom-trapped, cool body of water that allows boreal animals to live at lower latitudes. Dead ocean quahog shells were collected offshore of the DelMarVa Peninsula then radiocarbon-dated, evaluated for taphonomic condition, …

Analysis Of Fossil Pollen From A Pleistocene Cypress Forest Preserved On The Northern Gulf Of Mexico Continental Shelf, Kathryn Joyce Garretson

Master's Theses

This study presents the findings of fossil pollen analysis performed on terrestrial sediments preserved on the northern Gulf of Mexico continental shelf (site hereafter known as the Underwater Forest or DF). This research aims to establish vegetation composition on a continental shelf glacial refuge and provide a better understanding of vegetation response to sea-level rise. Two cores (15DF1 and 15DF3B) located at different locations within the forest were recovered and analyzed. Pollen results from both cores were similar, with high percentages of Taxodium and Nyssa pollen in the lowermost sections reflecting an assemblage typical of contemporary baldcypress swamps. Pollen assemblages …

Understanding Biogeochemical And Physical Controls On Methane Air-Sea Exchange Fluxes In The Pacific Ocean, Sarah Raney

Master's Theses

Methane and trace element samples were collected on GEOTRACES GP15 Pacific Meridional Transect (PMT) cruise conducted between the Aleutian Islands (57 °N) and Tahiti (20 °S) from September to November 2018. Uncertainty in methane air-sea exchange fluxes was determined using a propagation of errors approach. Fluxes ranged from -0.88 to 4.9 µmol CH₄ m^-2 d^-1. Average CH₄ flux along the Alaskan margin was 2.2 ± 2.9 µmol CH₄ m^-2 d^-1. Methane fluxes decreased moving southward and increased to their open ocean maximum around 20 °N before declining in equatorial waters. Near …

Assessing The Rates Of Post-Depositional Change Within 2004 Indian Ocean Sediments: Implications For Long-Term Records Of Paleotsunamis, Lillian Pearson

Master's Theses

Foraminifera are commonly used to examine patterns of tsunami inundation occurring over centennial to millennial timescales, but the impacts of post-depositional change on geologic reconstructions are unknown. In Sumatra, the taphonomic character (i.e., test surface condition) of a foraminifer can deteriorate over time, rendering them unidentifiable, and even dissolve them entirely. Here I investigate the rates of post-depositional change of foraminiferal assemblages found within the 2004 Indian Ocean Tsunami (IOT) deposit over a 15-year time interval in Aceh, Indonesia in a vegetated open coastal plain (Site 1: Pulot) and an unvegetated protected coastal cave (Site 2). I identified two zones …

Application Of Machine Learning Techniques To Forecast Harmful Algal Blooms In Gulf Of Mexico, Bala Tripura Sundari Yerrapothu

Master's Theses

The Harmful Algal Blooms (HABs) forecast is crucial for the mitigation of health hazards and to inform actions for the protection of ecosystems and fisheries in the Gulf of Mexico (GoM). For the sake of simplicity of our application we assume ocean color satellite imagery from the National Oceanic and Atmospheric Administration as a proxy for HABs.

In this study we use a deep neural network trained on the 2-Dimensional time series proxy data to provide a forecast of the HABs’ manifestations in the GoM.Our approach analyzes between both spatial and temporal features simultaneously. In addition, the network also helps …

Small-Scale Resuspension And Redistribution Of Surface Sediments In The Northeast Gulf Of Mexico, Austin Harris

Master's Theses

Following the release of ~4.9 million barrels of oil into the Gulf of Mexico from the Macondo wellhead, a vast area of the seafloor contained recently deposited marine sediments contaminated by the oil spill. The initial deposition of these contaminated marine sediments was likely not the end of the journey for the particles. Downslope gravitational processes and events of increased current speed in the deep ocean setting can result in recently deposited sediments to resuspend and be moved laterally with the current flow, increasing the area effected by the oil spill. Erosion experiments performed in a closed-loop resuspension flume were …

Assessing The Recalibration Interval For Nearshore Sediment Assemblages After Hurricane Irma: Implications For Developing Long-Term Records Of Overwash Deposits, Stephen Mitchell

Master's Theses

Surface distributions are commonly collected to assist with overwash interpretation; however, many of these are first established immediately after a major overwash event as part of a post-event field survey. This study documents the impacts of Hurricane Irma, a Category 5 storm, on nearshore sediments off the coast of Anegada (British Virgin Islands) using distributions of Homotrema rubra, an encrusting foraminifer with a defined provenance in coral reef ecosystems. Over four sampling intervals spanning 2 years, from six months pre-Hurricane Irma to 18 months post-Hurricane Irma, surface sediment was collected from three shore-perpendicular transects on both the northern and …

Freshwater Endmembers Impacting Carbonate Chemistry In The Mississippi Sound, Allison Savoie

Master's Theses

Coastal ecosystems are highly dynamic areas for carbon cycling and are likely to be negatively impacted by increasing ocean acidification. This research focused on dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Mississippi Sound in order to understand the influence of local rivers that supply alkalinity to the area and buffer against ocean acidification. This area receives large fluxes of freshwater from local rivers, in addition to episodic inputs from the Mississippi River through a human-built diversion, the Bonnet Carré Spillway. Sites in the Mississippi Sound were sampled monthly during August 2018 to November 2019 and at weekly …

The Variability Of High-Frequency Motions And Their Interactions With The Mesoscale On The Mississippi Shelf, Jordan Earls

Master's Theses

In this study, we examine the spatial and temporal variability of high-frequency and low-frequency motions across the Mississippi Shelf and how the high-frequency motions are modulated by low-frequency mesoscale motions. For this purpose, we use Acoustic Doppler Current Profiler (ADCP) measurements collected at nearshore (23 m), mid-shelf (60 m), and shelf break (88 m) stations. High-frequency motions are defined as motions with periods less than 36 hours, whereas mesoscale motions have larger periods. The collected datasets are analyzed through bandpass filtering, least square harmonic analysis, spectral analysis, and empirical orthogonal functions (EOF). We find that along-shelf barotropic mesoscale motions contain …

Response And Recovery Of Horn And Petit Bois Islands, Mississippi, Usa To Tropical Cyclone Impacts: 2004 – 2016, Shara Gremillion

Master's Theses

Horn and Petit Bois islands are two of five Mississippi (MS) barrier islands that provide physical protection from tropical cyclones threatening the MS Gulf Coast, in addition to critical habitat for the northern Gulf of Mexico (GOM). In September 2004, Hurricane Ivan removed a large volume of sediment from the eastern ends of Horn and Petit Bois islands with its 1-2 m storm surge and ~194 kph wind speeds. Then, in August 2005 Hurricane Katrina severely impacted the two islands again with its 3.5-5.5 m storm surge on Horn and Petit Bois islands, and up to 204 kph wind speeds …

Influence Of Natural And Anthropogenic Environmental Variability On Larval Fish Diet, Growth, And Condition In The Northcentral Gulf Of Mexico, Angie Hoover

Master's Theses

The northern Gulf of Mexico experiences high levels of freshwater runoff annually from various sources including the Mississippi River and Mobile Bay, among other sources. Early life history stages of fishes are especially vulnerable to environmental variability created by freshwater discharge. The objectives of this study were to describe the available prey field, diet, growth and condition of larval fishes with respect to various effects of freshwater discharge in the northern Gulf. The first chapter compared these parameters in larval Gulf Menhaden (Brevoortia patronus) collected from three different water masses characterized by physical and biological parameters after the …

Late Quaternary Evolution And Stratigraphic Framework Influence On Coastal Systems Along The North-Central Gulf Of Mexico, Usa, Robert Hollis

Master's Theses

Coastal systems in the Gulf of Mexico are threatened to reduced sediment supply, storm impacts and relative sea level rise (RSLR). The geologic record can provide insights of geomorphic threshold crossings (formation, progradation, transgression, destruction) to these forcing mechanisms to predict future barrier evolution to climate change. The stratigraphic framework and antecedent topography directly influence coastal evolution over geologic timescales. This study synthesizes ~2100km of geophysical data, 700+ sediment cores, and 63 radiocarbon dates to regionally map two sequence boundaries, multiple ravinement surfaces and fourteen depositional facies. One marine isotope stage (MIS) 6 valley’s fill provided up to 300 x10 …

The Utility Of Foraminifera In Documenting Sediment Provenance For Overwash Deposits: A Case Study Using Sediments Deposited By Tropical Cyclone Pam In Vanuatu, Thomas Kosciuch

Master's Theses

Tropical cyclone inundation is a major threat to the highly exposed islands of the South Pacific. This vulnerability was highlighted in March 2015 when Tropical Cyclone (TC) Pam made landfall on Vanuatu as a Category 5 storm, impacting coastlines with storm surges that produced high water marks up to 7 m above MSL and deposited sediments up to 400 m inland. We examined the foraminiferal assemblages contained within TC Pam sediments at two locations in Vanuatu: a mixed-carbonate embayment (Manuro), and a volcaniclastic beach (Port Resolution Bay; PRB). At Manuro, the TC Pam sediments were up to 10 cm thick …

Environmentally-Driven Variation In The Population Dynamics Of Gulf Menhaden (Brevoortia Patronus), Grant D. Adams

Master's Theses

Gulf Menhaden (Brevoortia patronus) is an abundant forage fish distributed throughout the Northern Gulf of Mexico (NGOM). Gulf Menhaden support the second largest fishery, by weight, in the United States and represent a key linkage between upper and lower trophic levels. Variation in the population dynamics can, therefore, pose consequences for the ecology and economy in the NGOM. Here we aim to understand variation in the individual and population dynamics of Gulf Menhaden throughout ontogeny and how such variation relates to environmental processes. We utilized a suite of fishery-dependent and –independent, remote sensing, modeled, and in situ data …

Age, Growth, And Reproduction Of Vermilion Snapper (Rhomboplites Aurorubens) In The North-Central Gulf Of Mexico, Trevor Dalton Moncrief

Master's Theses

Vermilion Snapper is a commonly harvested species of reef fish in the northern Gulf of Mexico (GOM). It supports both a large commercial and popular recreational fishery, however knowledge of this fish’s life history is limited spatially. Non-linear curve fitting was used to estimate growth parameters and Akaike information criteria (AIC) was used to determine relative model fit. The 2-parameter von Bertalanffy growth function provided the best model fit and lowest AIC score. Histological examination indicated that Vermilion Snapper are batch spawners with asynchronous oocyte development. Additionally, 17% of Vermilion Snapper in the actively spawning phase containing 24 hour POF’s …

A Multi-Millennial Drought Reconstruction For West-Central New Mexico Using Rocky Mountain Juniper (Juniperus Scopulorum, Sarg.), Joshua S. Oliver

Master's Theses

A new multi-millennial tree-ring record from living and remnant Rocky Mountain juniper (Juniperus scopulorum, Sarg.) wood from Candelaria in west-central New Mexico is used to determine the temporal and spatial variability of scPDSI over the past two millennia (B.C. 492 to A.D. 2014). Our record indicates extreme drought events found within other hydroclimatic proxy records in the Colorado Plateau region spanning the time period (16^th century and 2^nd century megadroughts). By ranking the extreme drought events by magnitude, duration, intensity, and overall score, the most extreme drought events of this record are compared to drought events …

Modern Fair-Weather And Storm Sediment Transport Around Ship Island, Mississippi: Implications For Coastal Habitats And Restoration Efforts, Eve Rettew Eisemann

Master's Theses

The Mississippi – Alabama barrier island chain is experiencing accelerated sea level rise, decreased sediment supply, and frequent hurricane impacts. These three factors drive unprecedented rates of morphology change and ecosystem reduction. All islands in the chain have experienced land loss on the order of hectares per year since records began in the 1840s. In 1969, Hurricane Camille impacted as a Category 5, breaching Ship Island, and significantly reduced viable seagrass habitat. Hurricane Katrina impacted as a Category 3 in 2005, further widening Camille Cut. To better understand the sustainability of these important islands and the ecosystems they support, sediment …

Bloom Or Bust: Retrospective Analysis Of The Giant Jellyfish, Nemopilema Nomurai (Scyphozoa: Rhizostomeae), Ecology In The East Asian Marginal Seas, Naomi Yoder

Master's Theses

The Giant Jellyfish, Nemopilema nomurai, is a large-bodied bloom-forming jellyfish that occurs in the semi-enclosed basins of the East Asian Marginal Seas. N. nomurai has bloomed more frequently in the past 20 years than in any period previously recorded. In Japan, recent N. nomurai blooms were responsible for millions of dollars in lost revenue and equipment damage to commercial fisheries alone. This study statistically analyzed 21 environmental factors in connection with N. nomurai occurrence (using occurrence as a proxy for blooms). Eight factors resulted in a statistically significant or marginally significant (p ≤ 0.10), linear or non-linear relationship with …

Determining The Viability Of Recent Storms As Modern Analogues For North-Central Gulf Of Mexico Paleotempestology Through Sedimentary Analysis And Storm Surge Reconstruction, Joshua Caleb Bregy

Master's Theses

The northern Gulf of Mexico has been devastated by recent intense storms. Camille (1969) and Katrina (2005) are two notable hurricanes that made landfall in virtually the same location in Mississippi. However, fully understanding the risks and processes associated with hurricane impacts is impeded by a short and fragmented instrumental record. Paleotempestology could potentially use modern analogues from intense storms in this region to extend the hurricane record back to pre-observational time. Existing empirically based models can back-calculate surge heights over coastal systems as a function of transport distance, particle settling velocity, and gravitational acceleration. We collected cores in a …

An Integrated Drought Index (Idi) Incorporating Physical And Social Aspects, Rebecca L. Lanier

Master's Theses

The purpose of this research was to determine significant bio-physical (physical and environmental) and social variables that can be integrated into a drought index to predict areas susceptible to drought. Severe drought events are capable of causing millions of dollars in damage. The 1988 drought caused the United States approximately $40 billion in damage. Drought forecasting, modeling, and detection have, therefore, become imperative to understand the social, economic and environmental impacts of droughts, and also to explore how these impacts play a role in the occurrence of a drought. A number of drought indices widely used in the U.S. rely …

A Statistical Model For The Prediction Of Dissolved Oxygen Dynamics And The Potential For Hypoxia In The Mississippi Sound And Bight, Andreas Moshogianis

Master's Theses

Hypoxia events occur when dissolved oxygen concentrations fall below the minimum threshold (dissolved oxygen concentrations < 2 mg O₂ L^-1) necessary to avoid respiratory distress among aquatic organisms. In the Mississippi Sound and Bight, hypoxia is most prevalent from late-spring through late summer. Since hypoxia events can have dramatic effects on coastal fisheries, the spatial and temporal magnitude of hypoxia presents a clear threat to the productive fisheries in the northern Gulf of Mexico. Long-term hydrographic data were collected from eight sampling stations on a monthly basis from January 2009 to December 2011 along a cross-shelf transect from the mouth of …

The Distribution Of Dissolved Barium Along The U.S. Geotraces North Atlantic Transect: Impact Of Biogeochemical Processes, Circulation And Phase Association, Karen Renee Grissom

Master's Theses

During the last four decades, since the completion of the GEOSECS program, there has been a growing interest in the biogeochemical cycle of barium (Ba) due to its potential as a proxy for interpreting the geologic record. The typical barium distribution exhibits removal in the upper water column and regeneration at depth, consistent with its classification as a bio-intermediate element and similar to the nutrient-like profiles of silicic acid and alkalinity. To better constrain the uses of Ba, trace element clean samples were collected during the North Atlantic US GEOTRACES cruises.

The cycling of barium in the North Atlantic region …

Marine Snow Settling Velocities At An Oil Spill Site And A Control Site In The Northern Gulf Of Mexico, Clayton Hugh Dike

Master's Theses

After budgeting for response efforts and natural processes, over one million barrels of oil from the BP oil spill were unaccounted for. A hypothesis coined "The Dirty Blizzard" formed subsequent to observations of large and numerous oiled marine snow aggregates amidst the surface slick proposed that a large quantity of oil sank to depth via the aggregates. Having reached the seafloor, aggregates were subject to microbial degradation and to redistribution due to bottom currents. To assist in characterizing redistribution of particles near the seafloor, sediment traps, marine snow cameras, and acoustic Doppler current profilers (ADCPs) were deployed at two sites …

Methane Dynamics In St. Louis Bay, Mississippi, Hannah Marie Roberts

Master's Theses

A method of dissolved methane analysis was developed utilizing cavity ring-down spectroscopy and headspace equilibration. Samples of 70 mL were collected in 140 mL plastic syringes and equilibrated with a methane free headspace. Reproducibility was high (i.e. 4% typical RSD), and samples were successfully measured in the low nanomolar to high micromolar range. During method development, multiple research cruises were undertaken in the northern Gulf of Mexico. Stations included the Orca Basin, the Deepwater Horizon site, and the surrounding area. The Deepwater Horizon site showed no continuing leakage from October 2010 to June 2013. Samples collected from the northern Gulf …

Effects Of Selective Grazing By Microzooplankton On Phytoplankton Composition In A Subtropical Estuary, Amanda Marie Mcgehee

Master's Theses

Rates of phytoplankton growth and microzooplankton grazing were measured at two locations within the Bay of St. Louis, MS, over the course of three months to explore the dynamics of the phytoplankton community. Community growth rates were estimated based on the changes in chlorophyll a (chl a) concentration using the dilution technique, (Landry and Hassett, 1982) and a C-specific rate was obtained using chl a labeling (Redalje and Laws, 1981). Concentrations of chl a were determined using high performance liquid chromatography (HPLC) and fluorometry. HPLC was also employed to obtain class specific growth and grazing rates, using either marker pigments …

Characterization Of Rain And Stormwater Nitrogen Inputs To The Mississippi Sound: A Landscape Approach, Joshua Michael Allen

Master's Theses

Urbanization in coastal watersheds is becoming an increasingly important issue in the world. Increased impervious surface cover, a factor of urbanization, has drawn more attention to stormwater runoff as a source of contamination to receiving waters. In this study, nitrogen species from rain and stormwater were analyzed across three different landscape types along the Mississippi Sound (hardened, residential, and pristine), as well as from drainage pipes that flow directly into to the Mississippi Sound. Nitrogen stable isotopes were used to trace the stormwater nitrogen to the surface waters and biota within the Sound.

The objective of this study was to …