Marine Biology Commons^™

Blue Crab Reproductive Output And Phenology In A Changing Climate, Blaise Rohan

Master's Theses

Globally, ecosystems are experiencing rising temperatures due to climate change, with potential consequences for reproductive investment and timing in many species. Blue crabs, Callinectes sapidus, support valuable commercial fisheries throughout the U.S. Atlantic and Gulf coasts, and understanding variation in reproductive output has important management and conservation implications. This study examined two components of blue crab reproduction: (1) reproductive investment across populations spanning multiple latitudes (New York, New Jersey, North Carolina, Mississippi, and Texas), using a space-for-time substitution to assess the effects of varying thermal regimes on fecundity and egg quality, and (2) spawning phenology in North Carolina from …

A Comparison Of Survival, Growth, And Stress Resilience In Three Different Lineages Of The Pacific Oyster (Crassostrea Gigas) Farmed On The California Central Coast, Victoria F. Hanshaw

Master's Theses

Aquaculture of Pacific oysters on the US West Coast is routinely impacted by seasonal unexplained mortality events. To better understand these large-scale mortality events in oyster aquaculture, shellfish growers and scientists in California have partnered together to conduct comparative, multi-estuary farm trials of discrete Pacific oyster (Crassostrea gigas) lineages. In this thesis we investigate how the more recently imported Midori lineage performs compared to the historically used Miyagi lineage, as well as a Hybrid (Midori x Miyagi) lineage. As part of a 7-month long field study from April-November of 2024 in Morro Bay and Tomales Bay, California, we evaluated …

Marine Heatwaves And Fish Reproduction: Endocrine Responses In The Eurythermal Sheepshead Minnow (Cyprinodon Variegatus), Isabel Villafuerte

Master's Theses

Marine heatwaves associated with climate change are increasing in frequency and severity, posing significant threats to fish populations in shallow habitats such as estuaries and salt marshes. Because temperature is a primary regulator of fish reproduction, understanding how heatwaves affect reproductive physiology is critical for anticipating the biological consequences of ongoing climate change for coastal fishes. Here we examined how simulated heatwave conditions affect the reproductive hypothalamic-pituitary-gonadal (HPG) endocrine axis in the estuarine sheepshead minnow (Cyprinodon variegatus), a eurythermal fish well suited to studying thermal stress responses in estuarine environments. Adult sheepshead minnows acclimated to a daily oscillating …

Evaluating The Commercial Aquaculture Potential Of The Native Pacific Littleneck Clam (Leukoma Staminea) As A Climate Resilient Alternative To The Non-Native Manila Littleneck Clam (Ruditapes Philippinarum)., Skylar M. Wuelfing

Master's Theses

The California shellfish industry’s near-exclusive reliance on the non-native Manila littleneck clam (Ruditapes philippinarum) creates an economic vulnerability to climate-driven disturbances, which can cause mortality events that eradicate up to 80% of stocks. This singular reliance on an introduced species highlights a need for the evaluation of native alternatives like the Pacific littleneck clam (Leukoma staminea). Our goal was to assess the feasibility of using the native Pacific littleneck in commercial aquaculture by comparing their performance to the non-native Manila littlenecks across the following conditions: 1) a five-month field outplant trial at high and low intertidal …

Seagrass Carbon Standing Stock In The Northern Gulf Of Mexico: The Role Of Seagrass Beds In Mississippi As Potential Blue Carbon Sinks, Devan Hildebrand

Master's Theses

Organic carbon stored in marine ecosystems is known as blue carbon. Seagrass beds have the ability to contribute to global blue carbon standing stocks through the uptake and sequestration of carbon from the water column. Through coastal management and conservation best practices, blue carbon habitats have the potential to help mitigate the effects of climate change. Although widely studied, knowledge gaps exist on the sediment carbon standing stock of seagrasses. I aim to better understand how persistent seagrass meadows surrounding barrier islands in the northcentral Gulf of Mexico contribute to long-term blue carbon standing stocks. Subaqueous sediment cores were collected …

Life History And Distribution Of Two Species Of Cownose Ray, Rhinoptera Bonasus And Rhinoptera Brasiliensis, In Mississippi Coastal Waters, Anna Millender

Master's Theses

Historically, the American Cownose Ray (Rhinoptera bonasus) was considered the only rhinopterid residing in the northern Gulf of Mexico (GOM); however, recent studies have confirmed the presence of the Brazilian Cownose Ray (Rhinoptera brasiliensis) throughout this region. The current study investigated the life history and distribution of both species within Mississippi waters, an area that previously represented a data gap for both species. From April 2016 – July 2025, 193 R. bonasus and 94 R. brasiliensis were analyzed to describe the reproductive biology. Reproductive timing, mating, gestation length, and parturition were similar among species. Although more …

Isolation Of The 2019 Bonnet Carré Spillway Effects On The Habitat Suitability Of Brown Shrimp (Farfantepenaeus Aztecus) And Blue Crab (Callinectes Sapidus) Using A Modeling Approach, Mallory Dyson

Master's Theses

In 2019, an unprecedented flood year, the Bonnet Carré Spillway (BCS) was opened on two separate occasions (February 27^th to April 11^th, and May 10^th through July 27^th) diverting a volume 6 times the volume of Lake Pontchartrain into the surrounding coastal waters of Louisiana, Mississippi, and Alabama. The goal of this research was to determine the spatio-temporal influence of these freshwater releases on two economically and ecologically important species (Farfantepenaeus aztecus and Callinectes sapidus) with variable responses to salinity and temperature depending on the age class. The Habitat Suitability Index (HSI) …

Understanding The Habitat Associations Of Nearshore Rockfishes Inside And Outside Of Marine Protected Areas Using Hook-And-Line Data, Kaila Raeanne Fritch

Master's Theses

Habitat is an important driver in shaping the distribution of a range of species. For demersal fish species, benthic habitat characteristics can drive distribution and community structure. Understanding the relationship between habitat and species distribution in important, especially for exploited species such as rockfishes (Sebastes spp.). Increased data on the relationship between rockfish and benthic habitat characteristics could enhance marine protected areas (MPAs) and management practices which are used to protect rockfishes along the U.S. West Coast. To address this, we used hook-and-line, catch-and-release data that were collected inside two MPAs on the central coast of California, and …

Movement Ecology And Trophic Dynamics In The Northern Gulf Of Mexico: Implications For Fisheries Management, Calvin Chee

Master's Theses

The northern Gulf of Mexico (nGOM) is a diverse and productive region for living marine resources. The region supports lucrative commercial and recreational fisheries ranging from low-trophic-level species, such as penaeid shrimps and forage fishes, to high-trophic-level predators (e.g. Yellowfin Tuna). This thesis contributes to the region’s ecological knowledge, with the primary aim of enhancing management efforts and providing direct management advice to two important fisheries. In Chapter 1, we develop a traditional per-recruit model for Southern Flounder, as well as a spatiotemporally integrated per-recruit model that incorporates the spatial distribution of fishing effort and the stock’s movement ecology. Fish …

Investigating Nekton Response To Changing Salinities In The Mississippi Sound: An Experimental And Statistical Approach, Adam Murray

Master's Theses

The Mississippi Sound provides nursery habitats for many coastal species and is recognized for its commercial fisheries. Previous freshening events linked to the Bonnet Carré Spillway, a Mississippi River flood diversion structure, proved catastrophic for oyster populations in the Mississippi Sound, but effects on mobile fish and shellfish species are not well-defined. The planned Mid-Breton Sediment Diversion (MBSD), an initiative to combat wetland loss, is also forecasted to lower salinities in the region, increasing the need to better understand responses of commercially and ecologically important species to freshening events. The objective of this study was to characterize effects of salinity …

Juvenile And Subadult Gulf Sturgeon (Acipenser Desotoi) Use Of The Pascagoula River Estuary, Sarah Stovall

Master's Theses

Gulf Sturgeon (GS) are an anadromous species currently listed as “Threatened” under the Endangered Species Act. They reside in habitats across the northern Gulf of Mexico including coastal rivers, estuaries, and marine waters, making annual migrations between freshwater and marine habitats for spawning/summer resting and feeding, respectively. Since past studies prioritize adult movement, understanding how and when juvenile and subadult GS use the Pascagoula River estuary (PRE), a complex, bifurcated river delta federally designated as critical habitat is necessary to improve conservation efforts. My thesis assessed juvenile and subadult GS use of the PRE across four years (2020-2024) by analyzing …

3d Printed Microfluidic Fabrication Methodology, Characterization, Mechanical Design, And Applications In Electrostatic Artificial Muscles And Benthic Microbial Fuel Cells, Terak B. Hornik

Master's Theses

The fabrication of microfluidic devices often requires specialized methods. The development of these methods requires careful characterization and understanding of the processes involved. Using primarily PolyJet 3D printing technology, microfluidics offers a wide scope of applications such as microfluidic benthic microbial fuel cells (MBMFCs) and electrostatic artificial muscles. MBMFCs benefit from the confinement of the microbes resulting in close proximity between the electrode and the organisms. Using a modular design called the Sponge, assembly and upscaling is possible. Electrostatic artificial muscles benefit from a microfluidic approach due to the non-linearity of electrostatic attraction creating disproportionate benefits when miniaturized. When designed …

Biometric Assessment Of Spotted Seatrout (Cynoscion Nebulosus) From Recreational And Commercial Fisheries In Mississippi, Usa, Nimah Folake Osho-Abdulgafar

Master's Theses

Quantitative stock assessments for Mississippi’s Spotted Seatrout use length-, age-, and sex-composition data from fishery-independent sources as proxies to estimate biostatistical characteristics of fisheries harvests due to lack of sector-specific data. In Chapter 2, I examined the age, length, and sex composition of Spotted Seatrout from three fishery-dependent sectors. Between April and December 2023, I collected 210 fish (n = 19, 124, and 67 from private, charter, and commercial sectors, respectively). The length ranged between 373-535mm, 285-523mm, and 345-568mm TL, with mean ± SD lengths of 453 ± 51mm, 393 ± 57mm, and 442 ± 53mm TL, respectively. Age ranged …

Projected Range Shift Of The Atlantic Surfclam, Spisula Solidissima, And The Ocean Quahog, Arctica Islandica, Under Climate-Induced Benthic Warming: Forecasting Fishery Influence In The Mid-Atlantic Bight Throughout The 21st Century, Molly Mae Spencer

Master's Theses

The Atlantic surfclam, Spisula solidissima, and ocean quahog, Arctica islandica, are biomass dominant bivalve species on the eastern North American continental shelf, both supporting lucrative commercial fisheries in the Mid-Atlantic with a combined value of $53.6 million in ex-vessel revenue per year. Rapid climate change is expected to modify the geographic range of these bivalve populations across the Mid-Atlantic Bight (MAB), suggesting transformative consequences for the surfclam fishery. This study forecasted future distributions of the two species from years 2016 – 2095, based on projected bottom water temperatures and a temperature-dependent population dynamics model, to project subsequent fishery-based indicators …

Development Of A Flow Cytometry Method For The Identification And Enumeration Of Enterococcus Faecalis, Riza Magbitang

Master's Theses

A multi-color flow cytometry method coupled with fluorescent staining was developed to detect and quantify E. faecalis concentrations in coastal waters as an alternative to the traditional membrane filtration method. The developed method was used to characterize E. faecalis during batch growth and yielded consistent results across the various physiological states of the cells. Additionally, the application of propidium iodide (i.e., a viability stain), afforded the method the ability to differentiate between cells with intact and compromised cell membranes, which raises the potential of quantifying cells that are in viable-but-non-culturable (VBNC) state. Initial field test using natural seawater samples spiked …

Examining The Effects Of Food Supply On Eastern Oyster (Crassostrea Virginica) Larval Performance And Settlement Potential In Delaware Bay And Mississippi Sound, James C. Klein

Master's Theses

Oyster population maintenance and growth require sufficient larval stocks capable of timely development, growth, and successful metamorphosis, whereby larval performance and settlement potential determines the capacity for a larval cohort to effectively establish into an existing population. Exogenous factors influencing larval performance include temperature, salinity, and particularly food supply. Regarding food, a sufficiently abundant and nutritionally balanced diet composed of protein, lipids, and carbohydrates is critical for successful metamorphosis. The influence of exogenous factors on Crassostrea virginica settlement potential were examined in Delaware Bay and Mississippi Sound by incorporating in situ environmental conditions and food supply metrics into a well-established …

Deep Ocean Vehicle Applications And Modifications, Nichole "Nikki" T. Arm

Master's Theses

This project had two primary goals: (1) to explore opportunities to further a deep-ocean vehicle’s reach using alternative pressure spheres, and (2) to implement an existing deep-ocean vehicle (lander) in active scientific research.

I gained a greater understanding of the limitations and design choices made for existing pressure spheres using Finite Element Analysis (FEA). My simplified FEA model predicted sphere failure for the existing 30% Fiber Glass 70% Nylon injection molded spheres at an external pressure of 3,954psi or 2,690m ocean-depth (only a 7.38% error compared to the tested minimum failure depth), so I determined it a valid model. I …

Evaluating Habitat Use By Nekton In Widgeon Grass (Ruppia Maritima), Shoal Grass (Halodule Wrightii), And Unvegetated Bottom Habitats In The Grand Bay National Estuarine Research Reserve, Jessica Woodall

Master's Theses

Seagrass beds support high biodiversity and animal abundance, serve as feeding grounds for a variety of animals, offer shelter from predation, and act as a nursery habitat for juveniles. The species composition of seagrass beds can impact their use as habitat by animals. Two common species of seagrass in the Gulf of Mexico are Ruppia maritima (widgeon grass) and Halodule wrightii (shoal grass). The shallow coastal waters of the Grand Bay National Estuarine Research Reserve (NERR) support both species, but the use of each seagrass as habitat by nekton is poorly understood, which can limit management decision-making. Nekton communities were …

Effects Of Intertidal Position On The Response To Oxygen And Desiccation Stress In The Common Acorn Barnacle, Balanus Glandula, Megan M. Dotterweich

Master's Theses

Sessile invertebrates in the rocky intertidal experience intermittent periods of air exposure due to tidal flux, presenting risks of temperature extremes, hypoxia, nutrient limitation, and most dangerously, desiccation. Microscale variation in severity and frequency of these risks is widely dependent on vertical position within the intertidal zone. Common acorn barnacles (Balanus glandula) have a wide vertical distribution in the intertidal, creating large differences in microhabitat between the highest and lowest individuals in the population. This study set out to explore whether tidal position dependent differences exist in the response to oxygen and desiccation stress in B. glandula. …

Marine Protected Areas And Oceanographic Variability: Impacts On Blue Rockfish (Sebastes Mystinus) And The Human Dimensions Of Collaborative Fisheries Research, Erin M. Johnston

Master's Theses

Fishing pressure and environmental variability are two of the most impactful drivers of fish populations worldwide. It is critical to effective management to understand the intersection between the two and how each may affect fish population dynamics, especially for exploited nearshore species like rockfishes (Sebastes spp.). This is especially true as models indicate that global climate change will dramatically increase the frequency and severity of large-scale oceanographic perturbations. We were interested in whether we could detect changes in relative abundance of nearshore rockfishes relative to large-scale oceanographic events using a broad-scale index like the Multivariate Ocean Climate Indicator …

Trace Dna Detection Using Diamond Dye: A Recovery Technique To Yield More Dna, Leah Davis

Master's Theses

This study aspires to find a new screening approach to trace DNA recovery techniques to yield a higher quantity of trace DNA from larger items of evidence. It takes the path of visualizing trace DNA on items of evidence with potential DNA so analysts can swab a more localized area rather than attempting to recover trace DNA through the general swabbing technique currently used for trace DNA recovery. The first and second parts consisted of observing trace DNA interaction with Diamond Dye on porous and non-porous surfaces.

The third part involved applying the Diamond Dye solution by spraying it onto …

Estimation Of Mortality Rates For The Gulf Menhaden Stock And Reference Point Implementation For The Fishery, Catherine Wilhelm

Master's Theses

The Gulf menhaden stock is the target of a large commercial fishery in the Gulf of Mexico. To address the needs of both the stock and fishery, I performed two studies. I first addressed the natural mortality rates currently used in the Gulf menhaden stock assessment. To update these rates, I used data from a tagging study conducted from 1970 to 1988. Adult and juvenile menhaden were tagged, released, and recovered in fish processing plants. To evaluate the data, I built a Bayesian model using the negative binomial distribution to estimate natural mortality, catchability, and the overdispersion factor parameters. I …

Rattus Norvegicus As A Biological Detector Of Clandestine Remains And The Use Of Ultrasonic Vocalizations As A Locating Mechanism, Gabrielle M. Johnston

Master's Theses

In investigations, locating missing persons and clandestine remains are imperative. One way that first responder and police agencies can search for the remains is by using cadaver dogs as biological detectors. Cadaver dogs are typically used due to their olfactory sensitivity and ability to detect low concentrations of volatile organic compounds produced by biological remains. Cadaver dogs are typically chosen for their stamina, agility, and olfactory sensitivity. However, what is not taken into account often is the size of the animal and the expense of maintaining and training the animal. Cadaver dogs are typically large breeds that cannot fit in …

Multispecies Use Of Various Habitats In The Mississippi Sound With An Emphasis On Future Oyster Reef Construction, Austin Draper

Master's Theses

Transient fish have high economic value and effective restoration projects must consider the variable impacts they may have on these fish in addition to the target organism or habitat being restored. Globally, oyster reef construction is common and will continue but data on their impacts to transient fish is lacking. This study used acoustic telemetry to provide baseline data on the potential for interaction between five transient fish species, and oyster reef construction activities. Overall, I noted that habitat preferences are hierarchical with sandy habitats nearest to bay or river mouths having high transient fish use. Oyster reef construction in …

Habitat Use Of Gulf Sturgeon (Acipenser Oxyrinchus Desotoi) In Pascagoula River Holding Areas And In Estuarine And Marine Environments Including Ship Island, Mississippi And Mobile Bay, Alabama, Elizabeth M. Greenheck

Master's Theses

Gulf Sturgeon (GS) are a federally threatened, anadromous species that inhabit coastal rivers in the northern Gulf of Mexico and make annual migrations between riverine and marine habitats. They are divided into western or an eastern river systems based on the location of their natal river relative to Mobile Bay. Tracking of GS movements using acoustic telemetry has occurred since the late 1990s but has increased in use since 2015 for monitoring important habitats that GS rely on throughout their lifetime. For this study, tagged GS were monitored in three areas throughout the central Gulf of Mexico: the Mobile Bay …

The Rise Of Terrorism In Africa And What It Means For U.S. Policymakers, Bridget Mary Hughes

Master's Theses

This thesis utilizes three case studies to measure the rise of terrorism in Africa. This qualitative data leads the reader to one ultimate question: what does the rise in terrorism in Africa mean for the United States (U.S.) and U.S. policymakers, National Security academia, students in National Security, if anything at all? The answer is: if civilian and military compounds are being targeted by these violent extremists, as these three case studies demonstrate, it is my recommendation that U.S. policymakers cease sending troops to the African theater and, instead, allocate funding to the citizens and nonprofits of the countries whom …

Effects Of Shoreline Development And Freshwater Discharge On Nekton Assemblage And Trophic Structure In A Northern Gulf Of Mexico Estuary, Glenn Schumacher

Master's Theses

Coastal salt marshes support a diversity of nekton and facilitate critical ecosystem functions but are threatened by shoreline development and climate change. Therefore, coastal ecosystem managers have begun incentivizing the use of living shorelines (LS), erosion control structures incorporating native plantings, to mitigate ecological consequences of marsh loss. However, post-restoration climate changes may shift habitat templates and negate positive effects of ecosystem restoration. I evaluated the ecology nekton along LS, natural marshes, hardened shorelines and greyed shorelines within Biloxi Bay, Mississippi, during a high freshwater discharge (HFD) period by comparing nekton assemblage (using species richness, Shannon-Wiener diversity, and relative abundance), …

Induced Spawning Of Captive Tripletail Lobotes Surinamensis, Nicholas Adams

Master's Theses

The Tripletail, Lobotes surinamensis, is an emerging candidate species for U.S. marine aquaculture. This work aimed to address two bottlenecks for hatchery production of the species by developing a hormonal induction protocol to obtain fertile spawns from captive brooders and a method for sex identification of candidate brooders.

Single pairs selected among a captive-held broodstock conditioned under a natural photothermal cycle were induced with one of five treatments (n = 5 or 6 replicates per treatment). Control (no hormone) and hCG (1,100 IU.kg^-1 for females, 550 IU.kg^-1 for males) pairs did not spawn. Pairs treated with GnRHa …

Using Deep Learning And Uav Imagery To Detect Elkhorn Coral In St. Croix’S East End Marine Park, Samuel Wyatt

Master's Theses

Elkhorn coral, or Acropora palmata, is an important reef building species that promotes species abundance and other ecological services to the communities in the US Virgin Islands. We captured high resolution imagery of a reef in St. Croix’s East End Marine Park using a Wingtra One UAV. We then used deep learning techniques to detect individual coral colonies. We compared two deep learning models, FasterRCNN and MaskRCNN, and found that the models achieved accuracy shores up to 0.78. These scores improved when examining only larger corals in shallow waters. The model was able to both detect Elkhorn coral and …

Effects Of Intertidal Position On The Capacity For Anaerobic Metabolism And Thermal Stress Response In The Common Acorn Barnacle, Balanus Glandula, Kyra Anderson

Master's Theses

Intertidal habitats are characterized by dynamic, tidally-driven fluctuations in abiotic and biotic factors. Many of the environmental stressors that vary across the intertidal (e.g., temperature, oxygen, food availability, predation pressure) are strong drivers of metabolic rate in ectotherms. As such, we predicted that there may be pronounced differences in the metabolic and stress physiology of conspecific sessile invertebrates occupying at different relative tidal heights. The common acorn barnacle Balanus glandula represents an ideal model organism in which to investigate the possibility of tidal height-dependent physiological differences, owing to their wide distribution in the intertidal zone and their eurytolerant nature. In …