Life Sciences Commons^™

Addition And Subtraction: Coral Reproduction And Disease In A Changing Ocean, Ashley Rossin

LSU Doctoral Dissertations

Marine diseases are changing the landscapes of coral reefs particularly throughout the Western Atlantic. Stony coral tissue loss disease (SCTLD) swept through this region impacting at least 22 stony coral species. White plague (WP) is a more ephemeral disease, but still has a significant impact on coral reef health and perseverance, especially under a changing ocean. While these impacts are seen on the reef-scale, we can zoom into the tissue-level to identify disease markers for both diseases and identify their differences. This has ramifications for disease intervention, as well as mitigation strategies. Despite continuous disease outbreaks, healthy corals persist and …

Leveraging Multiple Data Sources: How Catch Data, Metadata, And Genetic Samples Can Aid The Recovery Of Endangered Smalltooth Sawfish (Pristis Pectinata), Kelcee Smith

LSU Doctoral Dissertations

The small population sizes characteristic of many imperiled species means that they are vulnerable to both demographic and genetic extinction threats. Responses to these threats (e.g., population trends, genetic diversity estimates) are often difficult to obtain, but critical for conservation. Thus, researchers studying imperiled species may have to consult multiple data sources, collaborate with a wide variety of stakeholders, or ask new questions about previously collected data. I used this approach to understand more about the United States (U.S.) population of Pristis pectinata, an endangered elasmobranch that has declined up to 95% due to habitat loss and bycatch in …

The Roles Of Host Species, Geographic Scale And Environmental Stressors In Shaping The Composition Of Coral Microbiomes, Alicia Marie Riegel Parker

LSU Doctoral Dissertations

Reef-building corals are long-lived and may take many centuries to adapt, making them especially susceptible to climate change. However, corals host microbial symbionts that can change quickly, potentially speeding acclimation. My dissertation aimed to determine the degree of coevolution and flexibility between corals and their microbiomes among hosts, across space, and in response to stress.

Microbial communities are usually surveyed by sequencing the 16S rRNA gene, however the PCR primers used also amplify coral DNA, thereby limiting prokaryotic read coverage. To mitigate this contamination, I designed a peptide nucleic acid clamp that increased the recovery of bacterial reads by 2-11x …

Insights To Gray Seal (Halichoerus Grypus) Foraging Ecology From Stable Isotope And Dna Metabarcoding Analyses, Keith Michael Hernandez

LSU Doctoral Dissertations

The enactment of wide-ranging conservation laws in the United States enabled the recovery of many marine mammal species. However, as many species have surpassed predicted recovery goals, there is an increasing number of marine mammal-human interactions. For example, in the northeast US, the recovery of gray seals (Halichoerus grypus atlantica), coupled with declines in commercially important fishery species, has prompted discussions of revised management, and potentially lethal control measures. Much of this concern stems from seal-fisheries interactions, which necessitates an understanding of seal diets and foraging ecology. However, existing research is out of date and reliant primarily on …

The Evolution Of Bivalve Shell Matrix Proteins, Mark Ira Duhon Ii

LSU Doctoral Dissertations

This dissertation focuses on the molecular underpinnings surrounding the evolution of the biomineralized shells of marine bivalves. Bivalve molluscs synthesize remarkably complex shells from calcium carbonate and an organic matrix of proteins secreted from the dorsal edge of the mantle. Molecular analyses of shell matrix proteins (SMPs) have suggested high rates of gene turnover despite the conserved nature of the shell itself. Here, I used proteomic and transcriptomic data to identify the SMPs and other biomineralization proteins from seven bivalve species that diverged 3-513 Mya. Contrary to previous studies that identified only a few shared biomineralization transcripts across the Bivalvia, …

Natural Variation And Evolutionary Responses To Climate Change Stressors In Marine Invertebrates, Joanna Sarah Griffiths

LSU Doctoral Dissertations

Our rapidly changing climate is putting many species at risk of extinction and there is an urgent need to understand how species will respond to these changes. In this dissertation, I evaluate how three species of marine invertebrates (corals, oysters, and copepods) respond to stressful conditions in their current environments and how plasticity and evolutionary adaptation could alter their response to future climate change stressors. I first employed a space for time study to elucidate population differences in the response of cold-water corals, Balanophyllia elegans, to future ocean acidification. I found evidence that upwelling history (natural low pH exposure) influences …

Impacts Of The Deepwater Horizon Oil Spill On Reproduction And Ontogeny Of Gulf Killifish (Fundulus Grandis), Charles Alexander Brown

LSU Doctoral Dissertations

On April 20, 2010, the Deepwater Horizon oil spill released an estimated 779 million liters of Macondo-252 crude oil into the Gulf of Mexico, making it the largest marine oil spill in history. Over a thousand kilometers of marshland that many species of fish use as a spawning grounds and nurseries was oiled, exposing breeding adult fish and their offspring to oil. My dissertation investigates the impacts of the Deepwater Horizon oil spill and associated remediation efforts on the reproduction and ontogeny of a sentinel ecotoxicological species, the Gulf killifish (Fundulus grandis). Concerns were raised regarding use of …

Habitat Associations And Reproduction Of Fishes On The Northwestern Gulf Of Mexico Shelf Edge, Elizabeth Marie Keller

LSU Doctoral Dissertations

Several of the northwestern Gulf of Mexico (GOM) shelf-edge banks provide critical hard bottom habitat for coral and fish communities, supporting a wide diversity of ecologically and economically important species. These sites may be fish aggregation and spawning sites and provide important habitat for fish growth and reproduction. Already designated as habitat areas of particular concern, many of these banks are also under consideration for inclusion in the expansion of the Flower Garden Banks National Marine Sanctuary. This project aimed to gain a more comprehensive understanding of the communities and fish species on shelf-edge banks by way of gonad histology, …

Population Dynamics And Demographics Of Spotted Seatrout, Cynoscion Nebulosus, Through Spatial Analysis: Towards An Integrative Management Approach, Ashley Melancon Baer

LSU Doctoral Dissertations

Spotted seatrout (Cynoscion nebulosus) is one of the most highly prized sportfish along the Gulf of Mexico coast, particularly in Louisiana. Although spotted seatrout are considered to be well managed and sustainably fished according to the state’s most recent stock assessment, the spatial ecology of this species is largely understudied in Louisiana waters. Acoustic telemetry is an innovative technology that is commonly used to assess the movements and behavior of aquatic species, and can be used as a tool to address the paucity of information on the spatial dynamics of spotted seatrout. The focus of this study was …

The Influence Of River Discharge On Fishes And Invertebrates Associated With Small Oil And Gas Platforms In Nearshore Louisiana, David Bradley Reeves

LSU Doctoral Dissertations

The nearshore region off Louisiana’s coast is one of the most productive areas in the United States. Nutrient-rich discharge from the Mississippi and Atchafalaya rivers forms the base of this productivity, but it also contributes to the annual formation of a large hypoxic zone (DO < 2.0 mg l^-1). This region contains >900 oil and gas platforms (platforms) that are de facto artificial reefs and support fish and invertebrate communities. In this dissertation, I examined how select platform-associated fishes and invertebrates responded to river-driven productivity and hypoxia. Settlement plates were used to compare barnacle production at depths of 2 and 7-m along …