This work examines several volume attributes extracted from 3D seismic data with the goal of seismic facies classification and lithology prediction in intraslope minibasins. The study area is in the Keathley Canyon protraction (KC), within the middle slope of the Northern Gulf of Mexico (GOM). It lays within the tabular salt and minibasins province downdip of the main Pliocene and Pleistocene deltaic depocenters. Interaction between sedimentation and mobile salt substrate lead to the emergence of many stratigraphic patterns in the intraslope minibasins. Interest in subsalt formations left above salt formations poorly logged. Facies classification using Artificial Neural Network (ANN) was applied in those poorly logged areas. The resultant facies classes were calibrated and used to predict the lithology of the recognized facies patterns in an intraslope minibasin, away from well control. Three types of facies classes were identified: Convergent thinning, convergent baselaping and bypassing. The convergent baselaping are found to be the most sand rich among all other facies.

The deep-sea is the largest habitat on earth, containing over 90 percent of the world’s oceans and home to over 20,000 species. Deep-sea ecosystems are increasingly impacted by human activities including fishing and oil extraction. To understand potential impacts on deep-sea food webs, it is crucial to gather baseline data in these systems. I quantified the trophic interactions of three groups of deep-water animals across a range of trophic levels living in the northern and eastern Gulf of Mexico using stable isotope analysis. First, I propose methods for correcting δ15N values for the presence of nitrogenous metabolic waste products (e.g., urea) in muscle tissue using chemical extractions and/or species-specific mathematical normalizations. Significant differences in δ15N, %N, and C:N values as a result of extractions were observed in eight of ten shark and all three hagfish species. The δ15N values increased, but shifts in %N and C:N values were not unidirectional. Mathematical normalizations for δ15N values were successfully created for four shark and two hagfish species. I then describe the trophic interactions of three consumer assemblages. Carbon isotopic values indicate a heavy reliance on allochthonous nutrient inputs from surface waters. Nitrogen isotopic values reveal somewhat atypical taxa as top predators in the deep sea. Shark, teleost, and invertebrate species across a wide range of body sizes are feeding at a similar trophic level. This apparent lack of size structuring could be the result of a high degree of opportunistic scavenging or perhaps feeding at many trophic levels simultaneously in an oligotrophic system. There was a high degree of isotopic niche overlap among species within each consumer assemblage, perhaps the result of limited nutrient resources in the deep-sea. In general, individuals from the northern sampling stations displayed higher δ13C and δ15N values than those from the eastern sites. With the exception of a few species, there were no strong relationships between body size and isotopic values. The present study is among the first characterizations of the trophic structure of deep-sea organisms in the Gulf of Mexico and establishes system baselines for future studies describing deep-water systems and investigating anthropogenic impacts.

Artificial reefs have been deployed throughout the world’s oceans to act as habitat and fishing enhancement tools. To expand current research on the role of artificial reefs in the marine community, ordination and multivariate regression methods were used here to analyze survey data of natural and artificial reefs. The reefs, located in the Northern Gulf of Mexico (NGOM) and on the West Florida Shelf (WFS), had been previously surveyed from 2004 to 2015 using remote operated vehicle and stationary video techniques. This study tested the hypothesis that similar functional roles are accounted for at both natural and artificial reef sites even if species composition varies. Secondly, it examines the role of environment and fisheries in determining the assemblages. Artificial reefs tended to host communities that were as biodiverse as natural reefs, although not necessarily composed of the same species. Results of an ordination confirmed that as the classification was broadened from the level of species, to family, to functional group, the assemblages on each reef type (natural vs. artificial and NGOM vs WFS) appeared more similar. Dominant groups were present at all levels of classification and included the families Lutjanidae and Carangidae, as well as functional groups Red Snapper and Small Reef Fish. Both natural and artificial reefs tended to be dominated by one of the following: Lutjanidae, Carangidae, or Small Reef Fish, although a continuous gradient was found across the extremes of natural versus artificial reefs. Generalized Additive Models were developed to examine the influence of reef type, location, environment and fishing intensity covariates. Results indicated that for both natural and artificial reefs, the abundance of families and functional groups can be influenced by environmental factors. In both cases, there is strong spatial autocorrelation suggesting connectivity with neighboring reefs.

Several studies have found separation of biogeographic provinces on the West Florida Shelf (WFS), but the location of this separation differs depending on different organisms with faunal boundaries proposed at Apalachicola, Cedar Key, Anclote Key. Tampa Bay, Charlotte Harbor, Cape Romano, or Cape Sable. Biogeographic boundaries can be gradual over a given space and are often species-specific. Analyses of marine benthic mapping and community characterization of Florida’s West-central coast shallow water (depth) hardbottom habitats indicate a major shift in the benthos across Tampa Bay. Quantitative benthic surveys of 29 sites yielded a total of 4,079 individuals of nine stony coral species and 1,918 soft coral colonies. Populations were dominated by four species of corals: Siderastrea radians, Oculina robusta, Solenastrea hyades, and Cladacora arbuscula. Most corals were less than 10 cm in diameter. Cluster analyses of coral density and major functional group percent cover showed distinct differences in hard and soft coral densities and species demographics from south to north with clear spatial patterns between regions. These benthic hardbottom coral communities change over a relatively small spatial scale (10’s of km), indicating a biogeographical province or ecosystem region boundary in marine benthic communities at, or very near, the mouth of Tampa Bay. Broader studies are needed to identify the shifts in benthic community biogeography along the West Florida Shelf.

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The catchability coefficient is used in most marine stock assessment models, and is usually assumed to be stationary and density-independent. However, recent research has shown that these assumptions are violated in most fisheries. Violation of these assumptions will cause underestimation of stock declines or recoveries, leading to inappropriate management policies. This project assesses the soundness of stationarity and density independence assumptions using multi-species data for seven stocks and four gears in the U.S. Gulf of Mexico. This study also develops a multi-species methodology to compensate for failures of either assumption. To evaluate catchability assumptions, abundance-at-age was reconstructed and compared with catch-per-unit-effort data in the Gulf. Mixed-effects, Monte Carlo, and bootstrap analyses were applied to estimate time-varying catchability parameters. Gulf data showed large and significant density dependence (0.71, s.e. 0.07, p<0.001) and increasing trends in catchability (2.0% annually compounding, s.e. 0.6%, p < 0.001). Simulation modeling was also used to evaluate the accuracy and precision of seven different single-species and multi-species estimation procedures. Imputing estimates from similar species provided accurate estimates of catchability parameters. Multi-species estimates also improved catchability estimation when compared with the current assumptions of density independence and stationarity. This study shows that multi-species data in the Gulf of Mexico have sufficient quantity and quality to accurately estimate catchability model parameters. This study also emphasizes the importance of estimating density-dependent and density-independent factors simultaneously. Finally, this study shows that multi-species imputation of catchability estimates decreases errors compared with current assumptions, when applied to single-species stock assessment data. / Master of Science

Uniaxial consolidation experiments on Mass Transport Deposit (MTD) and non-MTD core samples from Ursa Basin, Gulf of Mexico, show MTDs have a lower porosity at a given effective stress compared to adjacent non-MTD sediments; a behavior observed in additional experiments on lab remolded Ursa core and resedimented Boston Blue Clay (BBC). I hypothesize debris flow action remolded the sediment: removing its stress history through shearing action, resulting in dense sediments at shallow depth. I supplement testing this hypothesis through lab remolding of BBC (in addition to Ursa clay) due to the greater availability and knowledge of this material. Ursa MTDs record multiple submarine slope failure events within the upper 200 meters below sea floor (mbsf); the most prominent is labeled MTD-2. MTDs have lower porosity and higher bulk density than surrounding, non-MTD, sediment. Porosity ([phi]) is 52% at 125mbsf – immediately below MTD-2; whereas [phi] is 46% at 115mbsf – within MTD-2. Comparison of non-MTD samples to MTD-2 samples, and intact to remolded samples, shows a decrease in sediment compressibility (Cc) within the MTD-2 and remolded sediments. Permeability within Ursa mudstones also declines with porosity according to: log (k) = A[phi] - B. Permeability is slightly higher within MTD-2; however grain size analysis indicates lower clay content in MTD-2 versus the non-MTDs. Pre-consolidation stress interpretations from the experiments show a linear trend in both MTD and non-MTD sediments, indicating both geologic units depict the same pore pressure profile. Remolding via debris flow explains the origin of MTDs at Ursa and governs the evolution of this geologic unit to its dense, highly consolidated, state today. At some point, slope failure triggered movement of the sediment down slope in form of a debris flow. The shearing action of the debris flow weakened the sediment, reducing its ability to support the overburden. As consolidation resumed, the remolded sediment followed a new, less steep, Cc curve. Within the geologic record, a distinctive dense, shallow unit is preserved; evidence for historical slope failure. / text

The vertical and horizontal distributions of Euphausiacea in the northern Gulf of Mexico, including the location of the Deepwater Horizon oil spill, were analyzed from 340 trawl samples collected between April-June, 2011. This study is the first comprehensive survey of euphausiid distributions from depths deeper than 1000 m in the Gulf of Mexico and included stratified sampling from five discrete depth ranges (0-200 m, 200-600 m, 600-1000 m, 1000-1200 m, and 1200-1500 m). In addition, this study encompasses the region heavily impacted by the Deepwater Horizon oil spill. Data presented here could potentially be used in ecosystem models investigating trophic effects of the spill because euphausiids are the preferred prey of a variety of higher trophic organisms. Lastly, these data represent the first quantification of euphausiid assemblages in this location after the Deepwater Horizon event and can serve as a basis of comparison against which to monitor recovery of the euphausiid assemblage after exposure to Deepwater Horizon hydrocarbons and dispersant in the water column.

This study aims to establish a depositional framework for an area of the Louisiana shelf, north-central Gulf of Mexico. The depositional history of the study area is poorly understood, especially within the last cycle of major eustatic fluctuation (~18, 000 yrs BP – present). Data sets used in this study include pre-existing and previously unanalyzed two-dimensional, highresolution seismic profile records (Acadiana 86 and Acadiana 89), geotechnical foundation boring data (Coleman and Roberts, 1988a), and an industry lease block survey report (Cole, 1983). Seismic sequence stratigraphic methods are employed in this study to analyze seismic profile data. Seismic sequence analysis results indicate the presence of five unconformable surfaces and five seismic facies units. Through correlation of seismic profile data with lithologic and chronologic data, it is possible to conclude that these seismic facies units represent shelf-margin deltaic deposition during the last lowstand of sea level (~18, 000 yrs BP), sourced by the Pearl River. .