Salt tectonics has important implications for hydrocarbon exploration in saltbearing basins since salt deformation can directly or indirectly form hydrocarbon traps, influence hydrocarbon migration, and can control deepwater depositional systems. In various basins around the globe, extensive research has been conducted on initiation of salt mobilization, subsequent deformation, and eventual cessation, mostly from subsurface two-dimensional (2D) sections. However, 3D seismic data has dominated the petroleum industry for the last 30 years. Despite the plethora of 3D seismic data acquired in salt-bearing basins, there has been hardly any published work on the 3D geometries of complex salt bodies. 3D salt mapping in the subsurface can reveal true distribution of salt bodies and their detailed intricacies of geometrical variations, aiding in the overall salt system interpretation. Using a large 3D seismic survey (3,350 km2), this study presents the first 3D salt mapping in the Gulf of Mexico, demonstrating how 3D visualization of the entire Louann Salt system within the Middle Jurassic to presentday stratigraphy can improve interpretation of salt feeder geometries, allochthonous salt canopies, initial salt distribution, and salt weld locations in the study area.

This Dissertation combines the investigation of the sedimentological impacts of the Deepwater Horizon (DwH) blowout event in the deep-sea benthos, with the refinement and advancement of methods and approaches for high-resolution investigations of events preserved in sedimentary records. An approach that combined, rapid collection of cores, a continued annual time series collection of cores, and high-resolution sampling and analyses, in particular short-lived Radioisotopes (SLRad), enabled the temporal resolution required to detect the sedimentary response to the short-duration DwH event, and evaluate post-event sedimentation patterns at a comparable time scale (months). The collection of 179 sediment cores from 80 sites between the fall of 2010 and 2016 included four sites that were utilized as an annual time-series collection to define the sedimentary response to the DwH blowout event and how the sedimentary system evolved/recovered post-event. High-resolution (2mm) sub-sampling was utilized to maximize the temporal resolution of analyses and age control using SLRad. The rapid collection of cores to define the immediate benthic impact(s), as well as the use of time-sensitive indicators of the event that may degrade over time, as well as indicators for very short time scale (months) sedimentation, such as 234Thxs. 234Thxs inventories and mass accumulation rates (MAR’s) were one of the most diagnostic characteristics of the sedimentary response. The DwH blowout event led to a Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA) event that caused a depositional pulse to the seafloor. This was defined by increased sedimentation rates and the shutdown of bioturbation as indicated by 234Thxs inventories and MAR’s. The annual collection of sediment cores as a time-series allowed for continued high-resolution analyses and use of 234Thxs to determine post-event sedimentation rates and baselines on monthly time scales for direct comparison to the depositional pulse. Within ~one year sedimentation rates decreased and within three years site specific return of bioturbation occurred and sedimentation rates on monthly scale (234Thxs) stabilized. Also, within ~three years the sedimentary signature of the depositional pulse became undetectable with respect to sediment texture and composition possibly due to dilution of this indicator by mixing/bioturbation and/or compaction of the event layer. Without the use of high-resolution sampling and geochronological tools such as 234Thxs the depositional pulse would not have been detected in the sedimentary system. The continued use of these high-resolution methods allowed for further defining the magnitude of the sedimentary response to the DwH event as well as provide baseline sedimentation patterns at a monthly time scale. The annual time series defines the post-event evolution of the sedimentary system as well as the assessment of the post-depositional alterations that influence the integration and preservation of such sedimentation events in the sedimentary record. This includes the potential for re-mobilization of event sediments, potential re-exposure of ecosystems to contaminated sediments and redistribution of event sediments. Alternatively, burial and alteration of the sedimentary signature over time influences the preservation potential of sedimentation events such as DwH, with decreasing ability to detect events due to bioturbation, degradation of signature and compaction. The refinement of methodology and approaches, in particular short-lived radioisotope (SLRad) geochronology, allowed for the high-resolution determination of the sedimentary impacts of the DwH blowout event. In turn, the opportunity to investigate the DwH event in real time provided the opportunity to advance high-resolution methodologies in an applied fashion. Continued refinement of high-resolution approaches and methods, in particular geochronologies, will allow for the detection of short-duration and subtle sedimentary events in real time as well as in the sedimentary record. Through the application of such approaches and methods to real events, these methods can be further refined and assessed for their utility and limitations.

archives@tulane.edu / Salt basins are complex structural systems, showing genetic relationships between salt structures, faults, and variable sediment depositional patterns. The dynamics of salt-fault interaction, the role of shale deformation, and the influence of salt evacuation on surface features have been poorly understood. A link between all these processes is the throw history of faults adjacent to and within a salt basin. In this dissertation, I interpret industry well logs and 3D seismic data from the Terrebonne Salt Withdrawal Basin (TSWB) of southeastern Louisiana, to understand these processes. The methodology includes the use of fault throw maps, throw variations along strike and with depth, and sediment expansion indices to understand fault kinematics adjacent to sediment loads and mobile material, i.e., salt or shale. I address the histories of three faults along the northern margin of the TSWB: the Lake Boudreaux, Montegut, and Isle de Jean Charles faults. Each shows Miocene and Quaternary active phases correlated with sediment loading, separated by relative inactivity during the Pliocene. The pattern of Quaternary activity and the surface projections of these faults are consistent with a fault-controlled pattern of wetland loss, suggesting that faults in southeastern Louisiana are active. Isle de Jean Charles fault and the Lake Boudreaux fault interact with the Bully Camp and Lake Barre Salt stocks, respectively. Each stock is interpreted to have grown by a different diapiric mechanism, consistent with different spatial patterns of throw variation on the two faults, despite similar temporal histories. Throw on the Isle de Jean Charles fault increases towards the Bully Camp stock, suggesting deformation inside and outside the stock. In contrast, a decrease in the throw on the Lake Boudreaux fault and an increase in diameter of the Lake Barre stock indicate that deformation exists only within the stock. Additionally, this dissertation considers throw patterns along the southern margin of the TSWB, showing that faults linking the Dog Lake and Caillou Island salt stocks are affected by shale deformation adjacent to salt. These results show that studies of fault-related subsidence and wetland loss in coastal Louisiana need to include observations from nearby salt structures. / 1 / Akinbobola Akintomide

Oyster reefs provide valuable ecosystemservices that contribute to coastal resilience. Unfortunately, many reefs have been degraded or removed completely, and there are increased efforts to restore oysters in many coastal areas. In particular, much attention has recently been given to the restoration of shellfish reefs along eroding shorelines to reduce erosion. Such fringing reef approaches, however, often lack empirical data to identify locations where reefs are most effective in reducing marsh erosion, or fully take into account habitat suitability. Using monitoring data from 5 separate fringing reef projects across coastal Louisiana, we quantify shoreline exposure (fetch + wind direction + wind speed) and reef impacts on shoreline retreat. Our results indicate that fringing oyster reefs have a higher impact on shoreline retreat at higher exposure shorelines. At higher exposures, fringing reefs reduced marsh edge erosion an average of 1.0 m y-1. Using these data, we identify ranges of shoreline exposure values where oyster reefs are most effective at reducing marsh edge erosion and apply this knowledge to a case study within one Louisiana estuary. In Breton Sound estuary, we calculate shoreline exposure at 500 random points and then overlay a habitat suitability index for oysters. This method and the resulting visualization show areas most likely to support sustainable oyster populations as well as significantly reduce shoreline erosion. Our results demonstrate how site selection criteria, which include shoreline exposure and habitat suitability, are critical to ensuring greater positive impacts and longevity of oyster reef restoration projects.

The West Florida Shelf (WFS) is one of the largest and most diversely-used continental shelf/slope systems in the world. The presence of paleoshorelines and scarped hardbottom outcrops (up to 4 m in relief) along the inner shelf (10-30 m depth) provide important habitat for a variety of infaunal, epifaunal, and fish assemblages that contribute to the productivity of the region. This dissertation will present a comprehensive overview of the geological, physical, and chemical settings of the inner West Florida Shelf, with particular focus on biological and ecological community dynamics of epibenthic macroinvertebrates, algae, and fish assemblages. Baseline and comparative data sets are presented in the form of historic and modern species lists, with focus on seasonal and intra-annual variations. Quantitative effects of disturbances (e.g., hurricanes, thermal stresses, and red tides) and subsequent recovery rates are discussed as they periodically perturb inner-shelf systems and can have significant effects on community structure. Benefits of and recommendations for using artificial reefs as restoration tools along the inner shelf, as mitigation for future disturbances, are presented.

Fishes within the family Scombridae (i.e. tunas, mackerels and bonitos) are of high ecological and economic value, as they are heavily targeted by commercial and recreational fisheries. In coastal and open-ocean environments, adults are high-level predators, while larvae and juveniles serve as prey for numerous species. Much is known about the distribution and abundance of adult tunas, but high taxonomic uncertainty and limited knowledge regarding the distributional patterns of larval and juvenile tunas have led to an “operational taxonomic unit” gap in our understanding of tuna ecology. Scombrids were collected across the Gulf of Mexico (GoM, hereafter) during seven research cruises from 2010-2011, as part of the NOAA-supported Offshore Nekton Sampling and Analysis Program, and during five research cruises from 2015-2017, as a part of the GOMRI-supported Deep Pelagic Nekton Dynamics of the Gulf of Mexico Consortium. In this thesis, species composition, distribution, and abundance of tunas collected from the surface to 1500 m depth are characterized in relation to depth, time of year, and physical oceanographic features. A synthesis of the morphological characteristics used to identify the taxonomically challenging larval and juvenile stages of tunas is presented, along with length-weight regressions to fill the data gap on the growth patterns of these early life stages. A total of 945 scombrid specimens were collected, representing 11 of the 16 species that occur in the GoM. The dominant species included: Euthynnus alletteratus (Little Tunny), Thunnus atlanticus (Blackfin Tuna), Auxis thazard (Frigate Mackerel), and Katsuwonus pelamis (Skipjack Tuna). Evidence of sampling gear selectivity was observed, with a MOCNESS (rectangular, research-sized trawl) collecting larvae predominantly, and a large, high-speed rope trawl catching only juveniles. Scombrids were collected primarily in the upper 200 m of the water column. Species-specific environmental preferences and seasonality were identified as the main drivers of tuna spatial distributions across the epipelagic GoM. Integrating aspects of scombrid ecology in neritic and oceanic environments improves management and conservation efforts for this highly important taxon.

Ocean models are increasingly able to synthesize a large temporal domain with fine spatial resolution. With this increase in functionality and availability, ocean models are in high demand by researchers, establishing a critical need for validating a model’s ability to represent interior ocean dynamics. Satellite measurements are typically used for validation, however these measurements are limited to the upper layers of the ocean and therefore satellite measurements of sea surface height and sea surface temperature are the most validated output parameters of three-dimensional ocean models. Unfortunately there is a paucity of model validation studies for the interior ocean. This study fills a knowledge gap by contrasting model data from the Hybrid Coordinate Ocean Model (HYCOM) for the interior ocean in the Tongue of the Ocean (TOTO), Bahamas and the Gulf of Mexico (GoM) against observational (i.e., in situ) data collected in both locations. Conductivity temperature and depth (CTD) data in the GoM were collected during five research cruises by the DEEPEND Consortium between May of 2015 and May 2017. These data were collected as part of the investigation into the impact of oil spills on faunal communities in deep water of the GoM. CTD and expendable CTD (XCTD) data in the TOTO were collected by the Naval Undersea Warfare Center (NUWC) detachment Atlantic Undersea Test and Evaluation Center (AUTEC) in support of U.S. Navy acoustic testing between 1997 and 2017 to characterize the sound velocity profile of the water column. The global 1/12° HYCOM configuration (GLBu0.08) was found to be a better fit in the upper 400 and 250 meters of the TOTO for temperature and salinity, respectively, than the GoM 1/25° HYCOM configuration (GOMI0.04 1/25°) fit the GoM in situ data for the same depths. The GoM 1/25° HYCOM configuration (GOMI0.04 1/25°) provided a better fit in the GoM for depths of 500 and 300 meters and deeper for temperature and salinity, respectively, than the global 1/12° HYCOM configuration (GLBu0.08) fit the TOTO in situ data at the same depths. A comprehensive comparison of the vertical profile between the model and observational data for each of the regions of interest provides insight into using HYCOM forecast data for future applications.

Human population growth and global industrial development are driving potentially irreversible anthropogenic impacts on the natural world, including altering global climate and ocean conditions and exposing oceanic environments to a wide range of pollutants. While there are numerous studies highlighting the variable effects of climate change and pollution on marine organisms independently, there are very few studies focusing on the potential interactive effects of these stressors. The deep-sea is under increasing threat from these anthropogenic stressors, especially cold-water coral (CWC) communities which contribute to nutrient and carbon cycling, as well as providing biogenic habitats, feeding grounds, and nurseries for many fishes and invertebrates. The primary goals of this dissertation are to assess the vulnerability of CWCs to independent and interacting anthropogenic stressors in their environment; including natural hydrocarbon seepage, hydrocarbon and dispersant concentrations released during an accidental oil spill (i.e. Deepwater Horizon), and the interacting effects of climate change-related factors and hydrocarbon/dispersant exposure. To address these goals, multiple stressor experiments were implemented to assess the effects of current and future conditions [(a) temp: 8C and pH: 7.9; (b) temp: 8C and pH: 7.6; (c) temp: 12C and pH: 7.9; (d) temp: 12C and pH: 7.6] and oil spill exposure (oil, dispersant, oil + dispersant combined) on coral health using the CWC Lophelia pertusa. Phenotypic response was assessed through observations of diagnostic characteristics that were combined into an average health rating at four points during exposure and recovery. Regardless of environmental condition, average health significantly declined during 24-hour exposure to dispersant alone and increased temperature resulted in a delay in recovery (72 hours) from dispersant exposure. The overall gene expression patterns varied by coral colony, but the dispersant exposure elicited the strongest response. Gene ontology (GO) enrichment analysis revealed that L. pertusa likely experienced varying stages of the cellular stress response (CSR) during exposure to oil, dispersant, and a decrease in pH. The most severe responses were associated with the dispersant exposure including GO terms related to apoptosis, the immune system, wound healing, and stress-related responses. However, the oil exposure induced an upregulation of metabolic pathways and energy transfer but a downregulation of cell growth and development, indicating that the coral nubbins could have been reallocating resources and reducing growth to maintain cellular homeostasis. The decrease in seawater pH elicited a similar response to oil through the enrichment of terms associated with a reduction in the cell cycle and development. Interestingly, the increase in temperature did not elicit a CSR that was detectable in the gene expression data. To further investigate the influence of hydrocarbon exposure on CWCs, comparisons of gene expression profiles were conducted using Callogorgia delta colonies that live in close proximity to active hydrocarbon seepage (“seep”) areas with no current active seepage (“non-seep”) at two different sites in the Gulf of Mexico. There were fewer differentially expressed genes in the “seep” versus “non-seep” comparison (n=21) than the site comparison (n=118) but both analyses revealed GO terms indicating slight alterations in natural biological housekeeping processes, as opposed to a CSR. Our results indicate that distinct stages of the CSR are induced depending on the intensity of stress. This bolsters the idea that there is a stress response shared by all corals in response to a variety of stressors. These data provide evidence that CWCs can be more negatively impacted, both on the phenotypic and molecular levels, by exposure to chemical dispersants than to hydrocarbons alone. Gaining an understanding of how these communities respond, not only to independent stressors, but the combination of these stressors, provides vital information about how CWC communities will fair in current and future conditions. / Biology

The Mississippi Alluvial Valley (MAV) was dominated by extensive lowland forests, but during the 20th century most of the MAV was converted to agricultural, aquaculture, and other human uses. These land-use changes created stopover migration and wintering habitats for waterfowl, shorebirds and other waterbird species. Before landscape modification of the MAV, shorebirds likely migrated past the MAV to wetlands along the northern Gulf of Mexico (NGoM). In 2010, the Deepwater Horizon oil spill impacted coastal marshes of the NGoM. The USDA Natural Resources Conservation Service implemented the Migratory Bird Habitat Initiative (MBHI) to provide waterbirds with wetlands inland of oil-impacted areas. My objectives were to 1) statistically model the waterbird community on wetlands in the MAV and NGoM, 2) estimate relative abundance of shorebird and other waterbirds in idled aquaculture ponds enrolled in MBHI and associated wetlands in the MAV and NGoM, and 3) collect shorebird feathers and blood for stable isotope analysis (13C/12C, 15N/14N) to assess foraging niches and potential migratory connectivity between MAV and NGoM habitats during 2012 – 2013. Consequently, autumns of these years were under a drought, extensively wet from Hurricane Isaac, and exhibited average precipitation in the post-hurricane recovery period which may have had an effect on waterbird assemblages differing by year, month, twice-monthly survey period, latitude, region, state, site, and water depth index. Latitude shifted north and water depth was narrowest when abundant wet habitat existed on the landscape in 2012. Bird abundances were greatest in 2011 and never recovered to these levels in 2012 or 2013, which may have reflected effects of drought concentrating birds on remaining wetlands in 2011 and subsequent to the hurricane. Stable isotope analysis of blood indicated spatial segregation of shorebird species. Neither blood nor feather carbon and nitrogen values revealed definitive linkage of sites between the MAV and NGoM. Shallow water habitat inland may be a limiting resource during migration for waterbirds, especially in drought years when other wetlands may have been limited. Thus, provision of wetlands (mudflat – 15 cm) by MBHI and other conservation strategies across the landscape may allow waterbirds access to needed resources during migration.

The objective of this study is to estimate the willingness to pay of U.S. Gulf Coast residents to support oyster reef restoration. The Gulf Coast is the leading commercial oyster- producing region in the United States, accounting for approximately 46% of the total commercial oyster harvest in 2021. My benefit estimates were based on data obtained from a contingent valuation survey of 6,475 Gulf Coast respondents. I estimated the willingness to pay (WTP) for oyster reef restoration using interval regression and Turnbull lower-bound methods. The estimated mean WTP value is in the range of $142 and $436 per household. The results show respondents who eat oysters and those that hold saltwater fishing licenses have significantly higher WTP.