The Kemp’s ridley sea turtle, Lepidochelys kempii, is recovering from devastating declines that reduced nesting activity from a single-day estimate of 10,000- 40,000 females in 1947 to fewer than 300 during all of 1985. Nesting beach monitoring is crucial to estimating population size and reproductive activity, but in-water data are essential for understanding population dynamics and evaluating management strategies. Hook-and-line, stranding, and nesting records, satellite telemetry, and diet analyses were used to characterize ridley population dynamics and movements in the northwestern Gulf of Mexico during 2003-2007. Recreational hook-and-line captures comprised approximately one third of non-nesting encounters along Galveston and Jefferson Counties, Texas. The hook-and-line dataset displayed similar geographical and monthly trends to that of strandings, but was devoid of pelagic-stage, subadult, and adult ridleys. Coastal and bay waters along the upper Texas and western Louisiana coasts were utilized by immature ridleys during warmer months. Nesting occurred along Galveston Island on both armored and unarmored beaches. Inter-nesting females exhibited fidelity to Galveston during nesting season and subsequently migrated to federal waters offshore Louisiana. Crabs were important components of benthic-stage (>25 cm SCL) ridley diet, while worm tubes were targeted by some individuals. Short satellite track durations for immature ridleys precipitated examinations of biofouling, attachment protocols, and turtle excluder device (TED) interactions. Antifouling paints drastically reduced fouling of transmitters. A less-rigid neoprene attachment method was developed to increase transmitter retention on fast-growing juveniles, but further trials are necessary. Transmitters were not damaged or lost during TED trials, but turtle escape times increased when transmitters wedged between TED bars. Projected population growth will increase numbers of Kemp’s ridleys utilizing the Gulf of Mexico and interacting with human activities. Future research should examine year-round distribution and abundance of all life history stages and further characterize recreational hook-and-line capture, nesting activity, movements, and diet. Education efforts targeting the beach-going public, beach residents and workers, and the recreational fishing sector should be employed to promote sea turtle reporting and minimize negative interactions. State and federal managers should examine anthropogenic impacts within the region and determine the need for mitigation and/or regulations to promote continued species recovery.

On Mesoscale Population Study cruises during summers 2004 and 2005 aboard the sailboat Summer Breeze, researchers from the Sperm Whale Seismic Study (SWSS) surveyed for sperm whales along the continental slope of the northern Gulf of Mexico. SWSS scientists tracked 35 groups of whales during these two summers, recording locations where they did and did not encounter whales. Whales were encountered during both summers at approximately the same frequency (19 groups in 38 survey days in 2004; 16 groups in 29 survey days in 2005), but fluke photo-identifications indicated that 85% of individuals encountered during summer 2005 had never been previously identified in the Gulf throughout 10 years of cetacean research. Composition and distribution of these groups also varied between summers. Oceanographic conditions at the edge of the continental shelf differed between 2004 and 2005, which may have modified the usual trophic cascade that begins with near-surface primary production to create local aggregations of prey at the depths where sperm whales forage. Sperm whales are apex, mesopelagic predators, but have been shown to associate with surface primary productivity over large spatial scales and time scales of months to years. The purpose of this thesis was to look for relationships between sperm whale presence and surface oceanography on smaller spatial and shorter temporal scales. Surface ocean color from NASA’s Moderate Imaging Spectroradiometer (MODIS) and surface dynamic height from NASA’s Earth orbital altimeters were evaluated to assess habitat occupied by sperm whales. Passive acoustic monitoring along transect lines for sperm whale clicks permitted determination of sperm whale presence and absence. Sperm whale encounters were in general associated with negative sea surface height and enhanced sea surface chlorophyll (SSC), especially in or near areas where local SSC anomaly was produced by cyclone induced upwelling of nutrients or from coastal water advected off-margin. During summer 2004, SSC was generally high all along the upper continental slope whereas summer 2005 saw relatively low SSC along the upper continental slope. Whales encountered in this study were most highly correlated with SSC two weeks after the initial development of locally highest-SSC anomalies.

Vertical structure of the low frequency horizontal currents at the northern edge of the Loop Current during eddy shedding events is observed using concurrent hydrographic, moored, and satellite altimetry data from 2005. Dynamic modes are calculated at three deep (~3000 m), full water-column moorings in the eastern Gulf of Mexico. Time-series of the barotropic and first two baroclinic modes are found using a least squares minimization that fits theoretically derived modes to observed moored velocity data. EOF analyses show that the majority of observed variance is explained by a surface-trapped mode that is highly coherent with the temporal amplitudes of the first baroclinic mode, and a lower, but significant percentage of variance is captured in bottom-intensified modes. Amplitudes of the second empirical mode indicate that currents are more coherent in the ocean interior approaching the Loop Current, as more variance is explained by this mode at the southernmost mooring near the Loop Current. A dynamic mode decomposition of the horizontal currents reveals that the barotropic and first baroclinic modes exhibit low frequency variability and eddy time scales of 10 – 40 days. Second baroclinic mode amplitudes show higher frequency variability and shorter time scales. A model utility test for the least squares fit of modeled to observed velocity shows that the second baroclinic mode is useful to the statistical model during 50 – 85 % of the mooring deployment, and is particularly necessary to the model when cyclonic features are present in the study area. The importance of the second baroclinic mode to the model increases significantly closer to the Loop Current. High-speed currents associated with the Loop Current and anticyclones stimulate a strong first baroclinic response, but the second baroclinic mode amplitudes are found to be similar in magnitude to the first baroclinic mode amplitudes at times. This happens episodically and could be an indication of higher order dynamics related to frontal eddies or Loop Current eddy shedding.

Thesis (M.A.)--United States International University, 1973. / Facsimile reproduction by microfilm-xerography. Includes bibliographical references (leaves [221]-226).

Anomaly timescales for the last 90 million years, derived from marine magnetic profiles and published prior to mid-1979, are summarized, illustrated for comparison, and critically reviewed. A revised timescale is constructed using calibration points which fix the ages of anomalies 2.3', 5.5, 24, and 29. An equation is presented for converting K-Ar dates that is consistent with the recent adoption of new decay and abundance constants. The calibration points used in the revised timescale, named NLC-80, are so converted, as are the boundary ages of geologic epochs within the range of the timescale. NLC-80 is then used, along with recently acquired and rigorously navigated underway geophysical data from the region of the mouth of the Gulf of California, to prepare detailed bathymetric, gravimetric, and seismo-tectonic maps of the area. The basement ages at DSDP Leg 63 drilling sites 471, 472, and 473 are estimated from magnetic anomalies fit to timescale NLC-80. The estimates agree with biostratigraphically determined basement ages and support the proposal that an aborted ridge of about 14 MY age has left a small fragment of the Farallon Plate beneath the Magdalena Fan. Several large inactive faults are identified on the deep-sea floor west of the tip of the peninsula of Baja California. Additional magnetic anomaly profiles and bathymetric profiles across the Rivera Ridge are interpreted. These contradict the existence of a 3.5 MY old aborted spreading center on the Maria Magdalena Rise. Instead, it is proposed that an episode of subduction of the Pacific Plate beneath the southeastern tip of Baja California, concomitant with strike-slip faulting west of the peninsula, occurred and that this subduction may be responsible for the uncentered location of the Rivera Ridge within the mouth of the Gulf of California. A single magnetic anomaly profile obtained northeast of the Tamayo Fracture Zone is used to determine that the rate of Pacific/North American plate motion, for the last 3 MY is 68 km/MY at this location. This result, if correct, indicates that the peninsula of Baja California is separating from mainland Mexico faster than the Rivera Ridge is generating oceanic crust in the wake of opening in the gulf. This, in turn, requires that either slow diffuse extension is occurring presently across the Maria Magdalena Rise, or across the Cabo Corrientes-Colima region, or that the portion of North America south of the trans-Mexican volcanic belt is moving right-slip with respect to the North American Plate at a rate of 10-20 km/MY. Large horsts and many smaller continental fragments are found within the southern gulf. Several of them have active seismic boundaries, while others have apparently foundered. The gulf began to open approximately 14-15 MY ago with slow, diffuse block-faulting and the deposition of the Maria Magdalena Fan at the mouth of the gulf. Oceanic crust was exposed in the gulf by about 9-10 MY, at the same time that the Rivera Ridge began reorienting by clockwise rotation. Strike-slip motion along the Tosco-Abreojos Fault took up some of the Pacific/North American motion with the remainder occurring within the gulf itself. During this period the Pacific Plate forming within the gulf was slowly subducting beneath Baja California. By 4-5 MY subduction ceased and all of the Pacific/North American plate motion was shifted to the Gulf of California fault system. The gulf and peninsula of California are still in the process of adjusting to the change from Pacific/Farallon to Pacific/North American motion. / Graduation date: 1982

A blowout is an uncontrolled flow of reservoir fluids into the wellbore to the surface, causing serious, sometimes catastrophic, problems in different types of petroleum engineering operations. If the formation's strength is low and the pore pressure is high, bridging can be a very effective method for blowout containment. In this method, the formation caves into the open hole or onto the casing and stops the flow of the formation's fluid, either naturally or intentionally. This method can be effective in deepwater blowouts where the formation has high pore pressure and considerable shale intervals with low strength. In this research, wellbore stability and fluid flow performance subroutines have been developed with Visual Basic for Applications (VBA) programming. By integrating the subroutines together, we made a simulation tool to predict wellbore stability during blowouts and, consequently, predict wellbore bridging during normal and blowout situations. Then we used a real case in the country of Brunei to investigate a field case of a bridged wellbore to validate the simulator. In addition to the field case, we used GMI SFIB 5.02, a wellbore stability software, to provide validation. In the final part of this research we studied the effect of water depth in bridging tendency during blowout for the deepwater Gulf of Mexico (GOM). Since we could not find any real data in this area, we used general trends and correlations related to the GOM. The results of our study showed that water depth delays the occurrences of breakout in the wellbore during blowouts (i.e. for greater depth of water, wellbore collapse occurs farther below the mudline). However, the depth in which collapse occurs is different for different maximum horizontal stress amounts.

During the Northeastern Gulf of Mexico Chemical and Hydrography study (NEGOM-COH), nine oceanographic cruises were fielded during the spring, summer and fall seasons from November 1997 to August 2000. Surface chlorophyll-? fluorescence, salinity, and temperature data were logged once a minute from the R/V Gyre and subsurface chlorophyll-? fluorescence, salinity, temperature, and nutrients were profiled when the ship stopped to make stations. Each cruise occupied 94-98 stations, partitioned among 11 cross-margin transects of water depths between 10 m to 1000 m. Overall chlorophyll-? abundance within the study area is forced by the amount of freshwater discharge. Seasonal and interannual differences are largely determined by the monthly mean streamflow for the major rivers within the NEGOM area, particularly the Mississippi River. However, an important forcing function for transport of river water to the outer continental shelf and slope is the periodic presence of anticyclonic slope eddies. Especially when these slope eddies were centered south and east of the Mississippi River delta, they entrained and so redistributed low salinity green water to a wider area within the NEGOM region than could be predicted by mean monthly streamflow alone. The mean surface chlorophyll-? concentrations, and in particular the distribution of relatively high surface chlorophyll-? concentrations off-shelf, were strongly dependent upon entrainment of freshwater by these slope eddies, especially during the three summer cruises. Interannual variability in the summertime entrainment of low salinity green water was driven by summer-to-summer differences in sea surface height (SSH) of the slope eddy(s), and in how far they extended on margin. Satellite observations of ocean color showed that freshwater entrainment by anticyclonic eddies persisted for a temporal scale of several weeks each summer. Satellite-derived surface chlorophyll-? concentrations were positively correlated with in situ measurements of surface chlorophyll-?, with greatest agreement between satellite and ship measurements of surface chlorophyll-? at concentrations <1.5 mg/m3. Because subsurface chlorophyll-? concentrations were often elevated at depths greater than the first optical depth, satellite measurements of chlorophyll-? concentration generally underestimated integrated chlorophyll-? standing stocks within the euphotic zone.

Factors related to operations of a well that impact drilling uncertainties in the shallow water region of the Gulf of Mexico (GOM) can be directly linked to the site specific issues; such as water depth and local geological depositional environments. Earlier risk assessment tools and general engineering practice guidelines for the determination of the conductor casing design were based more on traditional practices rather than sound engineering practices. This study focuses on the rudimentary geological and engineering concepts to develop a methodology for the conductor setting depth criteria in the shallow water region of the GOM.

Large aggregations of Sargassum, when at sea, provide important habitat for numerous marine species of vertebrates and invertebrates. It is especially important for the young of several species of sea turtles. However, when large aggregations of Sargassum come ashore on beaches frequented by tourist it is often viewed as a nuisance or even a health hazard. It then becomes a burden to beach management and has to be physically removed as quickly as possible. Many Gulf coast beaches suffer from Sargassum accumulation on a regular basis. Timely information on the size and location of the Sargassum habitat is important to developing coastal management plans. Yet, little is known about the spatial and temporal distribution of Sargassum in the Gulf of Mexico. There is no systematic program to assess the distribution of the macroalgae, therefore practical management plans are difficult to execute. In 2008, Gower and King of the Canadian Institute of Ocean Sciences along with Hu of the University of South Florida, using satellite imagery, identified extensive areas of Sargassum in the western Gulf of Mexico. These were not confirmed with ground truthing data. To date ground truthing observations have not been directly compared with the corresponding satellite images to confirm that it was in fact Sargassum, as the satellite images suggested. y building on the information and research methods of Gower and King, current ground truthing data taken from Texas Parks and Wildlife Gulf trawl sampling surveys was analyzed. In addition, shoreline information and imagery was used to substantiate the data derived from current Moderate-resolution Imaging Spectroradiometer (MODIS) Enhanced Floating Algae Index (EFAI) images. As part of the NASA sponsored research project Mapping and Forecasting of Pelagic Sargassum Drift Habitat in the Gulf of Mexico and South Atlantic Bight for Decision Support, NASA satellite MODIS EFAI images provided by Dr. Hu were used to identify and substantiate corresponding floating Sargassum patches in the Gulf of Mexico. Using the most recent advances in technology and NASA satellite remote sensing, knowledge can be obtained that will aid future decision making for addressing Sargassum in the Gulf of Mexico by substantiating the data provided by satellite imagery. Findings from this research may be useful in developing an early warning system that will allow beach managers to respond in a timely manner to Sargassum events.

archives@tulane.edu / The goal of this dissertation was to identify the large scale effects that seasonal hypoxia has on the benthic community, with a particular focus on groundfish, in the Gulf of Mexico (GOMEX) while also examining ecological and physiological factors that could explain how hypoxia alters benthic communities. Seasonal hypoxia is a rapidly growing threat, not just in the GOMEX, but globally. Hypoxic conditions are known to impact marine organisms at the individual level by altering behavior and reproductive physiology while also impacting marine communities by disrupting predator prey interactions, community biomass, community composition, and community spatial dynamics. Research into hypoxia in the GOMEX has historically been localized, focusing on specific sub-regions with temporally limited sampling. While this approach has produced findings of the highest quality and importance, it has also shown that the impacts of hypoxia can be variable making the overall impact of hypoxia on GOMEX benthic communities difficult to discern. In taking both a geographically and temporally broad approach in comparing the abundances of marine organisms between hypoxic sites and normoxic (normal levels of dissolved oxygen, not hypoxic) sites I found that hypoxic sites had significantly lower biodiversity compared to normoxic sites and that 102 out of 465 examined species had significantly lower abundances in hypoxic areas compared to normoxic areas. When I compared the diets of common groundfish species from hypoxic areas to the diets of the same species from normoxic areas a few key differences were noted for some species, while the diets of other species remained relatively unchanged. After comparing the reproductive condition and presence/absence of ovarian masculinization between hypoxic areas and normoxic areas in three species of groundfish, I found evidence of ovarian masculinization in all three species, and evidence of reproductive impairment in two species. In this dissertation I showed that hypoxia in the GOMEX alters the community composition and biodiversity of the benthic community, additionally finding evidence that hypoxic conditions alter the diets and reproductive biology of several fishes / 1 / Michael Vincent Cyrana