archives@tulane.edu / During the Deepwater Horizon (DWH) oil spill in 2010, approximately 0.5 billion liters (3.1 million barrels) of oil were released into the northern Gulf of Mexico during the largest marine oil spill in history . A significant portion of the released oil was weathered into residues by physical, photochemical, and biological processes prior to landing on 1773 km of coastline, including 754 km of marsh shoreline in Louisiana. Researchers endeavored to describe effects of oil residues in the soil on salt marsh organisms and communities. Many studies focused on two pillars of salt marsh ecology: the microbial communities through which a large portion of the salt marsh food web is connected and Spartina alterniflora, a foundational species of Gulf Coast salt marshes. In this dissertation I describe how cryptic, or difficult to observe, elements of salt marsh ecology, like microbial communities and plant genetics, respond to oil residues in the environment. Using a suite of field, growth chamber, and greenhouse experiments I show that these microbial communities are difficult to characterize and may respond to other factors more strongly than they do to oil residues. I present evidence that the plant is resilient to oil in the environment, and changes in its microbiome, but exerts a measurable influence on the biodegradation of oil residues and the microbiome in the soil. This dissertation provides a greater understanding of the complexity of the salt marsh response to an oil spill. / 1 / Stephen K. Formel

In April 2010, approximately 4.9 million barrels of oil were accidentally released into the Gulf of Mexico during the Deepwater Horizon Macondo Mc252 Oil Spill. Some of the surface oil was carried by prevailing winds and currents and reached the coast of Louisiana impacting marsh and marine ecosystems. One and a half years after this incident, a set of oiled marsh samples (2 grab samples) coupled with nearby subtidal and intertidal cores (12 cores) were collected from Barataria Bay, Louisiana to determine the probable source of petroleum residues present and to characterize the chemical composition of the oil. Plus, pre-spill core which was collected from Barataria Bay in 2007 was analyzed to identify the background hydrocarbon composition of the area. Polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH), biomarker, and stable carbon isotope compositions of selected samples were detected using a GC-MS and an elemental analyzer Conflo system coupled to a DeltaPlusXP isotope ratio mass spectrometer. The comprehensive chemical data allowed us to classify the pre and post-spill samples into 4 Groups. According to this classification, Group 1 and Group 2 samples had the highest concentrations of petroleum-derived hydrocarbons. Group 3 and background samples, on the other hand, was dominated by biogenic signatures. Although a direct connection between the detected and spilled Macondo oils results are complicated due to confounding factors (e.g., already present hydrocarbons and weathering processes), our biomarker data indicates that both oils have similar signatures. This close genetic relationship was also identified by stable carbon isotope analysis. The impact of the Macondo Mc252 Oil Spill in Barataria Bay appears to be limited to areas closer to the source. The oil has undergone moderate weathering and has penetrated into, the at least, the top 9 cm sediments. Additionally, to examine the decadal-scale history of sedimentation in these marshes, a sediment core was analyzed for the radioisotope 137Cs. The observed sedimentation rate of 0.39 cm/yr shows that oil pollutant input into Barataria Bay has been ongoing for at least 50-60 years.

Following the DWH oil spill event, crude oil reaching the shoreline of Gulf of Mexico produced petroleum oil deposit with a range of distinct geometries, including sphere tar balls and horizontal tar sheets. Numerical models were developed based on the Deep Water Horizon oil spill conditions to evaluate the influence of deposit geometry on long term persistence of residual NAPL oil. Two extreme deposit geometries were modeled in this study: the horizontal tar sheet and the spherical tar ball. Both two-dimensional modeling approach and three-dimensional modeling approach were applied to compare two contrasting geometries. The two-dimensional model results showed that sheet geometry deposits exhibited a greater obstruction to groundwater flow relative to the spherical deposits and induced a larger sulfate reducing zone downgradient of the NAPL source, resulting in significantly greater sulfate-based biodegradation of benzene. Three-dimensional models were constructed to assess the influence of key geometry parameters on oil deposit fate and persistence. Three parameters affecting deposit's geometric structure were recognized, including the upper horizontal area of the sheet deposit, the thickness of the sheet deposit, and the radius of the sphere deposit. The three-dimensional model results suggested that thickness of the sheet deposit and radius of the sphere deposit were important geometry factors impacting the fate and long term persistence of residual NAPL oil in the coastal environment. However, the influence of deposit geometry differed depending on the solubility of the different NAPL components. When high solubility compound and low solubility compound both exist in the oil deposit, the influence of deposit geometry on benzene degradation was significant, while the influence on naphthalene was almost negligible. / Master of Science

Abstract The purpose of this study was to explore the impact of the BP Deepwater Horizon oil spill on students of two coastal Louisiana secondary schools. Bronfenbrenner’s (1979) ecological systems theory was used as a framework to understand how exposure, gender, socioeconomic status, and resilience interact to influence the impact of the spill on students. Cross-sectional questionnaires were administered to 155 high school students in May 2012 and 225 middle school students in January 2013 out of 1247 possible for a return rate of about 30%. Results showed that exposure groups differed significantly on students’ Impact of Event Scale (IES; Horowitz, Wilner, & Alvarez, 1979) scores. Students with high exposure to the oil spill had significantly higher IES scores than those with no exposure and low exposure. Logistic regression results indicated that exposure was a significant predictor of higher IES scores and as exposure increased by 1, students were 1.46 times more likely to experience higher impact. Males were found to have significantly higher IES scores than females, with a low effect size. Students did not differ significantly across resilience levels. In the entire sample, lower-SES students did not score significantly different on IES scores than higher-SES students. However, in the high school significant differences were found between SES groups and SES was a significant predictor of higher IES scores. Implications are provided for counselor educators interested in disaster mental health. Conclusions include suggestions for counselors servicing areas affected by the oil spill and how individual and environmental characteristics of students can influence risk factors. Keywords: Disaster mental health, crisis intervention counseling, ecological systems theory, BP Deepwater Horizon oil spill, secondary school students, resilience, risk factors

The goal of this research is to understand the impacts of the 2010 Deepwater Horizon oil spill and the 1970-1980 IXTOC-I oil spill and other anthropogenic activity (e.g. dam construction) on surface water primary productivity by measuring sedimentary biogenic silica. It is known that sedimentary biogenic silica is distinct from mineral – bound silica, therefore it has been used as a proxy record for surface water primary productivity (e.g. diatom blooms). The Deepwater Horizon oil spill resulted in a widespread Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA) event. The IXTOC-I oil spill was one of the largest oil spills in history and it is likely that the MOSSFA event occurred as a direct result. MOSSFA is characterized by increased deposition of surface derived components and dramatic changes in post-depositional chemical (redox) and biological (benthic meio- and macro-fauna) conditions. Sedimentary biogenic silica provides an independent record of the surface derived portion of MOSSFA inputs. Occurrences of MOSSFA after IXTOC-I and Deepwater Horizon were compared by collecting sediment cores from the northern Gulf of Mexico (Deepwater Horizon) and the southern Gulf of Mexico (IXTOC-I). An age model for each core was developed using short-lived radioisotopes (i.e. 210Pbxs). Sedimentary biogenic silica was significantly elevated in sedimentary intervals affected by the Deepwater Horizon spill. This suggests that a significant portion of the surface biological materials entrained during the MOSSFA event were sourced by diatom production. However, only one core (of three from the oil spill influenced area utilized in this study) from shallower depth had elevated levels of sedimentary biogenic silica in the sedimentary interval associated with IXTOC-I. Also, the down-core profiles of sedimentary biogenic silica from the other cores collected in the southern Gulf of Mexico are consistent with the history of dam construction (1949 to 1989) on the Grijalva and Papaloapan river systems. These two river systems are the dominant freshwater and nutrient sources for primary production in the Bay of Campeche region in the southern Gulf of Mexico and therefore the dominant control on diatom productivity and sedimentary biogenic silica distribution. Consequently, distribution of annual fresh water outflow and nutrient supply has transitioned from seasonal (before 1940’s) to stable (after 1980’s). Overall, sedimentary biogenic silica provides an independent record of surface derived MOSSFA inputs and serves as a proxy for other anthropogenic influences related to surface primary productivity variability.

In 2010, the largest oil spill in U.S history occurred off the coast of Louisiana from April 20th to September 19th, when the well was declared officially sealed by the U.S Coast Guard, after releasing more than 4.4 million barrels of crude oil into the Gulf of Mexico (GOM) (McNutt et al., 2012). This spill was unique because it occurred in deep water approximately 1500 m below the ocean surface. Virtually nothing is known about the effects of oil spills on marine life in the deep sea, and there are limited data on mesopelagic and bathypelagic animals in the GOM before the Deepwater Horizon oil spill (DWHOS). The study presented here focuses on one of the most abundant and diverse groups of pelagic decapod crustaceans in the GOM – the family Oplophoridae and also includes one species from the family Pandalidae. Past studies on pelagic decapod crustaceans have been limited on both spatial and temporal scales. This study is unique because 1) it covers a large temporal range with data collected in 2011 and from 2015-2017, allowing for a more in-depth look at crustacean assemblage patterns, 2) it allows analysis of seasonality in reproduction, about which little is known for any deep-sea species, and 3) it assesses the potential effects of the Loop Current on species distribution and abundances, about which little is known. This information is important in understanding how the DWHOS may have affected the GOM ecosystem because pelagic decapod crustacean are intermediate components of the food web, and are in turn preyed upon by higher trophic levels. Unfortunately, there were little data on the mesopelagic ecosystem from this region before the spill, with the exception of a site in the eastern GOM (Standard Station, Hopkins et al., 1989; Hopkins et al., 1994). Therefore, these data, which incorporate samples taken one, five, six and seven years after the DWHOS, were analyzed with respect to year and season to determine if any trends were present. Results indicate that both biomass and abundance were significantly higher in 2011, than in subsequent years, indicating that the ecosystem has been declining since 2011. These two parameters were also lower in Loop Current water when compared to Common Water at all depths up to 1200 m, indicating that the Loop Current does have effects on deeper waters. The information obtained from this thesis will also act as a reference state for future studies in the GOM to monitor changes, or lack thereof, in the assemblage of deep-sea oplophorid and pandalid crustaceans.

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.

The Deepwater Horizon Oil Spill (DWH) released about 4.4 million barrels of crude oil into the Gulf of Mexico (GOM), making it one of the largest oil spills in U.S. history. Additionally, the depth of the spill (i.e., 1500 meters) created a unique research opportunity because most oil spills occur at the surface and affect coastal rather than deepwater habitats. Polycyclic aromatic hydrocarbons (PAHs) are the most toxic components of oil, and are often the focus of oil exposure studies. PAHs are quickly metabolized by vertebrates; therefore, indicators of biological responses to PAH exposure (PAH “biomarkers”) such as the levels of PAH detoxification enzymes and the resulting metabolites are commonly used to examine oil exposure. This study measured multiple PAH biomarkers including hepatic activity of the PAH detoxification enzymes cytochrome P4501a1 (CYP1A) and glutathione-S-transferase (GST), as well as biliary PAH metabolites in deep sea sharks and bony fishes from areas affected by the Deepwater Horizon Oil Spill. Samples were collected from 2011-2013 from seven species of sharks, with special focus on the four most abundant deep sea species: Centrophorus niakang, Centrophorus cf granulosus, Squalus cubensis and Squalus cf mitsikurii. Overall enzyme activity was low in these sharks, yet it was higher in oiled sites compared to reference locations. Additionally some species showed declining CYP1A activity since the time of the oil spill, suggesting exposure to CYP-inducing compounds during the beginning of the survey period. Last, PAHs of a petrogenic nature were more abundant in oiled sites compared to reference locations. Overall, this project provides the much need biomarker data for sharks as well as insight on exposure and metabolism of PAHs in deep sea sharks after the DWH.