The Gulf of Mexico commercial reef fish fishery has experienced significant management changes and disturbance in recent years, including transitioning two major fisheries from a traditional open access system into a limited entry individual fishing quota (IFQ) system in 2007 and 2010. Also in 2010, the Deepwater Horizon oil spill (DWH) released an estimated 4.9 million barrels of oil into the Gulf (~206 million U.S. gallons), and is still the largest U.S. environmental disaster to date. Emergency fishing closures initiated shortly after the oil spill began were successful in keeping tainted seafood from reaching markets. However, effects of DWH closures on fisher decision making, fishery productivity, and distribution of fishing effort all remain poorly understood. Understanding the range and magnitude of fishers’ responses to perturbations — including regulatory change and human-induced environmental disasters — is critical for designing effective management and disaster response policies that can meet biological, ecological, economic, social, and sustainability objectives. This work characterized the spatial and temporal patterns of productivity and fishing effort for the Gulf of Mexico (GoM) commercial reef fish fishery. Patterns of productivity and effort distribution were used to examine the response of fishers to management change and large-scale disturbance, namely the DWH fishing closures. Fisheries-dependent logbook trip reports were used to quantify revenue and catch-per-unit-effort (CPUE) patterns from 2000-2014. Novel to fisheries work in the GoM, complementary vessel monitoring systems (VMS) satellite tracking data were used to quantify high-resolution spatial distribution patterns over time, relative to the DWH fishing closures. A general linear modeling (GLM) approach was also used to examine which variables may have contributed to resilience of fishers after DWH closures. Results suggested that this fishery was largely resilient to the DWH fishing closures in 2010, although exact outcomes varied by region. Overall fleet-level productivity steadily increased over time, but regional patterns were based on major species in catch. Productivity in the western GoM was consistently highest over time, and trips in the west and central GoM were dominated by Red snapper (Lutjanus campechanus) and Vermilion snapper (Rhomboplites aurorubens). Trips in the east were dominated by Red grouper (Epinephelus morio) and Gag grouper (Mycteroperca microlepis). Shifts in spatial distribution to new productive fishing grounds or reduced competition via fewer vessels or trips may explain the increases in productivity observed over the study period. Consolidation in the fleet was apparent, with fewer individual vessels and fewer total trips over time. However, the rate of vessel drop out after DWH (5%) was far below the annual background attrition rate of ~14-20%. Relative productivity patterns inside vs. outside the boundaries of fishing closures did not change over time, and there were even some increases in productivity observed during and after DWH in the eastern GoM. Yet, vessels that dropped out after DWH were concentrated in the north-central and eastern GoM. Distribution of fishing grounds before and after DWH were highly similar, and there were increases in effort along the outer West Florida Shelf. Variability in revenue and CPUE, CPUE magnitude, and magnitude of grouper landings were significant predictors of dropping out of the fishery in the GLMs. Synergies with the Red snapper or Grouper-Tilefish IFQs may have “primed” the fishery for resilience by eliminating inconsistent or marginal fishers before the oil spill, and may further explain some of the spatially varying patterns of productivity and attrition after 2010. Resilience was likely also enhanced by the more than $2 billion in emergency compensation payments made to captains, crew, and vessel owners for lost fishing income and assistance with oil remediation efforts. This work stands to make a significant contribution to our understanding of how the DWH oil spill impacted fisheries and communities in the GoM. The results add to a growing body of literature suggesting that the acute population- and ecosystem-level impacts of the DWH oil spill were not as strong or severe as initially anticipated. This work also stands to make contributions to the broader understanding of how this fishery has performed in the wake of recent management change and major environmental disturbance.

Outdoor workers are often subjected to thermal conditions beyond the comfort zone, but to what degree do such conditions affect the health and safety of those workers is still a matter requiring further investigation. The purpose of this study is to examine the relationship between thermal conditions and (1) heat-related disorders and (2) acute injuries using injury and illness data collected during the BP Deepwater Horizon clean-up operations. Over an eleven month period, 5,485 cases were identified as either heat-related or an acute injury (incident type) and further divided by severity. Daily weather data were used to estimate the wet bulb globe temperature (WBGT) based on the time of day. Heat Stress Levels intervals were defined using the estimated WBGT. Labor-hours by month were estimated by the prevailing shift length in the month and the number of workers. The incidents were assigned a Heat Stress Level and the number of labor-hours by heat stress level were determined. The next step was to calculate the incident rate ratio by Heat Stress Level against the baseline of thermal comfort. The results indicated that the rate ratios for heat-related disorders and acute injury increased for thermal conditions from 24⁰C-WBGT to 30⁰C-WBGT. There was a further significant increase in rate ratio for heat-related injury above 33 °C-WBGT. It was notable that the incident rates for both heat-related disorders and acute injuries increased at thermal conditions generally considered to be below the occupational exposure limit (OEL) at 30 ⁰C-WBGT. The rate of heat-related disorders increased substantially above the occupational exposure limit.

On April 20, 2010 a tragic explosion aboard the Deepwater Horizon (DWH) drilling rig marked the beginning of one of the worst environmental disasters in history. For 87 days oil and gas were released into the Gulf of Mexico. In August 2010, anomalous phytoplankton activity was identified in the Northeastern Gulf of Mexico, using the Fluorescence Line Height (FLH) ocean color product. The FLH anomaly was bound by approximately 30-28 degrees North and 90 and 86 degrees West and there was a suggestion that this anomaly may have occurred due to the presence of oil. This study was designed to examine alternative explanations and to determine what influence the Mississippi River and the freshwater diversions, employed in the response efforts, may have had on the development of the FLH anomaly. The combination of the anomalously high flow rate in the Mississippi River observed in June-August 2010, the use of freshwater diversions, and three severe storms increased the flow of water through the adjoining marshes. We propose that these conditions reduced the residence time of water and nutrients on the wetlands, and likely mobilized nutrients leading to increased fresh water and nutrients being discharge to the coasts around the Mississippi Delta. Salinity contour maps created from data collected by ships operating in the Northeastern Gulf of Mexico showed that the 31 isohaline was upwards of 250km east of the Mississippi River Birds Foot Delta in August 2010. The American Seas (AmSeas) numerical circulation model was used to examine the dispersal and distribution of water parcels from the Mississippi River and freshwater diversions. Two virtual particle seeding locations were used to trace particles to obtain a measure of the percentage of particles entering a Region of Interest (ROI) located in the center of the FLH anomaly, i.e. 150 km east of the Mississippi Delta. All environmental data examined suggest that the eastward dispersal of the Mississippi River water including that derived from freshwater diversions and storm activity contributed to the development of FLH anomaly in August 2010. Chapter two examines the spectral characteristics of water and oil collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Several peaks in the spectral features of the total radiance of surface oil between 1907nm and 2400nm appear to be absent for water. An algorithm (Spectral Line Height) was created to measure the height of the peak at 2142nm relative to a baseline between 2013nm and 2390nm. A normalized difference technique developed by the USGS was used as a validation tool. Preliminary results of the SLH technique appear to compare favorably with the results derived using the USGS technique. The SLH technique worked in areas that did not show sunglint or shallow bottom features. Sunglint areas would require additional correction to remove the effect of specular reflection. The SLH technique shows promise but will require validation to develop into an operational remote sensing method.

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.

Research in the multidisciplinary science of ecotoxicology is crucial to assess injuries to ecosystem resources from chemical spills or other stressors used to support environmental decision-making. Established guidelines recommend the use of non-standard native species in toxicity investigations. This work focused on the use of native species for aquatic toxicity assessment to make more relevant conclusions on the potential for adverse biological effects to occur as a result to single chemical exposures or exposures to a complex mixture like oil. We apply these studies to investigate petroleum product impacts from the Deepwater Horizon incident and concerns for metal toxicity in estuarine environments using a new model organism. Data generated from comprehensive toxicity testing programs were used in the first probabilistic risk assessment of Deepwater Horizon oil toxicity highlighting a lack of appropriate data and representative phyla. Novel toxicity study methods and a stress-response index were developed and demonstrated sensitivity and success in using the starlet anemone in ecotoxicology studies. Swim performance was used as new method to investigate sublethal indicators of stress resulting in varied responses from sheepshead minnows and Florida pompano. These studies further our ability for better laboratory-to-field extrapolation and for decision-making. The use of native species and complex mixtures like oil presented novel challenges in conducting aquatic toxicity studies. Special emphasis is placed on the necessity to understand the appropriate laboratory conditions for native species not typically held in the laboratory and maintaining study parameters to obtain quality data for more accurate interpretation and replication.

Sulfate- and Fe(III)-reducing, and methanogenic prokaryotes (SRP, FRP, MGP) are key players in metabolic pathways involved in anaerobic biodegradation processes. Understanding the metabolic activity of these microbes in environments can enhance microbe-mediated processes such as oil spill bioremediation and methane biogas production. In this study, anaerobic microbial activities in Deepwater Horizon oil spill-impacted salt marsh sediments, and in methanogenic coal bed production water enrichment cultures amended with trace elements (TE), were elucidated by employing an approach combining methods in molecular biology and geochemistry. In situ metabolic activity of SRP, FRP and MGP were monitored seasonally and metabolically-active communities were identified in oil-impacted sediments using quantitative real time Reverse Transcription -PCR and clone library analysis of key functional genes: Dissimilatory (bi)sulfite reductase (dsrAB), Geobactereceae-specific citrate synthase (gltA), methyl coenzyme M reductase (mcrA), and benzyl succinate synthase (bssA). In situ application of montmorillonite clay was assessed for its potential at accelerating PHC degradation by stimulating microbial activities. Levels of dsrA, gltA and bssA transcripts suggested that PHC-oxidizing SRP are more active in summer while FRP are more active in winter, indicating their activities linked to the seasonal changes of redox potential and vegetation. BssA gene expression peaked in winter, and was highest at more highly oil-impacted sites. Expression of all genes was higher in clay-amended sites. bssA transcript level and Fe(II) production were highest in clay-amended microcosm. Total petroleum hydrocarbon (TPH) levels were lower in oil and clay-amended microcosm incubation than one with oil only amendment, suggesting enhanced TPH degradation by clay amendment. Pyrosequencing analysis 16S rRNA gene in clay-amended microcosms demonstrated the highest percentage abundance of groups closely related to known anaerobic aromatic degraders. Levels of mcrA transcripts correlated with methane production rates in TE-amended coal bed production water enrichments. The findings of the present study clearly support the advantage of gene expression analyses for estimating microbial activity. To the best of our knowledge, this is the first in situ study which employs key functional gene markers as molecular proxies for metabolic activity and diversity assessments in anaerobic oil-contaminated salt marsh sediment and also elucidates clay-enhanced in situ TPH degradation.

L'explosion de la plateforme de forage « Deepwater Horizon » dans le Golfe du Mexique en avril 2010 a provoqué le déversement d'un grand volume de pétrole brut dans les eaux de la région ce qui a conduit à des répercussions importantes sur la faune locale. Les impacts d'une telle catastrophe à long terme sur les oiseaux de mer ont peu été étudiés par la communauté scientifique. Pourtant, les effets délétères induits par l'action des hydrocarbures aromatiques polycycliques (HAPs) contenus dans le pétrole brut représentent la principale source d'inquiétude d'une exposition chronique sous-létale. L'île Bonaventure, situé dans le parc national de l'île-Bonaventure-et-du-Rocher-Percé, accueil l'une des plus grandes colonies de fous de bassan (Morus bassanus) au monde. Environ un quart de cette colonie migre dans le Golfe du Mexique une fois la saison de reproduction terminée, courant ainsi le risque d'être exposé au pétrole déversé soit directement (ingestion et absorption dermique) ou indirectement (consommation de proies contaminées). Une contamination au pétrole peut engendrer une détérioration de la condition physiologique des oiseaux exposés et altérer, entre autres, le fonctionnement du système endocrinien. Ainsi, il est justifié de craindre une portée sur la santé de ces oiseaux et donc, ultimement sur la dynamique de population de cette colonie (taux de survie, succès de reproduction, etc.). Cette étude avait pour but d'évaluer les effets potentiels de l'exposition aux HAPs, provenant du pétrole déversé dans le Golfe du Mexique, sur la santé de 34 fous de bassan de l'île Bonaventure lors de la période d'incubation à l'été 2011. Le premier objectif spécifique était de déterminer le lieu d'hivernage des fous de bassan à l'étude, soit le Golfe du Mexique ou la côte Atlantique, à l'aide de consignateurs d'intensité lumineuse afin de cibler les oiseaux potentiellement exposés au pétrole. Le second objectif consistait à déterminer le profil de contamination (HAPs) des oiseaux ainsi que de doser les concentrations hormonales (prolactine et corticostérone) circulant chez ces oiseaux. Finalement, il était question de mettre en relation le lieu d'hivernage, le profil de contamination et les concentrations hormonales des oiseaux en fonction du temps dans l'incubation (tôt ou tard). Il était attendu que les oiseaux ayant fréquenté le Golfe du Mexique aient des concentrations d'HAPs supérieures aux oiseaux de la côte Atlantique et que leurs concentrations en corticostérone et prolactine en soient affectés ce qui diminuerait leur succès de reproduction. Les concentrations sanguines en HAPs se sont révélées être sous les limites de détection de l'instrument analytique (HPLC). De plus, les concentrations hormonales ne semblaient pas différer selon le lieu de migration des oiseaux, ni le temps dans l'incubation. Leur succès de reproduction ne semblait pas affecté à l'été 2011. Toutefois, l'absence d'effets visibles au niveau de la reproduction de ces oiseaux n'implique pas nécessairement une absence d'impact physiologique. Finalement, cette étude a permis de démontrer l'utilité de la géolocation dans un contexte d'étude d'impact lors de déversement pétrolier, ce qui n'avait encore jamais été fait. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : prolactine, corticostérone, HAPs, Golfe du Mexique, Sulidae, oiseaux de mer

The BP Deepwater Horizon crisis in 2010 was one the largest catastrophes in the history of the oil industry. BP was sued over the disaster, and lost several billion dollars. This study examines the crisis response strategies and/or image repair strategies, which can be found in BP's press releases following the Deepwater Horizon crisis. In particular, the study looks closer at what established crisis communication strategies could be discerned in the material, and how they are used discursively. The theories used were the Image Repair Theory (IRT) and the Situational Crisis Communication Theory (SCCT). The results show that BP utilized a number of different established crisis response strategies and/or image repair strategies in their crisis communication work in the press releases. These strategies were concern, corrective action, ingratiation, transcendence, differentiation, denial, shifting the blame/scapegoating, defeasibility, compassion and attacking the accuser. They were used discursively by the CEO by expressing sympathy, promising that a similar event will never happen again, by stating appreciation for and praising the leadership of the U.S. President and public sector. What is more, it is used by describing in detail how the solution process progresses, by stating what the causes of the crisis were, by describing other involved actors' lack of taking responsibility and by establishing a fraud hotline. The main conclusions of the study are that BP used several crisis strategies in their press release s, though rather inconsistently. Additionally, BP used the strategies in an ambiguous manner, and changed strategies over time. Lastly, one main conclusion is also that a company is prepared to utilize crisis communication strategies in their practical communications work, though not entirely in the way prescribed by the theories.