Deepwater Horizon Oil Spill Research Articles

Rational Choice Theory in the Study of Deepwater Horizon Oil Spill

The Deepwater Horizon oil spill was the worst environmental disaster in US history. The oil spill reflects the dependence of the United States on the exploitation of fossil fuels. President Barack Obama seeks to bring about significant changes in US energy policy by promoting and expanding clean energy. However, the new policy faced resistance from Congress and the oil companies. This study aims to determine the impact of the Deepwater Horizon Oil Spill on US energy policy using rational choice theory. To achieve the expansion of rational choice theory in the Deepwater Horizon oil spill study, the researcher used qualitative methodology and case study method. The result of this study is that the Deepwater Horizon oil spill became a stepping stone for the transformation of US energy policy. The findings of this study are the linearity of clean energy development and US political commitment in developing the clean energy industry.

Exposure Group Development in Support of the NIEHS GuLF Study.

In the GuLF Study, a study investigating possible adverse health effects associated with work on the oil spill response and clean-up (OSRC) following the Deepwater Horizon disaster in the Gulf of Mexico, we used a job-exposure matrix (JEM) approach to estimate exposures. The JEM linked interview responses of study participants to measurement data through exposure groups (EGs). Here we describe a systematic process used to develop transparent and precise EGs that allowed characterization of exposure levels among the large number of OSRC activities performed across the Gulf of Mexico over time and space. EGs were identified by exposure determinants available to us in our measurement database, from a substantial body of other spill-related information, and from responses provided by study participants in a detailed interview. These determinants included: job/activity/task, vessel and type of vessel, weathering of the released oil, area of the Gulf of Mexico, Gulf coast state, and time period. Over 3000 EGs were developed for inhalation exposure and applied to each of 6 JEMs of oil-related substances (total hydrocarbons, benzene, toluene, ethylbenzene, total xylene, and n-hexane). Subsets of those EGs were used for characterization of exposures to dispersants, particulate matter, and oil mist. The EGs allowed assignment to study participants of exposure estimates developed from measurement data or from estimation models through linkage in the JEM for the investigation of exposure-response relationships.

Estimation of Aerosol Concentrations of Oil Dispersants COREXIT™ EC9527A and EC9500A during the Deepwater Horizon Oil Spill Response and Clean-up Operations.

The April 2010 Deepwater Horizon drilling unit explosion at the Macondo oil well resulted in the release of approximately 779 million l of oil into the Gulf of Mexico. As part of the response effort to break up oil slicks on the water's surface, 6.81 million l of chemical dispersants COREXIT™ EC9500A and COREXIT™ EC9527A were applied by plane or vessel or injected near the seabed. The GuLF Long-term Follow-up Study is investigating possible adverse health effects of workers involved in the oil spill response and clean-up (OSRC). In this paper, we describe potential dispersant-related air concentrations generated from aerial spraying of dispersants to provide insight as to what concentrations OSRC workers may have been exposed under worst-case conditions. Personal exposure measurement data were not collected. Modeling, therefore, was conducted to estimate airborne concentrations of total aerosol to COREXIT™ EC9527A and EC9500A. Using the AgDISP model, we estimated air concentrations to dispersant total aerosols, defined as all components of the dispersant including active ingredients, surfactants, and water, resulting from aerial and vessel applications, as average 1-h and 2-min concentrations. For comparison, 1-h air concentrations associated with aerial spraying were estimated using another model, AERMOD. At 152 m horizontal to the flight path, average 1-h total aerosol concentrations associated with aerial applications were estimated to be as high as 49.3 µg m-3 (9527A) and 45.4 µg m-3 (9500A), and both decreased with increased distance from the flight line. The estimates for spraying 9500A from vessels indicated that total aerosol concentrations were potentially as high as 0.33 µg m-3 at 10 m from the nozzles. These results suggest that personal exposures to dispersant aerosols were negligible.

In Situ Sensor for the Detection of Oil Spill in Seawater Using Microwave Techniques.

Nearly 30% of oil drilled globally is done offshore. Oil spillage offshore has far-reaching consequences on the environment, aquatic lives, and livelihoods as it was evident in the Deepwater Horizon and Bonga oil spills. A novel microwave in situ oil spill sensor was developed in this work. The device is comprised of two polydimethylsiloxane (PDMS)-encapsulated ultra-wideband underwater microwave trefoil antennas enclosed in a Faraday cage with one serving as the receiving antenna and the other as the transmitting antenna. Heavy aromatic-naphthenic Azeri crude oil was used as an inclusion in the seawater host medium. Substantial changes in the measured reflection (S11) and transmission (S21) coefficients were observed as the medium was adulterated with crude oil starting from 200 MHz to around 2500 MHz. The changes in the dielectric properties of the media resulted in changes in both the S11 and S21 signifying and detecting an occurrence of the oil spillage. Thus, by employing radio frequencies, oil spillage was detected using the in situ monitoring device in seawater.

A Comparative Analysis of In-Situ Optical Velocimetries for Oil Spill Flow Rate Estimation

In the Deepwater Horizon oil spill, optical plume velocimetry (OPV), a flow measurement technique for use in seafloor hydrothermal systems, was found to have the least uncertainty in estimating the rate at which oil was escaping from the well in the deep sea. However, OPV still had a high uncertainty of 21%, partly due to the limited accuracy of the temporal cross-correlation algorithm used. In this work, the accuracy of several in-situ optical velocimetries, namely wavelet-based optical velocimetry (WOV), OPV, and two classical correlation-based algorithms, namely fast Fourier transform (FFT) and normalized cross-correlation (NCC), for a plume flow with Reynolds numbers varying from 1847 to 11,656 was investigated. WOV, FFT, and NCC resulted in flow rates closer to the expected turbulent plume flow rate as compared to OPV. Moreover, a noisy velocity field was found using OPV. The accuracy of wavelet-based algorithm outperformed all cross-correlation based algorithms. The flow rate was measured with an error of 8.5% using WOV, whereas errors of 18.2%, 19.7%, to 21.1% were obtained when applying FFT, OPV, and NCC, respectively. There was a statistically significant difference between wavelet-based and correlation-based algorithms, but no statistically significant difference between the estimation of the three cross-correlation based velocimetries. WOV outperformed the other velocimetries and estimated flow rates with an error of 8.5%, whereas the OPV, FFT, and NCC were estimated with errors of 19.7%, 18.2%, and 50.8%, respectively.

A Bibliometric Review and Science Mapping Research of Oil Spill Response

This study aimed to evaluate the research output of oil spill response and citations from 2000 to 2022 through a bibliometric analysis. The primary findings were as follows: there has been a noticeable increase in the number of publications. The most active journal was Marine Pollution Bulletin. Environmental sciences ranked as the most popular subject area. The United States of America (USA) published the greatest number of single-authored, internationally collaborative, first-authored papers. Oil spill(s) was the most widely queried research term, ranking first in the article title, abstract, and author keyword analysis, respectively. The Deep-Water Horizon disaster, the largest marine oil spill in 2010, was the most frequently analyzed oil spill accident in the research as a sample. This study makes a significant contribution to the field of oil spill response science by being one of the few that applies network visualization and mapping technique. Further research is recommended in light of longer-term data and the diverse Web of Science (WoS) categories found in oil spill science, which may be visualized using a variety of bibliometric visualization applications.

Surfacing Ecological Disaster:Poets for Living Watersand the Deepwater Horizon Oil Spill

AbstractConsidering the 2010 Deepwater Horizon Spill, the largest environmental disaster in American history, this article examines the elemental intermixing of oil and water via the chemical agent Corexit, the substantial effects submerging oil into the water column had on ocean life, and the aesthetic translation of this environmental destruction by the poetry platformPoets for Living Waters. Functioning as a communal expression of grief, of remembrance, and a demand for change,Poets for Living Watersbrings together the work of hundreds of authors, figuratively raising oil’s toxic specter to the surface by challenging America’s failure to protect ocean ecosystems through an elementally-attentive poetics that highlights the characteristic traits of both water and oil and the deadly effects that occur when these two elements intermix.

Risk factors for acute mental health symptoms and tobacco initiation in Coast Guard Responders to the Deepwater Horizon oil spill.

Acute mental health symptoms experienced during oil spill response work are understudied, especially among nonlocal responders. We assessed potential risk factors for acute mental health symptoms and tobacco initiation among U.S. Coast Guard responders to the 2010 Deepwater Horizon (DWH) oil spill who completed a deployment exit survey. Cross-sectional associations among responder characteristics, deployment-related stressors (deployment duration, timing, crude oil exposure, physical symptoms, injuries), and professional help-seeking for stressors experienced with concurrent depression/anxiety and tobacco initiation were examined. Log-binomial regression was used to calculate adjusted prevalence ratios (aPRs) and 95% confidence intervals. Sensitivity analyses excluded responders with a history of mental health conditions using health encounter data from the Military Health System Data Repository. Of the 4,855 responders, 75.5% were deployed from nonlocal/non-Gulf home stations, 5.8% reported concurrent depression and anxiety, and 2.8% reported the initiation of any tobacco product during oil spill response. Self-report of concurrent depression and anxiety was more prevalent among female responders and positively associated with longer deployments, crude oil exposure via inhalation, physical symptoms and injuries, and professional help-seeking during deployment, aPRs = 1.54-6.55. Tobacco initiation was inversely associated with older age and officer rank and positively associated with deployment-related stressors and depression/anxiety during deployment, aPRs = 1.58-4.44. Associations remained robust after excluding responders with a history of mental health- and tobacco-related health encounters up to 3 years before deployment. Depression, anxiety, and tobacco initiation were cross-sectionally associated with oil spill response work experiences among DWH responders, who largely originated outside of the affected community.

An essential stupidity-based review of the Deepwater Horizon disaster

Though more than a decade has passed, there are compelling reasons to revisit the Deepwater Horizon disaster, the most expensive nonnuclear industrial disaster in history. It serves as an exemplar of what organizations should not do. Recent tragedies in Nigeria and Florida also demonstrate how organizations might avoid the risk of being overtaken by readily predictable events. In this article, we look to advance research on risk mitigation and decision-making as we create a more succinct view of how managers create—and might prevent—inaptitude. To this end, we look at how the evolving concept of stupidity is defined in recent research and how it manifested in the critical case of the Deepwater Horizon drilling rig. We present five proposals for organizations looking to address and avoid potentially unwise decisions that may lead to the next disaster.

Looking Over Our Shoulders at Disaster

In a journey spanning almost 20 years the Southern Food & Beverage Museum has become established as a solid and reliable museum and attraction in New Orleans, Louisiana. Its journey to established museum has been fraught with disaster and determination – from Hurricane Katrina in 2005, the financial crisis of 2008, the BP Oil Spill, and COVID - to more local disasters like floods and hurricanes. Today it is ready for whatever may happen, as well as prepared with a plan to pivot, innovate, and re-invent itself, all the while deepening its mission and continuing to be the Southern Food & Beverage Museum.

Mixing Oil and Water: The Shrimp–Petroleum Nexus in Coastal Louisiana

AbstractThe Shrimp‐Petroleum Festival is an annual event in Morgan City, Louisiana, that celebrates the history of the two industries in this coastal city. The festival came under media scrutiny and public criticism in the wake of the 2010 BP oil spill in the Gulf of Mexico, in part because of the seeming incompatibility and incongruence of the two things being celebrated. From a local perspective, however, the convergence of the two industries is far from incompatible and the two resources in question, shrimp and oil, are categorically similar within local discourses of identity, well‐being, and economic prosperity. In that capacity, it offers an insight into how precarious and contingent the seemingly self‐evident dichotomies commonly invoked in normative environmentalism are. It also offers insight and into the range of assumptions and signification practices involved in assigning meaning to particular kinds of resources and particular kinds of human–nature relations.

Quantification of synthetic-based drilling mud olefins in crude oil and oiled sediment by liquid column silver nitrate and gas chromatography

Synthetic-based drilling muds (SBMs) are complex mixtures of man-made fluids used during the drilling of oil and gas wells. SBM-derived chemicals can enter the environment through failed wells and routine or poor disposal practices, where they can persist and thereby warrant measurement. SBMs are commonly formulated with linear and methyl branched α- and internal-olefins mostly in the C14 to C20 carbon range, which are not native to crude oils. Thus, SBM-derived olefins can provide a basis to recognize the impact of these drilling wastes in the environment. However, the presence of abundant native hydrocarbons in oils and sediments can hinder the detection of trace level SBM-derived olefins by conventional organic sample preparation and analytical methods. Silver ion chromatography using silver nitrate (AgNO3) impregnated silica gel can serve to physically separate olefins from saturated aliphatic hydrocarbons native in crude oils, which can subsequently be analyzed and measured by conventional one-dimensional gas chromatography-flame ionization detection (GC-FID). In this study, SBM-derived olefins are measured in crude oils from the Deepwater Horizon oil spill and in their laboratory mixtures to a detection limit of approximately 5000 µg/g (0.5 wt%). In oiled sediment, SBM-derived olefins were reliably detected at concentrations as low as 1 µg/g-dry. An application of this method is demonstrated through analysis of crude oils and oil-contaminated seafloor sediment from the Taylor Energy oil spill site in the northern Gulf of Mexico where SBM was historically used and discharged.

Marine Snow-Oil Interaction Affects n-Alkane Biodegradation in Sediment

During the Deepwater Horizon (DwH) oil spill, an excessive production of marine snow was observed, and it was estimated that as much as 14% of the oil was transferred to the ocean floor by MOSSFA (Marine Oil Snow Sedimentation and Flocculent Accumulation). MOSSFA is an important pathway of transferring oil to the ocean floor. We performed experiments at laboratory scale in 15 aquaria, representing 5 exposures of marine snow with or without oil, only oil, and controls with only clay or sediment. We developed a method to produce artificial marine snow, which resembles the natural marine snow. Results showed 40% less biodegradation of alkanes in “marine snow with oil” compared to “only oil.” Most probably, this is due to preferred biodegradation of marine snow organics comparing to oil alkanes. Biodegradation of marine snow reduces the dissolved oxygen concentration, which might result in anaerobic conditions in the sediment layer. This finding can be projected to a potential ocean floor effect.

Association of Deepwater Horizon Oil Spill Response and Cleanup Work With Risk of Developing Hypertension

Exposure to hydrocarbons, fine particulate matter (PM2.5), and other chemicals from the April 20, 2010, Deepwater Horizon disaster may be associated with increased blood pressure and newly detected hypertension among oil spill response and cleanup workers. To determine whether participation in cleanup activities following the disaster was associated with increased risk of developing hypertension. This cohort study was conducted via telephone interviews and in-person home exams. Participants were 6846 adults who had worked on the oil spill cleanup (workers) and 1505 others who had completed required safety training but did not do cleanup work (nonworkers). Eligible participants did not have diagnosed hypertension at the time of the oil spill. Statistical analyses were performed from June 2018 to December 2021. Engagement in cleanup activities following the Deepwater Horizon oil spill disaster, job classes, quintiles of cumulative total hydrocarbons exposure level, potential exposure to burning or flaring oil, and estimated PM2.5 were examined. Systolic and diastolic blood pressure measurements were collected during home exams from 2011 to 2013 using automated oscillometric monitors. Newly detected hypertension was defined as antihypertensive medication use or elevated blood pressure since the spill. Log binomial regression was used to calculate prevalence ratios (PR) and 95% CIs for associations between cleanup exposures and hypertension. Multivariable linear regression was used to estimate exposure effects on continuous blood pressure levels. Of 8351 participants included in this study, 6484 (77.6%) were male, 517 (6.2%) were Hispanic, 2859 (34.2%) were non-Hispanic Black, and 4418 (52.9%) were non-Hispanic White; the mean (SD) age was 41.9 (12.5) years at enrollment. Among workers, the prevalence of newly detected hypertension was elevated in all quintiles (Q) of cumulative total hydrocarbons above the first quintile (PR for Q3, 1.29 [95% CI, 1.13-1.46], PR for Q4, 1.25 [95% CI, 1.10-1.43], and PR for Q5, 1.31 [95% CI, 1.15-1.50]). Both exposure to burning and/or flaring oil and gas (PR, 1.16 [95% CI, 1.02-1.33]) and PM2.5 from burning (PR, 1.26 [95% CI, 0.89-1.71]) for the highest exposure category were associated with increased risk of newly detected hypertension, as were several types of oil spill work including cleanup on water (PR, 1.34 [95% CI, 1.08-1.66]) and response work (PR, 1.51 [95% CI, 1.20-1.90]). Oil spill exposures were associated with newly detected hypertension after the Deepwater Horizon disaster. These findings suggest that blood pressure screening should be considered for workers with occupational hydrocarbon exposures.

Advocacy coalitions and political control

AbstractThe Advocacy Coalition Framework (ACF) posits that policy actors, including elected officials and bureaucrats, aggregate into coalitions based on shared beliefs and coordinate to achieve policy objectives. Yet, bureaucrats are often subject to political control mechanisms understood within a principal‐agent framework. Combining insights from principal‐agent theory and the ACF, we explore the nature of principal‐agent relationships within and across advocacy coalitions in the United States using case studies of nuclear waste management and fair housing policy. Specifically, we develop three propositions regarding principals and agents as members of advocacy coalitions and examine those propositions by comparing the two case studies. We find that powerful elected officials and expert bureaucrats are important resources for coalitions; bureaucrats are in coalitions but face cross‐pressure from principals in opposing coalitions; and control mechanisms embedded in policy designs by principals can limit bureaucratic discretion in a way that aligns with coalition goals.Related ArticlesNeill, Katharine A., and John C. Morris. 2012. “A Tangled Web of Principals and Agents: Examining the Deepwater Horizon Oil Spill through a Principal–Agent Lens.” Politics & Policy 40(4): 629–56. https://doi.org/10.1111/j.1747‐1346.2012.00371.xPeterson, Holly L., Mark K. McBeth, and Michael D. Jones. 2020. “Policy Process Theory for Rural Studies: Navigating Context and Generalization in Rural Policy.” Politics & Policy 48(4): 576–617. https://doi.org/10.1111/polp.12366Swigger, Alexandra, and Bruce Timothy Heinmiller. 2014. “Advocacy Coalitions and Mental Health Policy: The Adoption of Community Treatment Orders in Ontario.” Politics & Policy 42(2): 246–70. https://doi.org/10.1111/polp.12066

Modeling population effects of the Deepwater Horizon oil spill on a long-lived species.

The 2010 Deepwater Horizon (DWH) oil spill exposed common bottlenose dolphins (Tursiops truncatus) in Barataria Bay, Louisiana to heavy oiling that caused increased mortality and chronic disease and impaired reproduction in surviving dolphins. We conducted photographic surveys and veterinary assessments in the decade following the spill. We assigned a prognostic score (good, fair, guarded, poor, or grave) for each dolphin to provide a single integrated indicator of overall health, and we examined temporal trends in prognostic scores. We used expert elicitation to quantify the implications of trends for the proportion of the dolphins that would recover within their lifetime. We integrated expert elicitation, along with other new information, in a population dynamics model to predict the effects of observed health trends on demography. We compared the resulting population trajectory with that predicted under baseline (no spill) conditions. Disease conditions persisted and have recently worsened in dolphins that were presumably exposed to DWH oil: 78% of those assessed in 2018 had a guarded, poor, or grave prognosis. Dolphins born after the spill were in better health. We estimated that the population declined by 45% (95% CI 14–74) relative to baseline and will take 35 years (95% CI 18–67) to recover to 95% of baseline numbers. The sum of annual differences between baseline and injured population sizes (i.e., the lost cetacean years) was 30,993 (95% CI 6607–94,148). The population is currently at a minimum point in its recovery trajectory and is vulnerable to emerging threats, including planned ecosystem restoration efforts that are likely to be detrimental to the dolphins’ survival. Our modeling framework demonstrates an approach for integrating different sources and types of data, highlights the utility of expert elicitation for indeterminable input parameters, and emphasizes the importance of considering and monitoring long‐term health of long‐lived species subject to environmental disasters. Article impact statement: Oil spills can have long‐term consequences for the health of long‐lived species; thus, effective restoration and monitoring are needed.

Sex and habitat drive hantavirus prevalence in marsh rice rat populations impacted by the Deepwater Horizon oil spill

AbstractBayou orthohantavirus (BAYV) is one of several hantaviruses in the United States that cause hantavirus pulmonary syndrome in humans. Its host reservoir, the marsh rice rat (Oryzomys palustris), inhabits coastal saltmarshes of Louisiana, a region extensively impacted by anthropogenic disturbances, such as the 2010 Deepwater Horizon (DWH) oil spill. The oil spill presents an opportunity to investigate how a large‐scale ecological disturbance can influence the hantavirus host–pathogen dynamic by examining BAYV presence in its reservoir host species in areas with different oiling histories. Here, we: (1) quantify BAYV prevalence in the rice rat in coastal saltmarshes of Louisiana; (2) assess whether prevalence is driven by rice rat demographics, seasonality, or association with habitat characteristics; and (3) determine whether these factors differ by marsh oiling history. We collected mark–recapture data and blood and tissue samples over 5 years (2013–2017) at oiled, unoiled, and reference sites. Testing of the samples for BAYV revealed an antibody and RNA prevalence of 13.7%. Logistic regression analysis found that prevalence varied seasonally and inter‐annually, and in July of 2016 reached 30.8%. Sex (male) and increasing cover of Sporobolus alterniflorus and open water compared to Juncus roemerianus and bare ground were the strongest predictors of hantavirus prevalence. Abundance estimates derived from Huggins closed‐capture models were greatest at oiled sites, but oiling treatment had no residual influence on BAYV prevalence, and abundance and prevalence were not correlated. This study supports the hypothesis that habitat is a main driver of hantavirus prevalence in the host and implies that continued and future disturbances in the region will likely impact the rice rat–BAYV dynamic by altering plant communities and landscape structure.

Fine Particulate Matter and Lung Function among Burning-Exposed Deepwater Horizon Oil Spill Workers.

Background:During the 2010 Deepwater Horizon (DWH) disaster, controlled burning was conducted to remove oil from the water. Workers near combustion sites were potentially exposed to increased fine particulate matter [with aerodynamic diameter ()] levels. Exposure to has been linked to decreased lung function, but to our knowledge, no study has examined exposure encountered in an oil spill cleanup.Objective:We investigated the association between estimated only from burning/flaring of oil/gas and lung function measured 1–3 y after the DWH disaster.Methods:We included workers who participated in response and cleanup activities on the water during the DWH disaster and had lung function measured at a subsequent home visit (). concentrations were estimated using a Gaussian plume dispersion model and linked to work histories via a job-exposure matrix. We evaluated forced expiratory volume in 1 s (FEV1; milliliters), forced vital capacity (FVC; milliliters), and their ratio (FEV1/FVC; %) in relation to average and cumulative daily maximum exposures using multivariable linear regressions.Results:We observed significant exposure–response trends associating higher cumulative daily maximum exposure with lower FEV1 () and FEV1/FVC (). In comparison with the referent group (workers not involved in or near the burning), those with higher cumulative exposures had lower FEV1 [, 95% confidence interval (CI): , 3.7] and FEV1/FVC (, 95% CI: , 0.2). We also saw nonsignificant reductions in FVC (high vs. referent: , 95% CI: , 77.6; ). Similar associations were seen for average daily maximum exposure. Inverse associations were also observed in analyses stratified by smoking and time from exposure to spirometry and when we restricted to workers without prespill lung disease.Conclusions:Among oil spill workers, exposure to specifically from controlled burning of oil/gas was associated with significantly lower FEV1 and FEV1/FVC when compared with workers not involved in burning. https://doi.org/10.1289/EHP8930

Dispersed Crude Oil Induces Dysbiosis in the Red Snapper Lutjanus campechanus External Microbiota.

ABSTRACTThe fish external microbiota competitively excludes primary pathogens and prevents the proliferation of opportunists. A shift from healthy microbiota composition, known as dysbiosis, may be triggered by environmental stressors and increases host susceptibility to disease. The Deepwater Horizon (DWH) oil spill was a significant stressor event in the Gulf of Mexico. Despite anecdotal reports of skin lesions on fishes following the oil spill, little information is available on the impact of dispersed oil on the fish external microbiota. In this study, juvenile red snapper (Lutjanus campechanus) were exposed to a chemically enhanced water-accommodated fraction (CEWAF) of Corexit 9500/DWH oil (CEWAF) and/or the bacterial pathogen Vibrio anguillarum in treatments designed to detect changes in and recovery of the external microbiota. In fish chronically exposed to CEWAF, immunoglobulin M (IgM) expression significantly decreased between 2 and 4 weeks of exposure, coinciding with elevated liver total polycyclic aromatic hydrocarbons (PAHs). Dysbiosis was detected on fish chronically exposed to CEWAF compared to seawater controls, and addition of a pathogen challenge altered the final microbiota composition. Dysbiosis was prevented by returning fish to clean seawater for 21 days after 1 week of CEWAF exposure. Four fish exhibited lesions during the trial, all of which were exposed to CEWAF but not all of which were exposed to V. anguillarum. This study indicates that month-long exposure to dispersed oil leads to dysbiosis in the external microbiota. As the microbiota is vital to host health, these effects should be considered when determining the total impacts of pollutants in aquatic ecosystems.IMPORTANCE Fish skin is an immunologically active tissue. It harbors a complex community of microorganisms vital to host homeostasis as, in healthy fish, they competitively exclude pathogens found in the surrounding aquatic environment. Crude oil exposure results in immunosuppression in marine animals, altering the relationship between the host and its microbial community. An alteration of the healthy microbiota, a condition known as dysbiosis, increases host susceptibility to pathogens. Despite reports of external lesions on fishes following the DWH oil spill and the importance of the external microbiota to fish health, there is little information on the effect of dispersed oil on the external microbiota of fishes. This research provides insight into the impact of a stressor event such as an oil spill on dysbiosis and enhances understanding of long-term sublethal effects of exposure to aid in regulatory decisions for protecting fish populations during recovery.

Alterations of endophytic microbial community function in Spartina alterniflora as a result of crude oil exposure.

The 2010 Deepwater Horizon disaster remains one of the largest oil spills in history. This event caused significant damage to coastal ecosystems, the full extent of which has yet to be fully determined. Crude oil contains toxic heavy metals and substances such as polycyclic aromatic hydrocarbons that are detrimental to some microbial species and may be used as food and energy resources by others. As a result, oil spills have the potential to cause significant shifts in microbial communities. This study assessed the impact of oil contamination on the function of endophytic microbial communities associated with saltmarsh cordgrass (Spartina alterniflora). Soil samples were collected from two locations in coastal Louisiana, USA: one severely affected by the Deepwater Horizon oil spill and one relatively unaffected location. Spartina alterniflora seedlings were grown in both soil samples in greenhouses, and GeoChip 5.0 was used to evaluate the endophytic microbial metatranscriptome shifts in response to host plant oil exposure. Oil exposure was associated with significant shifts in microbial gene expression in functional categories related to carbon cycling, virulence, metal homeostasis, organic remediation, and phosphorus utilization. Notably, significant increases in expression were observed in genes related to metal detoxification with the exception of chromium, and both significant increases and decreases in expression were observed in functional gene subcategories related to hydrocarbon metabolism. These findings show that host oil exposure elicits multiple changes in gene expression from their endophytic microbial communities, producing effects that may potentially impact host plant fitness.