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Research investigating gastrointestinal (GI) symptoms from oil spill-related exposures is sparse. We evaluated prevalent GI symptoms among U.S. Coast Guard responders deployed to the Deepwater Horizon oil spill cleanup. Crude oil (via skin contact, inhalation, or ingestion routes), combined crude oil/oil dispersant exposures, other deployment exposures, deployment characteristics, demographics, and acute GI symptoms during deployment (i.e., nausea/vomiting, diarrhea, stomach pain, and constipation) were ascertained cross-sectionally via a post-deployment survey (median time between deployment end and survey completion 185 days) (N = 4885). Log-binomial regression analyses were employed to calculate prevalence ratios (PRs) and 95 % confidence intervals (CI). Effect modification was evaluated. In adjusted models, responders in the highest (versus lowest) tertile of self-reported degree of skin contact to crude oil were more than twice as likely to report nausea/vomiting (PR=2.45; 95 %CI, 1.85–3.23), diarrhea (PR=2.40; 95 %CI, 2.00–2.88), stomach pain (PR=2.51; 95 %CI, 2.01–3.12), and constipation (PR=2.21; 95 %CI, 1.70–2.89). Tests for trend were statistically significant (p < 0.05). Results were similar for crude oil exposure via inhalation and ingestion. Higher PRs for all symptoms were found with combined crude oil/dispersant exposure than with crude oil exposure alone. These results indicate positive associations between self-reported crude oil and combined crude oil/oil dispersant exposures and acute GI symptoms. [ABSTRACT FROM AUTHOR]

• Oiled marshes contained distinct soil microbial communities eight years later. • Spatial location and petroleum residue governed the structure of soil microbial communities. • The most abundant bacterial indicator for heavily oiled marshes was genus KCM-B-112. • Myxobacteria were indicators of reference sites. The Deepwater Horizon (DWH) oil spill significantly impacted salt marsh ecosystems, with numerous repercussions observed in the subsequent years. However, the long-term effects of chronic oil exposure on soil microbial communities remain unexplored. This study, conducted in 2018, aimed to identify how the legacy of heavy oiling from the DWH spill in 2010 influenced the soil microbial community. We surveyed vegetation and soil variables while simultaneously employing high-throughput 16s rRNA gene sequencing to examine microbial communities in soils across 21 marsh sites that exhibited varying degrees of initial oil contamination following the DWH incident. The effects of these variables, including geographic location, on taxonomic and phylogenetic metrics of community composition were disentangled using variance partitioning analysis and permutational ANOVA. Results showed a strong and significant longitudinal trend in microbial community composition that was partially confounded with degree of initial oil exposure and contemporary vegetation biomass. However, significant indicator species for heavily oiled sites included oil-degrading bacteria, and there were significant differences in microbial community composition among marshes that received variable levels of initial oiling after controlling for this spatial effect. The level of soil petroleum residues that remained in 2018 had significant explanatory power for community composition after controlling for location, whereas the effects of vegetation biomass were largely confounded with longitude. Collectively, our results indicate that persistent oil pollution as well as unidentified spatial processes, possibly associated with spill-induced alterations in erosion or wave dynamics, played a role in structuring soil microbial communities within this ecosystem. [ABSTRACT FROM AUTHOR]

We used high-resolution fisheries-dependent data and a quantitative modeling approach to examine resilience of a commercial reef fish fleet after the Deepwater Horizon oil spill (DWH) emergency closures in 2010. Our results indicate that the fleet was largely resilient to the closures, although there were spatially-varying differences in attrition, and concomitant management changes and emergency payouts that likely influenced resilience. Five percent of previously active vessels exited the fleet after DWH (compared to the background annual attrition rate of ˜20%). The predicted probability of exiting after DWH was lower for vessels with a pre-closure history of high catch-per-unit-effort, low snapper revenue variability, or low grouper revenue. There was ˜80% overlap in pre- to post-DWH effort distribution, although vessels that exited concentrated effort in the north-central and eastern Gulf of Mexico. The Vessels of Opportunity program and other emergency compensation likely ameliorated some of the negative economic impacts from DWH, allowing more vessels to remain in the fleet than may have otherwise. Implementation of gear restrictions and individual fishing quotas leading up to DWH may have also 'primed' the fleet for resilience by removing marginal fishers. This work is novel in its use of high-resolution spatial data, coupled with trip logbooks, to construct quantitative models identifying drivers of fisher resilience after significant and sudden perturbations to fishery resources in the Gulf of Mexico. This work also highlights the need to better understand fisher response to disturbance for long-term fishery sustainability and management. [ABSTRACT FROM AUTHOR]

Abstract Acute exposure to crude oil and polycyclic aromatic hydrocarbons (PAH) can severely impair cardiorespiratory function and swim performance of larval, juvenile and adult fish. Interestingly, recent work has documented an oil induced decoupling of swim performance (U crit) and maximum metabolic rate (MMR) whereby oil causes a decline in U crit without a parallel reduction in MMR. We hypothesize that this uncoupling is due to impaired mitochondrial function in swimming muscles that results in increased proton leak, and thus less ATP generated per unit oxygen. Using high resolution mitochondrial respirometry, we assessed 11 metrics of mitochondrial performance in red and cardiac muscle from permeabilized fibers isolated from red drum following control or 24 h crude oil (high energy water accommodated fractions) exposure. Two experimental series were performed, a Deepwater Horizon relevant low dose (29.6 ± 7.4 μg L−1 ∑PAH 50) and a proof-of-concept high dose (64.5 ± 8.9 μg L−1 ∑PAH 50). No effects were observed on any mitochondrial parameter in either tissue at the low oil dose; however, high dose exposure provided evidence of impairment in the OXPHOS respiratory control ratio and OXPHOS spare capacity in red muscle following oil exposure, as well as a shift from Complex I to Complex II during OXPHOS respiration. No effects of the high dose oil treatment were observed in cardiac muscle. As such, mitochondrial dysfunction is unlikely to be the underlying mechanism for decoupling of U crit and MMR following acute oil exposure in red drum. Furthermore, mitochondrial dysfunction does not appear to be a relevant toxicological impairment in juvenile red drum with respect to the Deepwater Horizon oil spill, although impairments may be observed under higher dose exposure scenarios. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract The Deepwater Horizon (DWH) oil spill was the biggest in US history and released 3.19 million barrels of light crude oil into the Gulf of Mexico. In this study, we compared the toxicity of water accommodated fractions (WAFs) of naturally weathered crude oils, source oil, and source oil with dispersant mixtures and their effects on developing sheepshead minnow and zebrafish. Although a freshwater fish, zebrafish has been used as a model for marine oil spills owing to the molecular and genetic tools available and their amenability to lab care. Our study not only aimed to determine the effect of crude oil on early life stages of these two fish species, but also aimed to determine whether dissolved crude oil constituents were similar in fresh and saltwater, and if freshwater fish might be a suitable model to study marine spills. Weathering and dispersant had similar effects on WAF composition in both fresh and saltwater, except that the saltwater source oil + dispersant WAF had markedly higher PAH levels than the freshwater equivalent. WAF exposure differentially affected survival, as the LC50 values in %WAF for the zebrafish and sheepshead minnow exposures were 44.9% WAF (95% confidence interval (C.I.) 42.1–47.9) and 16.8% WAF (95% C.I. 13.7–20.5); respectively. Exposure increased heart rate of zebrafish embryos, whereas in sheepshead, source oil exposure had the opposite effect. WAF exposure altered mRNA expression of biotransformation makers, vitellogenin and neurodevelopment genes in both species. Muscle deformations were only found in oil-exposed zebrafish. This is one of the most comprehensive studies to date on crude oil toxicity, and highlights the species-specific differences in cardiotoxicity, estrogenic effects, biotransformation enzyme induction and potential neurotoxicity of crude oil exposure. Graphical abstract Unlabelled Image Highlights • The addition of dispersant increased the toxicity of source oil WAFs. • Dispersant + source oil WAF in saltwater had higher PAH levels than the freshwater equivalent. • Free-swimming vs chorion bound exposure time may play a role in determining the toxicity of early life-stage exposures • There are limitations to using freshwater species, like zebrafish, to model marine oil spills. • Interspecies molecular and physiological responses to crude oil can differ significantly. [ABSTRACT FROM AUTHOR]

Abstract Coastal salt marshes provide the valuable ecosystem service of removing anthropogenic nitrogen (N) via microbially-mediated denitrification. During the 2010 Deepwater Horizon (DWH) spill, oil exposure killed marsh plants in some regions and contributed to rapid compositional shifts in sediment microbial communities, which can impact ecosystem denitrification capacity. Within 3–5 years of the spill, plant biomass and microbial communities in some impacted marshes can recover to a new stable state. The objective of this study was to determine whether marsh recovery 6 years after the DWH oil spill results in subsequent recovery of denitrification capacity. We measured denitrification capacity (isotope pairing technique), microbial 16S rRNA gene composition, and denitrifier abundance (quantitative PCR) at sites subjected to light, moderate, and heavy oiling during the spill that were not targeted by any clean-up efforts. There were no differences in plant belowground biomass, sediment extractable NH 4 +, inorganic nitrogen flux, 16S rRNA composition, 16S rRNA diversity, or denitrifier functional gene (nirS , norB , and nosZ) abundances associated with oiling status, indicating that certain drivers of ecosystem denitrification capacity have recovered or achieved a new stable state six years after the spill. However, on average, denitrification capacities at the moderately and heavily oiled sites were less than 49% of that of the lightly oiled site (27.7 ± 14.7 and 37.2 ± 24.5 vs 71.8 ± 33.8 μmol N m−2 h−1, respectively). The presence of heavily weathered oiled residue (matched and non-matched for MC252) had no effect on process rates or microbial composition. The loss of function at the moderately and heavily oiled sites compared to the lightly oiled site despite the comparable microbial and environmental factors suggests that oiling intensity plays a role in the long-term recovery of marsh ecosystem services. Graphical abstract Image 1 Highlights • Oiling intensity impacted salt marsh denitrification capacity 6 years post-spill. • Neither 16S diversity nor denitrifier functional markers were affected by oiling intensity. • Oiling intensity plays a role in the long-term recovery of marsh biogeochemical function. Six years after the Deepwater Horizon oil spill, denitrification capacities were nearly 2X lower at moderately and heavily oiled salt marsh sites compared to a lightly oiled site, indicating that ecosystem service recovery is occurring at a slower temporal scale than for plant or microbial communities. [ABSTRACT FROM AUTHOR]

Abstract Introduction Oil spill response and cleanup (OSRC) workers had potentially stressful experiences during mitigation efforts following the 2010 Deepwater Horizon disaster. Smelling chemicals; skin or clothing contact with oil; heat stress; handling oily plants/wildlife or dead animal recovery; and/or being out of regular work may have posed a risk to worker respiratory health through psychological stress mechanisms. Objective To evaluate the association between six potentially stressful oil spill experiences and lung function among OSRC workers 1–3 years following the Deepwater Horizon disaster, while controlling for primary oil spill inhalation hazards and other potential confounders. Methods Of 6811 GuLF STUDY participants who performed OSRC work and completed a quality spirometry test, 4806 provided information on all exposures and confounders. We carried out complete case analysis and used multiple imputation to assess risk among the larger sample. Potentially stressful work experiences were identified from an earlier study of these workers. The lung function parameters of interest include the forced expiratory volume in 1 s (FEV 1 , mL), the forced vital capacity (FVC, mL) and the ratio (FEV 1 /FVC, %). Results On average, participants in the analytic sample completed spirometry tests 1.7 years after the spill. Among workers with at least 2 acceptable FEV 1 and FVC curves, workers with jobs that involved oily plants/wildlife or dead animal recovery had lower values for FEV 1 (Mean difference: −53 mL, 95% CI: −84, −22), FVC (Mean difference: −45 mL, 95% CI: −81, −9) and FEV 1 /FVC (Mean difference: −0.44%, 95% CI: −0.80, −0.07) compared to unexposed workers in analyses using multiple imputation. Conclusions Workers involved in handling oily plants/wildlife or dead animal recovery had lower lung function than unexposed workers after accounting for other OSRC inhalation hazards. Highlights • Oil spill response and cleanup workers had unique experiences that may have adversely affected their respiratory health. • We examined the impact of these experiences on measured lung function 1-3 years after the Deepwater Horizon disaster. • Jobs that involved handling oily plants/wildlife or dead animal recovery were associated with lower lung function. • This large study is the first to examine lung function in relation to potentially stressful work experiences during the DWH disaster response and clean-up effort. [ABSTRACT FROM AUTHOR]

Abstract Oil residues originating from the Deepwater Horizon (DWH) incident persist on Gulf of Mexico beaches alongside oil from offshore industrial activity, natural seepage, and asphalt from parking lots and roads. To determine the primary differences in the chemical composition of these oil residues, a variety of samples were collected from beaches from Florida to Alabama over a two-year period from 2015 to 2017. Bulk chemical characteristics of the oil residues were examined via gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC–MS), as well as thin layer chromatography with flame ionization detection (TLC-FID), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR). These bulk chemical analyses revealed features unique to the different sample types, expanding our understanding of the chemical composition and variability of persistent oil residues, and providing a means to detect and monitor their long-term fate in the coastal environment. Highlights • Oil residues on Gulf coast beaches originate from anthropogenic and natural sources. • Deepwater Horizon oil residues continue to persist and oxidize in the environment. • Bulk chemical analysis can be used to rapidly distinguish different oil residues. [ABSTRACT FROM AUTHOR]

Highlights • Exposure to Deepwater Horizon oil affects transcription of immune related genes in red snapper. • Challenge with Vibrio anguillarum also altered immune gene expression. • Exposure to oil and bacterial pathogen affected fish length. • These effects were observed at very low (<20 ug/L ∑PAH 51) oil concentrations. Abstract This study examined the impacts of Macondo oil from the Deepwater Horizon oil spill, both alone and in conjunction with exposure to the known fish pathogen Vibrio anguillarum , on the expression of five immune-related gene transcripts of red snapper (il8 , il10 , tnfa , il1b , and igm). In order to elucidate this impact, six different test conditions were used: one Control group (No oil/No pathogen), one Low oil/No pathogen group (tPAH50 = 0.563 μg/L), one High oil/No pathogen group (tPAH50 = 17.084 μg/L, one No oil/Pathogen group, one Low oil/Pathogen group (tPAH50 = 0.736 μg/L), and one High oil/Pathogen group (tPAH50 = 15.799 μg/L). Fish were exposed to their respective oil concentrations for one week. On day 7 of the experiment, all fish were placed into new tanks (with or without V. anguillarum) for one hour. At three time points (day 8, day 10, and day 17), fish organs were harvested and placed into RNAlater, and qPCR was run for examination of the above specific immune genes as well as cyp1a1. Our results suggest that cyp1a1 transcripts were upregulated in oil-exposed groups throughout the experiment, confirming oil exposure, and that all five immune gene transcripts were upregulated on day 8, but were generally downregulated or showed no differences from controls on days 10 and 17. Finally, both oil and pathogen exposure had impacts on growth. [ABSTRACT FROM AUTHOR]

Graphical abstract Unlabelled Image Highlights • Incorporation of oil compounds into MOS depends on their physiochemical properties. • Trapping of oil drops by phytoplankton introduces insoluble oil compounds into MOS. • Sorption by phytoplankton introduces water-soluble oil compounds into MOS. • Dispersants increase the oil content of MOS. • Dispersants cause the enrichment of MOS in high molecular weight oil compounds. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pyrolysis-GC–MS (Py-GC–MS) is used to evaluate weathered oil. • Py-GC–MS quantifies traditionally GC-amenable hydrocarbons. • Thermal sublimation patterns indicate recalcitrance of weathered oil hydrocarbons. • High temperature cracking yields insight into oxy-hydrocarbons. Abstract In response to the Deepwater Horizon oil spill, critical research has tracked the changes in petroleum hydrocarbons with environmental weathering. There are limitations, however, whereby single analytical techniques cannot always identify the wide breadth of petroleum and petroleum-derived compounds. We explore the analytical capabilities of ramped pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS) to evaluate environmental samples of petroleum hydrocarbons from the Deepwater Horizon oil spill. We show that bulk flow Py-GC–MS can quantify the overall degree of petroleum hydrocarbon weathering. Furthermore, thermal slicing Py-GC–MS can quantify specific compounds in the “thermal desorption zone” (50–370 °C), as well as characterize pyrolyzed fragments from non-GC-amenable petroleum hydrocarbons (including oxygenated hydrocarbons) in the “cracking zone” (370–650 °C). Our data also suggest an increase in thermochemical stability, concentration of oxygenated products and complexity of high molecular weight and/or polar components with advanced weathering. This analysis not only elucidates weathering trends in Deepwater Horizon oil over several years, but also illustrates the analytical capacity of this method for future petroleum hydrocarbon investigations, filling a void in research connecting Py-GC–MS and environmentally weathered oil samples. [ABSTRACT FROM AUTHOR]

Abstract A distinctive feature of the Deepwater Horizon (DwH) oil spill was the formation of significant quantities of marine oil snow (MOS), for which the mechanism(s) underlying its formation remain unresolved. Here, we show that Alteromonas strain TK-46(2), Pseudoalteromonas strain TK-105 and Cycloclasticus TK-8 – organisms that became enriched in sea surface oil slicks during the spill – contributed to the formation of MOS and/or dispersion of the oil. In roller-bottle incubations, Alteromonas cells and their produced EPS yielded MOS, whereas Pseudoalteromonas and Cycloclasticus did not. Interestingly, the Cycloclasticus strain was able to degrade n -alkanes concomitantly with aromatics within the complex oil mixture, which is atypical for members of this genus. Our findings, for the first time, provide direct evidence on the hydrocarbon-degrading capabilities for these bacteria enriched during the DwH spill, and that bacterial cells of certain species and their produced EPS played a direct role in MOS formation. Highlights • Alteromonas cells and its EPS contributed to MOS formation during Gulf spill. • The chemical nature of bacterial cell surfaces and EPS contribute to MOS formation. • Cycloclasticus likely contributed to degradation of n -alkanes during the spill. • Certain bacterial species and their produced EPS played a role in MOS formation. [ABSTRACT FROM AUTHOR]

The coastal ecosystem in the northern Gulf of Mexico (GoM) has been seriously impacted by the 2010 BP oil spill. Two experiments were conducted to study the effect of temperature and addition of the dispersant on biodegradation of benzene, as a representative of petroleum hydrocarbon, in a coastal salt marsh sediment under aerobic conditions. The results show that benzene biodegradation was approximately 6 time faster under aerobic conditions (Eh > +300 mV) than under anaerobic iron-reduction conditions (+14 mV < Eh < +162 mV). Benzene biodegradation in response to temperature was in an order of 20 °C > 10 °C > 30 °C as expected in a saline environment. Application of the dispersant caused initial fluctuations of benzene vapor pressure during the incubation due to its hydrophobic and hydrophilic nature of the molecules. Presence of the dispersant shows an inhibitory effect on benzene biodegradation, and the inhibition increased with concentration of the dispersant. The Gulf coast sediment seems in a favorable scenario to recover from the BP oil spill with an average temperature around 20 °C in spring and fall season. Application of the dispersant may be necessary for the oil spill rescue operation, but its side effects may deserve further investigations. [ABSTRACT FROM AUTHOR]

During the Deepwater Horizon oil spill rapid natural weathering of Macondo crude oil occurred during the transport of oil to coastal areas. In response to the DWH incident, dispersant was applied to Macondo crude oil to reduce the movement of oil to coastal regions. This study aimed to assess the narcotic and phototoxicity of water-accommodated fractions (WAFs) of weathered Macondo crude oil, and chemically-enhanced WAFs of Corexit 9500 to Pacific ( Crassostrea gigas ) and eastern ( Crassostrea virginica ) oyster larvae. Phototoxic effects were observed for larval Pacific oysters exposed to combinations of oil and dispersant, but not for oil alone. Phototoxic effects were observed for larval eastern oysters exposed to oil alone and combinations of oil and dispersant. Corexit 9500 did not exhibit phototoxicity but resulted in significant narcotic toxicity for Pacific oysters. Oyster larvae may have experienced reduced survival and/or abnormal development if reproduction coincided with exposures to oil or dispersant. [ABSTRACT FROM AUTHOR]

The Gulf of Mexico was home to the Deepwater Horizon oil spill, and is also known to exhibit seasonal declines in oxygen availability. Oil exposure in fish is known to impact oxygen uptake through cardiac impairment, which raises questions about the additive effects of these two stressors. Here we explore this question on the Atlantic croaker using two measures of hypoxia tolerance: critical oxygen threshold (P crit ), and time to loss of equilibrium (LOE). We first demonstrated that 24 h exposure to 10.1 and 23.2 μg l −1 ΣPAH 50 significantly impaired oxygen uptake. There was no effect of exposure on P crit or LOE. Exposure did result in significantly different repeatability between pre- and post-exposure P crit , suggesting that hypoxia tolerant individual may see greater impacts following exposure. These results suggest oil exposure does not have wide scale detrimental outcomes for hypoxia tolerance in fish, yet there may be fine scale impairments of ecological significance. [ABSTRACT FROM AUTHOR]

Following the Deepwater Horizon (DWH) event in 2010, hydrocarbons were deposited on the continental slope in the northeastern Gulf of Mexico through marine oil snow sedimentation and flocculent accumulation (MOSSFA). The objective of this study was to test the hypothesis that benthic foraminiferal δ 13 C would record this depositional event. From December 2010 to August 2014, a time-series of sediment cores was collected at two impacted sites and one control site in the northeastern Gulf of Mexico. Short-lived radioisotopes ( 210 Pb and 234 Th) were employed to establish the pre-DWH, DWH, and post-DWH intervals. Benthic foraminifera ( Cibicidoides spp. and Uvigerina spp.) were isolated from these intervals for δ 13 C measurement. A modest (0.2–0.4‰), but persistent δ 13 C depletion in the DWH intervals of impacted sites was observed over a two-year period. This difference was significantly beyond the pre-DWH (background) variability and demonstrated that benthic foraminiferal calcite recorded the depositional event. The longevity of the depletion in the δ 13 C record suggested that benthic foraminifera may have recorded the change in organic matter caused by MOSSFA from 2010 to 2012. These findings have implications for assessing the subsurface spatial distribution of the DWH MOSSFA event. [ABSTRACT FROM AUTHOR]

Forensic chemistry assessments documented the presence of Macondo (MC252) oil from the Deepwater Horizon (DWH) spill in offshore water samples collected under Natural Resource Damage Assessment (NRDA) protocols. In ocean depths, oiled water was sampled, observed, photographed, and tracked in dissolved oxygen (DO) and fluorometry profiles. Chemical analyses, sensor records, and observations confirmed the shifting, rising oil plume above the wellhead while smaller, less buoyant droplets were entrapped in a layer at ~1000–1400 m and advected up to 412 km southwest. Near-surface oil samples showed substantial dissolution weathering from oil droplets rising through the water column, as well as enhanced evaporative losses of lighter n-alkanes and aromatic hydrocarbons. Dispersant effects from surface applications and injected at the wellhead were seen in oil profiles as enhanced weathering patterns (increased dissolution), thus implying dispersants were a functionally effective mediation treatment. Forensic assessment methods are detailed in the Supplemental information (SI). [ABSTRACT FROM AUTHOR]

During the Deepwater Horizon blowout, unprecedented volumes of dispersant were applied both on the surface and at depth. Application at depth was intended to disperse the oil into smaller microdroplets that would increase biodegradation and also reduce the volumes buoyantly rising to the surface, thereby reducing surface exposures, recovery efforts, and potential stranding. In forensically examining 5300 offshore water samples for the Natural Resource Damage Assessment (NRDA) effort, profiles of deep-plume oil droplets (from filtered water samples) were compared with those also containing dispersant indicators to reveal a previously hypothesized but undocumented, accelerated dissolution of the polycyclic aromatic hydrocarbons (PAH) in the plume samples. We interpret these data in a fate-and-transport context and conclude that dispersant applications were functionally effective at depth. [ABSTRACT FROM AUTHOR]

Oil spills on birds and other organisms have focused primarily on direct effects of oil exposure through ingestion or direct body fouling. Little is known of indirect effects of airborne volatiles from spilled oil, especially on vulnerable developing embryos within the bird egg. Here a technique is described for exposing bird embryos in the egg to quantifiable amounts of airborne volatile toxicants from Deepwater Horizon crude oil. A novel membrane inlet mass spectrometry system was used to measure major classes of airborne oil-derived toxicants and correlate these exposures with biological endpoints. Exposure induced a reduction in platelet number and increase in osmolality of the blood of embryos of the chicken ( Gallus gallus ). Additionally, expression of cytochrome P4501A, a protein biomarker of oil exposure, occurred in renal, pulmonary, hepatic and vascular tissues. These data confirm that this system for generating and measuring airborne volatiles can be used for future in-depth analysis of the toxicity of volatile organic compounds in birds and potentially other terrestrial organisms. [ABSTRACT FROM AUTHOR]

In response to the explosion of the Deepwater Horizon and the massive release of oil that followed, we conducted three annual research voyages to investigate how the oil spill would impact the marine offshore environment. Most investigations into the ecological and toxicological impacts of the Deepwater Horizon Oil crisis have mainly focused on the fate of the oil and dispersants, but few have considered the release of metals into the environment. From studies of previous oil spills, other marine oil industries, and analyses of oil compositions, it is evident that metals are frequently encountered. Several metals have been reported in the MC252 oil from the Deepwater Horizon oil spill, including the nonessential metals aluminum, arsenic, chromium, nickel, and lead; genotoxic metals, such as these are able to damage DNA and can bioaccumulate in organisms resulting in persistent exposure. In the Gulf of Mexico, whales are the apex species; hence we collected skin biopsies from sperm whales ( Physeter macrocephalus ), short-finned pilot whales ( Globicephala macrorhynchus ), and Bryde's whales ( Balaenoptera edeni ). The results from our three-year study of monitoring metal levels in whale skin show (1) genotoxic metals at concentrations higher than global averages previously reported and (2) patterns for MC252-relevant metal concentrations decreasing with time from the oil spill. [ABSTRACT FROM AUTHOR]

Benthic foraminifera (BF) have been commonly used as marine petroleum contamination indicators. The Deepwater Horizon (DWH) released 4.0 million barrels of petroleum into the northern Gulf of Mexico (nGoM) over 87 days in 2010, causing Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA). Previous BF studies have documented region-specific impacts associated with contaminant input and sediment redox conditions. This study determined benthic resilience as measured by BF test density, species richness and heterogeneity. Surface sediment samples (0–42 mm) from seven sites throughout the nGoM (2011–2015) showed a continuous increase in mean species richness (27.2% ±3.6%) and heterogeneity (19.8% ±0.2%). The greatest increase occurred from 2011 to 2013, followed by consistent values from 2013 to 2015, which suggested a resilience rate on the order of three years. This study demonstrated the importance of long-term time-series studies following events such as DWH and exemplified necessity for broad baseline measurements prior to the next marine petroleum accident. [ABSTRACT FROM AUTHOR]

Heavily weathered petroleum residues from the Deepwater Horizon ( DwH ) disaster continue to be found on beaches along the Gulf of Mexico as oiled-sand patties. Here, we demonstrate the ongoing biodegradation of weathered Macondo Well (MW) oil residues by tracing oil-derived carbon into active microbial biomass using natural abundance radiocarbon ( 14 C). Oiled-sand patties and non-oiled sand were collected from previously studied beaches in Mississippi, Alabama, and Florida. Phospholipid fatty acid (PLFA) analyses illustrated that microbial communities present in oiled-sand patties were distinct from non-oiled sand. Depleted 14 C measurements of PLFA revealed that microbes on oiled-sand patties were assimilating MW oil residues five years post-spill. In contrast, microbes in non-oiled sand assimilated recently photosynthesized carbon. These results demonstrate ongoing biodegradation of weathered oil in sand patties and the utility of 14 C PLFA analysis to track the biodegradation of MW oil residues long after other indicators of biodegradation are no longer detectable. [ABSTRACT FROM AUTHOR]

After Deepwater Horizon oil reached the Florida coast, oil was buried in Pensacola Beach (PB) sands to ~ 70 cm depth, resulting in Total Petroleum Hydrocarbon (TPH) concentrations up to ~ 2 kg per meter of beach. This study followed the decomposition of the buried oil and the factors influencing its degradation. The abundance of bacteria in oiled sand increased by 2 orders of magnitude within one week after oil burial, while diversity decreased by ~ 50%. Half-lives of aliphatic and aromatic hydrocarbons reached 25 and 22 days, respectively. Aerobic microbial oil decomposition, promoted by tidal pumping, and human cleaning activities effectively removed oil from the beach. After one year, concentrations of GC-amenable hydrocarbons at PB were similar to those in the uncontaminated reference beach at St. George Island/FL, and microbial populations that disappeared after the oil contamination had reestablished. Yet, oxihydrocarbons can be found at PB to the present day. [ABSTRACT FROM AUTHOR]

The Deepwater Horizon oil spill stimulated the release of marine snow made up of dead/living plankton/bacteria and their exopolymeric polysaccharide substances (EPS), termed marine oil snow (MOS), promoting rapid removal of oil from the water column into sediments near the well site. Mesocosm simulations showed that Macondo surrogate oil readily associates with the marine snow. Quantitative solid-state 13 C NMR readily distinguishes this oil from naturally formed marine snow and reveals that adding the dispersant Corexit enhances the amount of oil associated with the MOS, thus contributing to rapid removal from the water column. Solvent extraction of MOS removes the oil-derived compounds for analysis by one and two-dimensional GC/MS and evaluation of potential transformations they undergo when associated with the EPS. The results reveal that the oil associated with EPS is subjected to rapid transformation, in a matter of days, presumably by bacteria and fungi associated with EPS. [ABSTRACT FROM AUTHOR]

The objective of the present study was to determine whether the polycyclic aromatic hydrocarbons (PAHs) associated with the Deepwater Horizon ( DWH ) oil spill impacted the stress response of teleost fish. The hypothesis was that intraperitoneal (IP) treatment with PAHs associated with the DWH oil spill or waterborne exposure to DWH oil high energy water-accommodated fraction (HEWAF) would result in the downregulation of the stress response of Gulf toadfish, Opsanus beta, a benthic marine teleost fish that resides in the Gulf of Mexico. In vivo plasma cortisol levels and adrenocorticotropic hormone (ACTH)-mediated cortisol secretion by in vitro isolated kidney tissue were measured. Toadfish at rest IP-treated with naphthalene had higher plasma cortisol compared to fluorene-treated and control fish; phenanthrene-treated fish tended to have higher plasma cortisol levels that fluorene-treated and controls. When subjected to an additional crowding stress, naphthalene and phenanthrene-treated fish were no longer able to mount a stress response compared to fluorene-treated and control fish, suggesting exhaustion of the stress response. Supporting this in vivo data, there tended to be less cortisol released by the kidney in vitro from naphthalene and phenanthrene-treated fish in response to ACTH compared to controls. In contrast, toadfish at rest exposed to 3% Slick A HEWAF did not have significantly different plasma cortisol levels compared to controls. But, exposed fish did have significantly less cortisol released by the kidney in vitro in response to ACTH. When toadfish were subjected to an additional stress, there were no significant differences in plasma cortisol or ACTH, suggesting the action of a secondary secretagogue to maintain plasma cortisol in vivo . Combined, these data suggest that in response to acute PAH exposure, there may be internalization or downregulation of the melanocortin 2 receptor (MC2R) that mediates the action of ACTH. [ABSTRACT FROM AUTHOR]

The Deepwater Horizon oil spill was the largest in U.S. history, contaminating thousands of miles of coastal habitat and affecting the lives of many avian species. The Gulf of Mexico is a critical bird migration route area and migrants that were oiled but did not suffer mortality as a direct result of the spill faced unpredictable fates. This study utilized homing pigeons as a surrogate species for migratory birds to investigate the effects a single low level external oiling event has on the flight performance and behavior of birds flying repeated 161 km flights. Data from GPS data loggers showed that lightly oiled pigeons changed their flight paths, increased their flight durations by 2.6 fold, increased their flight distances by 28 km and subsequently decreased their route efficiencies. Oiled birds also exhibited reduced rate of weight gain between flights. Our data suggest that contaminated birds surviving the oil spill may have experienced flight impairment and reduced refueling abilities, likely reducing overall migration speed. Our findings contribute new information on how oil spills affect avian species, as the effects of oil on the flight behavior of long distance free-flying birds have not been previously described. [ABSTRACT FROM AUTHOR]

Benthic surveys of mesophotic reefs in the Gulf of Mexico post Deepwater Horizon (DWH) showed that Swiftia exserta octocorals exhibited significantly more injury than in years before the spill. To determine the vulnerability of S. exserta to oil and dispersants, 96 h toxicity assays of surrogate DWH oil water-accommodated fractions (WAF), Corexit® 9500 dispersant, and the combination of both (CEWAF) were conducted in the laboratory. Fragment mortality occurred within 48 h for some fragments in the dispersant-alone and oil-dispersant treatments, while the WAF group remained relatively unaffected. The 96 h LC 50 values were 70.27 mg/L for Corexit-alone and 41.04 mg/L for Corexit in CEWAF. This study provides new information on octocoral sensitivity to toxins, and indicates that combinations of oil and dispersants are more toxic to octocorals than exposure to oil alone. These results have important implications for the assessment of effects of the DWH spill on deep-water organisms. [ABSTRACT FROM AUTHOR]

Biodegradation is an important process for hydrocarbon weathering that influences its fate and transport, yet little is known about in situ biodegradation rates of specific hydrocarbon compounds in the deep ocean. Using data collected in the Gulf of Mexico below 700 m during and after the Deepwater Horizon oil spill, we calculated first-order degradation rate constants for 49 hydrocarbons and inferred degradation rate constants for an additional 5 data-deficient hydrocarbons. Resulting calculated (not inferred) half-lives of the hydrocarbons ranged from 0.4 to 36.5 days. The fastest degrading hydrocarbons were toluene (k = − 1.716), methylcyclohexane (k = − 1.538), benzene (k = − 1.333), and C1-naphthalene (k = − 1.305). The slowest degrading hydrocarbons were the large straight-chain alkanes, C-26 through C-33 (k = − 0.0494 through k = − 0.007). Ratios of C-18 to phytane supported the hypothesis that the primary means of degradation in the subsurface was microbial biodegradation. These degradation rate constants can be used to improve models describing the fate and transport of hydrocarbons in the event of an accidental deep ocean oil spill. [ABSTRACT FROM AUTHOR]

The Oil Pollution Act of 1990 (OPA) requires that the responsible party make the public whole for natural resource injuries attributable to an oil spill incident. We have presented our approach at establishing natural resource baseline conditions for multiple habitats in Coastal Mississippi and Alabama. This paper presents the subsequent steps that were taken to estimate natural resource injuries for the Deepwater Horizon Oil release (DWH) using AQUATOX Release 3.1 NME (Nearshore Marine Environments). TPAH (Total polycyclic aromatic hydrocarbon) exposure matrices in water and sediment were estimated over a spatial gradient based on observed data in Mississippi and Alabama. Bioaccumulation parameters were derived from literature and reasonable bioaccumulation calibration was verified using site specific data when available. TPAH was segregated into six different analyte groups, binned by Kow, based on observed sediment data. Toxicity data from NOAA and literature were used to estimate effects of TPAH and individual analytes on species observed on site. Combining each of these analyses, total injuries could be estimated for Mississippi and Alabama ranging from 0.2% to 4.2% of secondary and tertiary productivity lost over three years, depending on the habitat investigated and its spatial location in the study area. The analysis demonstrates the effectiveness of the AQUATOX model as a tool to quantify levels of injury by comparing the results of a baseline ecological model, calibrated and verified with pre-oiling observations, with post-oiling results. This alternative approach to injury assessment can be used to validate single-species approaches and also to evaluate the injury to, and recovery of, an integrated ecosystem. [ABSTRACT FROM AUTHOR]

The 2010 Deepwater Horizon (DWH) oil spill caused the release of 4.9 million barrels of crude oil into the Gulf of Mexico, followed by the application of 2.9 million L of the dispersant, Corexit™ to mitigate the spread of oil. The spill resulted in substantial shoreline oiling, potentially exposing coastal organisms to polyaromatic hydrocarbon (PAH) and dispersant contaminants. To investigate molecular effects in fish following exposure to environmentally relevant concentrations of DWH oil and dispersants, we exposed adult sheepshead minnows ( Cyprinodon variegatus ) to two concentrations of high-energy water-accommodated fraction (HEWAF), chemically enhanced water-accommodated fraction (CEWAF) or Corexit 9500™ for 7 and 14 days. Resulting changes in hepatic gene expression were measured using 8 × 15 K microarrays. Analytical chemistry confirmed PAH concentrations in HEWAF and CEWAF treatments were low (ranging from 0.26 to 5.98 μg/L), and likely representative of post-spill environmental concentrations. We observed significant changes to gene expression in all treatments (relative to controls), with Corexit and CEWAF having a greater effect on expression patterns in the liver than HEWAF treatments. Sub-network enrichment analysis of biological pathways revealed that the greatest number of altered pathways in high dose HEWAF and CEWAF treatments occurred following a 7-day exposure. Pathways related to immunity comprised the majority of pathways affected in each treatment, followed by pathways related to blood and circulation processes. Our results indicate that oil composition, concentration, and exposure duration all affect molecular responses in exposed fish, and suggest that low-concentration exposures may result in sub-lethal adverse effects. [ABSTRACT FROM AUTHOR]

The blowout of the Deepwater Horizon (DWH) drilling rig in 2010 released an unprecedented amount of oil at depth (1,500 m) into the Gulf of Mexico (GoM). Sedimentary geochemical data from an extensive area (∼194,000 km 2 ) was used to characterize the amount, chemical signature, distribution, and extent of the DWH oil deposited on the seafloor in 2010–2011 from coastal to deep-sea areas in the GoM. The analysis of numerous hydrocarbon compounds (N = 158) and sediment cores (N = 2,613) suggests that, 1.9 ± 0.9 × 10 4 metric tons of hydrocarbons (>C9 saturated and aromatic fractions) were deposited in 56% of the studied area, containing 21± 10% (up to 47%) of the total amount of oil discharged and not recovered from the DWH spill. Examination of the spatial trends and chemical diagnostic ratios indicate large deposition of weathered DWH oil in coastal and deep-sea areas and negligible deposition on the continental shelf (behaving as a transition zone in the northern GoM). The large-scale analysis of deposited hydrocarbons following the DWH spill helps understanding the possible long-term fate of the released oil in 2010, including sedimentary transformation processes, redistribution of deposited hydrocarbons, and persistence in the environment as recycled petrocarbon. [ABSTRACT FROM AUTHOR]

The 2010 Deepwater Horizon (DWH) oil spill in the northern Gulf of Mexico (NGOM) resulted in over 780 million liters of crude oil spilling into Gulf waters. In an effort to disperse the oil, nearly 7.6 million liters of dispersant was applied. Many commercially and recreationally important species reside in or near the area of the spill. The blue crab, Callinectes sapidus , is common in the NGOM and is both economically and ecologically important in this region. In this study, after exposing juvenile blue crabs to oil or a mixture of oil and dispersant we tested for relative expression of heat shock protein 90 ( hsp90 ) and vitellogenin ( vtg ) by measuring their corresponding mRNA expression. We also monitored crabs over two molts to test for effects on growth. Expression of hsp90 was significantly downregulated, and we did not detect any effects of exposure to oil or oil/dispersant mixture on growth or vtg expression. [ABSTRACT FROM AUTHOR]

The surface oil burns conducted by the U.S. Coast Guard from April to July 2010 during the Deepwater Horizon disaster in the Gulf of Mexico were simulated by small scale burns to characterize the pollutants, determine emission factors, and gather particulate matter for subsequent toxicity testing. A representative crude oil was burned in ocean-salinity seawater, and emissions were collected from the plume by means of a crane-suspended sampling platform. Emissions included particulate matter, aromatic hydrocarbons, polychlorinated dibenzodioxins/dibenzofurans, elements, and others, the sum of which accounted for over 92% by mass of the combustion products. The unburned oil mass was 29% of the original crude oil mass, significantly higher than typically reported. Analysis of alkanes, elements, and PAHs in the floating residual oil and water accounted for over 51% of the gathered mass. These emission factors, along with toxicity data, will be important toward examining impacts of future spill burning operations. [ABSTRACT FROM AUTHOR]

Following exposure to weathered and non-weathered oil, lethal and sub-lethal impacts on red drum larvae were assessed using survival, morphological, and cardiotoxicity assays. The LC50 for red drum ranged from 14.6 (10.3–20.9) to 21.3 (19.1–23.8) μg l − 1 ΣPAH with no effect of exposure timing during the pre-hatch window or oil weathering. Similarly, morphological deformities showed dose responses in the low ppb range. Cardiac output showed similar sensitivity resulting in a major 70% reduction after exposure to 2.6 μg l − 1 ΣPAH. This cardiac failure was driven by reduced stroke volume rather than bradycardia, meaning that in some species, cardiac function is more sensitive than previously thought. After the Deepwater Horizon oil spill, much of this type of work has primarily focused on pelagic species with little known about fast developing estuarine species. These results demonstrate similarity sensitivity of the red drum as their pelagic counter parts, and more importantly, that cardiac function is dramatically reduced in concert with pericardial edema. [ABSTRACT FROM AUTHOR]

A 3-year research program was undertaken to assess potential environmental disturbance caused by the Deepwater Horizon oil spill to the soft-bottom macrobenthic communities within Mexican waters of the northwestern Gulf of Mexico. Community properties and temporal/spatial variability were analyzed besides toxicant parameters such as hydrocarbons and trace-metals. Overall infaunal density increased, taxa proportion changed, and small-size opportunistic organisms prevailed throughout the study. Annual abundance-biomass comparison (ABC) curves revealed progressive stress scenarios from moderate to severe. Concentrations of vanadium, nickel, cobalt, PAHs and AHs increased gradually over time. However, low correlations between benthic density and biogeochemical variables were determined. Initially, sedimentary properties were the main drivers of benthic community structure; subsequently, nickel, vanadium and PAHs, indicative of anthropogenic effect, were highlighted. Interannual variability in the macroinfauna was attributed to the synergy of several environmental factors. Undoubtedly, compounds derived from fossil fuels had a significant disturbance role, but their source remains uncertain. [ABSTRACT FROM AUTHOR]

Comprehensive characterization of exposure media used in toxicology studies is still an area of significant divergence when evaluating potential oil spill impacts. When preparing exposure media used for toxicology testing, small variations in simple parameters such as mixing energy, oil type and loading can significantly affect the concentration of the oil components to which test organisms are exposed. The key goal of this study was compare and contrast the physical and chemical compositions of oil water mixtures prepared using fresh and weathered Macondo-related oils under different conditions of mixing and in the presence/absence of chemical dispersants. All samples were assessed for the presence of droplets, droplet size distribution, and detailed chemical composition including polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbon by fluorescence (TPHF). Preparations were also tested for stability over a 96 h period relevant to acute toxicity tests. The results indicate that water accommodated fractions (WAFs) produced consistent, droplet free solutions with concentration that represented the soluble components of the oil used. As expected, chemically-enhanced WAFs (CEWAFs) and high-energy WAFs (HEWAFs) generated large amounts of micron-size droplets and their chemical composition corresponded closely with that of the whole oil. However, the HEWAFs were highly dynamic, and unlike CEWAFs, much of the oil resurfaced within few hours of the initial preparation. Viscosity and lack of dispersability are the limiting factors for preparation of CEWAFs with weathered oils, in contrast HEWAFs did effectively introduce large amounts of weathered oil droplets in the test media. Despite this benefit, droplet sizes significantly decreased in HEWAFs with increase in weathering of the oil creating an additional variable to consider. Because the contribution of small droplets to toxicity is a topic that needs further investigation, the interpretation of results from high-energy preparations needs to be further evaluated. When the TPAHs concentrations of all preparations at all loadings were compared with the publicly available water-column data for samples analyzed during and after the DWH incident response they all ranked above the vast majority of the 10,828 samples reported. Until a better characterization of all the available DWH water column individual-component chemistry data is produced the question of environmental relevance and the pursuit of toxicological studies under more realistic conditions continues to be a significant challenge that should be further explored. [ABSTRACT FROM AUTHOR]

Purpose: The goal of the study was to characterize risk pertaining to seafood consumption patterns following the Deepwater Horizon oil spill, among school children (K to 4th grade) residing in close proximity to the Gulf of Mexico in Mobile County, Alabama.Methods: Responses on seafood consumption pattern including the type of seafood and intake rate during the pre and post oil spill periods, from parents of 55 school children from three schools located <20mile radius from the Gulf of Mexico shoreline (coastal group) were compared with those from parents of 55 children from three schools located ≥20miles away from the shoreline (inland group). We also estimated levels of concern (LOCs) in seafood for selected chemicals found in crude oil including heavy metals, and polycyclic aromatic hydrocarbons (PAH), and dioctyl sodium sulfosuccinate (DOSS), the primary compound in dispersants.Results: The coastal group ate more seafood consisting primarily of crustaceans (62% vs. 42%, p=0.04) and fin fish (78% vs. 58%, p=0.02) from the Gulf of Mexico compared to the inland group, while the inland group ate more fin fish not found in the Gulf of Mexico (62% vs. 33%, p<0.01). In the post-oil spill time period, both groups substantially reduced their consumption of sea food. On average, the coastal group ate ≥2 seafood meals per week, while the inland group ate ≤1 meal per week; these frequency patterns persisted in the post oil-spill period. Comparison of the estimated LOCs with contaminant levels detected in the seafood tested by the Food and Drug Administration and National Oceanic and Atmospheric Administration, post-oil spill, found that the levels of PAHs, arsenic, and DOSS in seafood were 1-2 orders of magnitude below the LOCs calculated in our study. Levels of methyl mercury (MeHg) in the seafood tested pre- and post- oil spill were higher than the estimated LOCs suggesting presence of higher levels of MeHg in seafood independent of the oil spill.Conclusion: In sum, the study found higher than average seafood consumption among children along the Mobile coastal area when compared to the inland children and the National Health and Nutrition Examination Survey (NHANES) estimates. Risk characterization based on the LOCs indicated no increase in risk of exposure despite higher seafood consumption rates among the study population compared to the general population. [ABSTRACT FROM AUTHOR]

During the Deepwater Horizon oil spill in 2010, subsea dispersant injection (SSDI) was utilized for the first time in an effort to reduce the amount of oil reaching the sea surface and thus potentially decrease its environmental impact and enhance responders' safety. Since then, controversy has developed about SSDI's effectiveness. Most of the analysis is based on modeling, with some models concluding SSDI significantly reduced surfacing oil volumes, and others predicting that processes unrelated to the dispersant caused most of the subsurface oil retention. This study utilized a multispectral aerial sensor image time series to correlate the surface area covered by freshly upwelled oil with changes in SSDI rates, accounting for an approximate 4 hour oil rise time lag. A significant negative correlation was found between oil-covered surface area and SSDI rates, providing direct observation support that the technique did reduce the amount of surfacing oil around the wellhead. • Multispectral aerial image series allows assessment of surfaced oil above the well head. • Negative correlation exists between oil-covered area and subsurface dispersant rates. • Correlation results support notion that subsurface dispersant injections were effective. [ABSTRACT FROM AUTHOR]

• Histology identified 14 microscopic hepatic changes in Gulf of Mexico Tilefish. • Inflammatory and vacuolar changes were most prevalent. Pre-neoplasia and neoplasia were rare. • Prevalence of inflammatory changes increased over time. • Lipid-type vacuolation decreased over time while glycogen-type vacuolation increased. • Certain microscopic hepatic changes were significantly associated with hepatic PAH concentrations. Following the 2010 Deepwater Horizon blowout, demersal longline surveys were conducted across the Gulf of Mexico (GoM) continental shelf to evaluate polycyclic aromatic hydrocarbon (PAH) exposure, tissue accumulation, and health indices in demersal fishes. Tilefish (Lopholatilus chamaeleonticeps), a target species due to Gulf-wide distribution with documented high exposure to PAHs, were collected in the north central GoM at repeat stations 2012 to 2015, and from the northwest GoM, Bay of Campeche, and Yucatán Shelf in 2015 and 2016. Liver samples (n = 239) were analyzed for microscopic hepatic changes (MHCs) by a board-certified veterinary pathologist. Histological analyzes identified 14 MHCs. Prevalence of MHCs was generally uniform throughout the GoM, except for low prevalence on the Yucatán Shelf. Inflammatory and vacuolar changes were most prevalent, while pre-neoplasia and neoplasia were rare. Tilefish sampled annually in the north central GoM showed increases in inflammatory MHCs and glycogen-type vacuolar change over time, while lipid-type vacuolar change decreased over time. Short-term exposure to PAHs was assessed by measuring PAH metabolites in bile (n = 100) using high performance liquid chromatography with fluorescence detection. Longer-term accumulation of PAHs in tissue was assessed by analyzing liver (n = 111) for PAHs and alkylated homologs using QuEChERS extractions and gas chromatography tandem mass spectrometry. Six MHCs including glycogen-type vacuolar change, biliary fibrosis, foci of cellular alteration, parasites, hepatocellular atrophy, and necrosis were significantly associated with hepatic PAH accumulation in Tilefish from the northern central GoM; however, no MHCs were associated with biliary PAH metabolites. Combined with previous studies of PAH exposure and health indices in north central GoM Tilefish post- Deepwater Horizon , which also identified decreases in hepatic lipid storage and Fulton's condition factor that were correlated to increasing PAH exposure, these data indicate concerning temporal trends and changes in hepatic energy storage. [ABSTRACT FROM AUTHOR]

• Chronic stress does not convincingly exacerbate effects of DWH PAHs on plasma cortisol concentrations in vivo. • DWH PAH exposure did not result in a change in plasma cortisol concentrations; however, there was a reduction in vitro isolated kidney cortisol secretion rate. • 5-HT does not appear to be acting as a secondary cortisol secretagogue but 5-HT systems appear to be sensitive to PAH exposure. • Impairment is not likely due to a lack of available cholesterol but may include the melanocortin 2 receptor (MC2R). The toxicity of the polycyclic aromatic hydrocarbons (PAHs) in Deepwater Horizon (DWH) oil is well-established, but a knowledge gap exists regarding how this combination of PAHs affects the vertebrate stress axis. We hypothesized that (1) marine vertebrates exposed to DWH PAHs experience stress axis impairment, and co-exposure to an additional chronic stressor may exacerbate these effects, (2) serotonin (5-hydroxytryptamine; 5-HT) may act as a secondary cortisol secretagogue in DWH PAH-exposed fish to compensate for impairment, and (3) the mechanism of stress axis impairment may involve downregulation of cyclic adenosine monophosphate (cAMP; as proxy for melanocortin 2 receptor (MC2R) functionality), total cholesterol, and/or mRNA expression of CYP1A and steroidogenic proteins StAR, P450scc, and 11β-h at the level of the kidney. We found that in vivo plasma cortisol and plasma adrenocorticotropic hormone (ACTH) concentrations in Gulf toadfish exposed to an environmentally relevant DWH PAH concentration (ΣPAH 50 = 4.6 ± 1.6 μg/L) for 7 days were not significantly different from controls, whether fish were chronically stressed or not. However, the rate of cortisol secretion by isolated kidneys after acute stimulation with ACTH was significantly lower in PAH-exposed toadfish compared to clean seawater (SW) controls. 5-HT does not appear to be acting as a secondary cortisol secretagogue, rather, PAH-exposed + stressed toadfish exhibited significantly lower plasma 5-HT concentrations than clean SW + stressed fish as well as a reduced sensitivity to 5-HT at the level of the kidney. There was a tendency for kidney cAMP concentrations to be lower in PAH-exposed fish (p = 0.069); however, mRNA expression of steroidogenic proteins between control and PAH-exposed toadfish were not significantly different and a significant elevation in total cholesterol concentration in PAH-exposed toadfish compared to controls was measured. Future work is needed to establish whether the slower cortisol secretion rate by isolated kidneys of PAH-exposed fish is detrimental, to determine the potential role of other secretagogues in compensating for the impaired kidney interrenal cell function, and to determine whether there is a reduction in MC2R mRNA expression or an impairment in the function of steroidogenic proteins. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) have been reported to absorb ultraviolet (UV) light, resulting in enhanced toxicity. Early developmental stages of bivalves may be particularly susceptible to photo-enhanced toxicity during oil spills. In the current study, toxicity tests were conducted with sperm and three larval ages of the eastern oyster ( Crassostrea virginica ) to evaluate the photo-enhanced toxicity of low-energy water-accommodated fractions (WAFs) of two weathered Macondo crude oils collected from the Deepwater Horizon incident. Larvae exposed to oil WAFs under UV-filtered light demonstrated consistently higher survival and normal development than larvae exposed to WAFs under UV light. The phototoxicity of weathered Macondo oil increased as a function of increasing UV light intensity and dose. Early developing oyster larvae were the most sensitive to photo-enhanced toxicity, whereas later shelled prodissoconch larvae were insensitive. Comparisons between two weathered crude oils demonstrated that toxicity was dependent on phototoxic PAH concentration and UV light intensity. [ABSTRACT FROM AUTHOR]

In order to characterize the state of oil spill research and describe how the field has changed since its inception in the 1960s and since the Deepwater Horizon spill in 2010, we examined approximately 10% of oil spill literature (1255 of over 11,000 publications) published from 1968 to 2015. We find that, despite its episodic nature, oil spill research is a rapidly expanding field with a growth rate faster than that of science as a whole. There is a massive post- Deepwater Horizon shift of research attention to the Gulf of Mexico, from 2% of studies in 2004–2008 to 61% in 2014–2015, thus ranking Deepwater Horizon as the most studied oil spill. There is, however, a longstanding gap in research in that only 1% of studies deal with the effects of oil spills on human health. These results provide a better understanding of the current trends and gaps within the field. [ABSTRACT FROM AUTHOR]

The effect of the Deepwater Horizon oil spill on benthic macrofauna in the deep-sea Gulf of Mexico was measured in September–October 2010. Macrofauna community diversity and abundance were lowest closest to the wellhead and increased with distance from the wellhead up to 10 km. The macrofauna loss was primarily in surface sediments, which could be due to the deposition of oil and other toxic chemicals. Crustacean taxa appeared to be sensitive to the deep-sea blowout. Polychaete taxa varied in their sensitivity, but Dorvilleidae which is often associated with organic enrichment, was responsible for the largest amount of dissimilarity between stations close and far from the wellhead. Several other taxa were classified as sensitive or tolerant to the deep-sea blowout by comparing their distributions among impacted and non-impacted zones. The macrobenthic communities in the deep Gulf of Mexico exhibit a toxic response to the blowout on the Deepwater Horizon well, and this is correlated with barium and petroleum hydrocarbons. [ABSTRACT FROM AUTHOR]

Exposure to polycyclic aromatic hydrocarbons (PAH) negatively impacts exercise performance in fish species but the physiological modifications that result in this phenotype are poorly understood. Prior studies have shown that embryonic and juvenile mahi–mahi ( Coryphaeus hippurus ) exposed to PAH exhibit morphological abnormalities, altered cardiac development and reduced swimming performance. It has been suggested that cardiovascular function inhibited by PAH exposure accounts for the compromised exercise performance in fish species. In this study we used in-situ techniques to measure hemodynamic responses of young adult mahi–mahi exposed to PAH for 24 h. The data indicate that stroke volume was reduced 44% in mahi–mahi exposed to 9.6 ± 2.7 μg l −1 geometric mean PAH (∑PAH) and resulted in a 39% reduction in cardiac output and a 52% reduction in stroke work. Maximal change in pressure over change in time was 28% lower in mahi–mahi exposed to this level of ∑PAH. Mean intraventricular pressures and heart rate were not significantly changed. This study suggests exposure to environmentally relevant PAH concentrations impairs aspects of cardiovascular function in mahi–mahi. [ABSTRACT FROM AUTHOR]

Adding clay to marine oil pollution represents a promising approach to enhance bacterial hydrocarbon degradation in nutrient poor waters. In this study, three types of regionally available clays (Ca-bentonite, Fuller's Earth and kaolin) were tested to stimulate the biodegradation of source and weathered oil collected from the Deepwater Horizon spill. The weathered oil showed little biodegradation prior to experimentation and was extensively degraded by bacteria in the laboratory in a similar way as the alkane-rich source oil. For both oils, the addition of natural clay-flakes showed minor enhancement of oil biodegradation compared to the non-clay bearing control, but the clay-oil films did limit evaporation. Only alkanes of a molecular weight (MW) > 420 showed significant reduction by enhanced biodegradation following natural clay treatment. In contrast, all fertilized clay flakes showed major bacterial degradation of the oil, with a 6–10 times reduction in alkane content, and an up to 8 fold increase in the rate of O 2 consumption. Compared to the control, such treatment showed particular reduction of longer chained alkanes (MW > 226). The application of natural and fertilized clay flakes also showed selective reduction of PAHs, mainly in the MW range of 200–300, but without significant change in the toxicity indices measured. These results imply that a large variety of clays may be used to boost oil biodegradation by aiding attachment of fertilizing nutrients to the oil. [ABSTRACT FROM AUTHOR]

Chemical analysis of sediment cores collected up to 8 km from the Macondo well in 2010/2011 demonstrates the extent of weathering of the Macondo oil deposited in deep-sea sediments following the Deepwater Horizon disaster. On average, dissolution and biodegradation of the oil on the seafloor increased with distance from the well indicating that weathering occurred rapidly and overwhelmingly during the oil's transport as dispersed oil droplets within the deep-sea plume. Beyond about 5 km from the well, the oil deposited on the seafloor had lost most mass below C 25 , was relatively enriched in n -C 25 + n -alkanes and C 3 – and C 4 -alkylated benz[ a ]anthracenes/chrysenes, the latter owing to 95% depletion of total PAHs. Biodegradation of C 28 and C 29 tricyclic terpanes, C 34 and C 35 17α(H),21β(H)-homohopanes, C 27 13β(H),17α(H)-dia and C 27 14β(H),17β(H)-steranes and dissolution of C 26 to C 28 triaromatic steroids occurred. The results provide a means to distinguish Macondo oil in deep-sea sediments from naturally-occurring seep oils and pervasive ambient background hydrocarbons. [ABSTRACT FROM AUTHOR]

Following the Deepwater Horizon oil spill, the spilled Macondo oil was severely weathered during its transport within the deep-sea plume as discrete particles, which were subsequently deposited on the seafloor. The Macondo oil deposited in deep-sea sediments was distinguished from ambient (background) hydrocarbons and naturally-seeped and genetically-similar oils in the Mississippi Canyon region using a forensic method based upon a systematic, multi-year study of 724 deep-sea sediment cores collected in late 2010 and 2011. The method relied upon: (1) chemical fingerprinting of the distinct features of the wax-rich, severely-weathered Macondo oil; (2) hydrocarbon concentrations, considering a core's proximity to the Macondo well or to known or apparent natural oil seeps, and also vertically within a core; and (3) results from proximal cores and flocculent material from core supernatants and slurp gun filters. The results presented herein establish the geographic extent of “fingerprintable” Macondo oil recognized on the seafloor in 2010/2011. [ABSTRACT FROM AUTHOR]

Knowledge of the spatial distribution of oil thickness patterns within an on-water spill is of obvious importance for immediate spill response activities as well as for subsequent evaluation of the spill impacts. For long-lasting continuous spills like the 2010 3-month Deepwater Horizon (DWH) event in the Gulf of Mexico, it is also important to identify changes in the dominant oil features through time. This study utilized very high resolution (≤ 5 m) aerial and satellite imagery acquired during the DWH spill to evaluate the shape, size and thickness of surface oil features that dominated the DWH slick. Results indicate that outside of the immediate spill source region, oil distributions did not encompass a broad, varied range of thicknesses. Instead, the oil separated into four primary, distinct characterizations: 1) invisible surface films detectable only with Synthetic Aperture Radar imaging because of the decreased surface backscatter, 2) thicker sheen & rainbow areas (< 0.005 mm), 3) large regional areas of relatively thin, “metallic appearance” films (0.005–0.08 mm), and 4) strands of thick, emulsified oil (> 1 mm) that were consistently hundreds of meters long but most commonly only 10–50 m wide. Where present within the slick footprint, each of the three distinct visible oil thickness classes maintained its shape characteristics both spatially (at different distances from the source and in different portions of the slick), and temporally (from mid-May through July 2010). The region over the source site tended to contain a more continuous range of oil thicknesses, however, our results indicate that the continuous injection of subsurface dispersants starting in late May significantly altered (lowered) that range. In addition to characterizing the oil thickness distribution patterns through the timeline of one of the world's largest oil spills, this paper also details the extension of using high resolution aerial imagery to calibrate medium resolution satellite data sources such as USA's Thematic Mapper (30 m) to provide larger-scale spatial views of major spills, and discusses implications for utilizing such data for oil spill characterizations and spill response. [ABSTRACT FROM AUTHOR]

Accidental crude oil releases, such as the Deepwater Horizon ( DWH ) accident, are always a potential threat to pristine marine ecosystems. Since the toxicity of crude oil heavily depends on its variable composition, the comprehensive characterization of crude oil compounds as a function of weathering is an important area of research. Traditional gas chromatography-based characterization presents significant limitations, and the use of ultrahigh-resolution mass spectrometric (UHRMS) techniques (that allow for the assignment of molecular formulae) has been shown to be better equipped to address the complex nature of crude oils. This study used an Orbitrap Q Exactive mass spectrometer operated at a resolving power of 140,000 FWHM with both electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) sources, in order to characterize a crude oil weathering series of the Macondo oil released during the DWH incident (the source oil, two differently weathered surface slicks, and a beached residue). Preliminary gas chromatography mass spectrometry (GC–MS) and gas chromatography flame ionization detection (GC–FID) results suggested that the four oils comprised a true weathering series (including biodegradation and photodegradation in addition to other well-known processes such as dissolution and evaporation). UHRMS results showed a clear increase in oxygenated compounds with weathering, and further suggested a significant gain of acidic compounds, as well as the transformation of phenols to ketonic and quinonic compounds with weathering. A complementary study on a weathered oil sample amended with selected model compounds contributed additional insight into the functional group types that are accessible in each ionization technique. [ABSTRACT FROM AUTHOR]

The April 2010 Deepwater Horizon (DWH) oil spill was the largest coastal spill in U.S. history. Monitoring subsequent change in marsh plant community distributions is critical to assess ecosystem impacts and to establish future coastal management priorities. Strategically deployed airborne imaging spectrometers, like the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), offer the spectral and spatial resolution needed to differentiate plant species. However, obtaining satisfactory and consistent classification accuracies over time is a major challenge, particularly in dynamic intertidal landscapes. Here, we develop and evaluate an image classification system for a time series of AVIRIS data for mapping dominant species in a heavily oiled salt marsh ecosystem. Using field-referenced image endmembers and canonical discriminant analysis (CDA), we classified 21 AVIRIS images acquired during the fall of 2010, 2011 and 2012. Classification results were evaluated using ground surveys that were conducted contemporaneously to AVIRIS collection dates. We analyzed changes in dominant species cover from 2010 to 2012 for oiled and non-oiled shorelines. CDA discriminated dominant species with a high level of accuracy (overall accuracy = 82%, kappa = 0.78) and consistency over three imaging dates (overall 2010 = 82%, overall 2011 = 82%, overall 2012 = 88%). Marshes dominated by Spartina alterniflora were the most spatially abundant in shoreline zones (≤ 28 m from shore) for all three dates (2010 = 79%, 2011 = 61%, 2012 = 63%), followed by Juncus roemerianus (2010 = 11%, 2011 = 19%, 2012 = 17%) and Distichlis spicata (2010 = 4%, 2011 = 10%, 2012 = 7%). Marshes that were heavily contaminated with oil exhibited variable responses from 2010 to 2012. Marsh vegetation classes converted to a subtidal, open water class along oiled and non-oiled shorelines that were similarly situated in the landscape. However, marsh loss along oil-contaminated shorelines doubled that of non-oiled shorelines. Only S. alterniflora dominated marshes were extensively degraded, losing 15% (354,604 m 2 ) cover in oiled shoreline zones, suggesting that S. alterniflora marshes may be more vulnerable to shoreline erosion following hydrocarbon stress, due to their landscape position. [ABSTRACT FROM AUTHOR]