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November 10, 2011

Contaminants and Pollution: Oil and Oil Spills

Deepwater Horizon

  • Graham, W.M., Condon, R.H., Carmichael, R.H., D'Ambra, I., Patterson, H.K., Linn, L.J., and Hernandez, F.J.  Oil carbon entered the coastal planktonic food web during the Deepwater Horizon oil spill.  Environmental Research Letters 5(4): art. 45301, 2010.
    Open Access >>
    Read Abstract >>

    The Deepwater Horizon oil spill was unprecedented in total loading of petroleum hydrocarbons accidentally released to a marine ecosystem. Controversial application of chemical dispersants presumably accelerated microbial consumption of oil components, especially in warm Gulf of Mexico surface waters. We employed δ13C as a tracer of oil-derived carbon to resolve two periods of isotopic carbon depletion in two plankton size classes. Carbon depletion was coincident with the arrival of surface oil slicks in the far northern Gulf, and demonstrated that subsurface oil carbon was incorporated into the plankton food web.

  • McCrea-Strub, A. and Pauly, D.  Oil and fisheries in the Gulf of Mexico.  Ocean and Coastal Law Journal 16(2): 473-480, 2011.
    Open Access >>
  • Fodrie, F.J. and Heck, K.L.  Response of coastal fishes to the Gulf of Mexico oil disaster.  PLoS ONE 6(7): art. e21609, 2011.
    Open Access >>   
    Read Abstract >>

    The ecosystem-level impacts of the Deepwater Horizon disaster have been largely unpredictable due to the unique setting and magnitude of this spill. We used a five-year (2006–2010) data set within the oil-affected region to explore acute consequences for early-stage survival of fish species inhabiting seagrass nursery habitat. Although many of these species spawned during spring-summer, and produced larvae vulnerable to oil-polluted water, overall and species-by-species catch rates were high in 2010 after the spill (1,989 ± 220 fishes km-towed-1 [μ ± 1SE]) relative to the previous four years (1,080 ± 43 fishes km-towed-1). Also, several exploited species were characterized by notably higher juvenile catch rates during 2010 following large-scale fisheries closures in the northern Gulf, although overall statistical results for the effects of fishery closures on assemblage-wide CPUE data were ambiguous. We conclude that immediate, catastrophic losses of 2010 cohorts were largely avoided, and that no shifts in species composition occurred following the spill. The potential long-term impacts facing fishes as a result of chronic exposure and delayed, indirect effects now require attention.

  • Williams, R., Gero, S., Bejder, L., Calambokidis, J., Kraus, S.D., Lusseau, D., Read, A.J., and Robbins, J.  Underestimating the damage: interpreting cetacean carcass recoveries in the context of the Deepwater Horizon/BP incident.  Conservation Letters 4(3): 228-233, 2011.
    Read Abstract >>

    Evaluating impacts of human activities on marine ecosystems is difficult when effects occur out of plain sight. Oil spill severity is often measured by the number of marine birds and mammals killed, but only a small fraction of carcasses are recovered. The Deepwater Horizon/BP oil spill in the Gulf of Mexico was the largest in the U.S. history, but some reports implied modest environmental impacts, in part because of a relatively low number (101) of observed marine mammal mortalities. We estimate historical carcass-detection rates for 14 cetacean species in the northern Gulf of Mexico that have estimates of abundance, survival rates, and stranding records. This preliminary analysis suggests that carcasses are recovered, on an average, from only 2% (range: 0-6.2%) of cetacean deaths. Thus, the true death toll could be 50 times the number of carcasses recovered, given no additional information. We discuss caveats to this estimate, but present it as a counterpoint to illustrate the magnitude of misrepresentation implicit in presenting observed carcass counts without similar qualification. We urge methodological development to develop appropriate multipliers. Analytical methods are required to account explicitly for low probability of carcass recovery from cryptic mortality events (e.g., oil spills, ship strikes, bycatch in unmonitored fisheries and acoustic trauma).

  • Belanger, M., Tan, L., Askin, N., and Wittnich, C.  Chronological effects of the Deepwater Horizon Gulf of Mexico oil spill on regional seabird casualties.  Journal of Marine Animals and Their Ecology 3(2): 10-14, 2010.
    Open Access >>
    Read Abstract >>

    In April 2010, the Deepwater Horizon (DH) oil platform in the Gulf of Mexico vented oil uncontrollably for 90+ days. This 'persistent' spill resulted in oil washing up daily on the shoreline of numerous Gulf of Mexico states, and created an oil spill lasting 30 times longer and 5 times larger than the 'rapid' 1989 Exxon Valdez (EV) spill. There is ongoing controversy regarding the effect of oil spills on seabird population, with few opportunities to analyze its daily effect. This paper describes the daily effect of the DH spill regarding the number of seabirds recovered alive and dead, and compared its overall population effect to the EV spill. Analyzing daily seabird collection data between days 38-138 after the DH spill, the dead bird collection average (48.2 + 35.5/day) was significantly (p < 0.05) more than the live bird collection average (20.8 + 27.0/day).  Data also shows a significant reduction in daily intake of live seabirds after day 110, while the daily dead bird intake saw a significant increase. Between days 110 to 138, live seabird collections only rose by 206 compared to the dead bird collection of 1834. The EV spill yielded 600+ live birds and 35,000 dead ones while the DH spill had 2053 live birds but only 7726 dead ones despite the DH spill being 5 times smaller in spill size. This data reveals that after 110 days of a 'persistent' spill, collecting live birds significantly decreases while the number of dead birds increases.  Also, there were a significantly lower number of dead birds collected during the 'persistent' DH spill than the 'rapid' EV spill.  This study reveals the first concrete evidence suggesting 'persistent' oil spills may have a greater environmental impact than 'rapid' spills, and immediate reaction is required to lessen the number of seabird casualties.

  • Antonio, F.J., Mendes, R.S., and Thomaz, S.M.  Identifying and modeling patterns of tetrapod vertebrate mortality rates in the Gulf of Mexico oil spill.  Aquatic Toxicology 105(1-2): 177-179, 2011.
    Read Abstract >>

    The accidental oil spill in the Gulf of Mexico in 2010 has caused perceptible damage to marine and freshwater ecosystems. The large quantity of oil leaking at a constant rate and the long duration of the event caused an exponentially increasing mortality of vertebrates. Using data provided by NOAA and USFWS, we assessed the effects of this event on birds, sea turtles, and mammals. Mortality rates (measured as the number of carcasses recorded per day) were exponential for all three groups. Birds were the most affected group, as indicated by the steepest increase of mortality rates over time. For sea turtles and mammals, an exponential increase in mortality was observed after an initial delay. These exponential behaviors are consistent with a unified scenario for the mortality rate for tetrapod vertebrates. However, at least for mammals, pre-spill data seem to indicate that the growth in the mortality rate is not entirely a consequence of the spill.

  • Campagna, C., Short, F.T., Polidoro, B.A., McManus, R., Collette, B.B., Pilcher, N.J., Sadovy de Mitcheson, Y., Stuart, S.N., and Carpenter, K.E.  Gulf of Mexico oil blowout increases risks to globally threatened species.  BioScience 61(5): 393-397, 2011.
    Read Abstract >>

    Fourteen marine species in the Gulf of Mexico are protected by the US Endangered Species Act, the Marine Mammal Protection Act, and the Migratory Bird Treaty Act. As the British Petroleum oil spill recovery and remediation proceed, species internationally recognized as having an elevated risk of extinction should also receive priority for protection and restoration efforts, whether or not they have specific legal protection. Forty additional marine species – unprotected by any federal laws – occur in the Gulf and are listed as threatened on the International Union for Conservation of Nature's (IUCN) Red List. The Red List assessment process scientifically evaluates species' global status and is therefore a key mechanism for transboundary impact assessments and for coordinating international conservation action. Environmental impact assessments conducted for future offshore oil and gas development should incorporate available data on globally threatened species, including species on the IUCN Red List. This consideration is particularly important because US Natural Resource Damage Assessments may not account for injury to highly migratory, globally threatened species.

  • McCrea-Strub, A., Kleisner, K., Sumaila, U.R., Swartz, W., Watson, R., Zeller, D., and Pauly, D.  Potential impact of the Deepwater Horizon oil spill on commercial fisheries in the Gulf of Mexico.  Fisheries 36(7): 332-336, 2011.
    Read Abstract >>

    Given the economic and social importance of fisheries in the Gulf of Mexico large marine ecosystem (LME), it is imperative to quantify the potential impacts of the Deepwater Horizon oil spill. To provide a preliminary perspective of the consequences of this disaster, spatial databases of annual reported commercial catch and landed value prior to the spill were investigated relative to the location of the fisheries closures during July 2010. Recent trends illustrated by this study suggest that more than 20% of the average annual U.S. commercial catch in the Gulf has been affected by postspill fisheries closures, indicating a potential minimum loss in annual landed value of US$247 million. Lucrative shrimp, blue crab, menhaden, and oyster fisheries may be at greatest risk of economic losses. Overall, it is evident that the oil spill has impacted a highly productive area of crucial economic significance within the Gulf of Mexico LME. This study draws attention to the need for ongoing and thorough investigations into the economic impacts of the oil spill on Gulf fisheries.

  • Finch, B.E., Wooten, K.J., and Smith, P.N.  Embryotoxicity of weathered crude oil from the Gulf of Mexico in mallard ducks (Anas platyrhynchos).  Environmental Toxicology and Chemistry 30(8): 1885-1891, 2011.
    Read Abstract >>

    Weathered crude oil in the Gulf of Mexico can result from oil spills such as the Deepwater Horizon incident that occurred on April 20, 2010 or from natural seeps. Adult waterbirds of the Gulf Coast region may become exposed to weathered crude oil while foraging, wading, or resting, and residues can then be transferred to nests, eggs, and hatchlings. Although the toxicity of many types of crude oil to avian embryos has been thoroughly studied, the effects of weathered crude oil on developing avian embryos are not well characterized. The objective of the present study was to examine embryotoxicity of weathered crude oil collected from the Gulf of Mexico in June 2010 using mallard ducks (Anas platyrhynchos) as a model species. Weathered crude oil was applied to fertilized mallard duck eggs by paintbrush in masses ranging from 0.1 to 99.9 mg on day 3 of incubation. Mortality occurred as early as day 7 and the conservatively derived median lethal application of weathered crude oil was 30.8 mg/egg (0.5 mg/g egg) or 30.7 µl/egg (0.5 µl/g egg). Body mass, liver and spleen mass, crown–rump and bill lengths, and frequency of deformities were not significantly different among hatchlings from oiled and control eggs. In comparison to published reports of fresh crude oil embryotoxicity, weathered crude oil was considerably less toxic. We conclude that avian toxicity varies according to the degree of crude oil weathering and the stage of embryonic development at the time of exposure. Results indicate bird eggs exposed to weathered crude oil from the Gulf of Mexico during summer 2010 may have had reduced hatching success.

  • Abbriano, R.M., Carranza, M.M., Hogle, S.L., Levin, R.A., Netburn, A.N., Seto, K.L., Snyder, S.M., and Franks, P.J.S.  Deepwater Horizon oil spill: A review of the planktonic response.  Oceanography 24(3): 294-301, 2011.
    Open Access >>
    Read Abstract >>

    On April 20, 2010, the explosion of the Deepwater Horizon (DWH) oil rig resulted in the loss of 11 lives and the largest oil spill in US history and perhaps the second largest in the world, after the first Gulf War Oil Spill from Kuwait. Over the 84 days following the explosion, an estimated 6.7 x 105 mT of Louisiana Sweet Crude oil and up to 500,000 mT of methane and gases were released from 1,480 m below the ocean's surface into the Gulf of Mexico (GoM). As oil continued to escape from the seafloor throughout the summer of 2010, images of oiled wildlife pervaded the news. These pictures, though troubling, only hinted at the fate of the plankton that form the foundation of the GoM ecosystem. This review discusses the potential effects of the DWH oil spill on the overlooked, but extremely important, members of the GoM ecosystem – the plankton. Our assessment is based on data collected in the aftermath of the DWH spill and supplemented with studies from past oil spills when information on the GoM spill was limited or unavailable. The time line we develop traces the spill from a "planktonic perspective," emphasizing the population dynamics of marine bacteria, phytoplankton, zooplankton, and fish larvae.

  • DeLaune, R.D. and Wright, A.  Projected impact of Deepwater Horizon oil spill on U.S. Gulf Coast wetlands.  Soil Science Society of America Journal 75(5): 1602-1612, 2011.
    Read Abstract >>

    The Deepwater Horizon spill oiled coastal wetland ecosystems along the northern Gulf of Mexico. We present data on probable impacts and recovery of these impacted wetlands. Based on numerous greenhouse and field studies conducted primarily in coastal Louisiana, we suggest that marsh vegetation will recover naturally without need for intensive remediation. Oiled marshes may reduce the availability of habitat for mobile fish species, resulting in their translocation to unimpacted areas. Impacts on benthic organisms may result in shifts in microbial community structure, but they will probably recover in lightly oil-impacted areas. The degradation rate or length of time oil remains in impacted wetlands depends on environmental conditions. Oil-impacted soils already contain adequate indigenous microorganisms capable of degradation under suitable environmental conditions. Nutrient addition, especially N, may increase the rate of oil biodegradation when sediment nutrient levels are low, but O2 availability appears to be the most important variable controlling oil degradation in marsh soils. Oil impacts on sediment O2 demand and restriction in O2 exchange at the sediment-water interface can alter biogeochemical processes and gaseous exchange (CO2 and CH4) with the atmosphere. Even though there were harmful impacts resulting from the Deepwater Horizon oil spill, prior research has demonstrated that Gulf Coast marshes are resilient and can recover. This view is supported by field observations of new shoots appearing in heavily oiled marshes 1 yr following the spill. Even though this review shows that Gulf Coast marshes have a high natural recovery potential, many ecological processes have not been adequately quantified or identified.

  • Kessler, J.D., Valentine, D.L., Redmond, M.C., Du, M.R., Chan, E.W., Mendes, S.D., Quiroz, E.W., Villanueva, C.J., Shusta, S.S., Werra, L.M., Yvon-Lewis, S.A., and Weber, T.C.  A persistent oxygen anomaly reveals the fate of spilled methane in the deep Gulf of Mexico.  Science 331(6015): 312-315, 2011.
    Read Abstract >>

    Methane was the most abundant hydrocarbon released during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. Beyond relevancy to this anthropogenic event, this methane release simulates a rapid and relatively short-term natural release from hydrates into deep water. Based on methane and oxygen distributions measured at 207 stations throughout the affected region, we find that within ~120 days from the onset of release ~3.0 x 1010 to 3.9 x 1010 moles of oxygen were respired, primarily by methanotrophs, and left behind a residual microbial community containing methanotrophic bacteria. We suggest that a vigorous deepwater bacterial bloom respired nearly all the released methane within this time, and that by analogy, large-scale releases of methane from hydrate in the deep ocean are likely to be met by a similarly rapid methanotrophic response.

  • Joye, S.B., MacDonald, I.R., Leifer, I., and Asper, V.  Magnitude and oxidation potential of hydrocarbon gases released from the BP oil well blowout.  Nature Geoscience 4(3): 160-164, 2011.
    Read Abstract >>

    The deep-sea hydrocarbon discharge resulting from the BP oil well blowout in the northern Gulf of Mexico released large quantities of oil and gaseous hydrocarbons such as methane into the deep ocean. So far, estimates of hydrocarbon discharge have focused on the oil released, and have overlooked the quantity, fate and environmental impact of the gas. Gaseous hydrocarbons turn over slowly in the deep ocean, and microbial consumption of these gases could have a long-lasting impact on oceanic oxygen levels. Here, we combine published estimates of the volume of oil released, together with provisional estimates of the oil to gas ratio of the discharged fluid, to determine the volume of gaseous hydrocarbons discharged during the spill. We estimate that the spill injected up to 500,000 t of gaseous hydrocarbons into the deep ocean and that these gaseous emissions comprised 40% of the total hydrocarbon discharge. Analysis of water around the wellhead revealed discrete layers of dissolved hydrocarbon gases between 1,000 and 1,300 m depth; concentrations exceeded background levels by up to 75,000 times. We suggest that microbial consumption of these gases could lead to the extensive and persistent depletion of oxygen in hydrocarbon-enriched waters.

  • Edwards, B.R., Reddy, C.M., Camilli, R., Carmichael, C.A., Longnecker, K., and Van Mooy, B.A.S.  Rapid microbial respiration of oil from the Deepwater Horizon spill in offshore surface waters of the Gulf of Mexico.  Environmental Research Letters 6(3): art. 035301, 2011.
    Open Access >>
    Read Abstract >>

    The Deepwater Horizon oil spill was one of the largest oil spills in history, and the fate of this oil within the Gulf of Mexico ecosystem remains to be fully understood. The goal of this study-conducted in mid-June of 2010, approximately two months after the oil spill began – was to understand the key role that microbes would play in the degradation of the oil in the offshore oligotrophic surface waters near the Deepwater Horizon site. As the utilization of organic carbon by bacteria in the surface waters of the Gulf had been previously shown to be phosphorus limited, we hypothesized that bacteria would be unable to rapidly utilize the oil released from the Macondo well. Although phosphate was scarce throughout the sampling region and microbes exhibited enzymatic signs of phosphate stress within the oil slick, microbial respiration within the slick was enhanced by approximately a factor of five. An incubation experiment to determine hydrocarbon degradation rates confirmed that a large fraction of this enhanced respiration was supported by hydrocarbon degradation. Extrapolating our observations to the entire area of the slick suggests that microbes had the potential to degrade a large fraction of the oil as it arrived at the surface from the well. These observations decidedly refuted our hypothesis. However, a concomitant increase in microbial abundance or biomass was not observed in the slick, suggesting that microbial growth was nutrient limited; incubations amended with nutrients showed rapid increases in cell number and biomass, which supported this conclusion. Our study shows that the dynamic microbial community of the Gulf of Mexico supported remarkable rates of oil respiration, despite a dearth of dissolved nutrients.

  • Ryerson, T.B. et al.  Atmospheric emissions from the Deepwater Horizon spill constrain air-water partitioning, hydrocarbon fate, and leak rate.  Geophysical Research Letters 38(7): art. L07803, 2011.
    Read Abstract >>

    The fate of deepwater releases of gas and oil mixtures is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water. Quantifying this partitioning is necessary to constrain simulations of gas and oil transport, to predict marine bioavailability of different fractions of the gas-oil mixture, and to develop a comprehensive picture of the fate of leaked hydrocarbons in the marine environment. Analysis of airborne atmospheric data shows massive amounts (~258,000 kg/day) of hydrocarbons evaporating promptly from the Deepwater Horizon spill; these data collected during two research flights constrain air-water partitioning, thus bioavailability and fate, of the leaked fluid. This analysis quantifies the fraction of surfacing hydrocarbons that dissolves in the water column (~33% by mass), the fraction that does not dissolve, and the fraction that evaporates promptly after surfacing (~14% by mass). We do not quantify the leaked fraction lacking a surface expression; therefore, calculation of atmospheric mass fluxes provides a lower limit to the total hydrocarbon leak rate of 32,600 to 47,700 barrels of fluid per day, depending on reservoir fluid composition information. This study demonstrates a new approach for rapid-response airborne assessment of future oil spills.

  • Socolofsky, S.A., Adams, E.E., and Sherwood, C.R.  Formation dynamics of subsurface hydrocarbon intrusions following the Deepwater Horizon blowout.  Geophysical Research Letters 38(9): art. L09602, 2011.
    Read Abstract >>

    Hydrocarbons released following the Deepwater Horizon (DH) blowout were found in deep, subsurface horizontal intrusions, yet there has been little discussion about how these intrusions formed. We have combined measured (or estimated) observations from the DH release with empirical relationships developed from previous lab experiments to identify the mechanisms responsible for intrusion formation and to characterize the DH plume. Results indicate that the intrusions originate from a stratification-dominated multiphase plume characterized by multiple subsurface intrusions containing dissolved gas and oil along with small droplets of liquid oil. Unlike earlier lab measurements, where the potential density in ambient water decreased linearly with elevation, at the DH site it varied quadratically. We have modified our method for estimating intrusion elevation under these conditions and the resulting estimates agree with observations that the majority of the hydrocarbons were found between 800 and 1200 m.

  • Hu, C.M., Weisberg, R.H., Liu, Y.G., Zheng, L.Y., Daly, K.L., English, D.C., Zhao, J., and Vargo, G.A.  Did the northeastern Gulf of Mexico become greener after the Deepwater Horizon oil spill?  Geophysical Research Letters 38(9): art. L09601, 2011.
    Read Abstract >>

    Assessment of direct and indirect impacts of oil and dispersants on the marine ecosystem in the northeastern Gulf of Mexico (NEGOM) from the Deepwater Horizon oil spill (April - July 2010) requires sustained observations over multiple years. Here, using satellite measurements, numerical circulation models, and other environmental data, we present some initial results on observed biological changes at the base of the food web. MODIS fluorescence line height (FLH, a proxy for phytoplankton biomass) shows two interesting anomalies. The first is statistically significant (>1 mg m-3 of chlorophyll-a anomaly), in an area exceeding 11,000 km2 in the NEGOM during August 2010, about 3 weeks after the oil well was capped. FLH values in this area are higher (i.e., water is greener) than in any August since 2002, and higher than ever since 2002 in an area of ~3,000 km2. Analyses of ocean circulation and other environmental data suggest that this anomaly may be attributed to the oil spill. The second is a spatially coherent FLH anomaly during December 2010 and January 2011, extending from Mobile Bay to the Florida Keys (mainly between 30 and 100-m isobaths). This anomaly appears to have resulted from unusually strong upwelling and mixing events during late fall. Available data are insufficient to support or reject a hypothesis that the subsurface oil may have contributed to the enhanced biomass during December 2010 and January 2011.

  • Kujawinski, E.B., Soule, M.C.K., Valentine, D.L., Boysen, A.K., Longnecker, K., and Redmond, M.C.  Fate of dispersants associated with the Deepwater Horizon oil spill.  Environmental Science and Technology 45(4): 1298-1306, 2011.
    Read Abstract >>

    Response actions to the Deepwater Horizon oil spill included the injection of ~771,000 gallons (2,900,000 L) of chemical dispersant into the flow of oil near the seafloor. Prior to this incident, no deepwater applications of dispersant had been conducted, and thus no data exist on the environmental fate of dispersants in deepwater. We used ultrahigh resolution mass spectrometry and liquid chromatography with tandem mass spectrometry (LC/MS/MS) to identify and quantify one key ingredient of the dispersant, the anionic surfactant DOSS (dioctyl sodium sulfosuccinate), in the Gulf of Mexico deepwater during active flow and again after flow had ceased. Here we show that DOSS was sequestered in deepwater hydrocarbon plumes at 1000-1200 m water depth and did not intermingle with surface dispersant applications. Further, its concentration distribution was consistent with conservative transport and dilution at depth and it persisted up to 300 km from the well, 64 days after deepwater dispersant applications ceased. We conclude that DOSS was selectively associated with the oil and gas phases in the deepwater plume, yet underwent negligible, or slow, rates of biodegradation in the affected waters. These results provide important constraints on accurate modeling of the deepwater plume and critical geochemical contexts for future toxicological studies.

  • Hayworth, J.S. and Clement, T.P.  BP's Operation Deep Clean – Could dilution be the solution to beach pollution?  Environmental Science and Technology 45(10): 4201-4202, 2011.
    Open Access >>

     

  • Avens, H.J., Unice, K.M., Sahmel, J., Gross, S.A., Keenan, J.J., and Paustenbach, D.J.  Analysis and modeling of airborne BTEX concentrations from the Deepwater Horizon oil spill.  Environmental Science and Technology 45(17): 7372-7379, 2011.
    Read Abstract >>

    Concerns have been raised about whether the Deepwater Horizon oil spill cleanup workers experienced adverse health effects from exposure to airborne benzene, toluene, ethylbenzene, and xylene (BTEX) which volatilized from surfaced oil. Thus, we analyzed the nearly 20 000 BTEX measurements of breathing zone air samples of offshore cleanup workers taken during the six months following the incident (made publicly available by British Petroleum). The measurements indicate that 99% of the measurements taken prior to capping the well were 32-, 510-, 360-, and 77-fold lower than the U.S. Occupational Safety and Health Administration's Permissible Exposure Limits (PELs) for BTEX, respectively. BTEX measurements did not decrease appreciably during the three months after the well was capped. Moreover, the magnitudes of these data were similar to measurements from ships not involved in oil slick remediation, suggesting that the BTEX measurements were primarily due to engine exhaust rather than the oil slick. To supplement the data analysis, two modeling approaches were employed to estimate airborne BTEX concentrations under a variety of conditions (e.g., oil slick thickness, wind velocity). The modeling results corroborated that BTEX concentrations from the oil were well below PELs and that the oil was not the primary contributor to the measured BTEX.

  • Kostka, J.E., Prakash, O., Overholt, W.A., Green, S.J., Freyer, G., Canion, A., Delgardio, J., Norton, N., Hazen, T.C., and Huettel, M.  Hydrocarbon-degrading bacteria and the bacterial community response in Gulf of Mexico beach sands impacted by the Deepwater Horizon oil spill.  Applied and Environmental Microbiology 77(22): 7962-7974, 2011.
    Open Access >>
    Read Abstract >>

    A significant portion of oil from the recent Deepwater Horizon (DH) oil spill in the Gulf of Mexico was transported to the shoreline, where it may have severe ecological and economic consequences. The objectives of this study were (i) to identify and characterize predominant oil-degrading taxa that may be used as model hydrocarbon degraders or as microbial indicators of contamination and (ii) to characterize the in situ response of indigenous bacterial communities to oil contamination in beach ecosystems. This study was conducted at municipal Pensacola Beach, FL, where chemical analysis revealed weathered oil petroleum hydrocarbon (C8 to C40 concentrations ranging from 3.1 to 4,500 mg kg-1 in beach sands. A total of 24 bacterial strains from 14 genera were isolated from oiled beach sands and confirmed as oil-degrading microorganisms. Isolated bacterial strains were primarily Gammaproteobacteria, including representatives of genera with known oil degraders (Alcanivorax, Marinobacter, Pseudomonas, and Acinetobacter). Sequence libraries generated from oiled sands revealed phylotypes that showed high sequence identity (up to 99%) to rRNA gene sequences from the oil-degrading bacterial isolates. The abundance of bacterial SSU rRNA gene sequences was ~10-fold higher in oiled (0.44 × 107 to 10.2 × 107 copies g-1) versus clean (0.024 × 107 to 1.4 × 107 copies g-1) sand. Community analysis revealed a distinct response to oil contamination, and SSU rRNA gene abundance derived from the genus Alcanivorax showed the largest increase in relative abundance in contaminated samples. We conclude that oil contamination from the DH spill had a profound impact on the abundance and community composition of indigenous bacteria in Gulf beach sands, and our evidence points to members of the Gammaproteobacteria (Alcanivorax, Marinobacter) and Alphaproteobacteria (Rhodobacteraceae) as key players in oil degradation there.

Oil Spills: Threats and Impacts

  • Jernelov, A.  The threats from oil spills: Now, then, and in the future.  Ambio 39(5-6): 353-366, 2010.  
    Read Abstract >>

    The ongoing oil spill from the blown-out well by the name of Macondo, drilled by the ill-fated rig Deepwater Horizon, has many features in common with another blowout in the Mexican Gulf that happened three decades ago. Then the oil gushed out from the Ixtoc I well drilled by the Sedco 135-F semi-submersible rig. In the years between these catastrophes, the source and nature of oil spills have undergone large changes. Huge spills from tankers that ran aground or collided used to be what caught the headlines and caused large ecological damage. The number and size of such accidental spills have decreased significantly. Instead, spills from ageing, ill-maintained or sabotaged pipelines have increased, and places like Arctic Russia, the Niger Delta, and the northwestern Amazon have become sites of reoccurring oil pollution. As for blowouts, there is no clear trend with regard to the number of incidences or amounts of spilled oil, but deepwater blowouts are much harder to cap and thus tend to go on longer and result in the release of larger quantities of oil. Also, oil exploration and extraction is moving into ever-deeper water and into stormier and icier seas, increasing potential risks. The risk for reoccurring spills like the two huge Mexican Gulf ones is eminent and must be reduced.

  • Kontovas, C.A., Psaraftis, H.N., and Ventikos, N.P.  An empirical analysis of IOPCF oil spill cost data.  Marine Pollution Bulletin 60(9): 1455-1466, 2010.
    Read Abstract >>

    This paper reports on recent analysis of oil spill cost data assembled by the International Oil Pollution Compensation Fund (IOPCF). Regression analyses of clean-up costs and total costs have been carried out, after taking care to convert to current prices and remove outliers. In the first place, the results of this analysis have been useful in the context of the ongoing discussion within the International Maritime Organization (IMO) on environmental risk evaluation criteria. Furthermore, these results can be useful in estimating the benefit of regulations that deal with the protection of marine environment and oil pollution prevention.

  • Dalton, T. and Jin, D.  Extent and frequency of vessel oil spills in US marine protected areas.  Marine Pollution Bulletin 60(11): 1939-1945, 2010.   
    Read Abstract >>

    Little is known about how marine protected areas (MPAs) may be vulnerable to vessel oil spills in the United States. This study investigated individual size, frequency, and total amount of vessel oil spilled in US MPAs, and how characteristics of MPAs and individual spill events influenced spills. Vessel oil spills in US waters (2002-06) and MPA boundaries were mapped. Total number and volume of oil spills inside and outside MPAs were computed. Results show that the presence of a MPA does not seem to prevent vessel oil spills or reduce the amount of oil spilled, and that a variety of MPA attributes (e.g., scale of protection, fishing restrictions, and others) and spill event characteristics (e.g., vessel type, year of spill, and others) affect oil spills inside and outside MPAs. These results can be used to develop MPA rules and marine transportation policies that reduce the vulnerability of sensitive resources to oil spills.

  • Yip, T.L., Talley, W.K., and Jin, D.  The effectiveness of double hulls in reducing vessel-accident oil spillage.  Marine Pollution Bulletin 62(11): 2427-2432, 2011.
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    While much work has been done in investigating determinants of oil spillage attributed to vessel accidents, little research has been conducted on the effectiveness of ship hull design in reducing marine pollution. This paper addresses whether the double-hull requirement reduces vessel-accident oil spillage. The volume of oil spillage due to oil-cargo vessel accidents was investigated using tobit regressions and an empirical data set of individual vessel accident pollution incidents investigated by the US Coast Guard from 2001 to 2008. The results indicate that the double hull design on average reduces the size of oil spills by 20% and 62% in tank barge and tanker ship accidents, respectively.

  • Iverson, S.A. and Esler, D.  Harlequin Duck population injury and recovery dynamics following the 1989 Exxon Valdez oil spill.  Ecological Applications 20(7): 1993-2006, 2010.
    Read Abstract >>

    The 1989 Exxon Valdez oil spill caused significant injury to wildlife populations in Prince William Sound, Alaska, USA. Harlequin Ducks (Histrionicus histrionicus) were particularly vulnerable to the spill and have been studied extensively since, leading to one of the most thorough considerations of the consequences of a major oil spill ever undertaken. We compiled demographic and survey data collected since the spill to evaluate the timing and extent of mortality using a population model. During the immediate aftermath of the spill, we estimated a 25% decrease in Harlequin Duck numbers in oiled areas. Survival rates remained depressed in oiled areas 6-9 years after the spill and did not equal those from unoiled areas until at least 11-14 years later. Despite a high degree of site fidelity to wintering sites, immigration was important for recovery dynamics, as the relatively large number of birds from habitats outside the spill zone provided a pool of individuals to facilitate numerical increases. On the basis of these model inputs and assumptions about fecundity rates for the species, we projected a timeline to recovery of 24 years under the most-likely combination of variables, with a range of 16 to 32 years for the best-case and worst-case scenarios, respectively. Our results corroborate assertions from other studies that the effects of spilled oil on wildlife can be expressed over much longer time frames than previously assumed and that the cumulative mortality associated with chronic exposure to residual oil may actually exceed acute mortality, which has been the primary concern following most oil spills.

  • Neff, J.M., Page, D.S., and Boehm, P.D.  Exposure of sea otters and harlequin ducks in Prince William Sound, Alaska, USA, to shoreline residues 20 years after Exxon Valdez oil spill.  Environmental Toxicology and Chemistry 30(3): 659-672, 2011.
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    We assessed whether sea otters and harlequin ducks in an area of western Prince William Sound, Alaska, USA (PWS), oiled by the 1989 Exxon Valdez oil spill (EVOS), are exposed to polycyclic aromatic hydrocarbons (PAH) from oil residues 20 years after the spill. Spilled oil has persisted in PWS for two decades as surface oil residues (SOR) and subsurface oil residues (SSOR) on the shore. The rare SOR are located primarily on the upper shore as inert, nonhazardous asphaltic deposits, and SSOR are confined to widely scattered locations as small patches under a boulder/cobble veneer, primarily on the middle and upper shore, in forms and locations that preclude physical contact by wildlife and diminish bioavailability. Sea otters and harlequin ducks consume benthic invertebrates that they collect by diving to the bottom in the intertidal and subtidal zones. Sea otters also dig intertidal and subtidal pits in search of clams. The three plausible exposure pathways are through the water, in oil-contaminated prey, or by direct contact with SSOR during foraging. Concentrations of PAH in near-shore water off oiled shores in 2002 to 2005 were at background levels (<0.05 ng/L). Median concentrations of PAH in five intertidal prey species on oiled shores in 2002 to 2008 range from 4.0 to 34 ng/g dry weight, indistinguishable from background concentrations. Subsurface oil residues are restricted to locations on the shore and substrate types, where large clams do not occur and where sea otters do not dig foraging pits. Therefore, that sea otters and harlequin ducks continue to be exposed to environmentally significant amounts of PAH from EVOS 20 years after the spill is not plausible.

  • Esler, D., Ballachey, B.E., Trust, K.A., Iverson, S.A., Reed, J.A., Miles, A.K., Henderson, J.D., Woodin, B.R., Stegeman, J.J., McAdie, M., Mulcahy, D.M., and Wilson, B.W.  Cytochrome P4501A biomarker indication of the timeline of chronic exposure of Barrow's goldeneyes to residual Exxon Valdez oil.  Marine Pollution Bulletin 62(3): 609-614, 2011.
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    We examined hepatic EROD activity, as an indicator of CYP1A induction, in Barrow's goldeneyes captured in areas oiled during the 1989 Exxon Valdez spill and those from nearby unoiled areas. We found that average EROD activity differed between areas during 2005, although the magnitude of the difference was reduced relative to a previous study from 1996/1997, and we found that areas did not differ by 2009. Similarly, we found that the proportion of individuals captured from oiled areas with elevated EROD activity (≥2 times unoiled average) declined from 41% in winter 1996/1997 to 10% in 2005 and 15% in 2009. This work adds to a body of literature describing the timelines over which vertebrates were exposed to residual Exxon Valdez oil and indicates that, for Barrow's goldeneyes in Prince William Sound, exposure persisted for many years with evidence of substantially reduced exposure by 2 decades after the spill.

  • Zabala, J., Zuberogoitia, I., Martinez-Climent, J.A., and Etxezarreta, J.  Do long lived seabirds reduce the negative effects of acute pollution on adult survival by skipping breeding? A study with European storm petrels (Hydrobates pelagicus) during the ''Prestige'' oil-spill.  Marine Pollution Bulletin 62(1): 109-115, 2011.
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    We estimated the survival probability of breeding European storm petrels before, during and after a severe oil-spill. We hypothesized that petrels might have deserted the breeding colony to maximize their own survival probability and we expected no major change on adult survival probabilities as a consequence of the spill. We used an information-theoretical approach and multi-model inference to assess the strength of the evidence in favour of different hypotheses. Evidence contained in the data clearly supported the non-effect of the spill on adult survival hypothesis while punctual impact of the spill on survival and expanded (3 years) impact alternatives received less support. The effect size of the spill on averaged survival estimates was negligible in every case. We suggest that petrels minimized the impact of acute pollution by not investing in reproduction. We suggest that short-medium term management actions after oil-spills and similar catastrophes should focus on ecosystem restoration.

  • Fernández-Tajes, J., Rábade, T., Laffon, B., and Méndez, J.  Monitoring follow up of two areas affected by the Prestige oil four years after the spillage.  Journal of Toxicology and Environmental Health Part A 74(15-16): 1067-1075, 2011.
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    The sinking of the oil tanker Prestige in November 2002 resulted in the spill of more than 63,000 tonnes of crude oil, and polluted more than 1,000 km of coastline, especially affecting Galicia (northwestern Spain). Four years after the accident, a new biological monitoring study was undertaken of two Galician areas intensely affected by the spill, Lira and Ancoradoiro, previously evaluated in the months following the accident (Laffon et al. 2006). The mussel Mytilus galloprovincialis was employed as bioindicator organism to determine both polycyclic aromatic hydrocarbons (PAH) levels and genotoxic effects. PAH were determined chromatographically in seawater samples and mussel tissues collected from November 2006 to January 2008. The results obtained showed that PAH pollution was still present in these areas, but bioaccumulation of these compounds in mussels was low, compared to reference mussels, and lower than in our previous study. DNA damage assessment was also performed in gills and hemolymph cells by means of the alkaline comet assay. DNA damage levels were higher in mussels from the exposed areas than in reference mussels. DNA damage decreased after a 7-d recovery period in the laboratory, but prolonging the recovery period up to 14 d did not contribute to less DNA damage in gill cells. Hemolymph cells were more sensitive than gill cells to the induction of DNA damage.

  • Moreno, R., Jover, L., Diez, C., and Sanpera, C.  Seabird feathers as monitors of the levels and persistence of heavy metal pollution after the Prestige oil spill.  Environmental Pollution 159(10): 2454-2460, 2011.
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    We measured heavy metal concentrations in yellow-legged gulls (n = 196) and European shags (n = 189) in order to assess the temporal pattern of contaminant exposure following the Prestige oil spill in November 2002. We analysed Pb, Cu, Zn, Cr, Ni and V levels in chick feathers sampled at four colonies during seven post-spill years (2003–2009), and compared results with pre-spill levels obtained from feathers of juvenile shag corpses (grown in spring/summer 2002). Following the Prestige wreck, Cu (4.3–10 μg g-1) and Pb concentrations (1.0–1.4 μg g-1) were, respectively, between two and five times higher than pre-spill levels (1.5–3.6 and 0.1–0.4 μg g-1), but returned to previous background concentrations after three years. Our study highlights the suitability of chick feathers of seabirds for assessing the impact of oil spills on heavy metal contamination, and provides the best evidence to date on the persistence of oil pollution after the Prestige incident.

  • Faksness, L.G., Brandvik, P.J., Daae, R.L., Leirvik, F., and Borseth, J.F.  Large-scale oil-in-ice experiment in the Barents Sea: Monitoring of oil in water and MetOcean interactions.  Marine Pollution Bulletin 62(5): 976-984, 2011.
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    A large-scale field experiment took place in the marginal ice zone in the Barents Sea in May 2009. Fresh oil (7000 L) was released uncontained between the ice floes to study oil weathering and spreading in ice and surface water. A detailed monitoring of oil-in-water and ice interactions was performed throughout the six-day experiment. In addition, meteorological and oceanographic data were recorded for monitoring of the wind speed and direction, air temperature, currents and ice floe movements. The monitoring showed low concentrations of dissolved hydrocarbons and the predicted acute toxicity indicated that the acute toxicity was low. The ice field drifted nearly 80 km during the experimental period, and although the oil drifted with the ice, it remained contained between the ice floes.

  • Thibodeaux, L.J., Valsaraj, K.T., John, V.T., Papadopoulos, K.D., Pratt, L.R., and Pesika, N.S.  Marine oil fate: Knowledge gaps, basic research, and development needs; a perspective based on the Deepwater Horizon spill.  Environmental Engineering Science 28(2): 87-93, 2011.
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    The various complex forms of transport as well as many other fate processes ongoing in the marine water column require research for the understanding and prediction of impacts of deepwater releases on the marine ecosystem. Such research is useful for assessing the context and limits of future deepwater oil and gas development in the Gulf of Mexico. The Deepwater Horizon incident in the Gulf represents the first oil spill occurring at significant depth, ~5,000 ft (1,500 m). It is also the first situation where dispersants were directly added to the hydrocarbon effluent from the wellhead in efforts to disperse the droplets over a large volume of the water column. In this regard, this perspective is an original work in that it provides an in-depth analysis of gaps and needs, which will guide future work in the field. Preliminary reports have led to a variety of images that highlight new physiochemical phenomena whose comprehensive understanding will be needed in assessing the oil and associated hydrocarbon chemical fate and environmental impact. Camera images of the oil and gas entering the water at depth and subsurface remote-operated vehicles have revealed droplet clouds and hydrocarbon plumes suspended thousands of feet below the surface moving horizontally with the water currents. Although preliminary, these and other observations are sufficient to piece together new hypothetical deepwater chemodynamic processes and phenomena that have yet to be fully understood. This position article focuses on unique and new research issues raised and relevant to this spill specifically. The ultimate fate of the oil constituents is a very broad subject. Our objective was concerned with the deepwater spill-initiating event. We focused on selected fate processes associated with the oil and dispersant chemodynamics from the blowout point, on the seabed, in the water column upward, and finally, into the marine surface mixed layer. An observation-conceived, process-based, mass balance-crafted engineering science predictive tool is proposed. It is needed for forecasting, projecting in anticipation of and managing the next spill, and answering the question ''where does it all go?''

  • Atlas, R.M. and Hazen, T.C.  Oil biodegradation and bioremediation: A tale of the two worst spills in U.S. history.  Environmental Science and Technology 45(16): 6709-6715, 2011.
    Open Access >>
    Read Abstract >>

    The devastating environmental impacts of the Exxon Valdez spill in 1989 and its media notoriety made it a frequent comparison to the BP Deepwater Horizon spill in the popular press in 2010, even though the nature of the two spills and the environments impacted were vastly different. Fortunately, unlike higher organisms that are adversely impacted by oil spills, microorganisms are able to consume petroleum hydrocarbons. These oil degrading indigenous microorganisms played a significant role in reducing the overall environmental impact of both the Exxon Valdez and BP Deepwater Horizon oil spills.

  • Ji, K. et al.  Genotoxicity and endocrine-disruption potentials of sediment near an oil spill site: Two years after the Hebei Spirit oil spill.  Environmental Science and Technology 45(17): 7481-7488, 2011.
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    The Hebei Spirit oil spill episode (December 7, 2007) has affected the western coastal area of South Korea; however, there is limited information on the potential toxicity of the oil spill to the ecosystem or humans. The potential toxicity of sediments collected from the affected area (n = 22) 2 years after the spill was evaluated. Acute lethal toxicity tests using Vibrio fischeri and Moina macrocopa and tests for genotoxicity and alteration of steroidogenesis using chicken DT40 cells and H295R cells, respectively, were conducted. Both crude and weathered oil extracts were evaluated in order to link the observed toxicity in the sediment extracts to the oil spill. Whereas toxicity to bacteria and daphnids was observed in only two elutriate samples, 10 of the 22 sediment extracts showed genotoxic potential in DT40 cells. The mechanisms of genotoxicity involved nucleotide excision repair (XPA-/), homologous recombination (RAD54-/-), and translesion synthesis pathways (REV3-/-). In addition, nine sediment extracts caused significantly greater production of E2 in H295R cells, and significant up-regulation of CYP19, CYP11B2, and 3βHSD2 by sediment extracts was observed. The pattern of toxicities observed in both crude and weathered oil samples was similar to that observed in the sediment extracts. The genotoxicicity and endocrine-disruption potential of the sediment extracts suggest a need for long-term followup for such toxicity in humans and wildlife in this area.

  • Donaghy, L., Hong, H.K., Lee, H.J., Jun, J.C., Park, Y.J., and Choi, K.S.  Hemocyte parameters of the Pacific oyster Crassostrea gigas a year after the Hebei Spirit oil spill off the west coast of Korea.  Helgolander Meeresunters 64(4): 349-355, 2010.
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    In marine bivalves, hemocytes support various physiological functions, including immune defense, nutrient transport, shell repair, and homeostatic maintenance. Although the effects of marine contaminants on the immunological functions of bivalves have been extensively investigated, the impacts of oil spills are not well understood. Therefore, we investigated hemocyte parameters in the Pacific oyster Crassostrea gigas 13 months after the Hebei Spirit oil spill (December 2007) off the west coast of Korea. The parameters studied included hemocyte concentration and mortality, relative proportion of hemocyte populations, and immunological functions such as phagocytosis and oxidative activity using flow cytometry. These immune-related parameters in oysters damaged by the oil spill were also compared to control oysters that were collected from an area unaffected by the spill. The flow cytometry study indicated that granulocyte population, phagocytic capacity, and reactive oxygen species production in oysters exposed to crude oil 13 months prior were depressed compared to the unexposed control oysters. Our data suggest that immunocompetence in oysters affected by the oil spill had not fully recovered 1 year after the accident, although more detailed studies on the physiology and disease resistance should be performed.

  • Schlacher, T.A., Holzheimer, A., Stevens, T., and Rissik, D.  Impacts of the 'Pacific Adventurer' oil spill on the macrobenthos of subtropical sandy beaches.  Estuaries and Coasts 34(5): 937-949, 2011.
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    Biological impacts of oil on sandy shore ecosystems remain incompletely understood, especially following smaller spills on subtropical beaches. Here we quantified changes to benthic assemblages on a sandy beach following the 270-t spill of heavy fuel oil from the Pacific Adventurer that occurred in March 2009 off Moreton Island in Eastern Australia. Assessments of ecological impacts are based on spatial contrasts between multiple reference and impact sites sampled 1 week and 3 months after the spill. Benthic invertebrate assemblages exposed to oil had significantly fewer individuals of fewer species 1 week after the spill, markedly changing their ecological structure. Biological differences consistent with oil-related mortality were significant on the lower shore and in the swash and remained so 3 months after the spill. This signals a lack of recovery of these communities in the short term, despite the fairly rapid removal of oil. Results show that, despite the relatively small size of the spill, heavy fuel oil contamination can cause substantial impacts on sandy beach ecosystems, and that recovery may be prolonged.

Oil and Marine Species

  • Baussant, T., Ortiz-Zarragoitia, M., Cajaraville, M. P., Bechmann, R. K., Taban, I. ngrid C., and Sanni, S.  Effects of chronic exposure to dispersed oil on selected reproductive processes in adult blue mussels (Mytilus edulis) and the consequences for the early life stages of their larvae.  Marine Pollution Bulletin 62(7): 1437-1445, 2011.  
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    Mussels (Mytilus edulis) were continuously exposed to dispersed crude oil (0.015-0.25 mg/l) for 7 months covering the whole gamete development cycle. After 1 month exposure to 0.25 mg oil/l, the level of alkali-labile phosphates (ALP) and the volume density of atretic oocytes in female gonads were higher than those in the gonads of control females, indicating that oil affected the level of vitellogenin-like proteins and gamete development. Spawning of mussels was induced after 7 months oil exposure. Parental oil exposure did not affect subsequent fertilization success in clean seawater but this was reduced in 0.25 mg oil/l. Parental exposure to 0.25 mg oil/l caused both slow development and a higher percentage of abnormalities in D-shell larvae 2 days post-fertilization; reduced growth 7 days post-fertilization. These effects were greatly enhanced when larval stages were maintained at 0.25 mg oil/l. Similar studies are warranted for risk assessment prognosis.

  • Irie, K., Kawaguchi, M., Mizuno, K., Song, J.Y., Nakayama, K., Kitamura, S.I., and Murakami, Y.  Effect of heavy oil on the development of the nervous system of floating and sinking teleost eggs.  Marine Pollution Bulletin 63(5-12): 297-302, 2011.
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    Heavy oil (HO) on the sea surface penetrates into fish eggs and prevents the normal morphogenesis. To identify the toxicological effects of HO in the context of the egg types, we performed exposure experiments using floating eggs and sinking eggs. In the course of development, HO-exposed embryos of floating eggs showed abnormal morphology, whereas early larva of the sinking eggs had almost normal morphology. However, the developing peripheral nervous system of sinking eggs showed abnormal projections. These findings suggest that HO exposed fishes have problems in the developing neurons, although they have no morphological malformations. Through these observations, we conclude that HO is strongly toxic to floating eggs in the morphogenesis, and also affect the neuron development in both floating and sinking eggs.

  • Incardona, J.P., Collier, T.K., and Scholz, N.L.  Oil spills and fish health: exposing the heart of the matter.  Journal of Exposure Science and Environmental Epidemiology 21(1): 3-4, 2011.
    Open Access >>   
    Read Abstract >>

    The chemical complexity of crude oil and its fuel products poses many important challenges for exposure science in marine ecosystems that support productive fisheries throughout the world. Meeting these challenges will enable better decisions on approaches to protecting and restoring these ecosystems.

  • Olsvik, P.A., Nordtug, T., Altin, D., Lie, K.K., Overrein, I., and Hansen, B.H.  Transcriptional effects on glutathione S-transferases in first feeding Atlantic cod (Gadus morhua) larvae exposed to crude oil.  Chemosphere 79(9): 905-913, 2010.
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    Polycyclic aromatic hydrocarbons (PAHs) and other oil compounds are known to induce stress and impact health of marine organisms. Water-soluble fractions of oil contain components known to induce glutathione S-transferases (GSTs), one of the major classes of phase II detoxifying enzymes present in essentially all eukaryotic organisms. In this study, the transcriptional responses of six GSTs (GST pi, GST mu, GST omega, GST theta, GSY zeta and GST kappa) were examined in early larvae of Atlantic cod Gadus morhua exposed to five concentrations of dispersed oil (containing oil droplets and water-soluble fraction) and water-soluble fractions (WSF) of oil. When Atlantic cod larvae were exposed to WSF (containing 1.31 ± 0.31 µg ΣPAH/L for 4 days), expression of GSTM3 and GSTO1 was significantly increased, whereas no differences in GST expression were observed in larvae exposed to a corresponding 50% lower amount of dispersed oil (containing 0.36 ± 0.10 µg ΣPAH/L for 4 days). The study suggest that although the oil clearly had severe negative effects on the larvae (i.e. concentration-dependent lethality and growth reduction), only minor effects on GST transcription could be observed using RNA obtained from pooled whole-larvae homogenates. This result indicates that the expression of these important detoxification enzymes is only moderately inducible at such an early developmental stage either reflecting low tolerance of cod larvae to dispersed oil or alternatively that using whole-larvae homogenates may have masked tissue-specific mRNA induction.

  • Scarlett, A.G., Clough, R., West, C., Lewis, C.A., Booth, A.M., and Rowland, S.J.  Alkylnaphthalenes: Priority pollutants or minor contributors to the poor health of marine mussels?  Environmental Science and Technology 45(14): 6160-6166, 2011.
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    Alkylnaphthalenes (AN) are relatively water-soluble hydrocarbons which, following spillages of crude oils, have been widely reported in contaminated marine organisms such as mussels. In the present report we show, by tandem-gas chromatography-time-of-flight-mass spectrometry (GC × GC-ToF-MS), that the range of AN in contaminated wild mussels from the UK extends beyond the previously GC resolved isomers to those with at least seven substituent carbon atoms. Since surprisingly little information on AN toxicity to such marine organisms has been reported we synthesized two C8 AN and measured the toxicity of C2-8 AN to mussels (clearance rate assay). C2-3 AN were appreciably toxic (concentration for 50% clearance rate inhibition, 48 h IC50 1.4-2.6 μmol g-1 dry weight tissue), but several C4, 6 and C8 AN, including branched isomers expected to be resistant to biodegradation and more accumulative, were relatively nontoxic (48 h IC50 > 10 μmol g-1) and longer term exposure (8d) failed to elicit a greater toxic response. The accumulation profiles of AN in laboratory mussels exposed to oil were similar to those of the wild mussels. Moreover, laboratory oil-exposed mussels depurated toxic C2-3 AN within 5 days in clean water and clearance rates recovered. The latter might imply that, in contrast with branched alkyl benzenes tested previously, AN are of less toxic concern, but such a straightforward conclusion cannot necessarily be drawn; a synthetic branched C8 AN persisted following depuration and was as toxic to mussels as a C3 AN (IC50 1.3 μmol g-1). This indicates that the structures of AN are also important.

  • de Hoop, L., Schipper, A.M., Leuven, R.S.E.W., Huijbregts, M.A.J., Olsen, G.H., Smit, M.G.D., and Hendriks, A.J.  Sensitivity of polar and temperate marine organisms to oil components.  Environmental Science and Technology 45(20): 9017-9023, 2011.
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    Potential contamination of polar regions due to increasing oil exploitation and transportation poses risks to marine species. Risk assessments for polar marine species or ecosystems are mostly based on toxicity data obtained for temperate species. Yet, it is unclear whether toxicity data of temperate organisms are representative for polar species and ecosystems. The present study compared sensitivities of polar and temperate marine species to crude oil, 2-methyl-naphthalene, and naphthalene. Species sensitivity distributions (SSDs) were constructed for polar and temperate species based on acute toxicity data from scientific literature, reports, and databases. Overall, there was a maximum factor of 3 difference in sensitivity to oil and oil components, based on the means of the toxicity data and the hazardous concentrations for 5 and 50% of the species (HC5 and HC50) as derived from the SSDs. Except for chordates and naphthalene, polar and temperate species sensitivities did not differ significantly. The results are interpreted in the light of physiological characteristics, such as metabolism, lipid fraction, lipid composition, antioxidant levels, and resistance to freezing, that have been suggested to influence the susceptibility of marine species to oil. As a consequence, acute toxicity data obtained for temperate organisms may serve to obtain a first indication of risks in polar regions.

  • Hicken, C.E., Linbo, T.L., Baldwin, D.H., Willis, M.L., Myers, M.S., Holland, L., Larsen, M., Stekoll, M.S., Rice, S.D., Collier, T.K., Scholz, N.L., and Incardona, J.P.  Sublethal exposure to crude oil during embryonic development alters cardiac morphology and reduces aerobic capacity in adult fish.  Proceedings of the National Academy of Sciences 108(17): 7086-7090, 2011.
    Open Access >>
    Read Abstract >>

    Exposure to high concentrations of crude oil produces a lethal syndrome of heart failure in fish embryos. Mortality is caused by cardiotoxic polycyclic aromatic hydrocarbons (PAHs), ubiquitous components of petroleum. Here, we show that transient embryonic exposure to very low concentrations of oil causes toxicity that is sublethal, delayed, and not counteracted by the protective effects of cytochrome P450 induction. Nearly a year after embryonic oil exposure, adult zebrafish showed subtle changes in heart shape and a significant reduction in swimming performance, indicative of reduced cardiac output. These delayed physiological impacts on cardiovascular performance at later life stages provide a potential mechanism linking reduced individual survival to population-level ecosystem responses of fish species to chronic, low-level oil pollution.

  • Hannam, M.L., Bamber, S.D., Moody, A.J., Galloway, T.S., and Jones, M.B.  Immunotoxicity and oxidative stress in the Arctic scallop Chlamys islandica: Effects of acute oil exposure.  Ecotoxicology and Environmental Safety 73(6): 1440-1448, 2010.
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    With increasing oil exploration in Arctic regions, the risk of an accidental oil spill into the environment is inevitably elevated. As a result, concerns have been raised over the potential impact of oil exposure on Arctic organisms. This study assessed the effects of an acute oil exposure (mimicking an accidental spill) on the immune function and oxidative stress status of the Arctic scallop Chlamys islandica. Scallops were exposed to the water accommodated fraction of crude oil over 21 d (maximum ΣPAH 163 µg l-1) and immune endpoints and oxidative stress parameters were measured. Mortalities were recorded during the exposure and reductions in immunocompetence were observed, with significant impairment of phagocytosis and cell membrane stability. Scallops were also subjected to oxidative stress, with a significant reduction in glutathione levels and induction of lipid peroxidation. After the acute oil exposure had subsided, no recovery of immune function was observed indicating potential for prolonged sublethal effects.

  • Lyons, M.C., Wong, D.K.H., Mulder, I., Lee, K., and Burridge, L.E.  The influence of water temperature on induced liver EROD activity in Atlantic cod (Gadus morhua) exposed to crude oil and oil dispersants.  Ecotoxicology and Environmental Safety 74(4): 904-910, 2011.
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    Juvenile Atlantic cod were exposed to either the water-accommodated fraction (WAF) or the chemically enhanced water-accommodated fraction (CEWAF) of Mediterranean South American (MESA), a medium grade crude oil at three different temperatures. Two concentrations of each mixture were tested, 0.2% and 1.0% (v/v) at 2, 7 and 10 °C. Corexit 9500 was the chemical dispersant tested. The liver enzyme ethoxyresorufin-O-deethylase (EROD) was measured during a 72-h exposure. The WAF of oil had significant (P < 0.05) effect on enzyme activity compared to controls at only one sampling time: 48 h at 10 °C. Exposure of CEWAF of oil resulted in significantly (P < 0.05) elevated EROD activity compared to controls. The level of EROD induction was temperature related with higher induction being observed in cod exposed to CEWAF at higher temperatures. Total polycyclic aromatic hydrocarbon (PAH) concentrations in exposure water were significantly higher in chemically dispersed mixtures. While PAH concentrations were lower in the 2 °C water compared to 7 or 10 °C (8.7 vs 11.9 μg mL-1), the level of EROD induction was approximately 9 and 12 times lower at 2 °C compared to 7 or 10 °C, respectively, suggesting the metabolic rate of the cod plays a role in the enzyme response. These data suggest the risk of negative impacts associated with exposure to chemically dispersed oil may be affected by water temperature and that risk assessment of potential effects of WAF or CEWAF should consider the effects of water temperature on the physiology of the fish as well as the effectiveness of dispersants.

  • Jensen, L.K. and Carroll, J.  Experimental studies of reproduction and feeding for two Arctic-dwelling Calanus species exposed to crude oil.  Aquatic Biology 10(3): 261-271, 2010.
    Read Abstract >>

    Copepods of the genus Calanus are keystone species in the transfer of energy from lower to higher trophic levels of the Arctic/sub-Arctic food web. We performed experimental tests on the reproduction and feeding of Calanus spp. exposed to the water-soluble fraction (WSF) of crude oil. Fecal pellet and egg production were examined for females of C. glacialis exposed to WSF (16-EPA) concentrations of 10.4 µg l-1 (high treatment; HT), 3.6 µg l-1 (low treatment; LT) and 0 µg l-1 (control treatment; CT). We observed no significant difference in cumulative egg or fecal pellet production. Egg hatching success was examined for 2 d after transferring eggs from treatment solutions to uncontaminated seawater. Hatching success was significantly lower in the HT compared to the CT. In a second experiment, feeding of C. finmarchicus was examined after exposure for 11 and 18 d to 7.0 (HT), 3.4 (LT) or 0 (CT) µg l-1 of WSF (16-EPA). Using algae cell concentrations as a proxy for feeding success, feeding was inhibited for C. finmarchicus specimens exposed to the HT of WSF compared to the CT. Our findings indicate that adult females of C. glacialis may withstand some exposure to crude oil components but the survival of offspring is negatively affected. Reduced feeding efficiency in C. finmarchicus exposed to high concentrations of WSF provides evidence that adult specimens are sensitive to exposure to crude oil. The study expands on the limited body of knowledge of potential changes to key life history traits of Arctic Calanus species resulting from exposure to chemical compounds in crude oil.

  • Milinkovitch, T., Ndiaye, A., Sanchez, W., LeFloch, S., and Thomas-Guyon, H.  Liver antioxidant and plasma immune responses in juvenile golden grey mullet (Liza aurata) exposed to dispersed crude oil.  Aquatic Toxicology 101(1): 155-164, 2011.
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    Dispersants are often used after oil spills. To evaluate the environmental cost of this operation in nearshore habitats, the experimental approach conducted in this study exposed juvenile golden grey mullets (Liza aurata) for 48 h to chemically dispersed oil (simulating, in vivo, dispersant application), to dispersant alone in seawater (as an internal control of chemically dispersed oil), to mechanically dispersed oil (simulating, in vivo, natural dispersion), to the water-soluble fraction of oil (simulating, in vivo, an oil slick confinement response technique) and to seawater alone (control condition). Biomarkers such as fluorescence of biliary polycyclic aromatic hydrocarbon (PAH) metabolites, total glutathione liver content, EROD (7-ethoxy-resorufin-O-deethylase) activity, liver antioxidant enzyme activities, liver lipid peroxidation and an innate immune parameter (haemolytic activity of the alternative complement pathway) were measured to assess the toxicity of dispersant application. Significant responses of PAH metabolites and total glutathione content of liver to chemically dispersed oil were found, when compared to water-soluble fraction of oil. As was suggested in other studies, these results highlight that priority must be given to oil slick confinement instead of dispersant application. However, since the same patterns of biomarker responses were observed for both chemically and mechanically dispersed oil, the results also suggest that dispersant application is no more toxic than the natural dispersion occurring in nearshore areas (due to, e.g. waves). The results of this study must, nevertheless, be interpreted cautiously since other components of nearshore habitats must be considered to establish a framework for dispersant use in nearshore areas.

  • Harris, K.A., Yunker, M.B., Dangerfield, N., and Ross, P.S.  Sediment-associated aliphatic and aromatic hydrocarbons in coastal British Columbia, Canada: Concentrations, composition, and associated risks to protected sea otters.  Environmental Pollution 159(10): 2665-2674, 2011.
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    Sediment-associated hydrocarbons can pose a risk to wildlife that rely on benthic marine food webs. We measured hydrocarbons in sediments from the habitat of protected sea otters in coastal British Columbia, Canada. Alkane concentrations were dominated by higher odd-chain n-alkanes at all sites, indicating terrestrial plant inputs. While remote sites were dominated by petrogenic polycyclic aromatic hydrocarbons (PAHs), small harbour sites within sea otter habitat and sites from an urban reference area reflected weathered petroleum and biomass and fossil fuel combustion. The partitioning of hydrocarbons between sediments and adjacent food webs provides an important exposure route for sea otters, as they consume ~25% of their body weight per day in benthic invertebrates. Thus, exceedences of PAH sediment quality guidelines designed to protect aquatic biota at 20% of the sites in sea otter habitat suggest that sea otters are vulnerable to hydrocarbon contamination even in the absence of catastrophic oil spills.

  • Harris, K.A., Nichol, L.M., and Ross, P.S.  Hydrocarbon concentrations and patterns in free-ranging sea otters (Enhydra lutris) from British Columbia, Canada.  Environmental Toxicology and Chemistry 30(10): 2184-2193, 2011.
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    With oil pollution recognized as a major threat to British Columbia's recovering sea otter (Enhydra lutris) population, it is important to distinguish acute from chronic exposures to oil constituent groups in this marine mammal. Concentrations and patterns of alkanes and polycyclic aromatic hydrocarbons (PAHs) were determined in blood samples from 29 live-captured sea otters in two coastal areas of British Columbia, as well as in representative samples of their invertebrate prey. Hydrocarbon concentrations in sea otters were similar between areas and among age and sex classes, suggesting that metabolism dominates the fate of these compounds in sea otters. Biomagnification factors derived from PAH ratios in otter:prey supported this notion. Although some higher alkylated three- and four-ring PAHs appeared to biomagnify, the majority of PAHs did not. The apparent retention of alkyl PAHs was reflected in the composition of estimated sea otter body burdens, which provided an alternative way of evaluating hydrocarbon exposure. Alkyl PAHs made up 86 ± 9% of estimated body burdens (4,340 ± 2,950 µg), with no differences between males and females (p = 0.18). The importance of measuring both parent and alkyl PAHs is underscored by their divergent dynamics in sea otters, with ready depuration of parent PAHs (metabolized or excreted) by sea otters on the one hand and biomagnification of alkyl PAHs on the other.

Dispersants: Toxicology and Risk Assessment

  • Hamdan, L.J. and Fulmer, P.A.  Effects of COREXIT® EC9500A on bacteria from a beach oiled by the Deepwater Horizon spill.  Aquatic Microbial Ecology 63(2): 101-109, 2011.
    Open Access >>   
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    Hydrocarbon-degrading bacteria are important for controlling the fate of natural and anthropogenic hydrocarbons in the marine environment. In the wake of the Deepwater Horizon spill in the Gulf of Mexico, microbial communities will be important for the natural attenuation of the effects of the spill. The chemical dispersant COREXIT® EC9500A was widely deployed during the response to the Deepwater Horizon incident. Although toxicity tests confirm that COREXIT® EC9500A does not pose a significant threat to invertebrate and adult fish populations, there is limited information on its effect on microbial communities. We determined the composition of the microbial community in oil that had been freshly deposited on a beach in Louisiana, USA, as a result of the Deepwater Horizon spill. The metabolic activity and viability in cultures obtained from oil samples were determined in the absence and presence of COREXIT® EC9500A at concentrations ranging from 0.001 to 100 mg ml-1. In length heterogeneity PCR (LH-PCR) fingerprints of oil samples, the most abundant isolates were those of Vibrio, followed by hydrocarbon-degrading isolates affiliated with Acinetobacter and Marinobacter. We observed significant reductions in production and viability of Acinetobacter and Marinobacter in the presence of the dispersant compared to controls. Of the organisms examined, Marinobacter appears to be the most sensitive to the dispersant, with nearly 100% reduction in viability and production as a result of exposure to concentrations of the dispersant likely to be encountered during the response to the spill (1 to 10 mg ml-1). Significantly, at the same concentration of dispersant, the non-hydrocarbon-degrading Vibrio isolates proliferated. These data suggest that hydrocarbon-degrading bacteria are inhibited by chemical dispersants, and that the use of dispersants has the potential to diminish the capacity of the environment to bioremediate spills.

  • Anderson, S.E., Franko, J., Lukomska, E., and Meade, B.J.  Potential immunotoxicological health effects following exposure to COREXIT 9500A during cleanup of the Deepwater Horizon oil spill.  Journal of Toxicology and Environmental Health Part A 74(21): 1419-1430, 2011.
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    Workers involved in the Deepwater Horizon oil spill cleanup efforts reported acute pulmonary and dermatological adverse health effects. These studies were undertaken to assess the immunotoxicity of COREXIT 9500A, the primary dispersant used in cleanup efforts, as a potential causative agent. COREXIT 9500A and one of its active ingredients, dioctyl sodium sulfosuccinate (DSS), were evaluated using murine models for hypersensitivity and immune suppression, including the local lymph node assay (LLNA), phenotypic analysis of draining lymph node cells (DLN), mouse ear swelling test (MEST), total serum immunoglobulin E (IgE), and the plaque-forming cell (PFC) assay. Dermal exposure to COREXIT 9500A and DSS induced dose-responsive increases in dermal irritation and lymphocyte proliferation. The EC3 values for COREXIT 9500A and DSS were 0.4% and 3.9%, respectively, resulting in a classification of COREXIT 9500A as a potent sensitizer and DSS as a moderate sensitizer. A T-cell-mediated mechanism underlying the LLNA was supported by positive responses in the MEST assay for COREXIT and DSS, indicated by a significant increase in ear swelling 48 h post challenge. There were no marked alterations in total serum IgE or B220+/IgE+ lymph-node cell populations following exposure to COREXIT 9500A. Significant elevations in interferon (IFN)-γ but not interleukin (IL)-4 protein were also observed in stimulated lymph node cells. The absence of increases in IgE and IL-4 in the presence of enhanced lymphocyte proliferation, positive MEST responses, and elevations in IFN-γ suggest a T-cell-mediated mechanism. COREXIT 9500A did not induce immunosuppression in the murine model.

  • Kilduff, C. and Lopez, J.  Dispersants: The lesser of two evils or a cure worse than the disease?  Ocean and Coastal Law Journal 16(2): 375-394, 2011.
    Open Access >>  

     

  • Berninger, J.P., Williams, E.S., and Brooks, B.W.  An initial probabilistic hazard assessment of oil dispersants approved by the United States National Contingency Plan.  Environmental Toxicology and Chemistry 30(7): 1704-1708, 2011.
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    Dispersants are commonly applied during oil spill mitigation efforts; however, these industrial chemicals may present risks to aquatic organisms individually and when mixed with oil. Fourteen dispersants are listed on the U.S. Environmental Protection Agency (U.S. EPA) National Oil and Hazardous Substances Pollution Contingency Plan (NCP). Availability of environmental effects information for such agents is limited, and individual components of dispersants are largely proprietary. Probabilistic hazard assessment approaches including Chemical Toxicity Distributions (CTDs) may be useful as an initial step toward prioritizing environmental hazards from the use of dispersants. In the present study, we applied the CTD approach to two acute toxicity datasets: NCP (the contingency plan dataset) and DHOS (a subset of NCP listed dispersants reevaluated subsequent to the Deepwater Horizon oil spill). These datasets contained median lethal concentration (LC50) values for dispersants alone and dispersant:oil mixtures, in two standard marine test species, Menidia beryllina and Mysidopsis bahia. These CTDs suggest that dispersants alone are generally less toxic than oil. In contrast, most dispersant:oil mixtures are more toxic than oil alone. For the two datasets (treated separately because of differing methodologies), CTDs would predict 95% of dispersant:oil mixtures to have acute toxicity values above 0.32 and 0.76 mg/L for Mysidopsis and 0.33 mg/L and 1.06 mg/L for Menidia (for DHOS and NCP, respectively). These findings demonstrate the utility of CTDs as a means to evaluate the comparative ecotoxicity of dispersants alone and in mixture with different oil types. The approaches presented here also provide valuable tools for prioritizing prospective and retrospective environmental assessments of oil dispersants.

  • Hemmer, M.J., Barron, M.G., and Greene, R.M.  Comparative toxicity of eight oil dispersants, Louisiana sweet crude oil (LSC), and chemically dispersed LSC to two aquatic test species.  Environmental Toxicology and Chemistry 30(10): 2244-2252, 2011.
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    The present study describes the acute toxicity of eight commercial oil dispersants, South Louisiana sweet crude oil (LSC), and chemically dispersed LSC. The approach used consistent test methodologies within a single laboratory in assessing the relative acute toxicity of the eight dispersants, including Corexit 9500A, the predominant dispersant applied during the DeepWater Horizon spill in the Gulf of Mexico. Static acute toxicity tests were performed using two Gulf of Mexico estuarine test species, the mysid shrimp (Americamysis bahia) and the inland silversides (Menidia beryllina). Dispersant-only test solutions were prepared with high-energy mixing, whereas water-accommodated fractions of LSC and chemically dispersed LSC were prepared with moderate energy followed by settling and testing of the aqueous phase. The median lethal concentration (LC50) values for the dispersant-only tests were calculated using nominal concentrations, whereas tests conducted with LSC alone and dispersed LSC were based on measured total petroleum hydrocarbon (TPH) concentrations. For all eight dispersants in both test species, the dispersants alone were less toxic (LC50s: 2.9 to >5,600 µl/L) than the dispersant–LSC mixtures (0.4–13 mg TPH/L). Louisiana sweet crude oil alone had generally similar toxicity to A. bahia (LC50: 2.7 mg TPH/L) and M. beryllina (LC50: 3.5 mg TPH/L) as the dispersant–LSC mixtures. The results of the present study indicate that Corexit 9500A had generally similar toxicity to other available dispersants when tested alone but was generally less toxic as a mixture with LSC.

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