Dispersed Oil Exposure Research Articles

Multilevel responses of adult zebrafish to crude and chemically dispersed oil exposure

BackgroundThe application of chemical dispersants is a common remediation strategy when accidental oil spills occur in aquatic environments. Breaking down the oil slick into small droplets, dispersants facilitate the increase of particulate and dissolved oil compounds, enhancing the bioavailability of toxic oil constituents. The aim of the present work was to explore the effects of water accommodated fractions (WAF) of a naphthenic North Sea crude oil produced with and without the addition of the chemical dispersant FINASOL OSR 52 to adult zebrafish exposed for 3 and 21 d. Fish were exposed to environmentally relevant concentrations of 5% and 25% WAFOIL (1:200) and to 5% WAFOIL+D (dispersant–oil ratio 1:10) in a semi-static exposure setup.ResultsThe chemically dispersed WAF presented a 20-fold increase of target polycyclic aromatic hydrocarbons (PAHs) in the water phase compared to the corresponding treatment without dispersant and was the only treatment resulting in markedly bioaccumulation of PAHs in carcass after 21 d compared to the control. Furthermore, only 5% WAFOIL+D caused fish mortality. In general, the undispersed oil treatments did not lead to significant effects compared to control, while the dispersed oil induced significant alterations at gene transcription and enzyme activity levels. Significant up-regulation of biotransformation and oxidative stress response genes (cyp1a, gstp1, sod1 and gpx1a) was recorded in the livers. For the same group, a significant increment in EROD activity was detected in liver along with significant increased GST and CAT activities in gills. The addition of the chemical dispersant also reduced brain AChE activity and showed a potential genotoxic effect as indicated by the increased frequency of micronuclei in erythrocytes after 21 d of exposure.ConclusionsThe results demonstrate that the addition of chemical dispersants accentuates the effect of toxic compounds present in oil as it increases PAH bioavailability resulting in diverse alterations on different levels of biological organization in zebrafish. Furthermore, the study emphasizes the importance to combine multilevel endpoints for a reliable risk assessment due to high variable biomarker responses. The present results of dispersant impact on oil toxicity can support decision making for oil spill response strategies.

Utilizing Recirculating Aquaculture Systems to Evaluate the Impact of Oil Toxicity on Marine Fishes: Design and Operation of a Large-Scale Experimental System

AbstractThe long-term damage of oil spills and recovery efforts on wild fishery populations are not well understood. In order to assess potential biological effects of dispersed oil exposure on Gulf of Mexico fishery populations, C-IMAGE (Center for Integrating Modeling and Analysis of the Gulf Ecosystem) scientists examined the sublethal impacts resulting from the 2010 Deepwater Horizon oil spill through a combination of field collections and controlled laboratory exposure experiments. Mote Marine Laboratory scientists and Complete Water Services, LLC (Marietta, GA), engineers partnered to design, develop, and operate a large-scale, zero-discharge, experimental oil contaminant exposure system at Mote Aquaculture Research Park in Sarasota, Florida. This exposure system is linked to a recirculating aquaculture system (RAS) designed to maintain water quality and water chemistry within acceptable parameters and to remove oil and dispersant from system water during the filtration process. Equipment was sourced to ensure that potential oil co-contaminants were not retained within the system. Water quality (oxygen, pH, salinity, temperature) and chemistry (ammonia, nitrite, nitrate, and alkalinity) parameters were monitored and controlled to maintain appropriate environmental conditions for marine fish during experimental trials. The concentrations of petroleum components throughout the system during exposure trials were monitored to ensure that the system was meeting the design parameters. Experimental trials were conducted using the exposure system with three important Gulf of Mexico marine fishes, Florida pompano (Trachinotus carolinus), red drum (Sciaenops ocellatus), and Southern flounder (Paralichthys lethostigma). These trials examined the impacts of dispersed oil exposure on facets of fish health including gene expression, transcriptome, immune function, DNA damage, shifts in the microbiome, reproductive potential and success, and the F1 generation from exposed parents. The system was operated successfully through the trials and allowed us to maintain consistent and appropriate water quality conditions in the experimental tanks. The recirculating filtration system successfully maintained water chemistry and removed oil contaminants during the fish exposure trials. The application of the system technology applied in this study has broader applications than the study of hydrocarbon impacts and opens the door for investigation of a wide range of different contaminants.

AN EXPERIMENTAL STUDY OF THE EFFECTS OF CHEMICALLY DISPERSED OIL ON FEATHER STRUCTURE AND WATERPROOFING IN COMMON MURRES ( URIA AALGE).

Following an oil spill in the marine environment, chemical dispersants, which increase oil droplet formation and distribution into the water column, are assumed to provide a net benefit to seabirds by reducing the risk of exposure to oil on the water surface. However, few data are available regarding acute, external impacts of exposure to dispersed oil. We evaluated the effects of known concentrations of dispersant and crude oil in artificial seawater on live Common Murres ( Uria aalge). Waterproofing and microscopic feather geometry were evaluated over time and compared to pre-exposure values. Birds exposed to a high concentration of dispersant experienced an immediate, life-threatening loss of waterproofing and buoyancy, both of which resolved within 2 d. Birds exposed to oil, or a dispersant and oil mixture, experienced dose-dependent waterproofing impairment without resolution over 2 d. Alterations in feather geometry were observed in oil-exposed or dispersant- and oil-exposed birds and were associated with increased odds of waterproofing impairment compared to control birds. At a given contaminant concentration, there were no significant differences in waterproofing between oil-exposed and dispersant- and oil-exposed birds. We found that acute, external effects of oil and dispersed oil exposure are comparable and dose-dependent. Our results also indicate that a zero-risk assumption should not be used when seabirds are present within the dispersant application zone.

Effects of dispersed oil exposure on biomarker responses and growth in juvenile wolfish Anarhichas denticulatus.

This study evaluated the sensitivity of the wolfish Anarhichas denticulatus exposed to crude oil, comparing the effects of mechanically dispersed versus chemically dispersed oil using sub-lethal endpoints. To test the toxicity of this controversial technique, two experiments involving exposure of the organisms for 48h were conducted. The first experiment assessed the effects of oil exposure on biomarker responses. The second experiment monitored the growth of juveniles over 5weeks after exposure. Overall, this study demonstrated that polycyclic aromatic hydrocarbon (PAH) biliary metabolites, ethoxyresorufin-O-deethylase (EROD), and acetylcholinesterase (AChE) are appropriate biomarkers to assess exposure of A. denticulatus. Growth rate, both in length and weight, was significantly higher in control compared to oil exposure treatments. The lack of differences between chemically and mechanically dispersed oils in biomarker response and growth suggests that dispersant application is no more toxic than the natural oil dispersion. The results indicate the potential for population-level effects resulting from exposure to oil.

TROPICS: 30-year Follow-up and Analysis of Mangroves, Invertebrates, and Hydrocarbons

ABSTRACT TROPICS (TRopical Oil Pollution Investigations in Coastal Systems) has been the seminal study on trade-offs for Net Environmental Benefit Analysis (NEBA) for dispersant use in tropical ecosystems. The study began in 1983/84 with the identification of suitable tropical island sites in Bahia Almirante, Bocas del Toro, Panama that contained mangrove, seagrass and coral habitats in close enough proximity to establish three 30m X 30m test sites. Controlled releases of Prudhoe Bay crude oil (dosed at 1L/m2) and Prudhoe Bay crude oil pre-dispersed with Corexit 9527 (to maintain 50 ppm water soluble fraction), were introduced into the Non- dispersed oil (Site O) and the Dispersed oil (Site D) sites, respectively, for 48 hours. A nearby Reference site (Site R) was not treated with oil/dispersed oil. Treatments were designed to simulate a realistic oil spill in adjoining mangrove, seagrass, and coral habitats. Following exposure and removal of oil, sites were studied periodically over 30 years for relative effects of dispersed and non-dispersed oil in coral, seagrass, mangrove, and invertebrate populations, as well as hydrocarbon presence. Early research focused on short- and mid-term effects compared to the Reference site (R), while later work focused on long-term effects and ecosystem recovery. In general, researchers found that Site O exhibited more overall long-term ecosystem disruption than Site D, and that Site D had recovered quickly to Site R and baseline levels. In November 2013 (29 years after oil and dispersed oil exposure), the TROPICS sites were re-visited under a grant provided by Clean Caribbean & Americas. Researchers collected data on mangroves, mangrove invertebrates, and hydrocarbons. The density of mangrove trees at Site D had remained at Site R and baseline levels. Site O, which had experienced early die off of trees, followed by peak production at 10 years (far in excess of Site R and baseline levels), exhibited a decline dominated by small trees. Mangrove snails and oysters increased sharply at Site O after the spill, but declined over 10-20 years. Sites D and R maintained gradual invertebrate increases during this time. This paper focuses on research from the November 2013 visit and draws on previous observations and TROPICS papers on overall ecosystem disruption and recovery as it pertains to the NEBA for nearshore dispersant use in tropical marine ecosystems.

Dispersed crude oil amplifies germ cell apoptosis in Caenorhabditis elegans, followed a CEP-1-dependent pathway

The Deepwater Horizon oil spill is among the most severe environmental disasters in US history. The extent of crude oil released and the subsequent dispersant used for cleanup was unprecedented. The dispersed crude oil represents a unique form of environmental contaminant that warrants investigations of its environmental and human health impacts. Lines of evidence have demonstrated that dispersed oil affects reproduction in various organisms, in a more potent manner than oil- and dispersant-only exposures. However, the action mechanism of dispersed oil remains largely unknown. In this study, we utilized the model organism Caenorhabditis elegans to investigate impacts of dispersed oil exposure on sex cell apoptosis and related gene expressions. Worms were exposed to different diluted levels of crude oil-dispersant (oil-dis) mixtures (20:1, v/v; at 500×, 2,000×, and 5,000× dilutions). The dispersed crude oil significantly increases the number of apoptotic germ cells in treated worms when compared with control at all exposure levels (p < 0.05). Genes involved in the apoptosis pathway were dysregulated, which include ced-13, ced-3, ced-4, ced-9, cep-1, dpl-1, efl-1, efl-2, egl-1, egl-38, lin-35, pax-2, and sir-2.1. Many aberrant expressed genes encoding for core components in apoptosis machinery (cep-1/p53, ced-13/BH3, ced-9/Bcl-2, ced-4/Apaf-1, and ced-3/caspase) displayed consistent expression patterns across all exposure levels. Significantly ced-3/caspase was upregulated at all dispersed oil-treated groups, consistent with the observed apoptosis phenotype. Given cep-1/p53 was activated at all dispersed oil treatments and the germ cell apoptosis was suppressed in the CEP-1 loss of function mutant, the increased apoptosis is likely CEP-1 dependent. In addition, the anti-apoptotic ced-9/Bcl-2 was activated in response to the increase in cell death. This study provides a mechanism understanding of dispersed crude oil-induced reproductive toxicity.

Effects of dispersed oil exposure on the bioaccumulation of polycyclic aromatic hydrocarbons and the mortality of juvenile Liza ramada

Dispersing an oil slick is considered to be an effective response to offshore oil spills. However, in nearshore areas, dispersant application is a controversial countermeasure: environmental benefits are counteracted by the toxicity of dispersant use. In our study, the actual toxicity of the dispersant response technique in the nearshore areas was evaluated through an experimental approach using juvenile Liza ramada. Fish were contaminated via the water column (i) by chemically dispersed oil, simulating dispersant application, (ii) by dispersant, as an internal control of chemical dispersion, (iii) by mechanically dispersed oil, simulating only the effect of natural mixing processes, without dispersant application, and (iv) by the water soluble fraction of oil, simulating the toxicity of an oil slick before recovery. Bioconcentrations of polycyclic aromatic hydrocarbons (PAH) and mortality were evaluated, and related to both total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) concentrations in seawater. Fish exposed to chemically dispersed oil showed both a higher bioconcentration of PAH and a higher mortality than fish exposed to either the water soluble fraction of oil or the mechanically dispersed oil. These results suggest that (i) dispersion is a more toxic response technique than containment and recovery of the oil slick; (ii) in turbulent mixing areas, dispersant application increases the environmental risk for aquatic organisms living in the water column. Even if the experimental aspects of this study compel us to be cautious with our conclusions, responders could consider these results to establish a framework for dispersant use in nearshore areas.

Immune function in the Arctic Scallop, Chlamys islandica, following dispersed oil exposure

With the current expansion of offshore oil activities in Arctic regions, there is an urgent need to establish the potential effects of oil-related compounds on Arctic organisms. As susceptibility to growth, disease and survival is determined partly by the condition of an organism's immune system, measurement of endpoints linked to the latter system provide important early warning signals of the sub-lethal effects of exposure to contaminants. This study assessed the impact of dispersed oil exposure on immune endpoints in the Arctic Scallop Chlamys islandica, using a combination of cellular and humoral biological responses. Laboratory exposures of C. islandica to sub-lethal dispersed oil concentrations (0.06 and 0.25 mg l −1) were conducted over 15 days, followed by a 7-day recovery period in clean, filtered seawater. Cellular endpoints were significantly altered following dispersed oil exposure: haemocyte counts ( P < 0.01) and protein levels ( P < 0.01) were significantly elevated, whilst cell membrane stability ( P < 0.001) and phagocytosis ( P < 0.01) demonstrated a significant reduction. Whilst these results indicate alteration in the immune endpoints measured, this appears to be reversible upon removal of the contaminant stress. However, the impact of long-term continuous exposure and high-level acute exposure to oil is still unknown, and may have consequences for disease resistance and hence survival.

Bioaccumulation of polycyclic aromatic compounds: 1. Bioconcentration in two marine species and in semipermeable membrane devices during chronic exposure to dispersed crude oil

Assessing the fate in marine biota of hydrocarbons derived from oil particles that are discharged during exploration and production is of relevant environmental concern. However, a rather complex experimental setup is required to carry out such investigations. In this study, a sophisticated tool, the continuous-flow system (CFS), was used to mimic dispersed oil exposure to marine biota. Polycyclic aromatic hydrocarbon (PAH) uptake was studied in two species, the blue mussel Mytilus edulis and juvenile of the turbot Scophthalmus maximus, and in semipermeable membrane devices (SPMD) exposed to crude oil dispersed in a flow-through system. After an exposure period of 8 to 21 d, elimination in organisms and devices was analyzed for 9 to 10 d following transfer to PAH-free seawater. Principal component analysis (PCA) revealed different PAH patterns. In mussel and SPMD, the PAH profiles were very close to that analyzed in seawater. Slight differences were, however, indicated for large molecules with log Kow above six. Nonachievement of steady-state concentration and bioavailability of PAH in oil droplets may account for these differences. The PAH composition in fish revealed only congeners with two to three aromatic rings. A combination of bioavailability and efficient metabolism of the larger PAH molecules may explain this pattern. The CFS made possible a better understanding of some critical factors governing bioconcentration in marine biota from dispersed oil. Yet the results illustrate that uptake of PAH from exposure to oil particles is complex and that different species may bioconcentrate different molecules depending on factors like life style and metabolic capability to degrade the potential harmful substances. Hence, risk assessment of the actual impact of discharges to marine biota should consider these essential biological and ecological factors.

Ethoxyresorufin- O-deethylase activity and fixed wavelength fluorescence detection of PAHs metabolites in bile in turbot ( Scophthalmus maximus L.) Exposed to a dispersed topped crude oil in a Continuous Flow System

Long term effects of sublethal concentrations of oil on the marine environment have become of general concern. Cytochrome P4501A activity (EROD) in liver and fixed wavelength fluorescence detection of PAHs metabolites (FF) have in this study been used as biomarkers for dispersed oil exposure on a long term period of juvenile turbot ( Scophthalmus maximus L.). A Continuous Flow System was used to carry out the study. The fish were continuously exposed to 0.125, 0.5 or 2.0 mg litre −1 dispersed topped crude oil for 6, 15, 24 h, 4 and 21 days followed by a 9 days recovery period in clean seawater. No induction of the cytochrome P4501A was measured. A maximum level in bile metabolites (4- to 5-fold) was recorded after 24 h of exposure revealing thereby a detoxification process, but a decline occurred from day 4 to day 21. This study demonstrated that FF detection of PAHs metabolites in bile could be a more sensitive biomarker than EROD activity in a long term exposure to sublethal concentration of oil.