Abstract
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.
Highlights
The application of chemical dispersants is a common remediation strategy when accidental oil spills occur in aquatic environments
Oil spills represent one of the most important potential sources of pollution in aquatic environments [140]. Anthropogenic activities such as offshore oil exploitation and transportation, or other contaminations caused by shipwrecks and industrial discharges, pose a high risk of an oil spill that could result in devastating consequences to aquatic organisms, such as fish [19, 52, 55]
Concentrations of all target Polycyclic aromatic hydrocarbons (PAHs) were below the limits of detection (LOD)
Summary
The application of chemical dispersants is a common remediation strategy when accidental oil spills occur in aquatic environments. 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. Oil spills represent one of the most important potential sources of pollution in aquatic environments [140]. Polycyclic aromatic hydrocarbons (PAHs), for example, represent up to 60% of crude oil constituents present in water accommodated fractions (WAF) [40]. Their capacity to provoke diverse toxic effects in aquatic organisms is well known. These effects range from cardiotoxicity and malformations at early developmental stages up to behavioural alterations and carcinogenesis in adults [27, 54, 78, 129]
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