Liver antioxidant and plasma immune responses in juvenile golden grey mullet (Liza aurata) exposed to dispersed crude oil

Abstract

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.

Growth and immune system performance to assess the effect of dispersed oil on juvenile sea bass (Dicentrarchus labrax)

“…In this study, similar concentrations of PAHs were observed in fish muscle at T0 (end of exposure) for the two dispersed oil conditions (CD and MD). The same results were obtained in a previous study using the same experimental setup (Milinkovitch et al, 2010). The major part of the PAH bioconcentration must be due to particular hydrocarbons present as oil droplet.…”

“…Indeed, for the two dispersed oil conditions (chemically or mechanically), a marked decrease in TPH concentrations was observed during the 48 h of exposure. This phenomenon, a consequence of the adhesion of oil droplets to the tanks of the experimental system, is in accordance with previous studies using the same experimental setup (Milinkovitch et al, 2010). This decrease can be considered as representative of field conditions.…”

“…The experimental setup has been previously described by Milinkovitch et al (2010). Briefly, each tank was equipped with amechanical stirring system operated bya submersible pump.…”

Toxicity of dispersant application: Biomarkers responses in gills of juvenile golden grey mullet (Liza aurata)

“…These results suggest 494 that, when an oil slick is naturally dispersed, the application of dispersant seems to not 495 increase its environmental toxicity. These results are in accordance with a similar previous 496 study (Milinkovitch et al, 2011). 497…”

“…In Milinkovitch et al (2011), a similar experimental approach was conducted with the same 431 exposure treatments as described in this study (C, CD, MD, WSF, D). The total glutathione 432 content in fish liver was evaluated and appeared to follow the same pattern as the total 433 glutathione content in gills (exposed in this study): CD treatment induced a significant 434 decrease of total glutathione when compared to control treatment; and no significant 435 difference was observed between CD and MD treatments.…”