Contribution to the study of oil-dispersant mixtures on the temperate species of seabass Dicentrarchus labrax: application to a cold water species /...


Thesis jointly supervised by the University of Western Brittany. PhD jointly supervised by: Karine Pichavant-Rafini, University of Western Brittany

Committee: Rachid Amara, Philippe Garrigues, Jérôme Cachot, Philippe Lemaire, Stéphane Le Floch, Michael Theron


Abstract: Since the 1970s, chemical dispersants have been used to respond to oil spills in the offshore environment. However the question of the relevance of their use has been raised. By increasing the bioavailability of the oil, dispersants can exacerbate the consequences of an oil spill. From this perspective, this PhD work aims to experimentally assess the effects of the chemical dispersion of oil on fish. It focuses on four main aspects. An acute toxicity study was conducted on sea bass (Dicentrarchus labrax) in order to compare different oil-dispersant mixtures. Thereafter, the sublethal effects of exposure were assessed on sea bass by focusing on three integrator parameters: growth, the immune system and antioxidant defences. The effects of an oil-dispersant mixture on the contractility of the myocardium and metabolic activity were assessed. Finally, the experimentation on cardiac metabolism was applied to a species representative of Arctic ecosystems, the polar cod Boreogadus saida.

This PhD work showed that dispersed oil could have an impact on the first level of organisation of individuals. At the subcellular level, the study of mitochondrial activities demonstrated the existence of interspecies variation. The study of the cardiac function highlighted compensatory phenomena in sea bass exposed to dispersant. These compensatory phenomena are found at the integrative level of growth but above all of immunity, whereby subcellular changes were compensated for at an integrator level.

This work also provided a better understanding of the interactions between oil, dispersant and organisms. The various studies showed that the differences in toxicity observed are mainly due to hydrocarbon concentrations. It was also shown that dispersant does not appear to exacerbate the intrinsic toxicity of oil. This would tend to indicate that there is no synergetic effect of oil and dispersant on toxicity.

Bibliographical reference: http://doc.cedre.fr/index.php?lvl=notice_display&id=9280

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