As recent events continue to show, resorting to chemical dispersants to deal with oil spills in coastal environments is a real but extremely controversial matter. At the centre of this controversy is whether the risk of ecological effects on marine species from toxic oil components increases or decreases when dispersants are used.
However, lacking for such a risk assessment is a proper understanding of the mechanisms through which toxic effects, classically observed at subcellular level, propagate through the levels of biological organisation to affect ecosystem functioning and services. Despite eye-catching titles, recent studies are largely unsuccessful at addressing this issue.
To promote an ecologically relevant approach to risk assessment, FishHealth investigated the impact of dispersant, oil and dispersant-treated oil on populations of juvenile European sea bass.
It discovered that:
· Seabass have the capacity to detect and avoid the water soluble fraction of oil ;
· Exposure (48 h) to dispersant alone has no effect on fish ability to cope with simulated environmental challenges (exercise and hypoxia);
· Exposure (48 h) to both oil and dispersant-treated oil temporarily impacted this coping ability;
· Four to six weeks post-exposure, tissues [PAH] and fish performance (cardiac pumping capacity, swimming capacity, hypoxia tolerance, thermal susceptibility) return back to control level;
· Post-exposure growth and survival (1.5 year) of experimental populations after transfer into field mesocosms indicates no difference between control and exposed populations;
· Thus, the long term post-exposure monitoring (1.5 year) of the juvenile seabass populations reveals no delayed effect on fish coping performance.
FishHealth is a consortium of four research institutes led by LEMAR (Laboratoire des Sciences de L'Environnement Marin, France), partnered with CEDRE (Centre de Documentation, de Recherche et d'Expérimentations sur les Pollutions Accidentelles des Eaux), CNR-IAMC Oristano (Consiglio Nazionale delle Recherche, Italy) and the Zoology Department at UBC (University of British Columbia, Canada). It won the first ITOPF R&D Award in 2012.
Find out more information on the FishHealth project.