Coastal marine ecosystems are under anthropogenic pressures. Among these anthropogenic pressures, two major growing threats are represented by hypoxia and oil pollution. However, very little is known about the biological impacts of their interaction. Consequently, this project evaluated the potential biological effects caused by oil pollution in hypoxic situations. Furthermore, this project considered the effect of dispersant use as a response technique for oil released in hypoxic areas. The research carried out during the project assessed the interactive biological effects of dispersant, oil and hypoxia on the teleost Dicentrarchus labrax. The approach firstly evaluated the hydrocarbon contamination induced by the interaction of stressors (Work Package 1, WP1). Then, biological effects were evaluated at the sub-individual level, by assessing sensitive indicators related to oxidative stress (Work Package 2, WP2). Finally, ecologically-relevant indicators related to fish behaviour, locomotion and metabolism, were assessed at the organismal level (Work Package 3, WP3).
In summary, our results showed a persistence of hydrocarbon compounds in organisms when the fish were exposed to chemically-dispersed oil (dispersant + oil) or when hypoxic conditions follow the contamination by oil (oil +hypoxia). Surprisingly, regarding hydrocarbons bio-concentration, no cumulative effect of both interaction (dispersant+oil+hypoxia) was detected.
At the cellular level, regarding the biomarkers of antioxidant defense, some significant effects were observed in the liver. However, regarding oxidative stress, it was only observed in the gills. Such antioxidant responses and oxidative stress have been shown to be transitory, suggesting no long term impact on cellular integrity. However, many other biological parameters than just oxidative stress and antioxidant response (such as cancer development and/or DNA damage) should be observed before drawing such a conclusion about long term impact of hydrocarbon compounds on cellular integrity.
At the individual level, an important impact was observed on escape responses when fish were exposed to hypoxia or oil. Maneuverability, directionality and escape trajectories were impacted by each experimental treatment. Moreover, our results suggest a cumulative impact of oil plus hypoxia treatment on escape response parameters. Regarding the metabolic parameters, the main results showed a reduction of the aerobic metabolic scope due to oil and an even more intense reduction due to hypoxia.
To conclude, this project provides scientific results situated at the cutting edge in the field of the impact of oil pollution on marine organisms, as well as progress beyond the state of the art concerning the effect of hydrocarbons on aquatic ecosystems. Such an impact on European research and development is being achieved through publications of papers, participation to congresses and through a workshop joining together the partner organization, stakeholder and experts in oil contamination.
