Deep-sea versus shallow conditions: a comparative ecobarotoxicological study

In the context of new oil exploration/production areas, knowledge of the biological impact of dispersed oil in the deep-sea environment is essential. Hence, the aim of this study was to perform a comparison, at atmospheric pressure (0.1 MPa) and at a high hydrostatic pressure corresponding to 1000 m depth (10.1 MPa), of lethal concentrations (LC) on a model fish, Scophthalmus maximus, exposed to chemically dispersed oil. Fish were exposed concomitantly at 0.1 and 10.1 MPa using two exposure tanks connected to the same source tank thanks to a closed circuit. Acute toxicity was evaluated at 24 h through the determination of LC 10 and LC 50 (respectively, 10 and 50% of mortality) calculated from measured total petroleum hydrocarbon concentrations in the water. No statistical differences were observed between the LC 10 at 0.1 MPa (46.1 mg L − 1 ) and the LC 10 at 10.1 MPa (31.0 mg L − 1 ), whereas the LC 50 of fish exposed to 0.1 MPa (90.8 mg L − 1 ) was significantly higher than the LC 50 at 10.1 MPa (50.9 mg L − 1 ). These results clearly show an increase in oil toxicity under high hydrostatic pressure. This effect may be due to synergistic effects of pressure and oil contamination on fish energetic metabolism.