Nickel and vanadium contamination of benthic invertebrates following the "Erika" wreck

Levels of nickel and vanadium, trace metals found in high concentration in the oil spilled from the "Erika" tanker off Brittany (France) in December 1999 (41 +/- 1 and 87 +/- 3 mg kg(-1) respectively), have been monitored over a one-year period following this accidental event in several benthic invertebrates. Ni and V in mussels (Mytilus edulis) and oysters (Crassostrea gigas) soft tissues were analysed twice a month by graphite furnace atomic absorption spectrometry and a scallop (Pecten maximus) shell daily growth bands were sampled every three bands by laser ablation and analysed by ICP-MS for these two contaminants. Survey data for mollusc tissues were compared with reference data arising from the national monitoring database. Ni concentrations in dried tissues, comparable with reference data (1.8 +/- 0.9 mug g(-1) in mussels and 1.2 +/- 0.5 mug g(-1) in oysters) do not show any additional input during the whole period. Conversely, a sharp increase in vanadium concentrations (up to 4.6 and 3.2 mug g(-1d) for mussels and oysters respectively) is observed around May 2000, i.e. 5 months after the wreck, compared with the monitoring data (1.4 +/- 0.6 mug g(-1) in mussels and 1.3 +/- 0.6 mug g(-1) in oysters). Furthermore, no Ni peak is detectable in the time profiles of scallop shell growth bands where a V peak is observed also in May 2000. This study shows that although a "mussel-watch-type" network, based on the monitoring of vanadium concentration in mollusc tissues, is able to identify contamination due to oil spills, similar information might be obtained a posteriori by analysing daily growth bands of scallop shells.