The petroleum spilt by the tanker “Erika” contained environmentally high
concentrations of nickel (45 mg kg−1) and vanadium (83 mg kg−1).
Our aim was to show that nickel and vanadium concentrations in marine
organisms could be used as tracers of their exposure to oil deposits along
the coast. Two biomarkers were determined, condition index (CI) and
metallothionein levels.
Samples were collected monthly from January to May 2000 from five sites
along the coast of Vendée and Loire Atlantique: (1) Lérat, (2) La
Govelle, (3) Saint Gildas, (4) La Bernerie and (5) La Fosse. Among benthic
invertebrates, mussels Mytilus edulis (filter-feeders), periwinkles Littorina littorea (grazing-feeders) and
dogwhelks Nucella lapillus (carnivora, bivalve predators) were selected. In addition,
mussels were collected from a control site, Fier d'Ars (Ré Island).
The species chosen as bioindicators have responded to the presence of oil in
their environment by accumulating nickel and vanadium. The bioaccumulation
of vanadium occurred early one month after oil spill whereas nickel
bioaccumulation was deferred, probably as a consequence of a lower stability
of vanadylporphyrins compared to nickelporphyrins which are known in
particular for their role in stabilizing emulsions (film at the water/oil
interface). Interspecific differences may be explained by different food
habits: periwinkles grazed contaminated algae; mussels as filter-feeders
retained particles and colloids from the water column; dogwhelks fed on
mussels. Spatio-temporal changes of nickel and vanadium concentrations may
result from (i) the arrival of new oil slicks, (ii) the action of cleaning
of the coasts contributing to the re-suspension of petroleum. In all of the
three species, few changes of the CI were observed from site to site. CI
variations were linked to sexual ripening in mussels. Mussels originating
from the control site showed MT concentrations significantly lower than
those in specimens from impacted sites. The highest MT concentrations were
observed in January and February, and then a consistent decrease was
registered in March and May. MT concentrations in periwinkles increased very
significantly in March and May. An increase in MT concentrations was also
shown at this period in dogwhelks. Depending on the species, positive
correlations were shown between MT and nickel and/or vanadium
concentrations.