Oil spills can have direct effects on organisms (mortality or morbidity),
indirect effects (through alteration of lower trophic levels) or be
associated to exposure to trace elements contained in oil (markers). An
effect of the “Erika” oil spill was investigated by spatio-temporally
comparing mortality, population structures, diets and concentrations of vanadium,
nickel and porphyrines in small delphinids, seals and otters from the French
Atlantic coasts. These species might differ in their vulnerability to oil.
Changes in mortality and its demographic structures were within previously
observed ranges. The diet of the common dolphin showed an extended period of
high inter-individual variability in the year 2000. Vanadium concentrations
in delphinids were chronically high, but did not increase significantly
after the oil spill. Porphyrins concentrations in seals and otters were low
suggesting a limited exposure to contaminants, but the ratio between proto-
and copro-porphyrins in otter spraints from oiled vs. unoiled sites varied
significantly. No measurable effect of the “Erika” oil spill
was found in dolphins and seals.