A 3-year survey was made of several biological markers in
mussels (Mytilus edulis) exposed in situ to the oil that came ashore after the wreck of the
“Erika” tanker on the Brittany (France) coast in December 1999. The mussel
response was assessed using a set of 7 biomarkers, most of them related to
the metabolism of organic contaminants. After a series of validation tests,
data was evaluated for only 5 biomarkers: acetylcholinesterase (AChE),
glutathione S-transferase (GST), catalase (CAT), malondialdehyde (MDA) and
deoxyribonucleic acid (DNA) adducts. No significant reductions in GST or CAT
levels were observed, levels of DNA adducts and MDA were high during the 6
months immediately following the accident and levels of AChE were
significantly lower during the first year of the survey suggesting a general
stress. A simple multivariate graphic method, the integrated biomarker
response index, was used to combine 4 of the 5 validated biomarkers and
quantify the degree of impact on mussels at different sites. The results
show that mussel populations were affected by the oil spill only during the
first year after the event.