Immunological alterations may be used as ecotoxicological biomarkers to
detect and monitor biological effects of chemical contaminants in polluted
environments. This study reports on a survey of Pacific oysters from the
Atlantic coast of Britanny (France) after the “Erika” oil spill. Reared stocks
were sampled twice a year from November 2001 to March 2003 at three impacted
sites and at an additional site outside the spill area. A multiparametric
diagnosis of the immune system was performed on individual hemolymph samples
to identify structural, immunopathological alterations and functional
impairment of immunocompetent cells. One year after the spill, severe
immunological alterations were observed in a site heavily impacted by oil.
Since the oysters there had higher contents of PAH compared to the other
sites, it was suggested that chronic contamination, possibly generated by
oil trapped in the sediments, had induced immunotoxicity. Moreover, moderate
variations in some hemolymph parameters observed at the non-impacted area
strongly suggested that natural environmental factors may have generated
physiological stress. An immunotoxicological index applied here in order to
integrate all measurements of defense-related functions appeared to be an
efficient tool to identify samples suffering immunological stress.