Relationship between two oxidative stress biomarkers, malondialdehyde and 8-oxo-7,8-dihydro-2'-deoxyguanosine, in the freshwater bivalve Unio tumidus.

This study addresses the question of the relation between cellular and genomic oxidative damages in freshwater bivalves in realistic conditions of exposure in the field. Membrane and genomic oxidative damages were studied by means of lipid peroxidation and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), respectively. Malondialdehyde (MDA) was used as an indicator of lipid peroxidation. The biomarkers were measured in the digestive gland and the gills of mussels (Unio tumidus) after 7 and 21 days of exposure in four ponds of the Moselle Basin, during three field studies conducted in 1999 and 2000. Effects measured at three sites (1R, 3C and 4M) were moderate and lipid peroxidation was slightly enhanced in mussels transferred in these ponds. In contrast, an important degradation was observed at site 2V reflected by a sharp increase in MDA and 8-oxodGuo concentrations in 2000. The biomarker responses agreed with the results of physicochemical analyses that indicated a worsening of water quality at the same site. Globally, a relationship was found between MDA increase and 8-oxodGuo formation, in the digestive gland after 7 days of exposure, and later in the gills (21 days). Responses of the digestive glands and gills to the oxidative parameters appeared correlated only after 21 days of exposure. The biomarkers selected confirmed their sensitivity for appraising the water quality of hydrosystems.