Comparison of two sentinel species Gammarus fossarum and Dreissena polymorpha for monitoring fecal viral contamination of continental waters

ABSTRACT Biomonitoring is a widely used strategy for evaluating chemical contamination. Two species are used in particular in French rivers: Dreissena polymorpha and Gammarus fossarum . Although biomonitoring of fecal contamination has been initiated in the freshwater mussel D. polymorpha , relatively few studies are available for crustaceans. This study aimed to determine, for the first time, the value of the freshwater crustacean G. fossarum for monitoring viral contamination in comparison with D. polymorpha . Laboratory exposure was first performed to determine their ability to accumulate infectious F-specific RNA bacteriophages (FRNAPH). In situ exposure was then conducted to confirm this ability in the field, and also to study the bioaccumulation of viral genomes (FRNAPH and norovirus), along a continuum of fecal contamination. Laboratory exposure showed a significant difference in accumulation, with D. polymorpha (bioaccumulation factor BAF ~ 1) accumulating six times more infectious FRNAPH than G. fossarum (BAF ~ 0.3). In situ exposure confirmed that G. fossarum (BAF ~ 17) accumulated less infectious FRNAPH compared with mussels (BAF ~ 3,500). Moreover, FRNAPH and norovirus genomes were only quantified in mussels. Finally, the concentrations measured in D. polymorpha evidenced a fecal contamination gradient. D. polymorpha therefore appears to be more relevant than G. fossarum for monitoring viral contamination of fecal origin in freshwater environments. IMPORTANCE Biomonitoring is a common method for assessing chemical contamination. In France, Dreissena polymorpha (zebra mussel) and Gammarus fossarum (a freshwater crustacean) are widely used species. This study aimed to compare, for the first time, their effectiveness in monitoring viral contamination, specifically F-specific RNA bacteriophages (FRNAPH) and noroviruses. Laboratory experiments showed that D. polymorpha accumulated six times more infectious FRNAPH than G. fossarum . Field exposures confirmed these findings, revealing that only mussels accumulated detectable levels of FRNAPH and norovirus genomes. Additionally, the viral concentrations in D. polymorpha reflected a gradient of fecal contamination across sites. These results demonstrate that D. polymorpha is significantly more effective than G. fossarum for monitoring viral contamination of fecal origin in freshwater environments, making it the more suitable species for such biomonitoring efforts.