River, generating a dilution or a concentration of the contaminants during the
respective sampling periods [65].
The final integration coherently synthesised the outputs of each LOE. Despite its
high integrative dimension, this method did not result in a loss of information. The
identification of the (class of) contaminants or biological endpoints responsive for
the HQ values is possible by calculating endpoint contribution within each LOE.
This procedure was able, for instance, to identify perfluorooctanesulfonic acid
(PFOS) as an ubiquitous contaminant along the segment of the Seine River studied,
with measured concentrations in the water column systematically above the environmental quality standard of 0.65 ng/L. This data examination also pinpointed the
herbicide metazachlor as a specific contaminant for the winter period. The contributions calculated within the LOE bioavailability indicated that PAHs were the main
problematic class of compounds regarding their bioaccumulation in gammarids at
the two downstream stations. In particular, pyrene and fluoranthene exceeded
more than 30- and 10-fold the gammarid basal impregnation levels in organisms
transplanted in Bougival and Triel-sur-Seine, respectively. Within the LOE
biomarker, contribution examinations resulted in differential response spectra
depending on the site. For the annual results, only a slight decrease in gammarid
survival was responsive for the BiomHQ calculated for Marnay-sur-Seine, whereas
in Triel-sur-Seine the response spectrum was more complex with noticeable contributions of reproduction, feeding, energy acquisition and survival markers. In a more
general way, contributions of HQ values to the annual WOE indexes were particularly high for the ChemHQs (from 80% for Marnay-sur-Seine to 54% for Triel-surSeine), indicating a noticeable contamination of the sites, including the upstream
station usually considered as a reference site. These contributions decreased for the
downstream sites as the annual ToxHQs and BiomHQs increased their contributions
to around 30% for Bougival and up to more than 40% at Triel-sur-Seine. This traced
the emergence of toxic responses in caged gammarids downstream of Paris in
relation to the contamination levels, thus classifying these sites as polluted.
4.4 Conclusion
One of the main challenges of the study was to propose a way to compile, synthesise
and interpret the countless results of the multi-marker study conducted between 2011
and 2012. The WOE approach developed was successfully applied in this context
and resulted in an integrative ERA based on the compilation of more than 150 endpoints to characterise the contamination/pollution status of each site. The results of
this method are easily interpreted and transferable to environmental stakeholders
through the generation of a global index of perturbation (WOE index) associated
with a hazard class. However, several biological responses studied during the
programme could not be integrated into the model due to the lack of available
references. In particular, modifications of bacterial communities and tolerance
acquisition in biofilms (pollution-induced community tolerance ‘PICT’ method)
Experience Gained from Ecotoxicological Studies in the Seine River and. . .
263
respective sampling periods [65].
The final integration coherently synthesised the outputs of each LOE. Despite its
high integrative dimension, this method did not result in a loss of information. The
identification of the (class of) contaminants or biological endpoints responsive for
the HQ values is possible by calculating endpoint contribution within each LOE.
This procedure was able, for instance, to identify perfluorooctanesulfonic acid
(PFOS) as an ubiquitous contaminant along the segment of the Seine River studied,
with measured concentrations in the water column systematically above the environmental quality standard of 0.65 ng/L. This data examination also pinpointed the
herbicide metazachlor as a specific contaminant for the winter period. The contributions calculated within the LOE bioavailability indicated that PAHs were the main
problematic class of compounds regarding their bioaccumulation in gammarids at
the two downstream stations. In particular, pyrene and fluoranthene exceeded
more than 30- and 10-fold the gammarid basal impregnation levels in organisms
transplanted in Bougival and Triel-sur-Seine, respectively. Within the LOE
biomarker, contribution examinations resulted in differential response spectra
depending on the site. For the annual results, only a slight decrease in gammarid
survival was responsive for the BiomHQ calculated for Marnay-sur-Seine, whereas
in Triel-sur-Seine the response spectrum was more complex with noticeable contributions of reproduction, feeding, energy acquisition and survival markers. In a more
general way, contributions of HQ values to the annual WOE indexes were particularly high for the ChemHQs (from 80% for Marnay-sur-Seine to 54% for Triel-surSeine), indicating a noticeable contamination of the sites, including the upstream
station usually considered as a reference site. These contributions decreased for the
downstream sites as the annual ToxHQs and BiomHQs increased their contributions
to around 30% for Bougival and up to more than 40% at Triel-sur-Seine. This traced
the emergence of toxic responses in caged gammarids downstream of Paris in
relation to the contamination levels, thus classifying these sites as polluted.
4.4 Conclusion
One of the main challenges of the study was to propose a way to compile, synthesise
and interpret the countless results of the multi-marker study conducted between 2011
and 2012. The WOE approach developed was successfully applied in this context
and resulted in an integrative ERA based on the compilation of more than 150 endpoints to characterise the contamination/pollution status of each site. The results of
this method are easily interpreted and transferable to environmental stakeholders
through the generation of a global index of perturbation (WOE index) associated
with a hazard class. However, several biological responses studied during the
programme could not be integrated into the model due to the lack of available
references. In particular, modifications of bacterial communities and tolerance
acquisition in biofilms (pollution-induced community tolerance ‘PICT’ method)
Experience Gained from Ecotoxicological Studies in the Seine River and. . .
263