Abstract
Differential tolerance to stress is partly responsible for the heterogeneity of biomarker responses between populations of a sentinel species. Although currently used for freshwater biomonitoring, studies concerning inter-populational variability in tolerance to contaminants for the zebra mussel (Dreissena polymorpha) are scarce. Moreover, this well-known invader is currently replaced by another, the quagga mussel (Dreissena rostriformis bugensis). To evaluate the differential tolerance between dreissenids, several populations of both species were exposed to a high concentration of nickel. A LT50 (time when 50% of individuals were dead) was established for each population. Biomarker responses and internal nickel concentration were also measured, to link tolerance with physiological status. Results evidenced that D. polymorpha populations are more heterogeneous and more tolerant than D. r. bugensis ones. For D. polymorpha populations only, LT50 values were positively correlated with the nickel contamination in situ, with higher anti-oxidative defences and a higher Integrated Biomarker Response value in the field. Such findings may be explained by local adaptation and invasion dynamic within each species. The significance of this differential tolerance when using biomarker responses for biomonitoring purposes is thus discussed.
Highlights
Aquatic ecosystems are the ultimate receptacle for many pollutants, and undergo many disturbances
D. polymorpha are more tolerant to Ni than D. r. bugensis populations
Inter-specific differences are very strong, with a mean LT50 for D. polymorpha (193.6 h ± 85.2) higher than for D. r. bugensis (67.8 h ± 16.7), and the highest value for D. r. bugensis never exceed the lowest value obtained for D. polymorpha
Summary
Aquatic ecosystems are the ultimate receptacle for many pollutants, and undergo many disturbances To face this environmental problem, the European Water Framework Directive (WFD) was designed to evaluate, protect and restore aquatic systems[1]. The implementation of multi-biomarker approaches enables the understanding of different toxicity mechanisms triggered by multiple stressors existing in the field, that may with time lead to an overall adverse effect[8,9,10]. Despite their usefulness, the deployment of biomarkers is still controversial[11,12,13]. To make a proper use of biomarkers, we need to know thoroughly the populations of sentinel organisms in order to be able to correctly interpret their responses to environmental changes
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