Towards a better understanding of biomarker response in field survey: A case study in eight populations of zebra mussels

• Biomarkers displayed high variation across eight populations living in dissimilar sites.
• Biomarkers, proteome and shell size were able to discriminate between populations.
• Proteome and shell size were under both genes and environment influence.
• Biomarkers (IBR index) were rather under environmental influence.
• The use of biomarkers implies to properly understand population responsiveness.

In order to provide reliable information about responsiveness of biomarkers during environmental monitoring, there is a need to improve the understanding of inter-population differences. The present study focused on eight populations of zebra mussels and aimed to describe how variable are biomarkers in different sampling locations. Biomarkers were investigated and summarised through the Integrated Biomarker Response (IBR index). Inter-site differences in IBR index were analysed through comparisons with morphological data, proteomic profiles and genetic background of the studied populations. We found that the IBR index was a good tool to inform about the status of sites. It revealed higher stress in more polluted sites than in cleaner ones. It was neither correlated to proteomic profiles nor to genetic background, suggesting a stronger influence of environment than genes. Meanwhile, morphological traits were related to both environment and genetic background influence. Together these results attest the benefit of using biological tools to better illustrate the status of a population and highlight the need of consider inter-population difference in their baselines.