This project aims to improve our knowledge of the transfer and toxic effects of mercury from phytoplankton to mussel using both chemical and molecular biology cutting edge approaches. The project will answer to the following questions: (i) do MMHg and IHg follow a similar transfer rate in mussels fed with diatoms or chlorophytes showing contrasted cell walls, (ii) does the proportion of diatoms in phytoplankton inversely correlate with Hg transfer in mussels? (ii) Does the subcellular fate of IHg and MMHg differ in waterborne and dietary exposures? (iii) Does molecular, cellular and individual response of IHg and MMHg differ in waterborne and dietary exposures? (iv) Can we statistically and biologically link an omic signature with apical effects in an exposome context? (v) Do Mytilus edulis and Dreissena polymorpha show similar responses to Hg exposure? Once these questions deciphered, we will use the data to further propose omic signatures of exposure and effect for improved monitoring of the flux and impact of contaminants through ecosystems. This fundamental knowledge is essential to better understand and predict the propagation of effects between trophic levels of aquatic systems and to identify innovative and more efficient biomarkers for improved risk assessment of contaminants.