In the aquatic environment, the organic form of Hg, methyl-Hg (MMHg) and inorganic Hg (IHg) are both toxic, but MMHg has been shown to biomagnify through food chain while IHg does not. Nonetheless, the precise factors controlling the transfer of Hg from primary producers to heterotroph consumers remains poorly understood. Macrophytes are key organism of shallow aquatic environment in which MMHg is produced, and have been identified as having a role in Hg transfer to food webs. The objective of this study was therefore to assess how the compartmentation of IHg and MMHg in a representative macrophyte, Elodea nuttallii, affects their bioaccumulation through dietary transfer in Gammarus fossarum chosen as surrogate species for aquatic herbivores and decomposers. Bioaccumulation of Hg in E. nuttallii was higher for cell wall than intracellular in line with previous studies showing an important role of binding of Hg in cell wall in E. nuttallii. Our data suggest no substantial demethylation or methylation during bioaccumulation in E. nuttallii in planta or in water. THg and MMHg concentrations increased in Gammarids in correlation with concentration found in E. nuttallii. MMHg was more transferable than IHg, based on THg, but a significant part was demethylated during the feeding, while no methylation was observed in the IHg exposure. Cell wall results in higher concentrations than intracellular, suggesting that Hg in cell wall in form of MMHg and IHg was significantly assimilated by Gammarids. Significant uptake fluxes were estimated by the first-order model: uptake fluxes in Gammarids were higher for cell wall than intracellular, while similar uptake rates were observed for IHg and MMHg. In conclusion, G. fossarum is able to feed on E. nuttallii and accumulates Hg from intracellular and cell wall compartments. In line with literature, when looking at THg, consumption of MMHg-exposed plants leads to slightly higher accumulation of Hg than IHg-exposed plants, but we observed a significant demethylation of MMHg in Gammarids vs plants. Opposite to literature, we did not observed a significant biomagnification of MMHg. In sum, although the subcellular metal distribution is determinant for many consumers that are unable to assimilate the insoluble fraction of cell walls, the digestive strategies to handle food of the consumer is also important. Differences in primary producers and consumers species composition may significantly influence the fate of Hg in food webs.