Mercury (Hg) represents an important risk for human health through the food webs contamination.Macrophytes bioaccumulate Hg and play a role in Hg transfer to food webs in shallow aquatic ecosystems.Nevertheless, the compartmentalization of Hg within macrophytes, notably major accumulation in thecell wall and its impact on trophic transfer to primary consumers are overlooked.The present work focusses on the trophic transfer of inorganic Hg (IHg) and monomethyl-Hg (MMHg)from the intracellular and cell wall compartments of the macrophyte Elodea nuttallii – considered a goodcandidate for phytoremediation – to the crustacean Gammarus fossarum. The results demonstrated thatHg accumulated in both compartments was trophically bioavailable to gammarids. Besides IHg from bothcompartments were similarly transferred to G. fossarum, while for MMHg, uptake rates were ∼2.5-foldhigher in G. fossarum fed with the cell wall vs the intracellular compartment. During the depuration phase,Hg concentrations in G. fossarum varied insignificantly suggesting that both IHg and MMHg were stronglybound to biological ligands in the crustacean. Our data imply that cell walls have to be considered as animportant source of Hg to consumers in freshwater food webs when developing procedures for enhancingaquatic environment protection during phytoremediation programs.