Bivalve production is an important aquaculture activity worldwide, but few environmental assessments have focused on it. In particular, bivalves' ability to extract nutrients from the environment by intensely filtering water and producing a shell must be considered in the environmental assessment. LCA of blue mussel bouchot culture (grown out on wood pilings) in Mont Saint-Michel Bay (France) was performed to identify its impact hotspots. The chemical composition of mussel flesh and shell was analyzed to accurately identify potential positive effects on eutrophication and climate change. The fate of mussel shells after consumption was also considered. Its potential as a carbon-sink is influenced by assumptions made about the carbon sequestration in wooden bouchots and in the mussel shell. The fate of the shells which depends on management of discarded mussels and household waste plays also an important role. Its carbon-sink potential barely compensates the climate change impact induced by the use of fuel used for on-site transportation. The export of N and P in mussel flesh slightly decreases potential eutrophication. Environmental impacts of blue mussel culture are determined by the location of production and mussel yields, which are influenced by marine currents and the distance to on-shore technical base. Bouchot mussel culture has low environmental impacts compared to livestock systems, but the overall environmental performances depend on farming practices and the amount of fuel used. Changes to the surrounding ecosystem induced by high mussel density must be considered in future LCA studies.