Native and exotic seaweeds frequently lie on the beach and sustain part of the benthic food
web. However, the role of exotic seaweeds as food sources for beach consumers has been
poorly studied. We studied the temporal and spatial variability in the trophic significance of
the invasive brown seaweed Sargassum muticum on sandy beaches. We measured the
stable isotopes (δ13C and δ15N) in the tissues of S. muticum and of invertebrate consumers
and estimated the dietary biomass proportion of S. muticum during four sampling dates at …