Origin of resources and trophic pathways in a large SW Atlantic estuary: An evaluation using stable isotopes

► The food web of the Río de la Plata estuary was evaluated with stable isotopes. ► Based on the 43 species sampled, four trophic levels were found. ► Sharks and rays were found as top predators. ► Results suggest that phytoplankton is an important in situ food source for some species. ► Other important source in this estuary is detritus from salt and freshwater marshes.