Benthic macroinvertebrates as indicators of environmental deterioration in a large microtidal estuary

► Benthic macroinvertebrate fauna in the Swan-Canning Estuary has changed since the 1980s. ► The densities and number of species of crustaceans have declined while those of polychaetes have increased. ► The compositions of the fauna altered markedly at both the species and family levels.