Abstract The evolution of the heteromyarian form and neotenous retention of the byssus into the adult stage were central to the colonization of hard substrata and the subsequent evolutionary success of epibyssate mytilids. In addition, these mussels are supreme filter feeders and exhibit many structural, behavioural and life-history traits which make them particularly successful colonizing species. As competitively dominant species, mussels can potentially monopolize epibenthic communities with a consequent reduction in diversity of the primary space-occupying species. However, mussel patches themselves are extremely diverse, offering numerous resources which are exploited by a range of associated organisms from most animal phyla. Mussel beds can influence large-scale coastal and estuarine processes such as productivity and eutrophication, and can significantly alter sediment biogeochemistry. Annual growth lines and tidal bands in mussel shells have been used to estimate age, and to investigate the effects of environmental factors such as seawater and air temperature, spring–neap lunar tidal cycles and exposure to chlorination regimes in power station culverts. Analysis of the elemental composition of the incremental record in long-lived mytilids has been used to assess the effects of anthropogenic inputs into coastal waters.