Mytilus galloprovincialis

Firstly, physical stress in the mid-intertidal zones was ameliorated by the presence of M. galloprovincialis beds. Secondly, habitat complexity was increased where M. galloprovincialis replaced bare rock or less complex secondary habitat. Thirdly, habitat became less patchy as mussel beds blanketed the shore. Consequently, invertebrate density and species richness increased substantially, and community composition changed significantly in the mid-shore. Lower on the shore, significant changes in invertebrate community structure were driven by a switch from mono-layered beds of the small indigenous mussel Aulacomya ater to multilayered beds of M. galloprovincialis, despite no change in total species richness.