Identity:

These communities occur on a substratum whose nature varies widely and depends largely on the typology of the nearby coast and of nearby infralittoral formations. This implies that substrata can sometimes be gravels and sands originating from predominant local rocks, sometimes shell debris from various molluscs, sometimes debris from branched bryozoans or debris of dead and more or less corroded Melobesiae spp. The interstices between these various components are partially filled by a greater or lesser proportion of sand and mud.