This habitat type contains two biotopes which, although have different physical habitat characteristics, share the fact that they colonise new areas of artificial substrata relatively quickly. The Ascidiella aspersa fouling biotope (A4.722) is found on wave-sheltered artificial substrata such as discarded fishing nets/mooring lines. A separate fouling biotope (A4.721) is described for open coast wrecks. This biotope has a characteristic faunal community of Alcyonium digitatum and the anemone Metridium senile. Other species recorded in this complex (primarily under subunit A4.721) include the hydroid Nemertesia antennina, the anemones Actinothoe sphyrodeta and Sagartia elegans, the cup coral Caryophyllia smithii, the bryozoans Flustra foliacea and Bugula plumosa, the crabs Necora puber, Cancer pagurus and Maja squinado and the lobster Homarus gammarus.