Biodiversity & Conservation

To assess the sensitivity of the biotope, the sensitivity of component species is reviewed. Those species that are considered to be particularly indicative of the sensitivity of the biotope, and for which research has been undertaken in detail are shown below (see selection criteria). The biology of other component species of the biotope is also taken into account wherever information is known to the researcher.

• Echinus esculentus
• Alcyonium digitatum
• Caryophyllia smithii
• Pododesmus patelliformis
• Parasmittina trispinosa
• Antedon bifida
• Crossaster papposus
• Asterias rubens
• Clavelina lepadiformis
• Pomatoceros triqueter

This biotope corresponds to the early successional epifaunal communities, with intense sea urchin grazing, dominated by encrusting algal crusts and faunal crusts (e.g. tubeworms and bryozoans) described by Sebens (1985, 1986). Sebens (1985, 1986) demonstrated epifaunal succession to faunal turf and eventually ascidian, Alcyonium or Metridium dominated communities after the removal of sea urchins. In similar experiments, Echinus esculentus was shown to control the lower limit of Laminaria species in the Isle of Man (Jones & Kain 1967; Kain 1979). Therefore, Echinus esculentus has been suggested as a key functional species, since its loss would result in major changes in the community. Alcyonium digitatum has been included as important characterizing since it occurs in most records of the biotope. Lithophyllum incrustans has been included to represent the encrusting coralline algae characteristic of the biotope. Parasmittina trispinosa and Pomatoceros triqueter are included as characteristic faunal crusts. In the absence of detailed research on Parasmittina trispinosa, reference was made to Electra pilosa and other bryozoans to represent its sensitivity.

The MNCR recorded 497 species within this biotope although not all species occurred in all records of the biotope.