Biodiversity & Conservation

Overhangs and caves



Image Keith Hiscock - A well developed overhang community with pendulous polyclinid tunicates. Image width ca 1 m.
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Distribution map

LR.LR.Ov recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Species indicative of sensitivity

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.

Community Importance Species name Common Name
Important characterizing Morchellium argus A compound ascidian
Important structural Botryllus schlosseri Star ascidian
Important structural Umbonula littoralis An encrusting bryozoan


Overhang and cave communities are colonised especially by encrusting animal species. The species identified as indicative of sensitivity are characteristic species and represent species that, if lost from the biotope, it would no longer be that biotope.

In undertaking this assessment of sensitivity, account is taken of knowledge of the biology of all characterizing species in the biotope. However, 'indicative species' are particularly important in undertaking the assessment because they have been subject to detailed research.

Additional information

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This review can be cited as follows:

Hiscock, K. 2002. Overhangs and caves. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25/11/2015]. Available from: <>