Biodiversity & Conservation

Caves and overhangs (deep)


Caves and overhangs (deep)
Distribution map

CR.FCR.Cv recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Ecological and functional relationships

The main components of the biotope probably interact very little and live independently. However, the corals provide a host for the barnacle Boschia anglica (in the south-west) and a calcareous substratum for boring species such as Hiatella arctica, Potamilla reniformis and the horseshoe worm Phoronis hippocrepia to live. Boring species may weaken the skeleton of the corals to the extent that they are easily detached (see Hiscock & Howlett,1976). The soft coral Alcyonium glomeratum may be predated on by the prosobranch Simnia patula. Encrusting sponges may overgrow other species and Harmelin (1990) has shown how encrusting bryozoans may engulf cup corals and kill them. Grazers such as the sea urchin Echinus esculentus, may occasionally pass through the biotope grazing away barnacles and erect bryozoans especially , possible freeing space for new colonization (Keith Hiscock, own observations).

Seasonal and longer term change

Most of the species in the biotope are long-lived. However, seasonal change occurs in the light-bulb ascidian Clavellina lepadiformis which grows rapidly in the spring to die-back in winter. A longer term decline has been recorded in the abundance of long-lived species (especially Leptopsammia pruvoti, Hoplangia durotrix and Alcyonium coralloides) at Lundy (K. Hiscock, own observations).

Habitat structure and complexity

There is little complexity in the habitat, most species living directly attached to the rock and not offering architectural complexity as shelter for other species.


No information found

Recruitment processes

Several of the species in the biotope appear to have short-lived benthic larvae. For instance, the soft coral Alcyonium hibernicum broods planulae larvae that are released at a late development phase and so probably has a short planktonic life (Hartnoll 1977 as Alcyonium coralloides). Leptopsammia pruvoti also seems to have short-lived planulae larvae which may settle immediately or very soon after release and recruitment at a site at Lundy has been extremely small (as low as 1% over the years 1983 to 1999 at least) (K. Hiscock, own observations). Sponges are likely to have a longer lived larva. Some species, such as the zoanthid anemones Parazoanthus axinellae and Parazoanthus dixoni, reproduce asexually to produce large colonies..

Time for community to reach maturity

As recruitment processes are so slow for many species and individual species will not colonize readily, the community will most likely take in excess of 25 years to reach maturity.

Additional information

Alcyonium hibernicum is named as Parerythropodium coralloides in the Species Directory (Howson & Picton 1997). Subsequently, McFadden (1999) has shown that it is taxonomically distinct species and should be known as Alcyonium hibernicum.

This review can be cited as follows:

Hiscock, K. 2000. Caves and overhangs (deep). 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: <>