Biodiversity & Conservation

Underboulder communities



Image Keith Hiscock - Underboulder community dominated by sponges from a rock pool habitat. Wembury, South Devon. Image width ca 1 m.
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Distribution map

LR.MLR.BF.Fser.Fser.Bo recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

Text page icon Habitat description

Map icon Distribution of biotope in Britain and Ireland All around Britain but known to be particularly well developed along the coast of Northumberland, in the Plymouth area, in the Isles of Scilly, in the Menai Strait (North Wales) and in tidal rapids at the entrances of sea lochs, Hebridean obs and (in Ireland) loughs.
National importance Common

Text page icon Description of biotope

For a full description of this biotope including characterizing species, distribution, survey information and references visit JNCC

Underboulder communities are found from midshore downwards on moderately exposed to sheltered boulder shores. The community present under boulders is of the character described here where the boulders are clear of sediment, in pools and/or on open rock from the lower midshore downwards. Characteristic species include the hairy porcelain crab Porcellana platycheles, the long-clawed porcelain crab Pisidia longicornis and juvenile edible crabs Cancer pagurus. Also present beneath the boulders are often high densities of the barnacle Balanus crenatus, the keel worm Pomatoceros spp., spirorbid worms, gammarid amphipods and a few small gastropods and mussels. The encrusting bryozoans Umbonula littoralis and Schizoporella unicornis and encrusting colonies of the sponges Hymeniacidon perleve and Halichondria panicea and the star ascidian Botryllus schlosseri are also typical of this habitat. The richest examples also contain a variety of brittlestars, ascidians and small hydroids. (Biotope description adapted from Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997b).

Additional information icon Additional information

MLR.Fser.Fser.Bo is also representative of MIR.Ldig.Ldig.Bo where the underboulder fauna is very similar.
Underboulder communities are entirely different from the communities present on the tops and sides of boulders in this biotope.

This review can be cited as follows:

Hiscock, K. 2005. Underboulder communities. 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: <>