Biodiversity & Conservation

Pomatoceros triqueter, Balanus crenatus and bryozoan crusts on mobile circalittoral cobbles and pebbles



Image Jon Davies - Cobbles with dense Pomatoceros species (ECR.PomByC). Image width ca 50 cm.
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Distribution map

CR.ECR.EFa.PomByC recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

Recorded distribution in Britain and Ireland

Scattered records from Fair Isle, Orkney; the rivers Teign and Dart, Devon; Lundy; the Bishops & Clerks, Skomer and off Dinas Head in Pembrokeshire; Cardigan Bay, Lleyn Peninsula, Bardsey and Menai Straits north Wales; Donlus Bay, south west Ireland; Tiree and Loch Roag, Isle of Lewis in west Scotland and St Kilda.

Habitat preferences

Temperature range preferences - No information found

Limiting Nutrients -

Other preferences - Mobile hard substrata and scour

Additional information

This biotope characterizes hard mobile substrata such as cobbles, pebbles and boulders with sand or gravel in areas of considerable water movement either due to wave action or tidal streams. The biotope occurs in very wave exposed to moderately wave exposed habitats, and/or in areas of strong to very weak tidal streams (Connor et al., 1997a; JNCC, 1999). Scour of the cobbles, pebbles and boulders by sand, or by mobilization of the cobbles and pebbles themselves results in a scour resistant or ephemeral fauna. For example, in the mouth of the Teign, Devon, ECR.PomByC occurs on cobbles sitting on coarse sand and gravel in a scour pit. This biotope is probably very similar to the impoverished Balanus-Pomatoceros assemblage described on hard substrata subject to severe scour or deep submergence by sand or gravel reported by Holme & Wilson (1985) in tide-swept areas of the central English Channel.

This review can be cited as follows:

Tyler-Walters, H. 2002. Pomatoceros triqueter, Balanus crenatus and bryozoan crusts on mobile circalittoral cobbles and pebbles. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 26/11/2015]. Available from: <>