Biodiversity & Conservation

Laminaria digitata, ascidians and bryozoans on tide-swept sublittoral fringe rock


<i>%Laminaria digitata%</i>, ascidians and bryozoans on tide-swept sublittoral fringe rock
Distribution map

IR.MIR.KR.Ldig.T recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • UK_BAP

Text page icon Habitat description

Map icon Distribution of biotope in Britain and Ireland MIR.Ldig.T has been recorded on the west coasts of Britain in the Isles of Scilly, Milford Haven, Holy Island off the Pembrokeshire coast, the Menai Strait, west Scotland and the Inner and Outer Hebrides. It has not been recorded from the east coast of Britain. In Ireland, it has been recorded in one site on the east coast (Wicklow Head), and from several sites on the west coast. Irish survey data has not been analyzed to identify biotopes although it seems likely that the biotope will occur in tidal sounds and rapids such as occur in Strangfrod Lough.
National importance Scarce

Text page icon Description of biotope

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

Very sheltered bedrock, boulders and cobbles that are subject to moderate to strong tidal water movement characterized by dense Laminaria digitata, ascidians and bryozoans. Species richness is generally greater than in the non tide-swept Laminaria digitata biotope (MIR.Ldig.Ldig), with a greater abundance and wider range of foliose red seaweeds. The increased water movement encourages several filter-feeding faunal groups to occur. The sponges Leucosolenia spp., Halichondria panicea and Hymeniacidon perleve frequently occur on steep and overhanging faces. In addition, the ascidians Ascidia conchilega, Dendrodoa grossularia and colonial ascidians are also found. Areas where increased tidal movement influences such a community are in the narrows and/or intertidal sills of sealochs. This biotope may be found immediately below the tide-swept Fucus serratus biotope (SLR.Fserr.T). The sublittoral fringe of similarly sheltered shores that are not tide-swept are generally characterized by mixed Laminaria saccharina and Laminaria digitata (SIR.Lsac.Ldig) or Laminaria saccharina (SIR.Lsac). (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Additional information icon Additional information

This review can be cited as follows:

Marshall, C.E. 2005. Laminaria digitata, ascidians and bryozoans on tide-swept sublittoral fringe rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 30/11/2015]. Available from: <>