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Marine Habitat Classification


Description of biotope or habitat type

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   Mytilus edulis beds with hydroids and ascidians on tide-swept exposed to moderately wave-exposed circalittoral rock


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Extremely exposed, Exposed
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn)
Substratum Bedrock, shells, pebbles, gravel
Zone Circalittoral
Depth Band 0-5 m, 5-10 m, 10-20 m, 20-30 m
Other Features

Download comparative physical and biological data. The comparative tables enable a rapid comparison of the species composition and principal physical characteristics between a given set of biotopes.

Distribution of habitat CR.MCR.CMus.CMyt <I>Mytilus edulis</I> beds with hydroids and ascidians on tide-swept exposed to moderately wave-exposed circalittoral rock

  • Records used to define the biotope (core records)
  • Other records assigned to this biotope, marked as 'certain'
  • Other records assigned to this biotope, marked as 'uncertain'
  • Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat

Point data based on records in the UK Marine Recorder Snapshot. Predicted habitat extent is from UKSeaMap.

Description

This biotope typically occurs on the upper faces of tide-swept circalittoral bedrock, boulders and mixed substrata exposed to varying amounts of wave action. The mussel Mytilus edulis forms dense beds, to the exclusion of other species. The starfish Asterias rubens is frequently recorded, and it predates heavily on the mussels. Occasionally, the anemone Urticina felina may be seen within crevices in the rock or on gravel patches. Crabs such as Necora puber and Carcinus maenas may be seen on the rock or mussels whilst fauna observed in crevices typically consists of the lobster Homarus gammarus and the crab Cancer pagurus. The anemone Sargatia elegans can be seen attached to bedrock and cobbles, whereas the barnacle Balanus crenatus may be seen attached to the mussels themselves.

Situation

No situation data available.

Temporal variation

Not known.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Urticina felina 8 Occasional 61-80 %
Sagartia elegans 3 Occasional 41-60 %
Balanus crenatus 1 Frequent 21-40 %
Homarus gammarus 1 Rare 21-40 %
Cancer pagurus 3 Rare 41-60 %
Necora puber 4 Occasional 41-60 %
Carcinus maenas 3 Common 21-40 %
Mytilus edulis 58 Abundant 81-100 %
Asterias rubens 12 Frequent 61-80 %

Similar biotopes

IR.LIR.IFaVS.MytRS
This biotope is found on wave-sheltered, tide-swept infralittoral rock and is characterised predominantly by M. edulis.

Photos

CR.MCR.CMUS.CMyt Mytilus edulis beds with hydroids and ascidians on tide-swept exposed to moderately wave-exposed circalittoral rock, N Porthysgadan. Sarah Fowler © JNCC
CR.MCR.CMUS.CMyt Mytilus edulis beds with hydroids and ascidians on tide-swept exposed to moderately wave-exposed circalittoral rock, N Porthysgadan. Sarah Fowler © JNCC
CR.MCR.CMUS.CMyt Mytilus edulis beds with hydroids and ascidians on tide-swept exposed to moderately wave-exposed circalittoral rock, NW Trwyn Glan. Sarah Fowler © JNCC
CR.MCR.CMUS.CMyt Mytilus edulis beds with hydroids and ascidians on tide-swept exposed to moderately wave-exposed circalittoral rock, NW Trwyn Glan. Sarah Fowler © JNCC

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