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Marine Habitat Classification

Description of biotope or habitat type

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   Acrocnida brachiata with Astropecten irregularis and other echinoderms in circalittoral muddy sand

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered, Very sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Fine to very fine muddy sand
Zone Circalittoral
Depth Band 0-5 m, 5-10 m, 10-20 m
Other Features

Biotope origin

Derived using data from Various
Faunal group Epifauna

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 SS.SSa.CMuSa.AbraAirr <I>Acrocnida brachiata</I> with <I>Astropecten irregularis</I> and other echinoderms in circalittoral muddy sand

  • 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.


In shallow, circalittoral non-cohesive muddy sand (typically less than 20% silt/clay) abundant populations of the brittlestar Acrocnida brachiata may occur with other echinoderms such as Astropecten irregularis, Asterias rubens, Ophiura ophiura and Echinocardium cordatum. Other infaunal species typically include Kurtiella bidentata, Lanice conchilega and Magelona filiformis. This biotope is likely to form part of the non-cohesive/cohesive muddy sand communities, which make up the 'off-shore muddy sand association' described by other workers (Jones 1951; Mackie 1990). It is possible that in some areas this biotope forms an epifaunal overlay which may cover a range of biotopes in years of good recruitment but does not develop into a settled or established community. If sampling epifauna, in addition to those described above, taxa such as Pagurus spp., Astropecten irregularis and Corystes cassivelaunus may be present, although their distribution is known to be extensive beyond this biotope.


No situation data available.

Temporal variation

No temporal data available. In some areas e.g. Liverpool Bay, SS.SSa.CMuSa.AalbNuc and SS.SMu.CSaMu.LkorPpel have exhibited cyclical behaviour with the community periodically switching from one biotope to another - possibly in relation to dredge spoil disposal (Rees et al. 1992) along with other environmental and biological factors. Both Lagis koreni and Phaxas pellucidus, are capable of tolerating sudden increases in the deposition of sediment and often dominate such areas following such an event. Indeed, it is likely that the two biotopes are merely different aspects of the same community as Lagis koreni is often recorded with high densities of Abra alba (Eagle 1975; Rees and Walker 1983). Densities of mature populations of L. koreni may exceed 1000 m2.

Characterising species

Taxon Relative importance of taxon for defining this community (%) % of core records where taxon was recorded Relative frequency %
Asterias rubens 18 1-20% 3.3
Amphiura 15 1-20% 2.4
Echinocardium cordatum 14 1-20% 4.2
Pagurus 12 1-20% 2.2
Ophiura ophiura 10 1-20% 2.2
Astropecten irregularis 7 1-20% 2.1
Corystes cassivelaunus 4 1-20% 1.6
Asterias 4 1-20% 0.7
Epizoanthus papillosus 3 1-20% 1
Acrocnida brachiata 2 1-20% 3.3
Neptunea antiqua 1 1-20% 0.6
Alcyonium digitatum 1 1-20% 0.5
Lanice conchilega 1 1-20% 0.8
Cerianthus lloydii 1 1-20% 1.2
Pagurus bernhardus 1 1-20% 1
Ensis 1 1-20% 0.6
Liocarcinus 1 1-20% 0.4

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SSa.CMuSa.AbraAirr Acrocnida brachiata with Astropecten irregularis and other echinoderms in circalittoral muddy sand
2004 (04.05) SS.SSa.CMuSa.AbraAirr Acrocnida brachiata with Astropecten irregularis and other echinoderms in circalittoral muddy sand

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