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Marine Habitat Classification


Description of biotope or habitat type

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   Phymatolithon calcareum maerl beds in infralittoral clean gravel or coarse sand


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed, Sheltered, Extremely sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Maerl gravel and sand
Zone Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 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 SS.SMp.Mrl.Pcal <I>Phymatolithon calcareum</I> maerl beds in infralittoral clean gravel or coarse 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.

Description

Maerl beds characterised by Phymatolithon calcareum in gravels and sands. Associated epiphytes may include red algae such as Dictyota dichotoma, Halarachnion ligulatum, Callophyllis laciniata, Cryptopleura ramosa, Brongniartella byssoides and Plocamium cartilagineum. Algal species may be anchored to the maerl or to dead bivalve shells amongst the maerl. Polychaetes, such as Chaetopterus variopedatus, Lanice conchilega, Kefersteinia cirrata, Mediomastus fragilis, Chone duneri, Parametaphoxus fultoni and Grania may be present. Gastropods such as Gibbula cineraria, Gibbula magus, Calyptraea chinensis Dikoleps pusilla and Onoba aculeus may also be present. Liocarcinus depurator and Liocarcinus corrugatus are often present, although they may be under-recorded; it would seem likely that robust infaunal bivalves such as Circomphalus casina, Mya truncata, Dosinia exoleta and other venerid bivalves are more widespread than available data currently suggests. It seems likely that stable wave-sheltered maerl beds with low currents may be separable from SMP.Pcal; having a generally thinner layer of maerl overlying a sandy /muddy substratum with a diverse cover of epiphytes (e.g. Bosence 1976; Blunden et al. 1977; 1981; Davies & Hall-Spencer 1996) but insufficient data currently exists on a national scale. Wave and current-exposed maerl beds, where thicker depths of maerl accumulate, frequently occur as waves and ridge / furrows arrangements (see Bosence 1976; Blunden et al. 1977; 1981; Irvine & Chamberlain 1994; Hall-Spencer 1995). At some sites where Pcal occurs, there may be significant patches of maerl gravel containing the rare burrowing anemone Halcampoides elongatus; this may be a separate biotope, but insufficient data exists at present. Northern maerl beds in the UK do not appear to contain L. corallioides but in south-west England and Ireland L. corallioides may occur to some extent in Pcal as well as Lcor, where it dominates.

Situation

No situation data available.

Temporal variation

No temporal data available.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Porifera 1 21-40 %
Porifera indet crusts 1 Frequent 21-40 %
Obelia dichotoma 2 Common 21-40 %
Nemertea 2 81-100 %
Nematoda 9 Common 81-100 %
Harmothoe impar 1 Common 61-80 %
Kefersteinia cirrata 4 Super abundant 81-100 %
Eurysyllis tuberculata 1 Common 61-80 %
Trypanosyllis coeliaca 1 Frequent 61-80 %
Sphaerosyllis taylori 2 Frequent 61-80 %
Aonides paucibranchiata 1 61-80 %
Mediomastus fragilis 4 Frequent 81-100 %
Polycirrus 3 Common 81-100 %
Chone duneri 5 Common 81-100 %
Grania 6 Abundant 81-100 %
Parametaphoxus fultoni 7 Common 81-100 %
Socarnes erythrophthalmus 4 Abundant 61-80 %
Austrosyrrhoe fimbriatus 1 Common 41-60 %
Ceradocus semiserratus 3 Common 61-80 %
Gammaropsis cornuta 2 Frequent 81-100 %
Leptocheirus hirsutimanus 2 Frequent 61-80 %
Leptocheirus pectinatus 3 Abundant 61-80 %
Cymodoce truncata 2 81-100 %
Vauntompsonia cristata 2 81-100 %
Cumella pygmaea 3 Common 61-80 %
Nannastacus unguiculatus 2 Common 61-80 %
Liocarcinus depurator 2 Occasional 21-40 %
Gibbula cineraria 3 Occasional 21-40 %
Dikoleps pusilla 2 Abundant 61-80 %
Onoba aculeus 3 Super abundant 61-80 %
Crisia 1 21-40 %
Alcyonidium diaphanum 2 Occasional 21-40 %
Scrupocellaria reptans 1 21-40 %
Escharoides coccinea 5 21-40 %
Microporella ciliata 1 21-40 %
Cellepora pumicosa 2 Occasional 21-40 %
Asterias rubens 7 Occasional 41-60 %
Amphipholis squamata 4 Super abundant 61-80 %
Clavelina lepadiformis 2 Occasional 21-40 %
Didemnidae 2 Rare 21-40 %
Callionymus lyra 4 Frequent 21-40 %
Hildenbrandia rubra 2 21-40 %
Corallinaceae 5 21-40 %
Corallina officinalis 3 21-40 %
Lithothamnion glaciale 1 21-40 %
Phymatolithon calcareum 36 81-100 %
Laminaria saccharina 1 Occasional 21-40 %

Similar biotopes

SS.SMp.Mrl.Pcal.R
Pcal.R is a shallower subtype with red seaweeds

SS.SMp.Mrl.Pcal.Nmix
Pcal.Nmix is a deeper subtype with notably less epiphytic seaweeds

Biotope history

Classification Habitat code
97.06 IGS.Mrl

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