Description of biotope or habitat type
To understand more about what this page is describing, see How to use the classification. See also How to cite.
Phymatolithon calcareum maerl beds in infralittoral clean gravel or coarse sand
Physical habitat 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 |
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.
- 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 algae such as Dictyota dichotoma, Halarachnion ligulatum, Metacallophyllis laciniata, Cryptopleura ramosa, Vertebrata 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, Psamathe fusca, Mediomastus fragilis, Chone duneri, Metaphoxus fultoni, and Grania may be present. Gastropods such as Steromphala cineraria, Gibbula magus, Calyptraea chinensis, Dikoleps nitens 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 SS.SMp.Mrl.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 SS.SMp.Mrl.Pcal occurs, there may be significant patches of maerl gravel containing the rare burrowing anemone Halcampoides purpureus; 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 SS.SMp.Mrl.Pcal as well as SS.SMp.Mrl.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 |
|---|---|---|---|
| Phymatolithon calcareum | 36 | 81-100% | |
| Nematoda | 9 | Common | 81-100% |
| Asterias rubens | 7 | Occasional | 41-60% |
| Metaphoxus fultoni | 7 | Common | 81-100% |
| Grania | 6 | Abundant | 81-100% |
| Corallinaceae | 5 | 21-40% | |
| Chone duneri | 5 | Common | 81-100% |
| Escharoides coccinea | 5 | 21-40% | |
| Amphipholis squamata | 4 | Super abundant | 61-80% |
| Callionymus lyra | 4 | Frequent | 21-40% |
| Psamathe fusca | 4 | Super abundant | 81-100% |
| Mediomastus fragilis | 4 | Frequent | 81-100% |
| Socarnes erythrophthalmus | 4 | Abundant | 61-80% |
| Animoceradocus semiserratus | 3 | Common | 61-80% |
| Corallina officinalis | 3 | 21-40% | |
| Cumella (Cumella) pygmaea | 3 | Common | 61-80% |
| Steromphala cineraria | 3 | Occasional | 21-40% |
| Leptocheirus pectinatus | 3 | Abundant | 61-80% |
| Onoba aculeus | 3 | Super abundant | 61-80% |
| Polycirrus | 3 | Common | 81-100% |
| Alcyonidium diaphanum | 2 | Occasional | 21-40% |
| Cellepora pumicosa | 2 | Occasional | 21-40% |
| Clavelina lepadiformis | 2 | Occasional | 21-40% |
| Cymodoce truncata | 2 | 81-100% | |
| Didemnidae | 2 | Rare | 21-40% |
| Dikoleps nitens | 2 | Abundant | 61-80% |
| Megamphopus cornutus | 2 | Frequent | 81-100% |
| Hildenbrandia rubra | 2 | 21-40% | |
| Leptocheirus hirsutimanus | 2 | Frequent | 61-80% |
| Liocarcinus depurator | 2 | Occasional | 21-40% |
| Nannastacus unguiculatus | 2 | Common | 61-80% |
| Nemertea | 2 | 81-100% | |
| Obelia dichotoma | 2 | Common | 21-40% |
| Sphaerosyllis taylori | 2 | Frequent | 61-80% |
| Vaunthompsonia cristata | 2 | 81-100% | |
| Porifera | 1 | 21-40% | |
| Aonides paucibranchiata | 1 | 61-80% | |
| Austrosyrrhoe fimbriatus | 1 | Common | 41-60% |
| Crisia | 1 | 21-40% | |
| Eurysyllis tuberculata | 1 | Common | 61-80% |
| Harmothoe impar | 1 | Common | 61-80% |
| Saccharina latissima | 1 | Occasional | 21-40% |
| Lithothamnion glaciale | 1 | 21-40% | |
| Microporella ciliata | 1 | 21-40% | |
| Porifera indet crusts | 1 | Frequent | 21-40% |
| Cradoscrupocellaria reptans | 1 | 21-40% | |
| Pseudosyllis brevipennis | 1 | Frequent | 61-80% |
Similar biotopes or habitat types
SS.SMp.Mrl.Pcal.R
SS.SMp.Mrl.Pcal.R is a shallower subtype with red seaweeds.
SS.SMp.Mrl.Pcal.Nmix
SS.SMp.Mrl.Pcal.Nmix is a deeper subtype with notably less epiphytic seaweeds.Classification history of this biotope or habitat type
| Classification version | Code | Habitat name |
|---|---|---|
| 2015 (15.03) | SS.SMp.Mrl.Pcal | Phymatolithon calcareum maerl beds in infralittoral clean gravel or coarse sand |
| 2004 (04.05) | SS.SMp.Mrl.Pcal | Phymatolithon calcareum maerl beds in infralittoral clean gravel or coarse sand |
| 1997 (97.06) | SS.IGS.Mrl.Phy | Phymatolithon calcareum maerl beds in infralittoral clean gravel or coarse sand |