Description of biotope or habitat type
Cerastoderma edule and polychaetes in littoral muddy sand
Habitat (physical) description
|Salinity||Full (30-35 ppt), Reduced (18-30ppt), Variable (18-35 ppt)|
|Wave exposure||Moderately exposed, Sheltered, Very sheltered, Extremely sheltered|
|Substratum||Fine sand or muddy sand|
|Depth Band||Lower shore, Mid shore, Upper shore|
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'
Point data based on records in the UK Marine Recorder Snapshot.
Extensive clean fine sand or muddy sand shores with abundant cockles Cerastoderma edule. The community consists of the polychaetes Eteone longa, Scoloplos armiger, Pygospio elegans, Spio filicornis and Capitella capitata, the crustaceans Bathyporeia sarsi, Bodotria arenosa arenosa and Crangon crangon, the spire shell Hydrobia ulvae, as well as the cockle C. edule and the baltic tellin Macoma balthica. This biotope carries commercially viable stocks of C. edule, and it is therefore possible to find areas of this habitat where the infauna may have been changed through recent cockle dredging. Cockle dredging can result in a reduced bivalve abundance and reduced densities of some polychaete species, including P. elegans (Moore, 1991). At the outer edges of large flats, there may be a zone between the cockle beds and more exposed sands, where there are fewer cockles and B. sarsi is the commoner species.
The community is found mainly on the mid and lower shore where the sediment is water-saturated most of the time. Where it occurs in muddy sand, CerPo has broad transition areas with MacAre and the MEST communities, and where it occurs on clean sand shores, it may have broad transition areas with Myt.Sa. Higher on the shore, adjacent to this biotope, BatCare is found, with fewer polychaete and bivalve species due to the drier sediment found on the upper shore.
A layer of mud with dense spionid polychaetes may build up on cockle beds in sheltered areas, creating a cohesive muddy layer 10-15 cm thick overlying the whole area. This may break up leaving a series of pits and patches with miniature cliffs, giving it an appearance similar to a stony shore when seen from a distance. It should be noted that where it occurs, Hydrobia ulvae tends to move a lot and may be highly variable in abundance.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||Typical abundance - (count per m2)||% of core records where taxon was recorded|
|Eteone longa||2||Common||67||61-80 %|
|Scoloplos armiger||4||Abundant||70||41-60 %|
|Pygospio elegans||8||Common||832||61-80 %|
|Capitella capitata||8||Common||160||41-60 %|
|Bathyporeia sarsi||1||Frequent||46||41-60 %|
|Bodotria arenosa arenosa||2||Common||69||21-40 %|
|Crangon crangon||1||Common||57||21-40 %|
|Hydrobia ulvae||1||Common||25||41-60 %|
|Brachystomia suboblonga||41||Abundant||5357||61-80 %|
|Cerastoderma edule||17||Abundant||715||81-100 %|
|Macoma balthica||11||Common||574||81-100 %|