Description of biotope or habitat type
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Piddocks with a sparse associated fauna in sublittoral very soft chalk or clay
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Moderately exposed |
| Tidal streams | Moderately strong (1-3 kn) |
| Substratum | Bedrock |
| Zone | Circalittoral |
| Depth Band | 5-10 m, 10-20 m |
| Other Features | Soft rock: chalk or clay. Often with vertical faces. |
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
This biotope occurs on circalittoral soft rock, such as soft chalk or clay, most often in moderately exposed tide-swept conditions. As soft chalk and firm clay are often too soft for sessile filter-feeding animals to attach and thrive in large numbers, an extremely impoverished epifauna results on upward-facing surfaces, although vertical faces may be somewhat richer. The rock is sufficiently soft to be bored by bivalves. Species vary with location, but Pholas dactylus is the most widespread borer and may be abundant. Other species present may include the sponges Dysidea fragilis and Suberites carnosus and the polychaete Bispira volutacornis. Foliose red algae may be present on the harder, more stable areas of rock. Mobile fauna often include the crabs Necora puber and Cancer pagurus.
Situation
Subtidal chalk reefs or clay outcrops, mostly known from south-east England.
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 |
|---|---|---|---|
| Pholas dactylus | 83 | Common | 81-100% |
| Rhodophyta | 4 | Occasional | 21-40% |
| Bispira volutacornis | 2 | Occasional | 21-40% |
| Suberites carnosus | 2 | Frequent | 21-40% |
| Necora puber | 1 | Rare | 21-40% |
Similar biotopes or habitat types
IR.MIR.KR.Ldig.Pid
This biotope is found on sublittoral fringe soft rock on moderately exposed coasts. It is characterised by boring bivalves and the kelp Laminaria digitata.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1997 (97.06) | CR.MCR.SfR.Pid |