Description of biotope or habitat type
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Hediste diversicolor and oligochaetes in littoral mud
Physical habitat description
| Salinity | Reduced (18-30ppt), Variable (18-35 ppt) |
|---|---|
| Wave exposure | Sheltered, Very sheltered, Extremely sheltered |
| Tidal streams | |
| Substratum | Sandy mud |
| Zone | |
| Depth Band | Lower shore, Mid shore, Upper shore |
| 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.
- 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.
Description
A species-poor community found in mud or slightly sandy mud in low salinity conditions, typically at the head of estuaries. The infauna is dominated by the ragworm Hediste diversicolor which is typically superabundant. Oligochaetes, including tubificids and Baltidrilus costatus, can be abundant, as well as spionids. The peppery furrow shell Scrobicularia plana may be present in low abundances. The mud is often very soft and fluid, with a 'wet' surface appearance, or it may be compacted and form steep banks in the upper parts of macro-tidal estuaries and along saltmarsh creeks.
Situation
There are three oligochaete dominated upper estuarine mud biotopes. Tben is the most extreme upper estuarine biotope, occurring at the head of estuaries where there is a very strong freshwater influence. Further towards the mid estuary, this biotope may occur at the top of the shore, with Hed.Ol further down. NhomStr occurs furthest towards the mid estuary, or on the lower shore with Hed.Ol and Tben higher up.
Temporal variation
Enteromorpha spp. or Ulva lactuca may form mats on the surface of the sediment during the summer months, particularly in areas of freshwater influence and/or where there is nutrient enrichment.
Characterising species
| 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 |
|---|---|---|---|---|
| Hediste diversicolor | 54 | Super abundant | 1899 | 81-100% |
| Naididae | 15 | Abundant | 1840 | 41-60% |
| Oligochaeta | 11 | Abundant | 2026 | 21-40% |
| Spionidae | 6 | Abundant | 468 | 21-40% |
| Baltidrilus costatus | 1 | Abundant | 2127 | 21-40% |
Similar biotopes or habitat types
LS.LMu.UEst.Tben
Occurs in similar physical conditions, but further up towards the head of estuaries. The species assemblage is much poorer, consisting only of oligochaetes and, in some cases, Capitella capitata.
LS.LMu.MEst.NhomMacStr
Occurs in similar physical conditions, but possibly lower down in estuaries (more saline). The polychaete assemblage is more diverse, and both Peringia ulvae and Macoma balthica are characterising species. It is the presence of these two species that primarily distinguishes LS.LMu.MEst.NhomMacStr from upper estuarine mud biotopes.
LS.LMu.UEst.Hed.Str
Occurs in similar physical conditions. The infauna is more diverse, with abundant Streblospio shrubsolii and a range of oligochaetes.
LS.LMu.UEst.Hed.Cvol
Occurs in similar physical conditions. The main difference in the infaunal species composition is the presence of common Corophium volutator.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1997 (97.06) | LMU.MU.HedOl (part) |
| 1997 (97.06) | LMU.MU.HedStr (part) |
| 1995 | LMUD.HO |
