Description of biotope or habitat type
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Hediste diversicolor, cirratulids and Tubificoides spp. in littoral gravelly sandy mud
Physical habitat description
| Salinity | Variable (18-35 ppt) |
|---|---|
| Wave exposure | Sheltered, Very sheltered, Extremely sheltered |
| Tidal streams | |
| Substratum | Gravelly 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
Sheltered gravelly sandy mud, subject to variable salinity. The infaunal community consists of the ragworm Hediste diversicolor, Pygospio elegans, Streblospio shrubsolii, and cirratulid polychaetes such as Tharyx killariensis. Nematodes and oligochaetes occur, as well as the bivalve Macoma balthica. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list.
Situation
It is probable that there are broad transition areas between this biotope and the corresponding muddy sediment biotope HedMac. The boundaries may be very indistinct, with HedMx.Cir present in patches of gravelly mud on areas of mudflat, where the main biotope is HedMac.
Temporal variation
Not known.
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 | 47 | Abundant | 1040 | 81-100% |
| Tharyx killariensis | 25 | Common | 145 | 81-100% |
| Nematoda | 6 | Frequent | 166 | 61-80% |
| Tubificoides pseudogaster | 5 | 150 | 61-80% | |
| Tubificoides benedii | 4 | Frequent | 106 | 61-80% |
| Enchytraeidae | 3 | Common | 247 | 21-40% |
| Streblospio shrubsolii | 3 | 984 | 61-80% | |
| Macoma balthica | 2 | 44 | 41-60% | |
| Baltidrilus costatus | 1 | 47 | 61-80% | |
| Pygospio elegans | 1 | 15 | 41-60% |
Similar biotopes or habitat types
LS.LMu.MEst.HedMac
Occurs in lower estuarine muds and sandy muds, without a gravel fraction. The infauna is dominated by similar species, though it is more diverse (this may be an artefact of greater sample numbers in the LS.LMu.MEst.HedMac biotope).
LS.LMx.GvMu.HedMx.Mac
Occurs in gravelly mud under less saline and slightly more sheltered conditions. The main differences in the infaunal assemblage are the abundance of M. balthica, and the absence of oligochaetes and a range of polychaetes including T. killariensis.
LS.LMx.GvMu.HedMx.Scr
Occurs in gravelly mud, higher up on the shore and under more sheltered conditions. The polychaete fauna is similar, but there are fewer oligochaetes. The bivalve infauna is more diverse, with abundant Scrobicularia plana.
LS.LMx.GvMu.HedMx.Str
Occurs in more sheltered gravelly mud. The main differences in the infaunal assemblage are the absence of T. killariensis, fewer oligochaetes, and the presence of occasional S. plana.