Description of biotope or habitat type
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Polychaete/oligochaete-dominated upper estuarine mud shores
Physical habitat description
| Salinity | Variable (18-35 ppt) |
|---|---|
| Wave exposure | Sheltered, Very sheltered, Extremely sheltered |
| Tidal streams | |
| Substratum | Sandy mud, 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
Upper estuarine sandy mud and mud shores, in areas with significant freshwater influence. Littoral mud typically forms mudflats, though dry compacted mud can form steep and even vertical structures, particularly at the top of the shore adjacent to saltmarshes. Little oxygen penetrates these cohesive sediments, and an anoxic layer is often present within millimetres of the sediment surface. The upper estuarine mud communities support few infaunal species and are principally characterised by a restricted range of polychaetes and oligochaetes.
Situation
There are three oligochaete dominated upper estuarine mud biotopes. Of these three, NhomStr occurs the furthest towards the mid estuary, and possibly lower on the shore than the other two. Tben is the most extreme upper estuarine biotope, occurring at the head of estuaries where there is no strong river flow and hence conditions are very sheltered, and 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 and NhomStr further down the shore.
Temporal variation
Enteromorpha spp. and Ulva lactuca may form mats on the surface of the mud during the summer months, particularly in areas of 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 | 40 | Super abundant | 1584 | 81-100% |
| Oligochaeta | 9 | Abundant | 6871 | 21-40% |
| Streblospio shrubsolii | 9 | Common | 1289 | 41-60% |
| Corophium volutator | 8 | Common | 1811 | 21-40% |
| Tubificoides benedii | 8 | Common | 2031 | 21-40% |
| Manayunkia aestuarina | 4 | Common | 1832 | 21-40% |
| Baltidrilus costatus | 3 | Abundant | 1699 | 21-40% |
| Nematoda | 2 | Common | 558 | 1-20% |
| Peringia ulvae | 2 | Common | 294 | 21-40% |
| Pygospio elegans | 2 | Common | 121 | 21-40% |
| Scrobicularia plana | 2 | Common | 36 | 21-40% |
| Cyathura carinata | 2 | Common | 121 | 1-20% |
| Nephtys hombergii | 1 | Common | 30 | 41-60% |
Similar biotopes or habitat types
Not applicable or unknown.