Description of biotope or habitat type
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Zostera noltei beds in littoral muddy sand
Physical habitat description
Salinity | Full (30-35 ppt), Variable (18-35 ppt) |
---|---|
Wave exposure | Sheltered, Very sheltered, Extremely sheltered |
Tidal streams | |
Substratum | Muddy sand |
Zone | |
Depth Band | Mid 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
Mid and upper shore wave-sheltered muddy fine sand or sandy mud with narrow-leafed eel grass Zostera noltei at an abundance of frequent or above. It should be noted that the presence of Z. noltii as scattered fronds does not change what is otherwise a muddy sand biotope. Exactly what determines the distribution of Z. noltii is not entirely clear. It is often found in small lagoons and pools, remaining permanently submerged, and on sediment shores where the muddiness of the sediment retains water and stops the roots from drying out. An anoxic layer is usually present below 5 cm sediment depth. The infaunal community is characterised by the polychaetes Scoloplos armiger, Pygospio elegans and Arenicola marina, oligochaetes, the spire shell Peringia ulvae, and the bivalves Cerastoderma edule and Macoma balthica. The green algae Ulva spp. may be present on the sediment surface. The characterising species lists below give an indication both of the epibiota and of the sediment infauna that may be present in intertidal seagrass beds. The biotope is described in more detail in the National Vegetation Classification (see the chapter on saltmarsh communities in Rodwell, 2000) (*** this will be a hyperlink to an electronic copy of the mentioned chapter).
Situation
Znol is most frequently found on lower estuary and sheltered coastal muddy sands, together with biotopes such as CerPo.
Temporal variation
There may be seasonal variation in the area covered by intertidal seagrass beds, as plants die back during cold temperatures in winter. Intertidal seagrass beds may also be subject to heavy grazing by geese, which can reduce the extent of the plant cover significantly. The rhizomes of the plants will remain in place within the sediment in both situations.
Characterising species
Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
---|---|---|---|
Zostera | 82 | 61-80% | |
Macoma balthica | 47 | Common | 81-100% |
Scoloplos armiger | 23 | Super abundant | 61-80% |
Arenicola marina | 11 | Abundant | 81-100% |
Arenicola marina | 7 | Abundant | 21-40% |
Pygospio elegans | 5 | Common | 41-60% |
Cerastoderma edule | 4 | Abundant | 41-60% |
Zostera noltei | 2 | Common | 21-40% |
Peringia ulvae | 2 | Common | 21-40% |
Ulva | 2 | 21-40% | |
Oligochaeta | 1 | Common | 21-40% |
Similar biotopes or habitat types
LS.LSa.MuSa.CerPo
Occurs under more estuarine but otherwise similar conditions. The infaunal communities are similar, but Zostera spp. are absent.Classification history of this biotope or habitat type
Classification version | Code |
---|---|
2015 (15.03) | LS.LMp.LSgr.Znol |
1997 (97.06) | LMS.Zos.Znol |
1996 (6.95) | LMS.PCer.Znol |
1995 | LMUD.HS.Z |