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Marine Habitat Classification

Description of biotope or habitat type

To understand more about what this page is describing, see How to use the classification. See also How to cite.

   Littoral seagrass beds

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams
Substratum Muddy sand
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.

Distribution of habitat LS.LMp.LSgr Littoral seagrass beds

  • 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.


Mid and upper shore wave-sheltered muddy fine sand or sandy mud with the narrow-leafed eel grass Zostera noltei at an abundance of frequent or above. 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 polychaetes Scoloplos armiger, Pygospio elegans and Arenicola marina, oligochaetes, spire shell Peringia ulvae, and 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.)


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

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) LMU.Zos

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