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Marine Habitat Classification


Description of biotope or habitat type

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   Barnacles and Littorina spp. on unstable eulittoral mixed substrata


Habitat (physical) description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams
Substratum Cobbles and pebbles on sand and gravel
Zone Eulittoral
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 LR.FLR.Eph.BLitX Barnacles and <I>Littorina</I> spp. on unstable eulittoral mixed substrata

  • 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

The eulittoral zone, particularly the mid shore zone, of sheltered to extremely sheltered mixed substrata shores is often characterised by flat banks or scards of cobbles and pebbles (on sediment) which are either too small or unstable to support a seaweed community. The boulders and larger cobbles are usually colonised by the barnacles Semibalanus balanoides or in areas with variable salinity Elminius modestus and often dense aggregations of the winkles Littorina littorea and Littorina saxatilis are present as well. Between the cobbles and pebbles the mussel Mytilus edulis occasionally occurs, but always at low abundance. Juvenile crabs Carcinus maenas and gammarids may occur between and underneath the pebbles and cobbles. Brown seaweeds are rare, although the wrack Fucus vesiculosus may occasionally occur on larger cobbles and small boulders in the mid and upper shore zones. Ephemeral green seaweeds such as Enteromorpha intestinalis may also be present. Shallow pools and patches of standing water may occur in low-lying areas and may contain amphipods and filamentous green seaweeds. Due to the unstable nature of the substratum the diversity and density of flora and fauna is characteristically low.

Situation

This biotope is found primarily on enclosed (estuarine) stony shores in wave-sheltered conditions (compare with Sem.LlitX) and may be subject to variable levels of salinity. It is found predominately in the mid shore zone below or at the same level as the biotope dominated by ephemeral green seaweeds (EphX). If it is found in the upper shore region it can be backed by salt marsh species such as Salacornia and Spartina sp. Below are biotopes dominated by the wracks Fucus serratus or F. vesiculosus (Fserr.X; Fves.X).

Temporal variation

Unknown.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Elminius modestus 15 Frequent 41-60 %
Semibalanus balanoides 18 Frequent 61-80 %
Carcinus maenas 7 Occasional 41-60 %
Littorina littorea 25 Frequent 81-100 %
Littorina saxatilis 15 Frequent 61-80 %
Mytilus edulis 6 Occasional 41-60 %
Fucus vesiculosus 3 Occasional 21-40 %
Enteromorpha intestinalis 3 Occasional 21-40 %

Similar biotopes

LR.HLR.MusB.Sem.LitX
Found on more exposed, open coast sites, but with similar substrata. It is more species rich than BLitX, and red seaweeds including coralline crusts, Mastocarpus stellatus and Chondrus crispus are present. There is also a higher abundance of the limpet Patella vulgata and S. balanoides.

LR.FLR.Eph.EphX
Occurs in a wider exposure range and similar physical conditions. It has a higher abundance of green seaweeds such as Enteromorpha spp. and Ulva lactuca and a lower abundance and frequency of occurrence of barnacles. Very low species diversity.

Biotope history

Classification Habitat code
97.06 BLit in part
6.95 LMXD.BLIT

Photos

LR.FLR.EPH.BLitX Barnacles and Littorina spp. on unstable eulittoral mixed substrata, Blyth Power Station, Blyth Estuary. Eleanor Murray © JNCC
LR.FLR.EPH.BLitX Barnacles and Littorina spp. on unstable eulittoral mixed substrata, Blyth Power Station, Blyth Estuary. Eleanor Murray © JNCC

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