Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA2.24 Polychaete/bivalve-dominated Atlantic littoral muddy sand

Polychaete/bivalve-dominated Atlantic littoral muddy sand

Quick facts

Red List habitat type code NEAA2.24
Threat status
Europe Data Deficient
EU Data Deficient
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


This muddy or fine sand habitat often occurs as extensive intertidal flats on open coasts and in marine inlets. It is predominantly a habitat of the mid and lower shore though can span the entire intertidal. Where it occurs in marine inlets, the habitat may be subject to variable salinity conditions. Fine sand or mobile sand communities may be present on the upper shore with muddy sand communities present lower down. The sediment generally remains water-saturated during low water and has a high organic content resulting from settlement of organic detritus and growth of heterotrophic autotrophic micro-organisms. There is also typically a high microbial population and high sediment stability due to cohesion. An anoxic layer may be present below 5 cm of the sediment surface, sometimes seen in the worm casts on the surface.  

Muddy sand habitats tend to support a relatively poor diversity of species, which are usually found in high abundances. These are predominately sessile tube-dwelling polychaetes with bivalves also well represented, amphipods and gastropods. Some species characteristic of subtidal areas may also occur. This habitat is also important for wintering and passage birds for feeding and roosting.  

Indicators of Quality:

Both biotic and abiotic indicators have been used to describe marine habitat quality. These include: the presence of characteristic species as well as those which are sensitive to the pressures the habitat may face; water quality parameters; levels of exposure to particular pressure, and more integrated indices which describe habitat structure and function, such as trophic index, or successional stages of development in habitats that have a natural cycle of change over time.

There are no commonly agreed indicators of quality for this habitat, although particular parameters may have been set in certain situations e.g. protected features within Natura 2000 sites, where reference values have been determined and applied on a location-specific basis.

Characteristic species
For full habitat description, please download the habitat factsheet.

Threat status

Synthesis of Red List assessment

This habitat has a large natural range in the North East Atlantic, from the Atlantic coast of Portugal and Ireland, to the southern North Sea coasts of Denmark, Germany and the Netherlands. While there have been known losses as a result of human pressures, the scale of these losses are unknown when considered within a regional context. The same limitations apply when trying to determine any historical and recent trends in quality. Littoral sediment features are generally dynamic, and change in extent is difficult to quantify due to the natural processes, such as current/drift, wave action and wind, but historical losses are known to have occurred. The communities associated with this habitat are also naturally extremely variable often reflecting the shifting seasonal nature of the shore sediment, which is predominantly influenced by weather and tidal events.
This habitat has a large EOO and AOO, and therefore qualifies as Least Concern under criterion B. However the habitat is assessed as Data Deficient both at the EU 28 and EU 28+ levels because of a lack of information on the area covered and on any trends in quantity and quality.
Red List Category Red List Criteria
Data Deficient -
Red List Category Red List Criteria
Data Deficient -

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Urbanisation, residential and commercial development
    • Discharges
  • Biological resource use other than agriculture & forestry
    • Fishing and harvesting aquatic resources
    • Professional active fishing
    • Benthic dredging
    • Leisure fishing
    • Bait digging / Collection
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Modification of hydrographic functioning, general
  • Climate change
    • Changes in abiotic conditions
    • Wave exposure changes

Habitat restoration potential

Recovery is dependent on the return of suitable sediment and recruitment of individuals. Overall recovery will vary between site location or hydrographic regime and the community may not recover exactly the same species composition as existed prior to disturbance. Once suitable substratum returns, recolonisation is likely to be rapid, especially for rapidly reproducing species such as polychaetes, oligochaetes and some amphipods and bivalves. Recolonisation and hence recovery may be aided by bedload transport of juvenile polychaetes and bivalves.

Trends in extent

Average current trend in quantity

Unknown Unknown
EU28 EU28+

Trends in quality

Average current trend in quality

Unknown Unknown
EU28 EU28+

Conservation and management needs

Beneficial management measures include the regulation of activities such as coastal developments and hard coastal defence structures that can have a direct impact by reducing the area of this habitat, as well as indirect effects by altering sediment movement and the wave exposure regime. Water quality improvement programmes to reduce the risk of toxic contamination and control, including restrictions on intertidal fisheries which affect the associated communities can also benefit this habitat.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • Measures related to spatial planning
    • Other marine-related measures
    • Establish protected areas/sites
  • Measures related to hunting, taking and fishing and species management
    • Regulation/Management of fishery in marine and brackish systems
  • Measures related to urban areas, industry, energy and transport
    • Urban and industrial waste management


For each habitat a distribution map was produced from a wide variety of sources indicating known and potential occurrences of the habitat in 10x10 km grids within Europe. Occurrences in grid cells were given in two classes: actual distribution from relatively reliable sources (surveys, expert knowledge), and potential distribution based on models or less reliable indicators. Please download the fact sheet to see the map.

Geographic occurrence and trends

Seas Present or presence uncertain Current area of habitat (Km2) Recent trend in quantity (last 50 years) Recent trend in quality (last 50 years)
Bay of Biscay and the Iberian Coast Present Unknown Unknown Unknown
Celtic Seas
Greater North Sea

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 928,083 457 Unknown EOO and AOO have been calculated on the available data. Although this data set is known to be incomplete the figures exceed the thresholds for threatened status.
EU28+ >457 Unknown EOO and AOO have been calculated on the available data. Although this data set is known to be incomplete the figures exceed the thresholds for threatened status.
AOO = the area occupied by a habitat measured in number of 10x10 km grid cells.
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).

Characteristic species

The full list of characteristic species and genus are available above from the Summary. The species available in the EUNIS database are shown here.
Invertebrates Arenicola marina
Invertebrates Cerastoderma edule
Invertebrates Eteone longa
Invertebrates Hydrobia ulvae
Invertebrates Macoma balthica
Invertebrates Pygospio elegans
Invertebrates Scoloplos armiger
Species scientific name English common name Species group
Arenicola marina Invertebrates
Cerastoderma edule Invertebrates
Eteone longa Invertebrates
Hydrobia ulvae Invertebrates
Macoma balthica Invertebrates
Pygospio elegans Invertebrates
Scoloplos armiger Invertebrates

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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