Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA2.31 Polychaete/ bivalve-dominated mid-estuarine Atlantic littoral mud

Polychaete/ bivalve-dominated mid-estuarine Atlantic littoral mud

Quick facts

Red List habitat type code NEAA2.31
Threat status
Europe Endangered
EU Endangered
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)

Summary

Mid-estuarine shores of fine sediment, mostly in the silt and clay fraction though sandy mud (mostly very fine and fine sand) can also be a component of the substrate. Littoral mud typically forms extensive 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. Most mid-estuarine muddy shores are subject to some freshwater influence, though at some locations more or less fully marine conditions may prevail. This habitat is mainly found along mid-estuarine shores and supports rich communities characterised by polychaetes, bivalves and oligochaetes. The mid-estuarine communities may also be present in sheltered inlets, straits and embayments which are not part of major estuarine systems, though there is usually some freshwater influence.

Indicators of quality:

Many indicators of quality have been used for this habitat with particular parameters 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. Indicators of quality of this habitat are frequently linked to those for the whole estuarine environment and therefore include morphological and physical characteristics, carrying capacity and water quality parameters. For the mudflat itself benthic indices, contaminant levels and productivity are some of the frequently used measures of quality.

Indices developed to assess the ecological status of coastal waters, including estuaries, according to the Water Framework Directive, include physical indicators, water quality indicators and measures of benthic diversity, species richness and abundance. The latter group, which is particularly relevant to benthic habitats, includes a Benthic Quality Index, an Infaunal Trophic Index, a Marine Biotic index based on ecological groups, and the Benthic Opportunistic Polychaetes/Amphipods index.

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

Threat status

Synthesis of Red List assessment

The majority of this habtiat in the North East Atlantic regional sea is hosted by the EU 28 countries. Historically, estuarine mudflats have suffered considerable declines in extent as a result of human activity. Whilst this no longer takes place on the scale practiced several centuries ago, piecemeal loss of areas of estuarine mudflat continues to occur. Declines in abiotic and biotic quality have also taken place, for example as a result of the discharge of industrial effluents and nutrient enrichment due to run-off from surrounding land, and this remains an issue in some estuaries.
Because of the very substantial historical loss in quantity of this habitat, expert opinion is that this habitat should be assessed as Endangered for both the EU 28 and EU 28+.
EU
Red List Category Red List Criteria
Endangered A3
Europe
Red List Category Red List Criteria
Endangered A3

Confidence in the assessment

medium
Red List of habitat categories and criteria descriptions

Pressures and threats

  • Urbanisation, residential and commercial development
    • Discharges
    • Disposal of industrial waste
  • Biological resource use other than agriculture & forestry
    • Fishing and harvesting aquatic resources
    • Professional active fishing
    • Leisure fishing
    • Bait digging / Collection
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Modification of hydrographic functioning, general
    • Other ecosystem modifications
    • Reduction or loss of specific habitat features
    • Anthropogenic reduction of habitat connectivity
  • Climate change
    • Changes in abiotic conditions
    • Changes in biotic conditions

Habitat restoration potential

The establishment and maintenance of mudflats is closely linked to physical processes. If the "natural" hydrographic regime no longer exists recovery is unlikely. Where the underlying conditions are suitable there can be rapid recovery as demonstrated where dykes have been removed and in managed retreat projects. The determination of effort required is therefore contingent on the retention of a residual state that will allow reinstatement of the habitat.

Trends in extent

Average current trend in quantity

Stable Stable
EU28 EU28+

Trends in quality

Average current trend in quality

Stable Stable
EU28 EU28+

Conservation and management needs

Conservation and management schemes to benefit this habitat have been applied at a number of scales ranging from whole estuary systems to small areas within an estuary. They include the removal of dykes, and managed retreat to reclaim areas of mudflat drained for agricultural land, and reconnecting sediment supplies to mudflats. Water quality improvement programmes have been introduced to reduce the risk of toxic contamination and of nutrient inputs leading to eutrophication
Spatial management including zoning of activities as part of Integrated Coastal Zone Management Schemes and Marine Protected Areas and controls of discharges throughout the watershed, are also beneficial as they facilitate management of the entire estuary complex.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
    • Restoring/Improving the hydrological regime
  • Measures related to spatial planning
    • 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

Distribution

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 Stable Stable
Celtic Seas
Greater North Sea
Kattegat

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 630,325 201 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+ >201 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.
Algae Ulva lactuca
Invertebrates Arenicola marina
Invertebrates Capitella capitata
Invertebrates Cerastoderma edule
Invertebrates Corophium volutator
Invertebrates Crangon crangon
Invertebrates Eteone longa
Invertebrates Hydrobia ulvae
Invertebrates Macoma balthica
Invertebrates Mya arenaria
Invertebrates Mytilus edulis
Invertebrates Polydora cornuta
Invertebrates Pygospio elegans
Invertebrates Tubificoides benedii
Species scientific name English common name Species group
Ulva lactuca Algae
Arenicola marina Invertebrates
Capitella capitata Invertebrates
Cerastoderma edule Invertebrates
Corophium volutator Invertebrates
Crangon crangon Invertebrates
Eteone longa Invertebrates
Hydrobia ulvae Invertebrates
Macoma balthica Invertebrates
Mya arenaria Invertebrates
Mytilus edulis Invertebrates
Polydora cornuta Invertebrates
Pygospio elegans Invertebrates
Tubificoides benedii Invertebrates

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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1050 Copenhagen K
Denmark
Phone: +45 3336 7100