Marine Atlantic littoral mud with associated communities
Quick facts
Red List habitat type | code NEAA2.33 |
---|---|
Threat status | |
Europe | Endangered |
EU | Endangered |
Relation to |
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Source | European Red List habitat factsheet |
European Red List of habitats reports | |
European Red List of habitats (Excel table) |
Summary
Intertidal flats along the open coast and near tidal inlets consist mainly of medium to coarse sand. In sheltered areas and near tidal watersheds the sediment is finer and may entirely consist of fine mud. This habitat type can occur in patches or grade into intertidal flats dominated by other soft sediments. Similarly whilst intertidal mudflats in large bays may be considered fully marine, there can still be a river influence and therefore reduced salinities across some of the habitat depending on location and outflow levels. Mudflats in fully marine waters, periodically falling dry at low tide, subject to great amplitudes of temperature, light and salinity, and may be subject to high eutrophication and input of organic substances from rivers and the open sea. Free of vegetation, of higher plants and of macroalgae but mostly covered by thin layers of diatoms and bluegreen algae. In some situations they may be colonised by seagrass. Sediments consist mainly of fine particles, mostly in the silt and clay fraction (particle size less than 0.063 mm in diameter), though sandy mud may contain up to 80% sand (mostly very fine and fine sand), often with a high organic content. Little oxygen penetrates these cohesive sediments, and an anoxic layer is often present within millimetres of the sediment surface. Intertidal mudflats in fully marine open sea (coast) only develop under macrotidal conditions such as those found in the German Bight and Mont Saint Michel, France. Also they form part of a habitat complex on a landscape scale within bays, barrier systems and estuaries. The intertidal mudflats support communities characterised by polychaetes, bivalves, snails and oligochaetes. The species composition of the macrobenthic communities are likely to show zoning from high to lower intertidal levels. In the Dutch, German and Danish Waddens Sea, for example, the high coastal tidal flats are generally characterised by a low number of species with numerous small individuals that are deposit feeders. Typical examples are Corophium volutator and Hydrobia ulvae. Large-sized species become numerous below mean tide levels and below this the biomass is dominated by the deposit feeding Arenicola marina. At mudflats well below mean low water, large filter-feeding bivalves such as Cerastoderma edule, Mya arenaria, Mytilus edulis and Ensis directus make up a significant proportion of the total biomass.
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.
Threat status
Synthesis of Red List assessment
Also relevant is the associated decline in the quality of habitat complexes (bays, barrier systems and estuaries) which include intertidal mudflats, but this is difficult to quantify. Localised reductions in quality are still taking place, for example in industrialised areas where the intertidal mudflat habitat may be degraded due to toxic contamination and elsewhere if run-off from the land leads to eutrophication. Invasive species such as the Pacific Oyster and razor clam have also modified the composition of the associated benthic communities, particularly in parts of the Wadden Sea. De-polderisation or managed retreat schemes (e.g. through the partial or total removal of dykes) have been undertaken on a small scale to try and restore areas of intertidal mudflat habitat. Overall the current situation is probably stable and with scope to improve with appropriate conservation and preservation measures. Nevertheless, because of the significant historical reduction in extent of this habitat it is assessed as being 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
Pressures and threats
- Biological resource use other than agriculture & forestry
- Marine and Freshwater Aquaculture
- Fishing and harvesting aquatic resources
- Hunting, fishing or collecting activities not referred to above
- Pollution
- Pollution to surface waters (limnic, terrestrial, marine & brackish)
- Pollution to surface waters by industrial plants
- Pollution to surface waters by storm overflows
- Diffuse pollution to surface waters via storm overflows or urban run-off
- Diffuse pollution to surface waters due to agricultural and forestry activities
- Input of contaminants (synthetic substances, non-synthetic substances, radionuclides) - diffuse sources, point sources, acute events
- Marine water pollution
- Oil spills in the sea
- Invasive, other problematic species and genes
- Invasive non-native species
- Natural System modifications
- Human induced changes in hydraulic conditions
- Landfill, land reclamation and drying out, general
- Polderisation
- Reclamation of land from sea, estuary or marsh
- Removal of sediments (mud...)
- Estuarine and coastal dredging
- Dykes, embankments, artificial beaches, general
- Sea defense or coast protection works, tidal barrages
- Climate change
- Changes in abiotic conditions
- Water flow changes (limnic, tidal and oceanic)
- Wave exposure changes
- Sea-level changes
- Changes in biotic conditions
- Habitat shifting and alteration
Habitat restoration potential
The littoral mudflat habitat is naturally resilient and can recuperate well from isolated physical and chemical disturbances, although they have been considered to be very sensitive to oil pollution as the oil enters lower layers of the mudflats where lack of oxygen prevents decomposition of the oil. Once the habitat disappears, due to agricultural land reclaim, infrastructure development or saltmarsh growth, the process is generally irreversible although since the 1980s there have been some intertidal habitat creation or restoration schemes (de-polderisation or managed retreat).
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
The designation of protected areas and management schemes has led to the introduction of measures to protect or improve the quality of this habitat. The largest of these, agreed by the governments of the Netherlands, Germany and Denmark is the trilateral Wadden Sea Plan. Other management measures include the regulation of dredging, coastal developmet, aquaculture, hard coastal defence structures and the control of invasive species such as the cordgrass Spartina anglica and the Pacific oyster Crassostrea gigas.
List of conservation and management needs
- Measures related to agriculture and open habitats
- Other agriculture-related measures
- Measures related to wetland, freshwater and coastal habitats
- Other wetland related measures
- Restoring/Improving water quality
- Restoring/Improving the hydrological regime
- Restoring coastal areas
- Measures related to marine habitats
- Other marine-related measures
- Measures related to spatial planning
- Other marine-related measures
- Establish protected areas/sites
- Legal protection of habitats and species
- Manage landscape features
- 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
- Measures related to special resouce use
- Regulating/Managing exploitation of natural resources on sea
Distribution
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 |
Extent of Occurrence, Area of Occupancy and habitat area
Extent of Occurrence (EOO) (Km2) | Area of Occupancy (AOO) | Current estimated Total Area | Comment | |
---|---|---|---|---|
EU28 | 102,147 | 71 | 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+ | >71 | 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. |
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).
Characteristic species
Species scientific name | English common name | Species group |
---|---|---|
Abra tenuis | Invertebrates | |
Arenicola marina | Invertebrates | |
Capitella capitata | Invertebrates | |
Cerastoderma edule | Invertebrates | |
Corophium volutator | Invertebrates | |
Crangon crangon | Invertebrates | |
Ensis directus | Invertebrates | |
Eteone longa | Invertebrates | |
Gammarus locusta | Invertebrates | |
Heteromastus filiformis | Invertebrates | |
Hydrobia ulvae | Invertebrates | |
Lanice conchilega | Invertebrates | |
Macoma balthica | Invertebrates | |
Mya arenaria | Invertebrates | |
Mytilus edulis | Invertebrates | |
Nereis diversicolor | Invertebrates | |
Phyllodoce mucosa | Invertebrates | |
Pygospio elegans | Invertebrates | |
Retusa obtusa | Invertebrates | |
Scoloplos armiger | Invertebrates |