Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA5.53 Seagrass beds on Atlantic infralittoral sand (non-Macaronesian)

Seagrass beds on Atlantic infralittoral sand (non-Macaronesian)

Quick facts

Red List habitat type code NEAA5.53
Threat status
Europe Critically Endangered
EU Critically Endangered
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)

Summary

This habitat type covers beds of submerged marine angiosperms in the genera Zostera, Ruppia, and Cymodocea, adjacent to mainland coasts of the North East Atlantic region. The Iberian coast is a transitional zone where Zostera dominated seagrass beds reach their southern limit and Cymodocea dominated seagrass beds reach their northern and western limits. Ruppia beds are restricted to brackish environments, where Zostera may be interspersed. Seagrass beds play an important role in the trophic status of marine and estuarine waters, acting in sediment stabilization as well as an important conduit or sink for nutrients and consequently some examples of Zostera marina beds have markedly anoxic sediments associated with them.  It is a spawning area and it harbours increased densities of juvenile and medium sized fish species.

This habitat occurs in shallow sublittoral sediments, generally in sheltered embayments, marine inlets, estuaries and lagoons, with weak tidal currents and under conditoins of low, variable and full salinity. Whilst generally found on muds and muddy sands, particularly marine examples of Zostera communities may also occur in coarser sediments. Whilst the seagrass may be considered an epibiotic overlay of established sedimentary communities it is likely that its presence will modify the community offering living space and feeding ground for epibionts and phytal specialists. For example, Zostera beds in the south-west of Britain may contain conspicuous and distinctive assemblages of Lusitanian fauna such as Laomedea angulata, Hippocampus spp. and Stauromedusae. These subtidal beds of Zostera contain the specific perennial variant of Zostera marina. Cymodocea nodosa forms large and dense patches with green leaves that can reach 100 cm long and 8 mm wide in well shorted fine sands or on superficial muddy sands in sheltered waters and depths of 1-30 meters. Frequently it is mixed with other habitat forming phanerogams Zostera noltei (formerly known as Z.noltii or Z.nana) and Zostera marina on muddy sands rich in organic nutrients. Shallow meadows of Cymodocea and Zostera are usually found in sheltered bays close to harbours or in areas subject to human impact.

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.

The overall quality and continued occurrence of this habitat is, largely dependent on the presence of Zostera marina, which creates the biogenic structural complexity on which the characteristic associated communities depend. The density and the maintenance of a viable population of this species is a key indicator of habitat quality, together with the visual evidence of presence or absence of physical damage. Seasonal and annual variations in shoot densities and canopy height can be used to evaluate habitat quality as well as acting as a proxy measure of habitat complexity and refuge capability. The vertical depth limit of submerged seagrass is used in several countries as a Water Framework Directive parameter for assessing ecological status. Other countries use area indices and/or density indices. Seagrass tissue nutrients have also been used as indicators of environmental change in these important ecosystems.

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 region, as it is present in locations as widely separated as the Atlantic coast of Portugal, the Isles of Scilly in the UK, and the Channel coast of France. There was a substantial reduction in the quantity and quality in the 1930s, which resulted in 100% loss in the Netherlands and most likely the same in Germany. In Denmark the decline between 1901 and 2000 is estimated to have been 92%. There have been some increases in recent years but this habitat has not recovered to its previous extent. Because of the substantial historical loss and continuing declines in this habitat it has been assessed as Critically Endangered for both the EU 28 and EU 28+.
EU
Red List Category Red List Criteria
Critically Endangered A3, C/D3
Europe
Red List Category Red List Criteria
Critically Endangered A3, C/D3

Confidence in the assessment

medium
Red List of habitat categories and criteria descriptions

Pressures and threats

  • Urbanisation, residential and commercial development
    • Urbanised areas, human habitation
  • Human intrusions and disturbances
    • Outdoor sports and leisure activities, recreational activities
    • Motorized nautical sports
    • Other human intrusions and disturbances
    • Shallow surface abrasion/ Mechanical damage to seabed surface
  • Pollution
    • Nutrient enrichment (N, P, organic matter)

Habitat restoration potential

Recovery requires the removal of threats in the first instance. Recoverability rates can vary with shelter, light levels, depth and substratum but also depends on scale of damage and whether there have been changes in the environmental conditions (e.g. water flow, substrate type). Regeneration from root systems is slow and recovery of entire beds, with characteristic structure and associated species will take much longer than re-establishment of the seagrass species. Anchoring rhizome fragments appears to be more successful than using seeds. Transplantation experiments have had limited success to date although recent analysis of restoration projects suggests the successful regrowth appears to required a minimum threshold of reintroduced introduced individuals so a critical mass is important. Recovery also appears to be more likely when transplantation is close to donor beds. Partial recovery is only likely to occur after about 10 years and full recovery may take over 25 years, or never occur.

Trends in extent

Average current trend in quantity

Decreasing Decreasing
EU28 EU28+

Trends in quality

Average current trend in quality

Decreasing Decreasing
EU28 EU28+

Conservation and management needs

The protection of this habitat is often incorporated into to legislation aimed at protection of seagrass beds. These range from local by-laws and regulations, to cross border agreements as in the case of the Wadden Sea. Protected areas and management measures include the regulation of fisheries and, waste water treatment (to reduce the risk of eutrophication) and reduction in suspended sediments.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • Measures related to marine habitats
    • Restoring marine habitats
  • Measures related to hunting, taking and fishing and species management
    • Regulation/Management of fishery in marine and brackish systems

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 Decreasing Decreasing
Celtic Seas
Kattegat
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 1,026,236 115 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+ >115 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 Chorda filum
Algae Lamprothamnium papulosum
Fishes Gasterosteus aculeatus
Flowering Plants Cymodocea nodosa
Flowering Plants Ruppia cirrhosa
Flowering Plants Zannichellia palustris
Flowering Plants Zostera marina
Invertebrates Arenicola marina
Invertebrates Corophium volutator
Invertebrates Heterochaeta costata
Invertebrates Hydrobia ulvae
Invertebrates Laomedea angulata
Species scientific name English common name Species group
Chorda filum Algae
Lamprothamnium papulosum Algae
Gasterosteus aculeatus Fishes
Cymodocea nodosa Flowering Plants
Ruppia cirrhosa Flowering Plants
Zannichellia palustris Flowering Plants
Zostera marina Flowering Plants
Arenicola marina Invertebrates
Corophium volutator Invertebrates
Heterochaeta costata Invertebrates
Hydrobia ulvae Invertebrates
Laomedea angulata Invertebrates

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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Denmark
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