Red List habitat classification > RL - Marine habitats > RLMED - Mediterranean > MEDA5.28 Faunal communities of sheltered Mediterranean infralittoral muddy sands

Faunal communities of sheltered Mediterranean infralittoral muddy sands

Quick facts

Red List habitat type code MEDA5.28
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 habitat is situated in sheltered environments, such as embayments, with low hydrodynamic regime, and thus in stable sedimentary systems, at depths between 1-15 m. The substrate consists of a muddy-sandy sediment where the sand fraction is usually composed by mollusc shells. Organic matter and silt-clay contents are the primary driving factors determining species composition. The very variable environmental conditions of these shallow environments in terms of salinity and water temperature determine that these habitats are colonized by euryhaline and eurytherm organisms.

This habitat can be naturally colonized by seaweeds or seagrasses. When seaweeds and seagrasses are absent, polychaetes dominate the invertebrate assemblages, mainly Neanthes caudata, Pseudomastus deltaicus, Notomastus latericeus, Ampharete finmarchica, Mediomastus fragilis, Aonides oxycephala and Heteromastus filiformis together with some crustaceans (Ampelisca brevicornis and Leucothoe incisa). The phoronid Phoronis psammophila is also very abundant. The bivalves Thracia papyracea and Cerastoderma glaucum dominate amongst filter-feeding invertebrates although the presence of Loripes lacteus is also frequent. Holothurians and gastropods Cyclope neritea and Nassarius reticulatus are common deposit-feeders, sliding on the substrate. The presence of sensitive species such as the mollusc Pinna nobilis is not very frequent but it can be occasionally observed. The eel Anguilla anguilla, the Sea Bass Dicentrarchus labrax, the gobids Gobius spp. and soles (Solea spp.) are amongst the most common fishes. When macroalgal species are present, Acetabularia calyculus, Ulva spp. and Cladophora spp. are the most abundant. The main seagrasses are Zostera noltii and Cymodocea nodosa.

Five different sub-habitats have been described for muddy sands habitat, with different dominant species and under slightly different conditions. These are the sub-habitat with Caulerpa prolifera on sheltered superficial muddy sands; and the sub-habitat with Pestarella (=Callianassa) thyrrena and Kellia sp. where the silt-clay fraction is >5% and the organic matter content reaches moderate to high values. There is a sub-habitat associated to freshwater discharge with Cerastoderma glaucum and Cyathura carinata in compact sediments which is characteristic of organically polluted environments in brackish waters; aub-habitat with Loripes lacteus and Ruditapes species in muddy sands on bays, estuaries, coastal lagoons and other sheltered environments, always at shallow zones that are highly influenced by seawater; and a sub-habitat of hydrothermal oozes with Cyclope neritea and nematodes which is only present in shallow waters (< 10m) with high sulfide concentrations, high sediment temperatures and high salinities. 

Indicators of quality:                                                                                                                   

Most of the species included in the habitat description are bioindicators of environmental quality. The majority of bivalves are very sensitive to eutrophication, and more tolerant and opportunistic species tend to dominate with increasing eutrophication. Changes in abundance and richness of fauna composition are good indicators of trends in habitat quality. Ruditapes decussatus has been proposed as a pollution bioindicator in areas where mussels are not available. The accumulation of pollutants in Ruditapes’ tissues has been used to assess environmental quality.

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

Threat status

Synthesis of Red List assessment

This is a relatively poorly studied habitat type and limited information exists regarding its distribution and habitat quantity across the Mediterranean Sea. Its wide distribution combined with the dominance by certain opportunistic and tolerant species, despite a slight decrease on habitat quality, seems to indicate the habitat could qualify for Least Concern under Criterion B. However given that the habitat has not been studied in enough detail in the past and that the territorial data does not provide information for most Mediterranean countries, the assessment of this habitat is assessed Data Deficient for both EU 28 and EU 28+
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
    • Marine and Freshwater Aquaculture
    • Professional active fishing
    • Benthic or demersal trawling
    • Benthic dredging
  • Pollution
    • Diffuse pollution to surface waters via storm overflows or urban run-off
    • Diffuse pollution to surface waters due to household sewage and waste waters
    • Nutrient enrichment (N, P, organic matter)
  • Natural System modifications
    • Dredging/ Removal of limnic sediments

Habitat restoration potential


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

There are no specific conservation actions currently in place for this habitat. The broad distribution of this habitat makes it likely that it occurs in protected areas, however detailed information is missing. A wide survey to assess the distribution of this habitat is needed in order to better evaluate its conservation and management. The designation of reference sites for long monitoring trends and the continuation of those monitoring schemes already in place will assist to examine the trends in this habitat.
Improving spatial and strategic planning of human activities, in particular to promote the wiser use of habitats where there are competing demands (e.g. fishing), and the reduction of coastal pollution and eutrophication and improvement of water quality are necessary to ensure the good conservation status of this habitat in the Mediterranean.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
    • Restoring coastal areas
  • 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 special resouce use
    • Regulating/Managing exploitation of natural resources on sea


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)
Aegian-Levantine Sea Present Unknown Unknown Unknown
Adriatic Sea
Ionian Sea and the Central Mediterranean Sea
Western Mediterranean 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 >50000 >50 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+ >50 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

Not available

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
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