Red List habitat classification > RL - Marine habitats > RLMED - Mediterranean > MEDA5.52A Algal dominated communities in the Mediterranean circalittoral sediment

Algal dominated communities in the Mediterranean circalittoral sediment

Quick facts

Red List habitat type code MEDA5.52A
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)


Habitats formed in circalittoral sediments that usually have detritic components that allow erect macroalgae to grow over the seabed. The algal cover can be very variable, not always growing necessarily together with the maërl, and with a number of dominant species. They develop at low irradiances, usually between 5% and 0.5% of subsurface irradiance, at moderate to low hydrodynamism levels.

Several sub-habitats can be distinguished:

- Meadows of Osmundaria volubilis and Phyllophora crispa growing over detritic and gravel bottoms, between 50 and 90 meters depth. They can be very common in the central and North Western Mediterranean

- Kelp forests with Laminaria rodriguezii, below 70 meters depth and down to almost 100 meters depth from all the Mediterranean. This subhabitat can also grow shallower in special environmental conditions

- Kelp forests with Laminaria ochroleuca and Sacccorhiza polyschides, only in the Alboran Sea, northwestern coasts of Africa and the Strait of Messina, in places subjected to very strong currents.

- Beds of Halopteris filicina, between 55 and 100 meters depth.

- Gravel beds with Arthrocladia villosa and Sporochnus pedunculatus, between 30 and 50 meters depth.

- Gravel beds with Cystoseira spp.


Indicators of quality:                                                                                                                              

Habitat very variable according to several factors (nutrients, sedimentation, temperature, salinity, hydrodynamism) and to the main species dominating the assemblages. Some sub-habitats are rather constant through time (kelp habitats, Osmundaria volubilis) but others, like the subhabitat of Arthrocladia villosa and Sporochnus, are subjected to huge interannual variation in species composition and biomass.

Trends in abundance distribution and local species richness could be used as a proxy to examine quality overtime.The habitat can also change to non-native habitats dominated by two invasive species, Caulerpa cylindracea and C. taxifolia.


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

Threat status

Synthesis of Red List assessment

This is a very poorly studied habitat type and few reports exist regarding its distribution at a handful of locations. Moreover, data on quality or quantity is lacking and the territorial data does not provide information for most Mediterranean countries.
The habitat has a large EOO and AOO. There are some cases of reported declines but overall trends are unknown and cannot be quanitified. This habitat has therefore been assessed as Data Deficient for both the 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
    • Urbanised areas, human habitation
  • Biological resource use other than agriculture & forestry
    • Intensive fish farming, intensification
    • Suspension culture
    • Benthic or demersal trawling
    • Benthic dredging
  • Invasive, other problematic species and genes
    • Invasive non-native species
  • Climate change
    • Temperature changes (e.g. rise of temperature & extremes)

Habitat restoration potential

Unknown. There is no information regarding the capacity of these major macroalgal-dominated assemblages on coastal detritic bottoms to recover from certain impacts. Some parts of the life cycle are more sensitive to impacts and potential intraspecific competition.

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

This habitat might be included within the limits of some marine protected areas (e.g. Alboran Island). Additional actions needed, might include the monitoring of the extension, abundance distribution and local species richness over time to examine trends and better regulation in certain areas of fishing activities, particularly trawling.

List of conservation and management needs

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


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)
Adriatic Sea Present Unknown Unknown Unknown
Aegian-Levantine 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 1,658,911 279 49,637 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+ 624 61,180 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
European Environment Agency (EEA)
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1050 Copenhagen K
Phone: +45 3336 7100