Red List habitat classification > RL - Marine habitats > RLMED - Mediterranean > MEDA5.6y Circalittoral biogenic habitats in the Mediterranean - corralligenous bioconcretions

Circalittoral biogenic habitats in the Mediterranean - corralligenous bioconcretions

Quick facts

Red List habitat type code MEDA5.6y
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 sometimes referred to as 'coral gardens' can be found on a variety of substrates and at depths ranging from 20 to 200 meters. The main characteristic is a relatively dense aggregation of colonies or individuals of one or more coral species but also coralline algae. For example, soft-bottom coral gardens may be dominated by solitary scleractinians and sea pens, whereas hard-bottom coral gardens are often dominated by gorgonians, and red or black corals. Red corals rarely occurs about 30m as they require reduced light levels.

Reef forming hard corals (e.g. Lophelia, Madrepora and Caryophylliidae), if present, occur only as small or scattered colonies and not as a dominating habitat component. The habitat can also include relatively large numbers of sponge species. Other commonly associated fauna include basket stars, brittle stars, crinoids, ascidians, molluscs, crustaceans and fish.

Indicators of quality:

Several indicators have been proposed to assess the health of coralligenous habitats based on the composition and abundance of species (biotic cover and conspicuous species richness), the percent cover of different benthic assemblages (encrusting calcified Rhodophyta, non-calcified encrusting algae and fauna, turf forming algae, and sediment), boring species marks, percent cover of each species and the percentage of necrosis, bryozoa percent cover, sludge percent cover and the builder species percent cover.

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

Threat status

Synthesis of Red List assessment

This habitat is present in all the Mediterranean sub-basins therefore the EOO exceeds the threshold for threatened status. The AOO suggest this habitat could be Vulnerable if there was evidence of continuing declines however this figure is believed to be an underestimate.
Infralittoral coralligenous habitats are known to be decreasing in quality and quanitity but there is a lack of quanitative data on trends for circalittoral corralligenous concretions. 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

  • Biological resource use other than agriculture & forestry
    • Professional passive fishing
    • Demersal longlining
    • Professional active fishing
    • Benthic or demersal trawling
    • Benthic dredging
    • Removal for collection purposes
  • Pollution
    • Marine water pollution
  • Invasive, other problematic species and genes
    • Invasive non-native species
  • Natural System modifications
    • Reduction or loss of specific habitat features
    • Applied (industrial) destructive research
  • Climate change
    • Changes in abiotic conditions
    • Changes in biotic conditions

Habitat restoration potential

As the most abundant and structuring species of coralligenous habitats are long-lived and slow growing species with limited recruitment rates, and native and non-native species can rapidily colonise the structures, local recovery can be difficult and extremely slow.
Some site specific studies for selected species (Corallium rubrum, Gorgonacea) have provide insights on the potential to recover after fishing activities or due to natural disasters (storms) and invasion of non-native species but these results cannot be generalized to other sites or to other species.

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

The designation of Marine Protected Areas and fisheries reserves are needed conservation of this habitat. Specific measures aimed at protecting the coralligenous environment include the prohibition of trawling in areas with coralligenous outcrops and their vicinity and management of traditional and recreational fisheries to prevent stock depletion of target fish and crustaceans. Quotas, closed areas and minimum sizes for red coral or any other commercialized anthozoan. Where this habitat occurs at diving depths, the regulation on the number of visitors per site/day as well as a detailed training on the diving behavior is needed to avoid incidental damage to this habitat.

List of conservation and management needs

  • Measures related to marine habitats
    • Other marine-related measures
  • Measures related to spatial planning
    • Establish protected areas/sites
    • Establishing wilderness areas/allowing succession
    • 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
  • 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)
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 >50,000 >38 163 This habitat is present in all the Mediterranean sub-basins. AOO figures recognised as an underestimate.
EU28+ >43 178 This habitat is present in all the Mediterranean sub-basins. AOO figures are known to be an underestimate.
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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