Red List habitat classification > RL - Marine habitats > RLBLS - Black Sea > BLSA4.26 Marmara coralligenous communities moderately exposed circalittoral rock

Marmara coralligenous communities moderately exposed circalittoral rock

Quick facts

Red List habitat type code BLSA4.26
Threat status
Europe Data Deficient
EU n/a
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


Coralligenous habitats are hard bottoms of biogenic origin mainly produced by the accumulation of calcareous encrusting algae growing in dim light conditions. Although more widespread in the circalittoral zone, they can also develop in the infralittoral zone, provided that light is dim enough to allow growth of the coralline algae that produce the build-up; therefore, infralittoral coralligenous concretions always develop in almost vertical walls, deep channels, or overhangs, and occupy reduced surfaces. Coralligenous bioconcretions are always very complex in structure allowing the development of several kinds of communities including those dominated by living algae (on the upper part of the concretions), suspension feeders (upper and lower part of the concretions, wall cavities, and overhangs of the build-up), borers (inside the concretions), and even soft-bottom fauna (in the sediment deposited in cavities and holes). This is a highly variable habitat that can be subdivided into different sub-habitats.

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), including 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. Pollution has a severe impact on coralligenous outcrops where coralline algae are substituted first by Mesophyllum alternanas and latterly by Peyssonnelia rosa-marina. High water turbidity decreases diversity, especially of Bryozoans, Crustaceans and Echinoderms. However the amount of bioeroders increases, i.e. Sipunculids and boring sponges (Cliona), along with more generalist species. Mechanical disturbance and breaks of the bioconstruction with increases of turbidity and sedimentation can also be observed. Fishing can affect the abundance of certain target species  and high sedimentation rates result in overgrowth and invasion by exotic algae, altering assemblage composition.

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

Threat status

Synthesis of Red List assessment

Detailed information on the abundance and extent of this habitat is lacking. Information on the quantity and quality of this habitat including historical or recent trends is unknown. For the purposes of Red List assessment this habitat is considered to be Data Deficient.
Red List Category Red List Criteria
n/a -
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
    • Fishing and harvesting aquatic resources
    • Professional passive fishing
    • Professional active fishing
    • Benthic or demersal trawling
  • Pollution
    • Marine water pollution
  • Invasive, other problematic species and genes
    • Invasive non-native species
  • Climate change
    • Changes in abiotic conditions
    • Temperature changes (e.g. rise of temperature & extremes)
    • Changes in biotic conditions
    • Decline or extinction of species

Habitat restoration potential

There is insufficient data and knowledge of this habitat to assess its capacity to recover

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 is not addressed by any legislation or management aimed at its conservation. Direct engagement of scientists and conservationists in the planning of the management process, analysis of social and economic costs and benefits of different management options, and involvement of diverse stakeholders will be essential to successful implementation of conservation actions.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
    • Restoring coastal areas
  • Measures related to marine habitats
    • Restoring marine habitats
  • Measures related to spatial planning
    • Establish protected areas/sites
    • Establishing wilderness areas/allowing succession
    • Legal protection of habitats and species
  • Measures related to urban areas, industry, energy and transport
    • Urban and industrial waste management
    • Specific management of traffic and energy transport systems
    • Managing marine traffic
  • 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)
Sea of Marmara Present Unknown Unknown Unknown

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 This habitat is only present in the Sea of Marmara therefore it does not occur in the EU28
EU28+ Unknown Unknown This habitat is only present in the Sea of Marmara therefore it does not occur in the EU28
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
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