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

Infralittoral biogenic habitats in the Mediterranean - corralligenous bioconcretions

Quick facts

Red List habitat type code MEDA5.6x
Threat status
Europe Data Deficient
EU Near Threatened
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)

Summary

Coralligenous habitats are hard bottoms of biogenic origin mainly produced by the accumulation of calcareous encrusting algae growing in dim light conditions. Although more extended 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 with different dominant species. For example coralligenous outcrops dominated;by Halimeda tuna and Mesophyllum spp. usually between 15 and 45 meters depth; by Peyssonnelia rosa-marina and other Peyssonneliaceae and Flabellia petiolata, in places with high sedimentation rates; on walls with Eunicella cavolini, in places with strong currents, between 15 and 40 meters depth; by Alcyonium acaule, in relatively shallow waters (15 to 45 meters depth) subjected to strong currents; and by Eunicella verrucosa, in places with high sedimentation rates.

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 is a widespread habitat throughout the Mediterranean Sea. Country information and literature show an ongoing decline in quality due to warming, fishing activities, water quality and invasive species. There are no evidences of a general decline in quantity in the country information, however, taking into account the impacts this habitat is submitted to and further evidence and decreases decribed in the literature, it must be considered that quantity decreases have happened. Both quality and quantity decreases are expected to continue in the future. Taking into consideration the decline in habitat extent and quality the habitat is classified as Near Threatened for EU 28 and Data Deficient for EU 28+.
Given the future climate change scenarios for the Mediterranean, the decline of some of the structural species and the ongoing impacts, it is suggested a revision of the assessment in 5-10 years time to provide more quantitative evidences as the habitat is close to Vulnerable status criteria.
EU
Red List Category Red List Criteria
Near Threatened A1, A2a, A2b, C/D1
Europe
Red List Category Red List Criteria
Data Deficient -

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
  • Biological resource use other than agriculture & forestry
    • Fishing and harvesting aquatic resources
    • Professional passive fishing
    • Professional active fishing
  • 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)
    • pH-changes
    • Habitat shifting and alteration
    • Decline or extinction of species

Habitat restoration potential

The effect of disturbances in coralligenous assemblages is poorly understood, and there are no data at all on the capacity of this environment to recover (with the exception of fish stocks after fishing ban). However, 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 recover can be difficult and extremely slow.

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

Besides the designation of protected areas and fisheries reserves, specific measures aimed at protecting the coralligenous environment might include the following: Improvements in water quality, 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.

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 spatial planning
    • Establish protected areas/sites
    • Legal protection of habitats and species

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)
Adriatic Sea Present 147,102 Decreasing Decreasing
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 2,483,265 1,913 137,180 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.
EU28+ 2,100 147,102 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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