Red List habitat classification > RL - Marine habitats > RLMED - Mediterranean > MEDA2.7x Biogenic habitats of Mediterranean mediolittoral rock

Biogenic habitats of Mediterranean mediolittoral rock

Quick facts

Red List habitat type code MEDA2.7x
Threat status
Europe Vulnerable
EU Vulnerable
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


This habitat is formed by the biogenic, tridimensional, hard structures built by either the red algae Lithophyllum byssoides or the red algae Neogoniolithon brassica-florida associated with the gastropod Dendropoma cristatum (in the central Mediterranean) or D. petraeum. The rims of L. byssoides are generally found just above the mean sea level, in the mesolittoral zone, where waves break. They can reach more than one metre of vertical thickness. For this reason, the habitat is host to different assemblages from its upper portion, which is situated in the lower mediolittoral zone, to the lower, submerged one. The development of this type of habitat in specific areas of the Mediterranean depends on several climatic, hydrological and sedimentary conditions. It seems to develop better over calcareous rocks, on steep shores in areas with strong hydrodynamism and where the temperature of surface coastal waters is no lower than 14°C in the winter. Under these environmental conditions, the L. byssoides rims are more frequent in the northwestern Mediterranean, but they can also be found in Sicily and the Adriatic Sea. Mediterranean bioconcretions composed of N. brassica- florida and D. petraeum may grow for thousands of years forming huge structures of several metres wide.

These reefs are host to many species, which distribute differently over the bioconcretion depending on wave action and the position on the reef. In the seaward part of the reef, the reef crest, the concretion is made of shells of Dendropoma actively growing while Neogoniolithon cements the reef and triggers the vermetid settlement. Behind the reef crest, a shallow lagoon covered by photophilic algal communities develops. This part ends close to the shore, where Neogoniolithon and Dendropoma dominate again. Neogoniolithon-Dendropoma reefs better develop in southern Mediterranean areas although tiny reefs can be found across 40º N latitudes at their northern limit.

Indicators of quality:

The Lithophyllum byssoides rims are particularly vulnerable to physical impacts and trampling, and they seem to be very sensitive to environmental stresses related to water quality. Rims are very sensitive to the increase or decrease of the water level. The amount of dead L. byssoides thalli in the upper part of the reef can be used as a health indicator. Both reefs represent unique archives to reconstruct past Mediterranean climate and especially sea level oscillations.

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

Threat status

Synthesis of Red List assessment

The habitat type is assessed as Vulnerable both at the EU 28 and at the EU 28+ levels in view of its restricted Area of Occupancy (AOO) (less than 50) and the fact that it is experiencing a continuing decline in spatial extent and biotic quality as a result of water discharge, pollution, trampling and climate change. There is also considered likely to be a severe quality decline affecting 30% of the habitat in a period from the past 20 years to the future 30 years in the EU 28+.
Red List Category Red List Criteria
Vulnerable B2a,b
Red List Category Red List Criteria
Vulnerable B2a,b, C/D2

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Human intrusions and disturbances
    • Other human intrusions and disturbances
  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
  • Natural System modifications
    • Human induced changes in hydraulic conditions
  • Climate change
    • pH-changes
    • Sea-level changes

Habitat restoration potential

Since the ability of the components of this habitat to disperse is very limited and the habitat is largely affected by water acidification and sea level rise, recovery is likely to be over a long time scale. It is worthy to note that the growth of the main engineering species is very slow and therefore its recovery capacity very limited. The search for intervention activities that could also include transplantations of the three different species that inhabit this habitat type are needed.

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

There are no specific conservation actions in place for this habitat at the present time although more than 50% of the habitat is thought likely to be present within Mediterranean Marine Protected Areas (MPAs) and Natura 2000 sites. No reefs are protected in Cyprus, while Turkey protects less than 20% of their reefs. Regulation of coastal development and measures to minimise potential environmental threats, such as those associated with water quality and trampling would benefit this habitat. Better knowledge about this habitat is also needed to determine appropriate conservation measures.

List of conservation and management needs

  • Measures related to spatial planning
    • Other marine-related measures
    • Establish protected areas/sites
    • Legal protection of habitats and species


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 Decreasing Decreasing
Ionian Sea and the Central Mediterranean Sea
Western Mediterranean Sea
Adriatic 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 1,305,051 27 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+ 37 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
European Environment Agency (EEA)
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