Red List habitat classification > RL - Marine habitats > RLMED - Mediterranean > MEDA3.13 Photophilic communities with canopy-forming algae in Mediterranean infralittoral and upper circalittoral rock

Photophilic communities with canopy-forming algae in Mediterranean infralittoral and upper circalittoral rock

Quick facts

Red List habitat type code MEDA3.13
Threat status
Europe Data Deficient
EU Endangered
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


This habitat occurs on rocky bottoms and is characterised by communities macroalgae that form canopies. The structure includes bush-forming, turf forming algae, encrusting fauna and epiphytes. The coverage of the “bush” and turf strata is usually higher than in an assemblage dominated by canopy algae. Assemblages are also highly miniaturized (less than 20 cm high) and very rich in species (up to 110 species in a 400 cm2 area).

This habitat is present from the upper infalittoral zone (0 m) to the upper circalittoral zone. Assemblages are always algal-dominated, although some invertebrates can be common in the understory and growing as epiphytes. Species composition greatly differs according to the environmental conditions. Factors accounting for the variability on the assemblages include light availability, hydrodynamism, nutrient concentration in seawater, substrate, sedimentation, temperature, salinity, grazing intensity, predation, frequency of disturbances. High densities of sea urchins (Paracentrotus lividus) can graze the algae, producing structurally less complex assemblages and even barren areas. Grazing by other fish species (Sarpa salpa or the exotic Siganus rivulatusS. luridus) can modify the species composition.

Several  associated biotopes have been described and are distinguished according to the dominant species. They include; Corallina elongata on shallow exposed shores; the red algae Haliptilon virgatum, growing on well-lit, shallow exposed shores in central and southern shores, usually accompanied by Laurencia obtusa, Laurencia majuscula and Dictyota fasciola; Colpomenia sinuosa growing on shallow sheltered rocks in nutrient-rich environments; Cladophoropsis membranacea growing on extremely sheltered zones in bays and lagoons; and Arthrocladia villosa and Sporochnus pedunculatus on moderately lit lower infralittoral to upper circalittoral rock, in places with strong unidirectional currents.

Indicators of quality:                                                                                                                            

This habitat is very variable according to the degree of anthropogenic disturbance. Indicators of quality can be measured by examining trends. The first signs of decline imply substitution of species, a decrease on diversity, an increase on invasive exotic species, and an increase in opportunistic, fast-growing species like some UlvaCladophoraAcinetospora, or stress resistant like Corallina elongata or Lithophyllum incrustans. Mussels can also replace the dominant algae in shallow waters when the charge of particulate organic matter is very high.

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

Threat status

Synthesis of Red List assessment

Although territorial data was not provided for all countries, there is an overall consensus in the expert opinion that this habitat has declined in quantity and quality in the EU 28 in the past 50 years. There is a lack of quantitative data for countries outside the EU 28 to infer the situation for the EU 28+.
Expert opinion that there has been a 77% reduction in the quantity of this habitat. and a substantial reduction in quality . This habitat is therefore assessed as Endangered under Criteria A. Due to the lack of quantitative data for countries outside the EU 28, the habitat is assessed as Data Deficient at the EU 28+ level.
Red List Category Red List Criteria
Endangered A1, A2b
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
    • Suspension culture
    • Fishing and harvesting aquatic resources
    • Benthic or demersal trawling
  • Human intrusions and disturbances
    • Penetration/ Disturbance below surface of the seabed
  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
    • Marine water pollution
  • Invasive, other problematic species and genes
    • Invasive non-native species

Habitat restoration potential

Little information exist about the recovery potential of this habitat over a certain degree of deterioration. The low dispersal capacity of most Cystoseira species makes natural recovery unlikely, so artificial reforestation may be an extremely valuable solution for lost forest .
In the case of Sargassum canopy but also species like C. barbarta, C. compressa and C. foeniculacea, the presence of aericysts facilitates dispersion and the recovery of populations from distant areas.

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

Some of these canopy-forming algae habitats are in protected areas and several Natura 2000 sites (e.g. Scandola, Bouches de Bonifacio, Cerbères-Banyuls, Calanque and Port-Cros in France, Formentera- Espardell and Dragonera in Spain; Kimolos in Greece; St Peter´s Island and Maratea in Italy). The declaration of other MPAs and the effective management of the existing ones where dense Cystoseira and other large brown algae forests thrive could favour the conservation of this habitat and its recovery when the herbivore pressure is not too high. Nonetheless, the protection of existing forests formed by Cystoseira and other subhabitats of canopy forming communities should complement regular monitoring programs in order to highlight potential threats and early signs of regression. Restoration of this habitat in priority areas with re-forestation methods has been suggested as a potential solution to assist fragmented/lost forests to recover and stimulate natural restoration of lost populations assisted at the same time with other measures such as improving sewage treatment or limitation of excessive herbivory at specific sites. An ecosystem-based management applied to a network of MPAs with long-term monitoring programs and restoration actions, where necessary, is probably the best perspective for the preservation of this habitat in the Mediterranean Sea.

List of conservation and management needs

  • Measures related to marine habitats
    • Restoring marine habitats
  • Measures related to spatial planning
    • Establish protected areas/sites


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 60,808 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 2,011,255 765 > 60,808 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+ 1,032 > 60,808 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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