Photophilic communities with canopy-forming algae in Mediterranean infralittoral and upper circalittoral rock
|Red List habitat type||code MEDA3.13|
|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 rivulatus, S. 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 Ulva, Cladophora, Acinetospora, 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.
Synthesis of Red List assessment
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|
|Red List Category||Red List Criteria|
Confidence in the assessment
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 to surface waters (limnic, terrestrial, marine & brackish)
- Marine water pollution
- Invasive, other problematic species and genes
- Invasive non-native species
Habitat restoration potential
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
Trends in quality
Average current trend in quality
Conservation and management needs
List of conservation and management needs
- Measures related to marine habitats
- Restoring marine habitats
- Measures related to spatial planning
- Establish protected areas/sites
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)|
|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.|
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).