Communities of moderately exposed Mediterranean lower mediolittoral rock

This is an intertidal habitat which occurs on rocky and boulder shores, just above the mid tide levels. It is present in locations that are moderately exposed to wave action and may be subject to strong or moderate currents. The associated biotopes are dominated by the red alga Corallina elongata in the most exposed conditions, and Gelidium pusillum and G.crinale where there are elevated nutrient levels. In some situation the habitat is almost devoid of erect macroalgae, grazed by Patella spp., and characterised by crusts of the Lithophyllum spp. In the inner parts of bays or close to the beaches, other red algae species (mainly Laurencia pyramidalis, Laurencia glandulifera, Palisada perforata and Osmundea verlaquei) but also Hypnea musciformis and Ceramium ciliatum may dominate. There is also an associated biotope dominated by Palisada tenerrima which forms dense, almost monospecific turfs that completely cover the rock in the central and southern part of the Mediterranean and a dominance by Haliptilon virgatum in several Mediterranean regions characterised by warm waters and relatively high light irradiances.

Indicators of quality
An increase in the abundance of many organisms: green algae, Gelidium spp., Scytosiphon lomentaria, Petalonia fascia, Mytilus galloprovincialis and, occasionally, Corallina elongata can be indicators of poor quality. Conversely species of the genus Osmundea, Laurencia and Palisada seem to avoid polluted waters. Their absence may therefore also be a potential indicator of changes in quality of the habitat. 

A "Quality of Rocky Bottoms index" (CFR by its Spanish acronym) used in Spanish Atlantic waters for the assessment of macroalgae communities on rocky shores may have some potentially application in assessment of quality of this habitat.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats