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the archipelago, always with top covers corals concretions. The roughness of
above 60-80%, and sometimes above limestones also increases the settlement
100%. In Marettimo, below the belt C. of meroplanktonic larvae and formation
amentacea var. stricta, populations of C. of shelters occupied by a rich endolitic
Mediterranean and / or C. elegans are fauna.
sometimes present. The MPA includes the largest (about
The vermetid “trottoir” (or reef), is a 7,700 hectares) and best preserved
biogenic construction, due to sessile Posidonia oceanica meadow of the
gastropod Dendropoma petraeum, Mediterranean Sea. The Posidonia o.,
which is extremely abundant and with is a priority habitat and represents
a great amount of structure on the the most important biotic community
coastal strip of the three islands of the as it is abundant and well distributed
archipelago. within the Egadi Islands, especially
It develops close to the mean sea level on medium-fine sand, which is scarce
for an estimated length of more than in deep water. The upper limit of the
10 km along the coast, playing a vital meadow ranges between -2/-9 m, at
role for protection against coastline Favignana, and -12/-15 m at Marettimo.
erosion. The Astroides calycularis, is a In the Egadi archipelago the foliar
thermophilic madrepore colony species length of Posidonia o. can reach more
–which suffers regression phenomena in than 2 m and it grows up to -52 m of
many areas along the Mediterranean– depth. At lower depth and in coves,
stretches over the first infralittoral fringe scattered Posidonia patches alternated
just below the vermetid reef: extensive with biotic photophilic and rocky
colonies are mainly found along the seabed are frequently observed.
submerged cliff of the integral reserve Posidonia is considered the green lung of
(Zone A) and in shallow water caves of the Mediterranean Sea, playing different
Marettimo. roles crucial to the marine ecosystem.
Both Dendropoma petraeum and Astroides In addition, the Posidonia o. forms
calycularis are among the species in an area of vital nursery as it protects
jeopardy or at risk of extinction within the youth of hundreds of species of
the Mediterranean. organisms, produces oxygen, absorbs a
The carbonate coasts of Egadi Islands very considerable amount of CO2, and
are characterised by a superficial and helps to mitigate the coastal erosion
deep karst system, which represents through the formation of “banquette”
a typical landscape. A large number on beaches, that are produced by the
of caves and coastal tunnels as well as accumulation of dead leaves in the
the underwater karst system are part of winter.
many submerged and semi submerged Another important species,discontinuously
caves. The whole carbonate component distributed on the seabed of Egadi Islands
habitat extension to the sea is estimated is Lithophyllum byssoides, a calcareous
to be about 4,000 hectares. algae that can form large concretions
The low brightness of the seabed (“trottoirs”), currently steadily distributed
overhanging, in many cases favours in various areas of the Mediterranean
the development of sciafili and Sea, which hosts specific and rich wildlife
5EAI Energia, Ambiente e Innovazione 4/2015
