Page 18 - Bioconstructions_2018

78 Gianmarco Ingrosso et al.

The vermetid reef or “trottoir à vermets” (according to Molinier and
Picard, 1953)isa biogenic formationbordering the rocky shores at the tide
level. They have very different morphologies (Antoniolietal.,1999), but
on the most developed vermetid reef platforms an outer and an inner margin
canbeidentified. Theouter marginisthemostbiologicallyactiveportionof
the platform expanding seaward and it is composed of a rich layer of
Dendropoma shells and Neogoniolithon brassica-florida (Harvey) Setchell & L.R.
Mason encrusting thalli. The inner margin,instead,isless dense of Dendropoma
individuals and it is subjected to emersion during low tide. Between the two
margins, shallow depressions—the cuvettes (Molinier and Picard, 1953; P ere `s
and Picard, 1952)—can be found, which usually hold water during low
tide and calm sea and are covered by perennial canopy-forming brown algae
and encrusting organisms. Below the outer margin, the vermetid reef is usually
fringed by a characteristic upper subtidalbeltmadebythe canopy-forming alga
Cystoseira amentacea var. stricta Montagne. Dendropoma snails and N. brassica-
florida encrustations can be supported in the process of bioconstruction by other
intertidal organisms, namely, the foraminiferan Miniacina miniacea (Pallas,
1766), the coralline algae Lithophyllum incrustans Philippi, L. byssoides and
Neogoniolithon mamillosum (Hauck) Setchell & L.R. Mason, by some encrusting
bryozoans, and the solitary vermetid Vermetus triquetrus Bivona-Bernardi, 1832
(Safriel, 1975). The bioconstruction is also subjected to strong bioerosion from
a rich group of boring organisms such as sponges, bivalves and sipunculid
worms (Bressan et al., 2001).
In Italy (Fig. 4B), most of the vermetid reefs are in northern Sicily,
between Milazzo Cape and the Egadi Islands (Chemello, 2009; Milazzo
et al., 2017). Some concretions are also reported in southeastern Sicily
between Catania and Syracuse, and on the Pelagian, Aeolian and Ustica
Islands (Chemello, 2009). To date, information on vermetid bioconcretions
in the rest of Italy is scarce: small vermetid ledges are reported at Ischia Island,
in the Gulf of Naples (Scuderi et al., 1998; Soppelsa et al., 2007) and on the
NE coast of Sardinia (Schiaparelli et al., 2003), likely representing the north-
ernmost records of this vermetid formation. In the south, some records also
exist for the Apulia and Calabria coasts (see Chemello and Silenzi, 2011),
while in the Campania region, reef formations are only present along a por-
tion of the coast around the Licosa islet and also on some close submerged
old walls (Donnarumma et al., 2018).

2.2.6 Sabellariid Reefs
Two polychaete species, Sabellaria alveolata (Linnaeus, 1767) and Sabellaria spi-
nulosa (Leuckart, 1849), family Sabellariidae are reported for the Mediterranean