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80 Gianmarco Ingrosso et al.

creating a honeycomb-like structure, hence the name “honeycomb worms”
for these polychaetes. The larvae settle mainly on existing Sabellaria reefs or
on their dead remains, and in marine shallow areas where suitable sedimen-
tological and hydrodynamic conditions occur. These bioconstructions
require a good supply of sand grains and a strong water movement and
can develop as thin crusts, mounds and hummocks, to tubular or barrier-like
aggregations (Delbono et al., 2003).
Sabellaria bioconstructions occur along the midlittoral–upper infralittoral
zone, from the lower shore into the sublittoral, arising from the sandy sea-
floor or they can form banks adhering to hard bottoms. They often reach the
sea surface and remain exposed at low tide. The Mediterranean S. spinulosa
reef does not host a distinctive associated fauna (Gravina et al., 2018), while
the faunal characterization of Italian S. alveolata reefs revealed the preferen-
tial and stable association with the phyllodocid polychaete Eulalia ornata
Saint-Joseph, 1888 along their range (Bertocci et al., 2017; Schimmenti
et al., 2016). In general, the sabellariid reef provides an array of microhabitats
suitable for the settlement of many hard and sandy bottom species, thus char-
acterizing it as an important hot spot of biodiversity (Cole and Chapman,
2007; Dubois et al., 2002, 2006).
Along the Italian coasts, Sabellaria reefs have been reported from the
coasts of Liguria (Delbono et al., 2003), Latium (Giordani Soika, 1956;
La Porta and Nicoletti, 2009; Taramelli-Rivosecchi, 1961), Southern Sicily
(Bertocci et al., 2017; Molinier and Picard, 1953; Schimmenti et al., 2016),
Apulia (Gravina et al., 2018; Lisco et al., 2017), Abruzzo (Gadaleta et al.,
2015) and Marche and Emilia Romagna (unpublished data) (Fig. 5B).
The reefs occurring in the Tyrrhenian Sea and in the Sicily Strait are built
by the species S. alveolata or by aggregations of tubes of both the sabellariid
species, with S. alveolata resulting the dominant bioconstructor (Bertocci
et al., 2017), while for the first time in the Mediterranean Sea, real reef struc-
tures constructed by S. spinulosa have been reported along the Apulian coasts
(Gravina et al., 2018; Lisco et al., 2017). Recently, S. spinulosa reefs have
been reported in the Southern Adriatic near San Foca (Lecce), seemingly
outcompeting and overgrowing P. oceanica meadow at its upper limit,
1.5m depth (S. Piraino, unpublished observations).

2.2.7 Cold-Water Coral Frameworks
Among the cold-water corals (CWCs), M. oculata and L. pertusa are certainly
the most charismatic building deep marine bioconstructions in the Mediter-
ranean Sea (Fig. 6A). These colonial species, together with the solitary