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Mediterranean Bioconstructions Along the Italian Coast 79

Sea. The first one is a bioengineer that builds relevant biogenic structures,
while the second one is mostly solitary, but can construct small clumps.
Sabellariid reefs are compact bioconstructions resulting from the aggre-
gation of tubes made up of sand grains and bioclasts, cemented with
mucus, which develop on both solid and soft bottoms (Fig. 5A). The worms
construct these tubes around themselves, in close proximity to one another,

Fig. 5 (A) Sabellariid reefs on soft bottoms. (B) Distribution of sabellariid reefs along Ital-
ian coast. Points represent data with no associated surface area. Boundaries of points of
data layers are enhanced for illustrative purposes and do not reflect the real habitat
extent. Panel (A): Alberto Gennari.