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Mediterranean Bioconstructions Along the Italian Coast 71

2.2.3 Coralligenous Assemblages
According to Ballesteros (2006), a coralligenous reef is a hard substratum of
biogenic origin that is mainly produced by the accumulation of calcareous
encrusting corallines (red algae, Rhodophyta) growing under dim light con-
ditions. It often develops on almost vertical walls, on gently sloping bottoms
near the base of a wall and on overhangs, but it can also form platforms on
the continental shelf (Fig. 3A and B). Recently, coralligenous atolls, whose
origin is still unresolved, have been discovered between 100 and 130m
depth off the northern coasts of Corse (Bonacorsi et al., 2012).
Coralligenous formations consist of carbonatic bioherms whose thick-
nesses range from 25cm to more than 2m, and they can characterize the

Fig. 3 The two main geomorphological categories of the coralligenous assemblages
(A) rims and (B) banks. (C) Spatial distribution of coralligenous formations. (D) Distribution
of the main banks of C. caespitosa. Points represent data with no associated surface area
and rectangles stand for polygons with a specific area characterized by the presence of
coralligenous assemblages. Boundaries of points and polygons of data layers are
enhanced for illustrative purposes and do not reflect the real habitat extent. Panels
(A) and (B): Alberto Gennari.