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Mediterranean Bioconstructions Along the Italian Coast 73

(Gordini et al., 2012). High concentrations of small- and medium-sized reefs
are distributed off the lagoons of Venice and Grado-Marano, and a larger reef
system is located 3–5km off Chioggia (Tosi et al., 2017). The high variability
at different spatial scales of the benthic assemblages in the Adriatic mesophotic
biogenic habitats, in relation to local abiotic features, distance from the coast
and outcrops, has been highlighted for both phyto- and zoobenthos (Curiel
et al., 2012; Ponti et al., 2011).
The onshore–offshore gradient of coastal freshwater inputs is the main
driver of nutrient dynamics in the northern Adriatic Sea, playing an important
role also in structuring the assemblages of the outcrops. These assemblages
occur in three main typologies based on the abundance of encrusting calcar-
eous red algae, algal turfs, sponges and ascidians. Algal turfs, encrusting sponges
(e.g. Dictyonella incisa (Schmidt, 1880) and Antho (Antho) inconstans (Topsent,
1925)) and bioeroders generally characterize large near shore reefs, strongly
affected by riverine inputs. Encrusting calcareous red algae and colonial
ascidians, e.g., Polycitor adriaticus (Drasche, 1883), dominate off shore reefs.
Both algal turf and noncalcareous encrusting algae (e.g. Peyssonnelia spp.)
are abundant, together with massive sponges (e.g. Ircinia variabilis (Schmidt,
1862), Tedania (Tedania) anhelans (Vio in Olivi, 1792) and Chondrosia reniformis
Nardo, 1847) that occur on the outcrops (Falace et al., 2015; Fava et al., 2016;
Ponti et al., 2011).
The Apulian coralligenous region has been known for decades (Parenzan,
1983; Sarà, 1966, 1968; Sarà and Pulitzer-Finali, 1970) and it represents a key
element of the seascape, covering about 38% of the seafloor between 10 and
100m depth (Bracchi et al., 2017). Here, coralligenous banks are predominant
and these show the maximum spatial dominance both in the 10–40m and in
the 70–90m depth ranges. At shallower bathymetric intervals (10–40m
depth), these formations occur both as coralligenous constructions sensu
stricto and in mosaic form with Posidonia meadows (Bracchi et al., 2017). Also,
the Apulian coralligenous region shows high spatial variability at different
scales, highlighting the patchy and complex nature of these assemblages
(Terlizzi et al., 2007). Several processes might generate the observed variabil-
ity. These include disturbance (Airoldi, 2000; Connell, 2005), topographic
heterogeneity (Archambault and Bourget, 1999), pre- and postsettlement bio-
logical interactions (Hunt and Scheibling, 1997; Sebens, 1986) and different
patterns of growth (individual vs modular organisms: Jackson, 1977).
In the Ligurian Sea there are different typologies of coralligenous bio-
constructions likely due to the different geomorphology of the coast; biolog-
ical assemblages are similarly diverse, and some still need to be described