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can be separated into functional groups based on the ways in which the fauna
uses the coral habitat and its complex substrata (Henry and Roberts, 2017).
It comprises microscopic fauna associated with the coral biofilm, macro-
benthic grazers, deposit feeders and small benthic predators that find refuge
among reef polyps, coral branches and other microhabitats, as well as larger
sessile suspension and filter-feeding epifauna. Many benthopelagic and ben-
thic demersal fish communities also visit the CWC frameworks to forage, find
refuge and breed. Mediterranean CWCs reefs account so far for over 500 asso-
ciated species (Rueda et al., 2018).
CWCs were once considered as being present in the Mediterranean Sea
only as dead skeletal remains from the Pleistocene, the postglacial conditions
having arrested their development (Delibrias and Taviani, 1985). Their sup-
posed extinction was disproved with the advent of the deep-sea exploration
technologies, first by occasional findings of living colonies (e.g. Fredj and
Laubier, 1985; Mastrototaro et al., 2002; Tunesi and Diviacco, 1997), soon
followed by the discovery of lush CWC sites, with highly developed bio-
constructions (Chimienti et al., 2018a,b). At least 20 living white coral
occurrences are known so far for Italian and Maltese waters and, at four
of these sites, the substantial coral growth and high colony density define
true CWC provinces (Taviani et al., 2011, 2016, 2017). These are located
in the Northern Ionian Sea (Santa Maria di Leuca), in the Southwestern
Adriatic Sea (Bari Canyon), in the Strait of Sicily (South Malta) and in
the Sardinia Sea (Nora Canyon: Taviani et al., 2017; Tavolara and Coda
Cavallo Canyons: Chimienti et al., 2018b; D. Moccia et al., personal com-
munication) (Fig. 6B). Only two more coral provinces have been currently
recognized within the Mediterranean basin: in the Gulf of Lion and in the
eastern Alboran Sea (Taviani et al., 2016). So far, the Italian seas play a crucial
role in the presence and distribution of CWC bioconstructions. Several
abiotic factors such as suitable substrate, water temperature, oxygen concen-
tration and water flow regimes influence their occurrence, distribution
and abundance in the deep sea (Gori et al., 2013; Roberts et al., 2009b).
In particular, appropriate currents are needed for an adequate trophic supply
and for preventing coral smothering by sediments; these are one of the main
drivers in CWC distribution (Carlier et al., 2009; Roberts et al., 2009a). The
Levantine Intermediate Water (LIW), formed in the northern portion of the
eastern Mediterranean and flowing westward, together with the cascading of
cold water from the Northern Adriatic cold engine towards the Ionian Sea,
has a profound influence on CWC growth and distribution (Freiwald et al.,
2009; Taviani et al., 2016).