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100 Gianmarco Ingrosso et al.

(Verlaque, 2010) suggest that, if the sea-level rise is sufficiently gradual, this
species can move upwards on the shore and grows in height. If the rate of
sea-level rise is too fast, however, the rims will not be able to cope with it
and the living alga will disappear and the growth of these structures will
no longer be possible.
More proximate effects of climatic changes have resulted in intensifying
atmospheric events, sea water warming and summer hot waves (Rivetti
et al., 2014). The increasing power of extreme sea storms expected under
the climate change scenario in the Mediterranean Sea will likely have a deep
physical impact on L. byssoides and Sabellaria reefs, given their prevalent shal-
low distribution (Firth et al., 2015; Nissen et al., 2014), but also on deeper
bioconstructions such as coralligenous outcrops (Cocito et al., 1998;
Teixido ´ et al., 2013). Multiple climate-driven effects, such as thermal anom-
alies and floods, can affect coralligenous outcrops (Bavestrello et al., 1994;
Cerrano et al., 2000), often interacting with local human impacts in altering
the composition and structure of coralligenous communities (Roghi et al.,
2010). Seawater warming and summer hot waves may induce mass mortality
episodes in gorgonians and other coralligenous organisms (Cerrano et al.,
2000), causing depth shifts of the communities (Gatti et al., 2017; Ponti
et al., 2014, 2018). These phenomena have caused repeated episodes of
bleaching and mortality in C. caespitosa reefs colonies in recent years
( Jim enez et al., 2016; Kersting et al., 2013; Kruz ˇi c et al., 2012, 2014;
Rodolfo-Metalpa et al., 2000, 2005). Recovery of C. caespitosa from impacts
of various kinds may be relatively rapid (Casado et al., 2015; Kersting et al.,
2014b), but this species is believed to be living close to its thermal limit
during the summer period, so that a long-term increase of sea water tem-
perature could be lethal for this coral (Rodolfo-Metalpa et al., 2006a,b).
Deep mass mortalities have been recently reported for red coral popula-
tions thriving on deep coralligenous concretions of the Gulf of Salerno at
a depth range between 80 and 100m and attributed possibly to local down-
welling currents inducing an unusual drop of the thermocline, sudden warm
water emissions or local landslides generating turbidity currents (Bavestrello
et al., 2014).
Climate change may have a positive effect on the thermophilic steno-
therm coral A. calycularis, whose distribution could extend northwards
due to warming of the superficial waters (Bianchi, 2007). However, this spe-
cies seems particularly sensitive to high summer temperatures, suggesting
that different climatic processes could combine in modifying the distribution
of bioconstructors (Prada et al., 2017). The interplay between sea water
warming and ocean acidification is particularly concerning. For instance,