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Mediterranean Bioconstructions Along the Italian Coast 99

changes in species composition, as addition of limiting nutrients can cause
shifts in competitive hierarchies (Emery et al., 2001) and promote alien
species invasions (Williams and Smith, 2007). Sessile habitat-forming
species characterizing bioconcretions are the most heavily impacted by
these threats (Altieri and Witman, 2006). Wastewaters profoundly affect
the structure of coralligenous communities by inhibiting coralline algae
growth, increasing bioerosion rates, decreasing species richness and densities
of the largest individuals of the epifauna, eliminating some taxonomic groups
and increasing the abundance of highly tolerant species (Ballesteros, 2006;
Cormaci et al., 1985; Hong, 1980, 1982).
Water eutrophication particularly affects Sabellaria reefs. Despite Sabellaria’s
tolerance to poor water quality, increasing inputs of nutrients along the shore
are responsible for the indirect impact to the reef, causing massive green
algae blooms, which significantly lower the rate of Sabellaria larval recruitment
(Dubois et al., 2006). Evidence for such damage has been recorded along the
Sicily coasts (F. Badalamenti, personal communication).
Although there are a general lack of studies on the impact of aquaculture
facilities situated over or near to bioconcretions such as coralligenous
outcrops or mae ¨rl beds, their effects should match those produced by
wastewater dumping. For instance, in the Adriatic Sea, Kruz ˇi c and Poz ˇar-
Domac (2007) documented the impact of tuna farming on the banks of
C. caespitosa.

4.1.3 Climate Change
Climate change is the threat to marine ecosystems that is causing most
concern worldwide. Regarding bioconstructions, the rise of both sea level
and water temperature, ocean acidification and the increasing intensity and
frequency of extreme weather events may act from local to large scale,
altering coastal and offshore environments, with severe consequences to both
shallow and deep-sea habitats (Hoegh-Guldberg et al., 2014; P€ortner et al.,
2014; Wong et al., 2014).
In the long term, the rise of sea level will cause profound changes of
midlittoral habitats, affecting bioconstructions in superficial waters, such
as those of L. byssoides that thrive only in the midlittoral zone. This species
cannot survive conditions of constant submersion, as it is rapidly covered and
overgrown by sublittoral algae (mainly soft red algae and articulated coral-
lines). The formation of large rims of L. byssoides is therefore possible only if
the sea level remains stable (or rises very slowly) over long periods (Faivre
et al., 2013). Recent observations in other areas of the central Mediterranean