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Mediterranean Bioconstructions Along the Italian Coast 103

systems by either increasing or decreasing sediment delivery. Most anthro-
pogenic alterations of the shoreline (e.g. urbanization, construction of
ports and coastal defences) could have some impact on bioconcretions
through the significant alterations of sedimentary regimes. The increase in
sedimentation rates is a major problem in coastal waters worldwide. Sedi-
mentation disproportionally impacts nearshore ecosystems such as coastal
estuaries, where increasing sediment loads lead to both burial of benthic
communities and increasing water turbidity, reducing light penetration
and leading to numerous associated negative effects (Thrush et al., 2004).
Increasing sedimentation is a major problem for rocky reefs (Airoldi,
2003), coral reefs (Rogers, 1990), sea-grass systems (Orth et al., 2006)
and soft-sediment communities (Thrush et al., 2004). Coralligenous com-
munities and Sabellaria reefs are also very vulnerable to changes in hydrolog-
ical and sedimentary regimes resulting from coastal engineering works
(Balata et al., 2007; Gatti et al., 2012, 2015a; Roghi et al., 2010;
Vorberg, 2000). Coastal urbanization and the artificial sheltering of inter-
tidal communities by the construction of jetties and marinas are a great
impact on vermetid reefs (Di Franco et al., 2011). Human-induced changes
to land cover, including urbanization, loss of forests and intensification of
agricultural practices in vulnerable areas (e.g. mountainous coastal regions),
may dramatically increase soil erosion and sediment deliveries to coastal
waters at regional levels, increasing turbidity and sedimentation and there-
fore threatening intertidal and subtidal bioconstructions (Mateos-Molina
et al., 2015).

4.1.6 Direct Physical Disturbance
Several activities, mostly related to human visitation and recreation, can lead
to impacts on bioconstructions through direct physical disturbance of the
building species (e.g. Milazzo et al., 2002). For instance, boat anchoring
(Fig. 10B) has a high destructive potential in coralligenous formations
(Ballesteros, 2006). Generally, bioconstructors characterizing this habitat
are very fragile and can be easily detached or broken by anchors and chains,
and they show a low recovery potential. Thus, in areas subjected to intense
anchoring, it is unlikely that this community will fully recover from damage.
Sometimes, due to lack of management, boat anchoring is a huge problem
even within protected areas. This kind of impact often overlaps with
recreational SCUBA diving (Chimienti et al., 2017). Due to their spectac-
ular appearance, coralligenous formations are the most popular habitat for
recreational diving in the Mediterranean Sea. Uncontrolled or too many