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66 Gianmarco Ingrosso et al.

2.2 Mediterranean Bioconstructions: Biodiversity
and Distribution Along the Italian Coasts
Marine bioconstructions are common throughout the Mediterranean
Sea, but complete cartographic data on their distribution are a major
knowledge gap. The distribution of marine bioconstructions along
the Italian seas reported here has been assembled from 468 documents
(peer-reviewed articles; international, national and regional reports; grey
literature) reporting spatial information (e.g. maps or detailed acoustic
mapping). Spatial information was also obtained from unpublished in situ
observations from various sources. All records have been validated and
georeferenced. When digital spatial information was not available, it
was created by digitizing image maps or by extracting spatial information
from the text, based on expert knowledge. The ArcGIS 10.1 software by
ESRI (Environmental System Resource Institute, https://www.esri.com/)
was used to integrate all the data into a geodatabase and to generate the
distribution maps.
Included in the proposed definition of bioconstruction are the mattes of
P. oceanica (i.e. the woody structures created by the rhizomes of this sea grass)
since the new rhizomes grow over the old ones, raising seafloor and making
it stable for thousands of years (Bianchi, 2002). Thus it is worthwhile to
include the distribution of Posidonia meadows (Fig. 1) due to the key eco-
logical role of this habitat in the Mediterranean Sea (Boudouresque and
Meinesz, 1982), in order to provide a complete picture of the main marine
bioconstructions of Italian seas. However, Posidonia meadows are still usually
considered as a distinct habitat from “reefs” and are treated further here in
only a limited way.
Bioconstructors comprise a wide range of organisms: calcareous algae,
sponges, corals, vermetids, oysters, mussels, polychaetes (serpulids and
sabellariids), barnacles, bryozoans and other noncalcified organisms such
as cyanobacteria and diatom biofilms (Goldberg, 2013; Wood, 1999).
The Mediterranean Sea hosts important biogenic structures (Relini, 2009)
and the main ones considered here are as follows:
• Lithophyllum byssoides concretions/trottoirs
• Astroides calycularis formations/reefs
• Coralligenous assemblages
• Cladocora caespitosa formations/reefs
• Vermetid reefs
• Sabellariid reefs
• Cold-water coral frameworks
• Serpulid reefs, including biostalactites