Page 2 - First assessment of the vermetid

372 PAOLO BALISTRERI ET ALII
coasts between Zafferano Cape and Trapani and
within the Marine Protected Area (MPA) “Egadi
Islands” (Chemello, 1989; Chemello et al., 1990a,
1990b; Badalamenti et al., 1992a, 1992b; Chemello
et al., 2000; Dieli et al., 2001; Chemello, 2009).
Isolated reefs are found at Milazzo Cape and only
small reefs are found around Taormina and Syra-
cuse, on the eastern coast of Sicily, and on the
Islands of Lampedusa and Ustica, that represent the
limit of distribution respectively on the south and
on the north of the Sicilian coasts (Chemello et al.,
1990a; Chemello et al., 2000; Dieli et al., 2001;
Consoli et al., 2008; Chemello, 2009). These
biogenic constructions, enclosed in the SPA/BIO
Protocol (Barcelona Convention) are now threatened
by environmental changes and human activities
(e.g. pollution, climate change, ocean acidification)
thus experiencing high mortality in several areas of
the Mediterranean Sea (Di Franco et al., 2011;
Galil, 2013; Milazzo et al., 2014).
Due to the high vulnerability of these habitats,
action plans for their conservation should be a
priority. We know that the increase of knowledge is
essential for the conservation and protection of this
highly valuable habitat. Since only a low percentage
of Sicilian vermetid reefs are subjected to conser-
vation and many of them are not yet investigated
(Chemello, 2009; Chemello & Silenzi, 2011), with
this study we provide a first baseline assessment
of the vermetid reefs present along the coasts of
Favignana Island (MPA “Egadi Islands”).
The aims of the present study were: i) to provide a
first description of the reef typology and ii) to test the
effect of the coastal exposure on the topographic
complexity of the reefs.
MATERIAL AND METHODS
Study area
The study was carried out at Favignana Island
(MPA “Egadi Islands”), located approximately five
kilometers from the west coast of Sicily. The Island,
part of the Aegadian Archipelago, represent an
example of a lower Pleistocene bioclastic cal-
carenite, characterized by a typic association known
as foramol (Kil, 2010). The west side is character-
ized by the presence of the calcareous Monte Santa
Caterina (300 metres high), flanked by areas with
lower relief. The mechanical and chemical erosion
Figure 1. Location of the study areas: Favignana Island.
produced detritic deposits that partially mask the
abrasion platform. The eastern side of the mountain
shows a high cliff in the northern part, that
gradually dips to the south. The coastline is highly
rugged and not very high. The south dipping surface
might be the result of either depositional or
erosional processes. From a geological point of
view, two main tectonic units can be recognized:
the Monte Santa Caterina and the Punta Faraglione.
Vermetid reef analysis
A preliminary survey allowed us to locate six
study areas characterized by the presence of a
vermetid reef: Faraglione, Pozzo, Arre Turinu,
Grotta Perciata, Cala Rotonda and Stornello (Fig. 1).
The areas were chosen in such a way to also test
the effects of the coastal exposure on the vermetid
reef topographic complexity. Three along the
northern side: Faraglione, Pozzo and Arre Turinu,
and three along the southern side: Grotta Perciata,
Cala Rotonda and Stornello. In each area the reef
topographic complexity was measured using a 1m
x 1m quadrat (three random replicates). The 4 sides
and the 2 diagonals of the quadrat were measured
using a meter with a resolution of 0.01m. Topo-
graphic complexity was calculated as the ratio
between the registered measures (real measure, Xi)
and the known measures of the used quadrat (Xn):
Xi/Xn (Graziano et al., 2009 ).
The more the ratio is far from 1, the more com-
plex is the substrate. To describe the reef typology
the following variables were considered: the reef
width from the inshore towards the open sea (meas-
ured using a meter with a resolution of 0.01m), the
height of the inner and the outer margin and the slopes
of the margins (measured using a goniometer).