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386 ANNA MARIA MANNINO & PAOLO BALISTRERI

further increase of sedimentation, as consequence
of the multi-layered mats trapping the sediment,
which favoured the establishment of several indi-
viduals of Branchiomma bairdi among the patches
of C. cylindracea. This biofouler worm, already
recorded at the Egadi Island MPA (Mytilineou et
al., 2016), clearly takes advantage of the additional
debris among the stolons of C. cylindracea, on
which it can easily settle. Even though this worm
was originally described from Bermuda and
Caribbean Sea (western Atlantic), its origin is cur-
rently unknown (Ramalhosa et al., 2014).
In the area 2, instead, where the rate of sedi-
mentation is low, sponges such as Chondrilla nu-
cula, take advantage behaving as pioneer species
and they also maintain low both the rate of sedi-
mentation and the biodiversity. Indeed, they do not
allow algal species, C. cylindracea included, to set-
tle well in the area, as clearly shown by the low
coverage values observed for C. cylindracea and
the native macroalgae. The low rate of sedimenta-
Table 1. Area 1: coverage values (mean ± SE, n = 6) tion does not allow also the settlement of Bran-
of Caulerpa cylindracea and the native macroalgae.
chiomma bairdi individuals, which do not find
suitable environment conditions for their establish-
ment. Therefore, C. cylindracea may have negative
effects on the habitat where it settles in two differ-
ent ways: a) affecting the structure of the native
algal community which presents a low diversity,
and b) favouring the settlement of other alien
species. It was already observed by Baldacconi &
Corriero (2009) how C. cylindracea (reported as
C. racemosa var. cylindracea) may significantly af-
fect the percentage cover of sponge assemblage of
coralligenous concretions, likely due to the ability
of C. cylindracea to overgrow several sponge
species.
Since Sicily and the circum-Sicilian Islands,
Table 2. Area 2: coverage values (mean ± SE, n = 6) of are vulnerable to biological marine invasions, reg-
Chondrilla nucula, Caulerpa cylindracea and the native ular monitoring programs are needed to assess the
macroalgae. spread dynamics of invasive species, particularly
in MPAs such as Egadi islands MPA. In the
MPAs, high rates of visitation could promote the
DISCUSSION AND CONCLUSIONS
introduction of invasive species through increased
disturbance and vectors (e.g., boat anchors,
First results showed how the rate of sedimenta- SCUBA equipment, hull fouling) and subsequent
tion has an important role in structuring the com- dispersal of propagules (Britton-Simmons & Ab-
munities in the studied areas. In the area 1 we bott, 2008; Burfeind et al., 2013), therefore an
assisted to a cascade process. Precisely, the high IAS strategy integrated into the management plan
rate of sedimentation favoured the growth and of the Egadi Islands MPA may be highly desir-
spread of C. cylindracea which in turn allowed a able.