Page 4 - Balistreri_Mannino_2017

108 Paolo Balistreri &Anna Maria Mannino

Grotta Perciata, Cala Rotonda, Stomello, Punta ances fell within the class 3 (cover <40% and

Longa, Cala Azzurra. These areas were surveyed in >20%) (Table 2). At San Giuseppe, patches of C. cyl-
order to check the presence of alien macroalgae. Six indracea were more or less continuously present up

of the studied areas (Faraglione, Pozzo, Arre Turinu, to 1 m depth (Fig. 5) whereas at Cala Azzurra only
Grotta Perciata, Cala Rotonda, Stomello) were isolated thalli were present beneath the reef. The
already checked for the presence of alien species in macroalgal community inhabiting the cuvettes was
summer 2012 (Balistreri, 2011/2012). The mac- dominated by the following five taxa: Cystoseira

roalgal community inhabiting the reef was also ana- amentacea (C. Agardh) Bory, Halopteris scoparia
lysed in terms of abundance values of the dominant (Linnaeus) Sauvageau, Jania rubens (Linnaeus) J.V.
taxa. Abundance values ofthe alien taxa together with Lamouroux, Laurencia obtusa (Hudson) J.V.

those ofthe dominant macroalgae were estimated, as Lamouroux and Padina pavonica (Linnaeus) Thivy.
substratum cover (%), by placing six replicated 400 No significant correlations were highlighted
2
cm quadrats within the colonized surface, and five between the abundance values of C. cylindracea
classes were considered: 1 (cover <10%), 2 (cover and those of the dominant macroalgae (Table 3).
<20% and >10%), 3 (cover <40% and >20%), 4
(cover <60% and >40%) and 5 (cover >60%).
DISCUSSION AND CONCLUSIONS

RESULTS Caulerpa cylindracea the only alien species we
,
recorded, was exclusively present within the cu-
The surveys showed the only presence of C. vettes and generally showed a patchy distribution.
cylindracea (Fig. 2), generally forming isolated Low abundance values were registered, with the

patches within the cuvettes of the vermetid reef exception of Punta Longa and San Giuseppe.
(Figs. 3, 4). Moreover, it has been observed that the Asparagopsis taxiformis (Delile) Trevisan de
stolons of C. cylindracea frequently grew strictly Saint-Leon, observed in summer 2008 only at San
intermingled with the thalli of other macroalgae, Giuseppe within the cuvettes near the outer margin

leading to a complex web (Figs. 3,4). of the reef (Balistreri, 2009/2010; Fig. 6), was
The alga was totally absent at Faraglione, Grotta totally absent both in 2012 and 2015.
Perciata, Pozzo and Stomello (Table 2). The abund- The comparison with data obtained from sur-

ance values of C. cylindracea were low and fell veys carried out in 2012 highlighted some differ-
within the class 1 (cover <10%), with the exception ences in the distribution of C. cylindracea. In
ofPunta Longa and San Giuseppe, where the abund- particular, at Faraglione, Grotta Perciata, Pozzo and

Stomello the alga, recorded in 2012, was totally

absent in 2015 whereas at Arre Turino and Cala
Reef
Study area 2015 Rotonda it was absent in 2012 but was present in
pattern 2012
2015 (Table 2). In both years low abundance values
Faraglione 1 1 -
were registered.
Pozzo 1 1 -
At the moment the presence of C. cylindracea

Arre Turino 3 - 1 doesn’t raise serious concern in the studied areas.
However, as it is a highly successful species (Car-
Grotta Perciata 2 1 -
mthers et al., 1993; Ceccherelli et al., 2000; Cec-
Stomello 2 1 -
cherelli & Piazzi, 2001; Raniello et al., 2007;
Cala Rotonda 3 - 1 Occhipinti-Ambrogi et al., 2011; Felline et al.,

San Giuseppe 2 ms 3 2012; Gorbi et al., 2014) and MPAs seem to be not
effective in protecting from the different threats and
San Nicola 1 ms 1
then from biological invasions, its spread and dis-
Cala Azzurra 2 ms 1 tribution should be regularly monitored. Moreover,

Punta Longa 2 ms 3 since this species takes advantage of ecosystem
degradation (Occhipinti-Ambrogi & Savini, 2003),

Table 2. Classes of abundance of Caulerpa cylindracea making fragmented or less structured habitats
in 2012 and 2015 (ms = missing data, - = absent). highly vulnerable to its invasion (Ruitton et al.,