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Effects of Caulerpa cylindracea Sonder on marine biodiversity 385

Figures 2–5. Area 1: multi-layered mats formed by Caulerpa cylindracea stolons (Fig. 2), Branchiomma bairdi
among patches of C. cylindracea (Fig. 3); Area 2: the sponge Chondrilla nucula (Figs. 3, 4).

spread rapidly, forming compact multi-layered tosh, 1885), a tropical tube-building sabellid poly-
mats which trap the sediment and host native chaete, among patches of C. cylindracea (Fig. 3).
macroalgae, growing strictly intermingled to C. In all 114 individuals were recorded, mainly con-
cylindracea stolons. In this area the diversity of centrated (88 individuals) where C. cylindracea
the algal community was not particularly high (see formed consistent mats entrapping a huge quantity
Table 1). The algal community was essentially of sediment.
dominated by red and green algae such as Instead, sponges, particularly Chondrilla nucula
Jania rubens (Linnaeus) J.V. Lamouroux, 1816 Schmidt, 1862 (Spugna Nocciolina, a mean % cov-
(Rhodophyta Corallinaceae) (a mean % coverage erage of 50±4.5), take advantage of the conditions
of 38±6.8), Cladophora prolifera (Roth) Kützing, in the area 2, characterized by a low rate of sedi-
1843 (Chlorophyta Cladophoraceae) (a mean % mentation, occupying quite all the available sub-
coverage of 10±1.4), and Laurencia dendroidea J. strate (Figs. 4, 5). In this area a few thalli of C.
Agardh, 1852 (Rhodophyta Rhodomelaceae) (a cylindracea and low coverage values of the native
mean % coverage of 10±4.5). The mats, entrap- macroalgae were observed (see Table 2). Jania
ping sediments, also favoured the establishment of rubens (a mean % coverage of 30±4.1) was the
another alien species, Branchiomma bairdi (McIn- dominant species, mainly growing as epiphyte.