Proceedings of the Second Mediterranean Symposium on Marine
Proceedings of the Second Mediterranean Symposium on Marine
Proceedings of the Second Mediterranean Symposium on Marine
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Williams<strong>on</strong> and Fitter, 1996; Piazzi et al. 2001; Boudouresque and Verlaque, 2002;<br />
Carlt<strong>on</strong>, 2002). Human disturbed habitats are <str<strong>on</strong>g>of</str<strong>on</strong>g>ten thought to be more susceptible to<br />
invasi<strong>on</strong>s (Ribera and Boudouresque, 1995; Ruiz et al., 1997; Leppäkoski et al., 2002).<br />
With reference to <str<strong>on</strong>g>the</str<strong>on</strong>g> <str<strong>on</strong>g>Mediterranean</str<strong>on</strong>g>, Boudouresque and Verlaque (2002) listed 84<br />
macroalgal species which have probably been introduced, 9 <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g>se are c<strong>on</strong>sidered<br />
invasive. Am<strong>on</strong>g <str<strong>on</strong>g>the</str<strong>on</strong>g>m <str<strong>on</strong>g>the</str<strong>on</strong>g> tropical green alga Caulerpa racemosa (Forsskål) J. Agardh<br />
has invaded in <str<strong>on</strong>g>the</str<strong>on</strong>g> last decade <str<strong>on</strong>g>the</str<strong>on</strong>g> western side <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> <str<strong>on</strong>g>Mediterranean</str<strong>on</strong>g>, spreading <strong>on</strong><br />
every kind <str<strong>on</strong>g>of</str<strong>on</strong>g> substrate, from <str<strong>on</strong>g>the</str<strong>on</strong>g> surface to 60 m depth, and becoming a severe threat<br />
to algal diversity (Piazzi et al., 2001). Recently, C. racemosa was also observed for <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
first time in <str<strong>on</strong>g>the</str<strong>on</strong>g> Gulf <str<strong>on</strong>g>of</str<strong>on</strong>g> Naples (Buia et al., 2001).<br />
About 2 000 000 <str<strong>on</strong>g>of</str<strong>on</strong>g> inhabitants live in <str<strong>on</strong>g>the</str<strong>on</strong>g> area <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> Gulf <str<strong>on</strong>g>of</str<strong>on</strong>g> Naples (Italy, Sou<str<strong>on</strong>g>the</str<strong>on</strong>g>rn<br />
Tyrrhenian Sea); a wide urban area and a big commercial port, with a maritime traffic<br />
volume near to 36000 vessels per year (Flagella, pers. comm.), is present in <str<strong>on</strong>g>the</str<strong>on</strong>g> inner<br />
side <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> gulf, and several fishing and touristic harbours, and aquaculture facilities are<br />
spread all around <str<strong>on</strong>g>the</str<strong>on</strong>g> coast. Such high density <str<strong>on</strong>g>of</str<strong>on</strong>g> populati<strong>on</strong> and c<strong>on</strong>sequent<br />
anthropogenic activities are able to determine str<strong>on</strong>g disturbances <strong>on</strong> marine ecosystems<br />
with possible changes in macroalgal communities.<br />
In <str<strong>on</strong>g>the</str<strong>on</strong>g> framework <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> ALIENS project, a survey al<strong>on</strong>g Neapolitan coasts was performed,<br />
during <str<strong>on</strong>g>the</str<strong>on</strong>g> summer 2002, with <str<strong>on</strong>g>the</str<strong>on</strong>g> aim to detect <str<strong>on</strong>g>the</str<strong>on</strong>g> distributi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> C. racemosa, also<br />
providing a descripti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> recipient communities, comparing habitats with a different<br />
degree <str<strong>on</strong>g>of</str<strong>on</strong>g> human interference. On <str<strong>on</strong>g>the</str<strong>on</strong>g> basis <str<strong>on</strong>g>of</str<strong>on</strong>g> macroalgal compositi<strong>on</strong>, differences am<strong>on</strong>g<br />
localities placed in human disturbed areas and localities far from possible source <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
disturbance were descried. The occurrence <str<strong>on</strong>g>of</str<strong>on</strong>g> C. racemosa in many studied localities was<br />
discussed in relati<strong>on</strong> to species richness, total algal coverage and presence <str<strong>on</strong>g>of</str<strong>on</strong>g> main taxa.<br />
MATERIALS AND METHODS<br />
Study area and sampling design<br />
In July 2002 a hierarchical survey in <str<strong>on</strong>g>the</str<strong>on</strong>g> Gulf <str<strong>on</strong>g>of</str<strong>on</strong>g> Naples (Fig. 1) was performed <strong>on</strong><br />
subtidal rocky substrate at both 5 and 10 m depth. Sampling localities were selected <strong>on</strong><br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> nor<str<strong>on</strong>g>the</str<strong>on</strong>g>rn and sou<str<strong>on</strong>g>the</str<strong>on</strong>g>rn sides <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> Gulf ; <str<strong>on</strong>g>the</str<strong>on</strong>g> inner part was not c<strong>on</strong>sidered because<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> its sandy and muddy bottoms. Six “impacted” localities (named from 1 to 6) were a<br />
priori selected in human disturbed areas (close to farming facilities, harbours and urban<br />
z<strong>on</strong>es), six (from 7 to 12) were chosen in relatively undisturbed areas: <str<strong>on</strong>g>the</str<strong>on</strong>g>y were<br />
c<strong>on</strong>sidered as “c<strong>on</strong>trols”. Each locality comprised a stretch <str<strong>on</strong>g>of</str<strong>on</strong>g> shoreline <str<strong>on</strong>g>of</str<strong>on</strong>g> about 0.2 - 1.5<br />
Km and included three sites, 15 m l<strong>on</strong>g, randomly selected; at each site three random<br />
quadrats (50 x 50 cm <strong>on</strong> sub-horiz<strong>on</strong>tal substrate at both depths) were examined by<br />
visual estimati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> coverage <str<strong>on</strong>g>of</str<strong>on</strong>g> c<strong>on</strong>spicuous macroalgal species (more than 2 cm in<br />
size or smaller, but forming patches occupying more than 4 square cm); species not<br />
recognised in field were collected and fixed in formol 4% to be identified in laboratory.<br />
Species richness (number <str<strong>on</strong>g>of</str<strong>on</strong>g> taxa) and total percent coverage were calculated for each<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> studied quadrats.(Fig.1)<br />
ACTES DU DEUXIEME SYMPOSIUM MEDITERRANEEN SUR LA VEGETATION MARINE (ATHENES, 12-13 DECEMBRE 2003)<br />
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