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316 C. Brugnano et al. / Journal of Marine Systems 81 (2010) 312–322
Fig. 4. Principal component analysis performed on log-transformed and normalised chemical–physical parameter data set (temperature, salinity, chlorophyll a and dissolved
oxygen).
Clausocalanus arcuicornis (6.9%), Corycaeus typicus (6.3%), and
Ctenocalanus vanus (5.6%). Group III included mostly intermediate
species with abundance maxima recorded in the pelagic system; eight
species accounted for 64.9% of similarity in this group: Corycaeus
furcifer (12.4%), Lucicutia flavicornis (11.4%), Pleuromamma gracilis
(10.7%), Haloptilus longicornis (6.0%), Oncaea mediterranea (6.0%),
Oithona atlantica (5.7%), C. vanus (5.4%) and C. typicus (5.4%). In group
IV, seven species accounted for 63.61% of similarity: P. gracilis (16.3%),
C. furcifer (12.5%), L. flavicornis (9.9%), P. abdominalis (8.0%), Oncaea
conifera (6.5%), Scolecithricella dentata (6.5%) and O. atlantica (3.9%).
Four main copepod assemblages were identified by cluster
analysis at 46% of similarity level (Fig. 7): group A included Acartia
clausi, with a wider horizontal distribution range extended from
coastal to pelagic surface areas, than Acartia adriatica and Isias clavipes and western waters in the Mediterranean. According to Sparnocchia
occurring only along the coastal area in front of Sicily; group B, in
which there are the dominant species, C. furcatus, A. negligens,
T. stylifera, that showed decreasing abundances from inshore to
offshore stations, and O. plumifera, more or less uniformly widespread
in coastal neritic and pelagic surface waters (Table 2); group C,
constituted by C. typicus, C. arcuicornis, C. jobei, N. minor and
Calocalanus pavo, occurring mostly in neritic and pelagic subsurface
waters (Table 3; Fig. 8A, E); group D, mostly composed of those
species that had a broad vertical distribution, ranging from the surface
to great depth. Among these, Heterorhabdus papilliger, O. atlantica
and O. conifera were generally more abundant in the layer between
40 and 80 m, L. flavicornis, C. furcifer and O. mediterranea in the layer
40–150 m, H. longicornis in the layer 100–200 m, and P. gracilis in the
layer 150–300 m (Fig. 8B, C, D).
All the other species, not belonging to the above-said groups,
generally, occurred in deeper waters with scarce abundances with re-
spect to the others, such as S. dentata, Neocalanus gracilis, P. abdominalis,
Lucicutia longicornis, Clausocalanus paululus, Clausocalanus pergens,
Eucalanus crassus, Lubbockia squillimana, Corycaeus flaccus, Lucicutia
clausi. Their mean abundances in these layers are shown in Table 3.
4. Discussion
The θ–S profiles show that the hydrological status of the area
around the Egadi Archipelago can be seen as a crossroad of eastern
et al. (1999), at the entrance of the Western Mediterranean Basin, just
after crossing the section Sicily–Tunisia, the eastern outflow of LIW
presents a core salinity of 38.77–38.78. This signature was found from
300 m depth to the bottom in stations 10 and 12. Two branches of
MAW flow at the surface towards the eastern Mediterranean and
cross the Sicily–Tunisia section (Astraldi et al., 1999), where the
presence of MAW is characterized by a high seasonal variability. In
late summer, the smaller stream along the southern Sicilian shelf
presents a subsurface core characterized by a minimum of salinity of
37.3 located at about 40 m depth (Sorgente et al., 2003). Our findings
are in agreement with this feature and put in evidence a more pelagic
character of the stations on the western side of Marettimo (DCM