Page 10 - Spatial _distribution_Brugnano_2010

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320 C. Brugnano et al. / Journal of Marine Systems 81 (2010) 312–322

Fig. 8. Vertical distribution of abundances of the most representative copepod species.

as resulted from PCA analysis. It shows three groups of depth along Atlantic water convergence determines copepod species overlapping
the water column, which are ordered according to the temperature with oceanic boreal temperate character, as O. atlantica and A. danae
and salinity gradients from surface to deeper layers. Therefore, the and tropical–subtropical character as C. furcatus and A. negligens.
correlation between biota and physical parameters was high, as However, these species occur in the entire Mediterranean, but their
confirmed by Spearman's coefficient. relative abundances vary in the different regions. In fact, our data
The structure of the mesopelagic copepod community is composed reveal no evident water masses indicator species in high abundance,
mainly by stenobiotic and weak migratory species that are generally such as H. longicornis, reported for Eastern Mediterranean mesope-
confined to intermediate waters and adapted to short ranges of lagic waters (Weikert and Trinkaus, 1990; Siokou-Frangou et al.,
physical parameters. In the Egadi Island area the spatial distribution 1997). Similar observations were made by Fernàndez de Puelles et al.
patterns of copepod communities, based on the concept of inshore– (2003).
offshore species overlapping and species turnover with depth, In the neritic and pelagic systems of the Egadi Island Archipelago,
generally, correspond to that proposed by Scotto di Carlo et al. maximum diversity occurred at 40–80 m depth interval, in the water
(1984) for Mediterranean pelagic system. The Egadi Islands exhibit a mass above the thermocline corresponding to the maximum
great species richness similar to the richer areas in the western and chlorophyll values; while lower diversity index values in the coastal
eastern Mediterranean Sea (Furnestin, 1979; Scotto di Carlo et al., area are due to the strong dominance of few autumnal species
1984; Estrada et al., 1985; Siokou-Frangou et al., 1997; Licandro and C. furcatus, A. negligens, T. stylifera and O. plumifera. A closer vertical
Icardi, 2009). This is probably due to their geographical position at the diversity trend was found by Isari et al. (2006), in Aegean Sea. The
entrance of Sicily Channel, where water mass exchanges between success of Clausocalanus and Oithona genera occurring as dominant
eastern and western basin occur (Astraldi et al., 1996). Levantine and species in our study area, as well as, in overall Mediterranean Sea, in