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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
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