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The small-sized copepod community structure (

The present work reports on recent biodiversity records of Mediterranean native species such as Olindias phosphorica in the Turkish Aegean Sea and extended distribution of eleven alien species in the Mediterranean. These are: Bursatella leachi (Mollusca, Gastropoda: Algeria); Callinectes sapidus (Crustacea, Decapoda: Greek Ionian Sea); Caprella scaura (Crustacea, Amphipoda: Mar Piccolo of Taranto); Fistularia commersonii (Fish: Saronikos Gulf, Aegean Sea); Sphoeroides pachygaster (Fish: South Turkey); Musculista perfragilis (Mollusca, Bivalvia: South Turkey); Sepioteuthis lessoniana (Mollusca, Cephalopoda: central eastern coast of Tunisia); Flabellina rubrolineata (Mollusca, opisthobranchia: central Aegean, Greece); Hesionura serrata (Polychaeta: Apulian coast); Stephanolepis diaspros (Fish: Saronikos Gulf, Aegean Sea); and Parvocalanus crassirostris (Crustacea, Copepoda: Lesvos Island, Greek Aegean Sea).

The present work reports on recent biodiversity records of Mediterranean native species such as Olindias phosphorica in the Turkish Aegean Sea and extended distribution of eleven alien species in the Mediterranean. These are: Bursatella leachi (Mollusca, Gastropoda: Algeria); Callinectes sapidus (Crustacea, Decapoda: Greek Ionian Sea); Caprella scaura (Crustacea, Amphipoda: Mar Piccolo of Taranto); Fistularia commersonii (Fish: Saronikos Gulf, Aegean Sea); Sphoeroides pachygaster (Fish: South Turkey); Musculista perfragilis (Mollusca, Bivalvia: South Turkey); Sepioteuthis lessoniana (Mollusca, Cephalopoda: central eastern coast of Tunisia); Flabellina rubrolineata (Mollusca, opisthobranchia: central Aegean, Greece); Hesionura serrata (Polychaeta: Apulian coast); Stephanolepis diaspros (Fish: Saronikos Gulf, Aegean Sea); and Parvocalanus crassirostris (Crustacea, Copepoda: Lesvos Island, Greek Aegean Sea).

Non-calanoid copepods (i.e., Cyclopoida), have been found to be numerically important in oligotrophic seas and to have such ecological impacts that set them apart from most other planktonic crustaceans. Despite the presence of the cyclopoid genus Farranula in the Mediterranean Sea and Atlantic Ocean, the available information regarding its spatial and temporal distribution is rather limited. Based on data collected from open sea as well as coastal regions of the Mediterranean Sea, we present here the first comparative overview of the spatial and seasonal variability of F.rostrata in different Mediterranean regions. We have studied data collected at four ongoing zooplankton time-series stations in the Mallorca Island (Balearic Sea), the Gulf of Naples (Tyrrhenian Sea), the northern Adriatic Sea and the Saronikos Gulf (Aegean Sea) as well as monthly data collected during one year in the Bay of Tunis. At all five areas, the absolute abundance of the species as well as the relative abundance among copepods was found to be low ; thus the species has not been referred among the abundant or even common species in the above areas, either in other Mediterranean coastal areas according to the literature, being almost absent in confined areas. Regarding the offshore waters, the relative abundance of this species is more important among copepods than in coastal waters and it seems to be a key component of the zooplankton in very oligotrophic areas e.g during June 1999, F. rostrata accounted more than 30% of the total copepod community (exceeding that Corycaeus spp. and Oncaea spp.) in the ultra-oligotrophic environment of Levantine Sea, and its contribution decreased gradually towards the West Mediterranean Sea. F.rostrata population was perennial throughout the year in almost all studied coastal areas. Pronounced seasonal signals in abundance and relative abundance were observed for F.rostrata in the Gulf of Naples, the northern Adriatic Sea, the Bay of Tunis and the Saronikos Gulf ; abundance minima occurred during early summer and maxima in fall-winter, when the influence of open sea becomes more intense in coastal waters. No clear seasonal pattern was observed in Balearic Sea, an area largely and continuously affected by offshore waters ; the above patterns confirm the pelagic character of the species. These first observations suggest that aspects of the reproductive strategy and its feeding behavior should be investigated in order in understand the ecological role of this species within the pelagic food web of oligotrophic areas.

Mesozooplankton samples were collected during October-November 1991 in the Eastern Mediterranean Sea from four discrete depth layers in the upper 300 m water column and were analysed at copepod species level. Differentiation of species composition with depth was clear, suggesting the existence of an epipelagic (0-100 m) and a mesopelagic (100-300 m) community. Correspondence analysis revealed similarities among areas for the 0-50 m layer, due to the dominance of Clausocalanus furcatus and Oithona plumifera. Dissimilarities among areas appeared below 50 m and increased with depth, discriminating between different copepod assemblages. These dissimilarities appear to be related to different hydrological features (cyclonic gyres or anticyclonic gyres) prevailing in the basin, rather than to the geographical position of stations and/or to water masses distribution.

The first synoptic basin-wide oceanographic survey in the Eastern Mediterranean Sea was carried out in October-November 1991 within the framework of the international programme POEM-BC (Physical Oceanography of the Eastern Mediterranean - Biology, Chemistry). Mesozooplankton samples were collected at 32 stations in the Sicily Channel, Ionian Sea, Cretan Sea, Cretan Passage, Rhodes area and central Levantine Sea. Vertical hauls were taken from four discrete depth layers in the upper 300 m water column. The gross features of the mesozooplankton communities, at the phyla, class or order level, are described. Depth-integrated abundances showed high homogeneity within each region, with the highest and lowest values recorded in the Sicily Channel (mean: 200 ind. m(-3)) and in the Cretan Sea (mean: 45 ind. m(-3)), respectively. Strong vertical gradients in zooplankton distribution were evident at all stations, the 0-50 m layer being the richest in numbers, whereas numbers sharply decreased at 100 m depth. Copepod relative abundances accounted for approximately 80% of the total zooplankton numbers, while ostracods (6.4%), chaetognaths (4.2%), appendicularians (4%) and pteropods (1.7%) followed in rank order. It seems that the zooplankton distribution is not always influenced by local meso-scale dynamics, but only when the physical forcing is strong and persistent over time, as in the Rhodes gyre area.