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Abstract. This paper is the outcome of a workshop held in Rome in November 2011 on the occasion of the 25th anniversary of the POEM (Physical Oceanography of the Eastern Mediterranean) program. In the workshop discussions, a number of unresolved issues were identified for the physical and biogeochemical properties of the Mediterranean Sea as a whole, i.e., comprising the Western and Eastern sub-basins. Over the successive two years, the related ideas were discussed among the group of scientists who participated in the workshop and who have contributed to the writing of this paper.Three major topics were identified, each of them being the object of a section divided into a number of different subsections, each addressing a specific physical, chemical or biological issue:1. Assessment of basin-wide physical/biochemical properties, of their variability and interactions.2. Relative importance of external forcing functions (wind stress, heat/moisture fluxes, forcing through straits) vs. internal variability.3. Shelf/deep sea interactions and exchanges of physical/biogeochemical properties and how they affect the sub-basin circulation and property distribution.Furthermore, a number of unresolved scientific/methodological issues were also identified and are reported in each sub-section after a short discussion of the present knowledge. They represent the collegial consensus of the scientists contributing to the paper. Naturally, the unresolved issues presented here constitute the choice of the authors and therefore they may not be exhaustive and/or complete. The overall goal is to stimulate a broader interdisciplinary discussion among the scientists of the Mediterranean oceanographic community, leading to enhanced collaborative efforts and exciting future discoveries.

The Mediterranean Sea is one of the most affected areas by alien invasions, which are continuously increasing due to the intense human activities and environmental changes that favor the introduction of species previously unable to colonize the basin. This is the case of the copepods of the genus Pseudodiaptomus, first described in the Indian Ocean and considered as one of the most resistant to unfavorable conditions but never recorded in the Mediterranean until 2011 though present in adjacent seas. Pseudodiaptomus marinus, in particular, is common in shallow marine-brackish waters and is one of the species often found in ballast waters and in aquaculture plants. Native of Japan, it has started spreading since 1950s, and its populations have established in several harbors, eutrophic inlets, and lagoons along the coasts of the Pacific and Indian Oceans. In the last few years, P. marinus has been increasingly reported in European Seas (Mediterranean Sea and North Sea).In this article, we review the invasion history of this species with a special emphasis on its records in the Mediterranean Sea, and its occurrence and establishment in Sicilian waters. We also compare the biological traits and population dynamics of P. marinus with those of other representative of the genus and discuss about the possible mechanisms of introduction in new environments. The aim of this work is to understand the reasons of successful invasion of P. marinus and the environmental and biological factors that may lead to its further biogeographic expansion.

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The incidence of parasitism and intersexuality in the dominant coastal copepod Paracalanus p a n w s was studied from 1984 to 1986 at a fixed station in the Gulf of Naples, Italy. Parasitic dinoflagellates belonging to the genera Atelodnium and Blastodlnium were the most plentiful forms respectively parasitizing the coelomic cavity and gut of their hosts. Infection by species of Atelodinium, the more common of the 2 parasitic groups, seems to be fatal. Parasitized individuals show striking morphological changes in shape and color as well as behavioral anomalies in swimming mode that reflect their poor physical condition. Infection by Blastodinium species is less devastating and does not seem to cause major structural or behavioural n~odifications. Both groups of parasites induce sexual castration in their hosts. Individuals infected by Atelodinium were seasonal in occurrence with highest abundances corresponding to a decline in P. parvus stocks suggesting a strong inverse relationship in the presence of parasites and their hosts. Infection was greatest for juveniles (up to 30 9") as opposed to females (8 %) and completely lacking in males. A strong correlation was also observed between the incidence of intersexes and females parasitized by Atelodinium, 20 '10 of which showed a modification of the P5 approximating that of juvenile and adult males. Most intersexes did not host internal parasites and only rarely were parasitized by Blastodinium suggesting early infection and later abandonment of the host by parasites of the digestive tract. Data are given on the incidence of intersexes in a number of coastal Mediterranean regions. These are discussed in relatlon to the possible role of parasitism in regulating seasonal fluctuations in species stocks in coastal communities.