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Quantitative information on the spatial distribution of meiofaunal abundance, biomass and biodiversity (as richness of higher taxa) is summarised from 476 sites of the deep- Mediterranean Sea, at depths ranging from ca. 200 to 4617 m. Meiofaunal abundance (46531 and 30624 ind 10 cm2 at 200–1000 and 1000–2000m depth intervals) and biomass (12516 and 11920 mgC 10 cm2 at 200–1000 and 1000–2000m depth intervals) in the bathyal sediments of the Mediterranean Sea are similar to those reported in oceans worldwide but at much higher depths (abyssal or hadal). Meiofaunal abundance, biomass and richness of taxa displayed a common decreasing bathymetric pattern, but showed a steeper negative slope than in other oceanic regions. Latitudinal and longitudinal gradients revealed idiosyncratic patterns when different basins (Western, Central and Eastern) and habitats (open slope, canyon, deep basin and trench) were considered. The results of the non parametric multivariate multiple regression analyses revealed that, conversely to what expected, depth is not the key factor in explaining the variance of meiofaunal assemblages living down to 2000m depth. The quality and quantity of food sources explained a larger fraction of the variance of meiofaunal variables (47, 25 and 33% for abundance, biomass and diversity, respectively) and the importance of food sources increased with increasing depth. However, most of the variance remains unexplained suggesting that other factors (such as episodic events, deep currents, other unexplored yet environmental characteristics) can act a key role in driving the observed meiofaunal spatial patterns. The analysis of rare taxa (on a data set of 183 samples), suggested that differences in the meiofaunal community were evident when dominating taxa (nematodes, copepods and polychaetes) were excluded. We report the presence of rare taxa exclusively present in open slope (amphipods) and canyon (cnidarians and decapod larvae) systems, whereas others are exclusively found in one of the two basins (e.g. gastrotrichs in the Western basin and amphipods and gastropods in the Eastern basin). The apparent preference of some rare taxa for a specific habitat or basin could have important implications for the identification of the hot spots of benthic diversity, for identifying the connectivity among systems and for an appropriate management of deep-sea habitats in the Mediterranean Sea.

Natural episodic events, such as gravity flows, submarine landslides, and benthic storms can determine severe modifications in the structure and functioning of deep-sea ecosystems. Here, we report and compare the ecosystem effects produced by dense water formation events that occurred in the Gulf of Lions (NW Mediterranean) and the Aegean Sea (NE Mediterranean). In both regions, the rapid sinking of cold dense waters, driven by regional meteorological forcings, results in important immediate modifications that can be summarised in: (i) increased organic matter content in the deep basin; (ii) diminished benthic abundance; and (iii) changes of benthic biodiversity. At longer time scale the analysis reveals, however, different resilience times in the two regions. The Gulf of Lions is characterized by a very fast (months) recovery whereas the Aegean Sea shows much longer (45 years) resilience time. New long-term studies are further needed to identify the potential effects that changes in the duration, intensity and frequency of episodic events could have on the structure, biodiversity and functioning of the deep Mediterranean Sea under environmental and climate change scenarios.

On the occasion of the 35th year from the publication of the first issue of the Proceedings of the Italian Association of Limnology and Oceanography (AIOL) we present here the results of a meta-analysis of all of the material included in the AIOL Proceedings, with the aim of analysing the last 30 years history of aquatic science in Italy as mirrored by the science presented by the AIOL members. The results of this meta-analysis were presented in September 2006 in Paris, on the occasion of the 100th anniversary of the ‘Institut oce´anographique, fondation Albert Ier, prince de Monaco’. We have screened the 17 volumes of the Proceedings and classified the articles into papers dealing with: (i) Biology and Ecology; (ii) Chemistry; (iii) Physics, and (iv) Geology, which represent the most relevant ‘disciplines’ of the AIOL. The articles were also classified as ‘oceanographic’ or ‘limnological’ papers, including all marine and freshwater aspects, respectively. Articles were finally classified on the basis of the environment where the studies were carried out: the water column or the benthic environment. The results of this analysis highlight the presence of wide fluctuations in the number of publications produced by the AIOL scientific community during more then three decades of the activity of the association in Italy. We also show that these fluctuations were associated with variable fluctuations in the availability of funding for aquatic research. The overall picture of the scientific outputs of the AIOL members as revealed by the analysis of the papers published on the AIOL Proceedings indicates that the Association had a fruitful activity during the last part of the past century, but experienced a major flaw during the first years of this century. Only in the last few years such activity restarted, thus giving rise to a possible new deal in the development of aquatic science in Italy.

Bottom trawling represents nowadays one of the most severe anthropogenic disturbances at sea, and determines large impacts on benthic communities and processes. Bottom trawling determines also local sediment resuspension and the effects of the injection of large amounts of surface sediments into the water column have been repeatedly investigated. Few studies have assessed the consequences of sediment resuspension caused by bottom trawling on the quantity, biochemical composition and bioavailability of suspended organic particles and how these eventually rival those exerted by natural storms. To provide insights on this poorly addressed issue, we investigated concentrations and biochemical composition of total and enzymatically digestible pools of particulate organic matter (POM) in the Thermaikos Gulf (Mediterranean Sea) under calm sea conditions, during intensive trawling activities, and after a severe storm. We show here that sediment resuspension caused by trawling can cause large effects on POM quantity, biochemical composition and bioavailability. Both during trawling and after the storm, the relative importance of the carbohydrate pools increased (in the upper water column) and the total lipid concentrations decreased (in the intermediate and bottom layers) when compared to values measured during calm conditions. These results would suggest that bottom trawling could inject in the upper water column POM pools more refractory in nature (e.g., carbohydrates) than those present in calm or after-storm conditions. By contrast, we show also that the bioavailable fraction of biopolymeric C increased significantly during trawling in the upper water column of the shallowest stations and in the bottom water column layer of the deepest ones. These results provide evidence that bottom trawling can influence the overall trophic status of coastal waters, exerting effects similar or stronger than those caused by natural storms, though of variable amplitude depending on the water depth. Since bottom trawling is carried out worldwide and natural storms at sea can be frequent and intense, we claim for the need of assessing new adapting management strategies of bottom trawling in order to mitigate the synergistic impacts of anthropogenic and natural sediment resuspension on coastal biogeochemical cycles.