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Location of the straits and seaways plotted in Figure 2 and the data used to build Figure 4

The Pontine Islands form a volcanic archipelago in the Tyrrhenian Sea. It consists of two edifices, the islands of Ponza, Palmarola and Zannone and the islands of Ventotene and Santo Stefano, respectively. The Archipelago developed during two main volcanic cycles in the Plio-Pleistocene: 1) the Pliocene episode erupted subalkaline, silica-rich volcanic units, which constitute the dominant products in the western edifice (Ponza and Zannone Islands); 2) the Pleistocene episode erupted more alkaline products, represented by evolved rocks (trachytes to peralkaline rhyolites) in the islands of Ponza and Palmarola and by basic to intermediate rocks in the eastern edifice (Ventotene and Santo Stefano Islands). In this paper we present new geochemical and petrological data from submarine rock samples collected in two oceanographic cruises and a scuba diving survey. The main result is the recovery of relatively undifferentiated lithotypes that provide further insights on the magmatic spectrum existing in the Pontine Archipelago, allowing modelling of the whole suite of rocks by fractional crystallization processes. New major and trace element data and thermodynamic constrains (by the software PELE) indicate the existence of three distinct evolutionary trends corresponding to a HK calcalkaline series in the Pliocene, followed by a transitional and then by a shoshonite series in the Pleistocene. In particular, the transitional series, so far overlooked in the literature, is required in order to explain the genesis of several peralkaline felsic rocks recognized in the Archipelago. On the whole, the new geochemical data i) confirm the orogenic signature of the suites, ii) allow to rule out an anatectic origin for both subalkaline and peralkaline rhyolites and iii) indicate highly heterogeneous mantle sources, due to crustal components variously recycled in the mantle via subduction.

Viruses are the most abundant life forms in the world's oceans and they are key drivers of biogeochemical cycles, but their impact on the microbial assemblages inhabiting hydrothermal vent ecosystems is still largely unknown. Here, we analysed the viral life strategies and virus-host interactions in the sediments of a newly discovered shallow-water hydrothermal field of the Mediterranean Sea. Our study reveals that temperate viruses, once experimentally induced to replicate, can cause large mortality of vent microbes, significantly reducing the chemoautotrophic carbon production, while enhancing the metabolism of microbial heterotrophs and the re-cycling of the organic matter. These results provide new insights on the factors controlling primary and secondary production processes in hydrothermal vents, suggesting that the inducible provirus-host interactions occurring in these systems can profoundly influence the functioning of the microbial food web and the efficiency in the energy transfer to the higher trophic levels.

Rhythmic bedforms of different spatial scales are common in the marine environment. In shallow seas, the monitoring of bedforms is important because changes in morphology may interfere with offshore infrastructure and navigation. In addition, investigating bedform dynamics improves our understanding of the processes that cause their behaviour. Quantified bedform characterization also contributes to the validation of morphodynamic models. Modern, high-precision and high-resolution bathymetric data enable the detailed analysis of bedforms. Several semi-automated methods (e.g. geostatistical and spectral techniques) have been developed to quantify the geometry (size and shape) and dynamics (growth, change in shape and migration) of subaqueous bedforms. An overview of these different approaches is given and differences in use and potential are described.

High-resolution seismic reflection profiles and multibeam bathymetry data collected in 2006 and 2008 around Pantelleria Island show the widespread occurrence of contourite drifts and erosional elements ~30 km from the narrowest part (~145 km) of the Sicily Channel, where water masses from the Eastern Mediterranean flow towards the Western Mediterranean. The contourite drifts are rather small (up to 10 km long and 3.3 km wide), at water depths of ~250–750 m. Most are elongated separated drifts with quite well-developed moats and crests, aligned roughly parallel to the regional bathymetric contours. Erosional elements include abraded surfaces, moats, scours and sub-circular depressions. In addition, a wide sector of the seafloor adjacent to a seamount located SW of Pantelleria Island is characterized by numerous biogenic build-ups colonized by deep-water corals (Madrepora oculata). The spatial distribution of sediment drifts, erosional features and biogenic build-ups suggests an origin from a north-westward-flowing bottom current, in this case the outflow of Levantine Intermediate Water and transitional Eastern Mediterranean Deep Water via the Sicily Channel. These findings for the Pantelleria offshore sector demonstrate that contourite processes are able to concentrate a high variety of closely spaced depositional and erosional features even in small areas (in this case, about 2,000 km2). This Pantelleria focusing can plausibly be related to a particular configuration of the prevailing bottom-current regime in complex interaction with an uneven bathymetry shaped mainly by tectonic and volcanic activity. The distribution of bottom currents seems to be strongly influenced by morphological features ranging from major seabed obstacles, such as the Pantelleria volcanic complex and the so-called southwest seamount, to smaller-scale escarpments and banks. This is consistent with previous findings for Mediterranean and other settings characterized by neotectonics and large topographic features.

Different seafloor areas affected by CO2 fluid emissions have been discovered offshore the Western Pontine Islands (central-Tyrrhenian Sea) along the outer insular shelf surrounding Zannone Island in a water depth varying from 120 to 140 m. These sites have been studied, in the framework of two research projects (MaGIC Project and Ritmare Project) integrating ROV video observations, high resolution multibeam bathymetry, high resolution seismic profiles, water, gas and sediment sampling. Different morphological and biological features such as pockmarks, giant pockmarks, lithified sediments, mounds, cones, gas plumes, bubble streams and bacterial mats have been detected. Geophysical, geochemical and geological data analysis has permitted to speculate the possible genesis, evolution through the time and gas source of such peculiar features, while biological study are being carried out with the aim to verify the influence of fluid emissions on benthic communities. The occurrence of giant and complex fluid emission depressions in shallow water (less than 140 m) represents a relevant finding due the scarcity of such features in the Tyrrhenian area and updates the current knowledge regarding the spatial distribution of the CO2 vents along the Tyrrhenian Sea margins. Furthermore, because the accessible depth this site could be considered optimal for the installation of a multi-disciplinary permanent seafloor observatory to study\monitor the effects of CO2 enriched fluids on benthic communities.

Discoveries from multibeam bathymetry and geochemical surveys performed off Zannone Island (western Pontine Archipelago, Tyrrhenian Sea) provide evidence of an undocumented hydrothermal field characterized by ongoing fluid emissions and morphologically complex giant depressions located in shallow water (250 m) that host pockmarks, mounds, small cones, and active fluid vents, which are interpreted as complex fluid-escape features developed both through vigorous-explosive events and steady seepage. Their spatial distribution suggests that the NE-SW trending faults bounding the Ponza-Zannone structural high and the shallow fractured basement are favorable conditions for the upward migration of hydrothermal fluids. Moreover, we performed a detailed geochemical study to investigate the source of the hydrothermal fluids. The geochemical signature of the collected fluids provides information of active CO2-dominated degassing with a significant contribution of mantle volatiles, with measured 3He/4He values>3.0 Ra that are similar to those recorded at Stromboli and Panarea volcanoes. The hydrothermal system produces volatiles that may originate from residual magma batches, similar to the Pleistocene trachytes cropping out in the SE sector of Ponza Island that were probably intruded in the shallow crustal levels and never erupted. The discovery of the Zannone hydrothermal field updates the record of active hydrothermal areas of the Mediterranean Sea. Moreover, the recognition of several giant hydrothermal depressions characterized by a complex morphology is peculiar for the Mediterranean Sea.

Discussing submarine canyons dynamics through a multidisciplinary approach allowed to identify both advances in knowledge and remaining gaps concerning the controlling factors underlying the formation, development, ecological functioning and vulnerability of canyons at various time scales. As a result, we identified a number of recommendations for future research and actions that the interested reader will discover in this synthetic chapter, drafted as a collective effort in the months following our meeting. The subsequent chapters, each written by a workshop participant, detail the specificities and dynamics of of submarine canyons within and beyond the Mediterranean domain. Versión del editor

The present study shows the preliminary micropaleontological results carried out on grab and multi corer samples collected during a research cruise "BOLLE 2014" carried out on June 2014 aboard to the R/V Urania in the Pontine Archipelago (Tyrrhenian Sea, Italy). This study highlights the strong role of the venting activity on sediment characteristics and on structural and compositional features of benthic communities, in response to the presence of stressed sea bottom conditions due to natural origin. The Western Pontine Archipelago, located about 30 km away from the Italian Peninsula, is composed of three volcanic islands (Ponza, Palmarola and Zannone). The active fluid emissions have been discovered 3 km off the eastern sector of Zannone Island, in a water depth ranging between 105-130 m (outer continental shelf), and affect the Late Quaternary lowstand and highstand deposits. This area appears as a large depression of about 0.5 km2 (900 m long and 500 m wide) with an elongated shape. Sediment, high resolution multibeam bathymetry, biological and video data were acquired in order to characterise both the morphological and biological features related to venting activity. Analysis of ROV videos and sediment sampling allowed us to define the specific living benthic communities within the large depression and among the surrounding seafloor. Great differences among the morphology, sedimentology and microfauna characters between vent and non-vent seafloor areas. As regard the micropaleontological analyses, all samples were stained with Rose Bengal to distinguish living and dead assemblages. Diversity index (?-Fisher index), Faunal density and Foraminiferal Abnormality Index (FAI) were calculated to define the structure of the assemblage and the degree of environmental stress. The benthic foraminiferal assemblages highlights the complete lack of both hyaline and porcelanaceous tests; this fact suggests the presence of strong dissolution processes whereas the patchiness distribution of agglutinant species suggests a direct relation between distribution and very local environmental conditions.

An active giant pockmark located offshore Zannone Island (central Tyrrhenian Sea, Italy), is here analyzed by integration of high resolution seismic profiles, very high resolution multibeam bathymetry and ground-truth data. The active fluid escape structure is located on the outer shelf at 110-130 m water depth, and affects the Late Quaternary lowstand and highstand deposits resting on the rocky bedrock. Evidence of active seepage includes both continuous and intermittent bubble release from the seafloor and a well-defined plume rising 70 m above the seafloor and a variety of fluid-escape features characterizes the area (e.g. craters, pockmarks, lithified pavements, mounds and bacterial mats). The Zannone giant pockmark (ZGP) is about 900 long and 500 m wide and represents the first evidence of an active shallow-water seepage area in the central Tyrrhenian Sea (Italy) and the first record of a morphologically complex giant pockmark in the entire Mediterranean Sea. Some speculations on processes originating the observed features are explored, including possible occurrence of multiple eruption events, processes of fluidization-liquefaction and minor slides that may have modified the original morphology. Factors peculiar to the study area (shallow depth, thin sedimentary cover resting on a faulted rocky basement, seeping occurring through sandy sediments) appear to have been key to the formation and morphology of the ZGP.

We analyse here contourite drifts presumably related to a topographic control given by promontories or seafloor depressions (e.g., slide scars) in some Italian Seas. We therefore investigate the local effect of a topographic unevenness (such as a landslide scar) on flow contouring a cape by applying the classical conservation of marine water potential vorticity (PV). We further analyse the presence of non-linear and/or baroclinic instabilities that may lead to erosive or depositional conditions which, in turn, inhibit or favour the formation of contourites. Such an analysis is performed by applying the classical theory for conservation of potential vorticity (PV) in a cylindrical frame, which is able to describe the fluid properties by means of bathymetric curvatures.

We shows preliminary results from high-resolution seismic reflection profiles (1.5 kJ Sparker and Chirp), multibeam bathymetry and oceanographic surveys (CTD and ADCP) carried out in 2011 and 2013 south Capo Vaticano (southern Tyrrhenian Sea, Italy). The collected data reveal the widespread occurrence of contourites on the upper slope-outer shelf sectors. These newly discovered contourites are interbedded with hemipelagic deposits and locally with turbidite a/o mass wasting deposits. The interaction between alongslope bottom currents and downslope processes can be observed both on the seafloor and within buried depositional sequences of upper Pleistocene age. Sequence stratigraphic interpretation suggests that Capo Vaticano contourite deposits developed within high-order depositional sequences formed during upper Pleistocene eustatic cycles, possibly during lowstand phases.

Recent studies demonstrated the capability of foraminifers to adapt to a wide range of environmental conditions and to give a response to environmental stress due to natural or human origin as environmental indicators (Alve, 1991; Hess et al., 2005; Carboni et al., 2009; Schönfeld et al., 2012). This work aims to document the benthic foraminiferal response to natural stressed environments in two areas, Azores Archipelago and Pantelleria Island, interested by similar active volcanism. The Azores area has been affected by a recent volcanic activity occurred in 2001, while the last submarine eruption of Pantelleria Island dates at 1891. The different periods of eruption of the two areas allow to investigate on the way and time of the re-colonisation process by foraminiferal assemblages. Petrographic, sedimentological and microfaunistic analyses were conducted on selected samples in order to obtain an environmental characterisation of the two active volcanic areas. The inorganic fraction of samples collected in both areas is constituted of blackish, sand-sized glass shards, whereas the organic component is mainly constituted by foraminifers. Faunal composition, diversity and density highlight two different structure of the assemblages relatively to the two areas. In fact the foraminiferal assemblages of the Azores area are dominate by opportunistic species (Angulogerina angulosa) and represent the first stage of re-colonisation after the eruption occurred in 2001, while the associations of Pantelleria Island (Globocassidulina subglobosa, Lenticulina rotulata, Lobatula lobatula and miliolids) have to be considered as an advanced stage of resettlement with stable rich and well diversified assemblages. Moreover, in the Azores area many morphological abnormalities were recognised confirming a more stressed environment than Pantelleria bottom. In both areas a lot of specimens showed test alterations probably due to hydrothermal fluids that lead to the dissolution of calcium carbonate.