Southern Tyrrhenian Research Articles

Seismotomographic detection of major structural discontinuity in northern Sicily

We present the results of tomographic inversion computed with the use of the LOTOS code for Sicily and surroundings, a region of great geodynamic interest located on the Nubia-Europe margin where previous analyses have progressively improved the knowledge of seismic velocity structure without, however, permitting fine detection of tectonic units and structural discontinuities. We used LOTOS's devices for inversion, grid rotation and adaptation to ray density for application to a dataset of 7105 local earthquakes of the period 1990-2012. Our tomographic model highlights a previously undocumented major discontinuity which is located approximately along the northern coast of Sicily and is characterized by a sudden transition from low velocity imbricate thrust sheets and accretionary wedge in mainland Sicily (to the south) to relatively high velocity Tyrrhenian continental crust (to the north). Combining this finding with available geological and geodynamic information, we conclude that this northern Sicily seismic velocity discontinuity, which approximately corresponds to a regional fault system known as Kumeta-Alcantara, may have played a major role in the Miocene to Middle Pliocene, when lithosphere tearing occurred between the Tyrrhenian sea and Sicily in response to trench retreat. The more recent geodynamic settings of northern Sicily and the southern Tyrrhenian can be unravelled from Quaternary geological observations, seismicity and GPS data, which indicate that (i) the northern Sicily discontinuity has ceased to be active in more recent times; and (ii) the reorganized slow convergence of Nubia with respect to Europe is currently accommodated ~100 km north of Sicily, along the east-trending seismogenic belt enclosing Ustica and the Aeolian Islands.

Styles and rates of deformation in the frontal accretionary wedge of the Calabrian Arc (Ionian Sea): controls exerted by the structure of the lower African plate

The Calabrian Arc is a narrow subduction-rollback system resulting from Africa/Eurasia plate convergence. We analysed the structural style of the frontal accretionary wedge through a multi-scale geophysical approach. Pre-stack depth-migrated crustal-scale seismic profiles unravelled the overall geometry of the subduction complex; high-resolution multi-channel seismic and sub-bottom CHIRP profiles, together with morpho-structural maps, integrated deep data and constrained the fine structure of the frontal accretionary wedge, as well as deformation processes along the outer deformation front.We identified four main morpho-structural domains in the western lobe of the frontal wedge: the proto-deformation area at the transition with the abyssal plain; two regions of gentle and tight folding; a hummocky morphology domain with deep depressions and intervening structural highs; a highstanding plateau at the landward limit of the salt-bearing accretionary wedge, where the detachment cuts through deeper levels down to the basement. Variation of structural style and seafloor morphology in these domains are related to a progressively more intense deformation towards the inner wedge, while abrupt changes are linked to inherited structures in the lower African plate. Our data suggest focusing of intense shallow deformation in correspondence of deeply rooted faults and basement highs of the incoming plate.Back-arc extension in the Southern Tyrrhenian Sea has recently ceased, producing a slowdown of slab rollback and plate-boundary re-organization along trans-tensional lithospheric faults segmenting the continental margin. In this complex setting, it is not clear if the accretionary wedge is still growing through frontal accretion. Our data suggest that shortening is still active at the toe of the wedge, and uplift rates along single folds are in the range of 0.25-1.5 mm/yr. An unconformity within the Plio-Quaternary sediments suggests a discontinuity in sedimentation and tectonic processes, i.e. a slowdown of shortening rate or an increase in sedimentation rate, but not a real inactivation of frontal accretion, which still contributes to the migration of the outer deformation front towards the foreland.

Pockmark morphology and turbulent buoyant plumes at a submarine spring

The input flow of groundwater from the seabed to the coastal ocean, known as Submarine Groundwater Discharge (SGD), has been only recently recognized as an important component of continental margin systems. It potentially impacts physical, chemical and biological marine dynamics. Independently of its specific nature (seepage, submarine springs, etc.) or fluid chemical composition, a SGD is generally characterized by low flow rates, hence making its detection and quantification very difficult, and explaining why it has been somewhat neglected by the scientific community for a long time. Along with the growing interest for SGDs emerged the need for in-situ observations in order to characterize in details how these SGDs behave. In this work, we describe the morphology of a pockmark field, detected in the Southern Tyrrhenian Sea (Mediterranean Sea), and provide observational evidences of the presence of active submarine springs over the coastal shelf area. We describe the effect of the fluid seeps on the water column stratification close to the main plumes and in the neighbouring areas, providing quantitative estimates of the intensity of the turbulent mixing and discussing their potential impact on the seabed morphology and pockmark formation in the context of turbulent buoyant plumes analytical modelling.

Coastal hazard due to submarine canyons in active insular volcanoes: examples from Lipari Island (southern Tyrrhenian Sea)

The recent high-resolution multibeam bathymetry surveys around Lipari Island allowed to evidence several submarine canyons, whose head often cut back up to very shallow water and at a few tens of meters far from the coast. These canyons are mainly located in the eastern and southern side of the island and are characterized by an ongoing retrogressive (landward) erosion, that also controlled the shape and the evolution of the coastline. The canyon heads are formed by minor slide scars. By coupling slide scar morphometry and simple numerical model we have been able to roughly estimate the potential tsunami wave amplitudes generated by related slope failures. Moreover, the retrogressive erosion of canyon heads can be claimed as a cause of the enhanced subsidence reported in the last few thousand years in the eastern part of Lipari, where the main villages are located. Based on these evidence, we propose a first assessment of the coastal hazard due to marine retrogressive activity in the largest and most densely populated island of the Aeolian Archipelago.

Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

Paola Ridge, along the NW Calabrian margin (southern Tyrrhenian Sea), is one of the few reported deep sea sites of precipitation of authigenic carbonates in the Tyrrhenian Sea. Here, the changing composition of the seeping fluids and the dynamic nature of the seepage induced the precipitation of pyrite, siderite and other carbonate phases. The occurrence of this array of authigenic precipitates is thought to be related to fluctuation of the sulfate-methane transition zone (SMTZ).Concretions of authigenic minerals formed in the near sub-bottom sediments of the Paola Ridge were investigated for their geochemical and isotopic composition. These concretions were collected in an area characterized by the presence of two alleged mud volcanoes and three mud diapirs. The mud diapirs are dotted by pockmarks and dissected by normal faults, and are known for having been a site of fluid seepage for at least the past 40 kyrs. Present-day venting activity occurs alongside the two alleged mud volcanoes and is dominated by CO2-rich discharging fluids. This discover led us to question the hypothesis of the mud volcanoes and investigate the origin of the fluids in each different domed structure of the study area.In this study, we used stable isotopes (carbon and oxygen) of carbonates coupled with rare earth element (REE) composition of different carbonate and non-carbonate phases for tracing fluid composition and early diagenesis of authigenic precipitates. The analyses on authigenic precipitates were coupled with chemical investigation of venting gas and sea-water.Authigenic calcite/aragonite concretions, from surficial sediments on diapiric structures, have depleted 13C isotopic composition and slightly positive δ18O values. By contrast, siderite concretions, generally found within the first 6 m of sediments on the alleged mud volcanoes, yielded positive δ13C and δ18O values. The siderite REE pattern shows consistent LREE (light REE) fractionation, MREE (medium REE) enrichment and positive Gd and La anomalies. As shown by the REE distribution, the 13C-depleted composition and their association with chemosymbiotic fauna, calcite/aragonite precipitated at time of moderate to high methane flux close to the seafloor, under the influence of bottom seawater. Authigenic siderite, on the other hand, formed in the subseafloor, during periods of lower gas discharges under prolonged anoxic conditions within sediments in equilibrium with 13C-rich dissolved inorganic carbon (DIC) and 18O-rich water, likely related to methanogenesis and intermittent venting of deep-sourced CO2.

Fishery-independent surface abundance and density estimates of swordfish (Xiphias gladius) from aerial surveys in the Central Mediterranean Sea

Fishery–independent surface density and abundance estimates for the swordfish were obtained through aerial surveys carried out over a large portion of the Central Mediterranean, implementing distance sampling methodologies. Both design- and model-based abundance and density showed an uneven occurrence of the species throughout the study area, with clusters of higher density occurring near converging fronts, strong thermoclines and/or underwater features. The surface abundance was estimated for the Pelagos Sanctuary for Mediterranean Marine Mammals in the summer of 2009 (n=1152; 95%CI=669.0–1981.0; %CV=27.64), the Sea of Sardinia, the Pelagos Sanctuary and the Central Tyrrhenian Sea for the summer of 2010 (n=3401; 95%CI=2067.0–5596.0; %CV=25.51), and for the Southern Tyrrhenian Sea during the winter months of 2010–2011 ( n=1228; 95%CI=578–2605; %CV=38.59). The Mediterranean swordfish stock deserves special attention in light of the heavy fishing pressures. Furthermore, the unreliability of fishery–related data has, to date, hampered our ability to effectively inform long-term conservation in the Mediterranean Region. Considering that the European countries have committed to protect the resources and all the marine-related economic and social dynamics upon which they depend, the information presented here constitute useful data towards the international legal requirements under the Marine Strategy Framework Directory, the Common Fisheries Policy, the Habitats and Species Directive and the Directive on Maritime Spatial Planning, among the others.

Living and dead foraminiferal assemblages from an active submarine canyon and surrounding sectors: the Gioia Canyon system (Tyrrhenian Sea, Southern Italy)

Living (rose Bengal stained) and dead benthic foraminiferal assemblages were studied from 23 stations located between 60 and 670 m depth along the Gioia Canyon and the adjacent continental shelf and slope (Southern Tyrrhenian Sea). The aim of this study is to investigate the relationships among sedimentary processes, hydrological patterns and benthic foraminiferal distribution, in a highly dynamic environment. High sedimentation rates on the shelf and occasional turbidity flows along the canyon, lead to unstable environmental conditions at the seafloor that reflect on the microbenthic community influencing faunal density, diversity, species composition and distribution inside the sediment. The foraminiferal distribution seems to be controlled by sedimentary processes, nutrient supply and organic matter recycling, which in turn are strongly controlled by the seasonal variability of riverine inputs and current dynamics in the Gulf of Gioia.From the inner shelf to the upper continental slope (550 m depth), the living foraminiferal assemblage is dominated by agglutinated taxa, likely favored by the high terrigenous supply. Frequent eutrophic taxa (Valvulineria bradyana and Nonionella turgida) tolerant high turbidity (Leptohalysis scottii,) and low oxygen (Bolivina spp. and Bulimina spp.) are recorded on the edge of the inner shelf, where channeling, deposition of coastal deposits and occasional sediment gravity flows occur. In the outer sector of the shelf a turnover of species is observed; L. scottii replaced by the opportunistic species Reophax scorpiurus, and taxa indicative of high energy conditions (Cassidulina spp.) become dominant in association with mesotrophic species like Globocassidulina subglobosa. Along the continental slope, lower sedimentation rates and more stable environmental conditions support richer and more diversified foraminiferal assemblage. The abundance of Bulimina marginata indicates eutrophic conditions at the shallower station (300 m depth) whereas at greater depth (550 m) typical open slope species dominate (Gyroidina spp., Uvigerina mediterranea).Within the Gioia Canyon, benthic assemblage indicates environmental conditions similar to those observed in other Mediterranean and extra-Mediterranean canyons. The assemblage is characterized by eutrophic and low oxygen taxa (Bolivina spp., Bulimina spp.) in relation to periodical fluxes of sediment and organic matter.Similar relationships arise from the analysis of dead foraminiferal assemblages. However, the comparison between living and dead faunas highlight compositional and structural changes related to taphonomic processes.

Ferrous iron- and ammonium-rich diffuse vents support habitat-specific communities in a shallow hydrothermal field off the Basiluzzo Islet (Aeolian Volcanic Archipelago).

Ammonium- and Fe(II)-rich fluid flows, known from deep-sea hydrothermal systems, have been extensively studied in the last decades and are considered as sites with high microbial diversity and activity. Their shallow-submarine counterparts, despite their easier accessibility, have so far been under-investigated, and as a consequence, much less is known about microbial communities inhabiting these ecosystems. A field of shallow expulsion of hydrothermal fluids has been discovered at depths of 170-400meters off the base of the Basiluzzo Islet (Aeolian Volcanic Archipelago, Southern Tyrrhenian Sea). This area consists predominantly of both actively diffusing and inactive 1-3 meters-high structures in the form of vertical pinnacles, steeples and mounds covered by a thick orange to brown crust deposits hosting rich benthic fauna. Integrated morphological, mineralogical, and geochemical analyses revealed that, above all, these crusts are formed by ferrihydrite-type Fe3+ oxyhydroxides. Two cruises in 2013 allowed us to monitor and sampled this novel ecosystem, certainly interesting in terms of shallow-water iron-rich site. The main objective of this work was to characterize the composition of extant communities of iron microbial mats in relation to the environmental setting and the observed patterns of macrofaunal colonization. We demonstrated that iron-rich deposits contain complex and stratified microbial communities with a high proportion of prokaryotes akin to ammonium- and iron-oxidizing chemoautotrophs, belonging to Thaumarchaeota, Nitrospira, and Zetaproteobacteria. Colonizers of iron-rich mounds, while composed of the common macrobenthic grazers, predators, filter-feeders, and tube-dwellers with no representatives of vent endemic fauna, differed from the surrounding populations. Thus, it is very likely that reduced electron donors (Fe2+ and NH4+ ) are important energy sources in supporting primary production in microbial mats, which form a habitat-specific trophic base of the whole Basiluzzo hydrothermal ecosystem, including macrobenthic fauna.

Living coccolithophores community from Southern Tyrrhenian Sea (Central Mediterranean — Summer 2009)

Abstract We present data on distribution patterns of living coccolithophores at 18 selected hydrographic stations, and oceanographic measurements collected at 68 stations during the TIR09 cruise carried out on board of R/V Urania in the southern Tyrrhenian Sea (central part of the Mediterranean Sea) during summer 2009. The survey enabled us to provide indications on the structure of calcareous phytoplankton associations in relation to oceanographic parameters and vertical water column stratification. The total number of coccospheres ranged from − 1 to ~ 6.8 ∗ 10 4 cells l − 1 (mean 8.28 ∗ 10 3 cells l − 1 ). Emiliania huxleyi dominated the assemblages, followed by Gephyrocapsa spp., small placoliths, Calciosolenia spp., Florisphaera profunda , Holococcolithophores spp., Syracosphaera pulchra and Umbellosphaera tenuis . The coccolithophore community showed a typical vertical zonation, with K-strategist taxa in the upper 75 m and the deep community down to 200 m. The local water circulation and summer stratification significantly affected the spatial and vertical distribution of coccolithophores.

Descriptions of eight species from the superfamilies Axioidea Huxley, 1879 and Callianassoidea Dana, 1852, with a revised key to the species of the genus Acanthaxius Sakai & De Saint Laurent, 1989 (Decapoda, Callianassidea)

In the present paper, two new species, Acanthaxius kashimaensis sp. nov. and A. pseudopolyacanthus sp. nov., are described and a revised key to the species of the genus Acanthaxius Sakai & De Saint Laurent, 1989 is presented. In addition, Balssaxius habereri (Balss, 1913) and Boasaxius princeps (Boas, 1880) of the family Axiidae Huxley, 1879, Neaxius glyptocercus (Von Martens, 1869) of the family Strahlaxiidae Poore, 1994, together with Trypaea truncata (Giard & Bonnier, 1890) of the family Callianassidae Dana, 1852, and two species, Calliax lobata (De Gaillande & Lagardère, 1966) and Calliaxina punica (De Saint Laurent & Manning, 1982), of the family Eucalliacidae Manning & Felder, 1991 [sensu Sakai, 2011], are commented upon. The descriptions given herein result from the examination of specimens collected from Ise-Shima, Mie Prefecture and Ôfunato-City, Iwate Prefecture, as well as from Iriomote Island, Ryukyu Islands, Japan, and from material collected from Salamis, Saronikos Gulf, Greece, and the Palinuro Seamount, southern Tyrrhenian Sea, Italy.

Temporal Evolution of the Microbiological Conditions of a Sicilian Area Designed for Aquaculture (Castellammare Gulf, Southern Tyrrhenian Sea)

Microbiological controls of coastal seawaters are a common practice to verify their safety for human recreational and productive uses. The aim of the present study is to describe the microbiological conditions of the Castellammare Gulf (Trapani, Sicily), an area traditionally used for aquaculture purposes. Particularly, the results obtained from three surveys (1993-1995, 2000-2001 and 2007) are compared in order to depict how the hygienic-sanitary conditions of this marine ecosystem have evolved over time. Attention has been given to the abundance and distribution of the bacterial indicators of faecal pollution (faecal coliforms, enterococci and Salmonella spp.) as well as halophilic vibrios, using the culture methods conventionally indicated by current legislation in force for the sanitary control of waters designed for aquaculture productions. The obtained results shows that the sanitary conditions of seawater samples met the criteria recommended by current legislations for shellfish farming approved areas. The low concentrations of faecal pollution indicators and of halophilic vibrios confirm the general suitability of the Gulf of Castellammare for seafood production. Nevertheless, the detection of low percentages of potentially pathogenic species of halophilic vibrios stresses the importance of extending microbiological controls also to these emerging pathogens.

Validation of HF Radar-Derived Currents in the Gulf of Naples With Lagrangian Data

A massive drifter deployment in the Gulf of Naples (Southern Tyrrhenian Sea, Western Mediterranean Sea) over a ten-day multidisciplinary in situ experiment in Summer 2012 provided sea-truth data for validating the performance of a high-frequency (HF) radar network. The buoys were frequently retrieved and relaunched to ensure an optimal coverage of the domain. The total velocity of the drifters, together with the associated zonal and meridional components, was compared with the HF radar surface current estimates. Divergence between virtual and real drifter trajectories, and also the simulated movement of clouds of particles give useful insights for scenarios of search and rescue. All comparisons were performed, considering both ideal and antenna radiation pattern-corrected fields. The results of the investigation testify the high precision of HF radars and confirm the necessity of periodically verifying the antenna pattern to ensure the optimal functionality of these systems.

Pleistocene volcaniclastic units from North-Eastern Sicily (Italy): new evidence for calc-alkaline explosive volcanism in the Southern Tyrrhenian Sea

AbstractA well-preserved volcaniclastic sequence crops out in Pleistocene marine sediments along the Tyrrhenian coastline of the Calabrian-Peloritani arc (Sicily, Italy), testifying the occurrence of Lower-Middle Pleistocene volcanic activity in Southern Tyrrhenian Sea. The presence of dominant highly vesicular and minor blocky glassy particles indicates that the volcanic clasts were originated by explosive events related to the ascent and violent emission of volatile-rich magmas accompanied by and/or alternated with hydromagmatic fragmentation due to magma-sea water interaction. Field investigations and sedimentological features of the studied volcaniclastic units suggest a deposition from sediment-water density flows. The chemical classification of the pumice clasts indicates prevalent rhyolitic and dacitic compositions with calc-alkaline to high-K calc-alkaline affinity. The geochemical features of immobile trace elements together with the presence of orthopyroxene are indicative of a provenance from an arc-type environment. The age (from 980-910 to 589 ka), the chemical composition and the evidence of subaerial explosive volcanic activity constrain the origin nature and temporal evolution of the arc-type volcanism in the Southern Tyrrhenian domain. Finally, the new information here provided contribute to a better understanding of the temporal geodynamic evolution of this sector of the Mediterranean domain.

Magnitude-frequency distribution of submarine landslides in the Gioia Basin (southern Tyrrhenian Sea)

Regional inventories and magnitude-frequency relationships provide critical information about landslides and represent a first step in landslide hazard assessment. Despite this, the availability of accurate inventories in the marine environment remains poor because of the commonly low accessibility of high-resolution data at regional scales. Evaluating high-resolution bathymetric data spanning the time interval 2007–2011 for the Gioa Basin of the southern Tyrrhenian Sea yielded a landslide inventory of 428 events affecting an area of >85 km2 and mobilizing approximately 1.4 km3 of sediment. This is the first time that this area is studied in such detail, justifying comparison with other areas both onland and offshore. Statistical analyses revealed that the cumulative distribution of the dataset is characterized by two right-skewed probability distributions with a heavy tail. Moreover, evidence of a rollover for smaller landslide volumes is consistent with similar trends reported in other settings worldwide. This may reflect an observational limitation and the site-specific geologic factors that influence landslide occurrence. The robust validation of both power-law and log-normal probability distributions enables the quantification of a range of probabilities for new extreme events far from the background landslide sizes defined in the area. This is a useful tool at regional scales, especially in geologically active areas where submarine landslides can occur frequently, such as the Gioia Basin.

Tephrochronology of a ~ 70 ka-long marine record in the Marsili Basin (southern Tyrrhenian Sea)

A sequence of tephra layers is studied in a 13.9m-long deep-sea core (MD01-2474G) from the southern Tyrrhenian Sea. The chronology of the succession is provided by a high-resolution age-depth model based on isotope stratigraphy and AMS radiocarbon dating, which place the succession of events in a time interval spanning the last 70ka. Based on a precise chronological framework and proximal-distal correlations, the Y-1, Y-6 and Y-7 main marker tephras were identified. Compositional data on fresh micro-pumice or glass shards of selected tephras were correlated with the coeval volcanic activity of Aeolian Arc (Vulcano and Salina), Mt. Etna, Phlegrean Fields Pantelleria and Ischia. The tephra sequence contains a number of deposits documenting recurrent activity on Vulcano Island at ca. 6.9kaBP (MD3), ca. 16.7kaBP (MD11), ca. 23.2kaBP (MD14), ca. 29.6kaBP (MD15), ca. 36.9kaBP (MD22) and ca. 42.5kaBP (MD27). The results presented in this study improve the southern Tyrrhenian Sea tephrostratigraphic framework and provide new insights into chemistry and dispersal area of Aeolian Arc pyroclastic deposits in this sector of the Central Mediterranean.

The Cenozoic fold-and-thrust belt of Eastern Sardinia: Evidences from the integration of field data with numerically balanced geological cross section

Newly collected structural data in Eastern Sardinia (Italy) integrated with numerical techniques led to the reconstruction of a 2-D admissible and balanced model revealing the presence of a widespread Cenozoic fold-and-thrust belt. The model was achieved with the FORC software, obtaining a 3-D (2-D + time) numerical reconstruction of the continuous evolution of the structure through time. The Mesozoic carbonate units of Eastern Sardinia and their basement present a fold-and-thrust tectonic setting, with a westward direction of tectonic transport (referred to the present-day coordinates). The tectonic style of the upper levels is thin skinned, with flat sectors prevailing over ramps and younger-on-older thrusts. Three regional tectonic units are present, bounded by two regional thrusts. Strike-slip faults overprint the fold-and-thrust belt and developed during the Sardinia-Corsica Block rotation along the strike of the preexisting fault ramps, not affecting the numerical section balancing. This fold-and-thrust belt represents the southward prosecution of the Alpine Corsica collisional chain and the missing link between the Alpine Chain and the Calabria-Peloritani Block. Relative ages relate its evolution to the meso-Alpine event (Eocene-Oligocene times), prior to the opening of the Tyrrhenian Sea (Tortonian). Results fill a gap of information about the geodynamic evolution of the European margin in Central Mediterranean, between Corsica and the Calabria-Peloritani Block, and imply the presence of remnants of this double-verging belt, missing in the Southern Tyrrhenian basin, within the Southern Apennine chain. The used methodology proved effective for constraining balanced cross sections also for areas lacking exposures of the large-scale structures, as the case of Eastern Sardinia.

Fisheries-related Tourism in Southern Tyrrhenian Coastline

Among several possible development activities, the Fishery Local Action Groups (FLAGs), activated with the EC Regulation 1198/2006, can promote fisheries-related tourism activities that may represent a driving sustainable force, for economic local development in coastal areas, in line with the EU objectives of reducing the fishing effort and, at the same time, fisheries-related tourism. The main objective of this study is to analyze the trend of the territory of the “Stretto” Coast FLAG in Calabria to diversify the fishing activities, also through the comparison with the Aeolian Islands, which are part of the “Islands of Sicily” FLAG. The methodology includes direct surveys through privileged witnesses such as fishermen and fishing cooperatives of the two areas. The results show some differences: in the Aeolian Islands the practice of fisheries-related tourism activities is conducted continuously all the year, in a few cases the fishermen also offer accommodation; on the contrary, in Calabria in the “Stretto” Coast FLAG vessels are of larger dimensions and fishing tourism is occasional and not widespread. Adequate promotion and marketing, and policy support are lacking in both areas.

Different key roles of mesoscale oceanographic structures and ocean bathymetry in shaping larval fish distribution pattern: A case study in Sicilian waters in summer 2009

Fish larvae data collected in year 2009 were used to examine the effects of particular environmental conditions on the structure of larval assemblages in two oligotrophic Mediterranean areas (the Southern Tyrrhenian Sea and the Strait of Sicily). For this purpose, relationships with environmental variables (temperature, salinity and fluorescence), zooplankton biomass, water circulation and bathymetry are discussed. Hydrodynamic conditions resulted very differently between two study areas. The Southern Tyrrhenian Sea was characterized by moderate shallow circulation compared to the Strait of Sicily. In this framework, distribution pattern of larval density in the Tyrrhenian Sea was mainly driven by bathymetry, due to spawning behavior of adult fish. There, results defined four assemblages: two coastal assemblages dominated by pelagic and demersal families and two oceanic assemblages dominated by mesopelagic species more abundant in western offshore and less abundant in eastern offshore. The assemblage variations in the western side was related to the presence of an anti-cyclonic gyre in the northern side of the Gulf of Palermo, while in the eastern side the effect of circulation was not very strong and the environmental conditions rather than the dispersal of species determined the larval fish communities structure. Otherwise in the Strait of Sicily the currents were the main factor governing the concentration and the assemblage structure. In fact, the distribution of larvae was largely consistent with the branch of the Atlantic Ionian Stream (AIS). Moreover, very complex oceanographic structures (two cyclonic circulations in the western part of the study area and one anti-cyclonic circulation in the eastern part) caused the formation of uncommon spatial distribution of larval fish assemblages, only partially linked to bathymetry of the study area. Typically coastal larvae (pelagic families: Engraulidae and Clupeidae) were mostly concentrated in the offshore areas and off Capo Passero, where the presence of a thermo-haline front maintained their position in an area with favourable conditions for larval fish feeding and growth.

Results of the first Wave Glider experiment in the southern Tyrrhenian Sea

<p>A wave-propelled autonomous vehicle (Wave Glider) instrumented with a variety of oceanographic and meteorological sensors was launched from Gulf of Naples on the 12<sup>th </sup>of September 2012 for a two-week mission in the Southern Tyrrhenian Sea. The main objective of the mission was a preliminary evaluation of the potential of commercial autonomous platforms to provide reliable measurements of sea surface parameters which can complement existing satellite based products moving from the local to the synoptic scale. To this aim Wave Glider measurements were compared to equivalent, or near-equivalent, satellite products achieved from MODIS (Moderate Resolution Imaging Spectroradiometer) sensors onboard the EOS (Earth Observing System) satellite platforms and from AVISO (Archiving Validation and Interpretation of Satellite Oceanographic Data). Level-3 near real time and Level-4 reprocessed sea surface foundation temperature products provided by the CMEMS (Copernicus Marine Environment Monitoring Service) were also included in this study as well as high resolution model output supplied by NEMO (Nucleus for European Modelling of the Ocean). The Wave Glider was equipped with sensors to measure temperature, salinity, currents, as well as Colored Dissolved Organic Matter (CDOM), turbidity and refined fuels fluorescence. The achieved results confirmed the emerging value of Wave Gliders in the framework of multiplatform monitoring systems of the ocean surface parameters. In particular, they showed that Wave Glider measurements captured the southern Tyrrhenian Sea major surface oceanographic features, including the coast to open sea haline gradient and the presence of a cyclone-anticyclone system in the southeastern sub-region. The Wave Glider also had the capability to monitor upper ocean currents at finer spatial and temporal scales than satellite altimetric observations and model outputs. Nonetheless, results stressed the existence of several limits in the combined use of satellite and Wave Glider observations and the necessity of further analyses concerning the monitoring of the ocean optical properties. In fact, Wave Glider and satellite-based products agree in terms of sea surface temperature and currents patterns, while bio-optical properties turned out to be less well correlated. No significant traces of refined fuels have been detected along the WG track.</p>

Occurrence and prevalence of Philometra filiformis (Stossich, 1896) on Pagellus erythrinus (Linnaeus, 1758) in the Southern Tyrrhenian Sea

In this paper the host-parasite relationship between Philometra filiformis and the common pandora Pagellus erythrinus from the Southern Tyrrhenian Sea were studied. A total of 305 (257 females and 48 males) specimens of common pandora were sampled from June 2009 to April 2011 from commercial landings as well as from bottom trawl surveys. A total of 39 P. erythrinus were parasitized (mean prevalence, P = 12.80%; mean abundance, A = 0.19), with the parasite occurring throughout the study area and with wide fluctuations in prevalence values ranging from 0 to 28.60%. Prevalence increased with age of the host, with most parasites (27.78%) found in the older common pandora whereby P. filiformis parasitized only the females. A significant correlation between prevalence, abundance and maturity stages of the fish was evident, with most parasites found in mature/spawning specimens. The varying degrees of gonadic damage caused by this nematode reveal a serious threat to the reproductive success of P. erythrinus.