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Coralligenous reefs are typical underwater seascapes of the Mediterranean Sea and are ranked among the most relevant ecosystems of the basin and a pole of biodiversity. For their critical importance for ecosystems conservation, coralligenous reefs are included among the indicators that should be assessed under the Marine Strategy Framework Directive (MSFD). However, information regarding their spatial distribution and the influence of environmental factors on their structure and biological characteristics is still poor. As part of monitoring regional programs for the implementation of the MSFD in Italy, an extensive study was performed along the Latium continental shelf, aimed to define and map the distribution of coralligenous reefs and to assess their environmental status in three different study areas, characterized by different environmental conditions and subjected to different potential levels of human pressure. For each area, a large dataset was collected, including multibeam bathymetry, side scan sonar records and ROV video transects. The integrated analysis of geophysical data and ROV videos allowed to identify the morpho-acoustic facies indicative of coralligenous outcrops and to map their distribution across the study areas. In parallel, a quantitative analysis of video transects was carried out, in order to characterize the megabenthic communities in terms of species composition, abundance, health status of structural species, and to evaluate the abundance of marine litter. The environmental status of the coralligenous communities was then assessed through the application of the Mesophotic Assemblages Conservation Status (MACS) index. The results obtained showed a large variability in the distribution and characteristics of coralligenous reefs and associated assemblages along the Latium continental shelf, likely reflecting the different environmental conditions and human pressure in the different areas. Coralligenous reefs were reported from all the investigated areas, hosting a rich and varied associated fauna with dense gorgonian forests, also featuring species of relevance for conservation such as Corallium rubrum. The application of MACS index allowed to distinguish among a wide range of ecological conditions of the coralligenous communities, spanning from high to poor environmental status across different sites. The assessment of the extent and diversity of coralligenous assemblages through the combination of geomorphological analysis, acoustic mapping and quantitative video analysis represents an efficient tool, which may help governments and stakeholders making informed management decisions for future coastal planning and conservation strategies.

19 pages, 15 figures, 2 tables, supplementary material https://doi.org/10.1016/j.margeo.2020.106372.-- Data availability: The datasets analysed during the current study are available from the corresponding author on reasonable request, The upper continental slope offshore Capo Vaticano (southern Tyrrhenian Sea) is characterized by a contourite depositional system with well-developed elongated sediment drifts. This system is related to a northward paleo-bottom current, similar to the present-day modified-Levantine Intermediate Water (modified-LIW) flowing from the Messina Strait. In this work, we show results from an integrated analysis of descriptive oceanography, high-resolution seismic profiles and core data (i.e., grain size, foraminiferal assemblages, tephrostratigraphy and AMS radiocarbon dating) collected from the crest and moat sectors of drift deposits. The studied succession formed since the mid Holocene, under the action of the modified-LIW and the stratigraphic architecture indicates an upslope migration of the moat and rather stable position of the crest sector. Grain-size features recorded from two sediment cores indicate the occurrence of a succession of complete bi-gradational sand-rich contourite sequences. Sandy facies were observed both as lag deposits formed in active moat channel and as coarser intervals of bi-gradational sequences forming drift deposits close to its crest. Their occurrence would highlight that upper slope environments impacted by intermediate water masses and proximal to sandy sources may represent favorable settings for accumulation of sandy sediment. The moat sector is characterized by a more complex stratigraphic record, where either moat sedimentation or lateral deposition of finer sediment occur, suggesting that further investigation is required to better understand this complex element of contourite systems. Based on available age information, some of the bi-gradational sequences probably formed during the Dark Age Cold Period, providing example of a small-scale cyclicity of contourite deposition, likely related to short-term (possibly multicentennial scale) fluctuations of the paleo modified-LIW. According to age constraints and analysis of foraminiferal assemblages, these fluctuations were likely governed by climate variations, with a weaker activity during warmer periods and faster currents during colder events, Core LGT5 was collected during the Gioia77 cruise funded by the Eurofleets2 Project. With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

29 pages, 10 figures, 4 tables, This article offers an overview of the main sedimentary systems defining the geomorphology of deep sea environments from low to high latitudes. Mass-transport deposits, turbidite systems, contourites, volcaniclastic aprons, glacial trough mouth systems, carbonate mounds and other bathyal systems, such as pelagites, hemipelagites, mid-ocean channels and polymetallic mineral deposits, are presented with special attention to their morphology, sediments, processes and controlling factors. The integration of the main systems on the continental margins and adjacent abyssal plains in the North Atlantic and westernmost Mediterranean allows to characterize different sedimentation models

Litter is a significant environmental issue, threatening all ocean environments including the deep sea, where little is known about the extent of the threat. This study collected underwater videos on shelf-indenting canyons (the Gioia and Petrace Canyon) and adjacent sectors to characterize benthic litter and its distribution patterns. A high density of litter was present in the canyon thalwegs (up to 56.3 items/100 m), where ∼95 % of observed debris was concentrated. Litter primarily comprised of plastic (∼90 %). The presence of household objects intermingled with vegetal material indicates a strong influence of land-based sources for litter in these areas. Sedimentary gravity flow processes transported natural and anthropogenic debris downslope and may determine its burial beneath the seafloor. Another litter transport mechanism is the presence of light items, observed while drifting above the seafloor under the action of down-canyon bottom currents. This phenomenon was frequently documented within Gioia Canyon, where up to 74 drifting items were counted in one hour of video. Conversely, a lower litter concentration was found along the continental margin, where items were mostly fishing-related. Findings from this study confirm that canyons act as conduits for land-sourced debris and litter transport from coastal to deep-sea environments. The funnelling of a large amount of plastic to the deep sea through multiple processes indicates that the magnitude of this pollution may be greater than expected. This pollution could concentrate in canyons along continental margins and possibly at the mouths of canyons at the base of the slope. This issue requires urgent attention, as understanding of deep-sea litter distribution is still limited and potential impacts to benthic ecosystems are poorly understood.

In the Mediterranean Sea, coralline algae assemblages (i.e. rhodolith beds and coralligenous assemblages) are considered biodiversity hotspots comparable to tropical reefs. However, information regarding their environmental distribution is still poor. In this view, relevant international actions have been adopted by the European Union to fill this gap. This work represents one of a few cases of predictive (fine-scale) habitats distribution map obtained through an integrated semi-automatic approach based on bathymetry, backscatter, seismic profiles, video, and sampling data. The used method has permitted the identification of nine morphological zones, four backscatter facies, and four benthic habitats distributed on the Zannone seafloor (western Pontine Archipelago; Tyrrhenian Sea). In particular, the finding of widespread sensitive habitats (i.e. coralligenous assemblages and rhodolith beds) reveals as the marine area off the western Pontine Archipelago (Tyrrhenian Sea) is highly suitable for their development (distance from the mainland, lack of river mouths), confirming the relevant ecological value of the Zannone area. Therefore, such information constitutes an update to the Mediterranean habitats distribution inventory, highlighting the need for the application of protection actions possibly targeted in the establishment of a Marine Protected Area.

A mono-specific population of Isidella elongata in the Ventotene Basin (Pontine Islands, western Mediterranean Sea) was recently revealed by ROV survey. This vulnerable marine community was found on top of a 3.6 km long morphological high, in water depths between 510 and 560 m. Side scan sonar data showed the presence of several trawl marks suggesting a high anthropogenic impact of the study area. Furthermore, multibeam and high-resolution seismic data revealed the presence of widespread pockmarks, indicating occurrence of fluids in the sub-seafloor.

Special issue Bridging the gap between the shallow and deep oceans: The key role of submarine canyons.-- 13 pages, 9 figures, 2 tables, The impacts of fishing activities on ecosystems represent an acknowledged environmental issue, especially considering the increasing demands for the conservation of biodiversity. Submarine canyons are complex environments that can harbor high biodiversity of benthic ecosystems and high biomass of fish species, thus representing preferential fishing areas for bottom trawling fleets. The effects of bottom trawling on the benthic epifauna were investigated over the soft-bottom margins of the Gioia Canyon (Southeastern Tyrrhenian Sea) by means of quantitative analysis of Remote Operated Vehicle (ROV) video transects and compared with the recent pattern of trawling intensity, reconstructed through processing of data collected with the Vessel Monitoring System (VMS). Four ROV transects were then performed at 320–540 m depth in areas affected by different trawling pressure. The analysis was focused on the bamboo coral Isidella elongata and the sea pen Funiculina quadrangularis, which are considered indicator taxa of Vulnerable Marine Ecosystems (VMEs) and relevant in terms of sustainable management priorities. I. elongata only occurred at the two deeper stations, below 400 m depth. This species showed a clear relationship with trawling intensity, since its abundance was significantly higher under low trawling intensity, where coexistence of large (>20 cm height) and small colonies was observed. The relatively high prevalence of small colonies in areas exposed to higher trawling effort was interpreted as a consequence of the trawling activity that removed the larger colonies. However, the frequent occurrence of dead colonies and the diffuse presence of epibionts (e.g. the anemone Amphianthus dohrnii and the hydroid Clytia linearis) on living colonies indicate stressful conditions for I. elongata even in areas where trawling intensity was lower. Conversely, the relationship between trawling intensity and species abundance was not straightforward for F. quadrangularis; despite the lowest abundance of this species was recorded in areas subject to high trawling intensity, relatively high abundances were observed in areas with intermediate trawling effort. Although such distribution may be driven by other environmental factors, it suggests that vulnerability to bottom trawling can be different for the two species

The new record of a shallow-water submarine hydrothermal field (

The collection of high-resolution multibeam bathymetry, single-channel seismic profiles, TOBI side scan sonar data, and gravity cores allowed the characterization of the main morpho-sedimentary processes acting along the lower reach of the shelf-indenting Gioia-Mesima canyon-channel system (GMS) and the surrounding continental slope (southern Tyrrhenian Sea). This last area, developing across a depth range of 1000–1700 m, shows a complex morphology due to the interaction between downslope gravitative processes (mainly turbidite sheet flows) and abrupt changes in slope gradients related to tectonically-controlled scarps. Particularly, several erosive-depositional features (levee deposits, sediment undulations, channels) have been related to overflow processes from the northern flank of the GMS, although the lower reach of the GMS is characterized by strong entrenchment (canyon height ranging from 120 to 270 m) and low sinuosity. Morphological and seismic stratigraphy data indicate that the distribution and dimension of these features vary in response both to the proximity to the external levee of the GMS and to the topographic gradient of the lower continental slope. Particularly, we were able to discriminate between a gently sloping sector (on average 1.5°) dominated by sedimentary bypass of the turbidity currents and a steeper sector (about 3°), where the erosional capability of these currents seems to increase. Indeed, three channels, 4,3–6,5 km long and up to 20 m deep, incise this steeper sector, running parallel to each other at a distance of 1250–1500 m. To support the capability of overbanking flow in producing these channels, we used a physical model for the ignition of turbidity currents that provides realistic values for the ignitive state of the overbanking turbidity flows. More generally, the methodological approach used in this study may be useful to provide constraints on the genesis and evolution of erosive-depositional features in other tectonically-controlled margins, where sedimentary gravity flows interact with an uneven morphology.

Recent investigations highlighted the occurrence of a giant depression related to hydrothermal activity off the Pontine Archipelago (central Mediterranean Sea, Italy). The new record of a giant seeping depression (Zannone Giant Pockmark, ZGP) in shallow-water provides the opportunity to study fluid vent impact on meiobenthic communities. The micropaleontological analyses on living (Rose Bengal stained) and dead assemblages recorded inside and outside the Zannone Giant Pockmark, allow to highlight changes in the structure and composition of the foraminiferal community that suggest variations of fluid emissions in different sectors of the study area. Inside the ZGP, under the direct influence of venting activity, a very peculiar living foraminiferal assemblage is found. It consists of agglutinated species (Spiculosiphon oceana, Jaculella acuta, Deuterammina rotaliformis) never found or very rare in the Mediterranean Sea. On the contrary dead assemblage testifies the changes on foraminiferal assemblages under carbonate dissolution process. Outside the pockmark in the nearby area of ZGP, the integrated meiofaunal and geochemical data suggest a transitional condition between vent influenced sedimentation and the typical carbonate sedimentation recorded in the rest of the Pontine Archipelago. In particular a possible spread of the venting activity in the northern and southern sectors of the study area, towards the edge of the Zannone insular shelf, is inferred. The impact of fluid emissions on foraminiferal assemblages can be summarized in the following observations: reduced biodiversity, increase of agglutinated species with predominant siliceous component in the test structure, limited distribution of living specimens inside the sediment, disappearance of porcelaneous taxa and presence of carbonate loss tests. As the result, the venting activity is likely to be the main environmental driver on the meiofaunal distribution. We also report, at the emission sites in the Pontine Archipelago, the presence of agglutinated species such as Spiculosiphon oceana, Jaculella acuta, Deuterammina rotaliformis, never found earlier in the Mediterranean Sea.

17 pages, 13 figures, 4 tables supplementary data https://dx.doi.org/10.1016/j.jmarsys.2016.01.005, In this paper, we used multibeam bathymetry and backscatter, high-resolution seismic profiles, ROV video images and sediment samples to identify the principal morpho-sedimentary features and related megabenthic communities along the upper reach of the Gioia Canyon (depth < 600 m) and the surrounding shelf and slope areas. Interpretation of the multidisciplinary dataset was undertaken to evaluate the relationships between seafloor characteristics and faunal distribution along a submarine canyon in an active tectonic setting. The results from this study indicate that physical disturbance on the seafloor at the canyon head and surrounding shelf, related to high sedimentation rates and occasional turbidite flows, may limit the variability of megabenthic communities. Evidence of diffuse trawl marks over soft sedimentary bottoms indicates anthropogenic impact due to fishing activities, which could explain low abundances of megabenthic species observed locally. The canyon margins and flanks along the continental slope host octocorals Funiculina quadrangularis and Isidella elongata, species that are indicative of vulnerable marine ecosystems (VMEs) and relevant in terms of sustainable management priorities. At the Palmi Ridge, the occurrence of outcropping rocks and bottom currents related to the presence of Levantine Intermediate Waters, provide conditions for the development of hard-bottom assemblages, including the black coral Antipathella subpinnata and deep-sea sponges fields, This research was performed in the framework of the Flagship Project RITMARE (SP4-WP2-A1)

Highlights: - Analysis of a combined new high-resolution 2D seismic and bathymetric data set offshore Mt Etna - Extensional domains are mapped at the shallow subsurface of the continental margin - Compressional structures are mapped at the toe of the continental margin - A coupled volcano edifice / continental margin instability is proposed Mount Etna is the largest active volcano in Europe. Instability of its eastern flank is well documented onshore, and continuously monitored by geodetic and InSAR measurements. Little is known, however, about the offshore extension of the eastern volcano flank, defining a serious shortcoming in stability models. In order to better constrain the active tectonics of the continental margin offshore the eastern flank of the volcano, we acquired a new high-resolution 2D reflection seismic dataset. The data provide new insights into the heterogeneous geology and tectonics at the continental margin offshore Mt Etna. The submarine realm is characterized by different blocks, which are controlled by local- and regional tectonics. A compressional regime is found at the toe of the continental margin, which is bound to a complex basin system. Both, the clear link between on- and offshore tectonic structures as well as the compressional regime at the easternmost flank edge, indicate a continental margin gravitational collapse as well as spreading to be present at Mt Etna. Moreover, we find evidence for the offshore southern boundary of the moving flank, which is identified as a right lateral oblique fault north of Catania Canyon. Our findings suggest a coupled volcano edifice / continental margin instability at Mt Etna, demonstrating first order linkage between on- and offshore tectonic processes.

An active giant pockmark located offshore Zannone Island (central Tyrrhenian Sea, Italy), is analyzed by very high resolution multibeam bathymetry, high resolution seismic profiles, ROV video observations, sediment and water sampling. The active fluid emission area is located on the outer shelf, between 110 and 130 m water depth, and affects the Late Quaternary lowstand and highstand deposits resting on rocky bedrock. A variety of fluid-escape features characterizes the area, including the Zannone giant pockmark, several smaller pockmarks, hummocky terrains and areas of positive relief. Ground-truth video data show active seepages, bacterial communities, widespread lithified pavements, mounds, and cone-shaped structures. 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. The Zannone giant pockmark is about 900 × 500 m (surface of some 0.5 km 2 ). It 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 non-cohesive sandy sediments – appear to have been key to the formation and morphology of the Zannone giant pockmark.

Publisher Summary The Tyrrhenian Sea is in the central part of the Mediterranean Sea between the mainland of Italy and the islands of Corsica, Sardinia, and Sicily. The sea is located in a geodynamically active area, with extensive tectonics and a young volcanism related to the opening of a back arc basin that started during Late Miocene to Pliocene times. The Tyrrhenian Sea is characterized by a microtidal regime, which has only a secondary influence on the coastal dynamics. The Tyrrhenian Sea is a young back arc basin with a continental shelf characterized by siliciclastic sediments, delivered mainly by rivers. However, areas of carbonate sediments are also found on the shelf, as is characteristic of mid-high latitudes. The Archipelago Pontino in the eastern central Tyrrhenian Sea consists of five islands formed mainly of volcanic rocks of Plio-Pleistocene age. The low siliciclastic sediment input in this area can be attributed to the lack of significant river runoff, because there are no major rivers on the islands, which are located about 30 km away from the mainland. The relatively high-energy hydrodynamic regime around the islands also prevents the deposition of muddy sediments. The biogenic sediment fraction comprises mainly coralline algae, foraminifers, bryozoans, and undifferentiated bioclasts, and to a lesser extent bivalves, crinoids, echinids, gastropods, ostracods, pteropods, serpulids, and sponge spicules. A variety of depositional units that characterize particular marine habitats have been identified in the area. The most significant habitats include those of Posidonia oceanica, rhodoliths (unattached red algae), and “coralligene."

The complex relationship between currents flowing around capes and their related contourite deposits (i.e. marine sediments deposited and/or reworked by the persistent action of bottom currents) is still an interesting and debated topic, both from a sedimentologic and oceanographic perspective. We analyze here contourite drifts located at intermediate depths off promontories in the southern Tyrrhenian and in the southern Adriatic Sea. The comparison between bathymetric-stratigraphic data and numerical, tank and analytic results, allows us to investigate the occurrence of contourite deposits around capes. We found that the presence of turbulence, and thus, of erosive conditions for sediments in the lee-side of a cape, can be detected by using dimensionless numbers related to cape dimension and ocean current features. We, moreover, analyze the additional sedimentary processes caused by seafloor unevenness offshore the cape such as local topographic depressions by applying the classical conservation of potential vorticity. The resulting effect is a steady cyclonic circulation over the depression that affects contourite deposition. We show that the application of the potential vorticity conservation provides a simple theoretical tool for the understanding of complex relations among ocean current, seafloor morphologies, and sedimentary processes. This work can be seen as a new approach to bridge the gap between marine sedimentology and physical oceanography.