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Spiculosiphon oceana Maldonado, López-Acosta, Sitjà, Aguilar, García & Vacelet, 2013 is a Mediterranean endemic giant stalked foraminifer described as a potential bio-indicator of acidic environments, thanks to its ability to cope with stressful chemical conditions. Here, we present the first record and the first video images of living specimens of this giant foraminifera in the Panarea Volcanic Complex (PVC; southern Tyrrhenian Sea), representing the third discovery worldwide. Specimens of S. oceana were identified through microscopic and remotely operated vehicle (ROV) image analyses, in two different areas characterised by water column physico-chemical parameters typical of the non-vented areas, but with some evidence of hydrothermal alteration. This new finding enhances knowledge on the ecology of S. oceana, enlarges its known spatial distribution, and corroborates its affinity to intermediate stress conditions related to hydrothermal activity.

The distribution of floating litter in marine waters, influenced by currents and wind drag, often determines the dispersal of its encrusting fauna. In the present paper, we observed for the first time the colonization of rafting floats from abandoned, lost or derelict fishing gears (ALDFG) by the four protected deep-sea species: Errina aspera, Desmophyllum pertusum, Madrepora oculata Pachylasma giganteum. Overall, 41 floats, colonized by deep benthic species, were found stranded on the shore of the Sicilian coast of the Strait of Messina, between 2016 and 2019. Species composition, number and occurrence of colonizing organisms were analyzed. On the basis of the species composition (the association between E. aspera, P. giganteum and Megabalanus tulipiformis), the knowledge on their ecology, biogeography, path of local currents, it was possible to define that the area of origin of the most part of these fishing net floats was the Strait of Messina.

The close relationship between a polyclad (Platyhelminthes, Rhabditophora, Polycladida) and the mesophotic Atlantic–Mediterranean black coral Antipathella subpinnata (Ellis & Solander, 1786) (Cnidaria, Hexacorallia, Antipatharia) is herein described for the first time. Worms, up to 50 mm long, are elongated with sparse dorsal papillae, an anterior, ruffled pharynx and caudal, well-separated gonopores. The bulbous vagina is connected to a very elongated Lang’s vesicle, while the male apparatus, hosting a cuticular penis papilla, consists in a muscular interpolated prostatic vesicle, formed by few chambers surrounding the ejaculatory duct, a major seminal vesicle and numerous spermiducal bulbs. These features, as well as the uniqueness of the symbiotic relationship and relative reproductive adaptations, support the description of a new taxon, Anthoplana antipathellae gen. et sp. nov. (Acotylea, Notoplanidae). The observed symbiosis is ascribable to exclusive inquilinism with some parasitic traits. The individuals, living in large numbers on the colonies, are highly cryptic thanks to a characteristic pigmentation and a wrapped habitus. They lay numerous annular yellow cocoons (rigid, nest-like structures containing the fertilised eggs), in single or multiple rows on the distal branches of the coral, temporarily denudated of coenenchyme. The occurrence of the polyclad is consistent with the Atlantic–Mediterranean geographical and bathymetrical distribution of the A. subpinnata forests as demonstrated by the analysed photo archive, and a summer reproductive peak can be hypothesised based on the temporal observations carried out in the study areas.

Settlement, recruitment and survival of sessile marine species are driven by many biotic and abiotic factors. Among them, substrate mineral composition is generally a neglected topic, despite it proved to be a relevant contributing variable in driving the structure of benthic communities. Thanks to their ecology, Chthamalus species are a good proxy to test the role of substrate in affecting settlement and final population density on exposed rocky shores. Differences in the number of individuals were analysed in eight localities along the Eastern Ligurian Riviera (north-western Mediterranean Sea), from Portovenere to Manara Cape. In this sector of the Ligurian littoral, the coast is constituted by different rocks characterised by variable concentrations of calcite, silicates and quartz. This situation constitutes an ideal setting to evaluate the influence of mineral composition of the rocks in structuring the epilithic macrobiota communities in energetic splash zones and under similar physical pressures. Rocks rich in calcites turned out to be more suitable for Chthamalus species than substrates containing high amounts of silicates, and of quartz in particular. Additionally, also the grain size of the main mineral component of the rocks, determining in turn the surface roughness seemed to influence barnacle densities, with a significant preference for finer-grained substrates.

Antipathella subpinnata (Ellis and Solander 1786) is one of the most frequently observed black corals at mesophotic depths (60–200 m) of the Mediterranean Sea, particularly in the northwestern part of the basin, where its populations can reach high densities and create forest-like aggregations, both along the coast and in offshore locations such as seamounts. Similar to other marine underwater forests, black coral gardens host a rich associated fauna and attract numerous species of commercial interest. As such, these corals are targeted by recreational and artisanal fisheries and are vulnerable to human impact due to their arborescent morphology and low growth rates. Genetic connectivity can provide valuable insight into the processes of population maintenance and replenishment following environmental disturbance and is often used as a proxy for population resilience. In our study, a restriction-site associated DNA analysis (2bRAD) was used to evaluate fine-scale population structure of the Mediterranean black coral A. subpinnata, and to understand which populations could serve as a potential source of genetic diversity for adjacent populations. Colonies from two offshore localities (a Ligurian seamount and a Tyrrhenian canyon) and four coastal populations from Liguria and Sicily were sampled and genotyped. Significant genetic differentiation was recorded between coastal and offshore localities. Moreover, offshore localities were genetically distinct from one another, while all coastal populations were characterized by panmixia. This indicates that offshore A. subpinnata gardens are potentially less resilient to human impact (i.e., demersal fishing activities) due to a limited influx of larvae from adjacent habitats. In addition, they are unlikely to supply coral propagules to coastal populations. Overall, this study highlights the vulnerability of Mediterranean A. subpinnata forests, and the importance of enforcing conservation and management measures to achieve Good Environmental Status (GES, EU Marine Strategy Framework Directive) of these valuable marine ecosystems.

Marine biodiversity underpins ecosystem health and societal well-being. Preservation of biodiversity hotspots is a global challenge. Molecular tools, like DNA barcoding and metabarcoding, hold great potential for biodiversity monitoring, possibly outperforming more traditional taxonomic methods. However, metabarcoding-based biodiversity assessments are limited by the availability of sequences in barcoding reference databases; a lack thereof results in high percentages of unassigned sequences. In this study we (i) present the current status of known vs. barcoded marine species at a global scale based on online taxonomic and genetic databases; and (ii) compare the current status with data from ten years ago. Then we analyzed occurrence data of marine animal species from five Large Marine Ecosystems (LMEs) classified as biodiversity hotspots, to identify any consistent disparities in COI barcoding coverage between geographic regions and at phylum level. Barcoding coverage varied among LMEs (from 36.8% to 62.4% COI-barcoded species) and phyla (from 4.8% to 74.7% COI-barcoded species), with Porifera, Bryozoa and Platyhelminthes being highly underrepresented, compared to Chordata, Arthropoda and Mollusca. We demonstrate that although barcoded marine species increased from 9.5% to 14.2% since the last assessment in 2011, about 15,000 (corresponding to 7.8% increase) new species were described from 2011 to 2021. The next ten years will thus be crucial to enroll concrete collaborative measures and long term initiatives (e.g., Horizon 2030, Ocean Decade) to populate barcoding libraries for the marine realm., the Department of Biological, Geological and Environmental Sciences (BiGeA) of the University of Bologna (UniBo). The CoMBoMed initiative was supported by the European Marine Research Network (EUROMARINE Network), the Inter-Departmental Research Centre for Environmental Sciences (CIRSA – UniBo), the Cultural Heritage Department (DBC - UniBo, https://beniculturali.unibo.it/it), the Fondazione Flaminia and the ERANet Mar-Tera Project SEAMoBB (Solutions for sEmi-Automated Monitoring of Benthic Biodiversity).

ALDFGs (abandoned, lost or otherwise discharged fishing gears) represent a major pollutant in the world’s oceans, including the Mediterranean Sea, but very little is known about their long-term fate in the underwater environment. Here we investigate the destiny of ALDFGs in a coralligenous benthic community by studying the biofouling growing on them at 30 m depth over a three-year period. Results indicate that ALDFGs are quickly covered by biofouling, reaching maximum values of cover in one year. At this depth, the biofouling community results highly influenced by light-dependent seasonal cycles and a general four-steps colonization scheme is tentatively depicted: i) biofouling community is initially dominated by fast-growing organisms, with algae and hydrozoans settling after two weeks; ii) small-sized carbonatic organisms (e.g. bryozoans) appear after two months; iii) the same organisms (including coralline algae) become abundant after five to eight months; iv) conspicuous carbonatic skeletons (serpulids, bivalves and bryozoans) occur after one year increasing in complexity in the following months. The biofouling settled on ALDFGs, as well as growth rates of large carbonatic species, could provide useful information to estimate the age of lost lines and nets in retrieved material and in situ photo footage complementing the overview of the fishing impact in this specific environment. Finally, no signs of nylon degradation are reported, suggesting that the prevailing physical conditions and the biofouling cover extent could alter microplastics release from nylon ALDFGs.

Black corals are important habitat-forming species in the mesophotic and deep-sea zones of the world’s oceans because of their arborescent colony structure and tendency to form animal forests. Although we have started unraveling the ecology of mesophotic black corals, the importance of the associated microbes to their health has remained unexplored. Here, we provide in-depth assessments of black coral-microbe symbioses by investigating the spatial and temporal stability of these associations, and make comparisons with a sympatric octocoral with similar colony structure. To this end, we collected samples of Antipathella subpinnata colonies from three mesophotic shoals situated along the Ligurian Coast of the Mediterranean Sea (Bordighera, Portofino, Savona) in the spring of 2017. At the Portofino shoal, samples of A. subpinnata and the gorgonian Eunicella cavolini were collected in November 2016 and May 2017. Bacterial communities were profiled using 16S rRNA gene amplicon sequencing. The bacterial community of E. cavolini was consistently dominated by Endozoicomonas. Contrastingly, the black coral microbiome was more diverse, and was primarily composed of numerous Bacteroidetes, Alpha- and Gammaproteobacterial taxa, putatively involved in all steps of the nitrogen and sulfur cycles. Compositional differences in the A. subpinnata microbiome existed between all locations and both time points, and no phylotypes were consistently associated with A. subpinnata. This highlights that local conditions may influence the bacterial community structure and potentially nutrient cycling within the A. subpinnata holobiont. But it also suggests that this coral holobiont possesses a high degree of microbiome flexibility, which may be a mechanism to acclimate to environmental change.

Antipatharians, also known as black corals, represent a small group of anthozoan hexacorallians found in all oceans of the world. They are generally considered a deep-water taxon; however, some of the most diverse communities are known from tropical shallow waters. With a few poorly detailed exceptions, shallow-water black corals from the Indian Ocean and especially those from Madagascar are mostly unknown. In this study, we report for the first time a highly diverse black coral assemblage of the Western Indian Ocean thriving in shallow waters and upper mesophotic depths (10–52 m depth) along the SW coast of Madagascar. A total of 22 species belonging to six genera (Antipathes, Arachnopathes, Cirrhipathes, Cupressopathes, Myriopathes and Stichopathes) and two families (Antipathidae and Myriopathidae) are described, of which 20 are found in the northern pass of the Great Reef of Toliara, thus representing the most diverse site of the areas investigated. Most of the shallow-water species from the Indian Ocean were originally described more than a century ago, sometimes without being reported again until now. All the descriptions herein rely solely on morphology and include detailed in situ pictures and scanning electron microscope images, in addition to range expansions for many species.

The Tavolara-Punta Coda Cavallo Marine Protected Area (North-eastern Sardinia, western Mediterranean Sea) includes, in a restricted area, substrates of different lithology. In fact, the Tavolara Island is characterized by limestone (high carbonate content), while the nearby Molara Island and the Molarotto islet are granitic (high quartz content). These peculiar features create a suitable condition to test the hypothesis that the taxonomic richness of the Mediterranean coralligenous communities could be also driven by the lithological characteristics of the substrate. Differences, in terms of recurrences of the macrobenthic sessile species, mainly macroalgae, sponges, anthozoans and bryozoans, of the coralligenous communities settled on limestone and granite, were investigated by image analysis. 240 photos on standard surfaces and four video transects were taken in 12 sites at comparable depth (40–50 m) but characterized by a different lithology. Multivariate analyses highlighted significant differences among sites, characterized by carbonate and granitic substrates. In general, limestone proved to be more suitable for the development of a thick differentiated coralligenous basal layer and showed a marked heterogeneity. Among structuring species, the gorgonian Eunicella cavolini was more recurrent on limestone than on granite, while the sponges Sarcotragus foetidus, Axinella polypoides and Axinella spp. were significantly more abundant on granite. Results suggest that a number of mechanisms could be involved to explain the observed patterns, such as a selective capacity of several sessile organisms, towards substrate, with ultimate repercussions on the structure of the whole coralligenous assemblage.

Exceptional meteo-marine events, such as storms, may have profound effects on the structure of benthic communities, yet their consequences on these ecosystems in the Mediterranean basin are still poorly known, mainly due to the unpredictability of such phenomena as well as the general lack of comparative datasets. The highly destructive storm of fall 2018, sustained by SE winds exceeding 130 kmh−1 and generating 10-m high waves, hit the coasts of the Ligurian Sea with devastating strength, producing vast damages and profound changes to the coastal morphology. Quantitative surveys performed soon after the catastrophic event were used to study the effects of the storm on the population structure of the habitat-forming gorgonian Paramuricea clavata (Risso, 1826) along the cliffs of the Portofino Promontory, a site particularly stricken by the storm. The same population was studied in 1997, 2002 and 2016, therefore it was possible to compare its health status before and after the impact of the storm. The P. clavata forest lost about one-third of the colonies between 2016 and 2018; colonies up to 25 m depth utterly disappeared, while below 30 m the storm effects were reduced, although the remaining population showed increased levels of epibiosis and necrosis. Over 21-years of observation, the effects of the storm have significantly slowed-down the recovery of the Portofino Promontory population after the massive mortality events of the last decades. Natural stress factors, although unpredictable, are fundamental to put into perspective changes in the benthic communities over time.

Cnidarians are known to undergo reverse development as a survival mechanism against adverse environmental conditions. Polyp bail-out consists in the polyps’ detachment from the mother colony due to stressful conditions, followed by a complete tissue and cells rearrangement and in some cases in a regression into a simple, ciliated form. Here we describe a massive polyp bail-out event occurred in the mesophotic black coral Antipathella subpinnata in reared conditions. This is the first report of a bail-out event in this species providing new insights into the life cycle and ecology of black corals.

Seamounts represent ecologically important marine environments and undeniably play a crucial role in the functioning of the deep-sea ecosystems, thanks primarily to their contribution in supporting offshore benthic and pelagic biodiversity. In the last decades, these features have received attention in all oceans of the world, but they were relatively overlooked in the Mediterranean Sea. In particular, the Ligurian Sea hosts six major structures, whose summits, ranging from 150 to nearly 2000 m depth, are virtually unknown from the biological point of view. The summit region of the Janua Seamount, located approximately at 40 nautical miles off the harbour of Genoa at 810 m depth, was explored for the first time using Remotely Operated Vehicles. The sea bed topography is characterized by a heterogeneous hard bottom, dominated by sub-fossil thanatocoenoses of Lophelia pertusa (Linnaeus, 1758) covered in a thick Ferrous-Manganese crust, and colonized by a scattered bathyal assemblage dominated by hexactinellids and benthic cnidarians showing a distinct regionalization around the summit. Cnidarians observed in this site include a rare Atlantic bamboo coral (Isididae, Chelidonisis aurantiaca Studer, 1890), described herein for the first time for the Mediterranean Basin. These findings provide new information on the biogeographic patterns of colonization of the bathyal Mediterranean fauna but also highlight the large knowledge gap that still exists for deep-sea biodiversity of this basin.

The development of novel and effective methods for the isolation of chitin, which remains one of the fundamental aminopolysaccharides within skeletal structures of diverse marine invertebrates, is still relevant. In contrast to numerous studies on chitin extraction from crustaceans, mollusks and sponges, there are only a few reports concerning its isolation from corals, and especially black corals (Antipatharia). In this work, we report the stepwise isolation and identification of chitin from Cirrhipathes sp. (Antipatharia, Antipathidae) for the first time. The proposed method, aiming at the extraction of the chitinous scaffold from the skeleton of black coral species, combined a well-known chemical treatment with in situ electrolysis, using a concentrated Na2SO4 aqueous solution as the electrolyte. This novel method allows the isolation of &alpha, chitin in the form of a microporous membrane-like material. Moreover, the extracted chitinous scaffold, with a well-preserved, unique pore distribution, has been extracted in an astoundingly short time (12 h) compared to the earlier reported attempts at chitin isolation from Antipatharia corals.

The predatory activity of the asteroid Peltaster placenta (Muller and Troschel, 1842) on the black coral Parantipathes larix (Esper, 1790) is here described for the first time based on video footage obtained during a Remotely Operated Underwater Vehicle (ROV) survey conducted in the Pontine Archipelago (Southern Tyrrhenian Sea, Mediterranean Sea). Feeding is carried out on the living coenenchyme of the basal axis and pinnules of the antipatharian and is confirmed by the occurrence of its cnidocysts in the sea star gut content. The chitinous skeletal parts of the black coral are left intact as bare tissue, which helps to relate colonies to the predation event. Among all black coral species present in the research area, P. placenta was observed grazing exclusively on P. larix, similarly to other goniasterids known to be deep-sea corallivores with a marked selectivity for their prey. The predatory behaviour of P. placenta was previously unknown. The extent of its feeding traces suggests a significant influence on benthic trophic relationships and, ultimately, on the functioning, structure and health status of deep Mediterranean black coral forests.

Cold-water corals (CWCs) are the main engineers of extensive deep coral frameworks hosting a lush diversity of species in certain areas of the world, including the Mediterranean Sea. In this basin, the most important bioconstructor species are the so-called “white corals”, i.e. the colonial scleractinians Madrepora oculata and Lophelia pertusa as well as the solitary coral Desmophyllum dianthus. Anthropogenic impacts (e.g., fishing pressure) and human-induced changes (e.g., rising temperatures and ocean acidification) are known to affect these important deep-sea bioconstructors. The present paper provides an overview of the horizontal and vertical distribution of white corals in the Mediterranean Sea. The knowledge of the present distribution of living CWCs represents a crucial baseline to understand how anthropogenic and natural changes are affecting these deep Mediterranean habitats.

An exceptional assemblage of the sea fan Leptogorgia sarmentosa (Anthozoa: Gorgoniidae) was observed inside the Genoa harbour, which represents one of the major Mediterranean ports. The studied assemblage is confined in a shaded portion of a floating dock thriving in extremely shallow water, with specimens even touching the sea surface. It represents the shallowest population of this species and of this genus known worldwide. A total of 188 specimens were observed and measured: the maximum density of 45 specimens m(-2) was reached in the most shaded part of the dock, where the maximum height of colonies (30 cm) was also recorded. Light measurements showed that the illuminance along the dock was comparable to that observed outside the harbour at 20 m depth, where the nearest colonies of L. sarmentosa were recorded for this region. This suggests that high levels of incident light might be putatively interpreted as the limiting factor in the upper bathymetrical distribution of the species. Despite the extremely shallow distribution, however, the population cannot be defined as intertidal as the floating dock avoids exposing the gorgonians to air. The chance to grow far from the silted bottom, but still in a turbid, sciaphilous and nutrient-enriched environment, probably enhanced the settling and growth of the colonies and allowed the formation of a dense and healthy population.

On marine rocky shores, several physical, chemical and biological processes operate to maintain the benthic assemblages’ heterogeneity, but among the abiotic factors, the composition and texture of the rocky substrata have been only sporadically considered. However, biomineralogical studies have demonstrated an unsuspected ability of the benthic organisms to interact at different levels with rocky substrata. Therefore, the mineralogy of the substratum can affect the structure of benthic communities. To evaluate this hypothesis, the macrobenthic assemblages developed on two different ophiolitic rocks (serpentinites and metagabbros) in contact at a restricted stretch of the western Ligurian Riviera (western Mediterranean Sea), with identical environmental and climatic conditions, were analysed. Samplings were carried out at four bathymetric levels (+1m, 0m, -1m, and -3m respect to the mean sea level) and the analysis of the data evidenced differences in terms of species distribution and percent coverage. Algal communities growing on metagabbros were poorer in species richness and showed a much simpler structure when compared to the assemblages occurring on the serpentinites. The most widely distributed animal organism, the barnacle Chthamalus stellatus, was dominant on serpentinites, and virtually absent on metagabbros. Our results suggest a complex pattern of interactions between lithology and benthic organisms operating through processes of inhibition/facilitation related to the mineral properties of the substratum.

During spring 2017, starting from 12 May, exceptional strandings of the purple snail Janthina pallida were recorded in the Ligurian Sea and along the western coast of Sardinia Island, under the effect of southern winds. The strandings continued for 3 days, until 15 May, when the winds shifted to the northern quadrant and the specimens were drifted back offshore. Such extensive strandings have never been previously reported in the scientific literature, either along the Mediterranean shores or elsewhere. Thanks to citizens’ help, it was possible to create a map of the strandings and obtain a gross estimate of the number of beached gastropods. The densities of the stranded animals reached an overall average of 801 ± 215 specimens m−2 (with peaks of over 2000 shells and rafts m−2 densely packed with hydrozoan Velella velella sails), corresponding to an average biomass of about 1.5 kg m−2. The size–frequency distribution of the shell heights showed a bi-modal trend, as is usual in the case of sequential hermaphroditism: almost all the specimens fitting the first mode (11 mm) showed a raft without eggs (males), while all the specimens belonging to the largest mode (23 mm) had rafts with settled egg cases (females). The general trend of the sea currents in the North-western Mediterranean Basin explains the spatial distribution of the strandings following 3 days of constant southern moderate breeze (up to 28 km h−1). The presence of such huge J. pallida banks in the Ligurian Sea is stochastic, probably linked to an Atlantic population entering through the Gibraltar Strait, as evidenced by the simultaneous presence of the buoy barnacle, Dosima fascicularis, a circumtropical species recorded here for the second time in the Mediterranean Sea.

The presence of fjords, islands and channels originating from glacial erosion and ice cap retreat, makes the Chilean benthic biodiversity difficult to explore and study. Our survey of this region allowed the identification of 29 Demospongiae species in total. Two of them are new to science and here described: Biemna lutea sp. nov., and Hamigera cleistochela sp. nov.. Two species (Clathria (Clathria) microxa and Lissodendoryx (Ectyodoryx) patagonica,) are new for the region and the Chilean fjords. Lissodendoryx (Ectyodoryx) patagonica was found for the second time after the original description by Ridley & Dendy, 132 years ago. These results – considering the small number of species identified on the whole – are promising and confirm that the marine biodiversity of Chilean fjords is remarkable but not well known yet.

The three-dimensional coral scaffolds formed by the skeletons of the cold-water corals Madrepora oculata and Lophelia pertusa represent an important deep-sea hard substratum and create an optimal shelter for a rich associated fauna in which the contribution of Porifera has still not been fully considered. The taxonomic analysis of sponges collected from two Sardinian canyons (Nora and Coda Cavallo, 256–408 m) and associated with the dead coral matrix resulted in 28 species, including new records for the Mediterranean Sea, Italian fauna or Central Tyrrhenian Sea. In addition, for many species this is the first finding associated with the coral framework or the first documentation of the in situ morphology. The taxonomic comparison with sponge assemblages associated with coral frameworks from Santa Maria di Leuca, Strait of Sicily and Bari Canyon, gave the opportunity to evaluate the similarities among geographically separated banks. Overall, the percentage of exclusive species (recorded only in one site), is very high (81%) and only one species is shared by all four sites, suggesting a low connectivity among the sponge communities. The percentage of shared species is higher for the Maltese community, supporting the role of the Sicily Channel as a crossroads between the communities of the eastern and western Mediterranean basins. Here, 55% of the sponges associated to the coral framework are also reported in shallow-water coralligenous assemblages, indicating a high bathymetric connectivity as well as an ecological plasticity allowing these species to occupy a wide range of small, dark refuges.

Remotely operated vehicle (ROV) investigations of the Mediterranean deep continental shelf and bathyal zone have provided, in the last decade, a large amount of data concerning an enigmatic group of anthozoans: the black corals. Taxonomic investigations as well as ecological and biological studies contributed to unveil the diversity, population structure, environmental preferences, bathymetric and geographical distribution of these corals. Remotely operated vehicle footage and accidental bycatch data have provided evidences of large impact by fishing activities on the Mediterranean black coral forests such that today, due also to their important ecological role as structuring species, they are considered part of vulnerable marine ecosystems and conservation strategies need to be developed targeting their protection.

The term cold-water coral sensu lato groups taxa with a more or less pronounced frame-building ability (e.g. Lophelia pertusa and Madrepora oculata) with forest-forming organisms both on hard (e.g. Leiopathes glaberrima, Parantipathes larix, Callogorgia verticillata and Viminella flagellum) and soft bottoms (e.g. Isidella elongata, Funiculina quadrangularis and Kophobelemnon stelliferum). Cold-water coral species and their occurrence in the Mediterranean Sea are here reviewed and discussed from a biogeographic point of view, considering geographical areas of occurrence and bathymetric distribution. The present-day occurrence of living cold-water corals is then compared to the main deep currents of the Mediterranean Sea. Due to the proper interaction between topography and a combination of cold, oxygenated and trophic-carrying water masses (i.e. Levantine Intermediate Water, deep waters and cascading effects), cold-water coral communities develop in a mosaic-like situation along the main paths that such water masses follow within the basin. Finally, knowledge gaps and future perspectives in the study of cold-water coral occurrence, distribution and biogeography are highlighted. The currently still scarce knowledge on the Mediterranean deep-sea and on the basin-scale distribution of the most important cold-water corals species represents crucial biogeographical information. This gives fundamental indications on the location of the Mediterranean vulnerable deep marine ecosystems for future management strategies.

Velella velella, the so-called by-the-wind sailor, is a common member of the open-ocean pleustonic fauna, worldwide distributed in tropical and temperate regions. Thanks to their sail protruding above the sea surface, floating polymorphic colonies of this hydrozoan are carried by winds, and tend to aggregate in large swarms, that often get stranded along the shores. Although these events are commonly observed in springtime along the Ligurian coasts (North-western Mediterranean Sea), no quantitative characterization was ever made. The aim of this study was to characterize the stranding events that occurred in spring 2016 along the Ligurian coast, by evaluating the influence of the local sea conditions and by quantifying the abundance of the stranded colonies in each event. Their size-frequency distribution and biomass were examined, and the associated mollusc fauna identified and counted. The magnitude of these episodes was so relevant that, along the Ligurian coasts, the V. velella strandings constitute one of the most important biological deposition of organic matter; nevertheless, the ecological role of these remarkable and stochastic accumulations of chitin along the coast is still unexplored.

Cnidarians are known for their simple body plan and their complex life cycles, involving high regenerative and asexual-reproduction potential. In particular, several asexual reproductive strategies are known for anthozoans, including fragmentation, carried out by tentacles, by groups of polyps or by portions of colonies. Here, we report the first observation of an extensive event of fragmentation in the Mediterranean black coral species Antipathella subpinnata (Antipatharia: Myriopathidae) in rearing conditions. Once detached, fragments lose their polarity and new anchorages are rapidly created with polyps and cnidocysts participating in the adhesion phases. Multiple attachments are frequently observed, with new skeletal plates produced through the expansion of spines. Dendritic spines gradually arise on these new plates. Fragments start to generate numerous new branchlets orientating upward and with a fixed arrangement. In 7 months of monitoring, fragments revealed fast growth rates, up to 1.85 and 1.58 cm month−1, for the whole fragments and new branchlets, respectively. Attachment of black coral fragments has never been recorded in the field; nevertheless, frequent adhesions observed in aquaria suggest that fragmentation could be a successful reproductive strategy in these anthozoans.

Coral gardens are increasingly being reported at 40–200 m depth in the Mediterranean Sea. These coral assemblages are composed of gorgonians from shallow coastal rocky bottoms extending their distribution to deeper areas, as well as by gorgonians and black corals with distribution restricted to the continental shelf and upper slope. Gorgonians and black corals are among the main structural species in deep benthic ecosystems, providing shelter and reproductive grounds for a highly diverse associated fauna. Due to their branching morphology and erect position, these deep coral gardens are extremely vulnerable to several fishing activities (bottom trawling, long-lines and trammel net fishing) and should consequently be protected through an ecosystem-based fishery management.

Association between habitat structuring organisms and other species has great relevance for ecosystem-based conservation measures. Those occurring in temperate areas, particularly in the upper portion of the continental margin, are mostly unknown or not properly understood because of the difficulty to discriminate co-occurrence and real functional linkages among species. Deep water coral assemblages over the Carloforte Shoal (south-west Sardinia; 180–210 m depth) were investigated using ROV surveys. During the surveys, more than 740 egg-capsules of the spotted catshark Scyliorhinus canicula, identified after hatching experiments in captivity, were found attached exclusively to colonies of the long-living black coral Leiopathes glaberrima. Although based on a spot finding, the results show that coral forests are not only hotspots of biodiversity, but can also serve as nursery grounds for S. canicula. The protection of these millennial coral forests is therefore to be considered a priority.

The aim of this paper is to supply an overview of all historical and recent knowledge on landings, fishing and geographic distribution of the red coral banks along the Italian coasts in order to ma...

The gorgonians Paramuricea clavata (Risso, 1826) and Eunicella cavolini (Koch, 1887) are important habitat-forming species within the Mediterranean coralligenous habitats, creating complex, three-dimensional forests that greatly contribute to the underwater landscape of the coastal hard grounds. Dense forests of both species are present within the Portofino Marine Protected Area (Ligurian Sea, NW Mediterranean Sea), showing a distinct bathymetric separation and site-specific differences. Quantitative evidences obtained with a monitoring census conducted in 2016 in 16 sites within the MPA support the existence of a widespread damage on these populations partially due to the mechanical injuries inflicted by recreational and professional demersal fishing gears. Considering all the studied populations, it resulted that 53% of the colonies of P. clavata and 36% of the colonies of E. cavolini were showing traces of impact, of which 10% in P. clavata and 7% in E. cavolini were due to direct entanglements with lost longlines. In the last decades, recurrent massive mortalities related to temperature anomalies and storms, have greatly reduced the gorgonian populations in this area and fishing impact severely affects survived or recovering colonies. Considering the vulnerable status of these species, and the increasing stress due to climate change, a correct management of the anthropic pressures is strongly needed to help preserving these relevant ecosystems.

Trophic relationships significantly influence ecosystem functioning, ultimately affecting populations’ abundance, size structure and distribution. There is still a substantial knowledge gap on the trophic ecology of deep-sea organisms, particularly those living in the mesophotic depths (30–150 m), despite their crucial importance as ecosystem engineers. The trophic ecology of the most common mesophotic black coral species of the Mediterranean Sea, Antipathella subpinnata (Ellis & Solander, 1786), was studied by means of stable isotopes analysis in two seasons. The δ13C and δ15N analysis of the tissue of A. subpinnata, of the sediment, as well as the main planktonic fractions (pico-nanoplankton, microplankton, and mesozooplankton) indicate a diet based on pico-nanoplankton in autumn and mesozooplankton in spring. We calculated a trophic enrichment of 1‰ in δ13C and of 2.5‰ δ15N between prey and predator. Such information contributes towards drawing a complete picture of the pelagic-benthic coupling in the Mediterranean mesophotic coral forests.

The geological, biological and geochemical features of a particular field of hydrothermal vents, discovered in the Panarea Volcanic Complex during a research survey carried out in 2015, are described for the first time. The site, located at 70-80 m depth off the South-western coast of the islet of Basiluzzo, was named Smoking Land for the presence of a large number of wide and high active chimneys and was characterized in terms of dissolved benthic fluxes, associated macrofauna and megafauna communities and preliminary mineralogy and geochemistry of chimney structures. On the whole field, a total of 39 chimneys, different in size and shape, were closely observed and described; 14 of them showed emission of low temperature hydrothermal fluids of marine origin characterized by acidified chemical conditions. The CTD and benthic chamber measurements highlighted that the Smoking Land is able to form a sea water bottom layer characterized by variable acidity and high DIC and trace elements concentrations; these characteristics weaken moving away from the chimney mouths. The SEM-EDS analysis of the collected solid samples revealed a chimney structure principally composed by amorphous and low crystalline Fe-oxyhydroxides of hydrothermal origins. The ROV explorations revealed a wide coverage of red algae (Peyssonnelia spp.) colonized by the green algae Flabiella petiolata and by suspension feeders, mainly sponges, but also bryozoans, and tubicolous polychaetes. Although novent-exclusive species were identified, the benthic communities found in association to the chimneys included more taxa than those observed in the surrounding no-vent rocky areas. These first findings evidence a submarine dynamic habitat where geological, chemical and biological processes are intimately connected, making the Smoking Land an important site in terms of marine heritage that should be safeguarded and protected.

During the last decades, the Mediterranean shallow-water benthic communities have experienced significant changes in taxa composition and distribution. These variations were related to a complex set of anthropogenic stressors as well as to mass mortality events starting from 1999 and related to the current climatic changes. To evaluate the effect of these changes on long-living species with a limited larval dispersal capacity, a quantitative and qualitative monitoring of the shallow-water hard bottom community structure was performed over a pluri-decennial interval of time. The aim of this work was the comparison of the quali-quantitative occurrence and seasonal cycles of several benthic taxa living on a rocky cliff of the Portofino Promontory (eastern Liguria, Mediterranean Sea), from 15 to 20 m depth. The studied community, within a Lithophyllo–Halimedetum tunae association, was analysed by sets of photographs repeated, exactly in the same site, at 25 years of distance (1987/88 and 2012/13). The results suggest that the macroalgal coverage of the surveyed cliff suffered, during the monitored span of time, a significant depletion in quali-quantitative terms, while the overall sponge coverage remained almost unvaried. Nevertheless, a discrete analysis of the most common sponge species present in the study area showed significant variations, with some taxa now more abundant (Axinella spp. and Agelas oroides), some virtually stable (Cliona viridis and the complex of red encrusting sponges), and others drastically depleted (Chondrosia reniformis, Phorbas tenacior, Acanthella acuta, Ircinia spp., Dysidea avara and Petrosia ficiformis). Finally, some sponge species showed clear seasonal cycles indicating recruitment periods and post-recruit mortalities.

Stichopathes pourtalesi Brook, 1889, the type species of the genus Stichopathes Brook, is redescribed on the basis of an examination of the type material originally identified by de Pourtales as Antipathes desbonni Duchassaing and Michelotti and as Antipathes spiralis Pallas. Because the type series consists of multiple species, it was necessary to select a lectotype to clearly define the species. The species is characterized by a spiral, unbranched corallum; triangular, compressed spines, some of which have one or more lobes at the apex; very faint elongate papillae on the surface of the spines extending from near the apex to as much as one-half the distance to the base; and large polyps with long tentacles (in preserved specimens). The species is similar to Stichopathes gracilis (Gray); however, scanning electron microscopy indicates that there are distinct differences between the two species in the microscopic surface ornamentation of the spines.

The IUCN Red List of Threatened SpeciesTM – Regional Assessment, This report presents the conservation status of the anthozoans occurring in the Mediterranean Sea, based on the assessment of 136 species using the IUCN Red List methodology. It identifies those species that are threatened with extinction at the regional level to guide appropriate conservation actions in order to improve their status

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 170-400 meters 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.

The whip-like gorgonian Viminella flagellum (Alcyonacea, Ellisellidae) has an Atlantic-Mediterranean distribution. In Italian seas, the species is a common component of deep-sea rocky environments from the north-western Mediterranean area to the Strait of Sicily. V. flagellum grows in deep habitats, sometimes outlining the environment with dense forests. This work describes its habitat in an area in the southeastern Sardinian waters (central-western Mediterranean Sea), where a dense forest of the species was found. The specimens were filmed and photographed between 120 and 260 m depth with a Remotely Operated Vehicle (ROV). High-resolution multibeam echosounder (MBES) bathymetry data of the area were acquired and morphometric parameters were derived. These parameters were assumed to be relevant for the distribution of the whip-like gorgonians and were used in an Ecological Niche Factor Analysis (ENFA) to explore the niche and habitat preference of the target species. In order to identify which Eco-geographical variables are useful to predict coral distribution, we used the Maximum Entropy model (MaxEnt). Our results gave a first description of the habitat preference of V. flagellum. Specimens were found in a distinctive habitat, with respect to the overall features of the entire studied area which was characterised by a marked slope in a simple rocky seabed system, within a water depth range of 125–150 m.

Paracoryne huvei is a rare encrusting hydrozoan living in the intertidal zone of the North-western Mediterranean Sea, from the Catalan coast to the Ligurian Sea. In 2014, a large bloom of P. huvei ...

A remotely operated vehicle (ROV) survey conducted in the deep (250–400 m) Maltese waters in 2013 revealed, for the first time, the characteristics of an extended coral forest, constituted almost exclusively by the arborescent, longevous black coral Leiopathes glaberrima. This species is a major component of the deep coral forests of the Mediterranean Sea and its occurrence in dense populations greatly enhances the benthic biodiversity of the sites in question. The existence of such a complex benthic ecosystem is particularly interesting for Malta, since this area represented, in the 1980s, the only sanctioned site within the Mediterranean basin for the commercial exploitation of black corals. The occurrence of the large black coral population hints that, at least within the investigated area, the coral resource has not greatly suffered from past coral harvesting activities. The major current concern, however, is represented by the massive anthropogenic impact due to benthic fishing activities car...

The existence of deep red coral (Corallium rubrum) banks in the gulfs of Naples and Salerno (South Tyrrhenian Sea, Mediterranean Sea) is well known in historical records due to the heavy coral harvesting that occurred during the 19th and 20th centuries, by both trawling gears and scuba diving. In 2010 and 2012, during two Remotely Operated Vehicle (ROV) surveys on board of the Research Vessel (R/V) Astrea, red coral banks were detected in 16 of the 25 visited localities, between 45 and 150 m depth. Seven of these banks, located in the inner part of the Gulf of Naples, were already explored in 1918 by a scientific survey reporting the occurrence of red coral. Healthy populations (densities > 90 colonies m−2) were present only around the coasts of the Phlegrean Islands (Ischia and Procida Islands). Very low densities (< 5 colonies m−2) or the absence of coral were recorded in all other sites of the Gulf of Naples (including all historical re-visited banks), and a variable percentage of dead coloni...

Black coral communities in the Mediterranean Sea are now recognized to be far more common than what was expected a few years ago; however, among the species reported for this basin, Parantipathes larix is one of the least well known. This species is characterized by tall, monopodial or sparsely branched colonies showing a distinctive bottle-brush pinnulation pattern and fairly elongated whitish polyps. Rarely reported in the literature, this species, despite frequently occurring as fishing bycatch, has never been observed in dense populations and all available information mainly concerns its morphological features. Two forests of P. larix were discovered during a remotely operated vehicle (ROV) survey conducted in July 2012 on board the R/V Astrea between 100 and 200 m on two continental rocky shoals located about 10 miles southeast of the Island of Montecristo (Tuscan Archipelago, Tyrrhenian Sea). Video footage was analyzed using the ROV imaging technique, and the coral communities were described...

In this study we characterized the deep assemblages dwelling at 200–250 m depth on a large shoal off Capo St. Vito Promontory (Northwestern coast of Sicily, South Tyrrhenian Sea) by means of ROV-imaging. Two assemblages of suspension feeders, dominated by the gorgonian Callogorgia verticillata and by the black coral Leiopathes glaberrima, together with a tanatocoenosis of the colonial yellow scleractinian coral Dendrophyllia cornigera, were examined. The three main species were significatively distributed into two areas corresponding to different habitat preferences: a more elevated hardground hosting black corals and a gently sloping, silted rocky bottom hosting the other coral species. The study area is subjected to a heavy pressure from the professional fishery, resulting in the mechanical damage of numerous colonies, some of which are then overgrown by various epibionts including a parasitic bioluminescent zoanthid, new for the Mediterranean fauna, and tentatively identified as Isozoanthus primoidus. In the Mediterranean Sea, these deep off-shore rocky banks are widely known among recreational and professional fishermen due to their rich fish fauna. However, there has been still little effort into quantifying and characterizing the extent of the impact and its consequences on the benthic communities, which may represent, as in this case, only a partial picture of their original structure and extent.

The Mediterranean red coral, Corallium rubrum, is one of the most precious corals worldwide. Below 50 m depth, C. rubrum populations are generally characterised by large and sparse colonies, whereas shallow populations (above 50 m depth) show high densities of small colonies. We show here instead that populations dwelling between 80 and 170 m depth exhibited a continuous range of population density (from 2 to 75 colonies per 0.25 m2), with less than 1% of variance explained by water depth. An inverse relationship between maximum population density and mean colony height was found, suggesting that self-thinning processes may shape population structure. Moreover, demographically young populations composed of small and dense colonies dominated along rocky vertical walls, whereas mature populations characterised by large and sparsely distributed colonies were found only in horizontal beds not covered by sediment. We hypothesise that, in the long term, shallow protected populations should resemble to present deep populations, with sparsely distributed large colonies. Since the density of red coral colonies can decay as a result of self-thinning mechanisms, we advise that future protection strategies should be based also on a measure of red coral spatial coverage instead of population density.

Microboring or euendolithic microorganisms, which colonize and penetrate various carbonate substrates, are abundant in coral reef ecosystems and play a major role in reef carbonate dissolution. A few studies reported the presence of euendoliths in stylasterid coral skeletons but the biological identity, distribution and abundance of these microorganisms remain largely unknown. Observations of over 100 stylasterid colonies, collected in the Indo-Pacific area, revealed for the first time that the association between these corals and euendolith organisms appears to be quite common in shallow tropical waters. The most abundant euendolith was identified as a cryptic stage in the development of the rhodophyte Porphyra (Conchocelis stage). The euendoliths were observed in the skeletons of seven species of three genera (four Stylaster, two Distichopora and one Lepidotheca). The presence of euendoliths inside skeletons conferred a particular colour to the studied stylasterid corals. Distribution and abundance of microborings varied significantly among stylasterid species and among branches of a single colony and so did the colour of their skeletons. Colonization of skeletons and the associated colour distribution were almost uniform in some stylasterids, forming an upward gradually diminishing or sharply limited gradient. This study shows that patterns of euendolith colonization and growth in stylasterid skeletons may depend on the stage of the euendolith development as well as on their environmental requirements such as light exposure.

Until now, there is a lack of knowledge about the presence of chitin in numerous representatives of corals (Cnidaria). However, investigations concerning the chitin-based skeletal organization in different coral taxa are significant from biochemical, structural, developmental, ecological and evolutionary points of view. In this paper, we present a thorough screening for the presence of chitin within the skeletal formations of a poorly investigated Mediterranean black coral, Parantipathes larix (Esper, 1792), as a typical representative of the Schizopathidae family. Using a wide array variety of techniques ( 13 C solid state NMR, Fourier transform infrared (FTIR), Raman, NEXAFS, Morgan-Elson assay and Calcofluor White Staining), we unambiguously show for the first time that chitin is an important component within the skeletal stalks as well as pinnules of this coral.

Little is known about density and structure of black coral populations of the continental Pacific coasts of Central and South America. Species diversity and ecology of the antipatharian fauna of Machalilla National Park (Province of Manabi, Ecuador) were surveyed using scuba, and two species, Myriopathes panamensis and Antipathes galapagensis, were identified. New information on the two species and their associated fauna was obtained through both underwater observations and laboratory analyses. Specific associations with stalked barnacles and parasitic zoanthids are described. An underwater visual census indicated that the black coral assemblage had a maximal density between depths of 15 and 30 m. Myriopathes panamensis commonly occurred below 20 m depth, and A. galapagensis was mainly recorded from deeper than 25 m depth. Surveyed sites were characterized by sparse rocks mixed with sandy patches, and occurrence of black corals was mainly related to availability of rocky substrate. With an avera...

The class Anthozoa is the largest meta- zoan group forming mutualistic symbioses with mi- croalgae. These algal symbionts (most commonly dino - flagellates of the genus Symbiodinium) are distributed across most anthozoan orders. Records of algal cells in antipatharian (black coral) tissues have been reported, but no detailed descriptions of a mutualistic endosym- biosis exist. Here we report on zooxanthellate speci- mens of an unidentified black coral species within the genus Cirrhipathes that were collected from reef slopes at depths of 15 to 38 m in the Indonesian Archi- pelago. Symbionts were abundant (~10 7 symbionts cm -2 ) and ultrastructural analysis revealed the presence of a distinct symbiosome surrounding the algae, as well as algal reproduction inside the gastrodermal layer. Mol- ecular analysis revealed the algae to be closely related to the symbionts (Symbiodinium clade G) of clionid sponges. There was also evidence for additional sym- bionts in clade C at low abundance. Taken together, these findings (high abundance, taxonomic identity, presence of symbiosome, in situ reproduction, and depth distribution) strongly suggest that these algae are functioning as mutualists. This study confirms and describes the symbiosis between Symbiodinium and a black coral species of the genus Cirrhipathes, supports the pervasiveness of mutualisms among anthozoan taxa, and highlights the diversity and flexibility of these symbiotic associations in a poorly studied group.

The life cycle of the stoloniferan Cornularia cornucopiae (Pallas, 1766) (Anthozoa: Octocorallia) was studied from March 2009 to October 2010 on the rocky cliff of the Conero Promontory (North Adriatic Sea, 43°34.865′ N, 13°34.320′ E). In this area the species showed unusual high densities never recorded in other sites of the Mediterranean Sea. The density trend of the species showed a marked seasonal cycle, with a winter minimum of about 1000 polyps m−2 and a summer maximum of about 30,000 polyps m−2. In accordance with other Mediterranean literature data, polyps were fertile during spring–summer, from March to August, but the number of eggs per polyp continuously decreased during this span of time. Variations of polyp density were strongly correlated to water temperature, which can be considered the main environmental factor triggering this seasonal behaviour. The possibility, for C. cornucopiae, to face adverse winter conditions is probably related to the presence of a characteristic perisarcal envelope covering the stolon and the calyx of each polyp, which isolates the living tissues from the exterior. During winter, polyps degenerate but the stolons remain dormant inside their envelopes. The perisarc covering represents a morphological convergence of C. cornucopiae with benthic hydrozoans. As the latter, the studied stoloniferans are able to live in habitats characterized by periodic favourable conditions thanks to a seasonal life strategy. A similar trend is shared also by other important components (cnidarians and some sponges) of the filter-feeding community of the North Adriatic Sea. Differently to the Western Mediterranean basin, this area is characterized by high food availability all year around, so benthic organisms are strongly constrained by the very low winter temperatures.

Natural populations of Aurelia aurita scyphopolyps, settled on a wreck in the northern Adriatic Sea, were monitored for 22 months in order to study their seasonal cycle. The trend of Aurelia polyps is strongly dependent on water temperature with a peak of abundance in summer and low densities in winter. The strobilation process occurs only once a year, during the cold season, and the estimated number of released ephyrae is 780,000–2,600,000/m2. The species has been recorded only on the iron wreck while it is completely lacking from the close rocky cliff of Conero Promontory, suggesting that the increase of underwater structures of anthropogenic origin could be related to the increases of jellyfish biomass.