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The by-the-wind sailor Velella velella is a cosmopolitan, pleustonic colonial hydrozoan, common in the Mediterranean Sea. It forms offshore aggregations that occasionally strand on the coasts, following strong wind conditions. Colonies are frequently discovered around Janthina pallida Janthina pallida, a pleustonic gastropod that feeds on them and floats on the secretion of a bubble raft. Because of the massive occurrence of these species along the Italian coasts, and their often neglected ecological roles, it is pivotal to increase the knowledge of their genetic structure. Analyses of the genetic variability of V. velella and J. pallida, stranded on the beach in springs 2016 and 2017 at ten locations along the Ligurian and Tyrrhenian seas, show the existence of panmictic Mediterranean populations. Nevertheless, V. velella showed high genetic variability with a high number of singleton haplotypes, while J. pallida showed a recent population expansion. Considering the ecological and socio-economic importance of gelatinous zooplankton in today's changing marine ecosystems, these results lay the basis for a better understanding of the ecological role and population dynamics of Mediterranean pleustonic species.

The precious coral Corallium rubrum (Linnaeus, 1758) is a charismatic Mediterranean species. A recent large-scale investigation along the Italian coast highlighted its widespread occurrence at mesophotic and upper bathyal depths, especially on coralligenous and bathyal vertical hardgrounds. The lack of morphometric data limited the considerations on the structure and health status of the populations, fundamental to identify the most vulnerable sites and the correct management actions. For this reason, a ROV dataset, consisting of 624 dives carried out between 40 m and 1825 m in the Ligurian Sea, Tyrrhenian Sea, and Sicily Channel, was analysed to extrapolate quantitative data to describe the populations. Ten random frames were obtained from each of the 170 sites hosting red coral. Density, height, and entanglement were evaluated for about 15700 colonies counted in the frames. The densest populations were mainly found between 40 m and 80 m, with a clear latitudinal density decrease. The mesophotic populations were characterized by both scattered and densely aggregated colonies, while the bathyal ones were dominated by sparse colonies. This study identified 17 major coral areas based on the geographic proximity of the sites hosting red coral and their topographic and oceanographic affinity. The size-frequency distribution of the heights was skewed towards the smaller classes in almost all populations, with a modal class between 2 cm and 4 cm. This study depicted a stress situation of the populations throughout the entire study area, which could be correlated also to the long-term harvesting pressure carried out in the basins. Two additional sources of direct mortality were pointed out in this study. Entanglement to artisanal and recreational fishing gear interested about 18% of the recorded colonies, mainly at mesophotic depths. Almost all populations suffered from mechanical entanglement, with the highest percentages in the Ligurian Sea and Sicilian areas. This study also highlighted a massive occurrence of recent deep mortality events, mainly along the eastern and southern coast of Sardinia and in the Campanian Archipelago. Thirty sites with extensive patches of dead colonies still in place were reported from 70 m to around 200 m, but their formation remains unclear.

Detailed knowledge about the distribution of species in need of protection is required for the management of Marine Protected Areas, a major tool to reduce marine biodiversity loss. Such knowledge is deficient for most marine invertebrates. Axinella polypoides is a marine sponge included on the list of protected species by the Barcelona Convention (1976) and the Bern Convention (1987). This large and erect species has an important ecological role in habitat forming and benthic–pelagic coupling. Bathymetrical, geographical and ecological data over the last 60 years were collated from publications and reports, together with new surveys to assess the distribution and protection status in Liguria of A. polypoides. It identified a more widespread distribution than previously thought, which points at a general need for dedicated investigations on the occurrence of species that require protection. Bathymetrical distribution was trimodal, with peaks corresponding to different geomorphological settings: coastal cliff bases (around 38 m depth), inner shelf shoals (52 m) and rocks amidst coarse sediment on the outer shelf (79 m). Density was significantly greater at the shallowest depths. The species was mostly found in the coralligenous biocoenosis, in association with other characteristic species or forming a monospecific facies. On (sub)vertical cliffs, A. polypoides often exhibited an unusual cane shape, rather than the typical bushy morphology, thus causing confusion with the congeneric A. cannabina, a more southern species. Records of the latter in the Ligurian Sea therefore need confirmation. Only a minority (22.6%) of A. polypoides records were in Marine Protected Areas, the remainder being located in areas with no current environmental protection plans in place. While the occurrence of this species in MPAs remained stable over the decades, the only quantitative historical data available indicated that populations in non‐protected areas were declining owing to anthropogenic impacts (fishing and anchoring).

The precious red coral (Corallium rubrum L.) represents one of the most fascinating marine species of the Mediterranean Sea. Several samples, including red coral together with its accompanying species, were found in the zoological collection of the Italian pioneer biologist Lazzaro Spallanzani (1729–1799), collected in the Messina Strait during his voyage in Sicily (1788). The study of these samples allowed the inclusion of numerous additional species in the traditional red coral facies as the large oyster Neopycnodonte cochlear, the giant barnacle Pachylasma giganteum, the mesophotic scleractinian Caryophyllia (Caryophyllia) cyathus. These specimens proved to be very useful in describing the diversity of the paleo-community including red coral, shedding light on its formation processes. In particular, some specimens are composed of red coral rubble consolidated and cemented with other carbonatic remains Probably, these peculiar specimens have a similar origin to those of the Sciacca Banks already known from the Sicily Channel. In fact, the two areas are prone to intense seismic activity that periodically causes mass mortalities of red coral from nearby rocky reliefs and the formation of biogenic detritus, while the resulting chemical environment of the water and the sediments allows the consolidation of the carbonatic remains.

During the last decades, the number of observations of the basket star Astrospartus mediterraneus (Risso, 1826) in the Mediterranean Sea has significantly grown, thanks to SCUBA diver and ROV sightings, citizen reports, as well as particularly large catches by the artisanal fishery. Having been generally considered rare in many areas of the basin, such a long-term increase of records might assign to this basket star the putative role of a winner species in the context of climate changes. In the present study, we combined the overall literature information with the data available for the Ligurian Sea collected during extensive ROV campaigns conducted between 2012 and 2022 at a depth ranging from 20 to 123 m, to better understand the distribution and abundance of this species. The basket star was observed in almost the whole explored bathymetric range living on gorgonians (Eunicella cavolini, E. verrucosa, Paramuricea clavata, and Leptogorgia sarmentosa) and massive sponges (Aplysina cavernicola, Sarcotragus foetidus, Spongia lamella, and Axinella polypoides). In the considered period, the number of recorded specimens did not show a clear trend, but differences emerged over years and months. These variations were strongly correlated with rainfall amounts that, in oligotrophic waters, such as those of the Ligurian Sea, represent an important input of organic matter for these passive filter feeders, especially in the summertime.

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.

Vulnerable Marine Ecosystems (VMEs) are characterized by prominent biological features susceptible to anthropogenic disturbances. Following international guidelines, the identification and protection of VMEs require a detailed documentation regarding both the community structure and the fishing footprint in the area. This combined information is lacking for the majority of the Mediterranean mesophotic rocky reefs that, similarly to deep-seabottoms, are known to host valuable animal forests. A deep coralligenous site exploited by artisanal fishermen in the NW Mediterranean Sea is here used as a model to assess the vulnerability of animal forests at mesophotic depths and evaluate the sustainability of artisanal fishing practices, particularly lobster trammel net. The Remotely Operated Vehicle (ROV) footage is used to document the biodiversity and health status of the megabenthic communities, while discard data are employed to quantify the entanglement risk, discard rates of fragile species and threats to sea floor integrity. A multidisciplinary approach is proposed for the assessment of the vulnerability criteria of an EU Special Area of Conservation, leading to specific management measures, including the delineation of fishing restrictions.

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.

In 2015, the Strait of Sicily, which includes several banks, was candidate as a future Specially Protected Area of Mediterranean Importance (SPAMI) by the Contracting Parties of the Barcelona Convention. In this context, the present study aims to provide the first biological and ecological characterisation of this poorly known area, focusing on habitats and species of conservation concern. Surveys were carried through a remotely operated vehicle (ROV) and allowed the identification of 19 habitat types, mostly considered of priority interest by the SPA/BD Protocol of the Barcelona Convention. A total of 269 taxa were also identified, mostly Porifera, Cnidaria and Pisces, among which 115 species are of conservation concern according to the International Union for Conservation of Nature (IUCN) Red Lists, the Habitats Directive, the Bern Convention, the SPA/BD Protocol and CITES. ROV surveys allowed some interesting observations on poorly known species and habitats. Results underlined that remarkable discrepancies in species conservation status assessment that exist between the several lists of protected species considered. The IUCN Red Lists, although not legally binding for European States, are the most complete, but, in spite of this, the conservation policies in the EU are largely focused on the Habitats Directive, which is really not exhaustive. An exhaustive and legally binding instrument to protect species of conservation concern at European scale is highly recommended. Acquired results could be useful for the delimitation of a future SPAMI or a network of Marine Protected Areas (including the investigated banks) and the identification of zones within them suitable for different area-based management measures.

The Mediterranean red coral, Corallium rubrum (L.), has been a valuable economic resource for more than 2000 years. The Sicily Channel and surrounding areas are one of the most famous red coral fishing grounds of the whole region, hosting the deepest ever found living colonies and large sub-fossil red coral deposits; the so-called Sciacca banks are a unique location in the whole Mediterranean Sea. In this paper, a morphometric description of this sub-fossil population is presented for the first time from studies of colonies in the collection of several coral factories from Torre del Greco (Naples), with radiocarbon age estimations and growth rate evaluations. From the results of this study, after several thousand years Sciacca red coral colonies maintained the organic matrix structure with evident annual discontinuities, allowing estimations of the annual growth rate (about 0.3 mm/year) and the average population age (about 33.5 years). These resulting data are similar to the values determined for deep-dwelling living red coral populations. The radiocarbon dating evidenced a range of ages, from 8300 to 40 years before 1950 CE, mostly falling between 2700 and 3900 YBP, suggesting that colonies accumulated over a wide span of time. In view of the tectonically active nature of the area, several catastrophic events affected these ancient populations, maintaining them in a persistent state of early-stage, structurally similar to the those in current over-exploited areas.

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).

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.

This study presents a description of Bispira riccardi sp. nov., a new habitat-forming sabellid polychaete from the mesophotic NW Mediterranean Sea. Individuals, up to 20 cm long, show a peculiar morphology of radioles, thoracic uncini, companion chaetae and ventral shield of the collar. The phylogenetic position of this new taxon in the genus Bispira has been validated using nuclear (18S rRNA) and mitochondrial (COI) markers. Aggregations of B. riccardi sp. nov. were found by ROV on horizontal muddy bottoms between 56 and 85 m, in areas subjected to high trophic inputs. Patches are fragmented and dense (up to 943 individuals m 2) probably accounting for various hectares. A 5-days continuous monitoring, carried out using an autonomous lander, revealed that the contraction of the branchial crown was positively affected by temperature and current, rapidly responding to meteorological events. The filtering activity and high density of these fields suggest a considerable impact on the pelagic-benthic coupling and the amount of organic matter in the sediments. Indeed, meiofaunal abundance and diversity within the aggregations resulted significantly higher than in outer stations. These findings highlight the undisclosed potential of the deep Mediterranean Sea for sabellid diversity and their importance as habitat-forming species on mesophotic soft bottoms.

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.

The project "Biodiversity MARE Tricase" aims to research and promote coastal and marine biodiversity at the MARE Outpost (Avamposto MARE), a marine station established in Tricase (Lecce, Italy) in 2015. From March 2016 to September 2017, the first biodiversity inventory of the Tricase coastal area (Ionian Sea) was realized with the aid of citizen scientists (e.g. local fishermen, divers, bathers, and tourists). Preliminary results include 556 taxa, of which the 95% were identified at the species level. Despite the broad knowledge on Mediterranean coastal biodiversity, 71 species represented new records for the Ionian Sea. In parallel with the research activities, people's awareness of the value of biodiversity was raised with scientific dissemination initiatives, involving about 1700 people. The "Biodiversity MARE Tricase" project realized a first small-scale species inventory contributing to the distributional, taxonomic, and ecological knowledge of the present Mediterranean biota. The coastal area of Tricase will be soon included in a new Marine Protected Area and this project represents a step forward for the sustainable development of the community of this coast.

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.

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.

Recent ROV surveys conducted on the Ragusa bank in the Sicily Channel (Mediterranean Sea) documented illegal and continuous use of the ‘ingegno’ gear for red coral fishing. Three lost gears were recorded showing different levels of epibiosis thus supporting multi-annual exploitation of the bank. The red coral population of the Ragusa bank showed a typical ‘forest-like’ configuration with upright, medium-sized colonies similar to those of other commercially exploited deep Mediterranean banks. The direct negative effect of this trawling gear was evident from numerous rocky boulders completely enveloped by lost nets and occasionally turned over. Red coral fragments as well as fragments of ‘ingegno’ nets were observed in high abundance on the sea floor. This evidence suggests that this gear is highly destructive even on rough sea floors, contrary to the traditional view, which is that it has a more random impact on rough rocky bottoms. The estimated coral uptake of ‘ingegno’ is 45% of the total coral biomass, while the estimated coral loss, in terms of fragments, is 9%, demonstrating the high impact of this gear. The study highlighted the infringement of the red coral fishing ban by trawling gears as well as a lack of effective policing. The strengthening of controls on landings at nearby harbours, and education programmes for the local maritime communities are among the management actions proposed to protect these surviving red coral populations from the ongoing illegal fishing activity.

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.

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.

About 63% of the known antipatharian genera occur at mesophotic depths (30–150 m), with the majority extending into the deep sea. Along the continental shelf and offshore sites, antipatharians tend to increase in diversity and abundance with depth, reaching a peak at mesophotic depths due to favorable environmental factors enhancing their settlement and growth and biotic factors associated with lower levels of competition for space. A review of taxonomic and ecological studies for shallow and mesophotic antipatharians is presented for four regionally based case studies, three in the tropics (1) Central Indo-Pacific, plus adjacent sections of the Western Indo-Pacific, (2) Eastern Indo-Pacific (primarily Hawaiʻi), and (3) the Caribbean Sea) and one at temperate latitudes in the Mediterranean Sea and adjacent sections of the Northeast Atlantic. The mesophotic fauna is mainly represented by the families Antipathidae, Aphanipathidae, and Myriopathidae. The most diverse community is found in the Central/Western Indo-Pacific, followed by the Caribbean Sea. The tropical antipatharians are represented by shallow species that extend their distribution into the upper mesophotic zone (30–60 m), while the temperate antipatharians consist of deepwater (> 150 m) species that extend upward into the lower part of the mesophotic zone. Black corals in mesophotic coral ecosystems can be habitat-forming components of benthic assemblages on hard substratum. They have an enormous potential for hidden biodiversity and play an important ecological role for the broader marine ecosystem. The threats to antipatharians consist of demersal fishing activities and coral harvesting, which may be highly destructive to these poorly understood systems.

Cold-water corals are recognised as a key component of Mediterranean deep-sea ecosystems but the knowledge of their associated biodiversity is still limited. To date, the fauna associated to the Central Mediterranean cold-water coral habitats is the best known (e.g. the cold-water coral provinces of Santa Maria di Leuca, Bari canyon and Strait of Sicily) but such knowledge should be extended to the whole Mediterranean Basin. The combined biodiversity censed so far for Mediterranean cold-water coral habitats and those of adjacent areas (Strait of Gibraltar-Gulf of Cadiz) includes a conspicuous number of species (ca. 520 spp.) with a high representation of sponges (ca. 90 spp.), polychaetes (ca. 90 spp.), cnidarians (ca. 80 spp.), bryozoans (ca. 75 spp.), crustaceans (ca. 60 spp.), molluscs (ca. 50 spp.), fishes (ca. 50 spp.), echinoderms (ca. 20 spp.) and brachiopods (7 spp.). Most species are not univocally linked to cold-water corals, but they benefit from the complex and diverse microhabitats provided by them. There is a clear need to continue the investigation of Mediterranean cold-water coral habitats to fully document the faunistic inventory, biogeographic connections and functions of the many species connected to such emblematic ecoystems of the deep-sea.

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.

Knowledge on basic biological functions of organisms is essential to understand not only the role they play in the ecosystems but also to manage and protect their populations. The study of biological processes, such as growth, reproduction and physiology, which can be approached in situ or by collecting specimens and rearing them in aquaria, is particularly challenging for deep-sea organisms like cold-water corals. Field experimental work and monitoring of deep-sea populations is still a chimera. Only a handful of research institutes or companies has been able to install in situ marine observatories in the Mediterranean Sea or elsewhere, which facilitate a continuous monitoring of deep-sea ecosystems. Hence, today’s best way to obtain basic biological information on these organisms is (1) working with collected samples and analysing them post-mortem and / or (2) cultivating corals in aquaria in order to monitor biological processes and investigate coral behaviour and physiological responses under different experimental treatments. The first challenging aspect is the collection process, which implies the use of oceanographic research vessels in most occasions since these organisms inhabit areas between ca. 150 m to more than 1000 m depth, and specific sampling gears. The next challenge is the maintenance of the animals on board (in situations where cruises may take weeks) and their transport to home laboratories. Maintenance in the home laboratories is also extremely challenging since special conditions and set-ups are needed to conduct experimental studies to obtain information on the biological processes of these animals. The complexity of the natural environment from which the corals were collected cannot be exactly replicated within the laboratory setting; a fact which has led some researchers to question the validity of work and conclusions drawn from such undertakings. It is evident that aquaria experiments cannot perfectly reflect the real environmental and trophic conditions where these organisms occur, but: (1) in most cases we do not have the possibility to obtain equivalent in situ information and (2) even with limitations, they produce relevant information about the biological limits of the species, which is especially valuable when considering potential future climate change scenarios. This chapter includes many contributions from different authors and is envisioned as both to be a practical “handbook” for conducting cold-water coral aquaria work, whilst at the same time offering an overview on the cold-water coral research conducted in Mediterranean laboratories equipped with aquaria infrastructure. Experiences from Atlantic and Pacific laboratories with extensive experience with cold-water coral work have also contributed to this chapter, as their procedures are valuable to any researcher interested in conducting experimental work with cold-water corals in aquaria. It was impossible to include contributions from all laboratories in the world currently working experimentally with cold-water corals in the laboratory, but at the conclusion of the chapter we attempt, to our best of our knowledge, to supply a list of several laboratories with operational cold-water coral aquaria facilities.

Bazairi, Hocein/0000-0002-1788-0580; Gattuso, Jean-Pierre/0000-0002-4533-4114; Gerovasileiou, Vasilis/0000-0002-9143-7480; Cerrano, Carlo/0000-0001-9580-5546; Turicchia, Eva/0000-0002-8952-9028; Topcu, Nur Eda/0000-0003-2734-2695; Ponti, Massimo/0000-0002-6521-1330; deudero, salud/0000-0001-5584-2801; Ledoux, Jean-Baptiste/0000-0001-8796-6163; Fraschetti, Simonetta/0000-0002-1780-1651; BERTOLINO, Marco/0000-0003-3233-303X; Duarte, Carlos M./0000-0002-1213-1361, WOS: 000499719400001, [No abstract available], postdoctoral contract Juan de la Cierva-Incorporacion [IJCI-2016-29329]; Ministerio de Ciencia, Innovacion y Universidades [PTA2015-10829-I]; Interreg Med Programme [MPA-Adapt 1MED15_3.2_M2_337]; European Regional Development Fund - Foundation Prince Albert II Monaco; European UnionEuropean Union (EU) [689518, FPU15/05457]; Spanish Ministry of EducationSpanish Government [UID/Multi/04423/2013]; FCT - Foundation for Science and TechnologyPortuguese Foundation for Science and Technology; European Regional Development Fund (ERDF)European Union (EU), MV-L was supported by a postdoctoral contract Juan de la Cierva-Incorporacion (IJCI-2016-29329) of Ministerio de Ciencia, Innovacion y Universidades. AI was supported by a Technical staff contract (PTA2015-10829-I) Ayudas Personal Tecnico de Apoyo of Ministerio de Economia y Competitividad (2015). Interreg Med Programme (grant number Project MPA-Adapt 1MED15_3.2_M2_337) 85% cofunded by the European Regional Development Fund, the MIMOSA project funded by the Foundation Prince Albert II Monaco and the European Union's Horizon 2020 research and innovation programme under grant agreement no 689518 (MERCES). DG-G was supported by an FPU grant (FPU15/05457) from the Spanish Ministry of Education. J-BL was partially supported by the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT - Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020.

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...

A new index of ecological status, named Mesophotic Assemblages Ecological Status (MAES) index, was elaborated on the basis of ROV (Remotely Operated Vehicle) photography and video footage in order to assess the status of mesophotic megabenthic assemblages from hard bottom. The index was tested on seven sites located between 50 and 150 m depth in the Ligurian and Tyrrhenian seas (western Mediterranean Sea). The MAES index considers three main parameters: (i) the community structure (number of megabenthic taxa, percent biotic cover in the basal layer, density of erect species); (ii) the condition of the dominant erect species (average height, percent of colonies with epibiosis/necrosis); (iii) the visible human impact (density of marine litter, including lost fishing gears). Two versions of the index have been elaborated, the complete version (MAES) and the quick version ( q -MAES), which showed comparable results, therefore suggesting the possibility of fastening assessment times. The sensitivity of the MAES index was correlated with the putative human pressure acting upon the site (semi-quantitatively assessed considering fishing effort and coastal urbanization). A standard working protocol related to the evaluation of the MAES index is here proposed with the intent to create an effective monitoring tool for the assessment of the ecological status of mesophotic assemblages on a large scale, as required by the EU Marine Strategy Framework Directive. MAES index will enhance the comprehension of the dynamics of mesophotic Mediterranean megabenthic assemblages with respect to human pressures and will also provide marine scientists and managers with a valuable tool specifically designed for the conservation of such vulnerable marine ecosystems.

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.

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.

Commercially harvested since ancient times, the highly valuable red coral Corallium rubrum (Linnaeus, 1758) is an octocoral endemic to the Mediterranean Sea and adjacent Eastern Atlantic Ocean, where it occurs on rocky bottoms over a wide bathymetric range. Current knowledge is restricted to its shallow populations (15–50 m depth), with comparably little attention given to the deeper populations (50–200 m) that are nowadays the main target of exploitation. In this study, red coral distribution and population structure were assessed in three historically exploited areas (Amalfi, Ischia Island and Elba Island) in the Tyrrhenian Sea (Western Mediterranean Sea) between 50 and 130 m depth by means of ROV during a cruise carried out in the summer of 2010. Red coral populations showed a maximum patch frequency of 0.20 ± 0.04 SD patches·m−1 and a density ranging between 28 and 204 colonies·m−2, with a fairly continuous bathymetric distribution. The highest red coral densities in the investigated areas were found on cliffs and boulders mainly exposed to the east, at the greatest depth, and characterized by medium percentage sediment cover. The study populations contained a high percentage (46% on average) of harvestable colonies (>7 mm basal diameter). Moreover, some colonies with fifth-order branches were also observed, highlighting the probable older age of some components of these populations. The Ischia population showed the highest colony occupancy, density and size, suggesting a better conservation status than the populations at the other study locations. These results indicate that deep dwelling red coral populations in non-stressed or less-harvested areas may diverge from the inverse size-density relationship previously observed in red coral populations with increasing depth.

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

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...

Deep-water fishing activities are impacting deep-water habitats worldwide, yet the extent of the damage caused is mainly unseen and not quantified. We used Remotely Operated Vehicle surveys to assess the extent of fishing impacts on rocky substrata on four offshore banks between 70 and 280 m depth in the Mediterranean Sea. Video analysis of the abundance and diversity of megafauna revealed communities dominated by arborescent cnidarian passive suspension feeders at all studied depth ranges. Between 19% and 62% of the video frames showed clear impacts from lost debris, the majority of which is ascribable to both professional and recreational fishing activities and the occurrence of fishing impact is generally correlated with the presence of entangled and overgrown corals. Broken coral colonies and strips where habitat-forming species were scattered provided additional evidence of widespread fishing disturbance. These data evidence the widespread impact of fishing activities on benthic hard bottom communities and suggest the need of specific conservation measures in coastal and off-shore management plans at both local and national levels in order to protect unique ecosystems that are progressively disappearing even before being studied.

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...