On two Eudendrium (Cnidaria, Hydrozoa) species from the Mediterranean Sea

Two species referable to the genus Eudendrium Ehrenberg are recorded from the central Mediterranean Sea. Eudendrium merulum is reported for the jirst time outside Australia, whereas Eudendrium carneum is recorded for the second time from Mediterranean waters. The structure of the nematocysts of E. merulum is elucidated by SEM analyses and the mechanism of penetration is compared to that of other hydroid

Aplysina aerophoba (Nardo, 1833) (Porifera, Demospongiae): an unexpected miniaturised growth form from the tidal zone of Mediterranean caves: morphology and DNA barcoding

In the Mediterranean Sea, the two sponges of the genus Aplysina (A. aerophoba and A. cavernicola) are identified on the basis of their external morphology and the environment in which they live. During a research program on the sponge fauna in semi-submerged caves of the Italian coasts, we have sampled an abundant very small yellow sponge, often living in the tidal zone, which were attributed to the genus Aplysina. Failing to assign the samples to a species through classical taxonomic methodologies (growth form and skeleton arrangement) and for the particular environment where this sponge lives, we have decided to use the COI analysis to solve the taxonomic problem offered by these miniaturized specimens. The analysis indicated that, in spite of the morphological differences, they belong to A. aerophoba. During old detailed surveys, conducted in the '60 years in some of the studied caves, this species was not recorded. It is possible that its abundant presence is related to the modifications occurred in the Mediterranean sponge communities occurred in the last decades in relation to global warming

The cold-water coral province of the eastern Ligurian Sea (NW Mediterranean Sea): historical and novel evidences

Several bathyal cold-water coral provinces, characterized by a lush growth of habitat-forming scleractinians, have been recognized in the Mediterranean Sea. However, the search for this biogenic habitat only marginally targeted the Italian coast of the Ligurian Sea (NW Mediterranean basin) despite historical and a few recent local studies in the region reporting the presence of corals. This study used bathymetry maps, side-scan sonar profiles, historical charts, and trawling routes to identify sites that could potentially host coral habitats in the eastern sector of the Ligurian Sea. Remotely operated vehicle video footage from various projects (2015-2021, 20 dives) was then used to characterize four sub-areas (Genoa Plateau, Portofino, Deiva Marina, and Monterosso) where corals were detected between 450 m and 750 m depth. Radiocarbon dating was used to trace back the geological history of the coral structures. A small coral mound, impacted by trawling activities, was found on the Genoa Plateau, while four massive coral structures were found in the other sub-areas, mainly located in a morphologically complex and highly energetic canyon region. High levels of megafaunal biodiversity, including rarely reported alcyonaceans as Placogorgia coronata, were observed together with moderate fishing impact. Overall, the identified coral areas potentially account for 9 km(2) of both subfossil mounds (as old as 13300 years BP), dominated by Desmophyllum pertusum, and living reefs, dominated by Madrepora oculata, the latter representing up to 23% of the substrate coverage. The few living colonies of D. pertusum in the area represent the first documented records for the Ligurian Sea. These data support the presence of a distinct eastern Ligurian cold-water coral province

The paleo-community of the Sciacca red coral

The sub-fossil red coral deposits of Sciacca (Sicily Channel) have attracted scientific attention for nearly 150 years. Their origin and formation have been long questioned and investigated, given the fact that they represent one of the most intriguing geobiological events ever to occur in the Mediterranean basin. Less attention was given to the paleo-community associated with the sub-fossil coral. Radiocarbon age determinations, in particular, were provided only for red coral, neglecting the possibility of understanding which species were simultaneously present in the coralline paleo-community and which was their role. The study of cemented coral rubble pieces revealed that Corallium rubrum covered the largest time interval (more than 3000 years) and was contemporary to many secondary epibionts over two millennia and to Madrepora oculata for about 500 years; this last finding suggested that an uncommon co-dominance between the two structuring species occurred in the nearby living communities. The lack of Fe-Mg deposits on the cemented coral rubbles coupled with the low bioerosion rate of the red coral skeletons by the demosponge Siphonodictyon coralliirubri (assessed through the analysis of the erosive paleo-scars) suggested that the deposits met with a rapid sediment cover-up. Moreover, for the first time, the analysis of a piece of cemented coral rubble of sub-fossil red coral coming from Sardinian waters confirmed that, albeit to a lesser extent, the conditions favouring the preservation of dead corals can occur also in different localities far from Sciacca

The influence of the rock mineralogy on population density of Chthamalus (Crustacea: Cirripedia) in the Ligurian Sea (NW Mediterranean Sea)

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

Population genomic structure of the black coral Antipathella subpinnata in Mediterranean Vulnerable Marine Ecosystems

none8siAntipathella 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.openTerzin M.; Paletta M.G.; Matterson K.; Coppari M.; Bavestrello G.; Abbiati M.; Bo M.; Costantini F.Terzin, M.; Paletta, M. G.; Matterson, K.; Coppari, M.; Bavestrello, G.; Abbiati, M.; Bo, M.; Costantini, F

The sub-fossil red coral of Sciacca (Sicily Channel, Mediterranean Sea): colony size and age estimates

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

The coral assemblage of an off-shore deep Mediterranean rocky bank (NW Sicily, Italy)

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

Hydrothermal waters enriched in silica promote the development of a sponge community in North Sulawesi (Indonesia)

Two shallow hydrothermal vents were investigated by SCUBA diving to evaluate their influence on the structure and diversity of a sponge community living close to the vent outflow, in the equatorial Pacific Ocean just off the coast of North Sulawesi, Indonesia (1°40.361ʹN, 125°8.112ʹE). No sponges identified were vent-obligate species, since they are found in the surrounding coral reefs too. The sponges were strongly attracted by the vent, concentrating in an area of a few meters around it, where they reached covering values up to 70% in the deeper vent and up to 42% in the shallower one. The high silica concentration, 8.5 mg L−1Si (deep vent) and 5 mg L−1Si (shallow vent), in hot spring water (90°C) was the putative environmental factor driving the sponge settlement and growth. These organisms take advantage of the increased silica availability that, facilitating skeleton formation, probably promotes sponge growth. This hypothesis is in agreement with the evidence that the spicules of the sponge specimens living around the hot springs have a thickness about double that of conspecific specimens present on the coral reefs at least 300 m away