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The pervasive presence of marine litter represents a significant threat to Mediterranean biogenic reefs, leading to habitat degradation and a negative impact on associated structuring organisms, such as sponges and gorgonians. This communication highlights one of the detrimental effects caused by abandoned or lost fishing gear on colonies of Paramuricea clavata (Risso, 1827) from MPA Asinara Island (Mediterranean Sea). The study is part of the Strong Sea Life project (Survey and Treatment ON Ghost Nets SEA LIFE), aimed at mitigating the effects of abandoned fishing gear and enhance the conservation status of priority habitats of Posidonia oceanica (Linnaeus) Delile, 1813 and coralligenous reefs. [ABSTRACT FROM AUTHOR]

A detailed analysis of the richness and abundance of invertebrates associated with three common sea fan species at Burdwood Bank is provided. Samples were acquired during a research cruise on board the RV Puerto Deseado (Argentina) in 2017. Thouarella sp., Dasystenella acanthina, and Bayergorgia vermidoma were frequently encountered octocoral species and found to provide habitat to at least 65 associated taxa. The majority of the recorded associate fauna consisted of filter or suspension feeders. Polychaetes and ophiuroids were the most frequently observed associated organisms, followed by bryozoans, bivalves, and brachiopods. We also report the presence of acariids on B. vermidoma and foraminifers on both Thouarella sp. and B. vermidoma. Dasystenella acanthina and Thouarella sp. have a complex three-dimensional structure. This increases the available substrate area for other organisms, thereby increasing the seafloor heterogeneity, which is demonstrated by the high richness and abundance registered here. In this sense, they act as habitat and niche multipliers, which led them to contribute structurally and functionally to the studied marine animal forests. [ABSTRACT FROM AUTHOR]

The sea pen Pteroeides spinosum (Ellis, 1764), belonging to the superfamily Pennatuliodea McFadden, van Ofwegen & Quattrini, 2022, is a little-known anthozoan species well-adapted to inhabit soft bottoms. Similar to other sea pens, it can form aggregations in both infra- and circalittoral zones, significantly enhancing the complexity and biodiversity of these habitats. We present the first in vivo video observation of rolling behaviour of a P. spinosum individual, documented during a Remotely Operated Vehicle (ROV) survey, in the northern Tyrrhenian Sea, at a depth range of 50–58 m. The animal assumed a wheel-like shape, likely by inflating its body with seawater. This led to a rolling motion along the seabed, covering a linear distance of approximately 7 m in just 4 min. The observed mobility of this species adds new information about its behaviour, emphasizing the role of video technology in capturing real-time information. [ABSTRACT FROM AUTHOR]

After 50 years, the dumping of red mud at the head of Cassidaigne Canyon (Southern France) was stopped in 2015. The area was surveyed in 2021 with an ROV at depths of 440–630 m. Biological findings reported here (images, sampling) have been obtained during a single ROV transect in the heavily impacted zone. In spite of the industrial waste deposit, a diverse faunal assemblage has persisted at the canyon head. Bioconstruction comprising large deep-sea oyster shells, scleractinian corals and hexactinellid sponge skeletons provides elevate and complex substrates for other organisms. Among the more significant findings, three live specimens of Neopycnodonte zibrowii Gofas, C. Salas & Taviani, 2009, previously only known as dead shells in that canyon, were documented and the rarely observed stenopodid shrimp Odontozona edwardsi (Bouvier, 1908) has been sampled (first record in the Mediterranean) and DNA barcoded. [ABSTRACT FROM AUTHOR]

Eudendrium capillaroides Schuchert, 2008 has not been reported since its original description. The new and abundant material found in Ceuta, southern coast of the Strait of Gibraltar, allows us to refine the morphological diagnosis of this species. Eudendrium capillaroides is characterized by small monosiphonic colonies, a dense ring at the base of the hydranth, and it seems to have a preference for growing on other hydroids. Male gonophores on atrophied polyps, two-chambered (occasionally one chamber), and female gonophores on reduced polyps in the initial stages of development but hydrants later completely atrophied. Nematocysts are heterotrichous microbasic euryteles of two size classes, a larger size densely distributed in a band on the hydrant body basally and a smaller size abundant mainly on the tentacles. Furthermore, we carried out molecular analyses to assess the status of E. capillaroides and its most similar congener E. capillare within the genus Eudendrium. The use of few morphological characters or incomplete descriptions may thus lead to an incorrect wide distribution of a nominal species that actually represents a species complex. This can particularly be the case in less conspicuous species, such as many hydroids, where the degree of diversity might be underestimated. The accurate description of tiny, inconspicuous and/or cryptic species is important in order to better estimate global marine diversity as well as to understand marine communities and the relationships between their components. [ABSTRACT FROM AUTHOR]

Pennatulaceans (Octocorallia: Pennatulacea) are among the most dominant octocoral species living in soft bottom communities. Some of them are cosmopolitan and have been recorded in all seas and oceans of the world, from shallow waters up to about 6260 m deep. In the present study, we try to find answers to questions about the biogeographical distribution of sea pens including most recently described species. We also evaluate the diversity and faunistic affinities among pennatulaceans of the world’s oceans, and determine the degree of faunistic isolation of the Mediterranean Sea from the Atlantic. Finally, we return to the old debate about the hypothetical oldest diversification center of sea pen lineages. [ABSTRACT FROM AUTHOR]

Distribution and occurrence data of the sea fan Leptogorgia sarmentosa (Esper, 1791) in the Mediterranean Sea were updated thanks to new photographic surveys, highlighting the presence of the species off NE Sardinia and, in particular, in the Tavolara-Punta Coda Cavallo Marine Protected Area (TPCCMPA). The estimated average distance among colonies strongly suggests that they are not able to sexually reproduce and that they probably can be considered a sterile pseudo-population supported by inputs of larvae from the Italian mainland coast towards Sardinia. The putative conveyor belt for larval input to this area is a small permanent gyre (the North-Tyrrhenian Gyre) counterclockwise moving from the Italian to the Sardinian coasts. In TPCCMPA, the growth of one colony settled at 30 m depth was investigated across 7 years (2016–2022). The morphometric parameters indicated a linear development of the colony, in terms of branch development and 3D complexity estimated through the fractal dimension. The observed growth rates were not regular but were reached through a highly variable positive and negative oscillation. A significant correlation was obtained between growth rate and average Autumn and Winter water temperature, suggesting that somatic growth occurs in these periods. In the context of long-lasting elevated seawater temperatures and local damage linked to fishing activities, L. sarmentosa was confirmed to be a resilient species compared with other erect seascape components, like other gorgonians and sponges. [ABSTRACT FROM AUTHOR]

Sea pens (Octocorallia, Pennatulacea) are a specialized and morphologically distinct group of octocorals. The majority of them have adapted to survive on soft sediments with the help of an anchoring muscular peduncle. The whip-like sea pen Protoptilum carpenteri is considered a deep-sea North Atlantic species, which recently has been documented also in the Mediterranean Sea, where its actual distribution and abundance are still unknown. Even less is known about its ecology and behaviour, its reactions after disturbance, and its possible escape strategies. Several species of pennatulaceans can withdraw partially or completely into the sediment, following an apparent rhythmic but unsynchronized procedure that is usually preceded by the closure of the autozooids and the expulsion of the water contained within the colony. The present study reports and discusses for the first time the extremely fast withdrawal behaviour of P. cf. carpenteri after in situ disturbance. [ABSTRACT FROM AUTHOR]

Sea pen species of the genus Calibelemnon are important components of soft bottom communities. Here, we formally describe Calibelemnon hinoenma sp. nov. from shallow waters in Amami Oshima, Kagoshima in the Ryukyu Islands, via molecular and morphological observations and analyses. This species can be distinguished from its congeners by the presence of paired autozooids, siphonozooids aligned irregularly in one to three rows at the side of the rachis between polyps, and the red-brown rufous color of the oral disks. Phylogenetically, the new species is located in an Anthoptilum–Umbellula–Calibelemnon clade. Ancestral state reconstruction analyses suggest that Calibelemnon species may have undergone at least two habitat changes, from shallow to deep waters, followed by a return to shallow waters. In the Ryukyu Islands, there have been many recent discoveries of unique marine species, with this sea pen species being the latest. [ABSTRACT FROM AUTHOR]

Chella Bank (also known as Seco de los Olivos seamount) is a volcanic submarine elevation (76–700 m deep) located ca. 16 km off the southern coast of Spain, within the Alboran Sea, in the Atlantic-Mediterranean transition zone. It represents a biodiversity hotspot for Europe, with more than 600 species listed to date, and contains several habitats included in the EU Habitats Directive. During three ship-based expeditions, several areas of Chella Bank were surveyed and sampled in a depth range of 95–729 m, resulting in new records that improve our knowledge on poorly studied phyla, such as bryozoans. In 14 of the 21 samples examined during this study, 43 bryozoan taxa could be identified. Among these, one species is described as new to science (Buskea medwaves sp. nov.) and three other ones are reported for the first time from the Mediterranean Sea, namely Terminoflustra barleei (Busk, 1860), Marguetta pulchra Jullien in Jullien & Calvet, 1903, and Schizomavella (Schizomavella) linearis profunda Harmelin & d’Hondt, 1992a. Some species were abundant in the samples, such as Adeonellopsis distoma (Busk, 1859), B. medwaves sp. nov., Entalophoroecia cf. deflexa, and Reteporella pelecanus López de la Cuadra & García-Gómez, 2001. The highest species richness was detected in rhodolith beds and on coral rubble bottoms (especially exposed above the sediments) compared with other bottom types and habitats such as sandy bottoms and muddy bottoms. The finding highlights the importance of these environments for bryozoans. [ABSTRACT FROM AUTHOR]

Limited research effort in the Central Mediterranean deep sea has reported a lower species diversity in this area than in adjacent regions. With the recent advent of remotely operated underwater vehicles (ROVs), the deep sea has become more accessible to surveys, especially rocky benthic areas such as canyons and escarpments. The aim of the present study was to assess diversity, spatial and bathymetric distribution, density, habitat, and microhabitat associations of echinoderms in deep waters around the Maltese Islands. Video data were acquired through ROV surveys as part of the LIFE BaĦAR for N2K project, at depths of 216 to 1031 m. In total, 25 echinoderm taxa were recorded, including the first Central Mediterranean records of the sea stars Marginaster capreensis (Gasco, 1876) and Sclerasterias neglecta (Perrier, 1891), and the first record of the holothuroid Mesothuria intestinalis (Ascanius, 1805) from Maltese waters. Six species were observed deeper than their currently accepted depth range in the Mediterranean. The most abundant species were the crinoids Antedon mediterranea (Lamarck, 1816) and Leptometra phalangium (Müller, 1841), which formed very dense aggregations of up to 2900 individuals/1000 m2 in a small area to the south of Malta. This area also supports the only known Mediterranean population of the Atlantic sea star Coronaster briareus (Verrill, 1882). Bathymetric distribution varied for each species, and the overall echinoderm diversity seemed stable across the surveyed depths. Since previous deep-sea studies in the area were based on trawling surveys, many deep-sea echinoderm species are reported in the literature as occurring on sedimentary bottoms. However, the present study revealed that several occur more often on rocky substrata, corals, or anthropogenic objects than on sediments. Our study based on video footage also provided insights into the microhabitat of many deep-sea species, yielding information that is not obtainable through remote sampling. [ABSTRACT FROM AUTHOR]

Sea pens are benthic marine organisms, which have important roles as three-dimensional structures and habitats on sandy and muddy seafloors. Although the behavior of a few species of sea pens has been sporadically reported since the seventeenth century, and despite their presence across a wide range of habitats, the behavior of most sea pen taxa has not been well studied or documented. In this study, via video images of an Echinoptilum sp. specimen in an aquarium (shown in this study at 128-times speed), we observed unreported aspects of behavior, namely mole-like movement within the seafloor sand, and bending of the colony when emerging from the sand. Such mole-like behavior may be advantageous to avoid dangerous and other unfavorable situations, such as predation and competition for space. Aspects of Echinoptilum sp.'s morphology, such as a digitiform colony shape, lack of an axis, and the presence of retractable autozooids and three-flanged sclerites may assist in this behavior. Finally, it appears that peristalsis and active movements are common features for anthozoans in sandy bottom environments, and have so far been reported from sea pens, zoantharians, and scleractinian corals. [ABSTRACT FROM AUTHOR]

The deep-sea elpidiid holothuroid, Penilpidia ludwigi, was recorded using a Remotely Operated Vehicle in the Western, Central, and Eastern Mediterranean Sea. This species, endemic to the basin, was previously captured above the seabed in sediment traps and based on these records its swimming ability was assumed. The present study reports the first in situ observations of swimming P. ludwigi and provides an update on the geographic and bathymetric distribution of this species. A large aggregation of thousands of specimens was observed in the Levantine Sea with a maximum local density 300 ind. m−2. The ROV surveys allowed observation of the behavior of the species and description of its mode of swimming. Active swimming using strokes of the tentacle crown is combined with drifting benefiting of the current, the former used for fast escape the latter mainly for energy-saving displacement. Swimming behavior allows P. ludwigi to exploit various deep-sea habitats including seamounts, canyons, and ridges inaccessible to non-swimming deposit feeders. [ABSTRACT FROM AUTHOR]

The predatory activity of the asteroid Peltaster placenta (Müller 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. [ABSTRACT FROM AUTHOR]

The sea star Coronaster briareus (Verrill Am J Sci (Ser III), 1882) is reported for the first time from the Mediterranean Sea. A total of 26 individuals were sighted in Maltese waters during ROV surveys made in July 2015 and June-July 2016. The identity of the species was confirmed through morphological examination of a specimen collected in June 2016. This identification is discussed in the light of inconsistencies in the published descriptions of species of Coronaster recorded from the Atlantic, and of individuals belonging to this genus recorded from the eastern Atlantic and whose coloration does not match that of C. briareus or C. volsellatus (the only species of Coronaster hitherto known from the Atlantic). The presence of numerous individuals of C. briareus in Maltese waters, recorded on two occasions a year apart over a relatively large area, indicates that there is an established population. This represents a considerable expansion of the distribution range of this species, which is mostly known from the western Atlantic. Possible reasons for its presence in Maltese waters are discussed, but the dynamics of the occurrence of C. briareus in the central Mediterranean remain unknown. [ABSTRACT FROM AUTHOR]

While living corals were mainly reported to live at depths shallower than 1200 m, their pleistocene fossils in the form of Pleistocene fossils are found at depths of ca. 2000 m in the Mediterranean Sea. This was found after in-situ observations during dives of the Nautile submarine in the Canyon of Stoechade (France). During these dives, living specimens of sea fans (Acanthogorgia hirsuta, Isidella elongata, Placogorgia massiliensis) and hard corals (Javania cailleti) were observed and collected at depths of between 1700 and 2200 m. In an attempt to explain this unexpected find, it has been speculated that general conditions in northern canyons may be more favorable to the deep occurrence of these organisms than the central and southern areas of the Mediterranean, where no living Scleractinia or Gorgonaria have been observed at similar depths. [ABSTRACT FROM AUTHOR]

Abstract Meiofauna are an important component of deep-sea benthic communities because they are highly abundant and play an important role in the sediment. This review describes trends in the ecology of deep-sea meiofauna based on results from studies published since the review by Soltwedel (2000), with a focus on spatial distribution patterns of deep-sea meiofauna communities at regional (~100–10,000 km), habitat (~0.1–100 km), local (~0.1–100 m), and small scales (~0.1–10 cm), and with reference to the effects of environmental variables and disturbance (biological and human) that influence these patterns. The focus of deep-sea meiofauna studies has shifted from investigations of patterns related to water depth, regions, and vertical gradients in the sediment to the effect of deep-sea habitats on meiofauna communities, the relative importance of different spatial scales, and the relative impacts of disturbance on meiofauna communities. Although deep-sea meiofauna community attributes (abundance, diversity, and community structure) are shown to vary across all spatial scales, the greatest variability is generally observed at regional and sediment depth scales. However, generalisations are difficult to make due to the limited number of studies that allow direct comparisons across multiple scales. At the regional scale, variation in meiofaunal communities appears mostly related to differences in surface productivity, other food proxies, and physical disturbance; however, geological history, oceanographic boundaries and ocean current flows may also contribute to regional patterns. At the small sediment depth scale, meiofauna communities are typically influenced by food proxies, oxygen availability, sediment characteristics, seafloor topography proxies, microhabitat heterogeneity, and bioturbation by larger fauna. Overall, there have been a limited number of studies of small horizontal scale patterns, at seamounts, and in certain geographic regions such as the Indian Ocean and Antarctica. Fewer studies have been conducted in deep ocean basins compared to continental margin. Most studies have focused on nematodes, while other meiofauna taxa such as harpacticoid copepods have not been investigated as often in deep-sea ecological studies. The findings of this review provide a new perspective on the state of knowledge of the factors influencing meiofauna in the deep-sea ecosystem, and highlights the need for future meiofauna studies to provide information that can assist the management of human activities in vulnerable deep-sea areas. [ABSTRACT FROM AUTHOR]

Dense aggregations of antipatharian corals have been discovered by means of remotely operated vehicle (ROV) photo-imaging off the western Pontine Islands (Central-Tyrrhenian Sea, Italy). These black coral assemblages are mainly composed of Parantipathes larix and Leiopathes glaberrima . This discovery constitutes an update of their habitat distribution for the Mediterranean Sea and is relevant for the development of focused protection measures for the study area. [ABSTRACT FROM AUTHOR]