Valuable megafaunal sessile assemblages in the southern Adriatic basin present a western–eastern asymmetric distribution. This is particularly evident when considering cold-water coral (CWC) ...communities, with most diverse and abundant live corals to be found along the western side. On the contrary, only spotty occurrences are documented in the eastern side and at times only in a sub-fossil state. We hypothesize that this asymmetry might derive from differential exposure of the Adriatic floor to polarized hydrological processes. In such a perspective, vigorous albeit a-periodical flushing of deep-sea bottoms at times of cascading processes could be beneficial to sessile deep-sea benthic communities by reinforcing the North Adriatic Dense Water (NAdDW), contrasting excess silting and by enhancing the trophic web. Although no experimental evidence has been yet produced to test this hypothesis, it gains some support by the observation that CWC are flourishing in the general area of the Bari Canyon and adjacent bottoms flushed by dense shelf water (DSW) cascading while they are much less developed on the basin's opposite side, unaffected by this phenomenon.
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.
The hard substrata of the Mediterranean twilight zone commonly host the large, white, branchedAntipathella subpinnata(Antipatharia, Myriopathidae). We discovered one of the largest populations of ...this black coral ever recorded in the Mediterranean Sea, forming a meadow of thousands of colonies in the deep waters off the Calabrian coast (South Italy, Tyrrhenian Sea). The meadow extends from 50 to 100 m depth and is a mixed assemblage of black coral and gorgonian colonies showing specific bathymetric ranges. Antipatharians inhabit the northern slopes of the explored rocky pinnacles receiving the northward moving current of the Strait of Messina. Up to 44% of the black corals are colonized by several encrusting epibionts.A. subpinnatadeserves protection since it creates an important 3-dimensional habitat and represents the most characteristic component of the lower fringe of the circalittoral twilight environment in the Mediterranean Sea.
The occurrence, relative abundance and bathymetric distribution of the deep Mediterranean heterobranch fauna were evaluated as a result of an extensive visual census down to 1825 m depth, carried out ...along the western Italian coasts, covering a latitudinal range of about 600 nautical miles. Observations were conducted using Remotely Operated Vehicles (ROVs) in 551 sites, focusing on the deepest part of the continental shelf, the shelf edge and the upper bathyal zone. The analysis of over 508 hours of video footage and more than 27,000 high-resolution photographs allowed to explore about 594,000 m
2
of rocky outcrops and nearby soft seafloors in four main coastal areas (Ligurian Sea, north-central Tyrrhenian Sea, southern Tyrrhenian Sea, and Sicily Channel) and twelve offshore seamounts. Thirty-six species of heterobranchs, for a total of 559 records, were identified. Sixteen were only sporadically spotted (< 1% of the total observations), while three (Paraflabellina ischitana, Tritoniidae nd and Peltodoris atromaculata) contributed each for more than 10% of the records. An extension of the known Mediterranean bathymetric distribution was reported for 80% of the observed species, with many typically shallow-water taxa being also found in mesophotic environments (40-200 m). The observed marked decrease in diversity and abundance suggested that Mediterranean heterobranchs are mainly a coastal benthic group. From the geographical point of view, the heterobranch fauna present in the Ligurian Sea appeared significantly different from that observed in the Tyrrhenian Sea and the Sicily Channel, and this latitudinal pattern was discussed. Particular attention was given to single out the bathymetric distribution of the food sources of the most frequently observed species, supporting stenophagy as a limiting factor for their colonisation of the deep sea.
Abstract
The three-dimensional coral scaffolds formed by the skeletons of the cold-water corals
Madrepora oculata
and
Lophelia pertusa
represent an important deep-sea hard substratum and create an ...optimal shelter for a rich associated fauna in which the contribution of Porifera has still not been fully considered. The taxonomic analysis of sponges collected from two Sardinian canyons (Nora and Coda Cavallo, 256–408 m) and associated with the dead coral matrix resulted in 28 species, including new records for the Mediterranean Sea, Italian fauna or Central Tyrrhenian Sea. In addition, for many species this is the first finding associated with the coral framework or the first documentation of the
in situ
morphology. The taxonomic comparison with sponge assemblages associated with coral frameworks from Santa Maria di Leuca, Strait of Sicily and Bari Canyon, gave the opportunity to evaluate the similarities among geographically separated banks. Overall, the percentage of exclusive species (recorded only in one site), is very high (81%) and only one species is shared by all four sites, suggesting a low connectivity among the sponge communities. The percentage of shared species is higher for the Maltese community, supporting the role of the Sicily Channel as a crossroads between the communities of the eastern and western Mediterranean basins. Here, 55% of the sponges associated to the coral framework are also reported in shallow-water coralligenous assemblages, indicating a high bathymetric connectivity as well as an ecological plasticity allowing these species to occupy a wide range of small, dark refuges.
Recently, the rich coral communities of the so called roche du large biocoenose of the Gulf of St Eufemia (southern Tyrrhenian Sea) between 90 and 130 m deep, have been described thanks to remotely ...operated vehicle (ROV) imaging. This preliminary survey evidenced the massive presence of a well-diversified sponge community living among the coral colonies. This work aims at giving an ecological overview of some of the dominant species of this environment, together with a taxonomic part including the description of new species: Topsentia calabrisellae sp. nov. and Haliclona (Soestella) fimbriata sp. nov. The silted, rocky outcrops of the Gulf of St Eufemia facilitate the settling mainly of massive sponges with erect habit which may also avoid sedimentation by growing on the coral colonies. On the other hand, the site Capo Vaticano, located at the southern boundary of the gulf, characterized by rocky boulders exposed to strong currents and completely devoid of corals, is inhabited by a poor megabenthic community, dominated by patches of massive sponges, such as Topsentia vaceleti, a species of recent description whose aspect in the field was still unknown. In the entire investigated area 19 species have been photographed (often for the first time in vivo), collected and identified, but the real sponge diversity is certainly under-estimated due to the difficulty of collecting all the sighted specimens through the ROV grabber. Similarly to the coral component, sponges also respond to the same environmental constraints by growing in heterogeneous patches or by showing different morphologies mainly associated with current and sedimentation conditions.
We developed a random, stratified, vertical longline survey in McMurdo Sound, Antarctica, to compare the local age and size composition, diet and reproductive status of Antarctic toothfish ...(Dissostichus mawsoni) with those observed from a vessel-based survey of the southern Ross Sea shelf that includes a McMurdo Sound stratum. Results indicated that southern McMurdo Sound toothfish were larger and older than those a short distance away in northern McMurdo Sound. These data, in addition to recoveries of tagged fish, suggest that the large toothfish in McMurdo Sound may have limited mixing with the rest of the population. The potential effects of climate change and fishing in northern areas on toothfish abundance in McMurdo Sound will depend on the mechanism of toothfish recruitment to McMurdo Sound. Understanding the ecological relationships between McMurdo Sound toothfish and the larger population is required to predict these impacts. Furthermore, because toothfish predators (type C killer whales Orcinus orca, Weddell seals Leptonychotes weddellii) are abundant in the south-west margins of the Ross Sea, it is important to monitor toothfish in McMurdo Sound as part of the monitoring programme for the Ross Sea region Marine Protected Area.
Black coral communities in the Mediterranean Sea are now recognized to be far more common than what was expected a few years ago; however, among the species reported for this basin, Parantipathes ...larix is one of the least well known. This species is characterized by tall, monopodial or sparsely branched colonies showing a distinctive bottle-brush pinnulation pattern and fairly elongated whitish polyps. Rarely reported in the literature, this species, despite frequently occurring as fishing bycatch, has never been observed in dense populations and all available information mainly concerns its morphological features. Two forests of P. larix were discovered during a remotely operated vehicle (ROV) survey conducted in July 2012 on board the R/V Astrea between 100 and 200 m on two continental rocky shoals located about 10 miles southeast of the Island of Montecristo (Tuscan Archipelago, Tyrrhenian Sea). Video footage was analyzed using the ROV imaging technique, and the coral communities were described in terms of abundance, size-frequency distribution and associated fauna. P. larix is the dominant component of both coral communities showing a maximal abundance of 4 colonies m ⁻². Sixteen different patches of P. larix , each covering an approximate area of 30 m ² and spaced on average 60 m apart, were counted on the rocky shoals, representing, with an average height of the colonies of about 1 m, the only true three-dimensional habitat of the study areas. The forests of P. larix of Montecristo represent, as far as we know, a unique case for the exceptional abundance of the colonies and their distribution in discrete patches, which is likely a result of the limited dispersal ability of the larvae. Moreover, their occurrence on isolated banks may suggest a preference for topographic structures subjected to local turbulent hydrographic regimes which are known to support filter-feeding communities.
Recent ROV (Remotely Operated Vehicle) exploration and bottom sampling in the southern Adriatic Sea (Apulian and Montenegrin margins) resulted in the discovery of cnidarian-rich deep-sea habitats in ...the depth range of ca. 400-700 m. In particular, ROV inspection of Montenegrin canyons reveals the existence of megabenthic communities dominated by a variety of cnidarians, including scleractinians (Madrepora oculata, Lophelia pertusa, Dendrophyllia cornigera), antipatharians (Leiopathes glaberrima) and gorgonians (Callogorgia verticillata) as major habitat forming taxa, often in association with sponges and, subordinately, serpulids. All such cnidarians are new records for the southeastern side of the Adriatic Sea. Our investigation indicates that an almost continuous belt of patchy cold water coral sites occurs along the entire southwestern margin (Apulian), basically connecting the Adriatic populations with those inhabiting the Ionian margin (Santa Maria di Leuca coral province).
A spectacular field of columnar carbonates has been discovered on the Montenegrin margin in the southern Adriatic Sea at a depth of about 450 m. The site exposes many columnar carbonates protruding ...from the substrate or abated on the bottom. Such carbonates attain maximum visible lengths of ca. 60 cm with diameters up to 20 cm; display an annular growth, and are either hollow or plugged by indurated sediment. Petrographic and geochemical analyses document the pervasive presence of dolomite, and δ13C values as low as −30‰ VPDB. These ‘chimneys’ are therefore interpreted as former conduits related to hydrocarbon expulsion in this sector of the Adriatic basin. However, available data suggest that hydrocarbon flows at this site have ceased. Our results show that chimneys formed inside the local depositional units, glacial Pleistocene shelf shelly-rich muddy sediment and were successively exhumed from the host sediment. Today, the chimneys offer substrate to benthic life, including cold water corals and sponges. The U-series dating of these carbonate concretions is complicated by the presence of a significant fraction of detrital sediment, which represents a major source of initial 230Th. AMS-14C and 87Sr/86Sr dating of shells embedded in one of the chimney provided ages beyond the range of radiocarbon dating and <600 kyrs, indicating a Pleistocene age of the host sediment. Uncorrected U-series dating of the carbonate chimneys yielded and age of ca. 250–270 kyrs, providing a temporal upper limit for conduit formation driven by lithification caused by the degradation of seeping hydrocarbons. In addition, U/Th dating of cold water coral bases settled on chimneys indicates a Holocene age for their first exposure after exhumation and subsequent function as hard substrate for benthic organisms. The Montenegrin ‘chimney forest’ is a rare case where many such carbonate columnar concretions are still in their original vertical position.
•First record of a submerged seep-carbonate conduit field in the Mediterranean.•Chimneys are dolomitic and share analogies with outcrop counterparts.•Mark hydrocarbon seepage in the Pleistocene of the S Adriatic Sea.
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