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22 Recent Discoveries of Extensive Cold-Water Coral Assemblages in Maltese Waters

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Abstract

Recent deep-water remotely operated vehicle surveys around the Maltese Islands resulted in the discovery of highly diverse habitats, including extensive hard bottom areas dominated by gorgonians and living cold-water corals with a rich variety of associated fauna. Black coral (Leiopathes glaberrima) forests were dominant at 200–400 m, whilst stony reef-forming corals (in particular Madrepora oculata) were most abundant in waters deeper than 500 m. The gorgonian Callogorgia verticillata was dominant in places over the entire depth range, but was particularly abundant at depths of 800–1000 m. Such cold-water coral assemblages are of high conservation interest, and offshore marine protected areas are urgently required in order to protect these very diverse, but highly vulnerable, deep-sea habitats.

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... Not surprisingly, the growing effort of the last decades to better understand the Mediterranean deep-sea realm, with special focus on the charismatic deep-(or cold-) water coral habitats, has resulted in a number of discoveries of new biotopes (e.g. Freiwald et al., 2009;Bo et al., 2011;De la Torriente et al., 2014;Grynió et al., 2018;Knittweis et al., 2019;Taviani et al., 2019) and updating of taxonomic lists (e.g. Gofas et al., 2007;Taviani et al., 2009;Mastrototaro et al., 2010Mastrototaro et al., , 2017D'Onghia et al., 2015;Rueda et al., 2019). ...
... Tentatively identified as Marionia blainvillea (Risso, 1818), one of the first occurrences of this nudibranch was reported by Bo et al. (2011) within a mixed coral assemblage in the Southern Tyrrhenian Sea, locally dominated by C. verticillata. Morphologically similar nudibranchs have been observed at bathyal depths in the Gulf of Lions (Fabri et al., 2014), Central Tyrrhenian Sea (Ingrassia et al., 2016), Sicily Channel (Knittweis et al., 2019) and Southern Adriatic Sea (Angeletti et al., 2014), always on C. verticillata, but they remained undetermined. The lack of actual samples hampered a formal identification and description of this nudibranch until a few specimens were at last collected by mean of a Remotely Operated Vehicle (ROV) in the south-eastern Adriatic Sea. ...
... Although previously observed, it has neither been collected nor described before and, considering that the species remained so far unidentified or misidentified, it is difficult to track all the documented records in the literature. Some previous observations refer to mixed coral assemblages dominated by C. verticillata South of Malta (Knittweis et al., 2019) and in the Lamezia Gulf (Bo et al., 2011). The latter showed density of C. verticillata comparable to our observations, being 1.2 ± 0.3 colonies m − 2 (Bo et al., 2011). ...
Article
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... Many species records have been made in the northeast Atlantic (e.g., Hansen 1975;Gebruk 1990;Billett 1991;Madsen and Hansen 1994) and on the Mid-Atlantic Ridge (Gebruk 2008;Rogacheva et al. 2012Rogacheva et al. , 2013, while in the Mediterranean Sea very few records have occurred to date. However, the use of ROVs significantly increases the amount of data on deep-sea species occurrences and behavior, allowing observations in the natural environment even for rare or uncommon species (e.g., Aguilar et al. 2011;Angeletti et al. 2014;Mastrototaro et al. 2016;Chimienti et al. 2018aChimienti et al. , 2018bKnittweis et al. 2019). Given the soft-body, gelatinous consistence of elasipodids, visual methods of study of these important representatives of deepsea communities are much more effective, as well as being less invasive compared to traditional sampling by grabs and dredges ). ...
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Chapter
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Chapter
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Chapter
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Chapter
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Chapter
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Chapter
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Data
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Article
Full-text available
White coral communities consist of scleractinian corals that thrive in the ocean’s bathyal depths (~ 200–4000 m). In the Atlantic Ocean, white corals are known to form complex, three-dimensional structures on the seabed that attract vast amounts of other organisms, accumulate suspended detritus, and influence the local hydrodynamic flow field. These attributes coincide with what we generally describe as a coral reef. With time, environmental change causes decline of the frameworkconstructing corals; this is followed by erosion of the reef sequence or its draping with noncoral-related deposits. After several such sequences, the structures are known as coral carbonate mounds, which can grow as high as 350 m. Both bathyal white coral reefs and mounds are widely distributed in the Atlantic Ocean and adjacent marginal seas, such as the Gulf of Mexico. The Mediterranean Sea, however, known for its richness of fossil white coral communities exposed in land outcrops, harbors very few extant coral communities. The HERMES project extended its study sites deep into the Mediterranean with state-of-the-art mapping and visualization technology. By doing so, many previously unknown coral sites were discovered during inspections of Mediterranean narrow shelves, canyon walls, escarpments, and seamounts by remotely operated vehicles. Such shelf and continental margin settings are characteristic of the dynamic margins of the Mediterranean Sea and contrast significantly with the much broader shelves of the Atlantic Ocean. This paper reports on a HERMES cruise that was dedicated to exploring these rough submarine topographies in search of white coral communities in the central Mediterranean, and re-evaluates the general perception of the assumed paucity of white corals in this sea.
Chapter
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.
Chapter
This chapter describes the main features of the circulation and properties of the intermediate water masses of the Mediterranean. Interaction with other water masses is also briefly summarised. Both observational and numerical studies described in the literature are used, as well as some more recent, unpublished data sets. It is shown that the main water mass important to cold-water coral habitats is the Levantine Intermediate Water which forms in the Levantine Sea, Eastern Mediterranean and spreads throughout the entire Mediterranean before leaving via the Gibraltar Strait. This pathway is described as well as the expected temperature and salinity along that pathway. Current speed regimes are estimated from the few studies that exist.
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A new cold-water coral (CWC) province has been identified in the Mediterranean Sea in the Capo Spartivento canyon system offshore the southern coast of Sardinia. The ‘Sardinia cold-water coral province’ is characterized in the Nora canyon by a spectacular coral growth dominated by the branching scleractinian Madrepora oculata at a depth of 380–460 m. The general biohermal frame is strengthened by the common occurrence of the solitary scleractinian Desmophyllum dianthus and the occasional presence of Lophelia pertusa. As documented by Remotely Operated Vehicle survey, this area is a hotspot of megafaunal diversity hosting among other also live specimens of the deep oyster Neopycnodonte zibrowii. The new coral province is located between the central Mediterranean CWC provinces (Bari Canyon, Santa Maria di Leuca, South Malta) and the western and northern ones (Melilla, Catalan-Provençal-Ligurian canyons). As for all the best developed CWC situations in the present Mediterranean Sea, the new Sardinian province is clearly influenced by Levantine Intermediate Water which appears to be a main driver for CWC distribution and viability in this basin.
Article
The precious red coral Corallium rubrum (L., 1758) lives in the Mediterranean Sea and adjacent Eastern Atlantic Ocean on subtidal hard substrates. Corallium rubrum is a long-lived gorgonian coral that has been commercially harvested since ancient times for its red axial calcitic skeleton and which, at present, is thought to be in decline because of overexploitation. The depth distribution of C. rubrum is known to range from c. 15 to 300 m. Recently, live red coral colonies have been observed in the Strait of Sicily at depths of c. 600–800 m. This record sheds new light on the ecology, biology, biogeography and dispersal mechanism of this species and calls for an evaluation of the genetic divergence occurring among highly fragmented populations. A genetic characterization of the deep-sea red coral colonies has been done to investigate biological processes affecting dispersal and population resilience, as well as to define the level of isolation/differentiation between shallow- and deep-water populations of the Mediterranean Sea. Deep-water C. rubrum colonies were collected at two sites (south of Malta and off Linosa Island) during the cruise MARCOS of the R/V Urania. Collected colonies were genotyped using a set of molecular markers differing in their level of polymorphism. Microsatellites have been confirmed to be useful markers for individual genotyping of C. rubrum colonies. ITS-1 and mtMSH sequences of deep-water red coral colonies were found to be different from those found in shallow water colonies, suggesting the possible occurrence of genetic isolation among shallow- and deep-water populations. These findings suggest that genetic diversity of red coral over its actual range of depth distribution is shaped by complex interactions among geological, historical, biological and ecological processes.
The IUCN Red List of anthozoans in the Mediterranean
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New depth record of the precious red coral Corallium rubrum for the Mediterranean
  • L Knittweis
  • R Aguilar
  • H Alvarez
Knittweis L, Aguilar R, Alvarez H, et al (2016) New depth record of the precious red coral Corallium rubrum for the Mediterranean. Rapp Comm Int Mer Médit 41:467