Deep Coral Oases in the South Tyrrhenian Sea

Abstract

A Mediterranean “roche du large” ecosystem, represented by four rocky shoals, located a few miles apart on a muddy bottom at 70–130 m depth in the gulf of St. Eufemia (Calabria, South Tyrrhenian Sea), was studied by means of Remotely Operated Vehicle (ROV) photo imaging. The shoals host highly diversified coral communities, mainly composed of arborescent colonies of gorgonians (Callogorgia verticillata, Paramuricea clavata, Paramuricea macrospina, Bebryce mollis, Villogorgia bebrycoides, Corallium rubrum, and Leptogorgia sarmentosa), and antipatharians (Antipathella subpinnata, Antipathes dichotoma and Parantipathes larix). The coral colonies reach high densities (up to ca. 17 colonies m−2) and large sizes, such as the over 1.5 m wide antipatharian colonies. We hypothesized that the abundance and composition of the coral assemblages differed significantly among the rocky shoals and with respect to the surrounding soft bottoms. Various environmental variables were tested as possible explanatory factors of the observed differences. Moreover, due to their off-coast localization, we report here that these unique ecosystems are potentially subjected to a strong pressure from the local fishing activities, which were tentatively characterized. The recorded coral β-diversity among the shoals supports the hypothesis that these habitats behave like small oases of hard substrata interspersed in a muddy bottom. Because of their intrinsic beauty and rarity and their biological and ecological value, we stress the need of specific actions aimed at the urgent protection of these oases of biodiversity.

Composition and abundance of octocorals in the Sea of Marmara, where the Mediterranean meets the Black Sea

“…It occurs on hard substrates of the circalittoral zone between 50-80 m deep (Carpine andGrasshoff 1975, Grasshoff 1992). It was recently reported from the Tyrrhenian Sea as a rare occurrence, on muddy substrates with patches of organogenic detritus at depths deeper than 70 m (Bo et al 2012). In the northern Marmara Sea, it occurs on hard substrates like rocks or small pebbles/shells on sandy/muddy bottom starting from 25 m until our limit of observation (42 m), with abundances varying from 1 to 3.1 colonies m -2 .…”

“…macrospina is a Mediterranean endemic known to occur on rocks, detritic or sandy/muddy bottoms, mainly at depths of 40 to 100 m but also deeper (Carpine and Grasshoff 1975). This species is mentioned in the literature dealing mainly with deep sea fauna of the Mediterranean Sea (Watling et al 2005, Aguilar et al 2009, Mastrototaro et al 2010, Bo et al 2012, Angeletti et al 2014) except in the Aegean Sea, where it was collected between 20 and 90 m (Vafidis et al 1994); P. macrospina-dominated assemblages were abundant, especially in the north of the Marmara Sea, and this species was suggested to have greater adaptability than other gorgonians in relation to a relatively fast growing rate (Bo et al 2012). Demir 1954Demir , Çınar et al 2014 On the other hand, S. klavereni, another common species in the northern Marmara Sea, is an endemic Mediterranean species on which very limited information is available.…”

“…This gorgonian was common in the Prince Islands coasts with densities of 0.1 to 3.1 colonies m -2 but rare in the South. In the Mediterranean it is found between 25-130 m on similar bottoms (Carpine and Grasshoff 1975, Vafidis et al 1994, Bo et al 2012). The species is distributed in the Mediterranean Sea but also present in the Northeast Atlantic coasts (Grasshoff 1992, Vafidis et al 1994, Watling and Auster 2005.…”

Population structure and conservation status of the red gorgonian Paramuricea clavata (Risso, 1826) in the Eastern Adriatic Sea

“…) and deeper (> 70 m depth; 22–44 cm; Bo et al . ) P. clavata populations from the Western Mediterranean. However, in this study the proportion of colonies >40 cm in height and the presence of large colonies (>80 cm) were greater than previously reported for most of the shallower (10–40 m depth) Western Mediterranean populations (Coma et al .…”

First characterisation of aLeiopathes glaberrima(Cnidaria: Anthozoa: Antipatharia) forest in Maltese exploited fishing grounds

“…In the Mediterranean Sea, black corals, together with a distinct number of deep accompanying zoanthids, gorgonians and scleractinian species, may be considered among the most important components of these vulnerable populations found along the deep rocky hardgrounds of the continental platform and slope (Bo et al 2009(Bo et al , 2011a(Bo et al , 2011b(Bo et al , 2012(Bo et al , 2014a(Bo et al , 2014b(Bo et al , 2014cOrejas et al 2009;Cerrano et al 2010;Lo Iacono et al 2012;Angeletti et al 2014;Fabri et al 2014). The occurrence and ecological role of these ecosystems has been recently confirmed in the Mediterranean Sea thanks to comprehensive remotely operated vehicle (ROV) explorations that have highlighted the high biodiversity of these habitats, the rich associated fauna of the structuring species, the nursery effect of some large, arborescent species and their extreme longevity (Buhl-Mortensen et al 2010;Mastrototaro et al 2010;Bo et al 2014c, in press).…”