This is the first description of a Mediterranean mesophotic coral reef. The bioconstruction extended for 2.5 km along the Italian Adriatic coast in the bathymetric range −30/−55 m. It appeared as a framework of coral blocks mostly built by two scleractinians, Phyllangia americana mouchezii (Lacaze-Duthiers, 1897) and Polycyathus muellerae (Abel, 1959), which were able to edify a secondary substrate with high structural complexity. Scleractinian corallites were cemented by calcified polychaete tubes and organized into an interlocking meshwork that provided the reef stiffness. Aggregates of several individuals of the bivalve Neopycnodonte cochlear (Poli, 1795) contributed to the compactness of the structure. The species composition of the benthic community showed a marked similarity with those described for Mediterranean coralligenous communities and it appeared to be dominated by invertebrates, while calcareous algae, which are usually considered the main coralligenous reef-builders, were poorly represented. Overall, the studied reef can be considered a unique environment, to be included in the wide and diversified category of Mediterranean bioconstructions. The main reef-building scleractinians lacked algal symbionts, suggesting that heterotrophy had a major role in the metabolic processes that supported the production of calcium carbonate. The large amount of available suspended organic matter in the area could be the main nutritional source for these species, as already suggested in the literature referred to Mediterranean cold-water corals.
The present paper provides a multidisciplinary fine-scale description of a Mediterranean mesophotic new habitat dominated by the bivalve Neopycnodonte cochlear (Poli, 1795), building large and thick pinnacles on vertical cliffs at two study areas along the southern Italian coast. The pinnacles, constituted by a multilayered aggregation of living and dead specimens of N. cochlear, were interconnected with each other to form a framework of high structural complexity, never observed before for this species. The bioconstruction, considerably extended, resulted very complex and diversified in the associated community of structuring organisms. This latter included 165 taxa attributable to different ecological groups occurring in different microhabitats of the bioconstruction. Among the secondary structuring taxa there were scleractinians, serpulids and bryozoans, all contributing to the deposition of calcium carbonate, and poriferans, helping to bind shells together or eroding carbonate by boring species. In comparison with coralligenous sensu stricto and the recently described Mediterranean mesophotic coral reef, the Neopycnodonte bioconstruction showed peculiar features, since it lacked the major contribution of encrusting coralline algae and scleractinians as reef builders, respectively.The main marine bioconstruction in the Mediterranean Sea is localized in the euphotic zone and is well known under the name of coralligenous which is typically considered to be the climax biocoenosis of the circalittoral zone 1 . Coralligenous reefs are widely distributed and consist of thick carbonate concretions mainly built by red calcareous algae, with the variable contributions of sessile invertebrate calcium carbonate depositors (e.g., scleractinians, serpulids, bryozoans) 2-4 . The large amount of different habitats associated with such bioconstructions support the highest values of biodiversity in the Mediterranean Sea 2 . However, with increasing depth and as a result of light attenuation, benthic sessile invertebrates progressively replace algal concretions, becoming the most important habitat builders 5 .The biogenic role of animal bioconstructors has been repeatedly studied in Mediterranean deep-water habitats, where the predominant colonial scleractinians build large three-dimensional (3D) carbonate structures referred to as Cold-Water Corals (CWC) and provide substrate and habitat for a multitude of other organisms 6-11 . Figure 3. Geophysical survey of the Santa Maria di Leuca area and localization of dive points. (a) Digital elevation model of the seafloor derived by the multibeam survey. (b) Details of the ESE-WNW-oriented slope. Note that the slope seems to be very irregular along the portion with a higher gradient. (c) Raw data from the Side-Scan Sonar survey. (d) Classification of the seafloor and localization of dive points (white circles); the bioconstructions can be easily mapped, while shallower and deeper sectors seem to have a similar, even though unclear, acoustic signal. Maps have been created with: (a) ES...
On November 3, 2002 a shallow submarine gas eruption occurred in an area of 2.3 km 2 east of Panarea (Aeolian volcanic arc, Southern Thyrrenian Sea, Italy). The exhalative area, surrounded by the islets of Dattilo, Panarelli, Lisca Bianca, Bottaro and Lisca Nera, has been known since historical times for the hydrothermal activity related to the Panarea volcanic complex. Due to the exceptional characteristics of the phenomenon, different geological, geochemical, geophysical and studies were carried out in this still poorly known volcanic area. A particular effort was devoted to producing a high resolution bathymetric map that also aimed to estimate the amount and location of the active exhalative centers and their variations in space and time. Data were obtained by three RTK multibeam surveys performed between December 2002 and December 2003. Here we show and discuss the technical details of the bathymetric surveys, the bathymetric map at 0.5 m resolution, and the accurate location of the 606 main exhalative centres active during the 2002-2003 crisis. The bathymetric data and the maps show two prevailing principal NE-SW and NW-SE alignments that match the spatial distribution of the exhalation centres. The accurate positioning at submeter accuracy of the gas vents is useful in the monitoring activity and to study their temporal and spatial variability.
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