Ligurian Seamounts: unveiling deep biodiversity and new Mediterranean VMEs

The Ligurian Sea is among the most studied Mediterranean basins due to the numerous research groups that, since the beginning of the last century, have characterized the benthic and pelagic biota, mainly thanks to SCUBA diving and trawl surveys. Nevertheless, a large knowledge gap still exists for deep circalittoral communities, which thrive in the deepest part of the continental shelf and upper slope. Recent reviews, however, suggest that this bathymetric zone may host the deepest extension of the shallow-water animal forest as well as a diverse deep circalittoral assemblage that constitutes the so-called roche du large community. Considering that hard grounds found at relatively short distances from the coastline attract a substantial amount of professional and recreational fishermen, it became very important to carry out an extensive investigation in this area.

Four years of ROV surveys (2012, 2015, 2016 and 2017) were performed along the Ligurian continental shelf and shelf break at depths of 50 to 220 m in order to characterize the main megabenthic biocoenoses and quantify the anthropogenic disturbance. More than 70 ROV dives were thoroughly examined to identify variations in substrate type, depth and slope, together with all megabenthic species and traces of human impact and lost litter. A comprehensive community analysis was then carried out to identify the main benthic assemblages and the most relevant environmental parameters that explain the patterns observed. A well-preserved deep circalittoral environment was found, with representatives of gorgonian and black coral forests, horny sponge grounds, Dendrophyllia cornigera aggregations as well as soft-bottom meadows of sabellids and alcyonaceans.

A georeferenced database has also been created, where community maps were overlapped with areas of high impact in order to identify a potential network of sensitive habitats that may constitute the basis to identify future Marine Protected Areas (MPAs).

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