Deepwater corals biodiversity along roche du large ecosystems with different habitat complexity along the south Sardinia continental margin (CW Mediterranean Sea)

Abstract

Rocky pinnacles arising from soft bottoms of the circa-littoral zone may host oases of deepwa- ter coral biodiversity: Engineer species that enhance ecosystem’s three-dimensional complexity often act- ing as shelter for associated fauna that can comprise commercially relevant species. Although variations in beta diversity of these coral oases were recently docu- mented at different spatial scales, information on the role of geomorphogical features of rocky outcrops can be considered mostly an unaddressed issue. To comply with this task, five rocky pinnacles showing different geomorphological features (average slope, ruggedness, sediment accumulation), dwelling between 120 and 170 m depth along south Sardinia continental margin, were investigated by means of ROV imaging. We tested the null hypothesis that coral abundance and diversity [estimated using four black corals (Antipatharia) and seven gorgonians (Alcyonacea) as target species] did not differ among investigated sites. Overall, total coral abundance varied from 1.35 to 7.23 col m2; Callogor- gia verticillata, followed by Eunicella cavolinii and Corallium rubrum were the most abundant gorgonians, while Antipathella subpinnata and Parantipathes larix were the most abundant black corals. Through uni- and multivariate analyses, significant differences in corals biodiversity were identified, allowing us to reject the null hypothesis, emphasizing a remarkable variability in beta diversity, apparently following variations in geo- morphological features of investigated pinnacles. More- over, a visual census of anthropogenic debris revealed that lost fishing gears represented the most frequently observed debris, stressing the need to identify further and more focused strategies of conservation to protect these oases of coral biodiversity

Leiopathes glaberrima millennial forest from SW Sardinia as nursery ground for the small spotted catshark Scyliorhinus canicula

“…The upper portion of the Mediterranean Sea continental slope is characterized by the patchy distribution of coral forests ( sensu Rossi, ) distributed over rocky outcrops rising from muddy bottoms, which are considered oases of biodiversity (Bo et al, , ; Cau et al, ). These forests serve as feeding, shelter, foraging and spawning grounds for many associated species (Etnoyer & Warrenchuk, ; Rossi, ).…”

“…In this regard, the black coral Leiopathes glaberrima (Esper, 1788) is both one of the most long‐lived organisms on Earth (Lartaud et al, , Roark, Guilderson, Dunbar, Fallon, & Mucciarone, ) and also one of the main contributors to the three‐dimensional development of the coral forest canopy. This species forms dense mono‐specific patches attached to exposed rocky bench terraces of rocky outcrops (Bo et al, ; Cau et al, ).…”

New sites expanding the “Sardinian cold‐water coral province” extension: A new potential cold‐water coral network?

“…Habitat constraints derived from their heterogeneity and complexity are known to play a pivotal role in shaping deep‐water coral assemblages across a variety of geological features (e.g . roche du large ecosystems or submarine canyons; Bo et al, ; Cau et al, , ; Cau, Moccia et al, ; Hixon & Menge, ; McClain & Barry, ). The three‐dimensional complexity provided both by seafloor morphology and coral communities renders these habitats suitable or not for other species to be associated (Auster, ).…”

“…roche du large ecosystems or submarine canyons; Bo et al, 2012;Cau et al, 2015Cau et al, , 2016Hixon & Menge, 1991; McClain & Barry, 2010). The three-dimensional complexity provided both by seafloor morphology and coral communities renders these habitats suitable or not for other species to be associated (Auster, 2007).…”

Reproductive patterns in deep versus shallow populations of the precious Mediterranean gorgonian Corallium rubrum (Linnaeus, 1758) (Sardinia, central-western Mediterranean)

“…Because of the wide bathymetric range of this species, which leads to huge sampling limitations for deeper populations (Genin et al, 1992), little attention is given to the deeper populations (50-200 m ) (Rossi et al, 2008;Cau et al, 2015bCau et al, , 2016Angiolillo et al, 2016;Benedetti et al, 2016).…”