Evaluating the ecological status of cold-water coral habitats using non-invasive methods: An example from Cassidaigne canyon, northwestern Mediterranean Sea

Abstract

Cold-water coral ecosystems have been identified as vulnerable, but quantitative data on their conservation status is very limited. The Marine Strategy Framework Directive (MSFD) is the tool implemented by the European Union's Integrated Maritime Policy to achieve Good Environmental Status (GES) of marine waters by 2020. In this context, the aim of this study was to evaluate the Ecological Status of benthic habitats in Cassidaigne canyon, focusing in particular on cold-water coral habitats dominated by Madrepora oculata. Data were collected during the Videocor1 cruise (2017). Videos and photos collected during eight dives of the H-ROV Ariane were used to reconstruct, in 3-dimensions, the areas where cnidarians have settled in the canyon. A total of 33 3D models were built, which allowed measuring the spatial and vertical distribution, surface, density and size structure of cnidarian populations at four different sites. When 3D reconstructions were not possible, GIS tools were used. The seven cnidarian species considered were the scleractinian M. oculata; three antipatharians: Leiopathes glaberrima, Antipathella subpinnata, Antipathes dichotoma; and three aclyonaceans: the precious red coral Corallium rubrum and the gorgonians Callogorgia verticllata and Viminella flagellum. Using photogrammetry, we were able to reveal the size structure of the dense population of M. oculata in the canyon, as well as to obtain knowledge on a complex site (Cassis-200) composed of 15 knolls, and to quantify the surface occupied by M. oculata at a separate site (Cassis-500) influenced by industrial discharges. At the southern flank of the canyon we found a highly diverse site (SW Flank) dominated by antipatharians and gorgonians composing large forests, and finally a reservoir of M. oculata was identified under overhangs at a site called the Wall. The diversity of accompanying species is also reported and marine litter quantified. Images collected before 2017 were compared to the 3D models to precisely locate them on the sites, and assess temporal changes in M. oculata colony sizes at Cassis-200 site. We also report on the ground-truthing of predicted habitat maps produced previously, and confirm their good representation of the distribution of cold-water coral habitats. Finally, we quantified the criteria defined by the MSFD, aimed at evaluating the GES of benthic habitats for M. oculata ecosystems, at the scale of the Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. Cassidaigne canyon. Measurements showed that the extent of loss of the observed M. oculata habitat reached 56% according to the MFSD definition. Highlights ► Cold-water corals distribution, density and size structure are reported. ► Size measurements were performed using 3D-models. ► A diverse site dominated by antipatharians and gorgonians forests was found. ► The extent of loss of the observed M. oculata habitat reached 56...

Spatial distribution and habitat characterization of marine animal forest assemblages along nine submarine canyons of Eastern Sardinia (central Mediterranean Sea)

“…Such differences result into a high degree of physical and biological variability at both the intra-and inter-canyon level (McClain and Barry, 2010;Wü rtz, 2012), so that understanding factors driving community composition can be very challenging. Recent advances in technology such as Remotely Operated Vehicles (ROVs), swath bathymetry and side-scan sonar have allowed to better understand geomorphological features, processes and biodiversity through a non-invasive procedure based on underwater footage (Fernández-Arcaya et al, 2017;Canals et al, 2019;Chimienti et al, 2019a,b;Fabri et al, 2019). However, knowledge of the benthic communities' species richness, composition, and factors regulating their variability at different spatial scales is still scant.…”

The “Corsica Channel Cold-Water Coral Province” (Mediterranean Sea)

“…To date, seven CWC provinces, structured by the colonial scleractinians Madrepora oculata and, subordinately, Desmophyllum pertusum (Lophelia pertusa; Addamo et al, 2016), have been identified in the Mediterranean Sea (Taviani et al, 2017(Taviani et al, , 2019Chimienti et al, 2019). From east to west, the CWC provinces are Bari Canyon (e.g., Freiwald et al, 2009;Angeletti et al, 2014Angeletti et al, , 2020 and Santa Maria di Leuca (Taviani et al, 2005;Vertino et al, 2010) in the Adriatic and Ionian seas, South Malta (Schembri et al, 2007;Freiwald et al, 2009;Knittewis et al, 2019), South Sardinia Nora Canyon (Taviani et al, 2017) in the Tyrrhenian Sea, Cassidaigne (Fabri et al, 2014(Fabri et al, , 2019 and Cap de Creus canyons (Orejas et al, 2009) in the Gulf of Lion, and Alboran Sea (Lo Iacono et al, 2019, with references therein).…”

The high biodiversity and vulnerability of two Mediterranean bathyal seamounts support the need for creating offshore protected areas

“…Entanglements in marine animal forests and related damage have been recognized as important indicators of stress for benthic communities in both shallow and deep waters (Angiolillo et al, 2015; Bo, Bava, et al, 2014; Bo, Cerrano, et al, 2014; Enrichetti et al, 2019; Galgani, Pham, Claro, & Consoli, 2018; Gori et al, 2017). Fragile, slow‐growing species, such as Callogorgia verticillata or cold‐water carbonate corals, provide useful insight into the resistance and resilience of deep benthic assemblages to mechanical stressors (Bo, Bava, et al, 2014; Bo, Cerrano, et al, 2014; Fabri et al, 2019). The Callogorgia verticillata population of the Ulisse Seamount is ultimately characterized by three distinct groups: (i) a large proportion of healthy juvenile colonies, indicating regular successful recruitment in the area; (ii) an intermediate proportion of medium‐sized adult colonies living on highly exploited, gently sloping, silted hardgrounds and dead coral frameworks, and showing evident traces of mechanical stress (dead, entangled, or broken); and (iii) a residual portion of large adult colonies with a relatively good health status thriving on the rough rocky outcrops of the shallowest part of the summit, which fishermen are likely to try to avoid to reduce gear loss.…”