3D-Representations for studying deep-sea coral habitats in the Lacaze-Duthiers Canyon, from geological settings to individual specimens

The Lacaze-Duthiers Canyon is located in the western Mediterranean Sea and long known for hosting cold-water coral colonies canyon head region at depths ranging from 250 to 550 m. In 2019 during CALADU cruise, three kinds of 3D-reconstructions were applied better understand distribution colonies, their habitat skeleton morphologies. canyon's flanks mapped using a hull-mounted echosounder an ROV multibeam echosounder. Digital terrain models built with resolutions 5 1 m examined dimensions. bathymetric data collected on made it possible highlight series sub-parallel structures identified as lithified sedimentary strata along which grow. Coral assemblages explored four locations photographic images assembled structure motion techniques build photogrammetric models. reconstructed 3D enabled geo-localizing recreating 16 over total area 4370 m2. Two colonial species, Madrepora oculata Desmophyllum pertusum plotted reported interpret location scale canyon. coordinates depth used calculate vertical (limited our small exploration, between 339 214 depth) density populations (up 4.3 per m2). spatial coverage measured 100 600 m2 each. sizes analyze population both species (mean 28 cm D. 18 M. oculata, maximum 0.5 m, respectively, bushes 2.5 long). addition, lost fishing gears quantified, longlines densities calculated (0.16 m/m2, up 0.30 m/m2). An exuberant orange was discovered first time Canyon. Five deep-sea scleractinian micro-tomographic scans computed view intrinsic organization. Micro-CT pertusum, dianthus, Caryophyllia smithii, Dendrophyllia cornigera longitudinal transversal cuts, highlighting morphological criteria identification multidirectional examination specimens. We observed thin canal connecting calices axis separate colonies.