Typology and distribution of deep-sea epibenthic Echinodermata in the Australian canyons: integrating data from Falkor's expeditions

The southern Australian continental slope is engraved by a series of submarine canyons. Approximately 80 km east of Albany city, there is the Bremer Canyon System (BCS). Between January and February 2020 it was explored during the oceanographic cruise “FK200126” lead by the Schmidt Ocean Institute, the Institute of Marine Sciences and the Institute of Polar Science of the Italian National Research Council (CNR-ISMAR, CNR-ISP). The BCS is known to host a rich biodiversity, thanks to its geomorphology. Studies on biodiversity documented the presence of a community of cold-water corals (CWC) and a rich associated fauna. Among these, Echinodermata. Echinodermata is a cosmopolitan Phylum. However, informations regarding the variables influencing its distribution in deep-sea environments are scarce. This thesis provide the first assessment of the factors influencing the distribution, the taxonomic diversity and abundance of Echinodermata in the BCS. Three ROV dives collected during the RV Falkor exploration, were analyzed for taxonomical identification. A total of 1252±1.76 echinoderms belonging to 62 different taxa have been individuated, among Crinoidea, Ophiuroidea and Echinoidea. The depth of dives and the concentration of dissolved oxygen in water were tested to explore the contribution of environmental conditions to the distribution of Echinodermata. No statistically significant relations were observed. A strong correlation between the Echinodermata richness and Cnidaria richness was obtained, with the highest values of both abundance and taxonomic richness of echinoderms in sites of occurrence of black corals, scleractinians and octocorals. The results suggest that biotic factors may play a major role in influencing the distribution of echinoderms in the BCS, especially crinoids, ophiuroids and echinoids, potentially benefiting from the presence of some Cnidaria’s order, in terms of refuge availability, as well as food supply and suitable substrate provided.