Sponges of the order Poecilosclerida (Porifera) from the Burdwood Bank and the Scotia Arc, SW Atlantic Ocean.

The Burdwood Bank (BB) hosts a Marine Protected Area in the SW Atlantic Ocean, situated within the Scotia Arc. Considering that the knowledge regarding sponges (Phylum Porifera) is still limited, in this study we attempt to estimate the richness of sponges of the order Poecilosclerida inhabiting the BB. We also compare these results with the richness recorded in adjacent regions of the Scotia Arc and neighboring areas (Tierra del Fuego, Malvinas, South Georgias, South Orkney and South Sandwich Is.). The studied material came from the Burdwood Bank, and it was collected during two research cruises in 2016 and 2017 onboard the OV "Puerto Deseado". We also compiled previous records from the BB and other regions using the published literature. A checklist of 150 species of poecilosclerid sponges, 39 from the BB (with 22 of them representing new records and probably a couple of them new species for science), 49 from Malvinas Islands, 30 from Tierra del Fuego, 55 from South Georgias, 25 from the South Orkney, and 3 from the South Sandwich Islands. In total, 87% of the species were only recorded in one region. Only Mycale (Aegogropila) magellanica, Iophon proximum, Isodictya setifera, Isodictya verrucosa, Myxilla (Myxilla) mollis, Tedania (Tedaniopsis) massa, and Tedania (Tedaniopsis) mucosa (3.60%) were widely distributed among the studied regions. These preliminary results confirmed that BB sponge richness was previously underestimated. Until the present study, only 18 taxa were known from the BB, and we have doubled the known richness. Our results also suggest that the recorded richness may also constitute an artifact of the sampling effort exerted in each region. These results will be complemented with future studies considering the other orders and classes of the phylum Porifera.