Porifera Associated with Deep-Water Stylasterids (Cnidaria, Hydrozoa): New Species and Records from the Ross Sea (Antarctica)

Stylasterid corals are known to be fundamental habitat-formers in both deep and shallow waters. Their tridimensional structure enhances habitat complexity by creating refuges for a variety of organisms and by acting as basibionts for many other invertebrates, including sponges. Porifera represent crucial components of marine benthic assemblages and, in Antarctica, they often dominate benthic communities. Here, we explore the sponge community associated with thanatocoenosis, mostly composed of dead stylasterid skeletons, collected along the Western and Northern edges of the Ross Sea continental shelf. Overall, 37 sponge species were identified from 278 fragments of the stylasterid Inferiolabiata labiata, of which 7 are first records for the Ross Sea, 1 is first record for Antarctic waters and 2 are proposed as new species. Despite the high biodiversity recorded in this and previous studies on Antarctic deep-sea communities, we are still far from capturing the true richness of Antarctic benthic assemblages. Long-term research programs designed to improve the knowledge of the deep-sea fauna inhabiting Antarctic waters are needed to support successful management and conservation plans, especially in this area, considered one of the main marine diversity hotspots worldwide.