Sea fans and their associated fauna in the marine animal forests of Burdwood Bank at 54°S, SW Atlantic Ocean

A detailed analysis of the richness and abundance of invertebrates associated with three common sea fan species at Burdwood Bank is provided. Samples were acquired during a research cruise on board the RV Puerto Deseado (Argentina) in 2017. Thouarella sp., Dasystenella acanthina, and Bayergorgia vermidoma were frequently encountered octocoral species and found to provide habitat to at least 65 associated taxa. The majority of the recorded associate fauna consisted of filter or suspension feeders. Polychaetes and ophiuroids were the most frequently observed associated organisms, followed by bryozoans, bivalves, and brachiopods. We also report the presence of acariids on B. vermidoma and foraminifers on both Thouarella sp. and B. vermidoma. Dasystenella acanthina and Thouarella sp. have a complex three-dimensional structure. This increases the available substrate area for other organisms, thereby increasing the seafloor heterogeneity, which is demonstrated by the high richness and abundance registered here. In this sense, they act as habitat and niche multipliers, which led them to contribute structurally and functionally to the studied marine animal forests.