“…In the North Atlantic, sponge grounds occur on gravel and coarse sand bottoms from 150 to 1700 m in depth, reaching densities of 5-25 sponges per m 2 , also increasing the number of associated fauna (Beazley, Kenchington, Murillo, & Sacau, 2013;Knudby, Kenchington, & Murillo, 2013). Hydroids, at their relative dimensional scale, also change the features of the geological habitat, becoming habitat formers by providing settling space, shelter, or food to several associated species, thereby enhancing local biodiversity (Di Camillo et al, 2017). Moreover, hydroid forests release a large number of planulae, medusoids, or medusae into the surrounding environment, contributing to benthic-pelagic coupling and affecting biogeochemical cycles (Gili et al, 1998;Rossi et al, 2012).…”