Cnidarians are a diverse group of soft-bodied and sometimes calcified animals united by a common body plan of only two cell layers separated by a jelly-like mesoglea which provides structural support in the water. Many cnidarians can reproduce asexually and sexually, and can also display an “alternation of generations”, a life cycle characterized by an attached polyp phase and a free-swimming larva or medusa phase: thus, cnidarians encompass both sessile and mobile species. Most are suspension feeders, but some are also predators. Lophelia itself appears to have a flexible feeding habit, ingesting a variety of zooplankton prey and particulates.
Cold-water coral reef frameworks are comprised of scleractinian corals, but these habitats host diverse assemblages of other cnidarians, which, like sponges associated with Lophelia habitats, often display high degrees of genetic diversity and new species have been discovered. Hydroids, anemones, zonathids and octocorals encrust both living and dead coral fragments, and species often co-occur, indicating local environmental conditions. The upright growth habit and often delicate nature of many cnidarians including Lophelia make these animals highly vulnerable to activities such as bottom fishing.