Precious corals, like this species of Hemicorallium, were common at depths explored on Carondelet Reef. Precious corals have been exploited for their commercial value throughout history. Most coral colonies also were home to sometimes more than one species of brittle stars (ophiuroids). Some brittle stars are thought to have a mutualistic symbiosis with deep-sea corals. Image courtesy of the NOAA Office of Ocean Exploration and Research, Discovering the Deep: Exploring Remote Pacific MPAs.