can help the corals to hide. These factors can lead to sediment tearing the soft tissue, resulting in death. In response, corals live near crevices, which allows much of their body to be protected. Ecology Habitat Black corals occur throughout all the oceans from the surface down to the deep-sea, though nearly 75% of species are only found at depths below . The sole oceanic area in which black corals have not been found are brackish waters, though they can inhabit areas with decreased salinity. Black corals are found on reefs, and may contribute to overall reef building, but are also often found as solitary colonies on isolated outcroppings. Most individuals require a hard surface for attachment. They will frequently grow where undersea currents flow, which allows them to feed on the meiofauna that is swept by. Since undersea currents benefit the corals, they will often grow on or by geographic structures that cause currents, such as continental slopes, cliffs, caves, or undersea plateaus. Species distributions of black corals are poorly understood, and while many deep sea black corals have large distributions, more recent work has indicated that shallow black coral species—such as Antipathes grandis—can be found spanning from the Indian to the Pacific Ocean. Diet Black corals are carnivorous, with the coral's polyps allowing it to feed mostly on meiofauna such as zooplankton. The polyps of cnidarians have an oral disk in their center which serves as the mouth for the coral. The disk is surrounded by the tentacles, which stings and digests food. The reason many corals are fan-shaped is to catch meiofauna. Many corals only have polyps on the downstream side of the coral, allowing them to catch nearly the same number of animals without wasting energy keeping unnecessary polyps alive. Predators Vertebrate predation is not a major threat to black corals. There are rare reports of parrotfish and butterflyfish gnawing and eating at the polyps of black corals and even if a polyp is gnawed off, it will not affect the coral. The skeleton of a black coral is hard and inert, due to its composition of protein and chitin, making it nearly inedible. Though black coral skeletons have been found in the stomachs of green sea turtles and sharks, these incidents are rare; it has thus been suggested that black corals are not a major part of any vertebrate diets. However, invertebrates such as muricids