Using a remote-controlled submarine, researchers at Smithsonian Institution, Washington, discovered five new species of black corals living as deep as 2,500 feet (760 metres) below the surface in the Great Barrier Reef and Coral Sea off the coast of Australia.
Black corals can be found growing both in shallow waters and down to depths of over 26,000 feet (8,000 metres), and some individual corals can live for over 4,000 years.
Many of these corals are branched and look like feathers, fans or bushes, while others are straight like a whip. Unlike their colourful, shallow-water cousins that rely on the sun and photosynthesis for energy, black corals are filter feeders and eat tiny zooplankton that are abundant in deep waters.
In the past, corals from the deep parts of this region were collected using dredging and trawling methods that would often destroy the corals.
The researchers first sent a robot down to these particular deep-water ecosystems, allowing the team to actually see and safely collect deep sea corals in their natural habitats. Over the course of 31 dives, the researchers collected 60 black coral specimens.
They then removed the corals from the sandy floor or coral wall using the rover’s robotic claws, placed the corals in a pressurised, temperature-controlled storage box and then brought them up to the surface.
The researchers then examined the physical features of the corals and sequenced their DNA.
Among the many interesting specimens were five new species – including one that was found growing on the shell of a nautilus more than 2,500 feet (760 metres) below the ocean’s surface.
Similarly to shallow-water corals that build colourful reefs full of fish, black corals act as important habitats where fish and invertebrates feed and hide from predators in what is otherwise a mostly barren sea floor.
For example, a single black coral colony researchers collected in 2005 off the coast of California, United States, was home to 2,554 individual invertebrates.