With the use of a remote-controlled submarine, researchers have found five new species of black corals in the Great Barrier Reef and Coral Sea, situated off the coast of Australia.
Some species of black coral can live for almost 4,000 years, and they can be found growing in seas as shallow as a few feet deep and as deep as over 25,000 feet. Some of these corals are straight as a sword, while others have many branches and resemble feathers, fans, or shrubs. Black corals are filter feeders, meaning they consume the plentiful zooplankton found in deep waters, as opposed to their colorful, shallow-water relatives, which rely on the light and photosynthesis for energy.
In 2019 and 2020, a researcher explored the Great Barrier Reef and the Coral Sea with a team of Australian scientists using a remotely operated vehicle (ROV) submarine from the Schmidt Ocean Institute. Their mission was to gather coral samples from depths of 130 feet to 6,000 feet (40 meters to 1,800 meters) in order to better understand the diversity of coral species found in these seas. Dredging and trawling were once common practices for extracting corals from the region’s depths, but they often resulted in the corals’ destruction.
To see and securely harvest deep sea corals in their natural habitats, these researchers were the first to send a robot to these specific deep-water ecosystems during their two missions. The researchers logged 31 dives and brought back 60 pieces of black coral. Using the rover’s robotic claws, they had carefully pry the corals from the sand on the floor or the wall of the reef, deposit them in a pressurized, temperature-controlled storage box, and then transport the box to the surface. After that, the researchers did things like sequence the corals’ DNA and look at their morphological characteristics.
Five new species were discovered among the many fascinating specimens, including one growing on the shell of a nautilus more than 2,500 feet (760 meters) below the ocean’s surface.
Black corals, like the colorful reefs they inspire at shallower waters, provide crucial habitats for fish and invertebrates by providing food and a place to hide from predators in an otherwise lifeless environment. For instance, in 2005, off the coast of California, researchers gathered a single black coral colony that was home to 2,554 different species of invertebrates.
The deep water may be home to many more species than was previously believed, according to new research. Only about 300 species of black corals have been described so far, so the team’s discovery of five new species in a relatively small area was both unexpected and thrilling. Illegal collection of black corals for the jewelry trade threatens many populations. Researchers need to know what species reside at these depths and the ranges of specific species in order to undertake wise conservation of these fascinating and hard-to-reach ecosystems.
Scientists continue to find new creatures in the deep water with each expedition they undertake. The best thing scientists can do to learn more about the species that reside there and their distribution is to simply explore more.
Since few deep-sea black coral specimens have been found and so many undescribed species are probably still out there, there is also a lot to learn about the evolutionary tree of corals. The more species that are discovered by scientists, the more we will learn about their evolutionary history, including how they have survived at least four great extinction catastrophes.
Next, the researchers continue their exploration of the ocean floor. Most of the black coral species known to science have not yet had their DNA collected. Scientists hope to better understand and conserve the Great Barrier Reef and other coral reef ecosystems in the Coral Sea by visiting other deep reefs on future expeditions.
JEREMY HOROWITZ et al. (2022). Five new species of black coral (Anthozoa; Antipatharia) from the Great Barrier Reef and Coral Sea, Australia, Zootaxa. DOI: 10.11646/zootaxa.5213.1.1