Deep-sea survey of Australian marine parks reveals striking species

South of Tasmania, hundreds of undersea mountains mark the deep ocean floor. Now, a monthlong survey of these seamounts in and around Australia’s Huon and Tasman Fracture marine parks has revealed a spectacular range of deep-sea species, from feathery corals and tulip-shaped glass sponges to bioluminescent squids and ghost sharks. The survey team has also uncovered more than 100 previously unnamed species that are likely new to science.

The seamounts within the marine parks occur at depths of 700 to 1,500 meters (2,300 to 4,900 feet). These mountains are home to cold-water corals that are slow-growing, fragile and threatened by fishing, deep-sea mining and climate change-induced variations in sea temperature and acidity. But accessing these harsh, dark, high-pressure depths is extremely hard. So scientists and park managers went aboard the Investigator, a research ship that’s part of Australia’s Marine National Facility, and used a special camera system designed by staff at the Australian government’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) to see what lies thousands of feet beneath the ocean’s surface.

The deep-tow system, weighing about 350 kilograms (770 pounds), has four cameras secured within high-strength aluminium housings, and a fiber-optic cable that feeds real-time footage of the deep-sea floor back to the ship. During the monthlong exploration, the researchers surveyed 45 seamounts using the deep-tow cameras, voyage chief scientist Alan Williams of CSIRO said in a statement. They covered 200 kilometers (124 miles) and collected 60,000 stereo images and some 300 hours of video. The footage captured hundreds of corals, including the main reef-building stony coral (Solenosmilia variabilis) and many other soft corals.

“While it will take months to fully analyse the coral distributions, we have already seen healthy deep-sea coral communities on many smaller seafloor hills and raised ridges away from the seamounts, to depths of 1450 meters [4,760 feet],” Williams said in the statement. “This means that there is more of this important coral reef in the Huon and Tasman Fracture marine parks than we previously realised.”

The team saw bioluminescent squids, ghost sharks, deep-water sharks, rays, orange roughy, and oreos near the seamounts. And close to the surface of the sea, they recorded data on 42 seabird species and eight whale and dolphin species. The researchers also used a net to collect some animals from the seamounts for identification. Many species, as one would expect from remote areas, were potentially new to science.

“For several of the museum taxonomists onboard, this was their first contact with coral and mollusc species they had known, and even named, only from preserved specimens,” Williams and Nic Bax, director of CSIRO’s NERP Marine Biodiversity Hub, write in the Conversation.

In one of the seamounts, the team saw what they say is the “world’s only known aggregation of deep-water eels.”

“We have sampled these eels twice before and were keen to learn more about this rare phenomenon,” Williams and Bax write. “Using an electric big-game fishing rig we landed two egg-laden female eels from a depth of 1,100 metres [3,610 feet]: a possible first for the record books.”

The areas now under the protection of the Tasman Fracture commonwealth marine reserve (created in 2007) and Huon commonwealth marine reserve (established in 1999), were once heavily fished by trawlers. Researchers say the present surveys can shed light on both what grows in the deep-sea environments, and if corals that were damaged by bottom-trawling are recovering after 20 years of protection.

“While we saw no evidence that the coral communities are recovering, there were signs that some individual species of corals, featherstars and urchins have re-established a foothold,” Williams said.