Scientists discovered 149 new deep-sea species near a collapsed volcano: 'It was a massive hole in the data'

Scientists found 149 new deep-sea species near a collapsed volcano. This discovery happened during an expedition to the Indian Ocean, an area that has not been studied much at great depths.

The Indian Ocean makes up about one-fifth of the world's ocean area. About 90% of it is deeper than 3,280 feet. However, its deep-sea life is less known compared to the Pacific and Atlantic oceans. This is especially true for the underwater mountains in its central eastern part.

Discovering New Life in the Deep Sea

An expedition explored dozens of these volcanic underwater mountains near Christmas and Cocos islands. These islands are southwest of Jakarta, Indonesia, between Australia and Sri Lanka. The team found amazing marine life on the Indian Ocean seafloor.

The study was published in Deep-Sea Research Part II: Topical Studies in Oceanography in June. It describes 149 new species. These include a sea cucumber from the Oneirophanta group, a new fish from the greeneye family (Chlorophthalmus), and a parasitic barnacle from the Rhizolepas group.

Researchers explored depths from 308 to 17,818 feet. They mapped a dark seafloor with volcanic seamounts that are 40 to 120 million years old and up to 43 miles across. These areas had never been studied before.

Tim O’Hara, a marine scientist at Museums Victoria in Melbourne and the study's lead author, told Mongabay that people had explored shallow waters around the islands, but no one had looked at deep-sea life. He called it "a massive hole in the data."

Mapping Remote Underwater Mountains

Reaching these sites took a lot of time. The islands are so remote that it took almost seven days to get to Christmas Island from Darwin, Australia. Cocos Island is nearly 600 miles southwest of Christmas Island.

These islands are Australian territories. In 2020, the Australian government approved the expedition to learn more about their marine life. This was two years before the Indian Ocean Territories Marine Parks were established.

The international team of 33 researchers started by mapping the seafloor and 22 seamounts in 2020. One seamount was named Green Eye, after the Chlorophthalmus fish family found there. These huge underwater mountains rise almost 3,300 feet above the seafloor. They disrupt deep-sea currents, creating a rich environment for filter feeders and other animals.

To do this deep-sea research, Australia’s Commonwealth Scientific and Industrial Research Organisation launched a special research vessel, the RV Investigator, in 2014. Before this, Australia mainly studied coastal waters, reaching depths of only 9,842 feet. The Investigator allowed the team to explore depths up to 3.10 miles.

Life in the Depths

O’Hara told Mongabay that finding new seamounts was one of the most interesting parts of the expedition. One seamount had a caldera, which is a bowl-shaped crater left after a volcanic eruption. Researchers named this caldera the Eye of Sauron, after J.R.R. Tolkien’s The Lord of the Rings, because its center looks like an eye. They found it 10,180 feet deep and 175 miles from Christmas Island.

The researchers did not take samples from the caldera. However, they collected samples from the seamounts. They found that the types of species changed gradually as they went deeper.

Living at these depths is hard. Jim Barry, a senior scientist at the Monterey Bay Aquarium Research Institute, who was not part of the study, told Mongabay that it is "dark, it’s cold." Animals there rely on food that sinks from the surface.

Seamounts can help with this, Barry added. He explained that currents speed up when they hit a seamount. Filter feeders can find more food by positioning themselves where currents are faster.

More Than 22 Million Years of Evolution

To collect these species, researchers mainly used a beam trawl. This is a 13-foot-wide beam with a long net. The Investigator pulled it with a 5-mile-long wire, dragging it along the seafloor at a slow pace. This net mostly caught jellyfish and worms. A smaller, conical net, 3 feet long and 1.5 feet wide, was attached above the main net. It caught tiny crabs, lobsters, and other crustaceans that the larger net missed.

Researchers also recorded video with a deep-towed camera. They collected data on temperature, saltiness, and dissolved oxygen in the water. They also gathered environmental DNA, which is genetic material shed by organisms. This helped reveal the species in the area. In total, researchers found 1,059 species, and 149 of them are new to science.

Barry said he is "amazed that every time we go somewhere and look carefully, we discover so many new species in the deep sea." He was surprised by all the fish. The study noted that 23 fish species had not been identified before in Australian waters.

O’Hara said the most memorable find was 1,000 shark teeth. These were pulled up during the last trawl along the Cocos Abyssal Plain. They covered more than 22 million years of evolution. The teeth included those from great white sharks (Carcharodon carcharias), mako (Isurus oxyrinchus), tiger (Galeocerdo cuvier), and even ancient Megalodon (Otodus megalodon) fossils. At this site, named "The Shark Graveyard," researchers also found polymetallic nodules (manganese nodules). These mineral-rich rocks were found within the shark teeth. These nodules are valuable for deep-sea mining and are used in electric vehicle batteries, wind turbines, and renewable energy.

Future Research and Threats

Since this expedition, O’Hara told Mongabay that other scientists are exploring seamounts in the Coral Sea Marine Park off Australia’s northeast coast. A German research vessel, Sonne, is also studying the seafloor off New Zealand's east coast.

Oceans face threats from climate change, including rising surface temperatures, marine heatwaves, overfishing, and deep-sea mining. All these impact deep-sea ecosystems. Because of this, deep-sea research remains important, according to O’Hara and Barry.

O’Hara called the deep sea "the last frontier." He believes it is crucial to understand how the deep sea works. He noted that few people experience the deep sea directly, only those who go down in submarines. He hopes to explore further into the Indian Ocean.

Deep Dive & References

Deep-Sea Research Part II: Topical Studies in Oceanography - Elsevier, June 2024