China-led team reveals secrets from one of the deepest places on Earth

Researchers from China, New Zealand make epic voyage to Kermadec Trench aboard Chinese submersible
Joint expedition aims to learn more about the geology and creatures of one of the most mysterious places on Earth

Science

Ling Xinin Beijing

Published: 6:00am, 13 Dec 2022

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In the Pacific Ocean, just north of New Zealand, lies one of the deepest places on Earth. At its deepest point, the Kermadec Trench stretches more than 10km (6.2 miles) into the abyss.

Few people have been down there – until recently.

Last month, an international team led by China conducted a systematic, crewed exploration of the trench for the first time. Now they are revealing what they saw.

“Chinese and New Zealand scientists are both excited to have this opportunity to appreciate the complexity and diversity of the geological and ecological systems of the Kermadec Trench,” said mission leader Peng Xiaotong, from the Institute of Deep Sea Science and Engineering (IDSSE) in Sanya, Hainan province.

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Peng was one of more than a dozen scientists from universities and research institutes in China, as well as two marine biologists from New Zealand’s National Institute of Water and Atmospheric Research (NIWA), who explored parts of the Kermadec Trench, collecting sediment, rocks, and biological and water samples for laboratory analyses.

The marine vehicle that took the researchers deep down into the trench was the Fendouzhe, or Striver, a deep-sea, three-person submersible that made it to the bottom of the Mariana Trench – the deepest oceanic trench on Earth – in 2020.

Peng, who studies deep-sea geology and geochemistry, collected rock samples during his dive and hopes their findings can help scientists better understand the movement of tectonic plates at the bottom of the ocean.

“We were all thrilled. It seemed like a pretty cool opportunity because it’s not easy to go down there and get samples,” said Daniel Leduc, one of the two NIWA marine scientists who crewed the Fendouzhe.

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The collaboration began in September 2021, he said, when Peng wrote to NIWA to ask about the possibility of doing a joint voyage to the trench.

It was Leduc’s first submersible ride. There were two pilots and one scientist on each dive, so as a scientist he did not need to know a lot about operating the vehicle. He said his main task was to come up with a science plan and decide when and where to obtain samples.

“Fendouzhe is probably the world’s best submersible to do trench sampling with, because it can go very deep, stay down there for a long time, and has all kinds of capabilities to get samples,” he said.

It took Leduc and the two Chinese pilots about three hours to descend to 9,110m (29,900 feet) below sea level at the north end of the trench. There were a few surprises along the way. The team saw strange and rarely seen sea creatures, including a red angler fish that swam upside-down.

The second ever observation of an upside-down angler fish, during a recent Fendouzhe expedition. Photo: IDSSE

As they went deeper, they saw more small animals along the sea floor, such as sea cucumbers, sea anemones, swimming bristle worms, and jellyfish.

There were also many delicate and translucent organisms too difficult to see with the naked eye. The researchers collected mud samples so the creatures could be examined later under an electron microscope.

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Being small was a big advantage for sea creatures that live in deep trenches, Leduc said, since there was not much food, and small bodies were better able to survive earthquakes and mudslides.

The team spent six hours surveying the bottom of the trench, gathering animal samples and sediment cores by using suction devices mounted on the robotic arms of the submersible. Leduc said that the ocean bottom was a very peaceful place to be.

“Some people think the deep sea is a weird, strange, or even scary place. Actually, we are the scary ones with our big submersible and the lights, motors, and robotic arms – sampling animals which have been there by themselves for thousands if not millions of years.”

Being small is a big advantage in very deep places, scientists say. Photo: IDSSE

After a short break and resupply, the Fendouzhe is now back at the Kermadec Trench until Christmas for the second leg of its expedition. Leduc said he would like to go back down again if there was a chance.

The next step for the collaboration is scientific analysis of the samples brought back. Leduc said NIWA would keep most of the specimens since they came from New Zealand waters. The IDSSE would take some rock samples back to China.

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“IDSSE was really nice to let us have quite a few samples; we never had this many samples from the trench before. The important thing is, all the samples will be analysed and the data shared between Chinese and New Zealand scientists. The collaboration has worked out really well for both of us.”