Chinese and New Zealand Scientists dive to one of the ocean's deepest regions

A New Zealand scientist and a submersible pilot from China have become the first women to dive to Scholl Deep in the Kermadec Trench, 10 km below sea level.

A New Zealand scientist and a submersible pilot from China have become the first women to dive to Scholl Deep in the Kermadec Trench, 10 km below sea level. 

HOV Fendouzhe is recovered by the RV Tansuoyihao. [Photo: Kareen Schnabel, NIWA]

The dive was undertaken by NIWA marine biologist Dr. Kareen Schnabel and submersible pilots DENG Yuqing and YUAN Xin from the Institute of Deep Sea Science and Engineering (IDSSE), Chinese Academy of Sciences (CAS). 

It was only the second crewed visit ever to explore the Scholl Deep and was done as part of a two-month scientific voyage on board the IDSSE’s research vessel Tansuoyihao.

HOV Fendouzhe is recovered by the RV Tansuoyihao. [Photo: Kareen Schnabel, NIWA]

Scholl Deep is the deepest known point of the Kermadec Trench, which lies to the north of New Zealand. The trench is over 1000 km long, is almost perfectly straight, and its deepest point is at a depth greater than the height of Mt Everest. 

Using the Human Occupied Vehicle (HOV) Fendouzhe, scientists collected deep-sea water samples, sediments, rocks, biological samples, and environmental data. 

Ready for deployment to the Scholl Deep, from left to right, HOV Fendouzhe pilots Xin Yuan and Yuqing Deng with Kareen Schnabel (NIWA). [Photo: Hanyu Zhang, IDSSE]

Dr. Schnabel and the submersible pilots spent six hours at the bottom of the sea exploring the Scholl Deep and the steep sides of the trench. 

“This extraordinary submersible technology has given us the privilege of studying parts of the ocean in ways that we aren’t usually able to, giving New Zealand researchers a rare chance to explore this fascinating and fragile environment."

Rare deep-sea starfish Hymenaster sp., this might be the species first discovered during the Galathea expedition in the 1950s, but had not been collected again until this voyage. [Photo: HOV Fendouzhe, IDSSE]

“Textbooks and images don’t compare to experiencing the light disappearing as you leave the surface of the ocean or seeing the deep sea floor with your own eyes. The fine sediments were covered in tracks, and we saw lots of small animals on the sea floor and in the water. It was jarring that there was still rubbish such as fishing floats and nets, even though we were more than 10,000 m below sea level,” says Dr. Schnabel. 

The second ever observation of an upside-down anglerfish, Gigantactis sp. At 5736 m depth. In contrast to other anglerfish, it swims upside-down and dangles its lure downward. [Photo: HOV Fendouzhe, IDSSE]

The first leg of the voyage was successfully completed on 24 November 2022. The HOV Fendouzhe undertook 16 dives between 5,747 m and 10,000 m depth, in addition to the deployment of other independent samplers such as a lander, CTD (water sampler), and a gravity corer. 

“It is really exciting for both Chinese and New Zealand scientists to have the opportunity to comprehensively appreciate the complexity and diversity of both the geo- and ecosystem of the Kermadec Trench,” says Dr. PENG Xiaotong, the leader of this voyage from IDSSE.

“Taking rock samples, for example, offers us a unique chance to understand the nature of the subducting and overriding plate, as well as the mechanism of the subduction initiation in Kermadec Trench,” says Dr. PENG. 

“A number of the animals have been tentatively identified and are either presumed new to science or have not been seen or collected since the first sampling voyage by the Danish research vessel Galathea in the 1950s.” says Dr. Schnabel. 

“It was fascinating to actually observe the tiny sea cucumbers at the bottom of the Kermadec Trench, which are three times smaller in size than those we have observed previously in the Mariana Trench. These sorts of differences between trenches show that mysteries remain as to how animals are adapted to live in extremely deep environments,” says Dr. ZHANG Haibin, a marine biologist from IDSSE. 

The vessel has returned to Auckland for re-supply and staff change-over, and the second leg will be completed before the end of December with another 16 dives planned. The voyage includes scientists from NIWA, IDSSE, Shanghai Jiaotong University, Tongji University, Zhejiang University, Hainan Tropical Ocean University and BGI-Qingdao. 

Diverse invertebrate community on a solitary rock at 6124 m deep. Sea stars, anemones, small corals, sponges and a sea squirt make this rock their home. [Photo: HOV Fendouzhe, IDSSE]

NIWA scientist Dr Daniel Leduc, who dove in the submersible in the north of the trench at 9110 m, says the samples obtained represent a step-change in our understanding of the biodiversity of New Zealand’s deepest marine environment.

“We saw highly diverse seafloor communities even at great depths and discovered strange and rarely seen organisms such as the upside-down angler fish. As we go deeper into the trench, seafloor ecosystems become dominated by small organisms, which will need to be examined using light and electron microscopy back on land. I expect we will find many new species”. 

IDSSE and NIWA will continue their collaboration following the voyage to analyse the large number of samples obtained to give a better understanding of New Zealand’s deepest environment, and the impacts that humans may have on it. 

Large cusk eel, Bassozetus sp., about 1 m long observed at around 6500 m depth. Cusk eels are commonly found in abyssal and hadal environments worldwide. [Photo: HOV Fendouzhe, IDSSE]