There is just such a biodiversity hotspot right here in the South China Sea - at a depth of 3,000 metres. Scientists aboard the mainland's submersible Jiaolong explored the underwater terrain during their first scientific mission to the bottom last month.
"As we were descending at 35 metres per minute, the ocean - illuminated by the vehicle's lights - was filled with fingernail-sized creatures floating like snowflakes," said Qiu Jianwen, the first Hong Kong scientist to embark on a deep-sea dive. He spoke at a press conference last month.
"I was astonished to see that the ocean floor was covered with blue mussels and porcelain crabs."
The 40-day expedition was a milestone for the mainland in a technological race in undersea exploration once dominated by the US. Jiaolong, a manned research vehicle named after a mythical sea dragon, has the third greatest diving range in the world. The only expeditions that have gone deeper were the now-retired Trieste bathyscaphe (a type of submersible) in 1960 and the Deepsea Challenger operated by Titanic filmmaker and explorer James Cameron in 2012. Both dove to Challenger Deep in the Pacific Ocean, which at 11,033m, is the deepest point on Earth.
Qiu was one of the six scientists who took turns diving down with two aquanauts, one of whom was in charge of navigation while the other communicated with the control centre. A professor at Baptist University, Qiu says geologists have been studying the shallow regions of the South China Sea for the past 10 years. But what lies 1,800m beneath the waves remained unknown until Jiaolong came along.
The ecosystem in cold seeps, where hydrocarbon-rich fluid seeps through the ocean floor, might not be as vibrant as that in hydrothermal vents, deep-sea sites of volcanic activity. But life has found a way there, too. Experts brought to the surface plenty of samples including glass sponges, deep-water shrimps, carbonate rocks and soft corals. Some of the deep-sea creatures could be new to science, Qui says. It will take months to classify the unidentified species.
"We are also interested in mutualism among the crabs, mussels and bacteria, and how they are genetically related to those found in seas [around Japan and India]," he says.
The mainland wants to make the cold vent a long-term research site so Jiaolong might go down to the depths once again next year.