"Our impacts are getting ahead of our understanding," said Taylor. The most obvious example she gives is trawler-fishing, dragging huge nets behind boats to catch fish.

At the moment it's fairly local, she says – most trawling is above 200 metres. "But the average depth of trawling is getting deeper, because we've overharvested," she said. "And that's worrying, because animals down there are pretty slow. They breed slowly and late in life." That means their populations replenish slowly and are easily damaged by overfishing and habitat destruction.

It's also devastating to coral beds, which "are to the deep sea what trees are to the rainforest", said Roterman – they provide structure, shelter, and food for the animals that live among them. Taylor compares trawler-fishing in coral beds to "smashing a rainforest to catch the birds". "Corals are dramatically understudied, given the huge role they play in constructing ecosystems," she said. "Some of the deep sea corals down there are 4,500 years old. Some of the oldest living things on this planet."

It's not just fishing, though. Habitats are also under threat from pollution, such as microplastics, and a growing interest in deep-sea mining. "There's a tech revolution happening right now," says Roterman. "We're on the cusp of large-scale mining in the deep sea." This isn't necessarily a bad thing, they say, but to protect the habitats, "we need fundamental information about how energy flows in the deep sea, how animals get their food, how populations of animals are connected". Then you can decide how big your marine reserves need to be, and what habitats you need to keep within them.

It's not all bad news. The good thing is that this research is getting cheaper and easier.