It takes an hour from the surface of the Indian Ocean, descending 3,000 metres in a submersible research pod, to reach the bizarre creatures that cluster around hydrothermal vents on the seabed. “You’re in a titanium sphere that is about two metres in diameter,” says evolutionary biologist Julia Sigwart, describing her voyage to Kairei hydrothermal
It takes an hour from the surface of the Indian Ocean, descending 3,000 metres in a submersible research pod, to reach the bizarre creatures that cluster around hydrothermal vents on the seabed. “You’re in a titanium sphere that is about two metres in diameter,” says evolutionary biologist Julia Sigwart, describing her voyage to Kairei hydrothermal vent field, east of Madagascar.
The vessel is equipped with robotic arms, probes and cameras – like a manned, underwater version of the Mars rover. In lieu of seats, there’s a padded floor. “So you’re hunched up together with the two pilots who are driving it and manipulating it,” she says.
With not even a loo on board, it’s definitely on the bijou side for an eight-hour working day, but for Sigwart, director of the marine laboratory at Queen’s University, Belfast, the experience is worth it.
“As you go down the light fades out rapidly. When you turn off the lights of the submersible you can see all of the bioluminescence of everything that’s alive in the water all around you – big and small. It’s like a beautiful starscape.”
While much of the ocean floor looks like a ghost town to the naked eye, the concentrated patches of life around hydrothermal vents are as densely, if not as diversely, populated as coral reefs.
The vents are where mineral-rich hot water, between 300C and 400C (572-752F), bursts out from below the Earth’s crust, swirling into the cold seawater like black smoke. “These smoking chimneys loom up at you, out of the blackness. They’re just incredible,” says Sigwart.
One current evolutionary hypothesis is that the special conditions around deep-sea thermal vents sparked the beginnings of life on Earth.
But these rare and vital ecosystems are under serious threat from deep-sea mining for minerals such as zinc, used for car batteries and mobile phone circuit boards, say campaigners. You might expect that in open water, which does not belong to anyone, the seabed would be safe from commodification, but in 2019 Greenpeace reported that 30 floor-exploration licences had been granted worldwide by the International Seabed Authority (ISA), a UN body.
Mining companies in Germany, China, Korea, India and the UK are among the recipients. “They’re not supposed to be used for commercial-scale mining, but several of the licences have been renewed and they’re into a second 10-year term, says Sigwart, adding that the ISA is currently developing a regulatory framework for commercial mining in the high seas.
The race is now on for Sigwart and other biologists to identify and learn more about the vent-dwelling creatures and lobby for their protection. Many are only found in these unique and isolated places. The vivid mottled orange snail, Gigantopelta aegis, has only been located in one area estimating 8km squared.
Elin Thomas, Sigwart’s PhD student, has set to work assessing the vent species discovered so far against the criteria for the International Union for the Conservation of Nature’s red list. Because of its small, singular habitat and the threat of mining in the Indian Ocean, the Gigantopelta aegis is now classified as “critically endangered”.
Another colourful character on the vent scene is Alviniconcha strummeri, named after the Clash’s Joe Strummer on account of its spiky shell resembling punk rockers. Its red list status is “vulnerable”.
In total, 15 hydrothermal vent species – described fondly as “super weird” by Sigwart – have been added to the red rist. The mythical-looking sea pangolin, AKA the scaly-foot snail, was the first to be identified as at risk (status: “vulnerable”). Resplendent in armoured skirts that would be the envy of any Roman centurion, the layers of black flaps around its foot, along with its helmet-like black shell, are a result of the very mineral riches that are attracting the mining industry.
“The iron that precipitates out of the vent fluid,” says Sigwart, “is incorporated into the shell and the scales of the scaly foot. It hasn’t grown an iron shell, but the available environmental iron on the surface has integrated into it.”
The scaly-foot snail and Gigantopelta aegis are the most fascinating to Sigwart, because each has independently evolved a cunning way to bypass the whole kerfuffle of having to eat. All life around the vents depends on bacteria for energy. There are no plants, so the creatures have to either graze on slimy microbial mats, or eat each other. Rather than bother with any of that, however, these two evolutionary geniuses have an internal organ inside which microbes live, providing all their energy needs.
It’s not all snails and germs down there, however. There are giant ghostly white crabs scuttling about, stalked barnacles, tube worms, shrimps and mussels. Different vent systems around the world have their own assemblages of animals. The first vents, discovered in the late 1970s, were in the east Pacific and are known for their metre-long lipstick worms.
In Sigwart’s experience, people often assume these ecosystems are “out of harm’s way, nobody can reach them. It’s all fine. But it’s no longer fine, because now we’re on a path to developing commercial-scale deep-sea mining and vents are a target. We can no longer naively hope that the depths of the oceans are still pristine and untouched.”
“More and more,” says Sigwart, “it’s clear that they are already impacted by human activities. We find plastic in deep-sea sediments, the ocean circulation patterns are being altered by global climate change.”
Crucially, she says, the tide is turning when it comes to scientists becoming more vocal about the animals that would otherwise stay out of sight and out of mind. “Deep-sea biology is fascinating and exciting, and it inspires a sense of wonder in everybody,” says Sigwart.
“There are very few of us that have the privilege of actually working on these animals and habitats. We have a burden of responsibility to try to explain them to other people before the damage is done.”