Remarkable images of creatures from one of the most inhospitable spots in the ocean have been captured by scientists.
Researchers have been surveying volcanic underwater vents – sometimes called black smokers – in the South West Indian Ridge in the Indian Ocean.
The UK team found an array of deep-sea creatures living in the super-heated waters, including yeti crabs, scaly-foot snails and sea cucumbers.
They believe some of the deep-sea creatures may be new to science.
Hydrothermal vents were first discovered in 1977. These fissures in the ocean floor spew out fiercely hot, mineral-rich water, yet somehow, diverse ecosystems are able to thrive in these hostile conditions.
The team, from the University of Southampton, was particularly interested in the vents on the South West Indian Ridge because this range is linked to the Mid Atlantic Ridge and the Central Indian Ridge, where vent life has been well documented.
This area is also unusual because it is an “ultra-slow spreading” ridge, which means it is less volcanically active than other ridges, with fewer vents that are further apart.
Dr Jon Copley, chief scientist of the Indian Ocean vents project, said: “This place is a real crossroads in terms of the vent species around the world.”
Using a remote-operated, underwater robot called Kiel 6000, from the Leibniz Institute of Marine Sciences (IFM Geomar), in Germany, the team was able to train their cameras on the vents.
In the hottest habitat around the black smokers, they found snails and shrimp, as well as mussels, sea cucumbers, crabs and many deep-sea creatures. They then compared these with the different deep-sea creatures found at vents on the neighbouring ridges.
Dr Copley said: “I was expecting there to be some similarities to what we know from the Atlantic, and some similarities to what we know from the Indian Ocean vents, and that was true, but we also found types of deep-sea creatures here which are not known from either of those neighbouring areas, and that was a big surprise.
“One was a type of yeti crab. There are two currently described species of yeti crab known from the Pacific, and it isn’t like those, but it is the same type of deep-sea creatures, with long, hairy arms.
“Also some sea cucumbers – not known from the Atlantic or Central Indian vents, but known from the Pacific.”
He added: “We’ve got links to lots of different parts of the world here, which is very exciting.”
The team was also surprised at the diversity of life they found during this expedition, which was funded by the Natural Environment Research Council (Nerc).
Dr Copley said: “In a lot of other vent fields I’ve been to, in this hot zone where you get the deep-sea creatures there is often just one type of animal living there: in the deep Mid Atlantic Ridge, it’s the shrimp. But here, we have seen three to four all in the same zone.”
The findings should help researchers to learn more about how life moves from vent to vent: vents are short lived, and without the ability to hop from one system to the next, life there would go extinct.
“That is why vents are a great place to understand how deep-sea creatures disperse and evolve in the oceans, because they are like little islands,” Dr Copley added.
Despite these findings, the researchers are worried about the future of this underwater terrain.
China has been granted an exploratory licence by the International Seabed Authority to explore the potential of mining the vents in this area for their rich minerals.
Dr Copley said: “This vent field is the size of a few football pitches, and it seems possible that it is the only known range of some of these species.
“It would be very premature to start disrupting it before we really know the true extent of what lives in it.” (Rebecca Morelle/BBC News)