Diving to understand evolution.
Research site: Cayman Trough, 5 km below the Caribbean
What?► The main aim, says Jon Copley, a marine ecologist at the University of Southampton in the UK, is to find out how different species evolve at the different hydrothermal vent outcrops strewn around the oceans. Also known as “black smokers”, these superhot deep-sea springs form where the earth’s crust is being pulled apart by the inexorable forces of plate tectonics.
If an ocean quest to identify species variation might sound slightly familiar, it should. “It’s similar to the way the 19th-century naturalists Alfred Russel Wallace and Charles Darwin travelled around islands and discovered how different species related to those on other islands, or the mainland, and figured out species dispersal and evolution. Similarly, the deep-sea vents can be thought of as little islands of life on the ocean floor. That’s why we do this,” says Copley.
The mineral-rich superheated seawater gushing out of a deep-sea vent is at 400 degrees Celsius. That means heat-loving creatures such as the Hairy Chested Hoff Crab can evolve around the vents. This denizen of warm Antarctic vent waters nurtures a garden of extremophile microbes on its hairy chest. It then uses comb-like mouth parts to harvest and eat them. Such critters are the quarry of Copley and his colleagues.
How?► In a manned submersible. In June 2013 Copley joined Japanese colleagues in one of the few craft that can carry people to depths of 5,000 metres, the Shinkai 6500, to investigate the hydrothermal vents in the Cayman Trough, 5 km below the Caribbean, between Jamaica and Cuba. “Although it looks like a 7-metre-long sub the bit that carries the people is actually a pressure-resisting titanium ball that’s 2 metres across on the inside. The titanium is 71.5 mm thick and if it were not perfectly spherical to within 1 millimetre it would not hold the pressure. It’s an incredibly precise piece of engineering,” Copley explains.
The Shinkai 6500 freefalls to just above the ocean floor – and then uses its own thrusters to explore the area. Bioluminescence in the creatures of the deep ensures that even at the seabed, 5 km down, there are some flashes of light in the gloom. What is most striking is how alien the landscape around the vents can look, Copley says. “That’s because the terrain has been shaped by very different forces to the features we are used to on land, like hills and valleys. That vast, dark landscape looks so different to anything we are used to. My nose was up against the porthole the whole time,” he says.
Special report by Paul Marks
Karin Sigloch, Geophysicist (2/5)