Caribbean (global-adventures.us): The world's most extreme known deep-sea volcanic vents are 3.11 miles (5 kilometers) under water in a rift in the Caribbean seafloor. The hot springs, which lie 2,625 feet (800 meters) deeper than any seen before, may be hotter than 842 degrees (450 Centigrade) and are shooting a jet of mineral-laden water more than 0.62 miles (one kilometer) into the ocean above. Despite these extreme conditions, the vents are teeming with thousands of a new species of shrimp that has a light-sensing organ on its back. Having found yet more ‘black smoker’ vents on an undersea mountain nearby, the researchers suggest that deep-sea vents may be more widespread around the world than anyone thought.
During an expedition in April 2010 aboard the Royal Research Ship James Cook, Dr. Doug Connelly, a marine geochemist at the National Oceanography Centre in Southampton, and Dr. Jon Copley, a marine biologist at the University of Southampton, used the National Oceanography Centre’s robot submarine called Autosub6000 and a 
deep-diving vehicle, HyBIS, to locate and study the vents at a depth of over 3 miles (five kilometers) in the Cayman Trough, an undersea trench south of the Cayman Islands.
The vents, which the team named the Beebe Vent Field after the first scientist to venture into the deep ocean, are gushing hot fluids that are unusually rich in copper, and shooting a jet of mineral-laden water four times higher into the ocean above than other deep-sea vents. Although the scientists were not able to measure the temperature of the vents directly, these two features indicate that the world's deepest known vents may be hotter than 842 degrees (450 Centigrade), according to the researchers. “These vents may be one of the few places on the planet where we can study reactions between rocks and 'supercritical' fluids at extreme temperatures and pressures,” says Connelly. The team found a new species of pale shrimp congregating in hordes (up to 2,000 shrimp per square meter) around the 20 feet (six-meter) tall mineral spires of the vents. Lacking normal eyes, the shrimp instead have a light-sensing organ on their backs, which may help them to navigate in the faint glow of deep-sea vents. The researchers have named the shrimp Rimicaris hybisae, after the deep-sea vehicle that they used to collect them.
The Cayman shrimp is related to a species called Rimicaris exoculata, found at other deep-sea vents 2,485 miles (4,000 kilometers) away on the Mid-Atlantic Ridge. Elsewhere at the Beebe Vent Field, the team saw hundreds of white-tentacled anemones lining cracks where warm water seeps from the sea bed. “Studying the creatures at these vents, and comparing them with species at other vents around the world, will help us to understand how animals disperse and evolve in the deep ocean,” says Copley.
The researchers also found black smoker vents on the upper slopes of an undersea mountain called Mount Dent. Mount Dent rises nearly three kilometers above the seafloor of the Cayman Trough, but its peak is still more than three kilometers beneath the waves. The mountain formed when a vast slab of rock was twisted up out of the ocean floor by the forces that pull the plates of the Earth's crust apart.
“Finding black smoker vents on Mount Dent was a complete surprise,” says Connelly. “Hot and acidic vents have never been seen in an area like this before, and usually we don’t even look for vents in places like this.” Because undersea mountains like Mount Dent may be quite common in the oceans, the discovery suggests that deep-sea vents might be more widespread around the world than previously thought.
The vents on Mount Dent, which the team has named the Von Damm Vent Field to commemorate the life of geochemist Karen Von Damm, are also thronged with the new species of shrimp, along with snake-like fish, and previously unseen species of snail and a flea-like crustacean called an amphipod. “One of the big mysteries of deep-sea vents is how animals are able to disperse from vent field to vent field, crossing the apparently large distances between them,” says Copley. “But maybe there are more ‘stepping stones’ like these out there than we realized.”
The UK expedition that revealed the vents followed a US expedition in November 2009, which detected the plumes of water from deep-sea vents in the Cayman Trough. A second US expedition is currently using a deep-diving remotely operated vehicle to investigate the vents further and the UK team also plans to return to the Cayman Trough in 2013 with Isis, the National Oceanography Centre’s deep-diving remotely operated vehicle, which can work at depths of up to 3.73 miles (six kilometers). The findings were first reported in the scientific journal Nature Communications.
After discovering more ‘black smoker’ vents in the Cayman Trough, scientists believe that deep-sea vents may be more widespread around the world than anyone thought. The picture shows a black smoker known as The Brothers. Photo: NOAA/Public Domain
