Science News

The Deepest Deep Sea Vents

Sun, 15th Jan 2012

Helen Scales

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Helen - Scientists have discovered the deepest and possibly the hottest undersea volcanic vents ever found and they're encrusted in extraordinary deep sea life.  The Cayman trough gouge as a gigantic trench in the seafloor 5 km beneath the waves in the Caribbean Sea and it’s there that a team of researchers led by Douglas Connelly and Jon Copley from the National Oceanography Centre in South Hampton detected a vast bloom of scorching mineral laden water reaching a kilometre up into the water column.  Here’s Geochemist Douglas Connelly.

Douglas -   Cayman trough was identified quite awhile ago as one of the interesting missing pieces of the global ridge systems.  It’s isolated, sits on its own and it’s also one of the deepest places, and one with the slowest spreading.  It has been postulated that there wouldn’t be any bending activity there at all, basically activities dependent upon spreading rate, as one of the old models that was out there.  In the deep side, we’ve got extremely high pressure and perhaps the existence of supercritical fluids.

Helen -   These supercritical fluids behave very strangely under the laws of physics.  They're lighter than water but denser than vapour and the team think that these extremely deep vents which they call the Beebe vent field after the first scientist who explore the Deep Ocean could be one of the only places on the planet to study these fluids in a natural setting, including their effect on the way minerals are leeched out of rocks.  Connelly and his colleagues found unusually high concentrations of copper in the fluids rising up from the vent which indicates the presence of these supercritical fluids.  And along with the height of the vent plume, four times higher than that of other Deep Sea vents, suggests that water could be as hot as 450 degrees Celsius.  And despite the enormous pressure, life down there is thriving as the team discovered by sending down a robotic submarine to take a look.  Here’s Marine Biologist Jon Copley.

Jon - Well as Biologists, we wanted to go and explore the Cayman trough Deep Sea vents for nearly a decade because we thought it might be a key missing piece in a global jigsaw puzzle.  What was a surprise was actually yes, we’ve seen new species of shrimp down there, there may be new species of anemone at the deepest site, in their hundreds around the cracks that seep warm water from the seafloor.  But these are very similar to animals that we know but from a long way away – 2,500 miles away in the Atlantic and it suggests there's a lot more traffic.  Animals are getting around in the deep ocean perhaps a lot more than we thought before.

Helen -   Another world first came from this study and that was the unexpected discovery of a hot vent in a much shallower site on the upper slopes of an undersea mountain called Mt. Dent.  This sticks 3 km above the Cayman trough although its peak is still 2 km beneath the waves.  The Mt. Dent vent was also found to be swarming in life and since submerged mountains like this are quite common, it hints that deep sea vents could be a lot more widespread than previously thought and they could offer stepping stones for vent animals to disperse between vent fields.

 

 

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