Deep, deeper down the trough

A site in the Cayman Trough, near where scientists found the world’s deepest underwater volcanic vents last month, contains more vents and may lead to even more amazing discoveries, according to the leader of the British expedition that found the now famous “black smokers”.

In March, Doug Connelly led a team of British scientists to explore the depths of the Cayman Trough, filming for the first time the world’s deepest volcanic vent, 3.1 miles below the surface.

But the day before the 31-day expedition was due to finish, they came across another site – this one spewed clear hot liquid rather than the cloudy, black smoke they found at the first location.

“We found a new site just before we left the area. This is in a different geological setting, with far more biology, and was not producing any black smoke, just lots of clear hot liquid.

“This may turn out to be far more exciting from a geology point of view, than the deeper site, and may have very important implications for the global distribution of these systems, as it was in a location where we would not normally expect to find vents,” said Connelly, of the National Oceanography Centre who is the principal scientist on the expedition.

Meanwhile, on land and up in the sky, another volcano was threatening to prevent the team from getting home.

The volcanic ash from the Eyjafjallajökull volcano in Iceland had shut down airports throughout Europe and as the team headed back to shore, to Montego Bay, Jamaica, on board the Royal Research Ship James Cook, airports in the UK were still closed.

“We were worried about the issue of getting back to the UK because of the ash cloud. Fortunately, our flight out was the first one to be allowed to fly back from Jamaica to the UK, [and] a very happy and tired party was very pleased to be back in the UK on schedule,” said Connelly.

The discovery 60 miles south of Grand Cayman of the “black smokers” – vents that emit murky water hot enough to melt lead from the ocean floor- drew media attention around the world.

After the footage of the vent emitting scalding dark water was released worldwide, the team sent its equipment back down another three times and took samples of water, particles, sediment and biology, as well as more footage of the vents.

The expedition team mapped more than 200,000 hectares of ocean floor with its multi-beam sonar and a towed ocean bottom instrument, and completed 750km of survey lines with the magnetometer.

The Autosub6000, an autonomous robot submarine, undertook nine missions, spent 8.3 days underwater and covered 690 km, while the HyBIS, a vehicle that was remotely-controlled from the ship which carried cameras into the depths and brought back samples, went on 10 dives, including its deepest ever, and spent a total of 3.9 days underwater.

The team left behind moorings carrying instruments to measure the currents and physical properties of the water around them on the ocean floor until the scientists can return for their second expedition.

They also left whalebones to see what colonises them in the Cayman Trough.

The team is keeping silent on what marine life they found near both vents, saying they will release details in a scientific paper in June, after which they will also release video of creatures they discovered and more footage of the vents.

And then, they will begin planning their return to the Cayman Trough.

“We will be returning to the Cayman Trough as fast as our ship schedule will allow. We will be taking the UK remotely operated vehicle Isis to get more detailed and precise samples from the area. We will also further explore the new site we located just the day before we had to leave to come home, so lots of exciting things to look forward to,” he said.

According to the scientists, studying life-forms that thrive in such hostile underwater environments provides insights into patterns of marine life around the world, the possibility of life on other planets, and even how life on Earth began.

They say that the unseen depths of the Cayman Trough contain an important missing piece of a global ‘jigsaw puzzle’ of marine life and that finding out what lives there boosts the understanding of the biodiversity of the deep ocean.

The deep sea vents also can give an insight into hidden chemical reactions deep within the Earth’s crust, which ultimately control the saltiness of the seas.

The scientists also hope that by revealing the previously unknown deep ocean circulation of the Cayman Trough, it will improve their understanding of how ocean currents transport heat and life around the planet and how that circulation may change over time.

By discovering the vents and studying the materials and samples taken from the sites, the team went home feeling they’d done what they had set out from Trinidad on 24 March to do.

Connelly said: “Everyone came off the cruise elated and feeling we had done something that was not only scientifically important and interesting, but that we had managed to capture the imagination of many people around the world through our outreach programme.”