Scientists return to Cayman Trough’s abyss

Scientists this week completed their latest exploration of the deepest hydrothermal vents on the planet, located three miles down the Cayman Trough. 

The team, using the Isis remotely operated vehicle or ROV, completed the last of 11 dives in the early hours of Monday, 25 February at the Beebe Vent Field, collecting the final samples from around the vents on an undersea mountain called Mount Dent. 

During the last three weeks, scientists have filmed hundreds of hours of video footage and taken thousands of still photographs of the creatures inhabiting the vents at the Von Damm, which is 1.4 miles underwater, and Beebe, at three miles deep, sites and also collected samples of the rocks, water, sediment and animal life that has been found down the abyss between the Cayman Islands and Jamaica. 

These include blind vent shrimp, echinoderms, tubeworms, lobsters, sponges, corals and anemones. Some of these creatures have only been found at these vents, which are known as “black smokers” for the dark water that emits from them at high speed and scalding temperatures. 

Chief scientist for the expedition of the United Kingdom’s National Oceanography Centre, Jon Copley, told The Associated Press on Wednesday that he believes laboratory analysis in the coming months will reveal some new life forms that have evolved in the pitch-black vent areas of the Cayman Trough. 

“From body form alone, I am confident that we have found several new species on this expedition: probably a new species of sea anemone, a few species of bristle worms and some small crustaceans,” Mr. Copley said. 

Blankets of shrimp 

Another scientist aboard the Royal Research Ship James Cook, Andrew David Thaler, a post-doctoral researcher at the Duke University marine laboratory in Beaufort, North Carolina, told AP there were abundant populations of some species around the vents, particularly an eyeless shrimp dubbed Rimicaris hybisae that was discovered by the research team in 2010. 

“They’re so thick that you often can’t even see the rock beneath because they’re buried in blankets of shrimp,” Mr. Thaler said in an e-mail. 

Such large amounts of anemones were found at the Beebe site that Mr. Thayer said they “look almost like meadows”. 

The researchers also placed half a pig’s carcass near the Von Damm vent field to see what scavengers it would attract.  

In a blog update from the RRS James Cook, team members Verity Nye, Rachel Mills and the biology team on board wrote: “One of our objectives has been to elucidate the biodiversity at the deepest vents and our final species list is still in preparation as we collate the data we’ve accumulated and begin to analyse what we’ve found.” 

The geologists on board explored, via the ROV, the entire main vent site, mapping its surrounding hills and valleys, and found volcanoes and lavas, as well as black fissures. 

At the bottom of the deepest valley, at 2.7 miles under water, they found what they described on their blog as “a carpet of bright orange mud”, coloured by the iron spewing from the water at the hydrothermal vents. The iron oxidises and falls as rust onto the seabed over thousands of years. 

They also found rocks of green, blue and purple, coloured by the copper from the vents, which spew out mineralised water at temperatures of up to 400 degrees Celsius. 

“Detailed analysis of samples back at the National Oceanography Centre and the Geosciences Environment Toulouse laboratory will enable us to relate the chemistry in the local vent environment to discoveries made by the geology and biology team on the distribution of different rock types and organisms across the Beebe and Von Damm vent fields.  

“This allows us to see how different species survive and tolerate different chemical environments. The micro-organisms that survive in these harsh, toxic conditions are an example of how life can survive in the most inhospitable places and may be our best model to search for life in other parts of our solar system,” the team’s blog reads.  

The hydrothermal vents in the Cayman Trough are the deepest and hottest ever discovered. They were first found in April 2010 by scientists from the UK’s National Oceanography Centre and the University of Southampton, some of whom returned two years later to take a closer look at the vents and the animals who survive in some of the most inhospitable conditions on Earth. 

This year, they came back with high definition cameras to get footage of the site and the creatures and spent 18 days at the site. The Isis ROV spent more than 196 hours on the ocean bed during its 11 dives. The average bottom time per dive was 17 hours, with the long dive lasting 35 hours and the shortest 10 hours 

The vents spew out an estimated 660 pounds of water every second, which contains high levels of hydrogen sulfide, the main food for the bacteria that feed the multitudes of blind shrimp that live on the sides of the vents.  

The team left from Montego Bay, Jamaica on 6 February. 

Garbage of the deep 

As well as the myriad sea creatures and geological finds, the ROV also came across marine debris, including beer bottles at depth, showing that people’s garbage is finding its way into the deepest and unexplored regions of the oceans. 

A blog entry by Mr. Copley on 13 February reads: “During today’s dive we found a beer bottle on the seafloor, one of a few pieces of rubbish that we have seen so far. Human-generated rubbish unfortunately has a long history in the deep ocean: in the age of steamships, for example, ships would dump “clinker” (the remains of burned coal from their engine rooms) during their journeys, which changed the nature of the seafloor along well-travelled routes. At that time, however, we only had hazy notions about the depth of the oceans, let alone what was going on down there.  

“Today, plastic has replaced clinker as a common contaminant of the deep ocean, and we plan to collect sediment cores here that will be analysed to see if they contain microplastics – tiny ground-down remnants of plastic that may now be quite ubiquitous in the oceans.” 

In May, more scientific explorers will be visiting the Cayman Trough, bringing the United States manned deep submersible, which has just undergone a US$41 million refit, with them.