Strange creatures await discovery

Ron Toft

October 2009 Issue

Back in the 1840s, British naturalist Edward Forbes pronounced—rather rashly in retrospect—that life could not exist more than 300 fathoms (540 metres) below the waves.
We now know that life flourishes in all manner of extreme environments on our planet. And they don’t come much more extreme than the long, narrow, very deep and totally lightless oceanic trenches where the temperature is near freezing and the pressure is mind-blowingly high. 
 “Getting anything down to these great depths and surviving is a major technical challenge,” said marine engineer Dr Alan Jamieson, of the University of Aberdeen’s Oceanlab sub-sea research facility.
 “These trenches—formed when tectonic plates collide and mostly found around the Pacific Rim—can plunge, at times quite dramatically, to nearly 11,000 metres, where pressures can exceed 1,000 bar (one ton per square centimetre).”
Unsurprisingly, given the difficulties involved, scientists have explored the hadal zone (the name given to the region between 6,000 and 11,000 metres deep) only a handful of times.
“This leaves a vast gap in our understanding of the oceans and marine life,” added Jamieson.
Despite the technological problems, engineers and scientists at Aberdeen and Tokyo Universities have succeeded during the past 18 months or so in doing what has never been done before—sending a pair of bait-carrying and camera-equipped free-fall landers to the bottom of several trenches in the Pacific Ocean, taking a wealth of temperature, pressure and salinity measurements, securing hours of video and time-lapse footage, as well as thousands of ‘still’ photographs, and bringing the craft back to the surface with biological samples for genetic and other analysis.
The most surprising discovery was the number and size of the animals living in this utterly alien, sunless world.
At the start of the Aberdeen-Tokyo Universities’ HADEEP (from ‘hadal’ and ‘deep’) project, there were no instruments or vehicles anywhere in the world capable of descending to the bottom of the Pacific trenches.
 “Moreover, we knew that any animals inhabiting the hadal zone would certainly die if brought to the surface, meaning that any behavioural or physiological observations had to be done in situ.”
Deep-sea life survives on food sinking down from the surface. There are two kinds: dead plankton and carrion, such as fish carcasses.
“Open ocean processes mean the quantity of plankton reaching the seafloor decreases with depth. Food is extremely scarce in the trenches.
Using bait: “But in principle, fish carcasses or food falls, can happen anywhere and are independent of depth. We can exploit this dependency on food falls by using bait to attract animals in front of a camera.”
The HADEEP team, which has designed and operated many free-fall landing vehicles over the years, built two landers for the exploration of the Pacific trenches: one equipped with a video camera and the other with a time-lapse stills camera.
“We worked closely with biologists on the experimental design to ensure we were giving them what they wanted.”
Although Jamieson conducted some initial development studies in 2004 as part of his PhD work, funding approval for the development of the landers wasn’t granted until late 2006.
The cash itself didn’t come through until the beginning of February 2007.
“That meant we had just six weeks to finalise the designs of a few years earlier and actually build the landers, for we had received a generous offer we couldn’t refuse by the University of Tubingen, Germany, in July 2007. It took eight weeks to sea-freight everything to Samoa, one of the packages making it with just one hour to spare!”
The battery-powered, tripod-shaped landers stand about two-and-half metres tall and weigh around 300 kg each. 
 “To save money, we used reliable, proven technology throughout, taking everything apart and adapting it to operate at extreme depths.”
Both landers carried bait to attract the denizens of the deep.
Once released over the side of a ship, the untethered landers sank slowly to the bottom of the ocean at a rate of about 1,000 metres every 30 minutes.
“Getting to the bottom of the trenches is a long, drawn-out process, compared with what we normally do,” said Jamieson. “It takes about five hours to descend 10,000 metres.”
The landers took a variety of scientific measurements on the way down, while on the bottom, and on the way up. When the HADEEP team wanted to recover one of the craft, it sent a unique acoustic command like a phone call.
As soon as the lander detected this command, it dropped its ballast weights and slowly float to the surface where it was picked up about five hours later.
The landers’ maiden voyage took place over a three-week period in the summer of 2007 at depths of 6,000 to 8,500 metres in the Kermadec Trench and 9,000 to 10,000 metres in the Tonga Trench. Both of these trenches lie between Samoa and New Zealand in the south-west Pacific.
 “Allowing autonomous landers to free-fall into the deep sea is nerve-racking at the best of times,” said Jamieson.
Successful: “The anxiety on board on this occasion was unbearable. I nearly fell off my chair when the first lander resurfaced! The expedition was unbelievably successful. It was probably one of the best I have ever undertaken, not least because of the time constraints involved.”
Later that year, the landers were also used to descend to 7,000 metres in the Japan Trench and to 5,500 metres in the Marianas Region, both in the north-west Pacific.
The engineering and scientific data obtained from the 2007 expeditions far exceeded Jamieson’s wildest expectations. 
 “There was not only the pleasure and relief of proving our landers could survive the 10,000-metre descent but that they could also survive the ascent afterwards.”
The footage obtained revealed “massive, bee-like swarms” of shrimp-like crustaceans called amphipods.
“Surprisingly, these creatures increased in numbers with depth. Most belonged to the genus Hirondellea, found throughout the oceans. Although we were amazed by the sheer volume of individuals feeding at the bait, this is what we expected to see at these depths.
“What we weren’t expecting to find, however, were much larger lobsters, crabs and prawns, known as decapods. Before the expedition, marine biologists assumed decapods had no hadal representatives.
“On the contrary, at 7,000 metres we saw one particular decapod, Benthescymus crenatus, in relatively large numbers in both the Kermadec and Japan Trenches.
“The shrimp-like amphipods were attracted to our bait, such as oily mackerel, which leaves an odour plume in its wake. The fish and decapods, however, weren’t the least bit interested in our bait. When they turned up, they didn’t even as much as sniff the mackerel. They were only after the amphipods and associated the smell with a high density of these creatures. It was a massacre. I guess I was one of the first people ever to see something killed in the hadal zone! I was an eyewitness to murder!”
Also found, at 7,000 metres in the Japan Trench—1,100 metres deeper than previously discovered—were deep-sea fish commonly known as grenadiers or ‘rat tails’.
Jamieson says “perhaps the most spectacular find” was the presence of sociable and highly active liparid or snailfish.
In the Kermadec Trench, the landers found a liparid species caught only once previously, in the 1950s, and never before seen alive.
“As if that wasn’t exciting enough, we found another liparid species, again never before seen alive, in the Japan Trench.”
In October 2008, Jamieson and his colleagues returned to the Japan Trench and secured footage of the deepest fishes ever filmed.
Strange creatures: Then, in March this year, they explored the Izu-Bonin Trench, south of Japan, where they found lots of amphipods at 8,000 metres and many more much bigger ones at 9,300 metres. All were apparently of the same species.
“If these creatures are moving between at least 8,000 and 9,300 metres, how do they cope with the huge pressure changes involved? Bizarrely, about one-third of the amphipods were laden with eggs. There are far more questions than answers at present.”
In just a few short years, the HADEEP researchers at the Universities of Aberdeen and Tokyo have become world leaders in the unmanned exploration of the deepest parts of the world’s oceans.
“As far as hadal biology is concerned, we are the only people doing it right now.”
Further exploration of the Tonga Trench is on the cards later this year.
“In 2010, we are hoping to explore part of the Peru-Chile Trench. That should be really interesting. Given the huge amount of organic material which must have ended up in that trench from the Andes, there should be a huge diversity of life down there.”
The team also wants to return to the Japan Trench at some point.
“It’s not surprising that microbes go unnoticed in extreme environments,” added Jamieson. “But to find entire schools of fish and 30cm prawns in some of the deepest parts of our oceans wer completely unexpected.”
Who knows what strange creatures still await discovery in the Pacific and other trenches? Only time and further exploration will tell.