PARIS – A vast area at the bottom of the Pacific Ocean earmarked for controversial deep sea mineral mining is home to thousands of species unknown to science and more complex than previously understood, according to several new studies.

Miners are eyeing an abyssal plain stretching between Hawaii and Mexico, known as the Clarion-Clipperton Zone (CCZ), for the rock-like “nodules” scattered across the seafloor that contain minerals used in clean energy technologies like electric car batteries.

The lightless ocean deep was once considered a virtual underwater desert but as mining interest has grown, scientists have scoured the region exploring its biodiversity. Much of the data over the last decade has come from commercially-funded expeditions.

And the more they look the more they have found, from a giant sea cucumber dubbed the “gummy squirrel” and a shrimp with a set of elongated bristly legs, to the many different tiny worms, crustaceans and molluscs living in the mud.

That has intensified concerns about controversial proposals to mine the deep sea. The International Seabed Authority on Friday agreed a two-year road map for the adoption of deep sea mining regulations, despite conservationists’ calls for a moratorium.

Abyssal plains more than 3km underwater cover more than half the planet but people still know surprisingly little about them.

They are the “last frontier”, said marine biologist Erik Simon-Lledo, who led research published on Monday in the journal Nature Ecology and Evolution. The research mapped the distribution of animals in the CCZ and found a more complex set of communities than previously thought.

“Every time we do a new dive, we see something new,” said Mr Simon-Lledo, of Britain’s National Oceanography Centre.

Campaigners say this biodiversity is the true treasure of the deep sea and warn that mining would pose a major threat by churning up huge plumes of previously-undisturbed sediment. The nodules themselves are also a unique habitat for specialised creatures.

“With the science as it is at the present day, there is no circumstance under which we would support mining of the seabed,” said Ms Sophie Benbow of the non-governmental organisation Fauna and Flora.

‘Mind-bogglingly vast’

The CCZ has both its age and size to thank for the unique animals discovered there, scientists say.

The region is “mind-bogglingly vast”, said Mr Adrian Glover of Britain’s Natural History Museum. He is a co-author both on the study with Mr Simon-Lledo and on the first full stock-take of species in the region published in Current Biology in May. That study found that more than 90 per cent of species recorded in the CCZ – some 5,000 – are new to science.

The region, which was considered to be essentially barren before an increase in exploration in the 1970s, is now thought to have a slightly higher diversity than the Indian Ocean, said Mr Glover.

He noted that sediment sampling devices from the region might capture only 20 specimens each time – compared to maybe 20,000 in a similar sample in the Antarctic – but that in the CCZ you have to go much farther to find the same creature twice.

Scientists are now also able to use autonomous underwater vehicles to survey the seabed.

These are what helped Mr Simon-Lledo and his colleagues find that corals and brittlestars are common in shallower eastern CCZ regions, but virtually absent in deeper areas, where you see more sea cucumbers, glass sponges and soft-bodied anemones.

He said any future mining regulations would have to take into account that the spread of animals across the area is “more complex than we thought”.

‘Serious harm’

The nodules likely started as a shard of hard surface – a shark tooth or a fish ear bone – that settled on the seabed and slowly grew by attracting minerals that naturally occur in the water at extremely low concentrations, Mr Glover said. Each one is likely millions of years in the making.

The area is also “food poor”, meaning fewer dead organisms drift down to the depths to eventually become part of the seafloor mud. Mr Glover said parts of the CCZ add just a centimetre of sediment per thousand years.

Unlike the North Sea, formed from the last ice age that ended 20,000 years ago, the CCZ is ancient. “The abyssal plain of the Pacific Ocean has been like that for tens of millions of years – a cold dark abyssal plain with low sedimentation rates and life there,” Mr Glover added.

Because of this, the environment impacted by any mining would be unlikely to recover in human time scales.

“You are basically writing that ecosystem off for probably centuries, maybe thousands of years, because the rate of recovery is so slow,” said Mr Michael Norton, environment programme director at the European Academies’ Science Advisory Council.

“It’s difficult to argue that that is not serious harm.” AFP