Pacific expedition may have discovered over 30 new deep sea species

One of the least explored regions of the world has revealed a collection of species unknown to science.

The new species were collected from the abyssal plains of the Clarion-Clipperton Zone in the central Pacific using a remotely operated vehicle (ROV). This allowed specimens to be brought to the surface, enabling scientists to get a much better idea of the organisms living at the bottom of the ocean.

Dr Guadalupe Bribiesca-Contreras is the lead author on a new study revealing this previously unknown diversity.

'This research is important not only due to the number of potentially new species discovered, but because these megafauna specimens have previously only been studied from seabed images,' the Museum researcher says. 'Without the specimens and the DNA data they hold, we cannot properly identify the animals and understand how many different species there are.'

Remarkably, of the 55 specimens recovered, 48 were different species. Merit Researcher Dr Adrian Glover, who leads the Museum's Deep Sea Research Group, says, 'We know that small millimetre-sized animals called macrofauna are extremely biodiverse in the abyss.'

'However, we have never really had much information on the larger animals we call megafauna, as so few samples have been collected. This study is the first to suggest that diversity may be very high in these groups as well.'

The findings, published in the journal Zookeys, add further evidence that the majority of deep sea life is yet to be discovered. 

What is the Clarion-Clipperton Zone?

The Clarion-Clipperton Zone (CCZ) covers over five million square kilometres in the Pacific Ocean, lying between Hawaii and Mexico. It is around 5,500 metres at its deepest, which is nearly as deep as Mount Kilimanjaro is high.

While the majority of Earth's surface is covered in similarly deep ocean, the CCZ attracts international attention. This is due to large portions of its flat abyssal plains being covered in potato-sized mineral lumps known as polymetallic nodules. They are rich in important metals such as cobalt, nickel, manganese and copper.

It has been estimated that there is more cobalt and nickel in polymetallic nodules than can be found on land. As these materials form a crucial part of net-zero energy technologies, such as wind turbines and electric cars, interest in extracting these metals continues to rise.

There are not enough of these metals available to recycle in the medium term, so instead, the possibility of seabed mining has been suggested as one way to meet demand.

While proponents of seabed mining argue that harvesting the polymetallic nodules will pave the way for a green revolution without impacting land-based ecosystems, opponents worry that it could devastate the oceans by causing irreparable damage to seafloor ecosystems.

The CCZ is a focus of scientific research to evaluate the impacts of seabed mining on this environment, which is remote and difficult to research.

'The deep sea is pretty understudied,' Guadalupe says. 'It's very expensive to go out on research cruises, and they don't generally return to the same areas. One problem is that in the CCZ, areas have been protected but we know rather little about them.'

'Our study looked at three of these protected Areas of Particular Environmental Interest (APEIs) thanks to grants from the Gordon and Betty Moore Foundation and the National Oceanic and Atmospheric Administration, and the leadership of Prof Emeritus Craig Smith of the University of Hawaii.'

'It is as important to sample the protected APEI regions as it is the commercially-contracted regions,' Adrian adds. 'Without comparative data on value of the regions we are protecting, we can't properly assess the impacts of mining.'

'We must also communicate the value of the protected regions to society so that we can see the importance of marine conservation.'

The researchers sampled the APEIs using a ROV, to collect 55 specimens in total from across the abyssal plains and undersea hills known as seamounts.

Co-author Dr Thomas Dahlgren, from the University of Gothenburg, studied the videos. He says, 'As they drove the ROV across the seafloor it first appeared that the animals were incredibly rare.'

'There were times when we did not see a single animal for quite a while. But incredibly, each animal we found was almost always a different species. It's a very unusual ecosystem.'

Why is it hard to identify deep sea species?

Overall, the ROV collected evidence of 48 different species, of which only nine are currently known to science. The remaining 39 may be new species, but it is difficult to assess.

'I was definitely not expecting to find so many animals,' Guadalupe says. 'We were not certain that there would be any known species from the area as so many species are yet to be described.

'We thought that some of the species we found were cosmopolitan, living across large areas of the ocean, but by looking more closely at their DNA we found that they are different species, possibly restricted to smaller habitats. There are probably not yet enough samples to understand the variation within them fully.'

Another difficulty the researchers face is comparing their specimens to the type specimens, which are the individuals used to represent and identify a species. The type specimen is normally the first of a species ever discovered, but historic collection methods mean they aren't always in the best condition.

'Older deep sea specimens are often damaged, as they were collected by less gentle methods such as trawling,' Guadalupe explains. 'For instance, brittle stars have delicate arms which are often snapped, such as those collected on the Challenger expedition.

'This is a problem because these individuals are often used as type specimens. If characteristics are missing when comparing two similar animals, it's difficult to tell whether this is because they were lost during collection or because they are a different species.

'Many older specimens were also put straight into formalin preservative, which makes it difficult to extract DNA.'

The Museum's deep sea research team hopes to overcome some of these difficulties by comparing these specimens to megafauna collected in a recent voyage, alongside broader-scale imagery surveys that are being led by the National Oceanography Centre, UK.

They intend to continue building up a picture of the deep sea to inform important decisions which will affect the path of the green revolution.

'Whilst deep sea mining is a very valid environmental concern, we are in a very positive situation where we have been able to conduct a lot of fundamental research while the industry is held back from full-scale exploitation,' Adrian says. 'This is very different to what has happened in the past with other ocean resources, such as fisheries.'

'A big societal decision with regard deep sea mining is on the horizon and our role is to provide as much data as we can to inform that decision as best we can.'