Newly discovered deep-sea species could help to protect fragile ocean habitats

Breathtaking images of deep-sea life have been captured by an expedition to the south Pacific.

Squat lobsters, sea urchins and deep-sea corals were among the wildlife pictured thousands of metres below the surface of the ocean. Many of these animals might be new species, though this will take many years to confirm.

Dr Javier Sellanes, the scientists leading the expedition for the Schmidt Ocean Institute, says, ‘We far exceeded our hopes on this expedition. You always expect to find new species in these remote and poorly explored areas, but the amount we found, especially for some groups like sponges, is mind-blowing.’

The sheer diversity of life discovered by the expedition gives added weight to calls to protect areas of the oceans outside national waters and protect the unique animals which live there.

Diving under the sea

Like the land above water, the bottom of the ocean isn’t a flat surface. The seafloor is covered in deep canyons, long ridges and mountains that provide a variety of different habitats for marine life.

However, currently just a quarter of the seabed has been mapped. Some maps still being made are even based on measurements taken hundreds of years ago.

Not only does this pose a hazard to ships and submarines, which sometimes collide with unmarked seamounts, it also makes it much harder to study marine life. The Seafloor 2030 hopes to change this by using a variety of different vessels and autonomous vehicles to map the entire seafloor by the end of the decade.

The Schmidt Ocean Institute expedition is one small part of this. The research vessel Falkor (too), named after a character from The Neverending Story, is exploring the waters off the coast of Chile to map the seafloor and discover the wildlife which live there.

Researchers are particularly interested in the Salas y Gómez, Nazca, and Juan Fernandez ridges that stretch over 2,900 kilometres across the seafloor.

The combination of different depths, currents and oxygen levels throughout these ranges gives them some of the highest rates of endemism in the sea, meaning that species living here are found nowhere else on Earth. Using a remotely-operated vehicle (ROV) named SuBastian, the team set out to look for more of these enigmatic animals.

Dr Lupita Bribiesca-Contreras, who researches deep-sea species at the Natural History Museum, adds, ‘Seamounts are like undersea islands, with unique biodiversity thanks to their isolation from each other. There can be a difference of thousands of metres between the abyssal plain and the top of the seamount, with animals adapting to different depths.’

‘This area of the Pacific is thought to be especially diverse, as it has relatively little food in it. This causes a phenomenon where there is really high diversity, but with low numbers of each species.

‘Why this happens is a big question in deep-sea research, but it means that almost every animal you encounter is likely to be a new species.’

What deep-sea animals were discovered?

More than 100 potential new species were revealed by the ROV as it explored 10 seamounts in the region. Each seamount had its own unique ecosystem based around deep-sea coral reefs and sponge gardens, which thrive in the still waters of the deep ocean.

Found living among the sponges and corals were animals like squat lobsters, a group of crustaceans with arms often much longer than their bodies. Despite their name, they’re actually more closely related to hermit crabs than to lobsters, with their similar shape an example of convergent evolution.

Sea urchins are also thriving in the depths, with the cactus-like Dermechinus among the species found on the seamounts. The exact lifestyle of these unusually long sea urchins remains mysterious, with hopes new footage and specimens might reveal more about how they survive in the deep.

The ROV also found evidence of a few bony animals, including fish from the Chaunacops genus, which are better known as the sea toads or coffinfish.

To survive where few other vertebrates can, these animals hold their breath for up to four minutes to reduce the amount of energy they use to breathe, and remain motionless on the seafloor for much of the time. They only move when panicked or ambushing prey that strays too close.

Detailed investigations of the genetics and physiology of the species will now be carried out to confirm whether these animals are new to science. This will take place over the next few years, as identifying deep-sea species is a time-consuming process.

‘Describing deep-sea species takes time, partly because of a lack of taxonomists which is causing a backlog,’ Lupita says.

‘It’s also difficult to compare animals to existing species, as many were collected over a century ago by expeditions like Challenger. The age of these animals means that key characteristics, like their spines, are lost, so it’s hard to know if a newly-discovered animal originally looked like them.’

Protecting the deep sea

The pictures captured by the ROV are a powerful reminder of the life living deep beneath the waves and of how little we know about it. It’s hoped that by raising awareness of these species the expedition can contribute to efforts to protect the Salas y Gómez, Nazca, and Juan Fernandez ridges.

While parts of the ridges lie within the waters of Chile, which has established marine protected areas at key sites along them, the majority of the underwater mountains lie in the high seas outside its jurisdiction.

There are concerns that as technology improves the same diversity that makes the seamounts so important for undersea life will make them increasingly tempting targets for fishing vessels. This would most likely involve bottom trawling, which drags nets along the seafloor.

These nets catch everything in their path and can damage and kill the sponges and corals that other species rely on. The resulting damage can take hundreds of years for these slow-growing species to recover from.

Following the passing of the High Seas Treaty by the UN in 2023, Chile is spearheading a campaign to have the Salas y Gómez and Nazca ridges declared one of the first high seas marine protected areas. Data from expeditions in the region will be crucial to highlight just why these waters need protecting.

‘Compared to the abyssal plains in the region, which have been surveyed for their potential for deep-sea mining, there hasn’t been as much exploration of seamounts,’ Lupita adds. ‘Focusing efforts on seamounts will help to understand the diversity of these areas and reveal just why they’re so special.’