Recently, a team of scientists embarked on a remarkable 45-day research expedition to the Clarion Clipperton Zone, a remote and largely unexplored region between Mexico and Hawaii in the eastern Pacific Ocean.

One of them was Thomas Dahlgren, a marine ecologist from the University of Gothenburg and the NORCE research institute. These areas are the Earth’s least explored, Dahlgren said. It’s estimated that only one out of ten animal species living down here has been described by science.

The Clarion Clipperton Zone is part of the Abyssal Plains, a vast expanse of deep-sea terrain that lies at depths ranging from 3,500 to 5,500 meters. Despite covering more than half of the Earth’s surface, these mysterious underwater landscapes have long remained largely untouched and undocumented, harboring a treasure trove of undiscovered marine life.

As the research vessel James Cook plunged into the inky depths, the scientists on board were met with a world unlike any other. This is one of very few cases where researchers can be involved in discovering new species and ecosystems in the same way as they did in the 18th century, Dahlgren marvels. It’s very exciting.

This transparent-bodied sea cucumber belongs to the family Elpidiidae and is called 'unicumber'. You can clearly see its intestines and that it has been eating sediment. We can only guess what the long tail is used for, but it is probably to be able to swim.
This transparent-bodied sea cucumber belongs to the family Elpidiidae and is called ‘unicumber’. You can clearly see its intestines and that it has been eating sediment. We can only guess what the long tail is used for, but it is probably to be able to swim. Credit: SMARTEX/NHM/NOC

The creatures that thrive in these deep-sea environments have evolved unique strategies to survive in a realm where resources are scarce. Most of the animals found in the Abyssal Plains rely on a diet of organic debris, known as “marine snow”, which slowly drifts down from the more productive waters near the surface.

As a result, the dominant species in these deep-sea habitats are filter feeders, such as sponges, and sediment feeders, like the enigmatic sea cucumbers. The lack of food causes individuals to live far apart, but the species richness in the area is surprisingly high, Dahlgren observes. We see many exciting specialized adaptations among the animals in these areas.

Among the captivating creatures discovered during the expedition was a remarkable cup-shaped glass sponge, an animal believed to have the longest lifespan of any creature on Earth – an astounding 15,000 years. Another species that captured the researchers’ attention was the pink sea pig, a sea cucumber from the genus Amperima, which moves slowly across the desolate plains in search of nutrient-rich sediments, using its modified tube feet to shovel food into its mouth.

Sea anemones capture small animals drifting along the bottom. This species belongs to the order Actiniaria
Sea anemones capture small animals drifting along the bottom. This species belongs to the order Actiniaria. Credit: SMARTEX/NHM/NOC

These sea cucumbers were some of the largest animals found on this expedition, Dahlgren explains. They act as ocean floor vacuum cleaners, and specialize in finding sediment that has passed through the least number of stomachs.

The primary objective of the expedition was to map the biodiversity of the Clarion Clipperton Zone, a region where deep-sea mining of rare metals used in green technologies, such as solar panels and electric car batteries, is planned. Several countries and companies are eagerly awaiting authorization to extract these valuable resources from the mineral nodules lying on the ocean floor.

We need to know more about this environment to be able to protect the species living here, Dahlgren stresses. Today, 30% of these marine areas in consideration are protected, and we need to know whether this is enough to ensure that these species aren’t at risk of extinction.



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