In the deepest parts of the ocean there’s no sunlight, temperatures hover just above freezing, and the pressure is so intense it’s like having 100 adult elephants laying on top of your body. Yet, at these depths live some of the most extraordinary creatures ever discovered.
Now, one such creature has climate researchers extra-intrigued: a crustacean with parchment-thin “skin” that uses its fan-like paddles to swim more than 6,000 meters below the surface in the Puerto Rico Trench. It’s the first time that the isopod—dubbed Bathyopsurus nybelini—has been filmed in its natural environment.
What’s more, B. nybelini was seen munching away on sunken pieces of algae from the surface. This is what’s got researchers excited. They say it means the creature could play an important role in combating climate change, since the algae they eat acts as a kind of carbon sink.
The findings were published Tuesday in the journal Proceedings of the Royal Society B.
The discovery that the isopod eats this leafy, brown type of algae—known as sargassum—came almost entirely by chance, the study’s lead author Mackenzie Gerringer told VICE. Her team were testing the capabilities of a newly-refurbished, human-occupied submersible they use called ‘Alvin.’
“We were putting Alvin through its paces after a recent overhaul,” said Gerringer. “Seeing how things like the camera systems were working and also doing some exploratory dives. On this expedition, we had the privilege of meeting this amazing animal.”
When they saw B. nybelini they were intrigued and hit record. “It’s a really beautiful organism,” Gerringer said. It’s the first time the deep-sea dweller has been caught swimming on camera.
However, While B. nybelini’s beautiful upside-down backstroke may have captivated Gerringer and her team, what really caught their attention was what it was holding. “Most of the time when we saw it, it was carrying the algae,” she said. By carefully observing hours of video footage—as well as DNA-sequencing its gut contents and 3D-imaging its mouthparts—her team concluded that B. nybelini wasn’t just holding the algae, it was eating it.
Feasting on sargassum is no easy feat. The algae is hardy and not very nutritious. “They have these really serrated mouthparts. Just like we have specialized knives for cutting into vegetables, they also have specialized teeth parts for cutting into this algae,” Gerringer explains. “Also, it has a specialized microbiome that’s able to help break down some of the nutrients in the algae. With that combination, this organism is really well suited to feeding on algae, even though it lives miles below the surface.”
Not only does their discovery show how specialized and amazing deep-sea organisms can be, but researchers think that animals like B. nybelini could help combat climate change. Algae like sargassum that floats on the ocean’s surface pulls carbon dioxide from the air and uses it to make energy through photosynthesis. Storms can then churn up ocean waters and cause the algae to break up and sink, where it’s eaten by deep-sea inhabitants. Other animals including sea cucumbers, crabs, and microorganisms eat sargassum too, but the isopod is the first creature scientists have discovered that feeds exclusively on the algae.
In recent years, researchers have proposed purposefully sinking sargassum to store carbon at the bottom of the sea. Some research teams are even building robots to help do so. But Gerringer is cautious about pinning all our climate hopes on this approach. “The quantity of how much carbon is being taken down and stored is not known yet. This is something that’s really important as we start thinking about connections to climate change. We need to know what will happen to [carbon] for a plan like that to work.”
B. nybelini was actually first discovered in 1948 when it was pulled up in a net during a deep-sea exploration. However, this damaged its delicate swimming paddles, so for a long time it was classified without them. This new study provides a much more detailed description because they were able to gently collect a couple of isopods to study back in the lab.
Regardless of its climate implications, this discovery shows how connected the deep sea is to the surface and even atmospheric environments, despite being many kilometers apart. “This animal that has no idea there is sunlight, will never see the sun, is relying on photosynthesis at the surface,” emphasises Gerringer. “It also means our activity at the surface is impacting deep-sea communities—in some cases, before we even know the community is there.”
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Previously: A Hidden Underwater Sea Bridge Just Changed Our Ideas About Ancient Humans
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