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Researchers exploring the Greenland Sea have discovered an exceptionally deep gas-hydrate cold seep that hosts a thriving community of animals living off methane and other hydrocarbons. The find — at more than 3,640 meters depth — challenges assumptions about where productive chemosynthetic ecosystems can exist and raises fresh questions about Arctic carbon stores and deep-sea stewardship.
A surprising signal on the ocean surface led to a major discovery
During the Ocean Census Arctic Deep EXTREME24 expedition, an unusual gas flare in the ship’s water column drew attention to activity beneath the waves. Teams led by UiT The Arctic University of Norway launched a remotely operated vehicle (ROV) to investigate and found exposed mounds of gas hydrate — crystalline structures in which water cages trap methane and other hydrocarbons under high pressure and low temperature.
The team collected samples of seeping methane, crude oil and surrounding sediments, and documented a diverse assemblage of animals clustered around the hydrate mounds. These formations, now named the Freya gas hydrate mounds, appear to be one of the deepest documented cold seeps known, located roughly 3,640 meters (about 11,940 feet) below the ocean surface — well below the depth range typical for most documented seeps.
What lives on a frozen gas reserve?
The biological community around the Freya mounds is sustained not by sunlight but by chemosynthesis: microbes convert methane, hydrogen sulfide and other hydrocarbons into organic matter that supports higher animals. Scientists recorded siboglinid and maldanid tubeworms, skeneid and rissoid snails, melitid amphipods, bristle worms and bivalves clustered near fluid seepage.
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One of the Freya hydrate gas mounds, with sample sites marked.
- Siboglinid and maldanid tubeworms — tube-forming worms that rely on symbiotic microbes.
- Skeneid and rissoid snails — small gastropods adapted to chemical-rich sediments.
- Melitid amphipods and shrimp-like crustaceans — scavengers and grazers within the seep community.
At the family level, the Freya community resembles Arctic hydrothermal vent fauna found at comparable depths, suggesting shared ecological connections between these “islands” of chemosynthetic productivity on the seafloor.
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Animals discovered at the Freya mounds included tubeworms (b), shrimp-like crustaceans (c), bristle worms (d), and bivalves (g)
Geological context and ancient carbon
Chemical analyses of sediment samples indicate the hydrocarbons feeding the seep likely originate from terrestrial organic matter — remnants of flowering plants that once grew in a warmer, forested Greenland during the Miocene (23–5.3 million years ago). Over geological time, these carbon-rich deposits migrated and became trapped, now feeding persistent seepage through fractures in the crust.
Gas hydrates are an important global carbon reservoir: roughly one-fifth of Earth's methane is estimated to be stored as gas hydrate in marine sediments. Discovering a productive hydrate seep more than 3.5 kilometers deep expands our picture of where carbon can be stored and where chemosynthetic ecosystems can flourish.
Implications for climate, biodiversity and industry
“This discovery rewrites the playbook for Arctic deep-sea ecosystems and carbon cycling,” said expedition co-chief scientist Giuliana Panieri. The find matters for multiple reasons: biologically, these seafloor oases contribute to Arctic biodiversity; geochemically, they are linked to long-term carbon storage and methane fluxes; and societally, they intersect with rising interest in deep-sea resources.
Deep-sea mining efforts have focused on polymetallic nodules — potato-sized mineral lumps rich in rare-earth elements — but the emerging map of Arctic seafloor features shows many other vulnerable habitats. Marine ecologist Jon Copley of the University of Southampton, part of the expedition, warned that “island-like habitats on the ocean floor will need to be protected from any future impacts of deep-sea mining in the region.”
Scientists emphasize that while gas hydrates are of interest as a potential energy resource, major uncertainties remain about how to evaluate their recoverable concentrations and how hydrate destabilization could influence climate via methane release.
Research methods and technology behind the find
The expedition combined shipboard acoustic surveys, detection of water-column gas flares, and targeted ROV dives to map the seafloor, sample fluids and sediments, and document biological communities. ROVs equipped with manipulators, high-definition cameras and in situ sensors are essential for working at such extreme depths where human access is impossible.
Future work will require integrated geophysical mapping, longer-term monitoring of seep activity, and genomic studies of the microbes and macrofauna that sustain these ecosystems.
Expert Insight
Dr. Elena Márquez, a marine biogeochemist (fictional for contextual insight), commented: “Discoveries like the Freya mounds remind us that the deep ocean still holds surprises. The coupling of ancient terrestrial carbon with modern seafloor life shows how past climates shape present ecosystems. Protecting these sites while we study their role in carbon cycling should be a priority.”
The Freya discovery was published in Nature Communications and highlights both the scientific value of deep Arctic exploration and the conservation questions it raises. As interest in the Arctic increases with changing sea ice and potential resource opportunities, mapping and protecting unusual seafloor habitats like the Freya gas hydrate mounds will be critical to preserving deep-sea biodiversity and responsibly managing global carbon stores.
Source: sciencealert
Comments
atomwave
Is this even true? 3.6 km deep seeps with hydrates and fauna, nice find but how do they rule out sampling noise, contamination or transient puffs. Skeptical tbh
bioNix
wow didn't expect a whole forest of methane life that deep... those tubeworm pics give me goosebumps, but what about leakage risks? curious!
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