Deep-Sea Discovery Reveals Hidden Methane Cycle

Forbes

2 days ago

This Deep-Sea discovery is so new it's rewriting the map of life on Earth. More than 9,000 meters below the Pacific Ocean, scientists have uncovered a 2,500-kilometer stretch of extraordinary life that doesn't depend on sunlight at all — it runs on methane.
Between Russia and Alaska, in the deep-sea of the Kuril–Kamchatka and Aleutian trenches, clams, red-tipped tube worms, and invisible microbes thrive on gases seeping from cracks in the seafloor. These are the deepest methane-fueled ecosystems ever recorded — and they may be doing far more than surviving. They might be helping regulate our climate.
The discovery, published July 30 in Nature by a team led by geochemist Mengran Du of the Chinese Academy of Sciences, challenges the assumption that the hadal zone — the deepest part of the ocean — is barren mud. Instead, it appears to be a vibrant biogeochemical engine.
"What makes our discovery groundbreaking is not just its greater depth - it's the astonishing abundance and diversity of chemosynthetic life we observed" The Deep-Sea Climate Link
Deep in the sediments, microbes produce methane by breaking down buried organic matter. That methane is a potent greenhouse gas — more than 80 times stronger than CO₂ at trapping heat over a 20-year period.
But here's the twist: other microbes — many living inside the clams and worms — consume methane, using it to make food before it can escape into the ocean or atmosphere. This process, called chemosynthesis, supports entire food webs in the absence of sunlight.
These trenches also lock away carbon in the sediments. Studies suggest hadal zones can bury up to 70 times more carbon per square meter than the average seafloor. Though trenches make up only about 1% of the ocean floor, they could store tens of millions of tonnes of CO₂ each year — making them small in area but potentially significant in climate impact.
How Scientists Measure Methane at 9,000 Meters
Why is it so hard to measure methane that deep
The hadal trenches are some of the most extreme environments on Earth — over 9,000 meters below the surface, under crushing pressure, in near-freezing water, and far from shore. Every measurement requires specialized technology and expensive expeditions, which is why data is scarce.
What tools do scientists use?
There are three main methods:
Benthic landers with flux chambers — These are heavy, tripod-like devices lowered to the seafloor to trap and measure methane as it seeps directly from sediments.
Isotopic analysis — By studying the chemical 'fingerprint' of collected methane, scientists can tell where it came from and how old it is.
In situ sensors on ROVs or submersibles — Instruments mounted on deep-diving robots or crewed subs record real-time methane levels right where they occur.
Why does this matter?
Without these tools, we'd have no way to know whether deep-sea ecosystems like the newly discovered hadal trench system are net methane sinks — helping the climate — or net sources that could accelerate warming.
But What If this Deep-Sea site is a Net Methane Source?
Some readers might wonder: if this system releases more methane than it consumes, why not simply remove it?
The problem is that physical disturbance could make things far worse:
In other words: without long-term monitoring, destroying the system would be like opening a sealed vault without knowing what's inside — and possibly triggering a much larger release.
Deep-Sea Mining Moves In Before the Science Is Done
While scientists race to understand these ecosystems, deep-sea mineral extraction is moving closer to reality. Governments and companies are eyeing the ocean floor for cobalt, nickel, rare earths, and other high-value resources used in industries from electronics to defense. A 2024 Forbes analysis, 'Deep-Sea Mining, 'Dark Oxygen' and Diplomatic Leadership,' notes that the scramble for ocean minerals is as much a diplomatic contest as an environmental gamble — underscoring the tension between economic ambitions and the unknown risks to fragile deep-sea ecosystems.
The International Seabed Authority (ISA) — the UN body that regulates mineral activity in international waters — is still debating rules for commercial deep-sea mining, and has not yet approved any mining operations, only exploration contracts.
Some nations are nonetheless moving forward in their own waters. In January 2024, Norway's parliament voted to open a vast Arctic seabed area to mineral exploration, despite strong warnings from scientists and environmental groups. Later that year, political pressure forced the government to pause licensing plans, though companies remain poised to resume if approvals restart.
The United States, while not a voting member of the ISA because it has never ratified the UN Convention on the Law of the Sea, signaled clear political support for seabed mining in April 2025. President Trump issued an executive order directing U.S. agencies to expedite permits for offshore critical mineral projects — including in areas beyond national jurisdiction — a move criticized by the ISA as potentially undermining international governance.
Deep-Sea Scars That Last for Generations
Decades of research warn that deep-sea mining leaves a long and damaging footprint. In the Clarion–Clipperton Zone of the Pacific, a small test carried out in 1979 left the seabed scraped bare of polymetallic nodules. When scientists revisited the site more than 40 years later, the scars were still sharply visible, and the disturbed areas remained largely devoid of the sponges, corals, and starfish that had once lived there. Mining doesn't just scar the seafloor where it happens — it can also generate sediment plumes that drift for tens or even hundreds of kilometers, carrying fine particles that smother distant habitats and clog the feeding apparatus of filter-feeding animals. And because many deep-sea organisms grow and reproduce extremely slowly — with some corals living for millennia — the collapse of such communities may take centuries to recover, if they recover at all.
How This Deep-Sea discovery Compares to Other Methane Systems
Methane seeps are not new to science — they have been documented in shallower waters off California, New Zealand, and in the Gulf of Mexico, and methane is also released when Arctic permafrost thaws. Most known methane seeps occur at depths of 500 to 5,000 meters, but the newly discovered hadal system plunges to more than 9,000 meters — almost twice as deep as any previously studied. It is vast in scale, forming a continuous 2,500-kilometer stretch along the Kuril–Kamchatka and Aleutian trenches. And unlike most methane systems, which tend to be either net producers or net consumers, this one appears to play a dual role — both generating and potentially consuming methane, while also locking away exceptional amounts of carbon.
Why This Deep-Sea Discovery Matters
This ecosystem is entirely new to science — a world more than 9,000 meters down that we didn't even know existed a year ago. It may be quietly helping slow climate change, acting as a vast methane sink and carbon store. Or it may be a net source of methane, whose effects ripple far beyond the trenches. The truth is, we simply don't know yet.
What we do know is that once such a system is disturbed or destroyed, it cannot be rebuilt. If it turns out to be a methane sink, protecting it could safeguard an irreplaceable natural climate service. If it turns out to be a source, disrupting it could trigger an even larger release of greenhouse gases — undoing centuries of natural storage in moments.
This discovery forces a choice: exploit the deep ocean in ignorance, or pause long enough to measure, understand, and decide with full knowledge. These hadal trenches may be one of Earth's most powerful hidden climate tools, and we stand at the edge of deciding their fate.
In the end, this is why science matters. It is our only way to reveal the invisible systems quietly sustaining life on our planet — and our only defense against dismantling them before we even realize what we've lost. The deep-sea still holds secrets that can shape the climate future for every living thing. Whether we give ourselves the time to listen is up to us.