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from https://spacedaily.com/t-six-miles-below-the-pacific-with-no-sunlight-and-no-photosynthesis-a-chinese-submersible-found-thousands-of-blood-red-tubeworms-and-white-clams-thriving-on-leaking-methane-the-deepest-anim/

Six miles below the Pacific, with no sunlight and no photosynthesis, a
Chinese submersible found thousands of blood-red tubeworms and white
clams thriving on leaking methane rCo the deepest animal ecosystem ever discovered on Earth
On 30 July 2025, a team from the Institute of Deep-sea Science and
Engineering (IDSSE) at the Chinese Academy of Sciences published a paper
in Nature reporting communities of tubeworms and clams living on the
floor of two Pacific trenches at depths down to 9,533 metres.

By Space Daily Editorial Team

Published July 18, 2026 -+ How we edit

Six miles below the Pacific, with no sunlight and no photosynthesis, a
Chinese submersible found thousands of blood-red tubeworms and white
clams thriving on leaking methane rCo the deepest animal ecosystem ever discovered on Earth
Representative image of the deep ocean. The tubeworm and clam
communities described here were recorded by the crewed submersible
Fendouzhe on the trench floor, and are not pictured. Photo: Francesco
Ungaro / Pexels.
On 30 July 2025, a team from the Institute of Deep-sea Science and
Engineering (IDSSE) at the Chinese Academy of Sciences published a paper
in Nature reporting communities of tubeworms and clams living on the
floor of two Pacific trenches at depths down to 9,533 metres. That is
close to six miles beneath the surface, in the hadal zone, where no
light reaches and photosynthesis is impossible. The paper, Flourishing chemosynthetic life at the greatest depths of hadal trenches, describes
the deepest animal communities yet recorded, and the most extensive chemosynthesis-based ecosystem found anywhere on Earth.

The observations were made from Fendouzhe (Striver), ChinarCOs crewed full-ocean-depth submersible, operating from the research vessel
Tansuoyihao. According to the paper, the team surveyed the trench floors between 8 July and 17 August 2024, in the KurilrCoKamchatka Trench and the western Aleutian Trench, the stretch of deep ocean that runs between the Russian Far East and Alaska.

What the submersible actually found
The communities are dominated by two groups of animals: siboglinid polychaetes, the family that includes deep-sea tubeworms, and bivalves,
the group that includes clams. In the footage released with the study,
the tubeworms grow in dense fields, some reaching around 30 centimetres,
their exposed plumes coloured deep red by haemoglobin. The clams cluster
in white beds across the sediment. None of it looks like what most
people picture at the bottom of a trench, which is usually described as sparse, slow, and reliant on scraps falling from far above.

The scale is the part that is hard to overstate without overstating it.
The paper reports that these communities span roughly 2,500 kilometres
along the trench floors, at depths from about 5,800 metres to 9,533
metres. That is not a single seep or a lucky patch. It is a distribution
long enough to reach from one end of a continent to the other, sitting
in one of the least accessible environments on the planet.

Life without sunlight
These animals do not eat, in the ordinary sense. They rely on
chemosynthesis, a process in which bacteria, rather than plants, sit at
the base of the food web. The tubeworms and clams host symbiotic
bacteria in their tissues. Those bacteria draw energy from chemical
reactions involving methane and hydrogen sulphide seeping from the
seafloor, and use it to build organic matter from inorganic carbon. The
host animal lives on what its resident bacteria produce.

The ocean looks like one vast sunlit body of water, but below about 600
feet there is too little light for photosynthesis, and below 3,300 feet sunlight disappears entirelyrColeaving much of EarthrCOs surface in
permanent darkness.

The Artful Age
Chemosynthetic communities are not new to science. They have been
studied at hydrothermal vents and cold seeps since the late 1970s. What
is new here is the depth, the extent, and the source of the chemicals. According to the IDSSE team, the methane and hydrogen sulphide are
carried upward along faults in the trench floor, and geochemical
analysis points to the methane being microbial in origin, produced by
microbes breaking down organic matter buried in deeper sediment layers.
That detail matters, because it implies an active community of life
beneath the seafloor feeding the community on top of it.

Why this changes the depth record
Before this expedition, chemosynthetic communities in the hadal zone
were known only from scattered observations. The announcement from the National Natural Science Foundation of China, which co-funded the work,
notes that the previous deepest record came from the Japan Trench at
7,434 metres, and that hadal sightings had been sporadic rather than continuous. The new observations push the confirmed depth down by more
than two kilometres and, more importantly, replace a handful of isolated sightings with a picture of communities distributed across a long
section of trench.

The researchers frame this as evidence for what they call a
rCLChemosynthetic Life CorridorrCY running through the worldrCOs deep trenches. It is worth being precise about what that phrase is doing. It
is a hypothesis drawn from a large but still single body of observations
along two connected trenches. It is not yet a demonstrated feature of
every trench on Earth. The paper supports the claim that these
communities are far more widespread at extreme depth than previously
assumed. It does not establish that they line every hadal trench, and
the authors do not claim that.

The Artful Age
What it means for the carbon question
The finding also touches the deep-sea carbon cycle. The long-standing
view has been that hadal ecosystems run mostly on organic particles
drifting down from surface waters, the slow rain of dead material from
the sunlit ocean above. These communities complicate that view by
showing that chemically fuelled life can be a substantial presence at
the very bottom, drawing on carbon stored in the sediment rather than
carbon delivered from above. How much that shifts the overall accounting
of carbon in the deep ocean is an open question, and one the paper
raises rather than settles.

There is a national dimension worth naming plainly. This is a
Chinese-led result, funded under ChinarCOs National Key R&D Programme and carried out with domestically built deep-sea hardware. Full-ocean-depth
crewed diving is a capability only a few countries hold, and the ability
to return to the same trench floors repeatedly is what made a survey on
this scale possible. The science and the platform are hard to separate here.

The immediate open questions are about breadth and mechanism. Do
comparable communities exist in the other major trenches, as the
corridor hypothesis predicts, or are the KurilrCoKamchatka and Aleutian systems unusual in the way their faults deliver methane and hydrogen
sulphide? How large is the sub-seafloor microbial community implied by
the methanerCOs microbial signature, and how much carbon does it actually process? Answering either will take more dives, more sampling, and
probably more than one national programme working the deep trenches. For
now, the record for the deepest known animal ecosystem sits at 9,533
metres, on a trench floor between Russia and Alaska, sustained by
chemistry rather than sunlight.

About this article

This article is for general information and reflection. It is not
professional advice. For your specific situation, consult a qualified professional.


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