More than nine kilometres below the ocean surface, the surprise was not a field of giant deep-sea animals. It was a dense community of millimetre-scale organisms attached to exposed rock, dominated by single-celled foraminiferans and accompanied by tiny members of several other branches of life.
Between 2020 and 2024, researchers used the crewed submersible Fendouzhe during a programme of 98 dives across seven hadal regions in the Indo-Pacific, a span of exploration described in reporting on the team’s work. The resulting study, published in Science on May 14, 2026, documented a hard-substrate fauna from 9,000 to 10,898 metres and described 32 species across six protist and metazoan phyla.
The discovery was smaller and stranger than it sounds
The formal Science paper, led by Xikun Song with an international group of researchers, describes most of the organisms as millimetre-sized and many as new to science. The richest patches could reach densities of up to about 4,300 individuals per square decimetre.
The dominant filamentous organisms were agglutinated foraminiferans, single-celled protists rather than animals in the usual sense. Researchers informally described their feather-like forms as “rock feathers,” and genetic and microscopic work helped establish what these otherwise simple-looking organisms actually were.
The community did include animals as well. Among the discoveries were a new bryozoan family and other metazoans living alongside the foraminiferans, which is why the researchers describe the assemblage broadly as a hard-substrate fauna rather than as a colony of one organism.
Why rocks this deep remained a blind spot
The hadal zone extends from roughly 6,000 metres to almost 11,000 metres and contains rock faces along trench walls, fracture zones and subducted seamounts. Recovering biological material attached to those surfaces is difficult, which meant the organisms living directly on deep rock had remained much less studied than many soft-sediment communities.
Fendouzhe changed what researchers could reach and sample. The Chinese Academy of Sciences lists it as a full-ocean-depth human-occupied vehicle with an operating depth of 11,000 metres, and the submersible reached 10,909 metres in Challenger Deep during sea trials in 2020.
That ability allowed researchers to photograph hard surfaces in place and recover material instead of inferring the community solely from what could be hauled upward from kilometres below. The difference matters when many of the organisms are only millimetres long and physically attached to rock.
Seven hadal regions, one recurring pattern
The strongest evidence came from the Kermadec and Mariana trenches, where the study documented the fauna at depths between 9,000 and 10,898 metres. Large-scale imagery and sampling then indicated that similar sessile communities occur across seven hadal regions around Oceania.
Besides Kermadec and Mariana, researchers reported comparable fauna from the Aleutian, Kuril–Kamchatka, Puysegur, Atacama and Mussau trenches. That does not mean every rock face in every trench carries an identical ecosystem, but it moves the discovery from a single-site curiosity toward a potentially widespread hadal pattern.
The project was Chinese-led rather than exclusively Chinese. The author group included researchers connected with institutions in New Zealand, the United Kingdom, Germany, Austria and Indonesia as well as several Chinese research institutions.
The food source was the bigger surprise
The identity of the dominant organisms was only part of the finding. An Institute of Deep-Sea Science and Engineering summary says the team found no typical chemosynthetic indicator groups such as siboglinid tubeworms or vesicomyid clams during these hard-substrate dives.
Metagenomic and metabarcoding work also failed to find known chemolithoautotrophic symbionts in the dominant organisms. Instead, researchers found terrestrial pine pollen inside several species at different stages of digestion, evidence that the foraminiferans were heterotrophs consuming organic material rather than depending primarily on microbes powered by chemicals leaking from the seabed.
The physical setting offers a possible explanation for how food reaches them. V-shaped trenches funnel organic material downslope, while turbidity currents can scour exposed surfaces and move particles through the trench system.
The foraminiferans were found mainly on vertical sides of rock outcrops, often hanging downward from their attachment points. The researchers interpret that posture as a possible way to reduce burial by sediment while intercepting organic particles carried by moving water.
Not the same as the tubeworm and clam fields
Fendouzhe was involved in another spectacular hadal discovery, but it was a different study. In 2025, researchers reported in Nature the deepest and most extensive chemosynthesis-based communities then known, found in the Kuril–Kamchatka and western Aleutian trenches.
Those communities were dominated by siboglinid worms and bivalves between about 5,800 and 9,533 metres and extended across roughly 2,500 kilometres. They were associated with methane- and hydrogen-sulphide-rich fluids moving along faults, making them fundamentally different from the heterotrophic hard-substrate assemblages described in the 2026 Science paper.
The distinction is scientifically important because both discoveries show abundant life at extreme depth, but they do not run on the same ecological machinery. One is a cold-seep system built around chemical energy from the seabed, while the other is dominated by organisms apparently feeding on organic material delivered from above and along the trench.
Some of the depth records belonged to animals
Although protists dominate the newly described hard-substrate assemblages, the survey also pushed the known depth limits of several animal groups. The IDSSE summary reports a bryozoan at 9,981 metres, scyphozoan polyps at 9,982 metres and hydrozoan polyps at 9,195 metres.
The bryozoan, Pierrella fendouzhei, belongs to a newly described family and an old evolutionary lineage. Findings like these show why describing the entire community simply as microbes or simply as animals misses what the submersible actually encountered.
A carbon hotspot hiding on rock
The study also gives the tiny sessile foraminiferans a larger ecological significance. Researchers estimate that their living biomass carbon could represent about 2 to 11 percent of total eukaryotic biomass carbon across global hadal trenches.
That estimate does not mean the discovery suddenly rewrites the global climate system. It does suggest that carbon held and processed by life attached to hadal rock has been easier to overlook than its abundance warrants, adding another component to attempts to understand how organic material moves through the deepest ocean.
What the lights revealed
The deepest parts of the ocean are not simply empty basins waiting for occasional scavengers to pass through. Rock faces near ten kilometres deep can hold dense communities whose dominant members were so poorly known that researchers first had to determine what kind of organisms they were and how they fed.
That is the lasting image from the 98 dives: not a barren wall at the apparent edge of habitability, but rock covered with tiny bodies hanging into moving water. Once Fendouzhe brought lights, cameras and sampling tools to those surfaces, an ecosystem that had been physically present all along finally became visible.
