The thousands of meters deep ditches at the bottom of the oceans were long considered an hostile zone. But now a research expedition has discovered true oases of life on the basis of two such deep -sea dugs – at up to 9533 meters depth. It is the deepest animal communities known to date, as the team reports. The colonies from bearded worms, tube worms, mussels, sea snails and other marine animals were found at the bottom of the Kurilen-Kamchatka grave and the Aleutengraben associated with it in the North Pacific. The organisms gain their energy there with the help of methane and hydrogen sulfide, which come from bacteria in the sediment of the deep -sea trenches and escape in cold sources. These busy zones extend over 2,500 kilometers in length and range from around 5000 meters of water to the lowest background of the Kuril trench. The discovery of this communities throws a new light on the geochemistry and living environment of the deep -sea trenches worldwide.
Although modern diving boats and underwater robots have already been pushed into many regions of the deep sea, the Hadal, the zone of the sea below 6,000 meters, is still considered to be a terra incognita of marine research. Because the extreme conditions make it difficult even with the latest technology to explore this living space more precisely. For a long time, the deep sea was also considered a dark, nutrient -poor “desert”, in which there are hardly any organisms anyway. But it is now clear that this is a mistake. Especially in recent years, expeditions have always delivered new evidence of species -rich life in the lightless deep sea. Hydrothermal chicks and methane sources have proven to be the hotspots of Mariner biodiversity. Because they deliver the resources to the deep -sea residents in order to gain energy and nutrients for their metabolism in a chemical way.
Discovery at the bottom of the deep sea dug
However, such chemosynthetic communities have so far only been examined and mapped. “Although they were found on many active and passive record boundaries and in a wide range of sea depths, such communities below 6000 meters are largely unexplored in deep -sea graves,” report Xiaotong Peng from the state laboratory for deep -sea research in Chinese Sanya and his colleagues. In order to change this, Peng and his team undertook an expedition in the summer of 2024 for the reason of two large deep -sea dugs in the North Pacific. The 2250-kilometer Kurilen-Kamchatka-Graben is located on the plate border between the Pacific earth plate and the Ochotsk plate reaching from Kamchatka to Japan. It is up to 10,500 meters deep. The Aleutengraben up to 7822 meters deep branches off in the northeast of the Kurilengraben and extends over 3500 kilometers to Alaska. The researchers used a manned special diving boat to explore the lower regions of both deep-sea trenches in 23 dives.
Peng and his team came across numerous places with unexpectedly rich life during their dives: in both deep -sea dugbits they discovered extensive communities of marine animals. These consisted of different types of tube worms, wild bristle worms, mussels and sea snails. “While 19 of these dives observed, documented, documented and tried out chemosynthetically based communities and were able to demonstrate their spread in a clearly recognizable zone along the Grabengrund,” report the researchers. “This zone extends over 2,500 kilometers along the Grabengrund and, despite previous studies of sediments and fauna, has not yet been recognized or described in these areas.” The deep-sea livelihoods were found wherever gas-rich liquids from deep-sea sources (Seeps) emerge. “The Seep communities we identify are characterized by an exceptionally high number and density of specialized species. We have found maximum density of up to 5813 tube worms and 293 mussels per square meter in both deep-sea dugs,” write Peng and his colleagues.
(Video: Institute of Deep Sea Science and Engineering, CAS)
Tube worms, mussels and methane -generating bacteria
In the Kurilengraben, these newly discovered communities are dominated by different types of tubular buildings (Siboglinidae). “Your colonies consist of thousands of individual animals that protrude from the sediment everywhere,” explain Peng and his team. These stuck worms are known for eating symbi- bacteria through chemo -autotrophic bacteria: with the help of these “roommates” living in their tissues, they can convert inorganic raw materials such as hydrogen sulfide and methane into high -energy molecules such as ATP and organic compounds. In addition to bearded worm-dominated communities, there were also extensive colonies of deep-sea mashed in the Aleutengraben, many genera are also known to obtain their nutrients and energy from chemo-autotrophic symbits. The researchers in the Kurilengraben discovered the deepest Hadal living community at a depth of 9533 meters. There, a large colony of tubular builders had developed at the transition between the Grabengrund and the reason of the sediment accumulated there.
“These are the deepest and most extensive communities based on chemosythesis that are known on Earth,” state Peng and his colleagues. The flourishing communities and their distribution areas examined here significantly expand the well -known habitat, the depths and the biogeographic spread of numerous species. “Your analyzes of the liquids escaping from the surface of the trenches show that methane and hydrogen sulfide in particular form the basis of this deep-sea ditch ecosystems. However, these gases are not originally originated, but are generated by bacteria that break down the organic material available in the grave. of the Grabengrund from the seabed. So far, it has been assumed that such deep sea organisms primarily feed on the organic material that is drowned out of higher sea zones. “The broad occurrence of the communities based on chemosynthesis now indicates a underestimated role of chemical energy for the Hadale ecosystem,” the team continued.
Source: Xiaotong Peng (1state Key Laboratory of Deep-Sea Science and Intelligence Technology, Sanya) et al., Nature, DOI: 10.1038/S41586-025-09317-Z
