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Deepest Chemosynthetic Ecosystems Revealed in Pacific Hadal Trenches

The Nature paper confirms submersible dives uncovered thriving chemosynthesis-based communities at record depths, prompting investigations into their adaptations and prevalence worldwide.

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A dense aggregation of mollusks called vesicomyid bivalves is seen in the seabed sediment of a deep ocean trench at a depth of 5,743 meters (18,800 feet) below the sea surface at a site called Clam Bed in the northwest Pacific Ocean, in this undated image.   Institute of Deep-sea Science and Engineering, CAS (IDSSE, CAS)/Handout via REUTERS.
Clusters of tube worms called "frenulate siboglinids", extending red hemoglobin-filled tentacles with small mollusks on the tops of the tubes near the tentacles, are seen at a depth of 9,320 meters (30,500 feet) beneath the sea surface at a site called Wintersweet Valley in the northwest Pacific Ocean, in this undated image.    Institute of Deep-sea Science and Engineering, CAS (IDSSE, CAS)/Handout via REUTERS

Overview

  • The human-crewed Fendouzhe completed 24 dives during summer 2024, surveying 2,500 km of the Kuril-Kamchatka and Aleutian trenches between 5,800 m and 9,533 m depths.
  • Researchers documented extensive fields of tube worms and clams sustained by hydrogen sulfide and methane seepage at 9,533 m, extending the known depth limit for complex ecosystems by nearly 25%.
  • Isotopic and genetic analyses confirm these hadal communities depend on chemosynthetic microbes, and some host species appear to be previously undescribed.
  • The discovery overturns assumptions that only single-cell organisms inhabit the deepest trenches and highlights the hadal zone’s role in global carbon cycling.
  • Following publication in Nature, scientists are investigating the physiological adaptations of trench dwellers and surveying other deep-sea trenches for comparable ecosystems.