Evaluation of nutrient and energy sources of the deepest known serpentinite-hosted ecosystem using stable carbon, nitrogen, and sulfur isotopes

• DOI: 10.1371/journal.pone.0199000
• Publication Date: 2018-06-15T17:45:56Z
• Authors: Yuji Onishi; Toshiro Yamanaka; Tomoyo Okumura; Shinsuke Kawagucci; Hiromi Kayama Wat...; Yasuhiko Ohara
• Keywords: 0301 basic medicine; Carbon Isotopes; Energy-Generating Resources; Geologic Sediments; Nitrogen Isotopes; Science; Q; R; Nutrients; 15. Life on land; 7. Clean energy; Bivalvia; 03 medical and health sciences; Hydrothermal Vents; 13. Climate action; Sulfur Isotopes; Medicine; Animals; Seawater; 14. Life underwater; Photosynthesis; Ecosystem; Research Article

The Shinkai Seep Field (SSF) in the southern Mariana forearc discovered in 2010 is the deepest (~5,700 m in depth) known serpentinite-hosted ecosystem dominated by a vesicomyid clam, Calyptogena (Abyssogena) mariana. The pioneering study presumed that the animal communities are primary sustained by reducing fluid originated from the serpentinization of mantle peridotite. For understanding the nutrient and energy sources for the SSF community, this study conducted four expeditions to the SSF and collected additional animal samples such as polychaetes and crustaceans as well as sediments, fragments of chimneys developing on fissures of serpentinized peridotite, seeping fluid on the chimneys, and pore water within the chimneys. Geochemical analyses of seeping fluids on the chimneys and pore water of the chimneys revealed significantly high pH (~10) that suggest subseafloor serpentinization controlling fluid chemistry. Stable isotope systematics (carbon, nitrogen, and sulfur) among animals, inorganic molecules, and environmental organic matter suggest that the SSF animal community mostly relies on the chemosynthetic production while some organisms appear to partly benefit from photosynthetic production despite the great depth of SSF.