title: Fossil evidence for serpentinization fluids fueling chemosynthetic assemblages.
abstract: Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-Atlantic Ridge (MAR) is remarkable both for its alkaline fluids derived from mantle rock serpentinization and the spectacular seafloor carbonate chimneys precipitated from these fluids. Despite high concentrations of reduced chemicals in the fluids, this unique example of a serpentinite-hosted hydrothermal system currently lacks chemosynthetic assemblages dominated by large animals typical of high-temperature vent sites. Here we report abundant specimens of chemosymbiotic mussels, associated with gastropods and chemosymbiotic clams, in approximately 100 kyr old Lost City-like carbonates from the MAR close to the Rainbow site (36 °N). Our finding shows that serpentinization-related fluids, unaffected by high-temperature hydrothermal circulation, can occur on-axis and are able to sustain high-biomass communities. The widespread occurrence of seafloor ultramafic rocks linked to likely long-range dispersion of vent species therefore offers considerably more ecospace for chemosynthetic fauna in the oceans than previously supposed.
authors.affiliation: Laboratoire d'Ecogéochimie des Environnements Benthiques, Centre National de la Recherche Scientifique, Laboratoire Arago, Université Pierre et Marie Curie-Paris 6, 66650 Banyuls-sur-Mer, France. franck.lartaud@obs-banyuls.fr.
authors.forename: Franck
authors.initials: F
authors.lastname: Lartaud
authors.forename: Crispin T S
authors.initials: CT
authors.lastname: Little
authors.forename: Marc
authors.initials: M
authors.lastname: de Rafelis
authors.forename: Germain
authors.initials: G
authors.lastname: Bayon
authors.forename: Jerome
authors.initials: J
authors.lastname: Dyment
authors.forename: Benoit
authors.initials: B
authors.lastname: Ildefonse
authors.forename: Vincent
authors.initials: V
authors.lastname: Gressier
authors.forename: Yves
authors.initials: Y
authors.lastname: Fouquet
authors.forename: Françoise
authors.initials: F
authors.lastname: Gaill
authors.forename: Nadine
authors.initials: N
authors.lastname: Le Bris
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D018533:Biomass; D002254:Carbonates / Q000737:chemistry; D017753:Ecosystem; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry; D055593:Geological Phenomena; D006358:Hot Temperature; D049879:Mytilidae / Q000737:chemistry
chemical_list: D002254:Carbonates