A relict oasis of living deep-sea mussels Bathymodiolus and microbial-mediated seep carbonates at newly-discovered active cold seeps in the Gulf of Cádiz, NE Atlantic Ocean

Abstract Extensive beds of the deep-sea mussel Bathymodiolus mauritanicus (currently also known as Gigantidas ) linked to active cold seeps related fissure-like activity on Al Gacel mud volcano, Gulf Cádiz, were filmed and sampled for first time during oceanographic expedition SUBVENT-2 aboard R/V Sarmiento de Gamboa. volcano is one up 80 fluid venting submarine structures (mud volcanoes volcano/diapir complexes) identified in Cádiz result explosive hydrocarbon-enriched fluids sourced from deep seated reservoirs. This a cone-shaped edifice, 107 m high, 944 diameter constituted by breccias and, partially covered pavements seep carbonates. this detected at northern flank 810–815 water depth associated with bacterial mats around intermittent buoyant vertical bubble methane plumes. High concentrations measured column above living beds. Other chemosymbiotic species ( Siboglinum sp., Solemya elarraichensis , Isorropodon Thyasira vulcolutre Lucinoma asapheus found different parts volcano. may currently represent most delivering significant amounts thermogenic hydrocarbon which contribute foster extensive chemosynthesis-based communities detected. finding paramount importance linking extremophile bivalve populations along North Atlantic, including México, hydrothermal vents Mid-Atlantic Ridge now, detailed documented Cádiz.