Vertical distribution of amino acids and chiral ratios in deep sea hydrothermal sub-vents of the Suiyo Seamount, Izu-Bonin Arc, Pacific Ocean

Abstract

A high temperature deep sea hydrothermal system related to dacitic arc volcanism has been drilled using a tethered, submarine rock drill system as a part of the Archaean Park Project. The benthic multi-coring system (BMS) employed allows for direct sampling of microorganisms, rocks and fluids beneath hydrothermal vents. The samples examined in this study are from sites APSK 08, 09 and 10 on the Suiyo seamount of the Izu-Bonin Arc in the Pacific Ocean. Based on the vertical distribution and stereochemistry of amino acids in this vigorous sub-vent environment, a model of deep sea subterranean chemistry and biology is proposed, describing optimal microbial activity rather than abiotically synthesized amino acids components. Total hydrolyzed amino acids in the hydrothermal sub-vent core samples are of the order of 10 1–10 2 nmol/g-rock. The ratios of β-alanine/aspartic acid and γ-aminobutyric acid/glutamic acid are low, consistent with a large microbial population and fresh subterranean bioorganic compounds. The d/ l ratios of chiral amino acids such as aspartic acid, glutamic acid and alanine in these rock samples were overall also quite low. Large enantiomeric excesses of l amino acids also support the existence of a vigorous subjacent microbial oasis in this seamount hydrothermal sub-system. The present findings represent crucial evidence that sub-vent regions are a previously unknown extreme environment biosphere, extending the known subterranean habitable spaces.