Abundance and distribution of fatty acids in hydrothermal vent sediments of the western Pacific Ocean

Sediments obtained from three active seafloor hydrothermal areas in the western Pacific Ocean were measured for the abundances and distributions of total fatty acids (TFAs). Approximately 50 fatty acids were identified, with the chain-length ranging from C₉ to C₂₉. The total concentrations of TFAs (∑TFA) show a wide range from 13.2 to 184 μg/g dry sediment. The values of ∑TFA, over 100 μg/g dry sediment, are significantly higher than those reported for non-hydrothermal seafloor sediments. Furthermore, the observed compositions of TFAs are rich in bacterial biomarkers especially monounsaturated fatty acids, which is common to sediments and symbiotic animal tissues from other sites associated with hydrothermal activities. High ratios of ∑TFA to total organic carbon content (TOC) relative to the non-hydrothermal seafloor sediment may also reflect a large contribution of organic matter produced at the vents. Due to the limited sample availability from these environments, the TFA compositions were not enough to evaluate relatedness between the vent sediment and vent animal community, while the wide diversity of TFAs suggests a large variation in source organisms in these hydrothermal environments. This study confirms the high contribution of bacteria and other vent organisms to organic matter in the sediments.